Soil aggregates determine the basic structure of soil,and their composition and stability are influenced by the various types of cementitious substances occurring in soil.To explore the main limiting factors of soil a...Soil aggregates determine the basic structure of soil,and their composition and stability are influenced by the various types of cementitious substances occurring in soil.To explore the main limiting factors of soil aggregation in the process of vegetation succession with granite as the parent material,five stages of vegetation succession in an eroded area were selected:bare land(BL),grassland(GL),grassland shrub transition land(GS),shrubland(SL)and secondary forest(SF).Soil samples were collected to determine the composition and stability of aggregates.The contents of organic and inorganic cementitious substances,including organic matter components and iron aluminum oxides,were determined at five soil aggregate grain levels.The results indicated that the stability of soil aggregates and the>0.25 mm water-stable aggregate content(WR_(0.25))increased with vegetation succession.Based on the Le Bissonnais(LB)method,the mean weight diameter(MWD)of soil aggregates increased,and the relative dissipation index(RSI)and relative mechanical crushing index(RMI)decreased.The humic acid(HA)and fulvic acid(FA)contents in soil aggregates increased with vegetation succession,and the soil humus content at the SF stage increased by more than 13.54%over the BL level.Upon different vegetation succession stage,the iron and aluminum oxides for the SL and the SF were at a high level,and the contents of free-form iron oxide(Fe_(d))and amorphous iron oxide(Fe_(o))for BL were high.Correlation analysis indicated that the soil humic degree(PQ)and the contents of amorphous alumina(Al_(o))were positively correlated with aggregate stability to varying degrees.Redundancy analysis(RDA)revealed that PQ values of 1-2 mm(PQ_(2))and 0.25-0.5 mm(PQ_(4))aggregates,the contents of Fe_(o) of bulk soil(Fe_(oB)),>2 mm(Fe_(o1)),1-2 mm(Fe_(o2)),and<0.25 mm(Fe_(o5))aggregates,and the contents of Al_(o) of>2 mm(Al_(o1))aggregates could explain 99.4%of the changes in soil aggregate stability at different vegetation succession stages.Al_(o1) had a contribution rate of 71.2%and is the key factor for improving the stability of soil aggregates.展开更多
The gradual shrinkage of the Aral Sea has led to not only the degradation of the unique environments of the Aral Sea,but also numerous and fast developing succession processes in the neighborhood habitats surrounding ...The gradual shrinkage of the Aral Sea has led to not only the degradation of the unique environments of the Aral Sea,but also numerous and fast developing succession processes in the neighborhood habitats surrounding the sea.In this study,we investigated the vegetative succession processes related to the Aral Sea shrinkage in the Eastern Cliff of the Ustyurt Plateau in Republic of Uzbekistan,Central Asia.We compared the results of our current investigation(2010–2017)on vegetative communities with the geobotany data collected during the 1970s(1970–1980).The results showed great changes in the mesophytic plant communities and habitat aridization as a result of the drop in the underground water level,which decreased atmospheric humidity and increased the salt content of the soil caused by the shrinkage of the Aral Sea.In the vegetative communities,we observed a decrease in the Margalef index(DMg),which had a positive correlation with the poly-dominance index(I-D).The main indications of the plant communities'transformation were the loss of the weak species,the appearance of new communities with low species diversity,the stabilization of the projective cover of former resistant communities,as well as the appearance of a new competitive species,which occupy new habitats.展开更多
To assess phosphorus(P)status of forest soil under naturally restored vegetation,P fractions in the 10-cm soil layer were quantified at different successional stages on the clear-cut site of mixed broadleaved and Kore...To assess phosphorus(P)status of forest soil under naturally restored vegetation,P fractions in the 10-cm soil layer were quantified at different successional stages on the clear-cut site of mixed broadleaved and Korean pine forest.Four communities of shrub,softwood broad-leaved forest,softwood and hardwood broad-leaved forest,and hardwood broad-leaved forest represented different successional stages.A soil sample from a primary broad-leaved and Korean pine stand was the control.A sequential P fractionation scheme extracted empirically defined pools of P and path analysis used to partition the direct and indirect contribution of soil P fractions to available P.The results show that available P increased significantly with long-term succession,while both sodium bicarbonate-extractable P(NaHCO_(3)-P)and sodium hydroxide-extractable P(NaOHP)fractions were reduced in early successional stages and increased in late stages.Compared to the primary forest,concentrations of P fractions in the four stages significantly decreased except for HCl-P,indicating that soil P supplements over the long-term did not return to primary forest levels.The results of related analysis also showed that NaHCO_(3)-P_(i)levels were significantly related to available phosphorus.According to the path analysis coefficient,NaHCO_(3)-P_(i)exhibited the highest effect on available P among eight P fractions;the indirect effects of other P fractions via NaHCO_(3)-P_(i)were larger than those with other P fractions.Overall,this study suggests that soil P bioavailability gradually improved during natural vegetation restoration on clear-cut sites mainly through the increase of NaHCO_(3)-P,where phosphorous is immediately available,and subsequently available phosphorus Na OH-P.展开更多
Aims The abandonment of agronomic practices in subalpine systems has led to shrub encroachment,which has transformed grasslands into woodlands.The competitive and facilitative interactions among incoming shrub species...Aims The abandonment of agronomic practices in subalpine systems has led to shrub encroachment,which has transformed grasslands into woodlands.The competitive and facilitative interactions among incoming shrub species might influence vegetation succession and might be affected by climate change.This study aimed to identify the nature of shrub species interactions between an early colonizer and a secondary succession shrub in the successional encroach-ment process and whether it differs between two contrasting cli-matic conditions.Methods The interactions between the two main encroaching shrub spe-cies in the Central Pyrenees(Spain),Buxus sempervirens and Echinospartum horridum,were studied at the current upper limit of the altitudinal range of B.sempervirens,where it coexists with E.horridum(high site),and in a milder location at lower eleva-tion(low site).in the studied areas,E.horridum is the first shrub species that encroaches upon the abandoned grasslands and B.sempervirens enters the system after E.horridum has become established.A neighbor-removal experiment was used to assess the bidirectional interactions between both species,and whether those interactions differed among the life stages of B.sempervirens(seed-lings,juveniles and adults),at the two study sites.Survival,annual crown growth and developmental instability(error in development caused by stress)were the performance indices used to quantify plant responses.Differences in air temperatures and soil nutrient amelioration were evaluated as possible mechanisms of facilitation of E.horridum on B.sempervirens.Important Findings E.horridum enhanced the survival of B.sempervirens seedlings under its crown,whereas,B.sempervirens adults outcompeted E.horridum.Therefore,the invasion of the grasslands by E.horridum facilitated the settlement and expansion of B.sempervirens,pro-moting vegetation succession at the Pyrenees.in addition,climatic differences associated with elevation affected shrub interactions.Under low temperatures at the upper limit of B.sempervirens alti-tudinal range,the presence of E.horridum enhanced the growth of B.sempervirens juveniles.At low elevation,under a milder climate,B.sempervirens exerted a high degree of competition toward E.hor-ridum.An increase in temperatures associated with climate change would benefit B.sempervirens juveniles growth which might affect the successional process because it would increase their competi-tive ability when B.sempervirens juveniles become adults.展开更多
Background:Shifting cultivation(locally known as“jhum”)is a major driver of deforestation and loss of ecosystem services in rainforests.For developing any effective conservation of biodiversity and carbon service pr...Background:Shifting cultivation(locally known as“jhum”)is a major driver of deforestation and loss of ecosystem services in rainforests.For developing any effective conservation of biodiversity and carbon service program,an indepth understanding to the recovery of vegetation and carbon after abandonment of jhum is essential.We estimated species richness,abundance and composition of trees,shrubs and herbs,carbon distribution in aboveground and belowground components along a chronosequence of jhum fallow in northeast India,and elucidated the factors affecting the recovery processes of jhum fallows.Methods:Species composition and other plant community attributes,carbon storage in different pools were studied in 5 jhum fallows(<5,5-10,11-15,16-20,21-25 years old)and an old-growth forest.The data were subjected to linear mixed effect modeling using R-package“nlme”for identifying the important factors contributing to the recovery of vegetation and carbon.Results:Species composition varied significantly(P<0.05)between jhum fallows and old-growth forest.Tree density varied from 28 stems ha−1 in 5 years old jhum fallow to 163 stems ha−1 in old-growth forest.Both biomass carbon in all components and soil organic carbon were significantly(P=0.01)lower in jhum fallows than in the old-growth forest except living non-woody biomass component.The recovery of aboveground biomass carbon was faster during early successive years than the mid-successive jhum fallows.Total ecosystem carbon and soil organic carbon stock in the oldest jhum fallow was 33%and 62%of those in the old-growth forest,respectively.The fallow age was found to be the most important explanatory factor in the recovery process of vegetation and carbon stock in re-growing fallows.Conclusion:The shifting cultivation fallows gradually recovered both vegetation and carbon and are potential repository sites for biodiversity conservation,which may take much longer time to reach up to old-growth forest in northeast India.展开更多
This study investigates the changes in soil microbial populations as vegetational succession progress from abandoned farmland to climax forest in the Ziwuling Forest,which is located in the northern part of the Loess ...This study investigates the changes in soil microbial populations as vegetational succession progress from abandoned farmland to climax forest in the Ziwuling Forest,which is located in the northern part of the Loess Plateau,China.Different organic C and total extractable N between the fumigated and non-fumigated soils were assumed to be released from soil microorganisms.Soil microbial C was calculated using Kec=0.38 and microbial N was calculated using Ken=0.45.The released P was converted to microbial biomass P using Kep=0.40.Soil bacteria,fungi,and actinomycetes increased as the vegetational succession progressed.Microbial C was of the highest amount in farmland.Microbial C,N,and P generally increased from abandoned land to climax community.The results indicated significant(P<0.05)diversities of soil microbial biomass under different vegetation.There was a significant correlation between microbial biomass and soil nutrients.Knowledge about soil microbial populations is important for forecasting vegetational succession and determining the ecological condition of the environment.展开更多
The Permian Taiyuan and Shanxi formations exposed in Shandong Province,eastern North China,contain abundant spores and pollen.In this study,a total of 42 genera and 146 species of spores and pollen from these Permian ...The Permian Taiyuan and Shanxi formations exposed in Shandong Province,eastern North China,contain abundant spores and pollen.In this study,a total of 42 genera and 146 species of spores and pollen from these Permian formations,native to northern China,are identified and related to the three epochs of the Permian Period(Cisuralian,Guadalupian,and Lopingian Epochs)as two assemblages:Assemblage I—the Laevigatosporites-Granulatisporites assemblage,inferred as the Cisuralian(~298.9-272.9 Ma);and,Assemblage II—the Gulisporites-Sinulatisporites assemblage,inferred as the Guadalupian(~272.9-259.1 Ma).Assemblage I represents growing ferns,whereas Assemblage II represents gymnosperms.The assemblage division and analysis indicated that the palaeoclimate of the study area during Early-Middle Permian time was dominated by warm and humid conditions,and later in the Middle Permian changed into moderately dry conditions.展开更多
Geographical barriers and distance can reduce gene exchange among animals,resulting in genetic divergence of geographically isolated populations.The Tibetan antelope(Pantholops hodgsonii)has a geographical range of ap...Geographical barriers and distance can reduce gene exchange among animals,resulting in genetic divergence of geographically isolated populations.The Tibetan antelope(Pantholops hodgsonii)has a geographical range of approximately 1600 km across the Qinghai-Tibet Plateau,which comprises a series of tall mountains and big rivers.However,previous studies indicate that there is little genetic differentiation among their geographically delineated populations.To better understand the genetic structure of P.hodgsonii populations,we collected 145 samples from the 3 major calving regions,taking into consideration their various calving grounds and migration routes.We used a combination of mitochondrial sequences(Cyt b,ATPase,D-loop and COX I)to investigate the genetic structure and the evolutionary divergence of the populations.Significant,albeit weak,genetic differentiation was detected among the 3 geographical populations.Analysis of the genetic divergence process revealed that the animals gradually entered a period of rapid genetic differentiation approximately 60000 years ago.The calving migration of P.hodgsonii cannot be the main cause of their weak genetic structure because this cannot fully homogenize the genetic pool.Instead,the geological and climatic events as well as the coupling vegetation succession process during this period have been suggested to greatly contribute to the genetic structure and the expansion of genetic diversity.展开更多
基金financial support for the research provided by the Guangxi Natural Science Foundation(2021GXNSFBA075017)the National Natural Science Foundation of China(No.42007055,42107350)the Guangxi Science and Technology Base and talent Special project(No.AD20159031)。
文摘Soil aggregates determine the basic structure of soil,and their composition and stability are influenced by the various types of cementitious substances occurring in soil.To explore the main limiting factors of soil aggregation in the process of vegetation succession with granite as the parent material,five stages of vegetation succession in an eroded area were selected:bare land(BL),grassland(GL),grassland shrub transition land(GS),shrubland(SL)and secondary forest(SF).Soil samples were collected to determine the composition and stability of aggregates.The contents of organic and inorganic cementitious substances,including organic matter components and iron aluminum oxides,were determined at five soil aggregate grain levels.The results indicated that the stability of soil aggregates and the>0.25 mm water-stable aggregate content(WR_(0.25))increased with vegetation succession.Based on the Le Bissonnais(LB)method,the mean weight diameter(MWD)of soil aggregates increased,and the relative dissipation index(RSI)and relative mechanical crushing index(RMI)decreased.The humic acid(HA)and fulvic acid(FA)contents in soil aggregates increased with vegetation succession,and the soil humus content at the SF stage increased by more than 13.54%over the BL level.Upon different vegetation succession stage,the iron and aluminum oxides for the SL and the SF were at a high level,and the contents of free-form iron oxide(Fe_(d))and amorphous iron oxide(Fe_(o))for BL were high.Correlation analysis indicated that the soil humic degree(PQ)and the contents of amorphous alumina(Al_(o))were positively correlated with aggregate stability to varying degrees.Redundancy analysis(RDA)revealed that PQ values of 1-2 mm(PQ_(2))and 0.25-0.5 mm(PQ_(4))aggregates,the contents of Fe_(o) of bulk soil(Fe_(oB)),>2 mm(Fe_(o1)),1-2 mm(Fe_(o2)),and<0.25 mm(Fe_(o5))aggregates,and the contents of Al_(o) of>2 mm(Al_(o1))aggregates could explain 99.4%of the changes in soil aggregate stability at different vegetation succession stages.Al_(o1) had a contribution rate of 71.2%and is the key factor for improving the stability of soil aggregates.
基金This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20020101).We also thank for the project"Modern Trends in the Development of Vegetation and Fauna of Ustyurt in the Process of Desertification"(F3MВ-2016-0910183457),which is supported by the Ministry of Innovative Development of the Republic of Uzbekistan.
文摘The gradual shrinkage of the Aral Sea has led to not only the degradation of the unique environments of the Aral Sea,but also numerous and fast developing succession processes in the neighborhood habitats surrounding the sea.In this study,we investigated the vegetative succession processes related to the Aral Sea shrinkage in the Eastern Cliff of the Ustyurt Plateau in Republic of Uzbekistan,Central Asia.We compared the results of our current investigation(2010–2017)on vegetative communities with the geobotany data collected during the 1970s(1970–1980).The results showed great changes in the mesophytic plant communities and habitat aridization as a result of the drop in the underground water level,which decreased atmospheric humidity and increased the salt content of the soil caused by the shrinkage of the Aral Sea.In the vegetative communities,we observed a decrease in the Margalef index(DMg),which had a positive correlation with the poly-dominance index(I-D).The main indications of the plant communities'transformation were the loss of the weak species,the appearance of new communities with low species diversity,the stabilization of the projective cover of former resistant communities,as well as the appearance of a new competitive species,which occupy new habitats.
基金supported by the National Forestry Industry Public Welfare Projects(grant number 201404202)。
文摘To assess phosphorus(P)status of forest soil under naturally restored vegetation,P fractions in the 10-cm soil layer were quantified at different successional stages on the clear-cut site of mixed broadleaved and Korean pine forest.Four communities of shrub,softwood broad-leaved forest,softwood and hardwood broad-leaved forest,and hardwood broad-leaved forest represented different successional stages.A soil sample from a primary broad-leaved and Korean pine stand was the control.A sequential P fractionation scheme extracted empirically defined pools of P and path analysis used to partition the direct and indirect contribution of soil P fractions to available P.The results show that available P increased significantly with long-term succession,while both sodium bicarbonate-extractable P(NaHCO_(3)-P)and sodium hydroxide-extractable P(NaOHP)fractions were reduced in early successional stages and increased in late stages.Compared to the primary forest,concentrations of P fractions in the four stages significantly decreased except for HCl-P,indicating that soil P supplements over the long-term did not return to primary forest levels.The results of related analysis also showed that NaHCO_(3)-P_(i)levels were significantly related to available phosphorus.According to the path analysis coefficient,NaHCO_(3)-P_(i)exhibited the highest effect on available P among eight P fractions;the indirect effects of other P fractions via NaHCO_(3)-P_(i)were larger than those with other P fractions.Overall,this study suggests that soil P bioavailability gradually improved during natural vegetation restoration on clear-cut sites mainly through the increase of NaHCO_(3)-P,where phosphorous is immediately available,and subsequently available phosphorus Na OH-P.
基金We gratefully acknowledge the financial support of the Spanish Economy and Competition Ministry(PN-MICINN)(CGL2008-00655/BOS and CGL2011-27259)Spanish National Park organization(DIPA 125/2010 MMAMRM).
文摘Aims The abandonment of agronomic practices in subalpine systems has led to shrub encroachment,which has transformed grasslands into woodlands.The competitive and facilitative interactions among incoming shrub species might influence vegetation succession and might be affected by climate change.This study aimed to identify the nature of shrub species interactions between an early colonizer and a secondary succession shrub in the successional encroach-ment process and whether it differs between two contrasting cli-matic conditions.Methods The interactions between the two main encroaching shrub spe-cies in the Central Pyrenees(Spain),Buxus sempervirens and Echinospartum horridum,were studied at the current upper limit of the altitudinal range of B.sempervirens,where it coexists with E.horridum(high site),and in a milder location at lower eleva-tion(low site).in the studied areas,E.horridum is the first shrub species that encroaches upon the abandoned grasslands and B.sempervirens enters the system after E.horridum has become established.A neighbor-removal experiment was used to assess the bidirectional interactions between both species,and whether those interactions differed among the life stages of B.sempervirens(seed-lings,juveniles and adults),at the two study sites.Survival,annual crown growth and developmental instability(error in development caused by stress)were the performance indices used to quantify plant responses.Differences in air temperatures and soil nutrient amelioration were evaluated as possible mechanisms of facilitation of E.horridum on B.sempervirens.Important Findings E.horridum enhanced the survival of B.sempervirens seedlings under its crown,whereas,B.sempervirens adults outcompeted E.horridum.Therefore,the invasion of the grasslands by E.horridum facilitated the settlement and expansion of B.sempervirens,pro-moting vegetation succession at the Pyrenees.in addition,climatic differences associated with elevation affected shrub interactions.Under low temperatures at the upper limit of B.sempervirens alti-tudinal range,the presence of E.horridum enhanced the growth of B.sempervirens juveniles.At low elevation,under a milder climate,B.sempervirens exerted a high degree of competition toward E.hor-ridum.An increase in temperatures associated with climate change would benefit B.sempervirens juveniles growth which might affect the successional process because it would increase their competi-tive ability when B.sempervirens juveniles become adults.
基金This study was financially supported by DST,Government of India(Sanction No.DST/IS_STAC/CO2-SR-227/14(G)-AICP-AFOLU-IV).
文摘Background:Shifting cultivation(locally known as“jhum”)is a major driver of deforestation and loss of ecosystem services in rainforests.For developing any effective conservation of biodiversity and carbon service program,an indepth understanding to the recovery of vegetation and carbon after abandonment of jhum is essential.We estimated species richness,abundance and composition of trees,shrubs and herbs,carbon distribution in aboveground and belowground components along a chronosequence of jhum fallow in northeast India,and elucidated the factors affecting the recovery processes of jhum fallows.Methods:Species composition and other plant community attributes,carbon storage in different pools were studied in 5 jhum fallows(<5,5-10,11-15,16-20,21-25 years old)and an old-growth forest.The data were subjected to linear mixed effect modeling using R-package“nlme”for identifying the important factors contributing to the recovery of vegetation and carbon.Results:Species composition varied significantly(P<0.05)between jhum fallows and old-growth forest.Tree density varied from 28 stems ha−1 in 5 years old jhum fallow to 163 stems ha−1 in old-growth forest.Both biomass carbon in all components and soil organic carbon were significantly(P=0.01)lower in jhum fallows than in the old-growth forest except living non-woody biomass component.The recovery of aboveground biomass carbon was faster during early successive years than the mid-successive jhum fallows.Total ecosystem carbon and soil organic carbon stock in the oldest jhum fallow was 33%and 62%of those in the old-growth forest,respectively.The fallow age was found to be the most important explanatory factor in the recovery process of vegetation and carbon stock in re-growing fallows.Conclusion:The shifting cultivation fallows gradually recovered both vegetation and carbon and are potential repository sites for biodiversity conservation,which may take much longer time to reach up to old-growth forest in northeast India.
基金the National Basic Research Program of China(No.2005CB121102)the State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau of China(No.10501-138)。
文摘This study investigates the changes in soil microbial populations as vegetational succession progress from abandoned farmland to climax forest in the Ziwuling Forest,which is located in the northern part of the Loess Plateau,China.Different organic C and total extractable N between the fumigated and non-fumigated soils were assumed to be released from soil microorganisms.Soil microbial C was calculated using Kec=0.38 and microbial N was calculated using Ken=0.45.The released P was converted to microbial biomass P using Kep=0.40.Soil bacteria,fungi,and actinomycetes increased as the vegetational succession progressed.Microbial C was of the highest amount in farmland.Microbial C,N,and P generally increased from abandoned land to climax community.The results indicated significant(P<0.05)diversities of soil microbial biomass under different vegetation.There was a significant correlation between microbial biomass and soil nutrients.Knowledge about soil microbial populations is important for forecasting vegetational succession and determining the ecological condition of the environment.
基金This study was supported by the Open Foundation for the Modern Key Laboratory of Paleontology and Stratigraphy,Nanjing Institute of Geology and Paleontology,Chinese Academy of Sciences(Grant No.123104).
文摘The Permian Taiyuan and Shanxi formations exposed in Shandong Province,eastern North China,contain abundant spores and pollen.In this study,a total of 42 genera and 146 species of spores and pollen from these Permian formations,native to northern China,are identified and related to the three epochs of the Permian Period(Cisuralian,Guadalupian,and Lopingian Epochs)as two assemblages:Assemblage I—the Laevigatosporites-Granulatisporites assemblage,inferred as the Cisuralian(~298.9-272.9 Ma);and,Assemblage II—the Gulisporites-Sinulatisporites assemblage,inferred as the Guadalupian(~272.9-259.1 Ma).Assemblage I represents growing ferns,whereas Assemblage II represents gymnosperms.The assemblage division and analysis indicated that the palaeoclimate of the study area during Early-Middle Permian time was dominated by warm and humid conditions,and later in the Middle Permian changed into moderately dry conditions.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23060602,XDA2002030302)Construction Fund for Qinghai Provincial Key Laboratories(2017-ZJ-Y23).
文摘Geographical barriers and distance can reduce gene exchange among animals,resulting in genetic divergence of geographically isolated populations.The Tibetan antelope(Pantholops hodgsonii)has a geographical range of approximately 1600 km across the Qinghai-Tibet Plateau,which comprises a series of tall mountains and big rivers.However,previous studies indicate that there is little genetic differentiation among their geographically delineated populations.To better understand the genetic structure of P.hodgsonii populations,we collected 145 samples from the 3 major calving regions,taking into consideration their various calving grounds and migration routes.We used a combination of mitochondrial sequences(Cyt b,ATPase,D-loop and COX I)to investigate the genetic structure and the evolutionary divergence of the populations.Significant,albeit weak,genetic differentiation was detected among the 3 geographical populations.Analysis of the genetic divergence process revealed that the animals gradually entered a period of rapid genetic differentiation approximately 60000 years ago.The calving migration of P.hodgsonii cannot be the main cause of their weak genetic structure because this cannot fully homogenize the genetic pool.Instead,the geological and climatic events as well as the coupling vegetation succession process during this period have been suggested to greatly contribute to the genetic structure and the expansion of genetic diversity.
