Influence and predictive capacity of climate anomalies on daily to decadal extremes in canopy photosynthesis
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Significant advances have been made over the past decades in capabilities to simulate diurnal and seasonal variation of leaf-level and canopy-scale photosynthesis in temperate and boreal forests. However, long-term prediction of future forest productivity in a changing climate may be more dependent on how climate and biological anomalies influence extremes in interannual to decadal variability of canopy ecosystem carbon exchanges. These exchanges can differ markedly from leaf level responses, especially owing to the prevalence of long lags in nutrient and water cycling. Until recently, multiple long-term (10+ year) high temporal frequency (daily) observations of canopy exchange were not available to reliably assess this claim. An analysis of one of the longest running North American eddy covariance flux towers reveals that single climate variables do not adequately explain carbon exchange anomalies beyond the seasonal timescale. Daily to weekly lagged anomalies of photosynthesis positively autocorrelate with daily photosynthesis. This effect suggests a negative feedback in photosynthetic response to climate extremes, such as anomalies in evapotranspiration and maximum temperature. Moisture stress in the prior season did inhibit photosynthesis, but mechanisms are difficult to assess. A complex interplay of integrated and lagged productivity and moisture-limiting factors indicate a critical role of seasonal thresholds that limit growing season length and peak productivity. These results lead toward a new conceptual framework for improving earth system models with long-term flux tower observations.
KeywordsEddy covariance Canopy photosynthesis Spectral analysis Carbon cycle
This manuscript would not have been possible with the numerous person-hours of support that going into the making of observations at WLEF including J. Thom at UW-Madison, A. Andrews and J. Kofler at NOAA-ESRL, R. Strand and J. Ayers at State of Wisconsin Educational Communications Board, K. Davis and current/former lab members at The Pennsylvania State University, P. Bolstad at University of Minnesota, and B. Cook at NASA GSFC. I also would like to thank A. Leakey for organizing this special issue. Observations and research were supported through NSF Biology Directorate grants #DEB-0845166 and #DBI-1062204.
- Bretherton CS, Widman M, Dymnikov VP, Wallace JM, Blade I (1999) The effective number of spatial degrees of freedom of a time-varying field. J Climate 12:1990–2009Google Scholar
- Kumar M, Monteith JL (1981) Remote sensing of crop growth. In: Smith H (ed) Plants and the daylight spectrum. Academic Press, London, pp 133–144Google Scholar
- Mahecha MD, Reichstein M, Jung M, Seneviratne SI, Zaehle S, Beer C, Braakhekke MC, Carvalhais N, Lange H, Le Maire G, Moors E (2010) Comparing observations and process-based simulations of biosphere-atmosphere exchanges on multiple time scales. J Geophys Res 115:G02003. doi: 10.1029/2009JG001016 Google Scholar
- Scheffer M, Carpenter S, Foley JA, Folke C, Walker B (2001) Catastrophic shifts in ecosystems. Nature 413:591–596Google Scholar
- Stoy PC, Richardson AD, Baldocchi DD, Katul GG, Stanovick J, Mahecha MD, Reichstein M, Detto M, Law BE, Wohlfahrt G, Arriga N, Campos J, McCaughey JH, Montagnani L, Paw UKT, Sevanto S, Williams M (2009) Biosphere-atmosphere exchange of CO2 in relation to climate: a cross-biome analysis across multiple time scales. Biogeosciences 6:2297–2312CrossRefGoogle Scholar