Abstract
Artificial grasslands play a role in carbon storage on the Qinghai–Tibetan Plateau. The artificial grasslands exhibit decreased proportions of graminate and increased species richness with age. However, the effect of the graminate proportions and species richness on ecosystem C stocks in artificial grasslands have not been elucidated. We conducted an in situ13C pulse-labeling experiment in August 2012 using artificial grasslands that had been established for two years (2Y), five years (5Y), and twelve years (12Y). Each region was plowed fallow from severely degraded alpine meadow in the Qinghai-Tibetan Plateau. The 12Y grassland had moderate proportions of graminate and the highest species richness. This region showed more recovered 13C in soil and a longer mean residence time, which suggests species richness controls the ecosystem C stock. The loss rate of leaf-assimilated C of the graminate-dominant plant species Elymus nutans in artificial grasslands of different ages was lowest in the 12Y grassland, which also had the highest species richness. Thus the lower loss rate of leaf-assimilated C can be partially responsible for the larger ecosystem carbon stocks in the 12Y grassland. This finding is a novel mechanism for the effects of species richness on the increase in ecosystem functioning.
Highlights
Prior studies in the alpine meadows of the Qinghai–Tibetan Plateau have indicated that community structure determines the ecosystem carbon storage capacity[18,35,36,37] and plant photo-assimilated carbon cycling[38]
In artificial grassland on the Qinghai–Tibetan Plateau, graminate is typically the cultivated grass species, some of which could be replaced by forbs with increasing planting years and different anthropogenic management strategies
The total carbon showed no significant differences in either above- or below-ground biomass for the three types of grassland
Summary
Prior studies in the alpine meadows of the Qinghai–Tibetan Plateau have indicated that community structure determines the ecosystem carbon storage capacity[18,35,36,37] and plant photo-assimilated carbon cycling[38]. In artificial grassland on the Qinghai–Tibetan Plateau, graminate is typically the cultivated grass species, some of which could be replaced by forbs with increasing planting years and different anthropogenic management strategies. The effects of the different graminate and of the species richness on the ecosystem C store of artificial grasslands of varying ages remains unclear. These differences may have significant effects on the restoration and management of degraded grassland. The purposes of this study were the following: (1) to quantify the partitioning of recently fixed carbon among shoot, root, and soil and fluxes in the plant-soil system and (2) to estimate the effects of graminate grasses and species richness of artificial grasslands on carbon cycling in the plant-soil system
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