Effects Of Light Intensity, Nitrogen, Water On Carbon Fixing Capacity In Pinus Tabulaeformis

Pinus tabulaeformis, by virtues of light favorite, drought resistance, barren soil resistance, strong adaptability and fast-growing, is the main afforestation tree species of northern region. With forestry carbon sinks become the focus of the international community, as the main afforestation tree species of warm temperate regions, carbon sequestration mechanism of Pinus tabulaeformis is also received increasing concern.In this study, regarding the warm temperate zone afforestation P. tabulaeformis as the main study target, by setting four light gradient [LI (full sun), L2(25%shade), L3(50%shade), L4(75%shade)], four nitrogen gradient [NO (0.0), Nl (0.5), N2(1.5), and N3(2.5) g/kg soil], and four soil moisture water gradient [W1(10%),W2(30%), W3(60%), W4(90%)], explored the effects of different light intensities, light*nitrogen interaction and light*water interaction on photo synthetic physiological characteristics and the carbon sequestration capacity of Pinus tabulaeformis seedlings, expecting to provide a theoretical basis for carbon increase technologies of warm temperate main afforestation tree. We obtained the following conclusions:Shade was conducive to the improve of Pn in Pinus tabulaeformis seedlings, and resulted in a little increase in PS II photochemical efficiency (Fv/Fm). Moderate shade can increase the growth and biomass of P. tabulaeformis compared to that exposed to full sunlight. This indicates that P. tabulaeformis Seedling is resistant shade, has the ability to adapt to weak light, could efficiently take use of low light to increase its photosynthetic rate, consequently improved growth and biomass.In the same light levels, Nitrogen nutrition not only increased the net photosynthetic rate of Pinus tabulaeformis seedlings significantly, but also enhanced photoinhibition resistance of seedlings in full sunlight. This trend shows that, in order to maximize the amount of carbon sequestration of Pinus tabulaeformis, high light intensity and high nitrogen invest is necessary. This pattern indicates that high light intensity energetic and nutritional cost was necessary to reach PNmax and P. tabulaeformis seedlings showed physiological plasticity which enables the adaptation to higher energy uptake.To some extent, Shading and watering treatment alleviated drought and high light stress, thus improving net photosynthetic rate and carbon sequestration efficiency of P.tabulaefonnis seedlings. But excessive shade and watering it reduced net photosynthetic rate and carbon sequestration efficiency of P.tabulaeformis seedlings. This shows, in a certain extent. P.tabulaeformis seedlings has shade resistance, and is drought-tolerant plants.