Studies On The Intraspecific,Interspecific Competition And Population Dynamics Of Dominate Species In Malan Forest Region Of The Loess Plateau

It is imperative under the situation to accelerate the recovery and restoration of degenerative ecosystem on the Loess Plateau, because the ecosystem is seriously degraded due to soil and groundwater depletion. The vegetation was the foundation of changing ecological environment and improving the positive ecological cycle. Malan forest region, a relative intact natural secondary forest on the Loess Plateau, is important water conversation and ecological availability forest for loess plateau central area. Malan forest region has crucial effect on adjusting regional climate, maintaining ecological balance and promoting ecologically sustainable economic development on the Loess Plateau. So the research on the mechanism of mutual reaction and population dynamics of dominate species has significant ecological meaning for recovery and restoration of degenerative ecosystem.In this paper, the intraspecific and interspecific competition intensity of Quercus liaotungensis and Pinus tabulaeformis in Malan forest region of Loess Plateau were quantitatively analyzed using Hegyi's single tree competition index model. Under combining natural and plantation Pinus tabulaeformis, the relationship of Quercus liaotungensis and Pinus tabulaeformis and other species was revealed. We simple indicated the developmental trend and reaction of dominate species and other species in the restoration of vegetation. Based on the self-regulation of P. tabulaeformis population depended on density, we investigated and analyzed the intraspecific competition of P. tabulaeformis population, explained the relationship of the intraspecific competition and self-alienation of species, revealed the rule of competition and mortality of different self-alienation stage. They all can offer the theory foundation to the plantation and management of P. tabulaeformis. We studied the age structure, life table and survival curve of P. tabulaeformis population in plantation P. tabulaeformis forest, natural P. tabulaeformis forest and Q. liaotungensis mixed forest, explained the growth and healthy of P. tabulaeformis population in different forest types and offered the theory foundation of the population protection, the recovery and restoration of vegetation in this region. The niche of P. tabulaeformis and Q. liaotungensis had great overlapped. They formed strong the intraspecific and interspecific competition. According to the competition, they mutually reacted and influenced the community appearance, the community structure and the community dynamics in this region. In P. tabulaeformis+ Q. liaotungensis mixed forest, P. tabulaeformis had great competition and expel to Q. liaotungensis. It represented the monopolization. Q. liaotungensis represented the tolerance. The competition happened in a Diameter Breast Height (DBH) less than 15 centimeters. They both decreased gradually with the DBH increase of objective tree and obeyed power function rule with DBH. Based on the forepart of competition occurrence, we can change the competition balance of the mixed forest by human disturbing and nurturing and adjust the growth of population.In different age plantation P. tabulaeformis forest, the intraspecific competition and mortality of P. tabulaeformis population represented in-phase and accordant. The mortality of P. tabulaeformis individuals was a self-alienation. This was an evident process concerned the development stage of plantation P. tabulaeformis forest. Plantation P. tabulaeformis forest had an accordant trend along with times. There were there stages. Firstly, the competition prophases under 10 age grade; Secondly, the competition phases at 20 age grade; thirdly, the competition anaphase after 35 age grade. We should adopt different management and protection to different age grade P. tabulaeformis forest.P. tabulaeformis population had some common characteristic in plantation P. tabulaeformis forest, natural P. tabulaeformis forest and Q. liaotungensis mixed forest. The theory of survival analysis indicated that the survival curves of P. tabulaeformis all tended to be the type Deeveyâ…¡. It showed that a blooming growth appeared in the stage of juniors and a continuant growth in the stage of middle and end. P. tabulaeformis population had "bottleneck" in the stage of juniors and had higher vanishing rate in the stage of adults. The three forest types had prominent differences. Plantation P. tabulaeformis forest and natural P. tabulaeformis forest had the trend of bottleneck, stable growth and rapid recessionary. Plantation P. tabulaeformis forest had limitation. It represented single species, frequent pest and instable community or ecosystem. It should be actively reconstructed by human management and protection. In order to make use of timber to maintain pure forest, we need to keep population stable growth by using natural or man-made gaps, plantation P. tabulaeformis seedlings, and human management to improve self-regeneration of P. tabulaeformis forest. In order to protecting soil and underwater and recovering vegetation, we need to import mixed species in old plantation P. tabulaeformis forest or make advantage of present excellent mixed species. At last, the state of stable mixed forest was formed between P. tabulaeformis and mixed species. Natural P. tabulaeformis forest was a forest type dominating P. tabulaeformis that was long-term evolved from plantation P. tabulaeformis forest. This forest types had preferably adapted the local environment, especially local microenvironment. But the upper vanishing of natural P. tabulaeformis forest made chance to the invasion and colonization of other tree. Finally it might develop the mixed forest. P. tabulaeformis+ Q. liaotungensis mixed forest was a typical forest types that P. tabulaeformis was stable. P. tabulaeformis had longer age grade, stability declined survival rate and less fluctuant mortality rate. The mixed growth between P. tabulaeformis and Q. liaotungensis improved the competition of Q. liaotungensis. It made P. tabulaeformis keep continued growth under the reaction of the intraspecific and interspecific competition. The mixed forest was more stable and healthy than other two forest types.