JIA-2018-09

2112 WANG Qian-feng et al. Journal of Integrative Agriculture 2018, 17(9): 2107–2117 consistent with the change for the whole study area, the mean values were higher and there was greater variation of ET in July and August every year, mainly due to the uneven distribution of summer precipitation. As illustrated in Fig. 4, Fig. 4-A and C show larger ET variations than Fig. 4-B and D in low-value months, primarily because the fact that broadleaved and needleleaved forests can effectively take up underground water for plant growth, but crops and grass rely on surface water and heat, resulting in higher spatial variability. A comparison of the four different types of vegetation manifests that herbaceous plants and woody plants show consistent spatial variability in summer, although differing in how they take up water. 4.2. Spatial pattern characteristics of ET during 2000–2014 We analyzed the spatial pattern to quantitatively evaluate spatial heterogeneity and variability of ET by equalizing the ET rate of each year from 2000 to 2014 on a grid 140 120 100 80 60 40 20 0 ET (mm) 140 120 100 80 60 40 20 0 ET (mm) 140 120 100 80 60 40 20 0 ET (mm) 140 120 100 80 60 40 20 0 ET (mm) 12/2000 12/2001 12/2002 12/2003 12/2004 12/2005 12/2006 12/2007 12/2008 12/2009 12/2010 12/2011 12/2012 12/2013 12/2014 Date (mon/yr) A B C D Fig. 4 Variability of evapotranspiration for different types of vegetation during 2000–2014. A, farmland. B, broadleaved deciduous forest. C, meandow. D, needleleaved evergreen forest. White line between gray area and black area represents monthly mean value. Gray area represents monthly mean value+standard deviation; black area represents monthly mean value–standard deviation.