Aboveground Plant Material Research Articles

Enhancing the Phytoextraction of Cd, Cu, Pb, and Zn by Portulaca oleracea in a Heavily Contaminated Soil Using Low Molecular Weight Organic Substances: Is Phytoremediation Viable?

Phytoremediation can be accelerated if contaminated soils are amended with releasing agents. We tested four such materials, citric acid (CA), EDTA, oxalic acid (OA), and tartaric acid (TA) at two doses, 20 and 40 mmol kg−1, amended in a pot experiment to a heavily contaminated soil cultivated with purslane (Portulaca oleracea). We found that Cd extracted with DTPA remained unchanged in all treatments compared to the control except for the treatment of added EDTA at 40 mmol kg−1 (“EDTA-40”). Similar was the case with Cu, Pb, and Zn. As a consequence, Cd in the aboveground plant material increased significantly from 1.21 (control) to 3.84 at EDTA-40 and 3.55 at EDTA-20 (mg kg−1). Similar was the case with all other metals, with Pb exhibiting an impressive fivefold increase to 280.35 mg kg−1 at EDTA-40 from the control. We conclude that EDTA was the most successful releasing agent among those tested, especially for Pb and Zn. However, we come to the conclusion that, based on calculations of the required time to meaningfully reduce soil metals contents, phytoremediation is not a practical option for extremely metal-elevated soils. These findings should be verified under field conditions.

Treatment Wetland Plant Harvests as a Tool for Soil Phosphorus Reduction in North Central US Agricultural Watersheds

Agricultural watersheds in the North Central United States have been intensively farmed for decades with widespread application of fertilizer and extensive tilling practices. Soil phosphorus built up in sediments over time as a result of these practices may be released under anaerobic conditions, such as flood events. These floods are increasing in frequency and intensity due to climate change, leading to downstream water-quality concerns. Edge-of-field best management practices, including constructed treatment wetlands, provide a natural buffer for excess phosphorus runoff, but may only be a temporary solution if soil becomes oversaturated with phosphorus over extended periods of time. Preventing wetlands from becoming sources of phosphorus to water bodies may be essential for management in future years when considering impacts from climate change. This research assesses how wetland plant harvesting can reduce soil phosphorus accumulation (measured as Olsen phosphorus) in edge-of-field treatment wetlands, thereby preventing these systems from becoming phosphorus sources and ensuring the longevity of water-quality benefits from these systems. Using several 380 L controlled wetland mesocosm experiments in 2018–2019, we assessed above-ground plant material (S. tabernaemontani and B. fluviatilis) and soil Olsen P through the growing season and after harvest. We observed a reduction in soil phosphorus from wetland plant harvesting between 1–50% over one year, with a mean reduction of 7.9 mg/kg. B. fluviatilis initially contained higher P concentration early in the season (0.82% P content) compared to S. tabernaemontani (0.76% P), but S. tabernaemontani retained higher P later in the season (0.3% P content) compared to B. fluviatilis (0.25%). Time of season may significantly impact plant P removal potential, including accessibility of treatment wetland sites. While controlled mesocosm experiments may not always be applicable to real landscape-level management, this study highlights the potential for reductions in soil phosphorus and corresponding downstream phosphorus fluxes in edge-of-field treatment wetlands through plant harvest during the growing season. Plant harvesting can be used by land managers in edge-of-field treatment wetlands as an adaptation mechanism for shifting environmental conditions, such as increased heavy rainfall occurrences and flood events, that are exacerbated by climate change in this region.

Assessing carbon storage capacity and saturation across six central US grasslands using data–model integration

Abstract. Future global changes will impact carbon (C) fluxes and pools in most terrestrial ecosystems and the feedback of terrestrial carbon cycling to atmospheric CO2. Determining the vulnerability of C in ecosystems to future environmental change is thus vital for targeted land management and policy. The C capacity of an ecosystem is a function of its C inputs (e.g., net primary productivity – NPP) and how long C remains in the system before being respired back to the atmosphere. The proportion of C capacity currently stored by an ecosystem (i.e., its C saturation) provides information about the potential for long-term C pools to be altered by environmental and land management regimes. We estimated C capacity, C saturation, NPP, and ecosystem C residence time in six US grasslands spanning temperature and precipitation gradients by integrating high temporal resolution C pool and flux data with a process-based C model. As expected, NPP across grasslands was strongly correlated with mean annual precipitation (MAP), yet C residence time was not related to MAP or mean annual temperature (MAT). We link soil temperature, soil moisture, and inherent C turnover rates (potentially due to microbial function and tissue quality) as determinants of carbon residence time. Overall, we found that intermediates between extremes in moisture and temperature had low C saturation, indicating that C in these grasslands may trend upwards and be buffered against global change impacts. Hot and dry grasslands had greatest C saturation due to both small C inputs through NPP and high C turnover rates during soil moisture conditions favorable for microbial activity. Additionally, leaching of soil C during monsoon events may lead to C loss. C saturation was also high in tallgrass prairie due to frequent fire that reduced inputs of aboveground plant material. Accordingly, we suggest that both hot, dry ecosystems and those frequently disturbed should be subject to careful land management and policy decisions to prevent losses of C stored in these systems.

Recovery of nitrogen fertiliser by drill-sown rice crops using best management practice: a

Context Optimising nitrogen (N) management strategies for drill-sown rice crops is essential for minimising input costs for growers and reducing the environmental impact of rice production. Aims The study aimed to determine the recovery of fertiliser-N in drill-sown Australian rice crops, following current N fertiliser recommendations where two-thirds of the N is applied at sowing (pre-flood) and one-third at panicle initiation. Methods 15N-labelled urea was used to quantify N recovery by field-grown rice crops on a Sodosol and a Vertosol, and to determine the contributions of fertiliser-N applied pre-flood vs that applied at panicle initiation to total N fertiliser recovery on the Vertosol. Results Recovery of 15N fertiliser in grain + straw was ∼50% of applied N on both soils, with a further 20% recovered from roots and soil to a depth of 30 cm. Recovery of N fertiliser applied at panicle initiation (59%) was significantly higher than of N fertiliser applied pre-flood (43%), likely due to the presence of actively growing roots and higher plant N demand. Crops that received N fertiliser took up more native soil N than unfertilised crops on the Vertosol; hence, apparent fertiliser N recoveries were 10–15% higher than N fertiliser recovery determined using 15N-labelled urea. Conclusions The recovery of 50% of fertiliser-N in aboveground plant material indicates that N fertiliser use efficiency in drill-sown rice is similar to that of dryland cereal crops in Australia when best management practice guidelines for N fertiliser use are followed.

入侵植物藿香蓟与常见伴生杂草的生态位特征

PDF HTML阅读 XML下载 导出引用 引用提醒 入侵植物藿香蓟与常见伴生杂草的生态位特征 DOI: 10.5846/stxb202104060881 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 浙江省自然科学基金项目(LY20C030002);浙江省教育厅一般项目(Y202045218) Niche characteristics of the invasive plant Ageratum conyzoides and its commonly associated weeds Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于传统生态位理论的生物入侵机制假说认为外来种和土著种生态位的差异是决定入侵成功与否和危害程度的关键。藿香蓟(Ageratum conyzoides L.)是一种在我国南方快速蔓延的恶性入侵种。为了了解藿香蓟与其他杂草在群落中的生态关系,探究造成藿香蓟成功入侵的可能机制及危害,在浙西南的丽水市开展了杂草群落调查,计算了藿香蓟和16种常见本地杂草的生态位宽度、生态位重叠和种间相关系数,并对主要物种进行典范对应分析(CCA)排序。结果表明(1)藿香蓟与常见本地杂草间的生态位重叠度显著高于本地杂草间的生态位重叠度,这与藿香蓟具有最大的生态位宽度有关;(2)藿香蓟与常见本地杂草的Pianka生态位重叠指数介于0.04-0.296之间,重叠度处于中下水平;(3)常见本地杂草对于藿香蓟的n-维超体积生态位重叠值显著高于藿香蓟对于常见本地杂草的n-维超体积生态位重叠值;(4)藿香蓟在CCA排序图上处于较中心的位置,说明其具有较高的中生性;不仅如此,外来杂草和本地杂草在排序图上充分混杂,说明外来种相对于本地种并无明显特化;(5)群落中大多数常见杂草间未出现显著种间负相关,仅7个种对显著正相关,大多数种对不相关。总的来说,丽水农村的杂草群落稳定较差,资源相对充足,种间生态位重叠较低,本地植物对于藿香蓟的竞争阻抗较小,加上藿香蓟本身较大的生态位宽度,导致了藿香蓟在本地区广泛而严重的入侵。 Abstract:According to the hypothesized mechanism of biological invasion, which is based on traditional niche theory, niche differentiation between alien species and native species is the key to the success of invasion and the damage it causes. Ageratum conyzoides L. is a malignant invasive species that is spreading rapidly in southern China. In order to understand the ecological relationships between A. conyzoides and native weeds in the community and to explore the possible mechanism of A. conyzoides invasion and its harmfulness, an investigation of the weed community was carried out in southwestern Zhejiang Province (28°06'-28°44'N, 119°32'-120°08'E) from 2014 to 2016. A total of 109 plots (1 m×1 m) and 286 plant species were investigated in the following habitats: roadside, abandoned farmland, streamside, and open forest. For each plot, all aboveground plant material was harvested, classified, and weighed according to species. In addition, slope, aspect, and altitude of the plot as well as the rate of sunshine arriving at the plot were measured. Moreover, pH value and the contents of total nitrogen, alkaline nitrogen, effective phosphorus, available potassium, and organic material in superficial soil (0-10 cm depth) of each plot were tested. Levin's niche breadth, Pianka's niche overlap, probability of n-dimensional niche overlap, and interspecific correlation coefficients of A. conyzoides and 16 common native weeds were calculated, and a canonical correspondence analysis (CCA) was conducted. The results showed that (1) the degree of niche overlap between A. conyzoides and common native weeds was significantly higher than that between any two native weeds, due to the largest niche breadth of A. conyzoides. (2) The Pianka niche overlap index between A. conyzoides and common native weeds was in the middle or lower level of 0.04-0.296. (3) The probabilities of n-dimensional niche overlap of common native weeds with A. conyzoides were significantly higher than those of A. conyzoides with common native weeds. (4) A. conyzoides was distributed in the central region of a CCA ordination chart, which indicated that A. conyzoides was a mesophilic species; moreover, exotic weeds (including A. conyzoides) and native weeds were fully mixed in the ordination chart, which indicated that there was no obvious specialization of exotic species relative to native species; and (5) there were no significantly interspecific negative correlations among the 17 common weed species; only 7 species pairs showed significantly positive correlation, and most species did not correlate with each other. In general, the weed community in the rural areas of southwestern Zhejiang Province is unstable, with relatively sufficient resources and low niche overlap among species. Low competition resistance from native plants and large niche width of A. conyzoides lead to extensive and serious invasion of A. conyzoides in the rural area of southwestern Zhejiang Province. 参考文献 相似文献 引证文献

Short-Term Influence of Burning on Species Abundance, Biomass Production, Wood Plant Density and Browsing Unit in an Albany Thicket of the Eastern Cape, South Africa

Fire is regarded as management practice for maintaining grasslands and savannas. The vegetation occurring in fire prone areas becomes highly adapted to fire occurrences in savannas and grasslands. However, documentation on the influence of burning on vegetation is still limited in an albany thicket biome. The aim of the study was to evaluate the short-term influence of burning on species abundance, biomass production, wood plant density and browsing unit. Six plots (2500 m2) were demarcated; in each plot two parallel transects of 120 m2 with 5 m distance apart were measured. Three plots were burned in spring season, while no burning was done on the other remaining plots. Forty points per plot were obtained using step-point method to determine the relative abundance at burned and unburned plots. Woody plants occurred within a transect were identified, counted and recorded to determine density and browsing unit. Three quadrats (i.e. 0.25 m2) per plot were randomly laid within the transect; aboveground plant material within a quadrat were harvested. A total of 18 samples were harvested and oven dried at 60˚C for 48 hours to determine biomass production. The results showed that Themeda triandra (14%) and Panicum maximum (10%) were most abundant grass species at the burned plots. Burned plots had significantly higher biomass production (4804 kg/ha) compared to unburned plots (3641 kg/ha). Vachellia karoo (burned: 65.85% & unburn: 13.70%) and Searsia pallens (burned: 26.83% & unburned: 6.85%) were most dominant wood plant species at both burned and unburned plots. Burned plots had the highest browsing unit (3221 BU/ha) compared to unburned plots (2058 BU/ha). The decrease of woody plants at the burned plots proved that fire has a tremendous potential for managing woody plants. This study provided information on short-term influence of burning, however further long-term trials are required to determine the effects of burning.

Effects of seasonal grazing and annual mowing on floristic composition and plant diversity in the Saral rangeland, Kurdistan, Iran

This study examined the impact of long-term (40 years) seasonal grazing and annual scythe mowing on changes in plant diversity, floristic composition and plant functional groups in the cold semi-arid rangelands of Mangahul-Zardawan located in Saral, Kurdistan. In this investigation, 900 plots (2 m2) were sampled in grazed (450 plots) and mowed sites (450 plots) to measure vegetation and plant characteristics. Data were collected in two consecutive growing seasons from late May to early June in 2017 and 2018. Both years recorded below average rainfall. The results showed that after 40 years, seasonal grazing compared to scythe mowing increased canopy cover and species richness of different functional groups including annuals, perennial grasses, perennial forbs and total vegetation. On the other hand, both the total above-ground plant material and the palatability index were higher for the mowed than the grazed sites, although scythe mowing had caused the Boraginaceae family to disappear. Based on these results, the mean of total plant material (above-ground live + standing dead + litter) was substantially higher in the mowed area, where two-year mean totals were 271 g/m2 compared with 216 g/m2 for the grazed area. In terms of a three-level palatability classification (high, medium and low), only the plants with moderate palatability differed in contribution between the sites, with mowed sites having a significantly greater proportion of this class than the grazed sites. Our results suggested that in the long term, grazing can maintain species richness and the typical floristic composition of rangelands; but when socio-economic issues have priority, mowing has more advantages. In rangelands with the same ecological and geographic conditions, users and managers can choose the most appropriate management approach based on their long- and short-term policies.

Lower soil moisture and deep soil temperatures in thermokarst features increase old soil carbon loss after 10 years of experimental permafrost warming

AbstractAlmost half of the global terrestrial soil carbon (C) is stored in the northern circumpolar permafrost region, where air temperatures are increasing two times faster than the global average. As climate warms, permafrost thaws and soil organic matter becomes vulnerable to greater microbial decomposition. Long‐term soil warming of ice‐rich permafrost can result in thermokarst formation that creates variability in environmental conditions. Consequently, plant and microbial proportional contributions to ecosystem respiration may change in response to long‐term soil warming. Natural abundance δ13C and Δ14C of aboveground and belowground plant material, and of young and old soil respiration were used to inform a mixing model to partition the contribution of each source to ecosystem respiration fluxes. We employed a hierarchical Bayesian approach that incorporated gross primary productivity and environmental drivers to constrain source contributions. We found that long‐term experimental permafrost warming introduced a soil hydrology component that interacted with temperature to affect old soil C respiration. Old soil C loss was suppressed in plots with warmer deep soil temperatures because they tended to be wetter. When soil volumetric water content significantly decreased in 2018 relative to 2016 and 2017, the dominant respiration sources shifted from plant aboveground and young soil respiration to old soil respiration. The proportion of ecosystem respiration from old soil C accounted for up to 39% of ecosystem respiration and represented a 30‐fold increase compared to the wet‐year average. Our findings show that thermokarst formation may act to moderate microbial decomposition of old soil C when soil is highly saturated. However, when soil moisture decreases, a higher proportion of old soil C is vulnerable to decomposition and can become a large flux to the atmosphere. As permafrost systems continue to change with climate, we must understand the thresholds that may propel these systems from a C sink to a source.

Comparison of nutrient accrual in constructed living shoreline and natural fringing marshes

Living shoreline marshes are coastal wetlands constructed as alternatives to “hardened shorelines” (e.g., bulkheads, riprap) to mitigate erosion and to allow for landward migration of intertidal habitat as sea level rises. Living shorelines are designed to mimic natural fringing marshes and over time should be sinks for carbon and other nutrients. We collected soil cores and aboveground plant material from 13 pairs of natural fringing marshes and living shoreline marshes of different ages and degree of isolation from more extensive marsh shorescapes to compare nutrient pools and accrual. Although the nutrient content of plants was similar within and between marsh types, soil nutrients were variable from both living shorelines aged 2–16 years and long-established natural marshes. Most—but not all—living shoreline marshes had lower soil organic content, higher bulk density, and lower soil % carbon, nitrogen and phosphorus than their natural marsh pair. Variation in soil nutrients from living shorelines was not strongly correlated with either marsh age or degree of isolation in the estuarine shorescape. Assuming constant accrual within individual marshes, we estimated soil nutrient levels in living shorelines would approach those observed in their paired, natural fringing marshes over timescales from less than 10 years to many decades. Living shoreline marshes are on trajectories to match natural marsh function with respect to carbon and nutrient storage in estuarine systems.

The multiple effects of hydrogen sulfide on cadmium toxicity in tobacco may be interacted with CaM signal transduction

Soilless culture experiments with tobacco were conducted to explore how the signal molecule H2S (0.3, 0.6, 0.9, and 1.2 μM) alleviated the toxicity of Cd2+ (50 mg/L). The results suggested that photosynthesis was enhanced as H2S improved the tobacco ΦPSII, ETR, Photo, Cond, and Tr, and that by increasing the NPQ, it consumed considerable amount of energy to enhance plant resistances during Cd2+ exposure. Furthermore, H2S increased the gene transcription of NtSOD3, NtPOD1, and CAT1, to enhance antioxidant enzyme activity, which reduces the generation of the reactive oxygen protective membrane integrity. Additionally, H2S increased the gene expression of the tobacco PC genes, Pr2 and Pr8 promoted the formation of the Cd2+ complexes and transportation to the vacuole, resulting in improved Cd-ATPase gene expression, away from organelles, to alleviate the Cd2+ poison. Furthermore, H2S regulated the relative absorption of K+ and Ca2+, which antagonized the Cd2+, and reduced its transportation to the aboveground plant material. Finally, the expression level of CaM increased with the application of H2S, and was highly correlated with the fitted results of a variety of resistance indicators, thereby indicating that H2S regulatory resistance mechanisms might be associated with Ca2+ signal transduction.

Sunlight Doubles Aboveground Carbon Loss in a Seasonally Dry Woodland in Patagonia

Photodegradation of aboveground senescent plant material (plant litter) due to exposure to solar radiation has been identified as a dominant control on carbon (C) loss in semi-arid ecosystems [1], upturning traditional models of C cycling based only on available moisture and litter quality. In addition to the photochemical mineralization of organic matter [1, 2], sunlight alters the chemistry of cell walls in plant litter [3, 4], making them more susceptible to subsequent biotic degradation [5-7]. Nevertheless, the interactive effects of sunlight exposure, climate seasonality, and biotic decomposition on C turnover remain unresolved in terrestrial ecosystems. We show here that exposure to sunlight accelerated litter decomposition in a Patagonian woodland with a marked dry summer season. Controls on initial decomposition varied seasonally from direct photochemical mineralization in the dry summer to biotic degradation in the wet winter. By manipulating sunlight received by plant litter using spectral filters that attenuated ultraviolet and short-wave visible light, we demonstrate that direct photodegradation and its legacy, associated with increased microbial access to labile carbohydrates, are responsible for the acceleration of aboveground C turnover in this Mediterranean-type climate. Across plant species and over a 2-year period, litter exposed to the full solar spectrum decomposed twice as fast as litter that received attenuated sunlight. Changes in vegetation cover or biodiversity due to projected increased drought and dry season length [8] will likely exacerbate C losses from aboveground litter due to sunlight exposure, negatively impacting the C balance in ecosystems that are particularly vulnerable to global change [9].

Impacts of Chilean forest subsidies on forest cover, carbon and biodiversity

In response to the important benefits forests provide, there is a growing effort to reforest the world. Past policies and current commitments indicate that many of these forests will be plantations. Since plantations often replace more carbon-rich or biodiverse land covers, this approach to forest expansion may undermine objectives of increased carbon storage and biodiversity. We use an econometric land use change model to simulate the carbon and biodiversity impacts of subsidy driven plantation expansion in Chile between 1986 and 2011. A comparison of simulations with and without subsidies indicates that payments for afforestation increased tree cover through expansion of plantations of exotic species but decreased the area of native forests. Chile’s forest subsidies probably decreased biodiversity without increasing total carbon stored in aboveground biomass. Carefully enforced safeguards on the conversion of natural ecosystems can improve both the carbon and biodiversity outcomes of reforestation policies. After forest loss, public subsidies often encourage reforestation with tree plantations. This modelling study finds that between 1986 and 2011, Chile’s forest subsidies probably reduced biodiversity without increasing carbon stored in aboveground plant material.

Sunlight Doubles Aboveground Carbon Loss in a Seasonally Dry Woodland in Patagonia

Photodegradation of aboveground senescent plant material (plant litter) due to exposure to solar radiation has been identified as a dominant control on carbon (C) loss in semiarid ecosystems [1], upturning traditional models of C cycling based only on available moisture and litter quality parameters. In addition to the photochemical mineralization of organic matter, sunlight alters the chemistry of cell walls in plant litter, making them more susceptible to subsequent biotic degradation. Nevertheless, the interactive effects of sunlight exposure, climate seasonality and biotic decomposition on C turnover remain unresolved in terrestrial ecosystems. We show here that accelerated litter decomposition in a Patagonian woodland is explained by the exposure of plant litter to sunlight, coupled with a marked dry summer season. The initial controls of decomposition varied seasonally from direct photochemical mineralization in the dry summer to biotic degradation in the wet winter. Nevertheless, manipulation of sunlight received by plant litter using spectral filters demonstrated that direct photodegradation and its legacy, associated with increased microbial access to labile carbohydrates, are responsible for the acceleration of aboveground C turnover in this mediterranean-type climate. Across plant species, exposure to solar radiation doubled rates of C loss to the atmosphere. Changes in vegetation cover or biodiversity due to projected increased drought and dry season length will likely exacerbate C losses from aboveground litter due to sunlight exposure, negatively impacting the C balance in ecosystems that are particularly vulnerable to global change.

Phytotoxic Effect of Invasive Heracleum mantegazzianum Essential Oil on Dicot and Monocot Species.

Spreading of the plant species in new areas is supported by the hypothesis in which chemicals produced by alien species are allopathic to native plants. A novel weapon hypothesis was tested by using essential oil of dangerous alien species Heracleum mantegazzianum in laboratory conditions. Aboveground plant material was collected in south-east part of Slovakia, dried and hydrodistilled for essential oil isolation. Dominant compounds as octyl acetate (62.6%), hexyl 2-metylbutyrate (10.7%), hexyl isobutyrate (7.5%) and hexyl butyrate (6.5%) were identified by GC-MS. Potential phytotoxic activity was tested on three dicot plant species garden cress (Lepidium sativum L.), radish (Raphanus sativus L.) and lettuce (Lactuca sativa L.) and on one monocot plant species wheat Triticum aestivum L. Germination of the seeds of model plant species after influencing by different doses of essential oil of H. mantegazzianum as well as the roots length was evaluated. Lepidium sativum L. and Raphanus sativus L. were generally not sensitive to applied doses of essential oil although a little stimulation effect at some concentrations prevailed over inhibition effect. Similarly, in monocot species Triticum aestivum L., stimulation was visible in both root length and root number at two or one highest doses, respectively.

Storage and drivers of soil organic carbon and nitrogen in a rangeland ecosystem across a lithosequence in western Iran

Identifying the drivers of soil organic carbon (SOC) and nitrogen (N) dynamics is profoundly needed to get insight into the nutrient cycling in the terrestrial ecosystems. Soil parent material is one of the important factors affecting SOC and N dynamics. The aim of this research was to explore C and N dynamics of a soil lithosequence with parent materials ranging from sedimentary to metamorphic and plutonic bedrock in the eastern Kurdistan province, in western Iran.We examined the hypothesis that SOC and N accumulation potential and turnover vary significantly with soil bedrock lithology. To test our hypothesis, we collected soil samples at three depth intervals (0–5, 5–25 and 25–50 cm) as well as aboveground plant materials in six geological contexts: clastic carbonate sedimentary (CCS), foliated metamorphic (FM), non-foliated metamorphic (NFM), intermediate plutonic (IP), felsic plutonic (FP) and intermediate felsic plutonic (IFP). Soil characteristics (SOC, total N, δ13C, δ15N, soil texture, pH, EC, carbonates, available P) and plant material properties (C and N contents and their stable isotopic signatures) were determined in 45 soil samples and 18 plant materials, respectively.Results showed that both geology and soil depth strongly influenced the SOC and total N concentrations as well as their stable C and N isotopic composition. Both SOC and total N were highest per site/lithology in the soils over FM geology (5.42 and 0.51 g kg−1 soil for SOC and total N, respectively) and least in the soils forming on FP parent material (0.97 and 0.12 g kg−1 soil for SOC and total N, respectively). In the case of stable C and N isotopic composition, the highest mean value per lithology was found in the NFM soils (−23.68‰ for δ13C) and FP soils (13.74‰ for δ15N), while the lowest mean signature was observed in the soils developed over FM geology (−25.41‰ and 7.88‰ for δ13C and δ15N, respectively). Vertical distribution of both δ13C and δ15N signatures in the studied soils showed an increasing trend by depth. The main controlling factors for organic C and N concentrations across the lithosequence were explored using PLSR and PCA analyses.Results indicated that different soil properties controlled the SOC and total N contents at the different depths. Soil stable C and N isotopic compositions and pH were the factors that influenced negatively the organic C and N contents across the studied lithosequence. Differently, soil C/N ratio was strongly positively associated with SOC and TN contents. Clay- and silt-size fractions had no substantial influence on the organic C and N concentrations, although importance of silt particles for SOC and TN storage increased with increasing soil depth. These findings provide evidence that geology, as soil parent material, can control both SOC and N accumulation and turnover. However, a more in-depth study is required to understand the mechanisms by which parent lithology affects the organic C and N dynamics.

LAESI mass spectrometry imaging as a tool to differentiate the root metabolome of native and range-expanding plant species

Main conclusionLAESI-MSI, an innovative high-throughput technique holds a unique potential for untargeted detection, profiling and spatial localization of metabolites from intact plant samples without need for extraction or extensive sample preparation.Our understanding of chemical diversity in biological samples has greatly improved through recent advances in mass spectrometry (MS). MS-based-imaging (MSI) techniques have further enhanced this by providing spatial information on the distribution of metabolites and their relative abundance. This study aims to employ laser-ablation electrospray ionization (LAESI) MSI as a tool to profile and compare the root metabolome of two pairs of native and range-expanding plant species. It has been proposed that successful range-expanding plant species, like introduced exotic invaders, have a novel, or a more diverse secondary chemistry. Although some tests have been made using aboveground plant materials, tests using root materials are rare. We tested the hypothesis that range-expanding plants possess more diverse root chemistries than native plant species. To examine the root chemistry of the selected plant species, LAESI-MSI was performed in positive ion mode and data were acquired in a mass range of m/z 50–1200 with a spatial resolution of 100 µm. The acquired data were analyzed using in-house scripts, and differences in the spatial profiles were studied for discriminatory mass features. The results revealed clear differences in the metabolite profiles amongst and within both pairs of congeneric plant species, in the form of distinct metabolic fingerprints. The use of ambient conditions and the fact that no sample preparation was required, established LAESI-MSI as an ideal technique for untargeted metabolomics and for direct correlation of the acquired data to the underlying metabolomic complexity present in intact plant samples.

Preliminary study on the dynamics of heavy metals in saline wastewater treated in constructed wetland mesocosms or microcosms filled with porous slag.

This study aims to evaluate the practical potential of using constructed wetlands (CWs) for treating saline wastewater containing various heavy metals. The results demonstrated that CWs growing Canna indica with porous slag as substrate could efficiently remove heavy metals (Cu, Zn, Cd, and Pb) from saline wastewater at an electrical conductivity (EC) of 7mS/cm, especially under low influent load. Salts with salinity level (characterized as EC) of 30mS/cm suppressed the removal of some heavy metals, dependent on heavy metal species and their influent concentrations. The presence of salts in CWs can improve the accumulation of Cu, Zn, and Pb in plant tissues as compared to control treatment, irrespective of metal concentrations in solution. The influence of salts on Cd accumulation depended on both salinity levels and Cd concentrations in solution. Although more heavy metals were accumulated in roots than in shoots, the harvesting of aboveground plant materials is still efficient addition for heavy metal removal due to the greater biomass and growth rate of aboveground plant material. Furthermore, replacing all plants instead of preserving roots from harvested plants in CWs over a period of time is essential for heavy metal removal, because the continued accumulation by roots can be inhibited by the increasing accumulated heavy metals from saline wastewater.

Prospects for Genetic Improvement in Internal Nitrogen Use Efficiency in Rice

While improving the efficiency at which rice plants take up fertiliser nitrogen (N) will be critical for the sustainability of rice (Oryza sativa L.) farming systems in future, improving the grain yield of rice produced per unit of N accumulated in aboveground plant material (agronomic N use efficiency; NUEagron) through breeding may also be a viable means of improving the sustainability of rice cropping. Given that NUEagron (grain yield/total N uptake) is a function of harvest index (HI; grain yield/crop biomass) × crop biomass/total N uptake, and that improving HI is already the target of most breeding programs, and specific improvement in NUEagron can only really be achieved by increasing the crop biomass/N uptake. Since rice crops take up around 80% of total crop N prior to flowering, improving the biomass/N uptake (NUEveg) prior to, or at, flowering may be the best means to improve the NUEagron. Ultimately, however, enhanced NUEagron may come at the expense of grain protein unless the N harvest index increases concurrently. We investigated the relationships between NUEagron, total N uptake, grain yield, grain N concentration (i.e., protein) and N harvest index (NHI) in 16 rice genotypes under optimal N conditions over two seasons to determine if scope exists to improve the NHI and/or grain protein, while maintaining or enhancing NUEagron in rice. Using data from these experiments and from an additional experiment with cv. IR64 under optimum conditions at an experimental farm to establish a benchmark for NUE parameters in high-input, high yielding conditions, we simulated theoretical potential improvements in NUEveg that could be achieved in both low and high-input scenarios by manipulating target NHIs and grain protein levels. Simulations suggested that scope exists to increase grain protein levels in low yielding scenarios with only modest (5–10%) reductions in current NUEagron by increasing the current NHI from 0.6 to 0.8. Furthermore, substantial scope exists to improve NUEveg (and therefore NUEagron) in high-yielding scenarios if maintaining current grain protein levels of 7.3% is not essential.

Variation in specific root length among 23 wheat genotypes affects leaf δ 13 C and yield

Abstract Identifying root traits that are associated with efficient nutrient and water utilization is crucial for improving plant functioning and productivity. In the case of wheat genotypes, such root traits could be used by plant breeders to improve grain yield and quality. In this study 23 wheat genotypes (Triticum spp.) belonging to different breeding groups were planted in a randomized block design field experiment in NSW, Australia and fertilized with 100 (LN) and 234 kg N ha−1 (HN). Root traits were measured at stem elongation, and aboveground plant material was collected at stem elongation, grain filling and plant maturity. Differences in specific root length (SRL, the ratio of root length to dry mass) among genotypes confirmed their genotypic variability. SRL in the topsoil at stem elongation was a good predictor of leaf δ13C (a proxy of leaf-scale water use efficiency, WUEi) both at grain filling and at plant maturity, and of grain yield in both LN and HN treatments. Notably, genotypes with higher SRL (longer and thinner roots) had a higher leaf δ13C (i.e. higher WUEi) and N concentrations and were associated with lower grain yield. High N rates increased leaf δ13C and N concentrations without overall increasing grain yield. Genotypes with higher SRL were more responsive to higher rates of fertilization producing leaves with higher N and grain with higher protein concentrations. Therefore, SRL is a key root trait affecting grain yield through control on soil water uptake, and affecting grain quality through control on soil N uptake when N availability is high. We suggest that SRL should be considered by plant breeding schemes as a target trait to modify grain yield and quality.

Recycling organic wastes to agricultural land as a way to improve its quality: A field study to evaluate benefits and risks

A field study was established to assess the effects of a sewage sludge (SS), a mixed municipal solid waste compost (MMSWC) and a compost produced from agricultural wastes (AWC), in a Vertisol, using Lolium multiflorum L. The amendments were applied for two consecutive years: 6, 12 and 24t dry matter ha−1 for SS, and the amendment doses for MMSWC and AWC were calculated to deliver the same amount of organic matter (OM) per unit area. The amendments had significant beneficial effects on some soil properties (e.g. soil OM, NKjeldahl, extractable P and K), and on plant productivity parameters (e.g. biomass yield, chlorophyll, foliar area). For instance, soil OM increased from 0.78% to 1.71, 2.48 and 2.51%, after two consecutive years of application of 24t dry matter ha−1 of SS, MMSWC and AWC, respectively, while the plant biomass obtained increased from 7.75tha−1 to 152.41, 78.14 and 29.26tha−1, for the same amendments. On the plant, effects were more pronounced for SS than for both compost applications, a consequence of its higher capacity to provide N to the plant in a readily available form. However, after two years of application, the effects on soil properties were more noticeable for both composts, as their OM is more resistant to mineralization, which endures their beneficial effects on soil. Cadmium, Cr, Ni and Pb pseudo-total concentrations, were not affected significantly by the application of the organic wastes to soil, in all tested doses, neither their extractability by 0.01M CaCl2. On the contrary, Cu and Zn pseudo-total concentrations increased significantly in the second year of the experiment, following the application of the higher rate of MMSWC and AWC, although their extractability remained very low (<0.5% of their pseudo-total fraction). Trace elements concentrations in the aboveground plant material were lower than their maximum tolerable levels for cattle, used as an indicator of risk of their entry into the human food chain. Despite these results, it is interesting to note that the SS promoted a significant increase in the foliar concentrations of Cu, Ni and Zn that did not happen in composts application, which can be explained by the reduction of the soil pH, as a consequence of SS degradation in soil. Concluding, if this type of organic wastes were to be used in a single application, the rate could be as high as 12 or even 24tha−1, however, if they are to be applied in an annual basis, the application rates should be lowered to assure their safe application (e.g. to 6tha−1). Moreover, it is advisable to use more stable and mature organic wastes, which have longer lasting positive effects on soil characteristics.