Lianas, Arrested Succession, and Decreased Carbon Storage: Examining the Links Between Topography, Liana Density, and the Persistence of Low-canopy Areas

Abstract

Tropical forests’ above-ground biomass comprises over 10% of the global terrestrial carbon stock. Carbon storage in above-ground biomass is impacted by tree mortality, standing-tree growth, and regeneration (new growth). Tree deaths create gaps in the canopy that normally regenerate to a closed-canopy forest within a few years. Lianas (woody vines) play an important role in this cycle: they increase tree mortality, decrease standing-tree growth rates, and arrest gap succession past a low-canopy state. However, the impact of liana dominated low-canopy areas on forest carbon storage is not well understood. Furthermore, lianas are increasing in abundance in Central and South America. What will the impacts be of increasing liana abundance? Understanding the dynamics of areas experiencing arrested succession is essential to determining the impacts of increasing liana abundance on carbon storage in tropical forests. Here, I analyze canopy height, topographic variables, and multispectral imagery of Barro Colorado Island, Panama to determine the dynamics of low-canopy areas from 1983-2019. I initially hypothesized that liana-dominated low-canopy areas are preferentially located near hydrological networks and are increasing in area causing a decrease in forest carbon storage capacity. However, the data does not support my hypotheses. Based on my results, I posit that low-canopy areas support higher liana densities than high-canopy areas and are located distant to stream networks in areas of negative topographic convexity and moderate slopes. In conclusion, total low-canopy areas are stable on Barro Colorado Island and decrease total above-ground carbon by 5-6% amount.