Land-cover and precipitation variability effects on water and atmospheric inputs
to tropical forest landscapes

Alexandra G Ponette-Gonzalez, University of North Texas, alexandra.ponette@unt.edu
Lisa Curran, Stanford University, lmcurran@stanford.edu (Presenter)
Kathleen c Weathers, Cary Institute of Ecosystem Studies, weathers@ecostudies.org

Land-cover changes that modify ecosystem structure and composition alter water and chemical fluxes to the Earth surface. Vegetation interacts with water as it flows through tree canopies (i.e., throughfall) and down tree stems (i.e., stemflow), regulating the amount, timing, and distribution of water inputs to soil. Water chemistry is additionally influenced by such canopy-level processes as foliar leaching and uptake. Therefore, we examined the influence of land-cover type - - cloud forest, coffee agroforestry, and clearings - - on water and atmospheric inputs to canopies and soils across 12 sites in Veracruz, Mexico. From 2005-2007, we measured bulk (primarily wet) and fog deposition, as well as throughfall Cl-, SO42--S, and NO3--N fluxes. Rain, fog, stemflow, and throughfall water inputs were sampled from 2005-2008. Coupled measurements of stand structure and composition were conducted in forest and coffee plots. Sulfate-S in forest and coffee throughfall, a robust indicator of total (wet+fog+dry) atmospheric deposition, was higher than bulk deposition to clearings at eight of twelve sites. Also, forest conversion dramatically accelerated the rate of water delivery to soil, especially when rainfall was heavy and frequent. Leaf area reductions associated with forest conversion resulted in a maximum eightfold decrease in canopy interception and a corresponding 18% increase in throughfall water flux to soil. Higher throughfall chloride inputs under coffee versus forest suggested that increased throughfall water inputs promoted foliar chloride leaching and wash-off of dry inputs from coffee canopies. Extending these findings to Bornean landscapes, where expanding oil palm plantations drive tropical forest and peatland conversion and increase vulnerability to fire, we anticipate fundamentally altered air quality through higher emissions; enhanced atmospheric deposition rates to rainforest ecosystems; and increased transfer of mobile elements from canopies to soils. ENSO events are likely to compound these effects by promoting drought, fire vulnerability, and related emissions.

Presentation Type:  Poster

Session:  Global Change Impact & Vulnerability   (Tue 11:30 AM)

Associated Project(s): 

• Curran, Lisa: Socio-economic and political drivers of oil palm expansion in Indonesia: Effects on rural livelihoods, carbon emissions and REDD ...details

Poster Location ID: 149