Nitrogen input by bamboos in neotropical forest: a new perspective

Area of Science:

• Ecology
• Forest Science
• Biogeochemistry

Background:

• Nitrogen (N) is a critical macronutrient for ecosystem productivity, with biological nitrogen fixation (BNF) being a key N source in tropical forests.
• Bamboo species dominate many Neotropical forests, yet their specific role in ecosystem functioning, particularly N cycling, is poorly understood.

Purpose of the Study:

• To investigate the contribution of a native bamboo species, Merostachys neesii, to the nitrogen (N) cycle in a Neotropical Atlantic Forest.
• To quantify the potential N input from BNF associated with bamboo.

Main Methods:

• Quantified Merostachys neesii abundance (clumps and culms) in 100 sample units (100 m² each) within a Brazilian montane Atlantic Forest.
• Calculated leaf area and litter production, estimating N content and potential N input based on known BNF rates for the species.
• Contextualized bamboo's N input within the broader N cycling components of the study area.

Main Results:

• Merostachys neesii contributes significantly to N input, with an estimated 4,000 live culms per hectare.
• Seasonal N input estimates range from 11.7 kg N ha⁻¹ in summer to 19.6 kg N ha⁻¹ in winter.
• Annual N contribution from M. neesii could exceed 60 kg N ha⁻¹ yr⁻¹.

Conclusions:

• The high N input is attributed to bamboo's abundance, providing habitat for microbial colonization, and the presence of free-living N fixers on its phyllosphere.
• This N input can mitigate the N deficit in the Atlantic Forest by at least 27%, despite some N loss during decomposition.
• Merostachys neesii plays a crucial role in regulating N input, potentially explaining the high biodiversity and carbon stocks observed in the region.