Nitrate attenuation in a small temperate wetland following forest harvest

Elevated nitrate concentrations in streams and groundwater are frequently observed following forest harvest. In addition to depleting nutrients available for forest regeneration, elevated nitrate export following harvest can have deleterious effects on downstream aquatic ecosystems. As part of a forest harvest experiment conducted at the Turkey Lakes Watershed, Ontario, Canada, stable isotope techniques were employed to investigate nitrate attenuation in a natural wetland receiving high concentrations of nitrate as a result of clear-cutting in the catchment. Isotopic analysis of nitrate (δ¹⁸O, δ¹⁵N) and vegetation (δ¹⁵N) demonstrated that both denitrification and plant uptake of nitrate resulted in significantly lower nitrate concentrations in wetland outflow compared to incoming stream water. Although the 0.2-ha forested swamp (4% of catchment by area) was too small to be featured on standard topographic maps, the wetland remove 65–100% of surface water nitrate inputs, thereby protecting downstream aquatic habitats from the full effect of N release from forest harvest. The δ¹⁵N enrichment factor associated with nitrate attenuation in wetland surface water was lower than typically observed during denitrification in groundwaters, suggesting that nitrate removal is complete in some areas of the wetland. Plant assimilation of nitrate was also partially responsible for the low observed enrichment factor. Wetland plants recorded the high δ¹⁵N associated with denitrification activity in portions of the wetland. Apportionment of nitrate sources using δ¹⁸O–NO₃⁻ at the outlet weir was unaffected by the wetland nitrate attenuation under pre- and post-harvest conditions due to the mid-catchment position of the wetland. Future forest management practices designed to recognize and preserve small wetlands could reduce the potentially detrimental effects of forest harvest on aquatic systems.     

Hurricane Katrina impacts on forest trees of Louisiana's Pearl River basin

Hurricane disturbance has the potential to markedly affect coastal forest structure and ecosystem processes. This study focused on the impacts of Hurricane Katrina in Louisiana's Pearl River basin, which lies just west of Katrina's final landfall at the Louisiana–Mississippi border. Prior to landfall, composition and structure of bottomland hardwood forests in this region were studied with permanent forest inventory plots sampled in 1989, 1998, 2005 and following the storm in 2006. This enabled a direct comparison of forest structure and dynamics before and after the disturbance, including species-specific tree mortality and damage rates, biomass production, and differences among forest types having varied hydrologic regimes. Background tree mortality rate before Hurricane Katrina was 1.9%, while average annual mortality was 20.5% for the census interval including the disturbance. Change in live tree biomass estimated from allometric models demonstrated a shift from an average annual production of 3.5 Mg ha⁻¹ before the disturbance, to an average loss of 77.6 Mg ha⁻¹ from the storm. Damage associated with Hurricane Katrina varied significantly with tree species but not tree size. Flooded cypress-tupelo swamp forests sustained the least damage and frequently flooded bottomland hardwood forests sustained the highest damage. Hurricane disturbance influenced the structure and composition of these coastal forests through species-specific differences in damage and mortality rates, and varied impacts dependent on forest flooding regime.     

长江三角洲湿地现状与保护研究

根据“全国湿地资源调查”结果,论述了长江三角洲湿地主要类型,针对长江三角洲湿地面临的围垦、污染、淤积和沼泽化、湿地资源过度利用等威胁因素,提出了如何缓解或消除威胁的建议,并针对长江三角洲区域一体化协调发展的大趋势,提出长江三角洲包括湿地在内的自然资源和生态环境保护,必须加强区域合作和交流。     

国际植物新品种保护公约的变迁及日本和韩国经验借鉴

国际植物新品种保护公约1991文本与1978文本的差异主要体现在品种权范围、保护植物范围、保护期限、实质性派生品种保护及农民特权等方面。文中总结日本经历公约文本转变过程以及韩国直接加入1991文本的经验, 指出我国加入国际植物新品种保护公约1991年文本所面临的问题, 并提出相应的政策建议。     

气候变暖对郑州黄河湿地鸟类分布的影响

2004年12月～2009年9月,对郑州黄河湿地自然保护区鸟类资源进行系统的调查,共记录到鸟类15目36科115种;郑州黄河湿地鸟类不断丰富,鸟类多样性呈上升趋势;部分东洋种鸟类的分布区向北扩散到郑州黄河湿地;部分鸟类的居留型发生变化。文献记录到的变化时间主要集中在1990年以后,与郑州地区（黄河中下游）气温的变化趋势相一致,与该地区气温上升,大气异常变暖呈正相关性。     

合肥经济圈湿地资源保护研究

合肥与周边六安、巢湖、淮南和桐城市共同形成的合肥经济圈分布有众多湿地,是安徽省湿地资源最为集中的区域,通过对合肥经济圈湿地资源的调查,结合实际情况,探讨了经济圈湿地资源在开发利用中存在的问题和资源破坏、生态退化的原因,并就湿地资源的保护和管理提出了明确的措施和建议,以期合肥经济圈湿地资源在区域生态环境改善和社会经济发展中发挥更大的生态服务功能。     

Conversion and recovery of Puerto Rican mangroves: 200 years of change

Human activities have dramatically reduced the world’s area of mangroves just as the ecological services they provide are becoming widely recognized. Improving the conservation tools available to restore lost mangroves would benefit from a better understanding of how human activities influence the conservation of these ecosystems. We took advantage of historical information and long-term landscape analyses to relate land use change with the area of mangroves in Puerto Rico. We found that mangroves experienced dramatic changes over the last 200 years, and four distinct eras of change were visible. During the agricultural era (1800–1940) the area of mangroves declined 45%. As the economy changed to industrial in the late 1940s the area of mangrove increase due to reduced land use pressure on the wetlands. Nevertheless, urban expansion between 1960s and 1970s produced another decline. Public concern for mangrove conservation resulted in the legal protection of all the mangroves in 1972, and since then their area has expanded. We found that past human activity altered the original proportion of mangrove species. The number and size of mangrove-forest fragments was impacted by land use, and urban areas had fewer and smaller fragments than vegetated areas. Uncontrolled expansion of urban areas emerged as a major threat to mangrove conservation. Mangroves are resilient and recover quickly when given an opportunity if the geomorphological and hydrological features of the habitat are not changed by their use. The key to conservation appears to be a combination of the type of human activity in mangrove watersheds combined with strong legal protection. The following steps are recommended: (1) identify the areas that satisfy the ecological requirements of mangrove development; (2) incorporate better zoning regulations to maintain these areas natural and to protect the fluxes of water, nutrients, and organisms in and out of the system; and (3) monitor results.     

《联合国海洋法公约》生效对公海渔业的影响

在归纳世界大多数沿海国家执行联合国海洋法公约，主要实施公海制度的实践，以及分析公约有关条款的基础上，指出今后渔业管理制度将朝着有利于沿海国的方向发展，远洋渔业国只有与沿海国密切合作，承担公约所规定的养护生物资源的义务，才能确保远洋渔业生产的持续稳定发展。根据我国渔业的实际状况，分析了海洋法公约生效对我国公海渔业生产产生的一些不利影响，并提出对海洋渔业发展的一些看法     

Responses of waterbirds to flooding in an arid region of Australia and implications for conservation

Floods are a frequent but irregular feature of Australia's dryland river catchments. We investigated changes in abundances of waterbirds in north western New South Wales with changes in wetland distribution at local, catchment and broad scales. The abundance of most functional groups of waterbirds changed in response to broad scale changes in wetland distribution, while local abundance remained highly variable. Patterns of abundance varied among functional groups of waterbirds, with some immediately responding to changes in wetland distribution and area flooded, and others apparently responding to sequences of wetting and drying. In Australia, the main conservation issue for waterbirds is water and its use across the landscape and not the spatial arrangement of any fixed array of reserves established to protect them.     

Wetland macrophyte decomposition under different nutrient conditions: Relationships between decomposition rate, enzyme activities and microbial biomass

We used oligotrophic, P-limited herbaceous wetlands of northern Belize as a model system, on which to document and explain how changes in nutrient content along a salinity gradient affect activities of extracellular enzymes involved in macrophyte decomposition. To determine what is more important for decomposition, the initial litter quality, or site differences, we used reciprocal litter placement in a combined “site quality” and “litter quality” experiment running from August 2003 to April 2004. The experiment was set up in long-term control and nutrient addition plots (P, N, and NP) established in 2001 in 15 limestone-based inland marshes with a wide range of water conductivities (200-6000 μS) and a uniform pH (7.0-7.7) dominated by emergent macrophytes, Eleocharis spp. There were no differences among the plots in total sediment N and water NH₄-N, but total and KCl-extractable sediment P and water PO₄-P were significantly higher in P and NP plots throughout the duration of the experiment. The initial litter N content was slightly but significantly different between control and N plots versus P and NP plots (5.7 and 7.1 mg g⁻¹, respectively). The difference was much bigger for litter P content, 0.1 and 0.7 mg g⁻¹, respectively. Enzyme activities of alkaline phosphatase, leucine-aminopeptidase, arylsulfatase, and β-glucosidase were measured fluorometrically in Eleocharis litter in both the litterbag experiment and the naturally decomposing material. Total phospholipid fatty acid (PLFA) content in litter samples was used as a measure of microbial biomass present. Phosphatase always exhibited the highest activity of the enzymes studied, followed by leucine-aminopeptidase, arylsulfatase and β-glucosidase. There were no significant differences between enzyme activities from litterbags and the unconfined litter. Phosphatase activity was significantly suppressed in P-addition plots under all salinity levels while the activities of the remaining enzymes were significantly higher in P-enriched plots. There was a strong correlation between decomposition coefficient k-values and most of the enzymes as well as between the amount of PLFA and enzyme activities. PLFA, arylsulfatase, and litter C/P were the best predictors of k-values.