Gap Characteristics Of Pinus Tabulaeformis Carr. Plantantion And Their Effects On Understory Regeneration

Gap characteristics are the base for further research on function, influence and law of dynamic change of gap. Logging gap produced by immediate cuttings are generally small-scale and transitory, but for forest stands where destructive interference is rather rare, this kind of small-scale interference plays a key role in the development of forest structure and status of forest lands, such as sunshine, soil moisture, litter decomposition and etc. Pinus tabulaeformis Carr. planted forest is one of the main forest types in Yanshan Mountain, playing an irreplaceable role in water and soil conservation of Yanshan Mountain and formation and maintenance of forest ecosystem. Therefore, the study on regeneration in logging gap of Pinus tabulaeformis Carr. has important practical significance for speedup of update of Pinus and promotion of sustainable management of planted forest.In order to further understand gap characteristics and its regeneration, data was gathered based on line transect method from Pinus tabulaeformis Carr. plantation of Xinfeng Forestry in Mulan Forestry Management Bureau of Hebei Centre which lies in Yanshan Mountain. The data included gap characteristics, canopy situation of leaves, regeneration in gap and diversity of shrubs and herbs. Afterwards, the data are analyzed by use of SPSS, ForStat, DPS, HemiView v2.1. The results are as follows:(1) Gap's characteristics shows: The majority of gaps (67.39%) range from 20 80m², among which gaps ranging from 40 60m² are in the majority. Anaphase and prophase gaps are the most whose percentages are respectively 31.11% and 40.00%. The gap markers are all stumps, which demonstrates that the existing gaps were mostly produced by intermediate cuttings or by illegal cuttings. Besides, the gap markers are mainly small-sized and medium-sized , which fully demonstrates that the gap of Pinus Tabulaeformis Carr plantation in the area are often influenced by people but the influence was not very much.(2)The regeneration within the gap may get benefit from proper gap interferences. The Pinus tabulaeformis Carr. in the 20 40m² gaps grow best; in the small gaps, the seedlings appeared earlier, but they are lower than average, and vice versa; the annual sampling's growing heights of regeneration in different areas of the gaps have significant differences without particular laws. The height of the seedling regeneration in the center areas>in the transitional areas>edge ares. That means the height of seedling regeneration in the center areas of the gaps is higher than that of the seedling regeneration in gaps around.(3) Though use of SPSS, it is found that there is a correlation between the abundance of Pinus tabulaeformis Carr. and environmental factor. The abundance of seedlings is influenced by the area of gaps and the height of gap border trees. The related equation is Y₁=11943.487-72.732X₁+0.535X₂ (R²=0.540, P=0.028), where Y₁ is the abundance of seedlings , X₁ is the area of gaps, X₂ is the average height of gap border trees; the scattered power of light in the gaps influences the abundance of seedlings directly, the related equation is Y₂=96559.143+1652.826X₃ (R²=0.311, P=0.004), where Y₂ stands for the abundance of seedlings, X₃ is the scattered power of light in gaps.(4)The diversity of shrubs and herbs in the gaps is much more than that of the seedlings under Pinus tabulaeformis Carr. (P≤0.01), fitting the herb species diversity, richness index and area relation curve presents a left shift of slope. The maximum value all in the gaps with 60 80m².