水氮控制对短花针茅荒漠草原根系分解的影响

Effects of water and nitrogen treatments on root decomposition in a Stipa breviflora desert steppe

全球变化导致氮沉降增加和降雨格局发生变化,从而影响短花针茅荒漠草原植物根系分解过程.为了解水氮变化对荒漠草原根系凋落物分解的影响,采用凋落物分解网袋法,以建群种短花针茅(Stipa breviflora)和优势种冷蒿(Artemisia frigida)、无芒隐子草(Cleistogenes songorica)3种植物混合根系为研究对象,分析其分解动态变化.试验采用裂区设计,主区为自然降雨(CK)、增雨30%(W)和减雨30%(R)3个水分处理,副区为0(N0)、30(N30)、50(N50)和100(N100)kg hm-2 a-1 4个氮素处理共12个处理.结果显示:分解630 d后,增雨显著降低根系质量残留率,3个水分处理分别在CK-N50、W-N50、R-N30处理下质量残留率最低,分别为63.13%、60.33%、69.90%,W-N50处理根系质量残留率显著低于其余11个处理(P <0.05).适量的氮输入可以促进根系分解,但过量氮会对根系分解产生抑制作用.本研究表明荒漠草原影响根系质量残留率的主要因素为水分,次要因素为氮素.水氮变化首先会影响根系的基质质量,从而进一步影响根系分解质量残留率,碳含量、氮含量、纤维素、木质素均是根系分解过程中的决定性因素.(图3表4参36)

Global climate change increases nitrogen deposition and modifies rainfall patterns, which in turn affects the whole root system decomposition process of the Stipa breviflora desert grassland ecosystem. This study used the litter decomposition net bag method to study the dynamic changes in the decomposition of the roots of three plant species, Stipa breviflora, Artemisia frigida, and Cleistogenes songorica, to understand how changes in water and nitrogen affect litter decomposition in a desert grassland root system. We used a split-zone test design to create 12 treatments comprising three moisture treatments: natural rainfall(CK), 30% rain enhancement(W), and 30% rain reduction(R);each of these comprised four different nitrogen(N) treatments: 0(N0), 30(N30), 50(N50), and 100(N100) kg hm-2 a-1. The results showed that after 630 days of decomposition, increasing the rainfall significantly reduced the root mass residue rate, and among the three moisture treatments, CK-N50, W-N50, and R-N30 treatments resulted in the lowest mass residue rates of 63.13%, 60.33%, and 69.90%, respectively. The residual rate of roots subjected to N50 treatment was significantly lower than that of roots subjected to the other 11 treatments(P < 0.05). Appropriate N input can promote root decomposition, but excessive N can inhibit root decomposition. Our study showed that water is the main factor affecting the residual rate of root mass in the desert steppe, with N being secondary factor. Changes in water and N concentrations will affect the quality of the root system’s matrix, which will further affect the residual rate of root decomposition. Additionally, the carbon, N, cellulose, and lignin contents are factors affecting the root decomposition process.