Soil micro‐organisms play a key role in soil biogeochemical cycles, but their growth and activities are often limited by resource availability. Understanding soil processes that are driven by micro‐organisms and resource limitation of microbes will help to elucidate controls on soil fertility and improve the ability to predict the responses of an ecosystem to global changes. As a widespread ecosystem type, karst ecosystem develops from limestone or dolomite with unique soil; however, karst ecosystems remain poorly understood regarding their soil microbial processes and microbial resource limitation. Here, ecoenzymatic stoichiometry was used as an indicator of microbial resource limitation, and to model major microbial processes (i.e. decomposition of soil organic carbon and microbial respiration) in a karst and a non‐karst forest. Results showed that the modelled decomposition and respiration rates were significantly higher in the karst forest than in the non‐karst forest. In addition, results of ecoenzymatic stoichiometry showed that the karst forest was more carbon‐limited than the non‐karst forest. In contrast, the karst forest was likely saturated with nitrogen, but the non‐karst forest was limited by nitrogen. Both the karst and non‐karst forests were limited by phosphorus, but phosphorus deficiency was more evident in the non‐karst forest than in the karst forest. These findings highlight the specific profiles of karst ecosystems, and they suggest that the responses of karst ecosystems to global changes should be very different compared to other ecosystems. A plain language summary is available for this article.

Agricultural abandonment is regarded as a major driver of soil organic carbon (C) dynamics, but the mechanisms underlying the direction and magnitude of soil C dynamics following agricultural abandonment are poorly understood. Here dynamics of soil C and N contents during postagricultural succession were investigated in areas underlain by dolomite or limestone by using a space‐for‐time substitution approach in a karst region, southwest China. One hundred twenty‐five sites from cropland, grassland, shrubland, and secondary forest were selected to represent different succession stages. Overall, soil C and N contents were greater (P < 0.05) over limestone than over dolomite mainly due to significantly greater contents of soil C and N in the cropland and grassland underlain by limestone. Both soil C and N contents were lowest in the cropland while highest in the forest. Further analysis indicated that the patterns of soil C and N dynamics differed between the two lithology types. Soil C and N contents increased significantly from cropland to forest over dolomite, while varied insignificantly among succession stages over limestone. Exchangeable calcium explained most of soil C and N variance. We proposed that higher dissolution rate of limestone could replenish the lost calcium so that the calcium levels, and in turn soil C and N contents, were stable from the cropland to the forest. Nevertheless, due to relatively low dissolution rate for dolomite, the calcium level was depleted in the cropland. Following agricultural abandonment, calcium level recovered due to decreased loss, which in turn resulted in recovery of soil C and N.