Mitigation of microclimate variation through agroforestry: Protecting coffee agriculture from the impacts of climate change

Because crops have narrow climate thresholds for developmental success, an increasing occurrence of extreme climate events will affect farmers who depend on rainfed agriculture. Increasing patterns of agricultural intensification may lead to still greater vulnerability for farmers because more intensively managed systems may be less resilient to the impacts of climate extremes. Because of farmer vulnerability, the different responses of management intensities to climate extremes should be explored so that sustainable management strategies can be developed to protect farmers from increased climate variability. This thesis explores the potential of agroforestry systems to protect coffee agriculture from climate variability in Chiapas, Mexico.; A set of experiments were conducted from July 2004 to November 2005 in the Soconusco region of Chiapas in a high (60-80%), medium (30-65%), and low (10-30%) shade coffee system, where shade is an indicator of management intensity. These sites were chosen to explore the qualitative differences among management systems as they relate to climate. Microclimate variables and soil moisture were measured in these systems to examine the effect of shade cover on microhabitat modification. Evapotranspiration rates were measured to examine water loss as a function of shade cover. Additionally, flower and fruit development were assessed to examine the effects of microclimate and soil moisture on coffee production.; Microclimate measurements showed that fluctuations in ambient microclimate decreased significantly as shade cover increased, with similar patterns in soil moisture measurements. Coffee plant evapotranspiration rates were reduced at shade levels ≥30%, with significant effects of light and vapor pressure deficit. Shade cover also affected flowering and fruit set. Flower development was significantly enhanced in sites with ≥30% shade cover, where greater soil moisture measurements were found. Fruit development was also greatly controlled by microclimate because of soil moisture and wind measurements associated with greater shade cover. These results show that shade tree use in agroforestry systems can mitigate microclimate and soil moisture fluctuations in agricultural sites and in turn, affect flowering, fruit development, and ultimately, coffee yield. Thus, the implementation of agroforestry management systems can enhance coffee production and should be considered an adaptive farming strategy in areas with increasing climate variability.