Abstract:

Objective: A Mytilaria laosensis plantation after strip clear-cutting was used to study the temporal and spatial dynamics of seed rain sand submerged seed in the reserved belts (hereinafter referred to as the reserved belts) and the stripclear-cutting sites (hereinafter referred to as the clear cutting sites), in order to provide scientific basis for the harvesting design and natural regeneration of the plantation. Method: After the plantation had been harvested with strip clear-cutting, three fixed plots were respectively set in the reserve belts and the clear-cutting sites, and the seed rain in the fixed plots was surveyed for two consecutive years. Based on the data of the surveys, the composition of the seed rain in different fixed plots was analyzed with the single factor variance analysis and t test. The seed rain densities and submerged seed densities on the strip clear-cutting sites with different distance to the forest edge, were respectively simulated and forecasted with a power function model, exponential function model, logarithm function model that transformed from the power function, and logarithm function that transformed from the exponential function. Results: For the seed rain of the plantation, the starting phase was in late September to October, the peak period was in the middle and late October to December, the fading period was from late December to early January of following year. In the reserve belts, both the seed rain and submerged seed densities had no significant difference in different plots in the same year, and in the same plot in different years. At the clear-cutting sites, both the seed rain and submerged seed densities with few equidistant location away from the forest edge, had a significant difference (P < 0.05) in different plots in the same year, or in the same plot in different years. Percentage of submerged seed with seed rain at the clear-cutting sites, was increasing at first then declining with the increase of distance to the forest edge. Spatial distribution of the seed rain and the submerged seed densities on the clear-cutting land of the reserve belts were approximately exponential distribution, the farthest distance away from their spread was 25 and 20 m respectively. Objective: In the forest plantation which reached the mature age, the seed source was very sufficient for natural regeneration. If harvesting time of the plantation is from December to the end of January of next year, when the seeds have been scattered and are sufficient, the strip clear-cutting with no limit width and clear-cutting could be chosen as the ways of harvesting and regeneration for the plantation, but ways of the strip clear-cutting and clear-cutting should be under the premise of meeting the national policy on artificial forest harvesting. If the harvesting time is from June to September, suitable width and maximum limit width of the strip clear-cutting should be respectively within 35 and 40 m. The logarithmic function model based on exponential function transformation is better to simulate and forecast dynamics of seed rain and submerged seed densities on the clear-cutting sites of the reserve belts with the increasing distance of forest edge.

Key words: Mytilaria laosensis plantation, strip clear-cutting, seed rain, submerged seed, spatial-temporal dynamics, distribution forecasting, cutting regeneration design