The Effects of Flooding on Forest Floristics and Physical Structure in the Amazon: Results from Two Permanent Plots

Abstract

I investigated how flooding affects floristics and physical structure of forests in the Amazon at the Area de Conservacion Regional Comunal de Tamshiyacu-Tahuayo, Loreto ProvinceIquitos, Peru and at the Yasuni Experimental Station, Yasuni National Park, Ecuador. Iset up and sampled 1 ha permanent plots next to a blackwater river (igapo forest) in Peru and next to a white-water river (varzea forest) in Ecuador. I found (1)16 families in the 1 haigapo plot with Fabaceae the most common family, (2) varzeastems conformed to a reverse J size pattern for stems less than 40 cm dbh but had more large stems, total stems were within other varzea forest ranges with a slightly larger average dbh, trees were clumped at a low level with 45% canopy closure and while the basal area was also within other varzeaforest ranges, above-ground biomass was lower, (3) igapostems conformed to the reverse J size pattern, total stems were lower than other igapoforest ranges with a slightly larger average dbh, trees were clumped at a higher degree than the varzea forest with 12% canopy closure while the basal area and aboveground biomass was less than both other igapo samplings and the varzea study plot, and (4) flooding produced reduced basal area in igapo, and smaller stems, stem densities and above-ground biomass for both flooded forests. I conclude that both study plots show a reduction of tree stem density and structure (basal area, above-ground biomass) with flooding, which reduces even more as months under water increase. More sampling in these forests is needed, however, before a conclusion about which aspect of the flooding regime –e.g., water quality, flooding duration or frequency – is most important in determining different aspects of forest structure. Permanent plot studies in the Amazon, like this one, provide much needed data for intelligent management decisions and the development of sustainability techniques.