Climate variability, ecological gradient and the Northeast China Transect (NECT)

The Northeast China Transect (NECT), one of the mid-latitude IGBP terrestrial transects, runs in parallel to 43°30′N and ranges from 42° to 46°N and from 106° to 134°E. The major global change gradient is precipitation decreasing gradually from the eastern mountainous region to the middle farmland and then to the western pastoral area. Vegetation along the transect varies gradually from temperate evergreen conifer-deciduous broad leaf mixed forests, deciduous broad leaf forests, woodlands, and shrublands in the east to typical steppes and desert steppes in the west, with agricultural fields, temperate savannas and meadow steppes in the middle. Temporal and spatial climatic variability, especially annual precipitation as well as substantial interannual fluctuations and innerannual changes, is one of the most notable features of the transect. Spatial climatic patterns in the NECT can be defined by three important features: a predominantly north–south gradient in mean annual temperature (MAT) from less than 3°C in the north–west and in the north-east to 3–7°C in the middle; a predominantly west–east gradient in mean annual precipitation (MAP) from 100–300 mm in the west, 300–600 mm in the middle, and 600–1000 mm in the east; and a north–south gradient of mean annual potential evapotranspiration (MAPET) that ranges from 500–600 mm in the north to 600–700 mm in the south. Temporal climatic patterns, the interannual and innerannual variabilities, are also high and this temporal variability is highest in the driest and coldest portions of the region. Human-induced climate changes will result in increases of MAT and MAP, which may in turn influence human use of the ecosystems on the NECT.