喀斯特区不同退化程度植被群落植物-凋落物-土壤-微生物生态化学计量特征

为摸清喀斯特植被退化对群落各组分C、N、P生态化学计量特征及内稳态特征的影响,为喀斯特退化生态系统植被恢复与重建提供科学依据,以桂西北喀斯特地区5种退化程度植被群落为研究对象,测定了不同退化程度植被群落植物叶片、凋落物、土壤和微生物生物量的C、N、P含量,分析其化学计量比特征、相互关系及植物内稳性特征。结果表明：(1)随着退化程度加剧,叶片C、N、P含量、N∶P和凋落物N∶P、微生物量C显著下降,而叶片C∶N、C∶P则显著增加,且植物叶片N∶P<14;随退化程度加剧,凋落物N、P含量、土壤C、N、P含量、微生物量N、P呈先略有增后显著降低的趋势,且不同退化程度群落土壤N∶P和微生物量C∶N无显著差异。(2)叶片N、P含量与土壤N、P含量,叶片C∶P与土壤C∶N、C∶P、N∶P,叶片N∶P与凋落物N、N∶P,叶片C、N、P含量与微生物量C呈显著或极显著正相关关系;叶片C∶N与土壤C、N,叶片C∶P与土壤N、P,叶片N∶P与土壤P呈显著或极显著负相关关系。(3)喀斯特地区植物叶片N、P元素的内稳性指数(H)平均值分别为2.74和2.31,属于弱稳态型,叶片N∶P的H值为5.14,为稳...

Carbon, nitrogen and phosphorus stoichiometry in plants, litter, soil, and microbes in degraded vegetation communities in a karst area of southwest China

Carbon (C), nitrogen (N) and phosphorus (P) stoichiometry in plants, litter, soil, and microbes in degraded vegetation communities were studied to provide a scientific basis for vegetation restoration and reconstruction for the karst area of southwest China. Five degraded vegetation communities in the karst area of northwest Guangxi were selected. C, N, and P contents of plant leaves, litter, soil and microbial biomass were determined. The stoichiometric characteristics of plant, litter, soil, microbial biomass and their relationships and the homeostasis of plant were analyzed. With the intensified degradation of the vegetation community, the leaf C, N, P content, N:P, litter N:P, and microbial biomass C decreased significantly, while the leaf C:N and C:P increased significantly and N:P of plant leaves was less than 14 in all communities. Litter N, P contents, soil C, N, P contents, microbial biomass N, P contents showed a trend of increase firstly and then significantly decreased with the intensified degradation degrees. There was no significant difference in soil N:P and microbial biomass C:N among communities with different degradation degrees. Leaf N and P were significant or extremely significantly positively correlated with soil N and P. Leaf C:P was significant or extremely significantly positively correlated with soil C:N,C:P, and N:P. The leaf N:P and litter N, N:P, as well as leaf C, N, P contents and microbial biomass C content were significantly positively correlated. The leaf N, P and soil C:P, N:P, leaf C:N and soil C, N, leaf C:P and soil N, P, leaf N:P and soil P showed significantly or extremely significantly negative correlations. The average values of the homeostasis index H of plant leaf N and P in the karst area were 2.74 and 2.31, respectively, which indicated the weak steady state. The H value of leaf N:P was 5.14, implying a steady state. Compared with N and P, the element ratio N:P had higher internal stability. The degradation of karst community caused the change of C, N, P contents and their stoichiometry. Plant N:P ratio showed somewhat homeostasis when soil nutrient changed, indicating that plants had a good adaptability to karst degraded ecosystem. The degradation resulted in increased limitation of plant growth by N. Our results suggest that soil N availability is critical for vegetation restoration in the karst areas of northwest Guangxi.