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141.
Abella SR 《Environmental management》2008,41(6):809-819
Wild burros (Equus asinus), protected by the 1971 Wild Free-Roaming Horse and Burro Act on some federal lands but exotic animals many ecologists and
resource mangers view as damaging to native ecosystems, represent one of the most contentious environmental management problems
in American Southwest arid lands. This review synthesizes the scattered literature about burro effects on plant communities
of the Mojave Desert, a center of burro management contentions. I classified 24 documents meeting selection criteria for this
review into five categories of research: (i) diet analyses directly determining which plant species burros consume, (ii) utilization
studies of individual species, (iii) control-impact comparisons, (iv) exclosure studies, and (v) forage analyses examining
chemical characteristics of forage plants. Ten diet studies recorded 175 total species that burros consumed. However, these
studies and two exclosure studies suggested that burros preferentially eat graminoid and forb groups over shrubs. One study
in Death Valley National Park, for example, found that Achnatherum hymenoides (Indian ricegrass) was 11 times more abundant in burro diets than expected based on its availability. Utilization studies
revealed that burros also exhibit preferences within the shrub group. Eighty-three percent of reviewed documents were produced
in a 12-year period, from 1972 to 1983, with the most recent document produced in 1988. Because burros remain abundant on
many federal lands and grazing may interact with other management concerns (e.g., desert wildfires fueled by exotic grasses),
rejuvenating grazing research to better understand both past and present burro effects could help guide revegetation and grazing
management scenarios. 相似文献
142.
The US Army Corps of Engineers often requires wetland creation or restoration as compensation for wetlands damaged during
development. These wetlands are typically monitored postconstruction to determine the level of compliance with respect to
site-specific performance standards. However, defining appropriate goals and measuring success of restorations has proven
difficult. We reviewed monitoring information for 76 wetlands constructed between 1992 and 2002 to summarize the performance
criteria used to measure progress, assess compliance with those criteria, and, finally, to evaluate the appropriateness of
those criteria. Goals were overwhelmingly focused on plant communities. Attributes used to assess the quality of restored
plant communities, including percent native species and the Floristic Quality Index, increased over time but were apparently
unrelated to the number of species planted. Compliance frequencies varied depending on site goals; sites often failed to comply
with criteria related to survival of planted vegetation or requirements that dominant plant species should not be exotic or
weedy, whereas criteria related to the establishment of cover by vegetation or by wetland-dependent plants were often met.
Judgment of a site’s success or failure was largely a function of the goals set for the site. Some performance criteria were
too lenient to be of value in distinguishing failed from successful sites, whereas other criteria were unachievable without
more intensive site management. More appropriate goals could be devised for restored wetlands by basing performance standards
on past performance of similar restorations, identifying consistent temporal trends in attributes of restored sites, and using
natural wetlands as references. 相似文献
143.
Phenylated arsenic compounds occur as highly toxic contaminants in former military areas where they were formed as degradation products of chemical warfare agents. Some phenylarsenic compounds such as roxarsone and aminophenylarsonic acids were applied as food additive and veterinary drugs in stock-breeding and therefore pose an environmental risk in agricultural used sites. Very few data exist in the literature concerning uptake and effects of phenylarsenic compounds in plants growing on contaminated soils. In this study, the accumulation, extractability, and metabolization of five different phenylarsenic compounds, phenylarsonic acid, p- and o-aminophenylarsonic acid, phenylarsine oxide, and 3-nitro-4-hydroxyphenylarsonic acid called roxarsone, by the terrestrial plant Tropaeolum majus were investigated. Ion chromatography coupled to inductively coupled plasma mass spectrometry was used to differentiate these arsenic compounds, and inductively coupled plasma atomic emission spectroscopy was used for total arsenic quantification. All compounds considered were taken up by the roots and transferred to stalks, leaves, and flowers. The strongest accumulation was observed for unsubstituted phenylarsonic acid followed by its trivalent analogue phenylarsine oxide that was mostly oxidized in soil whereas the amino- or nitro- and hydroxy-substituted phenylarsonic acids were accumulated to a smaller degree.The highest extraction yield of 90% for ground leaf material was achieved by 0.1 M phosphate buffer, pH 7.7, in a two-step extraction with a total extraction time of 24 h. The extraction of higher amounts of arsenic (50–70% of total arsenic present in leaves depending on arsenic species application) from non-ground intact leaves with deionized water in comparison with the buffer (20–40% of total arsenic) is ascribed to osmotic effects. The arsenic species analysis revealed a cleavage of the amino groups from the phenyl ring for plants treated with aminophenylarsonic acids. A further important metabolic effect consisted in the production of inorganic arsenate and arsenite from the phenylated arsonic acid groups. 相似文献
144.
Lead (Pb) accumulation in Sesbania drummondii shoots was enhanced by 654 and 415% in the presence of 100 microM IAA and 100 microM NAA, respectively, compared to control plants (Pb alone). However, when IAA or NAA was added along with EDTA, Pb accumulation further increased in shoots by 1349% and 1252%, respectively. Scanning electron microscopic observations revealed that Pb particles in both leaf and stem of Pb+EDTA+IAA and Pb+EDTA+NAA treated plants were concentrated in the region of vascular bundles. In root tissue, Pb particles were present between epidermis to stele region. Plant growth in both treatments (Pb+100 microM IAA and Pb+100 microM NAA) was comparable to control plants; however, it was significantly inhibited in the treatments containing Pb+EDTA and EDTA at concentrations of 10 microM of IAA or NAA. Moreover, the photosynthetic efficiency and strength of the treated plants were not affected in the presence of IAA or NAA and EDTA. 相似文献
145.
Micó C Li HF Zhao FJ McGrath SP 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):883-890
The influence of soil properties on the bioavailability and toxicity of Co to barley (Hordeum vulgare L.) root elongation was investigated. Ten soils varying widely in soil properties were amended with seven doses of CoCl2. Soil properties greatly influenced the expression of Co toxicity. The effective concentration of added Co causing 50% inhibition (EC50) ranged from 45 to 863 mg kg−1, representing almost 20-fold variation among soils. Furthermore, we investigated Co toxicity in relation to Co concentrations and free Co2+ activity in soil solution. The EC50 values showed variation among soils of 17- and 29-fold, based on the Co concentration in soil solution and free Co2+ activity, respectively. Single regressions were carried out between Co toxicity threshold values and selected soil properties. Models obtained showed that soil effective cation exchange capacity (eCEC) and exchangeable calcium were the most consistent single predictors of the EC50 values based on soil added Co. 相似文献
146.
2001-2005年新疆植被覆盖动态变化及原因分析 总被引:1,自引:0,他引:1
利用2001-2005年新疆归一化植被指数NDVI,得出该时间段新疆植被覆盖整体呈增加趋势,但局部有退化现象.对2001 - 2005年植被覆盖变化原因进行了分析,阐明降水是新疆植被覆盖变化的主要驱动因子之一. 相似文献
147.
Foliar emission of volatile organic compounds (VOC) from common Indian plant species was measured. Dynamic flow enclosure technique was used and the gas samples were collected onto Tenax-GC/Carboseive cartridges. The Tenax-GC/Carboseive cartridges were attached to the thermal disorber sample injection system and the gas sample was analysed using gas chromatography (GC) with flame ionisation detection (FID). Fifty-one local plant species were screened, out of which 36 species were found to emit VOC (4 high emitter; 28 moderate emitter; and 4 low-emitter), while in the remaining 15 species no VOC emission was detected or the levels of emission were below detection limit (BDL). VOC emission was found to vary from one species to another. There was a marked seasonal and diurnal variation in VOC emission. The minimum and maximum VOC emission values were < 0.1 and 87 microgg(-1) dry leaf h(-1) in Ficus infectoria and Lantana camara respectively. Out of the 51 plant species studied, 13 species are reported here for the first time. Among the nine tree species (which were selected for detailed study), the highest average hourly emission (9.69+/-8.39 microgg(-1) dry leaf) was observed in Eucalyptus species and the minimum in Syzygium jambolanum (1.89+/-2.48 microgg(-1) dry leaf). An attempt has been made to compare VOC emission from different plant species between present study and the literature (tropical and other regions). 相似文献
148.
149.
基于土地利用变化的生态服务价值损益估算--以大庆市为例 总被引:21,自引:0,他引:21
土地利用/覆盖变化遥感研究表明,大庆市自1988年以来土地利用状态变化很大,由此引起了该区域生态环境的一系列响应及其生态系统服务价值的变化。以大庆市1988年和2001年的Landsat TM图像解译数据为基础,应用Costanza等人对全球生态系统服务价值的测算方法,分析了该市土地利用变化及其所引起的生态系统服务价值的变化。研究结果表明,13年间,大庆市土地利用的变化损害了该区域生态系统的生态服务功能,使生态系统服务价值损失了20.76%-24.01%。 相似文献
150.