No abstract

The Qinghai–Tibetan Plateau is a very large land unit and an important terrestrial ecosystem within the Eurasian continent. Because of the harsh climate associated with the high altitude, alpine meadows on the plateau are susceptible to degradation from overgrazing. For this region, and for other alpine meadow pastures internationally, there is a need to define the sustainable stocking rate, to develop sound policy pertaining to future land use. Here we report biomass and liveweight gain per animal and per ha for pastures grazed by yaks at high, medium, or low stocking rates over 4 growing seasons from 2010 to 2013. Measures of herbage nutritive value are reported. The influence of inter-year variation in precipitation on standing herbage biomass was also evaluated. Higher precipitation increased standing herbage biomass and herbage nutritive value, indicating that vegetation suffered summer water deficit even in this environment. The sustainable stocking rate in this environment was determined to be approximately 1 yak ha-1 (grown from 80 kg to 120 kg liveweight in 90 d). At this stocking rate, yak weight gain per ha was 88% of that achieved at higher stocking rates typically used by farmers, but with little or no evidence of land degradation.

Difference in soil moisture, temperature and microclimate on sunny and shady slope aspect can lead to various plant community, sequentially modify soil microbial community. In this study, we measured soil properties including soil temperature, soil moisture, soil organic carbon (SOC), total nitrogen (TN); plant properties including aboveground and underground biomass, and microbial properties including microbial carbon (C), nitrogen (N) content and phospholipid fatty acids (PLFAs) to evaluate the effects of slope aspect on plant biomass, soil properties and microbial community in the alpine meadow on the Qinghai-Tibetan Plateau. The results showed that sunny sites had higher soil temperature, organic C and underground biomass (UB), while shady sites had higher soil moisture, TN and aboveground biomass (AB). Principal component analysis (PCA) indicated that bacteria were the dominant soil microbes at sunny sites, while the fungi was more abundant at sites with a shady aspect. Redundancy analysis (RDA) showed that temperature was the major factor affecting the composition of the microbial community. It can be concluded, that slope aspect can significantly alter microbial composition due to the differences in plant community, soil properties and especially environmental factors.

Switchgrass (Panicum virgatum L.) is a cellulosic biofuel feedstock and their effects on bacterial communities in deep soils remain poorly understood. To reveal the responses of bacterial communities to long-term switchgrass cultivation through the soil profile, we examined the shift of soil microbial communities with depth profiles of 0–60 cm in five-year switchgrass cultivation and fallow plots. The Illumina sequencing of the 16S rRNA gene showed that switchgrass cultivation significantly increased microbial OTU richness, rather than microbial Shannon diversity; however, there was no significant difference in the structure of microbial communities between switchgrass cultivation and fallow soils. Both switchgrass cultivation and fallow soils exhibited significant negative vertical spatial decay of microbial similarity, indicating that more vertical depth distant soils had more dissimilar communities. Specifically, switchgrass cultivation soils showed more beta-diversity variations across soil depth profile. Through network analysis, more connections and closer relationships of microbial taxa were observed in soils under switchgrass cultivation, suggesting that microbial co-occurrence patterns were substantially influenced by switchgrass cultivation. Overall, our study suggested that five-year switchgrass cultivation could generated more beta-diversity variations across soil depth and more complex inter-relationships of microbial taxa, although did not significantly shape the structure of soil microbial community.

BackgroundCultivated peanut (Arachis hypogaea L.) is an important oil and protein crop, but it has low disease resistance; therefore, it is important to reveal the number, sequence features, function, and evolution of genes that confer resistance. Nucleotide-binding site–leucine-rich repeats (NBS–LRRs) are resistance genes that are involved in response to various pathogens.ResultsWe identified 713 full-length NBS–LRRs in A. hypogaea cv. Tifrunner. Genetic exchange events occurred on NBS–LRRs in A. hypogaea cv. Tifrunner, which were detected in the same subgenomes and also found in different subgenomes. Relaxed selection acted on NBS–LRR proteins and LRR domains in A. hypogaea cv. Tifrunner. Using quantitative trait loci (QTL), we found that NBS–LRRs were involved in response to late leaf spot, tomato spotted wilt virus, and bacterial wilt in A. duranensis (2 NBS–LRRs), A. ipaensis (39 NBS–LRRs), and A. hypogaea cv. Tifrunner (113 NBS–LRRs). In A. hypogaea cv. Tifrunner, 113 NBS–LRRs were classified as 75 young and 38 old NBS–LRRs, indicating that young NBS–LRRs were involved in response to disease after tetraploidization. However, compared to A. duranensis and A. ipaensis, fewer LRR domains were found in A. hypogaea cv. Tifrunner NBS–LRR proteins, partly explaining the lower disease resistance of the cultivated peanut.ConclusionsAlthough relaxed selection acted on NBS–LRR proteins and LRR domains, LRR domains were preferentially lost in A. hypogaea cv. Tifrunner compared to A. duranensis and A. ipaensis. The QTL results suggested that young NBS–LRRs were important for resistance against diseases in A. hypogaea cv. Tifrunner. Our results provid insight into the greater susceptibility of A. hypogaea cv. Tifrunner to disease compared to A. duranensis and A. ipaensis.