Beyond Control: Short-Term Legacy Effects of Invasive Nonnative Trees May Halt Biodiversity Recovery

Abstract

Questions: Invasive nonnative trees can induce substantial and long-lasting changes in ecosystem structure and environmental conditions. Although numerous management efforts have removed invasive trees, the outcomes have been highly variable, and it remains uncertain whether such interventions are sufficient to restore biodiversity and microclimate. These differences often depend on the invasive species involved and the characteristics of the invaded ecosystem. Here, we evaluate whether the removal of Pinus contorta promotes short-term recovery of microclimate and plant diversity in two contrasting Patagonian vegetation types. Location: Southern Chile, in Araucaria araucana forests (−38° S) and Patagonian steppe (−45° S). Methods: We established paired invaded and removal plots along invasion gradients at both sites. Environmental variables (soil and air temperature, moisture, light, canopy cover, litter) and plant diversity were monitored for 2 years before and after mechanical removal of P. contorta. We used linear (LMM) and generalized linear mixed models (GLMM) to test for recovery versus persistent legacy effects. Results: Removal reduced pine litter and canopy cover, partially restoring microclimatic conditions moderating temperature extremes (i.e., increasing minimum temperatures and lowering maximum temperatures) and increasing soil moisture and light availability. However, native plant richness and abundance showed no signs of recovery, whereas nonnative species significantly increased in the Patagonian steppe. Conclusions: Our results demonstrate that, despite improvements in physical conditions, legacy effects of P. contorta invasion strongly constrain biodiversity recovery in both ecosystems. Effective management of invasive conifers must therefore move beyond tree removal to include complementary restoration actions that address persistent abiotic and biotic legacies.