Biology subjects

Eisenhauer, N.

Publications and source records attributed to Eisenhauer, N..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

Forest growth resistance and resilience to the 2018-2020 drought depend on tree diversity and mycorrhizal type

O_LIThe frequency of consecutive drought years is predicted to increase due to climate change. These droughts have strong negative impacts on forest ecosystems. Mixing tree species is proposed to increase the drought resistance and resilience of tree communities. However, this promising diversity effect has not yet been investigated under extreme drought conditions and in the context of complementary mycorrhizal associations and their potential role in enhancing water uptake. C_LIO_LIHere, we investigate whether tree diversity promotes growth resistance and resilience to extreme drought and whether drought responses are modulated by mycorrhizal associations. We used inventory data (2015 - 2021) of a young tree diversity experiment in Germany, manipulating tree species richness (1, 2, 4 species) and mycorrhizal type (communities containing arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) tree species, or both). For all tree communities, we calculated basal area increment (BAI) in the periods before, during, and after the drought and used the concepts of resistance and resilience to quantify growth responses to drought. C_LIO_LIWe found strong growth declines during the extreme 2018-2020 drought for most of the tree communities. Contrary to our hypothesis, we did not find that tree species richness per se can buffer the negative impacts of extreme drought on tree growth. However, while for EM communities, drought resistance, and resilience decreased with tree species richness, they increased for AM communities and communities comprising both mycorrhizal types. We highlight that among various tree species mixtures, only those with mixed mycorrhizal types outperformed their respective monocultures during and after drought. Further, under extreme drought, the community tends to segregate into "winner" and "loser" tree species in terms of diversity, indicating a potential intensification of competition. C_LIO_LIWhile we cannot disentangle the underlying mechanisms, or clarify the role of mycorrhiza during drought, our findings suggest that mixtures of mycorrhizal types within tree communities could help safeguard forests against increasing drought frequency. C_LIO_LISynthesis: Drought resistance and resilience of tree communities depend on tree diversity and mycorrhizal association types. Mixing tree species with diverse mycorrhizal types holds promise for forest restoration in the face of climate change. C_LI

ecology↗

bioRxiv2023

Mycorrhizal fungi modulate tree diversity effects on nutrient dynamics

Species-specific differences in nutrient acquisition strategies allow for complementary use of resources among plants in mixtures, which may be further shaped by mycorrhizal associations. However, empirical evidence of these relationships is scarce, particularly for tree communities. We investigated the impact of tree species richness and mycorrhizal types, arbuscular mycorrhizal fungi (AM) and ectomycorrhizal fungi (EM), on the above- and belowground carbon (C), nitrogen (N), and phosphorus (P) dynamics. Soil and microbial biomass elemental pools did not strongly respond to tree species richness or mycorrhizal type. Tree species richness increased foliage C and P pools depending on mycorrhizal type. Additive partitioning analyses showed that net biodiversity effects for C, N, P pools in EM tree communities, and N pools in AM tree communities, were driven by selection effects, while mixtures of both mycorrhizal types were influenced by complementarity effects. Furthermore, tree species richness enhanced soil nitrate uptake over two years but had no impact on ammonium and phosphate levels. Our results indicate that positive effects of tree diversity on aboveground nutrient storage are mediated by complementary mycorrhizal strategies. Given the prevalence of anthropogenic impacts on tree species richness globally, these results may have important implications for reforestation of multifunctional forests.

ecology↗

bioRxiv2023

Bioenergetic mapping of 'healthy microbiomes' via compound processing potential imprinted in gut and soil metagenomes

Despite mounting evidence of their importance in human health and ecosystem functioning, the definition and measurement of healthy microbiomes remain unclear. More advanced knowledge exists on health associations for compounds used or produced by microbes. Environmental microbiome exposures (especially via soils) also help shape, and may supplement, the functional capacity of human microbiomes. Given the synchronous interaction between microbes, their feedstocks, and micro-environments, with functional genes facilitating chemical transformations, there exists an intriguing opportunity to examine microbiomes in terms of their capacity to process compounds relevant to human health. Here we integrate functional genomics and biochemistry frameworks to derive new quantitative measures of the potential for human gut and environmental soil metagenomes to process major compound classes (e.g., lipids, carbohydrates) and selected biomolecules (e.g., vitamins, short-chain fatty acids) linked to human health. Metagenome functional potential profile data were translated into a universal compound mapping landscape based on bioenergetic van Krevelen mapping of function-level meta-compounds and corresponding functional relative abundances, reflecting imprinted genetic capacity of microbiomes to metabolize an array of different compounds. We show that measures of compound processing potential associated with human health and disease (examining atherosclerotic cardiovascular disease, colorectal cancer, type 2 diabetes and anxious-depressive behavior case studies), and displayed seemingly predictable shifts along gradients of ecological disturbance in plant-soil ecosystems (three case studies). Ecosystem quality explained 60-92% of variation in soil metagenome compound processing potential measures in a post-mining restoration case study dataset. With growing knowledge of the varying proficiency of environmental microbiota to process human health associated compounds, we might design environmental interventions or nature prescriptions to modulate our exposures, thereby advancing microbiota-oriented approaches to human health. Compound processing potential offers a simplified, integrative approach for applying metagenomics in ongoing efforts to understand and quantify the role and linkages of microbiota in environmental- and human-health.

bioinformatics↗

bioRxiv2023

Soil health is linked to primary productivity across Europe

A healthy soil is at the core of sustainable management and policy, but its importance for plant productivity across environmental gradients and land-use types remains poorly understood. To address this gap, we conducted a pan-European field study including 588 sites from 27 countries to investigate the link between soil health and primary productivity across three major land-use types: woodlands, grasslands, and croplands. We found that mean soil health (a composite index based on soil properties, biodiversity, and plant disease control) in woodlands was 31.4% higher than in grasslands, and 76.1% higher than in croplands. Soil health was positively linked to cropland and grassland productivity at the continental scale. Woodland productivity was best explained by climate. Among microbial diversity indicators, we observed a positive association between the richness of Acidobacteria, Firmicutes, and Proteobacteria and primary productivity. Among microbial functional groups, we found that nitrogen-fixing bacteria and mycorrhizal fungi positively related to primary productivity in croplands and grasslands, while plant pathogens showed a negative relationship. Together, our results point to the importance of soil biodiversity and soil health for maintaining primary productivity across contrasting land-use types.

ecology↗

bioRxiv2023

Improving forest ecosystem functions by optimizing tree species spatial arrangement

Reforestation and afforestation programs are promoted as strategies to mitigate rising atmospheric CO2 concentrations and enhance ecosystem services. Planting diverse forests is supposed to foster such benefits, but optimal tree planting techniques, especially regarding species spatial arrangement, are underexplored. Here, using field measurements from the subtropical BEF-China experiment, we simulated leaf litterfall and decomposition, as a function of various spatial arrangements of tree species, from clusters of species to random distributions. We show that increasing tree species spatial heterogeneity in forests composed of nine tree species led to more evenly distributed litterfall, increased litter decomposition and associated nitrogen cycling by 45%. These effects were amplified with increasing plot species richness, while species functional trait identity and diversity modulated these relationships. The spatial arrangement of tree species is a critical component determining biodiversity-ecosystem functioning relationships, and considering such spatial aspects is crucial for operationalizing biodiversity-ecosystem functioning theory in realistic re-/afforestation projects.

ecology↗

bioRxiv2023

Tree diversity increases forest temperature buffering

Global warming is increasing the frequency and intensity of climate extremes. Forests may buffer such extreme events by creating their own microclimate below their canopy via cooling hot and insulating against cold macroclimate air temperatures. This buffering capacity of forests may be increased by tree diversity and may itself maintain forest functioning and biodiversity. However, despite its relevance for many ecosystem processes, the effect of tree diversity on temperature buffering is largely unexplored. Here, we show that tree species richness consistently increases forest temperature buffering across daily, monthly, and annual scales over six years. This finding is based on data from a large-scale tree diversity experiment covering a species richness gradient of 1 to 24 tree species. We found that species richness strengthened both components of forest temperature buffering: the attenuation of hot and of cold macroclimate air temperatures, with the cooling effect being more pronounced. The buffering effect of tree species richness was mediated by canopy density and structural diversity, assessed as leaf area index and stand structural complexity index, respectively. Safeguarding and planting diverse forests may thus mitigate negative effects of global warming and climate extremes on ecosystem functions and communities below the tree canopy.

ecology↗

bioRxiv2023

Multidimensional responses of ecological stability to eutrophication in grasslands

Eutrophication usually impacts biodiversity, species composition, and functioning of grassland communities. Whether such effects propagate to influence the stability of these community aspects is unknown. Using standardized experiments across 55 global grasslands, we quantified the effects of nutrient addition on five stability facets (i.e., temporal invariability and resistance during and recovery after dry and wet growing seasons) for three community aspects (i.e., aboveground biomass, community composition, and species richness). Nutrient addition reduced the temporal invariability and resistance of species richness and community composition, but not biomass, during dry and wet growing seasons. Temporal invariability and resistance during, but not recovery after, dry and wet growing seasons were strongly positively correlated in both ambient and eutrophic conditions. This indicates that maintaining and restoring the stability of plant communities requires increasing resistance rather than recovery. Harnessing the complexity of ecological stability provides new insights for grassland ecosystem sustainability in a changing world.

ecology↗

bioRxiv2023

Tree diversity increases productivity through enhancing structural complexity across mycorrhizal types

Tree species diversity plays a central role for forest productivity, but factors driving positive biodiversity-productivity relationships remain poorly understood. In a biodiversity experiment manipulating tree diversity and mycorrhizal associations, we examined the roles of above- and belowground processes in modulating wood productivity in young temperate tree communities, as well as potential underlying mechanisms. We found that tree species richness increased forest productivity indirectly by enhancing structural complexity within communities. After six years, structurally complex communities were twice as productive as structurally simple stands. This pattern was consistent across stands with different mycorrhizal associations. Our results also demonstrate that taxonomic diversity and functional variation in shade tolerance, but not phenotypic plasticity, are key drivers of structural complexity in mixtures, which in turn lead to overyielding. Consideration of stand structural complexity appears to be a crucial element in predicting carbon sequestration in the early successional stages of mixed-species forests.

ecology↗

bioRxiv2023

Effects of recurrent summer droughts on arbuscular mycorrhizal and total fungal communities in experimental grasslands differing in plant diversity and community composition

Biodiversity loss and climate change have been determined as major global drivers affecting ecosystems and their functioning. In this context, drought was shown to have negative effects on ecosystems by disrupting ecological processes, which could be buffered in more biodiverse systems. Many studies, however, focus on effects on aboveground communities of single drought events, while dynamics of soil-borne communities are still widely unclear, despite their important roles in ecosystem functioning. To elucidate the effect of recurrent summer drought periods on fungal communities in a long-term grassland biodiversity experiment, roof shelters were installed on grassland plots ranging in plant species richness from 1 to 16 species and plant functional group richness (1-4 groups) and composition. After 9 years of summer droughts, bulk soil was sampled and used for Illumina sequencing of the ITS2 and SSU genes to characterize the total fungal and arbuscular mycorrhizal fungal (AMF) communities, respectively. We found shifts of AMF and total fungi community structures caused by recurrent drought and plant species richness, but no buffering of drought effects by plant diversity. Alpha-diversity (VT or ASV richness) of both AMF and total fungi increased with plant species richness but was not significantly affected by drought. Even though drought overall had minimal long-lasting effects, we found Diversispora and Paraglomus among the AMF and Penicillium among total fungal communities to be more abundant after the drought treatment. AMF communities were affected by the presence of individual plant functional groups, reacting stronger to presence of legumes under drought, while total fungal interaction with plant communities were similar under drought as control. AMF -diversity differed between plant functional groups in control conditions but was independent of plant community composition under drought. In contrast, total fungi -diversity was increased by presence of herbs and legumes only under drought. From our results, we conclude that recurring moderate summer droughts do not strongly affect soil fungal communities. All shifts can be explained by indirect effects through the plant community and its top-down effect on soils altered by drought. Further, AMF are not less affected than total fungal communities, but rather respond differently by interacting more strongly with legumes in response to drought. Consequently, not plant species richness, but plant functional composition, dominates in shaping fungal communities under recurrent droughts.

ecology↗

bioRxiv2023

Plant diversity stabilizes soil temperature

Extreme weather events are occurring more frequently, and research has shown that plant diversity can help mitigate impacts of climate change by increasing plant productivity and ecosystem stability1,2. Although soil temperature and its stability are key determinants of essential ecosystem processes related to water and nutrient uptake3 as well as soil respiration and microbial activity4, no study has yet investigated whether plant diversity can buffer soil temperature fluctuations. Using 18 years of a continuous dataset with a resolution of 1 minute ([~]795,312,000 individual measurements) from a large-scale grassland biodiversity experiment, we show that plant diversity buffers soil temperature throughout the year. Plant diversity helped to prevent soil heating in hot weather, and cooling in cold weather. Moreover, this effect of plant diversity increased over the 18-year observation period with the aging of experimental communities and was even stronger under extreme conditions, i.e., on hot days or in dry years. Using structural equation modelling, we found that plant diversity stabilized soil temperature by increasing soil organic carbon concentrations and, to a lesser extent, by increasing the plant leaf area index. We suggest that the diversity-induced stabilization of soil temperature may help to mitigate the negative effects of extreme climatic events such as soil carbon release, thus slow global warming.

ecology↗

bioRxiv2023

Widespread reductions in body size are paired with stable assemblage biomass.

Biotic responses to global change include directional shifts in organismal traits. Body size, an integrative trait that determines demographic rates and ecosystem functions, is often thought to be shrinking in the Anthropocene. Here, we assess the prevalence of body size change in six taxon groups across 5,032 assemblage time-series spanning 1960-2020. Using the Price equation to partition this change into within-species body size versus compositional changes, we detect prevailing decreases in body size through time. Change in assemblage composition contributes more to body size changes than within-species trends, but both components show substantial variation in magnitude and direction. The biomass of assemblages remains remarkably stable as decreases in body size trade-off with increases in abundance. One-Sentence SummaryVariable within-species and compositional trends combine into shrinking body size, abundance increases and stable biomass.

ecology↗

bioRxiv2023

Sustainable land management enhances ecological and economic multifunctionality under ambient and future climate

1.Anthropogenic activity is threatening ecosystem multifunctionality, i.e. the ability of ecosystems to provide multiple functions and services which are vital for human well-being. Here we assess how multifunctionality of agroecosystems in Central Germany depends on land-use type and climate change. Our analysis included 13 ecosystem functions in a large-scale field experiment with five different land-use types (three grassland and two farmland types either sustainably or intensively managed) under two different climate scenarios (ambient and future climate). We consider ecological measures of multifunctionality using averaging approaches with different weights, i.a. reflecting preferences of farmers and environmentalists, and assess an economic multifunctionality measure based on the total value of ecosystem services. Results show that intensive management and future climate decrease ecological multifunctionality for multiple weighting scenarios in both grassland and farmland. Only under a weighting according to farmers preferences, intensively-managed grassland shows higher multifunctionality as compared to sustainably-managed grassland. The economic multifunctionality measure, which includes economic benefits for society at large, reveals a multifunctionality about [~]1.7 times higher for sustainable compared to intensive management for both grassland and farmland. Above-belowground biodiversity correlates positively with ecosystem multifunctionality and is expected to be one of its main drivers. Based on these findings, we suggest to promote and economically incentivise sustainable land management that enhances both ecological and economic multifunctionality, also under future climatic conditions.

ecology↗

bioRxiv2023

Changes in biodiversity impact atmospheric chemistry through plant volatiles and particles

Climate extremes in tandem with biodiversity change affect emissions of biogenic volatile organic compounds (BVOCs) from plants and, as a result, the formation of biogenic secondary organic aerosols (BSOA). The resulting BSOA can have a wide variety of impacts, such as on Earths radiative balance or cloud- and precipitation formation. However, at present, it is unclear how changing biodiversity will lead to changes in BVOC emissions, BSOA formation and their corresponding effects. We present a conceptual framework of the relationships between biodiversity and BVOC emissions based on our current mechanistic understanding and combining knowledge from the fields of biology and atmospheric chemistry. Parts of this framework are tested in a case study using a tree diversity experiment with adjunct BVOC and BSOA characterisation. The relative differences in tree monocultures and mixtures show that the overall concentration of BVOCs decreases with increasing biodiversity (p < 0.01), but results for BSOA compounds are mixed and overall non-significant (p = 0.40). We suggest future studies should follow a multidisciplinary approach where the fields of biology, atmospheric chemistry and climate research interact.

ecology↗

bioRxiv2022

Population structure and genetic variance among local populations of an non-native earthworm species in Minnesota, USA

A variety of human activities have been identified as driving factors for the release and spread of invasive earthworm species in North America. Population genetic markers can help to identify locally relevant anthropogenic vectors and provide insights into the processes of population dispersal and establishment. We sampled the invasive European earthworm species Lumbricus terrestris at nine sites and several bait shops within the metropolitan area of Minneapolis-St. Paul in Minnesota, USA. We used microsatellite markers to infer genetic diversity and population structure, and 16S rDNA to address multiple introduction events, including bait dumping, which is a common source of L. terrestris introductions into the wild. Our results indicate multiple introductions but not from current bait dumping. Overall, genetic structure was low and earthworms >5000 m apart were genetically differentiated, except for one sampling location, indicating jump-dispersal followed by population establishment. Further, earthworms at one location north of Minneapolis established from one or few founder individuals, suggesting that earthworm invasions are ongoing. We therefore encourage further monitoring of earthworm populations using molecular markers, in order to disentangle the different human-related vectors contributing to the spread of earthworms and their establishment, which is essential to develop adequate management strategies.

molecular biology↗

bioRxiv2022

The global distribution and environmental drivers of the soil antibiotic resistome

BackgroundLittle is known about the global distribution and environmental drivers of key microbial functional traits such as antibiotic resistance genes (ARGs). Soils are one of Earths largest reservoirs of ARGs, which are integral for soil microbial competition, and have potential implications for plant and human health. Yet, their diversity and global patterns remain poorly described. Here, we analyzed 285 ARGs in soils from 1012 sites across all continents, and created the first global atlas with the distributions of topsoil ARGs. ResultsWe show that ARGs peaked in high latitude cold and boreal forests. Climatic seasonality and mobile genetic elements, associated with the transmission of antibiotic resistance, were also key drivers of their global distribution. Dominant ARGs were mainly related to multidrug resistance genes and efflux pump machineries. We further pinpointed the global hotspots of the diversity and proportions of soil ARGs. ConclusionsTogether, our work provides the foundation for a better understanding of the ecology and global distribution of the environmental soil antibiotic resistome.

ecology↗

bioRxiv2022

Global environmental drivers of local abundance-mass scaling in soil animal communities

The relationship between species body masses and densities is strongly conserved around a three-quarter power law when pooling data across communities. However, studies of local within-community relationships have revealed major deviations from this general pattern, which has profound implications for their stability and functioning. Despite multiple contributions of soil communities to people, there is limited knowledge on the drivers of body mass-abundance relationship in these communities. We compiled a dataset comprising 155 soil-animal communities across four countries (Canada, Germany, Indonesia, USA), all sampled using the same methodology. We tested if variation in local climatic and edaphic conditions drives differences in local body mass-abundance scaling relationships. We found substantial variation in the slopes of this power-law relationship across local communities. Structural equation modeling showed that soil temperature and water content have a positive and negative net effect, respectively, on soil communities. These effects are mediated by changes in local edaphic conditions (soil pH and carbon content) and the body-mass range of the communities. These results highlight ways in which alterations of soil climatic and edaphic conditions interactively impact the distribution of abundance, and thus energy, between populations of small and large animals. These quantitative mechanistic relationships facilitate our understanding of how global changes in environmental conditions, such as temperature and precipitation, will affect community-abundance distributions and thus the stability and functioning of soil-animal communities.

ecology↗

bioRxiv2022

Tree diversity effects on productivity depend on mycorrhizae and life strategies in a temperate forest experiment

Tree species are known to predominantly interact either with arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. However, there is a knowledge gap whether these mycorrhizae differently influence biodiversity-ecosystem functioning (BEF) relationships and whether a combination of both can increase community productivity. In 2015, we established a tree-diversity experiment by growing tree communities with varying species-richness levels (1, 2, or 4 species), and either with AM or EM tree species, or a combination of both. We investigated basal area and annual basal area increment from 2015 to 2020 as proxy for community productivity. We found significant positive relationships between tree species richness and community productivity, which strengthened over time. Further, AM and EM tree species differently influenced productivity; however, there was no overyielding when AM and EM trees grew together. EM tree communities were characterized by low productivity in the beginning, but an increase of increment over time, and showed overall strong biodiversity effects. For AM tree communities the opposite was true. While young trees did not benefit from the presence of the other mycorrhizal type, dissimilar mechanisms underlying BEF relationships in AM and EM trees indicate that maximizing tree and mycorrhizal diversity may increase ecosystem functioning in the long run.

ecology↗

bioRxiv2022

Higher aboveground carbon stocks in mixed-species planted forests than monocultures - a meta-analysis

Natural forest is declining globally as the area of planted forest increases. Planted forests are often monocultures, despite results suggesting that higher species richness improves ecosystem functioning and stability. To test if this is generally the case, we performed a meta-analysis of available results. We assessed aboveground carbon stocks in mixed-species planted forests vs (a) the average of constituent species monocultures, (b) the best constituent species monoculture, and (c) commercial species monocultures. We investigated whether any advantage of mixtures over monocultures was positively related to species richness, as well as potential mechanisms driving differences in carbon stocks between mixtures and monocultures. The meta-analysis dataset included 79 comparisons from 21 sites. Carbon stocks in mixed planted forests were higher than the average of stocks in monocultures of their constituent species, containing on average 70% more carbon. Mixed planted forests also out-performed commercial monocultures, containing on average 77% more carbon. There was c.25% more carbon in mixed planted forests relative to the best performing monocultures, although this difference was not statistically significant. Overyielding was highest in four-species mixtures (richness range 2-6 species). More data providing better coverage of richness and age gradients (study sites aged 3.5-28 years) is needed to increase confidence in these results. None of the potential mechanisms we examined (nitrogen-fixer present vs absent; native vs non-native/mixed origin; tree diversity experiment vs forestry plantation) consistently explained variation in the diversity effects. This suggests that our findings are driven by a combination of small (statistically insignificant) effects from these sources or further unidentified mechanisms or some combination of the two. We conclude that increasing tree species richness in planted forests can increase carbon stocks while bringing other potential benefits associated with diversification. However, implementation will depend on the balance of these benefits relative to the operational challenges and costs of diversification.

ecology↗