Differential effects of landscape and management on diversity and density of ground‐dwelling farmland spiders

Abstract

Summary 1.The distribution and abundance of animals are influenced by factors at both local and wider landscape scales. Natural enemies of pests in arable fields often immigrate from the surrounding landscape, and are also influenced by local management practices. Thus, landscape diversification and farming methods may both enhance farmland biodiversity, but their relative roles and possible interactions have been little explored. 2. The relationships of ground-dwelling spiders (Araneae) to landscape features and to organic agriculture were studied in 12 pairs of organic vs. conventional fields of winter wheat Triticum aestivum along a gradient of landscape complexity . 3. High percentages of non-crop habitats in the landscape increased local species richness of spiders from 12 to 20 species, irrespective of local management. This indicates that larger species pools are sustained in complex landscapes, where there is higher availability of refuge and overwintering habitats. 4. Organic agriculture did not increase the number of spider species, but enhanced spider density by 62%. Additionally, spider density was positively related to the percentage of non-crop habitats in the surrounding landscape, but only in conventional fields. 5. Synthesis and applications . The species richness of ground-dwelling spiders in crop fields was linked to large-scale landscape complexity, while spider densities responded to local management practices. Organic agriculture benefits farmland spiders and augments the numbers of predatory spiders, thereby contributing to pest control. However, measures to conserve species richness must also take landscape-scale factors into account. Complex landscapes including perennial non-crop habitats should be preserved or restored to achieve high levels of spider diversity.

Consequences of organic and non-organic farming practices for field, farm and landscape complexity

“…for birds; (Chamberlain and Wilson 2000;Freemark and Kirk 2001), for plants; (Aude et al, 2003;Roschewitz et al, 2005a;Gibson et al, 2007;Boutin et al, 2008) and for invertebrates; (Schmidt et al, 2005;Rundlof & Smith 2006;Holzschuh et al, 2007). Other studies looking at biodiversity differences between organic and conventional systems have shown that complexity at the farm and landscape scale, independent of farming system, explained biodiversity differences between farms (Weibull et al, 2003;Clough et al, 2005;Purtauf et al, 2005).…”

“…Other studies looking at biodiversity differences between organic and conventional systems have shown that complexity at the farm and landscape scale, independent of farming system, explained biodiversity differences between farms (Weibull et al, 2003;Clough et al, 2005;Purtauf et al, 2005). Recent work strongly suggests that for certain taxa, organic farming delivers fewer benefits when located within heterogeneous landscapes, with relatively large amounts of semi-natural vegetation, rather than simpler landscapes dominated by intensive farming (Roschewitz et al,2005b;Schmidt et al, 2005;Tscharntke et al, 2005;Rundlof and Smith 2006;Holzschuh et al, 2007) although differences may still exist (Gibson et al, 2007).…”

Local and Landscape Correlates of Spider Activity Density and Species Richness in Urban Gardens

“…Both local and landscape factors may also have significant effects on biological control in agricultural areas (Schmidt et al 2004). Specifically, for spiders, apparent variation in the extent to which local factors influence abundance and diversity could actually be due to differences at the landscape scale (Booij and Noorlander 1992, Feber et al 1998, Clough et al 2005, Schmidt et al 2005. Therefore, testing for the influences of both local and landscape factors at multiple scales is essential.…”

Spider community responds to litter complexity: insights from a small-scale experiment in an exotic pine stand

“…Schmidt et al, 2005;Corcuera et al, 2015;Marín et al, 2016), to our knowledge there are no published studies addressing such topic in Brazil, particularly regarding to pine plantations. Specifically in South Brazil, some attempts were done in order to compare spider diversity patterns between agroecosystems and adjacent native ecosystems, such as the studies of Baldissera et al (2008) in tree plantations, including pine, and native Araucaria forest, Rodrigues et al (2009) in rice field, grassland and native forest, and Rodrigues et al (2010) in Eucalyptus plantations and natural grasslands.…”

“…across a gradient of different fields) to more local-scales (e.g. within a specific field) (Benton et al, 2003, Schmidt et al, 2005. Heterogeneous habitats may present a larger variety of ecological niches to be exploited in comparison to simplified habitats, fostering possibilities of more species coexistence with a greater use of resources (Finke & Snyder, 2008).…”