鄱阳湖区灰鹤越冬种群数量与分布动态及其影响因素

1998—2011年,采用地面同步调查法开展了鄱阳湖越冬灰鹤种群监测,并整合1984—2011年鄱阳湖国家级自然保护区历年的越冬灰鹤最大种群数量,分析了鄱阳湖灰鹤越冬种群动态以及影响其数量变化与空间分布的环境因素。结果表明,近13年来鄱阳湖区越冬灰鹤种群平均数量为(2 335±651)只,种群数量呈增长趋势,2011年冬季记录到最大种群数量7 640只。灰鹤越冬种群数量与10月平均最低气温以及10月平均气温存在显著正相关,与10月平均最大风速存在显著负相关,与各月的平均水位没有显著的相关性。每年冬季灰鹤在鄱阳湖呈聚集型分布。大湖池、大莲子湖、三湖、汉池湖、企湖、珠湖、南湖(共青)、大汊湖等8个湖泊是灰鹤的重点活动区,(74.9±5.6)%的越冬灰鹤分布在保护区之外。灰鹤的空间分布与滩地面积存在显著的正相关,与农田面积、人口密度、村庄数量、8月份初级生产力、11月份初级生产力等环境因子存在显著负相关。滩地面积是影响灰鹤空间分布的重要因子,对灰鹤利用频次空间变化的解释率为15.0%,与11月份初级生产力共同解释了灰鹤年平均群体数量空间变化的24.6%。如竞争、小生境结构、干扰等局地尺度的环境要素对灰鹤空间分布的影响研究将有助于更全面地认识鄱阳湖越冬灰鹤种群动态的影响机制。

The dynamics and determinants of population size and spatial distribution of Common Cranes wintering in Poyang Lake

Poyang Lake has been an important wintering site for Common Cranes. In this paper we monitored the dynamics of population size and spatial distribution of Common Cranes wintering in Poyang Lake during 1998-2011 and analyzed the potential determinants of its population dynamics. This was combined with the monitoring record of the annual maximum number of Common Cranes wintering in the Poyang Lake National Nature Reserve during 1984-2011. We illustrated the changing trend of this Common Crane population over a long time scale, and analyzed the impact of climate variation and water level change on the population size dynamics.The results showed that the Common Crane population wintering in Poyang Lake significantly increased from 1998 to 2011, with an average population size of 2335±651 and a maximum of 7640 in the winter of 2011. The exponential curve fit well with the population growth trend (R²=0.808, F=46.234, df=12, P=0.000). The wintering Common Cranes clustered in the Poyang lakes, with the lakes of Dahuchi, Dalianzihu, Sanhu, Hanchihu, Qihu, Zhuhu, Nanhu (gongqing), and Dachahu being the hotspots used by them. On average, (74.9±5.6)% of Common Cranes wintered outside nature reserves.The spatial distribution of the common crane was significantly positively correlated with the areas of mudflat habitat, and was negatively correlated with areas of agricultural land, human density, village areas, and areas of net primary productivity (NPP) in August and November. The mudflat area was an important factor determining the spatial distribution of Common Cranes, which accounted for 15% of the spatial change in occurrence frequency, and when combined with the NPP factor in November, accounted for 24.6% of the spatial change in the average number of Common Cranes. The results mean that there are still factors which may affect the spatial distribution of Common Crane in Poyang lakes which were not assessed, such as competition, the structure of the microhabitat, and human interference, which maybe contribute to a more comprehensive understanding of the impact mechanisms of crane population dynamics wintering in the Poyang Lake.In the Poyang Lake National Nature Reserve, the average annual maximum number of Common Cranes was 276±51 (n=28), which showed a significant linear increase (R²=0.176, F=5.537, df=27, P=0.026), but there was a drastic annual fluctuation. The results of Pearson correlation analysis indicated that the annual maximum population number of Common Cranes wintering in the Poyang Lake National Nature Reserve was significantly positively correlated with the average air temperature in October (r=0.480, P=0.010, n=28) and the average minimum air temperature in October (r=0.480, P=0.010, n=28), and significantly negatively correlated with the average maximum wind speed in October (r=-0.450, P=0.016, n=28).As for the water level of Poyang Lake, no significant correlation was found between the annual maximum population size of Common Cranes in the Poyang Lake National Nature Reserve and the annual minimum water level (r=-0.259, P=0.192, n=27), or the annual maximum water level (r=-0.373, P=0.051, n=28). There was also no significant correlation between the population size and the monthly average water level in the wintering period. Although the water level of Poyang Lake in winter was tested and found to significantly change the structural landscape of Poyang Lake wetland, influencing the availability of habitat and food, the water level of those lakes in the nature reserve was largely determined by the artificial aquaculture discharge time and velocity of the lake, which eliminated the influence of water level in Poyang Lake.