Publications by authors named "Julia Siebert"

13 Publications

  • Page 1 of 1

Fertilized graminoids intensify negative drought effects on grassland productivity.

Glob Chang Biol 2021 Jun 21;27(11):2441-2457. Epub 2021 Mar 21.

Department of Soil and Environment, Sveriges Landbruksuniversitet (SLU), Uppsala, Sweden.

Droughts can strongly affect grassland productivity and biodiversity, but responses differ widely. Nutrient availability may be a critical factor explaining this variation, but is often ignored in analyses of drought responses. Here, we used a standardized nutrient addition experiment covering 10 European grasslands to test if full-factorial nitrogen, phosphorus, and potassium addition affected plant community responses to inter-annual variation in drought stress and to the extreme summer drought of 2018 in Europe. We found that nutrient addition amplified detrimental drought effects on community aboveground biomass production. Drought effects also differed between functional groups, with a negative effect on graminoid but not forb biomass production. Our results imply that eutrophication in grasslands, which promotes dominance of drought-sensitive graminoids over forbs, amplifies detrimental drought effects. In terms of climate change adaptation, agricultural management would benefit from taking into account differential drought impacts on fertilized versus unfertilized grasslands, which differ in ecosystem services they provide to society.
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http://dx.doi.org/10.1111/gcb.15583DOI Listing
June 2021

Global impacts of fertilization and herbivore removal on soil net nitrogen mineralization are modulated by local climate and soil properties.

Glob Chang Biol 2020 Dec 22;26(12):7173-7185. Epub 2020 Sep 22.

Grupo de Investigaciones en Biología de la Conservación, INIBIOMA (CONICET-UNCOMA), Bariloche, Argentina.

Soil nitrogen (N) availability is critical for grassland functioning. However, human activities have increased the supply of biologically limiting nutrients, and changed the density and identity of mammalian herbivores. These anthropogenic changes may alter net soil N mineralization (soil net N ), that is, the net balance between N mineralization and immobilization, which could severely impact grassland structure and functioning. Yet, to date, little is known about how fertilization and herbivore removal individually, or jointly, affect soil net N across a wide range of grasslands that vary in soil and climatic properties. Here we collected data from 22 grasslands on five continents, all part of a globally replicated experiment, to assess how fertilization and herbivore removal affected potential (laboratory-based) and realized (field-based) soil net N . Herbivore removal in the absence of fertilization did not alter potential and realized soil net N . However, fertilization alone and in combination with herbivore removal consistently increased potential soil net N Realized soil net N , in contrast, significantly decreased in fertilized plots where herbivores were removed. Treatment effects on potential and realized soil net N were contingent on site-specific soil and climatic properties. Fertilization effects on potential soil net N were larger at sites with higher mean annual precipitation (MAP) and temperature of the wettest quarter (T.q.wet). Reciprocally, realized soil net N declined most strongly with fertilization and herbivore removal at sites with lower MAP and higher T.q.wet. In summary, our findings show that anthropogenic nutrient enrichment, herbivore exclusion and alterations in future climatic conditions can negatively impact soil net N across global grasslands under realistic field conditions. This is an important context-dependent knowledge for grassland management worldwide.
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http://dx.doi.org/10.1111/gcb.15308DOI Listing
December 2020

Climate change and intensive land use reduce soil animal biomass via dissimilar pathways.

Elife 2020 07 28;9. Epub 2020 Jul 28.

Department of Community Ecology, Helmholtz-Centre for Environmental Research-UFZ, Halle, Germany.

Global change drivers, such as climate change and land use, may profoundly influence body size, density, and biomass of soil organisms. However, it is still unclear how these concurrent drivers interact in affecting ecological communities. Here, we present the results of an experimental field study assessing the interactive effects of climate change and land-use intensification on body size, density, and biomass of soil microarthropods. We found that the projected climate change and intensive land use decreased their total biomass. Strikingly, this reduction was realized via two dissimilar pathways: climate change reduced mean body size and intensive land use decreased density. These findings highlight that two of the most pervasive global change drivers operate via different pathways when decreasing soil animal biomass. These shifts in soil communities may threaten essential ecosystem functions like organic matter turnover and nutrient cycling in future ecosystems.
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http://dx.doi.org/10.7554/eLife.54749DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7386910PMC
July 2020

Microbial processing of plant remains is co-limited by multiple nutrients in global grasslands.

Glob Chang Biol 2020 08 10;26(8):4572-4582. Epub 2020 Jun 10.

German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.

Microbial processing of aggregate-unprotected organic matter inputs is key for soil fertility, long-term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro- and micro-nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak-season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains.
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http://dx.doi.org/10.1111/gcb.15146DOI Listing
August 2020

Nutrient availability controls the impact of mammalian herbivores on soil carbon and nitrogen pools in grasslands.

Glob Chang Biol 2020 Feb 3. Epub 2020 Feb 3.

Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.

Grasslands are subject to considerable alteration due to human activities globally, including widespread changes in populations and composition of large mammalian herbivores and elevated supply of nutrients. Grassland soils remain important reservoirs of carbon (C) and nitrogen (N). Herbivores may affect both C and N pools and these changes likely interact with increases in soil nutrient availability. Given the scale of grassland soil fluxes, such changes can have striking consequences for atmospheric C concentrations and the climate. Here, we use the Nutrient Network experiment to examine the responses of soil C and N pools to mammalian herbivore exclusion across 22 grasslands, under ambient and elevated nutrient availabilities (fertilized with NPK + micronutrients). We show that the impact of herbivore exclusion on soil C and N pools depends on fertilization. Under ambient nutrient conditions, we observed no effect of herbivore exclusion, but under elevated nutrient supply, pools are smaller upon herbivore exclusion. The highest mean soil C and N pools were found in grazed and fertilized plots. The decrease in soil C and N upon herbivore exclusion in combination with fertilization correlated with a decrease in aboveground plant biomass and microbial activity, indicating a reduced storage of organic matter and microbial residues as soil C and N. The response of soil C and N pools to herbivore exclusion was contingent on temperature - herbivores likely cause losses of C and N in colder sites and increases in warmer sites. Additionally, grasslands that contain mammalian herbivores have the potential to sequester more N under increased temperature variability and nutrient enrichment than ungrazed grasslands. Our study highlights the importance of conserving mammalian herbivore populations in grasslands worldwide. We need to incorporate local-scale herbivory, and its interaction with nutrient enrichment and climate, within global-scale models to better predict land-atmosphere interactions under future climate change.
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http://dx.doi.org/10.1111/gcb.15023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7155038PMC
February 2020

Climate change and land use induce functional shifts in soil nematode communities.

Oecologia 2020 Jan 28;192(1):281-294. Epub 2019 Nov 28.

German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.

Land-use intensification represents one major threat to the diversity and functioning of terrestrial ecosystems. In the face of concurrent climate change, concerns are growing about the ability of intensively managed agroecosystems to ensure stable food provisioning, as they may be particularly vulnerable to climate extreme-induced harvest losses and pest outbreaks. Extensively managed systems, in contrast, were shown to mitigate climate change based on plant diversity-mediated effects, such as higher functional redundancy or asynchrony of species. In this context, the maintenance of soils is essential to sustain key ecosystem functions such as nutrient cycling, pest control, and crop yield. Within the highly diverse soil fauna, nematodes represent an important group as their trophic spectrum ranges from detritivores to predators and they allow inferences to the overall state of the ecosystem (bioindicators). Here, we investigated the effects of simulated climate change and land-use intensity on the diversity and abundance of soil nematode functional groups and functional indices in two consecutive years. We revealed that especially land use induced complex shifts in the nematode community with strong seasonal dynamics, while future climate led to weaker effects. Strikingly, the high nematode densities associated with altered climatic conditions and intensive land use were a consequence of increased densities of opportunists and potential pest species (i.e., plant feeders). This coincided with a less diverse and less structured community with presumably reduced capabilities to withstand environmental stress. These degraded soil food web conditions represent a potential threat to ecosystem functioning and underline the importance of management practices that preserve belowground organisms.
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http://dx.doi.org/10.1007/s00442-019-04560-4DOI Listing
January 2020

Global mismatches in aboveground and belowground biodiversity.

Conserv Biol 2019 10 26;33(5):1187-1192. Epub 2019 Apr 26.

German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.

Human activities are accelerating global biodiversity change and have resulted in severely threatened ecosystem services. A large proportion of terrestrial biodiversity is harbored by soil, but soil biodiversity has been omitted from many global biodiversity assessments and conservation actions, and understanding of global patterns of soil biodiversity remains limited. In particular, the extent to which hotspots and coldspots of aboveground and soil biodiversity overlap is not clear. We examined global patterns of these overlaps by mapping indices of aboveground (mammals, birds, amphibians, vascular plants) and soil (bacteria, fungi, macrofauna) biodiversity that we created using previously published data on species richness. Areas of mismatch between aboveground and soil biodiversity covered 27% of Earth's terrestrial surface. The temperate broadleaf and mixed forests biome had the highest proportion of grid cells with high aboveground biodiversity but low soil biodiversity, whereas the boreal and tundra biomes had intermediate soil biodiversity but low aboveground biodiversity. While more data on soil biodiversity are needed, both to cover geographic gaps and to include additional taxa, our results suggest that protecting aboveground biodiversity may not sufficiently reduce threats to soil biodiversity. Given the functional importance of soil biodiversity and the role of soils in human well-being, soil biodiversity should be considered further in policy agendas and conservation actions by adapting management practices to sustain soil biodiversity and considering soil biodiversity when designing protected areas.
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http://dx.doi.org/10.1111/cobi.13311DOI Listing
October 2019

The effects of drought and nutrient addition on soil organisms vary across taxonomic groups, but are constant across seasons.

Sci Rep 2019 01 24;9(1):639. Epub 2019 Jan 24.

German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.

Anthropogenic global change alters the activity and functional composition of soil communities that are responsible for crucial ecosystem functions and services. Two of the most pervasive global change drivers are drought and nutrient enrichment. However, the responses of soil organisms to interacting global change drivers remain widely unknown. We tested the interactive effects of extreme drought and fertilization on soil biota ranging from microbes to invertebrates across seasons. We expected drought to reduce the activity of soil organisms and fertilization to induce positive bottom-up effects via increased plant productivity. Furthermore, we hypothesized fertilization to reinforce drought effects through enhanced plant growth, resulting in even drier soil conditions. Our results revealed that drought had detrimental effects on soil invertebrate feeding activity and simplified nematode community structure, whereas soil microbial activity and biomass were unaffected. Microbial biomass increased in response to fertilization, whereas invertebrate feeding activity substantially declined. Notably, these effects were consistent across seasons. The dissimilar responses suggest that soil biota differ vastly in their vulnerability to global change drivers. Thus, important ecosystem processes like decomposition and nutrient cycling, which are driven by the interdependent activity of soil microorganisms and invertebrates, may be disrupted under future conditions.
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http://dx.doi.org/10.1038/s41598-018-36777-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6345851PMC
January 2019

A niche for ecosystem multifunctionality in global change research.

Glob Chang Biol 2019 03 13;25(3):763-774. Epub 2018 Dec 13.

German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.

Concern about human modification of Earth's ecosystems has recently motivated ecologists to address how global change drivers will impact the simultaneous provisioning of multiple functions, termed ecosystem multifunctionality (EMF). However, metrics of EMF have often been applied in global change studies with little consideration of the information they provide beyond single functions, or how and why EMF may respond to global change drivers. Here, we critically review the current state of this rapidly expanding field and provide a conceptual framework to guide the effective incorporation of EMF in global change research. In particular, we emphasize the need for a priori identification and explicit testing of the biotic and abiotic mechanisms through which global change drivers impact EMF, as well as assessing correlations among multiple single functions because these patterns underlie shifts in EMF. While the role of biodiversity in mediating global change effects on EMF has justifiably received much attention, empirical support for effects via other biotic and physicochemical mechanisms are also needed. Studies also frequently stated the importance of measuring EMF responses to global change drivers to understand the potential consequences for multiple ecosystem services, but explicit links between measured functions and ecosystem services were missing from many such studies. While there is clear potential for EMF to provide novel insights to global change research, predictive understanding will be greatly improved by insuring future research is strongly hypothesis-driven, is designed to explicitly test multiple abiotic and biotic mechanisms, and assesses how single functions and their covariation drive emergent EMF responses to global change drivers.
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http://dx.doi.org/10.1111/gcb.14528DOI Listing
March 2019

The Dark Side of Animal Phenology.

Trends Ecol Evol 2018 12 9;33(12):898-901. Epub 2018 Oct 9.

Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands.

Research exploring the timing of recurring biological events has shown that anthropogenic climate change dramatically alters the phenology of many plants and animals. However, we still lack studies on how climate change might alter the phenology of soil invertebrates as well as how this can subsequently affect ecosystem functions.
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http://dx.doi.org/10.1016/j.tree.2018.09.010DOI Listing
December 2018

[Association of Health Insurance and Socio-economic Factors with Health Care for Malignant Melanoma].

Gesundheitswesen 2017 Jan 30;79(1):21-27. Epub 2015 Nov 30.

Institut für Versorgungsforschung in der Dermatologie und bei Pflegeberufen (IVDP), Universitätsklinikum Hamburg-Eppendorf, Hamburg.

To analyze the relationship between socio-demographic and regional factors, health insurance status and clinical features of malignant melanoma (MM). Primary data from a nationwide dermato-histopathologic laboratory on all consecutive excisions with proven diagnosis of MM over the 5-year period 2009-2013 were analyzed regarding tumor-specific and socioeconomic characteristics. The tumor depth (Breslow index) being a predictor of invasive MM progression and mortality was defined as a major indicator for early detection and intervention, thus reflecting quality of health care. N=4 840 histologically verified MM samples from 4 583 patients were analyzed; of these, 2 537 (52.4%) were invasive MM. The tumor depth, which was 1.09 mm on average, increased with age from 1.00 mm in the lowest to 1.56 mm in the highest age group, p<0.001). Controlled for age and sex, the members of agricultural health insurances (LKK) and of German local public health insurances (AOK) showed significantly increased tumor depths (1.67 resp. 1.20 mm). The lowest average levels were found in members of the substitute health funds (e. g. Barmer GEK 0.93 mm) and in privately insured persons (0.99 mm). Based on a regional 4-step classification, there was a gradient in MM depth from more populated to more rural areas, ranging from 1.05 mm in nucleated cities to 1.22 in small rural communities. Distribution of MM locations varied significantly by health insurance: The highest proportion of MM in the head/neck area was seen in members of the agricultural (52.3%) and of the local public health insurances (30.2%) vs. 18.5% in patients from the substitute health funds. In contrast, MM located on the trunk and lower extremities was more prevalent in private, substitute and company health insurance funds. Age, gender and health insurance status are relevant determinants of MM health care and progression risk in Germany. Prevention and early detection programs by health insurances should take this into account.
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http://dx.doi.org/10.1055/s-0035-1564164DOI Listing
January 2017

Health care characteristics of basal cell carcinoma in Germany: the role of insurance status and socio-demographic factors.

J Dtsch Dermatol Ges 2014 Sep;12(9):803-11

Competence Center for Health Services Research in Dermatology (CVderm), Institute for Health Services Research in Dermatology and Nursing, University Hospital Hamburg-Eppendorf, Hamburg, Germany.

Background: In Germany population-based data on health care of basal cell carcinoma (BCC) are rare.

Objective: To analyze the relationship between socio-demographic and regional factors, health insurance status and clinical features of BCC.

Methods: Data base was from a nationwide dermatopathology laboratory. All consecutive excisions from 2010 were analyzed regarding tumor-specific and socioeconomic characteristics of BCC.

Results: 9,467 histologically verified BCC derived from 7,116 patients (54.1 % male, mean age 70 years) were analyzed. 33 % of patients had multiple tumors. The average vertical depth of invasion of BCC was 1.27 mm. It was increased significantly (p ≤ 0.001) in men (1.33 mm vs. 1.19 mm in women) and in persons over 70 years of age (1.36 mm vs. 1.14 mm). Controlled for age and sex, members of agricultural health-insurances (LKK) and of German local public health insurances (AOK) showed the highest tumor depths (1.45 mm resp.1.42 mm). The lowest depths (1.17 mm) were found in insurees of the substitute health funds (Ersatzkassen) (p ≤ 0.001). Vertical depth of invasion was significantly increased for patients living in rural counties (1.34 mm) compared to patients from urban areas (1.21 mm). Furthermore, the distribution of BCC locations varied by type of health insurance.

Conclusions: Area of residence, health insurance status, age and gender are relevant determinants of BCC health care in Germany. Prevention programs and activities to improve early detection by health insurances should take this into account.
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http://dx.doi.org/10.1111/ddg.12415DOI Listing
September 2014