Showing papers by "Ernst Detlef Schulze published in 2021"

AusTraits, a curated plant trait database for the Australian flora.

Abstract: We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.

Changes in plant-herbivore network structure and robustness along land-use intensity gradients in grasslands and forests

Abstract: Land-use intensification poses major threats to biodiversity, such as to insect herbivore communities. The stability of these communities depends on interactions linking herbivores and host plants. How interaction network structure begets robustness, and thus stability, in different ecosystems and how network structure and robustness are altered along land-use intensity gradients are unclear. We analyzed plant-herbivore networks based on literature-derived interactions and long-term sampling from 289 grasslands and forests in three regions of Germany. Network size and nestedness were the most important determinants of network robustness in both ecosystems. Along land-use intensity gradients, networks in moderately grazed grasslands were more robust than in those managed by frequent mowing or fertilization. In forests, changes of network robustness along land-use intensity gradients relied on changes in plant species richness. Our results expand our knowledge of the stability of plant-herbivore networks and indicate options for management aimed at stabilizing herbivore communities.

The climate benefit of carbon sequestration

Abstract: . Ecosystems play a fundamental role in climate change mitigation by taking up carbon from the atmosphere and storing it for a period of time in organic matter. Although climate impacts of carbon emissions can be quantified by global warming potentials, it is not necessarily clear what are appropriate formal metrics to assess climate benefits of carbon removals by sinks. We introduce here the Climate Benefit of Sequestration (CBS), a metric that quantifies the radiative effect of taking up carbon dioxide from the atmosphere and retaining it for a period of time in an ecosystem before releasing it back to the atmosphere. To quantify CBS, we also propose a formal definition of carbon sequestration (CS) as the integral of an amount of carbon taken up from the atmosphere stored over the time horizon it remains in an ecosystem. Both metrics incorporate the separate effects of i) inputs (amount of atmospheric carbon removal), and ii) transit time (time of carbon retention) in carbon sinks, which can vary largely for different ecosystems or management types. In three separate examples, we show how to compute and apply these metrics to compare different carbon management practices in forestry and soils. We believe these metrics can be useful in resolving current controversies about the management of ecosystems for climate change mitigation.

5S-IGS rDNA in wind-pollinated trees (Fagus L.) encapsulates 55 million years of reticulate evolution and hybrid origins of modern species.

Abstract: Standard models of plant speciation assume strictly dichotomous genealogies in which a species, the ancestor, is replaced by two offspring species. The reality in wind-pollinated trees with long evolutionary histories is more complex: species evolve from other species through isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi-copy, potentially multi-locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra-genomic recombination. Therefore, it can provide unique insights into the dynamic speciation processes of lineages that diversified tens of millions of years ago. Here, we provide the first high-throughput sequencing (HTS) of the 5S intergenic spacers (5S-IGS) for a lineage of wind-pollinated subtropical to temperate trees, the Fagus crenata - F. sylvatica s.l. lineage, and its distant relative F. japonica. The observed 4963 unique 5S-IGS variants reflect a complex history of hybrid origins, lineage sorting, mixing via secondary gene flow, and intra-genomic competition between two or more paralogous-homoeologous 5S rDNA lineages. We show that modern species are genetic mosaics and represent a striking case of ongoing reticulate evolution during the past 55 million years.

Dispersal ability, trophic position and body size mediate species turnover processes: Insights from a multi‐taxa and multi‐scale approach

Abstract: Aim Despite increasing interest in β‐diversity, that is the spatial and temporal turnover of species, the mechanisms underlying species turnover at different spatial scales are not fully understood, although they likely differ among different functional groups. We investigated the relative importance of dispersal limitations and the environmental filtering caused by vegetation for local, multi‐taxa forest communities differing in their dispersal ability, trophic position and body size. Location Temperate forests in five regions across Germany. Methods In the inter‐region analysis, the independent and shared effects of the regional spatial structure (regional species pool), landscape spatial structure (dispersal limitation) and environmental factors on species turnover were quantified with a 1‐ha grain across 11 functional groups in up to 495 plots by variation partitioning. In the intra‐region analysis, the relative importance of three environmental factors related to vegetation (herb and tree layer composition and forest physiognomy) and spatial structure for species turnover was determined. Results In the inter‐region analysis, over half of the explained variation in community composition (23% of the total explained 35%) was explained by the shared effects of several factors, indicative of spatially structured environmental filtering. Among the independent effects, environmental factors were the strongest on average over 11 groups, but the importance of landscape spatial structure increased for less dispersive functional groups. In the intra‐region analysis, the independent effect of plant species composition had a stronger influence on species turnover than forest physiognomy, but the relative importance of the latter increased with increasing trophic position and body size. Main conclusions Our study revealed that the mechanisms structuring assemblage composition are associated with the traits of functional groups. Hence, conservation frameworks targeting biodiversity of multiple groups should cover both environmental and biogeographical gradients. Within regions, forest management can enhance β‐diversity particularly by diversifying tree species composition and forest physiognomy.

The size and the age of the metabolically active carbon in tree roots.

Abstract: Little is known about the sources and age of C respired by tree roots. Previous research in stems identified two functional pools of non-structural carbohydrates (NSC): an "active" pool supplied directly from canopy photo-assimilates supporting metabolism and a "stored" pool used when fresh C supplies are limited. We compared the C isotope composition of water-soluble NSC and respired CO2 for aspen roots (Populus tremula hybrids) cut off from fresh C supply after stem-girdling or prolonged incubation of excised roots. We used bomb radiocarbon to estimate the time elapsed since C fixation for respired CO2 , water-soluble NSC and structural α-cellulose. While freshly excised roots (mostly <2.9 mm in diameter) respired CO2 fixed <1 year previously, the age increased to 1.6-2.9 year within a week after root excision. Freshly excised roots from trees girdled ~3 months ago had respiration rates and NSC stocks similar to un-girdled trees but respired older C (~1.2 year). We estimate that over 3 months NSC in girdled roots must be replaced 5-7 times by reserves remobilized from root-external sources. Using a mixing model and observed correlations between Δ14 C of water-soluble C and α-cellulose, we estimate ~30% of C is "active" (~5 mg C g-1 ).

Among stand heterogeneity is key for biodiversity in managed beech forests but does not question the value of unmanaged forests: Response to Bruun and Heilmann-Clausen (2021)

Abstract: Schall et al. (2020) assessed how a combination of different forest management systems in managed forest landscapes dominated by European beech may affect the biodiversity (alpha, beta and gamma) of 14 taxonomic groups. Current forest policy and nature conservation often demand for combining uneven-aged managed and unmanaged, set-aside for nature conservation, beech forests in order to promote biodiversity. In contrast to this, Schall et al. (2020) found even-aged shelterwood forests, represented by different developmental phases, to support highest regional (gamma) diversity. By pointing out that unmanaged forests included in our study are not old-growth forests, Bruun and Heilmann-Clausen (2021) challenge our conclusion as not providing sound scientific advice to societies. It is true that the studied unmanaged forests are not representing old-growth forests as defined in the literature. However, we demonstrate the representativeness of our unmanaged forests for current beech forest landscapes of Central Europe, where managed forests were more or less recently set-aside in order to develop old-growth structures. We also show that the managed and recently unmanaged forests in our study already differ distinctively in their forest structures. We use this response to stress the role of forest reserves for promoting certain species groups, and to emphasise their importance as valuable research sites today and in the future. Synthesis and applications. We see two main conclusions from our study. First, unmanaged forests still matter. We agree with Bruun and Heilmann-Clausen (2021) on the general importance of unmanaged, old-growth or long-untouched forests, and we do not question the importance of set-aside forests for biodiversity conservation. However, a complete complementarity to managed systems may only reveal after many decades of natural development. Second, safeguarding biodiversity in largely managed forest landscapes should focus on providing a landscape matrix of different developmental phases with varying environmental conditions rather than on maximising the vertical structure within stands. Such landscapes can partly compensate for structures that are still missing in vital, dense and closed forests recently set-aside or for unsuitable phases that may occur due to a cyclic synchronisation of forest structures in unmanaged forests. © 2021 The Authors. Journal of Applied Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society

Direct and Indirect Effects of Management Intensity and Environmental Factors on the Functional Diversity of Lichens in Central European Forests.

Abstract: Using 642 forest plots from three regions in Germany, we analyzed the direct and indirect effects of forest management intensity and of environmental variables on lichen functional diversity (FDis). Environmental stand variables were affected by management intensity and acted as an environmental filter: summing direct and indirect effects resulted in a negative total effect of conifer cover on FDis, and a positive total effect of deadwood cover and standing tree biomass. Management intensity had a direct positive effect on FDis, which was compensated by an indirect negative effect via reduced standing tree biomass and lichen species richness, resulting in a negative total effect on FDis and the FDis of adaptation-related traits (FDisAd). This indicates environmental filtering of management and stronger niche partitioning at a lower intensity. In contrast, management intensity had a positive total effect on the FDis of reproduction-, dispersal- and establishment-related traits (FDisRe), mainly because of the direct negative effect of species richness, indicating functional over-redundancy, i.e., most species cluster into a few over-represented functional entities. Our findings have important implications for forest management: high lichen functional diversity can be conserved by promoting old, site-typical deciduous forests with a high richness of woody species and large deadwood quantity.

High-throughput sequencing of 5S-IGS in oaks: Exploring intragenomic variation and algorithms to recognize target species in pure and mixed samples.

Abstract: Measuring biological diversity is a crucial but difficult undertaking, as exemplified in oaks where complex patterns of morphological, ecological, biogeographical and genetic differentiation collide with traditional taxonomy, which measures biodiversity in number of species (or higher taxa). In this pilot study, we generated high-throughput sequencing amplicon data of the intergenic spacer of the 5S nuclear ribosomal DNA cistron (5S-IGS) in oaks, using six mock samples that differ in geographical origin, species composition and pool complexity. The potential of the marker for automated genotaxonomy applications was assessed using a reference data set of 1,770 5S-IGS cloned sequences, covering the entire taxonomic breadth and distribution range of western Eurasian Quercus, and applying similarity (blast) and evolutionary approaches (maximum-likelihood trees and Evolutionary Placement Algorithm). Both methods performed equally well, allowing correct identification of species in sections Ilex and Cerris in the pure and mixed samples, and main lineages shared by species of sect. Quercus. Application of different cut-off thresholds revealed that medium- to high-abundance (>10 or 25) sequences suffice for a net species identification of samples containing one or a few individuals. Lower thresholds identify phylogenetic correspondence with all target species in highly mixed samples (analogous to environmental bulk samples) and include rare variants pointing towards reticulation, incomplete lineage sorting, pseudogenic 5S units and in situ (natural) contamination. Our pipeline is highly promising for future assessments of intraspecific and interpopulation diversity, and of the genetic resources of natural ecosystems, which are fundamental to empower fast and solid biodiversity conservation programmes worldwide.

Insights from regional and short-term biodiversity monitoring datasets are valuable: a reply to Daskalova et al. 2021

Abstract: Reports of major losses in insect biodiversity have stimulated an increasing interest in temporal population changes. Existing datasets are often limited to a small number of study sites, few points in time, a narrow range of land‐use intensities and only some taxonomic groups, or they lack standardised sampling. While new monitoring programs have been initiated, they still cover rather short time periods. Daskalova et al. 2021 (Insect Conservation and Diversity, 14, 1‐18) argue that temporal trends of insect populations derived from short time series are biased towards extreme trends, while their own analysis of an assembly of shorter‐ and longer‐term time series does not support an overall insect decline. With respect to the results of Seibold et al. 2019 (Nature, 574, 671–674) based on a 10‐year multi‐site time series, they claim that the analysis suffers from not accounting for temporal pseudoreplication. Here, we explain why the criticism of missing statistical rigour in the analysis of Seibold et al. (2019) is not warranted. Models that include ‘year’ as random effect, as suggested by Daskalova et al. (2021), fail to detect non‐linear trends and assume that consecutive years are independent samples which is questionable for insect time‐series data. We agree with Daskalova et al. (2021) that the assembly and analysis of larger datasets is urgently needed, but it will take time until such datasets are available. Thus, short‐term datasets are highly valuable, should be extended and analysed continually to provide a more detailed understanding of insect population changes under the influence of global change, and to trigger immediate conservation actions.

AusTraits – a curated plant trait database for the Australian flora

Abstract: We introduce the AusTraits database - a compilation of measurements of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 375 traits across 29230 taxa from field campaigns, published literature, taxonomic monographs, and individual taxa descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological parameters (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual-, species- and genus-level observations coupled to, where available, contextual information on site properties. This data descriptor provides information on version 2.1.0 of AusTraits which contains data for 937243 trait-by-taxa combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data to increase our collective understanding of the Australian flora.

Forest management contributes to climate mitigation by reducing fossil fuel consumption: A response to the letter by Welle et al.

Abstract: In a letter to Global Change Biology Bioenergy, Welle et al. (2020) accuse us of severe errors in using and interpreting data in our publication on “Climate mitigation by sustainably managed forests in Central Europe.” Welle et al. (2020) also refer to earlier letters by Kun et al. (2020) and Both et al. (2020) on which we responded already (Schulze et al., 2020a). We showed that spatial and temporal scales led to misunderstandings about carbon benefits of bioenergy which we clarified. We are deeply disappointed by the fact that Welle et al. (2020) ignored our response. Welle et al. (2020) claim that we made a mistake, when calculating the change in stocks of Hainich National Park, and this has led to false conclusions of the contribution of unmanaged forest to climate change. Here we reject this claim. Forest inventories are made for regions that are geographically laid out before the inventory starts. In this case, it is the National Park Hainich covering an area of 7,500 ha. The Park is required to carry out periodic inventories of stocks using permanent plots along a grid-based inventory at intervals of 10 years. In Hainich National Park, a quadratic grid of 200 × 200 m is used, comprising 1,902 sample plots in total. The grid was set before the first inventory started in 2000. During an inventory all plots with forest cover are surveyed and measured. Following the German forest law, an inventory considers all plots that have a cover by forest trees being older than 5 years from seed or have a crown cover of >50% of the plot area. This includes old stands that collapse as well as regrowth and successional stages (BMEL, 2016). For Hainich National Park, two inventories have been carried out—the first in 2000 and the second in 2010. During the first inventory 1,200 plots were covered by forest with dbh >7 cm. During the second inventory the number of measured plots increased to 1,421 due to forest succession in parts of the National Park that were early successional stages in 2000. According to the report of the inventory results (Nationalparkverwaltung Hainich, 2012) the average standing stocks of wood (trees >7 cm diameter at breast height) were 367.5 m3/ha in 2010 based on the 1,421 plots and 363.5 m3/ha based on the 1,200 plots in 2000. Thus, the average standing stocks have not increased substantially. The difference is 3.97 m3/ha over 10 years, corresponding to 0.4 m3 ha−1 year−1, the figure used in our publication. Welle et al. (2020) claim that the evaluation of the inventory should only be based on the 1,200 plots of the first inventory. In this case, they claim that the average standing stocks are 453 m3/ha in 2010, as also published by the National Park (Nationalparkverwaltung Hainich, 2012), with increase of about 90 m3/ha since 2000, corresponding to 9 m3 ha−1 year−1. The National Park published selected data of the first and second inventory (including changes in the plot area) for four subareas of the National Park that differ in land use history, but these parts overlap preventing the calculation and extrapolation of a new average for the Park as a whole. More importantly, a selection of parts of the inventory is not an acceptable scientific practice. One cannot select the plots that support the conclusions one might want to see. Depending on how you do the selection, the result will differ compared to the standing stocks for the Park as a whole. One must be true to the initial design, as defined for the study area in beforehand. Thus, basing an interpretation on a subjectively selected area is scientifically not acceptable. The plots with natural succession are part of the Park's forest area and the design, even if not measured in 2000. This point is also valid for the National Forest Inventory (BMEL, 2016), which we chose for comparison and where changes in total plot numbers also occurred between the inventories. The acceptance of an inventory as a whole is especially important, if the numbers are used for reporting of greenhouse gas emissions. In this context it is also important to be aware that the changes in growing stock do not represent a periodic increment, because harvest has to be considered. In Hainich National Park, 30,000 m3 coniferous wood were harvested between 1998 and 2004. There is also loss of trees due to natural mortality that

Molecular Screening of Microorganisms Associated with Discolored Wood in Dead European Beech Trees Suffered from Extreme Drought Event Using Next Generation Sequencing.

Abstract: Drought events weaken trees and make them vulnerable to attacks by diverse plant pathogens. Here, we propose a molecular method for fast screening of microorganisms associated with European beech decline after an extreme drought period (2018) in a forest of Thuringia, Germany. We used Illumina sequencing with a recent bioinformatics approach based on DADA2 to identify archaeal, bacterial, and fungal ASVs (amplicon sequence variants) based on bacterial and archaeal 16S and fungal ITS genes. We show that symptomatic beech trees are associated with both bacterial and fungal plant pathogens. Although the plant pathogen sequences were detected in both discolored and non-discolored wood areas, they were highly enriched in the discolored wood areas. We show that almost each individual tree was associated with a different combination of pathogens. Cytospora spp. and Neonectria coccinea were among the most frequently detected fungal pathogens, whereas Erwinia spp. and Pseudomonas spp. were the dominant bacterial plant pathogens. We demonstrate that bacterial plant pathogens may be of major importance in beech decline.

Dissolved organic carbon vertical movement and carbon accumulation in West Siberian peatlands

Abstract: . Dissolved organic carbon is an additional path of carbon cycle but there is a lack of information about its distribution in peatland and rates of downward movement. We dated seven peat cores (separately the dissolved (DOC) and particulate (POC) organic carbon) from Mukhrino peatland (typical zonal oligotrophic bog) in western Siberia to assess the date distribution between those two peat fractions. Our results revealed that the DOC is younger than POC for the surface peatland layers (0–150 cm) and older for the deeper layers. The date differences increases with depth and reaches 2000–3000 years at the bottom layer (430–530 cm). In our hypothesis this date discrepancy caused by more young DOC moving to the deeper and older peat layers. The estimated average value of DOC downward movement was 0.047 ± 0.019 cm yr−1. Th oldest dates found at the lake bottom and ancient riverbed were 10 053 and 10 989 cal yr BP correspondingly. For the whole period of peatland functioning the average peat accumulation rate was estimated as 0.067 ± 0.018 cm yr−1 (0.013–0.332 cm yr−1), the carbon accumulation rate was estimated as 38.56 ± 12.21 g С m−2 yr−1 (28.46–57.91 g С m−2 yr−1).

5S-IGS rDNA in wind-pollinated trees (Fagus L.) encapsulates 55 million years of reticulate evolution and hybrid origins of modern species

Abstract: Summary Standard models of plant speciation assume strictly dichotomous genealogies in which a species, the ancestor, is replaced by two offspring species. The reality in wind-pollinated trees with long evolutionary histories is more complex: species evolve from other species through isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi-copy, potentially multi-locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra-genomic recombination. Therefore, it can provide unique insights into the dynamic speciation processes of lineages that diversified tens of millions of years ago. Here, we provide the first high-throughput sequencing (HTS) of the 5S intergenic spacers (5S-IGS) for a lineage of wind-pollinated subtropical to temperate trees, the Fagus crenata – F. sylvatica s.l. lineage, and its distant relative F. japonica. The observed 4,963 unique 5S-IGS variants reflect a complex history of hybrid origins, lineage sorting, mixing via secondary gene flow, and intra-genomic competition between two or more paralogous-homoeologous 5S rDNA lineages. We show that modern species are genetic mosaics and represent a striking case of ongoing reticulate evolution during the past 55 million years. Significance statement The evolution of extra-tropical wind-pollinated tree genera involves dynamic speciation processes. High-throughput sequencing of the multi-copy, potentially multi-locus 5S rDNA reveals a complex history of hybrid origins, lineage sorting and mixing, and intra-genomic competition between paralogous-homeologous loci in the core group of Eurasian beech trees (genus Fagus) and their distant relative, F. japonica. The modern species are genetic mosaics and represent a striking case of at least 55 million years of ongoing reticulate evolution.

High-Throughput Sequencing of 5S-IGS rDNA in Fagus L. (Fagaceae) reveals complex evolutionary patterns and hybrid origin of modern species

Abstract: Standard models of speciation assume strictly dichotomous genealogies in which a species, the ancestor, is replaced by two offspring species. The reality is more complex: plant species can evolve from other species via isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi-copy, potentially multi-locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra-genomic recombination. Here, we provide the first high-throughput sequencing (HTS) 5S intergenic spacer (5S-IGS) data for a lineage of wind-pollinated subtropical to temperate trees, the Fagus crenata – F. sylvatica s.l. lineage, and its distant relative F. japonica. The observed 4,963 unique 5S-IGS variants reflect a long history of repeated incomplete lineage sorting and lineage mixing since the early Cenozoic of two or more paralogous-homoeologous 5S rDNA lineages. Extant species of Fagus are genetic mosaics and, at least to some part, of hybrid origin. Significance statement The evolution of extra-tropical tree genera involves dynamic speciation processes. High-throughput sequencing data of the multi-copy, potentially multi-locus 5S rDNA reveal a complex history of hybrid origins, lineage sorting and mixing, and intra-genomic competition between paralogous-homeologous loci in the core group of Eurasian beech trees (genus Fagus) and their distant relative, F. japonica. The modern species are genetic mosaics and represent a striking case of at least 35 million years of ongoing reticulate evolution.