Biogenic volatile organic compound emissions from bamboo species in Japan

Transcription

1 Short Paper Journal of Agricultural Meteorology , 2018 Biogenic volatile organic compound emissions from bamboo species in Japan Motonori OKUMURA a,, Yoshiko KOSUGI b and Akira TANI c a Department of Environmental Research, Research Institute of Environment, Agriculture and Fisheries, Osaka Prefecture, 442 Shakudo Habikino, Osaka , Japan b Graduate School of Agricultural Science, Kyoto University, Kitashirakawa Oiwake-Cho, Sakyo-ku, Kyoto , Japan c Institute for Environmental Sciences, University of Shizuoka, 521 Yada, Suruga-ku, Shizuoka , Japan Abstract Recently, Moso bamboo forests have been expanding in Japan because they were left unmanaged and because of the characteristically fast growth rate of bamboo. In this study, trees of 14 bamboo species in two bamboo forests and an exhibition garden in Japan were screened for biogenic volatile organic compound BVOC emissions by using a leaf cuvette. The screening showed that 12 out of 14 species 86 emitted isoprene at rates of nmol m 2 s 1. No monoterpene and sesquiterpene emitters were identified. Our result indicated that several bamboo species, such as Phyllostachys spp., Semiarundinaria spp., and Bambusa spp., should be categorized as strong isoprene emitters. We also measured the diurnal patterns of isoprene emissions for Phyllostachys heterocycla and Phyllostachys bambusoides in spring and summer, The isoprene emission rates of both species increased on summer days, reaching a maximum level 78.1 nmol m 2 s 1 and 57.6 nmol m 2 s 1, respectively around noon, and were lower in spring <5 nmol m 2 s 1. Our results indicate that the increasing areas of bamboo forest in future could contribute to increasing atmospheric concentrations of ozone and other photochemical oxidants. Key words:bvoc, Hydrocarbon, Isoprene, Ozone, Phyllostachys heterocycla 1. Introduction More than 70 genera of bamboo occur naturally in tropical, subtropical, and temperate regions around the world, from sea level up to 4000 m a.s.l. Gratani et al., Although they are naturally absent in Europe, bamboo species are widely distributed in Asia including Japan, and are one of the familiar plants for eastern Asian people. Bamboo forests have been cultivated for years for the purpose of harvesting bamboo shoots and bamboo materials. However, recently, bamboo forests throughout Japan have been left unmanaged, likely because of the increased use of plastics as a replacement for bamboo stalks and the decrease in Japanese bamboo shoot market prices owing to the import of low-priced bamboo shoots from neighboring countries. A large percentage of Japanese bamboo forests consist of Moso bamboo Phyllostachys pubescens. Having a fast growing rate, unmanaged Moso bamboo have been invading neighboring farming fields and forests and are replacing surrounding vegetation, such as coniferous plantation forests and broad-leaved forests in eastern Asia, including Japan Isagi and Torii, 1998, Taiwan Chiou et al., 2009, and China Song et al., 2011, with an average expansion rate of 1.03 ha year 1 in Japan Shinohara et al., The possible issues posed by the abandoned bamboo forests have been researched from the perspectives of land management and ecosystem service, but there are only a few studies on the effects of these forests on the atmospheric environment. Many plant species emit biogenic volatile organic compounds Received; June 6, Accepted; September 3, Corresponding Author: m.fy7ecs.kyoto@gmail.com DOI: /agrmet.D BVOC, including terpenoids such as isoprene C 5 H 8, monoterpenes C 10 H 16, sesquiterpenes C 15 H 24, and alcohols. Isoprene is estimated to comprise approximately 50 of the annual global emission of BVOC Fuentes et al., Terpenoids are highly reactive with ozone and hydroxyl radicals as compared to most anthropogenic volatile organic compounds, therefore, terpenoids contribute to the formation of ozone and other photochemical oxidants in the lower regions of the atmosphere Peñuelas and Staudt, 2010; Kim et al., Furthermore, BVOC also play important roles in ecological communities and plant development in natural ecosystems Fineschi et al., The review of Kesselmeier and Staudt 1999 on BVOC emitted from plant leaves revealed that some species emit only isoprene or monoterpenes, while some other species emit both isoprene and monoterpenes. In Japan, Quercus serrata and Quercus mongolica var. crispula, which are major broad leaved trees species Shi et al., 2016, have been revealed to be isoprene emitters Tani and Kawawata 2008; Tani et al., 2017 and most coniferous tree species including Pinus densifl ora Yokouchi and Ambe, 1984 and Larix kaempferi Mochizuki et al., 2014 and a broad-leaved tree Quercus phillyraeoides Okumura et al., 2008b are monoterpene emitters. However, BVOC emissions from bamboo species including the species widely grown in Japan have rarely been investigated. In this study, BVOC emissions from leaves of 14 Bamboo species in a bamboo public park and two bamboo forests in Kyoto, Japan, in spring and summer 2015, were measured. We characterized the rate and composition of BVOC emissions from the leaves of all 14 species and evaluated diurnal variations in isoprene emissions from Phyllostachys heterocycla and Phyllostachys bambusoides, which are the major bamboo species in Japan. 40

2 M. Okumura et al. : BVOC Emissions from Bamboos 2. Materials and Methods 2.1 Study site and bamboo species BVOC emission measurements focused on the species of bamboo native to eastern Asia commonly cultivated in Japan 14 species in total from August 2015 to September BVOC emissions were measured in a Moso P. pubescens forest cultivated for bamboo shoots and a Madake P. bambusoides forest cultivated for making bamboo craft, both located in Kameoka, Kyoto Prefecture, Japan N, E. These two species are the two dominant bamboo species in Japan. Additionally, 12 species of bamboo in Kyoto City Rakusai Bamboo Park s exhibition garden Nishikyo-ku, Kyoto city, Kyoto, N, E were evaluated. The 12 bamboo species included Phyllostachys nigra var. henonis, Phyllostachys aurea, Tetragonocalamus quadrangularis, Sinobambusa tootsik, Bambusa oldhamii, Bambusa multiplex, Semiarundinaria fastuosa, Semiarundinaria yashadake, Pseudosasa japonica, Pleioblastus Simonii, Sasa veitchii, and Sasa kurilensis. Measurements were conducted on three sunlit leaves grown from a culm of a plant using a leaf cuvette, in the morning to mid-afternoon. The Moso bamboo and Madake forests are located in the same section of Kameoka. Mean air temperature of 14.6 C and annual precipitation of 2012 mm were recorded in 2015 in the study site. The 1.0-ha Moso bamboo forest has been producing shoots for over five decades. This forest has clay soil and that been fertilized with rapeseed meal at 18.0 ton ha 1 year 1 Tsuruta et al., The distance between the two sites in Kameoka forests and the Rakusai Bamboo Park is approximately 7.5 km. The weather conditions in the latter are nearly the same as those in both forests. In addition to the BVOC screening, in order to investigate potential seasonal fluctuations in isoprene emissions, we performed a detailed time-course analysis of BVOC emissions from plants in the Moso and Madake forests, on a spring day and a summer day in The measurements were taken every two hours between 9 a.m. and 5 p.m.. The isoprene emissions from three leaves grown from a culm of a bamboo plant were measured using the leaf cuvette method. 2.2 Measurement of BVOC emission rate from bamboo leaves Rates of isoprene emission I and net assimilation A, stomatal conductance g s, photosynthetic photon flux density PPFD, and leaf temperatures were measured using a portable photosynthesis system LI-6400; Li-Cor, USA. The system was modified to collect isoprene emitted from a leaf in a cuvette Harley et al., 1997; Pegoraro et al., 2004; Tani and Fushimi, 2005; Okumura et al., 2008a,b. To expose the leaf to sunlight, a natural-light unit was used for the leaf cuvette of the LI-6400 system. For isoprene sampling, the outlet tube from the leaf cuvette was replaced with a Teflon tube. The outlet air flow was divided into two streams by a Teflon T-junction. One stream was reconnected to a builtin infrared gas analyzer IRGA in the cuvette and the other was used as a sampling port for isoprene. The flow rate for sampling isoprene was 130 μmol s 1, and the inflow rate to the cuvette was 500 μmol s 1. The outflow rate was 370 μmol s 1. It was confirmed that the decreased rate of flow into the IRGA did not affect the IRGA output. A buffer box 30 L for air supply to the LI-6400 was placed 10 m apart from the LI-6400 cuvette to avoid any influence of a sudden CO 2 concentration change. The air was drawn from the box and sent through a granular activated-charcoal filter to remove trace contaminants, such as atmospheric BVOC. H 2 O and CO 2 concentrations in the cuvette were not controlled so that these concentrations remained similar to those in the natural environment. A blank measurement indicated that the cuvette and tube did not adsorb or emit isoprene. The rate of isoprene emission I, nmol m 2 s 1 from the leaf was calculated according to equation 1: I ={C out 1- w in - C in} v in LA, 1 1- w out where C in and C out are the isoprene concentrations nmol mol 1 in the inflow and outflow samples, respectively, and w in and w out are the water vapor concentrations mol mol 1 in the inflow and outflow samples, respectively. v in is the flow rate mol s 1 in the cuvette and LA is the enclosed leaf area m 2. To trap BVOC, adsorbents 200 mg Tenax TA and 100 mg Carbotrap b packed into stainless-steel tubes φ 1/4 inch 3.5 inch; PerkinElmer, USA were used. The tubes were preconditioned at 280 C for 10 min to remove BVOC and had been stored at approximately 5 C in the dark. When sampling isoprene in seasons expect spring, air was drawn into the tube using a portable pump MP-Σ30, Shibata, Japan for 5 min at a flow rate of 130 μmol s 1. The isoprene emitted from P. heterocycla and P. bambusoides in spring season were collected for 10 min, because isoprene emissions of leaves was estimated to be low in spring season. The sampling was initiated after values of A and g s became almost constant. The samples were brought to the laboratory promptly after collection and stored again at approximately 5 C in the dark until analysis, to prevent any photochemical reactions. The collected samples were analyzed within 4 weeks. BVOC emissions from leaves were identified and quantified using a gas chromatograph GC-17A, Shimadzu, Japan equipped with a flame ionization detector. Thermal desorption of the samples was conducted with a ATD400 system PerkinElmer. A calibration curve was generated by collecting and analyzing different volumes of isoprene standard gas 1.05 ppmv and 12 monoterpene standard solutions α-pinene, 3-carene, β-pinene, terpinolene, myrcene, camphene, d-limonene, sabinene, γ-terpinene, α-phellandrene, p-cymene, and trans-β-ocimene with absorbents. The monoterpene standards were diluted in methanol HPLC grade, Wako Inc., Japan and added directly to the adsorption tube. 2.3 Emission model The G93 algorithm Guenther et al., 1993 describes the PPFD and leaf temperature dependences of isoprene emission as follows: I =I S C L C T, 2 where I is the isoprene emission rate at given PPFD L, μmol m 2 s 1 and temperature T K, and I S is the basal emission rate at a standard PPFD 1000 μmol m 2 s 1 and temperature T S 303 K. C L and C T are correction terms for light and temperature, respectively. C L is defined as C L = αc L1 L, 3 α 1+ 2 L 2 41

3 S Journal of Agricultural Meteorology 74 1, 2018 where α = and C L1 =1.066 are empirical coefficients, which were determined from the measurement data of four tree species Guenther et al., The coefficient C L1 was determined to become C L equal to 1 at the standard PPFD of 1000 μmol m 2 s 1. C T is defined as exp{c T1 T-T S RT S T} C T =, 4 1+exp{C T2 T-T M RT S T} where R is the gas constant =8.314 J K 1 mol 1. T M is also a constant =314 K, and C T1 =95,000 J mol 1 and C T2 =230,000 J mol 1 are empirical coefficients. Values of I S for individual leaves were calculated using equation 2 and data sets of the measured emission rates of the leaves. 3. Results 3.1 BVOC emissions from leaves of 14 bamboo species Of the bamboo species screened, 12 P. heterocycla, P. bambusoides, P. nigra var. henonis, P. aurea, S. tootsik, B. oldhamii, B. multiplex, S. fastuosa, S. yashadake, P. japonica, P. simonii, and S. kurilensis emitted isoprene at rates I greater than Table 1. List of bamboo species measured in this study. GD stands for ground diameter. species Height m GD mm site Phyllostachys heterocycla Kameoka Phyllostachys bambusoides Kameoka Phyllostachys nigra var. henonis Rakusai bamboo park Phyllostachys aurea Rakusai bamboo park Tetragonocalamus quadrangularis Rakusai bamboo park Sinobambusa tootsik Rakusai bamboo park Bambusa oldhamii Rakusai bamboo park Bambusa multiplex Rakusai bamboo park Semiarundinaria fastuosa Rakusai bamboo park Semiarundinaria yashadake Rakusai bamboo park Pseudosasa japonica Rakusai bamboo park Pleioblastus simonii Rakusai bamboo park Sasa veitchii Rakusai bamboo park Sasa kurilensis Rakusai bamboo park 0.7 nmol m 2 s 1 Table 1 and Table 2. No monoterpene emitter was identified among the bamboo species in this study. The average basal isoprene emission rate Is at 303 K and a PPFD of 1000 μmol m 2 s 1 ranged from 0.7 to 63.9 nmol m 2 s 1 as shown in Table 2. The maximum and minimum Is were measured for B. oldhamii and P. japonica, respectively. When three leaves per bamboo plant were sampled, the standard deviation of the Is for each bamboo was always lower than 25 of the mean. 3.2 Diurnal course of isoprene emission from the leaves of P. heterocycla and P. bambusoides Diurnal course emissions of P. heterocycla and P. bambusoides were measured for three leaves grown from a culm of each bamboo plant on 21 March and 23 August, 28 March and 14 September, 2015, respectively. I, A, g s, PPFD, and leaf temperature T leaf were measured approximately every two hours between 9 a.m. to 5 p.m. Fig. 1. The I values for P. heterocycla on the summer days were Table 2. Isoprene emission rates I, nmol m 2 s 1, mean1sd, photosynthetic rates A, μmol m 2 s 1, and stomatal conductance g s, mmol m 2 s 1 of bamboo species. Measured isoprene emission rates for each PPFD μmol m 2 s 1 and leaf temperature T leaf, C were normalized to basal emission rates I s, nmol m 2 s 1, mean1sd under standard conditions of 30 C T leaf and 1000 μmol m 2 s 1 PPFD using the G93 isoprene algorithm Guenther et al., n.d. stands for not detectable. species I I S A g s T leaf PPFD P. heterocycla P. bambusoides P. nigra var. henonis P. aurea T. quadrangularis n.d. n.d S. tootsik B. oldhamii B. multiplex S. fastuosa S. yashadake P. japonica P. simonii S. veitchii n.d. n.d S. kurilensis leaf s (spring) Fig. 1. Temporal variations in isoprene emissions and photosynthesis rates of P. heterocycla and P. bambusoides. Three leaves were measured for each species and time point. I, rate of isoprene emission; A, net assimilation; g s, stomatal conductance; PPFD, photosynthetic photon flux density. Error bars denote1 standard deviation. 42

4 M. Okumura et al. : BVOC Emissions from Bamboos L T L T Fig. 2. Relationships between C L C T and the measured isoprene emission rate I of P. heterocycla and P. bambusoides on the summer days. higher than those for P. bambusoides as shown in Fig. 1. The I values of P. heterocycla and P. bambusoides on the summer days demonstrated similar diurnal variations, with maxima of 78.1 nmol m 2 s 1 and 57.6 nmol m 2 s 1, respectively, around noon. The I values of P. heterocycla and P. bambusoides were lower on the spring days <5 nmol m 2 s 1. In most leaves, A was correlated with g s. 3.3 Isoprene emission modeling Because a proportional relationship between C L C T and the measured I values could be expected from equation 2, I S of P. heterocycla and P. bambusoides were determined as the slope of the regression line of I against C L C T Fig. 2. The I values on the summer days were well correlated with C L C T for both bamboos r 2 =0.76 and 0.79 for P. heterocycla and P. bambusoides, respectively. On the other hand, the I values on the spring days were poorly correlated with C L C T for both bamboos r 2 =0.05 and 0.17, respectively. The calculated I S values of P. heterocycla and P. bambusoides on the summer days were determined to be 56.6 and 45.2 nmol m 2 s 1, respectively. 4. Discussion The results of this study showed that most bamboo species cultivated in Japan emit isoprene, which induces ozone formation at a higher rate than most anthropogenic VOCs do. The proportion of isoprene-emitting species found in this study was 86. Geron et al reported that 44 out of 95 plant species in southern Yunnan Province, China, emitted isoprene 46. Keller and Lerdau 1999 reported the proportion of isoprene-emitting species found in the canopy in a semi-deciduous forest in the Republic of Panama was 29. The review of Karlik and Winer 2001 revealed that the leaves of different species within the same genus are highly likely to exhibit similar isoprene emission characteristics. Thus, most bamboo species are highly likely to have high isoprene-emitting potential. Our results suggest that the isoprene emissions from leaves of P. heterocycla and P. bambusoides can be explained by the G93 algorithm using the original empirical coefficients α, C L1, C T1, and C T2 and the constant T M determined by Guenther et al Fig. 2. These coefficients have been widely used for the G93 algorithm in many studies. Kesselmeier and Staudt 1999 reported on basal isoprene emission rates I S from plant leaves from around the world. Comparing our results with those in the review of Kesselmeier and Staudt 1999, Phyllostachys spp., Bambusa spp., and Semiarundinaria spp. exhibited high average Is of 42.0, 53.5, and 43.5 nmol m 2 s 1, respectively. These levels are about the same as that emitted by Japanese oak Q. serrata Okumura et al., 2008a, which has a relatively high emission rate among Japanese trees Tani and Kawawata, Meanwhile, S. tootsik and S. kurilensis had average Is of 33.9 and 16.3 nmol m 2 s 1, respectively, which are considered moderate rates, while P. japonica and P. simonii did not emit a significant amount of isoprene. Most bamboo species constitute a clonal colony and are genetically identical individuals. Therefore, the isoprene emission rate of each bamboo measured in this study can be considered as representative value of each bamboo. However, it is possible that isoprene emission from the leaves varies with culm and leaf age. Some studies on BVOC emissions from bamboo forests in eastern Asia are available, but the number of reports on BVOC emissions from the leaves of bamboo species is very limited. Melnychenko and Rosenstiel 2015 conducted a screening test on BVOC emissions from leaves of bamboo species. However, the emission rates they observed were substantially lower than the rates we noted for Phyllostachys spp. and Bambusa spp. showing high isoprene emission. This discrepancy might result from the plant growth environments, age of leaf, etc. Guenther et al., Pétron et al investigated the influence of long-term variations in growth temperature on the isoprene emission capacity of bur oak, and found that the isoprene emission capacity measured at leaf temperature of 25 C and PPFD of 900 μmol m 2 s 1 increased as the growth temperature increased from 298 to 303 K. Pétron et al suggested that seasonal temperature variations strongly affect the isoprene emission capacity of mature oak leaves. Therefore, the basal emission rates of P. heterocycla and P. bambusoides could also increase drastically in summer. On the other hand, in spring season, activity of isoprene synthase and the availability of its precursor dimethylallyl diphosphate: DMAPP in the leaves might have been reduced due to lower growth ambient temperature Monson et al., 1992; Guenther et al., 1993; Wolfertz et al., Reports from Shanghai, China have demonstrated that isoprene concentrations are higher near bamboo forests than near other forest types Geng et al., Bai et al reported that canopy-scale isoprene emission rate at basal conditions as measured by a relaxed eddy accumulation method during the peak growing season in a bamboo plantation in China was 13.5 nmol m 2 s 1, demonstrating the importance of bamboo isoprene emissions for regional ozone and organic aerosol production. The difference between the amount of BVOC emissions from bamboo forests and those from other types of forest might be attributed to the fact that only certain types of forest vegetation release BVOC. In Japan, many bamboo forests are located around residential areas, i.e., near discharge sources of pollutants, such as NO x, 43

5 Journal of Agricultural Meteorology 74 1, 2018 originating from human activities. Therefore, even though bamboo currently accounts for less than 1 of Japan s total forest area, the future expansion of Moso bamboo forests and the fact that most bamboo is located in the suburbs and therefore is highly likely to come in contact with anthropogenic pollutants, must be considered in management practices. In conclusion, the potential future impact of bamboo on ozone formation cannot be ignored. Acknowledgments We thank Dr. Masatoshi Watanabe for organizing our research in Rakusai Bamboo Park. This work was supported by JSPS KAKENHI Grant Number JP15K References Bai J, Guenther A, Turnipseed A, Duhl T, Yu S, Wang B, 2016: Seasonal variations in whole-ecosystem BVOC emissions from a subtropical bamboo plantation in China. Atmospheric Environment 124, Chiou CR, Chen TH, Lin YJ, Yang YJ, Li SD, 2009: Distribution and change analysis of bamboo forest in northern Taiwan. 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