Decreasing Precipitation in Tropical Montane Cloud Forests: Belowground Responses and Their Effect on Global Climate Change

EPA Grant Number: F13B20247
Title: Decreasing Precipitation in Tropical Montane Cloud Forests: Belowground Responses and Their Effect on Global Climate Change
Investigators: Looby, Caitlin Irene
Institution: University of California - Irvine
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2014 through September 1, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Ecology


TMCF are biodiversity hot spots within the tropics and are characterized by persistent low-level cloud cover. Unfortunately, climate change is exposing these ecosystems to drier conditions due to the rise of the cloud layer. Few studies have investigated the soil community’s response to elevation and climate change, especially within TMCF, fostering a lack of understanding of how tropical regions will respond to and possibly augment global climate change. This research will utilize an elevation gradient in a TMCF in Costa Rica to determine how belowground communities and decomposition are affected by climate change.


An elevation gradient will be used on the Pacific Slope of the Cordillera de Tilarán within the Monteverde Cloud Forest Reserve in Costa Rica. A soil translocation experiment will be performed along this gradient to simulate the effects of the rising cloud layer on belowground communities, decomposition and microbial-associated CO2 emissions. Soil will be translocated from higher to lower elevations. This soil will be placed in nylon membrane bags that prevent the colonization of local fungi, but allow the passage of nutrients, water and organic compounds. Controlling for the colonization of new fungi will demonstrate how fungi from higher elevations will respond to the rising cloud layer. To determine how fungal communities and decomposition will change due the rising cloud layer, fungal diversity and enzymatic activity will be measured after 6 months and 1 year. Fungal diversity will be determined by high-throughput sequencing. Extracellular enzyme assays will be performed on these samples to determine the efficiency of fungal-associated decomposition.

Expected Results:

Such site characteristics as elevation, temperature and precipitation exert a strong influence on decomposition rates; decomposition decreases exponentially with increasing elevation. Decreases in precipitation due to the rising cloud layer result in a greater distinction between dry and wet seasons. This increased seasonality leads to more intense drying and rewetting cycles and, thus, increased microbial turnover. This may increase decomposition within these forests and increase the release of CO2 into the atmosphere, potentially accelerating the pace of climate change. This research directly tests how temperature and moisture affect fungal community structure and decomposition by translocating soil. Moreover, this approach will allow an experimental determination of how the rising cloud layer will influence CO2 emissions by microbes during decomposition. Decreased precipitation and increased temperatures may result in increased fungal-associated enzymatic activity, increased decomposition and increased CO2 emissions from microbes.

Potential to Further Environmental/Human Health Protection

TMCF offer natural shifts in temperature and soil moisture, making them ideal systems to assess how environmental changes are influencing important ecosystem processes, like decomposition. Any changes in decomposition may have consequences for CO2 emissions and global climate, as tropical ecosystems have a disproportionate influence over global C cycling. Results from this research will deliver a comprehensive understanding of how decreased precipitation can influence fungal communities, decomposition and microbial-associated CO2 emissions.

Supplemental Keywords:

climate change, decomposition, soil biome

Progress and Final Reports:

  • 2015
  • Final