Browsing by Subject "Soil moisture"

Now showing 1 - 5 of 5
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    Data for the manuscript: The effect of spatial and temporal variability in plant functional traits on ecohydrological processes in a desert shrubland: a model-data fusion approach
    (2019-07-23) Liu, Shaoqing; Ng, Gene-Hua; sqliu@umn.edu; Liu, Shaoqing; University of Minnesota Hydrology/Hydrogeology Lab
    The data contains the meteorological observation (including radiation, rainfall, specific humidity, wind speed, air pressure) at Kelmet and Globe site in Kelso Valley, CA from 2005 to 2010 as well as the reconstructed climate forcing from 1961 to 2005. The meteorological data were used to drive the model CLM 4.5. In addition, the MODIS leaf area index observation and in-site soil moisture at the two sites are included here, which were used for model-data fusion to constrain CLM model related vegetation trait parameters. The data also contains the downscaled climate model dataset (MACAv2-METDATA) at the two sites for the RCP 8.5 scenario simulation.
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    Impact of management practices on Minnesota's specialty crop production: from biochar to tillage practices
    (2014-09) Nooker, Eric
    Climate fluctuations have always been a risk to our ability to provide adequate food for the increasing global population. To reduce crop production uncertainties in this variable climate, two management practices were examined: biochar application and conservation ridge tillage. Different biochars, application rates, and soil types were evaluated for their effect on seedling emergence and plant growth of specialty crops. Increases and decreases were observed in seed emergence and plant growth rates from biochar amended soil in a greenhouse study. A slow pyrolysis corn cob biochar (5% w/w) improved seed emergence performance the greatest across five specialty crops in the 4 soil types, with increases in emergence ranging from 2 to 67%. Biochar weathering from previous trials also influenced plant growth responses, and eliminated initial negative growth effects. Yield from field plot studies were not significantly different between biochar and control treatments. No universal relationship between biochar and its impact on specialty crop growth were observed across different soil types. However, there was good correlation between the suppression in plant growth with lower availability of nitrate and higher amounts of sorbed organic compounds on the biochar. Biochar additions had the greatest positive plant impacts on sandy textured soils with low initial soil fertility, which increased growth and soil moisture retention.Secondly, the impacts of ridge and conventional tillage on the yield and quality of three sweet corn varieties, Overland, Protégé, and Ambrosia were investigated. Protégé had greater marketable yields when grown under ridge tillage compared to conventional tillage. During 2012, there were no significant differences noted between ridge and conventional tillage treatments. However, in 2013, ridge till increased cut corn yield and ear marketability compared to the conventional tilled plots, suggesting additional benefits that were not adequately captured in this 2 year study. This study suggests that increasing the soil moisture holding capacity (with biochar or other amendments) as well as utilizing ridge tillage offers a potential tool for agricultural production to buffer future climate uncertainties.
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    Impacts of agricultural management and landscape factors on soil carbon and nitrogen
    (2011-12) Van Vleck, Harriet E.
    Agricultural management has altered soil carbon (C) and nitrogen (N) inputs, losses, and turnover rates. Understanding how management interacts with landscape factors to regulate soil C and N losses is essential to addressing climate change. Through research conducted in agricultural systems in Minnesota I investigated: (1) how the loss of corn root-derived C as carbon dioxide (CO2), and N as nitrous oxide (N2O) differed among five management systems, and (2) how hillslope position and soil moisture affected the size and turnover of soil C pools. In a field study using stable isotope techniques, I found that the fraction of root-derived C and N emitted as CO2 and N2O, the C and N emission factors, were 35% and less than 1% respectively. Individually, each emission factor was lower in systems with increased rotation diversity. Conversely, the relationship between C and N emission factors differed with tillage and fertilization intensity, not with rotation diversity. The magnitude of root-derived C and N emission factors has agricultural policy implications. Currently an emission factor of 1% is used for all N inputs to agricultural systems. My research suggests that a lower emission factor would better reflect N2O emissions from belowground N sources.In a laboratory study, both position and soil moisture significantly impacted the size and mean residence time of soil C pools along a low slope hillslope. Intact core sections of the upper four horizons from three hillslope positions were incubated at 50, 75, 90 and 100% water-filled pore space (WFPS) for 355 days. Total soil C (TC), N, and the resistant fraction of TC (64%) increased downslope. Under saturated conditions, 100% WFPS treatment, the size and mean residence time of the labile C fraction (<1% of TC) increased. Increased moisture, between 50% and 90% WFPS, also lengthened the mean residence time of slow C. In this low slope landscape I found effects of both position and moisture on C pool dynamics; soil moisture had the most significant impacts on labile C pool size and the slow C pool mean residence time.
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    Investigation of soil and plant characteristics across a continuum of non-native earthworm invasion in hardwood forests, Tettegouche State Park, MN USA
    (2013-06) Bennett, Zachary David
    Invasive earthworms cause profound changes in forest floor thickness, soil structure and chemistry, and plant community composition within cold temperate hardwood forests. However, few studies have examined these effects across a continuum of earthworm invasion and in conjunction with canopy disturbance. The research objectives of this thesis were to determine the changes of earthworm invasion on the upper soil horizon's thickness, gravimetric water content, potential horizon field capacity, and available nitrogen and phosphorus; and plant communities in hardwood forest sites within Tettegouche State Park, MN USA. All sites were uneven-aged, unmanaged northern hardwood forests of an approximate age of 225 years. The canopies were dominated by sugar maple and had experienced substantial canopy disturbance (9.7 - 20.5% opening) during an ice storm in spring 2009. Earthworms were sampled in the fall of 2010-2011. Each of the four sites were invaded by differing earthworm assemblages ranging from minimally invaded (1 species and average biomass of 0.1729 AFDgrams/m2) to heavily invaded (5 species and average biomass of 14.12 AFDgrams/m2). In the upper soil horizons O horizon thickness decreased and A horizon thickness increased with increasing earthworm richness and biomass. Mineral soil gravimetric water content was measured biweekly (May-August 2011) but did not differ among sites. Total potential horizon field capacity, including the O horizon, determined that 53-59% of the available water in a 12 cm deep core at field capacity is held in the O horizon. Availability of NO3 was significantly higher in the heavily invaded site compared to all other sites. Plant communities were assessed in the summer of 2009-2011, nonmetric multidimensional scaling was used to analyze the relationship of herbaceous plant species richness and percent cover to environmental variables and that species richness and diversity indices were positively correlated with O horizon thickness and negatively correlated with earthworm richness and biomass. The main conclusions of this study are that 1) moderate canopy disturbance had no affect on soil characteristics, or earthworms and plant communities; 2) earthworm assemblages (richness and biomass) were strongly correlated with changes in forest floor thickness, moisture holding capacity, nitrogen availability and plant community composition in these sugar maple forests, and 3) traditional exclusion of the O horizon when measuring water holding capacity in forest soils should be reconsidered given the large proportion of potential water holding capacity it provides, and is lost when a site is heavily invaded by earthworms. The implications of the loss of the O horizon and the associated loss of water holding capacity on ecosystem functions and biotic communities of hardwood forest systems need to be more fully explored.
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    Soil moisture and soil frost regimes under annual, perennial and agroforestry Crops in Waseca, Minnesota.
    (2010-03) Byrne, Marin Johanna.
    The potential for agroforestry and other perennial crops to provide hydrologic benefits is of interest in the Minnesota River Basin, where the landscape is dominated by annual row crops and the river is plagued by water quality and quantity issues. Perennial herbaceous and woody crops are thought to have higher annual consumptive use of water than annual corn-soybean crops, influencing antecedent water status, creating more water storage, potentially decreasing discharge, and reducing the duration of soil frost and prevalence of concrete soil frost in the early spring. Quantification of potential hydrologic benefits is needed to provide support for more sustainable agroforestry and other alternative cropping practices in the basin. To this end, in the summers of 2004 and 2005, biweekly measurements of soil moisture under one annual crop (corn/soybean rotation), two perennial herbaceous crops (perennial flax and Illinois bundleflower) and two woody crops (hybrid hazelnuts and hybrid willow) were taken on replicated experimental plots at the University of Minnesota’s Southern Research and Outreach Center in Waseca, Minnesota. Similar measurements were taken in a stand of mature hybrid poplar and a field planted in a corn/soybean rotation. Likewise, soil frost depth, duration, and type were measured under the same crop types during the intervening winter. Analysis of soil moisture data showed few significant differences in soil moisture between the various crop types on the experimental plots, perhaps due to a combination of the perennial and agroforestry crops being in the establishment phase and unusually wet weather. The mature poplar stand had consistently drier soils than the cornfield during the 2004 season, although these differences disappeared during the course of the 2005 season, likely due to a change in management of understory plant cover in the poplar stand. During the winter, no significant differences in soil frost duration or type were observed, likely due to uniformly wet fall soil conditions, a lack of snow during the coldest part of the winter and rapid spring warm up. Thus, agroforestry and herbaceous perennial crops appear to provide little hydrologic benefit during the establishment phase or in winters with low snowfall, but when mature or in winters with heavier snowfall, could have the potential to provide such benefits.