Recruitment of seedlings versus ramets as affected by pasture degradation in alpine meadows and the implications for ecological restoration

Abstract

Background: The degradation of alpine meadows on the Qinghai-Tibetan Plateau (QTP) has an impact on vegetation recruitment from seedlings and ramets. Aims: Understanding the relative contribution of recruitment by seedling and ramet in alpine meadows is for the ecological restoration of degraded grasslands on the QTP. Methods: An experiment was conducted to investigate seedling and ramet densities, species composition and their relationships with standing vegetation in plots representative of non-degraded (ND), lightly (LD), moderately (MD) and severely degraded (SD) alpine meadows. Results: With increasing degradation and the reduction in vegetation cover, the number of seedlings and ramets declined. The proportion of young plants arising from seedlings was low, with the majority of species reproducing clonally. The establishment of seedlings of forbs in SD meadows led to species-rich, forb-dominant vegetation in these areas. Conclusions: LD and MD meadows appear to be able to be managed by reduced grazing for the restoration of grass-and sedge-dominated pastures. In contrast, restoration of SD meadows will require additional intervention, such as of seeding and weed eradication.

Interaction between root exudates and rhizosphere microorganisms facilitates the expansion of poisonous plant species in degraded grassland

“…Traditionally, the site is used for winter grazing of yak and sheep from December to March. We previously studied grassland degradation processes, soil nutrients and vegetation regeneration at the same site [32,37,38,39].…”

“…The site is 1.5 km 2 in size, approximately 3720 m a.s.l., and has a highland continental climate with no absolute frost-free days. Annually, average temperature is -0.1-1.2℃, average precipitation is 463-602 mm, evaporation is approximately 1460 mm, and total sunshine is 2272-2632 h. The grassland type is alpine meadow [32,37,38]. The dominant plant species of native grassland are Kobresia pygmaea, Stipa spp.…”

“…Poisonous plant species are more e cient in utilizing N in poor nutrient soil than sedges and grasses, which may have been their survival mechanism in alpine grassland [28]. However, during the spreading of poisonous plants, self-reinforcing is a key driving force in degraded grassland [4,8,36], with the interaction of root exudates and rhizosphere microorganisms a key factor in the process [4,24,37]. We hypothesized that the exudate from roots of poisonous plant species contain more compounds for speci c microorganisms to promote self-growth than non-poisonous plant species.…”