Effects of Litter Layers on the Establishment and Growth of Orchardgrass (Dactylis glomerata L.) Sown on the Cutover Land of Larch-tree Forest

The objective in a series of our field experiments is to improve the low-input method of pasture establishment by using effectively the tree litter resources. In this report, the effects of litter layers on the establishment and growth of orchardgrass (Dactylis glomerata L.) sown on the cutover land of larch-tree (Larix leptolepis MURRAY) forest without chemical fertilizer was investigated. L, F and H litter layers on the forest floor remained completely in the experimental field just after clear cutting. Weight of fresh litter was 1.47kg DM/m^2 in L and F layers and weight of decayed litter mixed with soil particles was 1.55kg DM/m^2 in H layer. Three different litter layer treatments were applied to seed-bed plots. They were; I: Seeds were sown on the forest floor, removing the all three litter layers. II: Seeds were sown on the H litter layer, removing L and F layers. III: Seeds were sown on the litter layers (without disturbance). Orchardgrass seeds were sown without chemical fertilizer in each plot, one week after seed-bed preparation. Nitrogen mineralization activity of tree leaf litter was also estimated by incubation, in order to evaluate the nitrogen supply in each litter layer. Results are summarized as follows: 1. Litter layers suppressively influenced the emergence of orchardgrass by their physical factors. However, the seedlings established on the bare soil suffered from frost damage due to retarded growth by the low levels of nutrients released from litter layers. The mortality during the winter was much higher in the I Plot compared with the other plots. The population numbers of orchardgrass after 10 months of sowing were 8,260 and 108 plants/m^2 in the Plots I, II and III, respectively. 2. Growth of individual orchardgrass was obviously stimulated by chemical factors of litter layers, so that the maximum weight per tiller after 10 months of sowing was obtained in the Plot III. However, dry matter weight was about 30g/m^2 in both plots II and III due to relatively high population. 3. The amounts of inorganic nitrogen released from tree leaf litter after 8 weeks of incubation were 0.24, 1.18 and 0.30mg/g litter in L, F and H layers, respectively. Those were equivalent to 0.8, 13.2 and 4.7kg N/ha. However, nitrogen mineralization activity of the surface soil was much lower than that of tree leaf litter. Larch-tree forest litter was considered to be useful for the low-input pasture establishment, but their nitrogen effect was evaluated to be relatively low as compared with that of deciduous broad-leaved forest which was investigated in the previous report.