关键词: 模型II回归, 功能性状, 生物标度, 异速生长, 资源分配, 线性回归

Abstract: Standardised major axis (SMA) regression, a typical Model II regression approach, explicitly accounts for variation in both variables and has become a key statistical tool for quantifying allometric relationships among plant traits. However, its underlying principles and methodological framework remain subject to some misunderstandings. Here, we provide a systematic synthesis of the theoretical basis, analytical workflow, and applications of SMA in plant ecology. First, we outline the theoretical framework of SMA regression and introduce its practical implementation in R (e.g. the smatr package). We then review its applications in plant trait research, including allometric relationships between organ size and whole-plant biomass, patterns of resource allocation and trade-offs among organs, and the internal associations of functional traits within organs (e.g. leaf economic spectrum). Finally, we highlight current limitations, including the applicability of log-transformed linearity assumptions, non-linear major axis regression, the integration of multi-level data, and the relative scarcity of studies on reproductive organs. We propose that future work should emphasise multidimensional data integration and cross-scale validation.

Key words: Model II regression, functional trait, biological scaling, allometry, resource allocation, linear regression