Stipa Krylovii Steppe Research Articles

Phenological characteristics of net ecosystem carbon exchange of Stipa krylovii steppe in Inner Mongolia, China and its remote sensing monitoring.

To accurately monitor the phenology of net ecosystem carbon exchange (NEE) in grasslands with remote sensing, we analyzed the variations in NEE and its phenology in the Stipa krylovii steppe and discussed the remote sensing vegetation index thresholds for NEE phenology, with the observational data from the Inner Mongolia Xilinhot National Climate Observatory's eddy covariance system and meteorological gradient observation system during 2018-2021, as well as Sentinel-2 satellite data from January 1, 2018 to December 31, 2021. Results showed that, from 2018 to 2021, NEE exhibited seasonal variations, with carbon sequestration occurring from April to October and carbon emission in other months, resulting in an overall carbon sink. The average Julian days for the start date (SCUP) and the end date (ECUP) of carbon uptake period were the 95th and 259th days, respectively, with an average carbon uptake period lasting 165 days. Photosynthetically active radiation showed a negative correlation with daily NEE, contributing to carbon absorption of grasslands. The optimal threshold for capturing SCUP was a 10% threshold of the red-edge chlorophyll index, while the normalized difference vegetation index effectively reflected ECUP with a threshold of 75%. These findings would provide a basis for remote sensing monitoring of grassland carbon source-sink dynamics.

Reduced moisture caused by short-term grazing prohibition results in a significant decrease of fungi abundance

The grassland ecosystem is an integral component of the global ecosystem. However, the changes in soil and soil microbial communities during the transition from natural grazing to grazing prohibition period in the Stipa Krylovii steppe, along with the driving factors behind the differences in soil microbial communities, remain unclear. In this study, soil characteristics and the fungal community diversity were measured and assessed. The results indicated that during the initial period of grazing prohibition, the dominant fungal species remained consistent, yet there were notable changes in their abundance and the physicochemical properties of the soil. Under natural grazing, a significant inverse relationship was observed between fungal abundance and pH. Conversely, a positive association was found between fungal diversity and volumetric water content (VWC), along with a highly significant positive correlation between fungal abundance, fungal diversity, and soil organic matter (SOM). In the initial period of grazing prohibition, fungal abundance exhibited a noteworthy positive association with SOM, VWC, and soil temperature (ST). Similarly, fungal diversity displayed a significant positive correlation with SOM and ST. Fungal abundance appeared to be more influenced by soil factors compared to fungal diversity, with VWC identified as the most crucial element impacting factor on fungal abundance.

Environmental factors rather than productivity drive autumn leaf senescence: evidence from a grassland in situ simulation experiment

Leaf senescence is crucial to the land biochemical cycle. However, there are still inconsistent results regarding autumn leaf senescence; in particular, there are few studies on leaf senescence in grasslands or its key factors. This study carried out a three-year in situ simulation experiment on the Stipa krylovii steppe in Inner Mongolia, aiming to explore the drivers, critical regulation periods, and regulation pathways of leaf senescence. The results showed that precipitation significantly changed the leaf senescence of Stipa krylovii, but the effects of temperature and their interactions were not significant. An increase in precipitation of 50% (W+50%) significantly delayed leaf senescence by 5.96 d, while a reduction in precipitation of 50% (W-50%) advanced it by 2.17 d. The dry mass of Stipa krylovii at the green-up, heading, flowering, seed formation, and beginning of the withering stage was significantly fitted with a quadratic‐down model with leaf senescence, which is different from most present studies. Summer soil water content (SWCsu) and spring soil temperature (STsp) were significantly correlated with leaf senescence. Including dry mass or not did not significantly influence structural equation model results, and dry mass did not drive leaf senescence significantly. Leaf senescence in both models with and without dry mass was directly regulated by precipitation and spring soil temperature. Therefore, in contrast to environmental factors, productivity was not a key driver of leaf senescence. Our results provided new evidence for the recently debatable question about the driver of leaf senescence and developed a new regression correlation between productivity and leaf senescence, which are necessary and meaningful to improve our understanding of grassland phenology.

克氏针茅草原群落物种多样性与生物量关系对放牧强度的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 克氏针茅草原群落物种多样性与生物量关系对放牧强度的响应 DOI: 10.5846/stxb202110162921 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（41861024，42161023）；内蒙古自然科学基金（2021BS04001）；内蒙古自治区高等学校科学技术研究项目（NJZZ21006） Relationship between species diversity and biomass of Stipa krylovii steppe community and its responses to grazing intensity 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:放牧强度引起的草原植物群落物种多样性与地上生物量变化是近年来草地生态系统研究的热点问题。以内蒙古锡林郭勒克氏针茅草原为研究对象，探究植物群落结构特征、物种多样性与地上生物量之间相互关系及其对不同放牧强度的响应。结果表明：随着放牧强度的增加植物群落结构逐步向退化方向演替；植物群落高度逐渐降低（P<0.05），密度逐渐增加（P<0.05），盖度总体呈下降趋势（P<0.05）；植物群落和原有群落优势种地上生物量总体呈下降趋势（P<0.05），而退化指示物种的地上生物量逐渐增加（P<0.05）；轻度、中度放牧条件下群落物种Margalef指数、Pielou指数、Simpson指数均显著高于重度放牧（P<0.05）；地上生物量与Shannon-Wiener指数、Margalef指数和Pielou指数呈正相关关系，而与Simpson指数呈负相关关系。综上所述，克氏针茅草原植物群落结构和功能在不同放牧强度下产生不同的响应，适度放牧有利于提高群落物种多样性与生物量。 Abstract:In recent years, the species diversity and aboveground biomass changes of steppe plant communities caused by grazing intensity have been hot issues in steppe ecosystem research. This paper takes the Stipa krylovii steppe of Xilin Gol in the Inner Mongolia as the research object, explores the relationship between characteristics of plant community structure, species diversity and aboveground biomass, and clarifies response to different grazing intensities. The results showed that the plant community structure gradually succeeded in the direction of degradation with the increase of grazing intensity. The height of the plant community gradually decreased (P<0.05) while the density of that gradually increased (P<0.05), and the overall coverage showed a downward trend (P<0.05). The aboveground biomass of plant communities and the dominant species of the original community showed a general downward trend (P<0.05), while that of the degraded indicator species gradually increased (P<0.05). The Margalef index, Pielou index, and Simpson index of community species under mild and moderate grazing conditions were significantly higher than those of heavy grazing (P<0.05). Aboveground biomass was positively correlated with Shannon-Wiener index, Margalef index and Pielou index, but showed a negative correlation with the Simpson index. In summary, the structure and function of the Stipa krylovii steppe plant community produce different responses in different grazing intensities, and moderate grazing is beneficial to increase the community's species diversity and biomass. 参考文献 相似文献 引证文献

Effects of nitrogen addition on vegetation and soil and its linkages to plant diversity and productivity in a semi-arid steppe.

Nitrogen (N) deposition and fertilization, which represent key sources of N input in many terrestrial ecosystems, influence all levels of the ecosystem and involve complex mechanisms. Quantitative and modelling approaches can be used to understand this complexity. In this study, we carried out in situ N addition experiments in a Stipa krylovii steppe in northern China. We evaluated the effects of N addition on plant diversity and productivity under two scenarios (fertilization and simulated increased N deposition) using a structural equation model (SEM). N addition had direct effects on community weighted means (CWM) of plant functional traits and soil properties but had indirect effects on community structure. The changes in community structure and soil properties caused by N addition decreased plant diversity, whereas productivity remained relatively stable and was mainly controlled by changes in community structure. The changes in soil properties and plant diversity caused by N addition had little effect on productivity or soil pH. We conclude that the changes in plant diversity and productivity with increased N input in the S. krylovii steppe were mainly due to differences in growth responses of different species to increased N and the resulting community responses, such as changes in community structure. The results of the present study provide a theoretical basis for grassland management and conservation in the wake of global environmental change.

Microbial diversity in the rhizosphere soils of three Stipa species from the eastern Inner Mongolian grasslands

Rhizosphere soil microorganisms affect the diversity and ecological distribution of aboveground plants and play an important role in the functions of terrestrial ecosystems. Using high-throughput sequencing, we have investigated the rhizosphere soil microbial communities of three species of Stipa from six plots, in the eastern steppe of Inner Mongolia, and analyzed the relationship between microbial diversity and vegetation diversity and soil physicochemical characteristics. The dominant bacteria phyla were: Actinobacteria, 31.73–44.73%; Proteobacteria, 15.79–23.85%; Acidobacteria, 9.42–15.14%; and Chloroflexi, 4.90–13.60%. While the dominant fungi phyla were: Ascomycota, 16.93–82.12%; Basidiomycota, 2.44–81.28%; and Zygomycota, 0.40–18.92%. Principal coordinates analysis (PCoA) indicated that the soil microbial community compositions in the Stipa baicalensis steppe in Hulunbuir and the Stipa krylovii steppe in the Xilingol plots, were significantly different from the others. The species characteristics of the plant communities were different in each plot for the vegetation diversity factors, the Shannon Weiner index, Simpson index, and the importance value indices of the Stipa and Leymus chinensis significantly affected the community structures of the bacteria and fungi. Among the physicochemical soil parameters, soil pH, ammonium nitrogen (AN), and sucrase (SC), significantly affected the community structures of the bacteria and fungi, and were inseparable from the interactions between the microorganisms and environmental factors. We found that microbial community diversity was complex in the rhizosphere soils of the Stipa, and that they were mainly affected by the vegetation diversity, soil pH, ammonium nitrogen, and soil sucrase activities. These results improve our understanding of the correlations between the Stipa rhizosphere soil microorganisms and the environmental factors, and provide guidance for future research on the distribution characteristics and growth of the Stipa.

Joint forcing by heat waves and mowing poses a threat to grassland ecosystems: Evidence from a manipulative experiment

AbstractThe frequency and intensity of heat waves (HWs) have increased in recent years, but it remains unclear how grassland ecosystems respond to such extreme weather. A 3‐year manipulative field experiment was conducted to simulate HWs under different mowing intensities in a Stipa krylovii steppe on the Mongolian Plateau to examine their effects on plant morphology, phenology, and community. At the species level, the morphology and phenology of the three main herb species (S. krylovii, Melilotoides ruthenica, and Potentilla tanacetifolia) showed species‐specific responses to the HW and mowing treatments. The major dominant species S. krylovii shed ~50% of the tiller outer layer to protect the internal tiller from HW stress thereby directly decreasing the heat load and water loss from green plant tissue and indirectly increasing the litter biomass. HWs also caused increases of community index (richness, diversity, and evenness) but also associated with a 30% decrease in the importance value of S. krylovii, whereas mowing enhanced this value by 27%. When HWs were combined with mowing, the joint forcing of mechanical damage and low carbon accumulation aggravated negative effects of stress on plant health and growth, which further decreased community index. We constructed a framework to fully describe the effects of HWs and mowing and their interrelationship on different ecological levels and explain how short‐term effects, such as extreme climate, produce long‐term effects on ecosystems. In conclusion, we found that synergisms between climate extremes (HWs) and human activities (mowing) can reduce ecosystem stability posing a threat to the grasslands.

The shift in the abundance of two Stipa species in response to land use change is associated with their divergent reproductive strategies

The divergent changes of plant species under land use changes are key mechanisms underlying vegetation succession. Stipa grandis steppe and Stipa krylovii steppe are two plant communities widely distributed on the Mongolian Plateau. They have been speculated to be able to succeed into each other under different land use types and intensities based on the observations on their presence and abundance at the sites with different land use history. However, no direct evidence, neither the underlying mechanisms, have been reported for this speculation. Here, we verified this speculation and explored the underlying mechanisms in the typical steppe region of Inner Mongolia. We investigated the abundance and reproductive behavior of S. krylovii and S. grandis under different land use types and intensities. We used 18 grassland paddocks to run a 6-year experiment with 6 management treatments (T0—unused, T1—grazing monthly in plant growing season, T2, T4, T6—grazing in different months in plant growing season, and T8—mowing) replicated three times. We measured the relative density and cover of S. krylovii and S. grandis using line sampling method and examined their number and biomass of vegetative and reproductive tillers using quadrat method in each paddock after treatments for 4 and 6 years. We also determined these plant attributes in 14 pairs of heavily versus lightly used grassland plots in a wide area (150 km × 200 km) of the typical steppe region. 1. Grazing largely and mowing moderately decreased the density ratio and coverage ratio of S. grandis to S. krylovii in grasslands (P < 0.05), and the differences in these ratios between grazed and unused grasslands increased with time. 2. Grazing, but not mowing, significantly enhanced the relative density (Nᵣₑₚ = reproductive tiller number/total tiller number) of, and biomass allocation (Bᵣₑₚ = reproductive tiller biomass/total biomass) to, reproductive tillers of S. krylovii (P < 0.05), but not S. grandis. This grazing enhancement to sexual reproduction of S. krylovii, and additionally inhibition to Nᵣₑₚ of S. grandis (P < 0.05), were found across the 14 pairs of heavily versus lightly used plots. 3. Seasonal pattern of grazing affected sexual reproduction of S. krylovii. The Nᵣₑₚ and Bᵣₑₚ was higher under grazing in July and September (T4) than in July and August (T6) or in May and July (T2) (P < 0.05), suggesting a relatively positive effect of grazing on sexual reproduction in July (tasseling phenophase) than in May or August. Our results provide direct evidence to the reciprocal change of S. grandis and S. krylovii in steppe communities under different management and indicate that gazing or mowing enhancement of sexual reproduction of S. krylovii relative to S. grandis is one of the mechanisms for the change.

Responses of plant 15N natural abundance and isotopic fractionation to N addition reflect the N status of a temperate steppe in China

Elevated anthropogenic nitrogen (N) deposition could alter N status in temperate steppe. However, threshold observations of N status change from N limit to N saturation by far are not conclusive in these ecosystems. Research on the natural abundance of ¹⁵N (δ¹⁵N) could greatly help provide integrated information about ecosystem N status. The goal of this study was to investigate the suitability of measurements of δ¹⁵N of major ecosystem N pools and several key species, plant ¹⁵N fractionation, together with key vegetation and soil indicators in response to N fertilization as a tool to identify the N status in a temperate steppe in Inner Mongolia. We carried out a N addition experiment during 2011–14 on a Stipa krylovii steppe in Inner Mongolia, Northern China. We investigated the response of several key N transformation processes, vegetation and soil properties to N addition. Aboveground biomass and belowground biomass (BGB) δ¹⁵N, root and foliar δ¹⁵N of three dominant species (Artemisia frigida, S. krylovii and Leymus chinensis), δ¹⁵N of soil total N and soil KCl-extractable NO₃⁻-N were determined. The responses of isotope fractionation during plant N uptake and reallocation to N addition were also determined. Our results suggest that the N addition rate of 5g N m⁻² yr⁻¹ could be regarded as threshold of early N saturation in this S. krylovii steppe as indicated by an increase in plant fractionation and a decrease in plant δ¹⁵N. When N input rate is >10 g N m–² yr–¹, increased N deposition can lead to an apparent reduction in species richness and BGB as well as an increase in NO₃⁻ in extractable soil pools <30-cm soil profile. With N addition, S. krylovii and A. frigida undergo earlier N status shift from N limitation toward N excess compared with L. chinensis, contributing to L. chinensis out-competing other species. Overall, this study provides a better understanding of N status change in temperate steppe based on isotope evidence and several other functional variables and contributes to predicting the responses of temperate steppe to future global N deposition scenario.

Heavy mowing enhances the effects of heat waves on grassland carbon and water fluxes

Heat waves (HWs) are a type of extreme weather event that is of growing concern in the scientific community. Yet field data based on sound experiment on the variation of ecosystem CO2 levels under HWs remain rare. Additionally, ecosystems react to HWs and the coupled human activities (such as grazing in grasslands) are unknown. Thus, a 3-year field experiment was conducted to simulate HWs in conjunction with different mowing intensities that mimicking grazing in a Stipa krylovii steppe on the Mongolian Plateau. HWs significantly decreased ecosystem exchange (NEE) of CO2, ecosystem respiration (Re) and gross ecosystem productivity (GEP) by 31%, 5% and 16%, respectively, over the three years. Continuous HWs over multiple years produced cumulative effects by reducing NEE at 20%, 34% and 40% in the first, second and third HW years, respectively. During three pre-defined three periods of HWs (during HW period, after HW period in the same year, and after HW period in the next year), variations in water use efficiency indicated that the grassland ecosystem exhibited a strategy for adapting to the continuous HWs to a certain extent, by adjusting community structure or increasing litter biomass. Finally, mowing increased the effects of HWs by extending the legacy effect, such that restoration of the grassland required a greater amount of time under the combination of HWs and mowing.

Response of aboveground biomass and diversity to nitrogen addition - a five-year experiment in semi-arid grassland of Inner Mongolia, China.

Understanding the response of the plant community to increasing nitrogen (N) deposition is helpful for improving pasture management in semi-arid areas. We implemented a 5-year N addition experiment in a Stipa krylovii steppe of Inner Mongolia, northern China. The aboveground biomass (AGB) and species richness were measured annually. Along with the N addition levels, the species richness declined significantly, and the species composition changed noticeably. However, the total AGB did not exhibit a noticeable increase. We found that compensatory effects of the AGB occurred not only between the grasses and the forbs but also among Gramineae species. The plant responses to N addition, from the community to species level, lessened in dry years compared to wet or normal years. The N addition intensified the reduction of community productivity in dry years. Our study indicated that the compensatory effects of the AGB among the species sustained the stability of grassland productivity. However, biodiversity loss resulting from increasing N deposition might lead the semi-arid grassland ecosystem to be unsustainable, especially in dry years.

Response of plant leaf traits to grazing intensity in Stipa krylovii steppe.

Grazing disturbance is one of the ways to influence plant traits, and plant leaf traits actually reflect the adaptability of plants to the environment. In this study, taking Stipa krylovii steppe under different grazing intensities in Hulunbuir as research area, the relationships of leaf traits and the variation of plant traits among plant life-form functional groups was investigated. Results showed that plant traits with different life-forms had no significant difference in S. krylovii steppe. However, the relationships between plant traits were strongly correlated. The leaf phosphorus content (LPC) and the ratio of nitrogen and phosphorus (N/P) in the heavy grazing treatment had significant difference from those in the moderate grazing and the light grazing treatments. For different life-form functional groups, grazing disturbance had significant effect on LPC and N/P in the perennial forbs, indicating the perennial forbs were sensitive to grazing, and the plant nutrient utilization strategy was changed by heavy grazing. It was suggested that reasonable grazing could improve the nutrient traits of plants and restrain the degradation in S. krylovii steppe.

模拟氮沉降对克氏针茅草原土壤有机碳的短期影响

模拟氮沉降对克氏针茅草原土壤有机碳的短期影响

China Forest-Steppe Ecotone Database

The China Forest Steppe Ecotone Database (GIVD ID AS-CN-001) contains releves of the forest-steppe ecotone, typical steppe and desert steppe in central part of Inner Mongolia, China as well as of the Zamin Ude region in Mongolia. Releves of the forest-steppe ecotone were recorded during the 1990s. The communities in the forest-steppe ecotone are classified in a phytocoenological way. 12 major types of forest, shrubland, meadow, fen, open woodland and steppe are differentiated and described according to 133 releves. Due to limited releves, the plant communities are named by their dominant species: 1. Quercus mongolicawoodland; 2. Betula platyphylla-woodland; 3. Betula dahurica-woodland; 4. Populus davidiana-woodland; 5. Picea meyeri-woodland; 6. Pinus tabulaeformis-woodland; 7. Ostryopsis davidiana-shrubland; 8. Polygonum viviparum-meadow; 9. Ranunculus japonica-fen; 10. Stipa baicalensis-steppe; 11. Leymus chinensis-steppe; 12. Ulmus pumila-open woodland. Other plant community types with less than 5 releves are Larix principis-ruprechtii-woodland, Pinus Betula fruticosa-scrub, Stipa krylovii-steppe, Filifolium sibiricumsteppe and Thymus serphyllum-steppe. During the 2000s, we extended our survey further to the dryer region, including typical steppes and desert steppes in central Inner Mongolia of China, including the huge sandy sheets, Otindag and Mu Us. Besides releve records, we systematically collected 344 soil profiles, with C, N content measured for most of the profiles, as well as grain sizes for all the profiles.

Environmental effects on net ecosystem CO 2 exchange at half-hour and month scales over Stipa krylovii steppe in northern China

The objectives of this research are to quantify the magnitude of CO 2 exchange and to investigate the responses of net ecosystem CO 2 exchange (NEE), gross ecosystem production (GEP) and ecosystem respiration ( R e) to environmental factors over a temperate Stipa krylovii steppe by an eddy covariance system in northern China. Differences in annual precipitation, soil water content (SWC), air temperature ( T a) and evapotranspiration (ET) were the most important factors which controlled patterns and variations of CO 2 exchange between atmosphere and the steppe. Precipitation received at study site was 297 mm in 2004, close to the average value during 1971–2000 (±S.D., 290 ± 82 mm), whereas precipitations in 2005 (174 mm) and 2006 (215 mm) were significantly below the average. The lowest values of precipitation and SWC in 2005 resulted in much lower carbon exchange rate related to those in 2004 and 2006. In 2005, daytime NEE reached the seasonal peak about −3 μmol C m −2 s −1, this was much lower than those in 2004 and 2006 (−7 to −8 μmol C m −2 s −1). Seasonal peaks of integrated monthly NEE was the lowest in 2005 (−8.8 g C m −2 mon −1) and the highest in 2004 (−34.3 g C m −2 mon −1). Compared with 2004, the peak values of monthly GEP and R e in 2005 reduced more than 30% and 20% due to soil water stress. SWC was an important environmental factor regulated the variation of CO 2 exchange. At hour time scale, daytime NEE was positive when SWC was less than 0.15 m 3 m −3, R e tripled when SWC increased from 0.075 to 0.225 m 3 m −3. At month time scale, SWC was the primary factor controlling monthly CO 2 fluxes, there was no net carbon uptake until SWC exceeded 18%, in the low (LAI < 0.5 m 2 m −2) and the high (LAI > 0.5 m 2 m −2) ranges of LAI, SWC explained about 71% and 90% variations in monthly NEE, and about 92% and 82% variations in monthly GEP. Except SWC, NEE–light response curve was also regulated by air temperature because it influenced both plant photosynthetic capacity and the variations of soil and plant respirations. The optimal air temperature for the carbon uptake of S. krylovii steppe was 10–20 °C, carbon uptake decreased in magnitude when air temperature departed from this range. The close relationship between ET and CO 2 fluxes was explained that ET was determined by both SWC and T a. At monthly scale, ET predicted 62% variations of NEE, 78% variations of GEP, 85% variations of R e. Accumulative ET and accumulative NEE in growing seasons were tightly coupled. The highest ET coincided with carbon sink in the growing season of 2006, and the lowest ET in 2005 resulted in the maximum carbon loss.

Comparison of CO2 effluxes and their driving factors between two temperate steppes in Inner Mongolia, China

Soil respiration is a key component of the global terrestrial ecosystem carbon cycle. The static opaque chamber method was used to measure the CO2 effluxes from soil of a semiarid Aneurolepidium chinense steppe and a Stipa krylovii steppe in the Xilin River Basin of Inner Mongolia, China from March 2002 to December 2004. The results indicated that the soil respiration rates of the semiarid Aneurolepidium chinense steppe and the Stipa krylovii steppe were both relatively high from mid-May to mid-September of each year and remained low during the rest of the year. The minimum value of soil respiration occurred in December or January and negative effluxes of CO2 appeared for several days during the non-growing season of individual years at the two sampling sites. A high annual variation was found in the two steppes with the coefficients of variance (CV) being over 94%, even high to 131%. The annual sums of soil CO2 efflux of the Aneurolepidium chinense steppe varied between 356.4 gC m−2 yr−1 and 408.8 gC m−2 yr−1, while those of the Stipa krylovii steppe in the three years were in the range of 110.6 gC m−2 yr−1 to 148.6 gC m−2 yr−1. The mean respiration rates of the Aneurolepidium chinense steppe were significantly higher than those of the Stipa krylovii steppe in different statistical periods with the exception of the non-growing season. About 59.9% and 80.6% of the soil respiration variations in both steppes for the whole sampling period were caused by the changes of temperature and soil water content. In the Aneurolepidium chinense steppe, the soil respiration rate has significant or extremely significant positive correlation (r = 0.58–0.85, p < 0.05 or p < 0.01) with air temperature and ground temperature of the topsoil except in 2002; the unique contributions of temperature change to the soil respiration variation of the three years were 53.3%, 81.0% and 58.6%, respectively. But, for the Stipa krylovii steppe in the same time interval, the soil water content (especially that of the 10–20 cm layer) has a greater effect on the change of soil respiration, and the unique contributions of the change of the 10–20 cm soil water content to the variations of soil respiration in 2002 and 2003 were 60.0% and 54.3%, respectively. In 2004, in spite of the higher contribution of temperature than soil water content, the contribution of ground temperature at a depth of 10 cm was only 46.2%, much weaker than that of any single year in the Aneurolepidium chinense steppe.

Restoration of Stipa kryloviisteppes in Inner Mongolia of China: Assesment of seed banks and vegetation composition

The landscapes of Inner Mongolia are widely known for the vast Stipa krylovii steppes. However, overgrazing and other improper land uses have extensively degraded the Stipa krylovii steppe ecosystem in recent decades. Knowledge about the soil seed banks and the remaining vegetation in these damaged ecosystems is crucial for guiding the restoration efforts. Using a germination method, this study examined the size, composition, and species richness of the soil seed banks in three field types: overgrazed steppe, enclosed steppe and abandoned crop field. The abandoned crop field had the largest soil seed bank with mostly annual and weedy plant species. Seeds of desirable perennial grass species were impoverished by the intensive cultivation in the abandoned crop field. The lack of desirable perennial species in the abandoned field was a critical limiting factor for restoration. Grazing decreased the size of the seed bank in the overgrazed steppe. But seeds of desirable grassland species were present in both the overgrazed and the enclosed steppes. As indicated by the Sorenson's indices of community similarity (50–67%), plant species abundance and composition in the soil seed banks were closely related to the corresponding vegetation for each of the three sites.