河漫滩湿地生态阈值——以二卡自然保护区为例

An investigation of the safety threshold of a floodplain wetland:a case study of the Er-Ka Nature Reserve,China

以典型河漫滩湿地———二卡自然保护区为研究区域,进行生态阈值研究。根据湿地补给河流———海拉尔河的月均流量频率分布特征,选取58.72 m3/s(P=74.6%)、119.26 m3/s(P=44.4%)、190.35 m3/s(P=23.8%)分别代表河流的低、中、高径流期,分析各径流期湿地分布特征。结果表明,低、中径流期内草本沼泽及盐化沼泽所占比例较高,而高径流期则以季节性河流湿地及湖泊湿地为主。低径流期内,作为湿地中心区的湖泊湿地景观破碎度出现一个较明显的跃变,由中径流期的0.57增加到1.37。此时的湿地状态可近似的作为区域的生态阈值,即维持湿地面积占全区域面积的43.03%。而中、高径流期湿地面积比例可近似作为保护区湿地面积的适宜值和理想值,分别为53.66%和69.53%。其研究结果为二卡自然保护区的管理及保护提供支持,并为河漫滩湿地研究提供思路。

We studied the safety threshold of an ecosystem in the Er-Ka Nature Reserve in the Inner Mongolia Autonomous Region of China, a typical floodplain wetland supplied by the Hai-La-Er River. Because information on the Er-Ka Nature Reserve is scarce owing to a lack of research done in the area, the safety threshold of the ecosystem is difficult to ascertain through traditional ecological methods. However, the floodplain wetland was closely associated with the river hydrology, and information on the river hydrology is abundant. It was therefore possible to study the safety threshold of the ecosystem by analyzing the relationship between the Er-Ka Nature Reserve and the Hai-La-Er River, using both ecological and hydrologic methods. The flow of the Hai-La-Er River was measured by obtaining 250 flow values every year from May to September from 1961 to 2010. From the data, three periods were selected to represent the low flow, middle flow, and flood periods, with runoffs of 58.72 m3/s （P=74.6%）, 119.26 m3/s （P=44.4%）, and 190.35m3/s （P=74.6%）, respectively. The wetland status in the Er-Ka Nature Reserve during these three periods was studied using satellite images. Results demonstrate that the wetland area in the Er-Ka Nature Reserve was 2797.5 hmz at the end of the low flow period. The majority of the area comprises herbaceous swampland （50.31%） and salinization swampland （24.44%）. At the end of the middle flow period, the wetland area was 3488.3 hm2, of which the temporary river wetland, herbaceous swampland, and salinization swampland made up 28.40%, 25.14%, and 28.31%, respectively. At the end of the flood period, the wetland area was4522.0 hm2, 52.3% of which was temporary river wetland. Lake wetlands, the core areas of the Er-Ka Nature Reserve, were only 47.3 hm2 at the end of the low flow period, far less than the area they covered during the middle flow period （259.2 hm2）, and in the flood period （2365.0 hm2）. Additionally, the degree of fragmentation of the lake wetland was 1.37 in the low flow period, which is much higher than that in the middle flow period （0.57） and in the flood period （ 0. 62）. These findings indicate that the wetland status of the Er-Ka Nature Reserve was unstable at the end of the low flow period. Thus, the status of the wetland at the end of the low flow period could be regarded to be approximately the safety threshold of the ecosystem, at which point the ratio of wetland area to the Er-Ka Nature Reserve area was above 43.03%, while the ratios at the end of the middle flow （53.66%） and flood （69.56%） periods may be acceptable wetland to reserve area ratios. This study can provide support for the management and protection of the Er-Ka Nature Reserve, and can provide a reference for future floodplain studies.