Ecological legacies in a tropical savanna: woody layer responses to long-term changes in soil chemistry.

Abstract

Nutrient availability and soil pH are key drivers of ecosystem functioning, and changes in these factors can generate lasting effects that are not well understood. In Brazilian tropical savannas, plant communities are adapted to nutrient-poor and acidic soils, therefore changes in soil chemistry can affect vegetation structure. Here, we report the legacy effects on woody plant species composition and taxonomic and functional diversity of enhancing nutrient availability and increasing soil pH in a long-term fertilization experiment, following five years of nutrient addition cessation. The treatments included N, P, N + P additions and liming in a typical savanna. We inventoried all woody species and collected functional traits related to nutrient use from 676 individuals from 18 species. Even five years after nutrient cessation, soil variables (pH and nutrient content) remain altered compared to the control, with higher pH in the liming treatment and lower pH in the nutrient addition treatments. NP addition and liming shifted the species composition benefiting few dominant species. Species diversity decreased across all treatments, except for the N treatment which pointed to the predominant role of P limitation and soil pH in these communities. Increased soil pH due to the legacy effect of liming decreased taxonomic and functional diversity. In these tropical savannas, changes in soil natural conditions, especially by the liming, threaten species and functional diversity, impacting ecosystem functioning. Plant communities may need a long time to recover and some ecosystems may not return to their historical configuration after nutrient enrichment.