School of Life Sciences, Arizona State University, Tempe, Arizona, USA.
PLoS One. 2010 Jun 10;5(6):e11061. doi: 10.1371/journal.pone.0011061.
The often dramatic effects of urbanization on community and ecosystem properties, such as primary productivity, abundances, and diversity are now well-established. In most cities local primary productivity increases and this extra energy flows upwards to alter diversity and relative abundances in higher trophic levels. The abiotic mechanisms thought to be responsible for increases in urban productivity are altered temperatures and light regimes, and increased nutrient and water inputs. However, another abiotic factor, wind speed, is also influenced by urbanization and well known for altering primary productivity in agricultural systems. Wind effects on primary productivity have heretofore not been studied in the context of urbanization.
METHODOLOGY/PRINCIPAL FINDINGS: We designed a field experiment to test if increased plant growth often observed in cities is explained by the sheltering effects of built structures. Wind speed was reduced by protecting Encelia farinosa (brittlebush) plants in urban, desert remnant and outlying desert localities via windbreaks while controlling for water availability and nutrient content. In all three habitats, we compared E. farinosa growth when protected by experimental windbreaks and in the open. E. farinosa plants protected against ambient wind in the desert and remnant areas grew faster in terms of biomass and height than exposed plants. As predicted, sheltered plants did not differ from unprotected plants in urban areas where wind speed is already reduced.
CONCLUSION/SIGNIFICANCE: Our results indicate that reductions in wind speed due to built structures in cities contribute to increased plant productivity and thus also to changes in abundances and diversity of higher trophic levels. Our study emphasizes the need to incorporate wind speed in future urban ecological studies, as well as in planning for green space and sustainable cities.
城市化对社区和生态系统特性的影响通常是戏剧性的，例如初级生产力、丰度和多样性，这些现在已经得到了很好的证实。在大多数城市，本地初级生产力增加，这些额外的能量向上流动，改变了更高营养级别的多样性和相对丰度。被认为导致城市生产力增加的非生物机制是改变温度和光照条件，以及增加养分和水的输入。然而，另一个非生物因素，风速，也受到城市化的影响，并且众所周知，它会改变农业系统中的初级生产力。迄今为止，风速对初级生产力的影响尚未在城市化背景下进行研究。
方法/主要发现：我们设计了一项野外实验，以测试在城市中经常观察到的植物生长增加是否可以通过建筑物的遮蔽效应来解释。通过防风林来保护沙漠残余物和偏远沙漠地区的 Encelia farinosa（脆叶灌木）植物，从而减少风速，同时控制水分供应和养分含量，在所有三个栖息地中，我们比较了防风林保护下和露天环境下 E. farinosa 的生长情况。在沙漠和残余物地区，受环境风保护的 E. farinosa 植物在生物量和高度方面的生长速度比暴露在风中的植物更快。正如预测的那样，在风速已经降低的城市地区，受遮蔽的植物与未受保护的植物没有区别。
结论/意义：我们的结果表明，由于城市中的建筑物导致的风速降低有助于提高植物生产力，从而也导致更高营养级别的丰度和多样性发生变化。我们的研究强调了在未来的城市生态研究中，以及在绿色空间和可持续城市规划中，需要纳入风速因素。
