不同取样尺度和数量下针阔混交林土壤呼吸的空间异质性
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摘要
区域土壤呼吸通量估算大多用样地尺度的测定结果进行外推,因此对样地尺度土壤呼吸(Rs)及其影响因子的空间关系和取样尺度、取样数量对测定结果的准确性进行评价非常重要.以山西省庞泉沟自然保护区针阔混交林作为研究样地,运用传统统计分析与地统计分析相结合的方法,分析了4、2、1 m取样尺度下土壤水分(Ws)、土壤温度(T10)、凋落物量(Lw)、凋落物含水量(Lm)、土壤全碳(C)、全氮(N)和全碳/全氮(C/N)对土壤呼吸速率(Rs)空间变异的影响.结果表明3个取样间隔下,Rs的均值没有显著差异,但其变异程度随着取样尺度的增大而增加,变异系数在16%~22%之间.在4 m取样间隔下,Rs与Ws、Lw、C、C/N呈极显著正相关(P<0.01),与N呈显著正相关(P<0.05);在2 m取样间隔下,Rs与T10呈极显著负相关(P<0.01),与其他因子相关不显著;在1 m取样间隔下,Rs与其他影响因子的相关性都不显著.随着取样尺度的减小,Rs的空间自相关性逐渐减弱,由高度自相关变为弱相关,表明随着采样距离的减小,结构因素对Rs的作用减弱,随机因素的作用逐渐增大.同一置信水平下相同取样数量随着取样尺度的减小,估计误差降低.95%置信水平下,2 m和1 m取样尺度时9个样本产生的Rs误差在±12%左右,而4 m尺度的误差为±16%;90%置信水平下,2 m和1 m取样尺度时9个样本产生的误差在±10%以内,4 m尺度则为±13%.研究结果可以为样地尺度进行Rs季节测定样点的科学布设提供依据.
By upscaling the observed results at the plot scale,the carbon efflux from soils in a region can be estimated.Therefore,it is very important to investigate the spatial relations of soil respiration(Rs) and its environment and to evaluate the effect of the sampling scale and number on the accuracy of Rsmeasurement at the spatial scale.Based on field observation data for a mixed broadleaf-conifer forest in the Pangquangou Nature Reserve of the Shanxi Province,two analysis methods,that is,traditional statistics and geostatistics,were used to analyze the influence of the soil water content(Ws),soil temperature(T10),litter mass(Lw),litter moisture content(Lm),soil total carbon(C),total nitrogen(N),and ratio of C/N and sulfur(S) on the Rsheterogeneity at 4,2,and 1 m sampling scales.The results show no significant differences between the average Rsvalues for the three sampling scales,but the degree of variation of Rs,which was evaluated based on the coefficient of determination,increases with increasing sampling scales,ranging from 16% to 22%.At the 4 m sampling interval,the correlations between Rsand Ws,Lw,C,and C/N are highly significant(P<0.01) and significant for N(P<0.05).At the 2 m sampling interval,Rsshows a highly negative significant correlation with T10(P<0.01) and insignificant correlations with the other factors.At the 1 m sampling interval,significant relations between Rsand all other factors were not observed.With the decrease of the sampling interval scale,the spatial autocorrelation of Rsdecreases gradually,ranging from high to weak autocorrelations.This indicates that the role the structural factors play decreases with the decrease of the sampling scale,but that of the random factors increases gradually.At the same confidence level for a certain sampling number,the estimated error in Rsdecreases with decreasing sampling scale.The analysis of the effect of the sampling number at different sampling scales on the accuracy of Rsshows that the error of Rsat both the 2 and 1 m sampling scales is approximately ± 12% at the 95%confidence interval and ± 16% at the 4 m sampling scale.At the 90% confidence interval,the error of Rsat both the 2 and 1 m sampling scales is less than ± 10%;at the 4 m scale,it is ± 13%.Our results provide insights into how to arrange the sampling sites at the plot scale to measure the seasonal Rs.
By upscaling the observed results at the plot scale,the carbon efflux from soils in a region can be estimated.Therefore,it is very important to investigate the spatial relations of soil respiration(Rs) and its environment and to evaluate the effect of the sampling scale and number on the accuracy of Rsmeasurement at the spatial scale.Based on field observation data for a mixed broadleaf-conifer forest in the Pangquangou Nature Reserve of the Shanxi Province,two analysis methods,that is,traditional statistics and geostatistics,were used to analyze the influence of the soil water content(Ws),soil temperature(T10),litter mass(Lw),litter moisture content(Lm),soil total carbon(C),total nitrogen(N),and ratio of C/N and sulfur(S) on the Rsheterogeneity at 4,2,and 1 m sampling scales.The results show no significant differences between the average Rsvalues for the three sampling scales,but the degree of variation of Rs,which was evaluated based on the coefficient of determination,increases with increasing sampling scales,ranging from 16% to 22%.At the 4 m sampling interval,the correlations between Rsand Ws,Lw,C,and C/N are highly significant(P<0.01) and significant for N(P<0.05).At the 2 m sampling interval,Rsshows a highly negative significant correlation with T10(P<0.01) and insignificant correlations with the other factors.At the 1 m sampling interval,significant relations between Rsand all other factors were not observed.With the decrease of the sampling interval scale,the spatial autocorrelation of Rsdecreases gradually,ranging from high to weak autocorrelations.This indicates that the role the structural factors play decreases with the decrease of the sampling scale,but that of the random factors increases gradually.At the same confidence level for a certain sampling number,the estimated error in Rsdecreases with decreasing sampling scale.The analysis of the effect of the sampling number at different sampling scales on the accuracy of Rsshows that the error of Rsat both the 2 and 1 m sampling scales is approximately ± 12% at the 95%confidence interval and ± 16% at the 4 m sampling scale.At the 90% confidence interval,the error of Rsat both the 2 and 1 m sampling scales is less than ± 10%;at the 4 m scale,it is ± 13%.Our results provide insights into how to arrange the sampling sites at the plot scale to measure the seasonal Rs.
引文
[1]Trumbore S.Carbon respired by terrestrial ecosystems-recent progress and challenges[J].Global Change Biology,2006,12(2):141-153.
[2]Liang N S,Nakadai T,Hirano T,et al.In situ comparison of four approaches to estimating soil CO2efflux in a northern larch(Larix kaempferi Sarg.)forest[J].Agricultural and Forest Meteorology,2004,123(1-2):97-117.
[3]Li H J,Yan J X,Yue X F,et al.Significance of soil temperature and moisture for soil respiration in a Chinese mountain area[J].Agricultural and Forest Meteorology,2008,148(3):490-503.
[4]Martin J G,Bolstad P V.Variation of soil respiration at three spatial scales:components within measurements,intra-site variation and patterns on the landscape[J].Soil Biology and Biochemistry,2009,41(3):530-543.
[5]Raich J W,Schlesinger W H.The global carbon dioxide flux in soil respiration and its relationship to vegetation and climate[J].Tellus B:Chemical and Physical Meteorology,1992,44(2):81-99.
[6]Chen S T,Zou J W,Hu Z H,et al.Global annual soil respiration in relation to climate,soil properties and vegetation characteristics:summary of available data[J].Agricultural and Forest Meteorology,2014,198-199:335-346.
[7]Song Q H,Tan Z H,Zhang Y P,et al.Spatial heterogeneity of soil respiration in a seasonal rainforest with complex terrain[J].i Forest-Biogeosciences and Forestry,2013,6(1):65-72.
[8]Riveros-Iregui D A,Mc Glynn B L.Landscape structure control on soil CO2efflux variability in complex terrain:scaling from point observations to watershed scale fluxes[J].Journal of Geophysical Research:Biogeosciences,2009,114(G2):G02010.
[9]Sheng H,Yang Y S,Yang Z J,et al.The dynamic response of soil respiration to land-use changes in subtropical China[J].Global Change Biology,2010,16(3):1107-1121.
[10]Fu X L,Shao M G,Wei X R,et al.Soil respiration as affected by vegetation types in a semiarid region of China[J].Soil Science and Plant Nutrition,2013,59(5):715-726.
[11]Bréchet L,Ponton S,Alméras T,et al.Does spatial distribution of tree size account for spatial variation in soil respiration in a tropical forest?[J].Plant and Soil,2011,347(1-2):293-303.
[12]Tang J W,Baldocchi D D.Spatial-temporal variation in soil respiration in an oak-grass savanna ecosystem in California and its partitioning into autotrophic and heterotrophic components[J].Biogeochemistry,2005,73(1):183-207.
[13]Shi B K,Gao W F,Cai H Y,et al.Spatial variation of soil respiration is linked to the forest structure and soil parameters in an old-growth mixed broadleaved-Korean pine forest in northeastern China[J].Plant and Soil,2016,400(1-2):263-274.
[14]Suchewaboripont V,Ando M,Yoshitake S,et al.Spatial upscaling of soil respiration under a complex canopy structure in an old-growth deciduous forest,central Japan[J].Forests,2017,8(2):36.
[15]Li Y Q,Xu M,Zou X M.Heterotrophic soil respiration in relation to environmental factors and microbial biomass in two wet tropical forests[J].Plant and Soil,2006,281(1-2):193-201.
[16]Luan J W,Liu S R,Zhu X L,et al.Roles of biotic and abiotic variables in determining spatial variation of soil respiration in secondary oak and planted pine forests[J].Soil Biology and Biochemistry,2012,44(1):143-150.
[17]陈书涛,胡正华,张勇,等.陆地生态系统土壤呼吸时空变异的影响因素研究进展[J].环境科学,2011,32(8):2184-2192.Chen S T,Hu Z H,Zhang Y,et al.Review of the factors influencing the temporal and spatial variability of soil respiration in terrestrial ecosystem[J].Environmental Science,2011,32(8):2184-2192.
[18]陈书涛,刘巧辉,胡正华,等.不同土地利用方式下土壤呼吸空间变异的影响因素[J].环境科学,2013,34(3):1017-1025.Chen S T,Liu Q H,Hu Z H,et al.Factors influencing the spatial variability in soil respiration under different land use regimes[J].Environmental Science,2013,34(3):1017-1025.
[19]Yim M H,Joo S J,Shutou K,et al.Spatial variability of soil respiration in a larch plantation:estimation of the number of sampling points required[J].Forest Ecology and Management,2003,175(1-3):585-588.
[20]Adachi M,Bekku Y S,Konuma A,et al.Required sample size for estimating soil respiration rates in large areas of two tropical forests and of two types of plantation in Malaysia[J].Forest Ecology and Management,2005,210(1-3):455-459.
[21]Perez-quezada J F,Brito C E,Cabezas J,et al.How many measurements are needed to estimate accurate daily and annual soil respiration fluxes?Analysis using data from a temperate rainforest[J].Biogeosciences,2016,13(24):6599-6609.
[22]Rodeghiero M,Cescatti A.Spatial variability and optimal sampling strategy of soil respiration[J].Forest Ecology and Management,2008,255(1):106-112.
[23]Oishi A C,Palmroth S,Butnor J R,et al.Spatial and temporal variability of soil CO2efflux in three proximate temperate forest ecosystems[J].Agricultural and Forest Meteorology,2013,171-172:256-269.
[24]Fóti S,Balogh J,Nagy Z,et al.Soil moisture induced changes on fine-scale spatial pattern of soil respiration in a semi-arid sandy grassland[J].Geoderma,2014,213:245-254.
[25]李世广,张峰.山西庞泉沟国家级自然保护区生物多样性与保护管理[M].北京:中国林业出版社,2014.
[26]Kosugi Y,Mitani T,Itoh M,et al.Spatial and temporal variation in soil respiration in a Southeast Asian tropical rainforest[J].Agricultural and Forest Meteorology,2007,147(1-2):35-47.
[27]严俊霞,李洪建,李君剑,等.山西高原落叶松人工林土壤呼吸的空间异质性[J].环境科学,2015,36(5):1793-1801.Yan J X,Li H J,Li J J,et al.Spatial heterogeneity of soil respiration in a planted larch forest in Shanxi Plateau[J].Environmental Science,2015,36(5):1793-1801.
[28]秦璐,吕光辉,张雪妮,等.干旱区艾比湖湿地土壤呼吸的空间异质性[J].干旱区地理,2014,37(4):704-712.Qin L,Lv G H,Zhang X N,et al.Spatial heterogeneity of soil respiration at Ebinur Lake wetland nature reserve in arid area[J].Arid Land Geography,2014,37(4):704-712.
[29]Saiz G,Green C,Butterbach-Bahl K,et al.Seasonal and spatial variability of soil respiration in four Sitka spruce stands[J].Plant and Soil,2006,287(1-2):161-176.
[30]Metcalfe D,Meir P,Arag2o L E O C,et al.Sample sizes for estimating key ecosystem characteristics in a tropical terra firme rainforest[J].Forest Ecology and Management,2008,255(3-4):558-566.
[31]严俊霞,李洪建,李君剑.庞泉沟自然保护区针阔混交林土壤呼吸的空间异质性[J].生态学报,2015,35(24):8184-8193.Yan J X,Li H J,Li J J.Spatial heterogeneity of soil respiration in a conifer-broadleaf mixed forest in the Pangquangou Nature Reserve Area[J].Acta Ecologica Sinica,2015,35(24):8184-8193.
[32]贾丙瑞,周广胜,蒋延玲,等.寒温针叶林土壤呼吸作用的时空特征[J].生态学报,2013,33(23):7516-7524.Jia B R,Zhou G S,Jiang Y L,et al.Temporal-spatial characteristics of soil respiration in Chinese boreal forest ecosystem[J].Acta Ecologica Sinica,2013,33(23):7516-7524.
[33]闫美芳,张新时,周广胜.不同树龄杨树(Populus balsamifera)人工林的土壤呼吸空间异质性[J].生态学杂志,2013,32(6):1378-1384.Yan M F,Zhang X S,Zhou G S.Spatial heterogeneity of soil respiration in Populus balsamifera plantation at different developmental stages[J].Chinese Journal of Ecology,2013,32(6):1378-1384.
[34]李洪建,高玉凤,严俊霞,等.不同取样尺度下亚高山草甸土壤呼吸的空间变异特征[J].环境科学,2014,35(11):4313-4320.Li H J,Gao Y F,Yan J X,et al.Spatial heterogeneity of soil respiration in a subalpine meadow at different sampling scales[J].Environmental Science,2014,35(11):4313-4320.
[35]Stoyan H,De-Polli H,B9hm S,et al.Spatial heterogeneity of soil respiration and related properties at the plant scale[J].Plant and Soil,2000,222(1-2):203-214.
[36]Buchmann N.Biotic and abiotic factors controlling soil respiration rates in Picea abies stands[J].Soil Biology and Biochemistry,2000,32(11-12):1625-1635.
[37]Shi W Y,Du S,Morina J C,et al.Physical and biogeochemical controls on soil respiration along a topographical gradient in a semiarid forest[J].Agricultural and Forest Meteorology,2017,247:1-11.
[38]Xu M,Qi Y.Soil-surface CO2efflux and its spatial and temporal variations in a young ponderosa pine plantation in northern California[J].Global Change Biology,2001,7(6):667-677.
[39]Yan J X,Hao Z,Li J J,et al.Soil respiration characteristics in three Shrublands along an elevation gradient in a semiarid Loess Plateau mountain Area[J].Communications in Soil Science and Plant Analysis,2017,48(9):977-988.
[40]Euskirchen E S,Chen J Q,Gustafson E J,et al.Soil respiration at dominant patch types within a managed Northern Wisconsin landscape[J].Ecosystems,2003,6(6):595-607.
[41]Davidson E A,Savage K,Verchot L V,et al.Minimizing artifacts and biases in chamber-based measurements of soil respiration[J].Agricultural and Forest Meteorology,2002,113(1-4):21-37.
[42]姚淑霞,张铜会.随机抽样必要样本容量的确定方法及其应用[J].干旱区研究,2012,29(3):547-552.Yao S X,Zhang T H.A method for determining necessary sample size in random sampling and its application[J].Arid Zone Research,2012,29(3):547-552.
[43]杨清云,曾锋.森林土壤空间变异性及其样本容量的确定[J].水土保持研究,2004,11(3):54-56.Yang Q Y,Zeng F.A research on spatial variability of forest soil and determining number of sample[J].Research of Soil and Water Conservation,2004,11(3):54-56.
[2]Liang N S,Nakadai T,Hirano T,et al.In situ comparison of four approaches to estimating soil CO2efflux in a northern larch(Larix kaempferi Sarg.)forest[J].Agricultural and Forest Meteorology,2004,123(1-2):97-117.
[3]Li H J,Yan J X,Yue X F,et al.Significance of soil temperature and moisture for soil respiration in a Chinese mountain area[J].Agricultural and Forest Meteorology,2008,148(3):490-503.
[4]Martin J G,Bolstad P V.Variation of soil respiration at three spatial scales:components within measurements,intra-site variation and patterns on the landscape[J].Soil Biology and Biochemistry,2009,41(3):530-543.
[5]Raich J W,Schlesinger W H.The global carbon dioxide flux in soil respiration and its relationship to vegetation and climate[J].Tellus B:Chemical and Physical Meteorology,1992,44(2):81-99.
[6]Chen S T,Zou J W,Hu Z H,et al.Global annual soil respiration in relation to climate,soil properties and vegetation characteristics:summary of available data[J].Agricultural and Forest Meteorology,2014,198-199:335-346.
[7]Song Q H,Tan Z H,Zhang Y P,et al.Spatial heterogeneity of soil respiration in a seasonal rainforest with complex terrain[J].i Forest-Biogeosciences and Forestry,2013,6(1):65-72.
[8]Riveros-Iregui D A,Mc Glynn B L.Landscape structure control on soil CO2efflux variability in complex terrain:scaling from point observations to watershed scale fluxes[J].Journal of Geophysical Research:Biogeosciences,2009,114(G2):G02010.
[9]Sheng H,Yang Y S,Yang Z J,et al.The dynamic response of soil respiration to land-use changes in subtropical China[J].Global Change Biology,2010,16(3):1107-1121.
[10]Fu X L,Shao M G,Wei X R,et al.Soil respiration as affected by vegetation types in a semiarid region of China[J].Soil Science and Plant Nutrition,2013,59(5):715-726.
[11]Bréchet L,Ponton S,Alméras T,et al.Does spatial distribution of tree size account for spatial variation in soil respiration in a tropical forest?[J].Plant and Soil,2011,347(1-2):293-303.
[12]Tang J W,Baldocchi D D.Spatial-temporal variation in soil respiration in an oak-grass savanna ecosystem in California and its partitioning into autotrophic and heterotrophic components[J].Biogeochemistry,2005,73(1):183-207.
[13]Shi B K,Gao W F,Cai H Y,et al.Spatial variation of soil respiration is linked to the forest structure and soil parameters in an old-growth mixed broadleaved-Korean pine forest in northeastern China[J].Plant and Soil,2016,400(1-2):263-274.
[14]Suchewaboripont V,Ando M,Yoshitake S,et al.Spatial upscaling of soil respiration under a complex canopy structure in an old-growth deciduous forest,central Japan[J].Forests,2017,8(2):36.
[15]Li Y Q,Xu M,Zou X M.Heterotrophic soil respiration in relation to environmental factors and microbial biomass in two wet tropical forests[J].Plant and Soil,2006,281(1-2):193-201.
[16]Luan J W,Liu S R,Zhu X L,et al.Roles of biotic and abiotic variables in determining spatial variation of soil respiration in secondary oak and planted pine forests[J].Soil Biology and Biochemistry,2012,44(1):143-150.
[17]陈书涛,胡正华,张勇,等.陆地生态系统土壤呼吸时空变异的影响因素研究进展[J].环境科学,2011,32(8):2184-2192.Chen S T,Hu Z H,Zhang Y,et al.Review of the factors influencing the temporal and spatial variability of soil respiration in terrestrial ecosystem[J].Environmental Science,2011,32(8):2184-2192.
[18]陈书涛,刘巧辉,胡正华,等.不同土地利用方式下土壤呼吸空间变异的影响因素[J].环境科学,2013,34(3):1017-1025.Chen S T,Liu Q H,Hu Z H,et al.Factors influencing the spatial variability in soil respiration under different land use regimes[J].Environmental Science,2013,34(3):1017-1025.
[19]Yim M H,Joo S J,Shutou K,et al.Spatial variability of soil respiration in a larch plantation:estimation of the number of sampling points required[J].Forest Ecology and Management,2003,175(1-3):585-588.
[20]Adachi M,Bekku Y S,Konuma A,et al.Required sample size for estimating soil respiration rates in large areas of two tropical forests and of two types of plantation in Malaysia[J].Forest Ecology and Management,2005,210(1-3):455-459.
[21]Perez-quezada J F,Brito C E,Cabezas J,et al.How many measurements are needed to estimate accurate daily and annual soil respiration fluxes?Analysis using data from a temperate rainforest[J].Biogeosciences,2016,13(24):6599-6609.
[22]Rodeghiero M,Cescatti A.Spatial variability and optimal sampling strategy of soil respiration[J].Forest Ecology and Management,2008,255(1):106-112.
[23]Oishi A C,Palmroth S,Butnor J R,et al.Spatial and temporal variability of soil CO2efflux in three proximate temperate forest ecosystems[J].Agricultural and Forest Meteorology,2013,171-172:256-269.
[24]Fóti S,Balogh J,Nagy Z,et al.Soil moisture induced changes on fine-scale spatial pattern of soil respiration in a semi-arid sandy grassland[J].Geoderma,2014,213:245-254.
[25]李世广,张峰.山西庞泉沟国家级自然保护区生物多样性与保护管理[M].北京:中国林业出版社,2014.
[26]Kosugi Y,Mitani T,Itoh M,et al.Spatial and temporal variation in soil respiration in a Southeast Asian tropical rainforest[J].Agricultural and Forest Meteorology,2007,147(1-2):35-47.
[27]严俊霞,李洪建,李君剑,等.山西高原落叶松人工林土壤呼吸的空间异质性[J].环境科学,2015,36(5):1793-1801.Yan J X,Li H J,Li J J,et al.Spatial heterogeneity of soil respiration in a planted larch forest in Shanxi Plateau[J].Environmental Science,2015,36(5):1793-1801.
[28]秦璐,吕光辉,张雪妮,等.干旱区艾比湖湿地土壤呼吸的空间异质性[J].干旱区地理,2014,37(4):704-712.Qin L,Lv G H,Zhang X N,et al.Spatial heterogeneity of soil respiration at Ebinur Lake wetland nature reserve in arid area[J].Arid Land Geography,2014,37(4):704-712.
[29]Saiz G,Green C,Butterbach-Bahl K,et al.Seasonal and spatial variability of soil respiration in four Sitka spruce stands[J].Plant and Soil,2006,287(1-2):161-176.
[30]Metcalfe D,Meir P,Arag2o L E O C,et al.Sample sizes for estimating key ecosystem characteristics in a tropical terra firme rainforest[J].Forest Ecology and Management,2008,255(3-4):558-566.
[31]严俊霞,李洪建,李君剑.庞泉沟自然保护区针阔混交林土壤呼吸的空间异质性[J].生态学报,2015,35(24):8184-8193.Yan J X,Li H J,Li J J.Spatial heterogeneity of soil respiration in a conifer-broadleaf mixed forest in the Pangquangou Nature Reserve Area[J].Acta Ecologica Sinica,2015,35(24):8184-8193.
[32]贾丙瑞,周广胜,蒋延玲,等.寒温针叶林土壤呼吸作用的时空特征[J].生态学报,2013,33(23):7516-7524.Jia B R,Zhou G S,Jiang Y L,et al.Temporal-spatial characteristics of soil respiration in Chinese boreal forest ecosystem[J].Acta Ecologica Sinica,2013,33(23):7516-7524.
[33]闫美芳,张新时,周广胜.不同树龄杨树(Populus balsamifera)人工林的土壤呼吸空间异质性[J].生态学杂志,2013,32(6):1378-1384.Yan M F,Zhang X S,Zhou G S.Spatial heterogeneity of soil respiration in Populus balsamifera plantation at different developmental stages[J].Chinese Journal of Ecology,2013,32(6):1378-1384.
[34]李洪建,高玉凤,严俊霞,等.不同取样尺度下亚高山草甸土壤呼吸的空间变异特征[J].环境科学,2014,35(11):4313-4320.Li H J,Gao Y F,Yan J X,et al.Spatial heterogeneity of soil respiration in a subalpine meadow at different sampling scales[J].Environmental Science,2014,35(11):4313-4320.
[35]Stoyan H,De-Polli H,B9hm S,et al.Spatial heterogeneity of soil respiration and related properties at the plant scale[J].Plant and Soil,2000,222(1-2):203-214.
[36]Buchmann N.Biotic and abiotic factors controlling soil respiration rates in Picea abies stands[J].Soil Biology and Biochemistry,2000,32(11-12):1625-1635.
[37]Shi W Y,Du S,Morina J C,et al.Physical and biogeochemical controls on soil respiration along a topographical gradient in a semiarid forest[J].Agricultural and Forest Meteorology,2017,247:1-11.
[38]Xu M,Qi Y.Soil-surface CO2efflux and its spatial and temporal variations in a young ponderosa pine plantation in northern California[J].Global Change Biology,2001,7(6):667-677.
[39]Yan J X,Hao Z,Li J J,et al.Soil respiration characteristics in three Shrublands along an elevation gradient in a semiarid Loess Plateau mountain Area[J].Communications in Soil Science and Plant Analysis,2017,48(9):977-988.
[40]Euskirchen E S,Chen J Q,Gustafson E J,et al.Soil respiration at dominant patch types within a managed Northern Wisconsin landscape[J].Ecosystems,2003,6(6):595-607.
[41]Davidson E A,Savage K,Verchot L V,et al.Minimizing artifacts and biases in chamber-based measurements of soil respiration[J].Agricultural and Forest Meteorology,2002,113(1-4):21-37.
[42]姚淑霞,张铜会.随机抽样必要样本容量的确定方法及其应用[J].干旱区研究,2012,29(3):547-552.Yao S X,Zhang T H.A method for determining necessary sample size in random sampling and its application[J].Arid Zone Research,2012,29(3):547-552.
[43]杨清云,曾锋.森林土壤空间变异性及其样本容量的确定[J].水土保持研究,2004,11(3):54-56.Yang Q Y,Zeng F.A research on spatial variability of forest soil and determining number of sample[J].Research of Soil and Water Conservation,2004,11(3):54-56.