1981-2001年珠穆朗玛峰自然保护区植被变化

Based on the NOAA AVHRR-NDVI data from 1981 to 2001, the digitalized China Vegetation Map （1：1,000,000）, DEM, temperature and precipitation data, and field investigation, the spatial patterns and vertical characteristics of natural vegetation changes and their influencing factors in the Mt. Qomolangma Nature Reserve have been studied. The results show that： （1） There is remarkable spatial difference of natural vegetation changes in the Mt. Qomolangma Nature Reserve and stability is the most common status. There are 5.04% of the whole area being seriously degraded, 13.19% slightly degraded, 26.39% slightly improved, 0.97% significantly improved and 54.41% keeping stable. The seriously and slightly degraded areas, which mostly lie in the south of the reserve, are along the national boundaries. The areas of improved vegetation lie in the north of the reserve and the south side of the Yarlung Zangbo River. The stable areas lie between the improved and degraded areas. Degradation decreases with elevation. （2） Degeneration in the Mt. Qomolangma Nature Reserve mostly affects shrubs, needle-leaved forests and mixed forests. （3） The temperature change affects the natural vegetation changes spatially while the integration of temperature changes, slopes and aspects affects the natural vegetation change along the altitude gradients. （4） It is the overuse of resources that leads to the vegetation degeneration in some parts of the Mt. Qomolangma Nature Reserve.     

Excessive reliance on afforestation in China's arid and semi-arid regions: Lessons in ecological restoration

Afforestation is a primary tool for controlling desertification and soil erosion in China. Large-scale afforestation, however, has complex and poorly understood consequences for the structure and composition of future ecosystems. Here, we discuss the potential links between China's historical large-scale afforestation practices and the program's effects on environmental restoration in arid and semi-arid regions in northern China based on a review of data from published papers, and offer recommendations to overcome the shortcomings of current environmental policy. Although afforestation is potentially an important approach for environmental restoration, current Chinese policy has not been tailored to local environmental conditions, leading to the use of inappropriate species and an overemphasis on tree and shrub planting, thereby compromising the ability to achieve environmental policy goals. China's huge investment to increase forest cover seems likely to exacerbate environmental degradation in environmentally fragile areas because it has ignored climate, pedological, hydrological, and landscape factors that would make a site unsuitable for afforestation. This has, in many cases, led to the deterioration of soil ecosystems and decreased vegetation cover, and has exacerbated water shortages. Large-scale and long-term research is urgently needed to provide information that supports a more effective and flexible environmental restoration policy.     

太湖藻源性颗粒物分解过程中氨基酸的变化特征

在实验条件下研究了高浓度蓝藻堆积后水体中的藻源性颗粒物中氨基酸的分解速率、分解量和氨基酸态氮形态的变化情况.在自然光照组中,颗粒态氨基酸(PAA)的浓度从实验前的0.46 mmol/L降至实验后的0.30 mmol/L;而在无光分解组中PAA从0.44 mmol/L降至0.06 mmol/L.两种处理下PAA的降解速率常数分别为0.03916和0.17424 d~(-1).溶解态氨基酸(DAA)在分解过程中浓度比较低,随时间的变化表现出先增大后减小的趋势,在两种不同的处理下,最大值分别为10.94和7.94μmol/L,21 d后减小到与实验开始时持平,甚至低于初始值.实验初期,PAA所占比例高达74%~80%,但迅速被分解转化为DAA和铵态氮(NH_4~+-N),随着实验的进行NH_4~+-N又逐渐转化为硝态氮,其中无光分解组中的分解更为彻底,而自然光照组中PAA分解量小于无光分解组.实验结果表明,氨基酸作为水体中浮游植物的潜在氮源,可以被分解为水华过程中藻类所需的NH_4~+-N,对水华的维持具有一定的促进作用.     

汉江中下游水华防控生态调度研究

汉江中下游1992-2021年冬春季节共计暴发了十余次大规模水华事件,水生态安全和饮用水安全频繁受到威胁.基于历次水华发生情况,分析总结了汉江中下游水华特征和暴发成因,根据水华与水文过程响应关系研究提出了抑制水华的关键指标及其调控阈值,构建了汉江中下游水利工程联合生态调度方案,明确了抑制水华的生态调度方式和调度持续时间...     

Assessment of the Present State and Future Fate of River Saraswati,India: Water Quality Indices and Forecast Models as Diagnostic and Management Tools

Water quality assessment is key to the conservation and management of rivers. River Saraswati, a distributary of the river Ganga, serves as a lifeline to many villages in the district Hooghly in West Bengal, India. As the river is gradually dying due to diverse man-made pollution, ten water quality parameters in two sampling spots (PR-1 and PR-2) in the river are monitored month-wise from March 2017 to February 2020,  and these are compared with those from a reference pond. The water quality index (WQI) is determined for the two riverine spots and the reference pond based on the Canadian Council of Ministers of Environment WQI (CCMEWQI) and weighted arithmetic WQI, respectively. In addition to actual observations, three different forecasting methods, exponential smoothing, autoregressive integrated moving average, and artificial neural network, are used to predict WQI for the next two years. This study indicates that free CO₂, dissolved oxygen, and turbidity are the key parameters to evaluate this river's anthropogenic stress and health. The actual and forecasted results reflect the precipitous degradation of CCMEWQI in PR-2. Therefore, the immediate intervention of all stakeholders is required to adopt an integrated and comprehensive river management plan to save the river from utter obliteration.     

岩溶山区不同植被群落土壤生态系统特性研究

自然植被演替成为次生植被、人工林或人工开垦利用后,岩溶山地土壤物理性能退化;沙化现象明显;坡耕地土壤长时间持水供水性能、抗旱性能降低;土壤种子库中草本种子比例大,木本植物种子少,土壤种子库退化更严重。研究区土壤有机质和全N受植被类型和土地利用强度影响明显,坡耕地土壤有机质较林草地系统低,退耕还林还草后,土壤有机质含量稳定增加。与自然植被相比,人工林、次生林系统土壤有机质含量仍较低。从弃耕地→灌草坡→次生林地的演替过程中,土壤种子库生态优势度呈降低趋势,物种丰富度和多样性增加。研究结果认为,岩溶生态系统土地退化的实质是土壤作为水库、养分库和土壤种子库功能的差异退化。     

与微囊藻胞外多糖降解相关的微生物菌群分析

从铜绿微囊藻培养液中提取胞外多糖,化学分析显示其为含8.3%蛋白质的酸性杂多糖.以胞外多糖为碳源接种自然水体的菌群进行富集培养,分析胞外多糖的微生物降解过程及降解菌的组成.结果表明,接种太湖水华期微生物富集菌群后,多糖立即开始被降解,大约在18d后多糖降解过程显著减慢,37d后仍有一部分多糖未能被降解.这些结果说明在自然界中微囊藻胞外多糖是可以被微生物降解的.比较不同水体的菌群对多糖的降解能力后显示,降解菌群只存在于微囊藻水华暴发的阶段.变性梯度凝胶电泳(DGGE)结果显示在整个降解过程中,降解菌群的组成未发生显著变化.对DGGE条带中的DNA片段进行序列分析和系统发育分析表明降解菌群包含以下几类:鞘氨醇单胞菌属(Sphingomonas)3个,褐螺菌属(Phaeospirillum)1个,假单胞菌属(Pseudomonas)1个,红环菌科(Rhodoeyclaceae)1个,Hylemonella(无译名)1个,分枝杆菌属(Mycobacterium)1个.     

海水入侵问题研究综述

在综合有关文献的基础上，分析了国内外海水入侵的研究现状，讨论了海水入侵的概念，认为海水入侵概念的核心是人为超量开采地下淡水造成海水与淡水的水动力平衡破坏；进行了海水入侵的影响因素和成因分析，指出发生海水入侵必须具备一定的水动力条件和水文地质条件；介绍了海水入侵的判别指标和三维动态监测方法，给出了海水入侵的防治措施，并提出了海水入侵有待加强研究的几个方面。     

2004年西北太平洋热带气旋的活动特点与成因研究

对2004年台风汛期西北太平洋热带气旋的活动特点进行研究总结,进而对其成因做了分析。结果指出：2004年西北太平洋热带气旋主要特点是生成总数较常年略偏多,热带气旋生命史普遍较长、：生成时间相对集中、生成源地偏东,转向路径偏多,登陆气旋数多于常年平均值,登陆地段集中且偏北,集中在华东到日本一带。其成因在于：（1）副高面积偏大、强度偏强、位置偏北且西伸脊偏西,同时副高分布形态多呈块状,使得2004年台风的高频活动区向北偏移,直接对华东到日本一带造成威胁,乃至正面登陆影响;（2）澳大利亚高压强大,越赤道气流强,赤道辐合带辐合偏强、位置偏东,造成台风活动比较活跃且源地偏东;（3）西风带环流经向度较常年偏大而且副高多呈块状分布,东西两环副高之间形成的鞍型场有利于台风过此通道北上转向,导致转向台风偏多。     

气温变化对多年冻土斜坡稳定性的影响

受气温变化影响,浅层冻土滑坡失稳涉及水分的固液相态转换,是一个复杂的水热力耦合过程。为揭示气温变化对多年冻土斜坡稳定性的影响,基于冻土水热力耦合数值模型,模拟了2020—2024年青海省多年冻土区斜坡水热力演化过程。研究结果表明：水分迁移速率呈周期性变化,每年5—10月活动层融化程度高,总体积含水率变化趋势显著;夏季多年冻土上限以下的高含冰量土层融化产生厚度约15 cm的富水层,孔隙水压难以消散;4年间多年冻土上限下移10.4 cm,导致活动层和富水层的厚度增大,上覆融土下滑力增大、抗滑力减小,土体抗剪强度进一步下降;活动层土体每年产生数厘米冻胀融沉变形,抗剪强度不断劣化,坡脚处最容易形成薄弱带。