Niche complementarity for nitrogen: an explanation for the biodiversity and ecosystem functioning relationship?

The relationship between plant diversity and productivity has largely been attributed to niche complementarity, assuming that plant species are complementary in their resource use. In this context, we conducted an 15N field study in three different grasslands, testing complementarity nitrogen (N) uptake patterns in terms of space, time, and chemical form as well as N strategies such as soil N use, symbiotic N fixation, or internal N recycling for different plant species. The relative contribution of different spatial, temporal, and chemical soil N pools to total soil N uptake of plants varied significantly among the investigated plant species, within and across functional groups. This suggests that plants occupy distinct niches with respect to their relative N uptake. However, when the absolute N uptake from the different soil N pools was analyzed, no spatial, temporal, or chemical variability was detected, but plants, and in particular functional groups, differed significantly with respect to their total soil N uptake irrespective of treatment. Consequently, our data suggest that absolute N exploitation on the ecosystem level is determined by species or functional group identity and thus by community composition rather than by complementary biodiversity effects. Across functional groups, total N uptake from the soil was negatively correlated with leaf N concentrations, suggesting that these functional groups follow different N use strategies to meet their N demands. While our findings give no evidence for a biodiversity effect on the quantitative exploitation of different soil N pools, there is evidence for different and complementary N strategies and thus a potentially beneficial effect of functional group diversity on ecosystem functioning.     

Identification of a reactive degradation zone at a landfill leachate plume fringe using high resolution sampling and incubation techniques

Vertical small-scale variation in phenoxy acid herbicide degradation across a landfill leachate plume fringe was studied using laboratory degradation experiments. Sediment cores (subdivided into 5 cm segments) were collected in the aquifer and the sediment and porewater were used for microcosm experiments (50 experiments) and for determination of solid organic carbon, solid-water partitioning coefficients, specific phenoxy acid degraders and porewater chemistry. Results from a multi-level sampler installed next to the cores provided information on the plume position and oxygen concentration in the groundwater. Oxygen concentration was controlled individually in each microcosm to mimic the conditions at their corresponding depths. A highly increased degradation potential existed at the narrow plume fringe (37.7 to 38.6 masl), governed by the presence of phenoxy acids and oxygen. This resulted in the proliferation of a microbial population of specific phenoxy acid degraders, which further enhanced the degradation potential for phenoxy acids at the fringe. The results illustrate the importance of fringe degradation processes in contaminant plumes. Furthermore, they highlight the relevance of using high-resolution sampling techniques as well as controlled microcosm experiments in the assessment of the natural attenuation capacity of contaminant plumes in groundwater.     

Watershed Management and Organizational Dynamics: Nationwide Findings and Regional Variation

Recent attention has focused on resource management initiatives at the watershed scale with emphasis on collaborative, locally driven, and decentralized institutional arrangements. Existing literature on limited selections of well-established watershed-based organizations has provided valuable insights. The current research extends this focus by including a broad survey of watershed organizations from across the United States as a means to estimate a national portrait. Organizational characteristics include year of formation, membership size and composition, budget, guiding principles, and mechanisms of decision-making. These characteristics and the issue concerns of organizations are expected to vary with respect to location. Because this research focuses on organizations that are place based and stakeholder driven, the forces driving them are expected to differ across regions of the country. On this basis of location, we suggest basic elements for a regional assessment of watershed organizations to channel future research and to better approximate the organizational dynamics, issue concerns, and information needs unique to organizations across the country. At the broadest level, the identification of regional patterns or organizational similarities may facilitate the linkage among organizations to coordinate their actions at the much broader river basin or ecosystem scale.     

Revolution or inch-by-inch? Campaign approaches on climate change by environmental groups

Climate change is a significant environmental, social and environmental problem that has been identified by scientists in consensus internationally. The Australian Government’s response is considered by environmental non-government organisations (NGOs) to be inadequate. NGOs are ‘change agents’ of society, and in this role they are agitating to influence political decision-making on climate change response. This paper outlines the campaign strategies being used by Australian NGOs to attract public and political attention to the issue of climate change. Using seven NGOs as case studies, the archival materials of these organisations were accessed and analysed. Current academic and other literature also was used to reflect on their effectiveness. Four campaign themes and, within these, fifteen activities were identified. The results indicate that the notion of whether NGOs are undertaking an ‘revolutionary’ or ‘incremental’ approach, or any other narrow strategic approach put forward by various scholars is too simple for analysing campaigns: none of the NGOs appear to intentionally favour one type of strategy. The question raised by this finding is whether the NGOs’ current ‘multi-strategic’ approach is effective. This research contributes to filling the information gap with regard to NGO campaign strategies on environmental issues, and highlights the need for further research.     

Impacts of quicklime (CaO) on the toxicity of copper (CuSO4, 5H2O) to fish and fish food organisms

Static bioassays of 96 h duration were conducted in the laboratory using fry of common carp (Cyprinus carpio), adult tubificid worm (Branchiura sowerbyi) and adult copepod plankton (Cyclops viridis) to determine LC50 values of Cu and CaO to these organisms and effects of interaction between Cu and CaO. Ninety-six hour LC(50) values of Cu to fry of common carp, worm and copepod were found to be 1.40 mgl(-1), 0.08 mgl(-1) and 0.03 mgl(-1) respectively. CaO up to 500 mgl(-1) did not produce any mortality of the fry of common carp up to 96 h. But 96 h LC50 values of CaO to worm and copepod were 83.00 mgl(-1) and 27.80 mgl(-1) respectively. When common carp fry, worm and the copepod were exposed to respective LC50 dose of Cu in presence of varying concentration of CaO, mortality of the organisms significantly reduced and was found inversely correlated with the doses of CaO [y = 48.36-0.807x, r = -0.99 (n = 7) for fish; y = 44.46-0.146x, r = -0.97 (n = 7) for worm; y = 49.46-0.66x, r = -0.99 (n = 7) for the copepod]. The present results indicate that CaO is non-toxic to fish and is capable of reducing the toxicity of Cu to fish while CaO and Cu are antagonistic to each other for the worm and the copepod. Potential of using CaO as antitoxic agent for Cu in water is discussed.     

Hydrology and grazing jointly control a large-river food web

Inputs of fresh water and grazing both can control aquatic food webs, but little is known about the relative strengths of and interactions between these controls. We use long-term data on the food web of the freshwater Hudson River estuary to investigate the importance of, and interactions between, inputs of fresh water and grazing by the invasive zebra mussel (Dreissena polymorpha). Both freshwater inputs and zebra mussel grazing have strong, pervasive effects on the Hudson River food web. High flow tended to reduce population size in most parts of the food web. High grazing also reduced populations in the planktonic food web, but increased populations in the littoral food web, probably as a result of increases in water clarity. The influences of flow and zebra mussel grazing were roughly equal (i.e., within a factor of 2) for many variables over the period of our study. Zebra mussel grazing made phytoplankton less sensitive to freshwater inputs, but water clarity and the littoral food web more sensitive to freshwater inputs, showing that interactions between these two controlling factors can be strong and varied.     

Sexual selection and female fitness in <Emphasis Type="Italic">Drosophila simulans</Emphasis>

There is a current debate over the net fitness consequences of sexual selection. Do preferred males increase female fitness or are these males manipulating females for their own benefit? The evidence is mixed. Some studies find that mating with attractive males increases female fitness components, while others show that preferred males decrease measures of female fitness. In this study, we examined some of the fitness consequences of pre-copulatory sexual selection in Drosophila simulans. Virgin females were either paired with one male and given an opportunity for one copulation or were exposed simultaneously to two males. This allowed us to compare female preference (copulation latency) and fitness (longevity, lifetime productivity and rate of offspring production) both with and without the influence of male–male competition. When females had access to a single male, neither female longevity, productivity, nor short-term rate of productivity were associated with female preference, and although females mated more quickly with larger males, male size was also not associated with any female fitness measure. Inclusion of male–male competition showed that female longevity was negatively affected by preference, while productivity and rate of productivity was unaffected. This latter experiment also indicated that females preferred larger males, but again, male size was not associated with female fitness. These results indicate that females may not benefit from mating with preferred males, but they may incur survival costs.     

核桃果皮炭粉对3种重金属离子吸附的影响

采用均匀设计的实验方法,研究了2种核桃果皮炭粉(提取水溶性混合物和未提取水溶性混合物的核桃皮炭粉)对Cr、Cu和Cd等重金属离子的吸附最优条件以及对3种离子吸附的影响因素。结果表明,核桃皮炭粉对Cr(Ⅵ)、Cd2+和Cu2+的吸附最优条件为:pH=4,温度为60℃,浓度为150μg/mL,吸附剂用量为2.4 g,时间为120 min;pH=4.5,温度为30℃,浓度为180μg/mL,吸附剂用量为5.4 g,时间为60 min;pH=5,温度为80℃,浓度为210μg/mL,吸附剂用量为0.4 g,时间为100 min;pH和Cr(Ⅵ)浓度增大,不利于2种吸附剂对Cr(Ⅵ)的吸附;pH和温度增大,不利于2种吸附剂对Cu2+的吸附;温度和吸附剂用量增加,有利于2种吸附剂对Cd2+的吸附。未提取水溶性混合物比提取水溶性混合物的核桃果皮炭粉对3种金属的吸附显著。2种吸附剂的吸附率均表现为Cr>Cd>Cu。