Use of Ecosystem Flux Data and a Simulation Model to Examine Seasonal Drought Effects on a Subtropical Coniferous Forest

다국어 초록 (Multilingual Abstract)

The Qianyanzhou (QYZ) forest site is located in the mid-subtropical region under typical subtropical continentalmonsoon climate. Despite its plentiful water and heat resources, changes in their seasonal distributions result in frequent occurrences of seasonal drought, influencing both the structure and function of forest ecosystems. In order to examine the effects of drought stress on energy and water fluxes and the related physiological processes, we used tower flux measurements from 2003 and 2004 from the QYZ site and the ecosystemmodel EALCO (Ecological Assimilation of Land and Climate Observations). The model explained almost 90%of the variance in the daily LE for both years; whereas 71%and 55% of the variance in H for 2003 and 2004, respectively. Simulations suggested that, during the 2003 summer drought, about 80% of water extraction by roots occurred below 0.45 m, and canopy stomatal conductance decreased in response to soil dryness at a threshold r (relative water content) of 0.5 m. The response of canopy stomatal conductance appeared to be linked to the soil water exposed to themajority of the roots, even if substantialwater was being extracted fromgreater depth. The decrease of canopy stomatal conductance made the ratio of transpiration to ET relatively constant along the years with only a small difference. The different extent of the seasonal drought resulted in different water fluxes for the two years with more distinct influence on evaporation than on transpiration.

목차 (Table of Contents)

• Abstract
• 1. Introduction
• 2. Materials and Methods
• 3. Results and Discussion
• 4. Conclusion
• REFERENCES

참고문헌 (Reference)

1 Yu, G. R, "Water-use efficiency of forest ecosystems in eastern China and its relations to climatic variables" 177 : 927-937, 2008a

2 Alexandrov,V.A, "Vulnerability and adaptation assessments of agricultural crops under climate change in the Southeastern USA" 67 : 45-63, 2000

3 Williams,M., "Use of a simulationmodel and ecosystem flux data to examine carbon-water interactions in ponderosa pine" 21 : 287-298, 2001

4 Wen, X., F, "Turbulence flux measurement above the overstory of a subtropical Pinus plantation over the hilly region in southeastern China" 48 : 63-73, 2005

5 Jacob, C. M. J, "The sensitivity of regional transpiration to land-surface characteristics: significance of feedback" 5 : 683-698, 1992

6 Irvine, J, "The response of Pinus sylvestris to drought: stomatal control of transpiration and hydraulic conductance" 18 : 393-402, 1998

7 Wen, X., F, "Soil moisture effect on the temperature dependence of ecosystemrespiration in a subtropical Pinus plantation of southeastern China" 137 : 166-175, 2006

8 Wang, S, "Simulation of evapotranspiration and its response to plant water and CO2 transfer dynamics" 9 : 426-443, 2008

9 Wang, S, "Simulation of canopy radiation transfer and surface albedo in the EALCOmodel" 29 : 615-632, 2007

10 Reichstein,M, "Severe drought effects on ecosystemCO2 andH2Ofluxes at three Mediterranean evergreen sites: revision of current hypotheses?" 8 : 999-1017, 2002

11 José, S. J, "Seasonal patterns of carbon dioxide, water vapor and energy fluxes in pineapple" 147 : 16-34, 2007

12 Kljun, N, "Response of net ecosystem productivity of three boreal forest stands to drought" 9 : 1128-1144, 2006

13 Kalvova, J., "Projections of climate change for the Czech Republic" 36 : 1997

14 Foti, S., "Plant indicators of available soil water in the perennial herbaceous crop Miscanthus×giganteus Greef et Deu" 23 : 29-36, 2003

15 Larcher,W, "Physiological Plant Ecology" Springer 212-, 1995

16 Reichstein,M, "On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm" 11 : 1424-1439, 2005

17 Grant, R. F, "Net ecosystem productivity of boreal aspen forests under drought and climate change: Mathematical modeling with Ecosys" 140 : 152-170, 2006

18 Mi,N, "Modeling seasonal variation of CO2 flux in a subtropical coniferous forest using the EALCO model" 31 : 1119-1131, 2007

19 Wang, S., "Modeling plant carbon and nitrogen dynamics of a boreal aspen forest in CLASS the Canadian Land Surface Scheme" 142 : 135-155, 2001

20 Wang, S, "Modeling carbon-coupled energy and water dynamics of a boreal aspen forest in a General CirculationModel land surface scheme" 22 : 1249-1265, 2002a

21 Wang, S, "Modeling carbon dynamics of boreal forest ecosystems using the Canadian Land Surface Scheme" 55 : 451-477, 2002b

22 Baldocchi, D, "Measuring and modeling carbon dioxide and water vapor exchange over a temperate broad-leaved forest during the 1995 summer drought" 20 : 1108-1122, 1997

23 Falge, E, "Gap filling strategies for long termenergy flux data sets" 107 : 71-77, 2001

24 Kimmins, J. P, "Forest. Ecology: A Foundation for Sustainable Management" Prentice Hall Inc 596-, 1997

25 Aubinet,M, "Estimates of the annual net carbon and water exchange of European forests: the EUROFLUXmethodology" 30 : 113-174, 2000

26 Yu, G. R, "Environmental control over carbon exchange of three forest ecosystem in eastern China" 14 : 2555-2571, 2008b

27 Li, Z. -Q, "Energy balance closure atChinaFLUX sites" 48 : 51-62, 2005

28 Bernier, P, "Drought constraints on transpiration and canopy conductance inmature aspen and jack pine stands" 140 : 64-78, 2006

29 Reid, P. B, "Diurnal variation of crop hydraulic resistance: a newanalysis" 82 : 827-834, 1990

30 Webb, E. K, "Correction of fluxmeasurement for density effects due to heat and water vapor transfer" 106 : 85-100, 1980

31 Song, X, "Comparison Study on Carbon Dioxide ,Water and Heat Fluxes of the Forest Ecosystem in Red Earth Hilly Zone over Winter and Spring" 26 : 96-104, 2004

32 Houghton, J. T, "ClimateChange 2001: The Scientific Basis - Contribution of Working group I to the Third Assessment Report of the IPCC" Cambridge University Press 2001

33 Zhang, P.C, "China's forest policy for the 21st century" 288 : 2135-2136, 2000

34 Fang, J.-Y, "Changes in forest biomass carbon storage in China between 1949 and 1998" 292 : 2320-2322, 2001

35 Hollinger, D. Y, "Carbon dioxide exchange between an undisturbed old-growth temperate forest and the atmosphere" 75 : 134-150, 1994

36 Ball, J. T., "Amodel predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions" Martinus-Nijhoff, Dordrecht 221-224, 1987

37 Mi,N, "A preliminary study for spatial representativeness of flux observation at ChinaFLUX sites" 49 : 24-35, 2006

38 Farquhar, G.D, "A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species" 149 : 78-90, 1980