去长期趋势

“Observed increasing water constraint on vegetation growth over the last three decades”

To examine whether the trends of observed productivity-moisture correlations were caused by long-term NVDI trends, we repeated the same analyses of RNDVI-SPEI03 and RNDVI-scPDSI on detrended NDVI time series, using both linear and nonlinear detrending methods. For the linear detrending method, we first tested the linear trend significance for each pixel from 1982 to 2015 and then removed the slope of any significant increasing or decreasing trend (p< 0.05) in each pixel. For non-linear detrend method, we extracted the non-linear trend using interannual moving average method. The non-linear trend was extracted using the decompose function in R.

不理解，为啥去掉长期趋势。。。。这样会对两者关系有影响吗？