Biogenic volatile organic compound emissions from Willow trees

In August 2012, emissions of biogenic volatile organic compounds (BVOCs) from willow (Salix) trees were measured in Lund, southern Sweden. Sweden has more than 16000 ha of short rotation willow plantations for biofuel production and willow trees are suspected to emit substantial amounts of BVOC to the atmosphere. BVOC emission measurements were carried out on two Salix fragilis trees and one Salix phylicifolia tree. The measurements were conducted using a dynamic flow through chamber covered with Teflon film. Salix trees were found to emit large amounts of isoprene. Especially Salix phylicifolia emitted 98% isoprene of total BVOC emission, whereas Salix fragilis trees released about 85% of the total BVOC mass as isoprene. Apart from isoprene, willow trees were found to emit significant amounts of ocimene as well. Emission rates of different BVOCs were found to vary between different individuals of the same species of willow trees as well as between the subspecies of willow trees. Emissions of BVOCs were detected to depend on temperature and photosynthetically active radiation. Isoprene emission potential for Salix phylicifolia was 56.4 µg g-1dw h-1 whereas 16.9 µg g-1dw h-1 and 44.4 µg g-1dw h-1 were measured for the Salix fragilis trees.Popular science Biogenic volatile organic compounds (BVOCs) are a versatile group of non-methane hydrocarbons (chemical compounds made of carbon and hydrogen) emitted by vegetation. The most common BVOCs from plants are some chemical compounds like isoprene, monoterpenes and sesquiterpenes. BVOCs are involved in plant growth, reproduction and defense mechanisms. Besides, BVOC play an important role in tropospheric (lower portion of atmosphere) chemistry and could increase methane’s lifetime, form tropospheric ozone and increase CO2 concentration. In August 2012, emissions of biogenic volatile organic compounds (BVOCs) from willow (Salix) trees were measured in Lund, southern Sweden. For the last 25 years willow has been cultivated as an agricultural crop for bioenergy production and played an important role in Swedish energy sector by producing wood fuel. During this period, more than 16000 ha of short rotation willow plantations have been planted in Sweden. But willow trees are suspected to emit substantial amounts of BVOC to the atmosphere. BVOC emission measurements were carried out on two Salix fragilis trees and one Salix phylicifolia tree. Emission rates of different BVOCs were found to vary between different individuals of the same species of willow trees as well as between the subspecies of willow trees. Emissions of BVOCs were detected to depend on temperature and light intensity. Salix trees were found to emit large amounts of isoprene. Especially Salix phylicifolia emitted 98% isoprene of total BVOC emission, whereas Salix fragilis trees released about 85% of the total BVOC mass as isoprene. But isoprene is an extremely reactive compound and reacts with other atmospheric gases. Isoprene emission potential for Salix phylicifolia was 56.4 µg g-1dw h-1 (microgram per gram dry weight of leaves per hour) whereas 16.9 µg g-1dw h-1 and 44.4 µg g-1dw h-1 were measured for the Salix fragilis trees. Isoprene emission potentials for Willows were higher compared to other vegetation. As isoprene is a highly reactive compound and has great impact on atmosphere and climate system, we should think about alternative bioenergy plants which emit less or no isoprene at all. Non-isoprene emitting poplars are an option for the future biofuel plantation

Exchanges of Biogenic Volatile Organic Compounds Between The Atmosphere and Agricultural Plants/Ecosystems in Controlled and Field Conditions

CROSTVO

Decrease in the photosynthetic performance of temperate grassland species does not lead to a decline in the gross primary production of the ecosystem

Plants, under stressful conditions, can proceed to photosynthetic adjustments in order to acclimatize and alleviate the detrimental impacts on the photosynthetic apparatus. However, it is currently unclear how adjustment of photosynthetic processes under environmental constraints by plants influences CO2 gas exchange at the ecosystem-scale. Over a two-year period, photosynthetic performance of a temperate grassland ecosystem was characterized by conducting frequent chlorophyll fluorescence (ChlF) measurements on three primary grassland species (Lolium perenne L., Taraxacum sp., and Trifolium repens L.). Ecosystem photosynthetic performance was estimated from measurements performed on the three dominant grassland species weighed based on their relative abundance. In addition, monitoring CO2 fluxes was performed by eddy covariance. The highest decrease in photosynthetic performance was detected in summer, when environmental constraints were combined. Dicot species (Taraxacum sp. and T. repens) presented the strongest capacity to up-regulate PSI and exhibited the highest electron transport efficiency under stressful environmental conditions compared with L. perenne. The decline in ecosystem photosynthetic performance did not lead to a reduction in gross primary productivity, likely because increased light energy was available under these conditions. The carbon amounts fixed at light saturation were not influenced by alterations in photosynthetic processes, suggesting photosynthesis was not impaired. Decreased photosynthetic performance was associated with high respiration flux, but both were influenced by temperature. Our study revealed variation in photosynthetic performance of a grassland ecosystem responded to environmental constraints, but alterations in photosynthetic processes appeared to exhibit a negligible influence on ecosystem CO2 fluxes

Impact of abiotic stresses on volatile organic compound production of field crops and grasslands

Abiotic and biotic stresses are known to alter biogenic volatile organic compound (BVOC) emission from plants. With the climate and global change, BVOC emissions are likely to increase. This increase on BVOC emissions could be driven by many environmental parameters like temperature, ozone and light availability for photosynthesis although it is still difficult to predict the impact of some environmental parameters, environmental controls on BVOC emission being species and BVOC-dependent. These BVOC are involved in a wide range of interactions of plants with their environment and these interactions could be affected by the global change. Moreover, BVOC also play a key role in the atmospheric chemistry and may contribute to ozone formation and an increase in methane lifetime, strengthening the global change. Yet, due to technical limitation, there are few studies examining the impact of multiple co-occurring stresses on BVOC emission at the ecosystem level although stress combination is probably more ecologically realistic in field. In the CROSTVOC (for CROp STress VOC) project, the impact of abiotic stresses (e.g. heat, drought, ozone and grazing) on BVOC emission will be investigated for field crops (maize and wheat) and grassland both at the ecosystem and plant scale.CROSTVO