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Existing Vegetation (existing + vegetation)
Selected AbstractsSeed predation, not seed dispersal, explains the landscape-level abundance of an early-successional plantJOURNAL OF ECOLOGY, Issue 4 2006JOHN L. ORROCK Summary 1Plants may not occur in a given area if there are no suitable sites for seeds to establish (microsite limitation), if seeds fail to arrive in suitable microsites (dispersal limitation) or if seeds in suitable microsites are destroyed by predators (predator limitation). 2We conducted a large-scale study to determine the importance of dispersal limitation and predator limitation in affecting the distribution of pokeweed, Phytolacca americana, in 401-ha experimental patches arrayed in eight groups of five patches distributed across a 300-km2 region. 3Microsite limitation was minimized by clearcutting and burning existing vegetation, creating the type of disturbed habitat in which P. americana readily germinates and establishes. The role of dispersal limitation was examined by adding approximately 7000 seeds to each of eight patches in March 2000. The role of seed predation was examined in all 40 patches using experimental exclosures from June 2000 to July 2001. 4The number of P. americana plants in September 2000 was unchanged by seed addition. However, fewer P. americana plants were found in patches where seed predators removed more P. americana seeds from experimental exclosures. These data suggest that P. americana is not limited by seed dispersal. Rather, in habitats where microsites are readily available, the abundance of P. americana among patches appears to be limited by the activities of seed predators. 5When dispersal and microsites are not limiting, the role of local seed predators can be important for generating emergent, large-scale patterns of plant abundance across landscapes. Moreover, because predators may generate large-scale patterns that resemble other forms of limitation and predators may target specific species, predator impacts should be more frequently incorporated into experiments on the role of seed limitation and plant community composition. [source] FIELD STUDY OF ALGAL RECRUITMENT BY CLEARING EXPERIMENT IN PING CHAU, HONG KONG SAR, CHINAJOURNAL OF PHYCOLOGY, Issue 2000S. L. Kong Recruitment, the entry of new individuals into a population, was investigated by a clearing experiment along the shore of A Ma Wan (AMW) in Ping Chau, Hong Kong SAR, China. Two types of clearing, with all the existing vegetation removed (cleared) and with the top 2 to three mm of the rock surface removed (hammered), were carried out monthly in AMW from November 1997 to June 1999. Observations were made one month after clearing and on a monthly basis thereafter. The number of algal species present on the cleared areas and their percentage cover were recorded. The experimental results showed that more algal species were recruited during March and April in 1998 (n=10) but in 1999, the number of species was found higher in February and March (n=8). Species richness dropped after May (more obvious in 1998), indicating that recruitment greatly declined in summer. A tuft complex composed of several filamentous algal species dominated over the others in all clearing areas (coverage mostly over 90%) but recruits of Caulerpa peltata, Colpomenia sinuosa, Enteromorpha sp., Hypnea charoides, Padina spp., Sargassum sp., Spyridia filamentosa, Ulva sp., etc. also were observed during the study period. Generally, there were no significant differences in terms of species richness and composition of the recruits between the two treatments (cleared vs. hammered) as well as with the controls. This implied that algae in AMW were more likely to be recruited de novo from elsewhere rather than regenerated from remnants of the previous year's growth. [source] Establishing native plants on newly-constructed and older-reclaimed sites along West Virginia highwaysLAND DEGRADATION AND DEVELOPMENT, Issue 4 2008J.G. Skousen Abstract Many state highway departments in the USA must use native plants for revegetating roadsides. We conducted two field studies in West Virginia to assess native plant establishment under two different conditions. On newly-constructed sites, native species were seeded alone or combined with non-native species. On older roadsides, native species were seeded in disturbed existing vegetation. In the first study, we used four seed mixtures comprised of seeds of native and non-native species, and two N-P-K fertilizer treatments at three newly-constructed sites. Native, warm-season grasses were slow to establish and only contributed 25 per cent cover in some plots after three years. Indiangrass (Sorghastrum nutans [L.] Nash), big bluestem (Andropogon gerardii Vitman), Brown-Eyed Susan (Rudbeckia triloba L.), and wild senna (Cassia hebecarpa Fernald) were the only seeded native species found. Fertilizer at 150,kg,ha,1 of 10-20-10 showed little influence on increasing plant cover. In the second study, we disturbed three different-aged established stands of vegetation composed of tall fescue (Festuca arundinacea Screb.) and crownvetch (Coronilla varia L.) by mowing, herbicide, or tillage, and native plants were seeded with and without fertilizer. Native cover was <10 per cent in all plots during the first year, but greatly increased by the second year to as much as 45 per cent in tilled plots, indicating that disturbance was necessary for natives to become important contributors within 2 years. Only switchgrass (Panicum virgatum L.), little bluestem (Andropogon scoparius Vitman), partridge pea (Chamaecrista fasciculate Michx.), and Brown-Eyed Susan were observed in plots. Fertilizer at 300,kg,ha,1 of 10-20-10 did not increase native plant cover on these sites. Based on our results, introducing or increasing the cover of native species along roadsides requires (1) reducing competition from non-native species, and (2) longer time periods for these slower-establishing species to be observed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Similarity between the soil seed bank and the standing vegetation in the Strandveld Succulent Karoo, South AfricaLAND DEGRADATION AND DEVELOPMENT, Issue 6 2003A. J. de Villiers Abstract The similarity in species composition and abundance between the soil seed bank and its associated vegetation was studied in six vegetation units of the Strandveld Succulent Karoo, South Africa. A total of 103 taxa were recorded in the vegetation, of which 34 taxa were also present in the seed bank. Five taxa were unique to the soil seed bank. In general, the taxa most abundant in the vegetation were also recorded in the seed bank and vice versa. Mean seed bank density varied between different plant types. Perennial taxa were most abundant in the vegetation, while annual taxa were most abundant in the seed bank. Annual taxa (excluding grasses) yielded the highest similarity between vegetation and seed bank (67,9 per cent), while that of perennial (excluding grasses) and grass taxa were 34,2 per cent and 40,0 per cent respectively. An overall similarity of 47,0 per cent between the seed bank and its associated vegetation was obtained for this part of the Strandveld Succulent Karoo. The seed bank of the study site will be a good source of future annual vegetation, but not of perennial vegetation. Topsoil replacement, sowing and transplanting of selected species will be essential for the success of post-mining revegetation efforts following complete destruction of the existing vegetation. Annual species may be recruited from the soil stored seed bank, while many perennial species will have to be reintroduced by means of sowing and/or transplanting. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||