Analysis of arable land loss and its impact on rural sustainability in Southern Jiangsu Province of China

Rapid urbanization and industrialization in southern Jiangsu Province have consumed a huge amount of arable land. Through comparative analysis of land cover maps derived from TM images in 1990, 2000 and 2006, we identified the trend of arable land loss. It is found that most arable land is lost to urbanization and rural settlements development. Urban settlements, rural settlements, and industrial park-mine-transport land increased, respectively, by 87 997 ha (174.65%), 81 041 ha (104.52%), and 12 692 ha (397.99%) from 1990 to 2006. Most of the source (e.g., change from) land covers are rice paddy fields and dryland. These two covers contributed to newly urbanized areas by 37.12% and 73.52% during 1990-2000, and 46.39% and 38.86% during 2000-2006. However, the loss of arable land is weakly correlated with ecological service value, per capita net income of farmers, but positively with grain yield for some counties. Most areas in the study site have a low arable land depletion rate and a high potential for sustainable development. More attention should be directed at those counties that have a high depletion rate but a low potential for sustainable development. Rural settlements should be controlled and rationalized through legislative measures to achieve harmonious development between urban and rural areas, and sustainable development for rural areas with a minimal impact on the ecoenvironment. (C) 2009 Elsevier Ltd. All rights reserved.

用氟里昴（freon）示踪棉兰老（Mindanao）岛以东海域海洋环流

菲律宾群岛以东的西太平洋赤道和热带海域以存在活跃和复杂的近表面环流而著称。北赤道流（North equatorial current）由东向西不断强化，当到达菲律宾群岛沿岸时，由于受菲律宾群岛的阻挡和β效应，海水在西边界堆积，在西边界形成两支强的西边界流，一支向北形成黑潮（Kuroshio current），一支向南形成棉兰老流（Mindanao current）。这两支西边界流对太平洋的热量重新分配将起着重要的作用。南下的棉兰老流到达棉兰老岛东南海域时，一部分成为印度尼西亚贯穿流（Indonesian throughflow），大部分转向东和苏拉威西海出来的海水及南赤道流（South equatorial current）越过赤道流进入这海域的海水混合，成为北赤道逆流（North equatorial countercurrent）。从1990年10月获得的水文资料算出本航次东边这条断面的纬向地转流断面图，可以看出，1990年晚秋北赤道汉分布在8°N以北的海域，强度最大的流集中在8～9°N之间相对狭窄的地带。而在76号站（3.41°N，128.76°N）到45号站（7.50°N，129.99°N）这条断面上，北赤道逆流分布在3°N～8°N之间，而强度最大流集中在靠近印度尼西亚的摩尔泰岛的南段，另从本航次获得的棉兰老岛以东海域-100米处动力米高度可以看出，在此海域存在两个气旋型涡旋（Cyclonic eddy）一个中心约在10.2°N，128°N，另一个中心在129°N以东，6.5°N左右的地方。用带~(63)Ni电子捕获检测器（ECD）的气相色谱对西太平洋的一些站在0米、50米、100米、150米、200米、300米等六层海水（有些站8～10层）中的氟里昴浓度进行了测定，发现在大部分站位位于300米以上的海水中氟里昴12浓度皆高于1.0 pmol·l~(-1)。表明表层温度混合层和温跃层之间的氟里昴-12交换的比较强烈，特别是靠近棉兰老岛的地方。用水下100米、200米氟里昴-12浓度等值线地域分布和变化，追踪北赤道流，棉兰老流，北赤道流之间的联系，结果与同一海域的动力米高度的地域分布十分吻合。再通过比较本航次东边这条断面的氟里昴-12浓度断面图和地转流断面图，我们能清楚地看的到，西向流区对应着高浓度的氟里昴-12分布，特别是在8～9°N流轴上面存在着氟里昴-12浓度最大值轴，而东向流区对应着相对低浓度的氟里昴-12分布，由以上结果，我们可以得出结论：用氟里昴示踪棉兰老岛以东海域的近表面环流是十分有效的，这样，氟里昴浓度在这海域的分布对今后建立本海域的大洋环流数学模式将能起重要作用。本文根据氟里昴主要来源是北半球的工业区，提出了一个氟里昴输入棉兰老岛以东海域的机制。