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The objective of this study was to investigate the effect of a low temperature tolerant lactic acid bacteria (LAB) inoculant on the fermentation characteristics and bacterial community of oat silage. Oats were harvested at the flowering stage and wilted to dry matter content of approximately 270 g/kg fresh weight. Wilted and chopped oats were used to make mini round bale silages. Silages were prepared without (control) or with a low temperature tolerant LAB inoculant including Lactobacillus plantarum BP18, Pediococcus pentosaceus HS1 and L. buchneri LP22 and then separately stored at different geographic locations (L, Chengdu Plain; H, Qinghai Tibetan Plateau) for 120 days. High contents of water soluble carbohydrate (WSC), crude protein (CP), neutral detergent fiber (aNDF) and acid detergent fiber (ADF) were found in LAB inoculated silage. Inoculation with LAB increased (P

Although photoperiod is known to be the main factor driving plant senescence in perennial plants, temperature has also been shown to modulate this process, which suggests that climate warming will significantly impact the length of plant growing season and affect terrestrial productivity. To test this assumption, we measured the effects of simulated autumn warming on four perennial herbaceous species, i.e. Elymus nutans , Koeleria macrantha , Vicia unijuga and Allium atrosanguineum , representing two major plant functional groups (grasses and forbs), in a typical alpine meadow of the Tibetan Plateau. Warming was simulated using open-top chambers, and its effects on degradation of chlorophyll and nitrogen (N) concentration in leaves and stems were determined during the senescence processes in autumn. The potential effects of autumn warming on total non-structural carbohydrate (TNC) in roots, growth and flowering phenology were further investigated in the following year. We found that warming delayed chlorophyll degradation of perennial herbs in early phase but accelerated it in later phase, regardless of functional groups, which led to higher N concentrations in leaves and stems during the whole senescence period. Autumn warming also significantly increased TNC in roots as a result of the delayed process of chlorophyll degradation, although the magnitudes were dependent on functional groups, which may be explained by inherent differences in growth patterns and phenology between grasses and forbs. We demonstrate that warming can increase carbohydrate accumulation not only by enhancing activities of photosynthetic enzymes proved by many previous studies but by altering chlorophyll degradation and preferential allocation of resources to different compartments. Furthermore, these results suggest that the net effect of climate warming on terrestrial ecosystems will be determined by floristic composition, as contrasting immediate and lasting (one year) changes in nutrient use and carbon allocation in response to warming were observed among species.

Plant senescence is a critical life history process accompanied by chlorophyll degradation and has large implications for nutrient resorption and carbohydrate storage. Although photoperiod governs much of seasonal leaf senescence in many plant species, temperature has also been shown to modulate this process. Therefore, we hypothesized that climate warming would significantly impact the length of the plant growing season and ultimate productivity. To test this assumption, we measured the effects of simulated autumn climate warming paradigms on four native herbaceous species that represent distinct life forms of alpine meadow plants on the Tibetan Plateau. Conditions were simulated in open-top chambers (OTCs) and the effects on the degradation of chlorophyll, nitrogen (N) concentration in leaves and culms, total non-structural carbohydrate (TNC) in roots, growth and phenology were assessed during one year following treatment. The results showed that climate warming in autumn changed the senescence process only for perennials by slowing chlorophyll degradation at the beginning of senescence and accelerating it in the following phases. Warming also increased root TNC storage as a result of higher N concentrations retained in leaves; however, this effect was species dependent and did not alter the growing and flowering phenology in the following seasons. Our results indicated that autumn warming increases carbohydrate accumulation, not only by enhancing activities of photosynthetic enzymes (a mechanism proposed in previous studies), but also by affecting chlorophyll degradation and preferential allocation of resources to different plant compartments. The different responses to warming can be explained by inherently different growth and phenology patterns observed among the studied species. The results implied that warming leads to changes in the competitive balance among life forms, an effect that can subsequently shift vegetation distribution and species composition in communities.