浙西北茶园土壤固碳能力及其不同形态有机碳的积累特点

Carbon sequestration potential of tea garden soil in northwest Zhejiang and its accumulation characteristic on different fractions of organic carbon

为了解茶园土壤的固碳能力及其积累特点,从浙西北茶区采集黄筋泥、黄红泥土和黄泥土等3类土壤上的9个代表性茶园土壤剖面的分层土样,每类土壤包括植茶年龄为5～10、15～20和〉30年的3个剖面,分析了有机碳、轻组分有机碳、颗粒态有机碳、微生物生物量碳和水溶性有机碳在土壤剖面中的积累特点,并与利用时间相似的旱地土壤进行比较。结果表明：茶园土壤的各类有机碳具明显的表聚特征,随剖面深度的增加,轻组分有机碳和颗粒态有机碳含量占土壤有机碳总量的比例较有机总碳的下降更为明显;随着植茶年龄的增加,表层土壤中各类有机碳含量及全剖面有机碳贮量明显地增加;表层土壤中〉2mm粒组的水稳定性团聚体明显增加,同时,表层土壤中积累的有机碳（特别是轻组分有机碳）趋向于分布在〉2mm粒组的水稳定性团聚体中;轻组分有机碳和颗粒态有机碳随植茶时间的增加幅度明显大于有机碳总量的增加,表明在植茶过程中有机碳主要以活性较高的轻组分有机碳和颗粒态有机碳的形式积累,且积累的有机碳主要分布在近地表的土层。比较分析表明,茶园土壤有机碳的积累量均高于旱地土壤,说明茶园比一般旱地具有更高的土壤固碳潜力。

Organic carbon is the basis of soil system,which plays an important role in the soil quality and regulating the supply of nutrients.Physical,chemical and biological properties and productivity of soil were all closely related to the content and character of organic carbon.Therefore,the maintenance of organic carbon in soils is emphasized by various soil researchers and land managers.Appropriate organic carbon contents in soils could increase cation exchange capacity（CEC）,moisture storage,mineral nutrients,and food source for soil organisms,and improve soil structure and aggregate stability.As an important component in carbon pool of terrestrial ecosystem,soil organic carbon plays an important role in regulating greenhouse effect and global warming.Organic carbon contents in soils depended on the factors such as climate condition,soil type,mineralization process,and land use type and management.For a given soil,the maximum amount of organic carbon generally accumulated in the topsoil under long-term undisturbed vegetation,typically grassland or forest.Loss of organic carbon is generally regarded as undesirable,though some reports pointed out that low soil carbon contents can reduce application rates of pesticides in soil due to lower sorption.It is well known that various kinds of soil management can cause changes in organic carbon concentrations,and the carbon contents of cropped and tilled soils are usually lower than those of undisturbed grassland or forest.The decline of organic carbon contents was often caused by top soil erosion and breakdown of stabilized soil.To understand the sequestering carbon potential of tea garden soil and its accumulation characteristic on different fractions of organic carbon,soil profile samples were collected from nine tea gardens and three uplands in northwest Zhejiang.Samples from nine tea gardens were divided into three groups（quaternary red clay,yellowred soil and yellowish red soil）,each group corresponding to three tea plantation ages（5-10 years,15-20 years,and 30years）.The contents of total organic carbon,light-fraction organic carbon,particulate organic carbon,microbial biomass carbon and water soluble organic carbon in the soil samples were analyzed,and compared with those local upland soils with similar utilization time.The results showed that different fractions of organic carbon in the tea garden soils had surface accumulation pattern,and the proportion of the light-fraction and particulate organic carbons in the total organic carbon decreased faster with depth than the content of total organic carbon itself.Furthermore,different fractions of organic carbon in the surface soil and storages of total organic carbon in the whole soil profile increased with the age of tea plantation;the water-stable aggregates with size 〉2 mm increased obviously in the surface soil.Meanwhile,the organic carbon accumulated in the surface soil tended to distribute in the water-stable aggregates of〉 2 mm,especially for the light-fraction organic carbon.Increase rate of the light-fraction and particulate organic carbons was greater than that of the total organic carbon with aging of tea plantation,suggesting that the light-fraction and particulate organic carbons with higher activity were the main forms accumulated,and the organic carbon accumulated in the soils was mainly distributed in the surface layer.It is concluded that the accumulation rate of organic carbon in the tea garden soil is significantly higher than that in the upland soil.Therefore,the tea garden soil has a greater potential of sequestering carbon than the upland.