Variation In Biomass Production Research Articles

Environmental drivers of wheat yield variability across China's production regions: Insights from field experiments

AbstractWheat crops underpin contemporary global food security. Predominant wheat production zones in China include the Huang‐Huai‐Hai‐Plain and the Mid‐Lower Reaches of the Yangtze River, although climatic effects on productive potential across these regions vary markedly in space and time. Here, we conducted field experiments during the wheat season of 2015–2018 to examine environmental effects on growth, with fertilization and irrigation provided at levels ensuring that nutrient and water stress exposure was minimal. Yields in Huang‐Huai‐Hai‐Plain and the Mid‐Lower Reaches of the Yangtze River averaged 8950 and 4818 kg ha−1, respectively. Yield variation across regions was primarily related to spike number per unit area and grain number per spike. Maturity biomass was higher in Huang‐Huai‐Hai‐Plain; this translated into higher grain yields. Lower temperature and longer growing duration between emergence and jointing in Huang‐Huai‐Hai‐Plain afforded higher tillering and spike numbers, whereas higher growth rates from jointing to maturity resulted in higher biomass production in Huang‐Huai‐Hai‐Plain compare with the Mid‐Lower Reaches of Yangtze River. Growth rate, grain numbers and yield were positively correlated with the ratio of daily intercepted solar radiation to mean temperature during jointing to anthesis, termed photothermal quotient. Collectively, our results suggest that growth rate accounted for more variation in biomass production compared with growth duration, and the photothermal conditions in the Mid‐Lower Reaches of the Yangtze River were restrictive for spike development and yield formation. Our results help disentangle drivers of crop growth through the development of agro‐environmental conceptual frameworks, enabling a better understanding of yield variability in space and time.

Economic potential of agricultural-riparian shrub willow: An evaluation of the biomass producing capabilities and costs of cultivating Salix viminalis downslope of potato cropping systems in PEI

Shrub willow (Salix spp.) is increasingly grown as a biomass crop and for a range of environmental applications. Merging the economic and environmental objectives of willow production may facilitate more widespread adoption by reducing production costs and justifying willow cultivation in traditional agricultural settings. Incorporating willow in agricultural-riparian transition areas, particularly in intensive or high-input agricultural systems, can enhance watercourse protection from diffuse pollutants, mitigate indirect agricultural N2O emissions, and sequester carbon. However, biomass accrual and economic feasibility needs quantification on localized scales.This study investigated the biomass accrual of 9 agricultural-riparian willow buffers in Prince Edward Island, Canada, receiving no direct fertilization. Carbon, nitrogen, and phosphorus assimilation was measured in stem and root biomass, limitations on growth assessed, and benefit-cost analysis was conducted to determine opportunities for bioenergy use and deployment. First rotation agricultural-riparian Salix viminalis displayed considerable site-to-site variation in biomass production, with water availability being the primary limiting factor on growth. Mean total plant biomass and annual yield ranged from 0.54 to 7.9 kg dry matter plant−1 and 0.25–16.59 Mg ha−1 yr−1 (mean 3.9), respectively. CO2 fixation was 0.67–46.64 Mg CO2 ha−1 yr−1, of which 0.23–15.7 Mg CO2 ha−1 yr−1 was root biomass, indicative of long-term sequestration. Nitrogen and phosphorus removal was 6.05–39.1 (mean 23.3) and 1.1–4.8 (mean 2.8) kg ha−1 yr−1. Benefit-cost analysis revealed that shrub willow production can be economically viable for on-farm heating when yields exceeding 5.6 Mg dry matter ha−1yr−1 are achieved, but off-farm sale is not currently economically justified.

Belowground plant traits and their ecosystem functions along aridity gradients in grasslands

Ecosystem responses to environmental change are usually studied solely using aboveground (usually leaf) traits. However, belowground plant traits, such as fine roots and coarse belowground organs, likely play a crucial role in ecosystem response, especially under aridifcation. We conducted a literature survey on belowground plant traits along aridity gradients in temperate grasslands to propose which effect traits might be connected with abrupt vegetation changes that would occur with aridification due to environmental change. With increasing aridity, seasonal regeneration decreasingly relies on recruitment from the belowground bud bank and increasingly relies on regeneration from seeds. This leads to greater inter-annual variability in biomass production. Other belowground traits, such as bud bearing organs and fine root distribution in the soil, also shifts along the aridity gradient. As aridifcation begins, we propose that plants would become more conservative in their belowground traits producing lower amounts of belowground litter. Increasing aridifcation would lead to the loss of rhizomatous plants from the community and a prevalence of deep rooting plants leading to changes in soil resource utilization and increasing susceptibility to soil erosion. Under extreme aridification, perennial plants, except those with bulbs, would be lost from the community and replaced by annuals which produce low amounts of litter and use only ephemeral water resources in the upper soil layers. Belowground plant traits, such as belowground clonal growth organs, bud banks, and fine root distributions, may provide a more mechanistic understanding behind shifts in ecosystem functioning due to environmental change.

Opportunity Costs of Forest Conservation in Nepal

Forest biomass may vary by species composition, location, management regimes, and management interventions. To assess the variation in biomass production by management regimes, we conducted a study in three physiographic regions (mid-hills, Siwaliks and Terai) of Nepal with four different management regimes (community forest, collaborative forest, protected area, and protected forest). As community forest is the dominant forest management regime in Nepal, it was studied in all physiographic regions whereas the other two regimes were drawn only from the Terai. We interviewed a total of 1,115 forest user households, which was supplemented by high-resolution satellite image analysis and forest inventory to estimate the costs and benefits of forest management and calculate the opportunity cost of conserving forest. Our estimates suggest that the opportunity cost of conserving forest in Nepal ranged from USD 654/ha in collaborative forest to USD 3,663/ha in protected forest in 2015. The associated opportunity cost of carbon sequestration was between USD 1.11 and USD 3.56 per tCO2. Of the forest management practices adopted, the silviculture-based intensive forest management practice had a far lower cost of forest conservation compared to the other forest management regimes. We found that such a practice is more beneficial to the forest-dependent communities as it allows them to collect the non-timber forest products that are necessary for their daily needs.

Species pool size and rainfall account for the relationship between biodiversity and biomass production in natural forests of China.

The strength of biodiversity–biomass production relationships increases with increasing environmental stress and time. However, we know little about the effects of abiotic (e.g., climate) and biotic (e.g., species pool and community composition) factors on this trend. Whether variation in biomass production is best explained by phylogenetic diversity metrics or traditional measures of species richness also remains elusive. We compiled estimates of community composition and biomass production for tree species in 111 permanent quadrats spanning three natural forests (tropical, subtropical, and temperate) in China. Based on ~10 years of data, we compared temperature, rainfall, species pool size, and community composition in each forest each year. We estimated species richness and phylogenetic diversity in each quadrat each year; the latter metric was based on the sum of branch lengths of a phylogeny that connects species in each quadrat each year. Using generalized linear mixed‐effect models, we found that top‐ranked models included the interaction between forest and biodiversity and the interaction between forest and year for both biodiversity metrics. Variation in biomass production was best explained by phylogenetic diversity; biomass production generally increased with phylogenetic diversity, and the relationship was stronger in subtropical and temperate forests. Increasing species pool size, temperature, and rainfall and decreasing inter‐quadrat dissimilarity range shifted the relationship between biomass production and phylogenetic diversity from positive to neutral. When considered alone, species pool size had the strongest influence on biomass production, while species pool size, rainfall, and their interaction with phylogenetic diversity constituted the top‐ranked model. Our study highlights the importance of species pool size and rainfall on the relationship between phylogenetic diversity and biomass production in natural forest ecosystems.

Invasive plant rhizome production and competitiveness vary based on neighbor identity

Abstract Aims Within-species genetic and phenotypic variation have well-known effects on evolutionary processes, but less is known about how within-species variation may influence community-level processes. Ecologically meaningful intraspecific variation might be particularly important in the context of anthropogenic impacts on natural systems, such as agriculture and species invasion, because human actions can cause strong selection pressures. Methods In a greenhouse study, we explored intraspecific (30 accessions) and ecotypic variation (representing agricultural and nonagricultural habitats) in biomass and rhizome production in response to inter- and intraspecific competition and soil fertility of Johnsongrass (Sorghum halepense), a widespread invasive species and agricultural weed. Important Findings Contrary to our expectations and previous results, we did not find variation in biomass production among Johnsongrass ecotypes at this early life stage. However, we did find that Johnsongrass biomass varied substantially depending on competitor identity, soil fertility treatments and among accessions. Rhizomes were 11% larger in the agricultural ecotype and up to 3-fold larger in fertilized treatment; while rhizome biomass increased by ~50% when fertilized, but did not differ among ecotypes. Interestingly, in competition, Johnsongrass produced 32% less biomass and 20% less rhizome mass with a conspecific than when competing interspecifically with corn. Our results indicate species-specific competitive responses and changes in rhizome allocation in response to neighbor identity; suggesting the possibility of adaptation by Johnsongrass to shift allocation under competition.

Enhancing the productivity of ryegrass at elevated CO2 is dependent on tillering and leaf area development rather than leaf-level photosynthesis.

Whilst a range of strategies have been proposed for enhancing crop productivity, many recent studies have focused primarily on enhancing leaf photosynthesis under current atmospheric CO2 concentrations. Given that the atmospheric CO2 concentration is likely to increase significantly in the foreseeable future, an alternative/complementary strategy might be to exploit any variability in the enhancement of growth/yield and photosynthesis at higher CO2 concentrations. To explore this, we investigated the responses of a diverse range of wild and cultivated ryegrass genotypes, with contrasting geographical origins, to ambient and elevated CO2 concentrations and examined what genetically tractable plant trait(s) might be targeted by plant breeders for future yield enhancements. We found substantial ~7-fold intraspecific variations in biomass productivity among the different genotypes at both CO2 levels, which were related primarily to differences in tillering/leaf area, with only small differences due to leaf photosynthesis. Interestingly, the ranking of genotypes in terms of their response to both CO2 concentrations was similar. However, as expected, estimates of whole-plant photosynthesis were strongly correlated with plant productivity. Our results suggest that greater yield gains under elevated CO2 are likely through the exploitation of genetic differences in tillering and leaf area rather than focusing solely on improving leaf photosynthesis.

Variation in biomass production of sunflower (Helianthus annuus) plants under the influence of Lemongrass (Cymbopogon erectus) extract

Plant extract is being used for crop yield and biomass enhancement since long time. Using plants extract for the enhancement of growth of other plant is a worthwhile strategy so as to enhance crop yield and crop biomass. Current study is an attempt to increase growth in sunflower plants using lemongrass foliar extract. For this purpose, various trials based on computer modeling have conducted. Pot experiment of sunflower plants has performed in greenhouse conditions that have irrigated by different concentrations of lemongrass extract. Results show that lower concentrations produced significant gain in biomass of crop i.e. greater fresh and dry weight was achieved by 1% samples (7.4±0.8mg and 2.0±0.3mg respectively) while lowest fresh and dry weight attained by 3% samples (2.5±0.2mg and 1.1±0.1mg respectively). Absolute growth rate (AGR) and Relative growth rate (RGR) of the plants are obtained in sequential order of treatment. Control, 0.5% and 2% samples form close linear fit to the model while 0.5% samples produce long tailed positive correlation fit whereas 3% samples are negatively fitted to the model. CDF model produce closely fitted relationship of 1% and control samples while 3% samples negatively corresponded to normal fit. Therefore, current study suggests promoting an efficient agriculture strategy that would be helpful in biomass gain of the crops to sequester carbon and effectively take part in climate mitigation.

Multiple facets of diversity effects on plant productivity: Species richness, functional diversity, species identity and intraspecific competition

Abstract Deciphering the mechanisms that drive variation in biomass production across plant communities of contrasting species composition and diversity is a main challenge of biodiversity–ecosystem functioning research. Niche complementarity and selection effect have been widely investigated to address biodiversity–productivity relationships. However, the overlooking of the specific role played by key species has limited so far our capacity to comprehensively assess the relative importance of other potential drivers of biodiversity effects. Here, we conducted a grassland diversity–productivity experiment to test how four potential facets of biodiversity effects, namely species richness, functional diversity, species identity and the relaxation of intraspecific competition, account for variations in above and root biomass production. We grew six plant species in monoculture, as well as in every combination of two, three and six species. Plant density was kept constant across the richness gradient but we additionally grew each species in half‐density monoculture to estimate the strength of intraspecific competition for each studied species. We characterized eight functional traits, including root traits, related to nutrient and light acquisition and computed both the functional dissimilarity and the community‐weighted mean (CWM) of each trait. We further partitioned above‐ground biodiversity effect into complementarity and selection effects. We observed strong positive biodiversity effects on both above‐ground and root biomass as well as strong positive complementarity effect. These arose largely from the presence of a particular species (Plantago lanceolata) and from CWM trait values more than from a higher functional dissimilarity in plant mixtures. P. lanceolata displayed the highest intraspecific competition, which was strongly relaxed in species mixtures. By contrast, the presence of Sanguisorba minor negatively affected the productivity of plant mixtures, this species suffering more from interspecific than intraspecific competition. This study provides strong evidences that the search for key species is critical to understand the role of species diversity on ecosystem functioning and demonstrates the major role that the balance between intraspecific and interspecific competition plays in biodiversity–ecosystem functioning relationships. Developing more integrative approaches in community and ecosystem ecology can offer opportunities to better understand the role that species diversity plays on ecosystem functioning. A free Plain Language Summary can be found within the Supporting Information of this article.

Co-processing of common plastics with pistachio hulls via hydrothermal liquefaction

Mixed, wet, plastic streams containing food waste residues are being increasingly collected at point of use, but are extremely challenging to recycle and are therefore largely sent to landfill. While a challenging waste problem, this also represents an underutilised feedstock, which could be co-processed with biomass, increasing the scope of products, easing out seasonal variation in biomass production and increasing the production capacity of a traditional biorefinery. One promising method of biomass conversion is hydrothermal liquefaction (HTL), where lignocellulosic residues are broken down in water at high temperatures and pressures to produce a bio-crude oil, a solid residue and an aqueous fertiliser. In this study, the co-processing of common plastic waste with pistachio hulls was assessed to investigate the suitability of the HTL approach. The HTL of pistachio hulls was undertaken at 350 °C over 15 and 60 min, with four commonly used plastics: polyethylene, polypropylene, PET and nylon-6, in blends of up to 20 wt% plastic to biomass. A novel FT-IR method was developed to estimate the conversion of plastics in the system, and the product phases were fully analysed. High yields of up to 35% bio-crude were achieved, and under optimal conditions, nylon-6 and PET were found to break down almost completely in the system. PET generated numerous products that distributed predominantly into the aqueous phase; the major decomposition product of nylon-6 was found to be the monomer ∊-caprolactam, also largely partitioning into the aqueous phase. The polyolefins were less reactive; a limited degree of decomposition formed oxidised products, which distributed into the bio-crude phase. This result represents a highly promising method for waste plastic valorisation.

Differences in uptake and accumulation of copper and zinc by Salix clones under flooded versus non-flooded conditions.

The climate-driven flooding poses a challenge for phytoremediation of contaminated soil, and the willow (Salix spp.) is a promising candidate coping with climate change and environmental pollution. In this study, uptake and accumulation of copper (Cu), zinc (Zn) and their bioavailability in the rhizosphere across the Salix clones under flooded versus non-flooded (control) conditions were investigated using a pot experiment. The tested Salix clones grew well without showing any toxic symptoms under non-flooded soil condition; in contrast, the clones showed 100% survival for long-term flooding with the development of hypertrophied lenticels and adventitious roots. There were wide clonal variations in biomass production and accumulation of Cu and Zn under flooded and non-flooded conditions. Flooded treatments dramatically decreased aboveground biomass across the Salix clones to different extents compared to the control. The non-flooded clones exhibited relatively high accumulation capacities of Cu and Zn in aerial parts. However, the flooded clones resulted in more substantial reductions in Cu and Zn accumulation in aerial parts, and most of Cu and Zn were limited in roots. EDTA-extractable Cu and Zn predicted well bioavailability of Cu and Zn to the Salix clones under the current condition. It was concluded that the Salix clones exhibited Cu and Zn phytoextraction traits (non-flooding) or phytostabilization traits (flooding), which provides a valuable insight into phytomanagement of contaminated soils by willows subjected to flooding stress.

Tobacco, Sunflower and High Biomass SRC Clones Show Potential for Trace Metal Phytoextraction on a Moderately Contaminated Field Site in Belgium.

Phytoextraction could be a potential management option for diffusely Cd-Zn-Pb-polluted agricultural land in Northeast Belgium. The use of high yielding crops with a sufficiently high metal accumulation is preferred as these are expected to both gradually decontaminate the soil while generating an income through biomass valorization. To find out which high biomass crop possessed the highest and most constant (in time) phytoextraction potential on these soils, different plant species and different mutants or clones of each species, were evaluated during consecutive years. Biomass production and metal accumulation of pre-selected tobacco somaclonal variants (Nicotiana tabacum L.) and pre-selected sunflower mutants (Helianthus annuus L.) were investigated for two productivity years, while the phytoextraction potential of experimental poplar (Populus) and willow (Salix) in short rotation coppice (SRC) was assessed at the end of the second cutting cycle (after two times four growing seasons). The tobacco clones and the sunflower mutants showed efficient extraction of, respectively, Cd and Zn, while the highest simultaneous extractions of Cd and Zn were gained with some SRC clones. Variation in biomass production and metal accumulation were high for all crops over the years. The highest biomass production was observed for the experimental poplar clone of the crossing type Populus deltoides (P. maximowiczii x P. trichocarpa) with 9.9 ton DW per ha per year. The remediation period to reach legal threshold values for the pseudo-total content of Cd in this specific soil was estimated to be at least 60 years. Combining estimated phytoextraction potential and economic and environmental aspects, the SRC option is proposed as the most suitable crop for implementing metal phytoextraction in the investigated area.

Mapping Ecological Production and Benefits from Water Consumed in Agricultural and Natural Landscapes: A Case Study of the Pangani Basin

Scarcity of information on the water productivity of different water, land, and other ecosystems in Africa, hampers the optimal allocation of the limited water resources. This study presents an innovative method to quantify the spatial variability of biomass production, crop yield, and economic water productivity, in a data scarce landscape of the Pangani Basin. For the first time, gross return from carbon credits and other ecosystem services are considered, in the concept of Economic Water Productivity. The analysis relied on the MODIS satellite data of 250 m and eight-day resolutions, and the SEBAL model, utilizing Monteith’s framework for ecological production. In agriculture, irrigated sugarcane and rice achieved the highest water productivities in both biophysical and economic values. Rainfed and supplementary irrigated banana and maize productivities were significantly lower than the potential values, reflecting a wide spatial variability. In natural landscapes, forest and wetland showed the highest biomass production. However, the transition to economic productivity was low but showed the potential to increase significantly when non-market goods and services were considered. Spatially explicit information, from both biophysical and economic water productivity, provides a holistic outlook of the socio-environmental and the economic water values of a land-use activity, and can identify areas for improvement, and trade-offs in river basins.

Cutting reduces variation in biomass production of forage crops and allows low-performers to catch up: A case study of Trifolium pratense L. (red clover).

Re-growth of fodder plants after grazing and mowing drives the profitability of their cultivation and is therefore an important target trait for plant breeding and agricultural engineering. However, for some fodder plants little is known about their re-growth dynamics in response to grazing or mowing. We analysed the native response of plant architecture, leaf morphology and growth performance to experimental cutting in wild Trifolium pratense L. (red clover) plants. A total of 150 potted clover plants were established under controlled field conditions, and half of the plants were cut to 5cm 3months after sowing. Each plant was measured every week for 5months. The cut and subsequently re-grown plants carried fewer main branches (-20%), as well as fewer (-13%) and smaller (-32%) leaves than the control plants. However, the cut plants produced an average of 17% more accumulated leaf area (cut + re-grown leaf area) than the control plants. This discrepancy was explained by variation in the growth strategy of the plants, where the cut plants invariably expressed a second growth phase, while almost half of the untreated plants did not. Our results suggest that cutting acted as an artificial trigger initiating a second growth phase in the cut plants and thereby contributed to yield increase. Exploiting this mechanism may set new goals for breeding and optimisation of the mowing regime.

Use of a duckweed pond for the domestic wastewater polishing in Ilha Solteira, SP, Brazil

PurposeThe purpose of this paper is to evaluate the efficiency of a duckweed pond in the polishing of a stabilization pond effluent, as well as quantify its biomass production. Once an adequate destination is given to the produced biomass, the wastewater treatment plant can work in a sustainable and integrated way.Design/methodology/approachThe duckweed pond consisted of a tank with volume 0.44 m3, operating in continuous flow with an outflow of 0.12 m3/day and hydraulic retention time of 3.8 days. Effluent samples were collected before and after the treatment, with analyzes made: daily-pH, dissolved oxygen and temperature; twice a week – total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD); and weekly – total solids (TS) and Biochemical Oxygen Demand (BOD5). The duckweeds were collected each for seven days for its production quantification.FindingsThe highest efficiency of TN, TP, COD, BOD5 and TS removal were of 74.67, 66.18, 88.12, 91.14 and 48.9 percent, respectively. The highest biomass production rate was 10.33 g/m2/day in dry mass.Research limitations/implicationsThere was great variation in biomass production, which may be related to the stabilization pond effluent conditions. The evaluation of the effluent composition, which will be treated with duckweeds, is recommended.Practical implicationsThe evaluated treatment system obtained positive results for the reduction in the analyzed variables concentration, being an efficient technology and with operational simplicity for the domestic effluent polishing.Originality/valueThe motivation of this work was to bring a simple system of treatment and to give value to a domestic wastewater treatment system in a way that, at the same time the effluent polluter level is reduced and it is also possible to produce biomass during the treatment process.

Is annual or perennial harvesting more efficient in Ni phytoextraction?

The use of perennial metal hyperaccumulators in phytoextraction provides an excellent gateway toward the removal of heavy metals from polluted sites, and the opportunity for the phytomining of valuable metals. In order to further advance our understanding of the effect of cropping systems on metal phytoextraction, it is important to investigate the effect of harvesting time. This study focuses on the variation in biomass production, Ni concentration and Ni mass across the different phenological stages, populations and organs of Alyssum lesbiacum, in order to evaluate when Ni phytoextraction is at a maximum. We sampled 60 single-phenological stage plots in three A. lesbiacum populations and we determined biomass production and Ni concentration at the plant organ level. Based on spontaneous A. lesbiacum vegetation, we were able to record remarkably high values of Ni phytoextraction. Biomass production and Ni concentration were found to be maximal on the third and fourth year of the A. lesbiacum life cycle respectively, while maximum phytoextraction capacity was reached in the third year. Our results: (1) demonstrate the significant variation in Ni phytoextraction across different phenological stages, populations and organs of A. lesbiacum, (2) imply that its phytoextraction potential is mostly influenced by biomass production and (3) suggest that perennial harvests could be an interesting alternative to consider in the future.

Describing the physiological responses of different rice genotypes to salt stress using sigmoid and piecewise linear functions

Rice is the staple food for almost half of the world population. In South and South East Asia, about 40% of rice production is from deltaic regions that are vulnerable to salt stress. A quantitative approach was developed for characterizing genotypic variability in biomass production, leaf transpiration rate and leaf net photosynthesis responses to salinity during the vegetative stage, with the aim of developing efficient screening protocols to accelerate breeding varieties adapted to salt-affected areas. Three varieties were evaluated in pots under greenhouse conditions and in the field, with average soil salinity ranging from 2 to 12dSm−1. Plant biomass, net photosynthesis rate, leaf transpiration rate and leaf conductance were measured at regular intervals. Crop responses were fitted using a logistic function with three parameters: 1) maximum rate under control conditions (Ymax), 2) salinity level for 50% of reduction (b), and 3) rate of reduction (a). Variation in the three parameters correlated significantly with variation in plant biomass production under increasing salinity. Salt stress levels that caused 50% reduction in net leaf photosynthesis and transpiration rates were higher in the tolerant genotype BRRI Dhan47 (16.5dSm−1 and 14.3dSm−1, respectively) than the sensitive genotype IR29 (11.1dSm−1 and 6.8dSm−1). In BRRI Dhan47, the threshold beyond which growth was significantly reduced was above 5dSm−1 and the rate of growth reduction beyond this threshold was as low as 4% per unit increase in salinity. This quantitative approach to screening for salinity tolerance in rice offers a means to better understand rice growth under salt stress and, using simulation modelling, can provide an improved tool for varietal characterization.

Phenology-Based Biomass Estimation to Support Rangeland Management in Semi-Arid Environments

Livestock plays an important economic role in Niger, especially in the semi-arid regions, while being highly vulnerable as a result of the large inter-annual variability of precipitation and, hence, rangeland production. This study aims to support effective rangeland management by developing an approach for mapping rangeland biomass production. The observed spatiotemporal variability of biomass production is utilised to build a model based on ground and remote sensing data for the period 2001 to 2015. Once established, the model can also be used to estimate herbaceous biomass for the current year at the end of the season without the need for new ground data. The phenology-based seasonal cumulative Normalised Difference Vegetation Index (cNDVI), computed from 10-day image composites of the Moderate-resolution Imaging Spectroradiometer (MODIS) NDVI data, was used as proxy for biomass production. A linear regression model was fitted with multi-annual field measurements of herbaceous biomass at the end of the growing season. In addition to a general model utilising all available sites for calibration, different aggregation schemes (i.e., grouping of sites into calibration units) of the study area with a varying number of calibration units and different biophysical meaning were tested. The sampling sites belonging to a specific calibration unit of a selected scheme were aggregated to compute the regression. The different aggregation schemes were evaluated with respect to their predictive power. The results gathered at the different aggregation levels were subjected to cross-validation (cv), applying a jackknife technique (leaving out one year at a time). In general, the model performance increased with increasing model parameterization, indicating the importance of additional unobserved and spatially heterogeneous agro-ecological effects (which might relate to grazing, species composition, optical soil properties, etc.) in modifying the relationship between cNDVI and herbaceous biomass at the end of the season. The biophysical aggregation scheme, the calibration units for which were derived from an unsupervised ISODATA classification utilising 10-day NDVI images taken between January 2001 and December 2015, showed the best performance in respect to the predictive power (R2cv = 0.47) and the cross-validated root-mean-square error (398 kg·ha−1) values, although it was not the model with the highest number of calibration units. The proposed approach can be applied for the timely production of maps of estimated biomass at the end of the growing season before field measurements are made available. These maps can be used for the improved management of rangeland resources, for decisions on fire prevention and aid allocation, and for the planning of more in-depth field missions.

Continuous cultivation of lipid rich microalga Chlorella sp. FC2 IITG for improved biodiesel productivity via control variable optimization and substrate driven pH control

A novel two-stage continuous heterotrophic cultivation of Chlorella sp. FC2 IITG was demonstrated for enhanced lipid productivity. Initially, effect of control variable e.g. dilution rate and feed stream substrate concentrations on biomass productivity was evaluated. This showed significant variation in biomass productivity from 2.4gL−1day−1 to 11.2gL−1day−1. Further, these control variables were optimized by using multi-nutrient mechanistic model for maximizing the biomass productivity. Finally, continuous production of lipid rich algal biomass was demonstrated in two sequential bioreactors for enhanced lipid productivity. The biomass productivity of 92.7gL−1day−1 was observed in the first reactor which was operated at model predicted optimal substrate concentrations of feed stream. The intracellular neutral lipid enrichment by acetate addition resulted in lipid productivity of 9.76gL−1day−1 in the second reactor. Both the biomass and lipid productivities obtained from current study are significantly high amongst similarly reported literatures.

Predicting intra-seasonal fluctuations of NDVI phenology from daily rainfall in the East Sahel: a simple linear reservoir model

ABSTRACTShort-term predictive models are essential for understanding the temporal relationships between the variability of impulsive daily rainfall and the attendant dynamics of vegetation development in rangelands, particularly for the water-limited, semi-arid East Sahel. After identifying selected rain-dependent sites in southeast Sudan, this report applies a procedure to predict seasonal biomass development in response to impulse-like daily storm events using a simple linear reservoir model as an analogue for the coupled soil–plant–atmosphere ecosystem. Key parameters are the characteristic time () of the reservoir and the number (n) of elementary reservoirs in series. Surface vegetative biomass is represented by the normalized difference vegetation index (NDVI) provided by the MODIS satellite MOD13A2 16 day 1 × 1 km product. Our specific metric is the commonly used differential NDVI, or δNDVI, the difference between the actual NDVI value and its long-term fallow season baseline. We review the concept of the modelling method, with selected application to 15 years (2000−2014) of NDVI data from a 51 × 51 km study area in the East Sahel, centred on the standard WMO Gauge 62752 at Gedaref City in southeast Sudan. Results indicate that as few as four – even as few as two – model parameters might be used to describe intra-seasonal to multiple-year vegetation dynamics. Allowing for inter-annually variable parameters, the predicted results exhibit a coefficient of determination of 0.96. An alternative formulation using a single set of four, seasonally dependent model parameters, globally determined from 15 years of observed reference data, results in a coefficient of determination of 0.90; a version using only two, globally determined model parameters works almost as well for the type of phenology characteristic of this area. In addition to enabling a number of applications that would benefit from the availability of a synthetic phenological time series that is solely dependent on daily rainfall, one of the most important applications may be for infilling data gaps in the observed time series, which for this area of the Sahel are typically encountered during early-season green-up; a critical time for most NDVI studies. We found that the 1 year lagged autocorrelation coefficient, and some version of the conventional rain use efficiency (RUE) factor with its associated annual correlation coefficient, are essential adjunct screening parameters when identifying sites with the highest inter-annual variability in biomass production (typical of the most natural rain-fed sites in this area).