Response Of Root Functional Traits To Environmental Gradient In Ningxia Grassland

Root functional traits are the core traits of plant nutrient acquisition and interspecific competition,and also the driving force of community dynamics,soil formation,soil carbon accumulation and nutrient cycling in terrestrial ecosystems.Therefore,it is of great significance to study the response of root functional traits to environmental gradient in order to reveal the adaptive mechanism of grassland plants and the restoration of grassland vegetation in Ningxia.In this study,12 typical plots of plant communities were set along the environmental gradient from north to south,11 root functional traits of 56 species of plants and soil nutrient data of 12 typical plots were measured,and the relationships between root functional traits and spatial,climatic and soil environmental factors were analyzed.Redundancy analysis(RDA)was used to reveal the driving factors of root functional traits and to quantify the contribution of environmental factors to the functional traits,and the variation law of root functional traits along the environmental gradient was discussed.The main results are as follows:(1)The root functional traits of 44 dicotyledons and 12 monocotyledons at the species level were significantly different in root nitrogen content,root C/N ratio,root diameter,root tip number and root cross number.(2)The 56 root functional traits measured were used to construct communities,and there were great differences among the communities in 12 plots.Root functional traits were significantly affected by spatial factors such as mid-latitude and altitude,but not longitude.The root carbon content,root phosphorus content,root N/P ratio,root surface area and root volume increased with the increase of latitude.Root C content,root P content,root N/P ratio,root surface area and root volume decreased with increasing altitude.The number of root tips and root crossing increased with elevation.(3)Hydrothermal differentiation had a great influence on root functional traits in Ningxia.The root carbon content,root nitrogen content,root N/P ratio,root surface area and root volume decreased with the increase of rainfall.Root carbon content,root nitrogen content,root N/P ratio,root surface area,root diameter and root volume increased with the increase of solar radiation.The root carbon content,root nitrogen content,root N/P ratio and root volume increased with the increase of average annual temperature,while the number of root tips and root crossings number decreased with the increase of average annual temperature.(4)Soil physical and chemical properties had the strongest effect on root functional traits.Root carbon content,root nitrogen content and root N/P ratio were negatively correlated with soil organic matter and total nitrogen.Root carbon content,root nitrogen content,root N/P ratio,root surface area,root diameter and root volume were negatively correlated with soil total P.Root N content,root P content,root N/P ratio,root surface area and root volume were positively correlated with soil bulk density.(5)Plant community level can better explain the response of root functional traits to environmental gradient changes than species level.RDA sequencing results showed that spatial factors,climate factors and soil factors accounted for 79.4%of the environmental factors affecting root functional traits in Ningxia,and the influence was soil factor>spatial factor>climate factor.After variance decomposition,spatial factors,climate factors and soil factors accounted for 76.9%of plant root functional traits,among which soil bulk density,soil total phosphorus and latitude had the greatest effects.(6)At the community level,root carbon content,root C/N ratio and root diameter significantly affected the community productivity.