Some Environmental Factors Relating Growth of Avicennia alba BI. and Avicennia marina (Forsk.) Vierh.

A study on some environmental factors relating growth of Avicennia a/ba BI. and A. marina (Forsk.) Vierh. was conducted in a mangroves of Western Mahachai bay, Samut Sakhon Province. Dendrometer bands were installed to measure monthly diameter increment for 13 months started from September 2008. Relations between diameter growth and some environmental factors were analyzed. The results indicated that rainfall and the number of rainy day in the previous month were related positively to the growth of A. alba (r = 0.80, 0.73; p<0.01), Maximum daily rainfall and mean monthly relative air humidity were related positively (r = 0.61, 0.68; p<0.05) while mean maximum monthly sea level and maximum sea level of the previous month had negatively related (r =-0.67; p<0.05). For A. marina monthly growth was positively related to mean minimum monthly sea level and minimum sea level of the previous month (r = 0.79, 0.83; p<0.01) and it was also positively related to maximum sea level and minimum sea level (r = 0.62. 0.59; p<0.05). However, the number of rainy day was negatively to its growth (r =-0.62; p<0.05). The responsive trends to these environmental factors of the two species were polar opposite. Therefore, these two species had clearly difference in ecological zonation.