Studies On Propagation And Diffusion Properties Of Sonneratia Apetala In Latitude Gradient

Sonneratia apetala, a popular afforestation species in China, was first introduced from Bangladesh in1985and has been planted throughout the southeast coastal provinces. To assess the potential invasion of S.apetala,we selected S.apetala from12sample sites with different latitude, including Sanya and Haikou in Hainan province, Leizhou, Zhanjiang, Dianbai, Shenzhen and Shantou in Guangdong province, Zhangpu, Xiamen and Quangang in Fujian province,.We studied on the propagation and floating properties of S.apetala. We aimed to explore whether the invasive potential of the exotic S.apetala has difference in different latitude. The results are as follows:1. Propagule numbers of S.apetala had very significant negative correlation with latitude (p<0.001), and had significant negative correlation with salinity (p=0.012). Propagule number of S.apetala in each site had no significant correlation with annual mean temperature, extreme low temperature, mean low temperature. It still had insignificant with carbon content of soil and nitrogen content of soil.2. Fruit properties (diameter, thickness, volume and weight) of S.apetala had significant positive correlation with latitude (p<0.001, p=0.012, p<0.01, p<0.01).Weight of a single seed had significant positive correlation with latitude (p=0.021). In addition, seed germinate rate in a single fruit had no significant correlation with latitude. It indicated that seeds inside a single fruit were larger but less in number in high latitude than in low latitude. In low latitude, seeds were smaller but higher in number, which would contribute more capacity for propagation and suggest more invasive potentials.3. With the increased of annual mean temperature, fruit properties (diameter, thickness, volume and weight) significantly increased and then descended (p<0.001). However, seed number, germinate rates, volume and weight had no significant correlations with annual mean temperature.4. Fruit properties (diameter, thickness, volume and weight) were significantly correlated with extreme low temperature (p<0.001, p<0.001, p<0.001, p<0.001). As the extreme low temperature increased, they increased first and then descended. Extreme low temperature had no significant influence on seed properties, such as seed number in one fruit, seed volume and weight; while seed germinate rates in one single fruit were significantly negative correlated with extreme low temperature (p=0.012).5. Fruit properties (diameter, thickness, volume and weight) had significantly negative correlation with the mean low temperature (p<0.001, p<0.001, p<0.001, p<0.001). Seed properties (volume, weight) were no significantly correlated with the mean low temperature, and seed number in one fruit were significantly correlated with the mean low temperature (p=0.021); while seed germinate rates in one single fruit were very significantly negative correlated with mean low temperature (p<0.01).6. In all sample sites, fruit density was largest in Zhangpu site and lowest in Fugong site. Fruit floating rates decreased with the increased floating treatment, which suggest significantly increased of fruit density in immerse processes. Floating properties had intimate correlation with fruit initial density. Mean fruit density had very significant negative correlation with fruit floating rate on the first day of floating treatment (p<0.01), while the mean fruit density had significant negative correlation with fruit floating rate on the fifth day immersed in water (p=0.031). Fruit with different density from different latitude had no certain pattern with floating properties.7. Salinity significantly influenced on seed germinate rate (p<0.001), while nitrogen had no significant influence on it (p=0.112). Salinity and nitrogen had no significant synergistic effects on seed germinate rates (p=0.118). Salinity significantly influenced on seed hypocotyl growth (p<0.001), and nitrogen had significant influence on it (p=0.001). Salinity and nitrogen had significant synergistic effects on seed hypocotyl growth (p<0.001).