Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544-2016, USA.
Conserv Biol. 2010 Dec;24(6):1606-16. doi: 10.1111/j.1523-1739.2010.01533.x.
In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9-ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3-year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more-lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already-declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.
在东非，野火和野生及家养有蹄类动物的啃食维持着稀树草原的生态系统。历史上，牧民通过使用称为“bomas”的临时畜栏来放火和放牧牲畜。近几十年来，传统的畜牧业做法有所减少，这可能会影响生物多样性。我们在东非一年的第一个和第二个旱季（分别代表大多数鸟类繁殖开始前和降雨之后）期间，调查了规定的火灾和 bomas 对稀树草原鸟类群落的影响。我们在 3 年的时间内，将 9 公顷的火烧地、最近废弃的 bomas 和未受干扰的基质栖息地的对照地进行了比较，比较了鸟类的丰富度、密度和群落组成。一般来说，最近被火烧过的区域和废弃的 bomas 吸引了更多的鸟类，并且与周围的基质具有不同的群落组合。干扰的影响受到初级生产力的相互作用的影响，初级生产力由归一化差异植被指数表示，并且与时间有关。在火灾发生后的几个月内，火烧地的鸟类密度最高，观察到的物种比例也最高。干旱条件在一年内使所有处理中的鸟类密度相等，并且在废弃的 bomas 上更常见地观察到更多物种的个体。bomas 上的丰度波动每年都比火烧地小，这表明尽管火灾可能在短期内对鸟类有益，但 bomas 可能会产生更持久的积极影响，并在干旱期间提供资源。无论降雨量如何，许多古北界候鸟都被吸引到火烧地，这表明持续的火灾抑制可能会威胁到它们已经减少的种群。值得注意的是，在对照地上观察到的鸟类稀少表明，基质的当前结构是由于火灾抑制而形成的。传统的畜牧业似乎对这些稀树草原鸟类多样性的维持至关重要。
