固氮树种引种对喀斯特区土壤-微生物生态化学计量特征的影响

Effects of introducing nitrogen-fixing tree species on soil-microbial ecological stoichiometric characteristics in karst areas

关键词:  喀斯特，固氮树种，化学计量比，微生物熵，化学计量不平衡性

Key words:  Karst, nitrogen-fixing tree species, stoichiometric ratios, microbial quotient, Stoichiometric imbalance

摘要:

生态化学计量学主要研究生态系统中生物体及其环境间化学元素的比例关系，是揭示生命活动与生态系统功能的基础。研究喀斯特地区不同类型树种的土壤-微生物生物量及其生态化学计量特征，对科学评估不同类型树种改善土壤养分状况的效能以及优化树种配置策略等方面具有关键作用。该研究以广西壮族自治区凭祥市中国林业科学研究院热带林业实验中心大青山石山树木园中5种固氮树种（nitrogen-fixing tree species，N-fixer）和7种非固氮树种（non-nitrogen-fixing tree species，non-N-fixer）为研究对象，研究喀斯特地区土壤-微生物生物量碳（C）、氮（N）、磷（P）对固氮和非固氮树种的响应特征，并分析其生态化学计量比、微生物熵（qMBC、qMBN、qMBP）以及土壤-微生物化学计量不平衡性（Cimb: Nimb、Cimb: Pimb、Nimb: Pimb）之间的关系。结果表明：（1）固氮树种土壤的全氮（Nsoil）含量和全磷（Psoil）含量显著高于非固氮树种，Csoil: Nsoil显著低于非固氮树种。（2）土壤微生物生物量碳（MBC）、微生物生物量氮（MBN）和微生物生物量磷（MBP）含量均表现为固氮树种显著高于非固氮树种；MBC: MBP和MBN: MBP表现为固氮树种显著低于非固氮树种；Cimb: Nimb、Cimb: Pimb和Nimb: Pimb在固氮树种与非固氮树种间无显著差异，具有一定的内稳性特征。（3）qMBC表现为固氮树种显著大于非固氮树种，而qMBN和qMBP在这两种类型树种间无显著差异。通过RDA结果可知，Csoil: Psoil、MBN: MBP和Csoil: Nsoil是影响土壤微生物熵的关键因素。该研究表明，相较于非固氮树种，固氮树种在改善喀斯特地区土壤养分状况和缓解土壤P限制方面具有显著优势，这将为生态修复过程中树种的选择提供重要的科学依据。

Abstract:

Ecological stoichiometry primarily investigates the proportional relationships of chemical elements between organisms and their environment within ecosystems. It serves as a fundamental framework for understanding life processes and ecosystem functions. The study of soil-microbial biomass and their ecological stoichiometric characteristics of different types of tree species in karst areas is crucial for scientifically assessing the effectiveness of various tree types in improving soil nutrient conditions and optimizing tree species configuration strategies. This study was conducted in the Experimental Center of Tropical Forestry, Chinese Academy of Forestry. It focused on five nitrogen-fixing tree species (N-fixer) and seven non-nitrogen-fixing tree species (non-N-fixer). The research investigated the response patterns of soil and microbial carbon (C), nitrogen (N) and phosphorus (P) contents to nitrogen-fixing and non-nitrogen-fixing tree species in karst ecosystems. It also analyzed ecological stoichiometric ratios, microbial quotient (qMBC, qMBN and qMBP), and stoichiometric imbalance (Cimb: Nimb, Cimb: Pimb and Nimb: Pimb). The results were as follows: (1) The total nitrogen (Nsoil) content and total phosphorus (Psoil) content of the soil in nitrogen-fixing species were significantly higher than those in non-nitrogen-fixing species, but Csoil: Nsoil was significantly lower than those in non-nitrogen-fixing species. (2) The contents of microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and microbial biomass phosphorus (MBP) were significantly higher in nitrogen-fixing tree species than in non-nitrogen-fixing tree species. In contrast, the ratios of MBC: MBP and MBN: MBP were significantly lower in nitrogen-fixing tree species than in non-nitrogen-fixing tree species. No significant differences were observed between nitrogen-fixing and non-nitrogen-fixing tree species for Cimb: Nimb, Cimb: Pimb and Nimb: Pimb, indicating that they were characterized by a certain degree of internal stability. (3) qMBC showed that nitrogen-fixing species were significantly larger than non-nitrogen-fixing species, while qMBN and qMBP showed no significant difference between these two types of species. The RDA results showed that Csoil: Psoil、MBN: MBP and Csoil: Nsoil were the key factors influencing soil microbial quotient. This study shows that compared with non-nitrogen-fixing tree species, nitrogen-fixing tree species have significant advantages in improving soil nutrient status and alleviating soil P limitation in karst areas, which will provide an important scientific basis for the selection of tree species in the process of ecological restoration.