Soil and climatic co-limitation drive productivity in mature Nothofagus pumilio forests of Tierra del Fuego, Argentina

Under Resource Optimisation Theory, plant productivity is regulated by multi-resource co-limitation rather than a single limiting factor. Nothofagus pumilio is a species of high ecological and economic importance. This study aimed to analyse how climatic, topographic and soil variables limit productivity of timber N. pumilio forests. We investigated 375 mature N. pumilio plots to analyse environmental variables associated with productivity, using dominant height (DH, 15-31 m) in mature plots as a proxy. We applied Generalised Linear Model (GLM) and Classification and Regression Tree (CART). GLM showed that DH was significantly associated with root content (ROO, p < 0.0004), soil nitrogen (SN, p < 0.0003), soil phosphorus (SP, p < 0.0010), mean annual temperature (MAT, p < 0.0030), and soil density (SD, p = 0.0239). CART identified SP and ROO as primary splitting variables, partitioning plots into three groups (DH: 21, 22 and 23 m). Results suggest that productivity is regulated by the co-limitation of soil and climatic factors rather than by a single limiting resource, with plots exhibiting lower DH being associated with more restrictive soil conditions. These findings improve our understanding of the environmental drivers behind mature N. pumilio productivity, highlighting research on soil-climatic interactions under changing conditions.