Soil gravels and plant species configuration control vegetation
restoration in Qinghai-Tibet Plateau
Abstract
Soil gravel content strongly affects ecological restoration; however,
the response and mechanism of plant traits to soil gravel content under
the sensitive and fragile natural environment of Qinghai-Tibet Plateau
remains unclear. Herein, soils with three gravel content (10%, 30%,
50%) in the southeastern Tibetan Plateau were selected, and three plant
species ( one indigenous specie of Elymus dahuricus (Ed), and two
introduced ones of Festuca elata ( Fe) and Medicago
sativa ( Ms)) were used in seven planting patterns with
different proportions ( Fe, Ed, Ms, Fe +
Ed (1:1), Fe+ Ms (2:1), Ed + Ms
(2:1), Fe+ Ed+ Ms (2:2:1)). Plant traits,
phytochemical properties and soil stoichiometric characteristics were
measured to explore the interactive effects of soil gravels and plant
species on vegetation restoration. Average plant height, coverage, shoot
biomass and total biomass were most affected by plant species
(F=277~611, p<0.01), followed by gravel
content (F=90~195, p<0.01) and their
interaction (F=5~51, p<0.05); root biomass was
most affected by gravel content (F=130, p<0.01). Among plant
species, shoot and root biomass, total biomass overall decreased in the
order of Fe+Ed+Ms˃Fe˃Fe+Ms˃Fe+Ed˃Ms˃Ms+Ed˃Ed. Plant total
biomass, shoot biomass, root biomass and shoot/root ratio among
different soils overall decreased in the order of low˃ high˃ medium
gravel contents. All plant species were restricted by soil nitrogen
except for Ed and Ed+ Ms (N:P>14). In
addition, average plant height, coverage, shoot biomass and total
biomass were separately negatively and positively correlated with bulk
density and total porosity (r=-0.88~-0.96 and
0.78~0.91, p<0.05), so did for total nitrogen,
total phosphorus, organic carbon, C:N and N:P of shoot fraction and
rhizosphere soils (|r|=0.69~0.97,
p<0.05), indicating that gravel content affects plant growth
through bulk density and nutrients. Therefore, optimizing the
configuration of soil properties (mainly nitrogen and compactness) and
plant species (isecologic niche plants) is an effective strategy for
ecological restoration in the Qinghai-Tibet Plateau.