EFFECT OF NITROGEN ADDITION ON SOIL METABOLISM OF DIFFERENT VEGETATION SUCCESSION STAGES OF KARST ECOSYSTEM IN SOUTHERN CHINA

Nitrogen (N) is a limiting component in the function and stability of karst ecosystems. Different amounts of N additions have been shown to influence the metabolic processes of microbial communities and vegetation. Thus, this study aimed to evaluate how soil metabolism responds to N addition amounts in grassland (GL), shrubland (SL), secondary forest (SF) and primary forest (PF) in karst areas of southern China. Three N addition treatments were applied: no N addition (CN, no N fertilizer), low N addition (LN, 50 kg N ha(-1) year(-1) ), and high N addition (HN, 100 kg N ha(-1) year(-1) ). The results revealed that N addition has a substantial impact on soil metabolite composition and abundance in GL, SL, SF, and PF. Additionally, N addition had distinct impacts on soil metabolism in different vegetation types. N addition significantly reduced several fatty acids in GL, including 9-oxooctadecanoic acid and cis-9,10-epoxystearic acid. N addition to SL resulted in an increase of organoheterocyclic compounds, including clothianidin and gabapentin related compound A. In SF, low N considerably reduced metabolite abundance, while high N dramatically increased metabolite abundance. N addition in PF mainly resulted in the upregulation of soil metabolites. These results provide valuable information for understanding the biochemical impact of N addition in various karst vegetation types.