Water table depth modulates productivity and biomass across Amazonian forests

Summary

This analysis of 344 long-term forest inventory plots across lowland Amazonia (1971–2019) demonstrates that forest productivity and biomass are jointly determined by climatic water availability and soil water table depth, rather than climate alone. Shallow water tables reduced productivity by 18% and biomass by 23% relative to deeper water tables, with productivity further suppressed in drier climates (maximum water deficit <−160 mm). The findings reveal a significant interaction effect: in dry climates, shallow water tables particularly constrain forest function, whilst in wetter climates this effect diminishes unless the water table is extremely shallow.

Regional applicability

These findings are specific to lowland Amazonian terra-firme forests and may have limited direct applicability to United Kingdom temperate forestry systems, which operate under entirely different hydrological and climatic regimes. However, the methodological approach—integrating long-term plot data with edaphic and hydrological variables to model forest productivity—could inform UK forest management research, particularly for understanding how drainage and water table management affect woodland productivity under variable precipitation patterns.

Key measures

Above-ground woody productivity (Mg ha⁻¹ year⁻¹), above-ground biomass stock (Mg ha⁻¹), water table depth (m), maximum cumulative water deficit (mm), precipitation, soil edaphic properties

Outcomes reported

The study measured above-ground woody productivity and biomass stock across 344 long-term forest inventory plots in Amazonia, analysing how water table depth and climatic water availability interact to shape forest structure and dynamics. Forests with shallow water tables (<5 m depth) exhibited 18% lower productivity and 23% lower biomass than those with deeper water tables, with productivity also affected by precipitation patterns and soil-water interactions.

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