Winter Biomass Research Articles

Seasonal changes on microbial metabolism and biomass in the euphotic layer of Sicilian Channel

As a part of a wider project on fisheries ecology, several biological and environmental parameters were monitored during two oceanographic cruises (BANSIC 2012 and NOVESAR 2013) in the Sicily Channel, which connects the Western and Eastern Mediterranean basins.The prokaryotic abundances and biomass as well as hydrolysis rates on organic matter were investigated in the euphotic layer of a retention area for fish larval stages including anchovy (Engraulis encrasicolus, Linnaeus, 1758) with the aim to investigate the different biogeochemical signatures in two seasonal conditions. The environmental parameters, particulate organic carbon and nitrogen together with heterotrophic production were also measured.Results showed significant increases for most of the studied parameters with increasing temperature during summer. This had effects on the Carbon cycle and recycling of nutrients; in fact total prokaryotic abundance and biomass, as well as carbon hydrolyzed by two enzymes (Leucine aminopeptidase and β-glucosidase), increased significantly during summer. Conversely Alkaline phosphatase activity, Chlorophyll concentration and Oxygen increased during winter. The same environmental parameters affected also the presence of fish eggs. Moreover high percentages of free enzymes (i.e., enzymes not associated with cells) were measured, accounting for percentages variable from 12 to 95 % of the total enzymatic activity, with values generally higher in summer than in winter.In this oligotrophic environment, the prokaryotic biomass was supported by the C hydrolyzed by enzymatic activities. The ratio between the hydrolyzed C and prokaryotic biomass was higher in winter than in summer, indicating that alkaline phosphatase activity contribute to an efficient incorporation of C into biomass in winter.

What to harvest when? Autumn, winter, annual and biennial harvesting of giant reed, miscanthus and switchgrass in northern and southern Mediterranean area

Side by side biomass productivities, harvesting time (autumn vs. winter) and frequency (annual vs. biennial) of three perennial grasses were compared under northern and southern Mediterranean climates. Miscanthus (Miscanthus×giganteus Greef et Deu.) was compared to giant reed (Arundo donax L.) in Catania (37°24′N, 15°03′E), and to switchgrass (Panicum virgatum L.) in Bologna (44°55'N, 11°45′E). Generally, giant reed produced about 50% higher biomass than miscanthus in Catania. Miscanthus almost halved biomass productivity in the driest year, while giant reed reduced biomass yield by only 30% under the same conditions. In Bologna, miscanthus and switchgrass produced similar amounts of cumulative biomass over 6 years. Switchgrass kept more stable annual yields than miscanthus, which, however, evidenced a higher potential under favorable climate conditions. Autumn harvest significantly reduced biomass productivity and quality (moisture content, ashes, cellulose and hemicellulose), particularly under South Mediterranean climate. In Catania, autumn biomass was 50% (giant reed) to 85% (miscanthus) lower than winter biomass, while in Bologna, autumn cut reduced switchgrass yield by 20%. Biennial harvesting resulted in almost 40% lower cumulative biomass yield than annual cut, after 6 years.

Characterization of distinct bloom phenology regimes in the Southern Ocean

AbstractIn this study, we document the regional variations of bloom phenology in the Southern Ocean, based on a 13-year product of ocean colour measurements co-located with observation-based estimates of the mixed-layer depth. One key aspect of our work is to discriminate between mixed-layer integrated blooms and surface blooms. By segregating blooms that occur before or after the winter solstice and blooms where integrated and surface biomass increase together or display a lag, we define three dominating Southern Ocean bloom regimes. While the regime definitions are solely based on bloom timing characteristics, the three regimes organize coherently in geographical space, and are associated with distinct dynamical regions of the Southern Ocean: the subtropics, the subantarctic, and the Antarctic Circumpolar Current region. All regimes have their mixed-layer integrated onset between autumn and winter, when the daylength is short and the mixed layer actively mixes and deepens. We discuss how these autumn–winter bloom onsets are controlled by either nutrient entrainment and/or reduction in prey-grazer encounter rate. In addition to the autumn–winter biomass increase, the subantarctic regime has a significant spring biomass growth associated with the shutdown of turbulence when air–sea heat flux switches from surface cooling to surface warming.

Decadal and seasonal changes in temperature, salinity, nitrate, and chlorophyll in inshore and offshore waters along southeast Australia

AbstractSixty years of oceanographic in situ data at Port Hacking (34°S) and Maria Island (42°S) and 15 years of satellite‐derived chlorophyll a (chl a) in inshore and offshore waters of southeast Australia show changes in the seasonality and trend of water properties consistent with long‐term intensification and southerly extensions of East Australian Current (EAC) water. Decadal analyses reveal that the EAC extension water at Maria Island increased gradually from the 1940s to 1980s, followed by a rapid increase since the 1990s. This acceleration coincided with enhanced winter nitrate, implying increased injections of subantarctic water at Maria Island. Satellite‐derived chl a at six coastal sites and offshore companion sites in the western Tasman Sea showed significant inshore‐offshore variations in seasonal cycle and long‐term trend. After 2004–2005, the Maria Island seasonal cycle became increasingly similar to those of Bass Strait and St. Helens, suggesting that the EAC extension water was extending further southward. Comparative analyses of inshore‐offshore sites showed that the presence of EAC extension water declined offshore. Seasonal cycles at Maria Island show a recent shift away from the traditional spring bloom, toward increased winter biomass, and enhanced primary productivity consistent with extensions of warm, energetic EAC extension water and more frequent injections of cooler, fresher nitrate‐replete waters. Overall, we find complex temporal, latitudinal, and inshore‐offshore changes in multiple water masses, particularly at Maria Island, and changes in primary productivity that will profoundly impact fisheries and ecosystems.

A dual stable isotope study for diet composition of juvenile Chinese horseshoe crab Tachypleus tridentatus (Xiphosura) on a seagrass-covered intertidal mudflat

To enhance our understanding on the foraging biology of juvenile Chinese horseshoe crab on a seagrass-covered intertidal mudflat, we used dual stable isotopes δ13C and δ15N to determine the diet composition and trophic position of 6th–11th instar juveniles in summer and winter. The δ13C and δ15N values in tissues of juveniles and their potential food sources suggested that the juveniles consumed a mixed diet mainly comprised a variety of polychaetes, crustaceans and bivalves, in which these food groups were abundantly available in the study site and largely supported by seagrass biomass in both summer and winter. While δ15N values in juvenile tissues were statistically similar between the two seasons, the δ13C values in tissues of juveniles had a minimal seasonal difference which was probably due to variations in the source values rather than the changes in diet composition of juveniles. There were no differences in δ13C and δ15N values among the size groups of juveniles through 6th–11th instars. Although juvenile Chinese horseshoe crabs may consume the prey in response to the seasonal availability on the mudflat, a healthy condition of habitat with high water quality is essential to support the juveniles and a wide range of intertidal invertebrates they consume.

Winter effect on soil microorganisms under different tillage and phosphorus management practices in eastern Canada.

Determining how soil microorganisms respond to crop management systems during winter could further our understanding of soil phosphorus (P) transformations. This study assessed the effects of tillage (moldboard plowing or no-till) and P fertilization (0, 17.5, or 35 kg P·ha(-1)) on soil microbial biomass, enzymatic activity, and microbial community structure in winter, in a long-term (18 years) corn (Zea mays L.) and soybean (Glycine max L.) rotation established in 1992 in the province of Quebec, Canada. Soil samples were collected at 2 depths (0-10 and 10-20 cm) in February 2010 and 2011 after the soybean and the corn growing seasons, respectively. Winter conditions increased the amounts of soil microbial biomasses but reduced the overall enzymatic activity of the soil, as compared with fall levels after corn. P fertilization had a quadratic effect on the amounts of total, bacterial, arbuscular mycorrhizal fungi phospholipid fatty acid markers after corn but not after soybean. The soil microbial community following the soybean and the corn crops in winter had a different structure. These findings suggest that winter conditions and crop-year could be important factors affecting the characteristics of the soil microbial community under different tillage and mineral P fertilization.

Rhizome starch as indicator for temperate seagrass winter survival

Key-ecosystems such as seagrass beds are disappearing on a global scale. In order to counter-act local loss of seagrass beds, seagrass restoration projects have been carried out with varying degrees of success. As seagrass biomass peaks in summer, most restoration projects are monitored during this period, while wintering processes are largely ignored. We here attempted to elucidate some important bottlenecks for wintering survival in temperate areas of the intertidal model species Zostera noltii, using a three-year transplant-monitoring dataset and a field experiment. We found that next year's transplant success could not be predicted based on the preceding year's growth success, emphasizing the winter as a crucial period for survival of seagrass transplants. In addition, transplant success was neither determined by abiotic site characteristics. Low autumn rhizome starch concentrations in unsuccessful transplants, compared to successful transplants and natural beds, hinted at the importance of starch for winter survival. Hence, we tested the importance of starch, accumulated in autumn, versus the importance of the presence of sparse aboveground photosynthetic winter biomass for winter survival of seagrass transplants in a field experiment. We clipped the overwintering-leaves of three natural beds that naturally varied in their autumn rhizome starch concentrations. Decreased leaf densities in winter did not affect seagrass biomass in June, nor did this treatment affect rhizome starch concentration in June. Autumn rhizome starch reserves did however provide a good indication of next year's growth success, confirming the importance of starch reserves for winter survival. We thus conclude that autumn rhizome starch can be a good predictor of next year's growth success, whereas the preceding growing season shoot density and the presence of leaves during the winter were bad indicators of next year's growth success.

Influence of the physical forcing of different water masses on the spatial and temporal distributions of picophytoplankton in the northern East China Sea

To investigate the temporal–spatial distribution of picophytoplankton in relation to different water masses in the northern East China Sea (ECS), picophytoplankton abundance and biomass were investigated using flow cytometry with environmental factors in May, August, and November 2010 and February 2012. Five picophytoplankton populations, including Prochlorococcus (Pro), low and high orange fluorescence Synechococcus (Syn1 and Syn2), and small and large sized picoeukaryotes (SPEuks and LPEuks) were discriminated, and each group responded differently to the water mass distribution. Syn1 was the predominant group in the picophytoplankton abundance in all seasons, indicating ecological importance as a primary producer in the northern ECS. LPEuks was a minor group in terms of the abundance but they contributed significantly to the total picophytoplankton carbon biomass in spring and winter due to their larger size among picophytoplankton groups. Two geographical groups were distinguished in the northern ECS. One group (including Syn1 and LPEuks) was distributed mainly in the western area affected by the Changjiang discharge and Chinese coastal waters, and the other group (including Pro, Syn2, and SPEuks) dominated picophytoplankton abundance in the eastern area characterized by the Kuroshio intrusion. Pro was detected in the eastern side of the study area during each survey, except in May, indicating the possible effect of the low Kuroshio intrusion on the northern ECS in late spring. This study shows that the distributions of these picophytoplanktons are strongly influenced by the seasonal fluctuations of the Changjiang discharge and Kuroshio intrusion in the northern ECS.

Interannual control of plankton communities by deep winter mixing and prey/predator interactions in the NW Mediterranean: Results from a 30-year 3D modeling study

A realistic modeling approach is designed to address the role of winter mixing on the interannual variability of plankton dynamics in the north-western (NW) Mediterranean basin. For the first time, a high-resolution coupled hydrodynamic–biogeochemical model (Eco3m-S) covering a 30-year period (1976–2005) is validated on available in situ and satellite data for the NW Mediterranean. In this region, cold, dry winds in winter often lead to deep convection and strong upwelling of nutrients into the euphotic layer. High nutrient contents at the end of winter then support the development of a strong spring bloom of phytoplankton. Model results indicate that annual primary production is not affected by winter mixing due to seasonal balance (minimum in winter and maximum in spring). However, the total annual water column-integrated phytoplankton biomass appears to be favored by winter mixing because zooplankton grazing activity is low in winter and early spring. This reduced grazing is explained here by the rarefaction of prey due to both light limitation and the effect of mixing-induced dilution on prey/predator interactions. A negative impact of winter mixing on winter zooplankton biomass is generally simulated except for mesozooplankton. This difference is assumed to stem from the lower parameterized mortality, top trophic position and detritivorous diet of mesozooplankton in the model. Moreover, model suggests that the variability of annual mesozooplankton biomass is principally modulated by the effects of winter mixing on winter biomass. Thus, interannual variability of winter nutrient contents in the euphotic layer, resulting from winter mixing, would control spring primary production and thus annual mesozooplankton biomass. Our results show a bottom-up control of mesozooplankton communities, as observed at a coastal location of the Ligurian Sea.

Comparison of Seasonal Soil Microbial Process in Snow-Covered Temperate Ecosystems of Northern China

More than half of the earth's terrestrial surface currently experiences seasonal snow cover and soil frost. Winter compositional and functional investigations in soil microbial community are frequently conducted in alpine tundra and boreal forest ecosystems. However, little information on winter microbial biogeochemistry is known from seasonally snow-covered temperate ecosystems. As decomposer microbes may differ in their ability/strategy to efficiently use soil organic carbon (SOC) within different phases of the year, understanding seasonal microbial process will increase our knowledge of biogeochemical cycling from the aspect of decomposition rates and corresponding nutrient dynamics. In this study, we measured soil microbial biomass, community composition and potential SOC mineralization rates in winter and summer, from six temperate ecosystems in northern China. Our results showed a clear pattern of increased microbial biomass C to nitrogen (N) ratio in most winter soils. Concurrently, a shift in soil microbial community composition occurred with higher fungal to bacterial biomass ratio and gram negative (G-) to gram positive (G+) bacterial biomass ratio in winter than in summer. Furthermore, potential SOC mineralization rate was higher in winter than in summer. Our study demonstrated a distinct transition of microbial community structure and function from winter to summer in temperate snow-covered ecosystems. Microbial N immobilization in winter may not be the major contributor for plant growth in the following spring.

Seasonal changes in the demersal nekton community off the Changjiang River estuary

The diversity, community structure and seasonal variation in demersal nekton off the Changjiang (Yangtze) River estuary was evaluated using monthly trawl survey data, collected between December 2008 and November 2009. A total of 95 species (56 teleosts, 11 cephalopods, and 28 decapod crustaceans) from 69 genera, 49 families and 15 orders were collected. These species could be classified into six groups on the basis of temporal distribution patterns. The resident crab Ovalipes punctatus dominated the community, both in number and biomass. A clear seasonal succession was observed in the species composition. Cluster analysis revealed three primary seasonal groups corresponding to the samples collected in winter-spring, late spring-summer and late summer-autumn. The highest biomass and lowest diversity were observed in summer, while the lowest biomass and highest diversity in winter. The abundance-biomass comparison curves and community composition suggested that the investigated community was moderately disturbed. The results suggest that reduction in fishing pressure and in the degree of seasonal hypoxia are essential for sustainable resource management off the Changjiang River estuary.

Sea temperature shapes seasonal fluctuations in seaweed biomass within the Ningaloo coral reef ecosystem

Environmental drivers of seaweed biomass were investigated at Ningaloo, Western Australia, a coral reef ecosystem with negligible anthropogenic influences on seaweeds from fishing, farming, or eutrophication. Periodic surveys of benthic macroalgae occupying seaweed‐dominated beds within the lagoon at two locations (Coral Bay, Tantabiddi) were made during winter, spring, and late summer over a 26 month period. Canopy‐forming Sargassum spp. biomass fluctuated over a seasonal growth—decay cycle, with highest values in the warm summer months (up to 1013 g fresh weight 0.25 m−2 at Coral Bay) and lowest values in winter (down to 155 g fresh weight 0.25 m−2 at Tantabiddi). Conversely, prominent understory seaweed genera Dictyopteris and Lobophora reached peak biomass in winter, when the Sargassum spp. canopy was lowest. Sargassum spp. biomass variation could be attributed largely to time (52%), location (21%), and site (26%), with low variation within individual seaweed beds (1%). Statistical analysis of the influence of five environmental variables (temperature, light, wind‐driven upwelling, rainfall, significant wave height) indicated that location and sea temperature (1 month antecedent to biomass) provided the best explanation for Sargassum spp. biomass fluctuations. While sea temperature is a key driver of seaweed temporal dynamics, heterogeneity at the kilometer scale suggests that spatial context is also important. Given the important role of seaweeds in many ecosystem processes, this strong biophysical coupling between Sargassum spp. biomass and sea temperature suggests that thermal climate change will significantly affect coral reef productivity and biodiversity.

Opportunities and challenges for improved management of foliar pathogens in annual clover pastures across southern Australia

Foliar pathogens result in significant losses in herbage and seed yields and regeneration capacity in annual clover pastures, the last leading to their rapid deterioration and lack of persistence. The most important pathogens include Kabatiella caulivora (clover scorch), Cercospora zebrina (cercospora), Uromyces trifolii-repentis (rust), Erysiphe trifoliorum (powdery mildew), and Leptosphaerulina trifolii (pepper spot). Several other foliar pathogens on annual clovers, in particular Phoma medicaginis (black stem and leaf spot), one or more Stemphylium spp. (stemphylium leaf spot), Pseudopeziza trifolii (common leaf spot), Stagonospora spp. (stagonospora leaf spot), Colletotrichum trifolii (anthracnose) and Sclerotinia trifoliorum (sclerotinia), occur widely and together contribute to reduce productivity in some localities. Severe attack by the most important pathogens (e.g. K. caulivora, U. trifolii-repentis, E. trifoliorum) not only greatly reduces winter–spring pasture production but frequently also coincides with the critical feed shortage across autumn–winter, leading to significantly decreased autumn–winter biomass production in regenerating stands. Approaches to disease control include a range of management strategies. Wider utilisation of cultural and fungicidal control strategies offers producers greater management flexibility, particularly in conjunction with deployment of cultivars with useful resistance. Host resistance offers the greatest potential for delivering the most cost-effective and long-term control. Many of these foliar pathogens co-occur, magnifying losses; this highlights the need for individual host genotypes with resistance to multiple pathogens and unique geographic locations such as Sardinia offer enormous scope to select such clovers. Future research opportunities and critical priorities to improve management of foliar pathogens in annual clover pastures across southern Australia include the need to: (i) define pathogen strain–race structures, particularly for K. caulivora and U. trifolii-repentis, and determine associated host resistances against specific strains–races to allow strategic deployment of host resistances; (ii) define relative resistances to major fungal foliar pathogens of all parental and near-release breeding genotypes and all commercial cultivars across important annual clover species; (iii) identify new sources of host resistance, particularly genotypes with cross-resistance to multiple pathogens, for breeders to utilise; (iv) identify and demonstrate the benefits to farmers of effective cultural (e.g. grazing, removal of infested residues) and fungicidal control options that allow greater management flexibility to reduce the impact of fungal foliar diseases; and (v) determine current incidences and impacts (losses and economic importance) of major fungal foliar diseases in the different agro-climatic regions across southern Australia. Failure to address these critical issues leaves livestock industries carrying the risks from release of new varieties of unknown susceptibilities to one or more of the major foliar diseases, and the risks from continued use of older varieties exposed to new pathogen races; with few if any flexible management options during periods of critical feed shortage; and without the basic information on current disease impacts that is needed to make sensible management and funding decisions.

Comment on “Annual cycles of ecological disturbance and recovery underlying the subarctic Atlantic spring plankton bloom”

Key Points The Dilution‐Recoupling Theory (DRT) computes biomass accumulation rates from depth‐integrated biomass in autumn and winter but from surface concentration in spring This formulation is valid during autumn and winter. Hence the DRT provides a useful explanation of winter ecosystem functioning This formulation is invalid during spring. As a consequence, the DRT does not provide an explanation for the evolution of the spring bloom.

An optimized fine root sampling methodology balancing accuracy and time investment

Aims Tree roots are spatially highly heterogeneous and it thus requires large numbers of samples to detect statistically significant changes in root biomass. The objectives of this study were to understand and quantify the sources of error in the assessment of fine root biomass (<2 mm) during the second year of a highdensity Populus plantation. Methods Soil cores were collected in winter (n035) and in summer (n020), and fine roots were picked by hand for varying lengths of time: 1, 2, 5, 20, 40, and 60 min. The root biomass data were used to identify the best combination of the time spent for root picking and the number of samples collected, that minimizes the overall uncertainty (i.e. the combination of the spatial error due to the incomplete sampling and the temporal error due to the incomplete core processing). Results On average, 25 min was enough time to pick 90 % of the fine root biomass in winter, while in summer only 10 min were needed. In winter fewer samples were needed, but more time for picking was necessary as compared to summer when root biomass was higher. Conclusions Fine root sampling can be optimized by minimizing the uncertainty of the biomass estimates and simultaneously decreasing root sampling time investment.

Summer and Winter Defoliation Impacts on Mixed-Grass Rangeland

Abstract Combined growing- and dormant-season pasture use has potential to increase herbage harvest without causing the undesirable shift in species composition that occurs with excessive utilization. The objective of this study was to determine the effect of summer clipping on winter pastures and winter clipping on summer pastures regarding standing crop, plant community composition, and forage quality. The study was conducted from 2003–2006 at the Antelope and Cottonwood Research Stations located in the mixed-grass prairie of western South Dakota. At each location, the experimental design was a randomized complete block with three replications that included 18 clipping treatments arranged as a split-split plot. Whole plots consisted of four summer clipping dates (May–August). Subplot treatments were two clipping intensities (clipped to residual height to achieve 25% or 50% utilization). Sub-subplots consisted of two winter clipping intensities (unharvested or clipped to a residual height to achieve a total utilization of 65%). Two winter control treatments were arranged in the subplot and split into two clipping intensities of 50% and 65% utilization. Winter biomass for the May 25% clipping treatment was similar to winter biomass for winter-only clipping. No increase in forage quality resulted from summer clipping compared with winter clipping. Three consecutive yr of combined growing-season and dormant-season defoliation to 65% utilization resulted in no change in functional group composition compared with ≤ 50% utilization treatments. Clipping in June resulted in reduced midgrass biomass at both stations and increased shortgrass biomass at Cottonwood. Results suggest that producers could combine growing and dormant-season grazing to increase the harvest of herbage on mixed-grass prairie, but should change season of use periodically to avoid an undesirable shift in plant composition.

Temporal and spatial variations of phytoplankton in the Caspian Sea

Geographic information system (GIS) can be used to perform a number of fundamental spatial analysis operations. Its major advantage is that it allows the user to identify the spatial relationships between various map features. In this study, phytoplankton cell abundance, biomass and species composition were evaluated in the Iranian coasts of the Caspian Sea during 1996 to 1997 and 2005 to 2006. Totally 1562 water samples were collected in Southern part of Caspian Sea (SCS) for durations of 1996 to 1997 and 2005 to 2006. There were changes in the highest seasonal means of phytoplankton biomass. While maximum phytoplankton biomass were recorded in spring and summer during 1996 to 1997, after the invasion of Mnemiopsis leidyi shifted to a winter period and biomass shifted to winter-spring during 2005 to 2006. Maximum cell abundance was observed in 2005 to 2006, contributed mostly by small size of phytoplankton, although its population decreased in 1996 to 1997 while maximum biomass was observed in 1996 to 1997, belonged to big size of phytoplankton such as Rhizosolenia calcaravis. Its population aggregated at the depth of 0 to 20 m more than 87% of the total cell abundance, due to some favorable conditions such as higher water temperature, light, dissolved oxygen and nutrient concentration. Phytoplankton was vertically distributed until the depth of 20 m, and the population decreased at the lower depths. Key words: Phytoplankton, seasonal variation, biomass, geographic information system (GIS) and Caspian Sea, Iran.

Long‐term yield and performance of 15 different Miscanthus genotypes in southwest Germany

AbstractA field experiment with 15 Miscanthus genotypes including M. × giganteus, M. sacchariflorus, M. sinensis and M. sinensis hybrids was conducted for 14 years at the experimental Ihinger Hof station of the University of Hohenheim in southwest Germany to evaluate interannual yield performance stability over 14 years of harvests of the different genotypes. In this article, a simple formula is presented which could be used to forecast late winter yields using morphological traits in autumn. The data obtained indicated a shorter establishment period to reach a yield plateau of M. × giganteus and M. sacchariflorus than M. sinensis hybrids and M. sinensis genotypes. The best performing genotype was M. × giganteus (Gig‐2, No. 16.21) with a mean spring harvestable yield of 14.1 t DM ha−1 year−1. A correlation analysis with climatic parameters revealed precipitation during the growing period as the key factor for high yields at this site. Likewise, but to a lesser degree, heat sum during the growing period was positively correlated with yields. It could be shown that precipitation/snow during the winter correlated with yield losses, until the harvest date in February/March. Phenological measurements indicated that a high yield potential of the tested genotypes is associated with either an absence of flowering or late flowering. Also, height of the plants and shoot diameter were indicators for high yield potential. Shoot density and plant height at senescence were found to be solid parameters to estimate harvestable biomass in late winter. Yield approximations with a mean accuracy of 80.9% for M.× giganteus genotypes were obtained using the newly developed equation. Yields of M. sinensis hybrid (Sin‐H7) were projected most accurately with this simple formula, resulting in a mean accuracy of 84.5%.

Biomass Yield and Nutrient Removal Rates of Perennial Grasses under Nitrogen Fertilization

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass (Panicum virgatum L.), giant miscanthus (Miscanthus x giganteus), giant reed (Arundo donax L.), weeping lovegrass [Eragrostis curvula (Shrad.) Nees], kleingrass (Panicum coloratum L.), and Johnsongrass (Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168 kg N ha−1) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate (p = 0.08), but was affected by year and species interactions (p < 0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0 Mg ha−1 in 2009, but only 13.0 Mg ha−1 and 9.8 Mg ha−1 in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0 Mg ha−1, respectively. Giant miscanthus established poorly, producing only 4.7 Mg ha−1. Across years, giant reed had the highest biomass yield, 33.2 Mg ha−1 at 168 kg N ha−1, and the highest nutrient concentrations and removal rates (162 to 228 kg N ha−1, 23 to 25 kg P ha−1, and 121 to 149 kg K ha−1) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75 kg N ha−1, 5 to 12 kg P ha−1, and 44 to 110 kg K ha−1) across years, demonstrating its merits as a low-input bioenergy crop.

Winter crop and residue biomass potential in China

Background: To estimate the scale of bioenergy winter crops and summer crop residue opportunities in China, winter rye (Secale cereal) yields were predicted using RyeGro, while straw production from corn, wheat and rice was calculated using a global agricultural database. Results: Potential winter rye biomass yields ranged from 11,099,000 to 23,745,700 Mg, while summer crop residues totaled 365,600,000 Mg after discounting for losses and alternative uses. Conclusion: Widespread existing double-cropping systems, as well as low winter precipitation and temperatures in China’s northern regions, limit the potential to directly increase biomass production using winter crops. However, winter crop synergies can increase sustainable harvests of summer crop residues, allowing China to provide a significant fraction of its energy needs from integrated food and biomass production systems.