Comparative footprint of alien, agricultural and restored vegetation on surface-active arthropods

Abstract

Both invasive alien trees and agricultural conversion have major impacts on biodiversity. We studied here the comparative impact of these two types of land transformation on a wide range of surface-active arthropod species using pitfall traps, with evergreen sclerophyllous natural vegetation (fynbos) as the control. The study was in the Cape Floristic Region, a global biodiversity hotspot, where alien trees are of major concern and where vineyards replace natural fynbos vegetation. Surface-active arthropods were selected as they are species rich, relatively immobile, and occur in high abundance. We hypothesized that the impact of the two types of land cover transformation would produce similar qualitative and quantitative effects on the arthropods. We also compared the results in the transformed and natural areas with those in areas cleared of alien trees. Arthropod species richness in cleared areas was higher than in vineyards and more similar to that in natural fynbos, while alien trees had the lowest. Overall abundance scores were highest in cleared areas, closely followed by fynbos, then vineyards and lowest in alien trees. Several species were restricted to each vegetation type, including alien trees. In terms of assemblage composition, all vegetation types were significantly different, although fynbos and vineyards grouped, suggesting that vineyards have less impact on the arthropod community than do alien trees. When rare species were excluded, vineyards and cleared sites grouped, indicating some recovery but only involving those species that were common and habitat tolerant. Our results suggest that vineyards retain a greater complement of indigenous species than alien trees, but that clearing of these aliens soon encourages establishment of indigenous species. Although there were significant differences in soil moisture and litter depth within and between vegetation types, we did not record them as significantly affecting species richness or abundance, even in alien vegetation, an encouraging sign for restoration.

Effects of woodland restoration and management on the community of surface-active arthropods in the metropolitan Chicago region

“…Other studies have also shown that vegetation management can have an impact on arthropod community composition (Samways et al, 1996;Gratton and Denno, 2005;Gratton, 2006;Magoba and Samways, 2012). For example, Horn (2011a, 2011b), discovered that opening up the sub-canopy by removing the invasive Chinese shrub (Ligustrum sinense) from a riparian woodland in southeastern United States resulted in a twofold increase in the abundance and diversity of butterflies and bees compared to unmanaged plots.…”

“…Longcore (2003) found that replanting native vegetation in a sage scrub in southern California resulted in lower arthropod abundance and diversity compared to invaded plots -an unexpected result. Other studies have found that arthropod diversity and community composition are affected by particular restoration/management procedures, including prescribed burning (Morris, 1975;Hanula and Wade, 2003), invasive-plant removal (Gratton and Denno, 2005;Emery and Doran, 2013), and replanting native vegetation (Samways et al, 1996;Magoba and Samways, 2012).…”

Surrounding vegetation matters for arthropods of small, natural patches of indigenous forest

“…Many studies have shown that exotic pine blocks support low arthropod diversity compared to natural forests (Samways et al ., ; Finch, ; Brockerhoff et al ., ; Pryke & Samways, ; Robson et al ., ; Holmquist et al ., ). Nevertheless, timber plantations can provide valuable habitat for some species (Wethered & Lawes, ; Brockerhoff et al ., ; Pryke & Samways, ), although many of these species are alien, generalists or opportunists (Schoeman & Samways, ; Magoba & Samways, ; Roets & Pryke, ). Furthermore, plantations can negatively affect natural forest specialists such as rare and endemic arthropod species as a result of altered vegetation structure (Taboada et al ., ).…”

Agroforestry: An Appropriate and Sustainable Response to a Changing Climate in Southern Africa?

“…Only a few studies investigated the biodiversity in southern Africa under different land uses including AFS. In [144], an increase in various soil invertebrate groups was shown in AFS in eastern Zambia, while Magoba and Samways [145] studied the biodiversity of arthropod communities around native and non-native trees in vineyards and natural South African Fynbos vegetation. For biodiversity conservation, AFS should be integrated into the ecological corridor concept and linked to the natural ecosystems [146], while AFS providing natural heterogeneity and edges in forest-like patches in open agricultural fields for faunal elements [147].…”