ESJ56 一般講演（ポスター発表） PB1-311
*Hoshino, A.，Okuro, T.（Tokyo Univ.）, Jamsran, U.（Mongolian Agriculture Univ.）, Takeuchi, K.（Tokyo Univ.）
The objectives were: (1) to study which life forms (annual forbs, annual grasses, perennial forbs, perennial grasses and shrubs) showed different patterns along the abandonment gradient, (2) to study effects of invasion by perennial grass (Leymus chinensis) (patch) on early stages of secondary succession, soil penetrability and soil moisture. We analyzed changes in plant cover and species richness along an 18-year chronosequence in abandoned cropland.
There were the correlations between DCA axes1 and age of abandonments, DCA axes 2 and soil penetrability, respectively. The cover of annual forbs and annual grasses were replaced by perennial grasses within 9 years after abandonment. This change of life forms was true for species richness of each life form. There were not the differences in species richness by the existence of patch. Soil penetrability was significantly lower under the patch. In addition, it was considered by the results of correlations between DCA axes 1 and existence of patch in the fields abandonment in 1999 and between DCA axis 1 and non-existence of the patch in the fields abandonment in 1992, that existence of the patch droved the succession stage until 9 years after abandonment, although, there were opposite effect in 18 years from abandonment.