Objective This study aims to reveal the nutrient utilization strategies and calcareous habitat adaptation mechanisms of different forest types in the limestone mountainous ecosystem of northern Guangdong, and to provide a theoretical basis for ecological restoration.

Method We investigated plantations (Cornus wilsoniana, Chukrasia tabularis, Liquidambar formosana) and natural secondary forests (Zenia insignis, Triadica rotundifolia, Celtis sinensis) in northern Guangdong, where the carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) contents and ecological stoichiometric characteristics of soil, roots, and leaves were measured and analyzed.

Result The soil concentrations of C, N, Ca, and Mg in natural secondary forests (59.02, 3.65, 7.43, and 4.61 g/kg, respectively) were higher than those in plantations (17.72, 1.74, 1.95, and 1.95 g/kg, respectively). Both forest types exhibited high Ca levels (soil Ca: 1.95 g/kg in plantations and 7.43 g/kg in natural secondary forests; leaf Ca: 32.91 g/kg in plantations and 38.60 g/kg in natural secondary forests). In plantations, root P content was significantly positively correlated with leaf N content (P<0.05), while root K/P was highly significantly negatively correlated with leaf N/K and Ca/K(P<0.01). Root C/P was highly significantly positively correlated with leaf C/N (P<0.01), and soil C/K was significantly negatively correlated with leaf C/N (P<0.05). These correlations indicate that plantations probably experience N limitation and may also face potential P or K limitations. In natural secondary forests, soil P content was significantly positively correlated with leaf P content (P<0.05), soil N content was significantly positively correlated with leaf C/P (P<0.05), and soil Ca content was significantly positively correlated with root N/P and leaf C/K (P<0.05), suggesting that natural secondary forests may be co-limited by P and K.

Conclusion The nutrient sequestration capacity of natural secondary forests is superior to that of plantations. Plantations require sustained increased inputs of N, while supplementation of P and K should be emphasized in natural secondary forests.