Straits forest floor carbon dioxide fluxes

Summary

This project measures the carbon dioxide (CO₂) released from the forest floor at the Straits Inclosure in Alice Holt Forest. This work supports our research into understanding forest carbon balances and the effects of woodland management.

Here is a short video summarising this work.

Research objectives

• Quantify the CO₂ release from the forest floor of a temperate oak forest in southern England (including both the soil and leaf litter components).
• Understand the effects of environmental change and weather on the CO₂ release from the forest floor.

• Provide data on forest floor CO₂ release for woodland carbon balance modelling (for example, to assess the possible climate change impacts).

Results so far

Two sets of measurements are collected in this project. At five points in the forest the soil CO₂ release from the forest soil (without leaf litter) is measured. From a further five points the CO₂ from the combined soil and leaf litter is measured. These measurements are taken weekly using a LI-COR Instruments LI-8100A analyser and 20 cm survey chamber.

The results from this long-term monitoring of forest soil CO₂ fluxes have shown that there is a distinct annual cycle. Soil CO₂ fluxes are larger in the summer and smaller in the winter, probably driven by the temperature and soil moisture, and by changes in root activity.

Previous studies at this site have also measured the CO₂ released from the forest floor. Heinemeyer et al. (2012) found that the annual rate of CO₂ released was 740 ± 43 g C m^-2 yr^-1 and Yamulki & Morison (2017) reported 894 g C m^-2 yr^-1.

The gross rate at which the forest in the Straits Inclosure took up CO₂ (1999-2010) was 2034 ± 145 g C m^-2 yr^-1. In the same period, the rate of CO₂ released by the Straits Inclosure was 1548 g C m^-2 yr^-1(Wilkinson et al., 2012). The previous studies have therefore shown that the CO₂ released from the soil is equivalent to 48-58% of the total CO₂ leaving this forest.

The graph above shows the mean CO₂ released from the soil (blue) and the soil and litter combined (green), as measured by this project since 2013. Error bars are ± 1 standard error.

The current project is continuing to add measurements to our dataset. These measurements, in addition to those from the eddy covariance tower, will help improve our understanding of the amount of CO₂ coming from the soil and what drives the processes that produce it.

Status

This project started in 2013 and is ongoing.

Funding and Partners

This project is part of the Assessing Resilience research programme.

Forestry Commission Policy

The project supports FC policy by investigating how forests help us address climate change, and policies on sustainable forest management. This includes those addressing protecting forests and the ecosystem services they provide, such as carbon storage in the soils, carbon sequestration in growing trees, and wood provision for timber and biomass markets. The work addresses knowledge gaps about quantifying the carbon balance of forests and the effect of disturbance, and helps underpin the values used in the Woodland Carbon Code.