The effects of organic and inorganic fertilizer applications to Miscanthus×giganteus,Arundo donax and Phalaris arundinacea,when grown as energy crops in Wales,UK

Two pot trials and one field trial were established to investigate the effects of organic and inorganic fertilizer applications to energy crops grown in mid‐Wales. Chicken litter and sewage cake applied at a high level in excess of MAFF recommendations produced an increased yield response in Miscanthus and Arundo plants. Miscanthus plants exhibited an increased growth response to all fertilizers applied in its second year. Fertilizer applications in accordance with MAFF recommendations produced no significant differences in yields for Miscanthus or Arundo potted plants. In the field there was an increased yield response of Miscanthus to inorganic nitrogen applications compared with organic manures, but not with control plots. Analysis of the Miscanthus plant material at harvest showed significant differences in the nitrogen, potassium and copper content between treatments. No mineral content differences were shown for Miscanthus rhizome material or Arundo plant material. The Phalaris plants did not exhibit significant differences in growth or yield parameters, but their plant matter showed differences in nitrogen, phosphorus, potassium, calcium, sulphur and boron content between treatments.     

Invasive riparian plant litter alters aquatic insect growth

In a laboratory study, we examined growth and survival of the caddisfly, Lepidostoma unicolor, feeding on two types of native leaf litter (Alnus rhombifolia [Alder] and a Salicaceae mix [Salix spp. and Populus fremontii]) and two invasive, non-native species (Tamarix ramosissima [saltcedar] and Arundo donax [giant reed]). Larval survival was high (>85%), and did not differ, among those fed Alnus, Salicaceae, or Tamarix litter, but was much lower (20%) for larvae fed Arundo litter. Mean dry biomass of larvae fed Tamarix was 45% greater than that of larvae fed Alnus, and both were significantly greater than the biomasses of insects fed Salicaceae or Arundo. Although both Alnus and Tamarix increased in percent nitrogen with conditioning, Alnus had a significantly higher nitrogen content (4.9 and 3.6%, respectively). Final C : N-values for Alnus and Tamarix were below 18, while C : N for Arundo and Salicaceae were 56 and 44, respectively. Greater growth of larvae fed Tamarix is likely due to the high nutritive value of the conditioned litter, whereas conditioning of Arundo litter did not result in improved nutritive values. Larvae in the Alnus and Salicaceae treatments fed on the entire surface of the leaves until only the skeletons remained. In contrast, larvae in the Arundo treatments focused feeding activity along the margins and the torn portions of the blades. The low nutritional quality of Arundo and the high quality, but ephemeral nature of Tamarix litter potentially have negative effects on stream invertebrate production owing to the quality and duration of availability of leaf litter, as compared with native riparian vegetation.     

Set‐backs in Replacing Phalaris arundinacea Monotypes with Sedge Meadow Vegetation

Reed canary grass (Phalaris arundinacea) invades wetlands, forms monotypes, and resists control efforts, suggesting that strong feedbacks sustain its dominance, as in the alternative states model. In nine field experiments, we tested the hypothesis that applying a graminicide (sethoxydim) for three years would progressively reduce Phalaris abundance, and that seeding sedge meadow species (except grasses) would reestablish native plant dominance. The graminicide prevented Phalaris from flowering, reduced its height by 50% and reduced its cover, often to less than 40%. However, only two of the nine sites showed progressive declines over the three‐year experiment. The first setback was that Phalaris recovered annually in nearly all treatment plots. A second setback was that seeding did not reestablish sedge meadow. In five sites, unseeded plots had similar numbers of native species as those seeded with either forbs, forbs and graminoids, or graminoids. In four formerly agricultural sites, however, non‐native weeds increased in species richness and cover (a third setback). In only one site did the graminicide's effect on Phalaris allow native species to increase in number and cover. But short‐term gains were not long‐lasting. In year four, three sites that developed high native‐species cover were again strongly dominated by Phalaris (a fourth setback). The feedbacks that sustain this invader include resistance to the graminicide aboveground and rapid and robust regrowth from rhizomes and seeds belowground. The weak effect of this graminicide was a surprise; hence, we recommend stronger management actions to control Phalaris.     

Responses of native and invasive wetland plants to hydroperiod and water depth

Monotypic stands of reed canary grass, Phalaris arundinacea, replace native wetland vegetation where stormwater runoff alters hydrologic conditions, nutrient inflows, and sedimentation rates. We asked if different hydrologic conditions could explain the dominance of Phalaris and/or loss of the native grass, Spartina pectinata, and we compared the growth of each species alone and together under four hydroperiods (varying inundation frequency and duration) each at two water depths (surface saturation and flooding to 15 cm). When grown alone, aboveground biomass was similar for the two species, but Phalaris produced twice the stem length of Spartina via its low tissue density. Per unit biomass, Phalaris distributed its leaves over a larger canopy volume. Flooding reduced belowground biomass and increased total shoot length and shoot:root biomass of each species. Phalaris produced the most biomass, shoots, and total shoot length when wetter and drier conditions alternated weekly, while Spartina grew best with prolonged (4-week) inundation. When grown with Spartina, Phalaris changed its morphology by increasing its total shoot length:biomass ratio by 50%. However, ratios of Spartina:Phalaris aboveground biomass, shoot number, and total shoot length in two-species pots were not significantly affected by water depth or hydroperiod. We conclude that two plant attributes facilitate Phalaris' dominance of wetlands: its high ratio of total shoot length:biomass and its adaptable morphology (characterized herein as increased total shoot length:biomass when grown with Spartina).     

Population studies ofCavelerius saccharivorus Okajima (Heteroptera: Lygaeidae): A few findings on population interchange

The change in population density of Cavelerius saccharivorus was studied in the sugar cane field and the Miscanthus habitats around it. This species spent 2 (or partly 3) generations a year. It was suggested that the density rose in the sugar cane field where the density had been low enough, when the population density increased in the nearby sugar cane fields. Likely, the density in the Miscanthus habitat increased with the density in the nearby sugar cane field. It seems that these are mainly due to flying movement of adults, and that the movement takes place in every season. It was found through the investigation in the sugar cane field that the percentage of long-winged adults increased with the population density. These adults seemed to emmigrate to the nearby sugar cane fields and Miscanthus habitats. The remarkable increase in the percentage of long-winged adults in the sugar cane field was probably due to the immigration into there. In the Miscanthus habitat the adult population was consisted mainly of long-winged ones. Through all the observations, it was suggested that the adult movement was associated with the population regulation and performed chiefly by long-winged adults.     

Factors controlling the distribution of aquatic macrophyte communities with special reference to the rapid expansion of a semi-emergent <Emphasis Type="Italic">Phalaris arundinacea</Emphasis> L. in Bibi River,Hokkaido, northern Japan

To identify the causes of the rapid expansion of the semi-emergent Phalaris arundinacea L. community in a nutrient-loaded river, we investigated the factors that determine the distribution of the Phalaris and other aquatic macrophyte communities and the shoot growth of P. arundinacea. The Phalaris community was distributed through areas with high organic nitrogen (Org-N), total phosphorus (T-P), PO₄-P and suspended solids (SS) concentrations and low dissolved oxygen (DO). P. arundinacea shoots grow better in deep mud and high SS and T-P, all of which were strongly correlated with slower stream currents. Accordingly, although the concentration of total nitrogen constantly increased from 1985 to 1998, the determining nutrient for the expansion of the Phalaris community and P. arundinacea shoot growth stimulation was phosphorus rather than nitrogen. The Phalaris community increased rapidly between 1991 and 1996, when brief but prominent loadings of phosphorus were observed. We concluded that the Phalaris community was restricted due to phosphorus deficiency under nitrogen excess until 1991 and subsequently rapidly expanded over the channel due to the temporary excess phosphorus present during this period. Thereafter, the rapid expansion of the Phalaris community was maintained by the clogging effect of the floating mats formed by shoots and their remains of P. arundinacea, which results in slower currents. A slower current resulted in low DO, the sedimentation of degraded plant remains (high Org-N), and the adsorption of phosphorus by suspended matter (high SS and T-P). The anaerobic conditions caused by low oxygen and the accumulation of decomposable organic matter ensure the continuous development of the Phalaris community through the release of soluble phosphorus from the sediment.     

水分对敦煌阳关湿地芦苇叶片与土壤C、N、P生态化学计量特征的影响

土壤水分是影响干旱区植物养分吸收和利用策略的关键因子之一。研究不同水分梯度叶片与土壤生态化学计量特征,有助于揭示植物对环境变化的响应特征及生态适应性。通过野外调查与实验分析,对敦煌阳关不同水分梯度芦苇叶片与土壤碳(C)、氮(N)、磷(P)生态化学计量特征及其关系进行了研究。结果表明:(1)随土壤含水率升高,叶片C、N、P含量降低,叶片C/N、C/P、N/P升高。(2)随土壤含水率升高,土壤有机碳(OC)、总氮(TN)、总磷(TP)含量及土壤N/P升高,土壤C/N降低,土壤C/P先升后降。(3)低水分梯度叶片N、C/N与土壤N、C/N显著负相关(P0.05),叶片C、P、C/P、N/P与土壤C、P、C/P、N/P无显著相关性(P0.05);高、中水分梯度叶片C、N、P与土壤C、N、P化学计量特征相关性均不显著(P0.05)。低水分梯度叶片受干旱胁迫和土壤养分制约,且能够保持较高的叶养分含量,体现了干旱区湿地植物异质生境下独特的养分调节机制。     

Miscanthus × giganteus leaf senescence,decomposition and C and N inputs to soil

Energy crops are currently promoted as potential sources of alternative energy that can help mitigate the climate change caused by greenhouse gases (GHGs). The perennial crop Miscanthus × giganteus is considered promising due to its high potential for biomass production under conditions of low input. However, to assess its potential for GHG mitigation, a better quantification of the crop's contribution to soil organic matter recycling under various management systems is needed. The aim of this work was to study the effect of abscised leaves on carbon (C) and nitrogen (N) recycling in a Miscanthus plantation. The dynamics of senescent leaf fall, the rate of leaf decomposition (using a litter bag approach) and the leaf accumulation at the soil surface were tracked over two 1‐year periods under field conditions in Northern France. The fallen leaves represented an average yearly input of 1.40 Mg C ha^?1 and 16 kg N ha^?1. The abscised leaves lost approximately 54% of their initial mass in 1 year due to decomposition; the remaining mass, accumulated as a mulch layer at the soil surface, was equivalent to 7 Mg dry matter (DM) ha^?1 5 years after planting. Based on the estimated annual leaf‐C recycling rate and a stabilization rate of 35% of the added C, the annual contribution of the senescent leaves to the soil C was estimated to be approximately 0.50 Mg C ha^?1yr^?1 or 10 Mg C ha^?1 total over the 20‐year lifespan of a Miscanthus crop. This finding suggested that for Miscanthus, the abscised leaves contribute more to the soil C accumulation than do the rhizomes or roots. In contrast, the recycling of the leaf N to the soil was less than for the other N fluxes, particularly for those involving the transfer of N from the tops of the plant to the rhizome.     

Understanding invasion as a process: the case of <Emphasis Type="Italic">Phalaris arundinacea</Emphasis> in wet prairies

Invasive plants that most threaten biodiversity are those that rapidly form a monospecific stand, like the clonal grass, Phalaris arundinacea. Understanding complex and potentially interacting factors that are common in urban and agricultural landscapes and underlie rapid invasions requires an experimental, factorial approach. We tested the effects of flooding and nutrient and sediment additions (3 × 3 × 3 = 27 treatments, plus a control with no additions) on invasion of Phalaris into mesocosms containing wet prairie vegetation. We discovered a three-step invasion and degradation process: (1) initially, resident native species declined with prolonged flooding and sediment additions, and (2) prolonged flooding, sedimentation, and nutrients accelerated Phalaris aboveground growth; biomass rose to 430 times that of the control within just two growing seasons. The dramatic expansion of Phalaris in the second year resulted in the formation of monospecific stands in over one-third of the treatments, as (3) native species continued their decline in year 2. Disturbances acted alone and in combination to make the resident wetland community more invasible and Phalaris more aggressive, leading to monospecific stands. Yet, Phalaris did not always “win”: under the least disturbed conditions, the resident plant canopy remained dense and vigorous and Phalaris remained small. When anthropogenic disturbances coincide with increases in the gross supply of resources, more tolerant, fast-growing, and morphologically plastic plants like Phalaris can invade very rapidly. The fluctuating resource hypothesis should thus be refined to consider the role of interacting disturbances in facilitating invasions.     

Girdling-induced nutrient accumulation in above ground tissue of peanuts and subsequent feeding by Spissistilus festinus, the three-cornered alfalfa hopper

Changes in nutrient partitioning in stems and leaves of peanut (Arachis hypogaea L.) were examined after girdling of stems by Spissistilus festinus (Say) (Homoptera:Membracidae), the three-cornered alfalfa hopper. Under field conditions amino acids increased more than 12-fold in concentration in the 2 cm stem section above the girdle compared to below the girdle or control stems for newly formed girdles (less than 7–11 days). Asparagine and proline were the predominant amino acids, and increased 40- and 60-fold, respectively, above the girdle compared to below the girdle. There was no buildup of nutrient assimilates for the older girdled stems that had callused (and presumably recovered from feeding injury). A time course from 1–11 days was followed under greenhouse conditions, and girdled regions remained enriched in sugars for one day and amino acids for four days after girdle formation. After girdle formation most S. festinus responded to nutrient sinks by feeding within 5 mm above the girdle. This behavior was most pronounced one day after girdle formation, but persisted for seven days after girdle formation. During this period a new girdle was often formed within 10 mm above the original girdle. Under field conditions, stems and leaves derived from stems that had sustained an early or late season girdle generally had a reduced dry weight, total nitrogen content, and total carbon content; however, significant differences did not always occur. Thus, although temporary changes occurred in nutrient partitioning in girdled stems, there appears to be longer term negative growth effects on leaves and stems.     

Nitrogen and sulphur requirements of Colletotrichum inamdarii Lal

Summary Nitrogen and sulphur requirements ofColletotrichum inamdarii Lal isolated from the leaves ofCarissa carandas L. have been studied. DL-serine, L-asparagine and L-phenylalanine have been found to be of good nitrogen source followed by potassium nitrate, calcium nitrate, magnesium nitrate, DL-alanine, ammonium nitrate, glutamic acid, ammonium sulphate, DL-valine, aspartic acid, ammonium chloride, ammonium hydrogencarbonate, L-histidine and potassium nitrite. There was no growth in the absence of nitrogen.Sporulation was excellent on calcium nitrate and sodium nitrate, Very good on DL-serine, potassium nitrate, and magnesium nitrate. Good on L-asparagine, L-phenylalanine and ammonium oxalate. Fair on DL-alanine, DL-leucine, ammonium sulphate, DL-valine, ammonium chloride and L-histidine whereas poor on glutamic acid, aspartic acid, ammonium tartarate and ammonium nitrate. Few spores were observed on ammonium hydrogencarbonate but potassium nitrite did not show any sporulation.Amongst the sulphur compounds sodium bisulphate gave the best growth and good sporulation, followed by sodium thiosulphate, magnesium sulphate, ammonium sulphate and potassium sulphate. Thiourea gave negligible growth whereas it failed to grow on zinc sulphate and potassium persulphate.     

Altering Light and Soil N to Limit Phalaris arundinacea Reinvasion in Sedge Meadow Restorations

Efforts to eradicate invasive plants in restorations can unintentionally create conditions that favor reinvasion over the establishment of desired species, especially when remnant invasive propagules persist. Reducing resources needed by the invader for seedling establishment, however, may be an effective strategy to prevent reinvasion. Propagules of Phalaris arundinacea persist after removal from sedge meadow wetlands and reestablish quickly in posteradication conditions, hindering community restoration. A study was conducted in two experimental wetlands with controlled hydrologic regimes to determine if reducing light by sowing short‐lived, nonpersistent native cover crops or immobilizing soil N by incorporating soil–sawdust amendments can prevent Phalaris reinvasion, allowing native communities to recover. A 10‐species perennial target community and Phalaris were sown with high‐diversity, low‐diversity, or no cover crops in soils with or without sawdust, and seedling emergence, establishment, and growth were measured. High‐diversity cover crops reduced light, decreasing Phalaris and target community seedling establishment by 89 and 57%, respectively. Short‐term nitrogen reduction in sawdust‐amended soils delayed Phalaris seedling emergence and decreased Phalaris seedling establishment by 59% but did not affect total target community seedling establishment. The target community reduced Phalaris seedling establishment as effectively as cover crops did. In plots where the target community was grown, amending soils with sawdust further reduced Phalaris seedling growth but not establishment. Results show that use of cover crops can reduce seedling establishment of desired species and is counterproductive to restoration goals. Further, establishing target species is more important and practical for limiting Phalaris reinvasion than is immobilizing nitrogen.     

Plant morphology,genome size,and SSR markers differentiate five distinct taxonomic groups among accessions in the genus Miscanthus

Information on genome size, ploidy level, and genomic polymorphisms among accessions of the genus Miscanthus can assist in taxonomic studies, help understand the evolution of the genus, and provide valuable information to biomass crop improvement programs. Taxonomic investigation combining variation in plant morphology, genome size, chromosome numbers, and simple sequence repeat (SSR) marker polymorphisms were applied to characterize 101 Miscanthus accessions. A total of 258 amplicons generated from 17 informative SSR primer pairs was subjected to cluster and principal coordinate analysis and used to characterize genetic variation and relationships among 31 Miscanthus accessions, including four interspecific Miscanthus hybrids created from controlled pollinations, and four Saccharum, six Erianthus, and one Sorghum bicolor accessions. Miscanthus accessions were distinct from accessions in the genera Erianthus and Saccharum. Miscanthus accessions fell into five taxonomic groups, including the existing taxonomic section Miscanthus, diploid and tetraploid Miscanthus sacchariflorus, and a fourth (M. × giganteus) and fifth group (Miscanthus ‘purpurascens’); the last two being intermediate forms. In contrast to previous work, our findings suggest diploid and tetraploid M. sacchariflorus are taxonomically different, the latter more closely related to M. sacchariflorus var lutarioriparius. We also suggest that Miscanthus ‘purpurascens’ accessions are interspecific hybrids between Miscanthus sinensis and diploid M. sacchariflorus based on DNA content and SSR polymorphisms. The evolution of Miscanthus and related genera is discussed based on combined analysis and geographical origin.     

Comparative assessment of ecosystem C exchange in Miscanthus and reed canary grass during early establishment

Land‐use change to bioenergy crop production can contribute towards addressing the dual challenges of greenhouse gas mitigation and energy security. Realisation of the mitigation potential of bioenergy crops is, however, dependent on suitable crop selection and full assessment of the carbon (C) emissions associated with land conversion. Using eddy covariance‐based estimates, ecosystem C exchange was studied during the early‐establishment phase of two perennial crops, C₃ reed canary grass (RCG) and C₄ Miscanthus, planted on former grassland in Ireland. Crop development was the main determinant of net carbon exchange in the Miscanthus crop, restricting significant net C uptake during the first 2 years of establishment. The Miscanthus ecosystem switched from being a net C source in the conversion year to a strong net C sink (?411 ± 63 g C m^?2) in the third year, driven by significant above‐ground growth and leaf expansion. For RCG, early establishment and rapid canopy development facilitated a net C sink in the first 2 years of growth (?319 ± 57 (post‐planting) and ?397 ± 114 g C m^?2, respectively). Peak seasonal C uptake occurred three months earlier in RCG (May) than Miscanthus (August), however Miscanthus sustained net C uptake longer into the autumn and was close to C‐neutral in winter. Leaf longevity is therefore a key advantage of C₄ Miscanthus in temperate climates. Further increases in productivity are projected as Miscanthus reaches maturity and are likely to further enhance the C sink potential of Miscanthus relative to RCG.     

Contribution of nitrogen fixation to first year Miscanthus × giganteus

Many characteristics make Miscanthus × giganteus an appealing bioenergy feedstock in temperate North America, but the degree to which this plant species interacts with nitrogen‐fixing bacteria remains understudied. Demonstration of associative nitrogen fixation in Miscanthus would support management with minimal fertilizer inputs that is demanded of long‐term biofuel sustainability. As a first step, we investigate the role of biological nitrogen fixation in nutrition of immature Miscanthus and temporal dynamics of plant‐associated nitrogen fixers. The contribution of biological nitrogen fixation to plant nitrogen acquisition in first year Miscanthus × giganteus was estimated using a yield‐dependent ¹⁵N isotope dilution model. Temporal changes in plant‐associated diazotroph relative abundance and community composition were analyzed with quantitative PCR and terminal restriction fragment length polymorphism of the nifH gene in rhizome and rhizosphere DNA extracts. We estimate 16% of new plant nitrogen was derived by nitrogen fixation during the growing season, despite non‐limiting soil nitrogen. Diazotroph communities from rhizome and rhizosphere changed with plant development and endophytic nitrogen fixers had significantly higher relative abundance and altered community composition at sampling dates in July and August. This study provides evidence for a small, but measurable, benefit of associative nitrogen fixation to first year Miscanthus × giganteus that underscores the potential and need for selection of breeding lines that maximize this trait.     

Changes in the chemical content of birch (<Emphasis Type="Italic">Betula pendula </Emphasis>Roth) leaves in the air polluted Krusne hory mountains

Analyses of birch leaves (Betula pendula Roth) sampled from trees in the air polluted Krusne hory mountains and Decin sandstone highlands were performed in 1995 and 1998. The results revealed a connection between reduction of air pollutants and overall decrease in sulphur and nitrogen content of the leaves. Simultaneously, in many stands an increase in calcium content and a decrease in contents of phosphorus, magnesium and potassium occurred. The content of microelements and non-nutrient elements did not change.     

Introducing Miscanthus to the greening measures of the EU Common Agricultural Policy

The EU Common Agricultural Policy regulations for the 2014–2020 period comprise three ‘greening measures’ aimed at climate change mitigation and biodiversity conservation. These three greening measures consist of the maintenance of permanent pastures, crop diversification and ecological focus areas (EFAs). Farmers are to assign 5% of their land as EFAs; this concerns for example grassland, hedges, buffer strips or nitrogen‐fixing crops. Short rotation coppice (SRC) as a perennial bioenergy crop is also considered as an eligible EFA within the EU greening measures, whereas Miscanthus is not. However, a quantitative comparison (t‐test) of SRC and Miscanthus revealed that both crops are similar in the delivery of a variety of ecosystem services, such as C storage and biodiversity. Moreover, Miscanthus may contribute to the reduction of greenhouse gas emissions due to a considerable CO₂ mitigation potential. Due to the overall consensus of the ecological significance of Miscanthus in agro‐ecosystems with the greening measures within the EU CAP reform, we recommend acknowledging Miscanthus as an eligible EFA with a similar payment as for SRC, boundary ridges or buffer strips. Along with Miscanthus, a number of other perennial renewables also may contribute to what the CAP intends. We predict that introducing Miscanthus and even other perennial energy crops could also make European agriculture more innovative and effective.     

Carbon sequestration and turnover in soil under the energy crop Miscanthus: repeated 13C natural abundance approach and literature synthesis

The stability and turnover of soil organic matter (SOM) are a very important but poorly understood part of carbon (C) cycling. Conversion of C₃ grassland to the C₄ energy crop Miscanthus provides an ideal opportunity to quantify medium‐term SOM dynamics without disturbance (e.g., plowing), due to the natural shift in the δ¹³C signature of soil C. For the first time, we used a repeated ¹³C natural abundance approach to measure C turnover in a loamy Gleyic Cambisol after 9 and 21 years of Miscanthus cultivation. This is the longest C₃–C₄ vegetation change study on C turnover in soil under energy crops. SOM stocks under Miscanthus and reference grassland were similar down to 1 m depth. However, both increased between 9 and 21 years from 105 to 140 mg C ha^?1 (P < 0.05), indicating nonsteady state of SOM. This calls for caution when estimating SOM turnover based on a single sampling. The mean residence time (MRT) of old C (>9 years) increased with depth from 19 years (0–10 cm) to 30–152 years (10–50 cm), and remained stable below 50 cm. From 41 literature observations, the average SOM increase after conversion from cropland or grassland to Miscanthus was 6.4 and 0.4 mg C ha^?1, respectively. The MRT of total C in topsoil under Miscanthus remained stable at ~60 years, independent of plantation age, corroborating the idea that C dynamics are dominated by recycling processes rather than by C stabilization. In conclusion, growing Miscanthus on C‐poor arable soils caused immediate C sequestration because of higher C input and decreased SOM decomposition. However, after replacing grasslands with Miscanthus, SOM stocks remained stable and the MRT of old C₃‐C increased strongly with depth.     

Metagenomic insights into the alteration of soil N-cycling-related microbiome and functions under long-term conversion of cropland to Miscanthus

Miscanthus spp. show excellent application prospects due to its bioenergy potential and multiple ecological services. Annual N export with biomass harvest from Miscanthus, even without fertilizer supplement, do not reduce soil N levels. The question arises regarding how Miscanthus can maintain stable soil N levels. Metagenomic strategies were used to reveal soil N-cycling-related microbiome and their functional contributions to processes of soil N-cycling based on the comparison among the bare land, cropland, 10-year Miscanthus × giganteus, and 15-year Miscanthus sacchariflorus fields. The results showed that, after long-term cropland-to-Miscanthus conversion (LCMC), 16 of 21 bacterial phyla and all the archaeal phyla exhibited significant changes. Soil microbial denitrification and nitrification functions were significantly weakened, and N fixation (NF) was significantly enhanced. The biosynthesis of amino acids, especially alanine, aspartate, and glutamate metabolism, in soil N-cycling-related microbiome was dramatically promoted. The genus Anaeromyxobacter contributed largely to the NF process after LCMC. Variations in the soil available potassium, available N, organic C, and total N contents drove a functional shift of soil microbiome from cropland to Miscanthus pattern. We conclude that Miscanthus can recruit Anaeromyxobacter communities to enhance NF benefiting its biomass sustainability and soil N balance.     

Sulphur requirements of certain isolates ofAlternaria tenuis Auct

The sulphur nutrition of three isolates ofAlternaria tenuis Auct., isolated from the diseased leaves ofMangifera indica L.,Musa paradisiaca L. andPsidium guajava L., was studied. They were grown on the medium devoid of sulphur as well as on media containing various sources of sulphur viz., ammonium sulphate, sodium hyposulphite, sodium thiosulphate, magnesium sulphate, potassium sulphate, potassium metabisulphite, zinc sulphate and thiourea. Sodium hyposulphite, sodium thiosulphate, magnesium sulphate, potassium sulphate and zinc sulphate were generally found to be satisfactory sources for the growth of all the isolates under study. Poor growth of the different isolates was observed on the medium devoid of sulphur.