台灣北部福山地區天然闊葉林土壤種子庫與樹種更新之研究

Abstract

種子及小苗的生物量雖然僅佔森林植物社會的小部分，卻是植物更新的主要依據。因此有關種子與小苗的研究，對於解釋森林植群的演替及物種的更新策略極為有用。 本研究在台灣北部林試所福山分所之白校欑—紅楠型植群的鬱閉森林中進行取樣調查，共設置50個10×10m2的小區，調查小區中胸高直徑（DBH）大於1公分喬木的胸徑、株數及出現層級，同時記錄林下胸徑小於1公分的樹種小苗。於此50個小區中選取23個小區進行土壤種子庫實驗，共取45公升的土量，帶回實驗室進行萌芽試驗。 植物調查分析結果顯示喬木層主要由白校欑、紅楠及黃杞等構成。優勢喬木植物的徑級結構為L型或反J型，顯示此植群型於演替上屬於成熟穩定狀態，優勢樹種都能自我更新。其中白校欑、黃杞及厚殼桂具有較高的萌蘗能力，更新的苗木多為萌蘗苗；而長葉木薑子、山紅柿及綠樟的主幹萌蘗能力偏低，更新的苗木多為種子苗。土壤種子庫組成方面有42種物種，共計1053顆種子，密度為1166 seeds/m2；所萌發出的物種多屬於本地區的先驅物種，如?白饅頭果、食茱萸及野牡丹等，其中有一半種類屬於非樣區現有的物種。若以生活型區分，則以灌木層植物的種子數量最多。另由物種面積關係曲線得知本林型之最小取土面積為0.46m2。 比較土壤種子庫組成與林下小苗組成，可以發現本林型優勢的成熟樹種大多以萌蘗苗或種子苗來更新，即在鬱閉林下形成能耐陰的小苗庫；而次生樹種則是以種子形式埋藏於土中，也就是形成土壤種子庫，等待森林孔隙發生以進行更新。

Seeds and seedlings are just a small part of the total forest biomass, but the regeneration of forest plants is controlled by them. Therefore the study of seeds and seedlings is useful to elucidate succession and regeneration of forest plants. In this study, 50 plots with a total area of 0.5 ha. were established in the Castanopsis carlesii var. sessilis - Machilus thunbergii type forest in nothern Taiwan. In each plot, DBH, individual number, layer of stratification and seedling number of tree species were recorded. I selected 23 plots from above 50 plots to collect soil sample for the study of soil seed bank. 45 liters (in volume) of soil sample were collected. The canopy of the forest dominated by Castanopsis carlesii var. sessilis, Machilus thunbergii, and Engelhardtia roxburghiana. The population structures of dominant tree species are L type or reverse J type, indicating that this forest is mature and stable in succession and dominant species are all self-regenerative. Sprouting abilities of Castanopsis carlesii var. sessilis, Engelhardtia roxburghiana and Cryptocarya chinensis are high, and the sprouts play an important part of their seedlings for regeneration. Litsea acuminata, Diospyros morrisiana and Meliosma squimulata seldom occur sprouting, and most of seedlings for regeneration are coming from their seeds. 1053 seeds of 42 species were present in the soil seed bank. The average density is 1166 seeds/m2. Most species from the seeds in the seed bank are pioneer species of this area, such as Glochidion acuminatum, Zanthoxylum ailanthoides and Melastoma candidum. Half of the species doesn't occur in the investigative plots. Shrub species have most of seeds of the seed bank than other three types of life form. According to the species- area curve, the least size of soil sample for buried viable seeds is 0.46 m2. From the results of the soil seed bank and seedling investigation, it was found that the dominant primary tree species could form seedling banks under the closed canopy, regenerating by meas of sprouts or seedlings; but the pioneer tree species could form soil banks, waiting for the opening of canopy for the stimultion of germination and regeneration.