Localization of denitrification activity in macropores of a riparian wetland

Soil structure heterogeneity in the form of macropores and preferential flow channels can complicate efforts to quantify the physical and biological characteristics of wetland systems. We collected soil cores from two riparian wetlands to determine whether soil associated with macropores had elevated denitrification potentials compared to bulk soil from the same core. Cores were inspected for obvious macropores, which were distinguished as visible holes in the core, sometimes with decaying root matter, or as highly unconsolidated layers that appeared to have a substantially lower bulk density than the surrounding soil. Denitrification potentials were significantly higher in pores (P<0.05) for six of the 16 cores that were obtained from the Cheraw State Park site. In cores obtained from a second site, denitrification potentials were significantly higher in pores for six of 20 cores and the trend of higher denitrification in pores was present in the majority of cores that had measurable activity. In cores with significant differences, denitrification was often 1-2 orders of magnitude greater in soil surrounding the macropore than in the bulk soil. Denitrification potentials of the bulk soils were similar in magnitude to the potentials measured in composited cores from previous studies. It is possible that the difference between macropore and bulk denitrification rates developed due to preferential flow of nitrate-rich water through the macropores. Previous work showed that water entering these riparian systems in groundwater and storm runoff had elevated levels of NO₃⁻.     

中国湿地资源的生态功能及其分区

湿地在调节气候、调蓄水量、净化水体、保持水土、生物多样性保护及文化休闲等方面具有重要作用。本文分析了中国湿地的现状、分布与存在问题,并根据湿地的生态系统服务功能,将中国湿地划分成3个一级区,7个二级区,为制定湿地生态环境保护与建设规划、维护湿地生态安全、合理利用湿地资源与生产布局提供依据。     

Fate and interaction with native soil N of ammonium N applied to wetland rice (Oryza sativa L.) grown under saline and non-saline conditions

Summary The effect of salts on the balance of fertilizer N applied as ¹⁵N-labelled ammonium sulphate and its interaction with native soil N was studied in a pot experiment using rice (Oryza sativa L.) as a test crop. The rice crop used 26%–40% of the applied N, the level of applied N and salts showing no significant bearing on the uptake of fertilizer N. Losses of fertilizer N ranged between 54% and 68% and only 5%–8% of the N was immobilized in soil organic matter. Neither the salts nor the rate of N application had any significant effect on fertilizer N immobilization. The effective use of fertilizer N (fertilizer N in grain/fertilizer N in whole plant) was, however, better in the non-saline soil. The uptake of unlabelled N (N mineralized from soil organic matter and that originating from biological N₂ fixation in thes rhizosphere) was inhibited in the presence of the salts. However, in fertilized soil, the uptake of unlabelled N was significantly enhanced, leading to increased A values [(1-% Ndff/% Ndff)x N fertilizer applied, where Ndff is N derived from fertilizer], an index of interaction with the added N. This added N interaction increased with increasing levels of added N. Since the extra unlabelled N taken up by fertilized plants was greater than the fertilizer N immobilized, and the root biomass increased with increasing levels of added N, a greater part of the added N interaction was considered to be real, any contribution by an apparent N interaction (pool substitution or isotopic displacement) to the total calculated N interaction being fairly small. Under saline conditions, for the same level of fertilizer N addition, the added N interaction was lower, and this was attributed to a lower level of microbial activity, including mineralization of native soil N, rootdriven immobilization of applied N, and N₂ fixation.     

Landscape context mediates influence of local food abundance on wetland use by wintering shorebirds in an agricultural valley

While it is widely understood that local abundance of benthic invertebrates can greatly influence the distribution and abundance of wetland birds, no studies have examined if wetland landscape context can mediate this relationship. We studied the influence of wetland food abundance and landscape context on use of agricultural wetlands by wintering dunlin (Calidris alpina) and killdeer (Charadrius vociferus) in the Willamette Valley of Oregon, USA, over two winters (1999-2000, 2000-2001) of differing rainfall and subsequent habitat distribution. We monitored bird use (frequency of occurrence and abundance) at a sample of wetlands differing in local food abundance (density and biomass) and landscape context [adjacent shorebird habitat (defined as ha of wet habitat with less than 50% vegetative cover and within a 2-km radius) and nearest neighbor distance]. We evaluated predictive models for bird use using linear regression and the Cp criterion to select the most parsimonious model. During the dry winter (2000-2001), dunlin exhibited greater use of sites with higher invertebrate density and biomass but also with more adjacent shorebird habitat and closest to a wetland neighbor. However, neither landscape context nor food abundance were important predictors of dunlin use during the wet winter (1999-2000). Use of sites by killdeer was unrelated to either local food abundance or landscape context measures during both winters. Our findings contribute to a growing recognition of the importance of landscape structure to wetland birds and highlight a number of implications for the spatial planning and enhancement of wetlands using a landscape approach.     

吉林省湿地资源价值组成分析

湿地是自然界最富有生物多样性和生态功能最高的生态系统,吉林省湿地生态系统在调节气候、涵养水源、蓄洪防旱、净化水质、保护生物多样性等方面有十分重要的环境功能和生态效益,在促进区域经济发展和维护生态平衡中发挥着重要的作用.然而,随着人口和经济发展压力的增长,湿地面积丧失及生态功能减退的风险加剧,湿地保护与管理面临严峻挑战.为了客观、全面地评价湿地生态系统在吉林省经济发展和生态环境保护中的地位和作用,该研究结合吉林省湿地的特点和质量状况,分析吉林省湿地生态系统服务功能的价值组成,为政府和有管部门湿地保护与管理提供依据.     

绵阳市湿地资源现状及其保护建议

在野外调查及查阅相关资料的基础上,分析了绵阳市湿地资源的特征、保护和管理的现状,阐述了绵阳市湿地资源保护利用中存在的主要问题,并针对湿地保护管理现状提出了相应的保护建议,旨在为绵阳市湿地资源的可持续利用及保护提供参考.调查分析结果显示,绵阳市湿地面积达28 913.84 hm2,以人工湿地和河流湿地为主,湿地类型较为单一且分布不均;湿地生物资源、水资源丰富,景观资源开发潜力大;当前,绵阳市湿地资源保护主要面临着湿地管理涉及部门多、协调难度大、湿地保护法律法规体系不健全、公众的湿地保护意识不强等问题.     

中国湿地的生态问题及保护对策

中国的湿地面积大,类型全,资源十分丰富,但正面临着人类不当开发与过度利用的威胁。在分析中国湿地污染加剧,湿地资源过度利用,盲目围湖造田,湖泊淤积,生物入侵和生物多样性递减等主要生态问题基础上,提出加强立法执法,湿地健康评价,生物修复湿地,建立自然保护区和开展湿地生态游等保护湿地对策。     

根河姑子庙湿地现状及分析

针对根河姑子庙的湿地的自然条件,独特的动植物特征、类型以及在人类生产、生活影响下的现状进行了阐述,并对其保护价值进行了分析评价。     

城市湿地公园植物配置研究——以银川阅海国家湿地公园为例

探讨了湿地植物的配置方法,认为在植物种类选择方面,水面应以水生植物成片种植为主,陆地以乔灌草搭配种植为主;在湿地植物配置方法上,应注重湿地植物的色彩景观营造,并将乔灌草搭配种植,营造陆地空间层次景观。以银川阅海国家湿地公园为例,介绍了公园概况及其植物配置现状,指出其植物配置存在的问题主要是湿地水生植物景观单一,陆地植物选择及配置单一。在此基础上,研究了阅海国家湿地公园的植物种类选择与配置方法,以营造多样性的生物景观序列,构建丰富的景观类型。     

达赉湖乌兰诺尔保护区白琵鹭繁殖生态的研究

2007年4～11月通过样带和定点观察以及对当地保护站的保护人员调查发现,白琵鹭春季于4月初至4月末从南方越冬地迁到乌兰诺尔,成群营巢,营巢在有厚密芦苇、蒲草等植物和附近有灌丛或树木的水域及其附近地区,5月底至7月中为繁殖期,每窝产卵通常3～4枚。秋季于9月末至10月南迁。体大(84 cm)的白色琵鹭,长长的嘴灰色而呈琵琶形,头部裸出部位呈黄色。与冬季黑脸琵鹭相比,其体型较大,脸部黑色少,白色羽毛延伸过嘴基,嘴色较浅。喜泥泞水塘、湖泊或泥滩,在水中缓慢前进,嘴往两旁甩动以寻找食物。一般单独或成小群活动;部分夜行性。