Human-Driven Shifts in Disturbance Patch Sizes across the World's Forest Biomes
Abstract
Stand-replacing disturbances play a fundamental role in forest dynamics by moulding forest structure and changing its composition. Disturbance regimes differ across regions and the spatial extent at which these events occur is determinant for multiple ecological processes (e.g. microclimate regulation, seed dispersal and habitat connectivity). Human activities have altered forest susceptibility to natural disturbance agents, such as fire, and added other types of perturbations, such as harvesting. However, the typical patch sizes that characterise disturbance regimes across regions and the shifts ensuing from human actions have not been quantified globally. We used the Landsat-based Global Forest Change tree cover loss dataset to delineate individual disturbance patches between 2001 and 2016 at 30-m resolution. Patches that are spatially and temporally contiguous were merged and those associated with forest conversion excluded. Patches were then classified by size and aggregated by forest biome and intactness to assess human influence among regions. In total, 218 million patches were identified within the eight forest biomes. Comparisons inside and outside intact forests suggest that disturbance patches are generally larger but spatially much less dense where human intervention is minimal. Globally, patches > 1000 ha prevail in intact forests, while those of 1-10 ha collectively account for most losses outside. Across biomes, patch sizes drop from > 1000 ha in intact forests to 10-100 ha in non-intact temperate conifer forests and to 1-10 ha in non-intact temperate broadleaf forests. This is possibly the result of forest management to suppress extensive fire and biotic events, combined with added small-to-intermediate scale anthropogenic disturbances. In tropical forests, where natural disturbances are rarely extensive, sizes increase from 0.1-1 ha in intact forests to 1-10 ha outside, likely reflecting the effects of small-scale logging and shifting agriculture. Only in the fire-prone boreal biome do patches larger than 1000 ha dominate both inside and outside intact forests. These results provide a global quantification of large shifts in the scale of forest dynamics due to human actions and give insight into the driving agents.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB042...07A
- Keywords:
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- 0430 Computational methods and data processing;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0466 Modeling;
- BIOGEOSCIENCES;
- 0480 Remote sensing;
- BIOGEOSCIENCES