The 23 years relationship between the climate data and the aboveground biomass in subtropical forest at Lanjenchi, southern Taiwan

Background/Question/Methods:  The changing climate has impacted the ecosystem carbon balance worldwide. Precipitation pattern and temperature are known to be the most important factors altering the above-ground biomass. However, in Lanjenchi plot, monsoon wind is the main factor influencing the vegetation pattern. To understand the long-term dynamics of aboveground biomass, its association with carbon storage, and their climatic drivers, we used 4 forest census data spanning 23 years to calculate the aboveground biomass and carbon storage. Then, we analyzed how climatic factors affect long-term forest dynamics.

Results/Conclusions:  Our results show that the overall carbon storage (averaged as 120.99 Mg ha^-1) change significantly between 1991 and 2013. In windward habitat, the biomass and carbon storage (counting for 55.73% of the entire forest) increased significantly, while the leeward habitat experienced no change. The stem density decreased in windward habitat induced by lower mortality in large trees and higher mortality in small trees, probably driver by increasingly competitive large trees against small trees under the decreasing wind stress year by year. Our results suggest that the North-east monsoon wind was the primary factor influencing the forest biomass and carbon storage: with the decrease in monsoon wind during the past two decades, large tree grows more above-ground biomass and storage more carbon than small trees, making the windward habitat grows faster than leeward. We conclude that the climate change in Lanjenchi Forest (primarily experienced in the decrease of monsoon wind speed) mostly affects the topography-driven windward habitat, but not the entire forest.