The dynamics of litter nitrogen (N) and phosphorus (P) release could be affected by soil fauna and environmental conditions. The objective of the present study was to investigate the effects of soil fauna on the dynam...The dynamics of litter nitrogen (N) and phosphorus (P) release could be affected by soil fauna and environmental conditions. The objective of the present study was to investigate the effects of soil fauna on the dynamics of N and P during foliar litter decomposition in three types of ecosystems (i.e., montane forest, ecotone, and dry valley) along an elevation gradient. A field experiment using litterbags with two different mesh sizes (0.04 and 3 mm) was conducted from November 2013 to October 2014. Nitrogen and P release rates in decomposing foliar litter from fir (Abies faxoniana) and birch (Betula albosinensis) in montane forest, oak (Quercus baronii) and cypress (Cupressus chengiana) in ecotone, and cypress and clovershrub (Campylotropis macrocarpa) in dry valley were investigated in the upper reaches of the Yangtze River. Soil fauna strongly affected N and P release across different decomposition periods and ecosystem types. The average release rate of N mediated by soil fauna across the entire year was higher in the dry valley (15.6–37.3%) than in the montane forest (0.5–6.4%) and the ecotone (- 3.7–4.9%). The effects of soil fauna on P release rate were manifest in both the montane forest and the dry valley. Moreover, the impacts of soil fauna can vary substantially among different decomposition periods. Our results indicated that soil fauna can significantly affect N and P release during litter decomposition. The N release rate mediated by fauna was likely to be more sensitive to the effects of plant species (i.e., initial litter chemical traits), while the P release rate mediated by soil fauna might be subject to the effects of local-scale environmental factors (e.g., temperature) to a greater extent.展开更多
Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter deco...Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter decomposition in those ecosystems. Here, we conducted a2-year-long litter decomposition experiment along an elevational gradient from 3000 to 3600 m to determine the potential effects of litter quality, climate warming and freeze-thaw on the mass losses of three litter types [dragon spruce（Picea asperata Mast.）, red birch（Betula albosinensis Burk.）, and minjiang fir（Abies faxoniana Rehd. et Wild）]. Marked differences in mass loss were observed among the litter types and sampling dates. Decay constant（k） values of red birch were significantly higher than those of the needle litters. However, mass losses between elevations did not differ significantly for any litter type.During the winter, lost mass contributed 18.3-28.8 % of the net loss rates of the first year. Statistical analysis showed that the relationships between mass loss and litter chemistry or their ratios varied with decomposition periods. Our results indicated that short-term field incubations could overestimate the k value of litter decomposition.Considerable mass was lost from subalpine forest litters during the wintertime. Potential future warming may not affect the litter decomposition in the subalpine forest ecosystems of eastern Tibetan Plateau.展开更多
To understand the decomposition characteristics of Pinus massoniana foliar litter and the degradation of its refractory compounds in plantations under five canopy densities,a litter bag experiment over a decomposition...To understand the decomposition characteristics of Pinus massoniana foliar litter and the degradation of its refractory compounds in plantations under five canopy densities,a litter bag experiment over a decomposition time of 392 days was carried out.The results show that canopy density significantly affected decomposition rates of litter and degradation rate of lignin and cellulose.Litter decomposition rates decreased significantly with decreasing canopy density.Both lignin and cellulose degradation rates were lower with canopy densities of 0.62 and 0.74 as compared with the three other densities.Lignin and cellulose losses were more rapid in the first 118 days.Soil fauna had significant impacts on litter decomposition and the degradation of refractory compounds.Canopy density had significant effects on factors such as soil properties and soil fauna community structure,which could be conducive to the decomposition of litter and the degradation of litter recalcitrant components.Canopy density between 0.6 and 0.7 might be a favorable management practice promoting litter decomposition and beneficial for the sustainable development of P.massoniana plantations.展开更多
By combining the observation of the soil profile at field and the chemical and physical analysis in laboratory, a study on the hydro-physical properties of soil in six different vegetation types and the dynamics of ...By combining the observation of the soil profile at field and the chemical and physical analysis in laboratory, a study on the hydro-physical properties of soil in six different vegetation types and the dynamics of water content after rain was conducted in Wanchanggou, Guangyuan City to find out the vegetation types with effective water-conservation functions in order to serve the ecological restoration in the low hill heavy rain area upper the Jialing River. Results showed that., the hydro-physical properties of soil in the mixed Alnus crernastogyne and Cupressua Leyland forest （AcCl） were best. But in the depth of 0-20 cm. The properties of soil in the abandoned cropland （Fm） was better than that in the AcCl. The soil bulk densities varied significantly between the layers of 0-20 cm and 20-40 cm in all the six vegetation types except that in the Robinia pseudoacacia shrub forest （RpII）, and the changes of the maximum and the capillary moisture capacity between layers were significant only in the Fm and in the AcCl. Of these stands, the AcCl had the shortest water-absorbing period and the strongest moisture changes in the upper layer （0-15 cm）. In the same stand, the deeper the soil layer, the slighter the soil moisture varied, and the longer the soil moisture accumulating process lasted.展开更多
Background:Stem CO_(2) efflux(E_(S))plays a critical role in the carbon budget of forest ecosystems.Thinning is a core practice for sustainable management of plantations.It is therefore necessary and urgent to study t...Background:Stem CO_(2) efflux(E_(S))plays a critical role in the carbon budget of forest ecosystems.Thinning is a core practice for sustainable management of plantations.It is therefore necessary and urgent to study the effect and mechanism of thinning intensity(TI)on E_(S).Methods:In this study,five TIs were applied in Larix principis-rupprechtii Mayr 21-,25-,and 41-year-old stands in North China in 2010.Portable infrared gas analyzer(Li-8100 A)was used to measure ES and its association with environmental factors at monthly intervals from May to October in 2013 to 2015.In addition,nutrients,wood structure and nonstructural carbon(NSC)data were measured in August 2016.Results:The results show that ES increased with increasing TI.The maximum ES values occurred at a TI of 35%(3.29,4.57 and 2.98μmol·m^(-2)·s^(-1))and were 1.54-,1.94-and 2.89-fold greater than the minimum E_(S) value in the CK stands(2.14,2.35 and 1.03μmol·m^(-2)·s^(-1))in July for the 21-,25-and 41-year-old forests,respectively.The E_(S) of the trees in low-density stands was more sensitive to temperature than that of the trees in high-density stands.Soluble sugars(SS)and temperature are the main factors affecting ES.When the stand density is low enough as 41-year-old L.principis-rupprechtii forests with TI 35%,bark thickness(BT)and humidity should be considered in addition to air temperature(T_(a)),wood temperature(T_(w)),sapwood width(SW),nitrogen concentration(N)and SS in the evaluation of ES.If a change in stand density is ignored,the CO_(2) released from individual 21-,25-and 41-year-old trees could be underestimated by 168.89%,101.94% and 200.49%,respectively.CO_(2) release was estimated based on the stem equation in combination with the factors influencing ES for reference.Conclusions:We suggest that it is not sufficient to conventional models which quantify ES only by temperature and that incorporating the associated drivers(e.g.density,SS,SW and N)based on stand density into conventional models can improve the accuracy of ES estimates.展开更多
Reducing the threats of sulfate ion(SO42-)deposition to terrestrial ecosystems is a great challenge.The canopy interception effect on SO42-deposition has been well documented,but the interception efficiency of the gap...Reducing the threats of sulfate ion(SO42-)deposition to terrestrial ecosystems is a great challenge.The canopy interception effect on SO42-deposition has been well documented,but the interception efficiency of the gap edge remains unknown.Therefore,a subalpine dragon spruce(Picea asperata)plantation was evaluated in the upper reaches of the Yangtze River.The dynamics of the SO42-concentration in the throughfall were investigated from the gap edge to the closed canopy during the rainfall and snowfall periods from August 2015 to July 2016.The annual input of SO42-totaled 2.56 kg/ha through rainfall and 0.69 kg/ha through snowfall.The total annual net interception fluxes(NIFs)of SO42-at the gap edge and in the closed canopy were 1.48 kg/ha and 0.66 kg/ha,respectively,and the net interception ratios(NIRs)accounted for 45.40%and 20.25%,respectively.The NIF and the NIR of SO42-at the gap edge were higher than those in the closed canopy.Therefore,the results suggested that a significant amount of SO42-deposition was intercepted by the tree canopy in the subalpine plantation,with more SO42-deposition at the gap edge than in the closed canopy,which is beneficial for improving the water quality in the upper reaches of the Yangtze River via forest management.展开更多
Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic...Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.展开更多
Soil productivity is the ability of a soil, in its normal environment, to support plant growth and can be evaluated with respect to crop production in unfertilized soil within the agricultural ecosystem. Both soil pro...Soil productivity is the ability of a soil, in its normal environment, to support plant growth and can be evaluated with respect to crop production in unfertilized soil within the agricultural ecosystem. Both soil productivity and fertilizer applications affect crop yields. A long-term experiment with a winter wheat-summer maize rotation was established in 1989 in a field of the Fengqiu State Key Agro-Ecological Experimental Station, a region typical of the North China Plain, including seven treatments： 1） a balanced application of NPK chemical fertilizers （NPK）; 2） application of organic fertilizer （OM）; 3） application of 50% organic fertilizer and 50% NPK chemical fertilizers （1/2OMN）; 4） application of NP chemical fertilizers （NP）; 5） application of PK chemical fertilizer （PK）; 6） application of NK chemical fertilizers （NK）; and 7） unfertilized control （CK）. To investigate the effects of fertilization practices on soil productivity, further pot tests were conducted in 2007-2008 using soil samples from the different fertilization treatments of the long-term field experiment. The soil sample of each treatment of the long-term experiment was divided into three pots to grow wheat： with no fertilization （Potunf）, with balanced NPK fertilization （POtNPK）, and with the same fertilizer（s） of the long-term field experiment （Potori）. The fertilized soils of the field experiment used in all the pot tests showed a higher wheat grain yield and higher nutrient uptake levels than the unfertilized soil. Soil productivity of the treatments of the field experiment after 18 years of continuous fertilizer applications were ranked in the order of OM 〉 1/2OMN 〉 NPK 〉 NP 〉 PK 〉 NK 〉 CK. The contribution of soil productivity of the different treatments of the field experiment to the wheat grain yield of Potori was 36.0%-76.7%, with the PK and NK treatments being higher than the OM, 1/2OMN, NPK, and NP treatments since the soil in this area was deficient in N and P and rich in K. Wheat grain yields of PotNPK were higher than those of Potori and Potunf. The N, P, and K use efficiencies were higher in POtNPK than Potori and significantly positively correlated with wheat grain yield. Soil organic matter could be a better predictor of soil productivity because it correlated more strongly than other nutrients with the wheat grain yield of Potuf. Wheat yields of POtNPK showed a similar trend to those of Potunf, indicating that soil productivity improvement was essential for a further increase in crop yield. The long-term applications of both organic and chemical fertilizers were capable of increasing soil productivity on the North China Plain, but the former was more effective than the latter. The balanced application of NPK chemical fertilizers not only increased soil productivity, but also largely increased crop yields, especially in soils with lower productivity. Thus, such an approach should be a feasible practice for the sustainable use of agricultural soils on the North China Plain, particularly when taking into account crop yields, labor costs, and the limited availability of organic fertilizers.展开更多
Aims The conifer litter is fairly recalcitrant and nutrient poor,and broadleaved litter promotes coniferous litter decomposition by increasing degradable nutrients and promoting microbial metabolism.Mixing Pinus masso...Aims The conifer litter is fairly recalcitrant and nutrient poor,and broadleaved litter promotes coniferous litter decomposition by increasing degradable nutrients and promoting microbial metabolism.Mixing Pinus massoniana litter and three broadleaved litters may increase the diversity and abundance of fungal decomposers compared with those in P.massoniana litter and vary depending on the number and proportion of broadleaved species included.Methods We analysed the composition and diversity of fungal communities during mixed litter decomposition in southwestern China with 35 treatments(P.massoniana,Toona sinensis,Cinnamomum camphora and Sassafras tzumu litter)using Illumina high-throughput sequencing.Important Findings The mixed litters increased fungal diversity and richness compared with those in the single-species litter,except in the following treatments:P.massoniana litter accounting for 70%-80%in the P.massoniana+T.sinensis,P.massoniana+S.tzumu+T.sinensis and P.massoniana+S.tzumu+C.camphora combinations,and P.massoniana+S.tzumu+C.camphora+T.sinensis combination with small proportion of T.sinensis litter.The diversity and richness of the 7:1:2 combination of P.massoniana+C.camphora+T.sinensis were significantly higher than those in the other treatments.Ascomycota and Basidiomycota were the dominant phyla,and Aspergillus was the most abundant genus.The decomposition of litters from one needleleaf and one broadleaved species(6:4)and one needleleaf species and two broadleaved species(broadleaved litter accounting for 30%-40%)exhibited synergistic interactions throughout the decomposition process,and the relative abundance of fungi that decompose refractory substances increased.The P.massoniana+C.camphora+T.sinensis combination and a 30%-40%broadleaf litter proportion increased fungal diversity and accelerated the decomposition of recalcitrant coniferous litter.Therefore,C.camphora and T.sinensis are a potential candidate species for mixed planting with P.massoniana.展开更多
The accumulation of soil organic matter and nutrients is an important pathway in effectivelyunderstanding the mechanisms of plant settlement and rock weathering, while the characteristics ofsoil organic carbon (C), ni...The accumulation of soil organic matter and nutrients is an important pathway in effectivelyunderstanding the mechanisms of plant settlement and rock weathering, while the characteristics ofsoil organic carbon (C), nitrogen (N) and phosphorus (P) under different vegetation remain unclear.In this study, the stocks and stoichiometry of soil organic C, N and P were determined in differentpositions and types of vegetation on the surface of the Leshan Giant Buddha. We found that the totalstocks of soil organic C, N and P were 1689.77, 134.6 and 29.48 kg, respectively, for the Buddha.The stocks of soil organic C, N and P under vascular plants were higher than those under othervegetation, with highest values observed under herb. Higher stocks per unit area (m2) of soil organicC, N and P were found on the left and right arms, shoulders, and two platforms. These results providea full primary picture in understanding soil organic C, N and P accumulation and distribution on thesurface of the Buddha, which could supply the fundamental data on weathering management of theBuddha and other similar open-air stone carvings.展开更多
Aims Plant litter decomposition is a key ecosystem process that determines carbon and nutrient cycling in terrestrial ecosystems.As a main component of litter,cellulose is a vital energy source for the microbes associ...Aims Plant litter decomposition is a key ecosystem process that determines carbon and nutrient cycling in terrestrial ecosystems.As a main component of litter,cellulose is a vital energy source for the microbes associated with litter decomposition.The important role of cellulolytic enzymes in litter cellulose degradation is well understood,but seasonal patterns of cellulose degradation and whether cumulative enzyme activities and litter quality forecast cellulose degradation in an alpine meadow remain elusive,which limits our understanding of cellulose degradation in herbaceous plant litter.Methods A two-year field litterbag experiment involving three dominant species(Ajuga ovalifolia,Festuca wallichanica,and Pedicularis roylei)was conducted in an alpine meadow of the eastern Tibetan Plateau to explore the seasonal patterns of cellulose degradation and how cumulative cellulolytic enzyme activities and initial litter quality impact cellulose degradation.Important findings Our study demonstrates that cellulose degraded rapidly and exceeded 50%during the first year,which mainly occurred in the first growing season(31.9%–43.3%).At two years of decomposition,cellulose degradation was driven by cumulative endoglucanase(R^(2)=0.70),cumulative cellobiohydrolase(R^(2)=0.59)and cumulative 1,4-β-glucosidase(R^(2)=0.57).In addition,the concentrations of cellulose,dissolved organic carbon,total phenol,lignin and lignin/N accounted for 52%–78%of the variation in cellulose degradation during the two years of decomposition.The best model for predicting cellulose degradation was the initial cellulose concentration(R^(2)=0.78).The enzymatic efficiencies and the allocation of cellulolytic enzyme activities were different among species.The cellulolytic enzyme efficiencies were higher in the litter of F.wallichanica with relatively lower quality.For the complete cellulose degradation of the leaf litter,A.ovalifolia and F.wallichanica required 4-fold and 6.7-fold more endoglucanase activity,3-fold and 4.5-fold more cellobiohydrolase activity and 1.2-fold and 1.4-fold more 1,4-β-glucosidase activity,respectively,than those required by P.roylei.Our results demonstrated that although microbial activity and litter quality both have significant impacts on cellulose degradation in an alpine meadow,using cellulose concentration to predict cellulose degradation is a good way to simplify the model of cellulose degradation and C cycling during litter decomposition.展开更多
A high-quality snow depth product is very import for cryospheric science and its related disciplines.Current long time-series snow depth products covering the Northern Hemisphere can be divided into two categories:rem...A high-quality snow depth product is very import for cryospheric science and its related disciplines.Current long time-series snow depth products covering the Northern Hemisphere can be divided into two categories:remote sensing snow depth products and reana-lysis snow depth products.However,existing gridded snow depth products have some shortcomings.Remote sensing-derived snow depth products are temporally and spatially discontinuous and tend to underestimate snow depth,while reanalysis snow depth products have coarse spatial resolutions and great uncertainties.To overcome these problems,in our previous work we proposed a novel data fusion framework based on Random Forest Regression of snow products from Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E),Advanced Microwave Scanning Radiometer-2(AMSR2),Global Snow Monitoring for Climate Research(GlobSnow),the Northern Hemisphere Snow Depth(NHSD),ERA-Interim,and Modern-Era Retrospective Analysis for Research and Applications,ver-sion 2(MERRA-2),incorporating geolocation(latitude and longitude),and topographic data(elevation),which were used as input indepen-dent variables.More than 30,000 ground observation sites were used as the dependent variable to train and validate the model in different time periods.This fusion framework resulted in a long time series of continuous daily snow depth product over the Northern Hemisphere with a spatial resolution of 0.25°.Here,we compared the fused snow depth and the original gridded snow depth products with 13,272 observation sites,showing an improved precision of our product.The evaluation indices of the fused(best original)dataset yielded a coeffi-cient of determination R2 of 0.81(0.23),Root Mean Squared Error(RMSE)of 7.69(15.86)cm,and Mean Absolute Error(MAE)of 2.74(6.14)cm.Most of the bias(88.31%)between the fused snow depth and in situ observations was in the range of−5 cm to 5 cm.The accuracy assessment of independent snow observation sites-Sodankylä(SOD),Old Aspen(OAS),Old Black Spruce(OBS),and Old Jack Pine(OJP)-showed that the fused snow depth dataset had high precision for snow depths of less than 100 cm with a relatively homogeneous surrounding environment.The results of random point selection and independent in situ site validation show that the accuracy of the fused snow depth product is not significantly improved in deep snow areas and areas with complex terrain.In the altitude range of 100 m to 2000 m,the fused snow depth had a higher precision,with R2 varying from 0.73 to 0.86.The fused snow depth had a decreasing trend based on the spatiotemporal analysis and Mann-Kendall trend test method.This fused snow depth product provides the basis for understanding the temporal and spatial characteristics of snow cover and their relation to climate change,hydrological and water cycle,water resource manage-ment,ecological environment,snow disaster and hazard prevention.展开更多
基金financially supported by the National Natural Science Foundation of China(31670526,31622018,31570445 and 31500509)the Doctoral Scientific Fund Project of the Ministry of Education of China(20135103110002)
文摘The dynamics of litter nitrogen (N) and phosphorus (P) release could be affected by soil fauna and environmental conditions. The objective of the present study was to investigate the effects of soil fauna on the dynamics of N and P during foliar litter decomposition in three types of ecosystems (i.e., montane forest, ecotone, and dry valley) along an elevation gradient. A field experiment using litterbags with two different mesh sizes (0.04 and 3 mm) was conducted from November 2013 to October 2014. Nitrogen and P release rates in decomposing foliar litter from fir (Abies faxoniana) and birch (Betula albosinensis) in montane forest, oak (Quercus baronii) and cypress (Cupressus chengiana) in ecotone, and cypress and clovershrub (Campylotropis macrocarpa) in dry valley were investigated in the upper reaches of the Yangtze River. Soil fauna strongly affected N and P release across different decomposition periods and ecosystem types. The average release rate of N mediated by soil fauna across the entire year was higher in the dry valley (15.6–37.3%) than in the montane forest (0.5–6.4%) and the ecotone (- 3.7–4.9%). The effects of soil fauna on P release rate were manifest in both the montane forest and the dry valley. Moreover, the impacts of soil fauna can vary substantially among different decomposition periods. Our results indicated that soil fauna can significantly affect N and P release during litter decomposition. The N release rate mediated by fauna was likely to be more sensitive to the effects of plant species (i.e., initial litter chemical traits), while the P release rate mediated by soil fauna might be subject to the effects of local-scale environmental factors (e.g., temperature) to a greater extent.
基金supported by the National Natural Science Foundation of China(3157044531570601+2 种基金31500509 and31570605)Postdoctoral Science Foundation of China(2013M540714 and 2014T70880)Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangze River
文摘Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter decomposition in those ecosystems. Here, we conducted a2-year-long litter decomposition experiment along an elevational gradient from 3000 to 3600 m to determine the potential effects of litter quality, climate warming and freeze-thaw on the mass losses of three litter types [dragon spruce（Picea asperata Mast.）, red birch（Betula albosinensis Burk.）, and minjiang fir（Abies faxoniana Rehd. et Wild）]. Marked differences in mass loss were observed among the litter types and sampling dates. Decay constant（k） values of red birch were significantly higher than those of the needle litters. However, mass losses between elevations did not differ significantly for any litter type.During the winter, lost mass contributed 18.3-28.8 % of the net loss rates of the first year. Statistical analysis showed that the relationships between mass loss and litter chemistry or their ratios varied with decomposition periods. Our results indicated that short-term field incubations could overestimate the k value of litter decomposition.Considerable mass was lost from subalpine forest litters during the wintertime. Potential future warming may not affect the litter decomposition in the subalpine forest ecosystems of eastern Tibetan Plateau.
基金supported by the National Natural Science Foundation of China(Grant Number 31370628)the National Science and Technology Support Project of China(Grant Number2011BAC09B05)the Sichuan Provincial Science and Technology Support Project(Grant Number 12ZC0017)
文摘To understand the decomposition characteristics of Pinus massoniana foliar litter and the degradation of its refractory compounds in plantations under five canopy densities,a litter bag experiment over a decomposition time of 392 days was carried out.The results show that canopy density significantly affected decomposition rates of litter and degradation rate of lignin and cellulose.Litter decomposition rates decreased significantly with decreasing canopy density.Both lignin and cellulose degradation rates were lower with canopy densities of 0.62 and 0.74 as compared with the three other densities.Lignin and cellulose losses were more rapid in the first 118 days.Soil fauna had significant impacts on litter decomposition and the degradation of refractory compounds.Canopy density had significant effects on factors such as soil properties and soil fauna community structure,which could be conducive to the decomposition of litter and the degradation of litter recalcitrant components.Canopy density between 0.6 and 0.7 might be a favorable management practice promoting litter decomposition and beneficial for the sustainable development of P.massoniana plantations.
文摘By combining the observation of the soil profile at field and the chemical and physical analysis in laboratory, a study on the hydro-physical properties of soil in six different vegetation types and the dynamics of water content after rain was conducted in Wanchanggou, Guangyuan City to find out the vegetation types with effective water-conservation functions in order to serve the ecological restoration in the low hill heavy rain area upper the Jialing River. Results showed that., the hydro-physical properties of soil in the mixed Alnus crernastogyne and Cupressua Leyland forest （AcCl） were best. But in the depth of 0-20 cm. The properties of soil in the abandoned cropland （Fm） was better than that in the AcCl. The soil bulk densities varied significantly between the layers of 0-20 cm and 20-40 cm in all the six vegetation types except that in the Robinia pseudoacacia shrub forest （RpII）, and the changes of the maximum and the capillary moisture capacity between layers were significant only in the Fm and in the AcCl. Of these stands, the AcCl had the shortest water-absorbing period and the strongest moisture changes in the upper layer （0-15 cm）. In the same stand, the deeper the soil layer, the slighter the soil moisture varied, and the longer the soil moisture accumulating process lasted.
基金funding from National Natural Science Foundation of China(No.31870387),China Scholarship Council.
文摘Background:Stem CO_(2) efflux(E_(S))plays a critical role in the carbon budget of forest ecosystems.Thinning is a core practice for sustainable management of plantations.It is therefore necessary and urgent to study the effect and mechanism of thinning intensity(TI)on E_(S).Methods:In this study,five TIs were applied in Larix principis-rupprechtii Mayr 21-,25-,and 41-year-old stands in North China in 2010.Portable infrared gas analyzer(Li-8100 A)was used to measure ES and its association with environmental factors at monthly intervals from May to October in 2013 to 2015.In addition,nutrients,wood structure and nonstructural carbon(NSC)data were measured in August 2016.Results:The results show that ES increased with increasing TI.The maximum ES values occurred at a TI of 35%(3.29,4.57 and 2.98μmol·m^(-2)·s^(-1))and were 1.54-,1.94-and 2.89-fold greater than the minimum E_(S) value in the CK stands(2.14,2.35 and 1.03μmol·m^(-2)·s^(-1))in July for the 21-,25-and 41-year-old forests,respectively.The E_(S) of the trees in low-density stands was more sensitive to temperature than that of the trees in high-density stands.Soluble sugars(SS)and temperature are the main factors affecting ES.When the stand density is low enough as 41-year-old L.principis-rupprechtii forests with TI 35%,bark thickness(BT)and humidity should be considered in addition to air temperature(T_(a)),wood temperature(T_(w)),sapwood width(SW),nitrogen concentration(N)and SS in the evaluation of ES.If a change in stand density is ignored,the CO_(2) released from individual 21-,25-and 41-year-old trees could be underestimated by 168.89%,101.94% and 200.49%,respectively.CO_(2) release was estimated based on the stem equation in combination with the factors influencing ES for reference.Conclusions:We suggest that it is not sufficient to conventional models which quantify ES only by temperature and that incorporating the associated drivers(e.g.density,SS,SW and N)based on stand density into conventional models can improve the accuracy of ES estimates.
基金funded by the National Key R&D Program of China (Grant No. 2017YFC0503906)the Nation Nature Science Foundation of China (Grant Nos. 31570445, 31622018, 31670526 and 31901295)the Sichuan Province and Technology Project for Youth Innovation Team (Grant No. 2017TD0022)
文摘Reducing the threats of sulfate ion(SO42-)deposition to terrestrial ecosystems is a great challenge.The canopy interception effect on SO42-deposition has been well documented,but the interception efficiency of the gap edge remains unknown.Therefore,a subalpine dragon spruce(Picea asperata)plantation was evaluated in the upper reaches of the Yangtze River.The dynamics of the SO42-concentration in the throughfall were investigated from the gap edge to the closed canopy during the rainfall and snowfall periods from August 2015 to July 2016.The annual input of SO42-totaled 2.56 kg/ha through rainfall and 0.69 kg/ha through snowfall.The total annual net interception fluxes(NIFs)of SO42-at the gap edge and in the closed canopy were 1.48 kg/ha and 0.66 kg/ha,respectively,and the net interception ratios(NIRs)accounted for 45.40%and 20.25%,respectively.The NIF and the NIR of SO42-at the gap edge were higher than those in the closed canopy.Therefore,the results suggested that a significant amount of SO42-deposition was intercepted by the tree canopy in the subalpine plantation,with more SO42-deposition at the gap edge than in the closed canopy,which is beneficial for improving the water quality in the upper reaches of the Yangtze River via forest management.
基金funded by the National Nature Science Foundation of China (No.32171775,31770671)。
文摘Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.
基金supported by the Knowledge Innovation Program of Chinese Academy of Sciences (Nos. KZCX2-YW-312 and KZCX2-YW-406-2)the National Natural Science Foundation of China (No. 40621001)
文摘Soil productivity is the ability of a soil, in its normal environment, to support plant growth and can be evaluated with respect to crop production in unfertilized soil within the agricultural ecosystem. Both soil productivity and fertilizer applications affect crop yields. A long-term experiment with a winter wheat-summer maize rotation was established in 1989 in a field of the Fengqiu State Key Agro-Ecological Experimental Station, a region typical of the North China Plain, including seven treatments： 1） a balanced application of NPK chemical fertilizers （NPK）; 2） application of organic fertilizer （OM）; 3） application of 50% organic fertilizer and 50% NPK chemical fertilizers （1/2OMN）; 4） application of NP chemical fertilizers （NP）; 5） application of PK chemical fertilizer （PK）; 6） application of NK chemical fertilizers （NK）; and 7） unfertilized control （CK）. To investigate the effects of fertilization practices on soil productivity, further pot tests were conducted in 2007-2008 using soil samples from the different fertilization treatments of the long-term field experiment. The soil sample of each treatment of the long-term experiment was divided into three pots to grow wheat： with no fertilization （Potunf）, with balanced NPK fertilization （POtNPK）, and with the same fertilizer（s） of the long-term field experiment （Potori）. The fertilized soils of the field experiment used in all the pot tests showed a higher wheat grain yield and higher nutrient uptake levels than the unfertilized soil. Soil productivity of the treatments of the field experiment after 18 years of continuous fertilizer applications were ranked in the order of OM 〉 1/2OMN 〉 NPK 〉 NP 〉 PK 〉 NK 〉 CK. The contribution of soil productivity of the different treatments of the field experiment to the wheat grain yield of Potori was 36.0%-76.7%, with the PK and NK treatments being higher than the OM, 1/2OMN, NPK, and NP treatments since the soil in this area was deficient in N and P and rich in K. Wheat grain yields of PotNPK were higher than those of Potori and Potunf. The N, P, and K use efficiencies were higher in POtNPK than Potori and significantly positively correlated with wheat grain yield. Soil organic matter could be a better predictor of soil productivity because it correlated more strongly than other nutrients with the wheat grain yield of Potuf. Wheat yields of POtNPK showed a similar trend to those of Potunf, indicating that soil productivity improvement was essential for a further increase in crop yield. The long-term applications of both organic and chemical fertilizers were capable of increasing soil productivity on the North China Plain, but the former was more effective than the latter. The balanced application of NPK chemical fertilizers not only increased soil productivity, but also largely increased crop yields, especially in soils with lower productivity. Thus, such an approach should be a feasible practice for the sustainable use of agricultural soils on the North China Plain, particularly when taking into account crop yields, labor costs, and the limited availability of organic fertilizers.
基金supported by an innovation research project of the National Natural Science Foundation of China(no.31370628)the National Science and Technology Support Project of China(no.2011BAC09B05).
文摘Aims The conifer litter is fairly recalcitrant and nutrient poor,and broadleaved litter promotes coniferous litter decomposition by increasing degradable nutrients and promoting microbial metabolism.Mixing Pinus massoniana litter and three broadleaved litters may increase the diversity and abundance of fungal decomposers compared with those in P.massoniana litter and vary depending on the number and proportion of broadleaved species included.Methods We analysed the composition and diversity of fungal communities during mixed litter decomposition in southwestern China with 35 treatments(P.massoniana,Toona sinensis,Cinnamomum camphora and Sassafras tzumu litter)using Illumina high-throughput sequencing.Important Findings The mixed litters increased fungal diversity and richness compared with those in the single-species litter,except in the following treatments:P.massoniana litter accounting for 70%-80%in the P.massoniana+T.sinensis,P.massoniana+S.tzumu+T.sinensis and P.massoniana+S.tzumu+C.camphora combinations,and P.massoniana+S.tzumu+C.camphora+T.sinensis combination with small proportion of T.sinensis litter.The diversity and richness of the 7:1:2 combination of P.massoniana+C.camphora+T.sinensis were significantly higher than those in the other treatments.Ascomycota and Basidiomycota were the dominant phyla,and Aspergillus was the most abundant genus.The decomposition of litters from one needleleaf and one broadleaved species(6:4)and one needleleaf species and two broadleaved species(broadleaved litter accounting for 30%-40%)exhibited synergistic interactions throughout the decomposition process,and the relative abundance of fungi that decompose refractory substances increased.The P.massoniana+C.camphora+T.sinensis combination and a 30%-40%broadleaf litter proportion increased fungal diversity and accelerated the decomposition of recalcitrant coniferous litter.Therefore,C.camphora and T.sinensis are a potential candidate species for mixed planting with P.massoniana.
基金This work was partially supported by the National Natural Science Foundation of China(31470636).
文摘The accumulation of soil organic matter and nutrients is an important pathway in effectivelyunderstanding the mechanisms of plant settlement and rock weathering, while the characteristics ofsoil organic carbon (C), nitrogen (N) and phosphorus (P) under different vegetation remain unclear.In this study, the stocks and stoichiometry of soil organic C, N and P were determined in differentpositions and types of vegetation on the surface of the Leshan Giant Buddha. We found that the totalstocks of soil organic C, N and P were 1689.77, 134.6 and 29.48 kg, respectively, for the Buddha.The stocks of soil organic C, N and P under vascular plants were higher than those under othervegetation, with highest values observed under herb. Higher stocks per unit area (m2) of soil organicC, N and P were found on the left and right arms, shoulders, and two platforms. These results providea full primary picture in understanding soil organic C, N and P accumulation and distribution on thesurface of the Buddha, which could supply the fundamental data on weathering management of theBuddha and other similar open-air stone carvings.
基金National Natural Science Foundation of China[31200345,31570605 and 31370628]China Scholarship Council(201706910039) to Y.C.(joint Ph.D.programme grant).
文摘Aims Plant litter decomposition is a key ecosystem process that determines carbon and nutrient cycling in terrestrial ecosystems.As a main component of litter,cellulose is a vital energy source for the microbes associated with litter decomposition.The important role of cellulolytic enzymes in litter cellulose degradation is well understood,but seasonal patterns of cellulose degradation and whether cumulative enzyme activities and litter quality forecast cellulose degradation in an alpine meadow remain elusive,which limits our understanding of cellulose degradation in herbaceous plant litter.Methods A two-year field litterbag experiment involving three dominant species(Ajuga ovalifolia,Festuca wallichanica,and Pedicularis roylei)was conducted in an alpine meadow of the eastern Tibetan Plateau to explore the seasonal patterns of cellulose degradation and how cumulative cellulolytic enzyme activities and initial litter quality impact cellulose degradation.Important findings Our study demonstrates that cellulose degraded rapidly and exceeded 50%during the first year,which mainly occurred in the first growing season(31.9%–43.3%).At two years of decomposition,cellulose degradation was driven by cumulative endoglucanase(R^(2)=0.70),cumulative cellobiohydrolase(R^(2)=0.59)and cumulative 1,4-β-glucosidase(R^(2)=0.57).In addition,the concentrations of cellulose,dissolved organic carbon,total phenol,lignin and lignin/N accounted for 52%–78%of the variation in cellulose degradation during the two years of decomposition.The best model for predicting cellulose degradation was the initial cellulose concentration(R^(2)=0.78).The enzymatic efficiencies and the allocation of cellulolytic enzyme activities were different among species.The cellulolytic enzyme efficiencies were higher in the litter of F.wallichanica with relatively lower quality.For the complete cellulose degradation of the leaf litter,A.ovalifolia and F.wallichanica required 4-fold and 6.7-fold more endoglucanase activity,3-fold and 4.5-fold more cellobiohydrolase activity and 1.2-fold and 1.4-fold more 1,4-β-glucosidase activity,respectively,than those required by P.roylei.Our results demonstrated that although microbial activity and litter quality both have significant impacts on cellulose degradation in an alpine meadow,using cellulose concentration to predict cellulose degradation is a good way to simplify the model of cellulose degradation and C cycling during litter decomposition.
基金supported by the National Science Fund for Distinguished Young Scholars(no.42125604)the National Nature Science Foundation of China(no.41771389,no.42001289 and no.42201159)the CAS‘Light of West China’Program(E029070101).
文摘A high-quality snow depth product is very import for cryospheric science and its related disciplines.Current long time-series snow depth products covering the Northern Hemisphere can be divided into two categories:remote sensing snow depth products and reana-lysis snow depth products.However,existing gridded snow depth products have some shortcomings.Remote sensing-derived snow depth products are temporally and spatially discontinuous and tend to underestimate snow depth,while reanalysis snow depth products have coarse spatial resolutions and great uncertainties.To overcome these problems,in our previous work we proposed a novel data fusion framework based on Random Forest Regression of snow products from Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E),Advanced Microwave Scanning Radiometer-2(AMSR2),Global Snow Monitoring for Climate Research(GlobSnow),the Northern Hemisphere Snow Depth(NHSD),ERA-Interim,and Modern-Era Retrospective Analysis for Research and Applications,ver-sion 2(MERRA-2),incorporating geolocation(latitude and longitude),and topographic data(elevation),which were used as input indepen-dent variables.More than 30,000 ground observation sites were used as the dependent variable to train and validate the model in different time periods.This fusion framework resulted in a long time series of continuous daily snow depth product over the Northern Hemisphere with a spatial resolution of 0.25°.Here,we compared the fused snow depth and the original gridded snow depth products with 13,272 observation sites,showing an improved precision of our product.The evaluation indices of the fused(best original)dataset yielded a coeffi-cient of determination R2 of 0.81(0.23),Root Mean Squared Error(RMSE)of 7.69(15.86)cm,and Mean Absolute Error(MAE)of 2.74(6.14)cm.Most of the bias(88.31%)between the fused snow depth and in situ observations was in the range of−5 cm to 5 cm.The accuracy assessment of independent snow observation sites-Sodankylä(SOD),Old Aspen(OAS),Old Black Spruce(OBS),and Old Jack Pine(OJP)-showed that the fused snow depth dataset had high precision for snow depths of less than 100 cm with a relatively homogeneous surrounding environment.The results of random point selection and independent in situ site validation show that the accuracy of the fused snow depth product is not significantly improved in deep snow areas and areas with complex terrain.In the altitude range of 100 m to 2000 m,the fused snow depth had a higher precision,with R2 varying from 0.73 to 0.86.The fused snow depth had a decreasing trend based on the spatiotemporal analysis and Mann-Kendall trend test method.This fused snow depth product provides the basis for understanding the temporal and spatial characteristics of snow cover and their relation to climate change,hydrological and water cycle,water resource manage-ment,ecological environment,snow disaster and hazard prevention.
