Weekly mean θ v at 1 m shows a significant trend of 0.63% per year ( p < .04) and years that develop significant drainage to the sub‐soil (1–5 m) provides a critical moisture reserve that maintains the gas exchange of the evergreen Eucalyptus / Corymbia tree species through the dry season (Figure 5b,c ), as has been observed by previous seasonal measures of tree transpiration (Hutley et al., 2000 ; O'Grady et al., 1999 ).
A positive trend in GPP and NEE could be related to woody thickening or encroachment that is being observed across savannas and rangelands, defined as increasing density of trees and woody shrubs (Stevens et al., 2016 ).
This finding differed from the observations, where the ecosystem‐scale GPP trend originated from a strong trend in the dry season (Table 3 ) with no trends evident in the wet season, suggesting a strong tree response.
With a strong trend in GPP and a weak trend in LE, WUE increased at Howard Springs, a result consistent with observed stand‐scale predictions and global modelling of WUE (Cheng et al., 2017 ; Donohue et al., 2013 ; Keenan et al., 2013 ; Mastrotheodoros et al., 2017 ; Walker et al., 2021 ; Zhang et al., 2016 ).