Plant biodiversity associated with corn cropping systems in the Philippines

A comprehensive inventory and assessment of plant diversity associated with 15 selected representative corn cropping systems in Isabela Province (Luzon, Philippines) showed that a relatively high total plant diversity level exists within the province, with H' value of 4.15 and a species richness of 268. On a per locality/study site basis, the species diversity index of study plots ranged from H' = 1.91 to 3.70 and species richness ranging from S = 16 to 60 (Table 17). Comparison of these values with those obtained from the border areas of study plots showed that the latter had a much higher species diversity index, ranging from H' = 1.11 to 7.20; the highest value being nearly twice the highest value recorded from the study plots. The border areas had species richness ranging from S = 19 to 96 which are also much higher than the highest value obtained from the study plots. Using Sorensen's Similarity Index (S.I.) formula, the similarity in species composition per study plot and their border area basis ranged from 6.5 to 100%. On the other hand, a similarity index of 71% was obtained for the entire Isabela Province where 147 species were found common to the study plots and their border areas out of a total of 268 species recorded from the 15 study localities. In terms of taxon composition, the 268 species recorded for the entire Isabela Province belong to 212 genera and 40 families. Of the 40 families, the top 5 families with the highest number of species are Gramineae (37 spp.), Papilionaceae (29 spp.), Euphorbiaceae (16 spp.), Compositae (12 spp.), and Moraceae (11 spp.). The rest of the 35 families had each a species number ranging from 1 to 9. In terms of habit composition, the 268 species were broken down into 37 grasses, 80 herbs, 2 lianas or woody vines, 3 large trees, 6 medium-sized trees, 12 shrubs, 10 small trees, and 13 vines.