Study On The Stand Growth-Environmental Relationships Of Larix Plantation At Saihanba Of Hebei Province

Based on the collection of existing materials and the complementary investigations, this research analyzes the forest types, the structural law of the forest community and the distribution law on Saihanba, explors the influence of the stand densities, the stand types, the altitudes and the slope positions of the plantation of the North China larix on Saihanba on the forest biodiversity, and their interaction relationship between each factor, studies the quantitative relationship between the tree growth and the geographical factors and the meteorological factors for the plantation of the North China larix on Saihanba, and investigates and analyses their pattern rules and influencing factors during their natural regeneration. The result shows:Saihanba is one of the areas in which there are relatively rich plant species in Hebei province. This area has the typical attribute of north temperate zone and the properties of transition between forest and grassland. Although it has many mesophytes, it also has considerable amount of drought-resistance grasses.The result of research on the biodiversity of the plantation of the North China larix on Saihanba shows: at the density of 600～900 trees/hm~2, the stand distribution is relatively uniform. The diversity index reache maximum. In this case the canopy density of the larix stand is relatively small. The light condition of forest understory is good, which provides the undergrowth herbage layer with suitable growing environment. This shows density has a ceitain influece on species richness in the forest of the North China larix. In the case of stand types, in the stands of different stand types, in the mixed forest the evenness index (Jsw) of bush plants based on the diversity index (H) and the evenness index (Jsi) based on the diversity index (D) are both higher than the index in the pure forest, which indicates that the distribution of shrub species in the mixed forest is more even than that in the pure forest. In the case of stand density, when altitude reaches 1600m, all the index reache maximum. When the altitude continues to increase, the index tend to decrease with the increase of altitude. The result also shows that slope position also has a certain influece on plant diversity. The index of plant diversity in gullies or in lower slope positions are higher than that in upper positions. The data analysis shows that the correlation between these different diversity index are very close. With the increase of diversity index (H), the correlation of all the other diversity index is very significant. The relationship between the evenness index of herb species (Jsw) and the diversity index (D) and the evenness index (Jsi) based on the diversity index (D) all present clearly positive correlation. The diversity index (D) and the evenness index (Jsi) based on the diversity index (D) also present clearly positive correlation.The research on the relation between the growth of the plantation of the North China larix on Saihanba and the geographical factors shows: slope direction has some influece of different degrees on breast diameter, tree height and volume growth per stem of the plantation of the North China larix. The influece of slope direction on breast diameter and volume growth per stem of the plantation of the North China larix at lower altitude is obvious, but the influece on the growth of tree height is not obvious. The growth of the plantation of the North China larix in shady slope is better than that in sunny slope. The influece of slope direction on breast diameter and volume growth per stem of the plantation of the North China larix at high altitude is not obvious. Slope direction has no influece on the growth of tree height. Density has some influece of different degrees on breast diameter, tree height and volume growth per stem. The influece on the growth of breast diameter is great. The influece on the volume growth per stem mainly appears in the late growth stage. The greater the stand density is, the smaller the average breast diameter of trees are, and the smaller the volume per stem is. Altitude has great influence on the growth of breast diameter of larix stand. The influence on the growth of tree hight is relatively small. The amount of growth of breast diameter is relatively great at high altitude. The influence of different altitude on the growth of tree hight is not obvious. Altitude has obvious influence on the volume growth per stem. Especially sunny slope forests are greatly influenced by altitude factors.The research on the relation between the growth of the plantation of the North China larix on Saihanba and the meteorological factors shows: the growth of standing trees of the plantation of the North China larix on Saihanba is closely related with meteorological factors. The relatively important influence of meteorological factors on tree hight, breast diameter and volume increment is annual precipitation and annual mean temperature. Another relatively important influence of meteorological factors on tree high and diameter increment is annual sunshine hours of the current year and mean ground temperature between November of previous year and January of current year. These influences show that annual temperature and precipitation are the most important key factors which restrict the tree growth of the plantation of the North China larix on Saihanba.The research on natural regeneration of the plantation of the North China larix on Saihanba shows: it is difficult for these plantation to regenerate naturally. Density is the key factor which influences the natural regeneration. Middle density (400-550 trees/hm~2) natural regeneration is better both for the regeneration quantity and for the structural regeneration. The greater the density is, the slower the natural regeneration is. When the stand density is above 1100 trees/hm~2, there is hardly any seedling of natural regeneration in the forest.