Canopy Gap Characteristic And Its Effects Of Larix Principis-rupprechtii Plantation In Yanshan Mountain

The forming and disappearing process of canopy gap is an important ecologicalprocess for the forest to grow and regenerate. The study on the basic characteristic andeffect of the canopy gap, can help to further find the rule of the canopy gap to the forestcommunity structure and its dynamic change, and to make the best of the mechanism ofthe canopy gap to forest regeneration, biodiversity, and the stability of the forestecological system., so that to provide the ecological foundation for the forest sustainablemanagement. The Yanshan Mountain is an important component of around-Beijing andTianjin ecological barrier, as well as the main water source area of the Luanhe Riverdraubage basin. But, because of human's frequently disturbance to the forest, the forestvegetation in this area has degenerated greately. Since the foundation of the People'sRepublic of China, large areas of Larix principis-rupprechtii plantations were cultivatedin the Yanshan Mountain. However, due to the shortage of the ecological basal researchon the Larix principis-rupprechtii plantations, and the relative lag of the forestmanagement, a large quantity of Larix principis-rupprechtii plantations has thecharacters of low self-regeneration ability, low production ability, irrational standstructure and instable ecosystem. So the plantation sustainable management has becomea significant task for the forestry development in this district.In this paper, Larix principis-rupprechtii plantations in Mulan Forest ManagementBureau located in Yanshan Mountain were researched, using the combinative method ofline transect and standard sample plot research. By studying the canopy gap characterand its effects to the environment of Larix principis-rupprechtii plantation, and therelationship between the canopy gap and the changes of plantation biodiversity, it can beconfirmed that due to the plantations were greatly disturbed by human beings, theplantation's canopy gap has lots of different characters with the natural forest, and theeffects of the canopy gap to the environment, growth of forest and biodiversity are alsodifferent.The canopy gap of Larix principis-rupprechtii plantation is mainly caused by thedisturbances of the human beings, in which tending is the most important interferencefactor, meanwhile other factors, such as fixing individual plant, unhealthy growth, deathand the non-surviving forestation, can also effect the forming of the canopy gap; theshape of the canopy gap is mainly rectangle and ellipse; the area changes of the canopygap is between 4.1 and 81.1 m~2, and is 25.4 m~2 on the average. The study indicates that the canopy gap has some effects to the environment factor,including the annual and daily changes of temperature and humidity. The averagetemperature in the canopy gap is higher than the non-canopy gap stand during April toAugust, in which the temperature of the central canopy gap is 1.2 to 2.8℃higher than inthe middle of the stands during May to July. In September to December, the averagetemperature in the canopy gap is higher than the non-canopy gap in sunny day, but it isreverse in the cloudy day. The rules were indicated that the temperature differences areobvious in the noon, but are small in the morning and dusk. The effect of the canopy gapto humidity embodied that the humidity in the canopy gap is lower than in the stand, andit is more obvious in the Sunny day, while relatively small in the cloudy day. Themaximum differences in humidity appeared in the evening of July to September, which is9.2 to 10.8 percents lower than in the stands. The character is that the humidity differenceis least in the morning, takes second place in the noon and is maximal in the dusk in theterm of daily changes.The existence of the canopy gap made the boundary wood a larger growth space.Therefore, the canopy gap can promote the growth of the boundary wood in somedegrees. The average DBH (diameter at breast height) in the canopy gap is obviouslyhigher than that in the stand, and the average growth rate is 0.15% higher, the averagevolume of each individual boundary wood is 0.0043m~3 higher than in the stand. In thesame time, the differentiation of boundary wood has a larger randomicity.The existence of the canopy gap created conditions for the herbage plants toimmigrate and grow. The plant species, general plants number, average height anddiversity index of the herbage plants in the canopy gap are higher than the non-canopygap stand. However, they were similar in the species component, general plant numberand species diversity index of the shrubs.