Changes in Plant Nitrogen Uptake Strategies Following Vegetation Recovery in Karst Regions
2025
Lin Yang | Lijun Liu | Hui Yang | Shuting Yang | Tongbin Zhu | Lei Meng | Dongni Wen
Understanding plant nitrogen (N) uptake strategies during vegetation recovery is essential for restoring and rehabilitating degraded ecosystems. However, there are few studies on plant N uptake strategies in karst regions. In this study, space-for-time substitution was used to investigate the dynamic changes in plant N uptake strategies during vegetation restoration. Grassland, shrub&ndash:grassland, shrubland, and woodland naturally recovering in karst ecosystems were chosen as the research objects. The dominant species at each stage were investigated. Dominant plant N uptake rates were measured using the 15N labeling technique, and plant root functional traits and available soil N were determined. Our results showed that soil inorganic N content and composition varied significantly with vegetation recovery. In early vegetation recovery stages, the soil inorganic N content was low and dominated by ammonium (NH4+), while in the late stages, soil inorganic N content increased, and nitrate (NO3&minus:) became the dominant form. In early vegetation recovery stages, dominant plants preferentially absorbed NH4+, contributing to 90.3%&ndash:98.5% of the total N uptake. With vegetation recovery, plants increased the NO3&minus: uptake ratio from 1.48%&ndash:9.42% to 30.1%&ndash:42.6%. Additionally, the root functional traits of dominant plants changed significantly during vegetation recovery. With vegetation recovery, specific root lengths and specific root areas decreased, while root N content and plant N uptake rates increased. In summary, plants developed N uptake strategies coordinated with soil N supply by modifying root functional traits following vegetation recovery in karst regions.
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