内蒙古和青藏高原草原植物叶片与根系氮利用效率空间格局及影响因素

Patterns and affecting factors of nitrogen use efficiency of plant leaves and roots in Nei Mongol and Qinghai-Xizang Plateau grasslands

氮利用效率是植物的关键功能性状,同时紧密关联生态系统功能,但是目前对氮利用效率的区域格局及影响因素仍然不清楚。该研究分析了内蒙古和青藏高原草原82个调查地点、139种植物叶片和根系的氮利用效率及其与环境因素、植物功能群之间的关系,实验结果显示:1)草甸草原植物叶片的氮利用效率为53 g·g^–1,显著大于高寒草甸(46g·g^–1)、荒漠草原(41g·g^–1)和典型草原(39g·g^–1)。高寒草甸根系氮利用效率为108g·g^–1,显著高于其他生态系统。2)叶片氮利用效率比根系对温度更加敏感,但随着干旱指数的增加,两者均表现出显著的降低趋势。3)杂类草叶片和根系氮利用效率低于莎草科和禾本科植物,豆科植物叶片和根系氮利用效率分别比非豆科植物低48%和60%。4)植物氮利用效率与土壤氮含量之间没有显著关系。总体上,内蒙古和青藏高原草原植物叶片和根系氮利用效率的空间格局存在差异,主要影响因素为植物功能群和干旱指数。本研究系统揭示内蒙古和青藏高原草原植物氮利用效率的空间格局及关键驱动因子,有助于在全球变化背景下了解我国草地生产力维持机制,同时为草原生态系统管理提供科学依据。

Aims Nitrogen use efficiency(NUE) is a key functional trait in plants, which closely relates to ecosystem functions. However, it is still unclear about the regional patterns and affecting factors of plant NUE. Methods This study quantified leaf and root NUE in 139 grassland plant species and explored their relationships with environmental factors and plant functional groups across 82 sampling sites in Nei Mongol and QinghaiXizang Plateau. Important findings 1) We found that leaf NUE(53 g·g^–1) in meadow steppe was significantly greater than those in alpine meadow(46 g·g^–1), desert steppe(41 g·g^–1) and typical steppe(39 g·g^–1). Root NUE(108 g·g^–1) in alpine meadow was higher than those in other ecosystems. 2) Leaf NUE was more sensitive to temperature than root NUE, but with increasing drought index they all showed a significant decrease. 3) Leaf and root NUE in forbs were significantly lower than sedges and grasses. In addition, leaf and root NUE of legume were 48% and 60% lower than those of non-legume, respectively. 4) Plant NUE did not show any significant relationship with soil nitrogen content. Overall, there was significant difference between leaf and root NUE in their spatial patterns in the Nei Mongol and Qinghai-Xizang Plateau grasslands. The main impacting factors were plant functional group and drought index. The findings are helpful for better understanding the mechanisms underlying the variation of grassland productivity in China, and also provide more scientific basis for grassland management.