JIA-2018-09

2114 WANG Qian-feng et al. Journal of Integrative Agriculture 2018, 17(9): 2107–2117 conductance at the lower part of the canopy was lower than those at the middle and upper parts of the canopy (Zhang et al. 2016). 4.3. Spatial trend characteristics of ET during 2000–2014 The analysis of spatial trend characteristics is a key technology to identify regions with abnormal variation based on the grid scale. In Fig. 6-A, the variation trend demonstrates sheet distribution over all the whole study area, mainly associated with the types of vegetation coverage. Spatial heterogeneity is obvious in the study area, with an increase in ET in the north where the dominated trends occur for the whole study area and a generally downward trend in the south, the trend is consistent with previous studies (Chen et al. 2014; Mo et al. 2017). ET conditions have trended significantly in the northeastern ( P <0.01) and other parts ( P <0.05). The spatial trends and significances of ET for the different types of vegetation were determined and is illustrated in Fig. 6-B–E. There was a widespread decline in the size of cultivated areas (Fig. 6-B), but there was a general increasing trend for the area of forests (Fig. 6-C and E) and grasslands (Fig. 6-D) which would result in reduced water consumption due to human activities and increased water consumption for natural vegetation, this result is is in line with Yang et al. (2012), decreasing trend with 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 140°E 115°E 116°E 117°E 118°E 119°E 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N 42°N 41°N 40°N 39°N 38°N 37°N –20 A B C E D –10 –5 0 5 10 ET (mm yr –1 ) P -value 0.01 0.05 Fig. 6 Trend of evapotranspiration during 2000–2014. A, all the vegetation types. B, farmland. C, broadleaved deciduous forest. D, meandow. E, needlelevaved evergreen forest.