摘要
【目的】藏东南地区高山生态系统有巨大的土壤碳汇潜力,研究其不同生态系统下土壤有机碳(SOC)储存的变化特征及其影响因子,有助于深入了解青藏高原土壤碳循环及区域碳源汇平衡。【方法】本研究在西藏色季拉山西坡海拔3000~4600 m开展密集土壤采样,研究不同海拔高度下不同植被类型SOC的储存特征,并分析其关键影响因子。【结果】表层0-5 cm的SOC含量随海拔升高而增加,4个植被带SOC含量平均值表现为高寒草甸(8.31%±0.77%)>暗针叶林(7.20%±0.90%)>高寒灌丛草甸(6.74%±0.80%)>针阔混交林(3.88%±0.46%)。在剖面5-10、10-15、15-20、20-30、30-40、40-60 cm各层SOC含量随海拔升高呈先增加后降低趋势,SOC含量在4种植被带的平均值表现为暗针叶林>高寒灌丛草甸>高寒草甸>针阔混交林。SOC含量随剖面深度增加而显著下降,高寒草甸和高寒灌丛草甸SOC垂直分布特征为表层聚集型,而针阔混交林和暗针叶林SOC垂直分布特征为普通递减型。剖面0-20、20-40、40-60 cm的SOC储量随海拔升高呈先增加后降低的特征。在表层0-20 cm高寒草甸SOC储量最高(C 95.66±4.81 t/hm^2);在剖面20-40和40-60 cm暗针叶林SOC储量最高,且其在整个0-60 cm剖面的SOC总储量在所有植被类型中最高(C 199.14±11.10 t/hm^2);针阔混交林SOC储量在剖面各层均为最低,且其在整个剖面的SOC总储量(C 111.45±10.30 t/hm^2)显著低于其他植被类型。剖面各层SOC储量与年平均温度、凋落物碳氮比呈显著负相关,而与海拔高度、年平均降水量和土壤含水量呈显著正相关。逐步回归显示土壤含水量是影响剖面各层以及整个剖面SOC储存的关键因子。随机森林模型对SOC储存的解释度为50.32%~65.82%,土壤含水量对表层土体SOC预测的相对贡献最高,年平均温度、年平均降水量和凋落物质量对各层SOC预测均有显著贡献,而植被类型对SOC预测的相对贡献随剖面加深而逐步增加。【结论】色季拉山西坡不同海拔高度下SOC的储存特征随不同植被类型和剖面深度而发生显著变化,环境因子(如土壤水分)对表层土体SOC储存有关键影响,植被类型对深层土体SOC储量变化的预测有重要贡献。
【Objectives】The montane ecosystems located in the southeastern part of Tibetan Plateau possess great potential of soil carbon sequestration.It is therefore necessary to investigate the variations of soil organic carbon(SOC)with different ecosystems and the influential factors,which can help to improve understanding of soil carbon cycling and the regional balance between carbon source and sink on the Qinghai-Tibetan Plateau.【Methods】The present study conducted an intensive soil sampling from 3000 m to 4600 m above sea level along the west slope of Mount Segrila.Vertical variations in SOC storage under different vegetation types along the elevation gradient were investigated,and the effects of various environmental factors were analyzed.【Results】We found that SOC concentration in 0–5 cm surface soil increased with the increasing of elevation.The averaged SOC content for the four vegetation types was alpine meadow(8.31%±0.77%)>dark coniferous forest(7.20%±0.90%)>alpine shrub meadow(6.74%±0.80%)>coniferous and broad-leaved mixed forest(3.88%±0.46%).SOC contents of 5–10 cm,10–15 cm,15–20 cm,20–30 cm,30–40 cm and 40–60 cm first increased and then decreased with elevation,and the averaged SOC content was dark coniferous forest>alpine shrub meadow>alpine meadow>coniferous and broad-leaved mixed forest.SOC concentration decreased significantly with the increasing of depths along soil profile.The vertical distribution of SOC content showed a surface-accumulated pattern under alpine meadow and alpine shrub meadow,but a gradually decreasing pattern under dark coniferous and coniferous and broad-leaved mixed forests.The variations in SOC stock of 0–20 cm,20–40 cm and 40–60 cm with elevation also presented a unimodal pattern.The SOC stock of surface 0–20 cm in alpine meadow(C 95.66±4.81 t/hm^2)was the highest among all four vegetation types on west slope of Mount Segrila.Dark coniferous forests had the highest SOC stock in 20–40 cm and 40–60 cm,and the total SOC stock of 0–60 cm(C 199.14±11.10 t/hm^2)was significantly higher compared to other vegetation types.The SOC stock in coniferous and broad-leaved mixed forests was significantly lower at each profile depth,making the total SOC stock(C 111.45±10.30 t/hm^2)the lowest among the four vegetation types.The variation in SOC stock was negatively correlated with mean annual temperature(MAT)and litter C/N,but positively correlated with elevation,mean annual precipitation(MAP)and soil moisture.Results of stepwise regression analysis suggested that soil moisture was the key influential factors controlling the variations of SOC in each soil layer and the whole soil profile.Random forest models explained 50.32%–65.82%of variation in SOC.Soil moisture was the most important predictor of variations in SOC storage in the topsoil.MAT,MAP and litter quality were significant predictors of SOC variations in both topsoil and subsoil.The relative importance of vegetation type in predicting SOC increased with soil depth.【Conclusions】The storage of SOC along an elevation gradient of Mount Segrila varies significantly with vegetation type and depth of soil profile.Environmental factors such as soil moisture are the key factors that control the variations of SOC in the topsoil,whereas vegetation types significantly contribute to the prediction of changes in SOC in deep layer of soil profile.
作者
史飞
徐梦
张旭博
王振波
孙志刚
张崇玉
SHI Fei;XU Meng;ZHANG Xu-bo;WANG Zhen-bo;SUN Zhi-gang;ZHANG Chong-yu(College of Agriculture,Guizhou University,Guiyang 550025,China;Key Laboratory of Ecosystem Network Observation and Modeling/Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China;College of Resources and Environment,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《植物营养与肥料学报》
CAS
CSCD
北大核心
2020年第5期942-953,共12页
Journal of Plant Nutrition and Fertilizers
基金
国家自然科学基金项目(41701333,41907036)
中国科学院战略性先导科技专项课题(XDA20040401)
中国科学院科技服务网络计划(STS计划)项目(KFJ-STS-ZDTP-049)。
关键词
土壤有机碳
海拔梯度
山地垂直植被带
剖面深度
青藏高原
soil organic carbon
elevation gradient
montane vegetation transect
profile depth
Qinghai-Tibetan Plateau