| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 87 === The effect of simulated acid rain on two-year-old seedlings of five native broad-leaved tree species in Taiwan (Palaquium formosanum Hay.、Garcinia subelliptica Merr.、Palaquium obovata (R.Br.) Lam、Pittosporum pentandrum (Blanco) Merr. and Acer buergerianum var. formosanum (Hay.) Sasaki) was examined. Simulated acid rain (SAR) was prepared according to the chemical components of the rain in Taipei city, and pH was adjusted to 5.5, 4.5, 3.5 and 2.5 with sulfuric acid. SAR was applied at 14.07mm for 23mins, 12 times a month. As the results, seedlings treated with SAR of pH 2.5 showed visible damage symptoms on foliar after fifth treatment under sunny day and high temperature in middle June of 1998, which showed the sunny and hot day accelerated the appearance, severity, and type of the symptoms. P. formosanum, P. pentandrum, and A. buergerianum var. formosanum showed large area of lesion and necrotic spots on foliar. Under SEM examination, leaves of these species have thinner cuticle layer, meanwhile their epicuticular wax was degraded and peeled seriously that made epidermal cells exposed. The leaves of P. obovata have thicker cuticle layer, and their lower epidermis with dense trichomes were less damaged. G. subelliptica has thickest cuticle layer and was the least damaged. The central-broken necrotic spots often have hyphae surrounding them and crystallites deposited in the central point, which was composed of sulfur and calcium examined with EDS. Seedlings treated with SAR of pH 3.5 showed no visible damage symptoms on foliar but the upmost layer of epicuticular wax was tore. Seedlings treated with SAR of pH 4.5 and 5.5 had neither visible damage symptoms nor wax alteration. After 3-month treatment, SAR induced significant changes of the chemical properties of growing media except the nitrogen concentration. SAR of pH 2.5 decreased the pH, CEC, concentration of exchangeable Ca2+, Mg2+, Na+ and K+, whereas increased concentration of exchangeable Al3+ and Mn2+. As the treatment continued, those chemical properties were changed more seriously. SAR treatment had no significant effect on the growth, dry wet, concentration of P, Al, Ca, Mg, Na and K, however the nitrogen concentration of seedlings exposed to SAR of pH 2.5 increased significantly. In summary, the SAR treatment in 3 months induced visible damage symptoms on foliar, changed the chemical properties of growing media, but didn't influenced the growth and nutrition status of the seedlings.
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