上海市环境变化对鸟类的影响

【作者】 蔡音亭；

【导师】 马志军；

【作者基本信息】 复旦大学 ， 生态学， 2011， 硕士

【摘要】 上海市有着丰富的鸟类多样性。作为我国东部人口密集的国际化大都市,经济的高速发展给上海的自然环境和生物多样性带来了巨大压力。大量研究表明,在最近二十多年,人类活动所带来的土地利用改变、外来生物入侵等造成上海市鸟类栖息环境发生了剧烈变化,气候变化也可能给上海市的鸟类群落带来影响。本研究通过大量的野外调查,结合历史整理资料和标本查阅,研究了从上世纪八十代到本世纪初上海市鸟类种类的变化情况及气候变化可能对其产生的影响,分析了上海市主要水鸟类群数量变化的原因,并以白头鹤(Grus monacha)为例,探讨了环境变化对鸟类栖息地利用的影响,以期为制定长期的上海市鸟类保护对策提供科学依据。本研究的主要结论如下：1.从二十世纪初至今,上海市有记录的鸟类共计20目70科436种,其中上海在二十世纪二十年代至九十年代初共记录到鸟类386种。2000年至今在上海市记录到的鸟类有370种。与二十世纪九十年代初的鸟类记录相比,上海新增鸟类新记录52种,但67种在历史上有记录的鸟类在近年没有记录到。对上海市气温和鸟类多样性变化情况分析,结果发现过去30年间上海市年均温和冬季气温增温现象明显。在上海市近年来的鸟类新记录中,尽管有大量鸟类可能是历史调查遗漏的种类,但从南方地区扩散而来的鸟类种类数显著多于从北方地区扩散而来的鸟类种类数。这表明气候变暖影响着上海市的鸟类组成,一些南方分布的种类更容易扩散到上海。因此,气候变化可能是造成上海记录到的鸟类种类发生变化的原因。另外,观鸟活动的开展也大大提高了发现鸟类新记录的机会。2.对上海市近二十年来数量有明显变化的53种水鸟的数量变化趋势与水鸟居留型、栖息地特征以及所属的生态类群之间关系的分析表明,包含水鸟的栖息地类型和水鸟的留居型两个自变量的模型(把雁鸭类当作自然湿地和人工湿地均为其主要栖息地的水鸟类群)或者包含栖息地类型一个自变量的模型(把雁鸭类的当作仅依赖自然湿地的水鸟类群)是解释水鸟数量变化的最佳模型。因此,栖息地变化是造成上海市水鸟数量变化的主要原因。近二十年来,对自然湿地有较强依赖性的鸟类的数量明显下降,这可能与上海市自然湿地的快速丧失和退化有直接关系；以人工湿地为主要栖息地的水鸟的数量有上升趋势,这可能与人工湿地(特别是水产养殖塘)面积的增加有关。由于不同水鸟类群对栖息地利用具有特异性,上海市应加强对自然湿地的保护以维持水鸟的种群数量。3.海三棱藨草(Scirpus mariqueter)球茎是白头鹤在冬季的主要食物。暴露在地表的海三棱藨草球茎的密度在11月有所增加,但随后逐渐下降。球茎密度在冬季早期显著高于冬季晚期,这显示鹤的可利用食物资源在冬季期间下降。潮汐活动也对暴露球茎的数量有影响,在大潮期间比两次大潮之间的其它时段发现了更多的暴露球茎。为了应对越冬期自然食物资源海三棱藨草球茎的大量减少,白头鹤改变了其在越冬期的觅食场所和食物类型,由原来整个冬季主要在海三棱藨草外带取食海三棱藨草球茎,变为越冬前期、中前期和后期取在滩涂食球茎,而越冬期的中末期在收获后的稻田取食散落的稻粒或在麦田中取食新长出的麦苗。白头鹤在冬季中期的农田中4分钟内的取食成功率显著高于任何时期在潮间带的取食成功率(早期滩涂：18.2±6.3%；中期滩涂：21.8±15.0%；晚期滩涂：25.9±14.7%；中期农田：54.1%±12.6%),然而白头鹤在农田中受到干扰的频率远高于在滩涂中的(农田中每小时1.41次,潮间带每小时0.27次)。白头鹤的觅食地选择可能是提高觅食效率和避免干扰之间的权衡。滩涂上放牧会造成海三棱藨草球茎的数量减少,重量下降,加剧了由于互花米草(Spartina alterniflora)扩散所导致的大面积海三棱藨草消失给白头鹤带来的不利影响。应当采取措施恢复鹤群的自然生境,减少在潮间带的放牧活动,并对收获后的稻田制定合理的管理措施,减少人类活动干扰。更多还原

【Abstract】 Shanghai is rich in bird diversity. As a densely populated international metropolis in eastern China, rapid economic development of Shanghai has added tremendous pressure on its natural environment. Many studies indicate that in the last twenty years, land use change, invasive alien species and other local environment alteration introduced by human activities have lead to dramatic changes of bird habitats status in Shanghai, while global climate change might also bring impact to bird community. Through the integration of field survey, specimen inspection and literature review, this study investigated changes of bird species in Shanghai from 1980s to the first decade of 21st century, discussed the causality of changes in birds numbers and potential impact of climate change. Hooded Crane(Grus monacha)was chose as a case study to explore bird adaptation under environmental changes, and to provide scientific basis for bird conservation policy in Shanghai.The main conclusions of this study are as follows:1. A total of 436 bird species, belonging to 20 orders and 58 families, have been recorded in Shanghai since early 20 century. Since 2000, there have been 370 bird species recorded. Comparing with the bird records in the early 1990s, there are 52 species of new records while 67 species of historical records were absent. Results from analysis into changes of air temperature and birds diversity of Shanghai in the last thirty years showed that the annual mean temperature and winter mean temperature had significantly increased, while in the newly-recorded birds, species number of birds spread from south was significantly larger than those from north, although many new records actually might be missing species in historical investigation. This showed the impact of climate warming on the composition of birds in Shanghai, which made species with southern distribution easier to spread into Shanghai. Therefore climate change and environmental alternation might be one of the reasons for the change of bird species change. Moreover, bird watching increased the opportunity of discovery of new records. Bird watching records of birdwatchers provide important references for understanding the current status and dynamics of bird diversity.2. Logistic regression analyses were employed to investigate the relationship of the population trends of 53 species of waterbirds that showed significant changes with their habitat characteristics, residential status, and ecological guild. The results showed that the best-fit model to explain waterbirds population trends is the model using habitat type and residential status as two independent variables (Anatidae treated as a waterbirds group whose major habitat type including both natural and artificial wetlands), or the single independent variable model only using habitat type (Anatidae treated as a waterbirds group that only depends on natural wetlands). The waterbirds population trends were mainly caused by habitat alterations. Birds strongly depended on natural wetlands showed significant population decline, which might be directly caused by the loss and degradation of natural wetlands in Shanghai in the last 20 years. On the other hand, waterbirds populations using artificial wetlands as major habitats showed increasing trends, which could be probably related to the raising area of artificial wetlands (especially aquaculture ponds). Since different groups of waterbirds have specified habitat use, the Shanghai government should intensify conservation on natural wetlands to maintain waterbird populations3. The corms of sea-bulrush(Scirpusmariqueter) are the main natural food resurces of hooded crane at Chongming Dongtan. Exposed corm density increased slightly during November, but then declined as winter progress. The increased corm density in early winter than late winter demonstrated a declining trend of food resource availability during wintering period. Tidal activity also showed a strong effect on the abundance of exposed sea-bulrush corms, more corms were found during spring tide than any other period between two succeeding spring tide. Hooded crane changed its foraging site and food type during wintering in response to the tremendous declining of its natural food-corms of sea-bulrush from foraging corms at outer sea-bulrush zone during the whole wintering period, to foraging corms at mudflat during early, early-middle and late period of wintering, and foraging rice panicles and wheat seedlings in the cultivated farmland at late-middle stage of wintering. Feeding success within 4 minutes in farmland during mid-winter was significantly higher than those in intertidal flat during any period (early period, mudflat:18.2%±6.3%; middle period, mudflat:21.8%±15.0%; late period, mudflat: 25.9%±14.7%; middle period, farmland:54.1%±12.6%, Kruskal-Wallis Test-χ2= 60.5, df=3,p<0.001), but the disturbance frequency to hooded crane was also much higher in farmland than that in mudflat (farmland:1.41 h"’;mudflat:0.27 h-1). Thus the foraging site choosing behavior of hooded crane could be a result from the trade-off of demands between raising feeding efficiency and avoiding disturbance.Grazing on the tidal flat caused declining of area-based corm production in sea-bulrush communities, which reinforced the negative impact of large-area sea-bulrush vanishing caused by the spread of Smooth Cordgrass (Spartina alterniflora)on hooded crane. Actions like grazing reducing at intertidal zone should be established to restore natural habitat for cranes, and sound management measures should also be developed for rice paddies after harvesting to reduce disturbance from human activities更多还原