Partitioning evapotranspiration fluxes from a Colorado grassland using stable isotopes:: Seasonal variations and ecosystem implications of elevated atmospheric CO2

被引:112
作者
Ferretti, DF
Pendall, E [1 ]
Morgan, JA
Nelson, JA
LeCain, D
Mosier, AR
机构
[1] Univ Wyoming, Dept Bot, Laramie, WY 82071 USA
[2] Univ Colorado, Inst Arctic & Alpine Res, Boulder, CO 80309 USA
[3] ARS, USDA, Ft Collins, CO 80526 USA
[4] ARS, USDA, Ft Collins, CO 80522 USA
关键词
Bouteloua gracilis; elevated CO2; O-18/O-16; plant transpiration; soil evaporation; Stipa comata;
D O I
10.1023/A:1025511618571
中图分类号
S3 [农学(农艺学)];
学科分类号
0901 ;
摘要
The stable isotopic composition of soil water is controlled by precipitation inputs, antecedent conditions, and evaporative losses. Because transpiration does not fractionate soil water isotopes, the relative proportions of evaporation and transpiration can be estimated using a simple isotopic mass balance approach. At our site in the shortgrass steppe in semi-arid northeastern Colorado, delta(18)O values of soil water were almost always more enriched than those of precipitation inputs, owing to evaporative losses. The proportion of water lost by evaporation (E/ET) during the growing season ranged from nil to about 40% ( to > 90% in the dormant season), and was related to the timing of precipitation inputs. The sum of transpiration plus evaporation losses estimated by isotopic mass balance were similar to actual evapotranspiration measured from a nearby Bowen ratio system. We also investigated the evapotranspiration response of this mixed C-3/C-4 grassland to doubled atmospheric [CO2] using Open-Top Chambers (OTC). Elevated atmospheric [CO2] led to increased soil-water conservation via reduced stomatal conductance, despite greater biomass growth. We used a non-invasive method to measure the delta(18)O of soil CO2 as a proxy for soil water, after establishing a strong relationship between delta(18)O of soil CO2 from non-chambered control (NC) plots and delta(18)O of soil - water from an adjacent area of native grassland. Soil -CO2 delta(18)O values showed significant treatment effects, particularly during a dry summer: values in ambient chambers (AC) were more enriched than in NC and elevated chamber (EC) plots. During the dry growing season of 2000, transpiration from the EC treatment was higher than from AC and lower than from NC treatments, but during 2001, transpiration was similar on all three treatments. Slightly higher evaporation rates from AC than either EC or NC treatments in 2000 may have resulted from increased convection across the soil surface from the OTC blowers, combined with lower biomass and litter cover on the AC treatment. Transpiration-use efficiency, or the amount of above-ground biomass produced per mm water transpired, was always greatest on EC and lowest on NC treatments.
引用
收藏
页码:291 / 303
页数:13
相关论文
共 49 条
[1]  
ALLISON GB, 1985, CHEM GEOL, V58, P145, DOI 10.1016/0168-9622(85)90035-1
[2]   ESTIMATION OF EVAPORATION FROM NON-VEGETATED SURFACES USING NATURAL DEUTERIUM [J].
ALLISON, GB ;
BARNES, CJ .
NATURE, 1983, 301 (5896) :143-145
[3]  
[Anonymous], 1967, ISOTOPES HYDROLOGY
[4]  
[Anonymous], J CHEM PHYS
[5]   ISOTOPE COMPOSITION (O-18, H-2) OF TRANSPIRED WATER-VAPOR - CONTROLLED EXPERIMENT [J].
BARIAC, T ;
DELEENS, E ;
GERBAUD, A ;
ANDRE, M ;
MARIOTTI, A .
GEOCHIMICA ET COSMOCHIMICA ACTA, 1991, 55 (11) :3391-3402
[6]   STABLE ISOTOPE COMPOSITION OF WATER-VAPOR AS AN INDICATOR OF TRANSPIRATION FLUXES FROM RICE CROPS [J].
BRUNEL, JP ;
SIMPSON, HJ ;
HERCZEG, AL ;
WHITEHEAD, R ;
WALKER, GR .
WATER RESOURCES RESEARCH, 1992, 28 (05) :1407-1416
[7]   Direct and acclimatory responses of stomatal conductance to elevated carbon dioxide in four herbaceous crop species in the field [J].
Bunce, JA .
GLOBAL CHANGE BIOLOGY, 2001, 7 (03) :323-331
[8]   A three-dimensional synthesis study of delta O-18 in atmospheric CO2 .2. Simulations with the TM2 transport model [J].
Ciais, P ;
Tans, PP ;
Denning, AS ;
Francey, RJ ;
Trolier, M ;
Meijer, HAJ ;
White, JWC ;
Berry, JA ;
Randall, DA ;
Collatz, GJ ;
Sellers, PJ ;
Monfray, P ;
Heimann, M .
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1997, 102 (D5) :5873-5883
[9]   A three-dimensional synthesis study of delta O-18 in atmospheric CO2 .1. Surface fluxes [J].
Ciais, P ;
Denning, AS ;
Tans, PP ;
Berry, JA ;
Randall, DA ;
Collatz, GJ ;
Sellers, PJ ;
White, JWC ;
Trolier, M ;
Meijer, HAJ ;
Francey, RJ ;
Monfray, P ;
Heimann, M .
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1997, 102 (D5) :5857-5872
[10]   REPORTING OF STABLE HYDROGEN, CARBON, AND OXYGEN ISOTOPIC ABUNDANCES [J].
COPLEN, TB .
PURE AND APPLIED CHEMISTRY, 1994, 66 (02) :273-276