Effect of drought on Carbon Balance of boreal forests

The boreal forest comprises 11% of the Earth’s vegetative (~16 million km2) surface accounts for 43% of Earth’s carbon in the soil and 13% in biomass. The climate of the boreal forest is characterized by strong seasonal variation with short, moderately warm and moist summers and long extremely cold and dry winters. During the recent 3-year drought (2001–2003) that affected large areas of western Canada including the Boreal Ecosystem Research and Monitoring Sites (BERMS) area, mature evergreen stands at Southern Old Black Spruce (SOBS) and a jack pine stand were reported to have had insignificant changes in C balance compared with those of mature deciduous aspen stand (SOA). At SOA Drought effects revealed in the interannual variations of Net Ecosystem Productivity were also reflected in the annual measurements of stemgrowth,which werewell correlated with those of gross ecosytem photosysnthesis. The drought significantly reduced full-leaf Leaf Area Index(LAI) and it remained lower than its pre-drought mean even 2 years after the drought.

Krishnan, P., Black, T. A., Barr, A. G., Grant, N. J., Gaumont-Guay, D., and Z. Nesic. Factors controlling the interannual variability in the carbon balance of a southern boreal black Spruce Forest. J. Geophys. Res.–Atmospheres, 113, D09109, doi:10.1029/2007JD008965, 2008 [PDF]
Krishnan, P., Black, T. A., Grant, N. J., Barr, A. G., Hogg, E. H., Morgenstern, K., Impact of changing soil moisture distribution on net ecosystem productivity of a boreal aspen forest during and following drought, Agric. For. Meteorol, 208–223, 2006 [ PDF]