Nitrogen and phosphorus additions negatively affect tree species diversity in tropical forest regrowth trajectories

• Published in: Ecology (Durham) 2010-07, Vol.91 (7), p.2121-2131
• Main Authors: Siddique, Ilyas, Vieira, Ima Célia Guimarães, Schmidt, Susanne, Lamb, David, Carvalho, Cláudio José Reis, Figueiredo, Ricardo de Oliveira, Blomberg, Simon, Davidson, Eric A
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biodiversity; biodiversity loss; Biological and medical sciences; Biomass; Biomass production; clay Oxisol; Ecosystem; ecosystem fertilization; ecosystems; Elements; Environmental Monitoring; Fertilizers; Fires; Forest ecology; Forestry; Forests; Fundamental and applied biological sciences. Psychology; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; grasses; mixed-effects models; N + P synergism; N and P co-limitation; niche dimensionality; Nitrogen; Nitrogen - pharmacology; Pastures; Phosphorus; Phosphorus - pharmacology; pioneer species; Plant ecology; Plant populations; reforestation; Rollinia; secondary succession; Soil nutrients; spatial heterogeneity; Species; Species diversity; Synecology; Terrestrial ecosystems; Trajectories; tree growth; tree species richness; tree-grass interactions; Trees; Trees - classification; Trees - drug effects; Tropical Climate; tropical moist forest recovery; tropical rain forests; vegetation development; vegetation structure; woody plants
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/09-0636.1

Nutrient enrichment is increasingly affecting many tropical ecosystems, but there is no information on how this affects tree biodiversity. To examine dynamics in vegetation structure and tree species biomass and diversity, we annually remeasured tree species before and for six years after repeated additions of nitrogen (N) and phosphorus (P) in permanent plots of abandoned pasture in Amazonia. Nitrogen and, to a lesser extent, phosphorus addition shifted growth among woody species. Nitrogen stimulated growth of two common pioneer tree species and one common tree species adaptable to both high- and low-light environments, while P stimulated growth only of the dominant pioneer tree Rollinia exsucca (Annonaceae). Overall, N or P addition reduced tree assemblage evenness and delayed tree species accrual over time, likely due to competitive monopolization of other resources by the few tree species responding to nutrient enrichment with enhanced establishment and/or growth rates. Absolute tree growth rates were elevated for two years after nutrient addition. However, nutrient-induced shifts in relative tree species growth and reduced assemblage evenness persisted for more than three years after nutrient addition, favoring two nutrient-responsive pioneers and one early-secondary tree species. Surprisingly, N + P effects on tree biomass and species diversity were consistently weaker than N-only and P-only effects, because grass biomass increased dramatically in response to N + P addition. The resulting intensified competition probably prevented an expected positive N + P synergy in the tree assemblage. Thus, N or P enrichment may favor unknown tree functional response types, reduce the diversity of coexisting species, and delay species accrual during structurally and functionally complex tropical rainforest secondary succession.