Phosphorus Dynamics in the Conversion of a Secondary Forest Into a Rubber Tree Plantation in the Amazon Rainforest

Abstract

During the past several decades, extensive areas of the humid tropical Amazon have been cleared for the introduction of pasture or subsistence farming and later abandoned after a few years of use. An option for recovering these areas is the planting of rubber trees because it is a native tree that could restore conditions similar to those existing before the clearing. In addition, the high economic value of natural rubber is a source of income for small producers. In soil management under the Amazon conditions, low phosphorus (P) has been the most limiting factor. Under natural conditions, P is provided to the plants almost exclusively by organic matter mineralization. The aim of this study was to evaluate a chronosequence of reforestation with rubber trees planted at different times in cleared areas, with primary forest as a reference. The amounts of litter and P content in the plant, in the litter, and in soil, as well as biological indicators (acid and alkaline phosphatase and P microbial biomass) associated with the P cycle in a Xanthic Ferralsol (Oxisol), in the Central Amazon were assessed. Rubber tree growth resulted in changes in total organic carbon, with an increase of 104.6% in the 45-year-old rubber trees compared with the 6-year-old rubber tree plantation. This was also observed for acid and alkaline phosphatase activities, which were close to those of the primary forest. The formation of litter and the P content of the microbial biomass in soil were higher in rubber areas. The P immobilized into microbial biomass was the main reserve to meet the plant's nutritional demand for phosphorus. The content of P available in the soil, regardless of the extractants (Mehlich 1, Mehlich 3, and Bray 1) and the age of vegetation cover were below the levels indicated as appropriate.

Does Soil Fertility Decline under Smallholder Rubber Farming? The Case of a West Sumatran Lowland in Indonesia

“…In fact, many previous studies reported the depletion of soil organic matter and mineral nutrients by land use change from primary or secondary forests to rubber plantation (e.g., Li et al 2012, de Blécourt et al 2013, Kotowska et al 2015, Allen et al 2015, and the soil degradation in rubber gardens can also increase with an increase in the age of the rubber tree stand (e.g., Aweto 1987, 2001, Cheng et al 2007. In contrast, other reports delivered inconsistent results to those previously documented: the soil fertility under rubber farming was similar to that under primary and secondary forests (e.g., Tanaka et al 2009, Moreira et al 2013, and little loss or even enhanced content of organic matter and some nutrients in the soil were found during rubber cultivation (Guillaume et al 2016, N'Dri et al 2018, Peerawat et al 2018. These contradictory findings warrant further research on the changes in soil fertility caused by rubber plantation.…”

Microbial community composition and activity controls phosphorus transformation in rhizosphere soils of the Yeyahu Wetland in Beijing, China

“…This knowledge gap potentially undermines our attempts to manage P retention in wetland systems. Previous studies have shown that rhizodeposition can induce changes in the composition of soil microbial communities by altering the quality and distribution of available organic matter, which may affect P fractions over time (Marschner et al, 2001;Moreira et al, 2013).…”

Atributos físicos, químicos e biológicos de Latossolo Amarelo na conversão de floresta primária para seringais na Amazônia

“…bras., Brasília, v.51, n.9, p.1061-1068, set. 2016 DOI: 10.1590/S0100-204X2016000900005 Durante muitas décadas, áreas extensivas da Amazônia têm sido desmatadas e, após poucos anos de uso, abandonadas (Cravo & Smyth, 1997;Moreira et al, 2013). Aumento populacional, exploração da madeira, conversão em pastagem, e em agricultura de subsistência são os principais vetores por esta transformação (Johnson et al, 2001).…”