Jens Dauber

The impact of biomass crop cultivation on temperate biodiversity

The urgency for mitigation actions in response to climate change has stimulated policy makers to encourage the rapid expansion of bioenergy, resulting in major land‐use changes over short timescales. Despite the potential impacts on biodiversity and the environment, scientific concerns about large‐scale bioenergy production have only recently been given adequate attention. Environmental standards or legislative provisions in the majority of countries are still lagging behind the rapid development of energy crops. Ranging from the field to the regional scale, this review (i) summarizes the current knowledge about the impact of biomass crops on biodiversity in temperate regions, (ii) identifies knowledge gaps and (iii) drafts guidelines for a sustainable biomass crop production with respect to biodiversity conservation. The majority of studies report positive effects on biodiversity at the field scale but impacts strongly depend on the management, age, size and heterogeneity of the biomass plantations. At the regional scale, significant uncertainties exist and there is a major concern that extensive commercial production could have negative effects on biodiversity, in particular in areas of high nature‐conservation value. However, integration of biomass crops into agricultural landscapes could stimulate rural economy, thus counteracting negative impacts of farm abandonment or supporting restoration of degraded land, resulting in improved biodiversity values. Given the extent of landconversion necessary to reach the bioenergy targets, the spatial layout and distribution of biomass plantations will determine impacts. To ensure sustainable biomass crop production, biodiversity would therefore have to become an essential part of risk assessment measures in all those countries which have not yet committed to making it an obligatory part of strategic landscape planning. Integrated environmental and economic research is necessary to formulate standards that help support long‐term economic and ecological sustainability of biomass production and avoid costly mistakes in our attempts to mitigate climate change.

Microbial activity and functional diversity in the mounds of three different ant species

Abstract Activity and functional diversity of the soil microflora in the mounds of Myrmica scabrinodis , Lasius niger and L. flavus were investigated. These three ant species strongly differ in foraging strategy and in the mode of mound construction. To take account of changing microbial performances during the cycle of mound building, immature mounds of L. flavus were compared to well established ones. The study was carried out with substrate sampled in the rural district of Hohenahr-Erda (Lahn-Dill Bergland, Central Hesse, Germany). Nest abundance as well as mound size and architecture were recorded for all three species. Microbial activity was quantified by determining the C mineralization rate ( C min ). Functional diversity of the microflora was measured by means of the Biolog method. Additional factors were substrate moisture and pH. Substrate moisture and pH value were not different in the mounds from that in the control. High C min values in all mound types indicate that the mounds of the three ant species investigated form a mosaic of microbial hot spots at the study site. Substrate diversity and evenness were higher in the mounds of both M. scabrinodis and L. niger than in the control soil, but lower in the two mound types of L. flavus . The results of the Biolog measurements suggest that different components of the microbial community were activated in the different mounds. The increase of C min in L. flavus mounds seems to be based on the stimulation of a comparatively small and specialized microbial community. The high microbial activity in the mounds of L. niger and M. scabrinodis , in contrast, is accompanied by an increase in functional diversity. Investigations on the developing L. flavus mounds show that typical features characterizing the microflora in the mounds of this species need a considerable time to develop. It is concluded that ants have an important role as soil engineers and that species specific differences in the effect on the soil microflora are related to feeding strategy and nest architecture. Methodological difficulties arising from the application of the Biolog approach are discussed.

Edge effects on ant community structure and species richness in an agricultural landscape

The effect of sharp edges between three different types of land use on the species richness and structure of ant communities was examined in an agricultural landscape within Central Hesse, Germany. Species richness and nest densities of ants at the centres and the edges of meadows, crop fields, and fallow land were recorded by hand sampling during 1997 and 1998. Edges between different land-use types did not increase ant species richness at the landscape scale, nor were they unique habitats for a specialised ant fauna. Nonetheless, most species shared ‘ecotonal effects’ in the way that their relative abundance either decreased (e.g. Myrmica scabrinodis) or increased (e.g. Lasius niger, Lasius flavus) at the edges, resulting in different community structure between edges and centres of the land-use types. This was influenced by two major factors: (i) the boundary contrast between the neighbouring habitats (i.e. in terms of disturbance caused by agricultural practices), and (ii) the response of different species to changing abiotic conditions. High nest densities of aggressive species with large colonies occurred along edges. We hypothesise that this can significantly reduce edge permeability for surface-dwelling arthropods.

Soil carbon sequestration during the establishment phase of Miscanthus × giganteus: a regional‐scale study on commercial farms using 13C natural abundance

The use of biomass for energy production is considered a promising way to reduce net carbon emissions and mitigate climate change. However, land‐use change to bioenergy crops can result in carbon emissions from soil and vegetation in amounts that could take decades to compensate. Perennial grasses such as Miscanthus offer a possible solution to this problem as measurements on experimental plots planted with Miscanthus have shown significant carbon sequestration in the soil. It can, however, be expected that sequestration potentials in commercial use might differ from those measured in experimental plots due to different farming practices and soil characteristics. For this study, Miscanthus plantations on 16 farms in SE Ireland as well as on‐farm controls representing the former land‐use (grassland and tillage) have been examined. The Miscanthus plantations were 2–3 years old. Soil organic carbon (SOC) content and a number of soil properties were measured and the amount of Miscanthus‐derived carbon was determined using the 13C natural abundance method. On both former tillage fields and grasslands, although there were no significant differences in SOC contents between Miscanthus and control sites, it was shown that 2–3 years after Miscanthus establishment, 1.82 ± 1.69 and 2.17 ± 1.73 Mg ha−1 of the SOC under former‐tilled and former grassland respectively were Miscanthus‐derived. Mixed‐effects models were used to link the total SOC concentrations and Miscanthus‐derived carbon to the land‐use parameters as well as to soil properties. It was shown that on control sites, pH had an effect on total SOC. In the case of Miscanthus‐derived carbon, the initial SOC content, pH, former land‐use and crop age had significant effects.

Carabid communities in the spatio-temporal mosaic of a rural landscape

Abstract The effect of landscape dynamics on carabid communities was investigated using a chronosequence of managed grassland sites. A total of 52 carabid species was found. Species richness was significantly higher in early than in later stages of grassland succession. The change from an arable land to a grassland carabid community was almost complete 10 years after the conversion to grassland. The accompanying change in the dominant feeding mode indicates a marked shift in the functional structure of the carabid community from arable land to grassland. Correlation analysis revealed a positive response of phytophagous species to dense and species-rich grassland vegetation that was only loosely related to grassland age. Invasion of grassland species was largely confined to the early stages of carabid succession. On the other hand, loss of species continued until the latest stage of the chronosequence, though many species preferring arable land had already vanished a short time after the conversion to grassland. The species turnover was independent of the dispersal abilities of the carabid species involved. This is probably due to the high spatial connectivity of suitable habitats in the small-scale landscape mosaic of the Lahn-Dill-Bergland. It is concluded that the variety of land use (arable land versus grassland) contributes considerably more to the species richness of carabids at the landscape level than the simultaneous availability of grassland sites of different age, provided that areas converted to grassland are allowed to persist for at least 10 years. The missing invasion of additional species into later stages of grassland succession can partly be explained by the premature state that is maintained at the older sites by management.

On the quality of soil biodiversity indicators: abiotic and biotic parameters as predictors of soil faunal richness at different spatial scales

Abstract Direct measurement of soil biodiversity is expensive, and therefore a substitution of measurement by indication is desirable. We analysed three large datasets for the potential to predict the diversity of soil faunal groups from other parameters. The datasets represent different spatial scales, namely grassland nematodes on an European scale, forest collembola on a regional scale, and grassland ants on a local scale. We tested two groups of parameters as possible surrogates for species richness: (1) environmental parameters, such as climate, soil and vegetation characteristics, and (2) community parameters, such as higher taxon richness, indicator taxa, and maximum dominance. Climate and soil parameters were significantly correlated with biodiversity in all datasets. However, in spite of the large variety of measurement types analysed, prediction quality of environmental variables was weak and the explained proportion of variance ranged generally below 50%. Richness was subject to considerable stochastic variation among subsamples (CV=20–60%) thereby evading a narrow correlation with environmental parameters. Higher taxon richness, based on taxa of intermediate hierarchical order, proved the best predictor of richness in collembola and nematodes explaining 55 and 89% of total variance, respectively. A combination of two ant species was the best predictor of ant richness explaining 59% of total variance. The authors conclude that a rough guess of soil faunal diversity can be cost-effectively derived from environmental data while an estimate of moderate quality can be obtained with reduced taxonomic effort. The precise richness of a soil community, however, is subject to autogeneous community dynamics, to biotic interactions with other populations, and to conditions in the past, and can therefore only be retrieved by immediate investigation of the community itself. Criteria for the quality of indicator parameters are discussed.

Species specific effects of ants on microbial activity and N-availability in the soil of an old-field

Microbial biomass and activity as well as N-availability were measured in the mounds of three ant species strongly differing in foraging strategy and mound architecture: Myrmica scabrinodis, Lasius niger and L. flavus. Soil microbial biomass (Cmic) was significantly increased in the mounds of all three ant species. This positive effect was due to the accumulation of organic matter (Corg) within the mounds. Microbial activity was increased in M. scabrinodis mounds only. Available Nmin was accumulated in all mound types, independent of the feeding mode of the ants, with Lasius mounds having significantly higher Nmin content than M. scabrinodis mounds. It is hypothesised that the differences between the mound types are due to differences in nest architecture, especially the integration of grassy vegetation. Higher microbial activity in M. scabrinodis mounds may be a consequence of supplementary energy provided by root exudates. The amount of Nmin in M. scabrinodis mounds may be reduced by increased plant uptake and by immobilisation within the microbial biomass.

Impact of agricultural subsidies on biodiversity at the landscape level

Agricultural management is a major factor driving the change of faunal richness in anthropogenic landscapes. Thus, there is an urgent need to develop tools that allow decision-makers to understand better intended and unintended effects of agricultural policy measures on biodiversity. Here we demonstrate the potential of such a tool by combining a socio-economic model with the biodiversity model GEPARD to forecast the response of bird and carabid species richness to two scenarios of agricultural subsidies: (1) subsidies based on production levels and prices and (2) direct income support that is independent of production levels. We focussed on farmland of the Lahn-Dill area, Germany, as an example of European regions with low intensity farming. GEPARD predicts faunal richness and is based on multi-scaled resource-selection functions. Under both scenarios the area of predicted losses in species richness of birds and carabids was larger than the area of predicted gains in species richness. However, the area with predicted losses of avian richness was smaller under the direct income support scenario than under the production-based subsidy scenario, whereas the area with predicted losses of carabid species richness was smaller under the production-based subsidy scenario than under the direct income support. Yet locally, richness gains of up to four species were predicted for carabids under both scenarios. We conclude that the sometimes contrasting and heterogeneous responses of birds and carabids at different localities suggest the need for spatially targeted subsidy schemes. With the help of the GIS-based approach presented in this study, prediction maps on potential changes in local and regional species richness can be easily generated.

Consequential life cycle assessment of biogas, biofuel and biomass energy options within an arable crop rotation

Feed in tariffs (FiTs) and renewable heat incentives (RHIs) are driving a rapid expansion in anaerobic digestion (AD) coupled with combined heat and power (CHP) plants in the UK. Farm models were combined with consequential life cycle assessment (CLCA) to assess the net environmental balance of representative biogas, biofuel and biomass scenarios on a large arable farm, capturing crop rotation and digestate nutrient cycling effects. All bioenergy options led to avoided fossil resource depletion. Global warming potential (GWP) balances ranged from −1732 kg CO2e Mg−1 dry matter (DM) for pig slurry AD feedstock after accounting for avoided slurry storage to +2251 kg CO2e Mg−1 DM for oilseed rape biodiesel feedstock after attributing indirect land use change (iLUC) to displaced food production. Maize monoculture for AD led to net GWP increases via iLUC, but optimized integration of maize into an arable rotation resulted in negligible food crop displacement and iLUC. However, even under best‐case assumptions such as full use of heat output from AD‐CHP, crop–biogas achieved low GWP reductions per hectare compared with Miscanthus heating pellets under default estimates of iLUC. Ecosystem services (ES) assessment highlighted soil and water quality risks for maize cultivation. All bioenergy crop options led to net increases in eutrophication after displaced food production was accounted for. The environmental balance of AD is sensitive to design and management factors such as digestate storage and application techniques, which are not well regulated in the UK. Currently, FiT payments are not dependent on compliance with sustainability criteria. We conclude that CLCA and ES effects should be integrated into sustainability criteria for FiTs and RHIs, to direct public money towards resource‐efficient renewable energy options that achieve genuine climate protection without degrading soil, air or water quality.

Response of farmland biodiversity to the introduction of bioenergy crops: effects of local factors and surrounding landscape context.

The recent growth in bioenergy crop cultivation, stimulated by the need to implement measures to reduce net CO2 emissions, is driving major land‐use changes with consequences for biodiversity and ecosystem service provision. Although the type of bioenergy crop and its associated management is likely to affect biodiversity at the local (field) scale, landscape context and its interaction with crop type may also influence biodiversity on farms. In this study, we assessed the impact of replacing conventional agricultural crops with two model bioenergy crops (either oilseed rape Brassica napus or Miscanthus × giganteus) on vascular plant, bumblebee, solitary bee, hoverfly and carabid beetle richness, diversity and abundance in 50 sites in Ireland. We assessed whether within‐field biodiversity was also related to surrounding landscape structure. We found that local‐ and landscape‐scale variables correlated with biodiversity in these agricultural landscapes. Overall, the differences between the bioenergy crops and the conventional crops on farmland biodiversity were mostly positive (e.g. higher vascular plant richness in Miscanthus planted on former conventional tillage, higher solitary bee abundance and richness in Miscanthus and oilseed rape compared with conventional crops) or neutral (e.g. no differences between crop types for hoverflies and bumblebees). We showed that these crop type effects were independent of (i.e. no interactions with) the surrounding landscape composition and configuration. However, surrounding landscape context did relate to biodiversity in these farms, negatively for carabid beetles and positively for hoverflies. Although we conclude that the bioenergy crops compared favourably with conventional crops in terms of biodiversity of the taxa studied at the field scale, the effects of large‐scale planting in these landscapes could result in very different impacts. Maintaining ecosystem functioning and the delivery of ecosystem services will require a greater understanding of impacts at the landscape scale to ensure the sustainable development of climate change mitigation measures.