Eurasian Steppe Research Articles

Structure and function of microbiomes in the rhizosphere and endosphere response to temperature and precipitation variation in Inner Mongolia steppes.

Owing to challenges in the study of complex rhizosphere and endophytic microbial communities, the composition and function of such microbial communities in steppe ecosystems remain elusive. Here, we studied the microbial communities of the rhizosphere and endophytic microbes of the dominant plant species across the Inner Mongolian steppes using metagenomic sequencing and investigated their relationships with changes in mean annual temperature (MAT) and mean annual precipitation (MAP). Metagenomic sequencing based on Illumina high-throughput sequencing, using the paired end method to construct a small fragment library for sequencing. Adaptation of root systems to the environment affected the composition and function of rhizosphere and endophytic microbial communities. However, these communities exhibited distinct community assembly and environmental adaptation patterns. Both rhizosphere and endophytic microbial communities can be divided into two unrelated systems based on their ecological niches. The composition and function of the rhizosphere microbial communities were mainly influenced by MAT, while those of the endophytic microbial communities were mainly influenced by MAP. MAT affected the growth, reproduction, and lipid decomposition of rhizosphere microorganisms, whereas MAP affected reverse transcription and cell wall/membrane/envelope biogenic functions of endophytic microorganisms. Our findings reveal the composition and function of the rhizosphere and endophytic microbial communities in response to changes in MAP and MAT, which has important implications for future biogeography and climate change research.

Nitrogen addition alters aboveground C:N:P stoichiometry of plants but not for belowground in an Inner Mongolia grassland

Abstract Nitrogen (N) deposition exhibits significant impacts on ecosystem functions and processes. Previous studies have indicated that N addition has an impact on the stoichiometry of plant leaf C:N:P ratios. However, few studies have focused on effects of N addition on belowground systems. This study aims to examine the impact of 7 years of N addition on above- and belowground C:N:P stoichiometry at plant community level in a temperate grassland located in Inner Mongolia. A 7-year field N addition experiment was conducted, which included six treatments: Cont: control; N1: 0.4 mol·m−2 N; N2: 0.8 mol·m−2 N; N3: 1.6 mol·m−2 N; N4: 2.8 mol·m−2 N; N5: 4 mol·m−2 N with six replicates. Above- and belowground plant biomass and C:N:P stoichiometry were measured and analyzed. Our results showed that N addition resulted in a reduction of aboveground C concentration, but an increase in aboveground N and P concentrations, with a decrease in C:N and C:P ratios and an increase in N:P ratio. Furthermore, the aboveground C, N, and P pools all exhibited an increase as a result of N addition. However, N addition did not have any significant effect on belowground C, N, P concentrations, ratios, pools, or stoichiometric characteristics in the soil layers of 0–10, 10–30, 30–50, and 50–100 cm. These results suggest that increasing levels of N deposition significantly alter the aboveground C:N:P stoichiometry at the plant community level, which may affect functions and processes in the grassland ecosystem, but have little effect on belowground C:N:P stoichiometry.

Comparative Transcriptome Analysis of Galeruca daurica Reveals Cold Tolerance Mechanisms.

Galeruca daurica (Joannis) is a pest species with serious outbreaks in the Inner Mongolian grasslands in recent years, and its larvae and eggs are extremely cold-tolerant. To gain a deeper understanding of the molecular mechanism of its cold-tolerant stress response, we performed de novo transcriptome assembly of G. daurica via RNA-Seq and compared the differentially expressed genes (DEGs) of first- and second-instar larvae grown and developed indoors and outdoors, respectively. The results show that cold tolerance in G. daurica is associated with changes in gene expression mainly involved in the glycolysis/gluconeogenesis pathway, the fatty acid biosynthesis pathway and the production of heat shock proteins (HSPs). Compared with the control group (indoor), the genes associated with gluconeogenesis, fatty acid biosynthesis and HSP production were up-regulated in the larvae grown and developed outdoors. While the changes in these genes were related to the physiological metabolism and growth of insects, it was hypothesized that the proteins encoded by these genes play an important role in cold tolerance in insects. In addition, we also investigated the expression of genes related to the metabolic pathway of HSPs, and the results show that the HSP-related genes were significantly up-regulated in the larvae of G. daurica grown and developed outdoors compared with the indoor control group. Finally, we chose to induce significant expression differences in the Hsp70 gene (Hsp70A1, Hsp70-2 and Hsp70-3) via RNAi to further illustrate the role of heat stress proteins in cold tolerance on G. daurica larvae. The results show that separate and mixed injections of dsHSP70A1, dsHsp70-2 and dsHsp70-3 significantly reduced expression levels of the target genes in G. daurica larvae. The super-cooling point (SCP) and the body fluid freezing point (FP) of the test larvae were determined after RNAi using the thermocouple method, and it was found that silencing the Hsp70 genes significantly increased the SCP and FP of G. daurica larvae, which validated the role of heat shock proteins in the cold resistance of G. daurica larvae. Our findings provide an important theoretical basis for further excavating the key genes and proteins in response to extremely cold environments and analyzing the molecular mechanism of cold adaptation in insects in harsh environments.

Variety of forms of phytoliths of Kulunda soils and their phytocenotic affiliation

Phytoliths are an important component of soil and vegetation cover. Thanks to phytolith analysis, it is possible to identify vegetation cover after a long time. There is practically no information about the transition of amorphous silica in the form of phytoliths from plant mass to soil. This very important stage in the formation of the soil phytolith spectrum was considered in the works of N. K. Kiseleva. When studying the phytolith spectra of dominant grasses and sedges, she calculated the coefficient of their participation for the Mongolian steppes, and further she proposed the concept of “phytolith spectrum" In this work, we made an attempt to assess the correlation of the set of phytolith forms and their ratio in the upper soil layer with the modern composition of vegetation. For this purpose, the phytolith spectra of soils and vegetation of three ecosystems were analyzed, and the phytolith spectra of modern soils were compared. We also applied the approach of Nina Kiseleva and the results we obtained of taxonomic diagnosis of plant species based on the forms of their phytoliths. The research was carried out on the territory of the North Kulunda lacustrine-alluvial plain. The phytolith complex of the surface layer of soils of the forb-fescue with wormwood steppe is characterized by the predominance of two groups of phytoliths: truncated cone-shaped (RONDEL) phytoliths and trapezoidal wavy plates (CRENATE). In the soils of the bushy feather-grass-forb steppe and solonetzic steppe with a cereal-licorice community, trapezoidal polylobed plates (CRENATE) and bilobed particles (BILOBATE) are added to them. Other indicator forms are presented in small quantities. Calculation of the soil phytolith complex allows one to diagnose the coenotic composition of cereals of the phytolith spectrum.

A VIEW FROM THE COUNTRYSIDE: RADIOCARBON CHRONOLOGY FOR ZAOLINHETAN OF THE PRE-ZHOU CULTURE IN EARLY DYNASTIC CHINA

ABSTRACTThe conquest of the Shang Dynasty at Anyang around 1046 BCE by the Zhou is one of the major events for not only Chinese Bronze Age but also early interaction between the pastoralist groups from the Eurasian Steppes and agriculture ones in the Central Plains of China. It is well-known from historical texts that the pre-Zhou people lived in the ancient Bin region (豳), the exact location of which is unclear, but most likely in the Jing River valley. At some point the leader Gugong Danfu (古公亶父) moved from Bin to the capital Qi (Zhouyuan), which preceded the Zhou invasion of Anyang. We have produced a new high resolution radiocarbon chronology for Zaolinhetan, a small settlement in the pre-Zhou heartland. This shows not only an exceptionally long chronological span for the site, but also a different phasing compared to the traditional pottery typology, which raises new questions regarding the regional variation of pottery typologies. Intriguingly, the analysis also reveals a rapid abandonment of Zaolinhetan around 1100 BCE, at the same time many larger sites, such as Zhouyuan, which later became the capital of the Western Zhou dynasty, were significantly expanding. We argue that the drastic decline of Zaolinhetan as revealed by the substantial number of radiocarbon dates and probably also the movement of pre-Zhou political center from Bin to Qin, was part of bigger picture that involved a range of social and environmental factors.

Non-linear effects of temperature and moisture on gross N transformation rates in an Inner Mongolian grassland

Understanding how soil nitrogen (N) turnover responds to temperature and soil moisture alterations is important for accurately predicting responses of soil N availability and plant productivity to global climate change. However, few studies had explored such questions under natural conditions. We investigated effects of temperature and moisture on soil gross N turnover with an annual scale field experiment in an Inner Mongolian grassland and a laboratory incubation experiment. In the field experiment, on the annual scale both gross ammonification and nitrification rates showed a hump-shaped response to temperature, with maximum rates occurring around 10 °C and 5 °C, respectively. Gross ammonification rates did not respond to soil moisture, and gross nitrification rates decreased first and then increasing with soil moisture, which the threshold was 35% water holding capacity (WHC). Totally, soil temperature explained more variation than moisture in gross ammonification (0.30 VS 0.04) and nitrification (0.24 VS 0.14) rates. On the seasonal scale, both soil temperature and moisture showed generally significant effects on gross N turnover. Grazing had no effects on soil temperature and moisture sensitivity of gross N turnover on the annual scale, but increased the sensitivity of gross ammonification to soil moisture during the spring freeze–thaw period. In the laboratory incubation experiment, gross ammonification and nitrification rates increased with the increase of temperature, although there was no difference between 20 °C and 30 °C. Gross ammonification rates reached a maximum at 50% WHC, while gross nitrification rates did not respond to soil moisture until 100% WHC. Soil temperature explained more variation than moisture in gross ammonification (0.71 VS 0.01) and nitrification (0.37 VS 0.25) rates. Our results imply that climate warming may have greater impact on gross nitrogen turnover compared to changes in rainfall, however it remains great uncertainty due to the low explanation of soil temperature and moisture.

Lipid profiling reveals Leymus Chinensis root insensitivity to Ca limitation

BackgroundLeymus chinensis (L. chinensis) is a perennial native forage grass widely distributed in the steppe of Inner Mongolia as the dominant species. Calcium (Ca) is an essential mineral element important for plant adaptation to the growth environment. Ca limitation was previously shown to strongly inhibit Arabidopsis (Arabidopsis thaliana) seedling growth and disrupt plasma membrane stability and selectivity, increasing fluid-phase-based endocytosis and contents of all major membrane lipids.ResultsIn this study, we investigated the significance of Ca for L. chinensis growth and membrane stability relative to Arabidopsis. Our results showed that Ca limitation did not affect L. chinensis seedling growth and endocytosis in roots. Moreover, the plasma membrane maintained high selectivity. The lipid phosphatidylcholine (PC): phosphatidylethanolamine (PE) ratio, an indicator of the membrane stability, was five times higher in L. chinensis than in Arabidopsis. Furthermore, in L. chinensis, Ca limitation did not affect the content of any major lipid types, decreased malondialdehyde (MDA) content, and increased superoxide dismutase (SOD) activity, showing an opposite pattern to that in Arabidopsis. L. chinensis roots accumulated higher contents of PC, phosphatidylinositol (PI), monogalactosyldiacylglycerol (MGDG), phosphatidylglycerol (PG), cardiolipin (CL), digalactosyldiacylglycerol (DGDG), and lysophosphatidylcholine (LPC) but less phosphatidylethanolamine (PE), diacylglycerol (DAG), triacylglycerolv (TAG), phosphatidylserine (PS), lysobisphosphatidic acids (LPAs), lysophosphatidylethanolamine (LPE), and lysophosphatidylserine (LPS) than Arabidopsis roots. Moreover, we detected 31 and 66 unique lipids in L. chinensis and Arabidopsis, respectively.ConclusionsThis study revealed that L. chinensis roots have unique membrane lipid composition that was not sensitive to Ca limitation, which might contribute to the wider natural distribution of this species.

Soil Hydrological Properties’ Response to Long-Term Grazing on a Desert Steppe in Inner Mongolia

Soil hydrological properties play an important role in maintaining ecosystem functions. It is critical to understand how those properties respond to human disturbance especially in semi-arid areas. In the present study, we investigated the effects of different long-term grazing intensities (no grazing, light grazing, moderate grazing, and heavy grazing) on eight parameters that related to soil hydrological properties in different soil depths based on a grazing platform that was established in 2004 on a desert steppe in Inner Mongolia. The relationships among different parameters and between hydrological and chemical properties were also analyzed. The results show that grazing intensity, soil depth, and their interaction all have significant effects on soil moisture content, saturation capacity, field capacity, and bulk density. At different soil depths (0–10, 10–20, and 20–30 cm), soil bulk density was negatively correlated with saturation capacity, capillary capacity, and non-capillary porosity but positively correlated with field capacity. Furthermore, we found that field capacity and soil moisture content were positively correlated but non-capillary soil porosity was negatively correlated with most soil nutrients. Our results indicate that overgrazing has detrimental effects on soil hydrological properties which may further negatively affect soil nutrient content. Light grazing may be an optimal grazing intensity on this semi-arid steppe with respect to soil hydrological properties.

Rule of Law Guarantee for Ecological Security of Inner Mongolian Grassland Based on Big Data Analysis

Abstract This paper carries out an environmental law big data analysis using big data computing based on the legislative framework of biodiversity in Inner Mongolia grassland. For the research and analysis of the rule of law guarantee for the ecological security of the Inner Mongolian grassland, it first establishes the early warning of the ecological security of the Inner Mongolian grassland through the gray prediction model and verifies the accuracy and feasibility of the prediction model precision. According to the early warning results of the ecological security of the Inner Mongolian grassland, it is suggested to enhance the legalization of grassland ecological compensation. The R 2 GM (1, 1) prediction model of Inner Mongolia grassland reaches 0.86, which shows that the prediction accuracy is good. The ecological security evaluation of Inner Mongolia from 2025 to 2035 presents, in terms of type, a safer state region > safer state region > mildly alerted state region > moderately alerted state region > seriously alerted state, and the percentage of each grade increases or decreases. Without distinguishing occupations, 93.3%-98.6% of all herders and grassland managers supported that grassland ecological compensation should be legalized. This shows that the construction of the rule of law guarantee for grassland ecological security in Inner Mongolia is an inevitable trend of development.

Quantifying the ecological carrying capacity of grasslands in Inner Mongolia.

Quantifying the ecological carrying capacity has emerged as a crucial factor for maintaining ecosystem stability for sustainable development in vulnerable eco-regions. Here, we propose a new framework for ecological carrying capacity quantification suitable for vulnerable eco-regions. We applied this framework to calculate the ecological carrying capacity of Inner Mongolia from 1987-2015 and used a geographical detector to identify the driving factors behind spatial heterogeneity. Our results revealed the following. (1) The above-ground net primary production (ANPP) required to support the ecosystem service of soil conservation (ANPPSC) decreased from northeast to southwest, whereas the distribution pattern of ANPP required to support the ecosystem service of sand fixation (ANPPSF) exhibited a contrary trend. The average annual ANPP required to support the ecosystem service of natural regeneration (ANPPNR) in Inner Mongolia from 1987 to 2015 was 101.27 gCm-2year-1, revealing a similar spatial distribution with ANPP. (2) The total ecological carrying capacity of Inner Mongolian grassland was 78.52 million sheep unit hm-2. The regions with insufficient provisioning service capability accounted for 4.18% of the total area, primarily concentrated in the east and northwest. (3) The average optimal livestock number for grasslands in Inner Mongolia was 1.59 sheep unit hm-2 from 1987-2015, ranging from 0.77 to 1.69 sheep unit hm-2 across different zones. The average ecological carrying capacity of the cold temperate humid, medium-temperate arid, and warm temperate semi-humid regions was less than 1.08 sheep unit m-2, suggesting a need to prohibit grazing in these areas. (4) The primary influencing factors affecting ecological carrying capacity distribution were normalized difference vegetation index (NDVI), precipitation, and soil type. The framework developed herein can help identify sustainable development potential from the ecosystem service perspective and effectively contribute to decision-making in grassland ecosystem management.

Nitrogen and phosphorus additions alter foliar nutrient concentrations of dominant grass species and regulate primary productivity in an Inner Mongolian meadow steppe

Excessive nitrogen (N) inputs shift grassland productivity from nitrogen (N) to phosphorus (P) limitation. However, how plant nutrient concentrations and stoichiometric dynamics at community and species level responding to variable soil N and P availability, and their roles in regulating net primary productivity in meadow steppe remain unclear. To address this issue, we carried out an experiment with fifteen treatments consisting of factorial combinations of N (0, 1.55, 4.65,13.95, 27.9 g N m−2 yr−1) and P (0, 5.24,10.48 g P m−2 yr−1) for three years in a meadow steppe in Inner Mongolia. We examined concentrations and stoichiometry of C (carbon), N, P in plants and soils, and their associations with plant primary productivity. Results revealed mean community N:P ratios for shoots (12.89 ± 0.98) did not exceed 14 within the control treatment, indicating that plant growth was primarily N-limited in this ecosystem. Shoot N:P ratios were significantly increased by N addition (>16 when N application rate above 4.65 g N m−2 yr−1), shifting the community from N- to P-limited whereas significantly reduced by P addition (N:P ratios <14), further aggravating N limitation. N addition increased leaf-N concentrations whereas decreased leaf C:N ratios of all four species, but only the values for two graminoid species were significantly influenced by P addition. Leaf-P concentrations significantly increased for graminoids but significantly decreased for forbs with the application of N. VPA analysis revealed that aboveground components, especially in grass leaves, explained more variation in aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP) than root and soil components. For grasses, leaf-N concentrations showed high association with ANPP, while leaf-P concentrations were associated with BNPP. These results highlight that N and P depositions could affect the leaf-nutrient concentrations of dominant grasses, and thereby potentially alter net primary productivity in meadow steppe.

An improved dynamic threshold method for determining the start of the vegetation greening season in remote sensing monitoring: The case of Inner Mongolia

The start of the greening season (SOS) is the beginning of vegetation phenology, and its time of occurrence affects the carbon cycle and organic matter production of the ecosystem. Accurate retrieval of vegetation phenology in remote sensing monitoring is important for sustainable management of vegetation resources. The dynamic threshold method (DTM) is one of the mainstream methods to retrieve vegetation phenology. However, it suffers the following two shortcomings. First, a subjective threshold percentage of the phenology nodes is used based on the user's empirical thresholds, and the determined threshold is not universal. Second, a common threshold is used for identifying the phenology globally with little consideration of the physiological characteristics of different vegetation types, thus blurring the phenology variability among vegetation types. Here, we developed an improved dynamic threshold method (IDTM) for the retrieval of the start of the greening season and tested it using temperate grassland and forest vegetation in Inner Mongolia. The algorithm in the IDTM uses the curvature of the EVI2 time series curves of different vegetation types to determine the threshold for the SOS, thus eliminating the subjectivity of the original DTM. The predicted SOS of the IDTM is in better agreement with the ground observations than the MCD12 Q2 vegetation phenology product or the DTM with different empirical thresholds. In terms of spatial correlations, the SOS of the IDTM was significantly correlated with that of the MCD12 Q2 phenology product (r = 0.72, p < 0.05). Our study indicates the efficacy of the IDTM in predicting the SOS of vegetation and that the average SOS of vegetation in Inner Mongolia is in early May (on Day 126) but has a large variation across vegetation zones.

Characterizing uncertainty in process-based hydraulic modeling, exemplified in a semiarid Inner Mongolia steppe

Assessing root sources of three uncertainties – parameterization of soil hydraulic characteristics, boundary conditions, and estimation of source/sink terms – is a significant challenge in soil water transport modeling. This study aims to evaluate the uncertainty of three each widely-used parameter estimation methods affecting plot-scale water dynamics. The study employs HYDRUS, a process-based hydrologic model, to incorporate these uncertainties and compare model predictions to measured values in a semiarid Inner Mongolia steppe, China. Soil hydraulic parameters are determined using two direct methods (laboratory-derived approach and evaporation method) and one indirect method (neural network). While each hydraulic parameter method generally simulates soil moisture dynamics, the evaporation method performed better, especially under dry conditions. This suggests that measuring the intensity properties, such as unsaturated hydraulic conductivity, with the evaporation method is crucial for reasonable soil moisture simulation. The study also demonstrates the impact of different applied boundary conditions on simulated soil moisture, specifically the partitioning of reference FAO evapotranspiration via one direct method (soil fraction cover) and two indirect methods (leaf area index and crop height). The partitioning via soil fraction cover reflected a better simulation. Additionally, the study compares the uncertainties of root water uptake function with root growth parameters and constant root depth referenced to grass and pasture, and finds no significant difference among them. Comparing three sources of uncertainty in predicting soil moisture, the study concludes that the input soil hydraulic parameter is more sensitive than evapotranspiration partitioning or representation of root water uptake function. Our study highlights that measuring soil intensity properties can better reflect the effects of land use change, such as compaction, on field water transports.

Land use/cover and land degradation across the Eurasian steppe: Dynamics, patterns and driving factors

Despite the ecological and socio-economic importance of Eurasian steppe, the land use/cover change, land degradation and the threats facing this precious ecosystem still have not been comprehensively understood. Taking advantages of the land use/cover change monitoring platform (FROM-GLC Plus), this study developed the annual land use/cover maps during 2000–2022, and the land use/cover change, especially the change of grassland, was further analyzed. The grassland area exhibited a net increase, predominantly transformed from cropland, forest, and bareland, accounting for 17.64 %, 31.91 %, and 45.60 %, respectively. To monitor land degradation, we adopted the framework suggested by the United Nations Convention to Combat Desertification (UNCCD). According to the monitoring result, grassland constituted the highest proportion of degraded land (39.82 %). This may due to its dominance in the Eurasian steppe's land use/cover, as the extent of grassland degradation (1.92 %) was lower than the overall land degradation level (2.83 %) across the region. To offer tailored and sustainable development recommendations, we quantified the driving factors behind land dynamics using the geographical detector model and convergent cross mapping (CCM), considering both spatial and temporal dimensions. Environmental and socio-economic factors, such as precipitation, temperature, urbanization, mining and grazing intensity, etc., were integrated into the analysis. We found that urbanization, cropland and moisture distribution emerged as key drivers influencing land degradation's spatial distribution in the Eurasian steppe, while temperature variations between years impacted vegetation changes. This research thus provides a deeper understanding of the region's land dynamics, enhancing comprehensive monitoring of the Eurasian steppe's land dynamics. Moreover, it serves as a foundation for policymakers and land managers to devise conservation strategies and sustainable development initiatives for this critical ecosystem.

A novel, post-Soviet fire disturbance regime drives bird diversity and abundance on the Eurasian steppe.

Many grassland ecosystems and their associated biodiversity depend on the interactions between fire and land-use, both of which are shaped by socioeconomic conditions. The Eurasian steppe biome, much of it situated in Kazakhstan, contains 10% of the world's remaining grasslands. The break-up of the Soviet Union in 1991, widespread land abandonment and massive declines in wild and domestic ungulates led to biomass accumulation over millions of hectares. This rapid fuel increase made the steppes a global fire hotspot, with major changes in vegetation structure. Yet, the response of steppe biodiversity to these changes remains unexplored. We utilized a unique bird abundance dataset covering the entire Kazakh steppe and semi-desert regions together with the MODIS burned area product. We modeled the response of bird species richness and abundance as a function of fire disturbance variables-fire extent, cumulative burned area, fire frequency-at varying grazing intensity. Bird species richness was impacted negatively by large fire extent, cumulative burned area, and high fire frequency in moderately grazed and ungrazed steppe. Similarly, overall bird abundance was impacted negatively by large fire extent, cumulative burned area and higher fire frequency in the moderately grazed steppe, ungrazed steppe, and ungrazed semi-deserts. At the species level, the effect of high fire disturbance was negative for more species than positive. There were considerable fire legacy effects, detectable for at least 8 years. We conclude that the increase in fire disturbance across the post-Soviet Eurasian steppe has led to strong declines in bird abundance and pronounced changes in community assembly. To gain back control over wildfires and prevent further biodiversity loss, restoration of wild herbivore populations and traditional domestic ungulate grazing systems seems much needed.

Quantifying key vegetation parameters from Sentinel-3 and MODIS over the eastern Eurasian steppe with a Bayesian geostatistical model

Accurate estimation of grassland leaf area index (LAI), fractional vegetation cover (FVC), and aboveground biomass (AGB) is fundamental in grassland studies. The newly launched Ocean and Land Color Imager (OLCI) sensor onboard Sentinel-3 (S3) provides images with comparable spatial and spectral resolution with MODIS data. However, the use of S3 OLCI imageries for vegetation variable estimation is rarely evaluated. This study evaluated the potential of S3 OLCI and MODIS data for estimating grassland LAI, FVC, and AGB in the eastern Eurasian steppe. A Bayesian spatial model (Integrated Nested Laplace Approximation with Stochastic Partial Differential Equation, INLA-SPDE) was used to address spatial autocorrelation of in-situ observation data and to enhance our predictions. Our results showed that the models based on S3 OLCI data presented higher accuracy than models with MODIS data. The RMSEs decreased by 3.7–10.8 %, 3.7–7.5 %, and 1.6–14.2 % for LAI, FVC, and AGB predictions, respectively. Through combinations of multiple predictors, we confirmed the robustness of red edge bands for grassland variable estimation, the models employing red edge variables yielded 3.5 %, 3.2 %, and 0.4 % lower RMSEs than models with conventional visible and NIR bands for LAI, FVC, and AGB prediction, respectively. INLA-SPDE spatial model produced lower bias and higher prediction accuracy than random forest and random forests kriging method in most of the models; the INLA-SPDE predicted LAI and FVC maps also showed a better agreement with ground observations than MODIS and PROBA-V land products.

Impact of precipitation and grazing on recovery of plant vegetation in temperate grasslands

AbstractGrasslands support a rich diversity that plays a pivotal role in ecological balance, carbon sequestration, and climate regulation. Grassland ecosystems are facing a loss of biodiversity and a decline in soil function due to precipitation variations caused by climate change. However, variations in grassland species diversity are not clearly known, especially under the combined effects of precipitation and grazing. Based on a 5‐year split‐plot experiment with two grazing regimes (i.e., moderate grazing and grazing prohibition) along with three precipitation controls (ambient precipitation and ±50% precipitation) in Inner Mongolian grasslands, we researched the response of precipitation variability and grazing prohibition to vegetation diversity indices and investigated the response of vegetation community composition and biomass to these factors. Five years results showed that increasing precipitation resulted in a significant increase in the coverage of perennial forbs, annual and biennial plants, and Gramineae. Grazing prohibition and increased precipitation significantly increased biomass and species richness compared to all other treatment combinations. Interestingly, grazing exclusion significantly reduced the percentage of Amaryllidaceae, especially in the presence of altered precipitation. The vegetation community composition of a typical grassland was correlated with soil volumetric water content (VWC), bulk density (SBD) and pH, soil organic carbon (SOC), and total nitrogen (TN). VWC, SBD, and TN were found to be the most significant factors affecting vegetation diversity under grazing. Partial canonical ordination revealed that soil moisture, soil bulk density, and SOC had the most significant correlation with vegetation diversity under both grazing prohibition and increased precipitation treatment conditions. These results suggested that alterations in precipitation can change the species composition and ecosystem function of plant communities, leading to a close relationship between species diversity and soil properties. Our results underline the importance of species diversity for soil characteristics and environmental factors in a typical Eurasian steppe ecosystem.

Holocene vegetation dynamics in southern Ukraine under changing land use and climate

The Holocene vegetation dynamics of the Eurasian steppe are underinvestigated despite its vast extension, chiefly because of the scarcity of suitable sites for palaeoecological research. Here, we present a palaeoecological reinvestigation from Kardashynskyi mire (southern Ukraine), approximately 4 km from a previously cored site. Using pollen, spores and microscopic charcoal, we have reconstructed vegetation dynamics, fire history and land use for the past c. 8300 years. Regionally, steppe vegetation with Poaceae, Chenopodiaceae and Artemisia was always dominant. However, pollen assemblages also reflect the presence of floodplain and upland tree stands. At the beginning of the sequence, c. 8300 years ago, Pinus stands were growing on the sandy terraces of the Dnipro dry upland sites. Later, at c. 7950 cal yr BP, diverse stands with Quercus, Ulmus, Fraxinus, Tilia and Alnus established along the riverbanks, where moisture availability was sufficient. Around 6100 cal yr BP, those deciduous broadleaved stands experienced a severe decline, likely in response to changing water table levels. Cultural indicators suggest land use activities after c. 7900 cal yr BP. During the Bronze Age, human impact intensified. Overall, both climate and humans drove vegetation dynamics in the Pontic steppe for millennia. Nowadays, this once extensive biome has almost completely been converted to cropland. Similarly, the wetland vegetation, the riparian forests and, above all, the pine forests growing on the sandy terraces were strongly reduced by millennial-long land use. Under the current conditions, even the last remnants of these special vegetation types are severely threatened.

Short term grazing increased growing-season N2O production and decreased its reduction potential by reducing the abundance and expression of nosZ clade II gene in a semi-arid steppe

Understanding nitrous oxide (N2O) production as well as reduction in response to grazing and mowing is essential for designing better management strategies to improve sustainability of grassland ecosystems. We evaluated how four years of grazing or mowing altered N2O production and reduction potential, gene abundance, and expression of microbial functional groups pertinent to N2O production in situ on a typical grassland in Inner Mongolia. In our study, we found that grazing dramatically raised soil ammonium (NH4+-N) and nitrate (NO3−-N) concentrations, AOB gene abundance and potential of N2O production through nitrification (NN2O) and denitrification (DN2O) in summer, but lessened the expression of nosZ clade II gene in all seasons. Mowing had minor effect on soil inorganic nitrogen (N) concentrations. Mowing diminished the quantity of denitrification genes (narG and nosZ), expression of nosZ and nosZ clade II genes, and DN2O concentration. The expression and abundance of nosZ clade II gene were related to DN2. These results suggested that short-term grazing could enhance N2O production potential in peak growing season, while the reduction in abundance and expression of nosZ calde II gene might be an important contributor to the enhanced N2O production of semi-arid typical steppe grasslands.

Response of Soil Respiration to Altered Snow Cover in a Typical Temperate Grassland in China

The snow cover in temperate areas is undergoing significant changes, which may affect soil respiration (Rs), the second largest carbon flux in global carbon cycling. However, currently, there are relatively few in situ field studies on the effects of altered snow cover on Rs in temperate areas during the non-growing season compared to the research on Rs during the growing season. Therefore, it limited the accurate prediction of the characteristics and magnitude of changes in soil carbon emissions in temperate areas under global change scenarios. Here, an in situ field experiment was conducted in a typical grassland in Inner Mongolia in China to explore the characteristics of Rs under three different snow cover treatments, i.e., increasing snow (IS), decreasing snow (DS), and ambient snow that was regarded as the control check treatment (CK). The results showed that the range of Rs flux and cumulative emission flux in all treatments in the non-growing season in the study area ranged from 5.87 ± 0.20 to 55.11 ± 6.42 mg CO2 m−2 h−1 and from 22.81 ± 0.68 to 26.36 ± 0.41 g C m−2, respectively. During the observation period, the depth of the largest snow cover for each treatment did not exceed 18 cm, and none of the snow treatments caused significant variations in Rs flux (p &gt; 0.05). However, the cumulative flux of Rs in the whole non-growing season was only stimulated significantly by 15.6% by the IS treatment compared with that of CK. The relatively high Rs flux in the non-growing season was observed to mainly occur in the soil deeply frozen period (DFP) and the soil melting period (SMP). Further analysis revealed that Rs flux under different snow treatments were mainly positively correlated with soil temperature during SMP. The main factors controlling Rs varied with different sampling periods. Our findings suggest that the non-growing season is also an important period of non-negligible carbon emissions from typical grassland soils in temperate zones.