Biophysical homoeostasis of leaf temperature: A neglected process for vegetation and land-surface modelling

Aim Leaf and air temperatures are seldom equal, but many vegetation models assume that they are. Land-surface models calculate canopy temperatures, but how well they do so is unknown. We encourage consideration of the leaf- and canopy-to-air temperature difference (ΔΤ) as a benchmark for land-surface modelling and an important feature of plant and ecosystem function. Location Tropical SW China. Time period 2013. Major Taxa studies Tropical trees. Methods We illustrate diurnal cycles of leaf- and canopy-to-air temperature difference (ΔΤ) with field measurements in a tropical dry woodland and with continuous monitoring data in a tropical seasonal forest. The Priestley–Taylor (PT) and Penman–Monteith (PM) approaches to evapotranspiration are used to provide insights into the interpretation and prediction of ΔT. Field measurements are also compared with land-surface model results obtained with the Joint U.K. Land Environment Simulator (JULES) set up for the conditions of the site. Results The ΔT followed a consistent diurnal cycle, with negative values at night (attributable to negative net radiation) becoming positive in the morning, reaching a plateau and becoming negative again when air temperature exceeded a ‘crossover’ in the 24–29 °C range. Daily time courses of ΔT could be approximated by either the PT or the PM model, but JULES tended to underestimate the magnitude of negative ΔT. Main conclusions Leaves with adequate water supply are partly buffered against air-temperature variations, through a passive biophysical mechanism. This is likely to be important for optimal leaf function, and land-surface and vegetation models should aim to reproduce it.

[1]  Frank Ewert,et al.  Heat stress is overestimated in climate impact studies for irrigated agriculture , 2017 .

[2]  Michael Kaspari,et al.  The energetic and carbon economic origins of leaf thermoregulation , 2016, Nature Plants.

[3]  Y. Malhi,et al.  Death from drought in tropical forests is triggered by hydraulics not carbon starvation , 2015, Nature.

[4]  Jizhong Zhou,et al.  Plant Thermoregulation: Energetics, Trait-Environment Interactions, and Carbon Economics. , 2015, Trends in ecology & evolution.

[5]  Guanglei Gao,et al.  How the Plant Temperature Links to the Air Temperature in the Desert Plant Artemisia ordosica , 2015, PloS one.

[6]  Shuangcheng Li,et al.  Local cooling and warming effects of forests based on satellite observations , 2015, Nature Communications.

[7]  S. Sherwood,et al.  A Drier Future? , 2014, Science.

[8]  I. C. Prentice,et al.  Balancing the costs of carbon gain and water transport: testing a new theoretical framework for plant functional ecology. , 2014, Ecology letters.

[9]  H. Jones.  Plants and Microclimate: Other environmental factors: wind, altitude, climate change and atmospheric pollutants , 2013 .

[10]  S. Harrison,et al.  Precipitation scaling with temperature in warm and cold climates: An analysis of CMIP5 simulations , 2013 .

[11]  Stanislaus J. Schymanski,et al.  Stomatal Control and Leaf Thermal and Hydraulic Capacitances under Rapid Environmental Fluctuations , 2013, PloS one.

[12]  I. Prentice,et al.  Dynamic Global Vegetation Models , 2013 .

[13]  M. Saurer,et al.  Examining the large-scale convergence of photosynthesis-weighted tree leaf temperatures through stable oxygen isotope analysis of multiple data sets. , 2011, The New phytologist.

[14]  P. Cox,et al.  The Joint UK Land Environment Simulator (JULES), model description – Part 2: Carbon fluxes and vegetation dynamics , 2011 .

[15]  P. Cox,et al.  The Joint UK Land Environment Simulator (JULES), model description – Part 1: Energy and water fluxes , 2011 .

[16]  Paolo De Angelis,et al.  Reconciling the optimal and empirical approaches to modelling stomatal conductance , 2011 .

[17]  Paul D. Colaizzi,et al.  Application of the Priestley–Taylor Approach in a Two-Source Surface Energy Balance Model , 2010 .

[18]  C. Körner,et al.  Tree surface temperature in an urban environment , 2010 .

[19]  B. Helliker,et al.  Subtropical to boreal convergence of tree-leaf temperatures , 2008, Nature.

[20]  A. Mäkelä,et al.  Predicting the decline in daily maximum transpiration rate of two pine stands during drought based on constant minimum leaf water potential and plant hydraulic conductance. , 2008, Tree physiology.

[21]  D. Hodáňová.  An introduction to environmental biophysics , 1979, Biologia Plantarum.

[22]  A. Zangerl.  Energy exchange phenomena, physiological rates and leaf size variation , 2004, Oecologia.

[23]  R. Ceulemans,et al.  Stomatal conductance of forest species after long-term exposure to elevated CO2 concentration: a synthesis. , 2001, The New phytologist.

[24]  Michael R. Raupach,et al.  Equilibrium Evaporation and the Convective Boundary Layer , 2000, Boundary-Layer Meteorology.

[25]  Richard Harding,et al.  A canopy conductance and photosynthesis model for use in a GCM land surface scheme , 1998 .

[26]  J. Monteith,et al.  The behaviour of a mixed-layer model of the convective boundary layer coupled to a big leaf model of surface energy partitioning , 1998 .

[27]  J. Lhomme.  An examination of the Priestley‐Taylor equation using a convective boundary layer model , 1997 .

[28]  B. Itier,et al.  Operational limits to the Priestley-Taylor formula , 1996, Irrigation Science.

[29]  John L. Monteith,et al.  A reinterpretation of stomatal responses to humidity , 1995 .

[30]  C. Jacobs,et al.  Direct impact of atmospheric CO2 enrichment on regional transpiration , 1994 .

[31]  W. Chow.  Photoprotection and Photoinhibitory Damage , 1994 .

[32]  D. R. Upchurch,et al.  MAINTENANCE OF CONSTANT LEAF TEMPERATURE BY PLANTS--II. EXPERIMENTAL OBSERVATIONS IN COTTON , 1988 .

[33]  D. R. Upchurch,et al.  Maintenance of constant leaf temperature by plants—I. Hypothesis-limited homeothermy , 1988 .

[34]  K. McNaughton,et al.  A mixed-layer model for regional evaporation , 1986 .

[35]  U. KyawThaPaw.  A theoretical basis for the leaf equivalence point temperature , 1984 .

[36]  H. D. Bruin,et al.  A Model for the Priestley-Taylor Parameter , 1983 .

[37]  Ray D. Jackson,et al.  Foliage and air temperatures: Evidence for a dynamic “equivalence point”☆ , 1981 .

[38]  W. Smith.  Temperatures of Desert Plants: Another Perspective on the Adaptability of Leaf Size , 1978, Science.

[39]  Thomas J. Givnish,et al.  Sizes and Shapes of Liane Leaves , 1976, The American Naturalist.

[40]  S. E. Taylor,et al.  Optimal Leaf Form , 1975 .

[41]  C. Priestley,et al.  On the Assessment of Surface Heat Flux and Evaporation Using Large-Scale Parameters , 1972 .

[42]  E. Linacre.  Leaf temperature, diffusion resistances and transpiration , 1972 .

[43]  D. M. Gates.  Transpiration and Leaf Temperature , 1968 .

[44]  E. Linacre.  Further studies of the heat transfer from a leaf. , 1967, Plant physiology.

[45]  E. T. Linacre,et al.  A note on a feature of leaf and air temperatures , 1964 .

[46]  J. Monteith,et al.  Radiative temperature in the heat balance of natural surfaces , 1962 .

[47]  BY D. F. PARKHURSTt.  OPTIMAL LEAF SIZE IN RELATION TO ENVIRONMENT * , 2022 .