Yo Toma

The ecology and agronomy of Miscanthus sinensis, a species important to bioenergy crop development, in its native range in Japan: a review.

Among several candidate perennial taxa, Miscanthus×giganteus has been evaluated and promoted as a promising bioenergy crop. Owing to several limitations, however, of the sterile hybrid, both at the taxon and agronomic production levels, other options need to be explored to not only improve M. ×giganteus, which was originally collected in Japan, but to also consider the development of other members of its genus, including Miscanthus sinensis, as bioenergy crops. Indeed, there is likely much to be learned and applied to Miscanthus as a bioenergy crop from the long history of intensive interaction between humans and M. sinensis in Japan, which in some regions of the country spans several thousand years. Combined with its high amount of genetic variation, stress tolerance, biotic interactions with fauna, and function as a keystone species in diverse grasslands and other ecosystems within its native range, the unique and extensive management of M. sinensis in Japan as a forage grass and building material provides agronomists, agroecologists, and plant breeders with the capability of better understanding this species in terms of potential contribution to bioenergy crop development. Moreover, the studies described in this review may serve as a platform for future research of Miscanthus as a bioenergy crop in other parts of the world.

Effect of crop residue C:N ratio on N2O emissions from Gray Lowland soil in Mikasa, Hokkaido, Japan

Abstract We studied the effect of crop residues with various C:N ratios on N2O emissions from soil. We set up five experimental plots with four types of crop residues, onion leaf (OL), soybean stem and leaf (SSL), rice straw (RS) and wheat straw (WS), and no residue (NR) on Gray Lowland soil in Mikasa, Hokkaido, Japan. The C:N ratios of these crop residues were 11.6, 14.5, 62.3, and 110, respectively. Based on the results of a questionnaire survey of farmer practices, we determined appropriate application rates: 108, 168, 110, 141 and 0 g C m−2 and 9.3, 11.6, 1.76, 1.28 and 0 g N m−2, respectively. We measured N2O, CO2 and NO fluxes using a closed chamber method. At the same time, we measured soil temperature at a depth of 5 cm, water-filled pore space (WFPS), and the concentrations of soil NH+ 4-N, NO− 3-N and water-soluble organic carbon (WSOC). Significant peaks of N2O and CO2 emissions came from OL and SSL just after application, but there were no emissions from RS, WS or NR. There was a significant relationship between N2O and CO2 emissions in each treatment except WS, and correlations between CO2 flux and temperature in RS, soil NH+ 4-N and N2O flux in SSL and NR, soil NH+ 4-N and CO2 flux in SSL, and WSOC and CO2 flux in WS. The ratio of N2O-N/NO-N increased to approximately 100 in OL and SSL as N2O emissions increased. Cumulative N2O and CO2 emissions increased as the C:N ratio decreased, but not significantly. The ratio of N2O emission to applied N ranged from −0.43% to 0.86%, and was significantly correlated with C:N ratio (y = −0.59 ln [x] + 2.30, r 2 = 0.99, P < 0.01). The ratio of CO2 emissions to applied C ranged from −5.8% to 45% and was also correlated with C:N ratio, but not significantly (r 2 = 0.78, P = 0.11).

Discovery of natural Miscanthus (Poaceae) triploid plants in sympatric populations of Miscanthus sacchariflorus and Miscanthus sinensis in southern Japan

PREMISE OF THE STUDY Looming petroleum shortages and projected negative impacts of human-induced climate change may be partly alleviated by the development and use of bioenergy feedstock crops. Miscanthus ×giganteus, a highly productive sterile triploid hybrid grass that was discovered in Japan several decades ago, has considerable potential as an alternative source of energy. Given the risks, however, involved in the reliance upon production of one clone of this hybrid, which is a natural cross between Miscanthus sacchariflorus and Miscanthus sinensis, for lignocellulosic bioenergy production, natural occurrences of triploidy were investigated in sympatric populations of tetraploid M. sacchariflorus and diploid M. sinensis in Japan. METHODS Seeds were counted and DNA content was estimated by flow cytometry for plants of M. sacchariflorus and M. sinensis in several sympatric populations throughout Japan. Chromosomes were also counted for select plants. KEY RESULTS Based on seed-set data, M. sacchariflorus has significantly lower seed set than M. sinensis in Japan. Putative triploid seeds were found on M. sacchariflorus plants in southern Japan. CONCLUSIONS This is the first report of the natural occurrence of Miscanthus triploid plants in several decades. If found to be sterile and similar in productivity to the commonly cultivated clone of M. ×giganteus, these triploid plants might serve as additional sources of genetic variation for bioenergy production. Seed set data also indicates that other triploid plants might be found in more northern regions of Japan.

Variation in the emission factor of N2O derived from chemical nitrogen fertilizer and organic matter: A case study of onion fields in Mikasa, Hokkaido, Japan

Abstract Variability in the emission factors of nitrous oxide (N2O) associated with the application of chemical fertilizer (EFF) and organic matter (EFO) were analyzed in two onion fields (GL, Gray Lowland soil [Gleysol; Food and Agriculture Organization/UNESCO]; BL, Brown Lowland soil [Fluvisol; Food and Agriculture Organization/UNESCO]) in Mikasa, Hokkaido, Japan. Nitrous oxide flux was measured using a closed chamber technique in four treatments (FOP, chemical nitrogen fertilization and organic matter application, with plants; F, chemical nitrogen fertilization only, without plants; OP, organic matter application only, with plants; C, control, no fertilization or organic matter application, without plants) for 4 years in GL (2000, 2003–2005) and for 1 year in BL (2005). The application rate of chemical fertilizer nitrogen ranged from 237 to 242 kg N ha−1 year−1 in GL and was 284 kg N ha−1 year−1 in BL; organic matter nitrogen ranged from 81 to 117 kg N ha−1 year−1 in GL and was 181 kg N ha−1 year−1 in BL. The emission factors (EF) were calculated using the equations: EFF (%) = (N2O emission in FOP–N2O emission in OP)/(applied chemical nitrogen fertilizer) × 100 and EFO (%) = (N2O emission in FOP–N2O emission in F)/(applied organic matter nitrogen) × 100. The annual N2O emissions for treatments FOP, F, OP and C were 7.2–17, 5.7–17, 3.2–9.9 and 2.0–12 kg N ha−1 year−1, respectively, in GL and 5.6, 2.8, 1.9 and 1.8 kg N ha−1 year−1, respectively, in BL. The EFF ranged from 1.3% to 5.5% in GL and was 1.3% in BL. The EFF was positively correlated with the mean annual air temperature (P < 0.01), suggesting that N2O emission derived from chemical nitrogen fertilizer increases as air temperature rises. The EFO, however, differed greatly between GL (ranging from −5.2% to 9.1%) and BL (1.5%). The EFO was positively correlated with the mean annual relative humidity, although the correlation was not significant (P = 0.23). This finding suggests that much wetter climatic conditions may increase N2O emissions derived from organic matter nitrogen. The estimated N2O emissions based on these EF values and the rate of nitrogen application coincided well with the measured N2O emissions in the FOP treatment in both soils.

Genetic structure of Miscanthus sinensis and Miscanthus sacchariflorus in Japan indicates a gradient of bidirectional but asymmetric introgression

Summary Using high-density genetic markers, gene flow is identified from diploid Miscanthus sinensis to tetraploid M. sacchariflorus in Japan, in contrast to genetic isolation between these species in China.

Carbon budget and methane and nitrous oxide emissions over the growing season in a Miscanthus sinensis grassland in Tomakomai, Hokkaido, Japan

Species in the Miscanthus genus have been proposed as biofuel crops that have potential to mitigate elevated atmospheric carbon dioxide (CO2) levels and nitrous oxide (N2O) and methane (CH4) emissions. Miscanthus sinensis is widespread throughout Japan and has been used for biomass production for centuries. We assessed the carbon (C) budget and N2O and CH4 emissions over the growing season for 2 years in a M. sinensis‐dominated grassland that was naturally established around 1972 in Tomakomai, Hokkaido, Japan, which is near the northern limit for M. sinensis grassland establishment on Andisols. Average C budget was −0.31 Mg C ha−1, which indicates C was released from the grassland ecosystem to the atmosphere. Dominant components in the C budget appeared to be aboveground net primary production of plants (1.94–2.80 Mg C ha−1) and heterotrophic respiration (2.27–3.11 Mg C ha−1). The measurement of belowground net primary production (BNPP) of plants in the M. sinensis grassland was extremely variable, thus only an approximate value could be calculated. Mean C budget calculated with the approximated BNPP value was 1.47 and −0.23 Mg C ha−1 for 2008 and 2009, respectively. Given belowground biomass (9.46–9.86 Mg C ha−1) was 3.1–6.5 times higher than that of aboveground biomass may provide additional evidence suggesting this grassland represents a C sink. Average CH4 emissions across years of −1.34 kg C ha−1 would indicate this grassland acts as an atmospheric CH4 sink. Furthermore, average N2O emissions across years were 0.22 kg N ha−1. While the site may contribute N2O to the atmosphere, this value is lower compared with other grassland types. Global warming potential calculated with the approximated BNPP value was −5.40 and 0.95 Mg CO2 Eq ha−1 for 2008 and 2009, respectively, and indicates this grassland could contribute to mitigation of global warming.

Nitrous oxide fluxes from upland soils in central Hokkaido, Japan.

Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November), for three years, in a total of 11 upland crop fields in central Hokkaido, Japan. The annual mean N2O fluxes ranged from 2.95 to 164.17 microgN/(m2 x h), with the lowest observed in a grassland and the highest in an onion field. The instantaneous N2O fluxes showed a large temporal variation with peak emissions generally occurring following fertilization and heavy rainfall events around harvesting in autumn. No clear common factor regulating instantaneous N2O fluxes was found at any of the study sites. Instead, instantaneous N2O fluxes at different sites were affected by different soil variables. The cumulative N2O emissions during the study period within each year varied from 0.15 to 7.05 kgN/hm2 for different sites, which accounted for 0.33% to 5.09% of the applied fertilizer N. No obvious relationship was observed between cumulative N2O emission and applied fertilizer N rate (P > 0.4). However, the cumulative N2O emission was significantly correlated with gross mineralized N as estimated by CO2 emissions from bare soils divided by C/N ratios of each soil, and with soil mineral N pool (i.e., the sum of gross mineralized N and fertilizer N) (P < 0.001).

Environmental Tolerances of Miscanthus sinensis in Invasive and Native Populations

Miscanthus sinensis is a moderately invasive ornamental grass species being considered as a bioenergy species in the USA and elsewhere. In this study, we show the range of environmental conditions tolerated by this species in wild populations in the USA and in Japan. Six naturalized populations in the USA and five native populations in Japan were sampled in summer 2009. In each population, environmental factors (canopy cover and soil fertility) were measured, along with measurements of size and morphology for 30 plants. Relationships between M. sinensis size and environmental variables in the two countries were determined using linear mixed effects models. Results indicated that M. sinensis can tolerate extremely wide variation in soil and climate conditions in the populations we sampled across both ranges, suggesting that it could be successfully grown across a wide distribution in the USA, both intentionally as a bioenergy crop and unintentionally as an escaped invader. Plant size generally responded to different environmental conditions in both ranges, with USA plants being negatively influenced by canopy cover and Japanese plants being positively influenced by soil fertility measures. We recommend caution in growing M. sinensis for bioenergy or ornamental purposes to minimize escape outside of its native range.

Nitrous oxide emission derived from soil organic matter decomposition from tropical agricultural peat soil in central Kalimantan, Indonesia

Our previous research showed large amounts of nitrous oxide (N2O) emission (>200 kg N ha−1 year−1) from agricultural peat soil. In this study, we investigated the factors influencing relatively large N2O fluxes and the source of nitrogen (N) substrate for N2O in a tropical peatland in central Kalimantan, Indonesia. Using a static chamber method, N2O and carbon dioxide (CO2) fluxes were measured in three conventionally cultivated croplands (conventional), an unplanted and unfertilized bare treatment (bare) in each cropland, and unfertilized grassland over a three-year period. Based on the difference in N2O emission from two treatments, contribution of the N source for N2O was calculated. Nitrous oxide concentrations at five depths (5–80 cm) were also measured for calculating net N2O production in soil. Annual N fertilizer application rates in the croplands ranged from 472 to 1607 kg N ha−1 year−1. There were no significant differences in between N2O fluxes in the two treatments at each site. Annual N2O emission in conventional and bare treatments varied from 10.9 to 698 and 6.55 to 858 kg N ha−1 year−1, respectively. However, there was also no significant difference between annual N2O emissions in the two treatments at each site. This suggests most of the emitted N2O was derived from the decomposition of peat. There were significant positive correlations between N2O and CO2 fluxes in bare treatment in two croplands where N2O flux was higher than at another cropland. Nitrous oxide concentration distribution in soil measured in the conventional treatment showed that N2O was mainly produced in the surface soil down to 15 cm in the soil. The logarithmic value of the ratio of N2O flux and nitrate concentration was positively correlated with water filled pore space (WEPS). These results suggest that large N2O emission in agricultural tropical peatland was caused by denitrification with high decomposition of peat. In addition, N2O was mainly produced by denitrification at high range of WFPS in surface soil.

Evaluation of the soil carbon budget under different upland cropping systems in central Hokkaido, Japan

Abstract To evaluate the carbon budget in soils under different cropping systems, the carbon dioxide (CO2) flux from soils was measured in a total of 11 upland crop fields within a small watershed in central Hokkaido over the no snow cover months for 3 years. The CO2 flux was measured using a closed chamber method at bare plots established in each field to estimate soil organic matter decomposition. Temporal variation in instantaneous soil CO2 fluxes within the sites was mainly controlled by soil temperature and moisture. Annual mean CO2 fluxes and cumulative CO2 emissions had no significant relationship with soil temperature and moisture (P > 0.2). However, there was a significant quadratic relationship between annual mean CO2 flux or cumulative CO2 emission and soil clay plus silt content (%) (R2 = 0.72∼0.74, P < 0.0003). According to this relationship, the optimum condition for soil CO2 emission is at a clay plus silt content of 63%. The cumulative CO2 emission during the no snow cover season within each year varied from 1,159 to 7,349 kg C ha−1 at the different sites. The amount of crop residue carbon retained in the soils following a cropping season was not enough to offset the CO2 emission from soil organic matter decomposition at all sites. As a consequence, the calculation of the soil carbon budget (i.e. the difference between the carbon added as crop residues and compost and the carbon lost as CO2 from organic matter decomposition) ranged from –7,349 to –785 kg C ha−1, except for a wheat site where a positive value of 4,901 kg C ha−1 was observed because of a large input of organic carbon with compost. The negative values of the soil carbon budget indicate that these cropping systems were net sources of atmospheric CO2.