DOI: 10.5061/dryad.j21n1
title: Data from: Defoliation by pastoralists affects savanna tree seedling dynamics by limiting the facilitative role of canopy cover

description: Recurrent tree defoliation by pastoralists, akin to herbivory, can
 negatively affect plant reproduction and population dynamics. However, our
 understanding of the indirect role of defoliation in seedling recruitment
 and tree–grass dynamics in tropical savanna is limited. In West African
 savanna, Fulani pastoralists frequently defoliate several fodder tree
 species to feed livestock in the dry season. We investigated the direct
 and indirect effects of recurrent defoliation of African mahogany (Khaya
 senegalensis) by Fulani people on seedling (&lt;2 cm basal diameter)
 and sapling dynamics in West Africa using four years of demographic data
 on seedling and sapling density, growth, and survival, coupled with fruit
 production and microhabitat data over the same time period. Tree canopy
 cover facilitated seedlings but had negative effects on sapling growth
 possibly via intraspecific competition with adult plants. Interspecific
 competition with grasses strongly reduced seedling survival but had a weak
 effect on sapling growth. Fire reduced seedling survival and weakly
 reduced growth of seedlings and saplings, but did not affect sapling
 survival. These results indicate that the effect of fire on seedlings and
 saplings is distinct, a mechanism suitable for an episodic recruitment of
 seedlings into the sapling stage and consistent with predictions from the
 demographic bottleneck model. Defoliation affected seedling density and
 sapling growth through changes in canopy cover, but had no effect on
 seedling growth and sapling survival. In the moist region, sapling density
 was higher in sites with low-intensity defoliation, indicating that
 defoliation may strengthen the tree recruitment bottleneck. Our study
 suggests that large-scale defoliation can alter the facilitative role of
 nurse trees on seedling dynamics and tree–sapling competition. Given that
 tree defoliation by local people is a widespread activity throughout
 savanna–forest systems in West Africa, it has the potential to affect
 tree–grass coexistence. Incorporating the influence of large tree
 defoliation into existing models of savanna dynamics can further our
 understanding of tree–grass coexistence and improve management. A rotating
 harvest system, which allows seedlings to recruit episodically, or a
 patchwork harvest, which maintains some nursery trees in the mosaic, could
 help sustain seedling recruitment and minimize the indirect effects of
 harvest.
description: Seedling demography for
 African mahogany in BeninThese data show the
 basal diameter (cm), heights (m) measured on individual seedlings and
 saplings of Khaya senegalensis (Meliaceae) yearly from 2004 to 2007. From
 2005-2007, we report if individual survived or not and the previously
 measured basal diameter and height (if applicable). Individuals have
 unique (aluminum) tag number within population. A total of 12 populations
 were monitored for 4 years and these populations were selected randomly in
 two ecological regions (wet or dry) and in each region populations were
 equally divided between high and low foliage and bark harvesting
 intensities.Khaya_Seedling_Demography.csvSeedling microhabitat for African mahogany in BeninWe collected four years (2004-2007) seedling and sapling microhabitat and abundance data within ten 10 x 10m plot within each of 12 population of Khaya senegalensis in Benin, West Africa. Within each plot, we collected data yearly on grass cover (%), percent plot burned, and percent cover of non-graminaceous understory species (2005-2007), and tree canopy cover (2006-2007). We also counted seedling (&lt;2 cm) and sapling number in each plot from 2004-2006. These microhabitats data are for the same individuals as in Data 1 file (Khaya_Seedling_Demography.csv).Khaya_Seedling_Microhabitats.csv