Gross primary production(GPP)is a crucial indicator representing the absorption of atmospheric CO_(2) by vegetation.At present,the estimation of GPP by remote sensing is mainly based on leaf-related vegetation indexes...Gross primary production(GPP)is a crucial indicator representing the absorption of atmospheric CO_(2) by vegetation.At present,the estimation of GPP by remote sensing is mainly based on leaf-related vegetation indexes and leaf-related biophysical para-meter leaf area index(LAI),which are not completely synchronized in seasonality with GPP.In this study,we proposed chlorophyll content-based light use efficiency model(CC-LUE)to improve GPP estimates,as chlorophyll is the direct site of photosynthesis,and only the light absorbed by chlorophyll is used in the photosynthetic process.The CC-LUE model is constructed by establishing a linear correlation between satellite-derived canopy chlorophyll content(Chlcanopy)and FPAR.This method was calibrated and validated utiliz-ing 7-d averaged in-situ GPP data from 14 eddy covariance flux towers covering deciduous broadleaf forest ecosystems across five dif-ferent climate zones.Results showed a relatively robust seasonal consistency between Chlcanopy with GPP in deciduous broadleaf forests under different climatic conditions.The CC-LUE model explained 88% of the in-situ GPP seasonality for all validation site-year and 56.0% of in-situ GPP variations through the growing season,outperforming the three widely used LUE models(MODIS-GPP algorithm,Vegetation Photosynthesis Model(VPM),and the eddy covariance-light use efficiency model(EC-LUE)).Additionally,the CC-LUE model(RMSE=0.50 g C/(m^(2)·d))significantly improved the underestimation of GPP during the growing season in semi-arid region,re-markably decreasing the root mean square error of averaged growing season GPP simulation and in-situ GPP by 75.4%,73.4%,and 37.5%,compared with MOD17(RMSE=2.03 g C/(m^(2)·d)),VPM(RMSE=1.88 g C/(m^(2)·d)),and EC-LUE(RMSE=0.80 g C/(m^(2)·d))model.The chlorophyll-based method proved superior in capturing the seasonal variations of GPP in forest ecosystems,thereby provid-ing the possibility of a more precise depiction of forest seasonal carbon uptake.展开更多
A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen (N) fluxes of typical N compounds (NH3, NH4-N, NO3-N, and NO2) and contribution of three sources (gas, ra...A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen (N) fluxes of typical N compounds (NH3, NH4-N, NO3-N, and NO2) and contribution of three sources (gas, rainwater, and particles) to N deposition. From July 2003 to June 2004, the total atmospheric N deposition was 70.7 kg N ha-1, with dry deposition accounting for 75% of the total deposition. Dry NH3 deposition accounted for 73% of the dry deposition and 55% of the total deposition. Moreover, NO2 contributed 11% of the dry deposition and 8% of the total deposition. Reduced N compounds (NH4+ and NH3) were the predominate contributors, accounting for 66% of the total deposition. Therefore, atmospheric N deposition should be considered when soil acidification and critical loads of atmospheric deposition on soils are estimated.展开更多
Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern Ch...Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower （P 〈0.05） organic C and total N in the soil （0-100 cm） compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0-10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels （P 〈0.05） of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.展开更多
To study the role of leaf litter in the mercury （Hg） cycle in suburban broadleaf forests and the distribution of Hg in urban forests, we collected leaf litter and soil from suburban evergreen and deciduous broadleaf...To study the role of leaf litter in the mercury （Hg） cycle in suburban broadleaf forests and the distribution of Hg in urban forests, we collected leaf litter and soil from suburban evergreen and deciduous broadleaf forests and from urban forests in Beijing. The Hg concentrations in leaf litter from the suburban forests varied from 8.3 to 205.0 ng/g, with an average （avg） of （49.7 ± 36.9） ng/g. The average Hg concentration in evergreen broadleaf forest leaf litter （50.8 ± 39.4） ng/g was higher than that in deciduous broadleaf forest leaf litter （25.8 ± 10.1） ng/g. The estimated Hg fluxes of leaf litter in suburban evergreen and deciduous broadleaf forests were 179.0 and 83.7 mg/（ha·yr）, respectively. The Hg concentration in organic horizons （O horizons） （（263.1 ± 237.2） ng/g） was higher than that in eluvial horizons （A horizons） （（83.9 ± 52.0） ng/g）. These results indicated that leaf litterfall plays an important role in transporting atmospheric mercury to soil in suburban forests. For urban forests in Beijing, the Hg concentrations in leaf litter ranged from 8.8–119.0 （avg 28.1 ± 16.6） ng/g, with higher concentrations at urban sites than at suburban sites for each tree. The Hg concentrations in surface soil in Beijing were 32.0–25300.0 ng/g and increased from suburban sites to urban sites, with the highest value from Jingshan （JS） Park at the centre of Beijing. Therefore, the distribution of Hg in Beijing urban forests appeared to be strongly influenced by anthropogenic activities.展开更多
To study the effect of thinning intensity on the carbon sequestration by natural mixed coniferous and broad-leaf forests in Xiaoxing’an Mountains,China,we established six 100 m×100 m experimental plots in Dongfa...To study the effect of thinning intensity on the carbon sequestration by natural mixed coniferous and broad-leaf forests in Xiaoxing’an Mountains,China,we established six 100 m×100 m experimental plots in Dongfanghong For-est that varied in thinning intensity:plot A(10%),B(15%),C(20%),D(25%),E(30%),F(35%),and the control sample area(0%).A principal component analysis was performed using 50 different variables,including species diversity,soil fertility,litter characteristics,canopy structure param-eters,and seedling regeneration parameters.The effects of thinning intensity on carbon sequestration were strongest in plot E(0.75),followed by D(0.63),F(0.50),C(0.48),B(0.22),A(0.11),and the control(0.06).The composite score of plot E was the highest,indicating that the carbon sequestration effect was strongest at a thinning intensity of 30%.These findings provide useful insights that could aid the management of natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains,China.This information has implications for future studies of these forests,and the methods used could aid future ecological assessments of the natural forests in Xiaoxing’an Mountains,China.展开更多
Aims Understanding of the ecophysiological dynamics of forest canopy photosynthesis and its spatial and temporal scaling is crucial for revealing ecological response to climate change.Combined observations and analyse...Aims Understanding of the ecophysiological dynamics of forest canopy photosynthesis and its spatial and temporal scaling is crucial for revealing ecological response to climate change.Combined observations and analyses of plant ecophysiology and optical remote sensing would enable us to achieve these studies.In order to examine the utility of spectral vegetation indices(VIs)for assessing ecosystem-level photosynthesis,we investigated the relationships between canopy-scale photosynthetic productivity and canopy spectral reflectance over seasons for 5 years in a cool,temperate deciduous broadleaf forest at‘Takayama’super site in central Japan.Methods Daily photosynthetic capacity was assessed by in situ canopy leaf area index(LAI),(LAI×Vcmax[single-leaf photosynthetic capacity]),and the daily maximum rate of gross primary production(GPPmax)was estimated by an ecosystem carbon cycle model.We examined five VIs:normalized difference vegetation index(NDVI),enhanced vegetation index(EVI),green–red vegetation index(GRVI),chlorophyll index(CI)and canopy chlorophyll index(CCI),which were obtained by the in situ measurements of canopy spectral reflectance.Important Findings Our in situ observation of leaf and canopy characteristics,which were analyzed by an ecosystem carbon cycling model,revealed that their phenological changes are responsible for seasonal and interannual variations in canopy photosynthesis.Significant correlations were found between the five VIs and canopy photosynthetic capacity over the seasons and years;four of the VIs showed hysteresis-type relationships and only CCI showed rather linear relationship.Among the VIs examined,we applied EVI–GPPmax relationship to EVI data obtained by Moderate Resolution Imaging Spectroradiometer to estimate the temporal and spatial variation in GPPmax over central Japan.Our findings would improve the accuracy of satellite-based estimate of forest photosynthetic productivity in fine spatial and temporal resolutions,which are necessary for detecting any response of terrestrial ecosystem to meteorological fluctuations.展开更多
Satellite-based remote sensed phenology has been widely used to assess global climate change.However,it is constrained by uncertain linkages with photo-synthesis activity.Two dynamic threshold methods were employed to...Satellite-based remote sensed phenology has been widely used to assess global climate change.However,it is constrained by uncertain linkages with photo-synthesis activity.Two dynamic threshold methods were employed to retrieve spring phenology metrics from four Moderate Resolution Imaging Spectro-radiometer(MODIS)products,including fraction of Absorbed Photosyntheti-cally Active Radiation(fAPAR),Leaf Area Index(LAI),Normalized Difference Vegetation Index(NDVI),and Enhanced Vegetation Index(EVI)for three temperate deciduous broadleaf forests in North America between 2001 and 2009.These MODIS-based spring phenology metrics were subsequently linked to the photosynthetic curves(daily gross primary productivity,GPP)measured by an eddy covariance flux tower.The 20% dynamic threshold spring onset metrics from MODIS products were closer to the photosynthesis onset metrics at the date of 2% GPP increase for NDVI and fAPAR,and closer to the date of 5%and 10% increase of GPP for EVI and LAI,respectively.The 50% dynamic threshold onset metrics were closer to the photosynthesis onset metrics at the date of 10%GPP increase for NDVI,and closer to the date of 20% GPP increase for fAPAR,LAI and EVI,respectively.These results can improve our knowledge on the photosynthesis activity status of remotely sensed spring phenology metrics.展开更多
Increasing attention is being paid to the various functions of forests, especially the conservation of biodiversity. In Japan, 67% of national land is covered by forest, 41% of which is artificial forest (i.e., planta...Increasing attention is being paid to the various functions of forests, especially the conservation of biodiversity. In Japan, 67% of national land is covered by forest, 41% of which is artificial forest (i.e., plantations). Therefore, efforts to conserve forest biodiversity should also target artificial forests. In this study, we investigated the increase in biodiversity resulting from broadleaf tree invasion of artificial coniferous forests. We examined diversity indices and combinations of indices to identify which ones can aid forest managers in evaluating forest diversity. We also studied classification according to the richness of diversity, which corresponded to the growth stages of Chamaecyparisobtusa and Cryptomeria japonica plantation forests. Moreover, we developed a model that will contribute to sustainable forest management and biodiversity over an entire area. The model, based on a specific rotation scenario in a geographic information system, is easy to use and presents spatial and temporal changes at sites visually.展开更多
In order to clarify the influence of different forest types on soil erosion resistance in water source area of Central Yunnan,with the soils under three different kinds of typical forest in Yizhe watershed as the rese...In order to clarify the influence of different forest types on soil erosion resistance in water source area of Central Yunnan,with the soils under three different kinds of typical forest in Yizhe watershed as the research object,this paper uses field simulation method and principal component analysis to analyze the soil erosion resistance of three kinds of soils. The results show that there is a significant difference in the shear strength of soil among three types of typical forest,and the size of soil shear strength is in the order of Pinus yunnanensis forest land >mixed broadleaf-conifer forest land > eucalyptus forest land. The difference in the soil erosion coefficient among different forests is not significant,and the soil erosion resistance is highest in mixed broadleaf-conifer forest land( 39. 0%),followed by eucalyptus woodland( 37. 0%)and Pinus yunnanensis forest land( 24. 0%). Under heavy rain intensity and long duration of rainfall,the ability of soil under eucalyptus ×Pinus yunnanensis mixed forests to resist disintegration is more obvious. Using principal component analysis to analyze soil erosion resistance of soils under three different forests,we get the comprehensive evaluation model for soil erosion resistance: Y = 0. 763Y1+ 0. 236Y2. The soil erosion resistance is in the order of mixed broadleaf-conifer forest land( 0. 150) > eucalyptus forest land( 0. 127) > Pinus yunnanensis forest land(-0. 079),indicating that the mixed forests have better water loss and soil erosion control effect than pure forests.展开更多
基金Under the auspices of the National Key Research and Development Program of China(No.2019YFA0606603)。
文摘Gross primary production(GPP)is a crucial indicator representing the absorption of atmospheric CO_(2) by vegetation.At present,the estimation of GPP by remote sensing is mainly based on leaf-related vegetation indexes and leaf-related biophysical para-meter leaf area index(LAI),which are not completely synchronized in seasonality with GPP.In this study,we proposed chlorophyll content-based light use efficiency model(CC-LUE)to improve GPP estimates,as chlorophyll is the direct site of photosynthesis,and only the light absorbed by chlorophyll is used in the photosynthetic process.The CC-LUE model is constructed by establishing a linear correlation between satellite-derived canopy chlorophyll content(Chlcanopy)and FPAR.This method was calibrated and validated utiliz-ing 7-d averaged in-situ GPP data from 14 eddy covariance flux towers covering deciduous broadleaf forest ecosystems across five dif-ferent climate zones.Results showed a relatively robust seasonal consistency between Chlcanopy with GPP in deciduous broadleaf forests under different climatic conditions.The CC-LUE model explained 88% of the in-situ GPP seasonality for all validation site-year and 56.0% of in-situ GPP variations through the growing season,outperforming the three widely used LUE models(MODIS-GPP algorithm,Vegetation Photosynthesis Model(VPM),and the eddy covariance-light use efficiency model(EC-LUE)).Additionally,the CC-LUE model(RMSE=0.50 g C/(m^(2)·d))significantly improved the underestimation of GPP during the growing season in semi-arid region,re-markably decreasing the root mean square error of averaged growing season GPP simulation and in-situ GPP by 75.4%,73.4%,and 37.5%,compared with MOD17(RMSE=2.03 g C/(m^(2)·d)),VPM(RMSE=1.88 g C/(m^(2)·d)),and EC-LUE(RMSE=0.80 g C/(m^(2)·d))model.The chlorophyll-based method proved superior in capturing the seasonal variations of GPP in forest ecosystems,thereby provid-ing the possibility of a more precise depiction of forest seasonal carbon uptake.
基金Project supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No. ISSASIP0205)the National Key Basic Research Support Foundation of China (No. 1999011805)+3 种基金the State Key Laboratory of Soil and Sustainable Agriculture, Chinathe Scientific Research Foundation for Returned Overseas Chinese Scholarsthe State Education Ministry of Chinaand the National Natural Science foundation of China (No. 40305019)
文摘A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen (N) fluxes of typical N compounds (NH3, NH4-N, NO3-N, and NO2) and contribution of three sources (gas, rainwater, and particles) to N deposition. From July 2003 to June 2004, the total atmospheric N deposition was 70.7 kg N ha-1, with dry deposition accounting for 75% of the total deposition. Dry NH3 deposition accounted for 73% of the dry deposition and 55% of the total deposition. Moreover, NO2 contributed 11% of the dry deposition and 8% of the total deposition. Reduced N compounds (NH4+ and NH3) were the predominate contributors, accounting for 66% of the total deposition. Therefore, atmospheric N deposition should be considered when soil acidification and critical loads of atmospheric deposition on soils are estimated.
基金Project supported by the National Natural Science Foundation of China (No. 30170770).
文摘Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower （P 〈0.05） organic C and total N in the soil （0-100 cm） compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0-10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels （P 〈0.05） of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.
基金supported by the National Natural Science Foundation of China (No. 40803033, 41073092)
文摘To study the role of leaf litter in the mercury （Hg） cycle in suburban broadleaf forests and the distribution of Hg in urban forests, we collected leaf litter and soil from suburban evergreen and deciduous broadleaf forests and from urban forests in Beijing. The Hg concentrations in leaf litter from the suburban forests varied from 8.3 to 205.0 ng/g, with an average （avg） of （49.7 ± 36.9） ng/g. The average Hg concentration in evergreen broadleaf forest leaf litter （50.8 ± 39.4） ng/g was higher than that in deciduous broadleaf forest leaf litter （25.8 ± 10.1） ng/g. The estimated Hg fluxes of leaf litter in suburban evergreen and deciduous broadleaf forests were 179.0 and 83.7 mg/（ha·yr）, respectively. The Hg concentration in organic horizons （O horizons） （（263.1 ± 237.2） ng/g） was higher than that in eluvial horizons （A horizons） （（83.9 ± 52.0） ng/g）. These results indicated that leaf litterfall plays an important role in transporting atmospheric mercury to soil in suburban forests. For urban forests in Beijing, the Hg concentrations in leaf litter ranged from 8.8–119.0 （avg 28.1 ± 16.6） ng/g, with higher concentrations at urban sites than at suburban sites for each tree. The Hg concentrations in surface soil in Beijing were 32.0–25300.0 ng/g and increased from suburban sites to urban sites, with the highest value from Jingshan （JS） Park at the centre of Beijing. Therefore, the distribution of Hg in Beijing urban forests appeared to be strongly influenced by anthropogenic activities.
基金funded by National Key Research and development project(2022YFD2201001)Project for Applied TechnologyResearch and Development in Heilongjiang Province(GA19C006).
文摘To study the effect of thinning intensity on the carbon sequestration by natural mixed coniferous and broad-leaf forests in Xiaoxing’an Mountains,China,we established six 100 m×100 m experimental plots in Dongfanghong For-est that varied in thinning intensity:plot A(10%),B(15%),C(20%),D(25%),E(30%),F(35%),and the control sample area(0%).A principal component analysis was performed using 50 different variables,including species diversity,soil fertility,litter characteristics,canopy structure param-eters,and seedling regeneration parameters.The effects of thinning intensity on carbon sequestration were strongest in plot E(0.75),followed by D(0.63),F(0.50),C(0.48),B(0.22),A(0.11),and the control(0.06).The composite score of plot E was the highest,indicating that the carbon sequestration effect was strongest at a thinning intensity of 30%.These findings provide useful insights that could aid the management of natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains,China.This information has implications for future studies of these forests,and the methods used could aid future ecological assessments of the natural forests in Xiaoxing’an Mountains,China.
基金This long-term study was partly supported by the JSPS 21st Century COE Program at Gifu Universitythe JSPS-NRF-NSFS A3 Foresight Program,a Global Change Observation Mission(GCOM-C,PI#102)of the Japan Aerospace Exploration Agency(JAXA)+2 种基金the Global Environment Research Fund(S-1)and the Environment Research&Technology Development Fund(D-0909 and S-9)of the Ministry of Environment Japan,the JSPS KAKENHI(22310008)the JSPS‘Funding Program for Next Generation World-Leading Researchers(NEXT Program)’S.N.is supported by JSPS-KAKENHI(24710021,Grant-in-Aid for Young Scientists B).
文摘Aims Understanding of the ecophysiological dynamics of forest canopy photosynthesis and its spatial and temporal scaling is crucial for revealing ecological response to climate change.Combined observations and analyses of plant ecophysiology and optical remote sensing would enable us to achieve these studies.In order to examine the utility of spectral vegetation indices(VIs)for assessing ecosystem-level photosynthesis,we investigated the relationships between canopy-scale photosynthetic productivity and canopy spectral reflectance over seasons for 5 years in a cool,temperate deciduous broadleaf forest at‘Takayama’super site in central Japan.Methods Daily photosynthetic capacity was assessed by in situ canopy leaf area index(LAI),(LAI×Vcmax[single-leaf photosynthetic capacity]),and the daily maximum rate of gross primary production(GPPmax)was estimated by an ecosystem carbon cycle model.We examined five VIs:normalized difference vegetation index(NDVI),enhanced vegetation index(EVI),green–red vegetation index(GRVI),chlorophyll index(CI)and canopy chlorophyll index(CCI),which were obtained by the in situ measurements of canopy spectral reflectance.Important Findings Our in situ observation of leaf and canopy characteristics,which were analyzed by an ecosystem carbon cycling model,revealed that their phenological changes are responsible for seasonal and interannual variations in canopy photosynthesis.Significant correlations were found between the five VIs and canopy photosynthetic capacity over the seasons and years;four of the VIs showed hysteresis-type relationships and only CCI showed rather linear relationship.Among the VIs examined,we applied EVI–GPPmax relationship to EVI data obtained by Moderate Resolution Imaging Spectroradiometer to estimate the temporal and spatial variation in GPPmax over central Japan.Our findings would improve the accuracy of satellite-based estimate of forest photosynthetic productivity in fine spatial and temporal resolutions,which are necessary for detecting any response of terrestrial ecosystem to meteorological fluctuations.
基金The authors gratefully acknowledge financial support provided for this research by the National Natural Science Foundation of China(41222008,91125003)the External Cooperation Program of the Chinese Academy of Sciences(GJH21123).
文摘Satellite-based remote sensed phenology has been widely used to assess global climate change.However,it is constrained by uncertain linkages with photo-synthesis activity.Two dynamic threshold methods were employed to retrieve spring phenology metrics from four Moderate Resolution Imaging Spectro-radiometer(MODIS)products,including fraction of Absorbed Photosyntheti-cally Active Radiation(fAPAR),Leaf Area Index(LAI),Normalized Difference Vegetation Index(NDVI),and Enhanced Vegetation Index(EVI)for three temperate deciduous broadleaf forests in North America between 2001 and 2009.These MODIS-based spring phenology metrics were subsequently linked to the photosynthetic curves(daily gross primary productivity,GPP)measured by an eddy covariance flux tower.The 20% dynamic threshold spring onset metrics from MODIS products were closer to the photosynthesis onset metrics at the date of 2% GPP increase for NDVI and fAPAR,and closer to the date of 5%and 10% increase of GPP for EVI and LAI,respectively.The 50% dynamic threshold onset metrics were closer to the photosynthesis onset metrics at the date of 10%GPP increase for NDVI,and closer to the date of 20% GPP increase for fAPAR,LAI and EVI,respectively.These results can improve our knowledge on the photosynthesis activity status of remotely sensed spring phenology metrics.
文摘Increasing attention is being paid to the various functions of forests, especially the conservation of biodiversity. In Japan, 67% of national land is covered by forest, 41% of which is artificial forest (i.e., plantations). Therefore, efforts to conserve forest biodiversity should also target artificial forests. In this study, we investigated the increase in biodiversity resulting from broadleaf tree invasion of artificial coniferous forests. We examined diversity indices and combinations of indices to identify which ones can aid forest managers in evaluating forest diversity. We also studied classification according to the richness of diversity, which corresponded to the growth stages of Chamaecyparisobtusa and Cryptomeria japonica plantation forests. Moreover, we developed a model that will contribute to sustainable forest management and biodiversity over an entire area. The model, based on a specific rotation scenario in a geographic information system, is easy to use and presents spatial and temporal changes at sites visually.
基金Supported by Research Project of Yunnan Provincial Department of Education(2013Y114)Applied Basic Research Projects of Yunnan Province(2012FD028)+1 种基金Key Disciplines(Ecology) Project of Yunnan Education Department(05000511311)Research Starting Capital Project of Southwest Forestry University(111168)
文摘In order to clarify the influence of different forest types on soil erosion resistance in water source area of Central Yunnan,with the soils under three different kinds of typical forest in Yizhe watershed as the research object,this paper uses field simulation method and principal component analysis to analyze the soil erosion resistance of three kinds of soils. The results show that there is a significant difference in the shear strength of soil among three types of typical forest,and the size of soil shear strength is in the order of Pinus yunnanensis forest land >mixed broadleaf-conifer forest land > eucalyptus forest land. The difference in the soil erosion coefficient among different forests is not significant,and the soil erosion resistance is highest in mixed broadleaf-conifer forest land( 39. 0%),followed by eucalyptus woodland( 37. 0%)and Pinus yunnanensis forest land( 24. 0%). Under heavy rain intensity and long duration of rainfall,the ability of soil under eucalyptus ×Pinus yunnanensis mixed forests to resist disintegration is more obvious. Using principal component analysis to analyze soil erosion resistance of soils under three different forests,we get the comprehensive evaluation model for soil erosion resistance: Y = 0. 763Y1+ 0. 236Y2. The soil erosion resistance is in the order of mixed broadleaf-conifer forest land( 0. 150) > eucalyptus forest land( 0. 127) > Pinus yunnanensis forest land(-0. 079),indicating that the mixed forests have better water loss and soil erosion control effect than pure forests.
文摘采用Granier热扩散探针法(Thermal Dissipation Probes, TDP),对中国南亚热带地区鼎湖山的过渡性针阔混交林中的主要树种——木荷(Schima superba)、马尾松(Pinus massoniana)和锥(Castanopsis chinensis)的树干液流变化进行了监测,并结合相对湿度、大气温度、光合有效辐射、太阳总辐射、降水量等环境因子进行了综合分析。研究发现,树干液流日变化特征表现为昼高夜低的单峰或双峰曲线,中午时液流密度达到峰值。具体而言,木荷液流密度的最高峰值为42.08 g m^(-2)s^(-1),马尾松为39.10 g m^(-2)s^(-1),锥为43.98 g m^(-2)s^(-1)。不同树种的液流密度存在差异,平均液流密度的大小关系为:锥>木荷>马尾松。此外,同一树种的不同个体之间也存在液流密度的差异。不同树种对各环境因子的响应程度不同,但整体而言,太阳辐射对液流速率的影响最大。揭示了鼎湖山过渡性针阔混交林中不同树种的水分利用特征及其与环境因素的关系,为过渡性针阔叶混交林的研究提供了新的见解。
