B. D. Amiro, Comparison of turbulence statistics within three boreal forest canopies, Boundary-Layer Meteorology, vol.8, issue.1-2, pp.99-121, 1990.
DOI : 10.1007/BF00120463

J. M. Anderson, Responses of Soils to Climate Change, Adv. Ecol. Res, vol.22, pp.163-210, 1992.
DOI : 10.1016/S0065-2504(08)60136-1

O. K. Atkin, D. Bruhn, V. M. Hurry, and M. G. Tjoelker, : The hot and the cold: unravelling the variable response of plant respiration to temperature, Functional Plant Biology, vol.32, issue.2, pp.87-105, 2005.
DOI : 10.1071/FP03176

M. Aubinet, Estimates of the Annual Net Carbon and Water Exchange of Forests: The EUROFLUX Methodology, Advances in Ecological Research, vol.30, pp.113-175, 2000.
DOI : 10.1016/S0065-2504(08)60018-5

D. Baldocchi, FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem???Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities, Bulletin of the American Meteorological Society, vol.82, issue.11, pp.82-2415, 2001.
DOI : 10.1175/1520-0477(2001)082<2415:FANTTS>2.3.CO;2

D. D. Baldocchi, Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems: past, present and future, Global Change Biology, vol.104, issue.3, pp.479-492, 2003.
DOI : 10.1029/2000JD900080

D. D. Baldocchi, B. E. Law, and P. M. Anthoni, On measuring and modeling energy fluxes above the floor of a homogeneous and heterogeneous conifer forest, Agricultural and Forest Meteorology, vol.102, issue.2-3, pp.2-3, 2000.
DOI : 10.1016/S0168-1923(00)00098-8

D. D. Baldocchi and T. P. Meyers, Turbulence structure in a deciduous forest, Boundary-Layer Meteorology, vol.113, issue.4, pp.345-364, 1988.
DOI : 10.1007/BF00121712

D. D. Baldocchi and T. P. Meyers, Trace gas-exchange above the floor of a deciduous forest .1. Evaporation and CO 2 efflux, J. Geophys. Res. Atmos, issue.D4, pp.96-7271, 1991.

D. D. Baldocchi, S. B. Verma, D. R. Matt, and D. E. Anderson, Eddy-Correlation Measurements of Carbon Dioxide Efflux from the Floor of a Deciduous Forest, The Journal of Applied Ecology, vol.23, issue.3, pp.967-975, 1986.
DOI : 10.2307/2403948

D. D. Baldocchi and C. A. Vogel, Energy and CO2 flux densities above and below a temperate broad-leaved forest and a boreal pine forest, Tree Physiology, vol.16, issue.1-2, pp.5-16, 1996.
DOI : 10.1093/treephys/16.1-2.5

D. D. Baldocchi, C. A. Vogel, and B. Hall, Seasonal variation of carbon dioxide exchange rates above and below a boreal jack pine forest, Agricultural and Forest Meteorology, vol.83, issue.1-2, pp.147-170, 1997.
DOI : 10.1016/S0168-1923(96)02335-0

D. D. Baldocchi, C. A. Vogel, and B. Hall, Seasonal variation of energy and water vapor exchange rates above and below a boreal jack pine forest canopy, Journal of Geophysical Research: Atmospheres, vol.260, issue.D24, pp.28939-28951, 1997.
DOI : 10.1029/96JD03325

D. D. Baldocchi and K. B. Wilson, Modeling CO2 and water vapor exchange of a temperate broadleaved forest across hourly to decadal time scales, Ecological Modelling, vol.142, issue.1-2, pp.155-184, 2001.
DOI : 10.1016/S0304-3800(01)00287-3

D. D. Baldocchi, L. K. Xu, and N. Kiang, How plant functionaltype , weather, seasonal drought, and soil physical properties alter water and energy fluxes of an oak-grass savanna and an annual grassland, Agric. Forest Meteorol, vol.123, pp.1-2, 2004.

T. A. Black, Annual cycles of water vapour and carbon dioxide fluxes in and above a boreal aspen forest, Global Change Biology, vol.98, issue.3, pp.219-229, 1996.
DOI : 10.1256/smsqj.44706

P. D. Blanken and T. A. Black, The canopy conductance of a boreal aspen forest, Prince Albert National Park, Canada, Hydrological Processes, vol.18, issue.9, pp.1561-1578, 2004.
DOI : 10.1002/hyp.1406

P. D. Blanken, Turbulent flux measurements above and below the overstory of a boreal Aspen forest, Boundary-Layer Meteorology, vol.89, issue.1, pp.109-140, 1998.
DOI : 10.1023/A:1001557022310

P. D. Blanken, Energy balance and canopy conductance of a boreal aspen forest: Partitioning overstory and understory components, Journal of Geophysical Research: Atmospheres, vol.177, issue.D24, pp.28915-28927, 1997.
DOI : 10.1029/97JD00193

W. Borken, K. Savage, E. A. Davidson, and S. E. Trumbore, Effects of experimental drought on soil respiration and radiocarbon efflux from a temperate forest soil, Global Change Biology, vol.34, issue.2, pp.177-193, 2006.
DOI : 10.1016/0038-0717(91)90185-M

D. R. Bowling, N. G. Mcdowell, B. J. Bond, B. E. Law, and J. R. Ehleringer, 13 C content of ecosystem respiration is linked to precipitation and vapor pressure deficit, Oecologia, vol.131, issue.1, pp.113-124, 2002.
DOI : 10.1007/s00442-001-0851-y

G. Campbell, An Introduction to Environmental Biophysics, 1977.

J. L. Campbell, O. J. Sun, and B. E. Law, Supply-side controls on soil respiration among Oregon forests, Global Change Biology, vol.63, issue.11, pp.1857-1869, 2004.
DOI : 10.1126/science.1084269

R. M. Cionco, A Mathematical Model for Air Flow in a Vegetative Canopy, Journal of Applied Meteorology, vol.4, issue.4, pp.517-522, 1965.
DOI : 10.1175/1520-0450(1965)004<0517:AMMFAF>2.0.CO;2

R. M. Cionco, A wind-profile index for canopy flow, Boundary-Layer Meteorology, vol.11, issue.2, pp.255-263, 1972.
DOI : 10.1007/BF02033923

J. Constantin, A. Grelle, A. Ibrom, and K. Morgenstern, Flux partitioning between understory and overstory in a boreal spruce/ pine forest determined by the eddy-covariance method, Agric. Forest Meteorol, pp.98-107, 1999.

C. Yuste, J. Janssens, I. A. Carrara, A. Ceulemans, and R. , Annual Q10 of soil respiration reflects plant phenological patterns as well as temperature sensitivity, Global Change Biology, vol.23, issue.2, pp.161-169, 2004.
DOI : 10.1029/2000GB001365

C. Yuste, C. Nagy, M. Janssens, I. A. Carrara, A. Ceulemans et al., Soil respiration in a mixed temperate forest and its contribution to total ecosystem respiration, Tree Physiology, vol.25, issue.5, pp.609-619, 2005.
DOI : 10.1093/treephys/25.5.609

E. A. Davidson, E. Belk, and R. D. Boone, Soil water content and temperature as independent or confounded factors controlling soil respiration in a temperate mixed hardwood forest, Global Change Biology, vol.4, issue.2, pp.217-227, 1998.
DOI : 10.1046/j.1365-2486.1998.00128.x

E. A. Davidson and I. A. Janssens, Temperature sensitivity of soil carbon decomposition and feedbacks to climate change, Nature, vol.63, issue.7081, pp.165-173, 2006.
DOI : 10.1038/nature04514

O. T. Denmead and E. F. Bradley, Flux gradient relationship in a forest canopy The Forest Atmosphere Interaction, pp.421-442, 1985.

A. Ekblad and P. Hogberg, Natural abundance of 13 C in CO 2 respired from forest soils reveals speed of link between tree photosynthesis and root respiration, Oecologia, vol.127, issue.3, pp.305-308, 2001.
DOI : 10.1007/s004420100667

M. U. Falk, S. Wharton, and M. Schroeder, Is soil respiration a major contributor to the carbon budget within a Pacific Northwest old-growth forest?, Agricultural and Forest Meteorology, vol.135, issue.1-4, pp.1-4, 2005.
DOI : 10.1016/j.agrformet.2005.12.005

I. Y. Fung, S. C. Doney, K. Lindsay, and J. John, Evolution of carbon sinks in a changing climate, Proceedings of the National Academy of Sciences, vol.102, issue.32, pp.11201-11206, 2005.
DOI : 10.1073/pnas.0504949102

W. Gao, R. Shaw, U. Paw, and K. T. , Observation of organized structure in turbulent flow within and above a forest canopy, Boundary-Layer Meteorology, vol.16, issue.1-4, pp.349-377, 1989.
DOI : 10.1007/BF00122339

D. Gaumont-guay, Influence of temperature and drought on seasonal and interannual variations of soil, bole and ecosystem respiration in a boreal aspen stand, Agricultural and Forest Meteorology, vol.140, issue.1-4, pp.203-219, 2006.
DOI : 10.1016/j.agrformet.2006.08.002

C. P. Giardina, D. Binkley, M. G. Ryan, J. H. Fownes, and R. S. Senock, Belowground carbon cycling in a humid tropical forest decreases with fertilization, Oecologia, vol.139, issue.4, pp.545-550, 2004.
DOI : 10.1007/s00442-004-1552-0

C. P. Giardina and M. G. Ryan, Evidence that decomposition rates of organic carbon in mineral soil do not vary with temperature, Nature, vol.404, issue.6780, pp.858-861, 2000.
DOI : 10.1038/35009076

C. P. Giardina and M. G. Ryan, Total Belowground Carbon Allocation in a Fast-growing Eucalyptus Plantation Estimated Using a Carbon Balance Approach, Ecosystems, vol.5, issue.5, pp.487-499, 2002.
DOI : 10.1007/s10021-002-0130-8

H. B. Granberg, M. Ottossonlofvenius, and H. Odin, Radiative and aerodynamic effects of an open pine shelterwood on calm, clear nights, Agricultural and Forest Meteorology, vol.63, issue.3-4, pp.3-4, 1993.
DOI : 10.1016/0168-1923(93)90059-Q

A. Granier, The carbon balance of a young Beech forest, Functional Ecology, vol.260, issue.3, pp.312-325, 2000.
DOI : 10.1016/S0168-1923(96)02383-0

P. Hogberg, Large-scale forest girdling shows that current photosynthesis drives soil respiration, Nature, vol.411, issue.6839, pp.789-792, 2001.
DOI : 10.1038/35081058

D. M. Howard and P. J. Howard, Relationships between CO 2 evolution, moisture-content and temperature for a range of soil types, Soil Biol. Biochem, issue.11, pp.25-1537, 1993.

E. Inoue, On the turbulent structure of airflow within crop canopies, J. Agric. Meteorol. (Jpn.), vol.41, pp.317-326, 1963.

J. Irvine, Age-related changes in ecosystem structure and function and effects on water and carbon exchange in ponderosa pine, Tree Physiology, vol.24, issue.7, pp.753-763, 2004.
DOI : 10.1093/treephys/24.7.753

A. F. Jacobs, J. H. Vanboxel, and R. M. Elkilani, Nighttime free convection characteristics within a plant canopy, Boundary-Layer Meteorology, vol.2, issue.4, pp.375-391, 1994.
DOI : 10.1007/BF00712176

I. A. Janssens, A. S. Kowalski, and R. Ceulemans, Forest floor CO2 fluxes estimated by eddy covariance and chamber-based model, Agricultural and Forest Meteorology, vol.106, issue.1, pp.61-69, 2001.
DOI : 10.1016/S0168-1923(00)00177-5

I. A. Janssens, Productivity overshadows temperature in determining soil and ecosystem respiration across European forests, Global Change Biology, vol.16, issue.3, pp.269-278, 2001.
DOI : 10.1038/35009084

I. A. Janssens, A. S. Kowalski, B. Longdoz, and R. Ceulemans, Assessing forest soil CO2 efflux: an in situ comparison of four techniques, Tree Physiology, vol.20, issue.1, pp.23-32, 2000.
DOI : 10.1093/treephys/20.1.23

R. Joffre, G. I. Agren, D. Gillon, and E. Bosatta, Organic matter quality in ecological studies: theory meets experiment, Oikos, vol.93, issue.3, pp.451-458, 2001.
DOI : 10.1034/j.1600-0706.2001.930310.x

H. Jones, Plants and microclimate?a quantitative approach to environmental plant physiology, 1992.

F. M. Kelliher, Carbon dioxide efflux density from the floor of a central Siberian pine forest, Agricultural and Forest Meteorology, vol.94, issue.3-4, pp.3-4, 1999.
DOI : 10.1016/S0168-1923(99)00014-3

M. U. Kirschbaum, The temperature dependence of soil organic matter decomposition, and the effect of global warming on soil organic C storage, Soil Biology and Biochemistry, vol.27, issue.6, pp.753-760, 1995.
DOI : 10.1016/0038-0717(94)00242-S

H. Koizumi and Y. Oshima, Light environment and carbon gain of understory herbs associated with sunflecks in a warm temperate deciduous forest in Japan, Ecological Research, vol.43, issue.2, pp.135-142, 1993.
DOI : 10.1007/BF02348525

P. Kolari, Forest floor vegetation plays an important role in photosynthetic production of boreal forests, Forest Ecology and Management, vol.221, issue.1-3, pp.1-3, 2006.
DOI : 10.1016/j.foreco.2005.10.021

J. Kondo and S. Akashi, Numerical studies on the two-dimensional flow in horizontally homogeneous canopy layers, Boundary-Layer Meteorology, vol.46, issue.3, pp.255-272, 1976.
DOI : 10.1007/BF00919389

B. Kruijt, Turbulence statistics above and within two Amazon rain forest canopies, Boundary-Layer Meteorology, vol.94, issue.2, pp.297-331, 2000.
DOI : 10.1023/A:1002401829007

E. Lamaud, J. Ogee, Y. Brunet, and P. Berbigier, Validation of eddy flux measurements above the understorey of a pine forest, Agricultural and Forest Meteorology, vol.106, issue.3, pp.187-203, 2001.
DOI : 10.1016/S0168-1923(00)00215-X

S. Launiainen, Eddy-covariance measurements of CO 2 and sensible and latent heat fluxes during a full year in a boreal pine forest trunk-space, Boreal Environ. Res, vol.10, issue.6, pp.569-588, 2005.

M. B. Lavigne, Comparing nocturnal eddy covariance measurements to estimates of ecosystem respiration made by scaling chamber measurements at six coniferous boreal sites, Journal of Geophysical Research: Atmospheres, vol.260, issue.D24, pp.28977-28985, 1997.
DOI : 10.1029/97JD01173

B. E. Law, D. D. Baldocchi, and P. M. Anthoni, Below-canopy and soil CO 2 fluxes in a ponderosa pine forest, Agric. Forest Meteorol, vol.94, pp.3-4, 1999.

B. E. Law, Spatial and temporal variation in respiration in a young ponderosa pine forest during a summer drought, Agricultural and Forest Meteorology, vol.110, issue.1, pp.27-43, 2001.
DOI : 10.1016/S0168-1923(01)00279-9

B. E. Law, P. E. Thornton, J. Irvine, P. M. Anthoni, and S. Van-tuyl, Carbon storage and fluxes in ponderosa pine forests at different developmental stages, Global Change Biology, vol.21, issue.7, pp.755-777, 2001.
DOI : 10.1256/smsqj.44706

X. Lee, Air motion within and above forest vegetation in nonideal conditions, Forest Ecol. Manage, vol.135, pp.1-3, 2000.

X. Lee and T. A. Black, Comparison of flux measurements with open- and closed-path gas analyzers above an agricultural field and a forest floor, Boundary-Layer Meteorology, vol.106, issue.1-2, pp.195-202, 1993.
DOI : 10.1007/BF00705514

X. H. Lee, R. H. Shaw, and T. A. Black, Modeling the effect of mean pressure-gradient on the mean flow within forests, Agric. Forest Meteorol, vol.68, pp.3-4, 1994.

Y. H. Lee and L. Mahrt, Effect of stability on mixing in open canopies, Agricultural and Forest Meteorology, vol.135, issue.1-4, pp.1-4, 2005.
DOI : 10.1016/j.agrformet.2005.11.013

L. Mahrt, X. H. Lee, A. Black, H. Neumann, and R. M. Staebler, Nocturnal mixing in a forest subcanopy, Agricultural and Forest Meteorology, vol.101, issue.1, pp.67-78, 2000.
DOI : 10.1016/S0168-1923(99)00161-6

T. P. Meyers, U. Paw, and K. T. , Testing of a higher-order closure model for modeling airflow within and above plant canopies, Boundary-Layer Meteorology, vol.33, issue.3, pp.297-311, 1986.
DOI : 10.1007/BF00122991

E. M. Middleton, Seasonal variability in foliar characteristics and physiology for boreal forest species at the five Saskatchewan tower sites during the 1994 Boreal Ecosystem-Atmosphere Study, Journal of Geophysical Research: Atmospheres, vol.17, issue.5254, pp.28831-28844, 1997.
DOI : 10.1029/97JD02560

L. Misson, Influences of canopy photosynthesis and summer rain pulses on root dynamics and soil respiration in a young ponderosa pine forest, Tree Physiology, vol.26, issue.7, pp.833-844, 2006.
DOI : 10.1093/treephys/26.7.833

L. Misson, K. P. Tu, R. A. Boniello, and A. H. Goldstein, Seasonality of photosynthetic parameters in a multi-specific and vertically complex forest ecosystem in the Sierra Nevada of California, Tree Physiology, vol.26, issue.6, pp.729-741, 2006.
DOI : 10.1093/treephys/26.6.729

A. S. Moren and A. Lindroth, CO2 exchange at the floor of a boreal forest, Agricultural and Forest Meteorology, vol.101, issue.1, pp.1-14, 2000.
DOI : 10.1016/S0168-1923(99)00160-4

M. Nunez and D. Bowman, Nocturnal cooling in a high-altitude stand of eucalyptus-delegatensis as related to stand density, Aust. Forest Res, vol.16, issue.2, pp.185-197, 1986.

S. A. Oliver, H. R. Oliver, J. S. Wallace, and A. M. Roberts, Soil heat flux and temperature variation with vegetation, soil type and climate, Agricultural and Forest Meteorology, vol.39, issue.2-3, pp.2-3, 1987.
DOI : 10.1016/0168-1923(87)90042-6

W. A. Pfitsch and R. W. Pearcy, Daily carbon gain by Adenocaulon bicolor (Asteraceae), a redwood forest understory herb, in relation to its light environment, Oecologia, vol.43, issue.4, pp.465-470, 1989.
DOI : 10.1007/BF00380067

R. T. Pinker and J. Z. Holland, Turbulence structure of a tropical forest, Boundary-Layer Meteorology, vol.27, issue.1-2, pp.43-63, 1988.
DOI : 10.1007/BF00153968

R. D. Pyles, T. P. Kyaw, and M. Falk, Directional wind shear within an old-growth temperate rainforest: observations and model results, Agricultural and Forest Meteorology, vol.125, issue.1-2, pp.1-2, 2004.
DOI : 10.1016/j.agrformet.2004.03.007

M. R. Raupach and A. S. Thom, Turbulence in and above Plant Canopies, Annual Review of Fluid Mechanics, vol.13, issue.1, pp.97-129, 1981.
DOI : 10.1146/annurev.fl.13.010181.000525

M. R. Raupach, Canopy Transport Processes, Flow and Transport in the Natural Environment: Advances and Applications, pp.95-127, 1987.
DOI : 10.1007/978-3-642-73845-6_7

P. B. Reich, The Evolution of Plant Functional Variation: Traits, Spectra, and Strategies, International Journal of Plant Sciences, vol.164, issue.S3, pp.143-164, 2003.
DOI : 10.1086/374368

M. Reichstein, Modeling temporal and large-scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices, Global Biogeochemical Cycles, vol.15, issue.4, 2003.
DOI : 10.1029/2003GB002035

A. D. Rovira, Use of the Warburg Apparatus in Soil Metabolism Studies, Nature, vol.37, issue.4366, pp.29-30, 1953.
DOI : 10.1038/172029b0

J. Ross, Radiative transfer in plant communities, Vegetation and the Atmosphere, pp.13-55, 1975.

W. H. Schlesinger and J. A. Andrews, Soil respiration and the global carbon cycle, Biogeochemistry, vol.48, issue.1, pp.7-20, 2000.
DOI : 10.1023/A:1006247623877

R. L. Scott, The understory and overstory partitioning of energy and water fluxes in an open canopy, semiarid woodland, Agricultural and Forest Meteorology, vol.114, issue.3-4, pp.3-4, 2003.
DOI : 10.1016/S0168-1923(02)00197-1

J. H. Shinn, Spiral vertical variation of wind in forests, Bull. Am. Meteorol. Soc, vol.52, issue.4, pp.308-316, 1971.

W. J. Shuttleworth, Observations of radiation exchange above and below Amazonian forest, Quarterly Journal of the Royal Meteorological Society, vol.12, issue.466, pp.1163-1169, 1984.
DOI : 10.1002/qj.49711046623

F. Smith, D. Carson, and H. Oliver, Mean wind-direction shear through a forest canopy, Boundary-Layer Meteorology, vol.90, issue.2, pp.178-190, 1972.
DOI : 10.1007/BF02033917

R. M. Staebler and D. R. Fitzjarrald, Measuring Canopy Structure and the Kinematics of Subcanopy Flows in Two Forests, Journal of Applied Meteorology, vol.44, issue.8, pp.1161-1179, 2005.
DOI : 10.1175/JAM2265.1

J. A. Subke and J. D. Tenhunen, Direct measurements of CO2 flux below a spruce forest canopy, Agricultural and Forest Meteorology, vol.126, issue.1-2, pp.157-168, 2004.
DOI : 10.1016/j.agrformet.2004.06.007

J. W. Tang, D. D. Baldocchi, and L. Xu, Tree photosynthesis modulates soil respiration on a diurnal time scale, Global Change Biology, vol.23, issue.8, pp.1298-1304, 2005.
DOI : 10.1029/2004GB002281

A. S. Thom, Momentum, mass and hear exchange of plant communities, Vegetation and the Atmosphere, pp.57-109, 1975.

DOI : 10.1126/science.260.5112.1314

R. Valentini, Respiration as the main determinant of carbon balance in European forests, Nature, vol.404, issue.6780, pp.861-865, 2000.
DOI : 10.1038/35009084

J. M. Vose, N. H. Sullivan, B. D. Clinton, and P. V. Bolstad, Vertical leaf area distribution, light transmittance, and application of the Beer???Lambert Law in four mature hardwood stands in the southern Appalachians, Canadian Journal of Forest Research, vol.25, issue.6, pp.1036-1043, 1995.
DOI : 10.1139/x95-113

M. Wedler, R. Geyer, B. Heindl, S. Hahn, and J. D. Tenhunen, Leaf-level gas exchange and scaling-up of forest understory carbon fixation rates with a ?patch-scale? canopy model, Theoretical and Applied Climatology, vol.67, issue.1, pp.1-3, 1996.
DOI : 10.1007/BF00866419

K. B. Wilson, P. J. Hanson, and D. D. Baldocchi, Factors controlling evaporation and energy partitioning beneath a deciduous forest over an annual cycle, Agricultural and Forest Meteorology, vol.102, issue.2-3, pp.2-3, 2000.
DOI : 10.1016/S0168-1923(00)00124-6

K. B. Wilson and T. P. Meyers, The spatial variability of energy and carbon dioxide fluxes at the floor of a deciduous forest, Boundary-Layer Meteorology, vol.98, issue.3, pp.443-473, 2001.
DOI : 10.1023/A:1018779506973

M. Xu, T. A. Debiase, Y. Qi, A. Goldstein, and Z. G. Liu, Ecosystem respiration in a young ponderosa pine plantation in the Sierra Nevada Mountains, California, Tree Physiology, vol.21, issue.5, pp.309-318, 2001.
DOI : 10.1093/treephys/21.5.309

P. C. Yang, T. A. Black, H. H. Neumann, M. D. Novak, and P. D. Blanken, concentration and flux in a boreal aspen forest, Journal of Geophysical Research: Atmospheres, vol.260, issue.D22, pp.27653-27661, 1999.
DOI : 10.1029/1999JD900295

W. Zhang, Soil microbial responses to experimental warming and clipping in a tallgrass prairie, Global Change Biology, vol.61, issue.2, pp.266-277, 2005.
DOI : 10.1007/s003740050533

G. P. Zogg, Compositional and Functional Shifts in Microbial Communities Due to Soil Warming, Soil Science Society of America Journal, vol.61, issue.2, pp.475-481, 1997.
DOI : 10.2136/sssaj1997.03615995006100020015x