Seasonal Dynamics of Tropical Forest Vegetation in Ngoc Linh Nature Reserve, Vietnam Based on UAV Data

Nguyen Dang Hoi,Ngo Trung Dung

doi:10.24259/fs.v5i2.13027

Abstract

Seasonal dynamics in tropical forests are closely related to the variation in forest canopy gaps. The canopy gaps change continuously in shape and size between the rainy and dry seasons, leading to the variation in the vegetative indicators. To monitor the variation of the canopy gaps, UAVs were used to collect datas in the mentioned tropical forests at an altitude of over 1,000m in Ngoc Linh Nature Reserve, Vietnam with a post-processing image resolution of about 8cm, which allows the detection of relatively small gaps. The analysis results at 10 squares of 1 ha showed a decrease in the area of canopy gaps from the rainy season in September 2019 to the dry season of May 2020. The mixed broad-leaved or broadleaf forest dominates with a greater variation, when the area of the gaps decreases significantly. The variation in forest canopy gaps and vegetative indicators are closely related to the high differentiation of terrain, the seasonal and the dry season climatic characteristics. The fluctuation of the vegetation cover affects the habitats of the species under the forest canopy such as animals, birds and soil fauna. This is one of the scientific bases that contributes to the management and conservation of flora and fauna biodiversity, especially in mountainous tropical forests such as Ngoc Linh Nature Reserve.

Highlights

Tropical forests are considered to be the highest-biodiversity ecosystems on earth
unmanned aerial vehicle (UAV) has been used as an equipment for the researchers to study the particular seasonal changes in tropical forests altitude above 1000m in Ngoc Linh nature reserve, Vietnam through analyzing the percentage of canopy gap and plant Triangular Greenness Index (TGI)
Based on the analysis of UAV images, we have shown the variation in forest canopy gaps and vegetation indicators during the wet and dry seasons

Summary

Introduction

In Vietnam, tropical forests occupy a large area, with a high diversity of vegetation cover and forest species composition. The deep differentiation of topography, climate and human impacts creates the diversity and abundance of forest vegetation types: closed evergreen broadleaf forest, mixed broadleaf and coniferous forests, forests coniferous forests, lowland broad leaved tropical forests, deciduous forests (Trung, 1978). In the process of formation and development, the factors representing the forest status have important implications in forest research. One of those states is the "void" of the forest canopy. The forest canopy gap plays an important role in the forest ecology, with impacts on the nutrient cycle of the forest vegetation cover, a factor in promoting the forest succession process. Previous studies have shown that they directly affect the intensity of light, soil moisture and soil biological properties, which are factors that directly affect the growth and development of trees (Gagnon et al, 2003; Muscolo et al, 2014)

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Discussion

Conclusion