Regeneration limitations of Hippophae rhamnoides population after
successfully encroached on the Qinghai-Tibetan Plateau
Abstract
Shrub encroachment can alter the structure and function of grassland
ecosystems, leading to their degradation. Therefore, population
regeneration dynamics after shrub encroachment on the influence of
grassland should not be ignored. H. rhamnoides, as a pioneer species,
has significantly encroached with large areas onto the Qinghai-Tibetan
Plateau (QTP) due to climate change and over-grazing. However, few
studies have focused on the dynamics of population regeneration
following successful encroachment. Therefore, we studied H. rhamnoides
natural population in the alpine grasslands, investigating population
regeneration pattern, seed, bud production and storage, and limitation
imposed by microhabitats (soil, light and feeding). Our aim was to
explore population regeneration strategies and identify key limiting
factors for population regeneration after successful encroachment. Our
findings revealed several key points: (i) H. rhamnoides entered the
alpine grassland by relying on seeds, it would seize resources by
low-cost clonal reproduction, then increase sexual reproduction to
improve genetic diversity. (ii) The production and storage of seeds and
buds was sufficient, seed vigor was high, seed emergence rate was higher
duo to mechanical restriction of hard seed coat was weakened by the
water transport channels in the palisade layer, and formation of
seedlings was less restricted. (iii) H. rhamnoides population
regeneration was mainly limited by microhabitats light and feeding.
However, light and feeding significantly affected seedlings
photosynthesis and carbon storage, their interaction significantly
reduced the seedlings survival, and further restricted population
regeneration. The results can provide theoretical basis for the
restoration and management of alpine grassland degradation caused by
shrub encroachment.