增温提高亚高山针叶林植物根系分泌物促进土壤氮循环

Enhanced root exudation stimulates soil nitrogen transformations in a subalpine coniferous forest under experimental warming

H U A J U N Y I N*?,Y U F E I L I*?,J U A N X I A O*?,Z H E N F E N G X U?,X I N Y I N C H E N G*?and

QING LIU*?

*Chengdu Institute of Biology,Chinese Academy of Sciences,P.O.Box416,Chengdu610041,China,?Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization,Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province,Chinese Academy of Sciences,Chengdu610041,China,?Institute of Ecology&Forestry,Sichuan Agricultural University,Chengdu611130,China

Abstract

Despite the perceived importance of exudation to forest ecosystem function,few studies have attempted to examine the effects of elevated temperature and nutrition availability on the rates of root exudation and associated microbial processes.In this study,we performed an experiment in which in situ exudates were collected from Picea asperata seedlings that were transplanted in disturbed soils exposed to two levels of temperature(ambient temperature and infrared heater warming)and two nitrogen levels(unfertilized and25g N mà2aà1).Here,we show that the trees exposed to an elevated temperature increased their exudation rates I(l g C gà1root biomass hà1),II(l g C cmà1root length hà1)and III(l g C cmà2root area hà1)in the unfertilized plots.The altered morphological and physiological traits of the roots exposed to experimental warming could be responsible for this variation in root exudation.More-over,these increases in root-derived C were positively correlated with the microbial release of extracellular enzymes involved in the breakdown of organic N(R2=0.790;P=0.038),which was coupled with stimulated microbial activ-ity and accelerated N transformations in the unfertilized soils.In contrast,the trees exposed to both experimental warming and N fertilization did not show increased exudation rates or soil enzyme activity,indicating that the stimu-latory effects of experimental warming on root exudation depend on soil fertility.Collectively,our results provide preliminary evidence that an increase in the release of root exudates into the soil may be an important physiological adjustment by which the sustained growth responses of plants to experimental warming may be maintained via enhanced soil microbial activity and soil N transformation.Accordingly,the underlying mechanisms by which plant root-microbe interactions in?uence soil organic matter decomposition and N cycling should be incorporated into climate-carbon cycle models to determine reliable estimates of long-term C storage in forests.

Keywords:exudation,N transformation,nutrient availability,subalpine coniferous forest,warming

Received7January2013and accepted24January2013

Introduction

The boreal forest has been indicated as one of the ter-restrial ecosystems that may have a larger sink strength than expected,but uncertainty regarding the persis-tence of the sink has hindered efforts to predict biotic feedback to climate change(Lindroth et al.,1998). Numerous studies have reported that an elevated tem-perature increases tree seedling carbon(C)assimilation rates(Saxe et al.,2001;Wang et al.,2003),plant growth and biomass accumulation(Xu&Juma,1994;Zhao& Liu,2009)and forest net primary productivity(NPP) (Scheller&Mladenoff,2005;Hudson&Henry,2009). Nutrient availability,mainly N,is the primary limiting factor for plant growth and productivity in boreal forest ecosystems,and thus,any continued enhancement of forest NPP will require either increases in the availabil-ity of resources or physiological adjustments that allow increased uptake of these resources(Phillips et al., 2011).

Many studies have reported an increased below-ground C allocation and?ne root production in trees that are exposed to an elevated temperature(Majdi& Ohrvik,2004;Bai et al.,2010),indicating that the trees are likely increasing their allocation to roots to explore the soil for nutrients such as N(Johnson,2006).How-ever,since most limiting nutrients are locked up in soil organic matter,merely increasing the amounts of roots will be insuf?cient to sustain enhanced uptake rates. Rather,trees will need to stimulate soil microbes to release extracellular enzymes to access nutrients bound up in soil organic matter(SOM)(Phillips,2007;Drake et al.,2011;Bengtson et al.,2012).

Correspondence:Qing Liu,tel.00862885229115,

fax00862885222753,e-mail:liuqing@https://www.sodocs.net/doc/cf13759261.html,

2158?2013Blackwell Publishing Ltd Global Change Biology(2013)19,2158–2167,doi:10.1111/gcb.12161

Microbial activity is generally limited by the avail-ability of labile C in soil.Trees are known to stimulate microbial activity and nutrient availability by releasing root exudates(Phillips et al.,2009).Most exudates are low molecular weight organic compounds that increase nutrients due to their chelating properties or preferen-tial use as substrates by soil microbes(Smith,1976; Phillips et al.,2012).In response to exudates,increases in microbial activity and population growth may stimu-late a microbial demand for nutrients,which can be met by increasing the enzyme synthesis and the depo-lymerization of N from SOM(Dijkstra et al.,2009).The stimulation of SOM decomposition and accelerated N cycling caused by inputs of labile C substrates has been recently invoked as an important mechanism to explain the long-term enhancement of forest productivity under elevated CO2(i.e.,Rhizo-Accelerated Mineraliza-tion and Priming or RAMP hypothesis;see Phillips et al.,2012).In recent studies,we also have invoked dif-ferences in root exudation to explain the changes in rhizosphere effects and soil N transformations between tree species under experimental warming(Yin et al., 2012a,b).Despite the perceived importance of root exu-dation to ecosystem function(Fransson&Johansson, 2010),there have been few measurements of the exuda-tion rates from?eld-grown plants or mature trees exposed to experimental warming.Thus,it is unknown how this widely hypothesized but rarely quanti?ed process will in?uence SOM decomposition and N cycling through the release of exudation under global warming(Phillips et al.,2012).

Hence,in this study,we conducted an experiment to examine plant root-microbe interactions in the soils of Picea asperata plots under experimental warming and varying N availability.The P.asperata species was chosen because it is widely distributed and important in the subalpine coniferous ecosystems in western,Sichuan.Moreover,P.asperata primarily functions as a keystone species in reforestation after logging.We predicted that P.asperata species growing under experimental warming would exude increased C into the soils and that the enhanced rates of exuda-tion would be associated with the increased enzyme activity and stimulated soil N transformations.We also predicted that the strength of these warming effects would be reduced for the plots fertilized with inorganic N.To test this hypothesis,we measured differences in root exudation rates,soil N transforma-tions and the associated enzyme activity in experi-mental plots exposed to elevated temperature and/or N fertilization.To our knowledge,this study is the ?rst study to investigate the interactive effects of experimental warming and N fertilization on root exudation and their impacts on soil N cycling.Materials and methods

Experimental design

The experiment was conducted at the Maoxian Ecological Station of the Chinese Academy of Sciences,Sichuan Province, China(31°41′N,103°53′E,1820m a.s.l.),where the mean annual temperature,precipitation and evaporation are8.9°C, 920mm,and796mm,respectively.Our experiment followed Wan et al.(2002)in using165915cm infrared heaters(Kalgo Electronics Inc.,Bethlehem,PA,USA)to generate an arti?-cially warmed environment.There were?ve pairs of292m plots(a warmed plot and a control plot),and each292m plot was divided into four191m subplots.The indigenous soil of all subplots was replaced,to a depth of50cm,by sieved topsoil from a coniferous forest.The soil was classi?ed as a mountain brown soil series(Chinese taxonomy).The soil properties,determined in March2007,were as follows:pH, 5.55;total N,4.5g kgà1;soil organic C,78g kgà1;and bulk density,0.89g cmà3.The warmed plot was heated by an infrared heater suspended 1.5m above the middle of the plots.The infrared heater had a radiation output of approxi-mately100W mà2,and its warming effect on the soil temper-ature was spatially uniform within the warmed plots.One ‘dummy’heater with the same shape and size as the infrared heater was suspended1.5m above each control plot to simu-late the shading effects of the infrared heater in the warmed plots.

Uniform4year old P.asperata seedlings from a local nurs-ery were selected based on plant height and stem base diame-ter.The average height and stem base diameter of the P.asperata seedlings were13.42?0.57cm and 3.12?0.45mm,respectively.In March2007,twenty healthy seed-lings were planted randomly in separate subplots within each plot.The seedlings that were grown in two of the diagonal subplots of each plot were watered weekly with200ml of 2.7m M ammonium nitrate solution(for a total equivalent to 25g N mà2aà1),and the seedlings in the other two subplots were watered with the equivalent amount of water.Nitrogen amounts were based on our previous studies(Yao&Liu, 2007;Zhao&Liu,2009).The fertilizer was prevented from moving between subplots by a70cm deep vertical polyvinyl chloride board.Arti?cial warming and nitrogen addition were conducted from April2007to the present.To disrupt the potential effects of soil water on soil processes,the warmed plots were watered as frequently as needed and were moni-tored with a hand-held probe(IMKO,Ettlingen,Germany). Moreover,all of the litter within the plots was removed once a month to examine the pure effects of the tree species on the soil processes via the roots and root exudation.The four treat-ments in this study were as follows:(1)unwarmed unfertil-ized(W0F0);(2)warmed unfertilized(W1F0);(3)unwarmed fertilized(W0F1);and(4)warmed fertilized(W1F1). Microclimate monitoring

Air temperature(at the height of20cm above the ground) and relative humidity were measured using DS1923G

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temperature/humidity iButton data loggers,and soil tempera-tures(5cm depth)were measured using DS1921G Thermo-chron iButton data loggers(DS1921G-F5,Maxim Integrated Products;Dallas Semiconductor Inc.,Sunnyvale,CA,USA)in ?ve pairs of plots at60min intervals during the experimental period.The soil moisture was measured gravimetrically in soil core samples(0–10cm)that were collected once or twice a month from April2010to December2011.The soil samples were dried at105°C for12h and were then weighed.The soil moisture was expressed as a percentage of dry soil on a mass basis.

Exudation measurements

Exudates were collected in May,late July and October of2011 using a modi?ed culture-based cuvette system developed especially for root exudation collection in the?eld(Phillips et al.,2008).The terminal?ne roots(2mm average diameter with laterals)that were attached to the coniferous trees were excavated from the topsoil(0–10cm).The soil particles adher-ing to the roots were carefully rinsed off with puri?ed water from a squirt bottle,and?ne forceps were used to dislodge SOM aggregates.The intact roots were placed into glass cuvettes,?lled with glass beads(c.1mm diameter)and sealed with a special rubber septum.The rubber septum had a small slit cut into it to accommodate the protruding root.The cuvettes(including the controls with beads only)were cov-ered in foil and reburied in the excavated area in the soil.After a2-day equilibration period,a fresh nutrient solution(0.5m M NH4NO3,0.1M m KH2PO4,0.2M m K2SO4,0.2m M MgSO4, 0.3m M CaCl2)was?ushed through each cuvette to remove soluble C.After24h,‘trap solutions’containing exudates were collected from each cuvette with an automatic electric vacuum pump and were then placed on ice and?ltered through sterile0.22l m syringe?lters within2–5h of collec-tion.A detailed description of this method is available in Phillips et al.(2008).

The exudates were collected randomly from two to three roots in?ve subplots of each treatment.For each sampling period,the exudates were collected over three consecutive days and from different plants on each sampling date.All of the roots were harvested following the?nal exudation collec-tion of each root and were then scanned so that the morpho-logical variables(i.e.,?ne root length,surface area,root tips, etc.)could be quanti?ed.All of the scanned images were visu-ally inspected,calibrated using materials of known size,and analyzed using WinRhizo software(Regents Instruments Inc., Qu e bec,Canada).

The?ltered trap solutions were analyzed for organic C on a TOC analyzer(Multi N/C2100;Analytic Jena,Jena, Germany).The control cuvettes(beads only)were used to account for C contamination resulting from nonexudates sources.The exudation rates were calculated as the mass of C (l g)?ushed from each root system(minus the average C con-centration in the control cuvettes)over the24h incubation period.The exudation rates I(l g C gà1root biomass hà1),II (l g C cmà1root length hà1),and III(l g C cmà2root area hà1)were calculated by dividing the total amount of C ?ushed from the root system by the total?ne root biomass,

the root length,and the root area,respectively,within each cuvette.

Growth characteristics analysis

Five soil samples were taken from the topsoil(0–15cm)with a 5-cm-diameter polyvinyl chloride core within each subplot.

The?ne roots(2mm)were carefully separated with?ne forceps,and the separated?ne roots were carefully washed and then analyzed with the WinRHIZO image analysis system (Regent Instruments Inc.,Sainte Foy,Qu e bec,Canada),which was used to measure the root length and the diameter of each root.The roots were rinsed free of soil,and0.5g samples of white,young roots were used immediately to assay?ne root activity(FRV)using the triphenyltetrazolium chloride(TTC) method,as described by Basile et al.(2007).Ectomycorrhizal infection was analyzed by counting the total number of mycorrhizal tips per seedling and by calculating the extent of the infection as the percentage of root tips that were mycorrhi-zal(Dehlin et al.,2004).Moreover,?ve randomly selected seedlings from each treatment were harvested in early August 2010and were then divided into leaf,stem,and root compo-nents.All of the plant parts were dried to a constant mass at 70°C before measuring the dry weight.Total biomass,coarse root biomass,?ne root biomass,and the coarse root/?ne root mass ratio were calculated based on the measured data.

Soil enzyme activity and N transformation assay

The soil samples were collected from the topsoil(0–15cm)in early May,mid-July,and late September of2011.The soils were sampled within1week of an exudation measurement.

Three cores(3cm in diameter,15cm deep)were randomly taken from each subplot.The collected soil cores were mixed to obtain one composite fresh sample for each subplot,and the samples were immediately delivered on ice to the labora-tory.Each composite sample was passed through a sieve (2mm diameter),and any visible living plant material was manually removed from the sieved soil.The sieved soils were kept in the refrigerator at4°C and were processed within 1week for enzyme analysis.

We measured the activities of two extracellular enzymes involved in the depolymerization of N from SOM.Urease is a hydrolytic enzyme involved in the hydrolysis of urea-type substrates.Given the chemistry of urea and its mass in the soil,N released from SOM by urease is considered to be a moderately fast cycling pool of N(Zhan et al.,2010).In con-trast,phenol oxidase is a lignolytic enzyme involved in the degradation of recalcitrant SOM,and an enzyme that is often used as a sentinel of SOM decomposition(Sinsabaugh,2010).

As lignin,tannins,and polyphenols may bind N,N released from SOM by phenol oxidase is considered to be a relatively slow cycling pool of N(Phillips et al.,2011).

Soil urease activity was measured as described previously by Kandeler&Gerber(1988).Five grams of soil was placed in a50mL Erlenmeyer?ask,1mL of toluene was added to the soil in the?ask,and the contents were allowed to stand for approximately15min until the toluene had completely ?2013Blackwell Publishing Ltd,Global Change Biology,19,2158–2167

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penetrated the soil.Then,a20-mL potassium citrate-citric acid buffer(pH6.7)and10mL of a10%urea solution were added to the sample.The?asks were stoppered,shaken and then incubated at37°C for24h.A control,in which10mL of dis-tilled water was substituted for the urea,was examined simul-taneously.After incubation,the contents of the?asks were ?ltered.The amount of ammonia released by hydrolysis of the urea was determined from the?ltrate using the colorimetric indophenol blue method.The unit of urease activity was reported as mg of NH4+-N released per kg dry soil per24h. Polyphenol oxidase was analyzed with pyrogallic acid as a substrate.The mixture of1g soil and10mL of1%pyrogallic acid was incubated at30°C.A4-mL disodium hydrogen phosphate-citric acid buffer(pH4.5)was added after2h incu-bation,and purpurogallin was extracted with ether.The sam-ple was then measured using a spectrophotometer set of a wavelength of430nm.The polyphenol oxidase activity was expressed as mg purpurogallin per g dry soil per2h(Zhou, 1987).All of the determinations of enzymatic activity were performed in triplicates,and all of the values reported are the averages of three trials performed on oven-dried soil(105°C). The rates of net N mineralization and net nitri?cation in May,July,and September were measured using the covered core incubation method(Adams et al.,1989).We selected these dates to coincide with a subset of the exudation sampling dates.The incubations were performed using perforated PVC tubes(15cm in height and6cm in diameter).Para?lm was used to cover the top of each tube to avoid leaching of nitrate. This technique prevents the plant’s uptake of mineralized nutrients but allows uptake by the microorganisms.The soil samples were transported to the laboratory in a cool box and were analyzed for ammonium and nitrate as the initial sample to measure net mineralization and net nitri?cation rates.The soil samples in the buried bags were retrieved after30days of incubation and were analyzed as the?nal sample.The differ-ence between the initial and?nal inorganic N concentrations (NH4+-N and NO3à-N)was used to calculate the net N miner-alization rates.The difference between the initial and?nal NO3à-N concentrations was used to calculate the net nitri?ca-tion rates.

The gross nitri?cation and denitri?cation rates were measured using a Barometric Process Separation(BaPS) instrument(UMS GmbH Inc.,Munich,Germany)through lab-oratory incubations,as described by Sun et al.(2009).Within each subplot,three intact soil cores were collected using soil containers with a diameter of5.6cm and a height of4.1cm. The soil containers were transported to the laboratory in cool-ers and were processed immediately.The BaPS instrument was closed so that it was gas-tight,and the samples were incu-bated for at least24h at25.0°C.

Statistical analyses

Analyses were performed with the software Statistical Pack-age for the Social Sciences(SPSS)software,version11.0(SPSS Inc.,Chicago,IL,USA).All of the response variables were averaged within each subplot,and the subplots were consid-ered to be the experimental units.Before analysis,all of the data were tested for the assumptions of ANOVA.If the data were heterogeneous,they were ln-transformed before analy-sis.A repeated measures ANOVA was used to assess the effects of warming,N fertilization and their interactions on all of the response variables.Because of our interests in the role of N in mediating warming effects,a one-way ANOVA was also per-formed to assess the effects of warming on root and soil vari-ables at a given nutrient level and sampling date.We used linear regression to examine the relationship between the exu-dation rate and the extracellular enzyme activity and soil N transformation.Given the limited number of soil samples, data from all of the experimental plots were analyzed across the sampling dates.The statistical tests were considered sig-ni?cant at the P<0.05level.

Results

Warming effects of the infrared heaters

As expected,the infrared heaters caused warming within the experimental plots.During the experimental time period,the daily air temperature(at20cm above-ground)and soil temperature(at5cm depth)within the warmed plots were increased,on average,by1.8°C and3.6°C,respectively,compared to the control plots (Fig.1a and b).The mean relative humidity of the air was slightly lower in the warmed plots(85.1%)relative to the control plots(94.5%)(Fig.1c).Moreover,there was no signi?cant difference in the soil water content between the control plots(25.7%)and the warmed plots (24.6%)(Fig.1d).

Warming and N fertilization effects on exudation

Our results showed that experimental warming had signi?cant effects on root exudation rates I,II,and III (Table1).Over the sampling dates,experimental warming signi?cantly increased root exudation rates I (l g C gà1root biomass hà1),II(l g C cmà1root length hà1),and III(l g C cmà2root area hà1)in unfer-tilized plots(Fig.2),with an average exudation rate increase of78.1%,68.6%,and55.0%,respectively (Fig.2d).In contrast,experimental warming induced a small but nonsigni?cant decrease in root exudation rates I,II,and III,with an average decrease of30.6%, 28.4%,and24.2%,respectively(Fig.2d).There were no signi?cant effects of N fertilization on root exudation rates I,II,and III,and there were no warming9N fertilization interactions(Table1).

Growth traits response to treatments

Experimental warming signi?cantly decreased the coarse root/?ne root mass ratio(C/F)for the P.asperata seedlings,which may have resulted from relatively more biomass partitioning to?ne roots in response

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to experimental warming in the unfertilized plots (Fig.3d).In contrast,experimental warming markedly increased the ?ne root activity (FRV),?ne root length

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Warmed plots Control plots Tair

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Apr MayJun Jul AugSep Oct NovDec Feb Mar Apr MayJun Jul AugSep Oct

Warmed plots Control plots

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Seasonal transitions and average differences in (a)daily air temperature at 20cm above ground,(b)daily mean soil temperature (5cm depth),(c)mean air relative humidity,and (d)soil water content (0–10cm)between the warmed plots (solid the control plots (dotted line ).The lower gray lines (symbol a,b,and c represent the daily mean differences in air tem-perature,soil temperature,and air relative humidity,respectively,the warmed plots and the control plots.The scales of the are 30-day intervals (a –c)from 1March 2010to 25May 2011.

T a b l e 1R e s u l t s o f t h e r e p e a t e d m e a s u r e s A N O V A s h o w i n g t h e P v a l u e s f o r t h e r e s p o n s e s o f r o o t e x u d a t i o n r a t e s I (l g C g à1r o o t b i o m a s s h à1),I I (l g C c m à1r o o t l e n g t h h à1),a n d I I I (l g C c m à2r o o t a r e a h à1),n e t m i n e r a l i z a t i o n ,n e t n i t r i ?c a t i o n ,g r o s s n i t r i ?c a t i o n ,d e n i t r i ?c a t i o n ,u r e a s e a n d p o l y p h e n o l o x i d a s e t o e x p e r i m e n t a l w a r m i n g (W ),N f e r t i l -i z a t i o n (F ),a n d s a m p l i n g d a t e s (D ).P v a l u e s l e s s t h a n 0.05a r e i n b o l d

F a c t o r

E x u d a t i o n I E x u d a t i o n I I E x u d a t i o n I I I N e t m i n e r a l i z a t i o n N e t n i t r i ?c a t i o n G r o s s n i t r i ?c a t i o n D e n i t r i ?c a t i o n U r e a s e P o l y p h e n o l o x i d a s e

D 0.001<0.0010.0350.2140.0070.2070.0280.5450.078D 9W 0.0250.0120.0860.7140.0250.3640.0420.1260.271D 9F 0.0680.0070.0430.1480.2190.0750.7630.2310.265D 9W 9T S 0.2150.1920.3250.3620.3980.1080.0670.4780.279W 0.0290.0230.0390.0250.0480.0370.0050.0250.005F 0.0520.0570.0680.9630.0390.1230.2490.034<0.001W 9F

0.0740.2160.0590.8260.7530.4820.9360.0040.021

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(FRL),?ne root biomass,ectomycorrhizal infection (EMI),and total biomass in the unfertilized plots,with average increases of 19.8%,66.0%,62.1%,56.7.0%,and 26.4%in FRV,FRL,?ne root biomass,EMI and total biomass,respectively (Fig.3).In the fertilized plots,however,experimental warming had no signi?cant effects on any root variable (Fig.3).Moreover,N fertil-ization signi?cantly increased the total biomass of the P.asperata seedlings in the unwarmed plots but not in the warmed plots (Fig.3f).

Soil N transformation response to treatments

Consistent with the response of root exudation,experi-mental warming signi?cantly increased the rates of net mineralization,net nitri?cation,gross nitri?cation,and denitri?cation on all of the sampling dates in the unfer-tilized plots,with the exception of May,during which there were no signi?cant differences between the treat-ments for gross nitri?cation rates (P =0.654;Fig.4).Moreover,the net mineralization rates were positively correlated with root exudation rate II (l g C cm à1root length h à1)(R 2=0.699;Fig.6a).In contrast,there were no signi?cant warming effects on any response vari-able of N transformations in the fertilized plots among the sampling dates (Fig.4).The net nitri?cation and denitri?cation rates signi?cantly varied among three sampling dates (P =0.007and 0.028,respectively;Table 1).

Soil enzyme activity response to treatments

Warming and N fertilization had signi?cant effects on the extracellular activities of the two enzymes (Table 1;P <0.05).The soil enzyme activities in the unfertilized plots responded more strongly to experimental warm-ing compared with the enzyme activities in the fertil-ized plots.Over the sampling dates,warming markedly increased polyphenol oxidase activity by 38%in the unfertilized plots,but it was increased by only 11.2%in the fertilized plots (Fig.5b).In contrast,N fertilization signi?cantly reduced the polyphenol oxidase activity by 32.5%in May and by 36.4%in September.In addi-tion,the urease activity was strongly correlated with the root exudation rate II (l g C cm à1root length h à1)(R 2=0.786;Fig.6b).

Unlike the warming effects on polyphenol oxidase activity,the warming effects on urease activity only occurred in May,which signi?cantly increased activi-ties by 34.1%in the unfertilized soils,whereas there were no considerable warming effects on the urease activity in the fertilized plots in May or in the unfertil-ized or the fertilized plots in September.Similarly,N fertilization also signi?cantly reduced the urease

W0F1

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May July September

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activity over the two sampling dates(Fig.5b;Table1). In addition,signi?cant combination effects of warming and N fertilization were observed in the polyphenol oxidase and urease activities in the soil(Table1). Discussion

The degree to which root exudation in?uences nutrient cycling in forest soils is poorly understood because associated ecological processes mediated by roots are believed to be temporally and spatially heterogeneous due to biotic(e.g.,plant growth,litter input,tree age, and belowground C?ux)and abiotic factors(e.g.,soil moisture,fertility,pH,and nutrient availability)(Bader &Cheng,2007).Therefore,the in?uences of tree species on soil processes and functions may be masked by the pedology of the site,edaphic and environmental vari-ability,and management effects.In this study,all of the experimental seedlings were grown in a common soil with similar?eld management,and the litter within the subplots was removed periodically to disrupt the effects of litter input on the soils.The differences in root exudation and associated soil processes between treat-ments were therefore assumed to re?ect the potential effects of a plant’s intrinsic physiological adjustment in response to different environmental changes. Warming and N effects on root exudation

Recent recognition of the importance of plant root–microbial–soil interactions has highlighted the need for more information on the mechanisms by which trees allocate C and cycle nutrients under environmental change,and these interactions have major conse-quences for the functioning of terrestrial ecosystems in response to global climate change.There have been sev-eral reports of CO2-induced changes in the root exuda-tion rates of trees(Johansson et al.,2009;Phillips et al., 2009;Fransson&Johansson,2010),but there have been few reports of the response of root exudation to experi-mental warming in trees.In this study,our results indi-cated that the exudation rates from P.asperata seedlings are signi?cantly increased by experimental warming but such effects strongly depend on N availability (Fig.2).The belowground C allocation and root mor-phological traits are thought to be the two primary aspects controlling root exudates(Badri&Vivanco, 2009),and based on ancillary data,several possible underlying mechanisms may explain the stimulatory effects of experimental warming on exudation.

It is possible that greater root exudation in the low-N soils resulted from the warming-induced changes in root morphological traits.In our study,the root length of the P.asperata seedlings was signi?cantly enhanced

W0F0W1F0

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by warming in the unfertilized plots(Fig.3b).A host of studies have demonstrated that plant root length is pos-itively correlated with root-released C(Xu&Juma, 1994;Darwent,2003).Additionally,the FRV and ecto-mycorrhizal infection of the P.asperata seedlings grown in the unfertilized soils was remarkably higher in the warmed plots relative to the control plots(Fig.3a and e).As a result,the capacity for enzyme synthesis,the nutrient uptake mechanisms and the respiration rate of the roots can differ for those trees grown under warm-ing conditions,and these differences can strongly in?u-ence the quantity and chemical quality of root exudation(Drake et al.,2011;Phillips et al.,2012).

In addition to altered root morphological traits,the increased root exudation at the elevated temperature might be associated with warming-induced changes in belowground C allocation.An important compensatory adjustment by plants exposed to environmental changes is the altered allocation patterns of C to below-ground tissues(Reich et al.,2006).Numerous growth chamber experiments and?eld experiments have reported an increased belowground production of C in trees that were exposed to an elevated temperature (Yin&Liu,2008;Hollister&Flaherty,2010).In this study,our results indicated that the C/F ratio of the P.asperata seedlings was signi?cantly decreased by experimental warming,resulting in increased C parti-tioning to the?ne roots in response to experimental warming,presumably so that the roots could forage for growth-limiting nutrients(Fig.3c and d).Collectively, these alterations will have profound impacts on the quantity and chemical quality of root exudates and C substrate inputs into the soils.However,the degree to which such factors mediate root exudates of tree spe-cies and feedbacks to soil ecological processes is unknown.Further examination of root exudation in response to environmental changes,with more detailed characterization of root morphological and physiologi-cal traits and belowground C allocation would be a worthwhile focus of future studies.

Ecological consequences of enhanced exudation Understanding the mechanism by which potential changes in root-derived C affect the microbial regula-tion of soil N cycling and nutrient availability under experimental warming is critical for predicting biotic feedbacks to climate change.In the present study,our results indicated that increases in the?ux of labile C from the roots to the soil under experimental warming conditions stimulated the rates of soil N transformation in the unfertilized plots(Fig.4),a mechanism that may contribute to continuous stimulation of plant growth or forest productivity under global warming.Increases in

the inputs of root-derived C can signi?cantly stimulate microbial activity and SOM decomposition via rhizo-sphere priming effect(Dijkstra et al.,2009).Here,we show that the increased labile C ef?ux from the warmed trees stimulated the soil transformation rates and the activity of two extracellular enzymes involved in the breakdown of organic N in the unfertilized plots.

Importantly,the soil urease activity(an indicator of moderately fast N turnover)and the net mineralization rates were positively correlated with the measured rates of exudation(Fig.6).We interpret these results as strong evidence of the in?uencing of the root-derived C on the microbial regulation of soil N cycling,i.e.,soil heterotrophic microbes such as actinomycetes used energy derived from the exudates to synthesize extra-cellular enzymes to release N from SOM(Bengtson et al.,2012;Phillips et al.,2012).This was not the case in the N-fertilized plots,in which the root exudation,the soil extracellular enzymes and the soil N transforma-tion did not respond strongly to the experimental warming.A possible explanation is that the soil microbes in the high-N soils use C-rich exudates for growth rather than for the production of enzymes to acquire N(Drake et al.,2011).This dramatic contrast between the fertilized and the unfertilized treatments provides evidence that enhanced exudation is a mecha-nism that trees employ to increase the soil N transfor-mation and nutrient availability(Phillips et al.,2011).

It must be noted,however,that other physiological adjustments by trees exposed to experimental warming, such as fungal rhizomorph production and the alloca-tion of C to ectomycorrhizal fungi(EMF),can also stim-ulate soil N cycling.Although the available data on EMF growth was limited in this study,our preliminary experiments indicated that the EMF infection of the P.asperata seedlings in the unfertilized plots was signif-icantly increased by experimental warming(Fig.3d).

EMF have broad enzymatic capabilities,decompose labile and recalcitrant components of soil organic mat-ter,access organic sources of N and transfer large amounts of N to host plants(Hobbie&Hobbie,2006;

H€o gberg&Read,2006).Such changes would presum-ably accelerate the N release from SOM pools.How-ever,the degree to which EMF mediates the exudation rates and priming effects in tree species exposed to experimental warming warrants further study.

In conclusion,this study demonstrates that the increase in the release of root exudation from trees under experimental warming is an important physio-logical adjustment that stimulates N cycling and nutri-ent availability in low fertility soil.Although we fully recognize the obvious limitations of our experimental systems because all of the data came from small plants growing in disturbed soils,our results are robust in ?2013Blackwell Publishing Ltd,Global Change Biology,19,2158–2167

2166H.YIN et al.

terms of the direction of treatment effects.Thus,our results provide evidence that the degree to which trees sequester C under global warming may depend on the magnitude and ecological consequences of changes in C released to the soil via root exudation.Accordingly, the underlying mechanisms by which plant root-microbe interactions in?uence soil organic matter decomposition and N cycling should be incorporated into climate-carbon cycle models to determine reliable estimates of long-term C storage in forests. Acknowledgments

We thank Jinsong Chen for assisting with the statistics,and Yan Zou and Bing Xia for their technical assistance in the laboratory. We also thank the staff in the Maoxian Mountain Ecosystem of CERN Research Station for their kind help with?eld investiga-tions.This study was supported jointly by the National Natural Science Foundation of China(No.31270552),the strategic Prior-ity Research Program of the Chinese Academy of Sciences (No.XDA01050303)and the National Key Technology R&D Program(No.2011BAC09B04).

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第四章【植物与土壤】第1-3节：参考答案

参考答案 例1：D 例2：(1)①② (2)不合理地上环境没有提供独立的、相同的生长空间 (3)甲、乙两种植物地上部分是否会争夺空气中的资源。 (4)水分和无机盐。 例3：C 例4：砂土类土壤黏土类土壤壤土类土壤。 例5：D 例6：(1)A根毛区；B伸长区；C分生区；D根冠。 (2)①的名称是根毛，它是由根毛区成熟的表皮细胞向外突起而形成的，其作用是增大根与土壤 的接触面积，利于吸收土壤中的水分和无机盐。 (3)保护分裂增大根毛区 (4)根毛区分生区 例7：B 例8：(1)D (2)验证植物生长是否需要无机盐。 (3)植物的生长需要无机盐。 (4)植物的生长需要无机盐。 (5)由于谷粒自身含有无机盐，因此在实验开始时应切去谷粒，从而避免植物自身的无机盐对实 验结果造成干扰。 1-5 CABCD 6-10 ABCCB 11-15 DCADC 16．(1)A与D B与C(2)探究光照强弱对两组植物生长影响(3)不合理甲、乙两盆植物土壤中都含有包括镁离子在内的各种无机盐 17．(1)少(2)A 18．(1)吸水A(2)乙小于失水 19．(1)没有控制变量，植物种类、浇水量、每天浇水次数应相同。(2)C 20．(1)1 (2)水、空气 (3)根部不能进行呼吸作用(4)样本数量少 21．(1)对照铬对玉米生长是否有影响？ (2)控制变量。 (3)该含铬溶液影响玉米幼苗正常生长。 22．(1)A瓶中的泥土经过强热，B瓶中的泥土未经过强热 A (2)A瓶中无变化，B瓶中澄清的石灰水变浑浊。 (3)若泥土中有微生物存在，微生物呼吸作用会产生二氧化碳，能使澄清的石灰水变浑浊。23．(1)对照实验变量。 (2)有利于植物的生长。 (3)用不同的植物进行重复实验。 (4)_蚂蚁筑巢前后土壤发生了怎样的变化？蚁巢中什么成分促进了植物的生长。 24．(1)同一植物在相同的生育期，对不同的无机盐的需求量不同。 (2)同一植物在不同的生育期对同一无机盐的需求量是不同的。 (3)不同的植物对无机盐的需求量是不同的。 1

植物全磷、全氮、全钾的测定方法

一、植物全氮测定 （一）H2SO4-H2O2消煮法 1、适用范围 本方法不包括硝态氮的植物全氮测定,适合于含硝态氮低的植物样品的测定。 2、方法提要 植物中的氮、磷大多数以有机态存在,钾以离子态存在。样品经浓H2SO4和氧化剂H2O2消煮,有机物被氧化分解,有机氮和磷转化成铵盐和磷酸盐,钾也全部释出。消煮液经定容后,可用于氮、磷、钾的定量。采用H2O2为加速消煮的氧化剂,不仅操作手续简单快速,对氮、磷、钾的定量没有干扰,而且具有能满足一般生产和科研工作所要求的准确度。但要注意遵照操作规程的要求操作,防止有机氮被氧化成N2气或氮的氧化物而损失。 3、试剂 （1）硫酸(化学纯,比重1.84); （2）30% H2O2(分析纯)。 4、主要仪器设备。消煮炉，定氮蒸馏器。 5、操作步骤 称取植物样品(0.5mm)0.3～0.5g(称准至0.0002g)装入100ml开氏瓶或消煮管的底部,加浓H2SO45ml,摇匀(最好放置过夜),在电炉或消煮炉上先小火加热,待H2SO4发白烟后再升高温度,当溶液呈均匀的棕黑色时取下。稍冷后加班10滴H2O2(3),再加热至微沸,消煮约7～10min,稍冷后重复加H2O2,,再消煮。如此重复数次,每次添加的H2O2应逐次减少, 消煮至溶液呈无色或清亮后,再加热10min,除去剩余的H2O2。取下冷却后,用水将消煮液无损地转移入100ml容量瓶中,冷却至室温后定容(V1)。用无磷钾的干滤纸过滤,或放置澄清后吸取清液测定氮、磷、钾。每批消煮的同时,进行空白试验,以校正试剂和方法的误差。 6、注释 （1）所用的H2O2应不含氮和磷。H2O2在保存中可能自动分解,加热和光照能促使其分解,故应保存于阴凉处。在H2O2中加入少量 H2SO4酸化,可防止H2O2分解。 （2）称样量决定于NPK含量,健状茎叶称0.5g,种子0.3g,老熟茎叶可称1g,若新鲜茎叶样,可按干样的5倍称样。称样量大时,可适当增加浓H2SO4用量。 （3）加H2O2时应直接滴入瓶底液中,如滴在瓶劲内壁上,将不起氧化作用,若遗留下来还会影响磷的显色。 （二）水杨酸-锌粉还原- H2SO4-加速剂消煮法 1、适用范围 包括销态氮的植物全氮测定,适合于硝态氮含量较高的植物样品的测定。 2、方法原理 样品中的硝态氮在室温下与硫酸介质中的水杨酸作用,生成硝基水杨酸,再用硫代硫酸钠及锌粉使硝基水杨酸还原为氨基水杨酸.然后按 H2SO4-加速剂消煮法进行消煮法进行消煮样品,使样品中全部氮转化为铵盐。 3、试剂 （1）固体Na2S2O3; （2）还原锌粉(AR); （3）水杨酸-硫酸:30g水杨酸溶于1L浓硫酸中。也可以该用含苯酚的浓硫酸:40g苯酚溶于1L浓硫酸中。 4、仪器设备。同上。 5、操作步骤 称取磨细烘干样品(过0.25mm筛)0.1000～0.2000g或新鲜茎叶样品1.000～2.000g,置于100ml开氏瓶或消煮管中,先用水湿润内样品(烘干样),然后加水杨酸-硫酸10ml,摇匀后室温放置30min,加入Na2S2O3约1.5g,锌粉0.4g和水10ml,放置10 min,待还原反应完成后,加入混合加速剂2g,按土壤全氮测定方法进行消煮, 消煮完毕,取下冷却后,用水将消煮液无损地转移入100ml容量瓶中,冷却至室温后定容(V1)。用于滤纸过滤,或放置澄清后吸取清液测定氮。每批消煮的同时,进行空白试验,以校正试剂和方法的误差。 （三）消煮液中铵的定量(凯氏法) 1、适用范围。适合于各种植物样品消煮液中氮的定量。 2、方法原理

第三章植物与土壤 知识点

科学八年级第4册第3章知识点提要 1、土壤的成分包括动物、植物、微生物等生物成分和矿物质（无机物）、腐殖质（有机物）、空气、水分等非生物成分。土壤中的有机物包括死亡的生物提（遗体）和生物的排泄物（遗物）。土壤中的微生物包括细菌、真菌和放线菌等。 2、土壤是在物理、化学和生物等因素共同作用下风化形成的。 3、影响土壤结构的主要因素是矿物质颗粒的大小和比例，土壤中矿物质颗粒根据大小分砂粒、粉砂粒和黏粒三种。根据土壤中三种颗粒的比例不同，将土壤分为砂土类土壤、 黏土类土壤和壤土类土壤三种。其中土壤通气性最强的是砂土类土壤，最弱的是 黏土类土壤；透水性最强的是砂土类土壤，最弱的是黏土类土壤；保水性最强的是黏土类土壤，最弱的是砂土类土壤。三种土壤中最适宜植物生长的是壤土类土壤，因为通气透水、保水保肥，该土壤中空气与水分的比例接近1：1 ，而在砂土类土壤中，空气的比例远远大于水分，黏土类土壤中，空气的比例远远小于水分。黏土类土壤最容易搓成条，因为其粉粒、黏粒多，黏性强，这样的土壤保水保肥能力强，但通气透水能力弱。 4、一棵植物体上所有根的总和叫根系，其中有明显主、侧根之分的叫直根系，没有明显主、侧根之分的叫须根系。植物的根系往往比地上部分的分布范围要略大，这有利于固定植物体和从土壤中吸收水分和无机盐。根在土壤中的分布与土壤结构、肥力、通气状况和水分状况等有关。双子叶植物的根系一般是直根系，单子叶植物的根系一般是须根系。 5、植物吸收水分和无机盐的主要器官是根，根上吸收水分和无机盐的主要部位是根尖的根毛区。植物的根尖分为四个部分，分别是根毛区、伸长区、分生区和根冠，其作用分别是吸收水分和无机盐、使根伸长、细胞分裂和保护根尖。 6、根毛是根尖表皮细胞的一部分向外突起形成，其作用是扩大了根尖与土壤的接触面积有利于根毛区从土壤中吸收水分和无机盐，根尖之所以是吸收水分和无机盐的主要部位，是因为根尖根毛区细胞液泡大，与土壤的接触面积大。移栽时要带土是为了保护根尖根毛。 7、植物细胞吸水的原理是根毛细胞的细胞液浓度大于周围土壤溶液的浓度。盐碱地不能种植农作物是因为盐碱地的土壤溶液浓度大于根毛细胞的细胞液浓度，导致根毛细胞不能从土壤中吸水，植物脱水而死，一次性施过量的化肥导致作物“烧苗”是土壤溶液浓度大于根毛细胞的细胞液浓度，导致根毛细胞不能从土壤中吸水，植物脱水而死。在探究细胞吸水的原理的实验中，加浓盐水的玻璃管中液面上升，而加清水的玻璃管中的液面下降。 8、植物需要量最大的无机盐是N 、P 和K ，其中主要针对叶起作用的是N ，对茎和根起作用的是K ，对花、果实和种子起作用的是P 。合理施肥的其中一个要求是针对不同作物应适当多施不同种类的化肥，如叶菜类可适当多施N 肥（青菜、包心菜等），

浙教版八年级下册科学第4章 植物与土壤 知识点归纳

第1、2节土壤的成分各种各样的土壤 A.土壤中的生命和非生命物质 B.从岩石到土壤 1.引起岩石风化的因素： 1)物理因素——风、流水、温度等 2)化学因素——化学物质的溶蚀作用 3)生物因素 2.岩石变为土壤：岩石在长期的风吹雨打、冷热交替和生物的作用下，逐渐风化成石 砾和砂粒等矿物质颗粒，最后经过各种生物和气候的长期作用形成土壤 C.土壤的结构和类型 1.土壤的结构 1)土壤主要由矿物质、腐殖质、水和空气等物质以及多种生物组成，这些成分之间 相互影响，使土壤形成一定的结构 2)矿物质颗粒的多少和排列方式是影响土壤结构最重要的因素 3)土壤的矿物质颗粒有粗有细，粗的叫砂粒，细的叫黏粒，介于两者之间的叫粉砂 粒

2.土壤的类型 1)砂土类土壤：砂粒多，黏粒少，土壤颗粒较粗 2)黏土类土壤：黏粒、粉砂多，土壤颗粒较细 3)壤土类土壤：砂粒、黏粒粉砂大致等量，土壤质地较均匀 D.土壤的性状与植物的生长 2.壤土类土壤的矿物质颗粒、空气、水和有机质等组成比例合理，土壤黏性适度，通 气、透水、保水和保肥能力强，是适合大部分植物生长的土壤 第3节植物的根与物质吸收 A.植物的根系 1.植物根的分类 1)主根：由胚根直接生长形成的根，数量只有一条，向下生长 2)侧根：从主根上依次生出的根，与主根相比，又细又短，但数量众多 3)不定根：从植物的茎或叶上长出的根 2.植物根系的分类 1)直根系：有明显的主根和侧根之分，大多数双子叶植物的根系为直根系 2)须根系：没有明显的主根和侧根之分，大多数单子叶植物的根系为须根系

B. 跟的吸水和失水 1. 根尖的结构和功能 2. 根毛细胞吸水和失水的原理 1) 根毛细胞液的溶质质量分数＞土壤溶液的溶质质量分数→细胞吸水 2) 根毛细胞液的溶质质量分数＜土壤溶液的溶质质量分数→细胞失水 3. 土壤中水分进入根部的途径 土壤水分→根毛细胞→皮层细胞→木质部细胞→植物体各部分 第4节植物的茎与物质运输 A. 茎的结构 1. 木质茎的结构 1) 表皮：细胞排列紧密，细胞间 隙小，起保护作用 2) 韧皮部：在茎横切面上呈筒状 根毛区：根毛区细胞是由伸长区细胞分化而来的，细胞壁薄，液泡较大，内涵丰富的细胞液，是根尖吸收水分和无机盐的主要部位 伸长区：细胞逐渐停止分裂，但能较快生长，使根不断地伸长生长 分生区：细胞壁薄，细胞核大，细胞质浓，细胞排列紧密，具有很强的分裂能力，外观呈黄色 根冠：细胞壁薄，外层排列比较疏松，内部细胞小，排列紧密。主要起保护作用

氮磷钾对植物作用

目录 1. 1 氮 2. 2 磷 3. 3 钾 氮磷钾氮 编辑 是植物生长的必需养分，它是每个活细胞的组成部分。植物需要大量氮。 氮素是植物体内蛋白质、核酸和叶绿素的组成成分[1]，叶绿素a和叶绿素b;都是含氮化合物。绿色植物进行光合作用，使光能转变为化学能，把无机物（二氧化碳和水）转变为有机物（葡萄糖）和氧气，是借助于叶绿素的作用。葡萄糖是植物体内合成各种有机物的原料，而叶绿素则是植物叶子制造“粮食”的工厂。氮也是植物体内维生素和能量系统的组成部分。 氮素对植物生长发育的影响是十分明显的。当氮素充足时，植物可合成较多的蛋白质，促进细胞的分裂和增长，因此植物叶面积增长快，能有更多的叶面积用来进行光合作用。 此外，氮素的丰缺与叶子中叶绿素含量有密切的关系。这就使得我们能从叶面积的大小和叶色深浅上来判断氮素营养的供应状况。在苗期，一般植物缺氮往往表现为生长缓慢，植株矮小，叶片薄而小，叶色缺绿发黄。禾本科作物则表现为分孽少。生长后期严重缺氮时，则表现为穗短小，籽粒不饱满。在增施氮肥以后，对促进植物生长健壮有明显的作用。往往施用后，叶色很快转绿，生长量增加。但是氮肥用量不宜过多，过量施用氮素时，叶绿素数量增多，能使叶子更长久地保持绿色，以致有延长生育期、贪青晚熟的趋势。对一些块根、块茎作物，如糖用甜菜，氮素过多时，有时表现为叶子的生长量显著增加，但具有经济价值的块根产量却少得使人失望。 我国土壤全氮含量的分布 植物养分的主要来源是土壤。我国土壤全氮含量的基本分布特点是：东北平原较高，黄淮海平原、西北高原、蒙新地区较低，华东、华南、中南、西南地区中等。大体呈现南北较高，中部略低的分布。但南方略高主要指水稻土，旱地含氮量很低。 一般认为土壤全氮含量<0.2%即有可能缺氮，我国大部分耕地的土壤全氮含量都在 0.2%以下，这就是为什么我国几乎所有农田都需要施用化学氮肥的原因。 我国农田相对严重缺氮的土壤主要分布在我国的西北和华北地区。如果把土壤全氮含量等于0.075% 作为严重缺氮的界限，严重缺氮耕地超过面积一半的有山东、河北、河南、陕西、新疆等五个省区。 氮磷钾磷 编辑

土壤取样方法

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浙江农林大学 怎么样 在浙江临安的

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浙江农林大学岩石与土壤复习资料(土壤学)重点

岩石与土壤学资料 第一章绪论 1.土壤概念 土壤是一种自然体，他是在母质、气候、生物、地形和时间5个自然因素综合作用下形成和发展起来的，并且也受人类活动的影响，有它本身的发展规律和特性。 2.土壤肥力 土壤肥力是指土壤能过够在多大程度上满足植物对于来自土壤的生活要素（即水分、养分、空气和热量）需求的能力。 3.土壤学在农业可持续发展中的地位和作用 （1）土壤是农业生产的场所。壤能持续协调地提供农作物生长所需的各种土壤肥力因素，保持农产品产 量与质量的稳定与提高。 1）营养库的作用 2）养分转化和循环的场所：无机养分的有机化，有机质的矿质化，养分元素的释放和散失，元素的结合，固定和归还 3）雨水的涵养作用占土壤水的1%-5% 4）生物的支撑作用：植物根系的机械支撑，土壤动物和微生物生存的场所 5）稳定和缓冲环境变化的作用：环境变化的缓冲功能，污染物的“过滤器”和“净化器” （2）土壤是陆地生态系统重要的组成部分。 （3）土壤是最珍贵的自然资源。 第二章矿物 1.矿物、岩石、风化作用的概念 1）矿物指地壳中的化学元素在各种地质作用下形成的相对稳定的自然产物。 2）在各种地质作用下形成的，由一种或多种矿物以一定的规律结合组成的矿物集合体叫做岩石。 3）受力影响引起岩石破碎和分解的作用称为风化作用 是母质、气候、生物、地形和时间5个自然因素 母质是土壤形成的物质基础，气候决定着成土过程的水热条件，生物是形成土壤的主导因子， 4.三大岩石的常见类型 岩浆岩：酸性岩类：花岗岩、流纹岩、石英斑岩中性岩类：闪长石、安山岩、粗面基性岩类：辉岩、辉长岩、橄榄岩、玄武岩火山碎屑岩：凝灰岩 沉积岩：碎屑岩：砾岩、砂岩、粉砂岩、粘土岩：页岩、泥岩、化学岩和生物化学岩：石灰岩、白云岩 变质岩：板岩、千枚岩、片岩、片麻岩、大理岩、石英岩 第三章土壤有机质 1.土壤有机质含义

第3章+植物与土壤基础知识答案

第3章植物与土壤基础知识 第1节土壤中有什么 1、土壤的层次结构：一般分枯枝落叶层、上土层和下土层，其中枯枝落叶层是小动物活动的主要场所；上土层植物根系大量分布。 2、土壤环境特点:主要指的是土壤的湿度、土壤疏松程度、土壤温度、光照和植物生长状况等环境因素。 3、在特定生态系统中数量较多的生物称优势物种。 4、在观察土壤生物的调查表格中，简要分析栏应着重分析土壤中生物，特别是优势物种的生活与 环境之间的相互关系。 5、我们把生活在土壤中的微生物、动物、和植物等称为土壤生物；其中微生物包括细菌、真菌、放线菌。土壤中含有的非生命物质有①空气；②水；③有机物（腐殖质）；④无机盐（矿物质）。 6、在烧杯内盛一定量的水，将干燥的土壤块慢慢放入水中，你观察到的现象有气泡产生。 说明土壤中有空气；其作用是为植物根呼吸和微生物的生命活动提供氧气。 7、书本P77页图3-2测量土壤中空气的体积分数实验： (1)在烧杯中放入一块土壤（土壤的体积为V），缓慢注入水，直到水面把土壤全部浸没为止。记录在烧杯中所加的水的体积。记做V1. (2)用与土壤体积相等的铁块替代土壤，重复上述实验。记录所加水的体积记做V2。 (3) V1大于 V2（大于，小于或等于），因为土壤间隙中有空气。土壤中空气的体积分数约为(V1-V2)/V ；在土壤中,空气约占土壤体积的 15%~35% 。 8、取少许土壤，放入试管中，在酒精灯上加热，观察到的现象是试管壁上有小水珠;试管口冒出水雾；这个实验说明土壤中有水；它是植物生长的必要条件；（其中小部分水供给植物光合作用，大部分水供给植物蒸腾作用。 9、实验：给你一只坩埚、一把刻度尺、一只酒精灯和一台精确度足够的天平，你有办法测量土壤水分体积占土壤体积的体积分数吗？ (1)选取一规则几何体状的土壤样本，用刻度尺测出其相关数据，算出土壤体积数V； (2)用天平称出其质量M ； (3)将土壤捣碎，放在坩埚上用酒精灯加热，让其水分充分汽化充分散失，再称其质量M1。 (4)将水分的质量换算成体积:V水= （M-M1）/ρ水； (5)土壤中水分的体积分数= （M-M1）/（ρ水V）。

第四章植物与土壤单元检测卷

第四章植物与土壤单元检测 一、选择题（每题2分，共40分） 1．一个塑料袋在土壤中的自然降解需200年时间，全国每天消耗塑料袋30亿个，制造塑料袋每日消耗石油13000吨，因此我国规定从今年6月1日起全国禁止生产销售超薄购物塑料袋，这一举措的主要目的是（） A．保护环境、节约能源B．防治空气污染 C．治理水污染D．节约能源 2．下列实验中，哪一个实验可以更好地证明土壤中含有能燃烧的有机物（） 3、我们行进在公园里时，经常发现草坪上有爱心提示牌：“请勿践踏，爱护我”。这是因为经常践踏 草坪会造成土壤板结，从而影响草的生长。其中的科学道理是（） A．植物缺少无机盐，影响生长B．植物缺少水，影响光合作用 C．土壤缺少氧气，影响根的呼吸D．气孔关闭，影响蒸腾作用 4、小明参加了假期夏令营，学会了如何利用植物年轮辨认方向的野外生存能力，下列有关年轮的知识，错误的是( ) A、根据树木年轮的数目，可以推知它的年龄 B、树木的每个年轮只包括茎的木质部 C、从植物的年轮可让我们知道南北方向的差异 D、植物年轮是由植物的韧皮部形成的5．嘉兴素有“浙北粮仓”的美誉，水稻是嘉兴最重要的粮食作物。下列对于水稻的叙述，正确的是( ) A．茎能不断加粗B．根为直根系C．能开花结果D．种子中有两片子叶 6.古人云：“野火烧不尽，春风吹又生”。生活中人们也发现，将植物的枯枝落叶焚烧后的灰烬留在 土壤里，有利于植物的生长。这说明植物的生长需要（） A．有机物 B．空气 C．二氧化碳 D．无机盐 7、在植树过程中，为了提高树苗成活率，王大爷应该采取的措施是（） ①带土移栽；②去掉部分叶片移栽；③在烈日炎炎的中午移栽 A．①③B．①②C．②③D．①②③ 8.杜仲是一种常见的中药，树皮可入药，但剥树皮时不能切口太深，否则会影响数的生长，其原因是与破坏树茎部的（）有关。 A．木质部 B．韧皮部 C．外树皮 D．形成层 9．有位科学家给一株黑麦创造了良好的条件，让黑麦的根能充分地生长．到它长出麦穗的时候，统计出这株黑麦的根系共有150亿条根毛，根毛全长约10000km，这么多的根毛的主要作用是（）A．把植物体固定在土壤里B．扩大吸收面积 C．运输大量的水分D．储存大量的水分

浙江农林大学 林木育种 整理

林木育种学：又称林木改良，是应用林木遗传性原理，以生物统计学为工具，与森林生态学等其他学科密切相关，研究林木新品种选育和良种繁育的原理和技术的学科。 林木品种：指产品的数量和品质符合生产需要，能适应一定自然和栽培条件，特性明显，性状遗传稳定，由人工选育的林木群体。重点在：产品要求、栽培范围、遗传相对一致的、人工选育、群体。 遗传力：反应遗传变量占表型变量的比率。 配合力：是指一个亲本(纯系、自交系或品种)材料在由它所产生的杂种一代或后代的产量或其他性状表现中所起作用相对大小的度量。 一般配合力：指某一亲本在一系列杂交组合中，子代某一性状平均值与子代总平均值的差值。 特殊配合力：指亲本在特定的杂交组合中，子代某一性状平均值与子代总平均值及双亲一般配合力的差值。育种值：一般配合力的两倍。 遗传增益：将选择响应除以亲本群体的平均值所得的百分率。G＝R/X×100％ 遗传相关：同一批供试材料的两个形状间由于遗传原因所体现的相关，即这个性状基因型值间的相关。 家系：由同一植株上产生的全部种子，属于同一个家系 无性系：由同一植株通过营养繁殖所产生的群体，称为一个无性系。对繁殖成无性系的最初植株，称为无性系原株，无性繁殖出来的植株称为无性系分株 遗传资源：也称基因资源，指以种为单位的群体内的全部遗传物质，或种内基因组、基因型变异的总和。种质资源:选育新品种的基础材料，包括各种植物的的栽培种、野生种的繁殖材料以及利用上述繁殖材料人工创造的各种植物的遗传材料。 育种资源：是遗传资源的组成部分，指在选育优良品种中直接利用的繁殖材料，往往是根据品种选育目标调查、收集的资源。 生物多样性：指地球上所有生物及其所拥有的基因，以及生物与其生存环境构成的复杂生态系统。 引种：把一个树种从原分布范围引入新地区栽培的过程。 驯化：通过人为干预使物种适应新环境或将动植物从野生状态改变为家养或栽培的过程。 种源：繁殖材料的地理来源，即最初的原产地。 种源试验：不同种源在同一地区的栽培对比试验。 种源选择：通过种源试验，为某一造林生境筛选最佳种源的过程。 种子园：是用优树无性系或家系按设计要求营建、实行集约经营、以生产优良遗传品质和播种品质种子为目的的特种人工林。 种子区：生态条件和林木遗传特性基本类似的地域单元，也是用种的基本单位。 种子区区划：根据生态条件、遗传性及行政区界，对林木种子供应范围进行的区划。 优树：在某一或某些性状上远远超过同等立地条件下，同种、同龄树木的单株。 杂种优势：指杂种后代可能综合双亲优良性状，或在生长、繁殖、抗性、品质等方面超过亲本的现象。 无性繁殖：采集植株的部分器官、组织或细胞，在适当条件下使其再生为完整植株的过程。 无性系选育：选择优良个体，通过无性繁殖成无性系，从中选育出优良无性系并用于生产的过程。 无性系选择：通过无性系对比试验，评选出优良无性系的过程。无性系选择充分利用了植株的加性效应、显性效应和上位效应。无性系选择增益大，方法简单。 采穗圃：是专门生产林木优良种条的场地，也是良种基地之一。 种子园：种子园是以优树无性系或家系为材料建立起来的以生产优质种子为目的的园地。 实生种子园：从优树上采取种子，通过有性繁殖建立的种子园。 自交：同一无性系的不同分株间授粉，或同一株树的自花授粉。 杂交：不同树种或同一树种不同种源、家系、无性系间的交配。 远缘杂交：不同种间、属间甚至亲缘关系更远的物种之间的杂交。 遗传测定：对入选植株后代进行田间对比试验，根据其性状表现进行评定的过程。 无性系测定：通过某一亲本的无性系进行田间试验，测定其遗传优势的方法。

浙教版八下第四章植物与土壤复习提纲修正版

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