Resilience in the Tropical Dry Forest under natural and anthropogenic alterations

• Author / Creator

  Stan, Kayla D.

• The primary objectives of this thesis included contributing to: (i) the state of knowledge on the TDF physiological response to climatic variables; (ii) the understanding of forest resilience through assessing productivity response to temperature and precipitation; and (iii) assessing the influence of legislation on the resilience and extent of tropical forests. Here, I present research which evaluates the resilience of the TDF both over decadal time periods and on regional, country, and cross-continental scales. This resilience is tested under a variety of climatic conditions, as well as under different legislative scenarios, and is then projected into the future.
  Chapter 2 provides a critical review of the current state of knowledge about the latitudinal variations in TDF expression, while also considering how the phenology, biomass, species diversity, and forest dynamics vary with precipitation, temperature, and natural disturbances. Finally, this study assesses the resilience of the TDF, using these ecosystem variations and projections of climatic change. Gaps in current research and information are outlined, and future paths to provide further insight into forest resilience are suggested.
  Forest management and forest resilience under anthropogenic changes in Costa Rica are assessed in Chapter 3. In this Chapter I found that forest recovery began before the majority of the legislative policies were put into place, and there is no increase in the rates of recovery after these policies were implemented. The trends in forest decline and subsequent recovery more closely follow the economic trends, with the recovery beginning when the meat market crashed and continuing with the diversification of the economy. These trends suggest that the Payments for Ecosystem Services and Protected Areas programs are not assisting the resilience of the forest. This result is supported by the finding that there are only 13 of the Protected Areas, encompassing less than 10% of the protected forests, which would experience a moderate or high probability of deforestation if the legislation was revoked.
  The future resilience of a regional scale TDF to climate change is assessed in Chapter 4. I found that the temperature is projected to warm between 2°C and 5°C and precipitation is projected on average to decrease below historic levels; however, it is mostly within the extremes of historical data. We also found that in the province, there is a quadratic relationship between biomass and Vapour Pressure Deficit (VPD), unlike the theoretical algorithms used by MODIS, which assume a linear relationship. This non-linear relationship means that above a certain point, increased wetness decreases the productivity in the Guanacaste forests. When these productivity trends are projected into the future, most forested areas are simulated to have stable or slight increases in productivity due to this quadratic function and a slight drying trend in the climate.
  Finally, in Chapter 5, the entire Meso and South American TDF is assessed for its water use efficiency, as well as for long-term changes that have already occurred. I found that TDFs across Meso and South America use water more efficiently in dry years compared to wet years. Overall, the productivity of the forests is correlated to the amount of precipitation, but changes in temperature have no impact on the productivity of the forests. The El Nino Southern Oscillation conditions can alter the productivity up to 30% at higher latitudes, but there is little variation near the equator. Overall, there are sites in Mexico which are greening and sites in Brazil which are losing productivity. There is no consistent correlative change in any climatic or geophysical variables. There are correlative changes with soil moisture, precipitation, and growing season duration at different sites.

• Subjects / Keywords

  • drought
  • Dinamica EGO
  • Land Cover Change
  • water use efficiency
  • modelling
  • resilience
  • climate change
  • Tropical Dry Forest

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-tj16-yd70

• License

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