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301.
Many “natural” areas are exposed to military or recreational off-road vehicles. The interactive effects of different types
of vehicular disturbance on vegetation have rarely been examined, and it has been proposed that some vegetation types are
less susceptible to vehicular disturbance than others. At Fort Riley, Kansas, we experimentally tested how different plant
community types changed after disturbance from an M1A1 Abrams tank driven at different speeds and turning angles during different
seasons. The greatest vegetation change was observed because of driving in the spring in wet soils and the interaction of
turning while driving fast (vegetation change was measured with Bray-Curtis dissimilarity). We found that less vegetation
change occurred in communities with high amounts of native prairie vegetation than in communities with high amounts of introduced
C3 grasses, which is the first experimental evidence we are aware of that suggests plant communities dominated by introduced
C3 grasses changed more because of vehicular disturbance than communities dominated by native prairie grasses. We also found
that vegetation changed linearly with vehicular disturbance intensity, suggesting that at least initially there was no catastrophic
shift in vegetation beyond a certain disturbance intensity threshold. Overall, the intensity of vehicular disturbance appeared
to play the greatest role in vegetation change, but the plant community type also played a strong role and this should be
considered in land use planning. The reasons for greater vegetation change in introduced C3 grass dominated areas deserve further study. 相似文献
302.
The influence of ionic composition on the water chemistry and thereby on aquatic flora was investigated. Two major wetlands
of North India were taken for the study. Quality parameters of the lakes showed the enrichment of the water especially in
the month of September with higher values of P and BOD in almost all of the lakes viz., LSJ, LCH, LSN, and LHT as <5.0, 9.0,
1.0, 1.7 and <7.3, 6.0, 6.3, and 4.0, respectively. Statistically correlated values of the ions in the water quality showed
an effect of one on another. An attempt has also been made to investigate if ionic constituent is one of the major causes
affecting the aquatic floral diversity. 相似文献
303.
盐碱池塘底栖动物的初步研究 总被引:9,自引:0,他引:9
研究了不同放养模式的高青盐碱池塘底栖动物的种类组成、生物量及其季节变动。结果表明,盐碱池塘底栖动物群落结构简单,主要优势种是羽摇蚊幼虫和奥特开水丝蚓,底栖动物密度和生物量无鱼对照池比养鱼池高得多,平均密度(nar/m^-2)和生物量(ρA/g m^-2)分别为1103(40-2085)m^-2和4.61(0.15-12.91)g m^-2,养地池底栖动物nar/m^-2和ρA/g m^-2分别为54-161m^-1和0.14-0.54g m^-2。底栖动物密度和生物量在春夏之交有一高峰,对盐碱池塘底栖动物种、量特点及其与鱼类捕食和一些生态因子的关系进行了讨论。 相似文献
304.
本文利用浮游植物指际来评价大庆水庠“十.五“期间水质变化状况、阐述变化发展趋势。通过评价、对比,得出大庆水库水质属于轻污-中污染水体,并有稍微好转的趋势,符合饮用水源地标准。 相似文献
305.
YAEL MANDELIK†‡ TAMAR DAYAN VLADIMIR CHIKATUNOV VASILIY KRAVCHENKO 《Conservation biology》2007,21(6):1506-1515
Abstract: A promising shortcut for quantifying species patterns is to use genera and families as surrogates of species. At large spatial scales, concurrence between patterns of richness, rarity, and composition of species and higher taxa is generally high. Only a few researchers, however, have examined this relationship at the local scale, which is frequently the relevant scale in land-use conflicts. We investigated the reliability of the higher-taxon approach in assessing patterns of species richness, rarity, and composition at the local scale. We studied diversity patterns of three commonly used surrogate taxa: vascular plants, ground-dwelling beetles, and moths. We conducted year-round field surveys for these taxa in the Jerusalem Mountains and the Judean foothills, Israel. Richness and composition of species were highly correlated with richness and composition of genera for all taxa. At the family level, correlations with richness and composition of species were much lower. Excluding monotypic genera and families did not affect these relations. Rarity representation based on higher taxa varied considerably depending on the taxon, and rarity scale and was weaker compared with richness and composition representation. Cumulative richness curves of species and genera showed similar patterns, leveling off at equivalent sampling efforts. Genus-level assessments were a reliable surrogate for local patterns of species richness, rarity, and composition, but family-level assessments performed poorly. The advantage of using coarse taxonomic scales in local diversity surveys is that it may decrease identification time and the need for experts, but it will not reduce sampling effort. 相似文献
306.
The small-rodent populations of five collective gardens have been studied. The example of one of the populations has been used to monitor the annual cycle of population size. The species composition and animal number depends on the biotope, climatic conditions, and the anthropogenic load. The ratios between species in the gardens and neighboring biotopes differ from each other, with different species being dominant. It is assumed that small mammals use garden plots as refugia. 相似文献
307.
308.
Laura Sokka Riina Antikainen Pekka E. Kauppi 《Resources, Conservation and Recycling》2007,50(4):475-488
Waste reduction was recognised as the main goal of waste management policy in the EU in the 1990s. Although knowledge of past waste generation is essential for effective waste reduction policy there are no comprehensive statistics on the past development of municipal solid waste (MSW) production. MSW management is currently under turmoil in many EU countries as the requirements of the EC landfill directive (1999/31/EC) are set into force. In this study, the production and composition of MSW in Finland between 1960 and 2002 is presented using historical data. The impact of population, affluence and technology on MSW production are analysed using the IPAT equation and three scenarios are constructed until year 2020. The results are compared with national future targets on MSW production. Production of MSW increased in Finland until 1990, declined to year 1997, increased to 2000 and then declined again. The share of organic and plastic waste increased over the study period while the share of paper and cardboard declined. The results suggest that so far national targets on MSW reduction have been set fairly low. Moreover, our scenarios depict a wide range of future MSW production, even though the time horizon is not longer than 15 years into the future. In order to narrow this range, continuous improvement of the statistics of MSW is essential. 相似文献
309.
Willem van Hees 《Journal of the American Water Resources Association》1977,13(2):215-230
ABSTRACT: A number of aspects of the discharging of non-oily wastewaters by transiting ships are treated in this overview paper. In the introduction, options to discharging (the use of holding tank, on board treatment) and the impact of changing regulations are discussed. Assessment of the effects of sewage discharges on coastal waters required that data, at first not available, be generated. An account is given of the characterization of Navy shipboard wastewaters and of experiments involving sewage discharges at sea, measurements of water quality before, during and after an amphibious operation, and fore and aft of transitting Navy ships. A better understanding of sewage dilution after discharge led to the verification of a method for controlled discharging of sewage (and other wastewaters). This method permits limiting the coliform bacteria count in the ship's wake to values below acceptable limits. The final sections contain information on long range effects of ships’sewage discharges, obtained in studies by the U.S. Navy and others, as well as public health considerations. 相似文献
310.