Landslide early succession in a neotropical dry forest

Abstract

Early succession on large landslides in highly humanized areas that have a tropical dry climate is not well studied. This study documented vegetation recovery during the first 4 years after disturbance at a landslide on Casita Volcano, Nicaragua. We aimed to determine the main pathways and causes of change in community features, such as richness, biovolume, and species composition and verify the role played by environmental heterogeneity. Data consisting on number, covers and mean height of woody species and several abiotic factors related to fertility and stability of substrates were obtained from permanent plots in previously defined zones. Pathways of early succession were highly contingent on abiotic heterogeneity and landscape context and were mainly controlled by abiotic factors associated with fertility of substrates, and incidence of human disturbances. Those results might form the basis of a model of early succession on landslides located in densely populated areas within tropical dry ecosystems. Our results suggest that, rather than focusing research on large-scale disturbances, the study of succession in landslides of the type that occurred on Casita Volcano must point towards the response of ecosystems to a much more complex disturbance regime, in which human-induced disturbances play a major role.

Changes in spatial point patterns of pioneer woody plants across a large tropical landslide

“…propagules through erosion, which was also likely to cause sudden and unexpected changes in species composition and diversity of woody plant communities between 1999 and 2001 (Velazquez and Gomez-Sal, 2008). Moreover, according to our results, patchy distributions of soil resources might have affected spatial patterns of mortality of W. wens individuals in this subzone (Fig.…”

“…These two species, however, have a high litterfall production and their leaves present high contents of nutrients such as Mn and Cu, which are not very abundant in harsh sites (Valencia-Duarte, 2012;da Trindade and Coelho, 2012). All these facts suggest that in subzone El, where nutrient concentrations were extremely low (Velazquez and Gomez-Sal, 2008), the observed patterns of density-dependent survival in El might result from the development of fertility islands (sensu Walker and del Moral, 2003) around established individuals of W. wens and I micrantha, which facilitate the establishment of individuals of these and other species through soil nutrient improvement. This hypothesis is supported by the spatial patterns of significant aggregation at small scales and regularity at intermediate scales observed in El in 2002 (Fig.…”

“…1). These subzones varied greatly with regard to slope, soil texture, nutrient contents, and species composition and diversity of woody pioneer communities (Velazquez and Gomez-Sal, 2008). The erosional zone was dominated by shrubs such as Wigandia wens and Melanthera nivea, and saplings of the pioneer tree Trema micrantha.…”

“…Plants usually interact with their neighbours up to a maximum distance of 2-2.5 m, coinciding with their zones of resource depletion (Casper et al, 2003), but in some semi-arid shrubs these zones can extend well up to 5 m and beyond (Hartle et al, 2006). Moreover, in many plots of the Casita Volcano landslide, the influence of habitat preferences in the spatial patterns of woody pioneer plants might appear between 5 and 10 m, due to their marked plot-scale abiotic heterogeneity (Velazquez, 2007;Velazquez and Gomez-Sal, 2008). Therefore, we finally considered a fixed bandwidth of R = 5 m.…”

“…In subzone E2, regular patterns persisted over the [2001][2002] period. This subzone presented a steep slope (Velazquez and Gomez-Sal, 2008), which has a highly negative influence on colonization of woody plants on landslides (Walker et al, 2013) by its association with post-landslide erosion (Walker and Shiels, 2008). Therefore, the continuation of regular spatial patterns in this subzone over the study period might be due to removal of early colonizing (Mian et al, 2008) per subzone were used under a null model of independence.…”