Yearly replanting of tillage crops increases soil erosion. Revegetation is the process of replanting and rebuilding the soil of disturbed land. Successive harvests give decreasing yields, eventually justifying replanting. Ancient bunjae trees were taken for replanting as bonsai in Japanese gardens. Plants with corms generally can be propagated by cutting the corms into sections and replanting. When well managed, the plantation soils can sustain endless replanting. This included upgrading worker housing, repairing old machines, and replanting farmland. Replanting and management of the oak forests was promoted at this time. Reforesting efforts have focused on replanting native tree species, versus those used for wood production. The target of replanting 60,000 trees a year was not met. Over time, there was a feedback policy on the amount spent for replanting forests. Replanting of brownfield land has created new parks and recreation areas. It represents the tree replanting effort that has been underway at the Presidio. Members of Maiduguri's official Association of Firewood Sellers provide labor for tree replanting efforts. The usual Monsanto claim involves patent infringement by intentionally replanting patented seed.