1954～2005年三江平原沼泽湿地农田化过程研究

Process of Land Conversion from Marsh into Cropland in the Sanjiang Plain during 1954-2005

作为中国重要的粮食生产基地和淡水沼泽湿地集中分布区,三江平原对于保障国家粮食安全和区域生态安全具有举足轻重的地位。由于人类活动的剧烈影响,1954～2005年期间,三江平原大面积的沼泽湿地已被农田所替代,并引发了一系列环境问题。国内以往的相关研究未能深入揭示区域尺度湿地农田化的过程与规律。基于遥感和地理信息系统技术,集成地形图与遥感影像(Landsat MSS,Landsat TM,CBERS)数据,分析了1954～2005年间三江平原湿地农田化过程及其主要驱动因素。研究结果表明:(1)从1954到2005年,三江平原沼泽湿地面积减少了77.03%;与湿地大面积减少相对应,耕地面积增加了2.5倍,2005年耕地面积占整个三江平原面积的55.14%,成为三江平原的主导景观。1954～1976年和1977～1986年为湿地农田化规模最大的2个阶段,沼泽湿地转化为耕地的面积分别为186.40×104hm2和120.29×104hm2。至2005年,三江平原沼泽湿地农田化过程基本结束,大面积成片的湿地仅存在于几个较大的湿地自然保护区内。1954～2005年期间,三江平原沼泽湿地农田化的面积为258.48×104hm2,为1954年沼泽湿地面积的73.3%。(2)三江平原发生湿地农田化过程的主要自然地理环境背景为:海拔为0～100m,坡度为0°～1°,地貌类型为河漫滩、河流阶地、沼泽洼地、冲积洪积平原和低台地,土壤类型为草甸土、沼泽土和白浆土。(3)1954～2005年间,三江平原地区年平均气温显著升高,增温速率为0.029℃/a。气候变暖为农业开垦提供了有利的前提条件。区域人口大量增加是湿地开垦为农田的最直接和最主要的驱动因素,1959～2005年间三江平原总人口增加了3.13倍,耕地面积与总人口及农业人口之间均存在显著线性相关关系。国家政策对于三江平原沼泽湿地农田化过程具有重要的影响作用。

The Sanjiang Plain, as one of main agricultural bases and the region distributing large - area freshwater marsh, plays an important role in safeguarding national food safety and regional ecological safety. Due to intensive human activities, large area marsh has been substituted by cropland during 1954 -2005. In addition, There are many environmental problems resulted from land use changes above mentioned in the area. Researches concerning could not discover the process and rules of regional land conversion from marsh into cropland. Based on remote sensing and geographic information system technology, in this paper topographic maps and remotely sensed data were integrated, and the process and driving factors of land conversion from marsh into cropland were analyzed during 1954 - 2005. Results showed that, from 1954 to 2005, marsh area decreased by more than 3/4, from 352.59 × 10^4 ha to 95.87 × 10^4 ha. In contrast, cropland increased by 2.3 times, from 171.34 × 10^4 ha in 1954 to 556.88 × 10^4 ha in 2005. In 2005, cropland occupied 51.17% of the total land area, and became the dominant landscape of the Sanjiang Plain. The period 1954 - 1976 and the period 1977 - 1986 were the two stages in ,which land conversion from marsh into cropland happened with the largest scales. In these two periods, land conversion area is 186.40 × 10^4 ha and 120.30 × 10^4 ha, respectively. By 2005, the land conversion process ended basically. Large patches of marsh only distributed in some big wetland nature reserves. During 1954 -2005, the land conversion area from marsh into cropland is 258.48 × 10^4 ha, and is 73.3% of marsh area in 1954. The main natural environmental features in relation to land conversion from marsh into cropland are those positions with elevation of 0 - 100 m, slope gradient of 0°-1°, physiognomies of river buffering area, river terrace, marsh low lands and low terraces, soils of meadow soil, marsh soil and bleaching soil. In the past 50 years, annual average air temperature of the Sanjiang Plain increased obviously, with an increasing rate of 0.029 ℃/a. Climate warming supplied favorable premise conditions for agricultural reclamation （especially the rice planting）. Regional large -scale population increasing was the most important and direct driving force resulting in land conversion from marsh into cropland. In the past decades, total population of the Sanjiang Plain increased by 3.13 times. Statistical cropland areas had good linear relationships with total population and agricultural population. National policy impacted the land conversion from marsh into cropland of Sanjiang Plain to a big extent.