Browsing by Person "Buchmann, Carsten M."

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Effects of land-use intensity on functional community composition and nutrient dynamics in grassland
(2024) Walter, Julia; Thumm, Ulrich; Buchmann, Carsten M.; Heinonen-Tanski, Helvi
Land-use intensity drives productivity and ecosystem functions in grassland. The effects of long-term land-use intensification on plant functional community composition and its direct and indirect linkages to processes of nutrient cycling are largely unknown. We manipulated mowing frequency and nitrogen inputs in an experiment in temperate grassland over ten years. We assessed changes in species composition and calculated functional diversity (FDis) and community weighted mean (CWM) traits of specific leaf area (SLA), leaf dry matter content (LDMC) and leaf and root nitrogen of the plant community, using species-specific trait values derived from databases. We assessed above- and belowground decomposition and soil respiration. Plant diversity strongly decreased with increasing land-use intensity. CWM leaf nitrogen and SLA decreased, while CWM LDMC increased with land-use intensification, which could be linked to an increased proportion of graminoid species. Belowground processes were largely unaffected by land-use intensity. Land use affected aboveground litter composition directly and indirectly via community composition. Mowing frequency, and not a land-use index combining mowing frequency and fertilization, explained most of the variation in litter decomposition. Our results show that land-use intensification not only reduces plant diversity, but that these changes also affect nutrient dynamics.
The importance of individual movement and feeding behaviour for long-distance seed dispersal by red deer: a data-driven model
(2020) Wright, Stephen J.; Heurich, Marco; Buchmann, Carsten M.; Böcker, Reinhard; Schurr, Frank M.
Background: Long-distance seed dispersal (LDD) has strong impacts on the spatiotemporal dynamics of plants. Large animals are important LDD vectors because they regularly transport seeds of many plant species over long distances. While there is now ample evidence that behaviour varies considerably between individual animals, it is not clear to what extent inter-individual variation in behaviour alters seed dispersal by animals. Methods: We study how inter-individual variation in the movement and feeding behaviour of one of Europe’s largest herbivores (the red deer, Cervus elaphus) affects internal seed dispersal (endozoochory) of multiple plant species. We combine movement data of 21 individual deer with measurements of seed loads in the dung of the same individuals and with data on gut passage time. These data serve to parameterize a model of passive dispersal that predicts LDD in three orientations (horizontal as well as upward and downward in elevation). With this model we investigate to what extent per-seed probabilities of LDD and seed load vary between individuals and throughout the vegetation period (May–December). Subsequently, we test whether per-seed LDD probability and seed load are positively (or negatively) correlated so that more mobile animals disperse more (or less) seeds. Finally, we examine whether non-random associations between per-seed LDD probability and seed load affect the LDD of individual plant species. Results: The studied deer dispersed viable seeds of at least 62 plant species. Deer individuals varied significantly in per-seed LDD probability and seed loads. However, more mobile animals did not disperse more or less seeds than less mobile ones. Plant species also did not differ significantly in the relationship between per-seed LDD probability and seed load. Yet plant species differed in how their seed load was distributed across deer individuals and in time, and this caused their LDD potential to differ more than twofold. For several plant species, we detected non-random associations between per-seed LDD probability and seed load that generally increased LDD potential. Conclusions: Inter-individual variation in movement and feeding behaviour means that certain deer are substantially more effective LDD vectors than others. This inter-individual variation reduces the reliability of LDD and increases the sensitivity of LDD to the decline of deer populations. Variation in the dispersal services of individual animals should thus be taken into account in models in order to improve LDD projections.
Improving measurements of the falling trajectory and terminal velocity of wind‐dispersed seeds
(2022) Zhu, Jinlei; Buchmann, Carsten M.; Schurr, Frank M.
Seed dispersal by wind is one of the most important dispersal mechanisms in plants. The key seed trait affecting seed dispersal by wind is the effective terminal velocity (hereafter “terminal velocity”, Vt), the maximum falling speed of a seed in still air. Accurate estimates of Vt are crucial for predicting intra‐ and interspecific variation in seed dispersal ability. However, existing methods produce biased estimates of Vt for slow‐ or fast‐falling seeds, fragile seeds, and seeds with complex falling trajectories. We present a new video‐based method that estimates the falling trajectory and Vt of wind‐dispersed seeds. The design involves a mirror that enables a camera to simultaneously record a falling seed from two perspectives. Automated image analysis then determines three‐dimensional seed trajectories at high temporal resolution. To these trajectories, we fit a physical model of free fall with air resistance to estimate Vt. We validated this method by comparing the estimated Vt of spheres of different diameters and materials to theoretical expectations and by comparing the estimated Vt of seeds to measurements in a vertical wind tunnel. Vt estimates closely match theoretical expectations for spheres and vertical wind tunnel measurements for seeds. However, our Vt estimates for fast‐falling seeds are markedly higher than those in an existing trait database. This discrepancy seems to arise because previous estimates inadequately accounted for seed acceleration. The presented method yields accurate, efficient, and affordable estimates of the three‐dimensional falling trajectory and terminal velocity for a wide range of seed types. The method should thus advance the understanding and prediction of wind‐driven seed dispersal.
What acceleration data from wildlife collars and animal body mass tell us about seed dispersal
(2023) Buchmann, Carsten M.; Dreyling, Lukas; Constantin, Mihaela; Schurr, Frank M.; Buchmann, Carsten M.; Institute of Landscape and Plant Ecology, University of Hohenheim, Stuttgart, Germany; Dreyling, Lukas; Institute of Landscape and Plant Ecology, University of Hohenheim, Stuttgart, Germany; Constantin, Mihaela; Institute of Landscape and Plant Ecology, University of Hohenheim, Stuttgart, Germany; Schurr, Frank M.; Institute of Landscape and Plant Ecology, University of Hohenheim, Stuttgart, Germany
Background: The seeds of many plant species can be dispersed over long distances in animal fur (epizoochory). Quantifying epizoochory in the wild is, however, challenging, since it is difficult to measure the retention times of seeds in fur. These retention times depend on the acceleration that seeds experience and that can detach seeds from fur. Wildlife collars containing accelerometers may thus provide crucial information on epizoochorous seed dispersal. However, this is only the case if acceleration of the animal’s neck (where collars are attached) is informative of acceleration of the animal’s main body (where most seeds are transported). Methods: We used accelerometers to simultaneously measure acceleration at the neck, breast and the upper hind leg of 40 individuals of eight mammal species spanning a large range of body masses (26–867 kg). We then quantified maximum acceleration as the 95%-quantile of the resultant acceleration (of all measured values in data intervals of 5 s). Results: Maximum acceleration was comparable between the neck and breast but substantially higher at the hind leg. Maximum acceleration measured by neck collars and body mass jointly explained 81% of the variance in maximum acceleration of the breast and 62% of the variance in maximum acceleration of the leg. Conclusions: Acceleration measured by neck collars is informative of the acceleration experienced by seeds attached to other body parts (breast and leg). When combined with animal movement data and lab measurements of how fur acceleration affects seed release and retention times, widely used collar accelerometers can thus be used to assess distances of epizoochorous seed dispersal.