| 1. |
- Birkhofer, Klaus, et al.
(författare)
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Density-dependent and -independent effects on the joint use of space by predators and prey in terrestrial arthropod food-webs
- 2011
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 120:11, s. 1705-1711
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Tidskriftsartikel (refereegranskat)abstract
- The spatial distribution of predators and their prey is affected by their joint use of space. While the formation of such spatial patterns may be driven by density-dependent and -independent factors our knowledge on the contribution of different land-use activities on the formation of spatial patterns between predators and prey remains very limited. Agriculture is one of the most prevailing land-use activities with strong effects on invertebrate densities and structural habitat conditions. Here, we used replicated conventionally and organically managed winter wheat fields to investigate the effects of agricultural land-use on the spatial patterns of generalist predators and decomposer prey. We then identified the explanatory power of density-dependent (prey and predator activity density) and density-independent (vegetation structure) predictors for the observed spatial patterns. Generalist predators were regularly distributed only in conventionally managed fields and this pattern intensified with decreasing Collembola prey availability and increasing spider activity density. Segregation between carabid and spider predators was strongest in fields with lowest wheat plant height, suggesting more intense intraguild interactions in structurally less complex habitats. Collembola were aggregated independent of management and aggregation was strongest in fields with highest Collembola and carabid activity density. Spiders and Collembola prey were associated, but higher aphid densities under conventional management weakened or interrupted this spatial relationship. We conclude that active control of crop plant physiognomy by growth hormones and herbicides in conventionally managed fields promotes predator–predator segregation and that a high availability of aphid prey seems to decouple predator–Collembola prey associations. Our results emphasise the need for a more mechanistic understanding of the effects of land-use on the formation of spatial patterns and species interactions, especially under scenarios of environmental change and an ongoing loss of biodiversity.
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| 2. |
- Birkhofer, Klaus, et al.
(författare)
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General Relationships between Abiotic Soil Properties and Soil Biota across Spatial Scales and Different Land-Use Types.
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- Very few principles have been unraveled that explain the relationship between soil properties and soil biota across large spatial scales and different land-use types. Here, we seek these general relationships using data from 52 differently managed grassland and forest soils in three study regions spanning a latitudinal gradient in Germany. We hypothesize that, after extraction of variation that is explained by location and land-use type, soil properties still explain significant proportions of variation in the abundance and diversity of soil biota. If the relationships between predictors and soil organisms were analyzed individually for each predictor group, soil properties explained the highest amount of variation in soil biota abundance and diversity, followed by land-use type and sampling location. After extraction of variation that originated from location or land-use, abiotic soil properties explained significant amounts of variation in fungal, meso- and macrofauna, but not in yeast or bacterial biomass or diversity. Nitrate or nitrogen concentration and fungal biomass were positively related, but nitrate concentration was negatively related to the abundances of Collembola and mites and to the myriapod species richness across a range of forest and grassland soils. The species richness of earthworms was positively correlated with clay content of soils independent of sample location and land-use type. Our study indicates that after accounting for heterogeneity resulting from large scale differences among sampling locations and land-use types, soil properties still explain significant proportions of variation in fungal and soil fauna abundance or diversity. However, soil biota was also related to processes that act at larger spatial scales and bacteria or soil yeasts only showed weak relationships to soil properties. We therefore argue that more general relationships between soil properties and soil biota can only be derived from future studies that consider larger spatial scales and different land-use types.
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| 3. |
- Birkhofer, Klaus, et al.
(författare)
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Soil fauna feeding activity in temperate grassland soils increases with legume and grass species richness
- 2011
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 43:10, s. 2200-2207
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Tidskriftsartikel (refereegranskat)abstract
- Edaphic fauna contributes to important ecosystem functions in grassland soils such as decomposition and nutrient mineralization. Since this functional role is likely to be altered by global change and associated shifts in plant communities, a thorough understanding of large scale drivers on below-ground processes independent of regional differences in soil type or climate is essential. We investigated the relationship between abiotic (soil properties, management practices) and biotic (plant functional group composition, vegetation characteristics, soil fauna abundance) predictors and feeding activity of soil fauna after accounting for sample year and study region. Our study was carried out over a period of two consecutive years in 92 agricultural grasslands in three regions of Germany, spanning a latitudinal gradient of more than 500 km. A structural equation model suggests that feeding activity of soil fauna as measured by the bait-lamina test was positively related to legume and grass species richness in both years. Most probably, a diverse vegetation promotes feeding activity of soil fauna via alterations of both microclimate and resource availability. Feeding activity of soil fauna also increased with earthworm biomass via a pathway over Collembola abundance. The effect of earthworms on the feeding activity in soil may be attributed to their important role as ecosystem engineers. As no additional effects of agricultural management such as fertilization, livestock density or number of cuts on bait consumption were observed, our results suggest that the positive effect of legume and grass species richness on the feeding activity in soil fauna is a general one that will not be overruled by regional differences in management or environmental conditions. We thus suggest that agri-environment schemes aiming at the protection of belowground activity and associated ecosystem functions in temperate grasslands may generally focus on maintaining plant diversity, especially with regard to the potential effects of climate change on future vegetation structure.
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| 4. |
- Diekötter, Tim, et al.
(författare)
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Landscape and management effects on structure and function of soil arthropod communities in winter wheat
- 2010
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Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 1873-2305 .- 0167-8809. ; 137:1-2, s. 108-112
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluates the impact of agricultural management (organic vs. conventional) and landscape context on species richness and abundance of five soilarthropod taxa (ground beetles, spiders, springtails, millipedes, woodlice) and associated ecosystem functions (soil biological activity, weed seed predation, litter decomposition). A significant interaction between management type and landscape context was revealed in several cases. Activity density of millipedes and wood lice and species richness of ground beetles were higher in fields where local and regional management types were complementary, indicating a beneficial effect of environmental heterogeneity. In addition, seed predation on arable weeds was higher in organically than conventionally managed fields. It is concluded that the effect of agricultural management on soilarthropod biodiversity and functioning is often context dependent. The diversity of functionally important taxa such as ground beetles and decomposers may be enhanced by increasing environmental heterogeneity, a measure that is also beneficial for other components of agrobiodiversity. Thus, in a conventional agricultural context even managing only a fraction of fields organically may help to increase environmental heterogeneity and thereby promote soilarthropod diversity and the associated ecosystem functions.
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