Soil moisture and its spatial pattern are important for understanding various hydrological,pedological,ecological and agricultural processes.In this study,data of rainfall and soil moisture contents at different depth...Soil moisture and its spatial pattern are important for understanding various hydrological,pedological,ecological and agricultural processes.In this study,data of rainfall and soil moisture contents at different depths(10 cm,20 cm,40 cm and 60 cm) in forestland and vegetable plot in the Taihu Lake Basin,China were monitored and analyzed for characteristics of soil moisture variation and its response to several typical rainfall events.The following results were observed.First,great temporal variation of soil moisture was observed in the surface layer than in deeper layer in vegetable plot.In contrast,in forestland,soil moisture had similar variation pattern at different depths.Second,initial soil moisture was an important factor influencing the vertical movement of soil water during rainfall events.In vegetable plot,simultaneous response of soil moisture to rainfall was observed at 10-and 20-cm depths due to fast infiltration when initial soil was relatively dry.However,traditional downward response order occurred when initial soil was relatively wet.Third,critical soil horizon interface was an active zone of soil water accumulation and lateral movement.A less permeable W-B soil horizon interface(40-cm depth) in vegetable plot can create perched water table above it and elevate the soil water content at the corresponding depth.Fourth,the land cover was an effective control factor of soil moisture during small and moderate rainfall events.In the forestland,moderate and small rainfall events had tiny influences on soil moisture due to canopy and surface O horizon interception.Fifth,preferential flow and lateral subsurface interflow were important paths of soil water movement.During large and long duration rainfall events,lateral subsurface flow and preferential flow through surface crack or soil pipe occurred,which recharged the deep soil.However,in more concentrated large storm,surface crack or soil pipe connected by soil macropores was the main contributor to the occurrence of preferential flow.Findings of this study provide a theoretical foundation for sustainable water and fertilizer management and land use planning in the Taihu Lake Basin.展开更多
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Under the auspices of National Natural Science Foundation of China(No.41271109,41030745)Key '135' Project of Chinese Academy of Sciences(No.NIGLAS2012135005)China Postdoctoral Science Foundation(No.2013M540470)
文摘Soil moisture and its spatial pattern are important for understanding various hydrological,pedological,ecological and agricultural processes.In this study,data of rainfall and soil moisture contents at different depths(10 cm,20 cm,40 cm and 60 cm) in forestland and vegetable plot in the Taihu Lake Basin,China were monitored and analyzed for characteristics of soil moisture variation and its response to several typical rainfall events.The following results were observed.First,great temporal variation of soil moisture was observed in the surface layer than in deeper layer in vegetable plot.In contrast,in forestland,soil moisture had similar variation pattern at different depths.Second,initial soil moisture was an important factor influencing the vertical movement of soil water during rainfall events.In vegetable plot,simultaneous response of soil moisture to rainfall was observed at 10-and 20-cm depths due to fast infiltration when initial soil was relatively dry.However,traditional downward response order occurred when initial soil was relatively wet.Third,critical soil horizon interface was an active zone of soil water accumulation and lateral movement.A less permeable W-B soil horizon interface(40-cm depth) in vegetable plot can create perched water table above it and elevate the soil water content at the corresponding depth.Fourth,the land cover was an effective control factor of soil moisture during small and moderate rainfall events.In the forestland,moderate and small rainfall events had tiny influences on soil moisture due to canopy and surface O horizon interception.Fifth,preferential flow and lateral subsurface interflow were important paths of soil water movement.During large and long duration rainfall events,lateral subsurface flow and preferential flow through surface crack or soil pipe occurred,which recharged the deep soil.However,in more concentrated large storm,surface crack or soil pipe connected by soil macropores was the main contributor to the occurrence of preferential flow.Findings of this study provide a theoretical foundation for sustainable water and fertilizer management and land use planning in the Taihu Lake Basin.
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.
