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Table 5 Partial correlation coefficients between environmental variables and net ecosystem exchange (NEE), ecosystem respiration (ER) and gross primary productivity (GPP)

From: Drivers of carbon flux in drip irrigation maize fields in northwest China

Carbon flux Year Rn Ta VPD SWC IP LAI
NEE 2014 − 0.47a − 0.320a 0.153 − 0.303a − 0.176b − 0.817a
2015 − 0.390a − 0.470a 0.044 − 0.148 − 0.146 − 0.806a
2016 − 0.625a − 0.666a − 0.407a − 0.266a − 0.175b − 0.497a
2017 − 0.581a − 0.638a − 0.449a − 0.148 − 0.109 − 0.749a
2018 − 0.480a − 0.666a − 0.11 − 0.293a − 0.188b − 0.765a
ER 2014 0.448a 0.395a − 0.037 0.231a − 0.013 0.775a
2015 0.258a 0.733a 0.350a 0.339a 0.034 0.742a
2016 0.313a 0.675a 0.217a 0.111 0.05 0.471a
2017 0.329a 0.770a 0.432a 0.272a 0.114 0.878a
2018 0.338a 0.618a − 0.202b 0.384a 0.154 0.929a
GPP 2014 0.499a 0.365a − 0.132 0.303a 0.137 0.859a
2015 0.376a 0.619a 0.106 0.237a 0.117 0.858a
2016 0.596a 0.748a 0.393a 0.247a 0.154 0.547a
2017 0.523a 0.727a 0.470a 0.204b 0.118 0.845a
2018 0.455a 0.687a 0.001 0.344a 0.186b 0.892a
  1. ER ecosystem respiration, NEE net ecosystem exchange, GPP gross primary productivity, Rn net radiation, Ta air temperature, VPD vapor pressure deficit, SWC soil water content, IP the sum of precipitation and irrigation, LAI leaf area index
  2. aSignificantly correlated at the 0.01 level (bilateral) and b significantly correlated at the 0.05 level (bilateral)