扎龙湿地植被覆盖度及其分布结构对水文气象要素的响应

Response of Vegetation Cover and Structure to Meteorological and Hydrologic Factors in Zhalong Wetland

扎龙湿地位于黑龙江省松嫩平原乌裕尔河尾闾,是世界上现存最大的芦苇湿地,也是丹顶鹤等珍稀鸟类重要的繁育场所和栖息地。基于遥感、气象和水文数据,通过像元二分法反演植被覆盖度,分析了扎龙湿地核心区2005-2017年植被覆盖度的时空分布特征,探究径流、降水和气温3项水文气象要素对湿地不同等级植被覆盖度的影响,为科学开展湿地生态需水核算和芦苇植被保护提供参考。结果表明,湿地中高植被覆盖和高植被覆盖区域主要分布于乌裕尔河来水和人工补水形成的河道及周围地区,2005-2017年,中高植被覆盖和高植被覆盖区域面积总体呈增长趋势,于2015年达到峰值,中高和高植被覆盖度区域面积占比达到87.48%,湿地植被生态质量整体改善。乌裕尔河来水及人工补水量与第二年湿地高植被覆盖区域面积呈显著正相关(r=0.555,P<0.05),表明径流量对湿地植被生长具有明显促进作用,特别是对高、中高覆盖度区域面积的增长具有促进作用,且存在年际滞后性;温度升高有利于湿地核心区内植被覆盖度整体的提高,但促进作用并不明显;降水对湿地核心区植被覆盖无明显影响,乌裕尔河来水及人工补水量是影响扎龙湿地核心区植被覆盖度的主要因素。

The Zhalong wetland, located in the lower reaches of the Wuyuer River, is the largest reed wetland in the world and provides an important breeding site and habitat for rare birds such as Grus japonensis. In this study, we explored the temporal and spatial distribution characteristics of vegetation cover in the core zone of Zhalong wetland for the period 2005-2017. The effects of runoff, rainfall and temperature on the proportions of different vegetation covers were analyzed based on meteorological and hydrological data. Vegetation cover was calculated using a dimidiate pixel model based on the normalized difference vegetation index(NDVI) derived from Landsat satellite images of the core area of Zhalong wetland. Meteorological and hydrological data were obtained from the Yian and Longanqiao hydrologic stations, and Pearson correlation analysis was used to analyze the relationship of vegetation cover and meteorological/hydrological factors. Regions of medium-high and high vegetation cover were mostly distributed near the river channel created by water scouring from river inflow and a water diversion project. From 2005 to 2017, the area of medium-high and high vegetation cover regions increased, peaking in 2015 at 87.48% of the core area. Vegetation ecology in Zhalong wetland improved during the investigation period. Input of water from the Wuyuer River had a significant effect on vegetation cover in the core area. The quantity of inflowing water from Wuyuer River, supplemented by water from the water diversion project, was positively associated with high vegetation cover area the following year(r=0.555,P<0.05). Vegetative cover is promoted by high inputs of water from Wuyuer River, but the positive response occurs the year after the increase in water quantity. Higher air temperature also promoted vegetation cover across the entire wetland, but the effect was moderate, and no significant effects of rainfall on vegetation cover were observed. Thus, the primary factor affecting vegetation cover in Zhalong wetland is the volume of water flowing into the wetland from Wuyuer River and the water diversion project. Our results provide a reference for estimating the ecological water flow required to support reed conservation and improve the ecological environment of Zhalong wetland.