Current research projects of ECO focus

Nationwide Mapping of Tree Species Diversity in the United States

The primary objective of this project is to estimate tree species diversity of more than 500,000 sample forest inventory and analysis (FIA) plots across the United States, in a unified continuum of diversity measures, which represent species richness, Shannon’s diversity(Shannon 1948), and Simpson’s diversity metrics(Simpson 1949). The secondary objective is to extrapolate point estimates derived from the first objective to map tree species diversity on all the forested areas across the United States, using statistical imputation and machine learning.

Team members: Jingjing Liang

Graduate Research Assistantship available for this study

Distribution patterns and drivers of breeding wood-warbler diversity across North American forests

The large-scale patterns of bird diversity have been predominantly estimated with large-scale variables such as climate, geography and vegetation index despite the ample evidence from the local- to landscape-studies that habitat characteristics hold a considerable potential to predict large-scale bird diversity. Forests are a particularly common habitat for many bird species, and their characteristics significantly determine bird behavior. This study utilized the ground-based forest measurements across North America with local- to large-scale predictor variables to identify the important variables for wood-warbler species diversity (family Parulidae) in the continental scale. We further examined the relationships between the important variables and wood-warbler species diversity and predicted the future diversity changes with future predictor values using a machine learning technique. The results showed that elevation, mean annual temperature, total annual precipitation, tree species richness, and soil organic carbon are the five most important variables out of 19, and relationships of each predictor and wood-warbler diversity have revealed the climatic and geographical characteristics of the wood-warbler distribution. Our results also showed that wood-warbler species richness is projected to decrease in the southeastern US and the Great Lakes west because of climate change, highlighting the significant influences of projected changes in climate, tree species richness, and soil organic carbon on wood-warbler species diversity. We emphasize that local-scale variables could be an important variable in a large-scale study, specifically tree species diversity and soil characteristics for forest-dependent birds like wood-warblers.

Team members: Akane Ota, Jingjing Liang

Global and continental estimates of tree species richness

One of the most fundamental questions in ecology is how many species are currently inhabiting the Earth. However, due to the massive logistical and financial challenges in characterizing all species on Earth, the global number of species still remains to be discovered. Even trees, which are among are among the most charismatic and widespread organisms on the planet, providing a wealth of ecosystem services for humans and shelter and habitat for more than 80% of terrestrial biodiversity, remain poorly characterized at a global scale. Despite the critical importance of tree species diversity for maintaining critical ecological processes such as terrestrial biodiversity and carbon sequestration, we lack a fundamental understanding of how many tree species exist on our planet. Moreover, identifying hotspots of tree diversity is necessary to inform and optimize forest conservation efforts across the globe. Here, based on a ground-sourced global forest community survey database, we developed the first estimate of the number of tree species at global and continental scales.

Team members: Roberto Cazzolla Gatti, Jingjing Liang

Other Projects to be updated soon…