Litterfall and the effects of thinning and seed cutting on carbon input into the soil in Scots pine stands in Turkey

摘要

Litterfall is one of the most important fractions of forest net primary production (NPP) and important carbon flux into soil, a large carbon pool in forests worldwide, and believed to account for about one-third of forest NPP. The aim of the study was to determine litterfall amount and carbon input into the soil via litterfall as well as to understand the effects of thinning (removing 20-25% of the initial basal area) and seed cutting (i.e. regeneration cutting with removing 60% of the initial basal area) on litterfall in Scots pine (Pinus sylvestris L.) stands. Litterfall samples were collected three times in a year from 32 sample plots for 5years in Turkey. Carbon concentrations of the litterfall components were determined by dry combustion. Data were evaluated by one-way ANOVA and multiple regression analysis. As a result, litterfall varied from 1389kgha(-1)year(-1) in young stands to 4488kgha(-1)year(-1) in mature stands. Carbon inputs into the soil changed between 714kgCha(-1)year(-1) and 2289kgCha(-1)year(-1) depending on the development stage and silvicultural treatment applied to the stands. Thinnings reduced litterfall amount at a ratio of 22% in mature stands while had no significant effect in overmature stands with a decrease ratio of 8%. Seed cutting reduced considerably the litterfall amount both in mature and overmature stands. A combination of basal area, site index, and stand age accounted for 75% of the variation in needle litterfall. In conclusion, seed cutting was recommended to do preferably in mature stands instead of overmature ones and thinning to be applied lightly in mature stands in order not to reduce carbon input into the soil via litterfall dramatically.