Study On The Carbon Metabolism And Growth To Pinus Taiwanensis At Different Elevations In Wuyi Mountain

The carbon metabolism and resource utilization strategies not only provide the materials and energy for plant's important physiological processes,which is become one of the important fileds for plant ecology research.In order to explore the Pinus taiwanensis carbon metabolism and resource efficiency at different elevations,analyse its main effects on growth situation,this study experimented on the Wuyishan National Nature Reserve in Jiangxi Province,and set a sample sites along the 1200m,1400m,1600m,1800m,2000m Pinus taiwanensis communities.The characteristic of Pinus taiwanensis needles and the photosynthesis and respiration rates were measured at each sample sites.Further,the responses to variations in light intensity and CO₂ concentration,the stoichiometric characteristics and the leaf mass per area were measured too.The growth and mortality rate of Pinus taiwanensis along the different elevations were integrated analyse and to elucidate the mechanism of carbon metabolism and resource utilization efficiency.The main findings are as follows:1.The photosynthetic rate-light response characteristics of Pinus taiwanensis at the different elevationsWith the increase of light intensity,the net photosynthetic rate of Pinus taiwanensis needles was the highest at 2000m and 1800m.There were significant differences in photosynthetic parameters of Pinus taiwanensis at different elevations and seasons:the autumn light saturation points were higher than summer's 13%-66%,and 49%-198%for winter,respectively.The autumn light compensation point is higher 73%than the summer at 1400m,but lower the 10%than 2000m in the summer;the maximum net photosynthetic rate in autumn was higher than that in summer,from 5%to 67%,which was higher 42%-138%than winter too.2.The photosynthetic rate-temperature response characteristics of Pinus taiwanensis at the different elevationsThe net photosynthetic rate of Pinus taiwanensis needles increased first and then decreased with temperature in three seasons?summer,autumn and winter?.The adaptability of Pinus taiwanensis needles in photosynthesis is stronger in winter than in summer and autumn,and the temperature adaptability increases with altitude?summer and winter?.The optimum temperature(T_opt)of net photosynthetic rate?A?of Pinus taiwanensis needles was higher than that of winter in summer and autumn,and the optimum net photosynthetic rate(A_opt)and net photosynthetic rate(A₂₅)at 25°C showed trends of autumn>summer>winter trends.At different elevations and seasons,the optimal temperature of Pinus taiwanensis needles decreased with elevations increased.Although the A_opt and A₂₅ of Pinus taiwanensis needles increased along elevations in summer and autumn,but it did not show significance in winter.The respiration rate(R₂₅)of Pinus taiwanensis needles at 25°C is lower than that of winter in summer and autumn,while the temperature sensitivity coefficient(Q₁₀)of respiration rate is higher than that in summer and autumn.The R₂₅ of Pinus taiwanensis needles increased along the elevations,and the elevations,seasons and their interactions have a significantly effects on Q₁₀.3.The photosynthetic rate-CO₂ response characteristics of Pinus taiwanensis at different elevationsWith the increase of CO₂ concentration,the net photosynthetic value of Pinus taiwanensis leaves reached a stable trend.The V_cmax values are higher in summer and autumn at different elevations and lower in winter.J_max is higher at different elevations in autumn and winter,and lower in summer.The V_cmax/J_max value and the V_cmax value change in a similar trend.After two-way analysis of variance,V_cmax,J_max,and V_cmax/J_maxax were significantly affected by seasons and elevations,and were influenced by seasons and elevations interactions.4.Effects of characteristics and nutrient use efficiency for Pinus taiwanensis on its carbon metabolismIn autumn and winter,the leaf dry mass per area of Pinus taiwanensis in different elevations was significantly higher than that in summer.There were no significant correlations between A_25mass,R_25mass and LMA in summer,but the negative relationships were showed in autumn and winter?p<0.05?,which indicated that the accumulation of leaf dry matter content have effect on the carbon metabolism for Pinus taiwanensis.The allometric relationships among the R_25mass and N,P,C/N,N/P and C/P were reflecting that the change of plant nutrient content maybe affecting its respiration.The nitrogen and phosphorus resource utilization efficiency of Pinus taiwanensis was positively correlated with photosynthesis in different seasons?p<0.001?,thus,the enhancement of plant resource utilization efficiency would increase its photosynthesis ability.5.The main influencing factors to the growth of Pinus taiwanensis treesThe height of Pinus taiwanensis decreased with elevations.In 2014 and 2017,the height of Pinus taiwanensis decreased by 72.39%and 71.75%from low altitude to forest line.The DBH and tree height of Pinus taiwanensis at different altitudes have a significant allometric sclaing relationships,Both all the scaling exponent was less than1.0,which is indicated that the growth rate of DBH was higher than that of tree height.The growth rate of Pinus taiwanensis from the lowest altitude(BAI=35.53cm² 3-year^-1)to the highest altitude(BAI=17.62 cm² 3-year^-1)decreased to 50.41%.The content of NSC,N and P in the needles of Pinus taiwanensis increased significantly with increase of the elevations.In summary,The temperature adaptation of photosynthesis rate of Pinus taiwanensis in different elevations was not significant in summer and autumn,but the temperature sensitivity coefficient Q₁₀ of respiration rate of Pinus taiwanensis at different elevations was not significantly different in winter.In this paper,the regulation of C metabolism for Pinus taiwanensis needles was affected by the growth and the environmental gradient.With the increase of warming stage,the high altitude of the subtropical Pinus taiwanensis will have the potential to increase forest productivity.By reducing the transient sensitivity to temperature in extreme low temperature climates,the minimum carbon acquisition necessary to maintain survival is one of the important C metabolic strategies that support it as a high mountain forest line species.Moreover,the annual growth rate of Pinus taiwanensis showed decrease trend,but the contents of NSC,N and P in the needles showed a significantly positive increased,which indicating that the Pinus taiwanensis species supported“growth inhibition”hypothesis.The research results will help to understand the environmental adaptation mechanism of Pinus taiwanensis and provide reference for management of forest ecosystems in humid subtropical mountains.