Dominant Grass Species Research Articles

Dominance by Spartina densiflora slows salt marsh litter decomposition

AbstractQuestionsCoastal vegetated systems are known to play a fundamental role in climate change mitigation as a result of their efficiency sequestering and storing atmospheric CO2. While most of the work evaluating carbon sequestration capacity has focused on global change factors that can affect carbon release from plant litter decomposition through changes in (large‐scale) environmental conditions, less is known about the possible effects of the loss (or replacement) of dominant species. We hypothesized that dominant marsh plants can influence decomposition not only through changes in litter quality but also through changes in (microscale) soil environmental conditions such as humidity, soil temperature or solar radiation.LocationWe performed a field manipulative experiment in a southwestern (SW) Atlantic salt marsh in Argentina.MethodsWe simulate a selective disturbance (i.e., removal of the dominant grass species Spartina densiflora) thus allowing removal plots to develop an alternative plant community. To evaluate the effect of the dominant grass species on litter decomposition, in an experiment we performed a litterbag approach three years after the establishment of the removal plots.ResultsResults showed that the presence of S. densiflora significantly decreased litter decomposition directly by producing less labile litter, but also by effects that seem to be related to its structure as standing dominant vegetation. The experimental removal of S. densiflora led to an alternative plant community, formed by otherwise subordinate species, which is less densely packed, allowing higher radiation incidence on the soil and elevated midday soil temperature.ConclusionsOur results suggest that salt marsh litter decomposition, and thus C sequestration, is determined in part by the identity of the dominant plant, not only because of the quality of the produced litter but also as a consequence of the vegetation structure . Changes in species diversity, above all changes in the dominant species in these coastal systems, could have large impacts on the carbon turnover and mitigation capacity of these ecosystems.

Defoliation and neighbouring legume plants accelerate leaf and root litter decomposition of Leymus chinensis dominating grasslands

Dominant plant species coexist with other species from the same or other trophic levels (e.g. neighbouring plants and herbivores), which may give rise to neighbourhood and defoliation effects on litter decomposition. Yet, little information exists on if and how neighbouring plant species and herbivore defoliation interactively affect the decomposition of dominant species, and further whether decomposition of leaves and roots has similar responses. Here, we simultaneously examined both the leaf and fine root litter decomposition of the dominant grass species, Leymus chinensis, in the presence and absence of a neighbouring plant species, Lathyrus quinquenervius (a functionally dissimilar legume species), and simulated herbivore defoliation by mowing. We found that both neighbouring legume plants and defoliation significantly accelerated both leaf and root litter decomposition of L. chinensis, and that neighbouring legume plants exerted stronger effects on litter decomposition than defoliation. The positive effects of neighbouring legume plants occurred across all study periods, whereas defoliation only had a positive effect during the first 15 days of litter decomposition. Neighbouring legume plants and defoliation exerted strong additive effects on root litter decomposition, and interactive effects on leaf litter decomposition. These findings highlight the significance of functionally dissimilar species coexistence to facilitate nutrient cycling in grasses - dominated grasslands.

Habitat suitability of wild water buffalo (Bubalus arnee) in Babai flood plain of Bardia National Park, Nepal

BackgroundWild water buffalo is an endangered species presently distributed in some countries of South and Southeast Asia with Nepal’s only population in the flood plain of the Koshi river at Koshi Tappu Wildlife Reserve (KTWR). Some of the individuals have been translocated to Chitwan National Park of central Nepal but the survival rate is not satisfactory. MethodsThis study was conducted in Babai flood plain of Bardia National Park (BNP) to identify a suitable habitat for wild water buffalo based on habitat parameters of KTWR. The study employed both the geospatial and vegetation analysis method. ResultsThe study found that Imperata cylindrica, Saccharum spontaneum, Cynodon dactylon were the three dominant grass species with important value index (IVI) of 74.15, 60.45, and 11.85 respectively in the Babai flood plain. Similarly, the dominant tree species in the Babai flood plain was Bombax ceiba with the IVI value of 127.81 followed by Shorea robusta, Termenalia tomentosa, Largestroemia parviflora, and Adina cardifolia with the IVI of 48.38, 21.04, 13.03 and 9.19 respectively. Out of the total 108.67 km2 of the entire study area of Babai flood plain, 8.26 km2 was found to be suitable, 100.12 km2 area moderately suitable, and 0.29 km2 area as less suitable. ConclusionsBabai flood plain of BNP is moderately suitable habitat for wild water buffalo. Grassland and wetland management and study of other parameters such as climate and prey-predator relationship is recommended before making the decision to translocate wild water buffaloes to the Babai flood plain of BNP.

Six-year removal of co-dominant grasses alleviated competitive pressure on subdominant grasses but dominant shrub removal had neutral effects in a subalpine ecosystem

The ‘stress-gradient hypothesis’ predicts increasing facilitative interactions with increasing environmental stress, but it remains unclear if the prevailing type of interaction (i.e. facilitative or competitive) between dominant and subordinate plant species occurring in harsh environments is dependent on the plant functional type. In addition, most plant-species removal experiments in grasslands are short-term (1–2 years), which may imprecisely reflect transient effects arising from methodological limitations. We conducted a dominant species removal experiment in a subalpine ecosystem, containing a mosaic of grass-dominated and shrub-dominated community patches, both of which are common in the subalpine zone of the Qinghai-Tibetan Plateau. We examined the direction and magnitude of the effects of three co-dominant grass and a dominant shrub species on subordinate species richness and biomass over a 6-year period. Removal of the dominant grass species alleviated their competitive pressure on subdominant grasses, which resulted in similar total and grass biomass detected in the final year of the study. By contrast, shrub removal showed no effects on its subordinate species biomass. Furthermore, neither the removal of the dominant shrubs nor the grasses altered their respective subordinate species richness. Thus, in subalpine ecosystems that experience harsh environmental conditions, our results showed that the direction of interactive effects of dominant plant species on subordinate species may be dependent on the plant functional type and are not necessarily facilitative. Furthermore, we showed that longer-term plant-removal experiment observations may be required to better determine the effects of species removal for this subalpine and other montane ecosystem(s).

Weak latitudinal gradients in insect herbivory for dominant rangeland grasses of North America.

Patterns of insect herbivory may follow predictable geographical gradients, with greater herbivory at low latitudes. However, biogeographic studies of insect herbivory often do not account for multiple abiotic factors (e.g., precipitation and soil nutrients) that could underlie gradients. We tested for latitudinal clines in insect herbivory as well as climatic, edaphic, and trait‐based drivers of herbivory. We quantified herbivory on five dominant grass species over 23 sites across the Great Plains, USA. We examined the importance of climate, edaphic factors, and traits as correlates of herbivory. Herbivory increased at low latitudes when all grass species were analyzed together and for two grass species individually, while two other grasses trended in this direction. Higher precipitation was related to more herbivory for two species but less herbivory for a different species, while higher specific root length was related to more herbivory for one species and less herbivory for a different species. Taken together, results highlight that climate and trait‐based correlates of herbivory can be highly contextual and species‐specific. Patterns of insect herbivory on dominant grasses support the hypothesis that herbivory increases toward lower latitudes, though weakly, and indicates that climate change may have species‐specific effects on plant–herbivore interactions.

Differences in relative air humidity affect responses to soil salinity in freshwater and salt marsh populations of the dominant grass species Phragmites australis

Soil salinity diminishes the dominance of species and affects their distribution. Phragmites australis is a dominant ecosystem engineer with broad distribution, high intraspecific variation and great socio-economic importance. Coastal ecosystems inhabited by P. australis are threatened by salinization. Here, we investigated salinity tolerance of freshwater and salt marsh population of the species, grown under two soil salinities and in two common gardens. Salinity significantly affected the growth, biomass, leaf physiological parameters and ion concentration. Climate altered morphology and ion concentration of P. australis. In contrast to our hypothesis, the salt marsh population was not more salt tolerant than the freshwater population, and both showed a low degree of salt stress, maintaining their photosynthesis and chlorophyll concentration, and only showing small decreases in biomass and height when salt-treated. We therefore ruled out local adaptation to soil salinity. Instead, both populations acclimated by phenotypic plasticity of biomass, root: shoot ratio, stomatal conductance and ion content. The salinity tolerance strategy of both populations was ion concentration by tissue desiccation, which was most efficient in the drier climate common garden. Hence, plants utilizing tissue desiccation as salinity tolerance strategy will have an advantage in areas where climate change leads to drier air humidity.

Plant–microbial interactions facilitate grassland species coexistence at the community level

Interspecific competition and plant–soil feedbacks are powerful drivers of plant community structure. However, across a range of edaphic conditions the interactive effects of these drivers on complex plant communities remain unclear. For example, plant–soil feedback studies focus on soil trained by a single plant species. We developed a method to assess effects of plant–microbial interactions (PMI) on a complex plant community. We established mesocosms with 13 grassland species, grown individually or together, in overgrazed or restored soil, with or without soil microbial inoculum collected from a productive and diverse native grassland. We assessed biomass production as influenced by edaphic conditions, interspecific competition and PMI. Furthermore, we assessed potential influences of interspecific competition and edaphic conditions on strength and direction of PMI. Our results indicate PMI drives negative growth responses for graminoids while forbs experience positive growth responses. Generally, interspecific competition did not alter the magnitude or direction of PMI‐mediated growth responses. Edaphic conditions altered the influence of soil microbial communities on individual plant growth while PMI facilitated plant evenness. In plant community mesocosms, PMI‐associated benefits were observed in overgrazed soil. However, interspecific competition overwhelmed plant growth benefits associated with soil microbial communities when plant communities were grown in restored soil. In mesocosms containing dominant grass species, interspecific competition had negative effects on species coexistence, but both positive and negative PMI partially counterbalanced this influence on plant species evenness. Understanding these mechanisms may improve our capacity to manage diverse and productive grasslands by enabling prediction of plant community composition following disturbance and subsequent restoration.

围封对天山高寒草原4种植物叶片和土壤化学计量学特征的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 围封对天山高寒草原4种植物叶片和土壤化学计量学特征的影响 DOI: 10.5846/stxb201901130107 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 新疆维吾尔自治区自然科学基金项目（2016D01A076） Effects of enclosure on leaves of four plants and soil stoichiometry in an alpine grassland of Tianshan Mountains 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:以中国科学院巴音布鲁克草原生态系统研究站长期围栏内外的羊茅（Festuca ovina）、天山赖草（Leymus tiansecalinus）、二裂委陵菜（Potentilla bifurca）和鹅绒委陵菜（Potentilla anserine）4种植物叶片和土壤为研究对象，分析了放牧与围封对植物叶片和土壤C、N、P的化学计量特征的影响。结果表明，围封样地土壤养分浓度整体高于放牧样地（P<0.05），全氮（TN）浓度除外。围封显著增加羊茅叶片C、N浓度（P<0.05），对P浓度影响不显著；围封显著增加鹅绒委陵菜叶片的C浓度，但是显著降低叶片的N和P浓度（P<0.05），围封对天山赖草和二裂委陵菜养分含量影响不显著。围封显著增加鹅绒委陵菜C：N和C：P（P<0.05）；围封显著降低羊茅C：N、C：P和增加N：P（P<0.05）；围封显著降低二裂委陵菜C：N（P<0.05），对天山赖草的化学计量特征影响不显著。不同植物对围封的响应不同，意味着长期围封可能会改变天山高寒草原生态系统的结构。围封降低优势种（羊茅）的固碳能力，增加退化期出现的代表性植物（鹅绒委陵菜）的固碳能力，表明在长期围封下植物凋落物中的杂类草（鹅绒委陵菜）可能更多的为土壤提供碳来源，也能促进优势禾本科物种的氮含量和碳含量的增加。 Abstract:To determine effects of grazing and enclosure on the ecological stoichiometry characteristics, we evaluated the carbon(C),nitrogen(N),and phosphorus(P) contents in soil and leaves of four plants, which were Festuca ovina, Leymus tiansecalinus, Potentilla bifurca and Potentilla anserine, inside and outside the fence of the Bayinbuluk Grassland Ecological Research Station, Chinese Academy of Sciences. The results showed that soil nutrient content of enclosed grassland was significantly higher than that of grazing site, except total nitrogen (TN) content (P<0.05). The enclosure significantly increased the content of C and N in the leaves of Festuca ovina (P<0.05), but it did not significantly affect the content of P. The enclosure significantly increased the C content (P<0.05), but it significantly reduced the N and P content in the leaves of Potentilla anserine. Effects of the enclosure on the nutrient content of Leymus tiansecalinus and Potentilla bifurca were not significant. The enclosure significantly increased C:N and C:P of Potentilla anserine (P<0.05), while it significantly reduced C:N, C:P and increased N:P of Festuca ovina(P<0.05). The enclosure significantly reduced C:N of Potentilla bifurca(P<0.05), but it had no significant effect on the stoichiometric characteristics of Leymus tiansecalinus. The different species had different responses to the enclosure, meaning that long-term enclosure may change the structure of the Tianshan alpine grassland ecosystem. The enclosure reduced the carbon sequestration capacity of the dominant plant species (Festuca ovina) and increased the carbon sequestration capacity of the forb (Potentilla anserine) in the degradation stage. In long-term enclosure, Potentilla anserine may provide more carbon for the soil, and it also could promote nitrogen and carbon content of the dominant grass species. 参考文献 相似文献 引证文献

Moose effects on soil temperatures, tree canopies, and understory vegetation: a path analysis

AbstractLarge vertebrate herbivores are ubiquitous and increasingly numerous in boreal forests where they are known to influence ecosystems in many ways. However, separating the direct effects of herbivores from their indirect effects on plant communities via forest structural changes and microclimate remains unexplored, limiting the predictability of herbivore impacts. We used an exploratory path analysis approach to investigate potential mechanistic pathways between herbivore removal, forest canopy cover, soil temperature, and understory vegetation dynamics. Moose (Alces alces) were excluded from 15 recently clear‐cut boreal forest sites in Norway using 20 × 20 m fences with paired open un‐fenced plots. Soil temperatures and vegetation data were recorded after eight years (total n = 98). Moose exclusion reduced summer soil temperatures but not winter soil temperatures, leading to no net effect over 344 d. Path analysis showed a strong positive effect of moose exclusion on canopy cover and subsequently reduced summer soil temperatures. There was some support for an increase in the dominant grass species Avenella flexuosa with increasing summer soil temperatures, but neither temperature, canopy cover, nor A. flexuosa had clear links to plant species densities. Moose exclusion directly increased herb biomass and shifted understory species composition toward less shrub‐dominated communities, resulting in increased species densities of vascular plants and bryophytes. Our results indicate that in early‐successional boreal forests, direct effects of large herbivores on plant communities are clearly visible, and indirect effects are detectable but much weaker.

Nitrogen and phosphorus addition differentially affect plant ecological stoichiometry in desert grassland

Plant C:N:P stoichiometric relations drive powerful constraints on ecological interactions and processes. However, information about plant stoichiometric responses to N and P availability in desert grassland is limited. We conducted two field experiments with 7 levels of N (from 0.5 g to 24 g N ∙ m−2 yr−1) and P (from 0.05 g to 3.2 g P ∙ m−2 yr−1) additions in a desert grassland of Kunlun Mountain in the northwest of China to investigate the effects of these addition rates on the N and P stoichiometry of the dominant grass species Seriphidium korovinii. Nitrogen and P additions both affected plant stoichiometry. N addition suppressed P concentrations, whereas P addition had no effect on plant N concentrations. The N:P ratios of green aboveground biomass (AGB) were positively correlated with N addition ranging from 14.73 to 29.08, whereas those for P additions decreased ranging from 14.73 to 8.29. N concentrations were positively correlated with soil available N:P ratios, whereas, P concentrations were negatively correlated with soil availably N:P. Our results suggest that chemistry and stoichiometry of S. korovinii was directly affected by soil nutrient availability. Soil N availability affects S. korovinii stoichiometry to a greater extent that does soil P availability in this ecosystem. These findings suggest that N-deposition could affect the stoichiometry of this desert grassland ecosystem, and thereby potentially alter litter decomposition, plant community composition, nutrient cycling, and food-web dynamics of these desert ecosystems.

Investigating Habitat Suitability and Conservation Issues of Re-introduced Wild Water Buffalo in Chitwan National Park, Nepal

With an ever present threat of extinction aggravated mostly by inbreeding, genetic introgression and flooding stress, translocation of wild water buffalo (Bubalus arnee) to another suitable habitat was a must since decades. Habitat suitability analysis for wild water buffalo has been done by using binary model in ArcGIS 10.2.2 and slope, elevation, distance to water bodies and land cover criteria were used to prepare habitat suitability map of Chitwan National Park. Vegetation compositions were assessed in the grassland of Old Padampur area in sample plots (n = 36) each of size 1m x 1m for grasses and 10m x 10m for trees by using random sampling strategy. Conservation issues were identified through key-informant interviews and on-site observation of enclosure area, where re-introduced wild water buffalo were soft released. 127.13 km2 of the park area was identified as suitable habitat for wild water buffalo with around 79% of Old Padampur area. Importance Value Index (IVI) indicated that Saccharum spontaneum was found to be the most dominant grass species (IVI = 100.43) followed by Imperata cylindrica (IVI = 56.70) in Old Padampur area. Old Padampur area lies in the lap of Rapti River with many streams and marshes in the area which contributes to its suitability. The grassland of Old Padampur area is the largest in the park. At present, the wild water buffalo is facing some conservation issues mainly due to improper execution of soft release strategy and few uncontrolled natural events, such as floods and predators attacks. Therefore, to maintain the viable population of wild water buffalo in Chitwan National Park in the long-run, it is crucial to regulate and enhance effective soft release strategy and more advance techno-based modality in close coordination with conservation partners and relevant stakeholders.

Native soil microbial amendments generate trade‐offs in plant productivity, diversity, and soil stability in coastal dune restorations

Given the important role that soil microbes play in structuring plant communities and mediating ecosystem functions, there is growing interest in harnessing microbial communities to restore degraded ecosystems. Dune restorations, in particular, may benefit from native soil amendments because microbial diversity and abundance are very low in unvegetated areas. In an outdoor mesocosm experiment simulating Texas Gulf Coast dune restorations, we tested how native soil microbial amendments and restored diversity of foundational grasses influenced three key restoration responses: plant performance, plant diversity (including the colonization of native forbs), and soil stability. We found that native microbial amendments increased plant diversity and have the potential to increase soil stability, but this came at the cost of decreased plant biomass. Our results suggest that soil enemies in the native microbial amendments increased plant diversity by decreasing the performance of the dominant grass species and that arbuscular mycorrhizal fungi in the native microbial amendments increased the density of fungal hyphae in the soil, which can increase soil stability. Depending on the goals of the restoration, native soil microbial amendments may be a simple and inexpensive method to provide restoration benefits.

Plant growth and aboveground production respond differently to late-season deluges in a semi-arid grassland.

Semi-arid ecosystems are strongly water-limited and typically quite responsive to changes in precipitation amount and event size. In the C4-dominated shortgrass steppe of the Central US, previous experiments suggest that large rain events more effectively stimulate plant growth and aboveground net primary production (ANPP) than an equal amount of precipitation from smaller events. Responses to naturally occurring large events have generally been consistent with experimental results, with the exception of large events occurring later in the growing season (e.g., August). These have been reported as less effective at increasing net C uptake, despite temperatures optimal for C4 plant growth. Since atmospheric warming is increasing the frequency of statistically extreme rain events (deluges) throughout the growing season, how late-season deluges affect semi-arid ecosystems remains to be resolved. We applied deluges in August of three sizes (1.0-2.5 times average August precipitation) to assess the potential for late-season deluges to stimulate plant growth and ANPP. These late-season deluges led to significant "green-up" of this grassland, with new leaf production, and an increase in flowering of the dominant grass species. Further, these responses increased as deluge size increased, suggesting that larger or multiple deluges may lead to even greater growth responses. However, despite strong plant-level responses, no increase in ANPP was measured. Our results confirm that aboveground plant growth in the C4-dominated shortgrass steppe does respond to late-season deluges; however, if there is an increase in plant biomass, net accumulation aboveground is minimal at this time of year.

Cattle grazing alters the interaction of seed-borne fungi and two foliar pathogens of Leymus chinensis in a meadow steppe

Intensive grazing by herbivores lead to major ecological changes in natural grasslands, including severe degeneration. However, the understanding of how grazing affects the incidence of pathogenic and saprotrophic fungi on leaves and seeds of dominant plant species in grasslands is limited. In this study, the presence of two fungal pathogens that cause lesions on leaves of a dominant grass species of the Hulunber meadow steppe in northeast China, Leymus chinensis, as well as saprotrophic fungi associated with lesions, was investigated in plots with different grazing intensities treatments (0, 0.42, 0.63, 0.83, 1.25, and 1.67 cattle ha−1). In addition, seeds of L. chinensis were harvested from plants of the different grazing intensities and the presence of seed-borne fungi, including pathogenic and saprotrophic fungi, were examined by fungal isolation. The results indicated that with the increase of grazing intensity, the incidence of two fungal diseases on leaves of L. chinensis, leaf blotch diseases caused by Leptosphaeria avenaria and Parastagonospora nodorum, decreased. On seeds, the two most frequently isolated fungi were Le. avenaria and P. nodorum, from 57.2% and 40.6% of seeds respectively. At the highest grazing plots, the frequency of isolation of these two fungi to 23.1 and 15.6% respectively. By contrast, the frequency of isolation of Epicoccum nigrum in the highest grazing plots was 88.9%, approximately 10-fold of that in control plots. In dual-culture studies, E. nigrum isolates had inhibitory effects on the growth of isolates of the two leaf pathogens.

Shrub persistence and increased grass mortality in response to drought in dryland systems.

Droughts in the southwest United States have led to major forest and grassland die-off events in recent decades, suggesting plant community and ecosystem shifts are imminent as native perennial grass populations are replaced by shrub- and invasive plant-dominated systems. These patterns are similar to those observed in arid and semiarid systems around the globe, but our ability to predict which species will experience increased drought-induced mortality in response to climate change remains limited. We investigated meteorological drought-induced mortality of nine dominant plant species in the Colorado Plateau Desert by experimentally imposing a year-round 35% precipitation reduction for eight continuous years. We distributed experimental plots across numerous plant, soil, and parent material types, resulting in 40 distinct sites across a 4,500km2 region of the Colorado Plateau Desert. For all 8 years, we tracked c. 400 individual plants and evaluated mortality responses to treatments within and across species, and through time. We also examined the influence of abiotic and biotic site factors in driving mortality responses. Overall, high mortality trends were driven by dominant grass species, including Achnatherum hymenoides, Pleuraphis jamesii, and Sporobolus cryptandrus. Responses varied widely from year to year and dominant shrub species were generally resistant to meteorological drought, likely due to their ability to access deeper soil water. Importantly, mortality increased in the presence of invasive species regardless of treatment, and native plant die-off occurred even under ambient conditions, suggesting that recent climate changes are already negatively impacting dominant species in these systems. Results from this long-term drought experiment suggest major shifts in community composition and, as a result, ecosystem function. Patterns also show that, across multiple soil and plant community types, native perennial grass species may be replaced by shrubs and invasive annuals in the Colorado Plateau Desert.

A population genetics perspective on the evolutionary histories of three clonal, endemic, and dominant grass species of the Qinghai-Tibet Plateau: Orinus (Poaceae).

We performed analyses of amplified fragment length polymorphism (AFLP) in order to characterize the evolutionary history of Orinus according to its population genetic structure, as well as to investigate putative hybrid origins of O. intermedius and to provide additional insights into relationships among species. The genus Orinus comprises three clonal grasses that are dominant species within xeric alpine grasslands of the Qinghai–Tibet Plateau (QTP). Here, we used eight selectively obtained primer pairs of EcoRI/MseI to perform amplifications in 231 individuals of Orinus representing 48 populations and all three species. We compared our resulting data to genetic models of hybridization using a Bayesian algorithm within NewHybrids software. We determined that genetic variation in Orinus was 56.65% within populations while the among‐species component was 30.04% using standard population genetics statistics. Nevertheless, we detected that species of Orinus were clustered into three highly distinct genetic groups corresponding to classic species identities. Our results suggest that there is some introgression among species. Thus, we tested explicit models of hybridization using a Bayesian approach within NewHybrids software. However, O. intermedius likely derives from a common ancestor with O. kokonoricus and is probably not the result of hybrid speciation between O. kokonoricus and O. thoroldii. We suspect that recent isolation of species of Orinus in allopatry via vicariance may explain the patterns in diversity that we observed, and this is corroborated by a Mantel test that showed significant positive correlation between geographic and genetic distance (r = 0.05, p < 0.05). Recent isolation may explain why Orinus differs from many other clonal species by exhibiting the highest diversity within populations rather than among them.

Arbuscular Mycorrhizal and endophytic (DSE) association in the dominant grasses of Melghat forest (Phase -I), India

Investigations on arbuscular mycorrhizal Fungi (AMF) and dark septate endophytic (DSE) association in some of the dominant grasses from Melghat forest (phase I) of Satpura terrain India, was carried out to examine their existence and symbiotic relationships with the host plants. This forest area was not surveyed earlier by anybody to evaluate the AMF status diversity hence it was decided to survey the buffer and core area. Rhizosphere soil of each sampled grass was analyzed for the AM fungal structures in the roots to study percent root colonization by AMF and AMF spore density in rhizospheric soils of respective samples. The composite soil sample was prepared for each site and used for physicochemical analysis by standard methods. In the first phase of project, forty-eight dominant grass species from twenty-one different sites were collected along with roots and rhizospheric soil to find out AMF and DSE status of grasses. Both type of fungal associations was found in almost all the grass species collected during studies. All of them were found colonized by AMF hyphae along with moderate to poor development of mycorrhizal structures in roots. DSE colonization was also found in maximum forty-three grasses. Physico- chemical characterization of all the soil samples were performed to find out its correlation with AM percent colonization and spore count. Mean AMF percent colonization were in between 1.33 to 52.85 and DSE in with 0.00 to 18.97. Viable AM spore count were in between 0 to 98 per 100g of soil. Altogether four AMF genera with its thirty-nine-different species were isolated and identified.&#x0D; A data base of indigenous AM species richness for Melghat forest has been generated to plan and design the future management practices for grasses establishment and development especially in burnt and over grazed areas.

Litter species diversity is more important than genotypic diversity of dominant grass species Stipa grandis in influencing litter decomposition in a bare field

Studies have indicated that plant litter diversity can affect litter decomposition at both species diversity and genotypic diversity level within a species. However, the essence and relative importance of these two diversity levels on litter decomposition remain unknown. Here, two independent one-factor experiments, litter species diversity and litter genotypic diversity of the dominant species—Stipa grandis, were carried out to explore the effects of initial litter quality, litter composition and diversity on decomposition of mass, nitrogen (N), carbon (C) and phosphorus (P) simultaneously. The results showed that: (1) there were significant relationships between the initial litter N, C/N, lignin/N and the decomposition rate of N, between the initial litter P, N/P and the decomposition rate of P, and the litter composition significantly influenced litter mass, N, C and P remaining in both litter species and genotypic diversity experiments; and (2) litter species diversity significantly affected litter mass, N, C and P remaining, and non-additive relative mixture effects were mainly contributed by synergistic effects especially in 6-species mixtures; however, similar patterns were not found in litter genotypic diversity experiment. The present results emphasized that initial litter quality played the most important role in influencing litter decomposition of mass N, C and P, and suggested that litter species mixtures rather than litter genotypic mixtures of a dominant species could favor nutrient cycling in ecosystem of the semi-arid Inner Mongolia Steppe of China.

Grasses and grazers in arid rangelands: Impact of sheep management on forage and non-forage grass populations

Ecological modeling that includes plant population processes as a critical determinant of vegetation dynamics is useful for sustainable rangeland management. However, we know little about how long-term sheep grazing pressure drives the plant community structure through changes in different native grass species at both individual and population levels. In this study, we hypothesized that plant populations perform differently under different grazing management due to their specified preference by livestock animals. We also tested whether grazing-rest management, aimed at increasing long-term rangeland sustainability, improves the plant growth of forage grass species. We evaluated plant density, individual morphology and plant-size distribution of dominant grass populations in permanent exclosures and open fields under moderate and intensive grazing pressures in Patagonian steppes (South America). We also examined the effects of seasonal grazing-rest managements on the growth and tillering (asexual reproduction) of forage species plants, using temporary mobile exclosures. Grazing intensity changed population density and structure according to species. Compared to permanent exclosures, moderate grazing maintained the plant density of palatable species highly preferred by sheep, reduced the standing-dead biomass proportion of individual plants, and promoted the green biomass of tussocks. Conversely, intensive grazing (double stocking rates) decreased the plant density and individual size of species highly preferred by sheep, and increased the plant density of non-preferred species. Grazing-rest enhanced forage grass species growth and reproduction compared with year-round grazing management, especially during the growing season of a wet year. Our studies support that sheep can be managed to control the plant-size distribution of dominant grass species, their population dynamics, and thereby the overall forage availability at the community level. Both moderate grazing and grazing-rest management can improve the forage availability and preserve the dominant native grasses. We suggest applying a plant population dynamics perspective to facilitate sustainable management of global rangelands.

De novo transcriptomic profiling of the clonal Leymus chinensis response to long-term overgrazing-induced memory

Sheepgrass (Leymus chinensis) is one of the dominant grass species present on typical steppes of the Inner Mongolia Plateau. However, L. chinensis has developed a dwarfing phenotype in response to the stressful habitat in grasslands that are severely degraded due to heavy grazing. The lack of transcriptomic and genomic information has prohibited the understanding of the transgenerational effect on physiological alterations in clonal L. chinensis at the molecular level in response to livestock grazing. To solve this problem, transcriptomic information from the leaves of clonal L. chinensis obtained from overgrazed (GR) and non-grazed (NG) grasslands was studied using a paired-end Illumina HiSeq 2500 sequencing platform. First, despite the influence of grazing being absent during the growth of clonal offspring in our hydroponic experiment, compared with those from the NG group, clonal L. chinensis from the GR group exhibited significant dwarf-type morphological traits. A total of 116,356 unigenes were subsequently generated and assembled de novo, of which 55,541 could be annotated to homologous matches in the NCBI non-redundant (Nr), Swiss-Prot, Clusters of Orthologous Groups (COG), gene ontology (GO), or Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The expression of 3,341 unigenes significantly differed between the GR group and the NG group with an absolute value of Log2 ratio ≥ 1. The altered expression of genes involved in defence and immune responses, pathogenic resistance and cell development indicates that livestock grazing induces a transgenerational effect on the growth inhibition of clonal L. chinensis. The results of the present study will provide important large-scale transcriptomic information on L. chinensis. Furthermore, the results facilitated our investigation of grazing-induced transgenerational effects on both the morphological and physiological characteristics of L. chinensis at the molecular levels.