Drought during canopy development has lasting effect on annual carbon balance in a deciduous temperate forest.
* Climate change projections predict an intensifying hydrologic cycle and an increasing frequency of droughts, yet quantitative understanding of the effects on ecosystem carbon exchange remains limited. * Here, the effect of contrasting precipitation and soil moisture dynamics were evaluated on forest carbon exchange using 2 yr of eddy covariance and microclimate data from a 50-yr-old mixed oak woodland in northern Ohio, USA. * The stand accumulated 40% less carbon in a year with drought between bud-break and full leaf expansion (354 +/- 81 g C m(-2) yr(-1) in 2004 and 252 +/- 45 g C m(-2) yr(-1) in 2005). This was caused by greater suppression of gross ecosystem productivity (GEP; 16% = 200 g) than of ecosystem respiration (ER; 11% = 100 g) by drought. Suppressed GEP was traced to lower leaf area, lower apparent quantum yield and lower canopy conductance. The moisture sensitivity of ER may have been mediated by GEP. * The results highlight the vulnerability of the ecosystem to even a moderate drought, when it affects a critical aspect of development. Although the drought was preceded by rain, the storage capacity of the soil seemed limited to 1-2 wk, and therefore droughts longer than this are likely to impair productivity in the region.
Noormets
Asko
A
North Carolina State University, Department of Forestry and Environmental Resources, Raleigh, NC 27695, USA.|Southern Global Change Program, USDA Forest Service, Raleigh, NC 27606, USA.
McNulty
Steve G
SG
Southern Global Change Program, USDA Forest Service, Raleigh, NC 27606, USA.
DeForest
Jared L
JL
Department of Environmental and Plant Biology, Ohio University, Athens OH 45701, USA.
Sun
Ge
G
Southern Global Change Program, USDA Forest Service, Raleigh, NC 27606, USA.
Li
Qinglin
Q
Timberline Natural Resource Group Ltd, Kelowna, British Columbia, V1Y 4R1, Canada.
Chen
Jiquan
J
Department of Environmental Sciences, University of Toledo, Toledo, OH 43606, USA.
D031002:Acer / Q000254:growth & development / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D017753:Ecosystem; D029963:Quercus / Q000254:growth & development / Q000378:metabolism*; D011891:Rain; D012621:Seasons; D012987:Soil; D013696:Temperature; D014197:Trees / Q000254:growth & development / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
D012987:Soil; D014867:Water; D002244:Carbon