Effect Of Shading On Morphology And Physiology In Juglans Mandshurica And Tilia Amurensis Seedlings

The study set four kinds of environment light treatments (FL, LS, MS and HS), relative intensity as100%,(70±5)%,(50±5)%and (25±5)%. We grew2-year-old J. mandshurica and T. amurensis seedings in pots under four shading treatments, and observed morphology and physiology characteristics during the growth season in three consecutive years. The results showed that:(1)Shading significantly promoted the growth of height and basal diameter of J. mandshurica. In the first two years, the height growth of Juglans mandshurica of three shading treatments were significantly higher than FL treatment (P<0.05). The basal diameter growth of MS and HS treatments was significantly higher than FL treatment (P<0.05). Shading treatments did not change significantly between years in three consecutive years.(2) Shading promoted seedling biomass accumulation of J. mandshurica, and the accumulation of LS and HS treatments were larger. The root shoot ratio of FL treatment was significantly higher than shading treatments (P<0.05). The leaf biomass accumulation of shading treatments were significantly higher than FL treatment in first year (P<0.05). The root, branch, leaf and total biomass accumulation of the appropriate processing (LS and MS treatment) were higher than FL and HS treatmentin later two years (P>0.05). Shading promoted seedling biomass accumulation of T. amurensis in the first year, and inhibited it in later two years. In the first year, the root, leaf and whole plant biomass accumulation of MS treatment of T. amurensis was significantly higher than FL treatment (P<0.05). In the later two years, the root and whole plant biomass accumulation of FL treatment of T. amurensis was significantly higher than HS treatment (P<0.05). J. mandshurica seedlings accumulated more biomass and grow faster under LS treatment. J. mandshurica seedlings were more suitable for growing in the LS treatments. T. amurensis seedlings accumulated more biomass and grow faster under LS treatment in later two years, and they were more suitable for growing in the FL treatment.(3) Shading promoted seedling biomass accumulation of J. mandshurica, and more time more obviously. In the three years, with the increasing of shading degree, the leaf area increased. For three consecutive years, the leaf area of HS treatment was significantly higher than FL treatment (P<0.05). Shading promoted seedling biomass accumulation of T. amurensis, but not significant (P>0.05). With the increasing of shading degree, leaf dry weight(LMA) and leaf fresh weight (LFA) of J. mandshurica and T. amurensis decreased, and more time more obvious. In the third year, LMA and LFA of J. mandshurica and T. amurensis of FL treatment were significantly higher than other shading treatments (P<0.05). (4) For three consecutive years, the order of maximum net photosynthetic rate (Pmax) of J. mandshurica seedlings was LS>FL>MS>HS. The light compensation point{LCP) increased with the decreasing of shading degree gradually. The apparent quantum efficiency (AQY) of shading treatment was significantly higher than FL treatment (P<0.05). The dark respiration rate (R&) changed insignificantly, but the LCP of HS treatment was significantly lower than FL treatment (P<0.05). The maximum net photosynthetic rate (Pmax) of T. amurensis seedings gradually decreased with the increasing of light intensity. In the second year, the Pmax of HS treatment was significantly lower than FL treatment (P<0.05). In the third year, with the degree of shade increasing, the light compensation point (LCP) reduced gradually, and it has significant differences between HS and FL treatment. The Rd decreased gradually in three consecutive years.(5) The content of C, N, P and K of J. mandshurica and T. amurensis under shading treatment were not consistent. The C content of the two species of HS treatment were significantly higher than FL treatment in early two years (P<0.05). Shade promoted N content of species increasing, and N content of HS treatment was significantly higher than the FL treatment (P<0.05). The P content of two species decreased in the second year under shading treatment, but increased in the third year. And the P content of HS treatment were significantly lower than FL treatment in the second year and higher in the third year (P<0.05). Shading increased the K content of J. mandshurica, and the K content of HS treatment were significantly higher than FL treatment. Shading decreased the K content of T. amurensis.The results showed that, the morphological and physiological parameters of J. mandshurica and T. amurensis under shade conditions, performanced the adaptation strategies to shading. In morphology, two species increased the parameters of height, diameter, biomass accumulation, leaf area, modulated biomass allocation mode and decreased leaf weight to adapt to the low light conditions. In physiology, they adapted to low light conditions by increasing the chlorophyll content, leaf N content and decreasing light compensation point, dark respiration rate, as well as modulating the P and K content. Based on morphological and physiological characteristics to determine the shade tolerance was that T. amurensis was shade tolerant than J. mandshurica. Shade-tolerant species have lower relative growth rate, photosyncesis rate, LCP, LMA and leaf nitrogen concentration, and big leaf area. These traits decide that T. amurensis was more shade-tolerant than J. mandshurica.