Ergebnisse zu entomologischen erhebungen und zur unkrautbekämpfung bei miscanthus und anderen c4‐pflanzen 1)

In zweijährigen Erhebungen zur Entomofauna an Miscanthus sinensis, Panicwn virgatum und Andropogon gerardii auf Flächen in Grcßbeeren und Güterfelde konnten erste Ergebnisse erzielt werden. Am Standort Güterfelde erfolgten gleichfalls mehrjährige Prüfungen der herbiziden Wirkung bei diesen C₄‐Pflanzen.

Die Besiedlung der Arthropoden mit 0,5 und 1,4 Individuen/Halm bzw. Horstpflanze erweist sich als sehr gering. Die Dominanz der Schad‐ und Nutzorganismen war im allgenmeinen ausgeglichen. Nur auf den Flächen mit P. virgatum und A. gerardii 1995 in Güterfelde lag der Schädlingsanteil durch die Blasenfüße (Thysanoptera) bei>90%, bedingt auch durch die trockene und warme Witterung im Juli/August. Das Schädlingsspektrum umfaßte Arten von Getreide u.a. Gramineen. Im gleichen Jahr 1995 verursachte die Gemeine Spinnmilbe (Tetranychus urticae) auf der Miscanthusfläche in Großbeeren bemerkenswerte Saugschäden. Das Nützlingsauftreten wurde von euryöken Arten bestimmt und war auf allen untersuchten Flächen gering.

Die Untersuchungen zur Unkrautbekämpfung im 1. bzw. 2. Standjahr zeigen, daß Präparate, die erfolgreich bei Mais und teilweise Getreide angewandt werden, auch auf Miscanthusflächen sowie bei Panicum und Andropogon vorrangig in der Nachpflanzanwendung zum Einsatz kommen können. Bedeutung erlangt auch die Anwendung der mechanischen Pflege. Es besteht ein direkter Zusammenhang zwischen der Effektivität der Unkrautbekämpfung im Anpflanzjahr und der Pflanzenentwicklung im Anpflanzjahr und den folgenden Etablierungsjahren. Bei unzureichender Unkrautbeseitigung im 1. Standjahr muß auch im 1. Folgejahr eine Unkrautbekämpfung erfolgen.     

Cultivation of Miscanthus under West European conditions: Seasonal changes in dry matter production,nutrient uptake and remobilization

There is increasing interest in cultivation of Miscanthus as a source of renewable energy in Europe, but there is little information on its nutrient requirements. Our aim was to determine the nutrient requirement of an established Miscanthus crop through a detailed study of nutrient uptake and nutrient remobilization between plant parts during growth and senescence. Therefore dry matter of rhizomes and shoots as well as N, P, K and Mg concentration under three N fertilizer rates (0, 90, and 180 kg N ha-1) were measured in field trials in 1992/93 and at one rate of 100 kg N h-1 in 1994/95.Maximum aboveground biomass in an established Miscanthus crop ranged between 25-30 t dry matter ha-1 in the September of both trial years. Due to senescence and leaf fall there was a 30% loss in dry matter between September and harvest in March. N fertilization had no effect on crop yield at harvest. Concentrations of N, P, K and Mg in shoots were at a maximum at the beginning of the growing period in May and decreased thereafter while concentrations in rhizomes stayed fairly constant throughout the year and were not affected by N fertilization.Nutrient mobilization from rhizomes to shoots - defined as the maximum change in nutrient content in rhizomes from the beginning of the growth period measured in 1992/93 was 55 kg N ha-1, 8 kg P ha-1, 39 kg K ha-1 and 11 kg Mg ha-1. This is equivalent to 21 N, 36 P, 14 K and 27 Mg of the maximum nutrient content of the shoots. Nutrient remobilization from shoots to rhizomes defined as the increase in nutrient content of rhizomes between September and March measured in 1994/95 was 101 kg N ha-1, 9 kg P ha-1, 81 kg K ha-1 and 8 kg Mg ha-1 equivalent to 46 N, 50 P, 30 K and 27 Mg of nutrient content of shoots in September. Results showed that nutrient remobilization within the plant needs to be considered when calculating nutrient balances and fertilizer recommendations.     

陕北黄土高原霸王菅群落生物量初步研究

研究了霸王菅群落地上和地下生物量季节和空间变化,结果表明,其地上生物量季节动态较为明显,８月中旬达峰值,地下生物量在返青期最低,枯黄期最高,这与植物生长发育阶段和物质运转有关。     

Root endophytic Chaetomium cupreum promotes plant growth and detoxifies aluminum in Miscanthus sinensis Andersson growing at the acidic mine site

Miscanthus sinensis Andersson grows naturally at the Hitachi mine. The root‐zone soil was acidic and contained high concentrations of Cu, Pb, Zn and exchangeable Al. Adventitious roots accumulated high concentrations of Al and Fe, but not other heavy metals. The purpose of this study was to elucidate the mechanism of tolerance of Al in M. sinensis, focusing on its chemical interaction with root endophytes. We isolated Chaetomium cupreum, which produced siderophores, from adventitious roots of M. sinensis via CAS assay. In inoculation tests, C. cupreum promoted M. sinensis seedling growth and increased Al and Fe uptake in the roots, although C. cupreum did not stimulate M. sinensis to produce Al detoxicants, such as citric and malic acids. Observation of the pattern of Al localization in the roots clarified that C. cupreum reduced Al toxicity in M. sinensis via compartmentalizing Al into fungal mycelia surrounding the roots and creating a less toxic Al‐localization pattern, allocating Al to the epidermis, endodermis and stele of roots. In conclusion, our results indicated that C. cupreum increases Al tolerance in M. sinensis growing at the acidic mine site.     

Miscanthus sacchriflorus exhibits sustainable yields and ameliorates soil properties but potassium stocks without any input over a 12‐year period in China

The perennial C₄ Miscanthus spp. is used in China for bio‐fuel production and its ecological functions. However, questions arise as to its economic and environmental sustainability in abandoned farmland where the costs should be very low. Little is known about its yield performance and effects on soil properties when it was harvested annually without any inputs in China. To address these questions, an experiment was implemented for 12 years on annually harvested Miscanthus sacchariflorus planted in 2006 and managed without fertilization, irrigation, or any other inputs. We determined biomass yields each year, biomass allocation, and soil properties before and after its cultivation. Biomass yields of M. sacchariflorus reached a peak value (29.67 t/ha) 3 years after cultivation and was maintained at a stable level (averaged 22.22 t/ha) during 2012–2017. Its root shoot ratio increased due to more biomass allocated below‐ground with time. Long‐term cultivation of M. sacchariflorus increased organic carbon contents, pH (for the absence of fertilization), microbial carbon, nitrogen and phosphorus contents, and soil carbon nitrogen ratios (0–100 cm). Soil bulk density was decreased significantly (p < .05) independent of soil depths. Annual harvest did not reduce total nitrogen and phosphorus, available nitrogen, and potassium, but total the potassium content of soil (0–100 cm). Cultivation of M. sacchariflorus increased available phosphorus contents in 40–100 cm soil and reduced that value in 20–40 cm soil. Biological nitrogen fixation provided ~218.74 kg ha^?1 year^?1 (1 m depth) nitrogen for the system offsetting nitrogen export by biomass harvest and stabilizing nitrogen levels of soil. In conclusion, M. sacchriflorus exhibited sustainable biomass yields and ameliorated soil properties but the decrease of total potassium contents after 12 years’ cultivation without any input. These conclusions could provide important information timely for the government and encourage farmers to promote large‐scale utilization of M. sacchriflorus on the abandoned farmland in China.     

Composition of cell wall phenolics and polysaccharides of the potential bioenergy crop –Miscanthus

The composition and concentrations of cell wall polysaccharides and phenolic compounds were analyzed in mature stems of several Miscanthus genotypes, in comparison with switchgrass and reed (Arundo donax), and biomass characteristics were correlated with cell wall saccharification efficiency. The highest cellulose content was found in cell walls of M. sinensis‘Grosse Fontaine’ (55%) and in A. donax (47%) and lowest (about 32%) in M. sinensis‘Adagio’. There was little variation in lignin contents across M. sinensis samples (all about 22–24% of cell wall), however, Miscanthus×giganteus (M × g) cell walls contained about 28% lignin, reed – 23% and switchgrass – 26%. The highest ratios of cellulose/lignin and cellulose/xylan were in M. sinensis‘Grosse Fontaine’ across all samples tested. About the same total content of ester‐bound phenolics was found in different Miscanthus genotypes (23–27 μg/mg cell wall), while reed cell walls contained 17 μg/mg cell wall and switchgrass contained a lower amount of ester‐bound phenolics, about 15 μg/mg cell wall. Coumaric acid was a major phenolic compound ester‐bound to cell walls in plants analyzed and the ratio of coumaric acid/ferulic acid varied from 2.1 to 4.3, with the highest ratio being in M × g samples. Concentration of ether‐bound hydroxycinnamic acids varied greatly (about two‐three‐fold) within Miscanthus genotypes and was also the highest in M × g cell walls, but at a concentration lower than ester‐bound hydroxycinnamic acids. We identified four different forms of diferulic acid esters bound to Miscanthus cell walls and their concentration and proportion varied in genotypes analyzed with the 5‐5‐coupled dimer being the predominant type of diferulate in most samples tested. The contents of lignin and ether‐bound phenolics in the cell wall were the major determinants of the biomass degradation caused by enzymatic hydrolysis.     

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.     

Modeling spatial and dynamic variation in growth,yield, and yield stability of the bioenergy crops Miscanthus × giganteus and Panicum virgatum across the conterminous United States

C₄ perennial grasses are being considered as environmentally and economically sustainable high yielding bioenergy feedstocks. Temporal and spatial variation in yield across the conterminious United States is uncertain due to the limited number of field trials. Here, we use a semi‐mechanistic dynamic crop growth and production model to explore the potential of Miscanthus × giganteus (Greef et. Deu.) and Panicum virgatum L. across the conterminous United States. By running the model for 32 years (1979–2010), we were able to estimate dry biomass production and stability. The maximum rainfed simulated end‐of‐growth‐season harvestable biomass for M. × giganteus was ca. 40 Mg ha^?1 and ca. 20 Mg ha^?1 for P. virgatum. In addition, regions of the southeastern United States were identified as promising due to their high potential production and stability and their relative advantage when compared with county‐level maize biomass production. Regional and temporal variation was most strongly influenced by precipitation and soil water holding capacity. Miscanthus × giganteus was on average 2.2 times more productive than P. virgatum for locations where yields were ≥10 Mg ha^?1. The predictive ability of the model for P. virgatum was tested with 30 previously published studies covering the eastern half of the United States and resulted in an index of agreement of 0.71 and a mean bias of only ?0.62 Mg ha^?1 showing that, on average, the model tended to only slightly overestimate productivity. This study provides with potential production and variability which can be used for regional assessment of the suitability of dedicated bioenergy crops.