地理学报 ›› 2015, Vol. 70 ›› Issue (4): 591-603.doi: 10.11821/dlxb201504007

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老挝北部刀耕火种农业变化及植被恢复效应

廖谌婳1,2(), 封志明1(), 李鹏1, 张景华1   

  1. 1. 中国科学院地理科学与资源研究所,北京 100101
    2. 中国科学院大学,北京 100049
  • 收稿日期:2014-05-08 修回日期:2014-12-03 出版日期:2015-04-20 发布日期:2015-06-11
  • 作者简介:

    作者简介:廖谌婳(1987-), 女, 江西吉安人, 博士研究生, 主要从事资源开发与区域发展研究。E-mail: liaoch.12b@igsnrr.ac.cn

  • 基金资助:
    国家自然科学基金项目(41301090, 41271117, 41401625);中国科学院战略科技重点项目(2012SJ008, 2014SJCB006)

Monitoring the spatio-temporal dynamics of swidden agriculture and fallow vegetation recovery using Landsat imagery in northern Laos

Chenhua LIAO1,2(), Zhiming FENG1(), Peng LI1, Jinghua ZHANG1   

  1. 1. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
    2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2014-05-08 Revised:2014-12-03 Online:2015-04-20 Published:2015-06-11
  • Supported by:
    National Natural Science Foundation of China, No.41301090, No.41271117, No.41401625;Key Program for Strategic Science and Technology, Chinese Academy of Sciences, No.2012SJ008, No.2014SJCB006

摘要:

基于“3S”技术研究了老挝北部1990-2011年刀耕火种农业时空变化的总体特征及其不同阶段土地利用变化、刀耕火种农业土地利用强度(利用频率、轮歇周期)及其对休耕期次生林自然恢复过程的影响。结果表明:① 1990-2011年,刀耕火种农业总体上呈增加趋势,由15.38万hm2增加到了23.84万hm2,增幅为54.98%;刀耕火种农业的增加主要发生在波乔省南部和琅勃拉邦省,减少主要发生在丰沙里省。② 刀耕火种农业主要分布在海拔高度500~1500 m、坡度10°~30°的地区,增加主要发生在海拔高度500~800 m、300~500 m和800~1000 m的地区,以及坡度10°~20°和20°~30°的地区。刀耕火种农业的地类转变方向主要是有林地,转入和转出率均高达80%。③ 2000-2011年,老挝北部刀耕火种农业的利用频率约为2~3次,时间间隔1~7年不等;轮歇周期有所缩短,变化幅度不大。④ 老挝北部刀耕火种农业的休耕期次生林自然恢复状况与轮歇周期关系显著,二者相关系数为0.9698。当轮歇周期长达10年时,次生林能够恢复到该区域有林地NDVI的平均水平。

关键词: 刀耕火种农业, 时空变化, 轮歇周期, 利用频率, 植被恢复, 老挝北部

Abstract:

Swidden agriculture is an age-old, prevailing but controversial farming practice in Montane Mainland Southeast Asia (MMSEA). In the uplands of northern Laos, swidden agriculture has become the predominant land use type for centuries. The swidden system has undergone dramatic transformations since the mid-1990s. The debate on the change of swidden cultivation is linked to global critical issues of land use/cover change, biodiversity and climate change. Since the implementation of Reducing Emissions from Deforestation and forest Degradation (REDD) by the United Nations, an increasing attention has been given to swidden agriculture in the humid tropics nationally and internationally. However, very little is known or reported about the explicit spatial information of swidden agriculture and the consequences of the transitions at macroscopic scale. For the purpose of understanding the spatial and temporal dynamics of swidden system, the intensity of swidden use and fallow forest recovery in northern Laos, in this study, the swidden agriculture in 1990, 2002, and 2011 were mapped and delineated with Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper plus (ETM+) imagery (30 m) with a decision tree classification method, followed by the analysis of spatio-temporal changes of swidden agriculture. Then, annual successive TM/ETM+ images during the period 2000-2010 were used to delineate the dynamics of burning phase and cropping phase. Subsequently, the burned pixels derived in 2000 were compared with those in the following years (2001-2011) under ArcGIS 10.0 to investigate the temporal development, land use frequency and swidden cycle with time-series Landsat-based NDVI data. Finally, as the swidden cycle changed from 1 to 11 years, the fallow vegetation recovery process was studied. The results showed that: (1) From 1990-2011, the area of swidden agriculture increased by 54.98%, from 153,800 to 238,400 ha. The increased swidden cultivation were mainly found in Luang Prabang and southern Bokeo; while the decreased parts were mainly in Phongsali. (2) The swidden agriculture mainly increased at the elevations of 500-800 m, 300-500 m and 800-1000 m and on the slopes of 10°-20° and 20°-30°. More than 80% of swidden farming land was transformed from forests. (3) During the period 2000-2011, the frequency of swidden use in northern Laos was about 2 or 3 times. The intervals of any two swidden use phases ranged from 1 to 7 years. In comparison with swidden cycles and the related proportion of swidden farming in the years of 2000, 2003 and 2007, swidden cycles in most parts were shortened. (4) There was a significant correlation between fallow vegetation recovery and swidden cycle, with a correlation coefficient of 0.9698. The NDVI of regenerated vegetation could be equal to the average NDVI value of forest when the swidden cycle reaches 10 years.

Key words: swidden agriculture, spatio-temporal changes, swidden cycle, frequency of swidden use, fallow vegetation recovery, Landsat, Laos