The % abundance for each species (see Table ), is computed using the formula below:

           

 

                                           N   

                        % Abundance =  ----------- x 100

                                                     N_Total

           

                                    N = number of mature trees for each species

                                     N_Total = total number of mature trees for all species

 

For Aegiceras floridum:          

                                         11

            % Abundance = ----------- x 100

                                         37

                                  =    29.73%

 

 

Table     .Species density, diversity and evenness of mature trees in the mangrove communities at the three sampling sites of Lawaan, Eastern Samar.

 

STATION	No. of Species	Number of Individuals	H’	D	J’	E
Bgy. Beta-og	13	558	1.91	0.20	0.75	0.70
Bgy. Taguite	12	1207	1.86	0.21	0.75	0.69
Bgy. Maslog	17	3741	2.06	0.15	0.73	0.83

 

 

For the Shannon-Weiner Index, (cited by Ludwig and Reynolds, 1988) the formula is:

           S       n_i                  n_i      

H’ = -S   (-----) ln (-----)

                                   i= 1      n                  n              

 

 

                        Where

                                         H’ = diversity index

                               S  = total number of species

                                n_i  = total number of individuals for each species

                                n = total number of individuals for all species

 

 

 

For the Simpson’s Index (cited by Ludwig and Reynolds, 1988), the formula is:

                     S           n_i (n_i – 1)

                                                D =  å       -------------

                               i = 1       n (n – 1)

 Where:

                        D = Simpson’s Index of Diversity

                     n_i = number of individuals for each species

                     n = total number of individuals for all species

 

 

 

                Evenness Index

 

                                        ln (N₁)

                        J’ (E₁)  =  -------------                Where:

                                          ln (S)                                  N₁ = e^H’

                                                                                       S  =  number of species                

                                                              N₂ = 1/D

                                        N₂ - 1               

                        E (E₅) =  -------------                             

                                                     N₁ -1                                 

 

 

 

 

Index of Similarity (IS)

                                                                  2C

IS = --------------- x 100

                                                            S₁ + S₂

                                Where:  C = number of species common to both communities

                                   S₁ and S₂ = number of species in community 1 and 2 respectively