半干旱黄土小流域不同植被类型植物与土壤生态化学计量特征

生态化学计量学是研究生态系统元素平衡与能量流动的有效方法，明确不同植被恢复类型下植物与土壤化学计量特征对揭示黄土高原植被恢复中生态系统养分循环具重要意义，可为黄土高原植被恢复类型的选择提供可行性依据。以典型半干旱黄土小流域3种植被恢复方式下（天然荒草、自然恢复、人工恢复）的5种植被类型（长芒草草地、赖草草地、苜蓿草地、柠条灌丛、山杏林）为研究对象，分析不同植被类型下叶、茎、根及土壤碳（C）、氮（N）、磷（P）含量及化学计量特征。结果表明：1）植物不同器官和植被类型对植物生态化学计量特征都具有显著影响，C、N、P含量在5种典型植被中均表现为叶>茎>根。人工恢复植被各器官C、N含量及N ∶ P均显著高于天然荒草地，与自然恢复植被无显著差异；其中，在人工恢复植被中山杏各器官C含量最高，柠条各器官N含量最高。叶、茎、根的C ∶ N则表现为自然恢复植被显著高于人工恢复植被与天然荒草地。P含量、C ∶ P则在不同植被恢复类型间无显著差异。2）不同植被恢复类型下土壤C、N、P含量及化学计量特征具一定差异。人工恢复植被土壤C、N、P含量及C ∶ P、N ∶ P均为最高，显著高于自然恢复植被土壤；人工恢复植被中柠条土壤C、N含量及C ∶ P、N ∶ P均显著高于其他植被土壤。土壤C ∶ N在各植被类型间无显著差异。3）不同植被恢复类型下C、N、P含量在植物叶片与土壤间的相关性存在差异，说明植物自身生长特性影响着养分在植物与土壤间转化与传递。以5种典型植被整体来看，植物叶、茎、根的生态化学计量特征在彼此间均呈显著正相关。在植物与土壤间，植物各器官N含量与土壤C、N、P含量呈显著正相关，植物各器官N ∶ P与土壤N ∶ P呈显著正相关，表明该黄土小流域生态系统中植物与土壤生态化学计量特征的变化是相互制约，相互影响的。

Ecological stoichiometry characteristics of plants and soil under different vegetation types in the semi-arid loess small watershed

Ecological stoichiometry is an effective method to study the element balance and energy flow of ecosystem. Defining the stoichiometry characteristics of plants and soil under different vegetation types is of great significance to reveal the nutrient cycling of ecosystem in the process of vegetation restoration on the Loess Plateau. It can provide a feasible basis for the selection of vegetation restoration types on the Loess Plateau. In this study, five vegetation types (Stipa bungeana grassland, Leymus secalinus grassland, Medicago sativa grassland, Caragana korshinskii shrub, and Armeniaca sibirica forest) under three vegetation restoration methods (natural grassland, natural restoration and artificial restoration) in the semi-arid loess small watershed were selected as research objects. The carbon (C), nitrogen (N), phosphorus (P) concentrations and ecological stoichiometry characteristics of leaves, stems, roots and soil under different vegetation types were analyzed. The results showed that: 1) plant organs and vegetation types had significant effects on plant ecological stoichiometry characteristics. The concentrations of C, N and P in five vegetation types were leaf > stem > root. The concentrations of C, N and N:P in all organs of the artificial restoration vegetation were significantly higher than those in the natural grassland. There was no significant difference between the artificial restoration vegetation and the natural restoration vegetation. Among them, C concentration in all organs of A. sibirica and N concentration in all organs of C. korshinskii were the highest in artificial restoration vegetation. The C:N of natural restoration vegetation was significantly higher than that of artificial restoration vegetation and natural grassland. The concentration of P and C:P had no significant difference among different vegetation types. 2) There were some differences in soil ecological stoichiometry characteristics under different vegetation types. The concentrations of C, N, P, C:P, and N:P in artificial restoration vegetation soil were the highest, significantly higher than those in natural restoration vegetation soil. The C, N concentrations and C:P, N:P of C. korshinskii soil in artificial restoration vegetation were significantly higher than those of other vegetation soils. There was no significant difference in soil P concentration and C:N between five vegetation types. 3) The correlation of C, N and P concentrations between plant leaves and soil was different under different vegetation types, which indicated that plant growth characteristics affected the transformation and transfer of nutrients between plant and soil. In conclusion, the ecological stoichiometry characteristics of leaves, stems and roots of vegetation showed a significantly positive correlation with each other. Between plant and soil, there was a significantly positive correlation between plant N concentration and soil C, N, P concentrations, and a significantly positive correlation between plant N:P and soil N:P, indicating that the changes of ecological stoichiometry characteristics of plant and soil in the Loess small watershed ecosystem were restricted and influenced each other.