Search for hidden pearl mussel populations at the Russian section of the Baltic Sea

The freshwater pearl mussel Margaritifera margaritifera (L., 1758) is considered to be a critically endangered species. It is important to obtain information on the distribution and status of the surviving populations of the species, but in Russia this work is still problematic due to the size of the country’s territory, combined with the insufficient number of available specialists. “Searching rules” have been proposed to remotely identify potential pearl mussel habitats in rivers. The most important criteria are relating to the lakes found at the rivers’ sources, as well as to the extent of the deforestation along river basins. About 200 watercourses of the Russian section of the Baltic Sea basin were evaluated using these “rules”. As a result, two previously unknown, viable populations were discovered (comprising about 53,000 specimens), while the absence of pearl mussels was made evident among some rivers which were traditionally believed to be their habitats. The obtained data provides an update on the status of pearl mussels in Russian territories located south of the 61 st degree of latitude. There are 10 populations of this species; 4 of them are almost extinct, 6 are relatively numerous but declining. The total number of pearl mussels hardly exceeds 90,000 individuals.     

西北欧全新世中期的Elm Decline研究新进展

在５０００ａ ＢＰ西北欧发生的Ｅｌｍ Ｄｅｃｌｉｎｅ，是全新世突发性环境事件或灾变过程的表现。它在６０年来一直是欧洲环境变迁，考古和＾１４Ｃ年代学界关心的热点论题，对其研究进展作了系统的评述，以了解其研究现状，促进我国全新世环境变迁和人地关系演变科学研究。     

Lg波Q值随震源深度的变化作为地壳本征衰减深度的判据

Lg波的Q_Lg值是描述区域地壳结构及介质衰减特性的重要参数之一,Q_Lg层析成像被广泛应用于地壳衰减结构横向不均匀性的研究中.但是,对Q_Lg在垂直方向上的不均匀性的研究较少.当发现一个地区发生Q_Lg值低时,我们希望进一步了解这种介质衰减深度.本文通过数值模拟合成地震图的方法,通过分析不同震源深度和介质模型计算Q_Lg,判断Lg波发生主要衰减的深度.研究结果显示：（1）当震源深度浅时,上地壳介质衰减对于Lg波Q值的影响明显比下地壳的影响更大.而震源深度深时,两者贡献基本相当;（2）如果上地壳介质衰减强,则随着震源深度的增加,η值逐渐减小;如果下地壳介质衰减强,η值先增大后减小;但如果下地壳存在低速层,则η值持续增大;（3）如果上地壳介质衰减强,则随着震源深度的增加,Q₀逐渐增大;反之如果下地壳介质衰减强,则Q₀逐渐减小.因此,我们可以通过调查某一区域不同深度地震的Lg波衰减规律,来判断这一地区的地壳介质衰减情况.     

新疆塔里木盆地环境变迁与人类文明兴衰初探——以克里雅河地区为例

本文以新疆克里雅河为重点研究,分析了塔里木盆地的环境变迁及其与人类文明兴衰的相关关系,并展示了未来的环境变化。盆地和沙漠的形成与青藏高原的隆起息息相关,第四纪的三次冰期和间冰期的发生,决定了高原和盆地环境变化的序列。其中,中更新世的高原隆升对现代地貌和环境有决定性意义,使沙漠和黄土形成,气候环境总体向旱化方向发展;全新世以来的环境变化或划分出早、中,晚三个不同的干湿期变化。历史时期,人类活动所引起的环境变化与塔里木盆地古丝绸南路文明兴衰紧密相连;近代人类正面临沙漠化扩展,气候变暖的严重挑战。     

Monitoring in the Western Pacific region shows evidence of seagrass decline in line with global trends

Seagrass systems of the Western Pacific region are biodiverse habitats, providing vital services to ecosystems and humans over a vast geographic range. SeagrassNet is a worldwide monitoring program that collects data on seagrass habitats, including the ten locations across the Western Pacific reported here where change at various scales was rapidly detected. Three sites remote from human influence were stable. Seagrasses declined largely due to increased nutrient loading (4 sites) and increased sedimentation (3 sites), the two most common stressors of seagrass worldwide. Two sites experienced near-total loss from of excess sedimentation, followed by partial recovery once sedimentation was reduced. Species shifts were observed at every site with recovering sites colonized by pioneer species. Regulation of watersheds is essential if marine protected areas are to preserve seagrass meadows. Seagrasses in the Western Pacific experience stress due to human impacts despite the vastness of the ocean area and low development pressures.     

精明收缩视角下乡村人居空间变化特征及类型划分——以江苏省常熟市为例

为应对快速城镇化带来的乡村人口收缩的现实,苏南地区提出了一系列引导乡村空间收缩发展的政策。以常熟市为例,基于2005年和2017年乡村人口统计数据和农村居民点矢量数据,定量分析县、镇、村不同尺度下乡村人居空间变迁特征及差异并进行了类型划分。研究发现,常熟市乡村人居空间利用集而不约;乡村人居活动和乡村人居空间的变化特征存在不同尺度的差异性;镇域层面人居空间变化存在城镇化主导型、产业主导型、交通主导型、产业-交通复合主导型、政策主导型等五种类型;城镇化、产业、交通和政策是引起乡村人居空间变化的主要驱动因素。研究结论可以从精明收缩视角为苏南地区乡村人居空间的转型发展提供理论支撑。     

西北内陆平原水资源开发引起的区域水文效应及其对环境的影响

内陆平原水资源主要的赋存形式是河流-含水层系统。无论是开发利用河水,还是开采地下水,都将引起区域性的水文效应——地下水位大幅度波动、泉水衰竭和水质恶化。在水资源开发条件下,人工绿洲与天然绿洲之间的水源分配是彼长此消的,防止生态环境退化的要义在于:从宏观上合理配置水源,并可靠地预测其可能引起的区域水文效应,防患于未然。