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Schuepp C.,University of Bern | Schuepp C.,Research Station Agroscope Reckenholz Tanikon | Schuepp C.,University of Koblenz-Landau
Proceedings. Biological sciences / The Royal Society | Year: 2014

Animal pollination is essential for the reproductive success of many wild and crop plants. Loss and isolation of (semi-)natural habitats in agricultural landscapes can cause declines of plants and pollinators and endanger pollination services. We investigated the independent effects of these drivers on pollination of young cherry trees in a landscape-scale experiment. We included (i) isolation of study trees from other cherry trees (up to 350 m), (ii) the amount of cherry trees in the landscape, (iii) the isolation from other woody habitats (up to 200 m) and (iv) the amount of woody habitats providing nesting and floral resources for pollinators. At the local scale, we considered effects of (v) cherry flower density and (vi) heterospecific flower density. Pollinators visited flowers more often in landscapes with high amount of woody habitat and at sites with lower isolation from the next cherry tree. Fruit set was reduced by isolation from the next cherry tree and by a high local density of heterospecific flowers but did not directly depend on pollinator visitation. These results reveal the importance of considering the plant's need for conspecific pollen and its pollen competition with co-flowering species rather than focusing only on pollinators' habitat requirements and flower visitation. It proved to be important to disentangle habitat isolation from habitat loss, local from landscape-scale effects, and direct effects of pollen availability on fruit set from indirect effects via pollinator visitation to understand the delivery of an agriculturally important ecosystem service. Source


Bassin S.,Research Station Agroscope Reckenholz Tanikon | Schalajda J.,ARNAL | Vogel A.,University of Munster | Suter M.,ETH Zurich | Suter M.,ART Agroscope Reckenholz Tanikon
Journal of Vegetation Science | Year: 2012

Question: Increasing emissions of reactive nitrogen (N) compounds threaten the composition of species-rich communities even in remote alpine areas. In the few studies available from (sub-)alpine grassland, N deposition altered species composition in favour of sedges, which are assumed to be less limited by phosphorus (P) compared to other species. Is the magnitude of the sedges' relative increase modified by availability of other nutrients, which is in turn influenced by site-specific edaphic and climatic conditions? Location: Swiss Central Alps. Methods: We selected ten sub-alpine sites that covered a broad range of communities and soil conditions, including both calcareous Seslerietum as well as acidic Nardetum pastures. As a model species, Carex sempervirens Vill. was present at each site. For two consecutive years, in addition to a control, two treatments were applied to the vegetation: (1) 50 kg·N·ha -1·yr -1 as NH 4NO 3 and (2) compound NPK fertilizer comprising the same amount of N. Total above-ground biomass, fraction of all sedges, leaf length and leaf N, P and potassium (K) content of C. sempervirens were recorded and analysed for their responses to treatments and interaction with variables linked to productivity and nutrient availability (including soil water potential, pH and soil P). Results: Biomass production was stimulated across all sites on average by 30% with elevated N deposition, and by 60% with NPK fertilizer application, revealing the sites to be similarly co-limited by N and by P and K. Also across all sites, the fraction of sedges was increased on average 33% by N addition, but remained constant with NPK application, suggesting stronger P and/or K co-limitation in non-sedge species. N treatment effects were consistent in their direction but varied between sites; nevertheless this variation could not be explained by the measured edaphic or climatic factors. However, by trend, sedges benefited more from N fertilization on sites with higher pH, but benefited less on very dry sites. Conclusion: Our findings reveal that the observed increase of sedges is a general response of sub-alpine grassland to elevated N deposition and thus can be regarded as universal both for Seslerietum as well as Nardetum pastures. © 2012 International Association for Vegetation Science. Source


Sedlacek J.,University of Zurich | Sedlacek J.,University of Konstanz | Schmid B.,University of Zurich | Matthies D.,University of Marburg | And 2 more authors.
PLoS ONE | Year: 2012

How climate-change induced environmental stress may alter the effects of inbreeding in patchy populations of rare species is poorly understood. We investigated the fitness of progeny from experimental self- and cross-pollinations in eight populations of different size of Echium wildpretii, a rare endemic plant of the arid subalpine zone of the Canarian island of Tenerife. As control treatments we used open pollination and autonomous selfing. The seed set of open-pollinated flowers was 55% higher than that of autonomously selfed flowers, showing the importance of animal pollination for reproductive success. The seed set, seed mass and germination rate of seedlings of hand-selfed flowers was similar to that of hand-crossed flowers, indicating weak inbreeding depression (seed set -4.4%, seed mass -4.1%, germination -7.3%). Similarly, under normal watering there were no significant effects of inbreeding on seedling survival (-3.0%). However, under low watering of seedlings inbreeding depression was high (survival -50.2%). Seed set of open- and hand-outcrossed-pollinated flowers was higher in large than in small populations, possibly due to more frequent biparental inbreeding in the latter. However, later measures of progeny fitness were not significantly influenced by population size. We predict that increasing drought duration and frequency due to climate change and reductions of population sizes may increase inbreeding depression in this charismatic plant species and thus threaten its future survival in the longer term. © 2012 Sedlacek et al. Source


Schuepp C.,University of Bern | Schuepp C.,University of Koblenz-Landau | Herzog F.,Research Station Agroscope Reckenholz Tanikon | Entling M.H.,University of Koblenz-Landau
Proceedings of the Royal Society B: Biological Sciences | Year: 2014

Animal pollination is essential for the reproductive success of many wild and crop plants. Loss and isolation of (semi-)natural habitats in agricultural landscapes can cause declines of plants and pollinators and endanger pollination services.We investigated the independent effects of these drivers onpollination of young cherry trees in a landscape-scale experiment.We included (i) isolation of study trees from other cherry trees (up to 350 m), (ii) the amount of cherry trees in the landscape, (iii) the isolation from other woody habitats (up to 200 m) and (iv) the amount of woody habitats providing nesting and floral resources for pollinators. At the local scale, we considered effects of (v) cherry flower density and (vi) heterospecific flower density. Pollinators visited flowers more often in landscapes with high amount of woody habitat and at sites with lower isolation from the next cherry tree. Fruit set was reduced by isolation from the next cherry tree and by a high local density of heterospecific flowers but did not directly depend on pollinator visitation. These results reveal the importance of considering the plant's need for conspecific pollen and its pollen competition with co-flowering species rather than focusing only on pollinators' habitat requirements and flower visitation. It proved to be important to disentangle habitat isolation from habitat loss, local from landscape-scale effects, and direct effects of pollen availability on fruit set from indirect effects via pollinator visitation to understand the delivery of an agriculturally important ecosystem service. © 2013 The Author(s) Published by the Royal Society. All rights reserved. Source

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