Analyzing the dynamics and inter-linkages of carbon and water fluxes in subtropical pine (Pinus roxburghii) ecosystem

Abstract The carbon and water fluxes are key aspects of ecosystem functions. Their coupling processes are complicated over terrestrial ecosystems. To understand the seasonal dynamics and coupling mechanism between these fluxes in deciduous subtropical coniferous vegetation in the western Himalayas, the present study involved systematic and concurrent measurements of micrometeorological variables and ecophysiological characteristics within a uniformly distributed young pine forest ecosystem at Forest Research Institute, India. Micrometeorological data were measured continuously for a 14-month period along with key ecophysiological measurements during a growth cycle (2010–2011). These measurements allowed an examination of daytime net canopy assimilation ( C nar), evapotranspiration (ET), light use efficiency (LUE), and water use efficiency (WUE) of this coniferous ecosystem. Results showed that daily variations of ET, C nar, LUE and WUE were strong functions of temperature and vapour pressure deficit (VPD) but within optimal limits, while these efficiency terms had a close relationship with LAI dynamics and phenology on the seasonal scale. ET being the principal component of water balance (∼50% of rainfall), varied between 0.7 and 4.2 mm d −1 depending on LAI and seasonal cycle. It was primarily driven by evaporative demand (VPD) ( R 2  = 0.696, P R 2  = 0.92, P R 2  = 0.35) in pine ecosystem is indicative of dominant role of stomatal control. The seasonal course of C nar (peak in post-monsoon and minimum during winter) followed the LAI dynamics except during monsoon. The C nar of pine varied between 1.2 and 10.5 μmol CO 2  m −2  s −1 while that of understory ( Lantana camara ) varied between 3.7 and 17.3 μmol CO 2  m −2  s −1 . Pooled data over the seasons showed significant linear relation between C nar and ET or evaporative fraction. The degree of coupling between water and carbon exchange was strongest in the post-monsoon and spring seasons, and weaker during winter and monsoon seasons. A remarkable strong link between resource use efficiencies (WUE and LUE) was observed particularly in the dry season. This study highlights specifically the response of carbon and water exchange to environmental conditions that would help in forest management by optimizing water resource use. The optimal mix of resource use efficiencies may be the ecophysiological reason of pine ingression into higher reaches of oak forests in the western Himalaya.

[1]  Sven Halldin,et al.  Water-use efficiency of willow: Variation with season, humidity and biomass allocation , 1994 .

[2]  H. Jones,et al.  Plants and Microclimate. , 1985 .

[3]  I. S. Bowen.  The Ratio of Heat Losses by Conduction and by Evaporation from any Water Surface , 1926 .

[4]  B. Law,et al.  Use of a simulation model and ecosystem flux data to examine carbon-water interactions in ponderosa pine. , 2001, Tree physiology.

[5]  Maosheng Zhao,et al.  Evolution of hydrological and carbon cycles under a changing climate , 2011 .

[6]  Tapash Das,et al.  Climatic Correlates of Tree Mortality in Water- and Energy-Limited Forests , 2013, PloS one.

[7]  S. Los,et al.  The impact of diffuse sunlight on canopy light‐use efficiency, gross photosynthetic product and net ecosystem exchange in three forest biomes , 2007 .

[8]  T. Vesala,et al.  Characterisation of ecosystem water-use efficiency of european forests from eddy covariance measurements , 2008 .

[9]  Thomas Foken,et al.  The Energy Balance Experiment EBEX-2000. Part III: Behaviour and quality of the radiation measurements , 2007 .

[10]  J. Bonnefond,et al.  Carbon dioxide and energy flux partitioning between the understorey and the overstorey of a maritime pine forest during a year with reduced soil water availability , 2008 .

[11]  H. Schmid,et al.  Uncertainty of annual net ecosystem productivity estimated using eddy covariance flux measurements , 2006 .

[12]  Gérard Dedieu,et al.  Methodology for the estimation of terrestrial net primary production from remotely sensed data , 1994 .

[13]  G. Campbell,et al.  An Introduction to Environmental Biophysics , 1977 .

[14]  Pamela L. Nagler,et al.  Relationship between evapotranspiration and precipitation pulses in a semiarid rangeland estimated by moisture flux towers and MODIS vegetation indices , 2007 .

[15]  Heikki Hänninen,et al.  Relationship between temperature and the seasonal course of photosynthesis in Scots pine at northern timberline and in southern boreal zone , 2007 .

[16]  T. Horie,et al.  Studies on Crop-Weather Relationship Model in Rice , 1985 .

[17]  S. T. Gower,et al.  Rapid Estimation of Leaf Area Index in Conifer and Broad-Leaf Plantations , 1991 .

[18]  S. G. Champion,et al.  A revised survey of the forest types of India. , 1968 .

[19]  S. Gower,et al.  Photosynthesis and light-use efficiency by plants in a Canadian boreal forest ecosystem. , 2001, Tree physiology.

[20]  Jun Asanuma,et al.  Response of gross ecosystem productivity, light use efficiency, and water use efficiency of Mongolian steppe to seasonal variations in soil moisture , 2008 .

[21]  S. Wofsy,et al.  Physiological responses of a black spruce forest to weather , 1997 .

[22]  T. Black,et al.  Processes Controlling Understorey Evapotranspiration , 1989 .

[23]  Peter A. Troch,et al.  Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought , 2009, Proceedings of the National Academy of Sciences.

[24]  A. Turner,et al.  Climate change and the South Asian summer monsoon , 2012 .

[25]  William J. Massman,et al.  Reflections on the surface energy imbalance problem , 2012 .

[26]  Xiaomin Sun,et al.  Water-use efficiency of forest ecosystems in eastern China and its relations to climatic variables. , 2008, The New phytologist.

[27]  Maosheng Zhao,et al.  A Continuous Satellite-Derived Measure of Global Terrestrial Primary Production , 2004 .

[28]  A. Mäkelä,et al.  Acclimation of photosynthetic capacity in Scots pine to the annual cycle of temperature. , 2004, Tree physiology.

[29]  Markus Reichstein,et al.  Mean annual GPP of Europe derived from its water balance , 2007 .

[30]  S. Launiainen.  Seasonal and inter-annual variability of energy exchange above a boreal Scots pine forest , 2010 .

[31]  P. Berbigier,et al.  CO2 and water vapour fluxes for 2 years above Euroflux forest site , 2001 .

[32]  Markus Reichstein,et al.  Temporal and among‐site variability of inherent water use efficiency at the ecosystem level , 2009 .

[33]  M. Novello,et al.  Geodesic motion and confinement in Gödel's universe , 1983 .

[34]  D. Baldocchi,et al.  Leaf area distribution and radiative transfer in open-canopy forests: implications for mass and energy exchange. , 2001, Tree physiology.

[35]  D. Baldocchi.  A comparative study of mass and energy exchange rates over a closed C3 (wheat) and an open C4 (corn) crop: II. CO2 exchange and water use efficiency , 1994 .

[36]  A. Lindroth,et al.  Heat storage in forest biomass improves energy balance closure , 2010 .

[37]  J. Bonnefond,et al.  Simultaneous measurements of CO 2 and water exchanges over three agroecosystems in South-West France , 2009 .

[38]  T. Hsiao,et al.  Maize canopies under two soil water regimes: III. Variation in coupling with the atmosphere and the role of leaf area index , 1998 .

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

[40]  B. Law,et al.  Effects of water availability on carbon and water exchange in a young ponderosa pine forest: Above- and belowground responses , 2012 .

[41]  J. Pereira,et al.  Stomatal Responses to Leaf-to-Air Vapour Pressure Deficit in Sahelian Species , 1997 .

[42]  Takeshi Horie,et al.  Leaf Nitrogen, Photosynthesis, and Crop Radiation Use Efficiency: A Review , 1989 .

[43]  John L. Monteith,et al.  Accommodation between transpiring vegetation and the convective boundary layer , 1995 .

[44]  Eero Nikinmaa,et al.  Wintertime photosynthesis and water uptake in a boreal forest. , 2006, Tree physiology.

[45]  Xiaofeng Guo,et al.  Quality control and flux gap filling strategy for Bowen ratio method: revisiting the Priestley–Taylor evaporation model , 2007 .

[46]  D. Baldocchi,et al.  Seasonal variation of carbon dioxide exchange rates above and below a boreal jack pine forest , 1997 .

[47]  T. A. Black,et al.  Effects of short-term variation in weather on diurnal canopy CO2 flux and evapotranspiration of a juvenile douglas-fir stand , 1990 .

[48]  H. Hasenauer,et al.  Ecohydrologic impact of reduced stomatal conductance in forests exposed to elevated CO2 , 2011 .

[49]  S. Prince.  A model of regional primary production for use with coarse resolution satellite data , 1991 .

[50]  G. Bonan.  Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests , 2008, Science.

[51]  William E. Emmerich,et al.  Carbon dioxide fluxes in a semiarid environment with high carbonate soils , 2003 .

[52]  Dennis D. Baldocchi,et al.  Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California , 2004 .

[53]  Lars Eklundh,et al.  Net primary production and light use efficiency in a mixed coniferous forest in Sweden , 2005 .

[54]  K. Davis,et al.  A multi-site analysis of random error in tower-based measurements of carbon and energy fluxes , 2006 .

[55]  F. Tian,et al.  A comparison of methods for determining field evapotranspiration: photosynthesis system, sap flow, and eddy covariance , 2013 .

[56]  M. G. Ryan,et al.  Hydraulic Limits to Tree Height and Tree Growth , 1997 .

[57]  Michael J. Savage,et al.  Field Evaluation of Polymer Capacitive Humidity Sensors for Bowen Ratio Energy Balance Flux Measurements , 2010, Sensors.

[58]  P. Berbigier,et al.  Radiation and water use efficiencies of two coniferous forest canopies , 1996 .

[59]  H. Franssen,et al.  Estimating random errors of eddy covariance data: An extended two-tower approach , 2013 .

[60]  G. Collatz,et al.  Profiles of photosynthetically active radiation, nitrogen and photosynthetic capacity in the boreal forest: Implications for scaling from leaf to canopy , 1997 .

[61]  J. Randerson,et al.  Terrestrial ecosystem production: A process model based on global satellite and surface data , 1993 .