Assessing the impact of lightning strike disturbances on vegetation regeneration in Nyungwe National Park's Tropical Forest Ecosystem

Abstract

Lightning is an often-overlooked yet powerful disturbance shaping tropical forest dynamics. In Nyungwe National Park, Rwanda, where thunderstorms occur on over 220 days annually, lightning is likely to play a critical role in vegetation regeneration and forest structure. This study investigated the ecological impacts of lightning strikes by comparing three disturbance regimes: lightning-damaged patches, non-lightning disturbed patches (caused by landslides, erosion, and other factors), and undisturbed forest controls. A total of 62 plots were surveyed to assess tree, shrubs and seedling density, species composition, and structural attributes such as diameter at breast height, height, canopy cover, crown formation, and leaf loss indices. Microclimate variables (temperature, humidity, rainfall, elevation) were measured alongside remote sensing analyses of vegetation greenness (NDVI). Results revealed that lightning strikes significantly reduced species diversity and community evenness by promoting dense regeneration dominated by a few light-demanding pioneer species, while suppressing shade-tolerant species. In contrast, non-lightning disturbed sites supported higher species richness but exhibited stunted structural development due to chronic abiotic stress. Undisturbed sites maintained the highest canopy cover, cooler temperatures, and more humid microclimates, favoring late-successional species. NDVI time-series analysis showed sharp declines in vegetation greenness immediately following lightning strikes, followed by gradual recovery in subsequent years. These findings demonstrate that lightning functions as an agent of ecological simplification, resetting successional trajectories and altering microclimates within canopy gaps. As climate change is projected to increase lightning frequency, these disturbances may become more significant for montane forest resilience and biodiversity conservation. Integrating lightning ecology into park management strategies is therefore essential for sustaining Nyungwe’s unique forest mosaic and guiding adaptive restoration efforts.