Desert Steppe Of Inner Mongolia Research Articles

Effects of Stocking Rate on the Variability of Peak Standing Crop in a Desert Steppe of Eurasia Grassland

Proper grazing management practices can generate corresponding compensatory effects on plant community production, which may reduce inter-annual variability of productivity in some grassland ecosystems. However, it remains unclear how grazing influences plant community attributes and the variability of standing crop. We examined the effects of sheep grazing at four stocking rate treatments [control, 0 sheep ha(-1) month(-1); light (LG), 0.15 sheep ha(-1 )month(-1); moderate (MG), 0.30 sheep ha(-1) month(-1); and heavy (HG), 0.45 sheep ha(-1) month(-1)] on standing crop at the community level and partitioned by species and functional groups, in the desert steppe of Inner Mongolia, China. The treatments were arranged in a completely randomized block design over a 9-year period. Standing crop was measured every August from 2004 to 2012. Peak standing crop decreased (P < 0.05) with increasing stocking rate; peak standing crop in the HG treatment decreased 40 % compared to the control. May-July precipitation explained at least 76 % of the variation in peak standing crop. MG and HG treatments resulted in a decrease (P < 0.05) in shrubs, semi-shrubs, and perennials forbs, and an increase (P < 0.05) in perennial bunchgrasses compared to the control. The coefficients of variation at plant functional group and species level in the LG and MG treatments were lower (P < 0.05) than in the control and HG treatments. Peak standing crop variability of the control and HG community were greatest, which suggested that LG and MG have greater ecosystem stability.

Sensitivity of Temperate Desert Steppe Carbon Exchange to Seasonal Droughts and Precipitation Variations in Inner Mongolia, China

Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO2 flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm) was close to the long-term average (183.9±47.6 mm), while the precipitation in 2008 (136.3 mm) and 2010 (141.3 mm) was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO2 throughout the study period, with a net ecosystem carbon dioxide exchange (NEE) of −7.2, −22.9, and 26.0 g C m−2 yr−1 in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEEsat) and the temperature sensitivity coefficient of ecosystem respiration (Reco) exhibited significant variations. The values of NEEsat were −2.6, −2.9, and −1.4 µmol CO2 m−2 s−1 in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP) and Reco, and the drought sensitivity of GPP was greater than that of Reco. The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution.

Effects of short-term warming and increasing precipitation on soil respiration of desert steppe of Inner Mongolia

Aims Our objective was to examine the effects of global warming inducing environmental and biological changes on soil respiration of desert steppe. Methods We used infrared heaters to carry out the interactive simulation of warming and increasing precipitation in a desert steppe of Inner Mongolia from June to September 2011. Our experimental design was set up with two temperature levels (control and warming) and three precipitation treatments (control, 15% and 30% increase of the average precipitation during 1987–2007), using a complete randomized block arrangement. Soil respiration rate was measured by a LI-8100 carbon flux system in these six different treatments. We analyzed the relationships between soil respiration and environmental factors, aboveground biomass, and belowground biomass at different soil layers (0–10, 10–20 and 0–20 cm). Important findings Soil respiration in the desert steppe reached its peak value in the middle of the growing season. The average soil respiration rate of the desert steppe from July to August was 1.35 μmol CO 2 ·m –2 ·s –1 . The soil respiration rate was 2.08 and 0.63 μmol CO 2 ·m –2 ·s –1 in July and August, respectively. Increasing soil moisture and temperature significantly influenced daily soil respiration, but their interaction had no significant effect on soil respiration. Soil moisture had greater impact on monthly soil respiration than soil temperature. Soil respiration rate showed a power function relationship with belowground biomass at different soil depths. The belowground biomass at 0–10 cm soil was the major part of the belowground biomass and could explain more variation of soil respiration rate (79.2%) than that at 10–20 cm (31.6%). Under the future climatic changes scenarios, soil moisture was a principal environmental factor affecting plant biomass, while belowground biomass was a major biological factor controlling soil respiration in the desert steppe. Soil moisture might control the heterogeneity of soilrespiration by influencing the distribution of belowground biomass at different soil depths.

Light Use Efficiency over Two Temperate Steppes in Inner Mongolia, China

Vegetation light use efficiency (LUE) is a key parameter of Production Efficiency Models (PEMs) for simulating gross primary production (GPP) of vegetation, from regional to global scales. Previous studies suggest that grasslands have the largest inter-site variation of LUE and controlling factors of grassland LUE differ from those of other biomes, since grasslands are usually water-limited ecosystems. Combining eddy covariance flux data with the fraction of photosynthetically active radiation absorbed by the plant canopy from MODIS, we report LUE on a typical steppe and a desert steppe in Inner Mongolia, northern China. Results show that both annual average LUE and maximum LUE were higher on the desert steppe (0.51 and 1.13 g C MJ−1) than on the typical steppe (0.34 and 0.88 g C MJ−1), despite the higher GPP of the latter. Water availability was the primary limiting factor of LUE at both sites. Evaporative fraction (EF) or the ratio of actual evapotranspiration to potential evapotranspiration (AET/PET) can explain 50–70% of seasonal LUE variations at both sites. However, the slope of linear regression between LUE and EF (or AET/PET) differed significantly between the two sites. LUE increased with the diffuse radiation ratio on the typical steppe; however, such a trend was not found for the desert steppe. Our results suggest that a biome-dependent LUEmax is inappropriate, because of the large inter-site difference of LUEmax within the biome. EF could be a promising down-regulator on grassland LUE for PEMs, but there may be a site-specific relationship between LUE and EF.

Impact of Grazing on Soil Carbon and Microbial Biomass in Typical Steppe and Desert Steppe of Inner Mongolia

The potential of grazing lands to sequester carbon must be understood to develop effective soil conservation measures and sustain livestock production. Our objective was to evaluate the effects of grazing on soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC) in Typical steppe and Desert steppe ecosystems, which are both important grassland resources for animal grazing and ecological conservation in China, and to derive region-specific soil C changes associated with different stocking rates (ungrazed, UG; lightly grazed, LG; moderately grazed, MG; heavily grazed, HG). This study substantiated that significant higher SOC, TN and MBC appeared with the treatment of LG in typical steppe. From 2004 to 2010, grazing treatments increased soil carbon storage in desert steppe, which was partly due to the grazing history. The higher MBC concentration and MBC/SOC suggest a great potential for carbon sequestration in the desert steppe ecosystem. The greater MBC in desert steppe than typical steppe was mainly the result of higher precipitation and temperature, instead of soil substrate. The change of MBC and the strong positive relationships between MBC and SOC indicated that MBC in the soil was a sensitive index to indicate the dynamics of soil organic carbon in both steppes in Inner Mongolia of China.

Estimating senesced biomass of desert steppe in Inner Mongolia using field spectrometric data

The amount of senesced biomass in vegetation plays an important role in estimation of carbon storage and plant stress. In this paper, the spectral predictors for estimating senesced biomass were evaluated based on field spectral and corresponding biophysical parameter measurements during the growing seasons of 2009 and 2010 in the desert steppe of Inner Mongolia. Results showed the cellulose absorption index (CAI) was the best one among senesced vegetation coverage indices and band depth indices. The model involving CAI yielded the highest coefficient of determination (R2=0.67) and the lowest root mean square error of leave-one-out cross validation (RMSECV=17.9gm−2) compared with normalized difference index (NDI) (R2=0.21, RMSECV=27.6gm−2), soil-adjusted corn residue index (SACRI) (R2=0.29, RMSECV=26.2gm−2), modified soil-adjusted crop residue index (MSACRI) (R2=0.1, RMSECV=29.5gm−2), dead fuel index (DFI) (R2=0.28, RMSECV=26.3gm−2), lignocellulose absorption depth (LCD) (R2=0.56, RMSECV=20.5gm−2) and lignocellulose absorption area (LCA) (R2=0.54, RMSECV=21.1gm−2). The results of this study suggest that CAI has good potential to estimate senesced biomass in desert steppe areas.

Evaluating cellulose absorption index (CAI) for non-photosynthetic biomass estimation in the desert steppe of Inner Mongolia

Accurate estimation of non-photosynthetic biomass is critical for modeling carbon dynamics within grassland ecosystems. We evaluated the cellulose absorption index (CAI), widely used for monitoring non-photosynthetic vegetation coverage, for non-photosynthetic biomass estimation. Our analysis was based on in situ hyperspectral measurements, during the growing seasons of 2009 and 2010, in the desert steppe of Inner Mongolia. ASD (Analytical Spectral Device)-derived and Hyperion-derived CAI were found to be effective for non-photosynthetic biomass estimation, yielding relative error (RE) values of 26.4% and 26.6%, respectively. The combination of MODIS (Moderate Resolution Imaging Spectroradiometer)-derived (MODIS2-MODIS5)/(MODIS2+MODIS5) and (MODIS6-MODIS7)/(MODIS6+MODIS7) showed a high multiple correlation (multiple correlation coefficient, r= 0.884) with ASD-derived CAI. A predictive model involving the two MODIS indices gave greater accuracy (RE=28.9%) than the TM (Landsat Thematic Mapper)-derived indices. The latter were the normalized difference index (NDI), the soil adjusted corn residue index (SACRI), and the modified soil adjusted crop residue index (MSACRI). These indices yielded RE values of more than 42%. Our conclusions have great significance for the estimation of regional non-photosynthetic biomass in grasslands, based on remotely sensed data.

Biophysical regulation of net ecosystem carbon dioxide exchange over a temperate desert steppe in Inner Mongolia, China

Measurements of net ecosystem carbon dioxide (CO 2) exchange (NEE) were made, using eddy covariance, to investigate the biophysical regulation of a temperate desert steppe characterized drought in Inner Mongolia, China during 2008. The half-hourly maximum and minimum NEE were −3.07 and 0.85 μmol CO 2 m −2 s −1 (negative values denoting net carbon uptake). The maximum daily NEE was −6.0 g CO 2 m −2 day −1. On an annual basis, integrated NEE was −7.2 g C m −2 y −1, indicating a weak carbon sink. The light response curves of NEE showed a rather low apparent quantum yield ( α) and saturation value of NEE (NEE sat). Moreover, α and NEE sat varied with canopy development, soil water content (SWC), air temperature ( T a), and vapor pressure deficit (VPD). Piecewise regression results suggested that the optimal SWC, T a, and VPD for half-hourly daytime NEE were 12.6%, 24.3 °C, and 1.7 kPa, respectively. The apparent temperature sensitivity of ecosystem respiration was 1.6 for the entire growing season, and it was significantly controlled by soil moisture. During the growing season, leaf area index explained about 26% of the variation in daily NEE. Overall, NEE was strongly suppressed by water stress and this was the dominant biophysical regulator in the desert steppe.

Estimation of green aboveground biomass of desert steppe in Inner Mongolia based on red-edge reflectance curve area method

Vegetation green aboveground biomass is an important parameter of terrestrial ecosystem process-based models, and is closely related to photosynthetic activity. In this paper, the hyperspectral predictors for estimating green aboveground biomass were evaluated based on field spectral and corresponding biophysical parameter measurements during the growing seasons of 2009 and 2010 in the desert steppe of Inner Mongolia. Results showed that the performance of red-edge reflectance curve area (between normalized reflectance curve and wavelength in 680–780 nm region) was better than that of traditional vegetation indices (VIs) and red-edge position (REP). The model based on red-edge reflectance curve area produced a lower standard error of prediction (26.4 g m−2) compared with the optimal narrow-band ratio vegetation index (RVI) (37.4 g m−2), normalized difference vegetation index (NDVI) (33.5 g m−2), soil-adjusted vegetation index (SAVI) (37.5 g m−2) and modified soil-adjusted vegetation index (MSAVI) (38.6 g m−2). Statistical analyses performed on the slopes and intercepts of the fitted lines between actual and predicted values demonstrated that no statistical differences (P > 0.05) were found in regards to slope = 1 and intercept = 0 for red-edge reflectance curve area and optimal SAVI and MSAVI, whereas the slope and intercept based on optimal RVI were different (P

Evapotranspiration and crop coefficient for a temperate desert steppe ecosystem using eddy covariance in Inner Mongolia, China

AbstractEvapotranspiration (ET), which links water, energy and the carbon cycle in terrestrial ecosystems, is an important eco‐hydrological process, especially in arid and semi‐arid regions. To determine the crop coefficient (Kc) over a 2‐year period for a temperate desert steppe in Inner Mongolia, China, ET was measured using the eddy covariance method and the reference evapotranspiration (ET0) was estimated from site meteorological data. The results showed that the seasonal variation of ET differed on an annual timescale between the 2 consecutive years, exhibiting a multi‐peak curve in 2008 and a single peak in 2009. The mean daily Kc values were 0·15 and 0·17 in 2 years, varying from 0·009 to 0·75 in 2008 and from 0·005 to 0·58 in 2009. The 5‐day moving average for Kc values was mainly affected by SWC10cm and Rn, and the regression coefficients (R2) were 58·9 and 69·5%, respectively. These results will aid in making accurate and quantitative assessments of the vulnerability of the sparse vegetation to climate change. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Carbon flux dynamics and its environmental controlling factors in a desert steppe

Net ecosystem carbon dioxide exchange ( NEE) above a desert steppe in Inner Mongolia was measured with eddy covariance technique in growing season of 2008. Environmental factors were also observed during the same period. Our results show that the minimum of growing season daily cumulative NEE appeared on August 26 (−1.6 g Cm −2), while the maximum appeared on June 11 (0.9 g Cm −2). Monthly cumulative NEE distributed in the growing season unevenly. The minimum of monthly cumulative NEE appeared in June (0.74 g Cm −2); the maximum appeared in September (−14.94 g Cm −2). The sum of the growing season NEE was −45.5 g Cm −2. The most important environmental factor affecting the half-hour average NEE was photosynthetically active radiation. The most important environmental factor affecting the daily cumulative NEE was 20–30 cm soil water content.

Characteristics and modeling of evapotranspiration over a temperate desert steppe in Inner Mongolia, China

The magnitude and seasonal dynamics of evapotranspiration (ET) over a temperate desert steppe in Inner Mongolia, China, were investigated during a growing season (from 1st May to 15th October 2008) using the eddy covariance (EC) technique. Diurnal variations of latent heat flux (LE) at different phenological stages showed similar patterns with the peak value around noon. The sensible heat flux dominated the latent heat flux at midday during the whole growing season. Seasonal variation in ET followed closely the variation in soil water content (SWC) and leaf area index (LAI). The maximum daily ET rate was 3.8 mm day−1. Cumulative ET during the study period estimated directly by EC method was 150.9 mm, exceeding the precipitation (PPT) received at the site during the same period (133.0 mm) by 13.4%. The daily crop coefficient (Kc, calculated as the ratio of the measured ET (from the EC system) to the reference ET (from the Penman–Monteith model)) also showed a distinct seasonal pattern, however its value on average was considerable lower (0.17) during the measurement period than the results reported from other grasslands, suggesting that this steppe was strongly affected by the deficit of available water. SWC was the most important environmental factor controlling ET in this steppe. The correlation analysis between daily Kc and its major environmental controls indicated that SWC, relative humidity (RH), and net radiation (Rn) were the major explanatory variables for daily Kc. Daily Kc showed a linear increase with SWC and Rn, and an exponential increase with RH. Thus, a daily Kc model would be developed as a function of SWC, RH, and Rn. An empirical daily ET model derived from the FAO 56 crop coefficient approach was developed based on this daily Kc model and the Penman–Monteith model. This ET model was validated by the data from the growing season in 2009, and showed a good consistency between the simulated and the measured ET values. Based on the developed ET model, an alternative ET model with the variable of SWC replaced by PPT was established, which may have the advantage of ET estimation under PPT more easily available than SWC.

Partitioning soil respiration in a temperate desert steppe in Inner Mongolia using exponential regression method

Accurately partitioning soil respiration into autotrophic and heterotrophic components is important for understanding how ecosystem carbon budgets will respond to climate change. Usually, heterotrophic respiration can be estimated by a linear relationship between soil respiration and root biomass. In this study, however, we found that an exponential relationship was more appropriate than a linear relationship for relating soil respiration to root biomass in a temperate desert steppe in Inner Mongolia, China.

Spatial vegetation patterns as early signs of desertification: a case study of a desert steppe in Inner Mongolia, China

Proper assessment and early detection of land degradation and desertification is extremely important in arid and semi-arid ecosystems. Recent research has proposed to use the characteristics of spatial vegetation patterns, such as parameters derived from power-law modeling of vegetation patches, for detecting the early signs of desertification. However, contradictory results have been reported regarding the suitability of those proposed indicators. We used an experiment with multiple grazing intensities as an analog of a desertification gradient and evaluated the performance of two predictors of desertification: percent plant cover and a transition from a patch-area distribution characterized by a power law to another portrayed by a truncated power law, in a desert steppe in Inner Mongolia, China. We found that spatial metrics, such as the largest patch index and coefficient of variation of mean patch area had negative linear relationships with grazing intensity, suggesting that vegetation patches became more fragmented and homogeneous under higher grazing pressure. Using a binning-based method to analyze our dataset, we found that the patch-area relationship deviated from a power-law to a truncated power-law model with increasing grazing pressure, while the truncated power law was a better fit than the power law for all plots when binning was not used. These results suggest that the selection of methodology is crucial in using power-law models to detect changes in vegetation patterns. Plant cover was significantly correlated with stocking rate and all spatial metrics evaluated; however, the relationship between cover and vegetation spatial pattern still deserves a thorough examination, especially in other types of ecosystems, before using cover as a universal early sign of desertification. Our results highlight a strong connection between the vegetation spatial pattern and the desertification associated with heavy grazing and suggest that future studies should incorporate information about vegetation spatial pattern in monitoring desertification processes.

Grazing intensity affected spatial patterns of vegetation and soil fertility in a desert steppe

Spatial heterogeneities of vegetation and soil can strongly affect ecological functions of ecosystems, particularly for arid and semi-arid ecosystems where vegetation has a patchy distribution and livestock grazing is one of the major land use types. However, little is known about the impact of grazing on spatial patterns of vegetation and soil, even though grazing has variously been shown to create, maintain or destroy those patterns. We studied how grazing intensity affected the spatial patterns of vegetation and soil fertility at scales ranging from 0.1 to 18.7 m in a desert steppe in Inner Mongolia, China. Increasing grazing intensity decreased the range of spatial autocorrelation of plant aboveground biomass at the fine scale (<2 m), indicating that vegetation patches were more fragmented under higher grazing pressure. Spatial heterogeneity of soil water content and organic C concentration decreased along the gradient of increasing grazing intensity at the fine scale. Light grazing increased soil NH 4 + availability and its overall variability. Soil NO 3 − only had significant cross-correlation with aboveground biomass in un-grazed plots at the fine scale, suggesting that the spatial correlation between plant and soil fertility was affected by grazing. Spatial patterns of studied variables did not respond to grazing intensities at a coarse scale (1–18 m). Our results demonstrated that the grazing intensity altered fine scale processes in this desert steppe and caused divergent responses of spatial distribution of vegetation and soil fertility.

THE EFFECT OF TRANSITION ZONE RESECTION RATE OF TRANSURETHRAL RESECTION OF PROSTATE(TURP) ACCORDING TO THE PROSTATE VOLUME

The amount of senesced biomass in vegetation plays an important role in estimation of carbon storage and plant stress. In this paper, the spectral predictors for estimating senesced biomass were evaluated based on field spectral and corresponding biophysical parameter measurements during the growing seasons of 2009 and 2010 in the desert steppe of Inner Mongolia. Results showed the cellulose absorption index (CAI) was the best one among senesced vegetation coverage indices and band depth indices. The model involving CAI yielded the highest coefficient of determination (R2 = 0.67) and the lowest root mean square error of leave-one-out cross validation (RMSECV = 17.9 g m−2) compared with normalized difference index (NDI) (R2 = 0.21, RMSECV = 27.6 g m−2), soil-adjusted corn residue index (SACRI) (R2 = 0.29, RMSECV = 26.2 g m−2), modified soil-adjusted crop residue index (MSACRI) (R2 = 0.1, RMSECV = 29.5 g m−2), dead fuel index (DFI) (R2 = 0.28, RMSECV = 26.3 g m−2), lignocellulose absorption depth (LCD) (R2 = 0.56, RMSECV = 20.5 g m−2) and lignocellulose absorption area (LCA) (R2 = 0.54, RMSECV = 21.1 g m−2). The results of this study suggest that CAI has good potential to estimate senesced biomass in desert steppe areas.

Influence of historic sheep grazing on vegetation and soil properties of a Desert Steppe in Inner Mongolia

Grazing intensity and grassland degradation in China has increased with a growing livestock population. The Desert Steppe is vulnerable to the impacts of livestock because of relatively short and sparse ground cover and sandy soil. This study investigates the effects of historic sheep grazing on the vegetation and soil properties of a Desert Steppe community. The experiment was conducted at three sites (replicates) in Siziwang Banner in Inner Mongolia with four treatments defined along an historic grazing gradient: ungrazed (control), lightly grazed (LG), moderately grazed (MG) and heavily grazed (HG). The grazing treatments were classified based on species composition and ground cover. The vegetation and soil properties in each treatment and replicate were assessed in fall 2005. The vegetation total N (TN) and P (TP) concentrations and δ 15N levels were not affected ( P > 0.05) by grazing. Grazing increased ( P = 0.02) soil bulk density but had no effect on soil TN and TP concentrations or δ 15N levels ( P > 0.05). However, HG resulted in 16.4, 11.4 and 7.6% reductions in soil organic carbon (OC), TN and TP concentrations, respectively. Grazing had no effect ( P > 0.05) on the concentrations of soil available P, available N (NO 3 − and NH 4 +), electrical conductivity, pH or soluble ions (Na +, K +, Ca 2+, Mg 2+, Cl − and SO 4 2−). The vegetation of the Desert Steppe is generally tolerant of grazing pressure but is relatively unproductive, supporting a smaller number of livestock than the more mesic grasslands. Therefore, treatment differences were generally not detected. However, the combination of sandy soils (∼70%) and generally reduced litter and plant cover with increased grazing pressure suggests that the Desert Steppe is vulnerable to soil erosion. This risk may be reduced by ensuring appropriate grazing pressure and animal distribution with judicious herding.

Changes in soil properties and vegetation following exclosure and grazing in degraded Alxa desert steppe of Inner Mongolia, China

Livestock grazing is recognized as one of the main causes of vegetation and soil degradation and desertification in arid and semiarid northern China. In this paper, soil properties and plant characteristics in a typical degraded area in desert steppe of Alxa were studied. The study focused on the effects of grazing on soil properties and vegetation changes under three management regimes: continuous year-long livestock grazing (FG), grazing excluded for 2 years (2EX) and grazing excluded for 6 years (6EX). Results showed that exclosure enhanced soil organic carbon (SOC) and total N accumulation, and decreased pH and bulk density. Soil organic carbon and total N in the 0–20 cm soil increased significantly with exclosure period, with 22% higher SOC, and 14% higher N in 6EX as compared with FG. Data indicated a considerable difference in soil particle size distribution between the exclosure and grazed area, and soil coarse sand fraction (>0.25 mm) in the grazed area was 16–26% higher than that in the exclosure. Plant cover was ranked according to 6EX > 2EX > FG, with a high of 46% (6EX) to a low of 31% (FG). Plant biomass was similarly ranked and vegetation diversity increased with increasing exclosure period. The results suggested that while continuous overgrazing in the erosion-prone desert steppe was detrimental to soil and vegetation, this can be reversed and significant increases in soil fertility, vegetation diversity, cover and biomass can be achieved with the implementation of protecting practices.