Effects of simulated nitrogen deposition on growth, biomass accumulation and photosynthetic characteristics responses of Quercus seedlings in Mid-subtropics of China
To clarify the effects of nitrogen deposition on the growth,photosynthetic characteristics and biomass accumulation and distribution of Quercus chenii,Q.acutissima,Q.variabilis,Q.fabri and Q.glandulifera var.brevipetiolata seedlings,a two-year term control experiment were conducted,in which NH4NO3 was added as the external nitrogen sources (four nitrogen depositions (0 (CK),5 g·m-2a-1(N5),15 g·m-2a-1(N15) and 30 g·m-2a-1 (N30)).The results show that (1) With increased nitrogen deposition levels,plants heights of Q.acutissima,Q.variabilis and Q.glandulifera var.brevipetiolata increased significantly,and medium and high concentrations of nitrogen deposition significantly promotes the diameter growth of Q.acutissima and Q.variabilis.(2) Light utilization efficiency of Quercus differed from each other species.Except Q.acutissima,maximum net photosynthetic rate,apparent quantum rate and light saturation point of Q.chenii,Q.variabilis,Q.fabri and Q.glandulifera var.brevipetiolata firstly increased,the peak was at the N15 level,then decreased;Meanwhile,light compensation point and respiration rate of Q.chenii and Q.acutissima increased gradually;in contrast,light compensation point and respiration rate of Q.fabri decreased,while on Q.variabilis and Q.glandulifera var.brevipetiolata increased at first and then decreased;Nitrogen deposition significantly favor the content increase of chlorophyll a,chlorophyll b and chlorophyll a+b in Q.fabri,Q.glandulifera var.brevipetiolata and Q.chenii,regardless of the nitrogen deposition levels.(3) As for the biomass accumulation in Quercus,regardless of the species,they gradually increased with the increase of nitrogen deposition level;however,biomass distribution in different species of Quercus significantly differed from nitrogen deposition levels,while the effects of nitrogen deposition levels on leaf weight ratio were insignificant;medium and high nitrogen levels increased the branches weight ratio of Q.acutissima and Q.chenii and significantly lead to higher stem weight ratio of Q.variabilis and Q.glandulifera var.brevipetiolata;root shoot ratio of the five Quercus tree seedlings were significantly reduced,and a higher nitrogen deposition level accelerated the reduction.
Quercussubtropicssimulation of nitrogen depositionseedlings growthbiomass accumulationphotosynthetic parameters
NETL
NSTL
万方数据
维普
