Failure to migrate-lack of tree range expansion in response to climate

Failure to migrate:lack of tree range expansion in response to climate change

K A I Z H U*,C H R I S T O P H E R W.W O O D A L L?and JAMES S.CLARK*?

*Nicholas School of the Environment,Duke University,Durham,NC27708,USA,?USDA Forest Service,Northern Research Station,St.Paul,MN55108,USA,?Department of Biology and Department of Statistical Science,Duke University,Durham,NC 27708,USA

Abstract

Tree species are expected to track warming climate by shifting their ranges to higher latitudes or elevations,but cur-rent evidence of latitudinal range shifts for suites of species is largely indirect.In response to global warming,off-spring of trees are predicted to have ranges extend beyond adults at leading edges and the opposite relationship at trailing https://www.sodocs.net/doc/891090006.html,rge-scale forest inventory data provide an opportunity to compare present latitudes of seedlings and adult trees at their range https://www.sodocs.net/doc/891090006.html,ing the USDA Forest Service’s Forest Inventory and Analysis data,we directly compared seedling and tree5th and95th percentile latitudes for92species in30longitudinal bands for43334plots across the eastern United States.We further compared these latitudes with20th century temperature and precipita-tion change and functional traits,including seed size and seed spread rate.Results suggest that58.7%of the tree spe-cies examined show the pattern expected for a population undergoing range contraction,rather than expansion,at both northern and southern boundaries.Fewer species show a pattern consistent with a northward shift(20.7%)and fewer still with a southward shift(16.3%).Only4.3%are consistent with expansion at both range limits.When com-pared with the20th century climate changes that have occurred at the range boundaries themselves,there is no con-sistent evidence that population spread is greatest in areas where climate has changed most;nor are patterns related to seed size or dispersal characteristics.The fact that the majority of seedling extreme latitudes are less than those for adult trees may emphasize the lack of evidence for climate-mediated migration,and should increase concerns for the risks posed by climate change.

Keywords:biogeography,climate change,Forest Inventory and Analysis,latitude,presence/absence,range shift,seedling,tree migration

Received19September2011and accepted19September2011

Introduction

Anticipating whether or not species range limits can track climate change is a goal of global change research (Clark et al.,2001;Davis&Shaw,2001;Jackson et al., 2009;Loarie et al.,2009;Dawson et al.,2011).Across the globe,mounting evidence con?rms widespread tem-perature increases,particularly at high northern lati-tudes(IPCC,2007).In the eastern United States,mean annual temperatures increased during the20th century in the Midwest and Northeast,but not in the Southeast, where warming summers were balanced by cooling winters(Fig.1a).When viewed in terms of a velocity, as has been advocated recently(Loarie et al.,2009), regions in the Northeast and Upper Midwest have seen climate shifts of more than100km during the20th cen-tury(Fig.1b).As the climate warms,new regions that become available for occupation may be colonized as those no longer suitable are abandoned.Inevitable time lags involved in plant dispersal,colonization,establish-ment,and maturation threaten not only rare species but also many that are abundant and provide vital ecosys-tem functions and services.Numerous datasets and models suggest a variety of species’responses to chang-ing climate,but robust empirical evaluation remains challenging.

Previous studies generally agree that plants will respond to climate warming by shifting their ranges to higher elevations and latitudes(Hughes,2000; McCarty,2001;Walther et al.,2002;Parmesan&Yohe, 2003;Parmesan,2006;Chen et al.,2011),but only eleva-tion responses are thus far readily apparent in data (Beckage et al.,2008;Holzinger et al.,2008;Kelly& Goulden,2008;Lenoir et al.,2008;le Roux&McGeoch, 2008;Bergamini et al.,2009;Crimmins et al.,2011;Van Bogaert et al.,2011).The most recent comprehensive meta-analysis by Chen et al.(2011)does not include lat-itudinal range shifts of plants.In fact,studies of plant latitudinal range boundaries rely heavily on models at global(Thomas et al.,2004),continental(Bakkenes et al.,2002;Thuiller et al.,2005;Meier et al.,2011),and

Correspondence:Kai Zhu,tel.+19196138037,

fax+19196815740,e-mail:kai.zhu@https://www.sodocs.net/doc/891090006.html,

1042?2011Blackwell Publishing Ltd Global Change Biology(2012)18,1042–1052,doi:10.1111/j.1365-2486.2011.02571.x

regional scales (Midgley et al.,2002;Broennimann et al.,2006).Species distribution models in general (Guisan &Thuiller,2005;Elith &Leathwick,2009),and bioclimatic envelope models in particular (Pearson &Dawson,2003;Heikkinen et al.,2006)provide valuable perspec-tives on potential effects of climate change (Botkin et al.,2007;McMahon et al.,2011).However,there is lit-tle empirical evidence to support the model predictions that populations are shifting to higher latitudes.

The Forest Inventory and Analysis (FIA)program of the USDA Forest Service provides an extensive tree inventory for examining tree species range distribution and migration from millions of observations across the country.FIA conducts the only systematic sampling of all forest tree species at a continental scale.Although this database has been extensively used in tree range projection models (Iverson et al.,2004,2008),it has been used to evaluate potential range shifts only in highly indirect https://www.sodocs.net/doc/891090006.html,ing FIA data,Murphy et al.(2010)found that 60%of 102eastern US tree species have peak abundances of ?tted distributions in the northern por-tion of their ranges.They suggested that this pattern could re?ect range contraction in the south and limited expansion in the north.If ranges are more strongly lim-ited by climate at high rather than low latitudinal limits (Dobzhansky,1950;MacArthur,1972;Brown et al.,1996),then the opposite pattern could be expected,with strong advance in the north and limited response in the south,depending on the effects of competition with invaders advancing from the south.In addition to ana-lyzing abundance,Woodall et al.(2009)compared the mean latitude of seedling and tree occurrence using FIA data throughout the eastern United States and found that northern species tend to show a shift north-ward,while southern species do not.They recognized

that these conclusions could be affected by their speci?c choice of study species (Woodall et al.,2010)and their use of mean latitude,which re?ects central tendency rather than range https://www.sodocs.net/doc/891090006.html,bining FIA,climate,geo-graphic data,and several emission scenarios,Iverson et al.(2008)predicted that the center of suitable habitats for 134eastern US tree species would move up to 800km northeast.For ?ve of the common species they analyzed,Iverson et al.(2004)predicted that migration in the next century will extend no more than 20km beyond their current northern range.Taken together,these different approaches suggest that trees might be responding to climate change with latitudinal range shifts,but the evidence is indirect and not in clear agreement.The in?uence of global climate change on range boundaries could bene?t from development of new techniques to exploit the FIA evidence at range boundaries across large spatial scales.

In this study,we develop a novel technique for exam-ining the latitudinal difference between offspring and adults of trees at both northern and southern range lim-its across the eastern United States,and we evaluate the number of species showing evidence for range expan-sion or contraction.We then compare these patterns with changes in 20th century temperature and precipi-tation,as well as functional traits expected to in?uence migration potential,speci?cally,seed size and dispersal properties.We test the widely held hypothesis that trees could track climate change by migration,showing differences between offspring and adult range limits (Neubert &Caswell,2000;Lewis et al.,2006),with the largest differences between offspring and adult extent being in areas where climate change has been most pro-nounced.There has been substantial effort in recent years to determine whether small-seeded species have

?95?90

?85?80?75

?7025

303540

45

Longitude (deg)

?95

?90

?85?80?75?70

0.1

1

10

10010003000Longitude (deg)

change in time and space during the 20th in the eastern United States.Data are from the Climate Research Unit dataset (Mitchell &Jones,2005).(a)Temporal denoting the slope of the linear regression decadal data:red –increasing trend,blue 0.05,open –insigni?cant slope with and square size being proportional of temperature change,de?ned as quotient of the temporal gradient (a)and 2000of temperature distribution (Loarie 2009).

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LACK OF MIGRATION I N FOREST TREE S 1043

greater migration potential than large-seeded species (reviewed by Angert et al.,2011).Four mutually exclu-sive and all-inclusive hypotheses are summarized by a four-quadrant diagram of range shifts at northern and southern frontiers(Fig.2):

1Overall range expansion:if a species is expanding at northern and southern frontiers,then offspring will have greater latitudinal extent than adults at both range limits(I in Fig.2),as would occur if the envi-ronment is changing in ways that bene?t the species in both areas.

2Northward range shift:if a species is expanding at northern frontiers and retreating from southern fron-tiers,then offspring will extend north of adults at the northern range limit,and adults will extend south of offspring at the southern range limit(II in Fig.2). This is the expected response to climate warming.

3Overall range contraction:if a species is contracting from northern and southern frontiers,then offspring will have less latitudinal extent than adults at both

range limits(III in Fig.2),as would occur if the envi-ronment is changing in ways that harm the species or bene?t its competitors in both areas.

4Southward range shift:if a species is retreating from northern frontiers and expanding at southern fron-tiers,then adults will extend north of offspring at the northern range limit,and offspring will extend south of adults at the southern range limit(IV in Fig.2). We further evaluate the hypotheses that species with greater dispersal ability might spread more rapidly under climate change(Clark et al.,2001;Angert et al., 2011;Nathan et al.,2011),and small-seeded species might show greater northward(II)or southward(IV) range shifts than large-seeded species(near the origin in Fig.2).

While providing perhaps the most direct evidence for subcontinental scale range shifts for a large number of species,it is important to recognize limitations of FIA data,and the fact that no analysis can de?nitively determine migration patterns.We compare results of our analysis with other empirical and modeling studies, recognizing how sampling designs,successional trends, and source-sink dynamics can in?uence study of adult and offspring distributions.

Materials and methods

Our analysis concerns the latitudinal extent of offspring and adults from FIA data distributed longitudinally across the eastern United States,combined with20th century tempera-ture and precipitation change,as well as seed size and dis-persal properties.A population that is migrating north in response to warming is expected to have offspring extending to higher latitudes than adults in regions that have warmed over the last century,but not in regions where climate has remained essentially constant.This is the signature of an expanding population front,as predicted by all models of migration(Okubo,1980;Neubert&Caswell,2000;Clark et al., 2001;Lewis et al.,2006).Likewise,a population retreating from a warming southern boundary is expected to have adults south of the southern extent of new recruitment by offspring. This is the basic assumption behind recent analyses of Woo-dall et al.(2009),but analyzed in our study at the range boundaries themselves.Lenoir et al.(2009)used this assump-tion when comparing seedling and adult distributions to detect altitudinal range shifts.In the following sections,we summarize our methods,including the FIA sampling design, the longitudinal band analysis(LBA)to detect range shifts, and comparisons of range shifts,climate change,and func-tional traits.

Forest inventory data

The FIA program is the primary source for information on the extent,condition,status,and trends of forest resources in

the

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United States(Smith et al.,2009).FIA applies a nationally con-sistent sampling protocol covering all ownerships across the United States,resulting in national sample intensity of one plot per2428ha(Bechtold&Patterson,2005)within forest lands(i.e.homogenous forest cover classes to reduce estimate uncertainty).Sample intensities vary somewhat by state;how-ever,because the inventory is systematic,varying sample intensities do not bias assessment of tree species locations (McRoberts et al.,2005).Forested land is de?ned to be>0.4ha in area and36.6m in width,with at least10%tree cover.FIA inventory plots in forested conditions consist of four7.2m ?xed-radius subplots spaced36.6m apart in a triangular arrangement with one subplot in the center(Bechtold&Patt-erson,2005).All trees(standing live and dead)with a diame-ter at breast height(dbh)of at least12.7cm,are inventoried on forested subplots.Within each subplot,a2.07m radius mi-croplot offset3.66m from subplot center is established where only live trees with a dbh between2.5and12.7cm are inven-toried.Within each microplot,all live tree seedlings are tallied according to species.Conifer seedlings must be at least 15.2cm in height with a root collar diameter<2.5cm.Hard-wood seedlings must be at least30.5cm in height with a root collar diameter<2.5cm.Inherent in any large-scale forest inventory,there is measurement error associated with tree species identi?cation.The FIA program has a quality assess-ment and quality control program associated with the national

inventory that monitors measurement error and continuously seeks to reduce said errors(Pollard et al.,2006;USDA Forest Service,2011).Nationally,FIA?eld crews have attained at least95%repeatability of tree species identi?cation with nearly9%of all inventory plot measurements remeasured for this repeatability assessment(ca.2010).

In this analysis,FIA data were extracted from annual inven-tories(1999–2008)in31eastern states for a total of43334 inventory plots from FIADB version4.0on16March2010(avail-able online http://?https://www.sodocs.net/doc/891090006.html,/;Fig.3).Because we focus on range limits,we used Little’s digitized geographic range maps (USGS,1999)to restrict analysis to the92species having their entire geographic range within the eastern United States (Table S1in Supporting Information includes the complete species list).To compare species in different life stages(off-spring vs.adult),we followed the FIA de?nition,dividing the data into two types of subgroups,(i)seedling(dbh<2.5cm) vs.tree(dbh>2.5cm),and(ii)sapling(2.5cm< dbh<12.7cm)https://www.sodocs.net/doc/891090006.html,rge tree(dbh>12.7cm).In other words, we conducted two offspring vs.adult comparisons:seedling vs.tree,and sapling https://www.sodocs.net/doc/891090006.html,rge tree.

Longitudinal band analysis

We developed a LBA for comparing occurrences of offspring vs.adults across the full northern and southern frontiers for each species.To allow for variation in migration response along range limits,we strati?ed the43334FIA plots into lon-gitudinal bands1°wide,from98°to68°W spanning the geo-graphic extent of the eastern United States(Fig.3).For each longitudinal band,we determined the5th and95th percentiles of latitudinal occurrence for all species for each of the life stages(seedling vs.tree,and sapling https://www.sodocs.net/doc/891090006.html,rge tree).In other words,5%of the occurrences are at lower latitudes than the 5th percentile and at higher latitudes than the95th percentile. The distributions of these percentiles across longitudinal bands were compared between stages to evaluate the assump-tion that offspring distributions extend to higher or lower lati-tudes than adults.We calculated the difference for longitudinal pairs of offspring and adults,yielding latitudinal difference distributions(LDD)at northern and southern boundaries for each species.For the x th latitudinal percentile,

LDD j;x?q offspring

eT

j;x

àq adult

eT

j;x

;e1Twhere q j,x is the latitude corresponding to percentile x in longi-tudinal band j.At a northern frontier,positive LDD j,x is con-sistent with northern expansion,because it implies that offspring extend further north than adults.At a southern fron-tier,positive LDD j,x is consistent with northward retreat (southern contraction).The mean of LDD at a range boundary (north or south)summarizes the mean latitudinal difference between small and large size classes.For each species,we summarized two mean LDD values,one at northern and one at southern frontiers.

With this explanation of the LBA method,underlying moti-vation is straightforward.Our analysis of offspring and adult latitudinal extents is fundamentally an examination of distri-butional extremes.The extreme value of a distribution has no statistical con?dence assigned to it,because it is observed once.Likewise,a comparison of locations for the extreme off-spring latitude with the extreme adult latitude has no statisti-cal uncertainty associated with it.However,by comparing these extreme events from a number of longitudinal bands 2

5

–95–90–85–80

Longitude (deg)

–75–70 3

3

5

4

4

5

Approximate Forest Inventory and Analysis plot loca-(black points)and one degree longitudinal study bands dashed lines)in the eastern United States.

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(i.e.the LDDs of Eqn 1)we introduce replication and the potential to evaluate the relationship between offspring and adults along their range margins across areas that have experi-enced different degrees of 20th century warming (Fig.1).It further introduces the potential for modeling,as LDDs may depend on the degree of climate change or other variables associated with each band (next section).To evaluate sensitiv-ity to a speci?c percentile,we repeated the analysis not only for the 5th and 95th percentiles of latitudes,but also for north and south extremes (the 0th and 100th percentiles),and the 10th and 90th percentiles.The sensitivity to discretizing longi-tude was assessed by repeating the analysis at 0.5°,1°,and 2°wide longitudinal bands.

Climate change and functional trait data

To determine if the tendency to expand or contract is related to the degree of climate change in a region,we compared the mean of LDD with 20th century climate change from the Cli-mate Research Unit (CRU)high resolution climate data,ver-sion 2.1(Mitchell &Jones,2005).Based on more than seven sources of meteorological station records,the CRU data are gridded with a spatial resolution of 0.5°90.5°,and temporal resolution of 10decades (1900–2000).Analysis was completed for the two most commonly used climate variables,mean annual temperature and mean annual precipitation.We ?rst calculated 20th century linear trends (slopes)for temperature and precipitation change for each longitudinal band location q j,x in Eqn (1).For each species,we determined the correlation between LDD and trends in temperature or precipitation,

q T ?cor LDD j ;x ;D T q j ;x

àáàá

q P ?cor LDD j ;x ;D P q j ;x àáàáe2T

where D T is temperature change and D P is precipitation change for offspring locations (q j,x ).At the northern frontier,positive ρT (ρP )is evidence that range expansion occurs where temperature (precipitation)increase has been greatest.At the southern frontier,positive ρT (ρP )is evidence that range con-traction occurs where temperature (precipitation)increase has been greatest.We used correlation for these comparisons,because there was no evidence of nonlinearity.

The correlations between climate change and spread can be made more transparent by placing them on the same dimen-sions,translating climate change over time to climate velocity (Loarie et al.,2009).Over much of the eastern US canopy for-ests date from the early 20th century.Seedlings in our data sets established approximately a century later.The velocity of climate change with latitude y is obtained from rate of change and the climate gradient (Fig.1b),

d y ?d T 0

d T :e3TW

e compared the mean LDD value for each species with the

velocity of climate change at its range limit.

To determine whether or not dispersal characteristics can explain the tendency to expand or contract,as being hypothe-sized in recent studies (Angert et al.,2011;Nathan et al.,2011),we compared mean LDD from the LBA method with plant

functional trait data from the USDA Natural Resources Con-servation Service’s PLANTS database (USDA NRCS,2010).We compared range expansion or contraction potential with two functional traits,(i)seed size,which is the reciprocal of seed per pound in an average seed lot,and (ii)seed spread rate,which is an ordinal variable (slow,moderate,or rapid)intended to describe the capability to spread compared with other species with the same growth habit (USDA NRCS,2010).All analyses were performed in R version 2.12.1(R Develop-ment Core Team,2010).

Results

Use of LBA to identify relationships consistent with range shifts is illustrated by example species,followed by summaries for the entire dataset.LDDs from the seedling vs.tree comparison (Eqn 1)show contrasting patterns for two species at northern range limits (Fig.4):expansion for Ilex opaca (American holly)and contraction for Diospyros virginiana (common persim-mon).For Ilex opaca ,seedlings (red)occur well north of the range for trees (blue,Fig.4a and b).If the northern extent of seedlings represents a sink population,then seeds are dispersed to and germinate at these latitudes,but do not survive to adulthood.This would occur,for example,if temperatures were too low to support pop-ulations of the species (e.g.bird-dispersed seeds germi-nate but do not survive).An alternative explanation is that the range is expanding.It is unlikely that seedlings could long survive winter temperatures too low to sup-port adult trees.Note that this is not one of the horticul-tural species of Ilex typically sold in nurseries.It is thus possible that Ilex opaca has expanded its range to take advantage of warming climate in the upper Midwest (Fig.1a).

A contrasting pattern was found for Diospyros virgini-ana (Fig.4c and d).Seedlings (red)do not extend as far north as trees (blue),as would be expected for a range contraction.This pattern is apparent across the full northern frontier,from Missouri to Delaware.Current information does not identify whether lack of Diospyros seedlings at the northern frontier results from recent cli-mate change,land use change,or other factors.These direct comparisons were extended to all the study’s 92species.

Across all species,patterns consistent with range con-traction at both northern and southern boundaries pre-dominate.This pattern is especially pronounced for the seedling vs.tree comparison,but it is also evident for the sapling https://www.sodocs.net/doc/891090006.html,rge tree comparison.The quadrant dia-gram (Fig.5)shows species having greater latitudinal extent for seedlings than trees at both northern and southern range limits (I),at northern but not southern range limits (II),at neither northern nor southern range

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limits(III),or at southern but not northern range limits (IV).The largest proportion of species has lower seed-ling latitudinal extent than trees at northern bound-aries,and higher latitudinal extent than trees at southern boundaries–in other words,contraction at both boundaries.In the seedling vs.tree comparison,54 out of92species(58.7%)show this pattern consistent with range contraction(III in Fig.5).In the sapling vs. large tree comparison,60out of92(65.2%)species show this pattern(Fig.S1).

The other three cases contain fewer species(Fig.5). In the seedling vs.tree comparison,19out of92species (20.7%)are consistent with range expansion in the north and contraction in the south(II in Fig.5), whereas15out of92species(16.3%)are consistent with range expansion in the south and contraction in the north(IV in Fig.5).In other words,slightly more spe-cies are consistent with a northward range shift(II in Fig.2)than with a southward range shift(IV in Fig.2). In the sapling https://www.sodocs.net/doc/891090006.html,rge tree comparison,12out of92spe-cies(13%)show the pattern consistent with northward range shift,and16out of92species(17.4%)show the pattern consistent with southward range shift(Fig.S1). Evidence consistent with expansion at both northern and southern limits is least well represented.Only four out of92species(4.3%)have lower5th and higher95th percentiles for seedlings than for trees(I in Fig.5).The same percentage(4.3%),albeit a different set of four species,was obtained for comparisons of saplings vs. large trees(Fig.S1).

In sum,our results suggest a pattern consistent with the following ranking in terms of number of species: overall range contraction>northward or southward range shift>overall range expansion.For species hav-ing comparisons consistent with range contraction,the magnitude of the latitude shift is greater for the

difference at the northern range

locations of seedlings(red)and trees

band.Points above the1:1line

would be expected if there is expansion

longitudinal bands where trees occur

clarity in the?gure,seedlings

Diospyros virginiana(c).

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LACK OF MIGRATION I N FOREST TREE S1047

seedling vs.tree than for the sapling https://www.sodocs.net/doc/891090006.html,rge tree com-parisons.This result is robust,being consistent across 0.5°,1°,and2°longitudinal bandwidths and for percen-tiles0th and100th(maximum and minimum),5th and 95th,and10th and90th.Across all92species the aver-age range contraction was0.37°(42km)at northern boundary,and0.26°(29km)at southern boundary for the seedling vs.tree comparison.

The relationship between LDD and20th century cli-mate trends(Eqn2)shows a similar pattern for both offspring vs.adult comparisons.For the seedling vs. tree comparison,62.2%of species have positiveρT at northern limits,implying that ranges expanded most where temperature increase was greatest,and44.4% have positiveρT at southern limits,implying that ranges contracted most where temperature increase was greatest.For the sapling https://www.sodocs.net/doc/891090006.html,rge tree comparison, these percentages are61.1%and44.4%,respectively (Table S2).There was no relationship between expan-sion patterns and precipitation change.

Contrary to the common assumption that migration potential is determined by seed characteristics,the LBA shows no relationship between range expansion or con-traction and functional traits(i.e.seed size and seed spread rate).Most species classi?ed as large seeded and slow spread potential fall in the category of overall reduction in range size(circle sizes and colors in III of Fig.5).Small-seeded species occur in all four catego-ries,including overall range expansion or contraction and northward or southward range shift.

Discussion

Despite caveats that must apply to any analysis of for-est plot data,evidence for climate-driven migration is essentially absent in this large analysis that considers distributions of offspring and adults across geographic gradients in climate change.Patterns are more consis-tent with range contraction of eastern US tree species than with northward migration.The results based on the direct comparisons of seedlings and trees at range limits do not inspire con?dence that tree populations are tracking contemporary climate change.If the seed-ling class integrates up to a decade or more of climate history(seedling banks range up to several decades in age),and trees integrate up to a century,then north-ward migration in response to warming would result in seedlings displaced to the north of mature individu-als of the same species.The greater the warming,the greater the expected displacement.Likewise,retreat from southern boundaries is expected where warming has reduced the competitive advantage previously enjoyed in a cooler climate.This assumption is the basis for a large number of analyses of climate and migration (Okubo,1980;Neubert&Caswell,2000;Clark et al., 2001;Lewis et al.,2006),but massive inventories of both seedlings and adults have not been analyzed in this way.The majority of species in our analysis shows a pattern consistent with range contraction at both north-ern and southern range limits.Some species are consis-tent with the expected but much debated poleward range shift(Parmesan&Yohe,2003;Chen et al.,2011). Range expansion at both northern and southern fron-tiers is observed for the smallest proportion of species among the four possible cases(Fig.5).Due to FIA’s sampling intensity,this study provides perhaps the most robust assessment of tree migration potential. Moreover,failure to?nd evidence that seedlings extend as far north as adults and absence of a relationship to local climate changes suggests cause for concern,given the temperature trends already underway during the 20th century(Fig.1).Before discussing implications we consider some of the important caveats of an analysis like this.

Sources of uncertainty,limitations,and caveats

The factors that could in?uence patterns we quanti?ed here include(i)sampling effects and data

limitations,

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(ii)successional changes,and(iii)sink populations beyond the range where the population is viable.The caveats that follow could apply to any of the many recent studies reporting evidence of range shifts,but are rarely considered.

Due to the inherent limits of FIA data(Woodall et al., 2009),the comparison of the presence/absence data could be biased if there is a higher probability of?nd-ing offspring than adults or vice versa.Our analysis that includes not only seedlings and trees but also sap-lings and large trees(see Forest inventory data), reduces this risk–our results are similar for both com-parisons.We further relied on the fact that the sample size is massive.A range of different stand ages will con-tribute variation to patterns we analyze,but not neces-sarily overwhelm them.The large sample sizes for both seedlings and trees can help to overcome bias toward particular life stages.However,the fact that sample sizes are substantial does not insure that plot design can be ignored.The54m2seedling sample area is still much smaller than the673m2tree plot(Bechtold& Patterson,2005),but seedlings can occur at much higher densities.

It is important to consider whether or not there are nonclimatic obstacles to migration.Species faced with physiographic barriers to migration(e.g.close to coast-lines,parent material heterogeneity,and mountains) should be interpreted carefully,because they may be more limited by geography than climate(Bakkenes et al.,2002;Clark et al.,2011).Species with range limits close to boundaries of the sample region may bias results.Our analysis includes few northern species, because they may extend their ranges into Canada. Careful attention to caveats yields conclusions robust to the widths of longitudinal bands(0.5°,1°,or2°),or the latitudinal percentiles(0th and100th,5th and95th,or 10th and90th).

The possibility that successional change and sink populations could be mistaken for range expansion has to be considered as an alternative explanation.Seed-lings can expand in areas where trees are rare or absent as successional species reinvade or recruitment declines with stand development.Successional changes could affect our results in at least two ways.Light demanding species can be common in forest overstories where recruitment of the same species in shaded understories is rare.Alternatively,early successional stands could support recruitment of light-demanding species at sites where few individuals have reached the adult stage.In both cases,a biased representation of particular stand ages could affect results in ways that are dif?cult to anticipate.There is also potential for interactions.Pres-ence of seedlings following recovery from disturbance would be especially confusing if there were a strong correlation between recent disturbance and climate change.Although there is substantial heterogeneity in land use across the eastern United States,much of the entire region is dominated by20th century afforesta-tion.We expect that land cover has contributed to pat-terns we report,but we are unaware of systematic geographic trends could explain our results.We exam-ined LDD by shade-tolerance classes and did not?nd a tendency for shade tolerant species to be expanding more than shade intolerant species.

Heterogeneous habitats may create sink populations for seedlings,outside the range of adult trees being supported by continual seed inputs(Pulliam,1988). While possible in principle,the bulk of seed for most species falls close to adults and long-distance dispersed seed faces competition from copious seed produced by local plants.Moreover,seedlings may be more sensitive to climate variation than adults(Grubb,1977;Harper, 1977).Thus,although we cannot ignore the possibility of sink populations,we assume that such effects would not dominate the broad geographic patterns we report. If there are sink populations,our method would mis-take them for range expansion.In other words,sink populations could not be an explanation for failure to ?nd the range shifts predicted by climate change. Comparison with other FIA studies

By directly analyzing tree and seedling distributions at range boundaries,our analysis of latitudinal extent addresses limitations of previous studies.Previous analyses using FIA data suggest that both seedlings and trees have higher abundance in the northern lati-tudes than the southern latitudes within their geo-graphic ranges,which could be interpreted as a signature of northward tree migration(Woodall et al., 2009;Murphy et al.,2010),but could also represent responses to a whole range of variables.Abundance and occupancy patterns(Murphy et al.,2006,2010) might not provide evidence of range shifts,because geographic range is de?ned by boundaries,not abun-dance or occupancy within boundaries(Cox&Moore, 2010,pp.204,38–40).Despite different approaches and assumptions,Murphy et al.(2010)suggested that the most common response could be range contraction in the south and limited expansion in the north,leading to a possible overall range size reduction.

Woodall et al.’s(2009)comparison of mean latitudes for seedlings and trees could likewise miss dynamics at population frontiers.Range shifts in response to climate change are expected to occur at the leading(northern) or trailing(southern)edges,with the changes in mean latitude being sensitive to other factors.Woodall et al. (2009)also examined maximum and minimum

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latitudes.Still,Woodall et al.’s(2009)results are consis-tent with range contraction in this analysis.At the southern range limits of northern species,12out of15 species show greater minimum latitude for seedlings. At the northern range limits of southern species,10out of15species show greater maximum latitude for trees (table2in Woodall et al.,2009).Many of the40species they studied have ranges that are not contained within the eastern United States(especially for northern spe-cies)so dynamics at northern range limits are unknown (Woodall et al.,2010).To minimize these effects on the analysis,we included all species having entire ranges within the study area(see Forest inventory data). Climate change has already been large(Fig.1)–we do not have to wait decades to evaluate whether or not climate change is affecting migration.Our?nding that the majority of species may experience range contrac-tion at both northern and southern limits does not square with the expectation that species will migrate rapidly north in response to climate change.Many models predict rapid tree migration(Clark,1998; McKenney et al.,2007),but some do not(Clark et al., 2001,2003;Nathan et al.,2011).Iverson et al.’s(2008) habitat distribution model predicts that61–68of134 species will increase at least10%,and50–58species will lose at least10%of their area-weighted importance value.Some of these predictions are consistent with our comparisons of offspring and adults(e.g.Acer nigrum and Juglans cinerea).On the other hand,Iverson et al. (2004)predicted that migration potential at northern

range limit for Diospyros virginiana,Liquidambar styraci-?ua,Oxydendrum arboreum,Pinus taeda,and Quercus fal-cata would be limited to within20km of the area currently occupied.Our analysis of these species all show contraction at northern limits,in general agree-ment with Iverson et al.’s(2004)expectation that migra-tion potential is limited.

Relationship with climate change and functional traits The fact that most species appear to be contracting at both northern and southern range limits is not consis-tent with the expectation that temperature change during the20th century should allow for rapid spread(Fig.6).At the northern frontier,in particular, calculations using climate observations suggest that species may need to migrate hundreds of km north-ward to track warming temperatures in the eastern United States(Fig.1b).However,making the reason-able assumption that the LDD observed in this study represents dynamics on a100year scale,our results suggest that most species have not tracked20th cen-tury temperature change(below the1:1line in Fig.6).

Our results should not be interpreted to say that cli-mate has no effect on species range limits.Sixty-two precent of species at nothern boundaries and44%at southern boundaries are positively correlated with tem-perature change(Table S2).There is no relationship with precipitation change.Many variables affecting these boundaries could preclude the large geographic shifts needed to track climate.For example,adults might be controlled by annual mean temperature and precipitation,but offspring might be driven by temper-ature variabilities and extremes,growing season tem-perature or drought,spring precipitation,?rst-last day of frost,and so forth.Soils,disturbance,and land use change could provide a backdrop for species interac-tions,including competition,herbivore,and disease.If habitat destruction,degradation,and fragmentation resulted from land use change are proximate factors limiting response to climate(Hof et al.,2011),vulnera-bility could shift from human effects in the near term to climate change in the near future.

Clark et al.(2003)emphasized that species range shifts cannot be predicted from seed dispersal charac-teristics and life history.The empirical evidence pre-sented here should not be misinterpreted to say

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1050K.ZHU et al.

seed characteristics have no impact.This study shows that most large-seeded species have patterns consistent with overall range contraction at both northern and southern range limits(Fig.5),a pattern that is sugges-tive of an effect,but different from the expected capac-ity to track warming at northern range limits.Like us, the meta-analysis of Angert et al.(2011)showed that seed mass and seed dispersal mode have low explana-tory power for range shifts of Swiss alpine plants. Crimmins et al.(2011)found that altitudinal range shifts of California plant species are unrelated to life-form,physiognomy,dispersal mechanism,and?re adaptation.Such studies do not establish that seed traits are unimportant,because they are comparisons across rather than within species.Seed traits could have an impact on spread of many species without emerging as‘signi?cant’predictors of spread across species.The result that species-level traits do not correlate with migration potential suggests that use of seed size as an indicator of which species may track climate could be of limited utility.

Slow migration potential from models,experiments,and observational data

Model predictions that tree responses to climate change would be slow and unpredictable(Clark et al.,2003) motivated an extensive seedling study to evaluate per-formance of residents and potential invaders(Ibanez et al.,2008,2009).Invasion of new regions means that rare seeds traveling long-distances face competition from overwhelming numbers of locally produced seed. To overcome these odds,rare dispersers require local microsites where they are clearly superior to residents (Clark et al.,2003),or locally disturbed sites,where local seed rain from potential competitors is low(Fastie, 1995).Models that make some effort to incorporate the many sources of uncertainty do not predict the rapid spread that comes from simple projection of dispersal kernels(Clark et al.,2001,2003).Fourteen thousand seedlings of residents and potential invaders were planted and followed in competition for light and soil moisture,in gaps and in the forest understory,from southeastern Piedmont to northern hardwoods(Ibanez et al.,2008,2009).Potential invaders consisted of spe-cies from warmer latitudes or elevations,likely to migrate north in response to contemporary climate change(Fig.1).Results showed no advantage to poten-tial invaders,certainly not the dominance needed if they were to overcome the numerical disadvantages required for rapid spread.Results of widespread seed-ling experiments on invasion(Ibanez et al.,2008,2009) coupled with the FIA record of offspring-adult compar-isons(this analysis)would appear to support model results that predict migration rates far below those required to track contemporary climate change. Acknowledgements

For comments on the manuscript,we thank Dave Bell,Carl Salk, and two anonymous referees.The study was supported by NSF grants CDI0940671and the Coweeta LTER.

References

Angert AL,Crozier LG,Rissler LJ,Gilman SE,Tewksbury JJ,Chunco AJ(2011)Do species’traits predict recent shifts at expanding range edges?Ecology Letters,14, 677–689.

Bakkenes M,Alkemade JRM,Ihle F,Leemans R,Latour JB(2002)Assessing effects of forecasted climate change on the diversity and distribution of European higher plants for2050.Global Change Biology,8,390–407.

Bechtold WA,Patterson PL(2005)The Enhanced Forest Inventory and Analysis Program: National Sampling Design and Estimation https://www.sodocs.net/doc/891090006.html,DA Forest Service,Southern Research Station,Asheville,NC.

Beckage B,Osborne B,Gavin DG,Pucko C,Siccama T,Perkins T(2008)A rapid upward shift of a forest ecotone during40years of warming in the Green Moun-tains of Vermont.Proceedings of the National Academy of Sciences of the United States of America,105,4197–4202.

Bergamini A,Ungricht S,Hofmann H(2009)An elevational shift of cryophilous bryo-phytes in the last century–an effect of climate warming?Diversity and Distribu-tions,15,871–879.

Botkin DB,Saxe H,Araujo MB et al.(2007)Forecasting the effects of global warming on biodiversity.BioScience,57,227–236.

Broennimann O,Thuiller W,Hughes G,Midgley GF,Alkemade JMR,Guisan A (2006)Do geographic distribution,niche property and life form explain plants’vulnerability to global change?Global Change Biology,12,1079–1093.

Brown JH,Stevens GC,Kaufman DM(1996)The geographic range:size,shape, boundaries,and internal structure.Annual Review of Ecology and Systematics,27, 597–623.

Chen I-C,Hill JK,Ohlemu¨ller R,Roy DB,Thomas CD(2011)Rapid range shifts of species associated with high levels of climate warming.Science,333,1024–1026. Clark JS(1998)Why trees migrate so fast:confronting theory with dispersal biology and the paleorecord.American Naturalist,152,204–224.

Clark JS,Lewis M,Horvath L(2001)Invasion by extremes:population spread with variation in dispersal and reproduction.American Naturalist,157,537–554.

Clark JS,Lewis M,McLachlan JS,HilleRisLambers J(2003)Estimating population spread:what can we forecast and how well?Ecology,84,1979–1988.

Clark JS,Bell DM,Hersh MH,Nichols L(2011)Climate change vulnerability of forest biodiversity:climate and resource tracking of demographic rates.Global Change Biology,17,1834–1849.

Cox CB,Moore PD(2010)Biogeography:An Ecological and Evolutionary Approach.Wi-ley,Hoboken,NJ.

Crimmins SM,Dobrowski SZ,Greenberg JA,Abatzoglou JT,Mynsberge AR(2011) Changes in climatic water balance drive downhill shifts in plant species’optimum elevations.Science,331,324–327.

Davis MB,Shaw RG(2001)Range shifts and adaptive responses to Quaternary cli-mate change.Science,292,673–679.

Dawson TP,Jackson ST,House JI,Prentice IC,Mace GM(2011)Beyond predictions: biodiversity conservation in a changing climate.Science,332,53–58. Dobzhansky T(1950)Evolution in the tropics.American Scientist,38,209–221.

Elith J,Leathwick JR(2009)Species distribution models:ecological explanation and prediction across space and time.Annual Review of Ecology Evolution and Systemat-ics,40,677–697.

Fastie CL(1995)Causes and ecosystem consequences of multiple pathways of pri-mary succession at Glacier Bay,Alaska.Ecology,76,1899–1916.

Grubb PJ(1977)The maintenance of species-richness in plant communities:the importance of the regeneration niche.Biological Reviews,52,107–145.

Guisan A,Thuiller W(2005)Predicting species distribution:offering more than sim-ple habitat models.Ecology Letters,8,993–1009.

Harper JL(1977)Population Biology of Plants.Academic Press,London.

Heikkinen RK,Luoto M,Araujo MB,Virkkala R,Thuiller W,Sykes MT(2006)Meth-ods and uncertainties in bioclimatic envelope modelling under climate change.

Progress in Physical Geography,30,751–777.

?2011Blackwell Publishing Ltd,Global Change Biology,18,1042–1052

LACK OF MIGRATION I N FOREST TREE S1051

Hof C,Levinsky I,Araujo MB,Rahbek C(2011)Rethinking species’ability to cope with rapid climate change.Global Change Biology,17,2987–2990.

Holzinger B,Hulber K,Camenisch M,Grabherr G(2008)Changes in plant species richness over the last century in the eastern Swiss Alps:elevational gradient,bed-rock effects and migration rates.Plant Ecology,195,179–196.

Hughes L(2000)Biological consequences of global warming:is the signal already apparent?Trends in Ecology&Evolution,15,56–61.

Ibanez I,Clark JS,Dietze MC(2008)Evaluating the sources of potential migrant spe-cies:implications under climate change.Ecological Applications,18,1664–1678. Ibanez I,Clark JS,Dietze MC(2009)Estimating colonization potential of migrant tree species.Global Change Biology,15,1173–1188.

IPCC(2007)Climate Change2007:The Physical Science Basis.Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.Cambridge University Press,Cambridge,UK/New York,NY,USA. Iverson LR,Schwartz MW,Prasad AM(2004)How fast and far might tree species migrate in the eastern United States due to climate change?Global Ecology and Bio-geography,13,209–219.

Iverson LR,Prasad AM,Matthews SN,Peters M(2008)Estimating potential habitat for134eastern US tree species under six climate scenarios.Forest Ecology and Man-agement,254,390–406.

Jackson ST,Betancourt JL,Booth RK,Gray ST(2009)Ecology and the ratchet of events:climate variability,niche dimensions,and species distributions.Proceedings of the National Academy of Sciences of the United States of America,106,19685–19692. Kelly AE,Goulden ML(2008)Rapid shifts in plant distribution with recent climate change.Proceedings of the National Academy of Sciences of the United States of America, 105,11823–11826.

Lenoir J,Gegout JC,Marquet PA,de Ruffray P,Brisse H(2008)A signi?cant upward shift in plant species optimum elevation during the20th century.Science,320,1768–1771.

Lenoir J,Gegout JC,Pierrat JC,Bontemps JD,Dhote JF(2009)Differences between tree species seedling and adult altitudinal distribution in mountain forests during the recent warm period(1986-2006).Ecography,32,765–777.

Lewis MA,Neubert MG,Caswell H,Clark JS,Shea K(2006)A guide to calculating discrete-time invasion rates from data.In:Conceptual Ecology and Invasions Biology: Reciprocal Approaches to Nature(eds Cadotte MW,Mcmahon SM,Fukami T),pp.

169–192.Springer,Dordrecht,The Netherlands.

Loarie SR,Duffy PB,Hamilton H,Asner GP,Field CB,Ackerly DD(2009)The veloc-ity of climate change.Nature,462,1052–1055.

MacArthur RH(1972)Geographical Ecology.Harper&Row Publishers,New York. McCarty JP(2001)Ecological consequences of recent climate change.Conservation Biology,15,320–331.

McKenney DW,Pedlar JH,Lawrence K,Campbell K,Hutchinson MF(2007)Potential impacts of climate change on the distribution of North American trees.BioScience, 57,939–948.

McMahon SM,Harrison SP,Armbruster WS et al.(2011)Improving assessment and modelling of climate change impacts on global terrestrial biodiversity.Trends in Ecology&Evolution,26,249–259.

McRoberts RE,Holden GR,Nelson MD et al.(2005)Estimating and circumventing the effects of perturbing and swapping inventory plot locations.Journal of Forestry, 103,275–279.

Meier ES,Lischke H,Schmatz DR,Zimmermann NE(2011)Climate,competition and connectivity affect future migration and ranges of European trees.Global Ecology and Biogeography,doi:10.1111/j.1466-8238.2011.00669.x.

Midgley GF,Hannah L,Millar D,Rutherford MC,Powrie LW(2002)Assessing the vulnerability of species richness to anthropogenic climate change in a biodiversity hotspot.Global Ecology and Biogeography,11,445–451.

Mitchell TD,Jones PD(2005)An improved method of constructing a database of monthly climate observations and associated high-resolution grids.International Journal of Climatology,25,693–712.

Murphy HT,VanDerWal J,Lovett-Doust J(2006)Distribution of abundance across the range in eastern North American trees.Global Ecology and Biogeography,15,63–71. Murphy HT,VanDerWal J,Lovett-Doust J(2010)Signatures of range expansion and erosion in eastern North American trees.Ecology Letters,13,1233–1244.

Nathan R,Horvitz N,He Y,Kuparinen A,Schurr FM,Katul GG(2011)Spread of North American wind-dispersed trees in future environments.Ecology Letters,14, 211–219.

Neubert MG,Caswell H(2000)Demography and dispersal:calculation and sensitiv-ity analysis of invasion speed for structured populations.Ecology,81,1613–1628. Okubo A(1980)Diffusion and Ecological Problems:Mathematical Models.Springer-Verlag,Berlin/New York.

Parmesan C(2006)Ecological and evolutionary responses to recent climate change.

Annual Review of Ecology Evolution and Systematics,37,637–669.

Parmesan C,Yohe G(2003)A globally coherent?ngerprint of climate change impacts across natural systems.Nature,421,37–42.

Pearson RG,Dawson TP(2003)Predicting the impacts of climate change on the distri-bution of species:are bioclimate envelope models useful?Global Ecology and Bioge-

ography,12,361–371.

Pollard JE,Westfall JA,Patterson PL,Gartner DL,Hansen M,Kuegler O(2006)Forest Inventory and Analysis National Data Quality Assessment Report for2000to2003.

USDA Forest Service,Rocky Mountain Research Station,Fort Collins,CO.

Pulliam HR(1988)Sources,sinks,and population regulation.American Naturalist, 132,652–661.

R Development Core Team(2010)R:A Language and Environment for Statistical Com-puting.R Foundation for Statistical Computing,Vienna,Austria.Available at:

https://www.sodocs.net/doc/891090006.html,(accessed20December2010).

le Roux PC,McGeoch MA(2008)Rapid range expansion and community reorganiza-tion in response to warming.Global Change Biology,14,2950–2962.

Smith WB,Miles PD,Perry CH,Pugh SA(2009)Forest Resources of the United States, https://www.sodocs.net/doc/891090006.html,DA Forest Service,Washington Of?ce,Washington,DC.

Thomas CD,Cameron A,Green RE et al.(2004)Extinction risk from climate change.

Nature,427,145–148.

Thuiller W,Lavorel S,Araujo MB,Sykes MT,Prentice IC(2005)Climate change threats to plant diversity in Europe.Proceedings of the National Academy of Sciences

of the United States of America,102,8245–8250.

USDA Forest Service(2011)Forest Inventory and Analysis Fiscal Year2010Business Report.U.S.Department of Agriculture,Washington,DC.

USDA NRCS(2010)The PLANTS Database.National Plant Data Center,Baton Rouge, LA,USA.Available at:https://www.sodocs.net/doc/891090006.html,(accessed11November2010).

USGS(1999)Digital Representations of Tree Species Range Maps from“Atlas of Uni-ted States Trees”by Elbert L.Little,Jr.Available at:https://www.sodocs.net/doc/891090006.html,/data/

atlas/little/(accessed21January2011).

Van Bogaert R,Haneca K,Hoogesteger J,Jonasson C,De Dapper M,Callaghan TV (2011)A century of tree line changes in sub-Arctic Sweden shows local and regio-

nal variability and only a minor in?uence of20th century climate warming.Journal

of Biogeography,38,907–921.

Walther GR,Post E,Convey P et al.(2002)Ecological responses to recent climate change.Nature,416,389–395.

Woodall CW,Oswalt CM,Westfall JA,Perry CH,Nelson MD,Finley AO(2009)An indicator of tree migration in forests of the eastern United States.Forest Ecology and

Management,257,1434–1444.

Woodall CW,Oswalt CM,Westfall JA,Perry CH,Nelson MD,Finley AO(2010) Selecting tree species for testing climate change migration hypotheses using forest

inventory data.Forest Ecology and Management,259,778–785.

Supporting Information

Additional Supporting Information may be found in the

online version of this article:

Figure https://www.sodocs.net/doc/891090006.html,titudinal range change at southern(5th per-

centile)and northern(95th percentile)boundaries from the

sapling https://www.sodocs.net/doc/891090006.html,rge tree comparison.

Table S1.Mean latitudinal range expansion(positive)or

contraction(negative)at the northern and southern bound-

aries for the seedling vs.tree and sapling https://www.sodocs.net/doc/891090006.html,rge tree com-

parisons(species mean of LDD in Eqn1).

Table S2.Correlation between species range shift and20th

century temperature change at the northern and southern

boundaries for the seedling vs.tree and sapling https://www.sodocs.net/doc/891090006.html,rge tree

comparisons(ρT in Eqn2).

Please note:Wiley-Blackwell are not responsible for the con-

tent or functionality of any supporting materials supplied by

the authors.Any queries(other than missing material)should

be directed to the corresponding author for the article.

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常用介词的用法

分考点1 表示时间的介词 Point 1 at, in, on 的用法 （1）at 的用法 At 表示时间点，用于具体的时刻（几点，正午，午夜，黎明，拂晓，日出，日落等），或把某一时间看作某一时刻的词之前以及某些节假日的词之前。 at 6：00 在6点钟 At noon 在中午 At daybreak 在拂晓 At down 在黎明 At Christmas 在圣诞节 【特别注意】在以下的时间短语中，at 表示时间段。 At dinner time 在（吃）晚饭时 At weekends/ the weekend 在周末 （2）in 的用法 ①表示时间段，与表示较长一段时间的词搭配，如年份，月份，季节，世纪，朝代，还可以用于泛指的上午、下午、傍晚等时间段的词前。 In 2009 在2009年 In April 在四月 In the 1990s 在20世纪90年代 In Tang Dynasty 在唐朝 In the morning在上午 ②后接时间段，用于将来时，表示“在一段时间之后”。 The film will begin in an hour. 电影将于一个小时之后开始。 【特别注意】当时间名词前有this，that，last，next，every，each，some等词修饰时，通常不用任何介词。 This morning 今天上午last year 去年 （3）on 的用法 ①表示在特定的日子、具体的日期、星期几、具体的某一天或某些日子。 On September the first 在9月1号 On National Day 在国庆节 We left the dock on a beautiful afternoon. 我们在一个明媚的下午离开了码头。 ②表示在具体的某一天的上午、下午或晚上（常有前置定语或后置定语修饰）。 On Sunday morning 在星期日的早上 On the night of October 1 在10月1号的晚上 【特别注意】“on +名词或动名词”表示“一...就...”. On my arrival home/ arriving home, I discovered they had gone. 我一到家就发现他们已经离开了。 Point 2 in，after 的用法 In 和after都可以接时间段，表示“在...之后”，但in 常与将来时连用，after 常与过去时连用。 We will meet again in two weeks.

英语介词用法大全

英语介词用法大全 TTA standardization office【TTA 5AB- TTAK 08- TTA 2C】

介词（The Preposition）又叫做前置词，通常置于名词之前。它是一种虚词，不需要重读，在句中不单独作任何句子成分，只表示其后的名词或相当于名词的词语与其他句子成分的关系。中国学生在使用英语进行书面或口头表达时，往往会出现遗漏介词或误用介词的错误，因此各类考试语法的结构部分均有这方面的测试内容。 1. 介词的种类 英语中最常用的介词，按照不同的分类标准可分为以下几类： (1). 简单介词、复合介词和短语介词 ①.简单介词是指单一介词。如： at , in ,of ,by , about , for, from , except , since, near, with 等。②. 复合介词是指由两个简单介词组成的介词。如： Inside, outside , onto, into , throughout, without , as to as for , unpon, except for 等。 ③. 短语介词是指由短语构成的介词。如： In front of , by means o f, on behalf of, in spite of , by way of , in favor of , in regard to 等。 (2). 按词义分类 {1} 表地点（包括动向）的介词。如： About ,above, across, after, along , among, around , at, before, behind, below, beneath, beside, between , beyond ,by, down, from, in, into , near, off, on, over, through, throught, to, towards,, under, up, unpon, with, within , without 等。 {2} 表时间的介词。如： About, after, around , as , at, before , behind , between , by, during, for, from, in, into, of, on, over, past, since, through, throughout, till(until) , to, towards , within 等。 {3} 表除去的介词。如： beside , but, except等。 {4} 表比较的介词。如： As, like, above, over等。 {5} 表反对的介词。如： againt ,with 等。 {6} 表原因、目的的介词。如： for, with, from 等。 {7} 表结果的介词。如： to, with , without 等。 {8} 表手段、方式的介词。如： by, in ,with 等。 {9} 表所属的介词。如： of , with 等。 {10} 表条件的介词。如：

信息化基础设施建设也需进行有效规划

信息化基础设施建设也需进行有效规划 导读：信息化基础设施(IT基础设施)建设也需要进行规划。如果只是盲目地花钱，增加硬件、软件投资，表面上看起来好看，但是会存在很多问题。再者，当今技术的发展也远超过了人们的预期，即使刚建设两三年的..... 信息化基础设施(IT基础设施)建设也需要进行规划。如果只是盲目地花钱，增加硬件、软件投资，表面上看起来好看，但是会存在很多问题。再者，当今技术的发展也远超过了人们的预期，即使刚建设两三年的基础设施也不可避免地面临一些新的挑战，如新出现的分布式业务系统非常复杂，它就会对基础设施提出新的要求，还有大量结构化数据的出现使得存储介质、存储结构都会发生很大的变化。因此，企业的这些基础设施期待重新进行规划，以适应新的发展。 IT基础设施规划定义 所谓IT基础设施规划，就是合理规划和安排各项信息化基础设施，使之形成良好的IT环境，让各种业务解决方案、应用系统和数据都能不受约束地在其上实现有效配合。 这些基础设施包括网络、硬件设备和基础软件。网络规划包括数据流量及约束条件分析、网络选型、拓扑结构设计、网络安全方案、网络建设方案等；硬件设备规划包括服务器、路由器、交换机、集线器、台式机、笔记本、打印机、手持设备等的规划和配置等；基础软件规划包括操作系统软件、数据库软件等软件的规划等等。 IT基础设施规划内容 网络规划 现在，企业和事业单位基本上建设有自己的网络系统，但是随着业务需求的增长和技术的发展，都不得不面临优化、扩容和升级的问题。 在进行网络的相关规划时，主要侧重几个方面，一是提出企业和事业单位的LAN/WAN(局域网/广域网)的网络拓扑结构的建设/改良方案；二是确定合理的网络协议；三是评估现有的结构化布线系统的容量、网络设备、广域网数据链路带宽是否满足未来新业务的需求，否则就要进行相应的扩充和升级等。 存储系统规划 存储系统的规划遵循以下原则: (1)存储架构必须满足数据集中的要求 存储架构能够适应大存储容量的需求，又能够对存储资源进行集中利用。

to与for的用法和区别

to与for的用法和区别 一般情况下, to后面常接对象; for后面表示原因与目的为多。 Thank you for helping me. Thanks to all of you. to sb.表示对某人有直接影响比如，食物对某人好或者不好就用to; for表示从意义、价值等间接角度来说，例如对某人而言是重要的，就用for. for和to这两个介词，意义丰富，用法复杂。这里仅就它们主要用法进行比较。 1. 表示各种“目的” 1. What do you study English for? 你为什么要学英语？ 2. She went to france for holiday. 她到法国度假去了。 3. These books are written for pupils. 这些书是为学生些的。 4. hope for the best, prepare for the worst. 作最好的打算，作最坏的准备。 2．对于 1．She has a liking for painting. 她爱好绘画。 2．She had a natural gift for teaching. 她对教学有天赋/ 3．表示赞成同情，用for不用to. 1. Are you for the idea or against it? 你是支持还是反对这个想法？ 2. He expresses sympathy for the common people.. 他表现了对普通老百姓的同情。 3. I felt deeply sorry for my friend who was very ill. 4 for表示因为，由于（常有较活译法） 1 Thank you for coming. 谢谢你来。 2. France is famous for its wines. 法国因酒而出名。 5．当事人对某事的主观看法，对于（某人），对…来说（多和形容词连用）用介词to，不用for.. He said that money was not important to him. 他说钱对他并不重要。 To her it was rather unusual. 对她来说这是相当不寻常的。 They are cruel to animals. 他们对动物很残忍。 6．for和fit, good, bad, useful, suitable 等形容词连用，表示适宜，适合。 Some training will make them fit for the job. 经过一段训练，他们会胜任这项工作的。 Exercises are good for health. 锻炼有益于健康。 Smoking and drinking are bad for health. 抽烟喝酒对健康有害。 You are not suited for the kind of work you are doing. 7. for表示不定式逻辑上的主语，可以用在主语、表语、状语、定语中。 1．It would be best for you to write to him. 2．The simple thing is for him to resign at once. 3．There was nowhere else for me to go. 4．He opened a door and stood aside for her to pass.

英语介词用法详解

英语常用介词用法与辨析 ■表示方位的介词：in, to, on 1. in 表示在某地范围之内。如： Shanghai is/lies in the east of China. 上海在中国的东部。 2. to 表示在某地范围之外。如： Japan is/lies to the east of China. 日本位于中国的东面。 3. on 表示与某地相邻或接壤。如： Mongolia is/lies on the north of China. 蒙古国位于中国北边。 ■表示计量的介词：at, for, by 1. at表示“以……速度”“以……价格”。如： It flies at about 900 kilometers a hour. 它以每小时900公里的速度飞行。 I sold my car at a high price. 我以高价出售了我的汽车。 2. for表示“用……交换，以……为代价”。如： He sold his car for 500 dollars. 他以五百元把车卖了。 注意：at表示单价(price) ，for表示总钱数。 3. by表示“以……计”，后跟度量单位。如： They paid him by the month. 他们按月给他计酬。 Here eggs are sold by weight. 在这里鸡蛋是按重量卖的。 ■表示材料的介词：of, from, in 1. of成品仍可看出原料。如： This box is made of paper. 这个盒子是纸做的。 2. from成品已看不出原料。如： Wine is made from grapes. 葡萄酒是葡萄酿成的。 3. in表示用某种材料或语言。如： Please fill in the form in pencil first. 请先用铅笔填写这个表格。 They talk in English. 他们用英语交谈(from 。 注意：in指用材料，不用冠词；而with指用工具，要用冠词。请比较：draw in penc il/draw with a pencil。 ■表示工具或手段的介词：by, with, on 1. by用某种方式，多用于交通。如by bus乘公共汽车，by e-mail. 通过电子邮件。

with的用法大全

with的用法大全----四级专项训练with结构是许多英语复合结构中最常用的一种。学好它对学好复合宾语结构、不定式复合结构、动名词复合结构和独立主格结构均能起很重要的作用。本文就此的构成、特点及用法等作一较全面阐述，以帮助同学们掌握这一重要的语法知识。 一、 with结构的构成 它是由介词with或without+复合结构构成，复合结构作介词with或without的复合宾语，复合宾语中第一部分宾语由名词或代词充当，第二部分补足语由形容词、副词、介词短语、动词不定式或分词充当，分词可以是现在分词，也可以是过去分词。With结构构成方式如下： 1. with或without-名词/代词+形容词; 2. with或without-名词/代词+副词; 3. with或without-名词/代词+介词短语; 4. with或without-名词/代词+动词不定式; 5. with或without-名词/代词+分词。 下面分别举例：

1、 She came into the room，with her nose red because of cold.(with+名词+形容词，作伴随状语) 2、 With the meal over ， we all went home.(with+名词+副词，作时间状语) 3、The master was walking up and down with the ruler under his arm。(with+名词+介词短语，作伴随状语。) The teacher entered the classroom with a book in his hand. 4、He lay in the dark empty house，with not a man ，woman or child to say he was kind to me.(with+名词+不定式，作伴随状语) He could not finish it without me to help him.(without+代词 +不定式，作条件状语) 5、She fell asleep with the light burning.(with+名词+现在分词，作伴随状语) 6、Without anything left in the cupboard， she went out to get something to eat.(without+代词+过去分词，作为原因状语) 二、with结构的用法 在句子中with结构多数充当状语，表示行为方式，伴随情况、时间、原因或条件(详见上述例句)。

(完整版)介词for用法归纳

介词for用法归纳 用法1：(表目的)为了。如： They went out for a walk. 他们出去散步了。 What did you do that for? 你干吗这样做？ That’s what we’re here for. 这正是我们来的目的。 What’s she gone for this time? 她这次去干什么去了？ He was waiting for the bus. 他在等公共汽车。 【用法说明】在通常情况下，英语不用for doing sth 来表示目的。如： 他去那儿看他叔叔。 误：He went there for seeing his uncle. 正：He went there to see his uncle. 但是，若一个动名词已名词化，则可与for 连用表目的。如： He went there for swimming. 他去那儿游泳。(swimming 已名词化) 注意：若不是表目的，而是表原因、用途等，则其后可接动名词。(见下面的有关用法) 用法2：(表利益)为，为了。如： What can I do for you? 你想要我什么？ We study hard for our motherland. 我们为祖国努力学习。 Would you please carry this for me? 请你替我提这个东西好吗？ Do more exercise for the good of your health. 为了健康你要多运动。 【用法说明】(1) 有些后接双宾语的动词(如buy, choose, cook, fetch, find, get, order, prepare, sing, spare 等)，当双宾语易位时，通常用for 来引出间接宾语，表示间接宾语为受益者。如： She made her daughter a dress. / She made a dress for her daughter. 她为她女儿做了件连衣裙。 He cooked us some potatoes. / He cooked some potatoes for us. 他为我们煮了些土豆。 注意，类似下面这样的句子必须用for： He bought a new chair for the office. 他为办公室买了张新办公椅。 (2) 注意不要按汉语字面意思，在一些及物动词后误加介词for： 他们决定在电视上为他们的新产品打广告。 误：They decided to advertise for their new product on TV. 正：They decided to advertise their new product on TV. 注：advertise 可用作及物或不及物动词，但含义不同：advertise sth＝为卖出某物而打广告；advertise for sth＝为寻找某物而打广告。如：advertise for a job=登广告求职。由于受汉语“为”的影响，而此处误加了介词for。类似地，汉语中的“为人民服务”，说成英语是serve the people，而不是serve for the people，“为某人的死报仇”，说成英语是avenge sb’s death，而不是avenge for sb’s death，等等。用法3：(表用途)用于，用来。如： Knives are used for cutting things. 小刀是用来切东西的。 This knife is for cutting bread. 这把小刀是用于切面包的。 It’s a machine for slicing bread. 这是切面包的机器。 The doctor gave her some medicine for her cold. 医生给了她一些感冒药。 用法4：为得到，为拿到，为取得。如： He went home for his book. 他回家拿书。 He went to his friend for advice. 他去向朋友请教。 She often asked her parents for money. 她经常向父母要钱。

高中英语45个介词的基本用法

——45个基本介词的用法 1、about 【原始含义】 a-b-out “A在B外面” 【引申含义】 [prep] （1）在…到处，在…各处here and there eg: We wandered about the town for an hour or so. He looked about the room. （2）在…附近next to a place eg. She lives about the office. （3）关于in connection with eg: a book about English study I don’t know what you are talking about. [adv] （1）大约close to eg: We left there about 10 o’clock. It costs about 500 dollars. （2）到处，各处 eg: The children were rushing about in the garden. （3）在附近 eg : There is no food about. 【常见搭配】 作介词时的搭配: 一.动词+(about+名词) （1）arrange (about sth) 安排关于某事（2）argue (about sth) 讨论某事 （3）ask (about sth) 询问关于某事（4）boast (about sb/sth) 吹嘘... （5）care (about sb/sth)关心…,对…感兴趣（6）chat(about sth) 谈论某事（7）complain(about sb/sth) 抱怨… （8）dream (about sb/sth) 梦见某人/某物（9）go (about sth) 着手做...；从事...

with用法归纳

with用法归纳 （1）“用……”表示使用工具，手段等。例如： ①We can walk with our legs and feet. 我们用腿脚行走。 ②He writes with a pencil. 他用铅笔写。 （2）“和……在一起”，表示伴随。例如： ①Can you go to a movie with me? 你能和我一起去看电影'>电影吗？ ②He often goes to the library with Jenny. 他常和詹妮一起去图书馆。 （3）“与……”。例如： I’d like to have a talk with you. 我很想和你说句话。 （4）“关于，对于”，表示一种关系或适应范围。例如： What’s wrong with your watch? 你的手表怎么了？ （5）“带有，具有”。例如： ①He’s a tall kid with short hair. 他是个长着一头短发的高个子小孩。 ②They have no money with them. 他们没带钱。 （6）“在……方面”。例如： Kate helps me with my English. 凯特帮我学英语。 （7）“随着，与……同时”。例如： With these words, he left the room. 说完这些话，他离开了房间。 [解题过程] with结构也称为with复合结构。是由with+复合宾语组成。常在句中做状语，表示谓语动作发生的伴随情况、时间、原因、方式等。其构成有下列几种情形： 1.with+名词(或代词)+现在分词 此时，现在分词和前面的名词或代词是逻辑上的主谓关系。 例如:1)With prices going up so fast, we can't afford luxuries. 由于物价上涨很快，我们买不起高档商品。（原因状语） 2)With the crowds cheering, they drove to the palace. 在人群的欢呼声中，他们驱车来到皇宫。（伴随情况） 2.with+名词(或代词)+过去分词 此时，过去分词和前面的名词或代词是逻辑上的动宾关系。

数据中心和网络机房基础设施规划指南

避免数据中心和网络机房基础设施因过度规划造成的资金浪费

典型数据中心和网络机房基础设施最大的、可以避免的成本就是过度规划设计成本。数据中心或 网络机房中的物理和供电基础设施利用率通常在50%-60%左右。未被利用的容量就是一种原本可以避免的投资成本，这还代表着可以避免的维护和能源成本。 本文分为三个部分。首先，介绍与过度规划设计有关的情况和统计数据。接下来，讨论发生这种情况的原因。最后，介绍避免这些成本的新的架构和实现方法。 任何从事信息技术和基础设施产业的人都曾见过未被利用的数据中心空间、功率容量以及数据中心中其他未加利用的基础设施。为了对这种现象进行量化，对讨论中用到的术语进行定义是很重要的。 表1中定义了本文中有关过度规划设计的术语： 建模假设 为了收集并分析过度规划设计的相关数据，施耐德电气对用户进行了调查，并开发了一个简化模型来描述数据中心基础设施容量规划。该模型假设： ?数据中心的设计寿命为 10 年； ?数据中心规划有最终的设计容量要求和估计启动IT 负载要求； ?在数据中心典型生命周期过程中，预期负载从预期的启动负载开始呈线性增长，在预期生命周期一半的时候，达到预期最终容量。 由以上定义的模型得出下面图 1 显示的规划模型。我们假定，它是具有代表性的“一步到位”模式的系统规划模型。 简介有关过度规划设计的情况和统计数据表1 过度规划的相关定义

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常用介词用法(for to with of)

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