The density of Cx. tritaeniorhynchus in each month of the total BOFP
The Fig. 2. shown the distribution of Cx. tritaeniorhynchus in each month in BOFP. During the trapping period, the density of vector mounted to the highest in September (11.2 mosquitoes per hour per light), and the density of the vector in July (0.35 mosquitoes per hour per light) and August (0.05 mosquitoes per hour per light) were smaller than 10 percent of that in September. As to predominance of Cx. Tritaeniorhynchus, it also arrived at the peak in September (26.92%), and the predominance of Cx. tritaeniorhynchus in July (2.81%) and August (1.12%) were not more than the five percent of total mosquito community.
The density of Cx. tritaeniorhynchus in each site
The Fig. 4 showed the vector density of each trapping site during each study month. There was no vector could be trapped in sites of east, northern-ease, center island, and southern in July and August; and only in September, the vector could be found in site east, northern-ease, center island, and southern. Both in July and August, the vector could only be trapped on site of wetland; and the density of the vector in September was the highest among all sites during each study month. Thus, the vector density and predominance spatial distribution pattern represented the same charters as that in total surveillance period. In the September, the Fig. 3 told us the density of the vector in each trapping position during the study period. The vector density in the wetland (13.58 mosquitoes per hour per light) was the highest among these trapping sites, and the vector density in east, northern-ease, and center island was 3.00 mosquitoes per hour per light, 4.25 mosquito per hour per light, and 10.00 mosquitoes per hour per light, respectively. Comparing to density distribution of Cx. Tritaeniorhynchus, the predominance of vector mosquito in trap sites displayed different distribution pattern, the center island ranks (72.73%) firstly among five sites following with north east (42.50%), east (29.27%) and wetland (16.15%), expect for the zero in south site (no vector could be detected here). Specially, the predominance of vector in wetland ranked bottom although its density lies on the top among trap sites.
Linear regression analysis of the density of the environmental factors
The factors, showing significant correlation level with vector density, was then involved into the linear regression model in the stepwise method, in which the factor entered the final model if the probability of F was smaller than 0.05 or was removed if the probability of F was larger than 0.05. In the end, the GW_400 and LT_100 was left and they could produce two linear regression models (Shown in Table 2). So, the finally linear regression model 2, as shown in Table 2, could be written in algebraic expression as:
Table 2
The relationship between environmental features vs mosquito vector density and landing rate
|
Correlational environmental feature
|
Regression model
|
Coefficients
|
R Square
|
Sig.
|
Coefficients
|
Sig.
|
Landing
Rate
|
GW_400
|
0.967
|
0.003**
|
2.816
|
0.003**
|
HT_100
|
0.003
|
0.004**
|
Vector
Density
|
GW_400
|
0.979
|
0.001**
|
1.535
|
0.001**
|
LT_100
|
-0.004
|
0.016*
|
**: P < 0.01; *: P < 0.05
|
Where the D is the density of Cx. tritaeniorhynchus, and the GW_400 and LT_100 are the summary acreage of grass-water and lower tress in 400 meters and 100meters buffer around the trapping sites, respectively. In the regression model, the GW_400(p = 0.001 < 0.01), and LT_100(p = 0.016 < 0.05) all showed significant linear relation with the density of Cx. tritaeniorhynchus, where the GW_400 was positive and the LT_100 was a negative linear relation to the density of Cx. tritaeniorhynchus.
Temporal dynamic of landing rates in different study positions in BOFP
During total survey period, landing rates in 5 sites display spatial diversity, with the landing rates climax in September at the site of wetland, east, and center-land; the bottom landing rates could be seen in July in north-east, south, and east, and the bottom landing rates also could be seen in August in wetland and center land(Fig. 4). In north-east gate of BOFP, the landing rates in August and September were higher than those in July. In the Wetland area, the landing rates reach its height in September and climax through in surveillance period among all trapping sites. In the south gate area, the landing rates is generally lower than the other position (the landing rates were no more than 4), even at the highest in August. In the East gate location, the landing rates grew step by step from July to September and peaked in September. In the center point area (one center island in the lake), the landing rates in August hit the bottom level through surveillance period.
Spatial dynamics of landing rates in each surveying month
From July to September, the landing rates in BOFP shown different distribution pattern among sites in different month. What’s more, peak landing rates site came out from wetland in July and September, the bottom landing rates could be seen twice in the south in July and September(Fig. 4). In July, the landing rates range from high to low in the following rank: wetland, central island, north-east gate, east gate, and south gate (Fig. 4). In August, the landing rates is highest in east gate location, and the landing rates here was higher than the highest point of the landing rates in July (at the wetland site); the landing rates in Wetlands was lower than that in July, even lower than that in the northeast gate. Mosquito landing rates in five sites ranked from high to low in the following sequence: the east gate – northeast gate- wetland -south gate - Center Island (Fig. 4). In September, the landing rates, as that in July, peaked in wetlands again, and landing rates in this site were also peaked among all sites during the surveillance period. In addition, the landing rates in east gate site ranked second among all sites in September as well as in total surveillance period (Fig. 4).
The correlation of landing rates to environmental features in BOFP
The regression analysis results, on the relationship between environmental features and landing rates, was listed in Table 2. As the Table 2 shown, the P values of F testing on all regression models were less than 0.05, which means the models could well predict the landing rates with environmental features respectively. Moreover, it was noticed from Table 2 that there were alternative environmental features being identified correlation with mosquito landing rates. That, landing rates was positive correlation to GW_400(Coefficients = 2.816, P = 0.003 < 0.01), and landing rates was positive correlation to HT_100 (Coefficients = 0.003, P = 0.004 < 0.01). Also, the finally linear regression model, as shown in Table 2, could be written in algebraic expression as:
HLD=3.2+2.816*gw_400+0.003*ht_100
Where the HLD is the landing rate of mosquito, and the GW_400 and HT_100 are the summary acreage of grass-water and higher tress in the 400 meters and 100meters buffer around the trapping sites, respectively.
Field inspection on the GW environmental factors
As results are shown above, the GW was correlative to both the density of Cx. Tritaeniorhynchus and mosquito landing rate. In order to make ensures what exactly filed landscape the GW is, we also check 30 sites (Fig. 1) that was categorized as GW in RS analysis. As the results shown, these sites could be divided into four categories including well-irrigated grades (Fig. 5A, account for 43.33%), regularly irrigating flower shrubs (Fig. 5B, account for 40%), wetland covering with aquatic vegetation (Fig. 5C, account for 10%), and Turf with water (Fig. 5D, account for 6.67%).