Effects of selective-logging, litter and tree species on forests in the Peruvian Amazon: seed predation, seed pathogens, germination

Abstract

Background: The Amazon basin contains mainly unflooded forests, and they are among the most important ecosystems in the world. Field experiments on seed processes are very important in order to understand the structure, function and dynamics of these forests. Methods: And so tree seeds of three species (Cecropia latiloba, Guarea macrophylla, Socratea exorrhiza) were set out in Amazon unlogged terra firme forest, in Amazon selectively-logged terra firme forest, in Amazon palm forest, and in Amazon white sand forest either on top of or beneath the litter layer, and after two weeks scored for seeds taken by predators, seeds destroyed by pathogens and seeds that germinated. Results: I found both terra firme forests (unlogged and selectively-logged) lost most of their seed to predators and the least of their seed to pathogens, white sand forests lost the least of their seed to predators and the most of their seed to pathogens, and the fewest seeds germinated in both terra firme forests and in palm forest. More specifically (1) within unlogged terra firme forest addition of litter reduced seed predation but increased seed losses to pathogens and germination, and C. latiloba lost the most seeds to pathogens, (2) within selectively-logged terra firme forest seeds showed the same trends as unlogged terra firme forest but without significant effects, (3) within palm forest addition of litter reduced predation but increased losses to pathogens, and S. exorrhiza lost the least seeds to pathogens, and (4) within white sand forests addition of litter increased germination. Combining the results from all forests together, predators took most of the seeds, pathogens took most of the seeds that escaped predation, and most of the seeds that survived predation and pathogens germinated. Conclusion: While such large losses of tree seed to predators and pathogens in these unflooded forests suggest limited recruitment, the variation demonstrated in these field experiments – among forest-types, among tree species, between litter situations on the forest floor – help to insure that recruitment does occur and that these unflooded forests continue to dominate the Amazon basin.

Modelling Climatically Suitable Areas for Mahogany (Swietenia macrophylla King) and Their Shifts across Neotropics: The Role of Protected Areas

“…Different scientific works have yielded that these tropical deforestation processes cause a reduction in evapotranspiration levels and precipitation at the local level, hence indirectly affecting a wide variety of plant species [13,14]. In many areas, this change in land use begins with the selective exploitation of timber species of high commercial value, an activity that also affects species of global commercial interest, such as Mahogany (Swietenia macrophylla King) [15,16], a timber tree whose native range covers much of the Neotropics.…”

“…Due to these multiple uses, it is considered one of the most commercially important plant species worldwide [23], reaching prices between USD 1700 and USD 11,000 per m 3 of wood [24,25]. Its great commercial interest has increased its overexploitation [15]. Mass extraction has generated significant negative impacts on the habitat of this species, with less than one individual per hectare found in small and dispersed populations [26,27].…”