Abstract:

A secondary succession of vegetation on clearcut sites was studied in Western Sichuan. The coverage and biomass of trees, shrubs and herbs at different stages of succession have been surveyed. The result showed that the coverage and biomass of trees and shrubs have changed greatly in the succession. After the forest was cut, raspberry’s (Rubus idaeus) coverage was the greatest during the first 0–15 years, Red birch’s coverage was the greatest during 16–29 years, while the total coverage of other shrubs was greater than those of raspberry and red birch during 10–20 years.The following empirical formulas with good fitness have been used:

Ctree=0.803+2.347t1/2 (r=0.88 p<0.01)

Cshrub=l0.481 +l0.392T+0.373T2 (r=0.87 p<0.01)

Cherb=0.489+87.001/T (r=0.93 p<0.01)

C: biomass, kilogram/ha T: time period, year

According to the curves, the succession of vegetation can be divided into four stages: herb stage. 0—3 years;

raspberry stage: 4—10 year; shrub and small broad-leaved forest stage: 11—20 years, and small broad–leaved

forest stage: 21—29 years.