關刀溪森林生態系土壤有機質週轉率與土壤呼吸通量

The Turnover of Soil Organic Matter and the Flux of Soil Carbon Dioxide at Guandaushi Forest Ecosystem

土壤有機質是生態系初級生產量的主要組成，本文闡述台灣中部關刀溪森林生態系之土壤有機質與土壤呼吸量之境況，以瞭解土壤有機質在生態系之碳循環中的角色與變化。在穿越集水區不同林分的人行步道上劃設的採樣點，分別取樣並帶回分析其中有機碳與氮等營養含量，以及現場量測土壤表面二氧化碳的釋放速率。落葉層中總碳含量從220到550 g C m-2，而土壤層則為18.2到41.4 kg C m-2；總氮含量則分別為4.5～13.9 g N m-2與1.62～3.74 kg N m-2，進一步計算其碳氮比，落葉層為32～79，土壤層為11.3～15.7。土壤呼吸量隨季節變化，累計各樣點的長期觀測結果，土壤二氧化碳的釋放量為1.24到2.35 kg C m-2 yr-1。因此地下部的土壤碳儲量估計至少為16.9到39.5 kg C m-2，以異營性呼吸量佔總呼吸量50%計算，土壤有機質的周轉率估計至少為19. 3～51.1年。 The soil organic matter is a major constituent of the primary production of ecosystem. The soil nutrient contents and soil respiration were monitored at Guandaushi Forest Ecosystem Research Station, Taiwan to understand the fate and role of soil organic matter in carbon cycle of ecosystem. The sampling sites were located at route cross of the watershed of Guandaushi Creek. The amounts of soil carbon, nitrogen, and the other nutrient contents were analyzed in laboratory and soil respiration rate was determined in the field. The amount of total carbon ranges from 220 to 550 g C m-2 in titter layer, and 18.2 to 41.4 kg C m-2 in soil pedon. The amounts of the total nitrogen are 4.5-13.9 g N m-2 and 1.62-3.74 kg N m-2 in litter and soil layer, respectively. The C/N ratios of titter and soil layer are 32-79 and 11.3-15.7. The soil respiration rates varied with season. The soil carbon dioxide efflux ranges from 1.24 to 2.35 kg C m-2 yr-1. The belowground carbon stock of soil was estimated 16.9 to 39.5 kg C m-2. The estimated turnover rate of soil organic matter ranged from 19.3 to 51.1 years.

The soil organic matter is a major constituent of the primary production of ecosystem. The soil nutrient contents and soil respiration were monitored at Guandaushi Forest Ecosystem Research Station, Taiwan to understand the fate and role of soil organic matter in carbon cycle of ecosystem. The sampling sites were located at route cross of the watershed of Guandaushi Creek. The amounts of soil carbon, nitrogen, and the other nutrient contents were analyzed in laboratory and soil respiration rate was determined in the field. The amount of total carbon ranges from 220 to 550 g C m-2 in titter layer, and 18.2 to 41.4 kg C m-2 in soil pedon. The amounts of the total nitrogen are 4.5-13.9 g N m-2 and 1.62-3.74 kg N m-2 in litter and soil layer, respectively. The C/N ratios of titter and soil layer are 32-79 and 11.3-15.7. The soil respiration rates varied with season. The soil carbon dioxide efflux ranges from 1.24 to 2.35 kg C m-2 yr-1. The belowground carbon stock of soil was estimated 16.9 to 39.5 kg C m-2. The estimated turnover rate of soil organic matter ranged from 19.3 to 51.1 years.