Abstract: The study on dry matter production, accumulation and return of Paulownia elongata in crop Paulownia intercropping system shows that the biomass of P.elongata increased with tree age, and its distribution in each organ followed the sequence: stem>branch>root>foliage>flower. The yearly dry matter production mainly occured from May to July, accounting for 77.3% of the whole yearly production. Defoliation accounted for 87.1% of the total litterfall. Litter fell throughout the whole yearly growth period, and showed two peaks annually. The yearly dry matter accumulation mainly occurred from May to July, accounting for 72.7% of the whole yearly accumulation, and the dry matter return ratio during its whole life period reached 33.73%.

Key words: Crop Paulownia intercropping, Paulownia elongata, Biomass, Law of allometric growth, soil physical property, Ordos Plateau, shrub encroachment, abandoned cropland