藏北3种高寒草地植物根系碳氮磷密度的非生长季和生长季差异

Variation of Root Carbon,Nitrogen and Phosphorus Densities in Three Alpine Grasslands in Non-growing Season and Growing Season

根系碳(C)氮(N)磷(P)密度影响植物与土壤间碳氮磷养分的循环过程,从而影响生态系统的地球化学循环。以申扎县高寒草原、高寒草甸草原和高寒草甸3种草地为对象,探究非生长季(4月)和生长季(8月)3种高寒草地根系C、N、P密度的分布规律及其差异。结果表明,(1)3种草地根系C、N、P密度在两个时期均呈现"T"字型空间分布,即3种草地根系C、N、P密度均随着土壤深度的增加而降低,且整体上高寒草甸的养分密度显著高于其他两种草地。3种草地根系C、N、P密度范围分别为57.287-1 130.753、1.457-38.243、0.090-3.217 g·m-2。(2)3种草地的C、N、P密度具有显著的季节差异。生长季,高寒草原总地下C、N密度显著高于非生长季,分别高出非生长季47.822%和60.910%,而总地下P密度无显著差异;而生长季高寒草甸草原总的和每层的地下C、N、P密度显著低于非生长季。高寒草甸总地下C、N、P密度表现为生长季高于非生长季。高寒草原和高寒草甸增加的养分密度集中在0-10 cm深度。高寒草甸、高寒草原及高寒草甸草原的物种组成不同,土壤养分含量差异及土壤水分状况的不同可能是导致3种草地根系养分密度差异的原因。本研究可以为高寒草地根系养分密度季节变化提供基础资料,进一步认识草地根系在养分循环中的作用提供理论支持。

Root carbon(C), nitrogen(N) and phosphorus(P) densities affects the cycling process of carbon, nitrogen and phosphorus nutrients between plants and soil, thus affecting the geochemical cycle of ecosystems. To explore variation and vertical distribution of root C, N and P densities in three types of grassland(alpine steppe, alpine meadow steppe and alpine meadow), a field experiment was conducted in non-growing season(April) and growing season(August) in 2013. The results showed that:(1) The root C, N and P densities showed a pattern of "T" distribution. The ranges of root C, N and P densities were 57.287-1 130.753 g·m-2, 1.457-38.243 g·m-2 and 0.090-3.217 g·m-2. Root C, N and P densities in alpine meadow were higher than alpine steppe and alpine meadow steppe in two periods. And(2) higher root C and N densities were observed in the growing season in alpine steppe, which increased by 47.822% and 60.910%, respectively. Decrease of root C, N and P densities were observed in the growing season of alpine meadow steppe, while C, N and P densities of alpine meadow showed the opposite variation. Increase of root C, N and P densities concentrate in the 0–10 cm depth for alpine steppe and alpine meadow. The different species composition, soil nutrient contents and soil water conditions might be the reasons for the differences in root nutrient density of the three grasslands. This study provides basic data of seasonal variation of alpine grassland root nutrient densities, which provides theoretical support for further understanding of the role of root system in nutrient circulation.