Data_Sheet_1_Landscape-Scale Effects of Irrigation on a Dry Cereal Farmland Bird Community.docx

Landscape modification and habitat fragmentation are one of the major current threats to biodiversity. The main source of habitat fragmentation is the loss of focal habitat area, but changes in the composition of the surrounding landscape also have a direct effect on biodiversity. These changes may lead to the loss of some species but also may favor species replacement. Farmland birds in Europe are affected by landscape changes due to farmland intensification, such as the spread of irrigation, which may occur at different spatial scales. As irrigation is expected to increase in the coming years, which may affect protected areas, it is necessary to evaluate its potential consequences over focal biodiversity. In this study we assess the relationship between the increase of irrigated land at different spatial scales and changes in a dry cereal farmland bird community, bird abundance and species richness, using generalized linear models. We used a dry cereal farmland affinity index to describe the level of community specificity for dry cereal farmland. The increase in irrigated tree orchards produced an increase in species richness up to 500 m away from the irrigated area, which had a negative effect on the dry cereal farmland bird community, by triggering a replacement of specialist by generalist species. Our results show the importance of landscape-scale effects of irrigation occurring outside protected areas on the farmland bird community inside Natura 2000 sites, as well as how these effects are detected even at long distances from the disturbance source.

景观改造与生境破碎化是当前生物多样性面临的主要威胁之一。生境破碎化的主要诱因是目标生境面积的丧失，但周边景观组成的变化同样会对生物多样性产生直接影响。这类变化既可能导致部分物种消失，也可能推动物种更替。欧洲的农田鸟类会受到农田集约化引发的景观变化影响，例如灌溉面积的扩张——这类变化可能在不同空间尺度上发生。鉴于未来灌溉面积预计会持续扩张，且可能对保护区造成影响，因此有必要评估其对目标生物多样性的潜在影响。本研究采用广义线性模型（generalized linear models），分析不同空间尺度下灌溉用地扩张与旱地谷物农田鸟类群落、鸟类多度及物种丰富度变化之间的关联。我们通过旱地谷物农田亲和性指数，描述鸟类群落对旱地谷物农田的特异性水平。灌溉型果园的扩张会在距离灌溉区500米范围内提升物种丰富度，但会通过触发专性物种被广适性物种取代的过程，对旱地谷物农田鸟类群落产生负面影响。本研究结果表明，保护区外灌溉活动带来的景观尺度效应，会对Natura 2000保护地内的农田鸟类群落产生影响；同时还证实，这类效应即使在距离干扰源较远的区域也能被观测到。