Stem Biomass Production Research Articles

Changes in light use efficiency explains why diversity effect on biomass production is lower at high planting density in mixed-species plantations of Eucalyptus grandis and Acacia mangium

Understanding the effect of planting densities and species proportions on light absorption and light use efficiency can help to improve the management of mixed-species forest plantations. Our study aimed to disentangle the role of light interception and light use efficiency (LUE) on the biomass production of Eucalyptus grandis (E), a highly productive species in tropical conditions, and Acacia mangium (A), a N2-fixing species, in monocultures and mixed-species plantations for contrasting planting densities. A randomized block experiment set up over 4 ha in southern Brazil was intensively monitored for 14 months at mid rotation. The absorbed photosynthetically active radiation (APAR) was simulated for each tree of the experiment using the tri-dimensional MAESPA model parameterized with detailed in situ measurements of tree and foliage. LUE for stem wood production was estimated as the ratio of measured stem biomass production (SBP) and simulated APAR. The APAR of Eucalyptus trees did not significantly differ between monocultures and mixed plantations, the reduction of Eucalyptus density being compensated by an increase in light absorption of Eucalyptus individuals. The LUE of Eucalyptus trees in monoculture and mixed-species stands was found to be comparable only at low planting densities. The replacement of Eucalyptus trees with Acacia trees resulted in a reduction in Eucalyptus LUE only at high planting density. The SBP of Eucalyptus trees was mainly explained by differences in APAR, while both APAR and LUE explained the SBP of Acacia trees. The maximum stand production was obtained with monoculture of Eucalyptus at high density and no mixture reached this productivity. Reducing the proportion of Eucalyptus in mixture lead to a substantial decrease in stand production at high planting density due to a decrease in LUE, while this stand production reduction was offset at low planting density, underlying a higher diversity effect at low planting density. In the perspective of increasing diversity in forest plantations to foster multifunctionality, mixed plantations of Acacia and Eucalyptus at low planting density can be an interesting option to maintain a relatively high productivity, which is similar to Eucalyptus monocultures at the same low planting density.

Morphological responses, biomass production and nutrient of Pennisetum purpureum cv. Pakchong under different planting patterns and harvesting ages

Abstract. Ernawati A, Abdullah L, Permana IG, Karti PDMH. 2023. Morphological responses, biomass production and nutrient of Pennisetum purpureum cv. Pakchong under different planting patterns and harvesting ages. Biodiversitas 24: 3439-3447. Napier grass is one of the most popular grasses in tropical and subtropical regions and is a promising forage crop due to its high biomass production, nutritional quality and wide-range adaptability. An optimal management practice is required to maintain production and quality of Napier grass. This experiment examined the morphological responses, forage biomass production, and nutrient biomass of the Napier grass var Thailand (Pakchong) grown under different planting patterns and harvesting ages. The experiment used a completely randomized factorial design 2 x 2, with the first factor was planting pattern (monoculture and intercropping with Indigofera zollingeriana) and the second factor was the harvesting age (50 and 60 days). Each treatment combination was trialed at 5x5 m plot with four replicates. The results showed that planting pattern and harvesting age had significant effect (p<0.05) on tiller numbers, leaves and stem biomass, stem-to-leaves ratio, fresh and dry weight production, and nutrient biomass, except for ash biomass. The highest tiller number was obtained in the intercropping pattern and harvesting age of 50 days. The highest leaves and stem biomass were produced in both planting pattern and harvesting age of 60 days. The fresh and dry weight production and nutrient biomass of Pakchong in intercropping pattern and harvesting of 60 days were higher than those of monoculture cropping. Nonetheless, effect on stem-to-leaves ratio had inconsistent result. The results of this study imply that the best production and nutrient biomass of Napier grass cv. Pakchong were obtained from the grass intercropped with Indigofera and harvesting age of 60 days.

Yield and Bioenergy Quality of Maralfalfa Biomass Obtained at Different Plant Strata and Cutting Dates

One viable option for meeting global energy demand is the creation of biofuels from plant species that demonstrate high biomass productivity and good energy characteristics. In this study, growth was evaluated using plant height (PH), the production of green (GB) and dry biomass (DB), and the energy quality of leaves, pods, and stems, considering apical and basal sections of maralfalfa plants at 28, 60, 90, and 140 days after applying a uniformity cut (AUC). The variables were analyzed with correlation tests and variance analyses (ANOVA) using a factorial array design; in addition, Tukey tests were performed. A steady increase in PH (72 to 239 cm) was found. The highest yield of stems was at 90 AUC (41,362 kg/ha) for GB and 140 days AUC (6331 kg/ha) for DB, and a high correlation was observed between PH and stem biomass production for both the GB (r = 0.91) and DB (r = 0.93). There was a strong correlation between higher heating value and DB from the apical stratum (r = 0.99) and the basal stratum (r = 0.97). Maralfalfa shows high biomass productivity and high energy production in short growth periods.

Mycorrhizae enhance drought tolerance of trifoliate orange by regulating circadian clock response patterns

Either arbuscular mycorrhizal fungus or circadian clock plays an important role in enhancing the tolerance of plants to soil drought, whereas it is not known whether the change of circadian rhythm is involved in mycorrhiza-enhanced drought tolerance in host plants. The purpose of this study was to investigate effects of an arbuscular mycorrhizal fungus Funneliformis mosseae on biomass production, root morphology, and expressions of circadian clock genes and drought-responsive genes in roots of trifoliate orange plants under drought stress conditions. After 8 weeks of soil drought, root mycorrhizal colonization rate and the length of soil mycelium significantly decreased, together with improved leaf, stem, and root biomass production and root morphology by mycorrhizal fungus. Expressions of six circadian clock genes (PtPRR7, PtCCA1, PtLHY, PtGI, PtPIF3, and PtSRR1) and three drought-responsive genes (PtMn-SOD, PtPOD, and PtCAT1) showed obvious circadian rhythm during the day. Under soil drought, F. mosseae induced the expression of PtPRR7, PtGI, and PtSRR1 at 17:00, PtPIF3 and PtSRR1 at 21:00, and PtPRR7, PtPIF3, and PtSRR1 at 1:00, whereas decreased the expression of PtLHY at all the tested time points. F. mosseae also up-regulated expressions of drought-responsive gene (PtFe-SOD, PtMn-SOD, PtCu/Zn-SOD, PtPOD, and PtLEA) at 17:00, 21:00 and 1:00 under drought conditions. Correlation analysis indicated the significant correlation between circadian clock gene expressions and drought-responsive gene expressions. These results conclude that mycorrhizal fungi regulate the circadian rhythm of trifoliate orange to respond to drought.

Close‐spaced plant arrangement optimizes castor biomass and seed yields in tropical fall–winter conditions

AbstractThe high seed yield and optimum harvesting of short‐height castor (Ricinus communis L.) genotypes have enabled its large‐scale cultivation and introduction in the Brazilian cropping systems. Thus, studies to optimize plant density are essential to adequate plant population since this is the key management to influence castor biomass and seed production. This study aimed to evaluate the influence of plant density by altering plant arrangement (i.e., spacing between and within rows) on growth, biomass production and partitioning, and seed yield of a castor cultivar in fall–winter cropping season. Field experiments were conducted over two seasons in southeastern Brazil. Two close‐spaced (0.45 × 0.23 m and 0.45 × 0.44 m) and a traditional (0.90 × 0.44 m) plant arrangements were tested. Plant arrangements influenced plant growth, biomass production and partitioning, and seed yield. Compared to the traditional layout, close‐spaced plant arrangements resulted in thinner basal stems and lower leaf area per plant, but increased leaf area index. The plant arrangement with higher plant density increased per‐unit area production of stem plus leaf biomass (43–48%), which also resulted in increased (24%) seed yield, compared to traditional layout. Although a greater amount of biomass was partitioned to reproductive organs in close‐spaced plant arrangements, this allocation was not enough to influence the harvest index. Therefore, the adaptive performance of short‐height castor adjusting biomass partitioning to maximize stem plus leaf biomass production and seed yield at close‐spaced plant arrangement demonstrated this to be a suitable option to cultivate in the Brazilian fall–winter season.

Aplikasi Pupuk Fosfor terhadap Pertumbuhan, Hasil Biji, dan Gula Brix Tanaman Sorgum

Kondisi lahan yang kering dan kesuburan tanah yang rendah menjadi permasalahan utama dalam pengembangan sorgum sebagai bahan pangan, pakan dan bahan baku industri (ethanol). Pemberian pupuk fospor (P) diharapkan dapat meningkatkan biomas batang, volume nira, kadar brix dan biji sorgum. Tujuan dari penelitian ini adalah untuk mengetahui pengaruh berbagai dosis pemberian pupuk P terhadap pertumbuhan, hasil, kadar gula brix dan biomas beberapa varietas sorgum. Penelitian di laksanakan di Kebun Percobaan Balai Penelitian Tanaman Serealia, Maros Sulawesi Selatan. Rancangan yang digunakan dalam percobaan ini adalah rancangan acak kelompok (RAK) tiga ulangan dengan 2 faktor. Faktor pertama adalah varietas (Super 1, Super 2 dan Numbu). Faktor kedua adalah penambahan pupuk tunggal Posfor (P) : P1= tanpa pupuk fosfor, P2= 25 kg/ha pupuk P, P3= 50 kg/ha pupuk P, P4= 75 kg/ha pupuk P, P5= 100 kg/ha pupuk P dan P6= 125 kg/ha pupuk P. Dosis pupuk acuan yang digunakan adalah 120 kg/ha N, 36 kg/ha P (P2O5) dan 90 kg/ha KCl (K2O). Data dianalisis menggunakan analisis sidik ragam Anova, apabila berpengaruh nyata dilakukan uji lanjut Duncan dengan taraf kesalahan 5%. Hasil penelitian menunjukkan pemberian pupuk P dosis 50 kg/ha menghasilkan panen biji tertinggi pada varietas Super 1 (2.73 t/ha), Numbu (1.93 t/ha) dan pupuk P dengan dosis 25 kg/ha menghasilkan bobot panen tertinggi pada varietas Super 2 (3.76 t/ha). Kadar gula brix tertinggi diperoleh pada varietas Super 1 dosis P 100 kg/ha (12.95%), Super 2 dosis P 125 kg/ha (15.61%) dan Numbu dosis P 125 kg/ha (14.19%).

Extended xylogenesis and stem biomass production in Juniperus przewalskii Kom. during extreme late-season climatic events

Late-season extreme climatic events induced variations in wood density and extended growth for more than a month in 2016 in Juniperus przewalskii Kom. growing on the Northeastern Tibetan Plateau, suggesting extraordinary growth resilience of the species in response to short extreme events over the cold and arid region. Monitoring xylem formation (xylogenesis) during extreme meteorological events helps assessing climate change impacts on tree growth. For better insight into tree-growth responses, here we compare the intra-annual formation of annual ring with and without intra-annual density fluctuation in J. przewalskii in a cold and arid environment on the Northeastern Tibetan Plateau. Cambial phenology and xylogenesis observations of five mature trees during the 2016 intra-annual density fluctuation growth ring and the five-preceding year (2011–2015) were used for comparison. The frequency of population level occurrence of intra-annual density fluctuation in 2016 was examined on additional 50 randomly selected trees. The return of precipitation in conjunction with warm temperatures after summer drought promoted the growth resumption in 64% of our study trees, resulting in the observed intra-annual density fluctuation. These trees experienced a growing season 1 month longer than trees without intra-annual density fluctuation. The extended growth period resulted in a 17% increase in stem biomass in trees that experienced intra-annual density fluctuation. Our results highlight the extraordinary resilience of J. przewalskii trees in response to extreme climatic events in the cold and dry conditions of the Tibetan Plateau.

Salinity and Simulated Herbivory Influence Spartina alterniflora Traits and Defense Strategy

Sea level rise is expected to push saline waters into previously fresher regions of estuaries, and higher salinities may expose oligohaline marshes to invertebrate herbivores typically constrained by salinity. The smooth cordgrass, Spartina alterniflora (syn. Sporobolus alterniflorus), can defend itself against herbivores in polyhaline marshes, however it is not known if S. alterniflora’s defense varies along the mesohaline to oligohaline marsh gradient in estuaries. I found that S. alterniflora from a mesohaline marsh is better defended than plants from an oligohaline marsh, supporting the optimal defense theory. Higher salinity treatments lowered carbon content, C:N, and new stem biomass production, traits associated with a tolerance strategy, suggesting that salinity may mediate the defense response of S. alterniflora. Further, simulated herbivory increased the nitrogen content and decreased C:N of S. alterniflora. This indicates that grazing may increase S. alterniflora susceptibility to future herbivory via improved forage quality. Simulated herbivory also decreased both belowground and new stem biomass production, highlighting a potential pathway in which herbivory can indirectly facilitate marsh loss, as S. alterniflora biomass is critical for vertical accretion and marsh stability under future sea level rise scenarios.

Modelling carbon and water balance of Eucalyptus plantations at regional scale: Effect of climate, soil and genotypes

Carbon and water budgets of forest plantations are spatially and temporally variable and hardly empirically predictable. We applied G’DAY, a process-based ecophysiological model, to simulate carbon and water budgets and stem biomass production of Eucalyptus plantations in São Paulo State, Brazil. Our main objective was to assess the drivers of spatial variability in plantation production at regional scale. We followed a multi-site calibration approach: the model was first parameterized using a detailed experimental dataset. Then a subset of the parameters were re-calibrated on two independent experimental datasets. An additional genotype-specific calibration of a subset of parameters was performed. Model predictions of key carbon-related variables (e.g., gross primary production, leaf area index and stem biomass) and key water-related variables (e.g., plant available water and evapotranspiration) agreed closely with measurements. Application of the model across ca. 27,500 ha of forests planted with different genotypes of Eucalyptus indicated that the model was able to capture 89% of stem biomass variability measured at different ages. Several factors controlling Eucalyptus production variability in time and space were grouped in three categories: soil, climate, and the planted genotype. Modelling analysis showed that calibrating the model for genotypic differences was critical for stem biomass prediction at regional scale, but that taking into account climate and soil variability significantly improved the results. We conclude that application of process-based models at regional scale can be used for accurate predictions of Eucalyptus production, provided that an accurate calibration of the model for key genotype-specific parameters is conducted.

Quantitative trait loci (QTL) mapping for intermittent drought tolerance in BRB 191 × SEQ 1027 Andean Intragene cross recombinant inbred line population of common bean (Phaseolus vulgaris L.).

Drought is a major constraint of common bean (Phaseolus vulgaris L.) production in Uganda where irrigation for the crop is very uncommon. This study aimed to identify quantitative trait loci (QTLs) underlying drought tolerance in 128 F5 RILs derived from an Andean intra-gene cross between drought-tolerant SEQ 1027 and BRB 191. Eighteen traits were evaluated under drought stress and non-stress conditions in the field for 2 years and in the greenhouse for 1 year, respectively. A linkage map spanning 486.29 cM was constructed using 53 single nucleotide polymorphic markers (SNP) markers obtained from the KASP genotyping assay. Eleven consistent QTLs were detected on five linkage groups at a threshold of Logarithm of Odds (LOD) ≥ 3.0. Four QTLs were constitutive, seven were adaptive and were associated with 100 seed weight, grain yield, chlorophyll content, harvest index, dry weight of leaf and stem biomass and yield production efficiency. The QTL associated with a 100 seed weight (sw3.1BS) was the most consistent with the highest percentage of variation explained (21%). Co-localization of five drought-related factors QTLs was detected on pv10 suggesting pleiotropic effects on this chromosome. Identification of molecular markers closely linked to the QTLs identified in this study will facilitate marker assisted breeding for drought tolerance.

Genotypic covariations of traits underlying sorghum stem biomass production and quality and their regulations by water availability: Insight from studies at organ and tissue levels

AbstractSweet and biomass sorghum are expected to contribute increasingly to bioenergy production. Better understanding the impacts of the genotypic and environmental variabilities on biomass component traits and their properties is essential to optimize energy yields. This study aimed to evaluate whether traits contributing to stem biomass growth and biochemical composition at different biological scales (co)vary with the genotype and the water status in sorghum. Height genotypes were studied over two years in field conditions in southern France under two water treatments (well watered vs. 25 days’ dry down during stem elongation). Main stem internode number, size, (non)structural carbohydrate, and lignin contents were measured at the end of the stress period and/or at final harvest, together with biochemical and histological analyses of the youngest expanded internode. The tallest genotypes showed the highest stem dry weights and lignin contents. Stem (structural) biomass density was positively correlated with lignin content, particularly in internode parenchyma. Stem soluble sugar and lignin contents were inversely proportional across genotypes and water conditions. Genotypes contrasted for drought sensitivity and recovery capacity of stem growth and biochemical composition. The length and cell wall deposition of internodes expanding under water deficit were reduced and did not recover, these responses being weakly correlated. Genotypic variability was pointed out in the growth recovery of internodes expanding under re‐watered conditions. According to the observed genotypic variability and the absence of antagonistic correlations between the responses of the different traits to water availability, it is suggested that biomass sorghum varieties optimizing their responses to water availability in terms of growth and cell wall deposition can be developed for different bioenergy targets.

Evaluation of the cumulative effect of drip irrigation and fertigation on productivity in a poplar plantation

Combined drip irrigation and fertigation significantly increased stem volume and biomass production in a poplar plantation, and showed a cumulative effect over years. The promoting effects were mainly attributable to increased nitrogen and water availability in the surface soil through the combined management. Fast-growing and high-yielding poplar plantations have been identified as major commercial forests in China. Intensive management of irrigation and fertilization can greatly increase productivity of plantations. Quantitative investigations on the cumulative effect of drip irrigation and fertigation over years are quite infrequent. We aimed to quantitatively evaluate the effects of drip irrigation and fertigation plans on tree growth and productivity in a poplar plantation, and to analyze their possible cumulative promoting effect over multiple years. Treatments including nine drip irrigation and fertigation combinations, and single furrow irrigation in spring as control, were conducted in a poplar plantation for three successive years. The combined treatments consist of three irrigation levels (WP−75, WP−50, and WP−25, in ascending order) and three levels of nitrogen addition (N60, N120, and N180, in ascending order). Soil nitrogen and water content were measured throughout the 3 years. Based on tree surveys, tree growth, volume, and biomass production were evaluated each year. Nitrogen and water availability in the surface soil increased in the drip irrigation- and fertigation-treated plots. Drip irrigation and fertigation treatments resulted in significant higher growth, stem volume, and biomass productions compared to control. Biomass increments in drip irrigation- and fertigation-treated plots were 4.8–50.0, 5.3–26.5, and 4.3–52.2% higher than control in the three experimental years, respectively, with WP−25N180 and WP−50N180 recording the highest increments. Fertigation showed cumulative effects over multiple years and the positive effects increased with the dosage. However, irrigation showed little cumulative effect and the greatest effect was obtained under medium level. Combined drip irrigation and fertigation greatly promoted the plantation productivity. The combined management effect varied with application plans and plantation ages, and showed a cumulative effect over years.

Performance evaluation and character association studies in arid region greenhouse tomato hybrids

Alike in other areas, greenhouse cultivation is getting special impetus in arid regions owing to providing favourable micro-climate, besides protecting crops from various external crop limiting factors which causes considerable losses to productivity. Cultivar selection is among the most critical aspect for successful greenhouse cultivation. In order to select appropriate cultivar for peculiar arid conditions, the performance of twenty indeterminate tomato hybrids were evaluated under greenhouse condition at Jodhpur during September to April, 2016–17. The performance of hybrids was assessed for their growth, yield and quality characteristics. Results obtained from the study reveal that the performance of tomato hybrids differ significantly for different growth and yield parameters among them. Shoot (leaf + stem) biomass production showed wide variation among the hybrids, ranging from 162g (IA05) to 225.7g (Avtar) per plant. Fruit yield also varied widely (2.36 kg to 4.94 kg plant−1). Hybrid Myla (4.94 kg) was found superior in per plant fruit yield, followed by TR4343 (4.71kg) and TR4266 (4.65kg). Significant differences were also observed for fruit quality attributes such as pericarp thickness, total soluble solids, pH and EC in different hybrids. The character association analyses show that the yield per plant had significant positive correlation with average fruit weight (0.72), fruit diameter (0.50) and pericarp thickness (0.45). The highest fruit number was found in TR4266 (68.4), which had statistically similar per plant fruit yield with Myla. Whereas, the highest average fruit weight (166.8g), though lowest fruit number (40.3) was recorded in TR4293. The high mean values of the yield associated parameters in high-yielding hybrids Myla, TR4343, TR4266, TR4293 corroborates their production potential under greenhouse in arid regions.

Extended light exposure increases stem digestibility and biomass production of switchgrass.

Switchgrass is a photoperiod-sensitive energy grass suitable for growing in the marginal lands of China. We explored the effects of extended photoperiods of low-irradiance light (7 μmol·m-2·s-1, no effective photosynthesis) on the growth, the biomass dry weight, the biomass allocation, and, especially, the stem digestibility and cell wall characteristics of switchgrass. Two extended photoperiods (i.e., 18 and 24 h) were applied over Alamo. Extended light exposure (18 and 24 h) resulted in delayed heading and higher dry weights of vegetative organs (by 32.87 and 35.94%, respectively) at the expense of reducing the amount of sexual organs (by 40.05 and 50.87%, respectively). Compared to the control group (i.e., natural photoperiod), the yield of hexoses (% dry matter) in the stems after a direct enzymatic hydrolysis (DEH) treatment significantly increased (by 44.02 and 46.10%) for those groups irradiated during 18 and 24 h, respectively. Moreover, the yield of hexoses obtained via enzymatic hydrolysis increased after both basic (1% NaOH) and acid (1% H2SO4) pretreatments for the groups irradiated during 18 and 24 h. Additionally, low-irradiance light extension (LILE) significantly increased the content of non-structural carbohydrates (NSCs) while notably reducing the lignin content and the syringyl to guaiacyl (S/G) ratio. These structural changes were in part responsible for the observed improved stem digestibility. Remarkably, LILE significantly decreased the cellulose crystallinity index (CrI) of switchgrass by significantly increasing both the arabinose substitution degree in xylan and the content of ammonium oxalate-extractable uronic acids, both favoring cellulose digestibility. Despite this LILE technology is not applied to the cultivation of switchgrass on a large scale yet, we believe that the present work is important in that it reveals important relationships between extended day length irradiations and biomass production and quality. Additionally, this study paves the way for improving biomass production and digestibility via genetic modification of day length sensitive transcription factors or key structural genes in switchgrass leaves.

Potassium fertilization increases water-use efficiency for stem biomass production without affecting intrinsic water-use efficiency in Eucalyptus grandis plantations

Adaptive strategies to improve tree water-use efficiency (WUE) are required to meet the global demand for wood in a future drier climate. A large-scale throughfall exclusion experiment was set up in Brazil to study the interaction between water status and potassium (K) or sodium (Na) availability on the ecophysiology of Eucalyptus grandis trees. This experiment focused primarily on the changes in aboveground net primary production, stand water use, phloem sap and leaf δ13C, net CO2 assimilation and stomatal conductance. The correlations between these response variables were determined to gain insight into the factors controlling water-use efficiency in tropical eucalypt plantations. The intrinsic WUE in individual leaves (the ratio of net CO2 assimilation to stomatal conductance) was estimated at a very short time scale from the leaf gas exchange. Sap flow measurements were carried out to assess the WUE for stemwood production (the ratio of wood biomass increment to stand water use).Averaged over the two water supply regimes, the stemwood biomass 3years after planting was 173% higher in trees fertilized with K and 79% higher in trees fertilized with Na than in trees with no K and Na addition. Excluding 37% of the throughfall reduced stemwood production only for trees fertilized with K. Total canopy transpiration between 1 and 3years after planting increased from about 750 to 1300mmy−1 in response to K fertilization with a low influence of the water supply regime. K fertilization increased WUE for stemwood production by approx. 60% with or without throughfall exclusion. There was a strong positive correlation between phloem sap δ13C and short-term leaf-level intrinsic WUE. Whatever the water and nutrient supply regime, the gas exchange WUE estimates were not correlated with WUE for stemwood production. Phloem sap δ13C and leaf δ13C were therefore not valuable proxies of WUE for stemwood production. The allocation pattern in response to nutrient and water supply appeared to be a major driver of WUE for stemwood production. In areas with very deep tropical soils and annual rainfall <1500mm, our results suggest that breeding programs selecting the eucalypt clones with the highest growth rates tend to select the genotypes with the highest water-use efficiency for wood production.

Stability and genetic control of morphological, biomass and biofuel traits under temperate maritime and continental conditions in sweet sorghum (Sorghum bicolour).

Eight morphological, biomass and biofuel traits were found with high broad-sense heritability and 18 significant QTLs discovered including one locus controlling the stem juice trait for sorghum grown in Denmark and China. Sweet sorghum with tall plant, fast maturation and high stem Brix content can be bred as a biofuel crop for Northern Europe. Sweet sorghum (Sorghum bicolour), a native tropical C4 crop, has attracted interest as a bioenergy crop in northern countries due to its juice-rich stem and high biomass production. Little is known about the traits important for its adaptation to high altitude climatic conditions and their genetic controls. Recombinant inbred lines derived from a cross between a sweet and a grain kaoliang sorghum were used in five field trials in Denmark and in China to identify the stability and genetic controls of morphological, biomass and biofuel traits during three consecutive summers with short duration, cool temperatures and long days. Eight out of 15 traits were found with high broad-sense heritability. Strong positive correlations between plant height and biomass traits were observed, while Brix and juice content were under different genetic controls. Using newly developed PAV (presence and absence variant) markers, 53 QTLs were detected, of which 18 were common for both countries, including a locus controlling stem juice (LOD score=20.5, r (2)=37.5%). In Denmark, the heading stage correlated significantly with biomass and morphology traits, and two significant maturity QTLs detected on chromosomes SBI01 and SBI02 co-localised with QTLs previously associated with early-stage chilling tolerance, suggesting that accelerating maturation might be a means of coping with low-temperature stress. Our results suggest that selection for tall and fast maturating sorghum plants combined with high Brix content represents a high potential for breeding bioenergy crop for Northern Europe.

Long-term changes in belowground and aboveground resource allocation of boreal forest stands

Age-related decline of forest stand growth is a common phenomenon, but the associated physiological causes remain uncertain. This study investigated a possible mechanism that could explain stand growth decline observed after canopy closure. We hypothesised that the proportion of resource allocation to roots increases with stand age as a response to a decrease in nutrient availability, which is related to the long-term accumulation of organic matter in boreal forests. Proxies based on soil respiration measurements and stem biomass production were used to describe temporal changes in the proportion of carbon allocated to belowground and aboveground stand components along a 1067-year post-fire chronosequence. The proportion of resources that were allocated belowground increased in the first 200years following fire and declined thereafter. The inverse pattern was observed for the organic matter decomposition rate. Stand-level decline in wood productivity that was observed during the first 60-year period after fire can be attributed to a greater proportion of carbohydrates being allocated to roots in response to a decrease in nutrient availability. However, the relatively low productivity of old-growth stands was not associated with high belowground allocation, suggesting that other mechanisms operating at the tree- or stand-level may be involved.

Measured and modeled interactive effects of potassium deficiency and water deficit on gross primary productivity and light-use efficiency in Eucalyptus grandis plantations.

Global climate change is expected to increase the length of drought periods in many tropical regions. Although large amounts of potassium (K) are applied in tropical crops and planted forests, little is known about the interaction between K nutrition and water deficit on the physiological mechanisms governing plant growth. A process-based model (MAESPA) parameterized in a split-plot experiment in Brazil was used to gain insight into the combined effects of K deficiency and water deficit on absorbed radiation (aPAR), gross primary productivity (GPP), and light-use efficiency for carbon assimilation and stem biomass production (LUEC and LUEs ) in Eucalyptus grandis plantations. The main-plot factor was the water supply (undisturbed rainfall vs. 37% of throughfall excluded) and the subplot factor was the K supply (with or without 0.45 mol K m(-2 ) K addition). Mean GPP was 28% lower without K addition over the first 3 years after planting whether throughfall was partly excluded or not. K deficiency reduced aPAR by 20% and LUEC by 10% over the whole period of growth. With K addition, throughfall exclusion decreased GPP by 25%, resulting from a 21% decrease in LUEC at the end of the study period. The effect of the combination of K deficiency and water deficit was less severe than the sum of the effects of K deficiency and water deficit individually, leading to a reduction in stem biomass production, gross primary productivity and LUE similar to K deficiency on its own. The modeling approach showed that K nutrition and water deficit influenced absorbed radiation essentially through changes in leaf area index and tree height. The changes in gross primary productivity and light-use efficiency were, however, driven by a more complex set of tree parameters, especially those controlling water uptake by roots and leaf photosynthetic capacities.

Phytoremediating coastal saline soils with oats: accumulation and distribution of sodium, potassium, and chloride ions in plant organs

Saline soil is considered to have a greater reserve of potentially cultivable land in China, especially in coastal areas with abundant rainfall. The possible use of oats (Avena sativa L. or Avena nuda L.) for phytoremediation of the salinity and thus to improve soil quality for other crops is receiving greater attention. Six varieties (Bayou-1, Baiyan-2, Baiyan-7, Huawan-6, Huazao-2 and Pin-16) of oat were studied for their accumulation and distribution of salt ions in plant organs using a saline coastal area near the Bohai sea of North China. The objective was to determine the effects of variety, plant organs and time of harvest on the phytoremediating potential of oat. Plant uptake of sodium, potassium and chloride ions as well as growth rate varied significantly according to variety, growth stage, plant organ, and their interactions. The peak uptake of sodium and chloride ions in leaves across varieties was at the heading stage but in stem it was at maturity; for most varieties, potassium concentration was much higher in the stem during the growth period. The partitioning of ions to stem, root and panicle increased from heading to maturity but declined from maturity to delayed harvesting stage. However, those in the leaf continually decreased from heading to delayed harvesting stage. Averaged across growth stages and organs, the highest uptake rate for sodium ion (1739.4 g ha−1 day−1) and chloride ion (3693.7 g ha−1 day−1) was in the stem of BaiYan-7 variety during heading to maturity. The uptake rates for potassium ion in the stem were also the highest (2880.2 g ha−1 day−1 in the stem of BaiYan-2 variety) but they occurred from elongation to heading stage. Since most of the ions were concentrated in the straw, especially the stem, managing oats to enhance stem or straw biomass production and optimizing harvest or clipping times would have both economic and remediation benefits. Data from this study have added new information on how best to use oat for reclaiming degraded saline soils.

Stem Biomass Production of Paulownia elongata × P. fortunei under Low Irrigation in a Semi-Arid Environment

In semi-arid regions, afforestation with fast-growing species cultured with low irrigation can be an effective approach for environmental protection. An experiment was conducted to evaluate the stem biomass production of Paulownia in a semi-arid climate and clay soils under contrasting low-irrigation and fertilization treatments. The stem biomass at the stand level was estimated by applying allometric equations fitted in sample resprouts and inventory data. The results show that biomass production improved when either irrigation or fertilizer was added, but the combination of a higher dose of irrigation and fertilization did not lead to the highest biomass production; thus water availability was the main factor controlling biomass production. Under the higher dose of irrigation, the absence of a fertilizer effect would be due in part to the fertile soil, which could supply sufficient nutrients for Paulownia growth at the higher level of soil moisture. The stem biomass estimated ranged from 2.14 to 4.50 t×ha−1 (lower irrigation dose without fertilization, and higher irrigation with fertilization). The greater production was similar to other studies in the Mediterranean area receiving more irrigation. Thus, this study permitted us to understand the potential of Paulownia to provide biomass in semi-arid environments with low irrigation due to water use restrictions.