重新被“激活”的土壤无机碳研究

荒漠区植被稀疏、土壤有机碳含量低,在全球碳循环研究中,一直被忽略。但2006年前后,若干研究显示干旱荒漠区具有潜在的碳汇功能,一直被认为是死碳的土壤无机碳开始受到关注,长期被忽视的干旱荒漠区无机碳碳循环重新进入人们的视野。后续的研究显示,土壤中的溶解性无机碳并非来自土壤本身的碳酸盐,而是来自土壤空气或大气,是现代碳循环的一个重要环节。土壤温度的变化改变了CO2在土壤溶液中的溶解度,催生出一个日出夜进的"无机呼吸"过程。这个"无机呼吸"过程在广义干旱、盐碱土区普遍存在;在土壤生物过程微弱的荒漠区,可以主导地-气界面的碳交换。盐碱土改良过程中溶解性无机碳的淋洗,更可以直接形成储存于地下咸水层的无机碳汇。总之,在生命过程微弱的干旱荒漠区,无机碳过程可以主导地-气界面碳交换与碳汇的形成:尽管这里起关键作用的不是土壤碳酸盐,而是土壤中的溶解性无机碳。

The Effort to Re-Activate the Inorganic Carbon in Soil

About ten years ago,the long-have-been neglected region in carbon cycle study,the desert region,started to get attentions,as several studies indicated that this was a huge potential carbon sink. The sparse vegetation and poor humus in desert soil made the inorganic carbon in desert soil the first candidate for seeking carbon sink. The following studies revealed that the dissolved inorganic carbon(DIC) is of atmospheric origin,and is an active participant in modern carbon cycle. Diurnal temperature variation changes the solubility of CO2 in soil water,which in turn created an“inorganic respiration”in the soil with CO2 pumped day-in/night-out. Extra irrigation,aimed at washing salt out of the soil in the largely saline/alkaline arid region,also washed the DIC out of the soil and forms a carbon sink in the groundwater. Studies thus far still can not prove that carbonates in the soil is an active player in modern carbon cycle,but can prove that in the desert soil with weak biotic processes,abiotic process may not only dominate CO2 exchange between soil and atmosphere,but also create carbon sink of inorganic nature.