Study On The Distribution Factors Of Amphibians Larvae In Agricultural Landscape In The Lower Reaches Of The Yellow River,China

The lower reaches of the Yellow River is a traditional agricultural area in China.Amphibians in agricultural play an important role for the biodiversity of agroecosystems.With the development of intensive agriculture,the living environment of amphibians has changed gradually.Faced with this situation,there is important theoretical and practical significance to explore the relationship between the amphibians distribution adult and larvae and environmental factors in the agricultural landscape of the lower reaches of the Yellow River,China.In present study,Fengqiu County in the lower reaches of the Yellow River was selected as study area.We investigated the number of amphibians adults and larvae and habitat environmental factors in the 32 pondsamples and calculated the landscape indices and landscape connectivity based on the remote sensing images.The environmental factors(habitat and landscape scales)affecting amphibian larvae and adults were analyzed through field investigation,laboratory experiment,regression analysis and redundancy analysis,so as to research the relationship between the distribution of amphibians and environmental factors in the agricultural landscape.Through investigation and analysis,the results wre shoen as follows:(1)Different of amphibian larvae appeared in different times.Most Bufo larvae appeared in April and May,and earlier than Pelophylax larvae;Large numbers of Pelophylax larvae appeared in June.In the same survey period,there were 448 Bufo gargarizans adult,919 Palophylax plancyi adult and 498 Pelophylax nigromaculata adult were found.(2)The effect of environmental factors on amphibian larvae was analyzed using a linear model based on Ordinary Least square Estimation(OLS),and the results showed that at 0.05 significance level,Pelophylax larvae were most affected by vegetation coverage in the pond,and the influence of other variables was not significant.The effect of environmental factors on Bufo larvae was shallow water slope> water depth > chemical oxygen demand > larvae predator > dissolved oxygen,in which shallow water slope and larvae predator were negative factors,and he other factors had a positive impact on them.(3)For the amphibian adults,based on the OLS model,the effect of environmental factors on the habitat scale on P.nigromaculata was distance from the nearest farmland > dissolved oxygen > total phosphorus > larvae predator > vegetation coverage in the pond > slope,in which except larvae predator was negative factors,and the other factors had a positive impact on them.The effect of environmental factors on the P.plancyi adult size was distance from the nearest pond > vegetation coverage in the pond > vegetation coverage around pond > water temperature > chemical oxygen demand > slope,in Which in addition to vegetation coverage around pond and chemical oxygen demand were negative factors,and the other factors had a positive impact on it.The influence of environmental factors on B.gargarizans was water depth > distance from the nearest road > chemical oxygen demand > pond area > dissolved oxygen > slope > vegetation coverage around pond,except distance from the nearest road and slope were negative factors,other factors had a positive effect on them.At the landscape scale,the relationship between amphibians adults and environmental factors was analyzed by redundancy analysis(RDA).The results showed that at 0.05 significance level,at the 250 m diffusion threshold,the landscape shape index(LSI)had a moderate correlation with the adults of B.gargarizans(r =-0.41);at the 500 m diffusion threshold,there was a moderate correlation between the adult population of B.gargarizans adults and the landscape shape index(LSI)(r =-0.43);at the 1000 m diffusion threshold,the adults of P.plancyi had a moderate correlation with landscape shape index(LSI)(r = 0.40),and the adult population of P.nigromaculata adults and Shannon’s evenness index(SHEI)(r = 0.40);at the 2000 m diffusion threshold,the adults of B.gargarizans had a moderate correlation with Shannon’s evenness index(SHEI)(r = 0.49).(4)The number of B.gargarizans adults was monthly declined,Large number of P.nigromaculata adult and P.plancyi adult appeared in June.The relationship between amphibians larvae and adults was analyzed by correlation analysis.The results showed that in June,the relationship between Perrophylax larvae and the sum of P.nigromaculata adults and P.plancyi was the most significant and presented a strong positive correlation(r = 0.69,P < 0.01).In May,Bufo larvae had the most significant relationship with B.gargarizans,with a moderate positive correlation(r = 0.48,P < 0.01).Studies on habitat scale indicate that Pelophylax and Bufo larvae are affected by different environmental factors,vegetation factors especially in ponds,are important factors affecting Pelophylax larvae and adult.Bufo larvae and B.gargarizans adults are more affected by pond water environmental factors(water depth(d),chemical oxygen demand(COD),dissolved oxygen(DO))and pond characteristics(slope(SL)).