Soil water conditions together with plant nitrogen acquisition strategies control vegetation dynamics in semi-arid wetlands undergoing land management changes

Abstract

Land management changes can significantly alter wetland soil environment, vegetation, and their interactions. Although the relationships between plant communities and environmental factors have been widely studied, the intrinsic driving mechanisms of vegetation dynamics are poorly understood because nutrient acquisition strategies play an important role in plant community assembly. This study compared the plant community characteristics of wetlands under different land management practices in the semi-arid western Songnen Plain, Northeast China, and investigated soil properties and plant community nutrient contents. Results showed compared with those in natural wetlands, the values of growth characteristics of plant communities were generally lower, whereas species diversity was higher in grazed or mowed wetlands. Furthermore, soil carbon (C), nitrogen (N), phosphorus (P) contents, their stoichiometric ratios, and soil water content were lower, and N contents in leaves and stems, soil bulk density, and pH were higher compared with those in natural wetlands. The plant community characteristics were significantly correlated with soil properties and plant nutrient contents. A redundancy analysis showed that soil water content, bulk density, and organic carbon, accounted for 59.3%, 15.6%, and 2.9%, respectively, the N in leaves, stems, and roots accounted for 62.8%, and the P in leaves and roots accounted for 12.2% of the variation in the plant community. Variation partitioning analysis further demonstrated that soil properties, plant nutrient contents, and their interactions explained 19.1 %, 11.8%, and 59.4% of the variation in the plant community, respectively. Therefore, the wetland vegetation dynamics are combinedly controlled by soil properties (especially soil water conditions) and plant nutrient acquisition strategies (especially plant nitrogen acquisition) under different land management practices. This study provides the theoretical basis for maintaining the stability of wetland ecosystems by designing plant resources-related managements in semi-arid regions.