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Changes in nitrogen and phosphorus limitation during secondary succession in a karst region in southwest China

Zhang, Wei, Zhao, Jie, Pan, Fujing, Li, Dejun, Chen, Hongsong, Wang, Kelin
Plant and soil 2015 v.391 no.1-2 pp. 77-91
agricultural land, alkaline phosphatase, alkaline soils, correlation, ecosystems, forest communities, grasslands, karsts, nitrogen, nutrients, phosphorus, primary forests, primary productivity, secondary forests, secondary succession, shrublands, soil organic carbon, China
BACKGROUND AND AIMS: Nitrogen (N) and/or phosphorus (P) limitation to primary productivity and other biological processes can change in a variety of ways as ecosystems develop. How N limitation and P limitation change from the early to the late stages of a secondary succession following farmland abandonment remains unclear in karst ecosystems in southwest China. METHODS: We used community foliar N:P ratio, soil alkaline phosphatase activity (APA) and other indicators of nutrient status (soil organic carbon [SOC], total soil N [TN], and total soil P [TP], Alkali-hydrolyzable N [AN], and available soil phosphorus [AP] concentrations) to examine changes in N and P status during secondary vegetation succession. Four types of plant communities (grasslands, shrublands, secondary forest, and primary forest) represented the early, middle, late, and very late successional stages, respectively. RESULTS: Community foliar N:P ratio, APA, and APA per unit SOC increased as succession proceeded from the grassland to the secondary and primary forest communities. Moreover, community foliar N:P ratios in the grassland were positively correlated with soil TN, while community foliar N:P ratios in the secondary forest and primary forest were negatively correlated with soil TP, but were not correlated with soil TN. Community foliar N:P ratios in the shrubland were not correlated with either soil TN or TP. CONCLUSIONS: Our results suggest that the grassland in the karst region of southwest China is N limited, that the secondary and primary forests are P limited, and that the shrubland is constrained by N and P together or by other nutrients.