Free-air carbon dioxide(CO_(2))enrichment(FACE)experiments provide an opportunity to test models of heat and water flow under novel,controlled situations and eventually allow use of these models for hypothesis evaluat...Free-air carbon dioxide(CO_(2))enrichment(FACE)experiments provide an opportunity to test models of heat and water flow under novel,controlled situations and eventually allow use of these models for hypothesis evaluation.This study assesses whether the United States Department of Agriculture SHAW(Simultaneous Heat and Water)numerical model of vertical one-dimensional soil water flow across the soil-plant-atmosphere continuum is able to adequately represent and explain the effects of increasing atmospheric CO_(2) on soil moisture dynamics in temperate grasslands.Observations in a FACE experiment,the Bio CON(Biodiversity,CO_(2),and Nitrogen)experiment,in Minnesota,USA,were compared with results of vertical soil moisture distribution.Three scenarios represented by different plots were assessed:bare,vegetated with ambient CO_(2),and similarly vegetated with high CO_(2).From the simulations,the bare plot soil was generally the wettest,followed by a drier high-CO_(2) vegetated plot,and the ambient CO_(2) plot was the driest.The SHAW simulations adequately reproduced the expected behavior and showed that vegetation and atmospheric CO_(2) concentration significantly affected soil moisture dynamics.The differences in modeled soil moisture amongst the plots were largely due to transpiration,which was low with high CO_(2).However,the modeled soil moisture only modestly reproduced the observations.Thus,while SHAW is able to replicate and help broadly explain soil moisture dynamics in a FACE experiment,its application for point-and time-specific simulations of soil moisture needs further scrutiny.The typical design of a FACE experiment makes the experimental observations challenging to model with a one-dimensional distributed model.In addition,FACE instrumentation and monitoring will need improvement in order to be a useful platform for robust model testing.Only after this can we recommend that models such as SHAW are adequate for process interpretation of datasets from FACE experiments or for hypothesis testing.展开更多
基金supported by the National Science Foundation(NSF)Long-Term Ecological Research(LTER)grants(Nos.DEB-0620652,DEB-1234162,and DEB-1831944)Long-Term Research in Environmental Biology(LTREB)grants(Nos.DEB1242531 and DEB-1753859)+2 种基金Biological Integration Institutes grant(No.NSF-DBI-2021898)supported by the Geology Foundation at The University of Texas at Austinsupported by an Ivanhoe Foundation Fellowship。
文摘Free-air carbon dioxide(CO_(2))enrichment(FACE)experiments provide an opportunity to test models of heat and water flow under novel,controlled situations and eventually allow use of these models for hypothesis evaluation.This study assesses whether the United States Department of Agriculture SHAW(Simultaneous Heat and Water)numerical model of vertical one-dimensional soil water flow across the soil-plant-atmosphere continuum is able to adequately represent and explain the effects of increasing atmospheric CO_(2) on soil moisture dynamics in temperate grasslands.Observations in a FACE experiment,the Bio CON(Biodiversity,CO_(2),and Nitrogen)experiment,in Minnesota,USA,were compared with results of vertical soil moisture distribution.Three scenarios represented by different plots were assessed:bare,vegetated with ambient CO_(2),and similarly vegetated with high CO_(2).From the simulations,the bare plot soil was generally the wettest,followed by a drier high-CO_(2) vegetated plot,and the ambient CO_(2) plot was the driest.The SHAW simulations adequately reproduced the expected behavior and showed that vegetation and atmospheric CO_(2) concentration significantly affected soil moisture dynamics.The differences in modeled soil moisture amongst the plots were largely due to transpiration,which was low with high CO_(2).However,the modeled soil moisture only modestly reproduced the observations.Thus,while SHAW is able to replicate and help broadly explain soil moisture dynamics in a FACE experiment,its application for point-and time-specific simulations of soil moisture needs further scrutiny.The typical design of a FACE experiment makes the experimental observations challenging to model with a one-dimensional distributed model.In addition,FACE instrumentation and monitoring will need improvement in order to be a useful platform for robust model testing.Only after this can we recommend that models such as SHAW are adequate for process interpretation of datasets from FACE experiments or for hypothesis testing.
