Across the American Southwest water development has played a critical role in managing rangelands.Earthen berms have been constructed throughout US rangelands to manage runoff and reduce erosion.The berms altered runo...Across the American Southwest water development has played a critical role in managing rangelands.Earthen berms have been constructed throughout US rangelands to manage runoff and reduce erosion.The berms altered runoff patterns to increase soil moisture with positive local vegetative response.However,altered runoff patterns can be considered a disturbance that affects broader scale vegetation patterns.We hypothesized that the hydrologic impacts of earthen berms in semiarid rangelands will be reflected in contrasting upslope and downslope vegetation patterns.A supervised classification of grass,shrubs,and bare soil was performed using orthographic imagery taken in June 2016 to quantify the effects of 181 earthen berms in the uplands and floodplain of the Altar Valley in Southern Arizona,US.Intact berms blocked runoff,creating downslope runoff"shadows"within which the precipitation is the dominant water input.We documented more bare soil downslope of intact berms in comparison with upslope.Grass and shrub cover affected by berms were related to soil texture.Grass and shrub cover were not different above and below intact berms on fine textured soils,but on sites with coarser textured soil,grass cover was lower downslope of berms.Where breaches occurred on coarser textured soils,the up and downslope differences in grass cover diminished.This study points to the role of conservation structures in adding additional complexity to already heterogeneous landscapes by creating patchwork assemblages of vegetation and bare soil proximal to earthen runoff and erosion control berms.展开更多
The U.S.Department of Agriculture’s Agricultural Research Service(USDAARS)maintains seven in situ soil moisture networks throughout the continental United States,some since 2002.These networks are crucial for underst...The U.S.Department of Agriculture’s Agricultural Research Service(USDAARS)maintains seven in situ soil moisture networks throughout the continental United States,some since 2002.These networks are crucial for understanding the spatial and temporal extent of droughts in their historical context,parameterization of hydrologic models,and local agricultural decision support.However,the estimates from these networks are dependent upon their ability to provide reliable soil moisture information at a large scale.It is also not known how many network stations are sufficient to monitor watershed scale dynamics.Therefore,the objectives of this research were to:(1)determine how temporally stable these networks are,including the relationships between various sensors on a year-to-year and seasonal basis,and(2)attempt to determine how many sensors are required,within a network,to approximate the full network average.Using data from seven in situ,it is concluded that approximately 12 soil moisture sensors are sufficient in most environments,presuming their locations are distributed to capture the hydrologic heterogeneity of the watershed.It is possible to install a temporary network containing a suitable number of sensors for an appropriate length of time,glean stable relationships between locations,and retain these insights moving forward with fewer sensor resources.展开更多
文摘Across the American Southwest water development has played a critical role in managing rangelands.Earthen berms have been constructed throughout US rangelands to manage runoff and reduce erosion.The berms altered runoff patterns to increase soil moisture with positive local vegetative response.However,altered runoff patterns can be considered a disturbance that affects broader scale vegetation patterns.We hypothesized that the hydrologic impacts of earthen berms in semiarid rangelands will be reflected in contrasting upslope and downslope vegetation patterns.A supervised classification of grass,shrubs,and bare soil was performed using orthographic imagery taken in June 2016 to quantify the effects of 181 earthen berms in the uplands and floodplain of the Altar Valley in Southern Arizona,US.Intact berms blocked runoff,creating downslope runoff"shadows"within which the precipitation is the dominant water input.We documented more bare soil downslope of intact berms in comparison with upslope.Grass and shrub cover affected by berms were related to soil texture.Grass and shrub cover were not different above and below intact berms on fine textured soils,but on sites with coarser textured soil,grass cover was lower downslope of berms.Where breaches occurred on coarser textured soils,the up and downslope differences in grass cover diminished.This study points to the role of conservation structures in adding additional complexity to already heterogeneous landscapes by creating patchwork assemblages of vegetation and bare soil proximal to earthen runoff and erosion control berms.
文摘The U.S.Department of Agriculture’s Agricultural Research Service(USDAARS)maintains seven in situ soil moisture networks throughout the continental United States,some since 2002.These networks are crucial for understanding the spatial and temporal extent of droughts in their historical context,parameterization of hydrologic models,and local agricultural decision support.However,the estimates from these networks are dependent upon their ability to provide reliable soil moisture information at a large scale.It is also not known how many network stations are sufficient to monitor watershed scale dynamics.Therefore,the objectives of this research were to:(1)determine how temporally stable these networks are,including the relationships between various sensors on a year-to-year and seasonal basis,and(2)attempt to determine how many sensors are required,within a network,to approximate the full network average.Using data from seven in situ,it is concluded that approximately 12 soil moisture sensors are sufficient in most environments,presuming their locations are distributed to capture the hydrologic heterogeneity of the watershed.It is possible to install a temporary network containing a suitable number of sensors for an appropriate length of time,glean stable relationships between locations,and retain these insights moving forward with fewer sensor resources.
