Contrasting effects of invasive insects and fire on ecosystem water use efficiency
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Biogeosciences. 11(23): 6509-6523.
We used eddy covariance and meteorological measurements to estimate net ecosystem exchange of CO2 (NEE), gross ecosystem production (GEP), evapotranspiration (Et), and ecosystem water use efficiency (WUEe; calculated as GEP / Et during dry canopy conditions) in three upland forests in the New Jersey Pinelands, USA, that were defoliated by gypsy moth (Lymantria dispar L.) or burned using prescribed fire. Before disturbance, half-hourly daytime NEE during full sunlight conditions, daily GEP, and daily WUEe during the summer months were greater at the oakdominated stand compared to the mixed or pine-dominated stands. Both defoliation by gypsy moth and prescribed burning reduced stand leaf area and nitrogen mass in foliage. During complete defoliation in 2007 at the oak stand, NEE during full sunlight conditions and daily GEP during the summer averaged only 14 and 35% of pre-disturbance values. Midday NEE and daily GEP then averaged 58 and 85%, and 71 and 78% of pre-defoliation values 1 and 2 years following complete defoliation, respectively. Prescribed fires conducted in the dormant season at the mixed and pinedominated stands reduced NEE during full sunlight conditions and daily GEP during the following summer to 57 and 68%, and 79 and 82% of pre-disturbance values, respectively.
Clark, K.L.; Skowronski, N.S.; Gallagher, M.R.; Renninger, H.; Schäfer, K.V.R. 2014. Contrasting effects of invasive insects and fire on ecosystem water use efficiency. Biogeosciences. 11(23): 6509-6523. https://doi.org/10.5194/bg-11-6509-2014.