Grassland Science最新文献

The addition of self-regenerating annual legumes into permanent pastures can benefit rapid forage growth in early spring, leading to increased pasture production and animal live weight gain (LWG). The objective of this 2-year grazing study was to evaluate the effects of balansa clover (Trifolium michelianum) and subterranean clover (Trifolium subterraneum) on pasture and animal production in an irrigated dairy system in western Oregon, USA. Study results showed that balansa clover has a high potential to increase legume content of establishing pastures in early spring. Legume content of pastures sown with annual legumes increased by 25.3% in early spring compared to pastures sown without annual legumes. However, no significant increase in legume content was observed past the initial year of establishment. The persistence of balansa clover and subterranean clover was low in 2021, at <1% of the botanical composition. The overall benefits of balansa clover in early spring in 2020 were offset by reduced perennial forbs, white clover (Trifolium repens) and chicory (Cichorium intybus), in paddocks that were sown with annual legumes. However, this did not negatively affect the LWGs of heifers. This study found no significant difference between pastures sown with and without annual clovers pastures on dry matter production and animal production. Balansa clover was competitive in the establishment year; however, further research into improving its persistence past establishment is warranted.

Foliar spraying of selenium (Se) during the wheat grain filling period can effectively increase grain Se concentration. However, it is unclear when foliar spraying Se can efficiently increase grain Se concentration. In this study, 0, 18.90, 37.80 and 56.70 g/ha of selenate were sprayed on the leaf blades on the 2nd and 9th day after grain filling, respectively, to investigate the effect of different spraying time points on Se concentration in aerial parts, especially the grains. The results indicated that Se concentrations in aerial parts increased with selenate levels at different time points. On the 7th day after spraying Se, Se concentrations in leaf blades, leaf sheaths, nodes, internodes and cobs sprayed with Se on the 2nd day after grain filling were significantly higher than those in corresponding parts sprayed with Se on the 9th day (p < 0.05). However, the Se concentrations of aerial parts on the 14th day after spraying Se and at grain maturity on the 2nd day after grain filling were significantly lower than those on the 7th day after spraying Se on the 9th day (p < 0.05). Furthermore, on the 7th day and 14th day after spraying Se and at grain maturity, grain Se concentrations sprayed with Se on the 2nd day after grain filling were significantly lower than those sprayed with Se on the 9th day (p < 0.05). These results suggested that spraying Se on the 9th day after grain filling was beneficial for increasing the Se concentration in aerial parts, especially grains. This study provides a theoretical basis for efficiently enhancing grain Se concentration and producing Se-enriched bran and straw, which is of great significance for improving Se intake of livestock, enhancing livestock immunity, and promoting the development of animal husbandry.

The body mass of small mammals is widely regarded as an indicator of habitat quality, with trade-offs between anti-predator and energy-building behaviors noted across many species and habitat conditions as suggested by optimal foraging theory. In this study, however, grazing by domestic yak was noted to mediate this effect, affecting both the body mass and behaviors of plateau pika, Ochotona curzoniae, which deviated from expected ecological patterns. Specifically, we compared conditions of plateau pika at 16 trap sites across a range of habitats on the Tibetan plateau, each characterized by herders according to their seasonal use as winter, spring, or summer pastures, and to their vegetative conditions. Plateau pika body mass at herders' tent sites where female and young domestic yak sleep was about 6% higher than at yak foraging sites and 10% higher than fenced areas (where yak are excluded) despite the additional disturbance encountered at tent sites. Mean body mass of plateau pika also decreased with increasing slope, and adult body mass was lower in spring compared to winter and summer seasons. Furthermore, more pika burrows were found near herders' tent sites, with burrows exhibiting significantly lower vegetation cover. Pika foraging behavior was most frequent in yak bedding areas (near herders' tent sites), and pika vigilant behavior at yak foraging areas. Recalling that foraging and vigilant (predator avoidance) behaviors constitute energy trade-offs, we speculate that these unexpected findings may result from the combined effects of soil erosion (due to surface disturbances) and fertilization (with yak dung) at yak resting sites, which could enable higher population densities and body masses of plateau pika despite lower vegetation cover at the tent sites – most likely due to critical behavioral adaptations, ecological dynamics such as predator-prey relations and other multi-dimensional and nonlinear reasons.

China launched the Grassland Ecological Subsidy Policy in 2011 for restoring grassland ecology by paying pastoralists to downsize stocking on the degraded grasslands and compensate their income loss from livestock reduction. The policy, the largest payment for ecosystem services program targeting pastoralism in the world, has been so far through two 5-year stages: 2011 to 2015 with a subsidy at 1.5 CNY per standard mu per year and 2016 to 2020 at 2.5 CNY increased to boost the stocking reduction. How was the boost effect? We investigated that stocking responses in 2010, 2015 and 2018 using the panel data of 410 herder households in the subpolicy forage-livestock balance areas in Inner Mongolia, China, tested various attributes on stocking rate and stocking reduction rate at the two stages of the policy using econometric models of random effects and ordinary least squares. This study is the first empirical case containing the two 5-year policy data and with both subsidy and precipitation effects. We confirmed the regulating impact of precipitation on the subsidy policy effect, and more precipitation in the second stage appeared to offset the effect of the increased subsidy. We suggested changing the subsidy targeting mechanism from rewarding stocking reduction to direct grassland restoration.

This study aimed to examine selenite uptake in Medicago sativa L. Potted alfalfa plants were grown in sterilized quartz sand and exposed to 1 and 10 μM selenite for 21 days. Thirty-day-old seedlings and excised roots were used to determine the mechanism of selenite uptake in alfalfa. The following patterns of Selenium (Se) distribution in roots were as follows: lateral roots > taproots and subcellular fraction (I) > fraction (III) > fraction (II). With increasing pH, Se uptake in roots decreased markedly. The dose-dependent Se net uptake at pH 5.5 followed the Michaelis–Menten kinetics. Addition of phosphate decreased Se uptake in the excised roots (P < 0.05), whereas a deficiency in phosphate increased Se uptake (P < 0.05). The results indicate that alfalfa mainly absorbed selenium through lateral roots. Selenite uptake by alfalfa root depended on pH, with the preferential form absorption of as H₂SeO₃ > HSeO₃¹⁻ > SeO₃²⁻. A portion of selenite was absorbed actively and may be mediated by phosphate transporter.

Root system characteristics are of fundamental importance to soil improvement and underground resource acquisition in riparian buffer strips. Root architectural traits determine the in situ space-filling properties of a root system. The aims of this study were to examine the grassland root morphological characteristics in the vegetation zone from the lower reaches of Yellow River. Five natural homogeneous grasslands including Imperata cylindrica, Phragmites australis, Cynodon dactylon, Artemisia argyi and Juncellus serotinus were selected. Seven root architecture parameters including fractal dimension, total root length, total root surface area, total root volume, average diameter, root crossing number and root tip number were analyzed, and comprehensive scores were evaluated using principal component analysis. The results showed that average root diameter of the five herbaceous plants was ranged from 0.42 to 0.78 mm. The total root length, total root surface area, total root volume, root crossing number and root tip number of I. cylindrica and P. australis were significantly higher than those of C. dactylon, A. argyi and J. serotinus. The main factors influencing root architecture were average diameter, total root surface area and total root volume through principal component analysis. I. cylindrica had the highest comprehensive score, followed by P. australis, A. argyi, C. dactylon and J. serotinus. I. cylindrica and P. australis would be good competitors for both soil resource acquisition and soil quality improvement due to their root traits. These results could provide a scientific basis for evaluating the ecological function of riparian vegetation.

To explore the effects of saline-alkali stress on the functional and physiological characteristics of Leymus chinensis leaves, L. chinensis plants were subjected to severe saline-alkali (pH = 9.73, electrical conductivity [EC] = 0.637 mS/cm), moderate saline-alkali (pH = 8.76, EC = 0.451 mS/cm), and control (pH = 7.37, EC = 0.22 mS/cm) soil treatments. Leaf functional traits, ion content, photosynthetic parameters, and antioxidant enzyme activity were determined, and the relationship between the functional traits and physiological characteristics was analyzed. With an increase in saline-alkali stress, the leaf density of L. chinensis decreased significantly (p < 0.05), the leaf mass per area (LMA) did not change significantly, and the leaf biomass ratio decreased significantly (p < 0.05). The Na⁺ mass fraction increased, and the K⁺ and Ca²⁺ contents and K⁺/Na⁺ and Ca²⁺/Na⁺ ratios decreased in response to saline-alkali stress. Except for intercellular CO₂ concentration, net photosynthetic rate, stomatal conductance, and transpiration rate were lower under saline-alkali stress. Except for dehydroascorbate reductase, the antioxidant enzymes increased significantly as a result of saline-alkali stress. Leaf density and leaf biomass ratio were significantly correlated with the measured physiological indicators except for net photosynthetic rate and peroxidase. Further study on large-scale cultivation of L. chinensis would be beneficial for the ecological recovery and exploitation of the saline-alkali soil.

Sorghum (Sorghum bicolor [L.] Moench) is an important annual forage crop. Multiple harvests per year not only increase the total yield of sorghum but also help to avoid its injury and damage by biotic and abiotic stresses. It is well known that S. bicolor subsp. drummondii, or sudangrass, regrows vigorously after cutting. To elucidate the genetic mechanisms underlying this ability, we evaluated recombinant inbred lines and advanced populations of bmr (brown midrib) sorghum × sudangrass under different environments and identified quantitative trait loci (QTLs) controlling regrowth ability. Although the dry matter weight at the second harvest varied among years, significant QTLs for increased regrowth ability were detected on chromosomes (Chrs.) 3, 6, 7 and 10. In particular, the sudangrass alleles of two QTLs detected on Chrs. 7 and 10 showed a positive effect on regrowth ability. We named the QTL on the short arm of Chr. 7 qRG7-1 and verified it in the QTL analysis of F₃ and BC₂F₃ populations. QTL analysis by using an F₃ population segregating for regrowth ability also showed a clear LOD peak in the qRG7-1 region. Substitution mapping using two BC₂F₃ populations placed qRG7-1 at 3.81–9.75 Mb on Chr. 7.

Orchardgrass (Dactylis glomerata) persists poorly in acidic soils. Not many studies have looked into the effects of fertilizers in improving orchardgrass persistence within acidic soils. We conducted experiments on 64 individual potted orchardgrass plants, which were defoliated to 5 cm and assigned to one of the following four treatment groups: unfertilized control (CNT), chemical fertilizer (CHE), grazing cattle dung (DNG), and cattle manure compost (CMP). Half the pots in each treatment received aluminum sulfate solution to induce further soil acidification (Al-add), while the others received water (no-Al). On days 20 and 47, after defoliation, soil properties and dry weights of aboveground biomass (AGB) (separated into leaves and stubble) and roots of four pots in each treatment group were measured. Al-add induced soil acidification in all fertilizers across the experiment (p < 0.05). On day 20, AGB and leaves in CHE was increased by acidification (p < 0.05), which was not observed in other fertilizer treatments (p > 0.1). Stubble growth increased following acidification in all fertilizer treatments (p < 0.05). Acidification did not increase AGB on day 47; no effect was seen on root growth at either day 20 or 47 (p > 0.1). On day 20, soil concentrations of inorganic nitrogen (IN), nitrate-nitrogen (NO₃-N), and ammonium-nitrogen (NH₄-N) were significantly elevated in Al-add pots (p < 0.05). The increment was greater in CHE and CMP than in CNT and DNG on day 20, with a similar trend being observed for IN and NH₄-N concentrations at day 47. IN and NH₄-N concentrations in DNG with no-Al increased over the regrowth period. These results indicate that orchardgrass regrowth in acidic soils can be improved by fertilizer addition, depending on fertilizer type. The increased concentration of soil IN, induced by soil acidification, is likely to be one of the factors encouraging growth. This increase of regrowth may favor the persistence of orchardgrass in strongly acidic soils.