Response of Soil CO₂ Efflux to Simulated Precipitation Pulses in a Canary Island Pine Forest at Treeline

Abstract

Pulse-like rapidly increasing CO₂ effluxes occur in soils under seasonally dry climates in response to summer rain events, and these CO₂ outbursts can have a marked influence on the ecosystem carbon balance. Two irrigation experiments were conducted at the end of the dry season in a Mediterranean Pinus canariensis forest at its upper distribution limit in Tenerife, Canary Islands. Soil CO₂ efflux was discontinuously monitored along with soil temperature and soil water content during and after irrigation. Correlation analysis suggested that soil moisture is the leading environmental factor regulating soil CO₂ efflux during summer rain events. Cumulative CO₂ efflux following a precipitation pulse was estimated to be 50% higher than the value calculated for the dry soil, which is approximately 3% of the year round soil CO₂ efflux. It is concluded that such CO₂ effluxes may have implications for the prediction of forest response to increasing dryness combined with an increase in the irregularity of summer rain events in Mediterranean regions.

Keywords:

• birch effect
• canary islands pine
• respiratory pulses
• soil respiration
• soil water content

Acknowledgments

The authors express their gratitude to the Spanish Government (Projects CGL2006-10210/BOS ME and CGL2010-21366-C04-04 MCI), University of La Laguna (MGC/08/14 and 2009), and Canarian Government-University of La Laguna (“Proyecto Estructurante”) all co-financed by FEDER. The authors also thank the National Park's Network for permission to work in Teide National Park. P. Brito received a fellowship from ACIISI, Canarian Government.

Notes

Note: c (=F _S at 10°C; µ mol m⁻² s⁻¹) and d (°C⁻¹) are regression coefficients, R ² is the proportion of variability explained by soil temperature in 10 cm soil depth. Q ₁₀ calculated from b (Q ₁₀  = e^10d ), and p-value. The standard errors of the regression coefficients are shown in brackets.