期刊
WATER RESOURCES RESEARCH
卷 55, 期 3, 页码 1833-1848出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2018WR023468
关键词
plant hydraulics; transpiration; tree mortality; climate change; subsurface water subsidy; xylem
资金
- National Science Foundation [IOS-1450650, IOS-1450679, EAR 1331408]
- Global Change and Sustainability Center at the University of Utah [NSF CNH 1714972]
- USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Programme, Ecosystem Services and Agro-ecosystem Management [2018-67019-27850]
The reliance of 10 Utah (USA) aspen forests on direct infiltration of growing season rain versus an additional subsurface water subsidy was determined from a trait- and process-based model of stomatal control. The model simulated the relationship between water supply to the root zone versus canopy transpiration and assimilation over a growing season. Canopy flux thresholds were identified that distinguished nonstressed, stressed, and dying stands. We found growing season rain and local soil moisture were insufficient for the survival of 5 of 10 stands. Six stands required a substantial subsidy (31-80% of potential seasonal transpiration) to avoid water stress and maximize photosynthetic potential. Subsidy dependence increased with stand hydraulic conductance. Four of the six subsidized stands were predicted to be stressed during the survey year owing to a subsidy shortfall. Since winter snowpack is closely related to groundwater recharge in the region, we compared winter precipitation with tree-ring chronologies. Consistent with model predictions, chronologies were more sensitive to snowpack in subsidized stands than in nonsubsidized ones. The results imply that aspen stand health in the region is more coupled to winter snowpack than to growing season water supply. Winters are predicted to have less precipitation as snow, indicating a stressful future for the region's aspen forests.
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