A Geostatistical Analysis On Spatial Patterns And Temporal Dynamics Of Aphis Gossypii Glover And Ladybirds In South Of Xinjiang

The spatial patterns and temporal dynamics of cotton aphid (Aphis gossypii Glover) and ladybird in Awati county of south part of Xinjiang were studied by using Geostatistics methods,and the key points are as follows:1. With the results of monitoring the spatial patterns of cotton aphid populations in various stages, there are distinct spatial heterogeneity in the distribution of cotton aphid under large and small scales in different stages. In the research field, the spatial heterogeneity was caused by aphid population spatial autocorrelation accounts for 77.6% under small scale, whereas accounts for 85% under large scale, thus the autocorrelation of aphid population in large scale was greater than the small scale.2. The spatial aggregations are various under large and small scales in different occurrence stage of cotton aphid.(1) The initial period of cotton aphid occurrence: The aphid population spatial patterns were conformed to exponential and nugget models in large scale, showing that the spatial patterns in prior period of occurrence exhibit to random distribution, whereas exhibit to aggregation pattern in the late period of occurence. Meantime, the cotton aphid spatial patterns were mainly confirmed to nugget models in small scale, it showed that most of the cotton aphid spatial patterns are fitted for random distribution(2) The peak period of cotton aphid occurrence: Most of models fitted for exponential showed that the spatial patterns of aphid population were aggregation pattern with strong continuity, the spatial range under large scale variated from 7.8 to 24.6m, whereas from 1.75 to 5.79m under small scale. (3) The regression period of cotton aphid: The spatial patterns of aphid population were confirmed to exponent, linear and nugget model under large scale along with the time sequence, respectively, results suggested that the spatial patterns were aggregated, medium intensity aggregation and random distribution, respectively, and the space continuity is decreasing. Under small scale, the variogram models are the spherical and linear model, the spatial patterns aggregated by the medium intensity gregation, Furthermore, the maximum value of C0/(C0+C) reached to 83.5% under small-scale model in the late period, it indicated that the effects of random factors to the spatial pattern of aphids are gradually dominated.3. According to the models of ladybird spatial patterns under different scales and stages, the spatial heterogeneity was caused by aphid population spatial autocorrelation accounts for 66.49% under small scale, whereas accounts for 93.35% under large scale, thus the autocorrelation of aphid population in large scale was greater than the small scale too.4. The characters of ladybird spatial patterns are distinct under different scales and stages.(1) The initial period of ladybird occurrence: Most of the ladybird's semi-variogram models are nugget under large scale, it reflected that the spatial patterns are mainly random distributions. The semi-variogram models are mainly exponent and gaussian model.(2) The peak period of ladybird occurrence: The spatial patterns of ladybirds more fitted for the models of sphere and exponent. It shows that population spatial patterns of ladybirds were mainly aggregated under large scale; whereas the spatial patterns more fitted for the model of nugget under small scale, showing that the spatial patterns were mainly random.(3) The regression period of ladybirds: The spatial patterns were conformed to the nugget models under both large and small scales. Similarly, it showed the spatial patterns were mainly random distribution.5. By the analysis of population dynamics, anisotropic variogram and simulation of 3D Kriging interpolation, result distinctly indicated that there are typical following relationship between populations of ladybird and cotton aphid under different scales, but it seems that the affection by random factors is bigger under small scale than that of under large scale, the population curve exhibited a certain degree of fluctuation.6. The results of Kriging interpolation show that the spatial distribution of aphid is aggregated during the whole life time, but the density value of aphid population is different with larger in early period than in later period.7. Results from the study of population spatial heterogeneity on cotton aphids and ladybirds in different directions show that both cotton aphids and ladybirds displayed similar the semi-variogram models in four directions, but the range of aphids and ladybirds model are different, it belongs to the geometric anisotropy.