Evaluating the effect of nutrient redistribution by animals on the phosphorus cycle of lowland Amazonia

Abstract

Abstract. Phosphorus (P) availability decreases with soil age and potentially limits the productivity of ecosystems growing on old and weathered soils. Despite growing on ancient soils, ecosystems of lowland Amazonia are highly productive and are among the most biodiverse on Earth. P eroded and weathered in the Andes is transported by the rivers and deposited in floodplains of the lowland Amazon basin creating hotspots of P fertility. We hypothesize that animals feeding on vegetation and detritus in these hotspots may redistribute P to P-depleted areas, thus contributing to dissipate the P gradient across the landscape. Using a mathematical model, we show that animal-driven spatial redistribution of P from rivers to land and from seasonally flooded to terra firme (upland) ecosystems may sustain the P cycle of Amazonian lowlands. Our results show how P imported to land by terrestrial piscivores in combination with spatial redistribution of herbivores and detritivores can significantly enhance the P content in terra firme ecosystems, thereby highlighting the importance of food webs for the biogeochemical cycling of Amazonia.

Soil fertility and anthropogenic disturbances drive mammal species richness and assemblage composition on tropical fluvial islands

“…Given that hunting is not random, with some species such as capybaras, peccaries and deers being preferentially sought by hunters rather than smaller-bodied taxa, sampling stations nearby to human communities are likely to experience more abrupt changes in assemblage composition (Chapin et al 2000;Mesquita & Barreto 2015). This change in mammal assemblage composition could compromise ecosystem services provided by mammals, such as pollination, seed dispersal, herbivory and redistribution of nutrients (Metcalfe et al 2014;Buend ıa et al 2018;Lavery et al 2020).…”

“…These species are also scansorial, which potentially provides advantages when responding to the flood regime (O'Connell 1989). Thus, the disappearance of larger mammals such as capybaras, peccaries, jaguars and deers from the islands may trigger several cascading effects, leading to a disruption in key ecosystem functions (Buend ıa et al 2018;Bogoni et al 2020).…”

“…Non-volant forest mammals are often keystone species that play an important role in ecosystem function via seed dispersal (Sobral et al 2017), pollination (Ollerton et al 2011) and redistribution of nutrients between flooded and non-flooded environments (Buend ıa et al 2018). Those non-volant mammals are an important part of the diet of local human communities across the Amazon, especially mediumto large-sized herbivores (Constantino 2015).…”

“…deers and capybaras) comprise vulnerable species to hunting pressure, being usually associated with areas presenting high productivity and low anthropogenic disturbances (Antunes 2015). Mammals and ecosystem functions are likely to interact reciprocally (Buend ıa et al 2018), with the colonisation of certain species shaping the ecological interactions within islands and therefore contributing to the within-system energy flow. This is possible because of the swimming competence of non-volant mammals, which allows for lateral displacement between islands and between them and the mainland, as well as determining differential persistence of species on the islands themselves (Benchimol & Peres 2015).…”

Soil fertility of fluvial islands increases with proximity to an Amazonian white-water river

“…In Amazonia, uvial island systems, together with ooded forests, represent 30% of Amazon Basin forest types (Junk 2013). As a result of differences in sediment loading by their inundating rivers (Marinho et al 2020), the input of sediments from Amazonian rivers acts in synchrony with annual phenological patterning of leaf and fruit production (Montero et al 2014), which are responsible for seasonal lateral movements of vertebrates between ooded and non-ooded environments (Buendía et al 2018).…”