武陵地區防火線土壤性質與菌根苗木之研究

Abstract

大甲溪事業區於 1960年代大面積種植臺灣二葉松 (Pinus taiwanensis)，為顧及火災潛在危險性因而闢建防火線，但防火線成效不彰，現今多以植生防火林帶取代之，然復育成效不佳，故本研究希望透過接種菌根幫助防火樹種生長，使造林苗木得以存活並生育良好。本研究調查防火線土壤化學性質，以了解土壤的限制因子，並調查防火線植群菌根感染情況與菌種調查，隨後將大頭茶 (Gordonia axillaris) 種子苗接種分離自防火線之菌根菌，栽植於防火線及溫室，觀察菌根對苗木之效益。結果顯示，防火線土壤呈酸性 pH 值在 4.80-5.20，土壤可置換性鋁含量高 (287.02-671.89 μg g-1)，土壤有效磷不足 (0.01-3.11 μg g-1)，屬植物的缺磷範圍，全氮量 (0.19-0.31%) 與有機質 (4.38-7.84%) 則屬正常範圍。防火線植群皆有菌根感染情況，調查發現菌根菌有 Acaulospora mellea、Ac. spinosa、Glomus. constrictum、Gl. mosseae、Paraglomus occultum。大頭茶種子苗接種菌根後降低死亡率，栽植於防火線之苗木植體鉀含量顯著較高，鈉、鋁含量顯著較低，且土壤球囊霉素相關土壤蛋白質 (glomalin-related soil protein, GRSP) 顯著較高，溫室試驗之菌根苗木苗高、葉面積、平均葉面積及生物量與植體氮、磷、鉀、鈣、鎂和土壤 GRSP 含量都顯著較高，雖鈉、鋁亦較高，但苗木生長健康且無病徵，從變性梯度凝膠電泳 (denaturing gradient gel electrophoresis) 發現苗木確實有菌根菌感染情況。因此菌根應是植物在防火線生長的關鍵因子，且試驗亦證實接種菌根具有菌根效益，減少苗木因逆境造成的生長遲緩或死亡的情況。

Dajashi National Forest had been established by way of a large-scale cultivation of Pinus taiwanensis in the 1960s. The fire line was built to prevent the potential risk of fire, but it was ineffective. Now the fire line is replaced by vegetative fire break, but it’s difficult to reforest. Therefore, the aim of this study was to improve the growth of fire-resistant tree species through inoculating arbuscular mycorrhizal fungi. This study investigated the soil chemical properties in fire line to identify the soil limiting factors, surveyed the status of mycorrhiza colonization and examined mycorrhizal species in fire line. To observe the benefit of mycorrhiza inoculation, seedlings of Gordonia axillaris were inoculated with mycorrhizal fungi spores isolated from fire line, then planted in fire line and greenhouse. The results showed that the soil was acidic, with pH value between 4.80 to 5.20. Soil exchangeable Aluminum was in high concentration between 287.02 to 671.89 μg g-1. Soil available phosphorus concentration was low between 0.01 to 3.11 μg g-1, which belonged to a phosphorus deficient range of plants. Total soil nitrogen (0.19-0.31%) and soil organic matter (4.38-7.84%) were moderate. Fire line vegetation were all mycorrhizaed, and the mycorrhizal species Acaulospora mellea, Ac. spinosa, Glomus. constrictum, Gl. mosseae and Paraglomus occultum were found. After Go. axillaris seedlings were inoculated with mycorrhiza, the death rate decreased. The accumulation of potassium and the glomalin-related soil protein were significantly higher in the field experiments of inoculation treatments, and sodium and aluminum accumulation were significant decreased. On the other hand, the Go. axillaris seedings height, leaf area, average leaf area, dry weight and tissue nutrients (N, P, K, Ca, Mg) of inoculation treatment in greenhouse experiments and the glomalin-related soil protein in soil were also significantly increased. Although the accumulation of sodium and aluminum were increased, plants grew well and healthly. Denaturing gradient gel electrophoresis profile of rRNA genes was present in arbuscular mycorrhizal fungi on roots of Go. axillaris seedings. This study indicated that the most important factor of plant growth in fire line was mycorrhiza, and the experiment proved that mycorrhiza inoculation could prevent seedlings from growth retardation or death due to stress.