Spatial patterns are one of the index to predict the forest structural development. Especially, spatial patterns of dead trees will influence the seedling germination and growth and it should be related to density dependent and some spatially autocorrelated agents (e.g., rain, wind). To understand what kind of factors influence the tree mortality in a forest, we used spatial analysis of dead trees species and try to know how the forest dynamic change. We collected survey data from the Lanjenchi plot, in southern of Taiwan, all free-standing trees ≥ 1 cm diameter at breast height (DBH) were identified, measured, and mapped in 1997, 2005, 2013 and 2018. The previous researches about the Lanjenchi plot showed that the individuals had gradually decreased in the past 23 years. In our study site, the major climatic stress is the northeast monsoon and the major disturbances come from typhoons. Therefore, we used the L-function to explore spatial patterns of dead trees in the Lanjenchi plot which based on the location of present dead trees and the past surviving trees in the same species.
Results/Conclusions
Our results demonstrated that 90% of the dead tree species showed random distribution on small scale (< 20 m) during the three periods, while only 10 % of the species showed aggregated distribution. However, it was interesting that only one species (Ardisia quinquegona) with regular distribution on a large scale (> 20 m). Moreover, to compare each period, most dead tree species showed the same spatial patterns. But the pioneer species (e.g., Mallotus paniculatus, Melastoma candidum) had different patterns due to some disturbance events (e.g., typhoons, heavy rain). To sum up, the density dependent might the major factor affect the spatial patterns of dead trees in the Lanjenchi plot. Additionally, the disturbance events (e.g. typhoon) made some species were aggregated distribution.