Assessment of volatile organic compound emissions from ecosystems of China

Abstract

[1] Isoprene, monoterpene, and other volatile organic compound (VOC) emissions from grasslands, shrublands, forests, and peatlands in China were characterized to estimate their regional magnitudes and to compare these emissions with those from landscapes of North America, Europe, and Africa. Ecological and VOC emission sampling was conducted at 52 sites centered in and around major research stations located in seven different regions of China: Inner Mongolia (temperate), Changbai Mountain (boreal-temperate), Beijing Mountain (temperate), Dinghu Mountain (subtropical), Ailao Mountain (subtropical), Kunming (subtropical), and Xishuangbanna (tropical). Transects were used to sample plant species and growth form composition, leafy (green) biomass, and leaf area in forests representing nearly all the major forest types of China. Leafy biomass was determined using generic algorithms based on tree diameter, canopy structure, and absolute cover. Measurements of VOC emissions were made on 386 of the 541 recorded species using a portable photo-ionization detector method. For 105 species, VOC emissions were also measured using a flow-through leaf cuvette sampling/gas chromatography analysis method. Results indicate that isoprene and monoterpene emissions, as well as leafy biomass, vary systematically along gradients of ecological succession in the same manner found in previous studies in the United States, Canada, and Africa. Applying these results to a regional VOC emissions model, we arrive at a value of 21 Tg C for total annual biogenic VOC emissions from China, compared to 5 Tg C of VOCs released annually from anthropogenic sources there. The isoprene and monoterpene emissions are nearly the same as those reported for Europe, which is comparable in size to China.

Volatile organic compounds from vegetation in southern Yunnan Province, China: Emission rates and some potential regional implications

“…Isoprene emissions from a different leaf on the same tree were over 50 mg C g À1 h À1 by late afternoon, while A was similar for both the late morning (8.5 mmol m À2 s À1 ) and late afternoon (8.0-10.5 mmol m À2 s À1 ) measurements. Three of 21 Ficus species sampled during both wet and dry periods showed higher isoprene emission rates in the dry season by factors of 2-10 compared to wet season values reported in Klinger et al (2002). None of the 21 species showed significantly greater emission in the wet season (Table 1).…”

“…Emission of this compound is sometimes light dependent as well, although this was not determined here. Monoterpene emissions (1.2 mg C g À1 h À1 ) were also detected from F. fistulosa, whereas Klinger et al (2002) observed very little from this species. However, low levels of monoterpenes (primarily a-pinene and limonene) were also detected in the LAN GEMS blanks prior to emission sampling, indicating that GEMS carryover artifacts may have induced a 10-50% positive bias in calculated monoterpene emission rates from this species.…”

“…H. brasiliensis emitted light dependent sabinene, a-pinene, and bpinene from green foliage at rates 2-13% of those observed during the wet season by Klinger et al (2002). The physical appearance and low A values (o2 mmol m À2 s À1 ) exhibited by the rubber tree leaves indicate onset of dry season senescence.…”

“…exceeds primary forest area by at least a factor of two. This usually results in a greater portion of landscape being occupied by early to mid-successional vegetation, which typically have greater BVOC emission potentials (Klinger et al, 2002). The Ficus species examined in this study occupy a range of successional stages in this region and may serve as an indicator of the possible effects of succession and disturbance on BVOC emissions.…”

“…Leaf-level measurements were taken after dissipation of morning fog between approximately 11:00 AM and 5:00 PM from 21 February to 8 March 2003. Klinger et al (2002) performed BVOC enclosure measurements in this region during the latter part (August through early October) of the wet season.…”