Tropical forest fires have become more common due to interactions between deforestation, land clearing, and drought. Forest recovery following fires may be limited by nitrogen. Biological nitrogen fixation (BNF) is the main pathway for new nitrogen (N) to enter most ecosystems, but BNF may be constrained by other nutrients, such as molybdenum and phosphorus, which are required for the process. We studied the role of BNF 7 years into the recovery of southeastern Amazon tropical forests that were burned experimentally either annually or every 3 years between 2004 and 2010. We hypothesized that, compared with unburned primary forests, BNF in burned forests would increase due to the depletion of N in the aboveground biomass pool and that soil concentrations of molybdenum and phosphorus from ash inputs would increase, reducing their potential constraints on BNF. Despite the fires depleting about half the aboveground N pool and rapid rates of recovery in leaf biomass and litterfall production, we found low rates of both free-living and symbiotic BNF. Higher concentrations of molybdenum and phosphorus in the mineral soils of the burned forests indicated that these elements were likely not limiting BNF. Our results suggest that despite the N demand for regrowth post-fire, substantial N stored in soils likely downregulates BNF. Overall, we found surprisingly low BNF rates (< 1.2 kg N ha−1 y−1) in this region of the Amazon, which contrasts with the traditional paradigm that (1) tropical forests fix large quantities of N and (2) that BNF increases after forest disturbance.
Assessing compliance with the Forest Code: A practical guide
Assessing compliance with the Forest Code: A practical guide
The goal of this guide is to help buyers of Brazilian forestry and agricultural commodities to verify compliance with the Brazilian Forest Code in their supply chain. It presents a range of available and evolving tools to ensure compliance with the Forest Code in the supply chain. The tools described are credible and practical instruments that buyers can use without the need for legal or environmental specialists. In this way, the private sector can support the transition to legal compliance in Brazil’s rural environment, also with the benefit of promoting commodities produced in Brazil in the domestic and international markets.
Authors: Pedro Amaral (Proforest), Tiago Reis (IPAM) e Roberta del Giudice (Instituto BVRio).