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Species Recruitment (species + recruitment)
Selected AbstractsWaterlogging and canopy interact to control species recruitment in floodplainsFUNCTIONAL ECOLOGY, Issue 4 2010Wiktor Kotowski Summary 1.,The extent to which seedling recruitment contributes to local functional diversity depends on the environmental filters operating in a plant community. Classical community assembly models assume that habitat constraints and competition act like hierarchical filters with habitat filtering as the dominant one. Alternative models assume a synergic interaction since responses to environmental stress and competition may impose physiological trade-offs in plants. 2.,River floodplains are an ideal system to test the relationship between habitat and competition filtering in community (re)assembly, as flooding causes changes in both habitat stress (waterlogging, resulting in anoxia and toxicity) and competition (dieback of vegetation) on one hand and acts as an effective seed dispersal vector on the other hand. 3.,We conducted a mesocosm experiment on early community assembly from a pool of 34 floodplain species covering a wetness gradient. Seed mixtures were sown in a full factorial design with water level, canopy and mowing as controlling factors. We measured the biomass of all species after one growing season and determined germination and seedling growth traits, both outside (response to waterlogging/no waterlogging) and in a growth-chamber (response to light/darkness). 4.,Species recruitment was analysed in relation to the controlling factors and measured functional traits using co-inertia analysis. Furthermore we analysed the effects of the controlling factors on several aspects of functional diversity. 5.,There was no establishment in grass sward, unless mowing was applied. Species-rich communities only developed when germination and early establishment phases occurred on waterlogged bare soil. High water level did not suppress establishment but reduced the total biomass and lowered inter-specific competition. The effect of mowing on species richness depended upon the interplay between waterlogging and canopy. 6.,Establishment success under canopy required seedling strategies to tolerate shade. The elimination of typical wetland specialists from oxic mesocosms was clearly an effect of their poorer and/or slower germination and lower competitive abilities in comparison to non-wetland plants, leading to their disappearance in this low-stress environment. 7.,Our results indicate that single stress factors can enhance species richness and functional diversity through limiting competition but a synergic interaction of different stresses can lead to reduced richness. [source] Effects of natural disturbance and selective logging on Nothofagus forests in south-central ChileJOURNAL OF BIOGEOGRAPHY, Issue 7 2002William Pollmann Aim Changes in stand structure, floristic composition and tree population dynamics during the last four centuries were described in southern temperate rain forests. The impacts of natural and anthropogenic disturbance since the late 1560s were examined for old-growth and logged forests. Location The study was conducted in montane Nothofagus alpina forests in the Andean Range of south-central Chile. Study sites were located at a range of altitudes between 1000 and 1250 m a.s.l. Methods Temporal variation in species recruitment and annual dendroecological data were used to determine the historical development and disturbance history of three old-growth forests, and three stands after selective logging in the late 1880s to early 1900s. Considering the spatial structure of evergreen vs. deciduous elements, the forests are a mixture of deciduous and evergreen tree species. Results Stem density, maximum stem diameter and basal area differed between the old-growth and logged stands, but species composition did not. At lower altitudes, N. alpina was the dominant canopy species in both old-growth and logged stands, but regeneration of N. alpina was significantly different in these stands. At higher altitudes, N. alpina and N. dombeyi were the dominant canopy species in both old-growth and logged stands, and here regeneration patterns of these Nothofagus species were similar. After selective logging, in mixed forests of shade-intolerant Nothofagus and more shade-tolerant trees (such as Laurelia philippiana) there has been a shift in regeneration from more shade-tolerant resprouting species towards Nothofagus. Major and moderate releases in radial growth, indicative of disturbance, occurred in most of the older trees during the last four centuries, and especially during the last 100 years. Growth rates of N. alpina are higher than those of associated shade-tolerant trees, and apparently increase after disturbances. Main conclusions Results suggest that under disturbance regimes dominated by treefall gaps, and additionally canopy openings by selective logging, maintenance of Nothofagus species appears to be associated with complementary differences in growth rate, sprouting capacity, canopy residence time, and longevity. Such small-scale canopy openings may help explain the relative abundance of N. alpina in montane mixed rain forests in the Andean Range, where the maintenance of Nothofagus species in many stands has been attributed to a high frequency of coarse-scale disturbance. My results serve to emphasize that understanding the species coexistence and forest dynamics in Nothofagus forests may require attention to interspecific differences in life-history characteristics. [source] Colonization of an island volcano, Long Island, Papua New Guinea, and an emergent island, Motmot, in its caldera lake.JOURNAL OF BIOGEOGRAPHY, Issue 11-12 2001Abstract Aim Long Island erupted catastrophically in c. 1645 with the probable destruction of its entire biota. While several expeditions have visited the island since, no survey of its flora has been published. In 1968 a small island, Motmot, emerged from its caldera lake. Motmot has been surveyed several times but not since 1988. The aim of this study was to investigate the colonization by vascular plants of this interesting nested pair of islands. Location Long Island is 55 km off the northeast coast of Papua New Guinea (PNG) and Motmot lies in its fresh water caldera lake, Lake Wisdom, c. 4 km from the rim of the surrounding volcano. Methods We conducted a complete survey of the vascular plants on Motmot and made ad hoc collections on Long Island, including surveying three small plots, over 15 days in 1999. In addition, we incorporated data from several collections lodged at the regional herbarium in Lae. Data on seed dispersal syndromes and plant habit were obtained from the literature. Results We recorded 305 species of vascular plants from Long Island, but most trees were small and the species diversity was low. Motmot was still very sparsely vegetated and only forty-five species of vascular plants were found. Communities on Motmot were unspecialized and common species widespread. The flora of Motmot was not significantly different from that on Long Island in terms of the number of species amongst higher taxa, seed dispersal syndromes or plant habits. Main conclusions Low rainfall combined with very porous soils may be responsible for the small stature and low diversity of the forest on Long Island's caldera rim. The absence of specialist littoral species on Motmot, as a result of its landlocked situation, is probably responsible for the very slow species recruitment on the island. This community appears to be functionally important for colonization by comparison with other small volcanic islands in a marine situation. [source] Capsule Treatments to Enhance Seedling Emergence of Gaura neomexicana ssp. coloradensisRESTORATION ECOLOGY, Issue 1 2005L. M. Burgess Abstract Management of riparian vegetation is difficult because these communities are frequently impacted by herbivores, invasive weeds, and altered hydrologic regimes. Multiple and intertwined factors affecting rare species recruitment are particularly difficult to identify. Gaura neomexicana ssp. coloradensis Munz (Gaura) is a short-lived perennial forb endemic to riparian areas in mixed-grass prairies of Wyoming, Nebraska, and Colorado, U.S.A. It became a federally listed threatened species in October 2000. Because the species is a recruitment-limited monocarpic perennial, we studied the effects of six capsule-collection dates, a 2-month cool-moist stratification, 24-hr leaching, and 24-hr imbibition on Gaura seedling emergence. Seedling emergence did not vary with collection date. Capsules collected from Gaura plants grown at the Bridger Plant Materials Center in Montana exhibited greater emergence than capsules harvested from endemic populations near Cheyenne, Wyoming, suggesting that maternal plant growing conditions impact dormancy. Because cool-moist stratification enhanced seedling emergence of Gaura and leaching did not, sufficient moisture during cool temperatures may be more critical than leaching of germination inhibitors as might occur with normal stream flows. Spring flooding may enhance Gaura recruitment by increasing the availability of riparian sites that are inundated during periods of cool temperatures. If so, hydrologic and climatic regimes must be considered in restoring the unique conditions needed for germination of this rare riparian endemic. [source] | ||||||||||