第七届青年地学论坛

Land use changes are of serious concern due to its effects on soil carbon stock, which is second largest anthropogenic source of atmosphere CO₂. To better understand these effects in typical and fragile ecosystems like dry-hot valley regions, we quantified changes in soil properties (pH, organic carbon, total nitrogen, phosphorus, microbial biomass carbon contents, activities of β-glucosidase, beta-N-acetyl-glucosaminidase, acid phosphatase) and CO₂ efflux before (degraded grassland) and after (mango plantation) land use change in a dry-hot valley region. Most soil chemical properties remained unaffected after conversion due to generally low regional nutrient levels. Principal component analysis revealed the decline of soil heterogeneity of the selected properties (pH, SOC, TN, TP, AP), which will be useful for future unified management. Compared to grassland, CO₂ efflux in mango plantation increased by 20–69% after land use change, more factors and their interactions were responsible for CO₂ efflux from soil in mango plantations. The temperature sensitivity (Q₁₀: 0.68–1.98) of CO₂ efflux in both land use types was low due to the low soil moisture at high temperatures. Soil water content was the primary factor affecting CO₂ efflux in the dry-hot valley region, followed by microbial biomass carbon. In summary, the CO₂ efflux increased shortly after the land use change (within first year), even though absence of significant quantitative change of soil properties, and low temperature sensitive (Q₁₀) before and after conversion and its difference between land use types is opposite in dry and wet season.

Fragile ecosystems;,Carbon emission;,land use pattern,soil microbial communities