Background
Secondary succession is defined as natural regeneration following complete forest clearance from anthropogenic or natural disturbances. During secondary succession, tropical forests increase in forest structural complexity and functional diversity. These changes lead to the accumulation of carbon and nutrients in above-ground vegetation and create habitats for forest-dwelling animal species (Sanchez-Azofeifa, 2005). Secondary succession is important for the growth and development of an ecosystem. Therefore, scientific understanding, cognition, and study for secondary succession in ecology and forestry is needed.
Traditional strategies aimed to map and characterize secondary succession using remote sensing are usually based on deterministic strategies, where transitions between main successional stages (early, intermediate, and late) are not considered (Figure 1a). However, the secondary succession should be a continuous process (Figure 1b), and transitions between main successional stages represent rich environments and play a key role in ecosystem regeneration (Li et al. 2017). They work like a buffer, like the ecotone. Forest structure can be defined as the distribution of foliage and woody mass within a forest. Previous studies have shown that different successional stages derive noticeable differences in horizontal and vertical forest structures, such as canopy height, canopy gaps, leaf area density (LAD), leaf area index (LAI), and photosynthetically active radiation (Gu et al. 2018). Li et al. (2017) proposed the existence of transitions between main successional stages. However, they did not further study the forest structure of transitions. Thus, based on these, this project will try to characterize the forest structure of transitions and to see if it shows differences with the main successional stages.
Light Detection and Ranging (LiDAR) is a remote sensing method that uses light as a pulsed laser to measure ranges (variable distances) to the Earth. As an active remote sensing technique, LiDAR systems have the capacity to penetrate dense forest canopies, making it easier to detect the vertical distribution of forest structural components (Figure 2). Over the years, LiDAR has been applied widely to study vegetation, forest structure, and carbon estimation using various methods (Castillo et al. 2012; Sanchez-Azofeifa et al. 2017; and Zhao et al. 2021).
Traditional strategies aimed to map and characterize secondary succession using remote sensing are usually based on deterministic strategies, where transitions between main successional stages (early, intermediate, and late) are not considered (Figure 1a). However, the secondary succession should be a continuous process (Figure 1b), and transitions between main successional stages represent rich environments and play a key role in ecosystem regeneration (Li et al. 2017). They work like a buffer, like the ecotone. Forest structure can be defined as the distribution of foliage and woody mass within a forest. Previous studies have shown that different successional stages derive noticeable differences in horizontal and vertical forest structures, such as canopy height, canopy gaps, leaf area density (LAD), leaf area index (LAI), and photosynthetically active radiation (Gu et al. 2018). Li et al. (2017) proposed the existence of transitions between main successional stages. However, they did not further study the forest structure of transitions. Thus, based on these, this project will try to characterize the forest structure of transitions and to see if it shows differences with the main successional stages.
Light Detection and Ranging (LiDAR) is a remote sensing method that uses light as a pulsed laser to measure ranges (variable distances) to the Earth. As an active remote sensing technique, LiDAR systems have the capacity to penetrate dense forest canopies, making it easier to detect the vertical distribution of forest structural components (Figure 2). Over the years, LiDAR has been applied widely to study vegetation, forest structure, and carbon estimation using various methods (Castillo et al. 2012; Sanchez-Azofeifa et al. 2017; and Zhao et al. 2021).
Research Objectives
Overall, this project regards the secondary succession as a continuous process, through LiDAR technique and derived metrics, the following objectives are expected:
(1) Characterize forest structure features of transitions between main successional stages in tropical dry forest.
(2) Evaluate forest structure differences between transitions and main successional stages based on derived LiDAR metrics.
(3) Support the perspective: the succession should be a continuous process, because transitions work as a buffer between main successional stages.
(1) Characterize forest structure features of transitions between main successional stages in tropical dry forest.
(2) Evaluate forest structure differences between transitions and main successional stages based on derived LiDAR metrics.
(3) Support the perspective: the succession should be a continuous process, because transitions work as a buffer between main successional stages.