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151.
Spatial clustering of habitat structure effects patterns of community composition and diversity 总被引:1,自引:0,他引:1
Natural ecosystems often show highly productive habitats that are clustered in space. Environmental disturbances are also often nonrandomly distributed in space and are either intrinsically linked to habitat quality or independent in occurrence. Theoretical studies predict that configuration and aggregation of habitat patch quality and disturbances can affect metacommunity composition and diversity, but experimental evidence is largely lacking. In a metacommunity experiment, we tested the effects of spatially autocorrelated disturbance and spatial aggregation of patch quality on regional and local richness, among-community dissimilarity, and community composition. We found that spatial aggregation of patch quality generally increased among-community dissimilarity (based on two measures of beta diversity) of communities containing protozoa and rotifers in microcosms. There were significant interacting effects of landscape structure and location of disturbances on beta diversity, which depended in part on the specific beta diversity measures used. Effects of disturbance on composition and richness in aggregated landscapes were generally dependent on distance and connectivity among habitat patches of different types. Our results also show that effects of disturbances in single patches cannot directly be extrapolated to the landscape scale: the predictions may be correct when only species richness is considered, but important changes in beta diversity may be overlooked. There is a need for biodiversity and conservation studies to consider the spatial aggregation of habitat quality and disturbance, as well as connectivity among spatial aggregations. 相似文献
152.
Peter E. Levy Renate Wendler Marcel Van Oijen Melvin G. R. Cannell Peter Millard 《Water, Air, & Soil Pollution: Focus》2004,4(6):67-74
Estimates of the global carbon sink induced by nitrogen enrichment range vary widely, from nearly zero to 2.3 Gt C year-1. It is necessary to reduce this uncertainty if we are to make accurate predictions of the future magnitude of the terrestrial carbon sink. Here, we present a Monte Carlo approach to uncertainty and sensitivity analysis of three ecosystem models, Century,BGCand Hybrid. These models were applied to a coniferous forest ecosystem in Sweden. The best estimate of the change in total carbon content of the ecosystem with the cumulative change in nitrogen deposition over 100 years, Ctotal/Ndeposition was 20.1 kg C (kg N)-1 using the pooled mean, with a pooled standard deviation of 13.8 kg C (kg N)-1. Variability in parameters accounted for 92% of the total uncertainty in Ctotal/Ndeposition, and only 8% was attributable to differences between models. The most sensitive parameters were those which controlled the allocation of assimilate between leaves, roots and stem. In particular, an increase in allocation to fine roots led to a large reduction in Ctotal/Ndeposition in all models, because the fine roots have a very high turnover rate, and extra carbon allocated there is soon lost through mortality and decomposition. 相似文献
153.
Woldetsadik Desta Simon Marcel Pierre Knuth Dennis Hailu Hillette Gebresilassie Araya Dejen Asmare Düring Rolf-Alexander 《Environmental geochemistry and health》2021,43(9):3597-3613
Environmental Geochemistry and Health - Khat (Catha edulis) chewing is widespread in the region of East Africa. Even low levels of organochlorine pesticides (OCPs) in khat could induce public... 相似文献
154.
In an experimental set-up, a colony of the stingless bee Melipona fasciata demonstrated its ability to choose the better of two nectar sources. This colony pattern was a result of the following individual
behavioural decisions: continue foraging, abandon the feeder, restart foraging and initiate foraging. Only very rarely did
individuals switch from one feeder to the other. With the first combination of a rich (2.7 M) and a poor (0.8 M) feeder M. fasciata behaved differently from Apis mellifera. Recruitment occurred to both feeders and the poor feeder was not abandoned completely. When the poor feeder was set to 0.4 M,
M. fasciata abandoned the poor feeder rapidly and allocated more foragers to the rich feeder. These patterns were similar to those reported
for A. mellifera with the first combination of feeders. Over a sequence of 4 days, experienced bees increasingly determined the colony patterns,
and the major function of communication between workers became the reactivation of experienced foragers. The foragers modulated
their behaviour not only according to the profitability of the feeder, but also according to previous experience with profitability
switches. Thus, experience and communication together regulated colony foraging behaviour. These findings and the results of studies with honeybees suggest
that M. fasciata and honeybees use similar decision-making mechanisms and only partly different tools.
Received: 21 December 1998 / Accepted: 5 January 1999 相似文献
155.
We combined a natural experiment with field surveys and GIS to investigate the effects of dust from recreational trails and
access roads on the federally threatened Valley elderberry longhorn beetle (“VELB,” Desmocerus californicus dimorphus) and its host plant, elderberry (Sambucus mexicana). Dust is listed in the species recovery plan as a threat to the VELB and unpaved surfaces are common throughout the riparian
corridors where the VELB lives, yet the effects of dust on the VELB have been untested. We found that dust deposition varied
among sites and was highest within 10 m of trails and roads, but was similar adjacent to dirt and paved surfaces within sites.
Elderberry density did not differ with distance from dirt surfaces. Despite similar within-site dust levels, elderberry adjacent
to paved surfaces were less stressed than those near dirt ones, possibly because increased runoff from paved surfaces benefited
elderberry. Dust deposition across sites was weakly correlated with elderberry stress symptoms (e.g., water stress, dead stems,
smaller leaves), indicating that ambient dust (or unmeasured correlates) influenced elderberry. Direct studies of the VELB
showed that its distribution was not negatively affected by the proximity to dirt surfaces. Dust from low traffic dirt and
paved access roads and trails, therefore, affected VELB presence neither directly nor indirectly through changed elderberry
condition. These results suggest that the placement of VELB mitigation, restoration, and conservation areas can proceed independently
of access roads if dust and traffic levels do not exceed those in our study site. Furthermore, dust control measures are likely
to be unnecessary under such conditions. The potential effects of increased traffic and dust levels are addressed through
a literature review. 相似文献
156.
Dröge Janis Moussaoui Ibrahim El Klingelhöfer Doris Held Hannelore Groneberg David. A. Verhoff Marcel A. Plenzig Stefanie 《Environmental science and pollution research international》2022,29(40):60519-60530
Environmental Science and Pollution Research - Particulate matter emitted during autopsies can serve as a vector for numerous viruses or bacteria and can lead to infections. Reducing the exposure... 相似文献