The long-term impact of human exploitation and environmental changes has led to a decline in grassland productivity and soil fertility, which eventually results in grassland degradation. The application of organic fertilizer is an effective improvement measure; however, it is still not fully understood how the addition of organic fertilizer influences grassland soil fertility and plant composition. A set of experiments were conducted in Inner Mongolia in China to reveal the tradeoff between steppe plants and soil microorganisms and the eco-physiological mechanisms involved, and how the addition of vermicompost and mushroom residues affect microbial diversity, enzyme activities, and the chemical properties of soil in degraded Leymus chinensis grassland. Organic fertilizer improved the soil nutrient status and shaped distinct bacterial communities. Compared with the control the available phosphorus (AP) and available potassium (AK) contents were highest under treatments a3 and b3, and the aboveground biomass was highest under the b3 treatment. Soil sucrase activities increased by 7.88% under the b3 treatment. Moreover, the richness index significantly increased by 7.07% and 7.23% under the a1 and b2 treatments, respectively. The most abundant Actinobacteria and Proteobacteria were detected in the organic fertilizer treatment. A linear discriminant analysis effect size (LEfSe) indicated that the bacterial community was significantly increased under the b3 treatment. A canonical correspondence analysis (RDA) and spearman correlation heatmap confirmed that total P (TP) and urease were the key driving factors for shaping bacterial communities in the soil. Our results indicated that the application of large amounts of vermicompost and mushroom residues increased the availability of nutrients and also enhanced the biodiversity of soil bacterial communities in L. chinensis grasslands, which will contribute to the sustainable development of agro-ecosystems.

Alfalfa, an important forage legume, is an ideal crop for sustainable agriculture and a potential crop for bioenergy resources. Drought, one of the most common environmental stresses, substantially affects plant growth, development, and productivity. MicroRNAs (miRNAs) are newly discovered gene expression regulators that have been linked to several plant stress responses. To elucidate the role of miRNAs in drought stress regulation of alfalfa, a high-throughput sequencing approach was used to analyze 12 small RNA libraries comprising of four samples, each with three biological replicates. From the 12 libraries, we identified 348 known miRNAs belonging to 80 miRNA families, and 281 novel miRNAs, using Mireap software. Eighteen known miRNAs in roots and 12 known miRNAs in leaves were screened as drought-responsive miRNAs. With the exception of miR319d and miR157a which were upregulated under drought stress, the expression pattern of drought-responsive miRNAs was different between roots and leaves in alfalfa. This is the first study that has identified miR3512, miR3630, miR5213, miR5294, miR5368 and miR6173 as drought-responsive miRNAs. Target transcripts of drought-responsive miRNAs were computationally predicted. All 447 target genes for the known miRNAs were predicted using an online tool. This study provides a significant insight on understanding drought-responsive mechanisms of alfalfa.

Alfalfa (Medicago sativa L.) is a nutritious forage plant in dryland regions with strong drought tolerance and broad adaptability. To understand the architectural characters and physiological functions of the root systems in response to different drought stress and rehydration, two experiments were conducted in a glasshouse. Experiment 1 used three alfalfa cultivars and four soil moisture treatments in a split-plot design with four replicates to investigate the response of root systems of different alfalfa cultivars to drought stress and subsequent rehydration. Experiment 2 used one alfalfa cultivar and four soil moisture treatments in a randomized complete block (RCB) design with three replicates to measure reactive oxidant species and antioxidant defense systems of alfalfa root. The soil moisture treatments included (1) 75–80% of the water-holding capacity (CK); (2) 60–65% of the water-holding capacity and subsequent rehydration to 75–80% of the water-holding capacity; (3) 45–50% of the water-holding capacity and subsequent rehydration to 60–65% and 75–80% of the water-holding capacity; and (4) 30–35% of the water-holding capacity and subsequent rehydration to 45–50%, 60–65% and 75–80% of the water-holding capacity. Our results demonstrated that plants had higher root biomasses (mean = 0.77 g), fractal dimensions (1.47), fractal abundances (3.84), and branching ratios (0.39) under severe water deficit and rehydration than under less stressful soil moisture conditions. Plant root systems tended to exhibit herringbone branching (Topological Index = 0.63) when soil moisture was at 60–65% water-holding capacity with the soil being then rehydrated, whereas they tended to have a smaller lateral root length, root surface area, root volume, and branching ratio and larger root diameter under more favorable soil moisture conditions for less stressful soil moisture treatments. Severe water stress and subsequent considerably improved superoxide (O₂⁻) generation rate, the content of hydrogen peroxide (H₂O₂) and Malondialdehyde (MDA), and non-enzyme antioxidant glutathione (GSH), and reduced the content of ascorbate (AsA) and activity of catalase (CAT), ascorbate peroxidase (APX), and glutathione peroxidase (GPX). It is concluded that Medicago sativa L. cv Zhaodong (ZD) and cv Aohan (AH) exhibited higher drought resistances than cv Golden empress (GE) using topological and fractal analyses. This could be a key contributor to altering optimum soil moisture conditions and screening alfalfa cultivars based on root system architecture and antioxidant defense systems. The molecular functions warrant further investigation which could help explain the observed root phenotypes after drought conditions and rehydration.

Semi-arid grassland in northern China faces degradation and desertification problems, with fertilizer application appearing to be a potential solution by improving soil fertility and plant fields or biodiversity. In this study, mineral and organic fertilizers were used in a semi-arid natural grassland in Hebei Province for three years. The plant characteristics, biomass and species diversity index were assessed and analyzed. In the years 2016 and 2017, mineral fertilizers (RC) significantly increased the total aboveground biomass and the aboveground biomass, natural height, density and coverage of Leymus chinensis compared with organic fertilizers (RO), especially at a moderate application rate (RC₂). Leymus chinensis was first divided into its own group and then separated into four groups via cluster tree analysis. The importance values of Leymus chinensis showed continuous increases in mineral fertilizer treatments, but not for organic fertilizers. Margalef’s species richness indexes increased significantly (to 2.09) in the organic treatment (RO₁) when compared with RC₂. Thus, it was concluded that mineral fertilizers could enhance the position of Leymus chinensis in the natural grassland, while organic fertilizers could promote species biodiversity. This study also provides recommendations regarding the use of fertilizers for the purposes of increasing plant biomass and biodiversity in semi-arid grasslands of northern China.

Alfalfa, an important legume forage, is an ideal crop for sustainable agriculture and a potential bioenergy plant. Drought, one of the most common environmental stresses, substantially affects plants’ growth, development and productivity. MicroRNAs (miRNAs) are newly discovered gene expression regulators that have been linked to several plant stress responses. To elucidate the role of miRNAs in drought stress regulation of alfalfa, a high-throughput sequencing approach was used to analyze 12 small RNA libraries comprising of 4 samples, each with 3 biological replicates. We identified 348 known miRNAs, belonging to 80 miRNA families, from the 12 libraries and 281 novel miRNAs using Mireap software. 18 known miRNAs in roots and 12 known miRNAs in leaves were screened out as drought-responsive miRNAs. Except for miR319d and miR157a which were upregulated under drought stress, the expression pattern of drought-responsive miRNAs were different between roots and leaves in alfalfa. This is the first study discovering miR157a, miR1507, miR3512, miR3630, miR5213, miR5294, miR5368 and miR6173 are drought-responsive miRNAs. Target transcripts of drought-responsive miRNAs were computationally predicted. All 447 target genes for the known miRNAs were predicted using an online tool. This study provides a significant insight on understanding drought-responsive mechanisms of alfalfa.