Sun Jingyao, Li Xinrong
Shapotou Desert Research and Experiment Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China.
Gansu Provincial Key Laboratory of Stress Eco-Physiology in Cold and Arid Regions, Lanzhou, China.
Front Plant Sci. 2022 May 26;13:835668. doi: 10.3389/fpls.2022.835668. eCollection 2022.
The species diversity of biocrusts is an important community characteristic in determining their multiple ecosystem functions. Hence, understanding the diversity patterns of biocrusts and their environmental drivers is of fundamental importance. However, explain variables often correlated with each other; thus, the confounding effects among them may arise and result in spurious causal relationships and biased ecological inferences. In this study, we investigated the richness of three biocrust-forming components (mosses, lichens, and cyanobacteria-algae) and their environmental variables across six desert regions of northern China. A comparison between conventional redundancy analysis (RDA) and structural equation model (SEM) was conducted to study the environmental driver-richness relationship and the confounding effects. Our results showed that three latent variables related to water availability, soil texture, and soil salinity and sodicity, could account for the main environmental variations and explain the diversity patterns of biocrusts at the intracontinental scale. Water availability was positively and negatively related to the richness of mosses and cyanobacteria-algae, respectively, while soil texture was positively related to the richness of lichens. In addition, environmental variables confounded with each other caused distinct driver-richness relationships between results of RDA and SEM. Therefore, we suggest that future multivariable studies should utilize path analysis in conjunction with conventional canonical ordination to facilitate more rigorous ecological inferences.
生物结皮的物种多样性是决定其多种生态系统功能的一个重要群落特征。因此，了解生物结皮的多样性模式及其环境驱动因素至关重要。然而，解释变量往往相互关联；因此，它们之间可能会产生混杂效应，导致虚假的因果关系和有偏差的生态推断。在本研究中，我们调查了中国北方六个沙漠地区三种生物结皮形成成分（苔藓、地衣和蓝藻-藻类）的丰富度及其环境变量。通过比较传统冗余分析（RDA）和结构方程模型（SEM）来研究环境驱动因素与丰富度之间的关系以及混杂效应。我们的结果表明，与水分有效性、土壤质地以及土壤盐分和碱度相关的三个潜在变量可以解释主要的环境变化，并解释大陆内部尺度上生物结皮的多样性模式。水分有效性分别与苔藓和蓝藻-藻类的丰富度呈正相关和负相关，而土壤质地与地衣的丰富度呈正相关。此外，相互混杂的环境变量导致RDA和SEM结果之间驱动因素与丰富度的关系明显不同。因此我们建议，未来的多变量研究应结合路径分析和传统的典范排序，以促进更严谨的生态推断。
