Study On Nutrient Uptake Strategies Of Cotinus Coggygria Seedlings In Barren Environment

Cotinus coggygria is an excellent silviculture harbingers in drought and barren mountain in north China and the south of northeast China.Because of its unique color leaves and beautiful landscape in summer and autumn,it is widely used in landscape forest construction.It not only becomes the preferred species on the northern landscaping or mountain greening,but also plays an important role in Beijing Fragrant Hill and Badaling Great Wall landscape.It is important to reveal the adaptability mechanism of Cotinus coggygria to the barren environment,which is of great significance to provide theoretical guidance for the rational cultivation and management of Cotinus coggygria seedlings in the future and understand the mechanism of plant adaptation to the environment.With Cotinus coggygria annual seedlings as the study materials,this paper applied the pot experiment in greenhouse and set up five different levels of nutrient supply to analyze.The growth index,morphology and biomass index(leaf weight ratio and root weight ratio),functional traits(root shoot ratio,leaf area root area ratio,specific leaf area,root morphological index,morphological index on different diameter fine roots)and distribution of nutrient content were analyzed,to stuty four different parts:nutrient uptake of Cotinus coggygria seedlings under different nutrient supply conditions,effects of nutrient supply on the growth and biomass allocation,nutrient uptake and utilization in different growth stages and nutrient absorption strategies in nutrient-limited environments.We have gotten the following four main conclusions.1.Nutrient-limited environmental conditions can increase the root shoot ratio and decrease reduce leaf area root area ratio.Inhibition of total biomass,aboveground biomass,leaf biomass,second order root biomass accumulation and increace of fisrt order root biomass were also found.However,it is not related to the distribution of stem and second order root biomass.2.N and P concentration of first order roots of Cotinus coggygria seedlings was significantly higher than that of other organs in the early growth stage.K concentration of leaves and stems was significantly higher than that of there different order roots,but there were no significant differences in N,P and K concentrations in the different organs at the end of growth stage.The reduction of nutrient supply can significantly increase the N,P and K contents of the low-order roots,especially first order roots.The reduction of nutrient supply promoted N,P and K use efficiency of leaves and stems in the early growth stage,but the sustained nutrient restriction could significantly reduce it.It can significantly improve N,P and K use efficiency of the second and third order roots.The higher the degree of nutrient limitation may lead to the greater increase of utilization efficiency.However,effect of N,P and K use efficiency of first order roots was obviously inhibited.3.The reduction of nutrient supply can significantly inhibit the carbon distribution of Cotinus coggygria seedlings leaves and stems,which makes them more inclined to allocate more carbon to the roots.With the growth of seedlings,C/N,C/P and N/P of stems,second and third order roots showed a downward trend,especially third order roots.While C/N,C/P and N/P of first order roots increased steadily,significantly lower than other organs in the early growth stage.There were no significant differences in C/N,C/P and N/P of different organs at the end of the growth stage.In the face of the reduction of nutrient supply conditions,seedlings chose to increase C/N,C/P and N/P of stems,first and second order roots rapidly at the beginning of growth.However,with the growth of seedlings,the increase was not obvious,and less than that in adequate nutrient conditions.The reduction of nutrient supply can significantly reduce C/N of third order roots,C/P and N/P of leaves and first order roots.4.Different levels of nutrient supply showed significant(p<0.01)interaction on root length,surface area,root tips,root forks,root tissue density,average root diameter,root fineness of the plant seedlings.In the pure sand environment,the seedlings were the most closely related to the root length,root surface area and root fineness.In the environment with limited nutrient restriction,the seedlings were mainly changed by root length,root surface area,root number and branch.However,the relationship between root tip density,root branch density,root diameter and root volume was the most closely related in the relatively light and medium environment.In the soil environment,the seedlings were mainly affected by the change of root tissue density.To a certain extent,limited nutrient supply can stimulate<1.0mm diameter fine roots and limit>1.0mm diameter fine roots.Morphological and functional plasticity in the plant seedlings reflected that the levels of nutrient supply significantly changed the strategies of nutrient absorption of Cotinus coggygria seedlings.From nutrient-sufficient to nutrient-limited and nutrient-deficient condition,seedlings tend to change their ecological strategies from enhancing the utilization ability in situ,enhancing the absorption ability in situ and expanding the absorption range,improving the storage and transportation ability,and finally change to the endurance strategies.