Ecol Lett. 2011 Sep;14(9):922-32. doi: 10.1111/j.1461-0248.2011.01642.x. Epub 2011 Jun 27.
A meta-analysis of crop pest and natural enemy response to landscape complexity.
Source
Abstract
Many studies in recent years have investigated the relationship between landscape complexity and pests, natural enemies and/or pest control. However, no quantitative synthesis of this literature beyond simple vote-count methods yet exists. We conducted a meta-analysis of 46 landscape-level studies, and found that natural enemies have a strong positive response to landscape complexity. Generalist enemies show consistent positive responses to landscape complexity across all scales measured, while specialist enemies respond more strongly to landscape complexity at smaller scales. Generalist enemy response to natural habitat also tends to occur at larger spatial scales than for specialist enemies, suggesting that land management strategies to enhance natural pest control should differ depending on whether the dominant enemies are generalists or specialists. The positive response of natural enemies does not necessarily translate into pest control, since pest abundances show no significant response to landscape complexity. Very few landscape-scale studies have estimated enemy impact on pest populations, however, limiting our understanding of the effects of landscape on pest control. We suggest focusing future research efforts on measuring population dynamics rather than static counts to better characterise the relationship between landscape complexity and pest control services from natural enemies.
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http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2699.2007.01774.x/abstract
Schmidt, M. H., Thies, C., Nentwig, W. & Tscharntke, T. Contrasting responses of arable spiders to the landscape matrix at different spatial scales. J Biogeography 0, 070901070439002–??? (2007).
Abstract
Aim Animal communities can be influenced by the composition of the surrounding landscape through immigration. Depending on habitat preferences, however, the effect of the landscape matrix can be positive or negative and can vary with scale. We tested this idea with arable spiders and tried to infer dispersal distances from relationships between local density and landscape composition at different spatial scales.
Location Thirty-eight landscapes around the cities of Göttingen and Giessen, Germany.
Methods Spiders were captured with pitfall traps in one field of winter wheat in each landscape. Landscape composition around the fields was characterized at 11 scales from 95 m to 3 km radius by land-use mapping and subsequent GIS analysis. Correlation tests were performed between landscape composition and local densities or species richness.
Results In both study regions, local species richness was enhanced by non-crop habitats on a landscape scale. The overall densities of wolf spiders (Lycosidae), long-jawed spiders (Tetragnathidae), crab spiders (Thomisidae), and dwarf sheet spiders (Hahniidae) increased significantly in landscapes with high percentages of non-crop habitats. Out of the 40 species tested, 19 responded positively to the percentage of non-crop habitats in the surrounding landscape, and five responded negatively. Depending on the species, the spatial scales with the highest explanatory power ranged from 95 m to 3 km radius around the study fields, potentially reflecting dispersal distances.
Main conclusions Arable spider species showed contrasting responses to the landscape context with respect both to the direction and to the spatial scale of the relationship. The variation in landscape requirements among species ensures high spider densities in a wide range of situations, which contributes to ecosystem resilience. However, species richness of arable spiders depends on heterogeneous landscapes with high percentages of non-crop habitats.
경관 환경 변수를 어떻게 요약할 것인가 고민하던 차에 접한 논문인데, 경관의 복잡성을 어떻게 척도 고려하면서 정량화 할 지 얘기해서 좋았습니다. 공통적으로 연구 질문 얘길 하다 보면 느끼는 것이, 1) 조사한 자료가 공간 상의 어떤 점 일 때, 어떻게 어느만큼 넓은 공간의 환경/경관 변수아 연결 시킬 것인가, 변수들을 어떻게 요약해서 연결할 것인가, 공선성을 어떻게 해결할 것인가 2) 이질적인 자료가 있을 때 (i.e., 조류와 곤충 다양성) 둘을 어떻게 동시에 볼 것인가, 따로 볼 것인가 3) 분명한 관계가 나타나지 않을 때 (생태학에선 어쩌면 당연한) 표면 아래서 작용하는 인과를 어떻게 꺼낼 것인가.