Effects of land use on surface–atmosphere exchanges of trace gases and energy in Borneo: comparing fluxes over oil palm plantations and a rainforest

"This paper reports measurements of land–atmosphere fluxes of sensible and latent heat, momentum,. CO2, volatile organic compounds (VOCs),NO,NO2, N2O andO3 over a 30 mhigh rainforest canopy. and a 12 m high oil palm plantation in the same region of Sabah in Borneo between April and July. 2008. The daytime maximum CO2 flux to the two canopies differs by approximately a factor of 2,. 1200 mg C m22 h21 for the oil palmand 700 mg C m22 h21 for the rainforest, with the oil palmplantation. showing a substantially greater quantum efficiency. Total VOCemissions are also larger over the. oil palm than over the rainforest by a factor of 3. Emissions of isoprene from the oil palm canopy represented. 80 per cent of the VOC emissions and exceeded those over the rainforest in similar light and. temperature conditions by on average a factor of 5. Substantial emissions of estragole (1-allyl-4-methoxybenzene). from the oil palm plantation were detected and no trace of this VOC was detected in or. above the rainforest. Deposition velocities for O3 to the rainforest were a factor of 2 larger than over oil. palm. Emissions of nitrous oxidewere larger from the soils of the oil palmplantation than from the soils. of the rainforest by approximately 25 per cent. It is clear from the measurements that the large change. in the species composition generated by replacing rainforest with oil palmleads to profound changes in. the net exchange of most of the trace gases measured, and thus on the chemical composition of the. boundary layer over these surfaces."