Stipa Grandis Research Articles

Cumulative effects of K-function in the research of point patterns

The spatial pattern of plant population is one of primary issues in ecological research. Point pattern analy-sis is considered as an important method to study the spatial pattern of plant population. Ripley's K function has been commonly used for point pattern analysis. However, the cumulative effect of Ripley's K function may lead to specific spatial pattern charcteristics. To explore how the cumulative effect of Ripley's K function affects population pattern, the data of clumped distribution, random distribution and regular distribution of Stipa grandis were simulated by R software. All data generated by R software were analyzed by Ripley's K function and the non-cumulative pairwise correlation function g(r). The results showed that for clumped distribution (or regular distribution), the cumulative effect of Ripley's K function was manifested in two aspects. On the one hand, the scale of clumped distribution (or regular distribution) was increased due to Ripley's K function. On the other hand, Ripley's K function could detect the difference of the distribution of cluster (or negative interaction range) in the sampling space, exhibiting different pattern characteristics. For random distribution, Ripley's K function had no cumulative effect. In conclusion, the combination of Ripley's K function and pairwise correlation function by collecting replicate samples could better reveal the essential characteristics of the pattern in the study of population pattern.

Preferences for different nitrogen forms in three dominant plants in a semi-arid grassland under different grazing intensities

Plant species generally absorb different nitrogen (N) forms from soil in ways that minimize N niche overlap, but whether and how grazing affects a plant’s preferred form of N remains unclear. Using the in-situ stable N isotope-labeling technique, we explored the preference of plants in taking up N of different chemical forms along an experimental gradient of grazing intensity in a semi-arid grassland in Inner Mongolia. 15N-labelled nitrate (NO3−), ammonium (NH4+) and glycine solutions were injected into the soil under nil (G0, as a control), light (G1) and heavy grazing (G2) grassland plots in June and August. Uptake of these three N forms was determined for three dominant plants, Leymus chinensis, Stipa grandis and Cleistogenes squarrosa. L. chinensis had the highest N acquisition capacity. Regardless of species, N absorption was higher in August than in June. While all three plant species absorbed glycine-N, they preferentially absorbed N in its inorganic forms (NO3−-N + NH4+-N), with NO3−-N having the highest uptake. Irrespective of grazing intensity, during peak growth (August) all three plant species preferred to absorb NO3−-N (the dominant N form) than NH4+-N or glycine-N. In contrast, in June plants differed in their preferred form of N uptake depending on the grazing treatment. Under heavy grazing (G2), all plants preferentially absorbed NO3−-N. Under light grazing (G1), all plants absorbing all three N chemical forms with no significant difference. Under no grazing (G0), L. chinensis preferentially absorbed NO3−-N but otherwise there was no significant effect of grazing intensity on the preferred form of N. Our results indicate that the three species of plants that we observed altered their N-uptake preference in response to grazing intensity differently in the early growth and vigorous growth stages. Plant N niche differentiation in time, space and chemical N forms needs to be explored systematically in future studies to aid understand of grazing effects on N processes in grassland ecosystem.

The effects ofEpichloëendophytes on the growth and competitiveness ofAchnatherum sibiricumare mediated by soil microbe diversity

AbstractMany grasses are infected by systemic fungal endophytes that occur in aboveground plant tissues. Both aboveground endophytic fungi and belowground soil microbes can influence plant growth, but studies on their simultaneous effects on plant growth and competitiveness are limited. This study aims to investigate whether the role of aboveground endophytic fungi in the growth and competitive ability of the host grasses was influenced by soil microbes. In this study, we used Epichloë endophyte-infected and endophyte-free Achnatherum sibiricum as plant materials. A wet sieving method was adopted to obtain microbial inocula with different diversities (com, combined microbe fraction, high diversity; sm, small microbe fraction, low diversity). A three-factor randomized block design was used. The first factor was the endophyte infection status of A. sibiricum. The second factor was the microbial composition of the soil inocula. The third factor was the planting type. Growth and competitive characters were measured after 16 weeks. The results showed that a soil microbe inoculation was detrimental to the growth of A. sibiricum. Epichloë endophytes significantly mitigated the inhibitory effect of soil microbes on A. sibiricum planted alone. When A. sibiricum was planted with Stipa grandis, there was a significant interaction between Epichloë endophytes and soil microbes on the interspecific competition of A. sibiricum. When inoculated with small microbial community fraction, Epichloë endophytes significantly improved the interspecific competitive ability of host plants. When inoculated with combined microbial community fraction, however, Epichloë endophytes had no significant effect on host competition. The results showed that the interaction between Epichloë endophytes and soil microbes contributed more to the interspecific competitive ability than either Epichloë endophytes or soil microbes alone.

Isolation of rhizosheath and analysis of microbial community structure around roots of Stipa grandis

Root zone microbial structure is particularly complex in plants with rhizosheaths, and greater understanding of the rhizosheath may play an important role in the future development of sustainable agricultural practices. However, one important reason to focus study on rhizosheath microbial structure is that there is no definite method for rhizosheath separation. The aim of this study was to explore rhizosheath isolation methods and the diversity characteristics of microorganisms around the rhizosphere. In this study, we isolated the rhizosheath of Stipa grandis, a dominant species in desert steppe, and the microorganisms in the roots, root epidermis, rhizosheath and rhizosphere soil were extracted and sequenced by 16S rRNA and ITS. The alpha diversity index of bacteria in Stipa grandis rhizosphere soil was the greatest, followed by rhizosheath, and the alpha diversity index of endophytic bacteria in root system was the smallest. The alpha diversity index of fungi in the rhizosheath and rhizosphere soil were significantly higher than that in the root epidermis and root system. There were significant differences in bacterial community structure between the root epidermis, endophytic bacteria, rhizosheath and rhizosphere soil. Unlike bacterial community structure, the community structure of fungi in the root epidermis was similar that of endophytic fungi, but significantly different from those in rhizosheath and rhizosphere soil. This study demonstrated a feasible method for separating plant rhizosheath and root epidermis. We suggest that the root epidermis can act as the interface between the host plant root and the external soil environment. We will have to re-examine the biological and ecological significance of rhizosheath and microorganisms in rhizosheath, as well as the mechanism explaining the close relationship of the rhizosheath and the plant root epidermis. This study provides theoretical and technical guidance for the isolation of the plant rhizosheath and the study of microorganisms in plant rhizosheath.

内蒙古围封草原枯落物累积对大针茅和羊草生长发育的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 内蒙古围封草原枯落物累积对大针茅和羊草生长发育的影响 DOI: 10.5846/stxb202106111552 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 内蒙古自治区重大科技专项(ZDZX2018020)；内蒙古自治区科技成果转化项目(2020CG0013) Effects of litter accumulation on growth of Stipa grandis and Leymus chinensis in a fenced typical steppe in Inner Mongolia 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:围封草原枯落物累积通过改变水分和热量的再分配影响植物的生长发育。为探究不同植物种群对枯落物累积的适应性,2015-2017年在内蒙古围封典型草原设置了枯落物去除实验,对土壤温度和水分进行了原位监测,也对群落优势物种大针茅(Stipa grandis)和亚优势物种羊草(Leymus chinensis)种群的生长发育过程及种群数量特征进行了测定。结果表明:枯落物累积显著降低生长季表层和深层土壤温度(1.3-4.6℃和1.5-3.2℃),并提高表层和深层土壤水分(1.4%-10.4%和1.0%-5.0%)。枯落物累积对大针茅种群返青时间的延迟(16.9-24.2 d)显著高于羊草种群的(5.2-6.7 d),但对大针茅和羊草种群的营养生长期无显著影响。枯落物累积显著提高大针茅种群的高度但显著降低其盖度和地上生物量,引起大针茅种群的重要值显著降低(0.38→0.22)。枯落物累积显著提高羊草种群的高度、盖度和地上生物量,进而显著提高其重要值(0.16→0.28)。大针茅和羊草种群重要值排序的更替驱动围封草原植物群落演替。本研究从植物种群的角度为阐明围封草原群落结构与功能改变提供新视角,也为科学合理制定围封政策提供理论依据。 Abstract:Litter accumulation affects growth of plant species by redistributing hydrothermal condition in fenced steppe ecosystems. To explore the ecological adaptations of different plant species with diverse morphological and ecological characteristics to litter accumulation, we conducted a litter removal experiment in a fenced typical steppe in Inner Mongolia during 2015-2017. Soil temperature and moisture were continuously monitored in situ. The growth and quantitative characteristic of the dominant and subdominant species (Stipa grandis and Leymus chinensis) were measured. The results were as follows. Litter accumulation significantly decreased surface and deep soil temperature (1.3-4.6 ℃ in surface soil and 1.5-3.2 ℃ in deep soil) but remarkably increased surface and deep soil moisture (1.4%-10.4% in surface soil and 1.0%-5.0% in deep soil). Litter accumulation delayed the returning greening day of S. grandis (16.9-24.2 days) more than that of L. chinensis (5.2-6.7 days) but had no significant effects on their vegetative period. Litter accumulation significantly increased the height of S. grandis but decreased its cover and aboveground biomass, which remarkably reduced the important value of S. grandis (0.38→0.22). Conversely, litter accumulation significantly increased the height, cover, and aboveground biomass of L. chinensis, which remarkably increased its important value (0.16→0.28). Comprehensively, the order change of important value in S. grandis and L. chinensis drove community succession in the fenced steppe. This study elucidates the changes of community structure and function in fenced steppe ecosystems from the perspective of plant population and provides the theoretical basis for scientific and rational formulation of enclosing policy. 参考文献 相似文献 引证文献

放牧和刈割对大针茅草原土壤微生物群落结构及多样性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 放牧和刈割对大针茅草原土壤微生物群落结构及多样性的影响 DOI: 10.5846/stxb202103290818 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 内蒙古自治区科技计划项目（2019ZD008）；内蒙古自治区自然科学基金项目（2020ZD03）；国家自然科学基金项目（31861143001，32160332） Effects of management regime on soil microbial community structure and diversity of Stipa grandis grassland 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:放牧和刈割是内蒙古草原的两种主要利用方式，然而，长期放牧和刈割对大针茅草原土壤微生物群落的影响知之甚少，因此，以内蒙古大针茅草原为研究对象，设置放牧和刈割两种利用方式，以围封不利用为对照，基于高通量测序技术，研究大针茅草原在不同利用方式下土壤微生物组成及多样性的变化，并结合土壤理化因子进一步探究土壤微生物群落组成的主要影响因素。研究结果表明：不同利用方式下土壤细菌α多样性指数无显著差异，而刈割显著提高了土壤真菌Observed_species、Chao1和ACE指数；土壤细菌群落的优势菌门是变形菌门（Proteobacteria）和放线菌门（Actinobacteria），土壤真菌群落的优势菌门是子囊菌门（Ascomycota）和被孢霉门（Mortierellomycota），不同利用方式下部分微生物类群的相对丰度差异显著，放牧显著提高了细菌群落的变形菌门、疣微菌门（Verrucomicrobia）和芽单胞菌门（Gemmatimonadetes）的相对丰度，刈割显著提高了真菌群落的担子菌门（Basidiomycota）相对丰度，此外，放牧和刈割均显著降低了厚壁菌门（Firmicutes）的相对丰度；冗余分析表明，土壤细菌主要受硝态氮和铵态氮影响，二者均与酸杆菌门（Acidobacteria）呈正相关，与变形菌门（Proteobacteria）呈负相关，土壤真菌主要受有效磷和硝态氮影响。综上所述，草地利用方式的改变通过土壤理化因子改变了土壤微生群落组成及多样性，其中土壤铵态氮、硝态氮和有效磷是微生物群落形成和演化的主要驱动因素。研究揭示了不同利用方式下大针茅草原土壤微生物群落结构特征及多样性的变化及其与土壤理化性质的关系，可为大针茅草原合理利用提供理论依据。 Abstract:Grazing and mowing are two dominant management regimes in the Inner Mongolia grassland, both of which have a profound impact on grassland ecosystem, and most of the previous studies have primarily focused on the effects on plant and soil. Soil microbial communities are the most abundant and diverse groups of organisms on earth and are responsible for numerous key ecosystem processes. They play an important role in the circulation of materials and nutrients between plants and soil ecosystems. However, their response to these management regimes has not been comprehensively explored in Stipa grandis grassland. In this study, two management regimes of grazing and mowing were set up in a typical S. grandis area, and enclosure was used as the control. Based on high-throughput sequencing technology, the changes of soil microbial composition and diversity under different management regimes was examined, Redundancy analysis was used to analysis soil physical and chemical characteristics influencing on it. The results showed that there was no significant difference in soil bacterial α diversity index under different management regimes, but mowing significantly increased soil fungal Observed_species, Chao1 and ACE index. Amplicon sequencing revealed Proteobacteria and Actinobacteria were the dominant bacterial phylum under different grassland management regimes, and the dominant phyla of soil fungal communities were Ascomycota and Mortierellomycota. Grazing significantly increased the relative abundance of Proteobacteria, Verrucomicrobia and Gemmatimonadetes of the bacterial community, and mowing significantly increased the relative abundance of Basidiomycota of fungal community. In addition, grazing and mowing significantly reduced the relative abundance of Firmicutes. Redundancy analysis showed that soil bacteria were mainly affected by nitrate nitrogen and ammonium nitrogen, which were positively correlated with Acidobacteria and negatively correlated with Proteobacteria. Soil fungi were mainly affected by available phosphorus and nitrate nitrogen. In conclusion, changes in grassland usage methods altered the composition and diversity of soil microflora through soil physicochemical factors, and soil ammonium nitrogen, nitrate nitrogen and available phosphorus were the main driving factors on microbial community formation and evolution. This study revealed the structural characteristics and diversity of soil microbial communities in the S. grandis steppe under different management regimes and their relationship with soil physicochemical properties, which may provide a theoretical basis for the rational utilization of S. grandis steppe. 参考文献 相似文献 引证文献

半干旱黄土区植被恢复对土壤团聚体稳定性及抗侵蚀能力的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 半干旱黄土区植被恢复对土壤团聚体稳定性及抗侵蚀能力的影响 DOI: 10.5846/stxb202202090324 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省回国留学人员科研资助项目（2021-097）；山西省基础研究计划（20210302123333）；国家自然科学基金项目（41971129） Effect of vegetation restoration on stability and erosion resistance of soil aggregates in semi-arid loess region 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:土壤水稳性团聚体强烈影响土壤过程和功能，是反映土壤质量和土壤抗侵蚀能力的重要指标。为探究半干旱黄土区植被恢复对土壤抗侵蚀能力的影响，以甘肃省定西市龙滩流域为研究区，选取3种恢复方式（天然荒草、自然恢复、人工恢复）7种植被类型（大针茅草地、长芒草草地、赖草草地、苜蓿草地、柠条灌丛、山杏林以及油松林）为研究对象，通过测定0-20 cm、20-40 cm和40-60 cm土壤水稳性团聚体，分析土壤团聚体组成、稳定性及抗侵蚀能力特征。结果表明：1）不同恢复方式不同植被类型间土壤水稳性团聚体稳定性差异显著（P<0.05），自然恢复方式的土壤水稳性团聚体平均重量直径显著高于天然荒草和人工恢复方式，且7种植被类型土壤大团聚体质量百分比均在67.97%-90.12%之间；人工恢复方式土壤水稳性团聚体稳定性较差，其中油松林稳定性最差。2）土壤团聚体破坏率和土壤抗侵蚀能力均表现出自然恢复方式更有利于土壤结构稳定性的提高。3）土壤水稳性大团聚体含量越高，土壤团聚体越稳定，土壤结构稳定性就越好；平均重量直径与土壤可蚀性因子K值呈极显著性负相关（P<0.01）。本研究结果表明自然恢复方式能够显著提高土壤团聚体的稳定性，从而提升土壤的抗侵蚀能力，建议当地在未来植被恢复规划中采取自然恢复方式更有利于生态恢复的有效进行。 Abstract:Soil water-stable aggregates strongly affect soil process and function, which is an important index to reflect soil quality and soil erosion resistance. In order to explore the effect of vegetation restoration on soil erosion resistance in semi-arid loess region, in this study, through three restoration methods (natural grassland, natural restoration, artificial restoration) and seven vegetation types (Stipa grandis grassland, Stipa bungeana grassland, Leymus secalinus grassland, Medicago sativa grassland, Caragana korsinskii shrub, Armeniaca sibirica forest and Pinus tabulaeformis forest) were selected in the Longtan catchment of Dingxi in Gansu Province. The composition, stability and erosion resistance characteristics of soil aggregates were analyzed by measuring 0-20 cm, 20-40 cm and 40-60 cm soil water-stable aggregates. The results showed that:1) there are significant differences in the stability of soil water-stable aggregates among different vegetation types and different restoration methods (P<0.05). The average weight diameter of soil aggregates in natural restoration grassland was significantly higher than that in natural restoration and artificial restoration vegetation, and the mass percentage of soil macroaggregates of the seven vegetation types was 67.97%-90.12%. The stability of soil water-stable aggregates under artificial restoration was poor, among which the stability of Pinus tabulaeformis forest was the worst. 2) The destruction rate of soil aggregates and the ability of soil erosion resistance showed that the natural restoration method was more beneficial to the improvement of soil structure stability. 3) The higher the content of water-stable macroaggregates in soil, the more stable the soil aggregate, the better the soil structural stability; there was a very significantly negative correlation between soil average weight diameter and soil erodibility factor K (P<0.01). The results of this study show that the natural restoration method can significantly improve the stability of soil aggregates, thus improving the soil anti-erosion ability, so as to improve the soil erosion resistance, suggested the plant in the future. 参考文献 相似文献 引证文献

Community Differentiation and Ecological Influencing Factors along Environmental Gradients: Evidence from 1200 km Belt Transect across Inner Mongolia Grassland, China

In this work, we conducted a 1200 km belt transect for field survey in typical and meadow steppes across Inner Mongolia Plateau in 2018. The field investigation, laboratory soil analysis, and quantitative ecology methods were utilized to explore the differentiation characteristics of the plant community, and their relationships with ecological factors. The results showed that a total of 140 vascular plants within 108 quadrats mainly comprised of Asteraceae, Poaceae, Rosaceae, and Fabaceae. Two-way Indicator Species Analysis (TWINSPAN) revealed eight vegetation typologies: I: Stipa sareptana var. krylovii + Dysphania aristata, II: Stipa grandis + Leymus chinensis, III: Stipa sareptana var. krylovii + Leymus chinensis, IV: Stipa grandis + Cleistogenes squarrosa, V: Stipa grandis + Carex duriuscula, VI: Stipa baicalensis + Leymus chinensis, VII: Carex pediformis + Stipa baicalensis, VIII: Leymus chinensis + Elymus dahuricus. Detrend Correspondence Analysis (DCA) confirmed the above eight vegetation typologies and indicated a relatively small variation. Redundancy analysis (RDA) revealed that the spatial differentiation characteristics in the typical steppe were chiefly driven by precipitation, while the influencing factor in the meadow steppe was soil nutrients, followed by temperature and precipitation. The contrast between typical and meadow steppes revealed that the spatial distribution of typical steppe was influenced by precipitation, while the contribution of heat and water in the meadow steppe was equal. The conclusion revealed that the temperature and precipitation conditions coupled with soil nutrients shaped the spatial differentiation characteristics of temperate steppe vegetation in the Inner Mongolia grassland. Therefore, this study advanced our knowledge of the spatial patterns of temperate steppe along longitude and latitude gradients, providing scientific and theoretical guidance for the biodiversity conservation and sustainable ecosystem management of the Inner Mongolia grassland.

High frequency of extreme precipitation increases Stipa grandis biomass by altering plant and microbial nitrogen acquisition

High frequency of extreme precipitation increases Stipa grandis biomass by altering plant and microbial nitrogen acquisition

Precipitation drives the floristic composition and diversity of temperate grasslands in China

Effects of environmental factors on plant diversity in temperate grasslands are of interest since experiments have found plant diversity is related to ecosystem function. Although previous studies have focused on the effects of environmental factors on plant diversity, the dominant environmental factors driving diversity differences among plant community types in temperate grasslands at regional scale remains unclear. We established 38 sampling sites (45 m × 45 m) in the main distribution areas of temperate grasslands to analyze the responses of plant community along different environmental gradients and identifies the dominant environmental factors driving the floristic composition and diversity in Inner Mongolia, China. In addition, environmental variables (annual mean temperature, annual precipitation, altitude, disturbance intensity, soil pH, soil density, soil water content, soil organic carbon, soil total nitrogen, soil total phosphorus, soil calcium carbonate), species diversity indices (richness, heterogeneity, evenness), functional diversity indices (abundance, evenness, divergence, dispersion) and plant biomass were analyzed. A total of 179 vascular plant species belonging to 43 families and 113 genera were recorded and classified into six plant community types ( Stipa grandis community, Leymus chinensis community, Stipa capillata community, Artemisia frigida community, Cleistogenes squarrosa community, Artemisia halodendron community) based on Ward's agglomerative hierarchical clustering. According to canonical correspondence analysis and Monte Carlo permutation test, mean annual precipitation was the dominant environmental factor driving temperate grasslands, promoting species richness, heterogeneity, evenness, functional divergence and biomass. Soil organic carbon, water content and total nitrogen played positive effects on species diversity, meanwhile, mean annual temperature, altitude, grazing intensity and soil pH inhibited species diversity, functional abundance, dispersion and biomass. Furthermore, the presence of these plant communities dominated by Cleistogenes squarrosa and Artemisia halodendron indicate that grassland degradation is imminent or has already begun. In summary, our results provide evidence on the responses of composition, functional traits and biomass among different plant community types to environmental factors and demonstrate that precipitation is the dominant factors driving the floristic composition and diversity in temperate grasslands. • Annual precipitation is the dominant environmental factor driving temperate grasslands. • Soil organic carbon play a positive effect on plant diversity and biomass. • Species diversity is more affected by environmental factors than functional diversity. • Cleistogenes squarrosa and Artemisia halodendron warn of grassland degradation.

The response of litter decomposition to phosphorus addition in typical temperate grassland in Inner Mongolia

The productivity of terrestrial ecosystems is limited by soil fertility, such assoil phosphorus (P). The decomposition of litter is the main process that affects nutrient cycling. To understand the characteristics of litter decomposition and nutrient release under P addition, we conducted a 2-year litter bag experiment at P addition rates (0–12.5 g P m−2 yr−1). All litter decomposed faster during the second growing season due to highly concentrated precipitation, and Stipa grandis litter decomposed faster (1.02–1.63 times) than Leymus chinensis under P treatments. The decomposition of L. chinensis and mixed litter was more thoroughly at 1 g P m−2 yr−1, while S. grandis decomposed more under 5 g P m−2 yr−1. P addition promoted nitrogen (N) and P immobilization and all litter reached its maximum at 12.5 g P m−2 yr−1. Phosphorus addition increased β-glucosidase production at 5 g P m−2 yr−1, but leucine aminopeptidase production was promoted at high P. The ratio of leucine aminopeptidase to phosphatase increased over time, indicating the N deficiency and P saturation during late stages of decomposition. Our results show that Inner Mongolia's grasslands was limited by P availability and that precipitation was important in the region's decomposition processes.

Grazing Intensity Rather than Host Plant's Palatability Shapes the Community of Arbuscular Mycorrhizal Fungi in a Steppe Grassland.

Arbuscular mycorrhizal fungi (AMF) are the predominant type of mycorrhizal fungi in roots and rhizosphere soil of grass species worldwide. Grasslands are currently experiencing increasing grazing pressure, but it is not yet clear how grazing intensity and host plant grazing preference by large herbivores interact with soil- and root-associated AMF communities. Here, we tested whether the diversity and community composition of AMF in the roots and rhizosphere soil of two dominant perennial grasses, grazed differently by livestock, change in response to grazing intensity. We conducted a study in a long-term field experiment in which seven levels of field-manipulated grazing intensities were maintained for 13 years in a typical steppe grassland in northern China. We extracted DNA from the roots and rhizosphere soil of two dominant grasses, Leymus chinense (Trin.) Tzvel. and Stipa grandis P. Smirn, with contrasting grazing preference by sheep. AMF DNA from root and soil samples was then subjected to molecular analysis. Our results showed that AMF α-diversity (richness) at the virtual taxa (VT) level varied as a function of grazing intensity. Different VT showed completely different responses along the gradient, one increasing, one decreasing, and others showing no response. Glomeraceae was the most abundant AMF family along the grazing gradient, which fits well with the theory of disturbance tolerance of this group. In addition, sheep-grazing preference for host plants did not explain much of the variation in AMF α-diversity. However, the two grass species exhibited different AMF community composition in their roots and rhizosphere soils. Roots exhibited a lower α-diversity and higher β-diversity within the AMF community than soils. Overall, our results suggest that long-term grazing intensity might have changed the abundance of functionally diverse AMF taxa in favor of those with disturbance-tolerant traits. We suggest our results would be useful in informing the choice of mycorrhizal fungi indicator variables when assessing the impacts of grassland management choices on grassland ecosystem functioning.

Transcriptome-Wide Gene Expression Plasticity in Stipa grandis in Response to Grazing Intensity Differences.

Organisms have evolved effective and distinct adaptive strategies to survive. Stipa grandis is a representative species for studying the grazing effect on typical steppe plants in the Inner Mongolia Plateau. Although phenotypic (morphological and physiological) variations in S. grandis in response to long-term grazing have been identified, the molecular mechanisms underlying adaptations and plastic responses remain largely unknown. Here, we performed a transcriptomic analysis to investigate changes in gene expression of S. grandis under four different grazing intensities. As a result, a total of 2357 differentially expressed genes (DEGs) were identified among the tested grazing intensities, suggesting long-term grazing resulted in gene expression plasticity that affected diverse biological processes and metabolic pathways in S. grandis. DEGs were identified in RNA-Seq and qRT-PCR analyses that indicated the modulation of the Calvin–Benson cycle and photorespiration metabolic pathways. The key gene expression profiles encoding various proteins (e.g., ribulose-1,5-bisphosphate carboxylase/oxygenase, fructose-1,6-bisphosphate aldolase, glycolate oxidase, etc.) involved in these pathways suggest that they may synergistically respond to grazing to increase the resilience and stress tolerance of S. grandis. Our findings provide scientific clues for improving grassland use and protection and identifying important questions to address in future transcriptome studies.

A direct comparison of the effects and mechanisms between species richness and genotype richness in a dominant species on multiple ecosystem functions.

Both species (interspecific) richness and genotype (intraspecific) richness of dominant species have significant effects on ecosystem functioning directly or indirectly by regulating plant community functional structure. However, the similarities and differences of the effects between inter‐ and intraspecific levels are poorly understood. In this study, we selected the main species in the semi‐arid Eurasian typical steppe as study objects and simultaneously carried out a species richness experiment and a genotype richness experiment of Stipa grandis which is one of the dominant species in this region. We investigated how plants at each of the two richness levels affected multiple ecosystem functions (biomass, soil C, N and P cycles) directly and indirectly by regulating community functional structure, including community‐weighted mean trait values (CWM) and functional dispersion (FDis). Both species richness and genotype richness showed significant direct effects on soil P cycle, and FDis significantly mediated the responses of aboveground biomass and soil N cycle to the changes of species richness and the response of belowground biomass to the changes of genotype richness in S. grandis. CWM showed significant effects on biomass in the species richness experiment and soil nutrient cycles in the genotype richness experiment, independently of the levels of plant richness. These findings provide experimental insights of intraspecific richness effects into the relationships between biodiversity and ecosystem functioning, and highlight the importance of conserving the intraspecific diversity of dominant species in the semi‐arid steppe regions.

Common response of dominant plants in typical grassland of Inner Mongolia to long‐term overgrazing revealed by transcriptome analysis

AbstractLeymus chinensis (Trin.) Tzvel. and Stipa grandis P. Smirn. are dominant species in grassland on the typical steppe of Inner Mongolia. Long‐term overgrazing, which is considered to represent multiple stresses, reduces the growth of L. chinensis and S. grandis. To gain an understanding of the molecular mechanisms underlying the responses of these plants to overgrazing, we explored the gene expression profiles of L. chinensis and S. grandis to discover the common features of these dominant plants in response to overgrazing. Using the Illumina RNA‐Seq platform, two sequencing libraries prepared from non‐grazed (Lc‐NG) and overgrazed samples (Lc‐OG) of L. chinensis were sequenced. Using Trinity software assembly, 129,087 unigenes with a mean length of 693 bp and an N50 of 1,093 bp were obtained by combining the Lc‐NG and Lc‐OG data. By comparing differentially expressed genes (DEGs) of L. chinensis with those of S. grandis, we identified 16 Kyoto Encyclopedia of Genes and Genomes pathways and 15 Gene Ontology terms that were significantly enriched with DEGs in both species. Most of these DEG‐enriched pathways, for example, phenylpropanoid biosynthesis and flavonoid biosynthesis, were related to stress responses. The results suggest that stress plays an important role in plants’ responsiveness to long‐term overgrazing and associated reductions in plant growth. The DEGs shared by these two species will be valuable for further research on key genes and molecular mechanisms involved in plants’ adaptation to overgrazing and associated stresses.

Effects of Mowing Height on Community Composition and Species Niche in Stipa grandis Steppe

Effects of Mowing Height on Community Composition and Species Niche in Stipa grandis Steppe

Single Grazing Is More Detrimental to Grasslands Than Mixed Grazing: Evidence From the Response of Functional Traits of Dominant Plants to Grazing Systems

Plant functional traits reflect species ecological strategies and determine how plants respond to environmental changes, however, how dominant species in the Inner Mongolia grassland adapt to different grazing systems by changing their functional traits has not been systematically investigated. In this study, we established four 7-year grazing treatments in the Inner Mongolia grassland: cattle grazing, sheep grazing, mixed sheep and cattle grazing, and no grazing. Fourteen functional traits of three dominant species (Stipa grandis, Leymus chinensis, and Cleistogenes squarrosa) were measured under the different grazing treatments. We found convergences of plant functional traits that indicate herbivory avoidance or tolerance. Plants reduced their vegetative height (VH) and stem: leaf ratio (SLR) to avoid grazing; increased their ability to acquire resources by increasing their specific leaf area (SLA), leaf nitrogen concentration (LNC), and leaf phosphorus concentration (LPC); and reduced their leaf dry matter content (LDMC) to tolerate grazing. Moreover, plants may adapt to grazing by increasing the intraspecific variability of their functional traits. Sheep-only grazing adversely affected L. chinensis growth and survival, while cattle-only grazing hindered S. grandis growth and increased the intraspecific variability of its plant functional traits. Our study emphasizes that intraspecific variability is an important indicator of the responses of plant functional traits to grazing. Since single grazing is more detrimental to the functional traits of dominant plants, we suggest that mixed cattle and sheep grazing may be a more environmentally friendly and sustainable practice for the Inner Mongolia grassland than single grazing.

Variations and factors characterizing ecological niches of species in a stable grassland plant community

To explore the primary factors affecting the ecological niches in a plant community, four dominant shrub species (Sophora viciifolia, Periploca sepium, Buddleja alternifolia, Clematis fruticosa) and six dominant grass species (Bothriochloa ischaemum, Artemisia sacrorum, Stipa bungeana, Cleistogenes squarrosa, Stipa grandis, Lespedeza bicolor) were selected from a stable grassland community in the Loess Plateau (China). The relative importance value and niche breadth were used as comprehensive quantitative indices to characterize the status, role, and degree of dominance of plant species in the community. We found that relative importance value and niche breadth were higher overall in shrub species than in most grass species, except B. ischaemum. Meanwhile, the relative importance value was significantly correlated with plant phosphorus concentration, plant carbon:nitrogen ratio, rhizosphere soil organic carbon, rhizosphere soil total nitrogen, rhizosphere soil total phosphorus, rhizosphere bacterial α-diversity. A stepwise regression analysis indicated that, among the plant and rhizosphere characteristics of these species, only their rhizosphere bacterial α-diversity and plant root carbon concentration primarily influence ecological niche patterns of these plant species in the community. In summary, our study reveals that shrub species occupy more advantageous ecological niches than grass species in a stable community due to the active rhizosphere interactions, providing a new opportunity to disentangle the mechanisms underlying the plant community assembly in grassland.

Interpreting the effects of plant species diversity and genotypic diversity within a dominant species on above- and belowground overyielding

Biodiversity loss, either intraspecific or interspecific level, could alter community processes and ecosystem functioning. Exploring the mechanisms by which biodiversity at different levels influences ecosystem functioning is a major challenge in the field of ecology. In this study, by constructing plant communities with different diversity levels of both dominant species (Stipa grandis) genotype and common species in a mesocosm experiment, we analyzed the relative importance of dominant genotype diversity and common species diversity on biomass production through Fox's tripartite partition, and the relationships between community functional diversity and biomass production. For common species mixtures (G0S5), a significant positive net diversity effect on belowground biomass was found, and the net effect was contributed by a significant positive dominance effect and a significant negative trait-independent complementarity effect. For genotype mixtures of S. grandis (G5S0), a significant positive net diversity effect on aboveground biomass and a non-significant positive net diversity effect on belowground biomass were found, and both the effects were driven by positive trait-independent complementarity effects. The increases in both dominant genotype and common species diversity (G5S5) led to remarkable positive net diversity effects, with a significant positive trait-independent complementarity effect on belowground biomass and all the three biodiversity effect components on aboveground biomass being significantly positive. Only a small proportion (3/22) of relationships between community functional diversity and biomass were linear by a first order polynomial estimation. The significant positive trait-independent complementarity effect in G5S0 and trait-dependent complementarity effect in G5S5 could not be explained by the smaller intraspecific trait variation. These findings highlight the underestimated and overlooked roles of dominant genotypic diversity for ecosystem functioning, and are very important for grassland protection and management, especially in the semi-arid typical steppe.

Changes of Aboveground and Belowground Biomass Allocation in Four Dominant Grassland Species Across a Precipitation Gradient.

Climate change is predicted to affect plant growth, but also the allocation of biomass to aboveground and belowground plant parts. To date, studies have mostly focused on aboveground biomass, while belowground biomass and allocation patterns have received less attention. We investigated changes in biomass allocation along a controlled gradient of precipitation in an experiment with four plant species (Leymus chinensis, Stipa grandis, Artemisia frigida, and Potentilla acaulis) dominant in Inner Mongolia steppe. Results showed that aboveground biomass, belowground biomass and total biomass all increased with increasing growing season precipitation, as expected in this water-limited ecosystem. Biomass allocation patterns also changed along the precipitation gradient, but significant variation between species was apparent. Specifically, the belowground biomass: aboveground biomass ratio (i.e., B:A ratio) of S. grandis was not impacted by precipitation amount, while B:A ratios of the other three species changed in different ways along the gradient. Some of these differences in allocation strategies may be related to morphological differences, specifically, the presence of rhizomes or stolons, though no consistent patterns emerged. Isometric partitioning, i.e., constant allocation of biomass aboveground and belowground, seemed to occur for one species (S. grandis), but not for the three rhizome or stolon-forming ones. Indeed, for these species, the slope of the allometric regression between log-transformed belowground biomass and log-transformed aboveground biomass significantly differed from 1.0 and B:A ratios changed along the precipitation gradient. As changes in biomass allocation can affect ecosystem functioning and services, our results can be used as a basis for further studies into allocation patterns, especially in a context of environmental change.