Fenced Grasslands Research Articles

Microbial necromass in soil profiles increases less efficiently than root biomass in long-term fenced grassland: Effects of microbial nitrogen limitation and soil depth

Grassland fencing is acknowledged as a crucial initiative to enhance biodiversity and to increase soil organic carbon (SOC) content in ecologically fragile regions or barren systems. Theoretical perspectives propose that fencing induced an increase in root biomass, and its penetration into the soil profile introduced organic matter that facilitated SOC formation through microbial necromass and root residues. It is hypothesized that long-term grassland fencing increases root biomass, thereby enhancing SOC formation within the soil profile through microbial residues in badland ecosystems. To test this hypothesis, we selected grasslands subjected to varying durations of fencing post-grazing (i.e., 10, 15, 20, 30, and 40 y). Our investigation aimed to clarify microbial necromass dynamics in 0–100 cm soil profiles after fencing and to identify the influencing factors. Long-term grassland fencing (i.e., >30 y) increased root biomass by 160 %, SOC by 69 %, and necromass by 41 % compared to grazed grassland within the 0–40 cm horizon; in contrast, increased root biomass by 870 %, SOC by 111 %, and necromass by 46 % in the 40–100 cm horizon. Necromass in deep soil (40–100 cm) accounted for about 50 % of total residues in the 0–100 cm profile. Increased root and living microbial biomass stimulated the necromass accumulation, with a more pronounced increase in fungal residues compared with bacterial residues. Nonetheless, microbial nutrient limitation increases C or N-acquisition enzyme coefficients, which subsequently reduced fungal and bacterial residues and stimulated their recycling. Despite substantial increases in root biomass within the soil profile after fencing, limitation of microbial N and depth reduced the effectiveness of enhancing SOC and necromass. In conclusion, although microbial residues were the important source of SOC in grasslands of the Loess Plateau, microbial N limitation impeded necromass accumulation, and the interplay of root biomass, soil depth, and nutrient limitation regulated the dynamics of necromass following grassland fencing.

Flooding Length Mediates Fencing and Grazing Effects on Soil Respiration in Meadow Steppe.

Grassland management affects soil respiration (Rs, consists of heterotrophic respiration and autotrophic respiration) through soil micro-ecological processes, such as hydrothermal, plant root, organic carbon decomposition and microbial activity. Flooding, an irregular phenomenon in grasslands, may strongly regulate the response of soil respiration and its components to grassland management, but the regulatory mechanism remains unclear. We conducted a 3-year experiment by grassland management (fencing and grazing) and flooding conditions (no flooding (NF), short-term flooding (STF) and long-term flooding (LTF)) to study their effects on Rs and its components in a meadow steppe in the Hui River basin of Hulunbuir. We found differences in the patterns of Rs and its components under grassland management and flooding conditions. In 2021-2023, the temporal trends of Rs, heterotrophic respiration (Rh) and autotrophic respiration (Ra) were generally consistent, with peaks occurring on days 190-220, and the peaks of grazing were higher than that of fencing. In NF, Rs of grazed grassland was significantly higher than that of fenced grassland in 2021-2022 (p < 0.05). In STF and LTF, there was no significant difference in Rs between fenced and grazed grassland (p > 0.05). The dependence of Rs on soil temperature (ST) decreased with increasing flooding duration, and the dependence of Rs on ST of grazed grassland was higher than fenced grassland under NF and STF, but there was no difference between fenced grassland and grazed grassland under LTF. In addition, Rh was more sensitive to ST than Ra. This may be due to the different pathways of ST effects on Rs under grazing in different flooding conditions. Our study indicates that the effect of flooding on Rs is the key to the rational use of grassland under future climate change. To reduce regional carbon emissions, we recommend grazing on flooding grassland and fencing on no-flooding grassland.

Different responses of leaf and root economics spectrum to grazing time at the community level in desert steppe, China

The plant economic spectrum can explain the trade-off strategies of vascular plants between resource acquisition and storage. Grazing can alter the plant functional characteristics of grassland ecosystems, resulting in a shift in plant resource acquisition strategies. Taking fenced grassland as a control, in this study we quantified six leaf traits and four root traits of 14 plant species (those that comprised >85 % of the species community abundance) of different grazing time grasslands in desert grasslands in Ningxia. We examined how grazing time shapes the functional structure of plant communities and the resource acquisition strategy. The results revealed an inverse pattern of the fast-slow economic spectrum of leaf and root traits; that is, as grazing time increased, the leaf traits shifted from an acquisitive type to a conservative type of resource acquisition strategy. In contrast, the root traits showed a shift from a conservative type to an acquisitive type of resource acquisition strategy. Grazing time leads to a whole plant economic spectrum, and plant functional traits may facilitate their response to environmental change, the study of which can hereby deepen our understanding of the plant economics spectrum. Our study provides new evidence that leaf and root resource acquisition and utilization are relatively independent under grazing pressure.

Grazing exclusion altered the pattern of the soil seed bank but not the aboveground vegetation along an altitudinal gradient in alpine grassland

AbstractGrazing exclusion by fencing is the principal option to restore degraded grassland, but its effects on recovery and succession of vegetation are not clear, especially in high mountain areas. In this study, we aimed to fill this gap by assessing the effect of seven‐year grazing exclusion on vegetation and soil seed bank along an altitudinal gradient in northern Tibet, China. Species richness, Shannon‐Wiener index and Simpson's diversity index of vegetation and soil seed bank, seed density, and the Sørensen index all displayed a mid‐domain (hump‐shaped) pattern with increasing altitude, except for the Shannon‐Wiener and Pielou indices of soil seed bank in fenced grasslands. These results demonstrated that the impact of grazing exclusion on the patterns of vegetation and soil seed bank change with altitude but are not synchronous. Grazing exclusion increased vegetation coverage but decreased soil seed bank density, and species diversity of vegetation and soil seed bank. The Sørensen index (0.03–0.2) and non‐metric multidimensional scaling (NMDS) analysis indicated that the species composition differed between vegetation and soil seed bank, but no difference was found between fenced and grazed grasslands. The low similarity suggests that the soil seed bank contributes little to vegetation recovery in alpine grassland. Seven‐year grazing exclusion had no effect on either vegetation succession or species composition of soil seed bank in alpine grassland. Overall, our findings suggest reconsidering the use of long‐term grazing exclusion to restore degraded grassland at high altitudes (above 4400 m above sea level) on the Tibetan Plateau.

Alpine Grassland Aboveground Biomass and Theoretical Livestock Carrying Capacity on the Tibetan Plateau

The accurate simulation and prediction of grassland aboveground biomass (AGB) and theoretical livestock carrying capacity are key steps for maintaining ecosystem balance and sustainable grassland management. The AGB in fenced grassland is not affected by grazing and its variability is only driven by climate change, which can be regarded as the grassland potential AGB (AGBp). In this study, we compiled the data for 345 AGB field observations in fenced grasslands and their corresponding climate data, soil data, and topographical data on the Qinghai-Tibetan Plateau (TP). We further simulated and predicted grassland AGBp and theoretical livestock carrying capacity under the climate conditions of the past (2000–2018) and future two decades (2021–2040) based on a random forest (RF) algorithm. The results showed that simulated AGBp matched well with observed values in the field (R 2 = 0.76, P < 0.001) in the past two decades. The average grassland AGBp on the Tibetan Plateau was 102.4 g m–2, and the inter-annual changes in AGBp during this period showed a non-significant increasing trend. AGBp fluctuation was positively correlated with growing season precipitation (R 2 = 0.57, P < 0.001), and negatively correlated with the growing season diurnal temperature range (R 2 = 0.51, P < 0.001). The average theoretical livestock carrying capacity was 0.94 standardized sheep units (SSU) ha–1 on the TP, in which about 54.1% of the areas showed an increasing trend during the past two decades. Compared with the past two decades, the theoretical livestock carrying capacity showed a decreasing trend in the future, which was mainly distributed in the central and northern TP. This study suggested that targeted planning and management should be carried out to alleviate the forage-livestock contradiction in grazing systems on the Tibetan Plateau.

Response of soil aggregate stability and erodibility to different treatments on typical steppe in the Loess Plateau, China

Vegetation restoration is an effective means to increase the stability of aggregates and the ability of soil to resist erosion. At present, there are few studies on soil aggregate stability in contour trench and fish‐scale pit grasslands (FPGs). Therefore, to determine the effects of different treatments on the stability of aggregates in the Loess Plateau, grazing grassland (GG), fencing grassland (FG), contour trench grassland (CG), and FPG were selected to compare distributions of soil aggregates, the soil aggregate stability, and soil erodibility K value. The results showed that &lt;0.25‐mm and &gt;5‐mm aggregates were the main components. The mass percentage of 5–0.25‐mm aggregates in FG was significantly higher than that in GG, CG, or FPG. The proportion of large water‐stable aggregates, mean weight diameter, and geometric mean diameter values were significantly higher in GG than in FG, CG, or FPG for topsoil, while FG had the highest WR0.25 (70.21%) for subsoil. The opposite trends were found for fractal dimension and percentage of aggregate destruction values. The K values for CG and FPG were found to be significantly higher than those for GG and FG. A correlation analysis indicated that soil organic carbon can promote the stability of soil aggregates. A negative correlation was found between the comprehensive score and K values. In summary, FG had positive effects on soil aggregate stability and erodibility. This finding can guide the local government to adopt enclosure measures when implementing ecological restoration of degraded grasslands.

半干旱黄土区不同管理措施下草地群落结构对短期氮、水添加的响应

氮沉降和降水变异显著影响草地群落结构和功能，但缺乏对不同管理措施下草地群落结构对氮沉降和降水变异响应的研究。为模拟不同管理措施下草地群落结构对氮沉降和降水变异的响应特征，以半干旱黄土区云雾山国家自然保护区典型草原为研究对象，系统分析了在封育、刈割和火烧三种管理措施下，氮添加和水添加对群落地上生物量、功能群组成和群落多样性的影响。结果表明，氮添加和水添加对地上生物量、功能群组成和群落多样性指数的影响因管理措施不同有所差异。（1）在封育草地上，氮添加显著降低物种多样性，对地上生物量影响较小；水添加显著增加物种多样性指数，氮添加和水添加的交互作用显著增加地上生物量、禾本科所占比例和莎草科所占比例；物种多样性指数均与地上生物量无显著相关，与不同功能群所占比例显著相关。（2）在刈割草地上，氮添加和水添加显著提高草地群落地上生物量，氮添加和水添加交互作用尤为显著；氮添加和水添加显著增加物种丰富度指数，对物种均匀度影响较小；杂草类所占比例和地上生物量对Shannon-Weiner多样性指数的贡献率较大。（3）在火烧草地上，氮添加和水添加显著提高群落地上生物量，对物种多样性的影响因年份不同有所差异，氮添加和水添加交互作用具有累加效应；Shannon-Weiner多样性指数与地上生物量呈显著负相关，与莎草科所占比例呈显著正相关。研究表明管理措施显著影响群落结构对氮添加和水添加的响应特征，亦改变生产力和物种多样性的关系模式，为更好地应对全球变化进行草地管理提供数据支撑。;In the context of global climate change, nitrogen (N) deposition and precipitation variation significantly affect grassland community structure and function. Grassland management has become the research focus in the field of ecology in the past decades. However, little research so far has explored the response of grassland community with different management practices to N deposition and precipitation variation. This study was conducted in the typical grassland of Yunwu Mountain National Grassland Nature Reserve, and systematically analyzed the effects of short-term N addition and water addition on aboveground biomass, functional group composition and community diversity in the fenced grassland, cut grassland and burned grassland, in order to simulate the response of grassland community with different management practices to N deposition and precipitation variation. Results showed that effects of N addition and water addition on aboveground biomass, functional group composition and community diversity indices varied with different management practices. 1) In the fenced grasslands, N addition significantly decreased species diversity indices and had no effect on aboveround biomass. Water addition significantly increased species diversity indices. The interaction of N addition and water addition significantly increased aboveground biomass and the proportions of gramineae and cyperaceae. Species diversity indices were not significantly correlated with aboveground biomass, but species diversity indices had significant correlations with the proportion of different functional groups. The proportion of gramineae and weeds contributed the most to Shannon-Weiner diversity index. 2) In the cut gasslands, N addition and water addition (especially for the interaction of N addition and water addition) significantly increased aboveground biomass. N addition and water addition significantly decreased the proportion of gramineae, but significantly increased the proportion of weeds. N addition and water addition significantly increased species richness index, but had little effect on species evenness. The proportion of weeds and aboveground biomass contributed significantly to Shannon-Weiner diversity index. 3) In the burned grasslands, N addition and water addition significantly increased the community above-ground biomass. The effects of N and water addition on functional group composition and community diversity indices varied with different years. The interaction of N addition and water addition had culnulative effect. Shannon-Weiner diversity index was negatively correlated with aboveground biomass, and positively correlated with the proportion of cyperaceae. In all, management practices significantly affected the response of community structure and functions to N addition and water addition. Management practices also altered the relationship between grassland community primary productivity and species diversity. Community functional group contributed significantly to species diversity. This research might provide data support for the grassland management in response to global climate change.

Grazing Exclusion Effects on the Relationship between Species Richness and Vegetation Cover in Mongolian Grasslands

Understanding the role of plant diversity in maintaining vegetation cover is a central focus of assessing the vegetation dynamics of grasslands. The present study assessed the relationship between species richness and vegetation cover, as well as underlying biological mechanisms in three Mongolian grasslands, namely meadow, dry steppe and mountain steppe.Each of three grasslands was set by two treatments: grazing exclusion by fence and freely grazing. I measured plant species richness, vegetation cover, height and phenology. I examined three biological mechanisms, namely plant interactions, the role of dominant species and vegetation growth periods.The results showed that higher species richness generally increased vegetation cover independent of fencing treatment and grassland type. Plant interactions were the strongest in fenced plots of the mountain steppe. Dominant plant species invested more in vegetation cover rather than the height in grazed plots than fenced ones in Mongolian grasslands. Taking vegetation growth periods into account did not alter the strength and the direction of the relationship between species richness and vegetation cover. I thus infer that examining changes in species diversity will allow for a better understanding of vegetation cover dynamics in grasslands. This will help to assess how ecosystem functioning might be impacted by grazing disturbances in Mongolia.

Asymmetric effects of litter accumulation on soil temperature and dominant plant species in fenced grasslands

AbstractExcess litter accumulates on the soil surface of fenced grasslands and alters the abiotic environment and plant population dynamics. However, little is known about the effect of litter accumulation on the interaction between environmental factors and plant population characteristics in fenced grasslands, especially over different time scales. We applied a three‐year litter removal experiment to two kinds of fenced grasslands in Inner Mongolia, China. We measured soil temperature in situ and plant phenology and population characteristics of three dominant species (Stipa grandis, S. krylovii, and Leymus chinensis). During the growing season, litter accumulation (i.e., the control) significantly decreased soil temperature, with a larger effect in the daytime than at night. The diurnal negative effect gradually weakened across the growing season, whereas the negative effect in the nighttime shifted to a positive effect on soil temperature in the late growing season. The decreased soil temperature delayed plant phenology, with longer delays in S. grandis and S. krylovii than L. chinensis. Litter accumulation also significantly increased the height, cover, root biomass, and relative dominance of L. chinensis but decreased cover, density, root biomass, and relative dominance of both Stipa, driving replacement of S. grandis or S. krylovii by L. chinensis in two grasslands. Our findings emphasize the critical function of litter in grassland management and provide a new insight to elucidating the mechanism of how litter accumulation regulates the abiotic environment, community composition and structure, and successional change in fenced grasslands.

Assessment of soil quality indexes for different land use types in typical steppe in the loess hilly area, China

Soil quality indexes (SQIs) are important for evaluating grassland ecosystems. The objective of this study was to assess different land-use soil quality using total data set, minimum data set (MDS), and revised minimum data set (RMDS) indicator selection methods and linear and non-linear scoring methods. Four land-use, which were including grazing grassland (GG), fencing grassland (FG), contour trench grassland (CG) and fish-scale pits grassland (FPG) in a typical steppe of loess hilly area in Ningxia, were taken as the research object. Eighteen indicators (soil bulk density; GMD: geometric mean diameter; MWD: mean weight diameter; FWC: field water-storage capacity; capillary porosity; total porosity; soil organic carbon; TN: total nitrogen; total phosphorus; AK: available potassium; available nitrogen; microbial biomass carbon; microbial biomass nitrogen; SA: sucrase activity; protease activity; CA: catalase activity; PPA: phosphatase activity; and urease activity) of soil physical, chemical, and biological characteristics of the 0–40 cm soil layer under different land use types were measured. Principal component analysis was used to select the MDS and RMDS. The results showed that three (SA, MWD, and PPA) and six (FWC, GMD, TN, AK, SA, and CA) soil indicators were included in the MDS and RMDS, respectively. The agreement values of SQIs for the linear scoring method were higher than those of the non-linear scoring method. The linear scoring-revised minimum data set was regarded as the most appropriate method to calculate the SQI because of its highest F and CV (Coefficient of Variation) values and correlation coefficient. The ranking of the SQI values of the four land use types was FG > GG > CG > FPG. The results showed that FG is the most beneficial measure for the restoration of degraded grassland, which has important guiding significance for the ecological construction of degraded grassland in the study area.

Studies on Edema Pathema in Hequ Horse in the Qinghai-Tibet Plateau.

As a consequence of contracted and fenced grassland, the incidence of edema pathema in the Hequ horse is rising. The main pathological symptoms are edema, emaciation, anemia, heterophilia, inappetence, and dyskinesia. To study the cause of edema disease in Hequ horse, the Hequ horse farm with a high incidence was chosen as the experimental pasture, and the Azi husbandry experimental station without edema disorder was the control pasture. The research methods in this paper are included: (1) The mineral contents in soil, forage, blood, and liver were analyzed. (2) Routine parameters and biochemical values in blood were also measured. (3) Conduct a prevention trial and a treatment experiment. The results showed that Se contents in soil and forage was much significantly lower than that in the control group (P < 0.01), and there was no significant difference in other elements. Se contents in blood and liver in affected animals were very significantly lower than those of the control group (P < 0.01). Hb, HCT, MCV, and MCH were greatly significantly lower than those in the control group (P < 0.01). Activities of GSH-Px in blood were very significantly lower than those of the control group (P < 0.01). Before the onset season of the disorder in the affected area, Na2SeO3 was used to conduct a prevention trial on 1576 Hequ horses. A dose of 0.03mg Na2SeO3 was given orally per kilogram of body weight, once every 15days and twice continuously. There was no edema illness that year. In the treatment experiment, 235 horses were administered Na2SeO3 orally at 0.04mg per kilogram of body weight, once every 3days for 4 consecutive times, and 198 horses were cured, with a cure rate of 84.26%. Therefore, it is possible that Hequ horse edema pathema is caused by Se deficiency in soil and forage.

Deep soil C and N pools in long-term fenced and overgrazed temperate grasslands in northwest China

Fencing for grazing exclusion has been widely found to have an impact on grassland soil organic carbon (SOC) and total nitrogen (TN), but little is known about the impact of fenced grassland on the changes in deep soil carbon (C) and nitrogen (N) stocks in temperate grasslands. We studied the influence of 30 years fencing on vegetation and deep soil characteristics (0–500 cm) in the semi-arid grasslands of northern China. The results showed that fencing significantly increased the aboveground biomass (AGB), litter biomass (LB), total biomass, vegetation coverage and height, and soil water content and the SOC and TN in the deep soil. The belowground biomass (BGB) did not significantly differ between the fenced and grazed grassland. However, fencing significantly decreased the root/shoot ratio, forbs biomass, pH, and soil bulk density. Meanwhile, fencing has significantly increased the C and N stocks in the AGB and LB but not in the BGB. After 30 years of fencing, the C and N stocks significantly increased in the 0–500 cm soil layer. The accumulation of SOC mainly occurred in the deep layers (30–180 cm), and the accumulation of TN occurred in the soil layers of 0 to 60 cm and 160 to 500 cm. Our results indicate that fencing is an effective way to improve deep soil C and N stocks in temperate grassland of northwest China. There were large C and N stocks in the soil layers of 100 to 500 cm in the fenced grasslands, and their dynamics should not be ignored.

Litter accumulation alters the abiotic environment and drives community successional changes in two fenced grasslands in Inner Mongolia.

Fencing is an effective and practical method for restoring degraded grasslands in northern China. However, little is known about the role of excess litter accumulation due to long‐term fencing in regulating abiotic environment and driving changes in community structure and function. We conducted a three‐year field experiment in two fenced grasslands in Inner Mongolia, and monitored light quantity, soil temperature, and soil moisture continuously, and determined community height, community aboveground net primary productivity (ANPP), and the relative dominance of different plant functional groups. Litter accumulation reduced light quantity and soil temperature but increased soil moisture. The regulating effects of litter accumulation on soil temperature and soil moisture fluctuated temporally and gradually weakened over the growing season. Litter accumulation also altered community vertical structure and function by increasing community height and ANPP. The increase in soil moisture increased the relative dominance of rhizome grasses but suppressed bunch grasses, thereby shifting bunch grass grasslands to rhizome grass grasslands. Our findings provide a potential mechanism for community succession in the context of litter accumulation in fenced grasslands and indicate that the vegetation and ecosystem services of degraded grasslands are improved after appropriate fencing.

Dynamic forage-livestock balance analysis in alpine grasslands on the Northern Tibetan Plateau

Forage-livestock balance is important for sustainable management of alpine grasslands under global change, but the robustness of diverse algorithms for assessing forage-livestock balance is still unclear. This study compiled long-term (2009–2014) field observations of aboveground biomass (AGB). Using climate and remote sensing data, we evaluated the inter-annual dynamics of the forage-livestock balance on the Northern Tibetan Plateau (NTP). Here, we assumed that AGB dynamics in fenced grasslands (AGBF) is only driven by climate change; whereas AGB dynamics in open grasslands grazed by livestock (AGBG) is driven by a combination of climate change and human activities. Thus, human-induced change in AGB (AGBH) could be estimated via the difference between AGBF and AGBG. Furthermore, differences in the temporal trends between AGBF and AGBH could indicate the state of forage-livestock balance, overgrazed or not, in alpine grasslands. Our results showed that the overall status of the forage-livestock balance from 2000 to 2006 was overgrazed owing to poor climatic conditions. Ecological projects and economic policies for alpine grassland conservation had not been implemented at that time, which also resulted in local overgrazing. From 2006 to 2014, the alpine grasslands in some areas were in a less-grazed state. We suggest that the livestock number could potentially increase in northern NTP and should be reduced or strictly controlled to maintain the balance between livestock and forage in the southern and southeast areas. In conclusion, the results of this study suggest that the evaluation of the forage-livestock balance in the NTP should include the local climatic conditions and make better use of grassland resources while ensuring ecological security.

Nitrogen addition decreased soil respiration and its components in a long-term fenced grassland on the Loess Plateau

Knowledge of the impact of N enrichment on soil respiration components is critical for understanding carbon (C) cycling and its feedback processes with climate change. We conducted three N level addition experiments, control (CK, 0 g N m−2yr−1), low nitrogen addition (LN, 10 g N m−2yr−1), and high nitrogen addition (HN, 20 g N m−2yr−1)) to investigate the response of microbial and root respiration to N enrichment in a long-term fenced grassland on the Loess Plateau of China. Compared to the control, both the LN and HN treatments generally decreased soil respiration and its two components for both years. Under N addition, the decreased rates of root respiration and microbial respiration were significantly and positively correlated with the monthly root production and soil microbial biomass C, respectively. Nitrogen addition decreased the Q10 values of root and microbial respiration, with the reduction more pronounced in root respiration. Overall, our results suggest that N enrichment may reduce the soil C loss through CO2 emissions. With global warming, soil C loss will be less due to the lower Q10 values of root and microbial respiration on the Loess Plateau of China under future scenarios of N deposition.

Effects of grazing exclusion on the grassland ecosystems of mountain meadows and temperate typical steppe in a mountain-basin system in Central Asia's arid regions, China

Grazing exclusion has been proposed as a method of restoring degraded grassland ecosystems. However, its effectiveness remains poorly understood in mountain-basin grasslands in arid regions. Thus, we investigated the plant community characteristics, C and N storage levels, and soil organic carbon and total nitrogen concentrations and storage within the upper 0–40 cm soil layer in a grazed grassland (GG) and a fenced grassland (FG) with grazing exclusion in mountain meadow (MM) and temperate typical steppe (TTS) habitats in a mountain-basin ecosystem in an arid region of Central China, which are both vital grassland resources for livestock grazing and ecological conservation. In MM, our investigation revealed that grazing exclusion was beneficial to the productivity, coverage, height, diversity, and C and N storage of aboveground plants. However, grazing exclusion was not an effective option for soil C and N sequestration. In TTS, grazing exclusion effectively improved the plant productivity, coverage, height, plant and soil C and N sequestration, although it was not beneficial for maintaining plant diversity. Our findings suggest that reduced or rotational grazing may be a better choice than grazing exclusion in MM. In addition, considering the trade-off between biomass productivity and species diversity in TTS, short-term grazing exclusion should be considered. Additionally, grazing exclusion should be combined with other appropriate measures rather than operating on a standalone basis.

Effects of fertilization, burning, and grazing on plant community in the long-term fenced grasslands

Fencing is the common management practice to restore degraded grasslands. However, long-term fencing decreases grassland productivity and species diversity. The study was therefore conducted as a three-year (2011–2013) experiment with a randomized complete block in a grassland fenced for 20 years in the Loess Plateau of China, and the effects of fertilization, burning and grazing on aboveground biomass, species and functional group composition, species and some functional group diversity were analysed. Our results showed that the functional group of perennial bunchgrasses dominated the grassland regardless of management practices. However, burning altered species composition (i.e. the unpalatable species, Artemisia sacrorum) more significantly than fertilization or grazing, and surprisingly, nearly quadrupled the functional group of shrubs and semi-shrubs. Fertilization had a positive effect on the aboveground biomass (44.0%), while clearly reducing species diversity (21.9%). Grazing decreased aboveground biomass, but increased species diversity by 15.9%. This study indicated that fertilization influenced plant community through its impact on aboveground biomass, while burning changed plant community by altering dominant species. Thus, it was concluded that fertilizer could further improve community biomass while burning reduced the edibility of grass. Grazing could be carried out to enhance the biodiversity in the long-term fenced grasslands.

Long-term grazing effects on vegetation characteristics and soil properties in a semiarid grassland, northern China.

Understanding the responses of vegetation characteristics and soil properties to grazing disturbance is useful for grassland ecosystem restoration and management in semiarid areas. Here, we examined the effects of long-term grazing on vegetation characteristics, soil properties, and their relationships across four grassland types (meadow, Stipa steppe, scattered tree grassland, and sandy grassland) in the Horqin grassland, northern China. Our results showed that grazing greatly decreased vegetation cover, aboveground plant biomass, and root biomass in all four grassland types. Plant cover and aboveground biomass of perennials were decreased by grazing in all four grasslands, whereas grazing increased the cover and biomass of shrubs in Stipa steppe and of annuals in scattered tree grassland. Grazing decreased soil carbon and nitrogen content in Stipa steppe and scattered tree grassland, whereas soil bulk density showed the opposite trend. Long-term grazing significantly decreased soil pH and electrical conductivity (EC) in annual-dominated sandy grassland. Soil moisture in fenced and grazed grasslands decreased in the following order of meadow, Stipa steppe, scattered tree grassland, and sandy grassland. Correlation analyses showed that aboveground plant biomass was significantly positively associated with the soil carbon and nitrogen content in grazed and fenced grasslands. Species richness was significantly positively correlated with soil bulk density, moisture, EC, and pH in fenced grasslands, but no relationship was detected in grazed grasslands. These results suggest that the soil carbon and nitrogen content significantly maintains ecosystem function in both fenced and grazed grasslands. However, grazing may eliminate the association of species richness with soil properties in semiarid grasslands.

Leaf meristems: an easily ignored component of the response to human disturbance in alpine grasslands.

Grazing and fencing are two important factors that influence productivity and biomass allocation in alpine grasslands. The relationship between root (R) and shoot (S) biomass and the root:shoot ratio (R/S) are critical parameters for estimating the terrestrial carbon stocks and biomass allocation mechanism responses to human activities. Previous studies have often used the belowground:aboveground biomass ratio (M b/M a) to replace the R/S in alpine ecosystems. However, these studies may have neglected the leaf meristem biomass, which belongs to the shoot but occurs below the soil surface, leading to a significant overestimation of the R/S ratio. We conducted a comparative study to explore the differences between the R/S and M b/M a at both the species (Stipa purpurea, Carex moorcroftii, and Artemisia nanschanica) and community levels on a Tibetan alpine grassland with grazing and fencing management blocks. The results revealed that the use of the M b/M a to express the R/S appeared to overestimate the actual value of the R/S, both at species and community levels. For S. purpurea, the M b/M a was three times higher than the R/S. The M b/M a was approximately two times higher than the R/S for the species of C. moorcroftii and A. nanschanica and at the community level. The relationships between the R‐S and M b‐M a exhibited different slopes for the alpine plants across all the management practices. Compared to the fenced grasslands, the plants in the grazing blocks not only allocated more biomass to the roots but also to the leaf meristems. The present study highlights the contribution of leaf meristems to the accurate assessment of shoot and belowground biomasses. The R/S and M b/M a should be cautiously used in combination in the future research. The understanding of the distinction between the R‐S and M b‐M a may help to improve the biomass allocation mechanism response to human disturbances in an alpine area.

Revegetation as an efficient means of improving the diversity and abundance of soil eukaryotes in the Loess Plateau of China

Different revegetation types have been used to restore degraded soil in the Loess Plateau, China. Most studies have focused on the impact of revegetation types on soil properties. However, we understand little about how different revegetation types influence the diversity and abundance of soil eukaryotic communities. Artificial revegetation types and natural grasslands were selected in semiarid areas, and slope farmland was as the control, and pyrosequencing of the 18S rRNA gene region was used to analyze changes in soil eukaryotic diversity and composition. A total of 41,965 valid sequences were generated using 454 pyrosequencing. The number of sequences per sites ranged from 5488 to 6288, with an average of 5967. At a genetic distance of 3%, the highest eukaryotic diversity was found in artificial forestry, while the lowest in natural fenced grassland. The dominant sampled taxa mainly included fauna, fungi, and flora. At the phylum level, the dominant phyla were: (faunal) Craniata, Nematoda, Arthropoda, Rhizaria; (fungi) Ascomycota, SAR, Mucoromycotina; and (flora) Streptophyta. pH, SWC, TP, SOC, and AP significantly influenced the abundance of some fauna, such as Craniata, Arthropoda, Annelida, Rhizaria, and Amoebozoa. Artificial revegetation has a beneficial impact in improving the diversity and abundance of soil eukaryotes, but long-term grazing exclusion of natural grassland may have a negative impact on the diversity and abundance of soil eukaryotes. Revegetation by afforestation is an ecologically efficient practice for eukaryotes recovery of degraded soil in the Loess Plateau.