Vegetation Composition,Dynamics, and Management of a Bracken–Grassland and Northern–Dry Forest Ecosystem

We investigated differences in vegetation composition and dynamics for two globally rare ecosystems, bracken–grasslands and northern–dry forests of northern Wisconsin. These ecosystems commonly have been viewed as degraded pine barrens. Bracken–grasslands contained a high dominance of exotic species, low native richness, and no obvious prairie species, suggesting logging-era anthropogenic origins. Differences in cover for common plants among ecosystems were examined using Mann-Whitney U tests of equivalence. Cover of all 8 graminoid species, 4 of 5 Ericaceae and Myricaceae species, and 10 of 17 species of forbs were significantly different between ecosystems. Vegetation changes over a 4-year period were examined through detrended correspondence analysis (DCA) and analysis of variance (ANOVA) repeated measures. DCA analyses of community composition failed to detect significant temporal trends within individual management units, although differences were apparent between ecosystems, regardless of sample year. In addition, no apparent patterns could be detected between years when comparing dominant individual species to management history (prescribed fire). This is contrary to what would be expected for a degraded pine barrens and questions the efficacy of using repeated prescribed fire as a management tool in bracken–grasslands. Methods for conservation and restoration of xeric ecosystems of northern Wisconsin have historically relied heavily on single species (e.g., sharp-tailed grouse) wildlife models, without full consideration of other factors. We suggest that stakeholders involved in these restoration projects examine historic processes and reference conditions prior to formulating management goals. Greater attention to the differentiation and individual management needs of pine barrens, northern–dry forests, and bracken–grasslands is needed.     

Throughfall and stemflow nutrient depositions to soil in a subtropical evergreen broad leaved forest in the Wuyi Mountains

１ＩｎｔｒｏｄｕｃｔｉｏｎＰｒｅｃｉｐｉｔａｔｉｏｎｉｓａｎｉｍｐｏｒｔａｎｔｓｏｕｒｃｅｏｆｎｕｔｒｉｅｎｔｉｎｐｕｔｔｏｆｏｒｅｓｔｅｄｅｃｏｓｙｓｔｅｍｓ，ｅｓｐｅｃｉａｌｙｗｈｅｒｅｒｏｃｋｗｅａｔｈｅｒｉｎｇｉｓｓｌｏｗ（Ｐａｒｋｅｒ，１９...     

元江干热河谷山地植被类型调查与恢复措施

元江干热河谷海拔1200m以下的山地残存的森林植被寥寥无几,山地严重退化,炎热、干燥的气候,旱涝、风沙灾害已成了元江县及周围山地的严重生态问题。通过对元江干热河谷山地植被类型的调查,提出了植被恢复的措施。     

西南地区酸沉降与天气系统的关系

根据1985年和1988年重庆市环境科研监测所和贵州省环境保护科研所观测的雨水酸度资料,我们对该地区的雨水酸度与天气系统的关系进行了分析.1.样品的采集及资料来源观测点均设在楼顶的平台上,共取雨水样品587分,其中重庆地区的大足68分,铜元     

纤维束直接过滤积泥结构的分形分析及其应用

用阳离子型聚丙烯酰（PAM）和聚合铝（PAC）作混凝剂进行了纤维束直接过滤实验，对纤维束上积泥进行了扫描电镜照像及图象分析，得出了积泥孔隙周界曲线的分维数，探讨了分维数与过滤过程的关系，指出了在直接过滤中阳离子型PAM较PAC效果好的原因所在。     

黄河断流的态势、成因与科学对策

从70年代以来，黄河持续断流，且断流情势日趋严重，它不仅发生在下游而且也已在源头出现。滔滔黄河缘何断流?70年代以来流域引黄水量剧增、到达下游水量锐减是主因；输沙需水量巨大和中游工程调节能力不足居次。归根结底，断流是人类活动所致，是人类对黄河水土资源过度利用的结果。流域降水量的丰枯波动对断流影响不大。为了缓解黄河断流，必须调整产业结构，切实提高水资源有效利用率；加强水土保持，增加生态用水量，改善生态环境，减少人黄泥沙；流域外调水是缓解北方省区缺水的重要措施之一，但应从长计议。     

中国近海近岸海域沉积物环境质量

于１９９８年８～１０月，对中国海域沉积物污染进行了监测。结果表明，全国海区沉积物质量总体良好，个别近岸海区受到一定程度的重金属和有机污染，其中大连湾、锦州湾、辽河口、珠江口、北海近岸污染较重。     

酸性沉降物—雨、雾、露酸化与污染组分在重庆地区的分布规律

本文对重庆地区的酸性沉降物-雨、雾、露进行综合分析与研究。从1988～1990年对3025场雨水、93场雾水及13场露水进行了采样、分析，取得了2000多个基础数据，并结合大气环境质量，阐明了雨、雾、露酸化与污染组分在重庆地区的分布规律。     

贵州梵净山自然保护区大气汞的沉降

以铜仁汞矿为点源，研究对梵净山汞的辐射、沉降及流通影响．在海拔５００ｍ的梵净山定位测定，应用Ｍｏｓｂａｇ方法，评价梵净山Ｈｇ的干湿沉降的累积是１１５μｇ·ｍ－２·ａ－１，干沉降大约占总沉降的５０％，通过测定苔藓生物量和Ｈｇ含量估算Ｈｇ的总沉降量为８５０μｇ·ｍ－２·ａ－１，Ｈｇ的流通量平均为２１０μｇ·ｍ－２·ａ－１，Ｈｇ的总沉降占总流通量８０％．Ｈｇ在梵净山沉降累积随高度变化关系明显，海拔２０００ｍ以下时汞的沉降累积量较大，和苔藓植物指示汞含量变化关系相一致．     

黄海西部大气湿沉降(降水)的离子平衡及离子组成研究

对黄海西部的千里岩、青岛的麦岛两个降水采样点１９９７、１９９８两年收集的１１３个降水样品进行了分析,测定了Ｈ＾＋、ＮＨ４＾＋、Ｋ＾＋、Ｎａ＾＋、Ｃａ＾２＋、Ｍｇ＾２＋、Ｆ＾－、Ｃ１＾－、ＮＯ３＾－、ＳＯ４＾２－共１０种离子成分的含量。计算了阴离子和阳离子的浓度总量,考察了∑－／∑＋值,对所８测１０种离子的含量顺序进行了探讨。结果表明：１１０个样品离子平衡（∑－／∑＋在０．７５～１．２５之间）,３个