桉树人工林种植初期土壤团聚体磷素有效性变化特征

Characteristics of Phosphorus Availability in Soil Aggregates of Early Age Eucalypt Plantations

研究土壤磷素有效性在团聚体尺度下的微观表征,对促进土壤生态系统磷素循环具有重要意义。以广西国有大桂山林场为研究区域,选择传统轮伐期内1年生、2年生和4年生巨尾桉人工林土壤以及邻近撂荒地土壤(CK)为研究对象。采集表层土壤(0~20 cm)并通过湿筛法将其分为>2 mm、1~2 mm、0.25~1 mm和<0.25 mm粒径团聚体,测定全土和团聚体中全磷和有效磷的含量和储量,并计算磷素活化系数。结果表明:各处理土壤全磷含量在各粒径团聚体中分布较均匀,而土壤有效磷含量和磷素活化系数在>2 mm粒径团聚体中最高。与CK相比,不同林龄桉树人工林土壤全磷和有效磷含量均有所升高,且产生显著差异。随林龄的增长,土壤全磷和有效磷储量均呈现下降趋势,在1年生时显著最高。不同粒径土壤团聚体全磷和有效磷储量与土壤团聚体组成比例显著相关,CK和不同林龄桉树人工林土壤磷素储量均在>2 mm粒径团聚体中较高。因此,在桉树人工林培育过程中,应重视土壤>2 mm粒径团聚体的保护,以维持土壤团聚体的稳定和土壤磷素的储存。

It is of significance to study the microscopic characterization of soil phosphorus(P)availability at aggregate scale to understand phosphorus cycling in soil ecosystems.In this study,the state-owned Daguishan Forest Farm in Guangxi was selected as the research area and the soils of 1,2 and 4–year-old Eucalyptus grandis×E.urophylla plantations and adjacent abandoned land(CK)were selected as the research objects over a traditional rotation period.The topsoil(0~20 cm)was collected and divided into aggregates of different sizes(including:>2 mm,1~2 mm,0.25~1 mm and<0.25 mm)by the wet screening method.The contents and stocks of total P and available P in the bulk soil and aggregate were determined by laboratory experiments.The results showed that the distribution of total soil P content in eucalypt plantations of different ages was uniform in the aggregates of different sizes,and the soil available P content and P activation coefficient were the highest in the>2 mm aggregates.Compared with CK,the contents of total soil P and available P in eucalypt plantations at different ages were increased,and there were significant differences among ages.With the increase of stand age,total soil P and available P storage showed a downward trend,and reached the highest value at age 1 year.The total soil P and available P storage of soil aggregates with different sizes were significantly correlated with the composition of soil aggregates.Soil P storage of CK and eucalypt plantations of different ages were highest in the>2 mm aggregates.Therefore,the protection of soil component comprising>2 mm aggregates should be emphasized in the cultivation process of eucalypt plantations to maintain the stability of soil aggregates and the storage of soil P.