Abstract:

Studying the dynamic characteristics, species coexistence and biodiversity conservation mechanisms of subtropical forest ecosystems is important in the study of the quantitative characteristics and spatial gap distribution patterns. Based on census data from the 20 ha dynamics plot of the subtropical evergreen broad-leaved forest in Dinghushan in 2015, we analyzed the geometric characteristics and spatial distribution pattern of gaps in the plot by combining aerial image processing technology of unmanned aerial vehicles and GIS. Results show that the gap fraction is 13.72%, the gap density is 35.75 no./ha, and the average gap area is 38.37 m². Results also show that: (1) The number of gaps in the area is negatively exponentially distributed with the increase of gap area, that is, the gap is small and the marginal effect is not significant. (2) The average area of ??forest gaps in over-mature forest stands is larger than that in mature forests, while the mature forest is more likely to have more small gaps and fewer large gaps. (3) In different habitats, the distribution of gaps in each habitat shows the same pattern as that found in the whole plot. However, the difference in the valley is significant when compared with other habitats, and gap area and gap density in the valley are larger than other habitats. The ridge gap is also distinctive, and its gap density is lower than other habitats. (4) Gap area is significantly correlated with topographic factors. It was significantly negatively correlated with altitude and convexity, and had a significantly positive correlation with aspect and gradient. Based on these comparative analyses, a monitoring system of forest canopy changes and patterns can be established using drones, to dynamically monitor forest gaps and the undergrowth community.

Key words: evergreen broad-leaved forest, gap density, gap area, gap fraction, drone