A 3-year survey was conducted to explore the relationships among plant composition, productivity, and soil fertility characterizing four different degradation stages of an alpine meadow in the source region of the Yangtze and Yellow Rivers, China. Results showed that plant species diversity, productivity, and soil fertility of the top 30-cm soil layer significantly declined with degradation stages of alpine meadow over the study period. The productivity of forbs significantly increased with degradation stages, and the soil potassium stock was not affected by grassland degradation. The vegetation composition gradually shifted from perennial graminoids (grasses and sedges) to annual forbs along the degradation gradient. The abrupt change of response in plant diversity, plant productivity, and soil nutrients was demonstrated after heavy grassland degradation. Moreover, degradation can indicate plant species diversity and productivity through changing soil fertility. However, the clear relationships are difficult to establish. In conclusion, degradation influenced ecosystem function and services, such as plant species diversity, productivity, and soil carbon and nitrogen stocks.Additionally, both plant species diversity and soil nutrients were important predictors in different degradation stages of alpine meadows. To this end, heavy degradation grade was shown to cause shift of plant community in alpine meadow, which provided an important basis for sustaining ecosystem function, manipulating the vegetation composition of the area and restoring the degraded alpine grassland.
Overgrazing and climate warming may be important drivers of alpine rangeland degradation in the Qinghai-Tibetan Plateau (QTP). In this study, the effects of grazing and experimental warming on the vegetation of cultivated grasslands, alpine steppe and alpine meadows on the QTP were investigated. The three treatments were a control, a warming treatment and a grazing treatment and were replicated three times on each vegetation type. The warming treatment was applied using fibreglass open-top chambers and the grazing treatment was continuous grazing by yaks at a moderately high stocking rate. Both grazing and warming negatively affected vegetation cover. Grazing reduced vegetation height while warming increased vegetation height. Grazing increased but warming reduced plant diversity. Grazing decreased and warming increased the aboveground plant biomass. Grazing increased the preferred forage species in native rangelands (alpine steppe and alpine meadow), while warming increased the preferred forage species in the cultivated grassland. Grazing reduced the vegetation living state (VLS) of all three alpine grasslands by nearly 70%, while warming reduced the VLS of the cultivated grassland and the alpine steppe by 32% and 56%, respectively, and promoted the VLS of the alpine meadow by 20.5%. It was concluded that overgrazing was the main driver of change to the alpine grassland vegetation on the QTP. The findings suggest that grazing regimes should be adapted in order for them to be sustainable in a warmer future.
A novel biosensing platform was developed by combining the advantages of electrospun poly(vinyl alcohol) (PVA)/chitosan nanofibers and graphene oxides (GO). Glucose oxidase (GOD) was employed as a model enzyme. By co-electrospinning the solution of PVA, chitosan, GOD and GO, the PVA/chitosan/GOD/GO nanofibers were directly modified on the platinum (Pt) electrode. The UV-vis spectra and the FTIR spectra were used to characterize the GO nanosheets. The morphologies of fabricated electrospun nanofibers were characterized by high resolution scanning electron microscopy. After a thin layer of nafion was modified on the surface of matrix, the as-prepared electrode was used to detect glucose. The electrode exhibited great advantages in high sensitivity, low detection limit and wide linear range. In the meantime, the electrode showed good stability, acceptable reproducibility, and excellent anti-interference capability for ascorbic acid, uric acid, lactose and sucrose. Moreover, the novel biosensor was successfully applied for the glucose determination in human serum samples. The mechanism of efficient biosensing of the nafion/PVA/chitosan/GOD/GO/Pt electrode was analyzed in detail and the results show that it can be due to the synergy effects of electrospun nanofibers and GO nanosheets.
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