黄土丘陵区柠条人工林土壤呼吸速率对碳输入方式改变的响应

凋落物和植物根系作为土壤碳储量的主要植物性碳源，其质及量的改变可影响土壤碳汇功能。以黄土丘陵区柠条人工林为对象，设置移除凋落物、双倍凋落物、切根、移凋切根和保持原状5种碳输入方式，利用LI-8100土壤碳通量测量仪测定生长季（5-10月）土壤呼吸速率，以期阐明柠条人工林土壤呼吸速率对碳输入方式改变的响应。结果表明:1）各碳输入方式5-10月土壤呼吸速率呈单峰趋势，均在7月最高，10月最低；相比保持原状，双倍凋落物下5-10月累计土壤呼吸速率增加了22.73%，而移凋、切根和移凋切根的5-10月累计土壤呼吸速率分别减少27.57%、40.90%和33.83%；2）根系呼吸、凋落物呼吸和土壤矿质呼吸对土壤呼吸的相对贡献率由大到小分别为土壤矿质呼吸(68.58%)>根系呼吸(38.41%)>凋落物呼吸(24.65%)；3）各碳输入方式下土壤呼吸速率与土壤温度呈显著指数相关，而与土壤湿度的二次关系不显著；土壤温度和湿度的双变量复合模型对土壤呼吸速率月变化解释率53%~93%，高于土壤温度和湿度的单因子模型对土壤呼吸速率月变化解释率53%~74%和0.6%~23.2%；相比保持原状，去凋、双倍凋落物、切根和移凋切根均降低了土壤温度敏感性。研究表明，柠条人工林地表凋落物的积累过多可能减弱土壤碳汇功能。

Response of Soil Respiration to Carbon Input in Caragana korshinskii Plantation in Loess Hilly Region

Litter and plant roots are the main plant carbon sources of soil carbon storage,and their qualitative and quantitative changes can affect the function of soil carbon sinks.In this study,taking the Caragana korshinskii plantation in the loess hilly area as the research object,five modes of carbon input were set up,i.e.,no litter (NL),double litter (DL),no root (NR),no litter and root (no carbon input,NI),and maintaining the original state (control).Soil carbon flux meter LI-8100 was used to measure the soil respiration rate (SRR) in growing seasons (May-October) to clarify the response of SRR of C.korshinskii plantation to the changes of carbon input.The results showed that 1) the SRR of each carbon input mode showed a single-peak trend from May to October,with the highest value in July and the lowest one in October.Compared with the control,the SRR with DL mode increased by 22.73% from May to October,while those with the modes of NL,NR,and NI decreased by 27.57%,40.90% and 33.83%,respectively.2) The relative contribution rates of root respiration,litter respiration and soil mineral respiration to soil respiration were 38.41%,24.65%,and 68.58%.3) There existed significant exponential relationship between SRR and soil temperature under five modes of carbon input,however,no significant quadratic relationship between SRR and soil moisture.The combined bivariate model of soil temperature and moisture explained the monthly variation of SRR by 53%-93%,while the single factor models of temperature and moisture explained by 53%-74% and 0.6%-23.2%,respectively.Compared with the control,other four modes of carbon input all reduced the soil temperature sensitivity.It was suggested that too much litter accumulation of on the ground of C.korshinskii plantation might weaken the soil carbon sink function.