| The increasing human activities and the extensive using of fossil fuels and fertilizer as well as development of animal husbandry emit a large number of nitrogen compounds, causing more and more serious environmental stresses such as affecting the normal growth of plants. At present, nitrogen deposition has become a hot topic in the international ecological and environmental research. Nitrogen is the essential for the growth of plant and is the element of material in leaf. Nitrogen deposition changes N cycle of ecosystem and influence the structure and function of ecosystem, the productivity of plant, pattern of competition of plant as well as compositions and diversity of species. The subtropical forest region in China seriously impacted by the nitrogen deposition due to the atmosphere pollution which caused as economic development rapidly.This paper selects the subtropical forest succession representative species of Masson pine Pinus massoniana Lamb, Schima superba, Cyclobalanopsis glauca to simulated nitrogen deposition experiments, a set of 4 nitrogen deposition processing gradient:control (CK: 0g·m-2·yr-1), nitrogen (LN:6g·m-2·yr-1), nitrogen (MN:12g·m-2·yr-1), nitrogen (HN:24g·m-2·yr-1), using real-time observation technology, using high spectral foundation data, through the analysis of different nitrogen deposition gradient on 3 kinds of plant chlorophyll content, light response curve, gas exchange parameters, spectral reflectance, spectral red edge parameters influence, on one hand deepen our understanding of the subtropical evergreen broad-leaved species seedlings physiological demand and ecological characteristics of the understanding, on the other hand by comparison, found that different nitrogen deposition rate on different successional stages representing species photosynthesis physiological ecological mechanism. In this experiment, we draw the following conclusions:Pinus massoniana Lamb:two experiments low nitrogen group of chlorophyll content, high nitrogen group is subject to different degrees of inhibition.In the autumn (2010 October and 2011 October) when the photosynthetic rate was significantly greater than that in summer, and the higher concentration of nitrogen deposition is generally promote the photosynthesis.Also found that the nitrogen treatment increases the stomatal conductance, intercellular CO2 concentration in the light intensity is less than 300μmol·m-2·s-1, no significant difference among different treatments to transpiration rate during the experiment showed an increasing trend year by year.The water use efficiency of Pinus massoniana Lamb during the experiment presented decreasing trend, in which the high nitrogen group water use rate of Pinus massoniana.2010 October trial period, Pinus massoniana Lamb in the control group, T1 leaf temperature and atmospheric CO2 concentration of Ca is influenced by the net photosynthetic rate of the main environmental factors.Low, high in nitrogen, group T1 leaf temperature, atmospheric temperature, atmospheric CO2 concentration of Ta,Ca RH and atmospheric humidity and net photosynthesis rate had significant regression.In 2011 June period of experiment, atmospheric CO2 concentration is the effect of Pinus massoniana Lamb net photosynthetic rate of the main environmental factors.Low, high nitrogen group is still in, leaf temperature, atmospheric temperature T, Ta, atmospheric CO2 concentration of Ca and RH is the main influencing factor of atmospheric humidity.In 2011 October period of experiment, the control group effects of net photosynthetic rate of environmental factor increase, mainly for T, leaf temperature, atmospheric temperature, atmospheric CO2 concentration of Ta,Ca and RH atmospheric humidity.But, in low, high nitrogen group, mainly leaf temperature, atmospheric CO2 concentration of T,, Ca two environmental factors.The two experiments can be compared to find, high nitrogen group of Pinus massoniana Lamb in the visible light emission rate has always been the largest, description of the persistence of nitrogen treatment on the in the visible light reflectance effsct.inus massoniana Lamb low nitrogen group of two normalized difference vegetation index NDVI, gNDVI and two ratio vegetation index are the largest.Schima superba:Schima superba in the two experiments:three nitrogen deposition gradient experiment group content of chlorophyll are subject to different degrees of inhibition, nitrogen group of Schima superba chlorophyll content was the lowest, and the obvious difference in different experimental groups.In different seasons, high nitrogen treatment of Schima superba photosynthetic rate is always the biggest.Stomatal conductance during the experimental period was increased year by year, the high nitrogen treatment of stomatal conductance is always the biggest.Schima superba of the intercellular CO2 concentration in the light more than 500μmol·m-2·s-1, along with the increases of decreased slowly, reaching saturation.Charge of the transpiration rate and light intensity showed a linear increase relation.In the light of 1500μmol·m-2·s-1, high nitrogen group of Schima superba transpiration rate, different seasons and years of transpiration rate directly, the gap is larger.Low nitrogen group of Schima superba water use rate is maximum, and the high nitrogen and nitrogen treatment on the superba water use efficiency difference was not significant, were lower than those of control group and low nitrogen group. In 2010 June period of experiment, leaf temperature, atmospheric temperature T1, Ta, atmospheric CO2 concentration of Ca and RH is the impact of atmospheric humidity of Schima superba net photosynthetic rate of the main environmental factors.In 2011 June period experiments leaf temperature T1, atmospheric CO2 concentration in Ca effect, high nitrogen group of Schima superba net photosynthetic rate of the main environmental factors.In 2011 October period of experiment, leaf temperature, atmospheric temperature T1, Ta, atmospheric CO2 concentration of Ca and RH is the impact of atmospheric humidity control group, low nitrogen and nitrogen were the main environmental factors.Leaf temperature, atmospheric CO2 concentration of T1, Ca and atmospheric humidity RH is the impact of high nitrogen group main environment factor.Low nitrogen and nitrogen group of Schima superba in red light absorption Valley band emission rate difference was not significant, are the maximum value.Schima superba is nitrogen in a group of two normalized difference vegetation index NDVI, gNDVI and two largest ratio vegetation index.Cyclobalanopsis glauca:cyclobalanopsis glauca in two experimental record, chlorophyll content in response to simulated nitrogen deposition is not obvious, different concentration gradient directly the difference was not significant, nitrogen deposition on chlorophyll content had no significant effect on.Different experimental treatments, photosynthetic rate change is not obvious. The control group stomatal conductance was significantly lower in nitrogen deposition processing, and high nitrogen group of stomatal conductance maximum. Cyclobalanopsis glauca different nitrogen deposition treatment of intercellular CO2 concentration were greater than the control group, and the high nitrogen group is the biggest.itrogen deposition treatment of Cyclobalanopsis glauca transpiration rate were higher than the control group, in which the low nitrogen group of Cyclobalanopsis glauca transpiration rate maximum. Summer experiment, low nitrogen treatments on water use efficiency was significantly greater than the other groups, and in the autumn, is the largest group. Different concentrations of nitrogen deposition processing differences between the not obvious.In 2010 June period of experiment, air temperature, atmospheric CO2 concentration of Ta Ca and RH is the impact of atmospheric humidity of low nitrogen and high nitrogen group net photosynthetic rate of the main environmental factors.Leaf temperature, atmospheric temperature T1, Ta, atmospheric CO2 concentration of Ca and RH is the impact of atmospheric humidity control combined nitrogen group main environment factor.In 2011 June period of experiment, leaf temperature, atmospheric temperature T1 Ta, atmospheric CO2 concentration of Ca and RH is the impact of atmospheric humidity of control group and the nitrogen and high nitrogen group main environment factor. While the leaf temperature, atmospheric CO2 concentration of T1, Ca was affected by low nitrogen group of net photosynthetic rate of the main factor.In 2011 October period of experiment, leaf temperature, atmospheric temperature T1, Ta, atmospheric CO2 concentration of Ca and RH is the impact of atmospheric humidity of different experimental group the main environment factors.Cvclobalanopsis glauca in visible light band reflectance fluctuation make clear, the maximum value from 2011 June period of experimental high nitrogen group changes for 2011 October period of low nitrogen group.Its vegetation index change lack of regularity, can well reflect the physiological effects of nitrogen deposition on. |
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