Browsing by Author "Hassa, Wassem"

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    Differential impacts of nitrogen addition on soil dissolved organic carbon in humid and non-humid regions: A global meta-analysis
    (Elsevier, 2025-03-01) Ren, Tianjing; Smreczak, Bożena; Ukalska-Jaruga, Aleksandra; Li, Xiaojie; Hassa, Wassem; Cai, Andong
    Soil dissolved organic carbon (DOC) is the most active carbon pool, providing essential carbon and energy to soil microorganisms while playing a crucial role in carbon sequestration, transport, and stabilization in soils. Nitrogen (N) addition, a key factor influencing terrestrial carbon cycling, can significantly alter soil DOC dynamics. However, the global patterns and underlying drivers of DOC responses to N addition, particularly across regions with varying aridity indices, remain unclear. This study analyzed 1132 paired observations from 103 independent studies to quantify the response pattern of DOC to N addition in humid (554 observations) and non-humid (574 observations) regions and identify the factors driving these effects. The findings revealed an asymmetrical effect of N addition on soil DOC between humid and non-humid regions, rather than on microbial biomass carbon (MBC) or soil organic carbon (SOC). Specifically, N addition significantly decreased soil DOC (􀀀 2.49%) in humid regions, while it increased DOC (7.30%) in non-humid regions. The effect size of soil DOC decreased linearly with the ratio of MBC to SOC in humid regions but increased linearly in non-humid regions. In humid regions, soil DOC response was positively correlated with initial MBC and inversely correlated with initial soil pH, whereas the opposite trend was observed in non-humid regions. Seasonal precipitation variability was identified as a significant driver of soil DOC response, independent of temperature, soil properties, and N addition rates. Moreover, initial SOC content was the primary driving factor for soil DOC response in humid regions, while the N addition rates were the primary driver in non-humid regions. These findings have important implications for enhancing soil carbon pool management, improving global carbon models, and addressing climate change, particularly under varying climatic conditions.