Biology subjects

Herzschuh, U.

Publications and source records attributed to Herzschuh, U..

At least 19 recordsLinked to original sources

bioRxiv2026

Microbial priming controls terrestrial carbon burial in marine sediments

Marine sediments are a globally important sink for organic carbon of both marine and terrestrial origin, yet far less terrestrial carbon is ultimately buried than rivers deliver to the ocean margins. This long-standing "terrestrial carbon conundrum" has resisted explanation, largely because conventional bulk proxies cannot distinguish marine, terrestrial and microbial-degrader carbon pools. Here we use sedimentary ancient DNA from five records spanning the Bering Sea to the Sea of Okhotsk over the past 30,000 years to reconstruct organic carbon resolved simultaneously by taxonomy and habitat. Integrating these taxon-resolved carbon estimates with environmental proxies across the last glacial-interglacial cycle, we find that terrestrial carbon burial is governed not only by supply but by biogeochemical interactions previously documented only in soils. Microbial processing splits into two competing pathways: under priming, marine organic matter fuels the degradation of terrestrial organic matter, whereas under preferential substrate utilization microbes consume marine organic matter and spare terrestrial carbon. Both pathways are triggered only once marine organic-matter availability crosses a critical, temperature-governed threshold. This temperature-sensitive cascade reveals a previously unrecognized vulnerability of the ocean's carbon sink to global warming.

biochemistry↗

bioRxiv2026

Taxon-resolved sources of organic carbon preserved in lake sediments using the sedaDNA GenC pipeline

Organic carbon (OC) burial in lakes is an important component of the global carbon cycle, but the source organisms of preserved OC remain poorly resolved. Here we develop the genC pipeline, which combines sedimentary ancient DNA concentrations, read-based taxonomic assignments, and group-specific priors for DNA and cellular carbon content to derive OCDNA-projected, a semi-quantitative proxy for the magnitude and taxonomic composition of preserved sedimentary OC. We apply genC to six high-latitude lake records spanning the last 30,000 years. OCDNA-projected broadly agrees with independent proxies for total organic carbon and aquatic contribution, supporting its reliability. Our results indicate that environmental conditions, especially warming, rather than preservation alone, are the main drivers of preserved OC variation. Terrestrial sources, mainly woody plants, dominate lake sediment OC. Eukaryotic algae as well as aquatic and terrestrial bacteria become more important during the warmer Holocene. These results establish sedaDNA as a taxonomically resolved tool for reconstructing long-term changes in preserved lake-sediment OC.

paleontology↗

bioRxiv2026

Forest expansion and open vegetation responses during the past 14 ka at Zhagaer Co on the eastern Tibetan Plateau

Forest expansion and retreat are key drivers of alpine ecosystem dynamics, yet it remains unclear how forest expansion shapes alpine plant communities and whether alpine assemblages that re-emerge after forest decline resemble those of the Late Glacial. Here, we integrate sedimentary ancient DNA (sedaDNA) and pollen records from Zhagaer Co on the eastern Tibetan Plateau to reconstruct vegetation changes over the past [~]14 ka. Using Picea abundance as a proxy for forest cover, we apply constrained ordination of sedaDNA-inferred plant communities to identify plant taxa as "winners" and "losers" of forest expansion and compare the composition of loser taxa between the late Glacial and late Holocene cold-open phases. Our results show that forest expansion during the early to mid-Holocene favoured woody and forest-margin taxa (e.g. Rhododendron, Salicaceae), while suppressing alpine forbs and graminoids (e.g. Carex, Thalictrum), consistent with patterns expected under ecological filtering. However, late Holocene reopening did not fully restore a late Glacial-like alpine community; instead, it was characterised by a stronger contribution of alpine meadow and shrub taxa. This difference may reflect contrasting environmental backgrounds, including higher atmospheric CO2 levels during the late Holocene, ecological legacies of prior forest expansion, and increasing human influence. These findings suggest that forest expansion may lead to long-term restructuring of alpine plant assemblages, and that late Holocene cooling did not simply restore late Glacial alpine communities but instead produced a distinct alpine ecosystem state. Together, these results highlight the long-term legacy of treeline dynamics in shaping alpine ecosystem trajectories.

ecology↗

bioRxiv2025

Global shifts in vegetation compositional resilience over the past 8,000 years

Vegetation resilience is critical for sustaining biodiversity and ecosystem services, yet its long-term dynamics and underlying drivers remain poorly resolved. Here, we assess changes in continental-scale vegetation compositional resilience over the past 8,000 years by applying established leading indicators (including autocorrelation, standard deviation, skewness, and kurtosis) to 482 fossil pollen records from all major landmasses except Antarctica. Using a machine learning approach, we evaluate the relative contributions of anthropogenic land cover change (ALCC) and climatic parameters (annual mean temperature, temperature seasonality, annual precipitation, and precipitation seasonality) in driving resilience shifts across continents. We further employ structural equation modeling (SEM) to disentangle how abiotic factors (ALCC and climatic variables) and biotic factors (species richness, evenness, synchrony, and temporal {beta} diversity) jointly shape long-term trends in vegetation resilience at the continental scale. Our results reveal a persistent, millennia-scale decline in resilience during the past 1.6 to 4.4 thousand years before present, with intensified anthropogenic land-use change identified as the dominant global driver. This finding suggests that the global decline in vegetation resilience observed over recent decades likely represents a continuation of the long-term trend established during the preceding Holocene. Notably, North America exhibited a resurgence in resilience over the past 1,200 years, primarily attributed to enhanced resilience in tundra and savanna ecosystems. SEM analyses uncover complex pathways through which abiotic and biotic predictors interact to shape millennial-scale resilience changes across continents. Despite the complexity of these underlying mechanisms, the analyses demonstrate that biotic factors collectively exert substantial, and often predominant, influences on long-term resilience dynamics. This underscores the indispensable role of biotic attributes in modulating long-term vegetation resilience, highlighting their potential as critical targets for ecosystem conservation and restoration.

ecology↗

bioRxiv2025

Different dispersal rates and declining climate suitability shape future vegetation compositions across the Arctic: implications for the boreal forest - tundra boundary

AimWe investigate how species-specific dispersal abilities might influence future Arctic plant distributions and large-scale dynamics at the boreal forest - tundra boundary until 2100 Locationcircumpolar terrestrial Arctic (boreal forest, taiga and tundra) Taxon1,550 plant species MethodsWe developed climate-driven species distribution models (SDM) to predict species-specific emerging climate niches under different climate scenarios. The model was parameterized using occurrence data from the Global Biodiversity Information Facility database (GBIF) and temperature and bioclimatic variables from the CHELSA data set. Dispersal rates were assigned to each species using a trait-based approach and were used to predict future habitat with a distance-based probability over time. ResultsPlant species are predicted to occupy on average only 12.3% (1.5 - 53.9 95% CI) of their emerging climate niches, with half of the species unable to colonize new habitat by 2100 due to limited dispersal distances. In dispersal limited predictions migration to higher altitudes played a greater role than northward shifts. Decolonization by species (extirpation) due to decreasing climate suitability had a larger effect on species composition change compared to dispersal limitations. Boreal tree species were predicted to expand into the tundra shrinking the treeless areas. Main conclusionsFuture plant species distributions and resulting large-scale compositions are affected by species-specific dispersal rates. Even though new suitable niches emerge prominently towards the north, higher altitudes might be more relevant given their accessibility by dispersal over the next century. Although climate niche dynamics could support higher plant species richness across the Arctic, overall richness is expected to decline with climate warming due to dispersal limitations. The colonization of new habitats via dispersal in combination with the decolonization of former habitats due to declining climatic suitability on species level are predicted to cause large-scale changes in species composition, especially at the boundary between the boreal forest and the tundra biome.

ecology↗

bioRxiv2025

Dynamic connectivities of plant metacommunities at a millennial time-scale: the Beringia testbed

Ecological connectivity shapes ecosystem responses to climate change and is thought to underpin stability, yet its millennial-scale dynamics remain poorly resolved. We asked how spatial and temporal connectivity of plant metacommunities changed over the last 40 ka and which processes drove it. We analysed and compiled plant sedimentary DNA from 20 lake cores across Beringia (Siberia, Alaska) to investigate community dynamics and, for a high-resolution subset, applied beta- and zeta-diversity to track connectivity. Vegetation changed coherently across the glacial-Holocene transition, with trait shifts mirroring functional composition. Connectivity peaked during the late MIS3 and Last Glacial Maximum--likely aided by the Bering Land Bridge, mass effects and facilitation--collapsed during the Deglacial with rapid turnover, and rebounded in the Holocene as shrub and boreal communities expanded. Temporal zeta within sites exceeded spatial zeta, indicating strong local persistence and resilience. Tundra sites uninvaded by forest maintained continuous species pools. Overall, these patterns underscore the value of a metacommunity perspective for assessing millennial-scale connectivity changes.

ecology↗

bioRxiv2025

Arctic defaunation initiated a cascade of mammal-plant interaction shift through dispersal dynamics

Amid accelerating defaunation, it remains unclear whether the loss of large mammals can trigger ecosystem collapse and through which functional pathways. Using sedimentary ancient metagenomics, we identify an overlooked role of large mammal defaunation in helping drive the collapse of the glacial mammoth-steppe. Network analyses identified rewiring of mammal interactions during the late glacial supporting cascading effects. Crucially, megafaunal-mediated long-distance seed dispersal buffered vegetation turnover during periods of rapid climate warming but weakened with progressive losses of vital dispersal interactions leading to the steppe-tundras transition to open woodland in the early Holocene. Trophic interactions did not offset turnover and became dominant afterwards with the more stable climate. We identified resilient interactions that may support recovery, suggesting the potential of rewilding to restore Arctic ecosystems. One-sentence abstractAncient metagenomics reveals disrupted long-distance seed dispersal helped drive mammoth-steppe collapse and informs Arctic rewilding efforts.

ecology↗

bioRxiv2025

DNA virus-host patterns in lake and marine environments over the last glacial cycle

Viruses are crucial to population control, biogeochemical cycling, and host evolution, making them essential for ecosystem function. Here, we explore long-term virus-host interactions in lake and marine environments across the late Pleistocene and Holocene. We analysed sedimentary ancient DNA (sedaDNA) from five Siberian lakes and four Subarctic/Antarctic marine cores to infer past DNA virus taxa from metagenomic sequences. Viruses accounted for 0.089% (357 161 reads) of mapped reads across 2084 taxa. Virus communities differ between lakes and marine sites, with lakes dominated by Caudoviricetes and marine environments featuring Caudoviricetes and Algavirales. Each time series shows compositional changes in virus communities from the Pleistocene to the Holocene, supporting the inference that sedaDNA can reconstruct time-resolved ancient viral assemblages. Among the most abundant viruses, we identified 83 virus-host pairs known from published literature to infect bacterial, archaeal, or eukaryotic hosts, and assessed their associations using co-variation patterns. Over millennia, virus-host co-variations are particularly stable in marine systems, especially for phytoplankton-infecting viruses. However, in the Bering Sea, we find a lack of virus-host correlation, likely because an Arctic Pelagibacter strain expanded rapidly after the Bering Strait opened, potentially due to absent viral infection. Antagonistic patterns also appear between bacteriophages and hosts, possibly linked to shifts between lytic and lysogenic cycles in response to environmental changes. This study shows that sedaDNA can reveal ancient viral community structures and long-term ecological patterns, highlighting the value of ancient viromes in understanding ecosystem- specific responses to environmental change.

ecology↗

bioRxiv2025

Woody plant encroachment enhances negative interactions in Arctic plant communities over the last 24,000 years

Woody taxa encroachment in the Arctic has been widely observed. However, it remains uncertain how plant interactions are affected by such encroachment due to the lack of long-term observational data. Here, we reconstruct plant composition and functional trait turnover during post-glacial woody encroachment using sedimentary ancient DNA from nine lakes in the Siberia-Alaska region. Environmentally constrained null models are applied to partition plant interactions from the pure environment driven plant co-occurrence signal. Our results show that plant interactions shifted from predominantly positive interactions (e.g. nurse-plant facilitation) during the glacial period to negative interactions (e.g. competition) during the Holocene. This shift coincided with a community transition from herbaceous to woody taxa, leading to an increase in average plant height and root length, as evidenced by leveraging plant trait information. We suggest that climate (an external factor) and plant interactions (an internal process) jointly supported rapid and widespread woody taxa expansion at the end of the last glacial, which may provide an analogy with contemporary "arctic greening". In turn, woody encroachment is likely to constrain the geographical ranges of native species, increasing the risk of local native taxa loss, while enhancing beta diversity.

ecology↗

bioRxiv2025

Human dimension of Holocene wildfire dynamics in boreal eastern Siberia

Severe wildfire seasons in the Republic of Sakha (Yakutia) raise questions regarding long-term fire dynamics and their drivers. However, data on long-term fire history remains scarce across eastern Siberia. We present the first composite of reconstructed wildfire dynamics in Yakutia throughout the Holocene, based on eight newly contributed records of macroscopic charcoal in lake sediments in combination with published data. Increased biomass burning occurred in the Early Holocene, c. 10,000 years BP, before shifting to lower levels at c. 6000 years BP. Independent simulations of climate-driven burned area in an individual-based forest model reproduce this reconstructed Holocene trend (rs = 0.85), but the correlation on centennial timescales turns negative in the Late Holocene (rs = -0.70). This mismatch suggests that climate alone cannot explain Late Holocene wildfire dynamics. We propose that a human dimension needs to be considered. By example of the settlement of the pastoralist Sakha people c. 800 years BP, we show that implementing reduced fuel availability from Indigenous land management in the forest model leads to improved centennial-scale correlations (rs = 0.96). This study highlights the need for a better understanding of the poorly reported human dimension of past fire dynamics in eastern Siberia.

ecology↗

bioRxiv2024

Phaeocystis blooms caused carbon drawdown during the Antarctic Cold Reversal from sedimentary ancient DNA

The Southern Ocean plays a crucial role in the global carbon budget. Modeling studies propose that the atmospheric CO2 plateau during the Antarctic Cold Reversal (ACR; 14,700 to 12,700 calibrated years before present (cal yr BP)) is related to increased marine productivity. However, proxy evidence relating environmental conditions as well as primary community composition and productivity to carbon drawdown is missing. Our ancient DNA shotgun metagenomic analysis of marine sediments revealed Phaeocystis antarctica (haptophyte) as a key element of the primary producer community. Independent proxy evidence (blooming-related bacteria, Ba/Fe ratio) from the same sediment record point to high productivity in response to enhanced sea-ice seasonality caused by ACR cooling. Post ACR, abrupt Phaeocystis community loss shows how sensitive this ecosystem is to warming, potentially representing a key tipping element that may be further enhanced by the Phaeocystis-related sulfur cycle-climate feedback. As an analogy for present warming, it highlights the importance of regions with high seasonal sea-ice variability and Phaeocystis-dominance, such as the Ross Sea, for stabilizing atmospheric CO2 content. Additionally, our shotgun metagenomic data portray complex Holocene ecosystem establishment including key Antarctic taxa such as penguins, whales, and Antarctic fishes with implications for ongoing conservation efforts.

ecology↗

bioRxiv2024

Dynamic land-plant carbon sources in marine sediments inferred from ancient DNA

Terrigenous organic matter in marine sediments is considered a significant long-term carbon sink, yet our knowledge regarding its source taxa is severely limited. Here, we leverage land-plant ancient DNA from six globally distributed marine sediment cores covering the Last Glacial-Holocene transition as a proxy for the share, accumulation rate, preservation, and composition of terrigenous organic matter. We show that the spatial and temporal plant composition as revealed by sedaDNA records reflects mainly the vegetation dynamics of nearby continents as revealed by comparison with pollen from land archives. However, we also find indications of a global north-to-south translocation of sedaDNA. The plant composition shows that upland vegetation is strongly underrepresented in the record compared to riverine and coastal sources. We also find that plant sedaDNA has a higher accumulation rate in samples from the Late Glacial, which is characterized by high runoff and mineral load. Thus plant DNA in marine sediments allows for new perspectives on the global linkages between the terrestrial and marine carbon cycle which would benefit from a more quantitative understanding of DNA preservation and dispersal. This represents the basis of how climate change and land-use change translate into carbon-sink dynamics and also informs about natural carbon-capture solutions.

ecology↗

bioRxiv2023

Tibetan terrestrial and aquatic ecosystems collapsed with cryosphere loss inferred from sedimentary ancient metagenomics

Glacier and permafrost shrinkage and land-use intensification threaten diverse mountain wildlife and affect nature conservation strategy. Our understanding of alpine ecological dynamics is, however, insufficient because time series portraying ecosystem complexity adequately are missing. Here, we present an ancient metagenomic record tracing 317 terrestrial and aquatic taxa, including mammals, fish, plants, and microorganisms retrieved from a lake sediment core from the southeastern Tibetan Plateau covering the last 18,000 years. We infer that steppe-meadow turned into woodland at 14 ka (cal BP) controlled by warming-induced cryosphere loss, further driving a change of herbivore dominance from wild yak to deer. Network analyses reveal that root hemiparasitic and cushion plants are keystone taxa, likely altering the terrestrial ecosystem via facilitation. These findings refute the hypothesis of top-down control by large herbivores in the alpine ecosystem. We also find that glacier mass loss significantly contributes to considerable turnover in the aquatic community at 14 ka, transitioning from glacier-related (blue-green) algae to abundant non-glacier-preferring picocyanobacteria, macrophytes, fish, and fish-eating otters. Human impact contributes little to shaping the alpine ecosystems. By applying network analysis, we provide the first sedaDNA-based assessment of the stress-gradient hypothesis. As cryosphere loss is ongoing due to climate warming, prioritizing the protection of habitats with rich nurse plants that aid neighbors in adapting to stressful conditions is likely to be a more beneficial conservation measure than livestock reduction in the Tibetan Plateau. Significance statementMerging ancient metagenomics and network analysis gives new insights into conserving the Tibetan alpine ecosystem under ongoing warming and human perturbations. We investigated the assembly of the Yak steppe-meadow ecosystem and an alpine lake system in response to cryosphere changes over the past [~]18,000 years on the Tibetan Plateau. Large herbivores cannot be a cost-effective natural climate solution to stabilize the Tibetan alpine ecosystem because they are not keystone taxa at the ecosystem scale. Furthermore, there is no support that land use considerably shapes the alpine communities and ecosystems. Protection policy should thus prioritize focus on alpine areas with intense land use and rich in root hemiparasitic and cushion plants because these taxa act as facilitators in the ecosystem.

ecology↗

bioRxiv2023

No evidence for highly pathogenic avian influenza virus H5N1 (clade 2.3.4.4b) in the Antarctic region during the austral summer 2022/23

The current highly pathogenic avian influenza H5N1 panzootic has substantial impacts on wild birds and marine mammals. Although major outbreaks occurred in South America, incursion to Antarctica emerged late in the breeding season of 2023/2024 and was confined the wider region of the Antarctic Peninsula. To infer potential underlying processes, we compiled H5N1 surveillance from Antarctica and Sub-Antarctic Islands prior to the first confirmed cases.

microbiology↗

bioRxiv2021

Regional opportunities for Siberian tundra conservation in the next 1000 years

The biodiversity of tundra areas in northern high latitudes is threatened by invasion of forests under global warming. However, poorly understood nonlinear responses of the treeline ecotone mean the timing and extent of tundra losses are unclear but policymakers need such information to optimize conservation efforts. Our individual based model LAVESI, developed for the Siberian tundra-taiga ecotone, can help improve our understanding. Consequently, we simulated treeline migration trajectories until the end of the millennium, causing a loss of tundra area when advancing north. Our simulations reveal that the treeline follows climate warming with a severe, century-long time lag, which is overcompensated by infilling of stands in the long run even when temperatures cool again. Our simulations reveal that only under ambitious mitigation strategies (RCP 2.6) will ~30% of original tundra areas remain in the north but separated into two disjunct refugia.

ecology↗

bioRxiv2021

Long-term fungus-plant co-variation from multi-site sedimentary ancient DNA metabarcoding in Siberia

Climate change has a major impact on arctic and boreal terrestrial ecosystems as warming leads to northward treeline shifts, inducing consequences for heterotrophic organisms associated with the plant taxa. To unravel ecological dependencies, we address how long-term climatic changes have shaped the palaeo-ecosystems at selected sites in Siberia. We investigated sedimentary ancient DNA from five lakes spanning the last 47,000 years, using the ITS1 marker for fungi and the chloroplast P6 loop marker for vegetation metabarcoding. After bioinformatic processing with the OBItools pipeline, we obtained 706 unique fungal operational taxonomic units (OTUs) and 243 amplicon sequence variants (ASVs) for the plants. We show higher OTU numbers in dry forest tundra as well as boreal forests compared to wet southern tundra. The most abundant fungal taxa in our dataset are Pseudeurotiaceae, Mortierella, Sordariomyceta, Exophiala, Oidiodendron, Protoventuria, Candida vartiovaarae, Pseudeurotium, Gryganskiella fimbricystis, and Trichosporiella cerebriformis. The overall fungal composition is explained by the plant composition as revealed by redundancy analysis. The fungal functional groups show antagonistic relationships in their climate susceptibility. The advance of woody taxa in response to past warming led to an increase in the abundance of mycorrhizae, lichens, and parasites, while yeast and saprotroph distribution declined. We also show co-occurrences between Salicaceae, Larix, and Alnus and their associated pathogens and detect higher mycorrhizal fungus diversity with the presence of Pinaceae. Under future warming, we can expect feedbacks between fungus compositional and plant diversity changes which will affect forest advance and stability in arctic regions.

ecology↗

bioRxiv2021

Fungal biodiversity in Arctic paleoecosystems assessed by metabarcoding of lake sedimentary ancient DNA

Fungi are crucial organisms in most ecosystems as they exert ecological key functions and are closely associated with land plants. Fungal community changes may therefore help reveal biodiversity changes in past ecosystems. Lake sediments contain DNA of organisms in the catchment area, which allows reconstructing past biodiversity by using metabarcoding of ancient sedimentary DNA. We developed a novel PCR primer combination for fungal metabarcoding targeting a short amplicon to account for length bias of amplification due to ancient DNA degradation. In-silico PCRs showed higher diversity using this primer combination than using previously established fungal metabarcoding primers. We analyzed existing data from sediment cores from four artic and one boreal lake in Siberia. These cores had been stored for 2-22 years and examined degradation effects of ancient DNA and storage time-related bias in fungal communities. Amplicon size differed between fungal divisions, however, we observed no significant effect of sample age on amplicon length and GC content, suggesting robust results. We also found no indication of post-coring fungal growth during storage distorting ancient fungal communities. Terrestrial soil fungi, including mycorrhizal fungi and saprotrophs, were predominant in all lakes, which supports the use of lake sedimentary ancient DNA for reconstructing terrestrial communities.

ecology↗

bioRxiv2020

Plant sedimentary ancient DNA from Far East Russia covering the last 28 ka reveals different assembly rules in cold and warm climates

Woody plants are expanding into the Arctic under a warming climate. The related impact on plant diversity is not well understood because we have only limited knowledge about plant assembly rules and because of a lack of time-series of plant diversity. Here, we applied sedimentary ancient DNA metabarcoding using the plant-specific g and h primers of the trnL gene to a sediment record from Lake Ilirney (central Chukotka Far Eastern Russia) covering the last 28 thousand years. Our results show that forb-dominated steppe-tundra and Saliceae-rich dwarf-shrub tundra communities dominated during the cold climate before 14 ka, while deciduous erect-shrub tundra was abundant during the warm period between 14 and 0 ka. Larix invasion during the late Holocene substantially lagged behind the period of densest vegetation and likely warmest period between 10 and 6 ka. Overall, we discovered the highest richness during 28-23 ka and a second richness peak during 13-10 ka: both periods are characterised by low shrub abundance. The richest communities during the cold pre-14 ka period were phylogenetically clustered, which probably originates from environmental filtering along with niche differentiation under limited resources. In contrast, the richest post-14 ka community was phylogenetically overdispersed, likely originating from an erratic recruitment process in the course of warming. Despite differences in timescale, some of our evidence can be relevant to arctic plant diversity changes. By analogy to the past, we expect a lagged response of tree invasion. In the long-term, ongoing expansion of deciduous shrubs will eventually result in a phylogenetically more diverse community but will also cause reduced plant taxonomic richness; however, richness may overshoot in the short-term.

ecology↗