高寒草甸根际土壤化学计量特征对草地退化的响应
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摘要
为深入理解高寒草甸退化过程中根际和非根际土壤中碳(C)、氮(N)和磷(P)的化学计量特征和土壤养分的变化规律,并获得退化草地土壤养分和微生物养分限制的信息,本研究以祁连山东缘4个不同退化程度高寒草甸为对象,通过采集优势植物根际土(0～2 mm)和非根际土(0～10 cm)的土壤样品,分析了土壤C、N、P浓度和比例,土壤中可提取的C、N、P(Ext-C、Ext-N、Ext-P)的浓度和比例,参与C、N、P循环的胞外酶(β-1,4-葡萄糖苷酶、N-乙酰-β-D-葡萄糖苷酶、亮氨酸基肽酶、酸性磷酸酶)的活性和比例,以及土壤微生物生物量碳、氮、磷(MBC、MBN、MBP)的含量及比例.结果表明:高寒草甸退化过程中优势植物根际养分含量高于非根际养分.随着高寒草甸退化程度的加剧,其土壤的C∶N∶P发生重大改变,表现出C∶N的严重失调,表明草地退化程度越高受到N的限制越严重.不同退化程度的高寒草甸中,经过对数转化的根际C-、N-和P-胞外酶的比例均偏离了在全球生态系统分析中获得的1∶1∶1比例,表明高寒草甸退化主要受到强烈的N限制,P次之.高寒草甸地区土壤全量养分含量较高,土壤中的速效养分较低,成为阻碍牧草生长的限制因子.
This study aimed to understand the stoichiometric characteristics of carbon(C), nitrogen(N) and phosphorus(P) and soil nutrients in rhizosphere and non-rhizosphere soils and to obtain information on the status of soil and microbial nutrient limitation in degraded alpine meadow. We collected soil samples from rhizosphere(0-2 mm) of dominant plant species and non-rhizosphere(0-10 cm) of the alpine meadow with four different degraded degrees in the Qilian Mountains. We measured the concentration of C, N and P and extractable C, N, P(Ext-C, Ext-N, Ext-P), the activity and proportion of extracellular enzymes(β-1, 4-glucosidase, β-1, 4-N-acetylglucosaminidase, leucine aminopeptidase and acid phosphatase) involved in C, N, P cycles, as well as soil microbial biomass(MBC, MBN, MBP). The results showed that nutrient concentrations in the rhizosphere of dominant species was higher than that in non-rhizosphere. With the increases of degradation degree, soil C:N:P changed significantly, and resulted in a serious imbalance of C:N and severe N limitation. In the degraded alpine meadows, the ratio of log-transformed rhizosphere C-, N-and P-extracellular enzymes deviated from the 1:1:1 of global ecosystem, indicating that nutrient supply was mainly restricted by N and followed by P. The contents of soil total nutrients in degraded alpine meadow was relatively high, but the contents of soil available nutrients were low, which would hinder plant growth.
This study aimed to understand the stoichiometric characteristics of carbon(C), nitrogen(N) and phosphorus(P) and soil nutrients in rhizosphere and non-rhizosphere soils and to obtain information on the status of soil and microbial nutrient limitation in degraded alpine meadow. We collected soil samples from rhizosphere(0-2 mm) of dominant plant species and non-rhizosphere(0-10 cm) of the alpine meadow with four different degraded degrees in the Qilian Mountains. We measured the concentration of C, N and P and extractable C, N, P(Ext-C, Ext-N, Ext-P), the activity and proportion of extracellular enzymes(β-1, 4-glucosidase, β-1, 4-N-acetylglucosaminidase, leucine aminopeptidase and acid phosphatase) involved in C, N, P cycles, as well as soil microbial biomass(MBC, MBN, MBP). The results showed that nutrient concentrations in the rhizosphere of dominant species was higher than that in non-rhizosphere. With the increases of degradation degree, soil C:N:P changed significantly, and resulted in a serious imbalance of C:N and severe N limitation. In the degraded alpine meadows, the ratio of log-transformed rhizosphere C-, N-and P-extracellular enzymes deviated from the 1:1:1 of global ecosystem, indicating that nutrient supply was mainly restricted by N and followed by P. The contents of soil total nutrients in degraded alpine meadow was relatively high, but the contents of soil available nutrients were low, which would hinder plant growth.
引文
[1] Chen N (陈宁),Zhang Y-J (张扬建),Zhu J-T (朱军涛),et al.Nonlinear responses of productivity and diversity of alpine meadow communities to degradation.Chinese Journal of Plant Ecology (植物生态学报),2018,42(1):50-65 (in Chinese)
[2] Gao Y,Schumann M,Chen H,et al.Impacts of grazing intensity on soil carbon and nitrogen in an alpine mea-dow on the eastern Tibetan Plateau.Applied Ecology & Environmental Research,2008,6:69-79
[3] Yang Y-S (杨永胜),Zhang L (张莉),Wei Y-X (未亚西),et al.Effects of degradation degree on soil physicochemical properties and soil water-holding capa-city in Zeku alpine meadow in the headwater region of Three Rivers in China.Chinese Journal of Grassland (中国草地学报),2017,39(5):54-61 (in Chinese)
[4] Yin Y-L (尹亚丽),Wang Y-Q (王玉琴),Li S-X (李世雄),et al.Effects of enclosing on soil microbial community diversity and soil stoichiometric characteristics in a degraded alpine meadow.Chinese Journal of Applied Ecology (应用生态学报),2019,30(1):127-136 (in Chinese)
[5] Luo Y-Y (罗亚勇),Zhang Y (张宇),Zhang J-H (张静辉),et al.Soil stoichiometry characteristics of alpine meadow at its different degradation stages.Chinese Journal of Ecology (生态学杂志),2012,31(2):254-260 (in Chinese)
[6] Ma J (马杰),Li L-H (李兰海),Liu X (刘翔),et al.Stoichiometry of nitrogen and phosphorus and the content in grassland ecosystem in the upper reaches of Hi River.Journal of Nanjing Forestry University (Natural Science) (南京林业大学学报:自然科学版),2017,41(3):7-14 (in Chinese)
[7] Zhang S-Y (张生楹),Zhang D-G (张德罡),Liu X-N (柳小妮),et al.Soil nutrient characteristics of alpine meadow at different degradation degrees in Eastern Qilian Mountains.Pratacultural Science (草业科学),2012,29(7):1028-1032 (in Chinese)
[8] Beermann F,Teltewskoi A,Fiencke C,et al.Stoichiometric analysis of nutrient availability (N,P,K) within soils of polygonal tundra.Biogeochemistry,2015,122:211-227
[9] Hagedorn,Frank,Jan M,et al.Mountain soils under a changing climate and land-use.Biogeochemistry,2010,97:1-5
[10] Craine JM,Morrow C,Stock WD.Nutrient concentration ratios and co-limitation in South African grasslands.New Phytologist,2008,179:829-836
[11] Kerkhoff AJ,Enquist BJ,Fagan EWF.Plant allometry,stoichiometry and the temperature-dependence of primary productivity.Global Ecology and Biogeography,2005,14:585-598
[12] Sugihara S,Shibata M,Ze ADM,et al.Effects of vegetation on soil microbial C,N,and P dynamics in a tropi-cal forest and savanna of Central Africa.Applied Soil Ecology,2015,87:91-98
[13] Zechmeister BS,Keiblinger KM,Mooshammer M,et al.The application of ecological stoichiometry to plant-microbial-soil organic matter transformations.Ecological Monographs,2015,85:133-155
[14] Bell C,Carrillo Y,Boot CM,et al.Rhizosphere stoichio-metry:Are C:N:P ratios of plants,soils,and enzymes conserved at the plant species-level?New Phytologist,2014,201:505-517
[15] Jiang Y-M (蒋永梅),Shi S-L (师尚礼),Tian Y-L (田永亮),et al.Characteristics of soil microorganism and soil enzyme activities in alpine meadows under different degrees of degradation.Journal of Soil and Water Conservation (水土保持学报),2017,31(3):244-249 (in Chinese)
[16] General Administration of Quality Supervision,Inspection and Quarantine of the People’s Republic of China (中华人民共和国国家质量监督检验检疫总局).Parameters for Degradation,Sandification and Salification of Rangelands (GB 19377-2003).Beijing:China Standards Press,2003 (in Chinese)
[17] Chen Z-X (陈正兴),Gao D-X (高德新),Zhang W (张伟),et al.Population spatial patterns of grassland plant communities in different slope aspects in the loess hilly area,China.Chinese Journal of Applied Eco-logy (应用生态学报),2018,29(6):1846-1856 (in Chinese)
[18] Chaudhary DR,Gautam RK,Yousuf B,et al.Nutrients,microbial community structure and functional gene abundance of rhizosphere and bulk soils of halophytes.Applied Soil Ecology,2015,91:16-26
[19] Zhang J-T (张金屯).Quantitative Ecology.Beijing:Science Press,1995 (in Chinese)
[20] Brookes PC,Powlson DS,Jenkinson DS.Measurement of microbial biomass phosphorus in soil.Soil Biology & Biochemistry,1982,14:319-329
[21] Vance ED,Brookes PC,Jenkinson DS.An extraction method for measuring soil microbial biomass carbon.Soil Biology & Biochemistry,1987,19:703-707
[22] Tao Y (陶冶),Zhang Y-M (张元明),Zhou X-B (周晓兵).Ecological stoichiometry of surface soil nutrient and its influencing factors in the wild fruit forest in Yili region,Xinjiang,China.Chinese Journal of Applied Ecology (应用生态学报),2016,27(7):2239-2248 (in Chinese)
[23] Arunachalam A,Pandey HN.Ecosystem restoration of Jhum fallows in northeast India:Microbial C and N along altitudinal and successional gradients.Restoration Ecology,2003,11:168-173
[24] Lin L (林丽),Zhang F-W (张法伟),Li Y-K (李以康),et al.The soil carbon and nitrogen storage and C/N metrological characteristics of chemistry in Kobresia humilis meadow in degradation succession stages.Chinese Journal of Grassland (中国草地学报),2012,34(3):42-47 (in Chinese)
[25] Yang Y (杨阳),Liu B-R (刘秉儒),Yang X-G (杨新国),et al.Soil stoichiometry characteristics of artificial Caragana korshinskii shrubs with different density in desert steppe.Bulletin of Soil and Water Conservation (水土保持通报),2014,34(5):67-73 (in Chinese)
[26] Wang S-Q (王绍强),Yu G-R (于贵瑞).Ecological stoichiometry characteristics of ecosystem carbon,nitrogen and phosphorus elements.Acta Ecologica Sinica (生态学报),2008,28(8):3937-3947 (in Chinese)
[27] Yang H (杨慧),Tu C-Y (涂春艳),Li Q-F (李青芳),et al.Analysis of C,N and P stoichiometry of secon-dary forest in different landforms in karst area.Journal of Southern Agriculture (南方农业学报),2015,46(5):777-781 (in Chinese)
[28] Griffiths BS.C:N:P stoichiometry and nutrient limitation of the soil microbial biomass in a grazed grassland site under experimental P limitation or excess.Ecological Processes,2012,1:6
[29] Khan KS,Joergensen RG.Relationships between P fractions and the microbial biomass in soils under different land use management.Geoderma,2012,173-174:274-281
[30] Sugihara S,Funakawa S,Kilasara M,et al.Effect of land management and soil texture on seasonal variations in soil microbial biomass in dry tropical agroecosystems in Tanzania.Applied Soil Ecology,2010,44:80-88
[31] Sugihara S,Shibata M,Ze ADM,et al.Effects of vegetation on soil microbial C,N,and P dynamics in a tropi-cal forest and savanna of Central Africa.Applied Soil Ecology,2015,87:91-98
[32] Wright CJ,Coleman DC.The effects of disturbance events on labile phosphorus fractions and total organic phosphorus in the southern Appalachians.Soil Science,1999,164:391-402
[33] Aponte C,Maraňón T,García LV.Microbial C,N and P in soils of Mediterranean oak forests:Influence of season,canopy cover and soil depth.Biogeochemistry,2010,101:77-92
[34] Spohn M,Widdig M.Turnover of carbon and phosphorus in the microbial biomass depending on phosphorus availa-bility.Soil Biology & Biochemistry,2017,113:53-59
[35] Tischer A,Potthast K,Hamer U.Land-use and soil depth affect resource and microbial stoichiometry in a tropical mountain rainforest region of southern Ecuador.Oecologia,2014,175:375-393
[36] Luo T (罗婷),Xu W-N (许文年),Cheng H (程虎),et al.Stoichiometric characteristics of rhizosphere soil in different restoration models of Xiangjiaba Hydropower Station.Resources and Environment in the Yangtze Basin (长江流域资源与环境),2019,28(2):450-458 (in Chinese)
[37] Wu X-Z (吴秀芝),Yan X (阎欣),Wang B (王波),et al.Effects of desertification on the C:N:P stoichiometry of soil,microbes,and extracellular enzymes in a desert grassland.Chinese Journal of Plant Ecology (植物生态学报),2018,42(10):1022-1032 (in Chinese)
[38] Yang N (杨宁),Zou D-S (邹冬生),Yang M-Y (杨满元),et al.Soil enzyme activities in different re-vegetation stages on sloping-land with purple soils in Hengyang of Hunan Province,China.Plant Nutrition and Fertilizer Science (植物营养与肥料学报),2013,19(6):1516-1524 (in Chinese)
[39] Sinsabaugh RL,Hill BH,Follstad SJJ.Ecoenzymatic stoichiometry of microbial organic nutrient acquisition in soil and sediment.Nature,2010,468:795-798
[40] Sinsabaugh RL,Lauber CL,Weintraub MN,et al.Stoichiometry of soil enzyme activity at global scale.Ecology Letters,2010,11:1252-1264
[41] Dijkstra FA,Pendall E,Morgan JA,et al.Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland.New Phytologist,2012,196:807-815
[42] Li H-J (李洪杰),Liu J-W (刘军伟),Yang L (杨林),et al.Effects of simulated climate warming on soil microbial biomass carbon,nitrogen and phosphorus of alpine forest.Chinese Journal of Applied and Environmental Biology (应用与环境生物学报),2016,22(4):599-605 (in Chinese)
[43] Hou F-J (侯扶江),Nan Z-B (南志标),Xiao J-Y (肖金玉),et al.Characteristics of vegetation,soil,and their coupling of degraded grasslands.Chinese Journal of Applied Ecology (应用生态学报),2002,13(8):915-922 (in Chinese)
[44] Cleveland CC,Liptzin D.C:N:P stoichiometry in soil:Is there a “Redfield Ratio” for the microbial biomass?Biochemistry,2007,85:235-252
[45] Wu X-Z (吴秀芝),Yan X (阎欣),Wang B (王波),et al.Effects of desertification on soil nutrients and extracellular enzyme activities in desert grassland.Ecology and Environment Sciences (生态环境学报),2018,27(6):1082-1088 (in Chinese)
[2] Gao Y,Schumann M,Chen H,et al.Impacts of grazing intensity on soil carbon and nitrogen in an alpine mea-dow on the eastern Tibetan Plateau.Applied Ecology & Environmental Research,2008,6:69-79
[3] Yang Y-S (杨永胜),Zhang L (张莉),Wei Y-X (未亚西),et al.Effects of degradation degree on soil physicochemical properties and soil water-holding capa-city in Zeku alpine meadow in the headwater region of Three Rivers in China.Chinese Journal of Grassland (中国草地学报),2017,39(5):54-61 (in Chinese)
[4] Yin Y-L (尹亚丽),Wang Y-Q (王玉琴),Li S-X (李世雄),et al.Effects of enclosing on soil microbial community diversity and soil stoichiometric characteristics in a degraded alpine meadow.Chinese Journal of Applied Ecology (应用生态学报),2019,30(1):127-136 (in Chinese)
[5] Luo Y-Y (罗亚勇),Zhang Y (张宇),Zhang J-H (张静辉),et al.Soil stoichiometry characteristics of alpine meadow at its different degradation stages.Chinese Journal of Ecology (生态学杂志),2012,31(2):254-260 (in Chinese)
[6] Ma J (马杰),Li L-H (李兰海),Liu X (刘翔),et al.Stoichiometry of nitrogen and phosphorus and the content in grassland ecosystem in the upper reaches of Hi River.Journal of Nanjing Forestry University (Natural Science) (南京林业大学学报:自然科学版),2017,41(3):7-14 (in Chinese)
[7] Zhang S-Y (张生楹),Zhang D-G (张德罡),Liu X-N (柳小妮),et al.Soil nutrient characteristics of alpine meadow at different degradation degrees in Eastern Qilian Mountains.Pratacultural Science (草业科学),2012,29(7):1028-1032 (in Chinese)
[8] Beermann F,Teltewskoi A,Fiencke C,et al.Stoichiometric analysis of nutrient availability (N,P,K) within soils of polygonal tundra.Biogeochemistry,2015,122:211-227
[9] Hagedorn,Frank,Jan M,et al.Mountain soils under a changing climate and land-use.Biogeochemistry,2010,97:1-5
[10] Craine JM,Morrow C,Stock WD.Nutrient concentration ratios and co-limitation in South African grasslands.New Phytologist,2008,179:829-836
[11] Kerkhoff AJ,Enquist BJ,Fagan EWF.Plant allometry,stoichiometry and the temperature-dependence of primary productivity.Global Ecology and Biogeography,2005,14:585-598
[12] Sugihara S,Shibata M,Ze ADM,et al.Effects of vegetation on soil microbial C,N,and P dynamics in a tropi-cal forest and savanna of Central Africa.Applied Soil Ecology,2015,87:91-98
[13] Zechmeister BS,Keiblinger KM,Mooshammer M,et al.The application of ecological stoichiometry to plant-microbial-soil organic matter transformations.Ecological Monographs,2015,85:133-155
[14] Bell C,Carrillo Y,Boot CM,et al.Rhizosphere stoichio-metry:Are C:N:P ratios of plants,soils,and enzymes conserved at the plant species-level?New Phytologist,2014,201:505-517
[15] Jiang Y-M (蒋永梅),Shi S-L (师尚礼),Tian Y-L (田永亮),et al.Characteristics of soil microorganism and soil enzyme activities in alpine meadows under different degrees of degradation.Journal of Soil and Water Conservation (水土保持学报),2017,31(3):244-249 (in Chinese)
[16] General Administration of Quality Supervision,Inspection and Quarantine of the People’s Republic of China (中华人民共和国国家质量监督检验检疫总局).Parameters for Degradation,Sandification and Salification of Rangelands (GB 19377-2003).Beijing:China Standards Press,2003 (in Chinese)
[17] Chen Z-X (陈正兴),Gao D-X (高德新),Zhang W (张伟),et al.Population spatial patterns of grassland plant communities in different slope aspects in the loess hilly area,China.Chinese Journal of Applied Eco-logy (应用生态学报),2018,29(6):1846-1856 (in Chinese)
[18] Chaudhary DR,Gautam RK,Yousuf B,et al.Nutrients,microbial community structure and functional gene abundance of rhizosphere and bulk soils of halophytes.Applied Soil Ecology,2015,91:16-26
[19] Zhang J-T (张金屯).Quantitative Ecology.Beijing:Science Press,1995 (in Chinese)
[20] Brookes PC,Powlson DS,Jenkinson DS.Measurement of microbial biomass phosphorus in soil.Soil Biology & Biochemistry,1982,14:319-329
[21] Vance ED,Brookes PC,Jenkinson DS.An extraction method for measuring soil microbial biomass carbon.Soil Biology & Biochemistry,1987,19:703-707
[22] Tao Y (陶冶),Zhang Y-M (张元明),Zhou X-B (周晓兵).Ecological stoichiometry of surface soil nutrient and its influencing factors in the wild fruit forest in Yili region,Xinjiang,China.Chinese Journal of Applied Ecology (应用生态学报),2016,27(7):2239-2248 (in Chinese)
[23] Arunachalam A,Pandey HN.Ecosystem restoration of Jhum fallows in northeast India:Microbial C and N along altitudinal and successional gradients.Restoration Ecology,2003,11:168-173
[24] Lin L (林丽),Zhang F-W (张法伟),Li Y-K (李以康),et al.The soil carbon and nitrogen storage and C/N metrological characteristics of chemistry in Kobresia humilis meadow in degradation succession stages.Chinese Journal of Grassland (中国草地学报),2012,34(3):42-47 (in Chinese)
[25] Yang Y (杨阳),Liu B-R (刘秉儒),Yang X-G (杨新国),et al.Soil stoichiometry characteristics of artificial Caragana korshinskii shrubs with different density in desert steppe.Bulletin of Soil and Water Conservation (水土保持通报),2014,34(5):67-73 (in Chinese)
[26] Wang S-Q (王绍强),Yu G-R (于贵瑞).Ecological stoichiometry characteristics of ecosystem carbon,nitrogen and phosphorus elements.Acta Ecologica Sinica (生态学报),2008,28(8):3937-3947 (in Chinese)
[27] Yang H (杨慧),Tu C-Y (涂春艳),Li Q-F (李青芳),et al.Analysis of C,N and P stoichiometry of secon-dary forest in different landforms in karst area.Journal of Southern Agriculture (南方农业学报),2015,46(5):777-781 (in Chinese)
[28] Griffiths BS.C:N:P stoichiometry and nutrient limitation of the soil microbial biomass in a grazed grassland site under experimental P limitation or excess.Ecological Processes,2012,1:6
[29] Khan KS,Joergensen RG.Relationships between P fractions and the microbial biomass in soils under different land use management.Geoderma,2012,173-174:274-281
[30] Sugihara S,Funakawa S,Kilasara M,et al.Effect of land management and soil texture on seasonal variations in soil microbial biomass in dry tropical agroecosystems in Tanzania.Applied Soil Ecology,2010,44:80-88
[31] Sugihara S,Shibata M,Ze ADM,et al.Effects of vegetation on soil microbial C,N,and P dynamics in a tropi-cal forest and savanna of Central Africa.Applied Soil Ecology,2015,87:91-98
[32] Wright CJ,Coleman DC.The effects of disturbance events on labile phosphorus fractions and total organic phosphorus in the southern Appalachians.Soil Science,1999,164:391-402
[33] Aponte C,Maraňón T,García LV.Microbial C,N and P in soils of Mediterranean oak forests:Influence of season,canopy cover and soil depth.Biogeochemistry,2010,101:77-92
[34] Spohn M,Widdig M.Turnover of carbon and phosphorus in the microbial biomass depending on phosphorus availa-bility.Soil Biology & Biochemistry,2017,113:53-59
[35] Tischer A,Potthast K,Hamer U.Land-use and soil depth affect resource and microbial stoichiometry in a tropical mountain rainforest region of southern Ecuador.Oecologia,2014,175:375-393
[36] Luo T (罗婷),Xu W-N (许文年),Cheng H (程虎),et al.Stoichiometric characteristics of rhizosphere soil in different restoration models of Xiangjiaba Hydropower Station.Resources and Environment in the Yangtze Basin (长江流域资源与环境),2019,28(2):450-458 (in Chinese)
[37] Wu X-Z (吴秀芝),Yan X (阎欣),Wang B (王波),et al.Effects of desertification on the C:N:P stoichiometry of soil,microbes,and extracellular enzymes in a desert grassland.Chinese Journal of Plant Ecology (植物生态学报),2018,42(10):1022-1032 (in Chinese)
[38] Yang N (杨宁),Zou D-S (邹冬生),Yang M-Y (杨满元),et al.Soil enzyme activities in different re-vegetation stages on sloping-land with purple soils in Hengyang of Hunan Province,China.Plant Nutrition and Fertilizer Science (植物营养与肥料学报),2013,19(6):1516-1524 (in Chinese)
[39] Sinsabaugh RL,Hill BH,Follstad SJJ.Ecoenzymatic stoichiometry of microbial organic nutrient acquisition in soil and sediment.Nature,2010,468:795-798
[40] Sinsabaugh RL,Lauber CL,Weintraub MN,et al.Stoichiometry of soil enzyme activity at global scale.Ecology Letters,2010,11:1252-1264
[41] Dijkstra FA,Pendall E,Morgan JA,et al.Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland.New Phytologist,2012,196:807-815
[42] Li H-J (李洪杰),Liu J-W (刘军伟),Yang L (杨林),et al.Effects of simulated climate warming on soil microbial biomass carbon,nitrogen and phosphorus of alpine forest.Chinese Journal of Applied and Environmental Biology (应用与环境生物学报),2016,22(4):599-605 (in Chinese)
[43] Hou F-J (侯扶江),Nan Z-B (南志标),Xiao J-Y (肖金玉),et al.Characteristics of vegetation,soil,and their coupling of degraded grasslands.Chinese Journal of Applied Ecology (应用生态学报),2002,13(8):915-922 (in Chinese)
[44] Cleveland CC,Liptzin D.C:N:P stoichiometry in soil:Is there a “Redfield Ratio” for the microbial biomass?Biochemistry,2007,85:235-252
[45] Wu X-Z (吴秀芝),Yan X (阎欣),Wang B (王波),et al.Effects of desertification on soil nutrients and extracellular enzyme activities in desert grassland.Ecology and Environment Sciences (生态环境学报),2018,27(6):1082-1088 (in Chinese)