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- Löbel, Swantje, et al.
(författare)
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Epiphytic bryophytes near forest edges and on retention trees : reduced growth and reproduction especially in old-growth-forest indicator species
- 2012
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 49:6, s. 1334-1343
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Tidskriftsartikel (refereegranskat)abstract
- Epiphytes are an important component in many forest ecosystems. The proportion of threatened epiphyte species is high, and the impact of clearcuts on key demographic processes via edge-influence is still poorly understood. There are few studies on epiphyte growth, and even less is known about how reproduction is affected by proximity to forest edges. For retention trees, demographic studies are even scarcer.Based on the results from a 6-month transplant experiment and a 3-year study of natural colonies, we modelled growth and reproduction of epiphytic bryophytes used as indicators of old-growth forests and widespread epiphytes in relation to distance from the forest edge. We also modelled growth and reproduction on retention trees within the clearcut. Species responses were linked to variation in canopy openness.Unlike the widespread species, the old-growth-forest indicators grew exponentially with distance from the edge, and this response was more pronounced at the south-east than north-west forest edge. In one red-listed species, reproduction was thoroughly inhibited near the edge, whereas the reproductive rate of the widespread species tended to increase. However, the widespread species also showed reduced shoot lengths on the retention trees.Reduced growth and inhibited reproduction of sensitive epiphytes near edges decrease the number of dispersing diaspores and may, in combination with lower local connectivity and increased tree fall rates close to edges, increase the risk of metapopulation extinction.Synthesis and applications. Two general management implications for boreal forests are drawn. First, retention trees may not have the capacity to act as a ‘lifeboat’ for epiphytic bryophytes and support their populations during the regeneration phase. Second, the creation of buffer zones is a useful conservation strategy for bryophytes. The exact width of zones depends on the forest structure and should be orientated in relation to the requirements of the most sensitive species. For the rather dense experimental forest, a width of at least 30 m was required for the south-facing buffer, whereas for the north-facing buffer 10 m was sufficient.
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| 2. |
- Löbel, Swantje, 1978-, et al.
(författare)
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Trade-offs and habitat constraints in the establishment of epiphytic bryophytes
- 2010
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 24:4, s. 887-897
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Tidskriftsartikel (refereegranskat)abstract
- 1. Diversity of patch-tracking epiphyte metacommunities depends on successful colonization of new habitats. Habitat constraints and critical stages in the establishment have gained little attention in metacommunity studies, but a trade-off between dispersal ability and establishment rate is often assumed. This assumption remains largely untested, and alternative dispersal and reproductive strategies offer several trade-offs to be explored. 2. We used in vitro experiments to identify critical stages in the establishment of obligate epiphytic bryophytes with contrasting dispersal strategies [sexual via small (< 20 mu m) or large (> 20 mu m) spores, asexual via gemmae or gemmae-like branchlets], and to identify habitat constraints of diaspore establishment and trade-offs among species traits. 3. Across all stages of the establishment process, large asexual diaspores performed better than small sexual ones. Asexual species also had a higher ability to establish from fragments than sexual species. Germination of all diaspore types was limited by pH with highest germination rates at intermediate pH. Large moss spores showed a higher desiccation tolerance than small ones, but lower germination and protonemal growth rates. Liverwort spores had the lowest desiccation tolerance, germination and protonemal growth rates, but rapidly developed gametophytic shoots once they had germinated. 4. Combining the results with earlier studies on dispersal distances in epiphytes, our study demonstrated a trade-off between dispersal distance and establishment ability, which may be central for the evolution of asexual dispersal in epiphytes. The evolution of spore size may additionally involve trade-offs between high germination and protonemal growth rates, desiccation tolerance, and a rapid development from protonema to shoots. We suggest that trade-offs in epiphytes are shaped by conflicting selection pressures imposed by habitat patchiness, landscape dynamics and irregular water supply.
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