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New Mexico State University (2020)

Landscape-Scale Modeling of Drought- and Insect-Related Tree Mortality in Northern New Mexico

Aney, Gjertrud E

Titre : Landscape-Scale Modeling of Drought- and Insect-Related Tree Mortality in Northern New Mexico

Auteur : Aney, Gjertrud E

Université de soutenance : New Mexico State University

Grade : Master of Applied Geography 2020

Résumé
Pinyon-juniper woodlands represent the third-largest vegetation type in the United States and an important ecotype for wildlife and humans. Large-scale woodland die-off events have implications for a range of ecosystem services and can contribute to increased wildfire hazard. Understanding the relationships between environmental factors and episodic drought- and insect-related mortality in pinyon-juniper woodlands can provide important information for land managers, particularly in the face of climatic changes, which may bring intense droughts with increasing frequency. I used random forest, logistic regression, and conditional inference trees with diverse bioclimatic, edaphic, topographic, and anthropogenic variables to predict and explain drought- and insect-related pinyon mortality in northern New Mexico. Mortality presence locations were identified using multiple endmember spectral mixture analysis. Bioclimatic variables were the most explanatory of mortality, followed by edaphic and then topographic variables. The anthropogenic factor, presence of grazing, had no influence on mortality. The final random forest model predicted mortality occurrence with 80 to 83 percent balanced overall accuracy, and contained four bioclimatic variables – isothermality, minimum temperature of the coldest month, precipitation of the warmest quarter, and Normalized Difference Moisture Index (NDMI). These data are all available either pre-packaged or easily calculated by land managers for locations in the conterminous U.S., and may represent a rapid and cost-effective means of evaluating risk for drought related mortality at the landscape scale. Correlation tables referenced in section 3.6.3 are included as a supplemental file, and are identical to the information presented in Appendix C.

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Page publiée le 3 décembre 2021