黄土高原典型植被恢复过程土壤与叶片生态化学计量特征

为揭示黄土高原典型人工植被恢复过程中植物叶片与土壤碳(C)、氮(N)、磷(P)元素变化特征及其交互作用,以延安庙咀沟流域恢复20—40a的刺槐(Robinia pseudoacacia)、柠条(Caragana korshinskii)、草地和坡耕地(对照)为研究对象,分析了各样地植物叶片和土壤C、N、P化学计量的变化特征及相互关系。结果表明:从20a到40a的恢复过程中,3种植被叶片C含量均显著增加,草地叶片P含量显著升高,而刺槐、柠条叶片N和P含量则显著降低。刺槐、柠条及草地土壤C、N、P含量随着恢复年限的延长而增加,比耕地分别增加了70%—349%、27%—202%、13%—62%(P0.05),其中刺槐的增幅最大。从增速来看,刺槐和柠条林土壤表层C、N增速表现为前期(0—20a)大于后期(20—40a),而草地则相反。在20—40a的恢复过程中,刺槐、柠条叶片C∶N、C∶P均显著增加,草地叶片C∶P、N∶P则显著降低。恢复过程中,土壤C∶P在刺槐和草地中显著增加,而土壤N∶P仅在草地中显著增加,土壤C∶N则没有显著变化。相关性分析显示叶片C和土壤C、N、P显著正相关,叶片N、P和土壤N显著正相关,叶片和土壤N∶P显著正相关,叶片P、C∶P与土壤C、N增速显著相关,表明叶片P可以指示土壤C、N增速的变化,而N∶P可以将植物和土壤联系起来。植被恢复过程中,叶片和土壤C、N、P含量及增速均发生显著变化,且存在密切的联系,这种变化的趋势在刺槐、柠条和草地中有所不同。

Ecological stoichiometry characteristics of soil and leaves during the recovery process of typical vegetation on the Loess Plateau

This study aimed to reveal the dynamics and interactions between plant leaves and soil carbon (C), nitrogen (N), and phosphorus (P) in the restoration of typical artificial vegetation on the Loess Plateau, through analysis of the contents and stoichiometric characteristics of C, N, and P in the leaves and soil of Robinia pseudoacacia and Caragana korshinskii, and the associated grassland growing for 20a and 40a in the Miaozuigou catchment area. An area of cropland was selected as the control. The results showed that, from 20a to 40a, the leaf C in the three restored vegetation types and leaf P in the grassland were significantly increased. However, the leaf N and P contents in both R. pseudoacacia and C. korshinskii were significantly deceased. The content of C, N, and P in the soil significantly increased with time since afforestation. Compared with the farmland, the content of C, N, and P in the soil increased by 70-349%, 27-202%, and 13-62% (P < 0.05) respectively, particularly, in Robinia pseudoacacia. Regarding the growth rates of C and N in the topsoil of R. pseudoacacia and C. korshinskii, they were higher in the first 20a (0-20a) than during the late subsequent (20-40a), but in the grassland the opposite trend was observed. From 20 to 40a, both C:N and C:P in R. pseudoacacia and C. korshinskii were significantly increased, while C:P and N:P in the grassland were significantly decreased. During the recovery process, soil C:P in Robinia pseudoacacia and Caragana korshinskii significantly increased, whereas significant increases in soil N:P were only observed in the grassland and soil C:N did not change significantly. The correlation analysis showed that the leaf C was positively and significantly correlated with the C, N, and P in soil; leaf N and P were positively and significantly correlated with soil N; leaf N:P was positively and significantly correlated with soil N:P; and the P and C:P in leaves were positively and significantly correlated with the C and N in soil. These results suggest that leaf P reflects the growth rates of C and N in soil and that the N:P ratio can link plants and soil. During recovery, both contents and growth rates of C, N, and P in soil and leaf changed greatly and differently in R. pseudoacacia, C. korshinskii, and grassland. In addition, the content of P can indicate the change in the growth rate and the N:P ratio in leaf can link soil and leaf.