Data-driven competitive facilitative tree interactions and their implications on nature-based solutions

TL;DR

This study uses data-driven analysis to understand how tree interactions, facilitative or competitive, vary with spatial scale and influence survival, with implications for nature-based solutions and climate moderation.

Contribution

It introduces a data-driven, hypothesis-free approach to quantify tree interactions across scales and links these interactions to survival and environmental effects.

Findings

Facilitation and competition coexist depending on spatial scale.

Tree size influences survival more than density.

Large trees help moderate land surface temperature.

Abstract

Spatio temporal data are more ubiquitous and richer than even before and the availability of such data poses great challenges in data analytics. Ecological facilitation, the positive effect of density of individuals on the individual's survival across a stress gradient, is a complex phenomenon. A large number of tree individuals coupled with soil moisture, temperature, and water stress data across a long temporal period were followed. Data driven analysis in the absence of hypothesis was performed. Information theoretic analysis of multiple statistical models was employed in order to quantify the best data-driven index of vegetation density and spatial scale of interactions. Sequentially, tree survival was quantified as a function of the size of the individual, vegetation density, and time at the optimal spatial interaction scale. Land surface temperature and soil moisture were also statistically explained by tree size, density, and time. Results indicated that in space both facilitation and competition coexist in the same ecosystem and the sign and magnitude of this depend on the spatial scale. Overall, within the optimal data driven spatial scale, tree survival was best explained by the interaction between density and year, sifting overall from facilitation to competition through time. However, small sized trees were always facilitated by increased densities, while large sized trees had either negative or no density effects. Tree size was more important predictor than density in survival and this has implications for nature based solutions: maintaining large tree individuals or planting species that can become large-sized can safeguard against tree less areas by promoting survival at long time periods through harsh environmental conditions. Large trees had also a significant effect in moderating land surface temperature.