土壤溫度、水勢和養分對土壤微生物呼吸的影響

Abstract

採自惠蓀林場杉木人工林地之土樣，於室內經不同土壤溫度 (12、20及28℃)、不同土壤水勢 (-0.33、-7.5及-15 bar) 及不同養分添加下 (NH4NO3、K2HPO4及不添加養分)，觀察土壤微生物呼吸速率變化情形。結果顯示，當土壤水勢為-7.5及-15 bar時，土壤溫度變化對土壤微生物呼吸有顯著的影響，土壤微生物呼吸速率隨著溫度的上升顯著地增加，分別由22.98增加至40.94 μg CO2 g soil-1 hr-1以及由25.91增加至37.89 μg CO2 g soil-1 hr-1；當土壤水勢為-0.33 bar時，三個溫度間之土壤微生物呼吸速率並無顯著差異，維持在31.90～35.93 μg CO2 g soil-1 hr-1之間。土壤微生物呼吸速率於不同土壤水勢條件下並無顯著差異，在不同溫度培育條件下，土壤微生物呼吸速率對土壤水勢所產生的反應亦有不一致的趨勢，當溫度為12℃時，以-0.33 bar土壤水勢下之土壤微生物呼吸速率較高；當溫度為20℃時，不同土壤水勢處理對土壤微生物呼吸速率並無影響；當溫度為28℃時，則以-7.5 bar土壤水勢下之土壤微生物呼吸速率較高。不論是何種土壤養分處理狀況下，土壤微生物呼吸速率皆隨著溫度上升而有增加的趨勢。土壤添加N養分後，不論於何種培育溫度條件下，皆具顯著增進土壤微生物呼吸速率之結果；在土壤中添加P養分，於12℃及20℃培育溫度條件下，對土壤微生物呼吸速率皆沒有影響，分別維持在21.88～24.69 μg CO2 g soil-1 hr-1及26.89～29.70 μg CO2 g soil-1 hr-1之間，當培育溫度為28℃狀態下，添加P養分處理之土壤顯著抑制了土壤微生物呼吸速率，由40.94降到30.07 μg CO2 g soil-1 hr-1。土壤微生物呼吸速率對於培育條件之改變所產生的反應有時不一致，推論應與土樣中微生物種類之變化有密不可分的關係，此部分仍有待進一步研究。

The soil used in this study was collected from China-fir plantation in Hui-Sun experiment forest. Soil samples were brought back to the laboratory and treated with different soil temperatures (12, 20 and 28℃), different soil water potentials (-0.33, -7.5 and -15 bar) and different soil nutrient additions (NH4NO3, K2HPO4 and controlled) to measure the variations of soil microbial respiration rate. The results showed that soil microbial respiration rate significantly increased with temperature when soil water potentials were -7.5 (from 22.98 to 40.94 CO2 g soil-1 hr-1) and -15 bar (from 25.91 to 37.89 CO2 g soil-1 hr-1). However, at soil water potential of -0.33 bar, soil microbial respiration rate ranged between 31.90 and 35.93 CO2 g soil-1 hr-1 which was not significantly different with temperatures. Soil microbial respiration rate was not significantly different with soil water potentials, and the variability of soil respiration rate incubated at different temperatures tended to be different with soil water potentials. When soil temperatures were at 12℃ and 28℃, those soils in -0.33 bar and -7.5 bar water potential had the higher soil microbial respiration rate, respectively, but it had no difference when temperature was at 20℃. Whatever the soil nutrient treatments were, soil microbial respiration rate tended to increase with temperatures. Nitrogen addition stimulated soil microbial respiration rate at three controlled temperatures. However, phosphorus addition had no effect on soil microbial respiration rate at 12℃ and 20℃ which were between 21.88～24.69 CO2 g soil-1 hr-1 and 26.89～29.70 CO2 g soil-1 hr-1, respectively. Otherwise, soil microbial respiration rate was reduced from 40.94 to 30.07 CO2 g soil-1 hr-1 at soil temperature of 28℃. It was suggested that soil microbial respiration has high relation to soil microbial species. Meanwhile, the effects of incubated conditions on soil microbial respiration rates were inconsistent. It was required more research in future.