| 1. |
- Altewischer, Andrea, et al.
(author)
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Habitat preferences of male Corn Buntings Emberiza calandra in north-eastern Germany
- 2015
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In: Acta Ornithologica. - 0001-6454 .- 1734-8471. ; 50:1, s. 1-10
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Journal article (peer-reviewed)abstract
- Agricultural ecosystems have faced dramatic changes during past decades, resulting in a dramatic loss of farmland biodiversity. The Corn Bunting Emberiza calandra is considered a suitable indicator for the conservation value of farmland habitats, and has recently suffered strong declines throughout much of its European range. As a basis for targeted conservation measures, we investigated the habitat preferences of this species in north-eastern Germany by comparing the composition of male territories with randomly chosen control sites. A territory was defined as the area within a radius of 150 meters around the assumed centre of the territory, as the majority of nests is found within this radius. To assess food availability for nestlings, arthropod abundance within the most abundant land use types i.e. crop fields, fallows, grassland as well as within unploughed strips was investigated. In total we found 102 male Corn Bunting territories, which were mainly composed of crop fields (50%), grassland (28%), and fallows (12%). Territories compared with control sites were characterized by a lower proportion of crop fields, a higher proportion of fallows, more diverse land use types, more abundant field boundaries, unploughed strips, and tracks, and a higher availability of song posts. However, neither the number of larger (≥ 1 cm), smaller (< 1 cm) or all arthropods differed significantly among analysed land use types i.e. crop fields, fallows, grassland, unploughed strips. Our study confirms the significance of habitat heterogeneity and especially of sites with sparse vegetation (fallows > 10%) and song posts (> 70 m ‘linear song posts’ or > 1 solitary post per ha) for the habitat selection of male Corn Buntings. We conclude that measures to halt population declines of Corn Buntings seem to be relatively easy to implement, provided that farmers are granted a fair compensation.
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| 2. |
- Blume-Werry, Gesche, 1985-, et al.
(author)
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Don't drink it, bury it : comparing decomposition rates with the tea bag index is possible without prior leaching
- 2021
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In: Plant and Soil. - : Springer. - 0032-079X .- 1573-5036. ; 465:1-2, s. 613-621
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Journal article (peer-reviewed)abstract
- Purpose: The standardized ‘Tea Bag Index’ enables comparisons of litter decomposition rates, a key component of carbon cycling, across ecosystems. However, tea ‘litter’ may leach more than other plant litter, skewing comparisons of decomposition rates between sites with differing moisture conditions. Therefore, some researchers leach tea bags before field incubation. This decreases comparability between studies, and it is unclear if this modification is necessary.Methods: We submerged green and rooibos tea bags in water, and measured their leaching losses over time (2 min – 72 h). We also compared leaching of tea to leaf and root litter from other plant species, and finally, compared mass loss of pre-leached and standard tea bags in a fully factorial incubation experiment differing in soil moisture (wet and dry) and soil types (sand and peat).Results: Both green and rooibos tea leached strongly, levelling-off at about 40% and 20% mass loss, respectively. Mass loss from leaching was highest in green tea followed by leaves of other plants, then rooibos tea, and finally roots of other plants. When incubated for 4 weeks, both teas showed lower mass loss when they had been pre-leached compared to standard tea bags. However, these differences between standard and pre-leached tea bags were similar in moist vs. dry soils, both in peat and in sand.Conclusions: Thus, despite large leaching losses, we conclude that leaching tea bags before field or lab incubation is not necessary to compare decomposition rates between systems, ranging from as much as 5% to 25% soil moisture.
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| 3. |
- Jurasinski, Gerald, et al.
(author)
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From Understanding to Sustainable Use of Peatlands : The WETSCAPES Approach
- 2020
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In: SOIL SYSTEMS. - : MDPI. - 2571-8789. ; 4:1
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Journal article (peer-reviewed)abstract
- Of all terrestrial ecosystems, peatlands store carbon most effectively in long-term scales of millennia. However, many peatlands have been drained for peat extraction or agricultural use. This converts peatlands from sinks to sources of carbon, causing approx. 5% of the anthropogenic greenhouse effect and additional negative effects on other ecosystem services. Rewetting peatlands can mitigate climate change and may be combined with management in the form of paludiculture. Rewetted peatlands, however, do not equal their pristine ancestors and their ecological functioning is not understood. This holds true especially for groundwater-fed fens. Their functioning results from manifold interactions and can only be understood following an integrative approach of many relevant fields of science, which we merge in the interdisciplinary project WETSCAPES. Here, we address interactions among water transport and chemistry, primary production, peat formation, matter transformation and transport, microbial community, and greenhouse gas exchange using state of the art methods. We record data on six study sites spread across three common fen types (Alder forest, percolation fen, and coastal fen), each in drained and rewetted states. First results revealed that indicators reflecting more long-term effects like vegetation and soil chemistry showed a stronger differentiation between drained and rewetted states than variables with a more immediate reaction to environmental change, like greenhouse gas (GHG) emissions. Variations in microbial community composition explained differences in soil chemical data as well as vegetation composition and GHG exchange. We show the importance of developing an integrative understanding of managed fen peatlands and their ecosystem functioning.
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| 4. |
- Kehl, Tobias, et al.
(author)
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Fat and sassy : factors underlying male mating success in a butterfly
- 2015
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In: Entomologia Experimentalis et Applicata. - : The Netherlands Entomological Society. - 0013-8703 .- 1570-7458. ; 155:3, s. 257-265
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Journal article (peer-reviewed)abstract
- Theory predicts that male mating success depends on resource holding potential (RHP), which is reflected by proxies of condition, such as body mass, fat content, strength, or weaponry. In species lacking any physical means to inflict injuries upon combatants, such as butterflies, the factors determining mating success are less clear. Against this background, we explored the determinants of male mating success in the tropical butterfly Bicyclus anynana Butler (Lepidoptera: Nymphalidae: Satyrinae), by comparing physiological, immunological, and morphological traits between winning and losing males. Our results showed that successful males are characterized by a better flight performance, evidenced by having longer wings, a heavier thorax, a lighter abdomen, a higher fat content, and higher phenoloxidase expression levels than their unsuccessful counterparts, when being compared after their first mating. Males that won three consecutive trials against the same combatant were also characterized by a better flight performance, having larger forewings, a higher body mass, and a higher fat content. Thus, successful males were larger and in better condition than unsuccessful ones. Strikingly, many differences found indicated an enhanced flight performance for the former, which we suggest ultimately plays the key role for male mating success in B. anynana. As fat is the main energy source for flying insects, being crucial to flight endurance and in turn presumably to male mating success, it may represent a key determinant at the proximate level.
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| 5. |
- Peters, Bo, et al.
(author)
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As good as human experts in detecting plant roots in minirhizotron images but efficient and reproducible : the convolutional neural network “RootDetector”
- 2023
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 13:1
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Journal article (peer-reviewed)abstract
- Plant roots influence many ecological and biogeochemical processes, such as carbon, water and nutrient cycling. Because of difficult accessibility, knowledge on plant root growth dynamics in field conditions, however, is fragmentary at best. Minirhizotrons, i.e. transparent tubes placed in the substrate into which specialized cameras or circular scanners are inserted, facilitate the capture of high-resolution images of root dynamics at the soil-tube interface with little to no disturbance after the initial installation. Their use, especially in field studies with multiple species and heterogeneous substrates, though, is limited by the amount of work that subsequent manual tracing of roots in the images requires. Furthermore, the reproducibility and objectivity of manual root detection is questionable. Here, we use a Convolutional Neural Network (CNN) for the automatic detection of roots in minirhizotron images and compare the performance of our RootDetector with human analysts with different levels of expertise. Our minirhizotron data come from various wetlands on organic soils, i.e. highly heterogeneous substrates consisting of dead plant material, often times mainly roots, in various degrees of decomposition. This may be seen as one of the most challenging soil types for root segmentation in minirhizotron images. RootDetector showed a high capability to correctly segment root pixels in minirhizotron images from field observations (F1 = 0.6044; r2 compared to a human expert = 0.99). Reproducibility among humans, however, depended strongly on expertise level, with novices showing drastic variation among individual analysts and annotating on average more than 13-times higher root length/cm2 per image compared to expert analysts. CNNs such as RootDetector provide a reliable and efficient method for the detection of roots and root length in minirhizotron images even from challenging field conditions. Analyses with RootDetector thus save resources, are reproducible and objective, and are as accurate as manual analyses performed by human experts.
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| 6. |
- Schwieger, Sarah, et al.
(author)
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Autumnal warming does not change root phenology in two contrasting vegetation types of subarctic tundra
- 2018
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In: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 424:1-2, s. 145-156
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Journal article (peer-reviewed)abstract
- Root phenology is important in controlling carbon and nutrient fluxes in terrestrial ecosystems, yet, remains largely unexplored, especially in the Arctic. We compared below- and aboveground phenology and ending of the growing season in two contrasting vegetation types of subarctic tundra: heath and meadow, and their response to experimental warming in autumn. Root phenology was measured in-situ with minirhizotrons and compared with aboveground phenology assessed with repeat digital photography. The end of the growing season, both below- and aboveground, was similar in meadow and heath and the belowground growing season ended later than aboveground in the two vegetation types. Root growth was higher and less equally distributed over time in meadow compared to heath. The warming treatment increased air and soil temperature by 0.5 A degrees C and slightly increased aboveground greenness, but did not affect root growth or prolong the below- and aboveground growing season in either of the vegetation types. These results imply that vegetation types differ in root dynamics and suggest that other factors than temperature control autumnal root growth in these ecosystems. Further investigations of root phenology will help to identify those drivers, in which including responses of functionally contrasting vegetation types will help to estimate how climate change affects belowground processes and their roles in ecosystem function.
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| 7. |
- Schwieger, Sarah, et al.
(author)
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Patterns and drivers in spring and autumn phenology differ above- and belowground in four ecosystems under the same macroclimatic conditions
- 2019
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In: Plant and Soil. - : Springer. - 0032-079X .- 1573-5036. ; 445:1-2, s. 217-229
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Journal article (peer-reviewed)abstract
- Background and aims: Start and end of the growing season determine important ecosystem processes, but their drivers may differ above-and belowground, between autumn and spring, and between ecosystems.Here, we compare above-and belowground spring and autumn phenology, and their abiotic drivers (temperature, water level, and soil moisture) in four temperate ecosystems (beech forest, alder carr, phragmites reed, and sedge reed).Methods: Root growth was measured in-situ with minirhizotrons and compared with aboveground phenology assessed with dendrometer data and NDVI.Results: Synchrony of above- and belowground phenology depended on ecosystem. Onset of root growth was later than shoot growth in all three peatlands (12–33 days), but similar in the beech forest. The growing season ended earlier belowground in the two forested ecosystems (beech forest: 27 days, understory of the alder carr: 55 days), but did not differ in the phragmites reed. Generally, root production was correlated with soil temperature (especially in spring) and water level in the peatlands, while abiotic factors were less correlated with leaf activity or root production in either spring or autumn in the beech forest.Conclusions: Root production on organic soils was ten times higher compared to the zonal broadleaf deciduous forest on mineral soils, highlighting the importance of peatlands. Belowground phenology cannot be projected from aboveground phenology and measuring root phenology is crucial to understand temporal dynamics of production and carbon fluxes.
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| 8. |
- Schwieger, Sarah, et al.
(author)
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Rewetting prolongs root growing season in minerotrophic peatlands and mitigates negative drought effects
- 2022
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In: Journal of Applied Ecology. - : John Wiley & Sons. - 0021-8901 .- 1365-2664. ; 59:8, s. 2106-2116
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Journal article (peer-reviewed)abstract
- Root phenology influences the timing of plant resource acquisition and carbon fluxes into the soil. This is particularly important in fen peatlands, in which peat is primarily formed by roots and rhizomes of vascular plants. However, most fens in Central Europe are drained for agriculture, leading to large carbon losses, and further threatened by increasing frequency and intensity of droughts. Rewetting fens aims to restore the original carbon sink, but how root phenology is affected by drainage and rewetting is largely unknown.We monitored root phenology with minirhizotrons in drained and rewetted fens (alder forest, percolation fen and coastal fen) as well as its soil temperature and water table depth during the 2018 drought. For each fen type, we studied a drained site and a site that was rewetted ~25 years ago, while all the sites studied had been drained for almost a century.Overall, the growing season was longer with rewetting, allowing roots to grow over a longer period in the year and have a higher root production than under drainage. With increasing depth, the growing season shifted to later in time but remained a similar length, and the relative importance of soil temperature for root length changes increased with soil depth.Synthesis and applications: Rewetting extended the growing season of roots, highlighting the importance of phenology in explaining root productivity in peatlands. A longer growing season allows a longer period of carbon sequestration in form of root biomass and promotes the peatlands' carbon sink function, especially through longer growth in deep soil layers. Thus, management practices that focus on rewetting peatland ecosystems are necessary to maintain their function as carbon sinks, particularly under drought conditions, and are a top priority to reduce carbon emissions and address climate change.
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| 9. |
- Schwieger, Sarah, et al.
(author)
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Root biomass and root traits of Alnus glutinosa show size-dependent and opposite patterns in a drained and a rewetted forest peatland
- 2021
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In: Annals of Botany. - : Oxford University Press. - 0305-7364 .- 1095-8290. ; 127:3, s. 337-346
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Journal article (peer-reviewed)abstract
- BACKGROUND AND AIMS: Forest peatlands represent 25 % of global peatlands and store large amounts of carbon (C) as peat. Traditionally they have been drained in order to increase forestry yield, which may cause large losses of C from the peat. Rewetting aims to stop these losses and to restore the initial storage function of the peatlands. As roots represent major peat-forming elements in these systems, we sampled roots with diameter <5 mm in a drained and a rewetted forest peatland in north-east Germany to evaluate differences in tree biomass investments below ground, root functional characteristics and root age.METHODS: We cored soil next to Alnus glutinosa stems and sorted root biomass into <1, 1-2 and 2-5 mm diameter classes. We measured biomass distribution and specific root area (SRA) in 10-cm depth increments down to 50 cm, and estimated root age from annual growth rings.KEY RESULTS: Root biomass in the rewetted site was more than double that in the drained site. This difference was mostly driven by very fine roots <1 mm, which accounted for 51 % of the total root biomass and were mostly (75 %) located in the upper 20 cm. For roots <1 mm, SRA did not differ between the sites. However, SRA of the 1-2 mm and 2-5 mm diameter roots was higher in the drained than in the rewetted site. Root age did not differ between sites.CONCLUSIONS: The size-dependent opposite patterns between root biomass and their functional characteristics under contrasting water regimes indicate differences between fine and coarse roots in their response to environmental changes. Root age distribution points to similar root turnover rates between the sites, while higher root biomass in the rewetted site clearly indicates larger tree C stocks below ground under rewetting, supporting the C sink function of the ecosystem.
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| 10. |
- Schwieger, Sarah, et al.
(author)
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Wetter is Better : Rewetting of Minerotrophic Peatlands Increases Plant Production and Moves Them Towards Carbon Sinks in a Dry Year
- 2021
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In: Ecosystems (New York. Print). - : Springer. - 1432-9840 .- 1435-0629. ; 24:5, s. 1093-1109
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Journal article (peer-reviewed)abstract
- Peatlands are effective carbon sinks as more biomass is produced than decomposed under the prevalent anoxic conditions. Draining peatlands coupled with warming releases stored carbon, and subsequent rewetting may or may not restore the original carbon sink. Yet, patterns of plant production and decomposition in rewetted peatlands and how they compare to drained conditions remain largely unexplored. Here, we measured annual above- and belowground biomass production and decomposition in three different drained and rewetted peatland types: alder forest, percolation fen and coastal fen during an exceptionally dry year. We also used standard plant material to compare decomposition between the sites, regardless of the decomposability of the local plant material. Rewetted sites showed higher root and shoot production in the percolation fen and higher root production in the coastal fen, but similar root and leaf production in the alder forest. Decomposition rates were generally similar in drained and rewetted sites, only in the percolation fen and alder forest did aboveground litter decompose faster in the drained sites. The rewetted percolation fen and the two coastal sites had the highest projected potential for organic matter accumulation. Roots accounted for 23–66% of total biomass production, and belowground biomass, rather than aboveground biomass, was particularly important for organic matter accumulation in the coastal fens. This highlights the significance of roots as main peat-forming element in these graminoid-dominated fen peatlands and their crucial role in carbon cycling, and shows that high biomass production supported the peatlands’ function as carbon sink even during a dry year.
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