Characteristics And Regeneration Of Schima Superba Forest Gap Caused By Snow Disturbance

An unusually severe freezing rain and snow disaster of continuous low temperature covered a wide range of southern China from January to February in early 2008. This disaster caused signiifcant loss to human's work and life, especially on forests. There were many studies focusing on damaged forest ecosystems. The paper, in order to show characters of distribution and formation of Schima superba forest gap, rules of temporal-spatial distribution of the gap microclimate, characters of regeneration in the gap after the snow disaster, the characters of gap and regeneration of Schima superba forest gap, a typical forest type of the stricken area, were analyzed by sample survey and mathematical statistics. All these will provide the scientific basis for the succession and restoration of Schima superba forest. The main results are as follows:(1) Quantitative studies on Schima superba forest in Jianglang Mountain of Zhejiang Province showed that: the gaps of 50～100 m~2 of most expanded gaps occupied the highest percentage in number (45% of the total),while those of 50～100 m~2 also occupied the highest percentage in size (30.31% of the total). The gaps of 25～50 m~2 occupied the highest percentage in number and size (50% of the total and 36.39% of the total). The most important manner of gap formation was Breakage on trunk (BT), and the secondly important manner was Uprooting (U). Gaps were most formed by 4～6 gap makers(65.91%). The gap maker of 6～10m high occupied the highest percentage in number (53% of the total).(2) Microclimate factors of Schima superba forest gap were analyzed, and the results indicated that: daily change of light intensity, temperature, humidity and other climatic factors in gaps of different size and non-gap stands revealed a unimodal. The Peak of the light intensity and the temperature was at 11:00 to 13:00 and 12:00 to 14:00 respectively. Daily change of the humidity of the air was high in the morning and afternoon but low at noon. The minimum of air humidity appeared at 12:00 to 14:00. The soil water content displayed in the vertical direction that top layer was higher compared to lower level; from center to the non-gap stand showed a gradient changing pattern,the soil water content decreased with distance from gap center to understory. There was little different between the Soil pH of the gap and the non-gap.The pH of soil in the gap was slightly higher than the non-gap for each vertical layer correspondingly. And the soil pH inereased gradually with depth. But there were significantly difference for nutrients in vertical layers. Besides the total potassium content which inereased gradually from the surface layer to the deeper layer, other nutrient elements were just in reverse, and the nutrient content in the surface layer was higher obviously than other layers. The contents of the organic matter, the total nitrogen, the alkaline hydrolysis nitrogen,the rapidly available phosphorus and the rapidly available potassium in non-gap were higher than those in gap,but the contents of the total phosphorus, the total potassium in soil in gap were higher than those in non-gap. The results supplyed a basis in further studying canopy gap microclimate and the relevant ecological phenomena.(3) In the gaps, the growth status of seedlings and saplings were better than them in the control stands. And the seedlings and the saplings grew better in the medium gaps than them in the small gaps and the large gaps. And there were obvious difference in the density, the height and the basal diameter of seedlings and saplings. Moreover, there were a significant difference in the height and the basal diameter of seedlings and the basal diameter of saplings of Schima superba, but there was no obvious difference in the height of saplings. The density of regeneration seedlings increased with the gap size, the maximum value of regeneration density was in gap of 76m~2, then the density rapidly reduced with increasing of gap size. Regeneration seedlings in medium and small gaps were mainly small seedling, seedlings of Schima superba in the gap over 100m~2 grew rapidly, and the proportion of medium seedlings was higher.