基于不同退耕模式的黄土丘陵区生态环境建设地域分异特征   总被引：2，自引：0，他引：2  

徐勇  马定国  郭腾云 《山地学报》2004,22(4):385-392

退耕是目前国家关于黄土丘陵区生态环境建设的主体措施。在总结"赈济退耕25"、"赈济退耕15"和"梯田退耕"各模式基本特点的基础上,根据土地利用、耕地坡度分级数据、农业人口数据和不同模式生态环境建设标准,分别计算了黄土丘陵区各县(市、区)退耕25°和15°以上坡耕地、新建园地、新修梯田、林草植被恢复的面积以及相应的投资需求额度。在构建并采用生态环境建设指数、政策性补贴资金密度指数和投资需求密度指数等指标,对55个县(市、区)进行类型划分的基础上,分析了黄土丘陵区不同退耕模式下的生态环境建设规模及投资需求地域分异特征。  相似文献   

天津市湿地环境变迁及成因分析   总被引：11，自引：4，他引：11  

曹喆  丁立强  梅鹏蔚 《湿地科学》2004,2(1):74-79

应用3S技术对天津湿地环境进行调查，结合地面采集的历史和现状数据，全面分析了天津湿地环境变迁的自然和人为因素。近一个世纪以来，天津湿地持续减少，天然湿地丧失殆尽，人为因素影响是天津湿地环境变迁的主要原因。城市拓展、经济开发对湿地的占用以及水环境污染是目前湿地面临的主要威胁。保护天津湿地要从搞好城市土地利用规划、调整产业结构、控制水污染、加强湿地保护区管理、尽快制定湿地保护法等方面入手。、  相似文献   

松嫩平原湿地植被对生境干-湿交替的响应   总被引：9，自引：0，他引：9  

田迅  卜兆君  杨允菲  郎惠卿 《湿地科学》2004,2(2):122-127

扎龙湿地和向海湿地水分布存在不均一性，生境中有“干-湿”交替过程。选取“干-湿”界面上沼泽植被与草甸植被共存的群落片断分别设置15个固定样方，生长季内4个月观测结果表明：扎龙湿地和向海湿地生境旱生化时羊草为优势种群，湿生化时芦苇为优势种群，芦苇沼泽群落和羊草草甸群落随生境“干-湿”交替过程相互演替，演替过程既受生境水分波动的影响，又由优势种群内在生物学特性决定。  相似文献   

乌拉苔草光合速率日变化及日同化量   总被引：10，自引：0，他引：10  

徐惠风  刘兴土  徐克章 《湿地科学》2004,2(2):128-132

乌拉苔草沼泽是长白山沟谷湿地的重要类型 ,对其光合速率研究的结果表明 ,乌拉苔草光合速率日变化呈单峰曲线 ,最高峰出现在 1 0时 ,最大值是 1 8.0 7μmol(CO2 ) / (m2 ·s) ;与其该群落伴生的修氏苔草光合速率日变化出现“午休”现象。影响光合速率最大的环境因素是光量子通量密度和叶温 ,呈极显著的正相关 ,其他因素亦多呈正相关 ,环境因子综合影响了乌拉苔草的光合日进程。乌拉苔草光合作用的日总同化量为 1 896 0 1 .2 μmol(CO2 ) /m2 ,是光合能力较强的一种沼泽植物  相似文献   

黑麦草在净化富营养化水的人工湿地生态工程中的作用   总被引：6，自引：0，他引：6  

牛晓音  葛滢  常杰  关保华  徐青山 《湿地科学》2004,2(3):202-207

在人工湿地生态工程中利用黑麦草(Lolium perenne L．)净化污水，得到了较好的效果。结果表明：利用黑麦草在冬春季节的生长，可使亚热带地区人工湿地常年运行，黑麦草在3—4月份对水体就有明显的净化作用。在春夏季节，特别在5月份黑麦草可以获得较高的生物量和N、P的积累量，因而净化贡献最大。从产草量方面考虑，延长黑麦草的生长期能获得较高的生物量；从植物体所含营养物质状况和饲用价值看，增加收割次数的黑麦草N、P含量高，饲用价值高；但从黑麦草对污水中N、P的吸收和积累量方面考虑，收割次数过高则不利于黑麦草对污水的净化及N、P的累积。从上述几方面综合考虑，在黑麦草整个生长期收割次数以2．3次为宜。  相似文献   

Testing links between river patterns and in-channel characteristics using MRPP and ANOVA     

Leif M. Burge   《Geomorphology》2004,63(3-4):115-130

This study tests the assumption that the characteristics of channels within multiple channel rivers are different from those of single channel rivers. Some river restoration approaches propose radical transformation of river patterns, from multiple to single channels, based on the link between river patterns and their in-channel characteristics. Determining the links between river patterns and their in-channel characteristics is complicated by differences in geology, history, climate and discharge among rivers. Furthermore, multiple channel rivers are composed of a mosaic of channel types with a range of in-channel characteristics. This study minimizes these problems by analysing a single river containing neighbouring single and multiple channel patterns with little change in discharge downstream, and by analysing all channel types. The study addressed two objectives: to determine the hydraulic geometry, energy, and sediment mobility characteristics of neighbouring single and multiple channel river patterns, and to test for statistical differences in these characteristics between patterns. The Renous River shows a wandering pattern for 11.5 km, with multiple channels around semipermanent islands and abandoned channels in the flood plain. The river displays a single channel river pattern where channels are confined by their valley walls, upstream and downstream of wandering. The analysis was conducted at three scales. First, the confined single channel and wandering multiple channel patterns were compared (pattern scale). Second, the confined channel pattern was compared to single and multiple channel sections within the wandering pattern (section scale). Third, all channel types were compared (channel type scale). Multi response permutation procedure (MRPP) and analysis of variance (ANOVA) were used to analyze differences between channels. Difference tests found no simple discrimination between the single and multiple channel river patterns of the Renous River. Tests between the single confined and multiple wandering channel patterns found few differences in the in-channel variables. The tests did find differences between multiple channel sections within the wandering pattern and confined single channels; however, a greater number of differences were found between multiple channel and single channel sections within the wandering pattern, highlighting the variability within the wandering pattern. Two groups emerged when all channel types were tested for differences: perennial main-channels containing the thalweg, and ephemeral side-channels. Therefore, side-channels define the in-channel characteristics of wandering rivers because few differences were found among main-channels in either pattern. This analysis suggests that all channel types, not just main-channels, should be investigated to obtain a complete picture of a river pattern prior to any restoration efforts. Engineers must exercise caution when applying the link between river patterns and in-channel characteristics to river restoration efforts.  相似文献   

Channel Bed Mobility Downstream from the Elwha Dams,Washington*     

Molly Pohl 《The Professional geographer》2004,56(3):422-431

Dams are a major source of fragmentation and degradation of rivers. Although substantial research has been conducted on the environmental impacts of large structures in the United States, smaller dams have received less attention. This study evaluated the impact of two dams of moderate size, the Elwha Dams, on the downstream channel system using field data collection at river cross‐sections. The relationship of average boundary shear stress (τ_o) to critical shear stress (τ_cr) served as the basis for determining channel bed material mobility under the two‐year and ten‐year flood events. The channel had the greatest channel bed mobility at the natural cross‐section upstream from the dams, low bed mobility between the structures, and an increase in channel bed mobility in the low gradient river segment near the mouth of the river. Low bed mobility tended to be associated with a lack of channel system complexity, including reduction or loss of bars and low alluvial terraces and their associated young riparian communities. Although these run‐of‐the‐river dams do not modify streamflow greatly, the loss of sediment from the channel system has had a substantial impact on bed mobility and geomorphic and biotic complexity of the Elwha River.  相似文献   

Local provenance in rehabilitation of degraded landscapes: a case study from the Hawkesbury–Nepean catchment, Australia     

Shelley Burgin  J Carson  B Maheshwari 《Area》2005,37(3):324-331

Throughout Australia thousands of volunteers are engaged in Landcare projects that should help rehabilitate degraded landscapes. Many of these projects involve tree planting, but their seed is not necessarily of local provenance. Based on a survey of 85 Landcare groups working in the Hawkesbury–Nepean catchment, data were collected about Landcare groups' knowledge of their seed source, understanding of local provenance and the ecosystem in which they were planting trees and the source of funding for their projects. The findings from the study indicate that about one in five (21%) of the groups surveyed that introduced plant material were not aware of local provenance issues. Indirect indications were that a large number of Landcare groups state-wide may be doing more harm than good to the landscape while trying to rehabilitate it. The data also showed that one in seven (13%) of the groups funded by the Australian Government through the Natural Heritage Trust (NHT) had limited awareness of local provenance issues. With millions of dollars being spent on 'works on the ground', it would be prudent to allocate some funds to document and monitor current Landcare activities, so that the environmental outcomes can be quantified and more effective Landcare policies can be developed in the future.  相似文献   

三江平原毛果苔草湿地CH4排放研究   总被引：5，自引：4，他引：5  

王毅勇  赵志春  宋长春 《湿地科学》2005,3(1):37-41

用密闭不透明箱 -气相色谱法对三江平原毛果苔草湿地进行了近两年的观测研究 ,结果表明 :三江平原毛果苔草湿地全年甲烷排放通量有着明显的季节变化 ,在非冰冻期 (5～ 10月 )CH4通量范围在 4 .6 4～ 2 1.4 8mg·m-2 ·h-1之间 ,平均值为 11.15mg·m-2 ·h-1;冰冻期 (11月到次年 4月 )CH4通量范围在 0 .4 6～ 4 .30mg·m-2 ·h-1之间 ,平均值是 1.6 9mg·m-2 ·h-1。经估算 ,三江平原毛果苔草湿地全年CH4排放总量为 0 .2 32 4Tg/a-1。  相似文献   

南洞庭湖湿地景观文化的结构与特征研究   总被引：1，自引：0，他引：1  

王保忠  何平  安树青  王彩霞  王保明  沈守云 《湿地科学》2005,3(4):241-248

洞庭湖是我国传统的风景名胜区，也是世界上唯一一个由三个国际重要湿地组成的湖泊。作为洞庭湖的最重要组成部分，南洞庭湖国际重要湿地蕴藏着独特的景观文化资源，在长江文明、中华文明乃至世界文明的发展中占有重要地位。根据1999～2005年的调查结果，系统地分析了南洞庭湖湿地景观文化资源的结构特征：①物质文化（稻耕文化、船文化、建筑文化、生产文化、工程文化等）；②精神文化（端午节、民俗艺术、湖乡忌禁、饮食文化、抗洪抢险、植物文化等）；③制度文化（傩文化、楚文化、历史遗迹、湿地文物等）；阐述了湿地文化的起源及地位，重点研究了15种景观文化内容。研究结果表明，南洞庭湖景观文化的本质特征（湿地文化与水文化）具有国际重要湿地背景，典型的湘楚文化特点，突出的湿地特色，独特的世界遗产特点，同时具有高度的真实性及完整性。  相似文献