14 Oct 2022
14 Oct 2022
Status: this preprint is currently under review for the journal BG.

Throughfall exclusion and fertilization effects on tropical dry forest tree plantations, a large-scale experiment

German Vargas G.1,2, Daniel Perez-Aviles3, Nannette Raczka4, Damaris Pereira-Arias3, Julián Tijerín-Triviño5, L. David Pereira-Arias3, David Medvigy6, Bonnie G. Waring7, Ember Morrisey8, Edward Brzostek4, and Jennifer S. Powers1,3 German Vargas G. et al.
  • 1Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN USA 55108
  • 2School of Biological Sciences, The University of Utah, Salt Lake City, UT 84112
  • 3Department of Ecology, Evolution, & Behavior, University of Minnesota, St. Paul, MN USA 55108
  • 4Department of Biology, West Virginia University, Morgantown, WV USA 26506
  • 5Department. de Ciencias de la Vida, Grupo de Ecología Forestal y Restauración, Universidad de Alcalá, Madrid, España 28801
  • 6Department of Biological Sciences, University of Notre Dame, Notre Dame, IN USA 46556
  • 7Grantham Institute on Climate Change and the Environment, Imperial College London, London UK, SW7 2AZ
  • 8Division of Plant and Soil Sciences, West Virginia University, Morgantown, WV USA 26506

Abstract. Across tropical ecosystems, global environmental change is causing drier climatic conditions and increases in nutrient depositions. Such changes represent large uncertainties due to unknown interactions between drought and nutrient availability in controlling ecosystem net primary productivity (NPP). Using a large-scale manipulative experiment, we studied whether nutrient availability affects the responses of three component NPP fluxes (stem growth, fine roots production, and litterfall) to through-fall exclusion in 30-year-old unmanaged mixed plantations of six tree species native to the tropical dry forest of Costa Rica. We used a factorial design with four treatments: control (CN), fertilization (F), drought (D), and drought+fertilization (D+F). While we found that a 13–15 % reduction in soil moisture only led to modest effects in the studied ecosystem processes, NPP increased as a function of F and D+F. At the same time, NPP increases with nutrient additions were larger in the plots without throughfall exclusion. The relative contribution of each biomass flux to NPP varied depending on the treatment, with woody biomass being more important for F and root biomass for D+F and D. Moreover, seasonal canopy cover was maintained longer in the fertilized plots. Belowground processes such as nodulation and microbial carbon use efficiency (CUE) also responded to experimental treatments, with a decrease in nodulation for F plots and an increase in CUE for F and D plots. Species functional type (i.e., N-fixation or deciduousness) and not the experimental manipulations were the main source of variation in tree relative growth rates. Our results emphasize that nutrient availability moderately constrains ecosystem processes in tropical dry forests, but this depends on water availability.

German Vargas G. et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-203', Anonymous Referee #1, 03 Nov 2022
  • RC2: 'Comment on bg-2022-203', Anonymous Referee #2, 04 Nov 2022

German Vargas G. et al.

German Vargas G. et al.


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Short summary
To study whether nutrient availability controls tropical dry forest responses to reductions in soil moisture, we established the first trough-fall exclusion experiment in a tropical dry forest plantation system crossed with a fertilization scheme. We found that the effects of fertilization on net primary productivity are larger than the effects of a ~15 % reduction in soil moisture. Although in many cases we observed an interaction between drought and nutrient additions, suggesting co-limitation.