互花米草入侵九段沙河口湿地对当地昆虫多样性的影响

为认识因互花米草(Spartinaalterniflora)入侵而给九段沙河口湿地昆虫多样性带来的影响,我们于2004年5月到2005年10月间用网捕和收割植株两种方法对3个典型植物群落中昆虫多样性作了连续调查。研究期间,共采集到昆虫11,300头。经鉴定为97个种,隶属于12目69科。互花米草群落中昆虫的物种数、个体数量以及Shannon-Wiener多样性指数均显著低于土著植物芦苇(Phragmitesaustralis)群落和海三棱藨草(Scirpusmariqueter)群落中的;而Simpson优势度指数较土著植物群落中高。聚类分析结果表明:芦苇与海三棱藨草群落中昆虫群落结构更为相似。互花米草的入侵将可能导致九段沙湿地昆虫多样性的降低和群落结构的改变。     

上海九段沙互花米草种群动态遥感研究

该研究应用遥感技术(RS),结合地理信息系统(GIS)、全球定位系统(GPS)和野外实地调查,对长江口新生沙洲九段沙互花米草(Spartina alterniflora)引种7年来的种群扩散过程进行了调查分析。通过不同时相遥感卫星影像的解译,结合现场调查,分析了外来种互花米草种群自1997年引种后7年期间的种群扩散动态过程。至2004年,互花米草群落已从种植的100 hm²扩展到1 014 hm²。互花米草种群扩散过程可分为3个阶段:1997年的成活定居期;1998至2000年的滞缓期;2000年以后的快速扩散期。互花米草种群的增长速度远高于土著种芦苇(Phragmites australis),显示了互花米草极强的扩散能力、竞争优势和更广的生态幅。研究结果表明,3S技术可应用于植被分类、群落动态和生物入侵动态监测。3S技术具有宏观、快速、动态和综合的优势,可为外来植物的定量调查、分布格局和扩散动态研究提供有效的手段,为滩涂资源生物多样性保护和可持续开发利用提供科学依据。     

基于CA模型的上海九段沙互花米草和芦苇种群扩散动态

基于1997年以来上海九段沙栽种芦苇和互花米草种群扩散格局的多年现场调查与遥感解译分析,并结合3S技术,构建了适合滩涂盐沼植物种群动态的元胞自动机（CA）模型．结果表明：该模型能较好地模拟九段沙上芦苇和互花米草种群扩散的格局和趋势,并验证了互花米草和芦苇的空间抢先占有模型以及锋面状连续扩散格局;土著植物芦苇与外来植物互花米草占据相同的生态位,而互花米草的种群扩散速度是芦苇的3—5倍,随着九段沙的不断淤涨,互花米草种群的快速扩展还将持续．构建的CA模型有助于深入研究外来物种扩散格局与其生态学过程之间的相互关系,对湿地生物多样性保护和资源管理具有重要意义．     

Subaqueous hydrochory: open‐channel hydraulic modelling of non‐buoyant seed movement

1. Subaqueous transport may be a significant dispersal and migration mechanism of non‐buoyant seeds of aquatic and riparian plants, and also secondary transport of seeds once they have lost buoyancy, but the efficiency of this difficult to observe process is largely unexamined. This study uses hydraulic modelling to establish the discharges that move the non‐buoyant seeds of Hymenocallis coronaria as bedload or suspended load; uses stream gauge data to examine the frequency of effective discharges from late June to late September, the seed maturation and germination period; and the potential transport distance of the seeds. 2. The results show that the majority of non‐buoyant seeds of H. coronaria can be transported as bedload through entire modelled stream reaches of lengths 10.8, 18 and 14.4 km with the 0.5 year return interval flow. Bedload apparently has the ability to move seeds over great distances, and may be a substantial factor determining the genetic structure, demography and dynamics of populations and communities. However, prolonged movement of non‐buoyant seeds in suspension appears to be quite rare. 3. Although insect mediated pollination and biochory occur concurrently with bedload transport, bedload transport alone may be sufficient to account for the established gene flow rate of H. coronaria. The potential transport distance of many of the seeds exceed that between populations, and migration may occur more frequently than the species’ generation time. 4. This is the first known study to use open‐channel hydraulic modelling and sediment transport analysis to determine the effectiveness of non‐buoyant seed transport. This method of analysis shows promise for application in other contexts, and especially where flow management is a critical issue for maintenance of rare species.     

Response of soil microbial respiration of tidal wetlands in the Yangtze River Estuary to different artificial disturbances

To clarify the effects of artifical disturbances on the soil microbial respiration (SMR) of existed tidal wetlands, the SMR of three typical areas in Chongming Dongtan and Jiuduansha of the Yangtze River Estuary, China, were evaluated. The causes of the differences in the SMR were also evaluated by analyzing the microbial activity factors and community structure, as well as the physical-chemical characteristics of the different wetland soils. The results showed that the SMR of the existed wetlands in the area of siltation promotion was significantly higher (P < 0.01) than that of the natural area. Different agricultural practices on the inner land also affected the SMR of the tidal wetlands. Overall, the results indicated that the difference in soil microbial characteristics between the artificially disturbed and natural tidal wetlands may be the primary cause of their different SMR. Path analysis indicated that the correlation between soil bacterial diversity and SMR were especially strong. Phylogenetic analysis showed that the bacterial microbial community structure in wetland soil that had been subject to artificial disturbance was changed due to the alteration of the soil physicochemical characteristics, and Pseudomonas sp., Bacillus sp., Uncultured Lactococcus sp. and Streptococcus sp., which have high heterotrophic metabolism or stress tolerance capability, became the dominant bacterial flora in the artificially disturbed wetland soil, ultimately strengthening the SMR. This may be the essential cause of the higher SMR in wetland soils that have been subjected to artificial disturbance, resulting in a low organic carbon accumulation capability.     

Carrying capacity for shorebirds during migratory seasons at the Jiuduansha Wetland, Yangtze River Estuary, China

The carrying capacity of food resources for migrating shorebirds was estimated at a stopover site in the Yangtze River Estuary during the two migratory seasons (spring and autumn). From March to May and September to November 2005, the macrobenthos resources of the Jiuduansha Wetland were investigated, and most of the macrobenthos species in the newly-formed shoal were found to be appropriate food for shorebirds. Biomass measurements showed that the total food resource was about 4541.20 kg AFDW (Ash-Free Dry Weight) in spring and about 2279.64 kg AFDW in autumn. Calculations were also done in the available habitats (intertidal bare mudflat and Scirpus × mariqueter/Scirpus triqueter zones) for the shorebirds. The food resources in the available areas were about 3429.03 kg AFDW in spring and about 1700.92 kg AFDW in autumn. Based on the classification (by lean weight, basic metabolic rate and body length) of the shorebird community, and using the energy depletion model, it was theorized that all of the food resources in the Jiuduansha Wetland could support about 3.5 million shorebirds during spring season and 1.75 million shorebirds during autumn season. The shorebird carrying capacities in terms of the available food were about 2.6 million and 1.3 million birds during the two respective migration seasons. Considering the effect of intake rate, the potential carrying capacity was about 0.13–0.26 million shorebirds in the study area. The main factor restricting use of the area by shorebirds was the scarcity of available habitats for roosting at high tide rather than availability of food supply. We recommend restoring some wading pools in the dense Phragmites australis and Spartina alterniflora zones for shorebirds to roost in, to improve shorebirds’ utilization efficiency of the resources in the Jiuduansha Wetland. __________ Translated from Acta Ecologica Sinica, 2007, 27 (1): 90–96 [译自:生态学报]     

九段沙湿地鸻形目鸟类迁徙季节环境容纳量

根据对九段沙湿地2005年春、秋季食物资源调查来计算迁徙期鸻形目鸟类的环境容纳量。结果表明，九段沙湿地春季食物总量为4541．20kgAFDW（去灰分干重），秋季为2279．64kgAFDW，按鸻形目鸟类有效栖息生境计算，春季鸟类可利用食物资源量为3429．03kgAFDW，秋季为1700．92kgAFDW。通过鸟类体型类群分类（根据去脂净重、基础代谢率和体长）和能量消耗模型可以得出，九段沙湿地迁徙季节总食物量理论上可维持的鸻形目鸟类最大数量约为春季350万只，秋季175万只。按有效生境计算，春季约为260万只，秋季约为130万只。考虑到食物取入率的影响，九段沙湿地实际可容纳约13～26万只鸟类。根据地理信息分析可知，高潮位期有效栖息地的缺乏可能是限制鸟类数量达到估计上限的主要原因，建议在不危害保护区生态安全的前提下，开辟一些隐蔽性强的裸地和浅水塘，以提高鸻形目鸟类对九段沙湿地资源的利用率。     

九段沙湿地植被群落演替与格局变化趋势

长江口新生湿地九段沙由上沙、中沙和下沙三部分组成。2004年对湿地植被群落的演替与格局变化进行了研究。结果表明,九段沙湿地植被群落由芦苇(Phragmites austra-lis)、互花米草(Spartina alterniflora)、海三棱藨草(Scirpus mariqueter)和藨草(S.triqueter)构成。芦苇和互花米草生长于潮滩高程,海三棱藨草和藨草生长于低潮位。1998—2004年,上沙植被覆盖面积年平均约增长17%,中沙22%,下沙38%~39%,植被群落处于快速增长演替状态,这可能与沙洲发育速度有关。由于在中沙、下沙人为种植过外来物种互花米草,其增长速度最快,覆盖面积占九段沙植被总面积的比例从1998年不足1%上升到2004年的22%,地上部分总生物量的年平均增长率为79.79%,互花米草对藨草-海三棱藨草的竞争压力较大。鉴于互花米草对九段沙的影响尚无定论,本文提出了初步的植被管理措施。     

长江口九段沙植物群落研究

长江口九段沙属于发育早期的河口沙洲,植被完全保持着自然演替的早期状况。对九段沙湿地高等植物群落的结构特点及演替特征进行研究。研究结果表明：九段沙湿地植被分布几乎覆盖整个沙岛,生物量丰富。高等植物中多克隆植物,植物群落结构简单,生物多样性低,植被具原生性,群落演替的早期原生特征明显,演替过程在没有引种互花米草之前人为干扰少,互花米草的引种加速了九段沙湿地植被的陆地化演替进程。最后提出保护和开发利用九段沙植被的适应原则。     

长江口九段沙湿地大型底栖动物群落结构的季节变化规律

2004年11月至2005年10月,调查了长江口九段沙湿地大型底栖动物群落特征的季节变化及其土壤因子影响,共调查到大型底栖动物30种,主要由甲壳动物、环节动物、软体动物及昆虫幼体组成,光滑狭口螺(Stenothyra glabra)、堇拟沼螺(Assiminea violacea)、焦河蓝蛤 (Potamocorbula ustulata)、中国绿螂 (Glaucomya chinensis)和谭氏泥蟹(Ilyrplax deschampsi)为优势种,且生物密度四季变化明显.春季大型底栖动物生物密度和生物量处于最高水平,多样性指数最高.夏季密度和生物量最低,物种多样性也较低,分布较不均匀.秋、冬季生物种类数与生物量差异不显著,生物密度冬季较秋季高.春、夏、秋季底栖动物种类数、密度和生物量均未与土壤因子达到显著相关水平.冬季土壤湿度与有机质含量与底栖动物密度显著相关.