Temperate Typical Steppe Research Articles

Interannual fluctuations in precipitation shape the trajectory of ecosystem respiration along a grazing exclusion chronosequence in a typical steppe in Inner Mongolia

Grazing exclusion (GE), as an effective strategy for revitalizing degraded grasslands, possesses the potential to increase ecosystem respiration (Re) and significantly influence the capacity of grassland soils to sequester carbon. However, our current grasp of Re dynamics in response to varying durations of GE, particularly in the context of precipitation fluctuations, remains incomplete. To fill this knowledge gap, we conducted a monitoring of Re over a 40-year GE chronosequence within Inner Mongolia temperate typical steppe across two distinct hydrologically years. Overall, Re exhibited a gradual saturation curve and an increasing trend with the duration of GE in the wet year of 2021 and the normal precipitation year of 2022, respectively. The variance primarily stemmed from relatively higher microbial biomass carbon observed in the short-term GE during 2022 in contrast to 2021. Moreover, the impacts of GE on the sensitivities of Re to moisture and temperature were intricately tied to precipitation patterns. increasing significantly with prolonged GE duration in 2022 but not in 2021. Our study highlights the intricate interplay between GE duration, precipitation variability, and Re dynamics. This deeper understanding enhances our ability to predict and manage carbon cycling within typical steppe in Inner Mongolia, offering invaluable insights for effective restoration strategies and climate change mitigation.

Drought and nitrogen deposition regulate plant nutrient resorption in a typical steppe

The impending rise in drought events in grasslands of northern China over the next few decades, coupled with escalating nitrogen (N) deposition, will have an important impact on nutrient resorption. Previous research has mostly focused on examining the individual effect of specific drought scenario or N enrichment on nutrient resorption. Nonetheless, the impacts of different drought regimes on the resorption of nutrients have rarely been distinguished, especially under the scenario of N enrichment in temperate typical steppe in Inner Mongolia, we studied how intense drought (excluding 100 % rainfall in June), chronic drought (excluding 50 % rainfall during June-August), reduced rainfall frequency (reducing half rainfall events without changing rainfall amount in June-August), and N deposition (0 and 10 g N m−2 yr−1) affected the efficiency of plants in reabsorbing N and phosphorus (P). Both intense and chronic drought significantly reduced N (by 9.41 % and 9.53 %, respectively) and P resorption efficiency (by 6.71 % and 6.62 %, respectively) in plant communities (defined as the proportion of N and P nutrient resorption from senescing leaves), however reducing rainfall frequency had less effects on plant community N and P resorption efficiency. Nitrogen deposition had no effects on N and P resorption efficiency. Drought and N addition interacted to affect plant community P resorption efficiency. Structural equation modeling (SEM) showed that drought reduced N and P resorption efficiencies in plant communities by directly decreasing soil moisture, suppressing nutrient concentrations in green leaves, and enhancing soil nutrient content. Nitrogen deposition reduced P resorption efficiency by reducing P concentration in green leaves, but this effect was offset by the reduction of soil P availability. These results imply that rainfall amount is more important than rainfall frequency in determining the nutrient resorption efficiency of plant communities in the typical steppe. This study highlights the importance of soil water and N availabilities as well as nutrient concentrations in green leaves in modulating the responses of plant nutrient resorption to global change in the typical steppe.

Variation in and Regulation of Carbon Use Efficiency of Grassland Ecosystem in Northern China

Ecosystem carbon use efficiency (CUE) is a key parameter in the carbon cycling of terrestrial ecosystems. The magnitude of CUE reflects the ecosystem’s potential for CO2 sequestration. China’s grasslands play an important role in the carbon cycle. Here, we aimed to investigate the comparation of CUE and its environmental regulation among different grassland in Northern China based on eddy covariance carbon fluxes measurements of 31 grassland sites. The results showed that the average CUE of grassland in Northern China was 0.05 ± 0.22, with a range from −0.42 to 0.66. It was demonstrated that there were significant differences in CUE among different grassland types, and CUE values were ranked by type as follows: alpine grassland > temperate meadow steppe > temperate typical steppe > temperate desert steppe, driven by a combination of climatic, soil, and biological factors, with net ecosystem productivity (NEP) having the greatest impact on them. Except for meadow steppes, moisture had a greater impact on grassland CUE in Northern China than temperature. While temperate desert grassland CUE decreased with increasing soil water content (SWC), the CUE of other grassland types increased with higher precipitation and SWC. These findings will advance our ability to predict future grassland ecosystem carbon cycle scenarios.

Spatiotemporal Variation Characteristics and Driving Force Analysis of Precipitation Use Efficiency at the North Foot of Yinshan Mountain

The northern foothills of Yinshan Mountain are situated in northern China’s agricultural and pastoral ecotone, serving as a crucial ecological barrier. To comprehensively assess the impact of grassland resource restoration in this region since the initiation of the Grain-for-Green conversion project in 2000, this study analyzes the spatiotemporal characteristics of precipitation use efficiency (PUE) and investigates climate-driven factors during 2001–2021. The results showed that the grassland types at the north foot of Yinshan could be divided into four categories: warm-arid, warm subtropical semidesert (WSS), warm temperate-arid, warm temperate zonal semidesert (WZS), warm temperate-semiarid, warm temperate typical steppe (WTS), and warm temperate-subhumid forest steppe (WFT). The NPP of the four grassland species were 151.34 (WSS), 196.72 (WZS), 283.33 (WTS), and 118.06 gC·m−2 (WFT), and correspondingly, the PUE of the four grassland species were 0.66 (WSS), 0.66 (WZS), 0.80 (WTS), and 0.57 gC·m−2·mm−1 (WFT). From 2001 to 2021, PUE in grassland showed an overall upward trend, rising from 0.57 to 0.99 gC·m−2·mm−1. The trend analysis found that the vegetation ecological area of the northern foot of Yinshan became better, of which 54.36% was improved and 15.72% was degraded. It is worth pointing out that WSS had the highest degree of improvement, while WFT was in a degraded state. The climate driving force analysis shows that the regional contribution of precipitation is 19.57%, temperature is 28.33%, potential evapotranspiration is 13.65%, wind speed is 10.79%, and saturated vapor pressure is 27.66%.

Improving grassland classification accuracy using optimal spectral-phenological-topographic features in combination with machine learning algorithm

Accurate mapping of large-scale grassland types is important for grassland and water resources management. The similarity of spectral characteristics between grassland types lowers the classification accuracy of different grassland types. To improve the classification accuracy of large-scale grasslands, this study proposed a new framework which integrates Sentinel-2 images with DEM and climate zones data. In this framework, optimal spectral-phenological-topographic features are fed into Random Forest (RF) model based on Google Earth Engine (GEE) platform. The proposed framework was applied in Inner Mongolia, China. A grassland map of the region was obtained with an overall accuracy (OA) exceeding 80 %, which is higher than the OA (60 %-70 %) of current large-scale grassland type classification studies. In WIM (Western Inner Mongolia) and NEIM (Northeast Inner Mongolia), the OA reaches 96.97 % and 95.85 %, respectively. SWIR2 band and elevation have a clear advantage in distinguishing different grassland types. Compared to 1980s, the area of temperate meadow steppe (TMS) and temperate desert steppe (TDS) have increased by 111.94 % and 126.00 %, respectively. The area of temperate typical steppe (TTS) decreased by 7.38 %. The framework proposed in this study has a great potential to be applied to improve large-scale grassland classification in other regions in future.

Changes in Competitors, Stress Tolerators, and Ruderals (CSR) Ecological Strategies after the Introduction of Shrubs and Trees in Disturbed Semiarid Steppe Grasslands in Hulunbuir, Inner Mongolia.

To reveal the changes in the life history characteristics of grassland plants due to vegetation restoration, plant species and communities were analyzed for their competitor, stress tolerator, and ruderal (CSR) ecological strategies after the introduction of woody plants in the damaged steppe grassland and were compared with those in reference sites in Hulunbuir, Inner Mongolia. As a result, it was found that the introduction of the woody plants (Corethrodeneron fruticosum, Caragana microphylla, Populus canadensis, and Pinus sylvestris var. mongolica) into the damaged land greatly increased the plant species diversity and CSR eco-functional diversity as the succession progressed. The plant strategies of the temperate typical steppe (TTS) and woodland steppe (WS) in this Asian steppe are CSR and S/SR, respectively, which means that the plants are adapted to disturbances or stress. As the restoration time elapsed in the damaged lands exhibiting (R/CR) (Corispermum hyssopifolium), the ecological strategies were predicted to change in two ways: (1) →R/CSR (Cynanchum thesioides, Astragalus laxmannii, etc.) → CSR in places (TSS) (Galium verum var. asiaticum, Saussurea japonica, etc.) where only shrubs were introduced, and (2) → S/SR (Allium mongolicum, Ulmus pumila, etc.) → S/SR in sites (WS) (Ulmus pumila, Thalictrum squarrosum, etc.) where trees and shrubs were planted simultaneously. The results mean that the driving force that causes succession in the restoration of temperate grasslands is determined by the life-form (trees/shrubs) of the introduced woody plants. This means that for the restoration of these grasslands to be successful, it is necessary to introduce woody tree species at an early stage.

Carbon budget response to climate change varies with grassland type in Qilian Mountains, China

Carbon budget estimation is crucial for scientifically assessing the ecosystem’s carbon sequestration capacity. Grasslands in the Qilian Mountains are widely recognized as vulnerable and sensitive to ongoing climate change. However, it is still unclear how the carbon budget of different grassland types responds to climate change in this area. Here, we evaluated the net primary productivity (NPP), soil heterotrophic respiration (RH), and net ecosystem productivity (NEP) of grassland ecosystems in the Qilian Mountains. Correlation analysis, linear regression, and standardized coefficient methodologies were employed to explore the response of NPP, RH, and NEP in various grassland types to changes in temperature, precipitation, and solar radiation over the past two decades. The results showed that the alpine meadow has the highest NPP and NEP while the temperate typical steppe has the highest RH. Grassland NPP, RH, and NEP increased significantly from 2001 to 2020, with a distinct spatial pattern of being low in the northwest and high in the southeast of the Qilian Mountains. NPP and NEP correlated with precipitation and solar radiation more closely than with temperature. Precipitation and solar radiation, respectively, explained 43.7% and 52.9% of grassland NEP alterations, and there was a threshold effect on the response of NEP and NPP to climate factors. Specifically, the NPP and NEP increased at first and then decreased as the precipitation, temperature, and solar radiation increased. The highest NEP and NPP occurred when precipitation ranged from 415 to 455 mm, along with temperatures between − 0.1–1.5 ℃ and solar radiation reaching 7685–7905MJ/m2. The warming and humidification of climate is conducive to the increase of NPP and NEP in alpine meadows and alpine steppes, but when the precipitation exceeds 415 mm and the temperature is greater than 1.5 ℃, the NPP and NEP begin to decrease. Solar radiation dominated changes in NPP and NEP of alpine meadows, alpine steppes, and temperate desert steppes. With the increase of solar radiation, NPP and NEP of these three grasslands first increased and then decreased. However, the changes in NPP and NEP of the temperate typical steppe were most affected by precipitation, and NPP and NEP first increase and then decrease with the increase of precipitation The higher the temperature, the higher the NPP, RH, and NEP of the temperate typical steppe. This study helps better understand how climate change impacts the carbon budget components of different grassland types in the Qilian Mountains and provides more theoretical thoughts on managing local grasslands sustainably.

Integrated vegetation cover of typical steppe in China based on mixed decomposing derived from high resolution remote sensing data

Grasslands represent the largest ecosystem in China, accurate and efficient extraction of its integrated vegetation cover (IVC) plays a crucial role in supporting policy decisions. This study presented a method for grassland monitoring via IVC derived from high-resolution satellite data. Taking the multispectral data of Gaofen-1 (GF-1) and Gaofen-6 (GF-6) with 16 m resolution as the main data source, vegetation cover of six representative regions was assessed based on mixed-pixel decomposition model. Using grassland vegetation cover and ratio of grassland area, the IVC in each site was calculated and verified against ground-measured sample data. The results showed that the IVC of grassland was closely related to vegetation habitat driven by regional hydrothermal regime. Yichang grassland, dominated with warm-temperate shrub tussock type, had the highest IVC (80.06 %) due to its favorable hydrothermal conditions. For the main grassland types in Hulunbuir and Gansu Province (temperate meadow steppe and temperate typical steppe), the IVC was 79.38 % and 58.46 %, respectively. In both Xilin-Gol and Nagqu, vegetation cover decreased gradually from east to west, and the IVC was merely 42.83 % and 42.61 %, respectively. Both regions are endowed with less hydrothermal resources to different degrees. Alxa, with a predominately temperate desert landscape, had the lowest IVC of 15.58 % where precipitation is extremely scarce. Based on the grass species of measured samples, the dominant species and biodiversity of different grassland types in Gansu Province and Hulunbuir Municipality of Inner Mongolia Autonomous Region were analyzed. The results showed that the meadow grassland has the richest biodiversity. The temperate mountain meadows in Gansu Province have a high species diversity, with a total of 90 grass species, and the lowland meadows in Hulunbuir have a total of 49 grass species. This study utilizes high-resolution data to conduct large-scale vegetation monitoring, which is a viable alternative for efficient assessment of steppe ecology.

Divergent environmental responses of long-term variations in evapotranspiration over four grassland ecosystems in China based on eddy-covariance measurements

Understanding the long-term variation in evapotranspiration (ET) for the spatially distributed grasslands is crucial for the accurate prediction of ET response to climate change. In this study, we analyzed the interannual variability (IAV) of ET and its responses to environmental conditions at four grassland ecosystems across a wide range of climatic and biome conditions based on the long-term (9–11 years) eddy-covariance measurements. The four ecosystems encompassed the most prevalent grassland vegetations in China, containing a typical temperate steppe, an alpine meadow-steppe, an alpine shrubland meadow, and an alpine marsh meadow. The IAVs of annual ET at the typical temperate steppe and the alpine meadow-steppe were primarily affected by either change in precipitation (P) or relative humidity (RH). Leaf area index (LAI) was the dominant factor controlling the IAVs of annual and growing-season ET at the alpine shrubland meadow, and the IAV of LAI was significantly correlated with P variation. As to the alpine marsh meadow, net radiation turned to be the dominant factor for the IAV of annual ET, additionally with significant effects from water supply condition (P and RH) on the IAV of growing-season ET. Similar environmental responses were also found for the IAVs of mean surface conductance (gs) across the sites. Specifically, annual and growing-season mean gs significantly increased with increases in LAI at the alpine shrubland meadow, and appeared to be more sensitive to changes in water availability and VPD at the typical temperate steppe and the alpine meadow-steppe. Significant linear relationships were also observed among the IAVs of mean Priestley-Taylor coefficient (α = ET/ETeq, where ETeq is the equilibrium evaporation), decoupling coefficient (Ω), and gs on both the annual and growing-season basis in this study. Moreover, the variabilities of annual mean gs, Ω, and α further demonstrated the energy-limited conditions at the alpine marsh meadow, and the overall water-limited conditions at the other three grasslands. This study reveals the divergent environmental responses of long-term ET variations over grassland ecosystems, and contributes to the comprehensive understanding on the ET process and modeling efforts as well.

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.

Climatic controls on stable carbon and nitrogen isotope compositions of temperate grasslands in northern China

The natural abundances of stable carbon (C) and nitrogen (N) isotopes (δ13C and δ15N) are extensively used to indicate the C and N biogeochemical cycles at large spatial scales. However, the spatial patterns of δ13C and δ15N in plant-soil systems of grasslands in northern China and their main driving factors across regional climatic gradient are still not well understood. We measured plant and soil δ13C and δ15N compositions as well as their associated environmental factors across 2000 km climatic gradient (-0.2 to 9 °C; 152 to 502 mm) in grasslands of northern China. The soil δ13C and δ15N values in surface were lower than those in bottom for temperate typical steppe but had no significant differences for temperate meadow steppe and temperate desert steppe. Soil δ13C values declined with increasing soil organic carbon (SOC) but increased as mean annual temperature (MAT). These changes were attributed to the microbial decomposition rate. The δ15N values in soil and plant were negatively correlated with MAT and mean annual precipitation (MAP), which were mainly related to the low soil organic matter mineralization rate and the shift of dominant species from C4 to C3. Our results indicate the spatial patterns and different influencing factors on δ13C and δ15N values along the climatic gradient in grasslands of northern China. The findings will provide scientific references for future research on the C and N biogeochemical cycles of temperate grasslands.

Aboveground net primary productivity was not limited by phosphorus in a temperate typical steppe in Inner Mongolia

AbstractPhosphorus (P) is an essential element for plant growth, however, whether the aboveground net primary productivity (ANPP) of typical steppe was limited by P remains obscure. To detect the effects of P addition on primary productivity and aboveground biomass of different plant functional groups both under ambient and N addition conditions, ANPP and aboveground biomass of grasses and forbs were measured from 2016 to 2020 on a 16-year N and P addition experiment platform in a temperate typical steppe in Inner Mongolia. The soil available N and P concentrations were also determined to test the relationship between ANPP and the availability of soil nutrients. We found that P addition under ambient condition had no significant effect on ANPP and the aboveground biomass of grasses and forbs. However, under N addition, P addition significantly increased ANPP and the aboveground biomass of forbs. Furthermore, soil available N and P concentrations were increased significantly by N and P addition, respectively. Moreover, there was no significant correlation between ANPP and soil available P concentration, while ANPP was positively correlated with soil available N concentration. These results suggest that P is not the key factor limiting the primary productivity of the temperate typical steppe in Inner Mongolia. However, under N addition, P addition can promote ANPP and alter the community composition. These findings provide valuable information for the management of the temperate typical steppe.

Vulnerability of grassland ecosystems to climate change in the Qilian Mountains, northwest China

With climate warming and frequent extreme weather events, the structure and function of grassland ecosystems have been significantly altered. The Qilian Mountains are a wet island, serving as an important ecological barrier in China and central Asia. It is highly sensitive and prone to climate change, yet the vulnerability of grasslands to climate variability in this region remains unclear. In this study, based a NDVI dataset and meteorological data, we evaluated the relative vulnerability of grassland ecosystems to short-term climate variability by combining three indices: exposure, sensitivity, and resilience, and explored its relationship with water use efficiency (WUE). The results show that the spatial distribution patterns of grassland vulnerability in the Qilian Mountains from 2000 to 2018 were largely determined by exposure, and sensitivity is positively correlated with exposure and negatively correlated with resilience. The vulnerability of alpine meadow and alpine steppe is higher than that of temperate typical steppe and temperate desert steppe. Climate and topography gradients together affect the degree of grassland vulnerability. Grasslands with higher vulnerability are mainly found at medium elevation (3200–4000 m) area, where the topography is flat. The northern grasslands are primarily influenced by temperature, while the western and southern parts are mainly affected by precipitation. Alpine meadow and alpine steppe are more vulnerable to temperature and temperate desert steppe is more vulnerable to changes in precipitation. The higher the vulnerability, the lower the WUE of the grasslands. This study provides a reference for assessing the impact of climate change on grassland ecosystems and developing grassland vegetation management strategies.

Subsoil organic carbon turnover is dominantly controlled by soil properties in grasslands across China

Soil organic carbon turnover time (τ, year) is an important indicator of soil carbon stability and a major factor determining soil carbon sequestration capacity. Many previous studies have investigated τ in the topsoil layers, but little is known about subsoil τ and its environmental drivers. We estimated subsoil τ (the ratio of subsoil organic carbon (OC) stock to net primary production) using field observations from the published literatures and employed regression analysis and the structural equation model (SEM) to identify the effects of climate, soil, and vegetation variables on subsoil τ in China’s grasslands. The results showed that the average subsoil τ over 0.2–1 m varied greatly from 5.5 to 702.2 years, with a mean (±standard deviation) of 118.5 ± 97.8 years. Subsoil τ varied significantly among different grassland types, with 164.0 ± 112.0 years for alpine meadow, 107.0 ± 47.9 years for alpine steppe, 177.0 ± 143.0 years for temperate desert steppe, 96.6 ± 88.7 years for temperate meadow steppe, and 101.0 ± 75.9 years for temperate typical steppe. Subsoil τ was significantly negatively correlated (p < 0.05) with normalized difference vegetation index, leaf area index, and gross primary production. Mean annual (air) temperature and precipitation had a negative impact on τ, indicating a faster turnover of soil carbon with a changing climate. Based on SEM, soil properties mainly drove subsoil τ, challenging our current understanding and providing evidence that different factors control topsoil and subsoil τ. In this sense, different environmental factors should be considered to reliably predict soil carbon dynamics at the top of 1 m and subsoils in biogeochemical models or Earth system models at regional or global scales.

Grassland type-dependent spatiotemporal characteristics of productivity in Inner Mongolia and its response to climate factors

Grassland located in the arid and semi-arid ecosystems has an evident ecological fragility and is easily vulnerable to climatic variations. Although several studies have shown the close relationship between net primary production (NPP) and seasonal or annual climate changes, it is currently unclear that whether such response in semi-arid regions is associated with grassland types that have different physiological characteristics, especially in the grassland ecosystem of Inner Mongolia that spans meadow-typical-desert steppe. This study used NPP estimated by Carnegie–Ames Stanford Approach (CASA) model, and focused on grassland type-dependent spatiotemporal changes of NPP and its response to climate factors on annual and seasonal scales. The results showed that the NPP simulated by the CASA model was in good agreement with the ground-observed NPP (R2 = 0.62, P < 0.001), and the RMSE value was 22.91 gC ∙ m−2. From 2001 to 2018, grassland NPP increased marginally with the increment of 0.89gC ∙ m−2 ∙ yr−1, the average NPP was 341.55gC ∙ m−2 ∙ yr−1, and there was a gradual decline from northeast to southwest. On the annual scale, grassland NPP had the strongest positive correlation with precipitation, followed by solar radiation and a negative correlation with temperature. On the seasonal scale, precipitation still had the greatest impact on NPP. In spring, grassland and solar radiation were positively correlated, but in summer and autumn, there was no significant correlation. In autumn, grassland had a positive correlation with temperature, while in spring and summer, there showed a negative correlation. For different grassland types, precipitation was the most important factor that influencing temperate typical steppe and temperate salted meadow in spring and summer, while solar radiation had the strongest effect on temperate desert steppe and temperate meadow. Temperate meadow steppe and temperate swamp meadow were most affected by precipitation in spring, while they were most affected by solar radiation in summer.

Effects of grazing exclusion on spring and autumn pastures in arid regions of China: Insights from field surveys and landsat images

Overgrazing has caused serious grassland degradation, and grazing exclusion (GE) has been considered an effective and economic approach for restoring vegetation and soils in degraded grassland. In this study, we evaluated the ecosystem restoration of two types of degraded spring and autumn pasture in arid regions of northwest China, based on field surveys (community structure characteristics, soil C and N) and Landsat images (greenness and wetness). In temperate typical steppe (TS), our findings indicated that GE significantly increased plant height, coverage, biomass, soil C and N, as well as greenness and wetness values from Landsat images, however GE decreased plant density and species diversity. Restoration on greenness and wetness peaked in the fourth and fifth years, respectively, following GE. The restoration of greenness and wetness showed bimodal curves during growing season. In temperate desert (TD), results revealed that community structure characteristics, greenness, and wetness improved after GE, and the restoration of greenness and wetness increased with duration of GE. Soil C and N however, did not recover significantly after six years of GE. The restoration of greenness and wetness remained stable during growing-season months. Our findings suggest that longer GE might be considered in the restoration of TD, whereas short-term (not more than 4–5 years) GE, reduction in the livestock load or mowing regularly may be more appropriate for TS. Decision to adopt measures of GE and the duration of GE should be reasonably determined according to the specific grassland type. This research can provide guidance for the restoration of degraded grassland ecosystems in arid and semi-arid regions all over the world.

Effects of grassland utilization on the functional traits of dominant plants in a temperate typical steppe

Effects of grassland utilization on the functional traits of dominant plants in a temperate typical steppe

连续氮添加14年对温带典型草原土壤碳氮组分及物理结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 连续氮添加14年对温带典型草原土壤碳氮组分及物理结构的影响 DOI: 10.5846/stxb202004150898 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（31770519）；国家重点研发计划（2017YFC0503805） Effects of 14-year continuous nitrogen addition on soil carbon and nitrogen composition and physical structure at different depths in a typical temperate steppe 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:全球氮沉降对生态系统造成了深远的影响，研究长时间氮沉降对草地生态系统土壤理化特征的影响有助于加强生态系统对氮沉降响应的长效机制的理解。通过连续14年长期施加N0（0 g N m-2 a-1）、N2（2 g N m-2 a-1）、N4（4 g N m-2 a-1）、N8（8 g N m-2 a-1）、N16（16 g N m-2 a-1）、N32（32 g N m-2 a-1）六种浓度尿素模拟氮沉降，并将土壤分成0-10、10-20和20-40 cm三个深度土层，研究温带草原生态系统土壤碳氮组分及物理结构对氮添加的响应及其相互关系，结果表明：（1）氮添加显著降低0-10 cm土壤酸碱度及土壤微生物量碳含量，N32相比N0分别下降了27.63%和58.40%（P<0.05）；各土层总有机碳和全氮含量对氮添加处理无显著响应，0-10 cm土层显著高于20-40 cm土层。（2）同一土层深度不同梯度氮添加处理显著增加土壤无机氮离子含量（P<0.05），0-10 cm土层铵态氮含量N32相比N0增加了88.72%，20-40 cm土层硝态氮含量N32相比N0增加了19.55倍，土壤深度与氮添加对无机氮离子含量影响具有显著的交互效应。（3）同一土壤深度不同梯度氮添加处理土壤粒度分形维数及土壤团聚体差异不显著，相关分析表明土壤碳氮元素含量与土壤结构显著相关。土壤碳氮组分在适宜浓度氮添加的增加趋势说明氮添加在一定程度上可能促进土壤理化性质的改良，氮添加对土壤物理结构的影响还需要进一步的深入研究。 Abstract:Global nitrogen deposition has a profound impact on terrestrial ecosystems. Studying the effects of long-term nitrogen (N) deposition on the soil physical and chemical characteristics of the grassland ecosystem help to understand the permanent mechanism of ecosystem response to nitrogen deposition. In this study, six gradients of urea application (0, 2, 4, 8, 16 and 32 g N m-2 a-1, treatments demonstrated as N0-N32) were applied to simulate N deposition for 14 consecutive years, and the soil samples were collected with three soil depths (0-10, 10-20, 20-40 cm from soil surface), to study the response of soil carbon (C) and nitrogen (N) components and physical structure to N addition and their correlations in temperate grassland ecosystem. The results showed that: (1) N addition significantly reduced soil pH and microbial biomass carbon (MBC) in the 0-10 cm soil layer, and N32 decreased by 27.63% and 58.40% (P<0.05), respectively, compared with N0. The content of total organic carbon and total nitrogen in all soil layers showed no significant response to N addition treatment, but the content in 0-10 cm soil layer was significantly higher than that in 20-40 cm soil layer. (2) N addition at each soil depth significantly increased inorganic nitrogen (ION) content (P<0.05); The ammonium nitrogen content in the 0-10 cm soil layer increased by 88.72% compared to N0, and the nitrate nitrogen content in the 20-40 cm soil layer increased by 19.55 times compared to N0; Soil depth and N addition had significant interaction effect on ION. (3) There was no significant difference in the fractal dimension of soil particle sizes or soil aggregates at each soil depth, and correlation analysis demonstrated that soil carbon and nitrogen nutrient contents were significantly associated with the soil structure. In conclusion, the increasing trend of C and N components in soil with optimal N addition concentration indicates that N addition may favor soil physical and chemical properties to some extent, thus the effect of N addition on soil physical structure needs further in-depth study. 参考文献 相似文献 引证文献

Response of Vegetation and Soil Characteristics to Grazing Disturbance in Mountain Meadows and Temperate Typical Steppe in the Arid Regions of Central Asian, Xinjiang.

Grazing is one of the most common causes of grassland degradation, therefore, an assessment of soil physicochemical properties and plant nutrients under grazing is important for understanding its influences on ecosystem nutrient cycling and for formulating appropriate management strategies. However, the effects of grazing on grassland soil physicochemical properties and plant nutrients in mountain meadow and temperate typical steppe in the arid regions are still unclear. Therefore, we investigated the vegetation nutrient concentrations of nitrogen, phosphorus and potassium (N, P, and K) as well as soil physicochemical properties in the topmost 40 cm depth soil, to evaluate how these factors respond to grazing disturbance in a mountain meadow and temperate typical steppe within a mountain basin system in arid regions. Our results revealed that the soil bulk density values at depth of 0–40 cm increased after grazing in the mountain meadow and temperate typical steppe, whereas the soil water content decreased in the mountain meadow and increased in the temperate typical steppe after grazing. In the mountain meadow, soil total N and available P in addition to vegetation N and P concentrations increased in response to high-intensity grazing, while soil available N, available K and vegetation K decreased after grazing; in addition, soil pH, soil total P and K showed no significant changes. In the temperate typical steppe, the soil total P, soil available N, P, and K, and vegetation N, P, and K increased under relatively low-intensity grazing, whereas soil pH and soil total K showed no significant changes except for the deceasing soil total N. Our findings showed the different responses of different grassland ecosystems to grazing. Moreover, we propose that further related studies are necessary to better understand the effects of grazing on grassland ecosystems, and thereby provide a theoretical basis for the sustainable use of animal husbandry and ecological restoration of grasslands.

Defense strategies of dominant plants under different grazing intensity in the typical temperate steppe of Nei Mongol, China

Defense strategies of dominant plants under different grazing intensity in the typical temperate steppe of Nei Mongol, China