Soil microbial communities affect nutrient cycling and ecosystem functioning. However, the variations in microbial diversity and community composition within degraded landscapes remain unclear. Using high-throughput sequencing of bacterial 16S ribosomal RNA genes and internal transcribed spacer fungal sequences, we investigated the rhizosphere microbial diversity and community of coniferous Pinus tabulaeformis Carr. forests in degraded lands across a chronosequence that spanned over 60 years (10, 25, 40, and 60 years since restoration, four forest stands). We found significant differences in soil bacterial and fungal communities among stand ages. Actinobacteria, Proteobacteria, and Acidobacteria dominated the rhizosphere, whereas Basidiomycota, Ascomycota, and Zygomycota prevailed as fungal components.With stand development, bacterial diversity decreased, but fungal diversity increased.Nonmetric multidimensional scaling analysis separated bacterial community clusters well by stands. Fungal community clusters of 25-and 60-year-old stands overlapped.The dominant bacteria Acidobacteria showed the highest relative abundance at the 40-year-old stands. Soil microbial communities correlated significantly with the macro-nutrients (soil organic carbon, total nitrogen, and total phosphorous). Additionally, the relative abundance of Acidobacteria at the phylum level correlated positively with soil total phosphorous; Deltaproteobacteria at the class level correlated positively with soil organic carbon and total nitrogen. Thus, restoring vegetation in degraded temperate forests enhanced some macronutrients and influenced microbial communities. Our results revealed that restoring vegetation in degraded lands decreased the diversity of bacterial communities over time. In contrast, the soil fungal diversity increased after restoration, and fungal communities in the 25-and 60-year-old forest stands overlapped on degraded soils.

Soil microbes are involved in the fundamental processes that underpin an ecosystem's function. However, little is known about the microbial communities that inhabit deep soil horizons, especially in degraded forest ecosystems. Here, we used high‐throughput sequencing to investigate the vertical distribution of soil bacterial communities to a depth of 20 m in Pinus tabulaeformis and Robinia pseudoacacia forests on the Loess Plateau, China. We found that bacterial richness declined from the topsoil to a depth of 2 m in P. tabulaeformis forests and declined from the topsoil to a depth of 1 m in R. pseudoacacia forests, and thereafter increased. The relative abundance of α‐Proteobacteria was higher in subsoils than in topsoils of P. tabulaeformis forests. It was highest at the depth of 20 or 14 m in both forest types, suggesting that α‐Proteobacteria can survive dry, alkaline, low‐nutrient environments. We also found a higher relative abundance of Acidobacteria in topsoils than in subsoils, indicating that Acidobacteria can grow well in nutrient‐rich environments. Our results suggest that soil bacterial communities respond to nutrient changes associated with soil depth and plant species. These findings revealed that soil microorganisms persisted in deep and carbon‐starved soils, especially for α‐Proteobacteria, which may be adapted to resource‐poor environments in deep soils.

Grass tetany is a nutritional disease of ruminants caused by low dietary Mg.Previous research has shown that early spring P‐fertilization increases the leafMg concentration of tall fescue (Festuca arundinacea Schreb.) hay.However, little is known about how P‐fertilization alters the mineralconcentration of tall fescue under grazing. Our objective was to compare, undergrazing, the Mg, K, Ca, and P concentration of tall fescue when soil P wasconsidered either adequate or low. The treatments were tall fescue grown on soilfertilized to achieve 30 lb/acre P (P‐fertilized) or left unfertilized at 6 lb/acre P(Control). Three cow/calf pairs grazed each pasture from 15 February to 11April, 2000, and 6 March to 1 May, 2001. Forage samples were collected at thestart of grazing and at 14 day intervals thereafter. Under grazing, fertilization with P increased tall fescue forage Mg, K, and Ca concentrationonce spring growth started. However, the ratio of K/(Ca+Mg) never approached thecritical level thought to induce grass tetany. These results suggest thatfertilizing tall fescue pastures to an adequate soil P level improves the amountof dietary Mg available to ruminants during early spring and decreases the grasstetany potential of the forage.

Non‐toxic endophytes are being inserted into cultivars of tall fescue (Festuca arundinacea Schreb.) to improve plant persistence and eliminate tall fescue toxicosis. Seed for these new cultivars could be produced in Missouri, which leads the nation in acreage of tall fescue harvested for seed. However, few studies have investigated the feeding value of straw baled after seed harvest from these cultivars. Our objectives were to evaluate (i) the nutritive value of straw from ‘Kentucky 31’ and ‘HiMag9’ tall fescue, and (ii) performance of steers fed ammoniated straw of Kentucky 31 and HiMag9. Cultivar had no effect on steer intake, gain, or rectal temperature. Ammoniation of straw improved steer performance. Averaged across cultivars, ammoniation of straw increased intake by 20% and improved average daily gain of steers from ‐0.15 lb/day to 0.46 lb/day when compared to untreated straw. Our results indicate that ammoniating straw improves its feeding value.