Percentage Of Biomass Research Articles

تأثیر کودهای آلی، شیمیایی و زیستی بر عملکرد و کارایی مصرف نیتروژن و فسفر در خرفه (Portulaca oleracea L.)

AbstractBackground and Objectives: Purslane (Portulaca oleracea L.) is an annual and C4 plant that belongs to the family of Portulacaceae. The plant is drought- and salt-tolerant which contains high amounts of beneficial omega-3 fatty acids and antioxidant vitamins. Nitrogen is the key element in soil fertility and crop production. Attention to the soil quality and health has increased in recent years, especially for sustainable production of medicinal crops. So that, for production of healthy food in industrialized countries, using natural and on-farm inputs has been considered. One of the practical ways to achieve this goal is organic and biofertilizers. Given the importance of Purslane as a medicinal plant and due to the fact that there is not detailed information about the nitrogen requirement for this plant, this study was conducted to effect of organic, biological and chemical fertilizers on yield, N and P use efficiency Purslane (Portulaca oleracea L.) in Birjand, Iran Materials and Methods: In order to investigate the effect of organic, biological and chemical fertilizers on the yield and yield components of purslane seed, an experiment was conducted in a factorial randomized complete block design with three replications in Birjand University Research Farm in crop years 2015-2016 and 2017- 2018. Experimental treatments were based on a combination of four sources of nitrogen supply: cow manure, vermicompost, fertilizer (NPK) and control (without any fertilizer application), and four types of biofertilizer including: nitroxin (including azotobacter and azospirillum), mycorrhiza (Glomus intraradices), Biosulfur (including thiobacillus with sulfur) and control (without any fertilizer). The traits studied in this experiment included: biomass yield, grain yield, nitrogen and phosphorus biomass percentage, nitrogen and phosphorus biomass content, nitrogen and phosphorus uptake efficiency, seed based nitrogen and phosphorus uptake efficiency, agronomic efficiency of nitrogen and phosphorus based They were. Results: The results showed that the effect of nitrogen sources on all studied traits (except physiological grain nitrogen efficiency) was significant. The highest grain yield (1959.99 kg.ha-1) and biomass yield (9782.43 kg.ha-1) were obtained from NPK treatment with no significant difference with cow manure. Also, the most nitrogen efficiency indices were obtained from NPK treatment. However, no significant difference was observed between agronomic efficiency of grain and cow manure. The highest phosphorus content and biomass phosphorus content were obtained from NPK treatment. However, with the use of organic and chemical fertilizers, the efficiency of phosphorus use decreased. The effect of biofertilizers on most of the studied traits (except biomass P percent) was not significant. Interaction of nitrogen sources and biofertilizers was significant on most of the studied traits (except grain yield, agronomic efficiency of N and P). Conclusions: Based on the results of this experiment, considering the environmental effects and increasing the efficiency of nitrogen use for sustainable production of purslane seed in Birjand region can be used as fertilizer replacement (NPK).

Co-Combustion Characteristics of Typical Biomass and Coal Blends by Thermogravimetric Analysis

In this study, the co-combustion characteristics of coal and biomass blends (20, 40, 60, 80, and 100 wt%) were investigated by thermogravimetric analysis. All the samples were operated under an oxidative atmosphere, with a heating rate of 20 C/min. The reaction stages, ignition and burnout temperature, maximum weight loss rate, and different combustion indices were determined. When the percentage of biomass in the blends was increased, the maximum mass loss rate was enhanced in the second region, and the ignition and burnout temperature was lowered, indicating the higher reactivity and better combustion performance of the samples. The comprehensive performance index presented an N shape with the increasing biomass blending ratio. Based on various combustion indices, 20% was an optimum percentage for the co-utilization of coal-biomass blends. A significant promoting interaction was observed between corn straw and rice straw blends, while inhibiting effects occurred between rice husk and coal. The kinetic parameters of the blends were evaluated by the Coats and Redfern method using the nth-order reaction model. The value of activation energy and the pre-exponential factor increased with the decreasing biomass percentage in the blends.

Longleaf pine seedling growth and survival: Effects of season and intensity of simulated prescribed burning

Restoration of longleaf pine (Pinus palustris Mill.) forests is an important land management goal in the southern United States. To achieve this goal, longleaf pine is increasingly being planted across its range. Fire is an important ecological factor that has historically shaped and sustained longleaf pine forests. However, we have limited information on how fire impacts longleaf pine seedlings in newly established plantations. We conducted this study in Northwest Florida to examine the effects of fire intensity (low intensity ((LI), ∼100 °C), medium intensity ((MI), ∼300 °C), high intensity ((HI), ∼500 °C), and an untreated control) on survival, growth (root collar diameter (RCD) and height), physiological processes (net assimilation (A), stomatal conductance (gsw), and intrinsic water use efficiency (iWUE)), and biomass allocation of longleaf pine seedlings over a period of six months after fire was applied in four seasons (summer, fall, winter, spring). Within a given season, the survival of seedlings did not significantly differ at different fire intensities, except in the summer (α = 0.05). For the summer application, survival was lower (18%) in the HI treatment compared to the MI (98%), LI (93%), and control (93%) (p = 0.003). RCD growth was significantly affected by fire intensity treatment only for the summer application. For the summer application, RCD growth six months after treatment (MAT) was highest (7.3 mm) in the control compared to the LI (2.7 mm), MI (2.7 mm), and HI (2.0 mm) (p = 0.021). The height growth of seedlings did not significantly differ at different fire intensities, though their values were greater at 6 months compared to 3 months. The effect of fire temperature on percent biomass allocation was only significant for the fall foliage (p = 0.004). Neither root, stem, nor total shoot percent biomass significantly differed for any other season. Largely, A, gsw, and iWUE were not significantly affected by fire temperature. iWUE did differ for MAT (p = 0.003), however, no pattern could be discerned. Overall, our observations suggest that longleaf pine seedlings are highly resistant and resilient to fire intensity in different seasons, with some vulnerability to high-intensity summer fires which can adversely affect their survival and growth. Summer burning is still a viable option for seedling survival provided conditions on the ground favor low/medium intensity fire.

Environmental bioremediation for uranium removing from aqueous solution by modified polyvinyl alcohol (PVA) embedded with Aspergillus versicolor

Development of new functional materials for heavy metals removal from environmental system has attracted considerable attention. In this paper, novel functional polymer consists of modified polyvinyl alcohol (PVA) embedded with Aspergillus versicolor biomass, using gamma radiolysis is prepared for uranium ions removal. Twenty two samples, with different physical conditions, were prepared to investigate the capability of the proposed functional polymer for adsorption and removal of uranyl ions from aqueous solution. Furthermore, comprehensive study was conducted to examine effect of A. versicolor particle size, embedded biomass percentage inside the functional polymer, and gamma ray radiation dose on adsorption efficiency of UO2 2+ ions. Obtained results illustrated that modified PVA with acetic acid, embedded with 1% A. versicolor biomass that has 45 µm particle size, and gamma irradiated at 10kGy is considered as the optimum functional polymer with the highest removal efficiency of UO2 2+ ions of 57.20%. The optimum functional polymer, before and after uranium ions adsorption, were characterized using SEM and FTIR techniques. It was found that the adsorbed UO2 2+ ions can be desorbed effectively by 0.1 M EDTA.

Optimization of multi variant process parameters to reduce emissions of high sulfur coal during combustion in fluidized bed facility

Pakistan has 185 billion tonnes reserves of coal but unfortunately the quality of 80% of this coal is not good. As the country has a shortage of energy so it is necessary to refine the coal before it can be used to produce electricity. In this sense, this research is very important as it enables indigenous coal to meet the increasing energy demand. This study is focused on the control of sulfur emissions during the combustion of high sulfur Pakistani coal from the Trans Indus Range and the Salt Range. Parameters like Ca/S molar ratios (MRs), limestone particle size, bed temperature, and different percentages of biomass in co-firing with coal have been studied. It is showed that desulfurization of coal was maximum with the fine-sized particles of limestone. Co-firing of moderate quantity biomass exhibited a considerable decrease in SO2 emissions. Results achieved are presented in the form of tables and plots. This study for control of the gaseous emissions from combustion in FBC facility has great potential for new coal based power projects, especially in Pakistan.

Yield of ‘Gigante’ cactus pear cultivated under biofertilizer doses and application intervals

ABSTRACT Due to the water restriction, associated with the high cost of fertilizers, and the need to produce forage in the semi-arid regions, studies using biofertilizers in cactus pear production tend to become impactful. The aim of this study was to evaluate the morphometric characteristics and yield of ‘Gigante’ cactus pear cultivated under doses and application intervals of bovine manure biofertilizer. The experimental design was in randomized blocks, in a 2 × 5 factorial scheme, with two biofertilizer application intervals (14 and 21 days) and five biofertilizer doses (0, 15, 30, 45 and 60 m3 ha-1). Three replicates were used, totaling 30 experimental units. The following variables were evaluated: plant height, number of cladodes, cladode length, cladode width and cladode area index, dry biomass percentage, and green and dry biomass yields. The use of 60 m3 ha-1 of liquid cattle manure biofertilizer increased the yield of ‘Gigante’ cactus pear. The application of 60 m3 ha-1 of biofertilizer at the interval of 14 days increased the yield of ‘Gigante’ cactus pear.

Combined application of two Bacillus species enhance phytoremediation potential of Brassica napus in an industrial metal-contaminated soil

This study aimed to assess the impact of individual as well as combined application of Lysinibacillus macroides and Bacillus safensis in phytoremediation potential of Brassica napus grown in soil contaminated by industrial effluents. In response to five metals; copper, chromium, nickel, lead, and cadmium, results revealed that germination percentage, fresh and dry weights, and photosynthetic pigments of B. napus decreased under contaminated soil. On the other hand, electrolyte leakage due to cellular injury, metabolites (proline and glycine betaine), antioxidant enzymes (superoxide dismutase, catalase, peroxidase, ascorbate peroxidase), accumulation of hydrogen peroxide and metals in plant’s roots, shoots and leaves increased. Inoculation significantly reduced these effects as proved by the enhancement of germination percentage, fresh and dry biomass, and photosynthetic pigments. Simultaneously, the antioxidant enzymes, metabolites contents (proline and glycine betaine) and metal concentrations in plant’s roots, shoots and leaves decreased. Combined application of both Bacilli strains was found more effective as compared to individual inoculation. It was concluded that metal resistant Bacillus species in combination had growth effects on B. napus and enhanced its phytoremediation efficiency in contaminated soil. Novelty statement Brassica napus; a hyper-accumulator of metals, loses phytoremediation potential with the passage of growth. Two Bacillus species (Lysinibacillus macroides and Bacillus safensis) having known bioremediation abilities were employed individually as well as in combination under metals contaminated soil to increase phytoremediation efficiency of B. napus. The metals containing soil used is a unique aspect in this study because selected soil, contaminated by industrial effluents, has not been evaluated or reported earlier. Combined application of Bacilli improved phytoremediation potential of B. napus more as compared to application of individual Bacillus strain which is yet another unique aspect of this investigation.

Drone RGB Images as a Reliable Information Source to Determine Legumes Establishment Success

The use of drones in agriculture is becoming a valuable tool for crop monitoring. There are some critical moments for crop success; the establishment is one of those. In this paper, we present an initial approximation of a methodology that uses RGB images gathered from drones to evaluate the establishment success in legumes based on matrixes operations. Our aim is to provide a method that can be implemented in low-cost nodes with relatively low computational capacity. An index (B1/B2) is used for estimating the percentage of green biomass to evaluate the establishment success. In the study, we include three zones with different establishment success (high, regular, and low) and two species (chickpea and lentils). We evaluate data usability after applying aggregation techniques, which reduces the picture’s size to improve long-term storage. We test cell sizes from 1 to 10 pixels. This technique is tested with images gathered in production fields with intercropping at 4, 8, and 12 m relative height to find the optimal aggregation for each flying height. Our results indicate that images captured at 4 m with a cell size of 5, at 8 m with a cell size of 3, and 12 m without aggregation can be used to determine the establishment success. Comparing the storage requirements, the combination that minimises the data size while maintaining its usability is the image at 8 m with a cell size of 3. Finally, we show the use of generated information with an artificial neural network to classify the data. The dataset was split into a training dataset and a verification dataset. The classification of the verification dataset offered 83% of the cases as well classified. The proposed tool can be used in the future to compare the establishment success of different legume varieties or species.

Is the Life History Flexibility of Cold Desert Annuals Broad Enough to Cope with Predicted Climate Change? The Case of Erodium oxyrhinchum in Central Asia.

Simple SummaryThe broad objective of our study was to evaluate the life history flexibility of the annual Erodium oxyrhinchum in relation to the predicted changes in precipitation in the cold desert due to climate change. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring- and autumn-germinated seeds of the cold desert annual E. oxyrhinchum from 2016–2020. Also, the future climate for the region was modeled. Our results found that given the flexibility in the life history of E. oxyrhinchum, it seems unlikely that future climate change will have much of an impact on the life history and dominant position of this species in the herbaceous plant community in the unpredictable-rainfall environment of the cold desert. Our study challenges the commonly-held perception that desert organisms may be negatively affected by climate change.Interannual seasonal variability in precipitation may strongly affect the life history and growth of desert annual plants. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring (SG)- and autumn (AG)-germinated seeds of the cold desert annual Erodium oxyrhinchum. Vegetative and reproductive growth and F2 seed dormancy and germination were monitored from September 2016 to November 2020 in the sandy Gurbantunggut Desert in NW China in Central Asia. Dry autumns decreased the density of AG plants, and dry springs decreased the density of SG plants and growth of SG and AG plants. In dry springs, SG plants were more sensitive to precipitation than AG plants, while in wet springs SG and AG plants had similar responses to precipitation. During growth in both dry and wet springs, most morphological characters of SG and AG plants initially increased rapidly in size/number and then plateaued or decreased, except for SG plants in dry springs. In dry springs, most morphological characters of AG plants were larger or more numerous than those of SG plants, and they were larger/more numerous for SG plants in wet than in dry springs. The percentage biomass allocated to reproduction in SG plants was slightly higher in a wet than in a dry spring. A much higher proportion of dormant seeds was produced by AG plants in a wet spring than in a dry spring. Projected changes in precipitation due to climate change in NW China are not likely to have much of an effect on the biology of this common desert annual plant.

Spatial Variability of Nitrogen Uptake and Net Removal and Actual Evapotranspiration in the California Desert Carrot Production System

Nitrogen (N) and irrigation water must be effectively used in mineral soils to produce carrots with high yield and minimal environmental impact. This study attempts to identify optimal N and irrigation management practices for low desert carrot production in California by investigating consumptive water use and N uptake and removal rates in fresh market and processing carrots. Field experiments were conducted at the University of California Desert Research and Extension Center and nine farmer fields during two growing seasons. The actual evapotranspiration (ETa) was measured using the residual energy balance method with a combination of surface renewal and eddy covariance equipment. Crop canopy coverage, actual soil nitrate-N from multiple depths as well as total N percentage, dry matter, and fresh biomass in roots and tops were measured over the growing seasons. The length of the crop season had a wide range amongst the experimental sites: from a 128-day period in a processing carrot field to as long as 193 days in a fresh market carrot field. The seasonal ETa varied between 305.8 mm at a silty loam furrow irrigated processing carrot field and 486.2 mm at a sandy clay loam sprinkler irrigated fresh market field. The total N accumulated at harvest ranged between 205.4 kg ha−1 (nearly 52% in roots) and 350.5 kg ha−1 (nearly 64% in roots). While the mean value of nitrogen removed by carrot roots varied from 1.24 to 1.73 kg N/Mg carrot roots, it appears that more N was applied than was removed by carrot roots at all sites. Within the range of N application rates examined at the experimental sites, there was no significant relationship between carrot fresh root yield and N application rate, although the results suggested a positive effect of N application on carrot yield. Sufficient soil N availability over the growing season and the lack of significant yield response to N application illuminated that optimal N rates are likely less than the total amounts of N applied at most sites.

Oncogene-regulated release of extracellular vesicles.

Oncogenes can alter metabolism by changing the balance between anabolic and catabolic processes. However, how oncogenes regulate tumor cell biomass remains poorly understood. Using isogenic MCF10A cells transformed with nine different oncogenes, we show that specific oncogenes reduce the biomass of cancer cells by promoting extracellular vesicle (EV) release. While MYC and AURKB elicited the highest number of EVs, each oncogene selectively altered the protein composition of released EVs. Likewise, oncogenes alter secreted miRNAs. MYC-overexpressing cells require ceramide, whereas AURKB requires ESCRT to release high levels of EVs. We identify an inverse relationship between MYC upregulation and activation of the RAS/MEK/ERK signaling pathway for regulating EV release in some tumor cells. Finally, lysosome genes and activity are downregulated in the context of MYC and AURKB, suggesting that cellular contents, instead of being degraded, were released via EVs. Thus, oncogene-mediated biomass regulation via differential EV release is a new metabolic phenotype.

Approach to the Functional Importance of Acropora cervicornis in Outplanting Sites in the Dominican Republic

Coral restoration has been recognized as an increasingly important tool for coral conservation in recent years. In the Caribbean, the endangered staghorn coral, Acropora cervicornis has been studied for restoration for over two decades with most studies focusing on evaluating simple metrics of success such as colony growth and survivorship in both nurseries and outplanted sites. However, for reef restoration to aid in the recovery of ecological function in outplanted sites, there is a need to measure the functional ecology of the impact of outplanting. Here, we present and identify positive ecological processes and ecological functions (such as increased fish biomass, coral cover, and increased in structural complexity) relative to active reef restoration. In the Southeastern Reefs Marine Sanctuary in the Dominican Republic, we monitored the percentage of benthic cover and fish biomass alongside active reef restoration over the period of 12 months in four zones. Subsequently, we developed multidimensional analyses in conjunction with generalized linear models (GLM) and linear models. Our results show there is a remarkable spatial and temporal differentiation favoring greater ecological function in restored areas. We observed the most noticeable patterns of change in the benthos and coral species composition. We found a positive relationship between amounts of outplanted colonies with the total fish biomass for the three outplanted sites. We highlight that Scarus iseri, a parrotfish critical for grazing maintenance, was the species with the greatest benefit. Our results provide evidence of the functional importance of Acropora cervicornis in coral reef active restoration efforts.

Influence of microwave-assisted chemical treatment on delignification of rice straw biomass

Lignocellulosic biomass (like rice straw) provides an alternative for depleting non-renewable energy sources through its value-added utilization (like production of biofuels and nanocellulose) owing to its abundance, renewability, polymer presence and environmental friendliness. Prior to its utilization, any lignocellulosic biomass is subjected to a time-consuming delignification process for lignin free biomass recovery. The present study aims to reduce the time of delignification of rice straw along with enhancing the delignification percentage of biomass by use of microwave assisted sodium chlorite method. The experiments were done at two microwave power levels (640, 800 W), three bleaching solution concentrations (0.4, 1.7, 3.0 %) and three microwave treatment times (4, 8, 12 min). The delignification percentage of the rice straw for the whole experimentation varied from 24.7 to 90.12%. The results revealed that the time of delignification was greatly reduced (12 min) with a very high delignification (90.12%) percentage. The morphology of the delignified samples also revealed the deconstruction of the lignin structure. The improved method can thus be applied for the delignification of other biomasses as well for quick and effective delignification

Predicting the effects of reservoir impoundment on phytoplankton and shoreline vegetation communities using the space-time substitution method

Abstract The prediction of the influence of reservoir impoundment on water quality and phytoplankton community is the basis of ecological compensation or restoration. The aim of the current study was to predict the effects of reservoir impoundment on phytoplankton and shoreline vegetation communities using the space-time substitution method. The Huangjinxia Reservoir under construction on the Han River was selected as the research object. The space-time substitution method indicated that the average values of the total phosphorus (TP) and ammonia (NH4+-N) increased from 0.049 and 0.279 mg L−1 to 0.139 and 1.132 mg L−1, respectively, after reservoir impoundment. The percentage of diatom biomass exceeded 95% before the reservoir impoundment. However, it was gradually decreased to 75% after the reservoir impoundment. Meanwhile, the biomass of Chlorophyta, Cryptophyta and Pyrrophyta increased significantly, accounting for 32, 20 and 13% of the total biomass, respectively, after reservoir impoundment. Cynodon dactylon (65.3%), Polygonum hydropiper (51.7%) and Aster subulatus (50.3%) were the dominant shoreline vegetation before the reservoir impoundment, whereas after the reservoir impoundment, the dominant species shifted to Alternanthera philoxeroides (62.3%), Lobelia chinensis (55.7%) and C. dactylon (53.9%). Our results suggested that the percentage of bloom-forming phytoplankton would gradually increase after the reservoir impoundment. In addition, A. philoxeroides, C. dactylon and L. chinensis would be the plants suitable for living in the shoreline of reservoirs in this area.

Genetics of robustness under nitrogen‐ and water‐deficient conditions in field‐grown lettuce

AbstractRobustness is the measure of the ability to perform well across multiple environments. The genetics of robustness in lettuce (Lactuca sativa L.) under changing nitrogen (N) application was studied by two parameters obtained from linear regression analysis. Robustness in changing water application was assessed by two parameters: relative efficiency component (REC) and susceptibility component (SC). The efficiency, sensitivity, and the effect of reduced irrigation on these parameters was assessed for 50 lines of lettuce in 2011. Efficiency, sensitivity, and plant N uptake and utilization were important traits in robustness under changing N application. Eight cultivars were re‐evaluated in 2012, 2014, and 2016 under high‐ and low‐N treatments in order to estimate the repeatability of efficiency and sensitivity. Repeatability was greater for efficiency than sensitivity. In addition, the genetics of efficiency, sensitivity, REC, SC, nutrient concentration, nutrient content, dry‐to‐fresh biomass percentage, bolting, and shoot biomass production were studied by quantitative trait locus (QTL) analysis of a recombinant inbred line (RIL) population derived from the cultivars Grand Rapids and Iceberg. The population was phenotyped in three experiments and genotyped by sequencing. Major clusters of QTL for these traits were identified in linkage groups (LGs) 3, 7, and 9. Minor‐effect QTL for sensitivity were identified in LGs 3 and 4. Intermediate‐effect QTL for SC were identified in LGs 4 and 7. These results provide evidence that the components of robustness under changing N (efficiency and sensitivity) and water (REC and SC) availability are genetically independent and can be improved through breeding.

Effects of elevated CO2 on resistant and susceptible rice cultivar and its primary host, brown planthopper (BPH), Nilaparvata lugens (St\xe5l)

The elevated CO2 (eCO2) has positive response on plant growth and negative response on insect pests. As a contemplation, the feeding pattern of the brown plant hopper, Nilaparvata lugens Stål on susceptible and resistant rice cultivars and their growth rates exposed to eCO2 conditions were analyzed. The eCO2 treatment showed significant differences in percentage of emergence and rice biomass that were consistent across the rice cultivars, when compared to the ambient conditions. Similarly, increase in carbon and decrese in nitrogen ratio of leaves and alterations in defensive peroxidase enzyme levels were observed, but was non-linear among the cultivars tested. Lower survivorship and nutritional indices of N. lugens were observed in conditions of eCO2 levels over ambient conditions. Results were nonlinear in manner. We conclude that the plant carbon accumulation increased due to eCO2, causing physiological changes that decreased nitrogen content. Similarly, eCO2 increased insect feeding, and did alter other variables such as their biology or reproduction.

Comperative study of aboveground biomass and carbon storage between Tembawang and conventional rubber agroforestry in West Kalimantan Indonesia

In the era of intensive oil palm and rubber plantations in Kalimantan, some local communities of Dayak's tribe in West Kalimantan preserved the traditional agroforestry system "Tembawang". In the last two decades, rubber has been planted traditionally by local communities since the expansion of rubber industries. This study aimed to compare tree above ground biomass (AGB) distribution and carbon storage in different DBH (diameter at breast height) classes between Tembawang and conventional rubber plantation in West Kalimantan, Indonesia. Vegetation transect analysis was carried out on two types of traditional agroforestry namely Tembawang and conventional rubber. AGB estimation was based on the existing allometric, carbon storage was estimated from the percentage of biomass. Total AGB of Tembawang was higher than conventional rubber plantation and significantly different (p < 0.01). The highest AGB accumulation both Tembawang and conventional rubber was found at above 50 cm diameter class. The aboveground carbon storage from Tembawang and conventional rubber plantation were 90.26 and 42.01 Mg C ha-1, respectively. The highest contribution to carbon storage was found at above 50 cm diameter class, estimated 62.58 % from Tembawang and 49.24 % from conventional rubber. AGB and carbon storage at traditional agroforestry in West Kalimantan were greater than varied different agroforestry system, also the estimated value was closed to tropical secondary forests. Tembawang agroforestry has good potential contribution to carbon storage and conservation of native fruit trees of Kalimantan.

Plant community changes determine the vegetation and soil δ13C and δ15N enrichment in degraded alpine grassland

Abstractδ13C and δ15N are extensively used to understand the biogeochemical mechanisms that moderate ecosystem carbon (C) and nitrogen (N) processes. Little is known about the responses of δ13C and δ15N to alpine grassland degradation on the Qinghai‐Tibetan Plateau (QTP), which prevents a full understanding of degradation‐induced changes in C and N cycling there. We investigated the vegetation δ13C and δ15N, soil δ13C and δ15N, soil properties, and plant community composition of alpine grassland on the QTP that were in different states of degradation. Our results show that the vegetation δ13C and δ15N, and soil δ13C and δ15N, increased with the severity of degradation, whereas soil organic carbon (SOC) and total N content decreased as degradation became more severe. The aboveground biomass percentage of forbs was positively correlated with the soil C/N ratio, vegetation δ13C, and soil δ13C, and accounted for the largest proportion of the variance for both vegetation δ13C and soil δ13C (17.25 and 23.65%, respectively). The vegetation δ15N and soil δ15N were negatively correlated with the soil C/N ratio, which explained the largest proportion of the variance (18.01 and 25.81%, respectively). Our results suggest that C cycling is strongly moderated by plant community composition, because forbs species and C4 species, were more prevalent in degraded alpine grassland. Meanwhile, N cycling is indirectly regulated by changes in community composition via its effect on the soil C/N as the degradation became more severe for alpine grassland on the QTP.

Improving tree biomass models through crown ratio patterns and incomplete data sources

Aboveground biomass quantification is essential for determining carbon stocks in forests. Multiple tree biomass models are available, but estimations can be biased outside the fitting range. This is due to the lack of data for larger trees, mainly because of the cost and time required. This study proposed a methodology based on tree crown biomass ratio (crown biomass: total aboveground biomass) modelling. The original data used in the existing biomass models in Spain have been notably extended by the inclusion of stem data from First Spanish National Forest Inventory and other databases, covering better tree size variability. The analysis of the crown biomass ratio against tree size (d2h), allowed us to distinguish three different patterns: an increasing pattern, a constant one, and a decreasing pattern. A new system of biomass models was fitted simultaneously by species, including a model for crown biomass ratio according to the identified pattern, a stem biomass model, and a total aboveground biomass model. Using this methodology, models were fitted for the 29 most important species in Spain. The fitted models result in more accurate and unbiased predictions for stem biomass, and realistic estimations for the crown biomass. This methodology means more robust and flexible biomass estimations with the possibility of using different data sources. The absence of crown information is not an obstacle because this component is a percentage of total aboveground biomass. Moreover, determining the crown biomass ratio pattern allows improving the accuracy of tree biomass estimation beyond the range of tree sizes (2–70 cm) for which these models were fitted.

基因型多样性对羊草种群年龄结构的影响

基因型多样性作为遗传多样性的重要组成部分，不仅在群落水平，而且在种群水平均可以发挥重要生态作用。以羊草（Leymus chinensis）为研究对象，设置5种基因型多样性梯度试验控制小区，进行基因型多样性对羊草种群年龄结构的影响研究。结果表明：随基因型多样性梯度的逐步增加，2a分蘖株生物量和数量均显著增加（P<0.05）；1-4龄级羊草根茎生物量、长度和干物质积累量多数呈极显著性增加的变化趋势（P<0.01）。在1、2、4、8和12种基因型多样性梯度时，分蘖株生物量及数量年龄结构均以1a或2a分蘖株所占比例为最高，年龄结构表现为增长型或稳定型；而羊草种群根茎生物量和长度也以2a根茎所占比例为最高，年龄结构表现为稳定型。随基因型多样性水平的增加，羊草种群分蘖株数量和生物量的年龄结构从增长型向稳定型过渡，但根茎长度和生物量的年龄结构均为稳定型。12基因型多样性水平的4龄级分蘖株和根茎的特征高于其他基因型多样性水平。因此，在不同基因型多样性水平羊草种群分蘖株和根茎具有增长型或稳定型的年龄结构，适当的基因型多样性数量显著促进了各龄级羊草分蘖株和根茎的生物量和数量特征的升高，但高度的基因型多样性水平会增加羊草种群中高龄级的分蘖株和根茎所占的比例，种群发展表现出衰退信号。;Genotypic diversity is an important part of biodiversity, which plays an important ecological role not only at the community level, but also at the population level. In this study, we set up five gradients of genotypic diversity to explore the effects of genotypic diversity on Leymus chinensis population from the perspective of age structure. The results showed that the biomass and number of 2nd age class tillers of L. chinensis population increased significantly with the increase of genotypic diversity (P<0.05),and the biomass of rhizome,length and dry matter accumulation of L. chinensis in different ages increased significantly (P<0.01). At five gradients of genotypic diversity,percentage of biomass and tiller number of 1st or 2nd age class tillers were the highest among different ages and showed expanding or stable age structure. But percentage of rhizome length and biomass in L. chinensis population of 2nd age rhizomes were highest proportion among different ages and showed stable age structure. With the increase of genotypic diversity,the age structure of tiller number and biomass of L. chinensis population transited from expanding type to stable type,but the age structure of rhizome length and biomass were stable type. The characteristics of tillers and rhizomes at age 4th of 12 genotypic diversity level were higher than other genotypes. The cumulative length of the rhizome of L. chinensis not only reflects the asexual reproduction ability, but also reflects its spatial expansion ability. High genotypic diversity significantly increases the length of the rhizome of L. chinensis population. The reason is that genotypic diversity can improve the soil nutrient absorption efficiency of L. chinensis, thus effectively promoting the root growth and providing conditions for population expansion. Therefore,the tillers and rhizomes of L. chinensis population have an expanding or stable age structure at different genotypic diversity levels. Moderate genotype number promotes the increase of the biomass and number characteristics of tillers and rhizomes at different age levels. This is due to the contribution of complementary effect to the positive effect of genotypic diversity. There are some differences in morphological and physiological characteristics among different genotypic levels of L. chinensis, resulting in different nutrient requirements and resource utilization ability of different genotype of L. chinensis. The increase of genotypic diversity can improve the utilization rate of resources and promote the development of L.chinensis population.However, over high genotypic diversity will increase the proportion of senior tillers and rhi senior zomes in the population of L. chinensis,and the development of population showed a decline signal.