To explore organic carbon distribution characteristics in different soil aggregates of Wutai Mountain vertical zone

the soil samples which including subalpine meadow soil

mountain meadow soil

brown soil

leached cinnamon soil

and calcareous cinnamon soil from high altitude to low altitude were collected in August 2016. Water-stable aggregates in different levels (＞2 mm

2～0.25 mm

0.25～0.053 mm and ＜0.053 mm) of different type soils were harvested through wet-sieving method and physical fractionation technique

and the TOC

POC

and MOC of all level aggregates and soils were further analyzed. The results showed that subalpine meadow soil

mountain meadow soil

and brown soil all mainly composed by ＞2 mm aggregates

which accounted for 45.13% of all water-stable aggregates. However

cinnamon soil and calcareous cinnamon soil were mainly composed by 2～0.25 mm and 0.25～0.053 mm aggregates respectively

reached 33.79% and 39.95%. With the decrease of altitude

soil organic carbon content decreased. Besides

the organic carbon content of ＞2 mm and 2～0.25 mm aggregates in different type soils had a great significant positive correlation with the corresponding soil organic carbon content and the correlation coefficients were r＞2 mm=0.986

r2～0.25 mm=0.966 (P＜0.01). Although with the decrease of soil aggregates diameter

the POC contents of sub alpine meadow soil

mountain meadow soil

and brown soil decreased

and the POC contents of leached cinnamon soil and calcareous cinnamon soil increased. The MOC content of subalpine meadow soil

mountain meadow soil and brown soil were highest in ＞2 mm aggregates

and the MOC content of leached cinnamon soil

calcareous cinnamon soil were highest in 2～0.25 mm and 0.25～0.053 mm aggregates

respectively. The soil MOC content was significantly greater than the POC content

and these two showed a positive correlation in soils and all level macro-aggregates (P＜0.05). In addition

the content of POC and MOC in soils also showed a positive correlation with the content of soil organic carbon (P＜0.05). Therefore

the soil aggregates turned from macro-aggregates to micro-aggregates with the decrease of altitude

and the carbon capture ability of subalpine meadow soil

mountain meadow soil and brown soil was stronger than leached cinnamon soil and calcareous cinnamon soil.