黄土丘陵区侵蚀坡面CO2通量空间分异格局驱动机制

以黄土丘陵区不同有机碳水平的完整侵蚀坡面为对象，解析了CO₂通量的空间分异格局驱动因子及过程机制，并构建了CO₂通量的分段测算模型.结果表明：（1）侵蚀导致坡面土壤CO₂通量的空间分异格局，具体表现为沉积区（S）>对照区（CK）>侵蚀区（E）；有机碳水平的提高可以整体促进各部位CO₂通量的增加.（2）侵蚀可导致土壤水分、容重和团聚体稳定性降低，引起土壤养分流失，降低细菌、真菌多样性；沉积则引起相反的现象.侵蚀/沉积过程对土壤温度的影响并不显著.有机碳水平的增加可以有效改善土壤颗粒、土壤水分，增加容重，抑制土壤养分的流失、增加细菌，降低真菌多样性.（3）结构方程模型解析了侵蚀部位、土壤温度、土壤水分、有机碳（SOC）、水溶性碳（DOC）、微生物碳（SMBC）、真菌多样性、细菌多样性对于CO₂通量的多因素耦合驱动机制（R²=77%），明确了土壤温度、土壤水分、微生物碳为CO₂通量的直接影响因子.在水热双因子模型的基础上，嵌入能够间接表征微生物活性和有效碳底物的C因子，分段（按照坡面侵蚀部位）建立T&M&C模型，可以较为准确地测算侵蚀坡面不同部位CO₂通量（R²>67%）.

Driving mechanism of spatial differentiation patterns of CO2 flux on eroded slope in loess hilly region

On eroded slopes with different soil organic carbon (SOC) levels in loess hilly region, the spatial differentiation patterns driving factors and process mechanisms of CO₂ fluxes were analyzed, and a subsection model of CO₂ fluxes was constructed. The results showed that: (1) The spatial differentiation patterns of soil CO₂ flux on slopes caused by erosion was as follows: sedimentary area (S) > control area (CK) > eroded area (E); the increase of SOC level can promote the increase of CO₂ flux in all parts of slope. (2) The erosion reduced soil moisture, bulk density and aggregate stability, cause soil nutrient loss, reduce bacteria diversity and fungal diversity; sedimentation caused the opposite phenomenon. The effect of erosion/sedimentation process on soil temperature was not significant. The increase of SOC level can effectively improve soil particles, soil moisture, increase bulk density, inhibit soil nutrient loss, increase bacteria diversity but reduce fungal diversity. (3) Our structural equation model analyzed the multi-factor driving mechanism of erosion location, soil temperature, soil moisture, SOC, DOC, SMBC, fungal diversity and bacterial diversity on CO₂ flux (R²=77%). Our model also identified soil temperature, soil moisture and SMBC as the direct influencing factors of CO₂ flux. Based on the two-factors hydrothermal model, the T&M&C model was built by embedding the C factor which could indirectly represent the microbial activity and available carbon substrate, thus allowing to estimate more accurately the CO₂ flux in different parts of the erosion slope (R²>67%).