Blank Peter J, Sample David W, Williams Carol L, Turner Monica G
Department of Zoology, University of Wisconsin, Madison, Wisconsin, United States of America.
Wisconsin Department of Natural Resources, Madison, Wisconsin, United States of America.
PLoS One. 2014 Oct 9;9(10):e109989. doi: 10.1371/journal.pone.0109989. eCollection 2014.
Demand for bioenergy is increasing, but the ecological consequences of bioenergy crop production on working lands remain unresolved. Corn is currently a dominant bioenergy crop, but perennial grasslands could produce renewable bioenergy resources and enhance biodiversity. Grassland bird populations have declined in recent decades and may particularly benefit from perennial grasslands grown for bioenergy. We asked how breeding bird community assemblages, vegetation characteristics, and biomass yields varied among three types of potential bioenergy grassland fields (grass monocultures, grass-dominated fields, and forb-dominated fields), and assessed tradeoffs between grassland biomass production and bird habitat. We also compared the bird communities in grassland fields to nearby cornfields. Cornfields had few birds compared to perennial grassland fields. Ten bird Species of Greatest Conservation Need (SGCN) were observed in perennial grassland fields. Bird species richness and total bird density increased with forb cover and were greater in forb-dominated fields than grass monocultures. SGCN density declined with increasing vertical vegetation density, indicating that tall, dense grassland fields managed for maximum biomass yield would be of lesser value to imperiled grassland bird species. The proportion of grassland habitat within 1 km of study sites was positively associated with bird species richness and the density of total birds and SGCNs, suggesting that grassland bioenergy fields may be more beneficial for grassland birds if they are established near other grassland parcels. Predicted total bird density peaked below maximum biomass yields and predicted SGCN density was negatively related to biomass yields. Our results indicate that perennial grassland fields could produce bioenergy feedstocks while providing bird habitat. Bioenergy grasslands promote agricultural multifunctionality and conservation of biodiversity in working landscapes.
对生物能源的需求正在增加，但生物能源作物在生产用地的种植所带来的生态后果仍未得到解决。玉米目前是主要的生物能源作物，但多年生草地可以生产可再生生物能源资源并增强生物多样性。近几十年来，草原鸟类数量有所下降，而种植用于生物能源的多年生草地可能会让它们尤其受益。我们研究了三种潜在的生物能源草地类型（单一草种草地、以草为主的草地和以杂类草为主的草地）中繁殖鸟类群落组成、植被特征和生物量产量如何变化，并评估了草地生物量生产与鸟类栖息地之间的权衡。我们还将草地中的鸟类群落与附近的玉米地进行了比较。与多年生草地相比，玉米地中的鸟类较少。在多年生草地中观察到了10种最需要保护的鸟类（SGCN）。鸟类物种丰富度和总鸟类密度随着杂类草覆盖度的增加而增加，且以杂类草为主的草地中的这两项指标高于单一草种草地。SGCN密度随着垂直植被密度的增加而下降，这表明为实现最大生物量产量而管理的高大、茂密的草地对濒危草原鸟类物种的价值较小。研究地点1公里范围内草地栖息地的比例与鸟类物种丰富度、总鸟类密度和SGCN密度呈正相关，这表明如果在其他草地地块附近建立草地生物能源田，可能会对草原鸟类更有益。预测的总鸟类密度在最大生物量产量以下达到峰值，预测的SGCN密度与生物量产量呈负相关。我们的结果表明，多年生草地可以在提供鸟类栖息地的同时生产生物能源原料。生物能源草地促进了农业多功能性以及生产用地景观中生物多样性的保护。
