| The arthropods were investigated from 2006 to 2008 in 8 stands of Zhifanggou area on the loess plateau in China. The species-area and species-abundance relationship of arthropods in various stands were discussed by some mathematical models,Structure of arthropods community, space-time dynamics, diversity comprehensive index and stability in various stands were concluded by the analysis on diversity, principal component and clustering. And the multidimensional niches of the pests and their enemies in Periploca sepium and Caragana mocrophylla and spatial distribution pattern of Pontania dolichura larvae and sampling technique were analyzed as follows:1.The species-area relationship of arthropods in various stands accorded with the formula Sq=Cqm , the smallest investigation area was computed, and the order was: Natural bush > Natural arbor > Populus davidiana+Robinia pseudoacacia > Hippaphae rhamnoides L+Caragana mocrophylla >Periploca sepium> Hippaphae rhamnoides L > Robinia pseudoacacia > Caragana mocrophylla, the more complex stand type was, the larger the need to investigate minimum area was. On the basis of sampling investigation, species-abundance model of arthropods in various stands was established, lognormal distribution model was the most suitable in natural recovery stand, there were more species of medial individual amount ,and there were fewer abundant species and rare species in community。logcauchy distribution model was the most suitable in mixed stand and pure stand, there were more abundant species and rare species than in natural recovery.2.There were 420 spcies of arthropods in different stands; they belong to 93 families and15 orders. Most of them were Lepidoptera, 25 families and 122 species, followed by Coleoptera, 12 families, 107 species. In various stands, arthropods species in natural recovery stand were the most, followed by mixed stand, and species in pure stand were the least. Most arthropods dominant families in various stands were Lepidoptera and Coleoptera. The proportion of dominant species was the most in pure stand, followed by mixed stand, and dominant species were obvious. The proportion of dominant species was the least in natural recovery stand, and dominant species were not prominent. The result showed that arthropods were stable in natural recovery stand, which had more complex bio-system, followed by mixed stand; pure stand eco-system was single and had the least stability.3.The arthropod community structure of natural recovery stand was the most complex in different orders, and the species of arthropods were the most, followed by mixed stand, pure stand was the least. Lepidoptera and Coleoptera had the most families and orders, followed by Hemiptera, Hymenoptera, Araneae, Diptera and Homoptera, etc, and other orders were the least. From individual numbers in different orders, the arthropod amounts of natural stand were relative mean in various population, followed by mixed stand, pure stand were the worst. The phytophagous group is common dominance group, and species and individuals were the highest in different function groups. The species and individuals of natural enemies in natural recovery stand were obviously higher than other stand. From season changes of arthropod community in various stands, arthropods chiefly occurred from late April to September. the species number of arthropod were more from late July to mid August, and the most in Natural bush and Natural arbor. the individuals of arthropods was more from mid-June to early August, and the most in Periploca sepium and Caragana mocrophylla, followed by mixed stand, Hippaphae rhamnoides L and Robinia pseudoacacia, the individual change of arthropods in the natural recovery forests were the smallest4.From features index: arthropods community in different orders had the diversity index(H), the eveness index(J), the dominanc index(D)and probability of interspecific encounter(PIF), which associated with stand complexity. The more complex the stand was, the more orders which had higher indexes in H, J and PIF was, and H, J and PIF increased in majority of orders. On the contrary, the less complex the stand was, the larger dominance was, and dominance index increased. the sequence of H,J and PIF in various function sub-community was natural recovery stand, mixed stand, pure stand. Evenness index of arthropods community changed in the following order: natural stand, mixed stand, and pure stand. D was the highest in pure stand, followed by mixed stand, and the the lowest in natural recovery stand. In time series, diversity index of arthropods community in various stands was: natural recovery stand> mixed stand> pure stand, and diversity index of arthropods community in various stands was the highest from late July to late August. Evenness index of arthropods community changed larder in pure stand and mixed stand, smaller in natural recovery stand. Dominance of community was opposite to PIF and J.5.Based on the principal component analysis,the synthetic indices for community diversity evaluation were established.The results of the order of arthropods'synthetic index in order level, sub-community and season showed that natural recovery stand> mixed stand> pure stand. The clustering of order level and sub-community synthetic index showed that Natural bush and Natural arbor had shorter distance, Populus davidiana + Robinia pseudoacacia and Hippaphae rhamnoides L+Caragana mocrophylla had shorter distance , and four pure stands had shorter distance. The clustering of timing synthetic index showed that Natural bush and Natural arbor had shorter distance, Populus davidiana+Robinia pseudoacacia, Hippaphae rhamnoides L+Caragana mocrophylla, Periploca sepium and Hippaphae rhamnoides L had shorter distance, Robinia pseudoacacia and Caragana mocrophylla had shorter distance. Using the optimal segmentation, time pattern of arthropods community was divided, and all kinds of stands were divided to three phases by ordered phase, which could better reflect the community's variation.6.Arthropods community had the higher stability in natural recovery stand, and lower stability in mixed stand and pure stand, which had small community stability synthetic index. The sort of community stability synthetic index was not completely consistent with diversity synthetic index in various stands. Community diversity synthetic index was high, and community stability of arthropods was not necessarily high, but they showed that natural recovery stand> mixed stand> pure stand. It illustrated that natural recovery stand bio-system was complex, it increased the relative stability of arthropods community, and provided a theoretical basis for pest ecological control.7.Niche analyses showed that three kinds of seed pests had higher dimensional niche overlap between pests in Periploca sepium, and they had fierce competition each other, secondly .From dimensional niche overlap of natural enemies, Phanerotomella sp. and Entedon sp. had the highest overlap index and fierce competition. From dimensional niche overlap of natural enemies and pests, Phanerotomella sp., Entedon sp. had higher overlap index with three kinds of seed pests, Phanerotomella sp. and Kytorhinus immixtus Motschulsky had the highest overlap index, which showed that Phanerotomella sp. had the strongest control to Kytorhinus immixtus Motschulsky among them. Among all the natural enemies of aphid, Aphidius sp. had the highest overlap index. Pandemis heparana and Aphrophora costalis had the highest overlap index between pests in Caragana mocrophylla, which showed that they had fierce competition in time and space resources. From niche overlap of natural enemies, Coccinella septempunctata and Harmonia ascyridis had the highest overlap index, which had fierce competition. From niche overlap of pests and enemies, Coccinella septempunctata and Tuberolachnus salignus had the highest overlap, which showed that Coccinella septempunctata had the strongest control and follow function to Tuberolachnus salignus. So niche overlap should be considered in controlling pests, and took measures to control the pests. In pests'ecological regulation, natural enemies'protection measures should be taken to give full play to their roles.8.The spatial distribution pattern of Pontania dolichum larvae was analyzed with Taylor's power law, Iwao's distribution function, and six aggregation indexes.The results showed that the spatial distribution pattern of P. dolichura larvae was of aggregated, and the basic component of the distribution was individual colony, with the aggregation intensity increased with density. On branches, the aggregation was caused by the adult behavior of laying eggs and the spatial position of leaves, while on leaves, the aggregation was caused by the spatial position of news leaves in s pring when m < 2.37 ,and by the spatial position of news leaves in spring and the behavior o f eclosion and laying eggs when m >2.37.By using the parametersαandβin Iwan's,m*-m regression equation, the optimal and sequential sampling numbers were determined...
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