气候变化对鄱阳湖白鹤越冬种群数量变化的影响

分析了1983—2011年鄱阳湖国家级自然保护区越冬白鹤种群数量的年际变化趋势,检验了白鹤种群动态与繁殖地和越冬地气候变化的相关性,气候变量包括月平均气温、月平均最高气温、月平均最低气温和月降水量。研究结果表明,鄱阳湖国家级自然保护区内的白鹤年最大数量平均为(2 130±153)只,呈显著地线性增长趋势(R2=0.454,F=22.441,df=28,P=0.000),但年际波动较大。在越冬地,越冬当年10月、11月、12月的气候变量与白鹤种群数量没有显著的相关性,但越冬初期10月份和越冬后期翌年3月份的气温变量与第4年、第5年、第6年及第7年的白鹤种群数量存在显著的正相关,表明越冬地气候对白鹤种群大小的影响存在时滞效应。越冬初期和末期可能是白鹤补充能量的关键阶段,而且越冬初期的气候可能也与冬季食物的数量或质量相关,因此这两个阶段的适宜气温可能有利于个体尤其是幼鹤的存活,使更多的个体参加繁殖,由于白鹤的性成熟年龄在3—5a,因此其对白鹤种群增长的有利影响会在3a以后表现出来。白鹤种群数量变化与繁殖地繁殖期的降水量没有显著的相关性,而与7月份的气温变量存在显著的正相关。多元线性回归分析结果表明,6a前的10月份平均最低温度、2a前的10月最高温度及5a前的10月平均气温是白鹤种群数量变化的显著预测因子,共同解释了鄱阳湖国家级自然保护区白鹤种群数量变化的74.8%(F=23.807,df=27,P=0.000)。

The effect of climate change on the population fluctuation of the Siberian crane in Poyang Lake

Siberian crane (Grus leucogeranus) is a critically endangered species and has been a bird species under second class protection. In recent years, almost the entire population winters at or very near Poyang Lake, China. Based on the annual maximum population size of Siberian crane wintering in the Poyang Lake National Nature Reserve during 1983 and 2011, we tested the correlation between population size and the climate variables of its wintering and breeding areas. The climate variables included monthly average air temperature, monthly average maximum air temperature, monthly average minimum air temperature and monthly precipitation. The results showed that the annual maximum population size of Siberian crane in the Poyang Lake National Nature Reserve was 2130±153, with a significant linear increase (R²=0.454, F=22.441, df=28, P=0.000) and drastic annual fluctuation. The Pearson correlation analysis results indicated that there were no significant correlations between the population size and the climate variables in the same year. However, the air temperature variables of October and March of the following year during a wintering period showed a significant positive correlation with the population size of the Siberian crane after 3, 4, 5 and 6 years, which indicated that the influence of the wintering area climate on the Siberian crane population size has a time-lag effect. October and March were the early and late periods of winter when the Siberian crane finishes and starts its long-distance migration, respectively. We speculated that early and late winter may be key stages for the crane to replenish energy. The climate in these two months may be correlated with the quantity or quality of winter food, therefore, presumably a suitable temperature in these periods could improve individuals, especially encouraging young crane's survival, allowing more individuals to participate in breeding. Furthermore, the age of sexual maturity of the Siberian crane is usually 3-5 years, therefore, the increase in population numbers caused by the suitable temperature during wintering periods becomes obvious after 3-5 years. As for the climate in breeding areas, there was no significant correlation between Siberian crane population size and precipitation during the breeding period. However, the population size of Siberian crane in the Poyang Lake National Nature Reserve was significantly positively correlated with the air temperature variables in July in its breeding area during the same year. The air temperature in July in breeding areas may be correlated with the food availability for Siberian crane, which is especially important for bringing up young cranes. The stepwise linear regression result showed that the average minimum air temperature in October before the 6th year, the average maximum air temperature in October before the 2nd year, and the average air temperature in October before the 5th year were significant predictive factors for the population size fluctuation of the Siberian crane and accounted for 74.8% of the total population size change (R²=0.748, F=23.807, df=27, P=0.000). The climate-related prediction model for the Siberian crane population size was Y=-18 101+53.150X₁+29.610X₂+22.363X₃, where Y was the annual maximum population size of the Siberian crane in the Poyang Lake National Nature Reserve, X₁ was the average minimum air temperature in October before the 6th year, X₂ was the average maximum air temperature in October before the 2nd year, and X₃ was the average air temperature in October before the 5th year. Only considering the climate factor, the model predicted that the population size of Siberian crane will show an obvious decrease in 2016.