Typical Steppe Research Articles

Эколого-ценотическая характеристика растительных сообществ с участием Colchicum bulbocodium subsp. versicolor (Colchicaceae) в Нижнем Поволжье

The article presents a phytocoenotic description of 23 plant communities with Colchicum bulbocodium subsp. versicolor studied during the period of mass flowering in 2014–2018. It was found that, across the Lower Volga region, the studied communities with C. bulbocodium subsp. versicolor are mostly confined to the slopes of south- and east-facing arroyos and more seldom to the southern and northern hill slopes, plains, arroyo and liman bases, and floodmeadows. During the period of mass flowering, 207 vascular plants were detected in the studied communities. Every community description included 9 to 36 species. Biological diversity was assessed with the Shannon index and polydominance index; the degree of dominance was measured with the Simpson index. The species similarity of the communities was evaluated through pairwise comparison with the Jaccard coefficient. It was revealed that C. bulbocodium subsp. versicolor occurs in communities varying in diversity and species composition. The subspecies is not confined to specific phytocoenoses. It usually grows on rich and, more seldom, fairly rich and slightly saline soils. Their alluviality is more often weak rather than moderate. Watering usually corresponds to the dry steppe or semi-desert climate type, rarely to the middle steppe type, being moderately variable and in some cases highly variable. The impact of grazing is usually weak, but it is either moderate or strong in some communities. The communities with C. bulbocodium subsp. versicolor are dominated by hemicryptophytes: mostly tap-root, short-rhizome and long-rhizome herbaceous perennials. In phytocoenotic terms, most species belong to the zonal type of vegetation, namely steppe vegetation. The participation of meadow species is prominent. The share of weed species is rather high, which indicates a significant anthropogenic load on the studied communities.

Vegetation Characteristics of the Main Grassland Types in China Respond Differently to the Duration of Enclosure: A Meta-Analysis

Enclosure is one of the useful measures to protect and restore degraded grasslands, and it is widely used around the world. The vegetation characteristics of grasslands directly reflect the recovery status of degraded grasslands; however, conflicting results of plant traits were continually achieved in the numerous on-site studies of enclosure in the last two decades. It is necessary to conduct a systematic assessment to find a general conclusion for the effects of enclosure on different grasslands. Studies on the enclosure grasslands in China were taken as the objects to refine the relationships between grassland vegetation characteristics and enclosure measures using meta-analysis. Enclosure had positive effects on the restoration of vegetation coverage, aboveground and belowground biomass, and diversity of degraded grasslands. Different vegetation characteristics and grassland types showed different responses to enclosure duration. The vegetation productivity reached a maximum in the 11–15 years of enclosure for alpine grasslands and typical steppe grasslands, 6–10 years for desert grasslands, and more than 15 years of enclosure for meadow grasslands. Plant species diversity reached the peak values when alpine grasslands and typical steppe grasslands were enclosed approximately 10 years, desert grasslands approximately 11–15 years, and meadow grasslands approximately 5 years. These results indicated that the management strategies of enclosed grasslands should be adjusted reasonably according to the types and the management objectives of grasslands in order to maintain or even improve the condition and services of grassland ecosystems.

Plant α‐and β‐diversity, and soil microbial stoichiometry co‐regulate the alterations in ecosystem multifunctionality in response to grazing and N addition in a typical steppe

AbstractDespite their significance, how interactions of plant diversity at multiple spatial scales and soil microbial stoichiometry alter a series of ecosystem functions (multifunctionality, EMF) in response to anthropogenic nitrogen (N) input and herbivores are poorly known. We conducted a 17‐year sheep grazing experiment with 6‐year N addition to explore the impacts of grazing (0, 2.7, 5.3 and 8.7 sheep ha−1) and N addition (N0, N5, N10 and N20, i.e., 0, 5, 10 and 20 g N m−2 yr−1, respectively) on grassland functions and EMF via changes in plant α‐and β‐diversity, and carbon to nitrogen ratio (C:N) of soil microbes in a typical steppe. The results show that grazing or N addition alone significantly affected EMF with a treatment order of 2.7 and 8.7 sheep ha−1 > 0 and 5.3 sheep ha−1 for grazing intensity or N5 > N10 and N20 > N0 for N addition, which resulted in a significant higher EMF in the combination treatment of 2.7 sheep ha−1 and 5 g N m−2 yr−1. Plant α‐and β‐diversity, and soil microbial C:N were the predominant drivers of changes in EMF. Grazing reduced EMF indirectly by decreasing the plant β‐diversity. N addition promoted EMF indirectly by decreasing plant α‐diversity. In addition, lower plant α‐diversity enhanced EMF indirectly by increasing soil microbial C:N. Our results suggest that the negative effects of herbivore on EMF were stronger at larger spatial scales compared to the smaller local communities, while N addition could maintain a higher level of EMF at smaller scales rather than at the larger ones. Our results highlight that multiple spatial scales should be considered to fully unravel the effects of herbivore and eutrophication on ecosystem functions. Our results also demonstrate the important role of soil microbe in maintaining higher grassland multifunctionality, thus we should include the soil microbial functions (i.e., C and N transformation) in further studies. Our results suggest that grazing at a low grazing intensity of 2.7 sheep ha−1 with a low N supplementation of 5 g N m−2 yr−1 could maintain the most important ecosystem functions. Our work provides important insight into grassland conservation and management, aiming to maintain the capacity of grasslands to sustainably supply ecological and productive functions.

Diminishing influence of negative relationship between species richness and evenness on the modeling of grassland α-diversity metrics

Species richness and evenness have been widely used to investigate the spatiotemporal variation of α-diversity. However, some studies have indicated that a negative relationship exists between species richness and evenness. The question is how the differing sensitivity of α-diversity metrics and interactive behavior between richness and evenness affect the modeling of α-diversity variation. Here, we explored the response of species diversity, represented by three Hill numbers (i.e., species richness, exponential of Shannon index – expShannon, and inverse of Simpson index – invSimpson) focusing on the abundance of rare and common species, and Pielou index underlining the evenness of a community, to α-diversity variation through structural equation modeling (SEM). The model scheme integrated three categories of variables, spectral variation hypothesis (SVH), community pattern, and vertical structure, along the precipitation gradient spanning three steppes, including meadow steppe, typical steppe, and desert steppe. Our results showed that there were large differences in species richness across the three steppes, with v-shaped patterns emerging along the gradient (low-point in the typical steppe). Differences between steppes were diminished in the expShannon or invSimpson indices, though the v-shaped patterns persisted. The Pielou index showed the opposite pattern, with the peak in the typical steppe. Accordingly, a negative relationship between species richness and Pielou index was found across the three steppes. The concurrent increases in annual species number and dominant species abundance in response to precipitation variations led to the negative relationship. As a result, the SEM fitness on expShannon and invSimpson indices over the region was substantially diminished by the negative relationship. Overall, community pattern better explained the variation in species richness, invSimpson and Pielou indices. The performance of SVH differed among α-diversity metrics due to the collinearity with the variables of community pattern and vertical structure. This study emphasizes the variability of α-diversity metrics in response to environmental change. Particularly, distinguishing the asynchronous behaviors between species richness and evenness is paramount to account for α-diversity variation over heterogeneous ecosystems.

Spider Diversity in the Fragmented Forest-Steppe Landscape of Northeastern Ukraine: Temporal Changes under the Impact of Human Activity

Semi-natural forests and dry grasslands are highly fragmented and influenced by human activity. Despite the small area, they serve as the refuge for habitat-specific species and enhance agrolandscape biodiversity. We studied spiders in Velykoburlutskyi Steppe Regional Landscape Park (northeastern Ukraine) for 10 years and found 224 species of 26 families; of these, 27 are rare and require protection. The araneofauna of small forests in gullies is poorer than that of the large oakeries and hosts fewer sylvatic species; the dry grassland fauna is rich, has typical steppe traits, and varies depending on topography and grazing history. The ungrazed gully hosted 125 spider species. The richest assemblages (97 species) were at the bottom, and they were similar to those of meadows and forest edges. The most typical steppe assemblages were formed on the ungrazed slope (77 species). The human-induced disturbance had a negative effect on spiders: we found only 63 species at the grazed bottom and 62 on the slope. After abrupt grazing cessation, four spider species appeared and occurred constantly at the bottom, while no species left this habitat. Grazing on the slopes declined gradually, and spider assemblages did not change significantly after the final cessation; moreover, they enriched on the abandoned slope (75 species). The presence of rare species and a variety of spider assemblages confirm the conservation value of the study site and the need to maintain its mosaic pattern.

Patterns and Drivers of Aboveground Insect Diversity along Ecological Transect in Temperate Grazed Steppes of Eastern Eurasian

Insects are important components of biodiversity and play significant roles in the steppe ecosystem. They are abundant, easy to sample, and sensitive to changing conditions, making them useful indicators of environmental changes. This study aims to describe patterns (α and β) of insect diversity across two steppe types (a typical steppe and a desert steppe) along the Eastern Eurasian Steppe Transect (EEST), as well as evaluate the effects of environmental variables in determining these patterns and the influence of plant diversity alterations on these effects. To this end, we collected 5244 individual insects and found an n-shaped diversity distribution along the latitudinal gradient and a significant difference in insect communities across the two steppe types. Further, the Mantel test and path analysis indicate that climate and grazing activities combine to influence insect diversity, and these effects are mediated through plant diversity, strongly supporting the role of bottom-up effects in situations of climatic and grazing pattern changes. Moreover, the contribution of plant diversity varied with steppe types and insect functional groups, with greater effects seen in the typical steppe and herbivorous insects. This indicated the importance of protecting species diversity in steppes through managing plant diversity and assessments of local environmental factors such as grazing intensity and temperature.

Environmental changes promoted vegetation growth and reduced water yield over the temperate semi-arid grassland of China during 1901–2016

As an important part of global semi-arid grassland, adequately understanding how eco-hydrological processes in the Temperate Semi-Arid Grassland of China (TSGC) respond to environmental change over a century-long time scale is of critical importance to environmental change adaptation and mitigation policy in the semi-arid region. We investigated the dynamics and driving forces of key eco-hydrological variables (leaf area index (LAI), gross primary production (GPP), evapotranspiration (ET), water yield (WY), and water use efficiency (WUE)) of 8 typical locations within the TSGC during the period 1901–2016, using a well-tested mechanistic eco-hydrological model, seamlessly integrating land-surface energy balance, hydrological and carbon cycle, vegetation dynamics, and soil biogeochemistry. Results show that dominated by the elevated CO2, the annual LAI, GPP, and WUE increased significantly during 1901–2016, indicating that the environmental conditions were conducive to vegetation growth. Warming conditions were a promoter of vegetation growth in sandy grassland but a suppressant in typical steppe due to water stress increase. For the same reason, ET of sandy grassland exhibited a significant increasing trend, in response to warming, while that of typical steppe had an insignificant decreasing trend, controlled by the precipitation decline. Warming and the vegetation growth acceleration due to the elevated CO2 negatively influenced WY, which showed a decreasing trend, especially in the sandy grassland, suggesting the reduction of available water resources. Overall, our results revealed that this region, especially sandy grassland, exhibited an “enhanced vegetation but decreased water yield” trend under environmental changes occurred in the past century.

Spatiotemporal Distribution and Main Influencing Factors of Grasshopper Potential Habitats in Two Steppe Types of Inner Mongolia, China

Grasshoppers can greatly interfere with agriculture and husbandry, and they will breed and grow rapidly in suitable habitats. Therefore, it is necessary to extract the distribution of the grasshopper potential habitat (GPH), analyze the spatial-temporal characteristics of the GPH, and detect the different effects of key environmental factors in the meadow and typical steppe. To achieve the goal, this study took the two steppe types of Xilingol (the Inner Mongolia Autonomous Region of China) as the research object and coupled them with the MaxEnt and multisource remote sensing data to establish a model. First, the environmental factors, including meteorological, vegetation, topographic, and soil factors, that affect the developmental stages of grasshoppers were obtained. Secondly, the GPH associated with meadow and typical steppes from 2018 to 2022 were extracted based on the MaxEnt model. Then, the spatial-temporal characteristics of the GPHs were analyzed. Finally, the effects of the habitat factors in two steppe types were explored. The results demonstrated that the most suitable and moderately suitable areas were distributed mainly in the southern part of the meadow steppe and the eastern and southern parts of the typical steppe. Additionally, most areas in the town of Gaorihan, Honggeergaole, Jirengaole, as well as the border of Wulanhalage and Haoretugaole became more suitable for grasshoppers from 2018 to 2022. This paper also found that the soil temperature in the egg stage, the vegetation type, the soil type, and the precipitation amount in the nymph stage were significant factors both in the meadow and typical steppes. The slope and precipitation in the egg stage played more important roles in the typical steppe, whereas the aspect had a greater contribution to the meadow steppe. These findings can provide a methodical guide for grasshopper control and management and for further ensuring the security of agriculture and husbandry.

Monitoring of long‐term vegetation dynamics and responses to droughts of various timescales in Inner Mongolia

AbstractThe characteristics of vegetation and drought for different seasons between 1982 and 2015 in Inner Mongolia were studied based on the normalized difference vegetation index (NDVI) and the standardized precipitation evapotranspiration index (SPEI). The response of vegetation to drought over various timescales for different seasons and vegetation types was investigated using the maximum Pearson correlation, allowing a discussion about the possible causes of any changes. The results indicate that the vegetation NDVI in Inner Mongolia showed an increasing trend in different seasons, with spring vegetation NDVI (April–May) having the largest significant increasing rate, followed by the growing season (April–October), autumn (September–October), and summer (June–August). Accordingly, the proportion of stations with decreasing SPEI was, in descending order, summer, growing season, autumn, and spring. Additionally, the magnitude of the SPEI decrease was greater in eastern Inner Mongolia. NDVI and SPEI were positively correlated in most regions of Inner Mongolia, indicating that changes in vegetation in most parts of this region were affected by the spatial and temporal characteristics of drought, the correlation being them being strongest in the growing season, followed by summer, then spring and autumn. Considering the different types of vegetation, forests were less affected by drought, with broadleaf forests more affected than coniferous forests. The meadow steppes and typical steppes were more affected by 12‐month droughts in the growing season and summer, 6‐month droughts in spring, and 3‐month droughts in autumn, with desert steppes mainly affected by 3‐month droughts. The shrubs, sandy vegetation, and cropland were mostly affected by droughts in summer, and show a greater response to 3‐month droughts in autumn. Finally, the water balance was found to be the most important factor affecting the response of vegetation to drought in Inner Mongolia.

Response of Grassland Soil Quality to Shallow Plowing and Nutrient Addition.

Due to differences in the soil environment and grassland management measures, the change characteristics of soil microbial entropy and soil comprehensive quality in different types of grassland may vary significantly. In this study, the spatial variation characteristics of grassland soil microbial entropy under shallow plowing and nutrient addition measures were studied using a networking experimental platform established in a temperate meadow steppe, typical steppe, and desert steppe in northern China. The grassland soil quality was comprehensively evaluated to provide a theoretical basis for the scientific and reasonable management of grasslands under global climate change. The results show that in the meadow steppe, shallow plowing and nutrient addition significantly decreased the soil microbial biomass carbon and microbial entropy in the region, resulting in a decrease in the comprehensive score of soil quality. In the typical steppe, due to the influence of shallow tillage measures, the microbial biomass of the grassland soil in the region was higher than that of the control group and its two treatments, and the comprehensive score of soil quality was ranked first among the four treatments. In the desert steppe, the interaction of shallow plowing and nutrient addition significantly increased the soil microbial entropy in the region. Under the nutrient addition measures, the soil microbial entropy of the desert steppe showed a downward trend. In addition, the soil C/N ratio of the desert grassland under nutrient addition measures increased significantly, and the comprehensive score of soil quality ranked first among the four treatments as the microbial entropy decreased significantly.

Relationship of Plant Species Diversity and Sampling Area Under Different Grazing Intensities in the Steppe of Northern China

The relationship between sampling area of plant community and number of species contained in it has an importance in vegetation ecology. Using a nested quadrat survey, the relationship between plant species and sampling area was discussed under different grazing pressure in the steppe and the determination of minimum sampling area was calculated herein. Ten curve models were selected to fit the species-area relation of plant community in a typical steppe of northern China. The residual standard deviation, correlation index, average value of absolute deviation, and average value of absolute relative deviation were used as the evaluation indexes for model fitting. The results show that the curve equations S = B + CAZ and S = C(1-e−BA)Z have the best simulation effect. According to the simulation results, the minimum sampling areas are determined as 1.16 m2 (T0), 1.23 m2 (T7), 1.28 m2 (T10), and 1.10 m2 (T14), presenting the minimum sampling area is feasible when the second derivative is zero. Generally, sheep grazing reduced the species richness of steppe, though some of the plans flourished while some others disappeared or dismissed, but increased spatial heterogeneity, especially on a smaller scale. However, there are also variances in different area scales and grazing intensities. When the sampling area was small (< 2 m2), heavy grazing T14 increased the number of plant species per unit area, yet light grazing T8 reduced the number of plant species per unit area of steppe. When the sampling area was large (> 16 m2), grazing reduced the number of plant species per unit area in the natural steppe. Anyhow, the effect of grazing intensity on plant species fluctuated greatly when the sampling area was medium (2 m2 ∼ 16 m2). In general, the similarity of plant communities had an increasing trend with accumulated sampling area, though it varied at different grazing intensities.

Exogenous fibrolytic enzymes promoted energy and nitrogen utilization and decreased CH4 emission per unit dry matter intake of tan sheep grazed a typical steppe by enhancing nutrient digestibility on China loess plateau.

Exogenous fibrolytic enzyme (EFE) products in ruminant nutrition may be an important alternative to meet the increased demands for animal products in the future with reduced environmental impacts. This study aimed to evaluate the dose-response of EFE supplementation on the nutrient digestibility, nitrogen and energy utilization, and methane (CH4) emissions of Tan sheep grazed in summer and winter. A total of 20 Tan wether sheep with an initial body weight of 23.17 ± 0.24 kg were used in a randomized complete block design and categorized into two groups. Animals fed orally with 1 g of EFE (10,000 U/g) mixed with 30 mL of water using a drencher constituted the EFE group. For experimental accuracy, the control (CON) group was orally administered with 30 mL of normal saline daily before grazing. The following results were obtained: EFE in the diet increased dry matter intake (DMI) (P < 0.05), average daily gain (ADG) (P < 0.05), and digestibility (P < 0.05) compared with CON in summer and winter. DMI increased but ADG and digestibility decreased in winter compared with those in summer. Sheep fed with the EFE diet increased the concentrations of rumen ammonia nitrogen (P < 0.05) and total volatile fatty acids (P > 0.05), but reduced pH (P > 0.05), compared with CON in summer and winter. EFE increased nitrogen (N) intake, digestible N, retained N, and retained N/digestible N (P < 0.05) but reduced fecal N/N intake, urinary N/N intake, and excretion N/N intake in summer and winter (P < 0.05), compared with CON. Retained N/N intake was reduced and excretion N/N intake increased in winter relative to those in summer. In winter, gross energy (GE), manure E/GE, CH4 emissions, CH4/DMI, and CH4/GE increased but digestion energy and metabolic energy decreased compared with those in summer. Sheep fed with the EFE diet had a greater GE intake than those fed with the CON diet (P < 0.05) but had lesser CH4/DMI and CH4E/GE (P < 0.05) than those fed with the CON diet in both summer and winter. In conclusion, EFE supplementation increased DMI, apparent digestibility, and N deposition rate. These effects were beneficial for animal production. The CH4 emission per unit DMI of grazing Tan sheep was lesser and conducive for augmenting the environmental benefits.

宁夏草地土壤有机碳空间特征及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 宁夏草地土壤有机碳空间特征及其影响因素 DOI: 10.5846/stxb202201040022 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（42061037） Spatial characteristics of soil organic carbon in grassland of Ningxia and its influencing factors 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:草地是重要的碳汇资源库，在陆地生态系统碳循环中扮演着重要角色。探明草地土壤有机碳的空间分布格局及其影响因素对于推动区域生态系统碳汇管理，实现"双碳"目标和绿色高质量发展具有重要意义。以宁夏三种主要草地类型为研究对象，基于野外样点调查，采用结构方程模型，分析了草地土壤有机碳的空间分布特征及其影响因素。结果表明：不同类型草地土壤有机碳含量表现为草甸草原高于典型草原，荒漠草原最低，垂直剖面上均随土壤深度的增加而降低。草甸草原和荒漠草原有机碳空间变异自表层向下逐渐增大，典型草原在20-40 cm土层变异系数达到最大。有机碳分布在区域上从南部六盘山山地向中部干旱风沙带逐渐降低。路矩分析发现，海拔高度、地上生物量、降水量、温度和土壤含水量可解释土壤有机碳空间变异的91.4%。海拔高度对土壤有机碳总效应最大（作用系数为0.78），海拔高度引起的降水和温度等要素区域分异间接影响土壤有机碳含量；地上生物量对土壤有机碳的直接正向效应最大（0.559）；降水量对土壤有机碳效应分为直接效应和作用于生物量及土壤含水量的间接影响；温度表现为通过生物量对土壤有机碳间接产生负向效应（-0.259）。宁夏草地土壤有机碳的空间分布主要受降水量和与其密切相关的生物量的支配作用。近20年来降水量增多和草地人为干扰减少，宁夏草地碳汇作用显著。 Abstract:Grasslands are important contributors of carbon sequestration among terrestrial ecosystems, which play an important role in the global biogeochemical cycle and energy exchange. Based on field surveys in July-August 2021, soil samples of meadow steppe, typical steppe and desert steppe in Ningxia were collected. The organic carbon contents, bulk density, total nitrogen, and pH of these soil samples were measured. We also monitored factors affecting carbon distribution such as altitude, annual precipitation, annual mean temperature, aboveground biomass and soil water content. Results indicated that content of the soil organic carbon decreased along the vertical soil profile, the average organic carbon content followed the order of meadow steppe > typical steppe > desert steppe. The distribution of grassland soil organic carbon gradually decreased from the Liupan Mountains in the south to the dry sand belt in the middle along the altitude. Soil organic carbon was significantly positively correlated with aboveground biomass, annual precipitation, altitude and soil total nitrogen density, and significantly negatively correlated with annual mean temperature (P<0.001), positively correlated with soil water content, and negatively with soil bulk density (P<0.01), and no obvious correlation with soil pH. Amos structural equation model was applied to evaluate the combined effects of environmental factors on grassland soil organic carbon. The most important factors affecting organic carbon was altitude (r=0.78), which mainly caused regional differentiation of precipitation and temperature to affect soil organic carbon indirectly; followed by aboveground biomass (r=0.559); then annual precipitation (0.539), which not only directly but also indirectly affected the soil organic carbon by altering aboveground biomass and soil water content positively. Annual mean temperature indirectly affected organic carbon negatively by influencing aboveground biomass (r=-0.259). The spatial distribution of grassland organic carbon in Ningxia was dominated by precipitation and aboveground biomass closely related to precipitation. In the past 20 years, with the increase of precipitation and the reduction of grassland anthropogenic disturbance, grassland ecosystem in Ningxia had a very significant carbon sink function. 参考文献 相似文献 引证文献

Patterns of net primary production changes in eurasian steppes

The aim of the study. The aim of the study was to analyze changes in the above-ground (ANP), below-ground (BNP) and total net primary production (NPP), expressed in dry matter, in meadow, true and dry steppes along the latitudinal (from 56o to 43o N) and longitudinal (from 36o to 116o E) gradients. Methodology. Production characteristics of 32 steppes (9 meadow, 14 true and 9 dry steppes), obtained by the same method of minimal estimate, were analyzed. Main results. The ANP value in meadow steppes decreases from 10,2 to 3,1 t/ha per year, in true steppes from 6,7 to 0,7 t/ha per year and in dry steppes from 3,7 to 0,6 t/ha per year. The value of BNP in meadow steppes varies from 26,8 to 10,1 t/ha per year; in true steppes - from 25.7 to 7.7 t/ha per year; and in dry steppes - from 24,8 to 4,9 t/ha per year. The BNP changes from West to East were found not to follow the ANP changes: a decrease in ANP may be accompanied by an increase in BNP. According to the ANP estimates the analyzed steppes can be grouped as following: 1) ANP from 10 to 5; 2) ANP from 5 to 3; 3) ANP from 3 to 1; 4) ANP less than 1 t/ha per year. The first group is located between 56o and 51o NL and includes six meadow steppes and one true steppe. The second group includes all three types of steppes (three meadow, six true and one dry steppe) between 56o and 50o N. The third group of steppes, between 54° and 43° NL, consists of six true and seven dry steppes. At 50°N one true and one dry steppes are located with the smallest ANP. The first and the second groups are located in the same territory (from 56o to 50o N) and include both meadow and true steppes. About 70% of the meadow and half of the true steppes are characterized by the ANP ranging from 6.7 to 3.1 t/ha per year. In the northern part of the explored zone there are highly productive meadow steppes, whereas in its southern part there are true steppes with both high and low production. The third group of steppes, with production from 3 to 1 t/ha per year, includes seven low-productive true and eight dry steppes. The average ANP of true and dry steppes of this group are similar (2,2 t/ha per year). Consequently, the area from 54° to 43°N can be considered as a zone of dry steppes. Conclusion. There are no separate zones of meadow and real steppes, but there is a steppe zone that includes meadow and true steppes. The proposed division of the steppes and their zoning is made on the basis of ANP, which is the most important characteristic of any ecosystem.

Класс Festuco-Brometea в Южном Зауралье (степная зона Челябинской области)

Класс Festuco-Brometea в Южном Зауралье (степная зона Челябинской области)

Степной орёл в Алтае-Саянском регионе – результаты исследований 2019–2023 годов

Степной орёл в Алтае-Саянском регионе – результаты исследований 2019–2023 годов

Dynamic Characteristics and Possible Causes for the Propagation from Meteorological to Hydrological Drought over a Temperate Typical Steppe

Abstract Knowledge gain in the characteristics and mechanisms of drought propagation is indispensable for timely drought early warning and risk reduction over the grassland eco-region. This study focused on the Xilin River basin, which is a typical inland river basin located in the Inner Mongolia temperate steppe, China. The characteristics of meteorological and hydrological drought were assessed by applying the standardized precipitation index and standardized streamflow index. The propagation relationship between meteorological and hydrological droughts was then investigated from both static and dynamic perspectives, and the possible reasons for its temporal dynamics were discussed by considering environmental factors. Our results showed that the Xilin River basin has suffered from more serious meteorological drought than hydrological drought during the past 60 years, with a stationary evolution of meteorological drought but an overall drying trend in hydrological drought. The propagation from meteorological to hydrological droughts exhibited obvious seasonality, characterized by stronger intensity and shorter response time in the wet season. Nonstationary behaviors were identified for the temporal patterns of drought propagation time, especially showing a significant trend in April, May, and August. The dynamic changes in propagation time affected by regional forces were principally ruled by the precipitation variation positively and strongly, and they were moderately controlled by temperature, vegetation cover, and deep-layer soil moisture, with season-dependent effects. The effects of low-frequency atmospheric anomalies on drought propagation will be further investigated in future studies, which are expected to provide a better understanding of the physical mechanism of the large-scale climate forcing on local drought condition. Significance Statement A new research approach was proposed to assess the propagation relationship between meteorological and hydrological drought from both static and dynamic perspectives, and the possible reasons for the temporal dynamics were discussed by considering environmental factors. Focusing on an inland river basin over the Inner Mongolia typical steppe, the propagation from meteorological to hydrological droughts showed obvious seasonality. Nonstationary behaviors were identified for the temporal patterns of drought propagation time, which could be explained by the regional hydrometeorological conditions. The advanced understanding of drought propagation provides a scientific base for water resources planning and drought management within a grassland region.

Wind Power Increases the Plant Diversity of Temperate Grasslands but Decreases the Dominance of Palatable Plants

As an important clean energy source, the scale and quantity of wind power have steadily increased under the background of global change. The construction and operation of wind power facilities have massive impacts on grassland microclimates. However, the effect of wind power operation on the plant community composition is still unclear. To investigate this issue, we selected wind farms in 6 meadow grasslands and 6 typical steppes in the central region of Inner Mongolia, the province with the largest scale of grassland wind power operations in China. At these sites, we conducted field sample surveys to obtain species information, measure plant biomass, calculate plant diversity, and take soil samples to determine soil nutrients. The results showed that wind power operation significantly reduced the dominance of Poaceae and Cyperaceae plants in both types of grasslands and significantly increased the Shannon diversity of meadow grasslands. The inconsistent responses at each experimental site led to a nonsignificant overall effect of wind power operation on the plant beta diversity. In addition, wind power operation significantly increased plant biomass in meadow grasslands. Wind power operation did not change the soil total carbon, total nitrogen, ammonium nitrogen, or nitrate nitrogen. On the basis of the results, we suggest strengthening the long-term monitoring of temperate grassland plant community composition in wind farms, and replanting of community-building species could be done at appropriate times.

Mechanism for the restoration of degraded typical steppe by nitrogen and phosphorus co-addition.

The reduction of soil nutrient content is one of the major reasons caused grassland degradation in China. Nutrient addition is thus considered as an effective measure for the restoration of degraded grasslands. However, over-fertilization can lead to decrease in plant diversity. To clarify the appropriate amount of nutrient addition and the underlying mechanism that promotes grassland restoration, we set up a nitrogen and phosphorus co-addition experiment in a degraded typical steppe of Inner Mongolia, and examined the responses at community, functional group and species levels to nutrient addition. The results showed that nutrient addition enhanced biomass while did not reduce species richness at the community level. The biomass showed a saturation response with the increases of nutrient addition, which approached saturation under the 12.0 g N·m-2, 3.8 g P·m-2 treatment. Species richness increased significantly under the lower nutrient treatments (N <9.6 g·m-2, P < 3.0 g·m-2) compared with the control, while the two high nutrient treatments did not alter species richness. At the functional group level, biomass and abundance of perennial rhizome grasses increased significantly with the increases of nutrient addition levels. Biomass and density of annuals increased significantly under high nutrient addition levels. However, the abundance and biomass of perennial bunchgrasses and perennial forbs were rarely affected. At the species level, six target species responded differently to nutrient addition. Biomass of Leymus chinensis was significantly increased due to the increase of population density and individual biomass. Biomass of Stipa grandis, Agropyron cristatum and Cleistogenes squarrosa change little. Biomass of Potentilla acaulis and Carex korshinskyi were reduced due to the decreases in individual biomass and population density, respectively. As a measure of restoring degraded grassland, nutrient addition could significantly increase biomass and species diversity, decrease biomass of the degradation indicator species, and increase biomass of perennial rhizomes grasses.

Псаммофитная растительность долины реки Худан (Республика Бурятия)

Псаммофитная растительность долины реки Худан (Республика Бурятия)