CONTRIBUTION OF SOIL RESPIRATION TO THE CARBON BALANCE OF AN APPLE ORCHARD

Soil respiration was recorded in an apple orchard near Bonn, Germany, over 2 years (1995–96) with a portable, battery-driven infrared gas analyzer and a soil respiration chamber (soil respiration system ‘SRS’ from PP Systems, Hitchin, UK) to examine the contribution of soil respiration to the CO₂ balance of a fruit orchard and to study the effects of heat, frost, herbicide, drought and rainfall:

1. In the summer, maximum soil respiration of 27 μmol CO₂ m^-2 s^-1 was at a temperature of 37°C. A further increase in temperature reduced soil respiration.

2. Simulated rainfall of 30 mm after a prolonged dry spell increased soil respiration from an average of 5 to 7 μmol CO₂ m^-2 s^-1 on a warm autumn day in October.

3. Freezing and thawing processes in January released organic carbon which induced respiration rates of 1.2–2.2 μmol CO₂ m^-2 s^-1.

4. Soil respiration rates of 1–3 μmol CO₂ (winter), 3–8 μmol CO₂ (spring/autumn) and 9–18 μmol CO₂ m^-2 s^-1 (summer), based on alleys comprising 33% of orchard acreage and equivalent to 0.5–1.4 kg (winter), 1.4–3.8 kg (spring/autumn) and 4.3–8.6 kg (summer) CO₂ ha^-1 h^-1 exceeded root and tree respiration, contributed significantly to the CO₂ flux in a fruit orchard, and may be a pertinent source of CO₂ for tree photosynthesis.
   More research is needed for different soil types and planting systems over a wide range of environmental conditions.

VI International Symposium on Integrated Canopy, Rootstock, Environmental Physiology in Orchard Systems

M. M. Blanke

apple, Malus domestica Borkh., bioenergetics, biometerology, CO₂, environment, greenhouse effect, micro-climate

https://doi.org/10.17660/ActaHortic.1997.451.39