Lemessa Debissa, Hambäck Peter A, Hylander Kristoffer
Leuphana University Luneburg, Scharnhorststr 1, Germany.
Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
PLoS One. 2015 May 11;10(5):e0126639. doi: 10.1371/journal.pone.0126639. eCollection 2015.
Bird and arthropod predation is often associated with natural pest control in agricultural landscapes, but the rates of predation may vary with the amount of tree cover or other environmental factors. We examined bird and arthropod predation in three tree-rich and three tree-poor landscapes across southwestern Ethiopia. Within each landscape we selected three tree-rich and three tree-poor homegardens in which we recorded the number of tree species and tree stems within 100 × 100 m surrounding the central house. To estimate predation rates, we attached plasticine caterpillars on leaves of two coffee and two avocado shrubs in each homegarden, and recorded the number of attacked caterpillars for 7-9 consecutive weeks. The overall mean daily predation rate was 1.45% for birds and 1.60% for arthropods. The rates of arthropod predation varied among landscapes and were higher in tree-poor landscapes. There was no such difference for birds. Within landscapes, predation rates from birds and arthropods did not vary between tree-rich and tree-poor homegardens in either tree-rich or tree-poor landscapes. The most surprising result was the lack of response by birds to tree cover at either spatial scale. Our results suggest that in tree-poor landscapes there are still enough non-crop habitats to support predatory arthropods and birds to deliver strong top-down effect on crop pests.
鸟类和节肢动物的捕食行为通常与农业景观中的自然虫害控制相关，但捕食率可能会随树木覆盖量或其他环境因素而变化。我们在埃塞俄比亚西南部的三种树木繁茂和三种树木稀少的景观中研究了鸟类和节肢动物的捕食情况。在每个景观中，我们选择了三个树木繁茂和三个树木稀少的家庭菜园，记录了围绕中央房屋100×100米范围内的树种数量和树干数量。为了估计捕食率，我们在每个家庭菜园的两棵咖啡树和两棵鳄梨树的叶子上附着了橡皮泥毛虫，并连续7 - 9周记录被攻击毛虫的数量。鸟类的总体平均每日捕食率为1.45%，节肢动物为1.60%。节肢动物的捕食率在不同景观之间有所不同，在树木稀少的景观中更高。鸟类则没有这种差异。在景观内部，无论是树木繁茂还是树木稀少的景观中，鸟类和节肢动物的捕食率在树木繁茂和树木稀少的家庭菜园之间都没有差异。最令人惊讶的结果是，在任何空间尺度上，鸟类对树木覆盖都没有反应。我们的结果表明，在树木稀少的景观中，仍然有足够的非作物栖息地来支持捕食性节肢动物和鸟类，从而对作物害虫产生强大的自上而下的影响。
