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31.
Effects of cover soil stockpiling on plant community development following reclamation of oil sands sites in Alberta 总被引:1,自引:0,他引:1
Stockpiling of cover soil can influence vegetation development following reclamation. Cover soil, comprising the upper 15–30 cm of the surface material on sites scheduled for mining, is commonly salvaged prior to mining and used directly or stockpiled for various lengths of time until it is needed. Salvaging and stockpiling causes physical, chemical, and biological changes in cover soils. In particular, stockpiling reduces the availability and vigor of vegetative propagules and seed, and can lead to increases in the abundance of some weedy species. This study uses data from monitoring plots to assess how stockpiling of cover soil impacts plant community development on reclaimed oil sands mine sites in northern Alberta. Development of plant communities differed distinctly between directly placed and stockpiled cover soil treatments even 18 years after reclamation. Direct placement of cover soil resulted in higher percent cover, species richness, and diversity. Nonmetric multidimensional scaling and multiresponse permutation procedure revealed compositional differentiation between the treatments. Indicator species analysis showed that direct placement treatment was dominated by perennial species while grasses and annual forb species dominated sites where stockpiled soil was used. Results indicate that stockpiling leads to slower vegetation recovery while direct placement of cover soil supports more rapid succession (from ruderal and annual communities to perennial communities). In addition, direct placement may be less costly than stockpiling. However, scheduling of salvage and placement remains a challenge. 相似文献
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33.
Patterns of species associations have been commonly used to infer interactions among species. If species positively co‐occur, they may form predominantly neutral assemblages, and such patterns suggest a relatively weak role for compensatory dynamics. The main objective of this study was to test this prediction on temporal samples of bird assemblages (n = 19, 10–57 years) by the presence/absence and quantitative null models on assemblage and guild levels. These null model outcomes were further analyzed to evaluate the effects of various data set characteristics on the outcomes of the null models. The analysis of two binary null models in combination with three association indices revealed 20% with significant aggregations, 61% with random associations, and only 19% with significant segregations (n = 95 simulations). The results of the quantitative null model simulations detected more none‐random associations: 61% aggregations, 6% random associations, and 33% segregations (n = 114 simulations). Similarly, quantitative analyses on guild levels showed 58% aggregations, 20% segregations, and 22% random associations (n = 450 simulations). Bayesian GLMs detected that the outcomes of the binary and quantitative null models applied to the assemblage analyses were significantly related to census plot size, whereas the outcomes of the quantitative analyses were also related to the mean population densities of species in the data matrices. In guild‐level analyses, only 9% of the GLMs showed a significant influence of matrix properties (plot size, matrix size, species richness, and mean species population densities) on the null model outcomes. The results did not show the prevalence of negative associations that would have supported compensatory dynamics. Instead, we assume that a similar response of the majority of species to climate‐driven and stochastic factors may be responsible for the revealed predominance of positive associations. 相似文献
34.
Laura Arriaga 《Plant Ecology》1988,78(1-2):73-79
The magnitude of natural disturbances by treefalls and their spatial occurrence were studied in a pine-oak forest of Sierra de La Laguna, located at the southern part of the Peninsula of Baja California in Mexico.Twenty transects covering 4 ha, perpendicular to north- and south-facing slopes were sampled. The percentages of rocky outcrops, slope, orientation, and gap size created by treefalls were recorded. The mode of tree death, treefall direction, trunk length, and basal diameter were also measured. Data were analyzed using principal component analysis, one-way ANOVA, multiple comparison tests by contrasts, and chi-square independence tests.Results suggest that exogenous disturbances have an important effect in this community. A mean number of 80 gaps per ha was recorded comprising 18.1% of the observed area. Gap sizes were fitted to a lognormal distribution as 2.3±1.4 and patches were found to be created by single treefalls. Analysis of dead material shows that there are significant differences between numbers of fallen trees on N vs S facing slopes, and that forms of dead trees are significantly associated with species. Snapped trees represent 39.5% of treefalls, dead standing trees 26.4%, uprooted trees 20.5% and cut-down trees 0.9%. The frequency of occurrence of various forms of the dead trees suggests that the cause of mortality is primarily due to the high incidence of tropical hurricanes, and secondly to the combined effect of wind and natural fire which occurs during the rainy summer season. 相似文献
35.
Horak IG Fourie LJ Heyne H Walker JB Needham GR 《Experimental & applied acarology》2002,27(1-2):113-136
This paper records the identities of 558 ixodid ticks feeding on 194 humans in South Africa. These ticks belonged to 20 species
in six genera and those most frequently encountered were Amblyomma hebraeum, Haemaphysalis leachi, Hyalomma
marginatum rufipes, Hyalomma truncatum, Rhipicephalus appendiculatus, Rhipicephalus gertrudae and Rhipicephalus simus. With the exception of the larvae of R. appendiculatus, the incidents of these ticks feeding on humans correlated well with their seasonal occurrences on preferred hosts. Ticks
were also collected at monthly intervals, for 14 consecutive months, from the clothing of a game-guard providing protection
for field-workers engaged in the collection, by means of flannel strips, of free-living ticks from the vegetation of four
localities in the southern region of the Kruger National Park. In addition, with the exception of 3 months when the particular
worker was absent, ticks that fed on one of the field-workers were collected over the same 14-month period. A total of 54,429
free-living ticks belonging to 14 species and six genera were collected from the vegetation at the four localities during
this time and 3751 ticks belonging to 11 species and six genera from the clothing of the game-guard. The larvae of A. hebraeum and Boophilus decoloratus were the most numerous of the immature ticks, and H. leachi and R. simus of the adults on both the vegetation and the guard’s clothing. Ticks fed on the field-worker on six occasions and 14 were
collected, all of which were A. hebraeum larvae.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
36.
C. Kenneth Waters 《Biology & philosophy》1998,13(1):5-36
Former discussions of biological generalizations have focused on the question of whether there are universal laws of biology. These discussions typically analyzed generalizations out of their investigative and explanatory contexts and concluded that whatever biological generalizations are, they are not universal laws. The aim of this paper is to explain what biological generalizations are by shifting attention towards the contexts in which they are drawn. I argue that within the context of any particular biological explanation or investigation, biologists employ two types of generations. One type identifies causal regularities exhibited by particular kinds of biological entities. The other type identifies how these entities are distributed in the biological world. 相似文献
37.
安徽省花生田3种常见金龟子灯诱种群数量动态分析 总被引:1,自引:0,他引:1
2009-2011年连续3年利用频振式杀虫灯调查安徽省花生田3种常见金龟子成虫的种群动态,结果表明:2009-2011年3种金龟子灯诱总数整体呈下降趋势,且诱捕量为铜绿丽金龟暗黑鳃金龟华北大黑鳃金龟。华北大黑鳃金龟趋光性差,灯诱量低;暗黑鳃金龟和铜绿丽金龟初见日一般为5月中下旬,高峰期为6月中旬,但暗黑鳃金龟比铜绿丽金龟一般晚7-10 d。金龟子出土与气候关系密切,当平均气温上升至20℃-25℃持续数日并保持上升的过程中,暗黑鳃金龟和铜绿丽金龟诱捕量增大,但性比未呈现规律性差异。 相似文献
38.
39.
Sophie L. Nedelec Stephen D. Simpson Erica L. Morley Brendan Nedelec Andrew N. Radford 《Proceedings. Biological sciences / The Royal Society》2015,282(1817)
Anthropogenic noise impacts behaviour and physiology in many species, but responses could change with repeat exposures. As repeat exposures can vary in regularity, identifying regimes with less impact is important for regulation. We use a 16-day split-brood experiment to compare effects of regular and random acoustic noise (playbacks of recordings of ships), relative to ambient-noise controls, on behaviour, growth and development of larval Atlantic cod (Gadus morhua). Short-term noise caused startle responses in newly hatched fish, irrespective of rearing noise. Two days of both regular and random noise regimes reduced growth, while regular noise led to faster yolk sac use. After 16 days, growth in all three sound treatments converged, although fish exposed to regular noise had lower body width–length ratios. Larvae with lower body width–length ratios were easier to catch in a predator-avoidance experiment. Our results demonstrate that the timing of acoustic disturbances can impact survival-related measures during development. Much current work focuses on sound levels, but future studies should consider the role of noise regularity and its importance for noise management and mitigation measures. 相似文献