Browsing by Subject "soil moisture"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    Daily environmental conditions determine the competition–facilitation balance for plant water status
    (Wiley, 2015) Wright, Alexandra; Schnitzer, Stefan A; Reich, Peter B
    Plants compete with their neighbours for a finite set of limiting resources, and this decreases individual plant performance, growth and survival. However, neighbouring plants also affect each other in positive ways. Positive facilitative effects can occur when neighbouring plants ameliorate harsh abiotic conditions (temperature, wind and high irradiation). Thus, when environmental conditions are severe, the importance of facilitation may increase. The co-occurrence and masking effects of competition and facilitation among neighbouring plants have made it difficult to tease them apart in the past. We planted bur oak acorns (Quercus macrocarpa) into an experimental diversity gradient in a central MN grassland that provided a gradient in plant biomass. We predicted that greater biomass of neighbours would increase both competition and facilitation as measured by impacts on the minimum leaf water potential reached on any given day. Under moderate conditions, competition should predominate, but under hot/dry conditions, facilitation should become more important. We measured temperature, humidity and soil moisture in these plots for two growing seasons, as well as oak seedling leaf water potential across a range of daily conditions. On cool/humid days, plant interactions were dominated by competition for soil water: leaf water potentials of juvenile oaks were lower in plots with greater herbaceous biomass (and higher diversity). Conversely, on hot/dry days, facilitation of the microclimate determined the net effect of plants on their neighbours: leaf water potentials of juvenile oaks were higher in plots with higher herbaceous diversity and biomass. Synthesis. In terms of plant water status, plant interactions among neighbours can flip from net negative (competition) to net positive (facilitation) depending on daily abiotic conditions. The relative importance of both positive and negative interactions for plant water status may affect the overall performance of plants over time.
  • Thumbnail Image
    Item
    The Effect of Annual and Seasonal Variation in Precipitation on Temporal Water Storage Dynamics in Six Headwater Peatland Catchments: Marcell Experimental Forest, Minnesota
    (2023-06) Adams, David
    Using data collected from six headwater peatland catchments at the Marcell Experimental Forest in northern Minnesota, I assessed the relationship between variability in annual precipitation and annual changes in catchment water storage. Three hypotheses are addressed; (1) annual variability in precipitation is a primary driver of catchment storage change, (2) years of below average precipitation drive the relationship between precipitation and catchment water storage change, and (3) winter and fall precipitation variability are significant seasonal drivers of the annual catchment water storage change. The above relationships were analyzed via cross-correlation lag analysis and linear regression analysis of long-term precipitation, peatland water table elevation (WTE), and upland soil moisture (SM) time series, where WTE and SM served to quantify catchment water storage. Results indicate strong correlations between annual water storage change and annual precipitation variability, both in contemporaneous and antecedent years. Concurrent fall precipitation and antecedent winter precipitation were found to have the most influence on a given year’s water storage change. Years in which precipitation fell below the catchment average (dry years) exhibited a moderately significant linear relationship with annual catchment water storage change. Results of the above analysis were used to create a series of multivariate linear regression models, both with and without moving-average (MA) errors; these models were able to explain between approximately 50% and 70% of the variance found in the annual water storage change time series. Boreal peatlands play a vital role in the planet’s carbon cycle; developing a better understanding of the hydrologic function of these environments will likely prove important to future climate management practices.
  • Thumbnail Image
    Item
    Golf Course Superintendents’ Knowledge of Variability within Fairways
    (2018-11) Straw, Chase; Horgan, Brian
    Precision turfgrass management (PTM) relies heavily on mapping technologies (e.g. drones, GPS-equipped sensor devices) for identifying variability within turfgrass systems to implement variable rate or site-specific applications that can reduce management inputs. Despite recent advancements of mapping technologies in turfgrass, a number of factors have inhibited widespread adoption amongst managers; for example, cost and training associated with obtaining, analyzing, and interpreting spatial data. While focus continues towards improving mapping technologies, turfgrass managers’ knowledge of variability may be an overlooked and underutilized tool for PTM. Demonstrating the extent of knowledge that turfgrass managers encompass regarding variability, and how they can apply this knowledge to management practices, could offer a practical, low cost starting point for PTM implementation.
  • Thumbnail Image
    Item
    Modeling Direct Recharge of Surficial Aquifers
    (Water Resources Research Center, University of Minnesota, 1983-04) Knoch, Brian C.; Larson, Curtis L.; Slack, Donald C.
    A one-dimensional, physically-based computer model was developed for predicting direct groundwater recharge. The model was verified using three years of data from an instrumented site in east central Minnesota. Although the processes of infiltration and redistribution during frozen soil periods were not modeled, the model is capable of operating during both frozen and non-frozen soil periods. The model includes submodels for evapotranspiration, soil water extraction, snowmelt, surface depressional storage, infiltration and redistribution. The model predicts water table level and soil moisture. Water extraction may also be modeled. The model predicted both water table levels and soil moisture with reasonable accuracy over the the three year period modeled.
  • Thumbnail Image
    Item
    Precision Irrigation for Golf Courses Using Sensor and Mapping Technologies
    (2019-11) Straw, Chase; Friell, Joshua; Horgan, Brian
    The golf course industry is under increasing public pressure to improve environmental impacts by reducing management inputs, particularly irrigation. Precision irrigation is a viable strategy; however, in practice, adoption of soil moisture sensors (SMS) and mapping technologies necessary for implementation has been slow. The purpose of this research is to demonstrate that adoption of currently available SMS and mapping technologies can provide golf course superintendents with appropriate, actionable information that can result in significant water and cost savings relative to evapotranspiration (ET)-based and traditional irrigation scheduling methods.
  • Thumbnail Image
    Item
    Snow Cover and Winter Soil Temperatures at St. Paul, Minnesota
    (Water Resources Research Center, University of Minnesota, 1971-06) Baker, Donald
    The objectives of this study of winter soil temperatures under a sod cover were to show the configuration of the soil isotherm patterns, in particular that of OC, and to determine which soil thermal characteristics can be estimated by the snow cover. The temperature data were obtained at the University of Minnesota Agricultural Experiment Station plots on the St. Paul campus with copper-constantan thermocouples during the winter of 1961-62 through 1968-69. Based upon the depth and persistence of the snow cover there were in effect 3 kinds of winters: one with deep and persistent snow cover, one with very little snow cover and all other winters. There was a close relationship between the kinds of winters and the maximum depth to which the OC isotherm penetrated, and a fair relationship to the rate of movement of the OC isotherm into the soil. The combination of type of winter (snow depth and duration) with cumulative heating degree days proved to be a simple and effective means of predicting the maximum freezing depth.