Influence of spring phenology on seasonal and annual carbon balance in two contrasting New England forests.

Spring phenology is thought to exert a major influence on the carbon (C) balance of temperate and boreal ecosystems. We investigated this hypothesis using four spring onset phenological indicators in conjunction with surface-atmosphere CO(2) exchange data from the conifer-dominated Howland Forest and deciduous-dominated Harvard Forest AmeriFlux sites. All phenological measures, including CO(2) source-sink transition dates, could be well predicted on the basis of a simple two-parameter spring warming model, indicating good potential for improving the representation of phenological transitions and their dynamic responsiveness to climate variability in land surface models. The date at which canopy-scale photosynthetic capacity reached a threshold value of 12 micromol m(-2) s(-1) was better correlated with spring and annual flux integrals than were either deciduous or coniferous bud burst dates. For all phenological indicators, earlier spring onset consistently, but not always significantly, resulted in higher gross primary productivity (GPP) and ecosystem respiration (RE) for both seasonal (spring months, April-June) and annual flux integrals. The increase in RE was less than that in GPP; depending on the phenological indicator used, a one-day advance in spring onset increased springtime net ecosystem productivity (NEP) by 2-4 g C m(-2) day(-1). In general, we could not detect significant differences between the two forest types in response to earlier spring, although the response to earlier spring was generally more pronounced for Harvard Forest than for Howland Forest, suggesting that future climate warming may favor deciduous species over coniferous species, at least in this region. The effect of earlier spring tended to be about twice as large when annual rather than springtime flux integrals were considered. This result is suggestive of both immediate and lagged effects of earlier spring onset on ecosystem C cycling, perhaps as a result of accelerated N cycling rates and cascading effects on N uptake, foliar N concentrations and photosynthetic capacity.

[1]  H. Lieth.  Modeling the Primary Productivity of the World , 1975 .

[2]  H. Odum,et al.  Primary Productivity of the Biosphere , 1978, Ecological Studies.

[3]  M. Lechowicz,et al.  Predicting the timing of budburst in temperate trees , 1992 .

[4]  J. Lloyd,et al.  On the temperature dependence of soil respiration , 1994 .

[5]  J. William Munger,et al.  Exchange of Carbon Dioxide by a Deciduous Forest: Response to Interannual Climate Variability , 1996, Science.

[6]  C. Tucker,et al.  Increased plant growth in the northern high latitudes from 1981 to 1991 , 1997, Nature.

[7]  Denis-Didier Rousseau,et al.  Fitting models predicting dates of flowering of temperate‐zone trees using simulated annealing , 1998 .

[8]  Eric A. Davidson,et al.  Seasonal patterns and environmental control of carbon dioxide and water vapour exchange in an ecotonal boreal forest , 1999 .

[9]  T. A. Black,et al.  Effects of climatic variability on the annual carbon sequestration by a boreal aspen forest , 1999 .

[10]  Christopher B. Field,et al.  Increases in early season ecosystem uptake explain recent changes in the seasonal cycle of atmospheric CO2 at high northern latitudes , 1999 .

[11]  Ye Qi,et al.  Effects of climate variability on the carbon dioxide, water, and sensible heat fluxes above a ponderosa pine plantation in the Sierra Nevada (CA) , 2000 .

[12]  Wenjun Chen,et al.  Increased carbon sequestration by a boreal deciduous forest in years with a warm spring , 2000 .

[13]  Dennis D. Baldocchi,et al.  Modeling CO2 and water vapor exchange of a temperate broadleaved forest across hourly to decadal time scales , 2001 .

[14]  W. Oechel,et al.  Seasonality of ecosystem respiration and gross primary production as derived from FLUXNET measurements , 2001 .

[15]  W. Oechel,et al.  FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities , 2001 .

[16]  J. Canadell,et al.  Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems , 2001, Nature.

[17]  S. Wofsy,et al.  Factors Controlling Long- and Short-Term Sequestration of Atmospheric CO2 in a Mid-latitude Forest , 2001, Science.

[18]  T. A. Black,et al.  Comparing the carbon budgets of boreal and temperate deciduous forest stands , 2002 .

[19]  J. Schaber.  Phenology in Germany in the 20th century : methods, analyses and models , 2002 .

[20]  J. Peñuelas,et al.  Changed plant and animal life cycles from 1952 to 2000 in the Mediterranean region , 2002 .

[21]  W. Oechel,et al.  Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation , 2002 .

[22]  W. Oechel,et al.  Phase and amplitude of ecosystem carbon release and uptake potentials as derived from FLUXNET measurements , 2002 .

[23]  M. D. Schwartz.  Phenology: An Integrative Environmental Science , 2003, Tasks for Vegetation Science.

[24]  David R. Anderson,et al.  Model selection and multimodel inference : a practical information-theoretic approach , 2003 .

[25]  Ramakrishna R. Nemani,et al.  Canopy duration has little influence on annual carbon storage in the deciduous broad leaf forest , 2003 .

[26]  Arnaud Carrara,et al.  Net ecosystem CO2 exchange of mixed forest in Belgium over 5 years , 2003 .

[27]  Tiina Markkanen,et al.  Air temperature triggers the recovery of evergreen boreal forest photosynthesis in spring , 2003 .

[28]  Tiina Markkanen,et al.  Interannual variability and timing of growing‐season CO2 exchange in a boreal forest , 2003 .

[29]  P. Bakwin.  Tall Tower and Aircraft Measurements of Carbon Dioxide: Prospects for the North American Carbon Program (NACP) , 2003 .

[30]  Dennis D. Baldocchi,et al.  Phenology of Vegetation Photosynthesis , 2003 .

[31]  Ramakrishna Nemani,et al.  Enhancement of understory productivity by asynchronous phenology with overstory competitors in a temperate deciduous forest. , 2004, Tree physiology.

[32]  Eric A. Davidson,et al.  Spatial and temporal variability in forest–atmosphere CO2 exchange , 2004 .

[33]  J. Schaber,et al.  Responses of spring phenology to climate change , 2004 .

[34]  T. Black,et al.  Inter-annual variability in the leaf area index of a boreal aspen-hazelnut forest in relation to net ecosystem production , 2004 .

[35]  C. Wirth,et al.  Reconciling Carbon-cycle Concepts, Terminology, and Methods , 2006, Ecosystems.

[36]  T. A. Black,et al.  Predicting the onset of net carbon uptake by deciduous forests with soil temperature and climate data: a synthesis of FLUXNET data , 2005, International journal of biometeorology.

[37]  Christian Bernhofer,et al.  Relating tree phenology with annual carbon fluxes at Tharandt forest , 2005 .

[38]  Xiangming Xiao,et al.  Spatial analysis of growing season length control over net ecosystem exchange , 2005 .

[39]  J. Gove,et al.  Application of a dual unscented Kalman filter for simultaneous state and parameter estimation in problems of surface‐atmosphere exchange , 2006 .

[40]  Dennis D. Baldocchi,et al.  A multiyear evaluation of a Dynamic Global Vegetation Model at three AmeriFlux forest sites: Vegetation structure, phenology, soil temperature, and CO2 and H2O vapor exchange , 2006 .

[41]  D. Hollinger,et al.  Use of digital webcam images to track spring green-up in a deciduous broadleaf forest , 2007, Oecologia.

[42]  J. O'keefe,et al.  Phenology of a northern hardwood forest canopy , 2006 .

[43]  Russell K. Monson,et al.  Coupling between carbon cycling and climate in a high-elevation, subalpine forest: a model-data fusion analysis , 2007, Oecologia.

[44]  Allison L. Dunn,et al.  A long‐term record of carbon exchange in a boreal black spruce forest: means, responses to interannual variability, and decadal trends , 2007 .

[45]  Natascha Kljun,et al.  Climatic controls on the carbon and water balances of a boreal aspen forest, 1994–2003 , 2007 .

[46]  Scott V. Ollinger,et al.  Environmental variation is directly responsible for short‐ but not long‐term variation in forest‐atmosphere carbon exchange , 2007 .

[47]  S. Wofsy,et al.  Factors controlling CO2 exchange on timescales from hourly to decadal at Harvard Forest , 2007 .

[48]  Markus Reichstein,et al.  Statistical properties of random CO2 flux measurement uncertainty inferred from model residuals , 2008 .

[49]  S. Frolking,et al.  Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks , 2008, Proceedings of the National Academy of Sciences.

[50]  P. Ciais,et al.  Net carbon dioxide losses of northern ecosystems in response to autumn warming , 2008, Nature.

[51]  D. Baldocchi.  ‘Breathing’ of the terrestrial biosphere: lessons learned from a global network of carbon dioxide flux measurement systems , 2008 .

[52]  J. Abatzoglou,et al.  Tracking the rhythm of the seasons in the face of global change: phenological research in the 21st century. , 2009 .