Patterns of seed rain and seedling regeneration in abandoned agricultural clearings in a seasonally dry tropical forest in India

Abstract

Abstract:Forest recovery in abandoned pastures and agricultural fields is often impeded, therefore it is important to understand the factors limiting regeneration. Patterns of seed arrival and regeneration in five abandoned agricultural clearings nested within a seasonally dry tropical forest in India were examined along five transects radiating from the forest edge into the clearings. Wind-dispersed seeds dominated the seed arrival in clearings compared with vertebrate-dispersed seeds: 5563 wind-dispersed seeds and 1094 vertebrate-dispersed seeds of 14 and 13 tree species, respectively, were recorded. Numbers of the former declined steeply with increasing distance from the forest, whereas the latter showed no evident pattern with distance. Seeds of the invasive herb, Chromolaena odorata, were abundant in clearings. Although wind-dispersed seeds greatly outnumbered vertebrate-dispersed seeds, seedlings and saplings of vertebrate-dispersed species were three times more abundant than those of wind-dispersed species, indicating distinct differences in patterns of actual and effective seed dispersal. This points to recruitment limitation, and suggests that seed arrival may not be the principal barrier to regeneration in these clearings. Nonetheless, the clearings are likely to revert to forest over time.

Does proximity to a mature forest contribute to the seed rain and recovery of an abandoned agriculture area in a semiarid climate?

“…) and anthropogenic‐disturbed forests (Teegalapalli et al . ), as reported in our study. Nonetheless, despite the predominance of autochorous species in our study, species dispersed by animals were least represented in the young forest, indicating that dispersal by animals has not yet been completely re‐established.…”

“…Moreover, the predominant dispersal syndrome in dry environments tends to vary with aridity and the predominance of life forms (herbs, vines, shrubs or trees). In some dry forests, dispersal by animals predominates (Griz & Machado 2001;Jara-Guerreiro et al 2011;Mart ınez-Garza et al 2011)' however, in other forests (primarily in semiarid environments), self-dispersal and wind dispersal predominate in both mature (Machado et al 1997;Ara ujo et al 2007;Lima et al 2008) and anthropogenic-disturbed forests (Teegalapalli et al 2010), as reported in our study. Nonetheless, despite the predominance of autochorous species in our study, species dispersed by animals were least represented in the young forest, indicating that dispersal by animals has not yet been completely re-established.…”

Seed dispersal limitations shift over time in tropical forest restoration

“…Previous studies show that forest amount and proximity are positively correlated with bird abundance and composition (Lindenmayer et al 2010, Van Bael et al 2013, and many authors suppose that seed rain and seedling recruitment should respond similarly , Rodrigues et al 2009, Tambosi et al 2013). However, empirical evidence has been mixed with some studies finding landscape effects on forest regeneration (Purata 1986, Teegalapalli et al 2010) and others not (Howe et al 2010). …”

Natural Experiment Demonstrates That Bird Loss Leads to Cessation of Dispersal of Native Seeds from Intact to Degraded Forests

“…Several studies in regions with healthy frugivore communities have directly monitored seed rain and seedling recruitment in degraded areas adjacent to intact forests and have shown that vertebrate frugivores do move seeds, sometimes from far away, into degraded areas, often acting as the major (or only) source of native seed rain (e.g. [18], [19], [32]–[35]). The importance of vertebrate seed dispersal has been recognized by the implementation of restoration techniques which encourage dispersal, such as the planting of fruiting trees and ‘tree islands’ within degraded areas [36]–[38].…”