Studies On The Dynamics Of Arthropod Communities And Relations Between Dominant Pest And Its Natural Enemies In Two Kinds Of Lawns

Based on the thorough investigation ,the dynamics of the arthropod communities in lawn and interaction of main insects with its natural enemies were studied by means of community analysis, grey system theory and path analysis ,which is not only beneficial to the effective control of lawn pests , but promote the research of community ecology in lawn.1. There is no obvious distinction in each index after analyzing their difference by T-test of the arthropod community in two different kinds of lawns.2. Based on the constitution and number of arthropod species, community can be classified into four sub-communities: phytophages, predators, parasitoids and neutralities by nutrition and preying relation. The results were as follows:2.1 Arthropod community in Festuca arundinaceSpecies investigated were 52 species belonging to 51 families, including 30 species of phytophages belonging to 29 families; 15 species of predators belonging to 15 families; 7 species of parasitoids belonging to 7 families. The relative abundance of phytophages is 0.62162. Early dominant insects Areerigonidium graminidola, while later ones are Gryllidae; the relative abundance of predators is 0.22748 and Erigonidium graminicolum and Aarneidae are their dominant natural enemies. Then, the dominance and dominant concentration of total communities are 0.0468. The dominance and dominant concentration of sub-communities: parasitoids (0.3144) > predators (0.1435)> phytophages (0.0834).2.2 Arthropod community in Ophiopogon japonicusThere are 52 species investigated all together which belong to 52 different kinds of families. (Phytophages: 30 species, 29 families; predators: 15 species, 15 families; parasitoids and neutralities:7 species, 7 families). The relative abundance of phytophages and predators are 0.5961 and 0.2852 respectively. Chactocnema ingenuna are main pests in ophiopogon japonicus. Also, Erigonidium graminicolum are their main dominant natural enemies. The relative abundance of parasitoids and neutralities is 0.0490. The dominance and dominant concentration of sub-communities: parasitoids (0.1642) > predators (0.0962) > phytophages (0.068)3. The diversity and seasonal dynamics of arthropods sub-community in the lawn are in line with those of total community. The relationship between their diversity index (H') and others are as follows.3.1 Arthropod community in Festuca arundinaceDiversity index (H') is in close relation to species (0.9288), individuals (0.8963), and species richness (0.9245). It can be indicated from Principle components analysis and the order of indexes of communities that diversity, evenness, species richness and dominant concentration are synthetic indexes of community construction.3.2 Arthropod community in ophiopogon japonicus:Diversity index (H') is in close relation to species (0.8425), individuals (0.8273), and species richness (0.7771). It can be indicated from Principle components analysis and the order of indexes of communities that diversity, evenness, species richness and dominant concentration are synthetic indexes of community construction.4. Diversity indexes of arthropod communities are analyzed by clustering and optimization partitions.4.1 Arthropod community in Festuca arundinace:When D= 2.20, total community can be divided into 4 kinds.When D= 2.10, phytophage sub-community can be divided into 4 kinds.When D= 1.45, predator community can be divided into 4 kinds.4.2 Arthropod community in ophiopogon japonicus:When D= 2.20, total community can be divided into 4 kinds.When D= 1.91, phytophage sub-community can be divided into 4 kinds.When D= 1.99, predator community can be divided into 4 kinds.5. Study on the relationship of Chactocnema ingenuna and its natural enemies by grey theory, the result showed Erigonidium graminicolum and Aarneidae are its ideal dominant enemies and Tetragnathidae are main enemies.6. By testing spatial construction of Chactocnema ingenuna and Areerigonidium graminidola through Taylor's power lawand and Iwao's distribution function, it can be shown that they are in aggregated distribution in the lawn community.