Response On Growth Status And Gas Exchange Of Castanopsis Fargesii And Castanopsis Sclerophylla Seedlings To The Warming And Nitrogen Application

Broad-leaved evergreen forest is a zonal vegetation type. The effect and response of itsimportant species to global change is one of the key research contents in vegetationdynamics.Castanopsis fargesii and Castanopsis sclerophylla are the dominant species oftypical evergreen broad-leaved forest in mid-subtropical zone. A sequential interaction oftemperature by the artifical warming facilities MSR-2420and nitrogen by NH4NO3applicationto the soil to Castanopsis fargesii and Castanopsis sclerophylla seedlings was set up in JiangxiDagangshan State Forest Ecosystem Research Station from2009to2011. By the application ofseveral international advanced instruments and Farquhar photosynthetic biochemicalmechanism model, at the same time, through the methods of plant physiological ecology,biochemistry, data collection outside and data analysis inside, the Castanopsis fargesii andCastanopsis sclerophylla seedlings response of growth and leaf gas exchange was illustrated.The results showed that the effects of warming, nitrogen application and its interaction to theCastanopsis fargesii and Castanopsis sclerophylla seedlings was different. On the basis ofintegrated analysis of the experimental data, the adaptive ability of Castanopsis sclerophyllaseedlings to warming, nitrogen application and its interaction was higher than that ofCastanopsis sclerophylla seedlings. The results will provide the theory in the leaf level for thecarbon cycle and caron sink/source change of evergreen broad-leaved forest in mid-subtropicalzone under future climate change scenarios.The main results are as the following：(1)Overall, in a different light intensities, the order of the photosynthetic capacity isCastanopsis sclerophylla> Cyclobalanopsis glauca(Thunb.) Oerst> Cyclobalanopsismyrsinaefolia (Blume) Oerst. The increase of CO2concentration has a significant role on thethree tree species photosynthesis, net photosynthetic rate, water use efficiency increases, lightcompensation point, stomatal conductance, transpiration rate decreases, it is favorable for thethe growth of leaf to CO2increases, which Castanopsis sclerophylla photosynthesis to promote the most significant effect, followed by Cyclobalanopsis glauca(Thunb.) Oerst andCyclobalanopsis myrsinaefolia (Blume) Oerst.(2)The photosynthetic capacity of Castanopsis fargesii is significantly higher thanCastanopsis sclerophylla. When the low air relative humidity (RH), high water vaporpressure between leaf and air (VPD), stomatal conductance (Gs) is reduced, the stomatallimitation value (Ls) increases, lower intercellular CO2concentration (Ci), netphotosynthetic rate (Pn) decreased; photosynthetically active radiation (PAR) at noon ishighest, the water vapor pressure difference (VPD), stomatal limitation value (Ls) reachesthe maximum, relative air humidity (RH), stomatal conductance degrees (Gs), intercellularCO2concentration (Ci) reaches a minimum for photosynthetic midday depression.(3)With the increase in the amount of nitrogen, Castanopsis fargesii and Castanopsissclerophylla, net photosynthetic rate (Pn), transpiration rate (E), stomatal conductancedegrees (Gs), apparent quantum yield (AQY) efficiency, CO2carboxylation efficiency(CCE) have significantly increased, but the increased amount of nitrogen does notsignificantly affect leaf water use efficiency (WUE), and the same nitrogen rate, water useefficiency (WUE) is not a significant difference. With the increase of the amount of nitrogen,chlorophyll a (Chl a), chlorophyll b (the Chl b), Chl a+Chl b of Castanopsis fargesii andCastanopsis sclerophylla were significantly increased, which reflects the two plants are on leafage increase in a certain degree of self-adaptive mechanisms.(4)On the contrast, low nitrogen, high nitrogen, warming, warming and facilities withlow nitrogen, warming and applying high nitrogen significantly improved diameter and treeheight of Castanopsis fargesii and Castanopsis sclerophylla. The same measurement time, thesame processing conditions, Castanopsis sclerophylla diameter and height were significantlyhigher than Castanopsis fargesii(P <0.01)regardless of the control. On the contrast, warming,nitrogen, warming and nitrogen fertilization significantly improve Castanopsis sclerophyllatotal biomass, aboveground biomass and underground part of the biomass. However, on thecontrast, nitrogen fertilizer caused the value of the aboveground biomass and underground part of the biomass significantly improved, there was no significant difference with control ofwarming and nitrogen fertilization.(5)Compared with the respective control, elevated warm and applied nitrogen alone andin combination significantly improved Castanopsis fargesii and Castanopsis sclerophylla,maximum net photosynthetic rate and apparent quantum efficiency respectively. Under thesame treatments, the maximum net photosynthetic rate and apparent quantum in Castanopsissclerophylla,was bigger than Castanopsis fargesii.Regardless of the control, elevated warm andapplied nitrogen alone and in combination, Castanopsis fargesii the dark respiration rate doesnot seem to did not show the apparent size of the order. the respective control, warming,nitrogen, elevated warm and applied nitrogen alone and in combination significantlyimproved the content of chlorophyll a, chlorophyll b and total chlorophyll content in theCastanopsis sclerophylla and Castanopsis fargesii. The same processing conditions,Castanopsis sclerophylla was much more than Castanopsis fargesii based on the contents ofchlorophyll a, chlorophyll b and total chlorophyll.