关键词: 长白山, 原始阔叶红松林, 白桦山杨次生林, 地下生物量, 地下碳、氮贮量

Abstract: Yancheng coastal wetland is one of the biggest inter-tidal ecosystems in China, and plays important roles in supporting regional biodiversity and mai ntaining offshore water quality. Owing to the continuous exploitation in recent decades, this wetland has experienced significant changes. To reveal the dynamic changes of this wetland at landscape level, the land use/cover change (LUCC) si nce 1975 was investigated, based on the Landsat remote sensing data in 1975, 199 1, 2002, and 2006. From 1975 to 2006, the natural wetland in Yancheng coastal we tland decreased by 56% (15×105 hm2), while fish pond and farmland increas ed by 892% (82×104 hm2) and 165% (59×104 hm2), respectively. Recla mation and fish pond exploitation were the main forms of LUCC, accounting for 75 % of the total changed area, and natural succession and Spartina spp. invasi on accounted for 11% and 7%, respectively. In the LUCC in Yancheng coastal wetla nd, there were three main transition processes, i.e., intertidal mudflat → Suaeda salsa community → fish pond (farmland), intertidal mudflat → Suaeda salsa  cummunity → Phragmites communis community → fish pond (farmland), and i ntertidal mudflat → Spartina anglica community → fish pond. The large scal e shrinking of natural wetland would further reduce the survival space of wildli fe and exacerbate the offshore water quality, and accordingly, reclamation contr olling and wetland conservation should be strengthened.

Key words: Changbai Mountains, Primitive Korean pine and broad-leaved climax forest, Secondary Populus davidiana and Betula platyphylla forest, Root biomass, Underground C and N storage