Publications by authors named "Helene-Bracht Jørgensen"

6 Publications

  • Page 1 of 1

Effects of simulated drought on biological soil quality, microbial diversity and yields under long-term conventional and organic agriculture.

FEMS Microbiol Ecol 2020 11;96(12)

Department of Soil Sciences, Research Institute of Organic Agriculture (FiBL), 5070 Frick, Switzerland.

Drought and agricultural management influence soil microorganisms with unknown consequences for the functioning of agroecosystems. We simulated drought periods in organic (biodynamic) and conventional wheat fields and monitored effects on soil water content, microorganisms and crops. Above the wilting point, water content and microbial respiration were higher under biodynamic than conventional farming. Highest bacterial and fungal abundances were found in biodynamically managed soils, and distinct microbial communities characterised the farming systems. Most biological soil quality parameters and crop yields were only marginally affected by the experimental drought, except for arbuscular mycorrhizal fungi (AMF), which increased in abundance under the experimental drought in both farming systems. AMF were further strongly promoted by biodynamic farming resulting in almost three times higher AMF abundance under experimental drought in the biodynamic compared with the conventional farming system. Our data suggest an improved water storage capacity under biodynamic farming and confirms positive effects of biodynamic farming on biological soil quality. The interactive effects of the farming system and drought may further be investigated under more substantial droughts. Given the importance of AMF for the plant's water supply, more in-depth studies on AMF may help to clarify their role for yields under conditions predicted by future climate scenarios.
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http://dx.doi.org/10.1093/femsec/fiaa205DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7705324PMC
November 2020

Combined effects of agrochemicals and ecosystem services on crop yield across Europe.

Ecol Lett 2017 11 12;20(11):1427-1436. Epub 2017 Sep 12.

Department of Ecology, Swedish University of Agricultural Sciences, SE-75007, Uppsala, Sweden.

Simultaneously enhancing ecosystem services provided by biodiversity below and above ground is recommended to reduce dependence on chemical pesticides and mineral fertilisers in agriculture. However, consequences for crop yield have been poorly evaluated. Above ground, increased landscape complexity is assumed to enhance biological pest control, whereas below ground, soil organic carbon is a proxy for several yield-supporting services. In a field experiment replicated in 114 fields across Europe, we found that fertilisation had the strongest positive effect on yield, but hindered simultaneous harnessing of below- and above-ground ecosystem services. We furthermore show that enhancing natural enemies and pest control through increasing landscape complexity can prove disappointing in fields with low soil services or in intensively cropped regions. Thus, understanding ecological interdependences between land use, ecosystem services and yield is necessary to promote more environmentally friendly farming by identifying situations where ecosystem services are maximised and agrochemical inputs can be reduced.
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http://dx.doi.org/10.1111/ele.12850DOI Listing
November 2017

Soil networks become more connected and take up more carbon as nature restoration progresses.

Nat Commun 2017 02 8;8:14349. Epub 2017 Feb 8.

NIOO-KNAW, Microbial Ecology, Droevendaalsesteeg 10, Wageningen 6708 PB, The Netherlands.

Soil organisms have an important role in aboveground community dynamics and ecosystem functioning in terrestrial ecosystems. However, most studies have considered soil biota as a black box or focussed on specific groups, whereas little is known about entire soil networks. Here we show that during the course of nature restoration on abandoned arable land a compositional shift in soil biota, preceded by tightening of the belowground networks, corresponds with enhanced efficiency of carbon uptake. In mid- and long-term abandoned field soil, carbon uptake by fungi increases without an increase in fungal biomass or shift in bacterial-to-fungal ratio. The implication of our findings is that during nature restoration the efficiency of nutrient cycling and carbon uptake can increase by a shift in fungal composition and/or fungal activity. Therefore, we propose that relationships between soil food web structure and carbon cycling in soils need to be reconsidered.
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http://dx.doi.org/10.1038/ncomms14349DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5309817PMC
February 2017

Intensive agriculture reduces soil biodiversity across Europe.

Glob Chang Biol 2015 Feb 17;21(2):973-85. Epub 2014 Nov 17.

Department of Ecology, School of Biology, Aristotle University, Thessaloniki, 54124, Greece.

Soil biodiversity plays a key role in regulating the processes that underpin the delivery of ecosystem goods and services in terrestrial ecosystems. Agricultural intensification is known to change the diversity of individual groups of soil biota, but less is known about how intensification affects biodiversity of the soil food web as a whole, and whether or not these effects may be generalized across regions. We examined biodiversity in soil food webs from grasslands, extensive, and intensive rotations in four agricultural regions across Europe: in Sweden, the UK, the Czech Republic and Greece. Effects of land-use intensity were quantified based on structure and diversity among functional groups in the soil food web, as well as on community-weighted mean body mass of soil fauna. We also elucidate land-use intensity effects on diversity of taxonomic units within taxonomic groups of soil fauna. We found that between regions soil food web diversity measures were variable, but that increasing land-use intensity caused highly consistent responses. In particular, land-use intensification reduced the complexity in the soil food webs, as well as the community-weighted mean body mass of soil fauna. In all regions across Europe, species richness of earthworms, Collembolans, and oribatid mites was negatively affected by increased land-use intensity. The taxonomic distinctness, which is a measure of taxonomic relatedness of species in a community that is independent of species richness, was also reduced by land-use intensification. We conclude that intensive agriculture reduces soil biodiversity, making soil food webs less diverse and composed of smaller bodied organisms. Land-use intensification results in fewer functional groups of soil biota with fewer and taxonomically more closely related species. We discuss how these changes in soil biodiversity due to land-use intensification may threaten the functioning of soil in agricultural production systems.
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http://dx.doi.org/10.1111/gcb.12752DOI Listing
February 2015

Soil food web properties explain ecosystem services across European land use systems.

Proc Natl Acad Sci U S A 2013 Aug 12;110(35):14296-301. Epub 2013 Aug 12.

Soil and Ecosystem Ecology, Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.

Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.
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http://dx.doi.org/10.1073/pnas.1305198110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3761618PMC
August 2013

Selective foraging of fungi by collembolans in soil.

Biol Lett 2005 Jun;1(2):243-6

Department of Terrestrial Ecology, National Environmental Research Institute, Silkeborg, Denmark.

Soils contain highly diverse communities of microorganisms and invertebrates. The trophic interactions between these species are largely unknown. Collembolans form an abundant part of the invertebrate community in soils. A prevailing view is that soil collembolans are generalist feeders on fungi, lichens, fragmented litter and bacteria. However, in laboratory food choice experiments, it has been shown that collembolans preferentially select certain taxa of fungi. To examine this apparent contradiction, we developed a molecular technique based on the analysis of 18S ribosomal DNA (rDNA) sequences to explore the diversity of fungi in soils and in the guts of collembolans. We report that the diversity of fungi found in the natural soil was 33 times higher than that in the guts of the collembolan Protaphorura armata. The data support the view that collembolan species can be highly selective when foraging on fungi in soils.
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http://dx.doi.org/10.1098/rsbl.2004.0286DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1626218PMC
June 2005