Ground-dwelling arthropod assemblages of partially improved heathlands according to the species of grazer and grazing regime

Abstract

Abstract. The creation of improved areas is one way of increasing the productivity of livestock on Cantabrian heathland (NW Spain), a habitat that is frequently located in less favourable mountainous areas where the development of sustainable husbandry is limited. The effect of this on the biodiversity of heathland is unclear and likely to depend on several factors, such as the grazing regime. In order to clarify this situation, the effects of type of vegetation, species of grazer and grazing regime on the composition of the ground-dwelling arthropod fauna of partially improved heathland were determined. The effects of grazing by cattle or sheep and two grazing regimes (cattle or sheep, or both of them together with goats) were studied in eight plots (two replicates per treatment). Each plot included two types of vegetation, gorse (Ulex gallii)-dominated shrubland and improved grassland (Lolium perenneTrifolium repens). Arthropods were surveyed using pitfall traps. Overall, the composition of the arthropod fauna did not differ between plots grazed by different species of grazer or using different grazing regimes but was significantly associated with the type of vegetation. Most of the opilionids and several carabids clearly preferred shrubland, while lycosids and various carabids were mainly associated with grassland. While the species of grazer affected the faunal composition of grassland, grazing regime was more important in shrubland. Arthropod responses to the grazing treatments were determined by the grazing behaviour of the large herbivores and the habitat requirements of each arthropod taxon. The great structural heterogeneity of the vegetation and the more microhabitats in shrubland grazed by mixed flocks was mainly a result of the goats preferring to browse on the woody vegetation in these areas. The grazing by either sheep or cattle had less of an affect on the fauna of shrubland than grassland.

Impact of management on foliage-dwelling arthropods and dynamics within permanent pastures

“…Previous studies also detected links between specific plants and arthropod communities in crops 21 , and a positive relationship between pollinators and plant species richness in cut grasslands 22 . Global responses of the wider community of arthropods to changes in plant community composition under different land management strategies (including mowing/fertilization regimes) have been detected 21 and linked to changes in the availability of key plant resources 23–25 , including the abundance and richness of grasses or forbs 22 . This supports the conclusion that small-scale plant community characteristics must be taken into account for a better understanding of arthropods’ response to the farming system 21 .…”

Evaluation of the design effects of different agropastoral systems on the diversity and density of spiders

“…In this way we can support the last hypothesis, where the composition of guilds is different in agropastoral environments compared to those that are agricultural. However, in C2 the "Sensing web weavers" were not found as their families are only found in natural environments, indicating once again that the incorporation of natural areas and fields with pastures will generate heterogeneous environments suitable for the establishment of different groups of spiders (Cardoso et al, 2011;García et al, 2011).…”

Recognising the potential role of native ponies in conservation management

“…Cattle + sheep + UK (Evans et al, 2006b;Evans et al, 2015) Arthropods Araneae Combined Cattle + sheep Cattle + goats + Spain (Garcia et al, 2011) Opiliones Combined Cattle + sheep Cattle + goats +/-Spain (Garcia et al, 2011) Coleoptera Combined Cattle + sheep + UK (Dennis et al, 2008) Table 1: Examples of responses of different taxa to mixed grazing of semi-natural vegetation communities; where + = positive effects from mixed grazing, +/-= no response to mixed grazing; compared to single-species grazing treatments. Study duration ranged from 3 to 10 years.…”