To explore the effects of drought and salt stress on germination characteristics of halophytes, this study simulated drought stress with different concentrations of PEG-6000 and four sodium salts (NaCl, Na₂SO₄, NaHCO₃, Na₂CO₃) to evaluate the effects of those treatments on the seed germination characteristics of Halogeton glomeratus. It was found the germination percentage and germination energy decreased with increasing PEG-6000 concentration, while the seedling fresh weight, dry weight, plant height and root activity initially increased and then decreased at higher PEG-6000 concentration. Cluster analysis and principal component analysis showed that the different PEG-6000 concentrations could be divided into two groups with 6% PEG-6000 as the point of separation. Fresh weight appeared to be an important parameter. In addition, germination percentage germination energy, seedling fresh weight, dry weight, plant height and root activity declined with increase in concentration of the four sodium salts. This indicated that salt stress inhibited seed germination and seedling growth, with the effects of the four tested sodium salts ranked: Na₂CO₃>NaHCO₃>NaCl>Na₂SO₄. Cluster analysis and principal component analysis showed that the sodium salt concentrations were divided into two groups with the separation points falling at 50.00 mmol·L^-1 NaHCO₃, 62.50 mmol·L^-1 Na₂SO₄, 25.00 mmol·L^-1 Na₂CO₃ and 100.00 mmol·L^-1 NaCl. Among the plant traits evaluated as indicators of H. glomeratus stress tolerance in the germination stage, the germination index was the key indicator of NaHCO₃ and Na₂SO₄ stress, root activity emerged as the primary indicator of Na₂CO₃ stress and dry weight was the major indicator of NaCl stress in H. glomeratus.

Understanding of the transformations and recycling processes of carbon, nitrogen and phosphorus in the soil rhizosphere is fundamental to solving the problems currently limiting the sustainable utilization of grassland agricultural ecosystems and improving grassland productivity. Rhizosphere processes in grassland can reflect the soil carbon, nitrogen and phosphorus nutrient turnover rates, affect the competition for and capture of nutrients by plants and soil microorganisms, and also determine the nutrient balance of each component in the rhizosphere microenvironment. Compared with crop systems, the coupling between carbon, nitrogen and phosphorus in grassland is stronger. Therefore, the structure and function of rhizosphere micro-ecosystems play an important role in maintaining nutrient transformation and circulation. Many literature reports indicate that the critical factor that regulates the rhizosphere microenvironment is the key substance of the plant and soil for material exchange and information transmission. The root exudates and rhizosphere exudates are also the key substances that mediate rhizosphere microorganisms and enzyme activities. When the grassland environment changes, the rhizosphere exudates, rhizosphere enzyme activities, and the composition and diversity of rhizosphere soil microorganisms will also change fundamentally, which will cause a change of supply and availability of soil nutrients, and in turn will affect grassland productivity and utilization efficiency of nutrients. So, further research on the regulation mechanism of nutrient cycling in grassland rhizosphere process is very important for revealing the distribution and utilization of nutrients and nutrient exchanges between grassland plants and microorganisms. This article reviews the mechanisms and interactions involving rhizosphere exudates, rhizosphere enzymes, and rhizosphere microorganisms involved in nutrient cycling, summarizes the mechanisms of grassland rhizosphere processes contributing to nutrient cycling and provides a perspective for consideration when formulating future research on rhizosphere microdomains in grassland ecosystems.

This study investigated the relationship between soil moisture and vegetation cover in alpine steppe meadow in the Qilian Mountains with the aim of improving the precision of remote sensing estimates of soil moisture and vegetation cover. Six sample areas with different stocking rates of Cervus elaphus kansuensis (1.00, 1.45, 2.45, 3.45, 4.85, 6.90 AUM·ha^-1) in were set up, AUM means animal unit. Through comparing data from monthly field measurement of vegetation cover and soil moisture and SPOT-TM images combining Landsat5 multispectral images and SPOT2 panchromatic images, we analyzed the relationship between soil moisture, vegetation cover and normalized difference vegetation index (NDVI) and quantitatively explored the dynamics of seasonal change in vegetation cover and soil moisture in the sample areas in the Qilian Mountain alpine steppe. Except for Achnatherum inebrians, Convolvulus ammannii and Stragalus leucocephalus, the response of population cover to surface soil moisture was relatively sensitive, with the population cover of species inversely proportional to soil moisture in the range between c. 5% and c. 25%. The response of plant community cover to surface soil moisture was also relatively sensitive. In the soil moisture range from 10.0% to 1.1%, the community cover increased in the inverse proportional function. The results are highly relevant to remote sensing monitoring of the drought resistance and water use efficiency of plant species, populations and communities in arid and semi-arid steppe grassland, and provide scientific data for vegetation and soil moisture management in steppe grasslands.

Based on a light-use efficiency model and MODIS data, the net primary productivity (NPP) of grassland during the growing seasons from 2000 to 2018 in native grassland in Inner Mongolia was continuously estimated, and the spatial-temporal change trend of NPP over the past 20 years was also analyzed using a least square method at pixel scale to determine the degree of grassland degradation. It was found that NPP increased from west to east across Inner Mongolia, with an annual average of 198.04 g C·m^-2·yr^-1. An area of potential grassland degradation of 162200 km² was identified. The areas of severely and heavily degraded grassland identified were 2000 and 11100 km², respectively. The latter were mainly distributed in areas with intensive human activities, such as mining areas, or construction land and its surrounding areas. In terms of grassland types, the potentially degraded areas of temperate steppe, temperate meadow, temperate desert and temperate desert-steppe were 52200, 14000, 40400 and 22100 km² respectively. Through analyzing the correlation between NPP and climate factors in the last two decades, it was found that NPP is significantly correlated with precipitation, but has no correlation with temperature. The response of NPP to precipitation was the most sensitive in temperate meadow, that of temperate desert steppe was the second, and that of temperate steppe was the lowest. Based on the above results, this paper puts forward some suggestions for grassland ecological protection.

This research aimed to clarify the effects of fungicides applied in Medicago sativa production on the safety of an important pollinating insect, the honeybee (Apis mellifera), One-day-old adult honeybees were fed a diet containing dimetachlone, prochloraz, iprodione, at a range of concentrations (diluted with water 1:500, 1:1000, 1:1500, 1:2000 and 1:2500) or no fungicide (Control). Subsequently, the activities of three protective enzymes, superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and three detoxifying enzymes, carboxylesterase (CarE), glutathione S-transferase (GST), cytochrome P450 (P450) in the honeybees were measured. It was found that different concentrations of all the three fungicides could induce increased activities of SOD and POD in the honeybees. In particular, treatment with prochloraz solution at the 1:1500 dilution (0.17 mg·L^-1) induced a 1.82-fold SOD activity and a 5.40-fold POD activity compared to the Control treatment. All three fungicides showed low concentration induction and high concentration inhibition of CAT, CarE and GST activities, and showed inhibition (prochloraz) or induction (dimetachlone and iprodione) of P450 activity. With extended treatment time, the 1:1000 dilution of all three fungicides (0.40, 0.25 and 0.50 mg·L^-1 of dimetachlone, prochloraz, and iprodione, respectively) showed an overall induction effect on the activities of the three protective enzymes in Italian bees, but a variable effect on the activities of detoxifying enzymes. Specifically, dimetachlone initially increased the activities of the three protective enzymes and then inhibited activity after 6 h; iprodione induced P450 activity at all times, but inhibited the activities of CarE and GST in the first 12 h, then induced their activity thereafter; prochloraz elicited a gradual decrease in P450 activity with time, but initially induced then later inhibited the activities of CarE and GST. The results indicate that Italian bees can reduce the negative effects of fungicides by regulating the activities of protective and detoxifying enzymes in their bodies, but the fungicides have an impact on the normal physiology and metabolism of bees, even so. Therefore, care should be taken when applying fungicides to protect bees and ensure their safety while pollinating agricultural crops.

This research studied the distribution of plant communities in response to soil environmental factors in desert steppe. We selected a soil habitat transition gradient from sierozem to sandy soil in Yanchi, Ningxia, China. Within, at the edge of, and outside of the sierozem habitat, vegetation characteristics and soil sampling were conducted using a line transect method. Based on the soil environmental factors and community species composition data, we quantitatively classified the plant communities using multivariate regression trees and redundancy analysis. Then we analyzed the differences between the different plant communities using principal component analysis. It was found that dominant species of the plant communities changed from Stipa breviflora+Cleistogenes squarrosa+Thermopsis lanceolate to Sophora alopecuroides+Pennisetum centrasiaticum and to Artemisia scoparia+Salsola collina across the soil gradient. Key soil factors associated with the shift of plant community species dominance included soil coarse sand, soil organic carbon and soil total phosphorus contents. Across the habitat gradient from sierozem to sandy soil, height, cover and biomass of the plant communities showed a statistically significant increase, community species abundance showed a significant decrease, and plant community diversity showed an increase and then a decrease. As soil texture became coarser and soil nutrient content decreased along the gradient, perennial plant communities were replaced by annual plant communities. Compared with the plant communities in the sierozem habitat, the proportion of perennial plant species, plant species diversity and biomass were low in sandy habitats.

Grassland is an important natural resource and plays a key role in maintaining the stability of ecosystems on a regional scale. Confirmation of grassland contracts and property rights provides an institutional guarantee for grassland ecological protection and development, and is a specific measure to implement the relevant central government requirements. Previous research showed that the speed of determining grassland ownership varies from region to region due to unique local factors in the various grassland areas in China, and in some regions the progress towards determining the ownership of grasslands is relatively slow. Based on analysis of the historical background and current situations relating to contract and property confirmation for grasslands, we here summarize the basic work in grassland contract and property confirmation, including data collection, contract content, contract optimization, issuing of certificates of ownership, landholder training, information management and improvement of grassland dispute resolution mechanisms, et al. The thinking of the planning sector in grassland management including the main building blocks, basic function, workflow, key technologies, is put forward. Finally, consideration of and suggestions for the next stage of the work involving ‘three property rights separation’ are put forward. This research is of great significance to furthering the development of the contract and information management of grasslands in China.

The effect of nitrogen fertilizer application rate on chlorophyll fluorescence characteristics and dry matter accumulation of switchgrass (Panicum virgatum) is of great significance for the improvement of light use efficiency and biomass yield of switchgrass in saline-alkali land. In this research, the patterns of variation in chlorophyll fluorescence parameters and dry matter accumulation in switchgrass were studied in field conditions with a range of nitrogen application treatments: no nitrogen (0 kg·ha^-1, N₀), low nitrogen application (60 kg·ha^-1, N₆₀), medium nitrogen application (120 kg·ha^-1, N₁₂₀) and high nitrogen application (240 kg·ha^-1, N₂₄₀), and the comprehensive effect of nitrogen application on chlorophyll fluorescence and dry matter accumulation in switchgrass was evaluated using a multivariate Grey relational analysis procedure. It was found that: under N₆₀, N₁₂₀ and N₂₄₀ treatments, the PSⅡ maximum photochemical efficiency (F_v/F_m), PSⅡ actual photochemical quantum efficiency (Φ_PSⅡ), potential activity (F_v/F_o), photochemical quenching (qP), non photochemical quenching (NPQ) and biomass yield were significantly higher, and the heat dissipation of quantum ratio (F_o/F_m) was significantly lower than for the N₀ treatment during the flowering and seed maturation stages of switchgrass development. During the flowering period of switchgrass, the PSⅡ potential activity (F_v/F_o) was initially increased and subsequently decreased across the range of nitrogen application rates, with a maximum observed value of 3.13 at N₁₂₀ (increased 16.26% compared with N₀). The effect of nitrogen application rate on dry matter accumulation differed between the crop growth stages. Dry matter accumulation was high during jointing and booting periods, reached its maximum at the seed filling stage, and decreased slightly thereafter. The maximum observed dry matter accumulation (378.13 g·hole^-1) occurred under the N₂₄₀ treatment during the post-flowering stage and was, respectively, 24.33%, 20.09% and 7.24% higher than that of the N₀, N₆₀ and N₁₂₀ treatments. Grey relational analysis showed that the association between the weighted correlation index and the ideal fertilization level was the highest under the N₂₄₀ treatment. In summary, the N₂₄₀ treatment in this study in the Yinbei saline-alkali area of Ningxia optimized the photochemical activity of PSⅡ and dry matter accumulation of switchgrass.