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681. [Article] A comparison of modeling schemes for mapping daily evapotranspiration at high resolution using remote sensing
Evapotranspiration (ET) is an important component of the hydrologic cycle that transfers large quantities of water vapor away from Earth's surface into the atmosphere. In addition to having agricultural ...Citation Citation
- Title:
- A comparison of modeling schemes for mapping daily evapotranspiration at high resolution using remote sensing
- Author:
- Ring, Theresa
Evapotranspiration (ET) is an important component of the hydrologic cycle that transfers large quantities of water vapor away from Earth's surface into the atmosphere. In addition to having agricultural water management applications, including monitoring water rights compliance and irrigation scheduling, estimating ET is also important to quantify water used by other landscapes for soil-vegetation-atmosphere-transfer (SVAT) modeling schemes. This can only be done by estimating ET at large scales and this is most efficiently achieved by remote sensing. Daily ET was retrieved from two remote sensing modeling schemes: a) Reconstructed METRIC: Mapping EvapoTranspiration at high Resolution with Internalized Calibration (R-METRIC) that uses thermal band data from the Landsat 8 satellite; and b) Fusion: ALEXI/DisALEXI (Atmosphere-Land EXchange Inverse/Disaggregated ALEXI) and STARFM (Spatial and Temporal Adaptive Reflectance Fusion Model) that combines GOES (Geostationary Operational Environmental Satellite), MODIS (Moderate-resolution Imaging Spectroradiometer) and Landsat 8. High resolution, daily ET was mapped over two predominately wooded or forested, water stressed study locations at Tonzi Ranch in California and Metolius Forest in Oregon for the summer months of 2013. Both sites have established networks of eddy covariance instruments that acquire high temporal resolution moisture flux data. Instantaneous surface energy fluxes estimated by R-METRIC at the Tonzi study site showed reasonable agreement with in situ measurements over the flux tower footprint with relative errors (RE) less than 15% for all fluxes except latent heat (λET) which showed RE = 31%. Validation at the Vaira and Metolius towers showed similar results with the exception of significantly overestimating λET (RE = 297%) at Vaira and soil heat flux at Metolius (RE = 169%). DisALEXI showed good agreement for solar and net radiation (RE < 13%) at all sites. Significant overestimations of λET (RE up to 540%) and underestimations of sensible heat (RE up to 65%) were produced at each site. Additionally, soil heat flux at Metolius showed errors up to 167%. While daily ET at Tonzi modeled with R-METRIC agreed well with observed measurements, modeled values of daily ET were significantly overestimated at Vaira (RE = 395%). DisALEXI showed severe overestimations of daily ET at both Tonzi and Vaira (RE = 428 and 596%, respectively). It should be noted that the observed daily ET at these sites is very low compared to the sensible heat flux which leads to the unexpectedly high error. At Metolius, the two models produced comparable results though they both overestimated the observed daily ET. Because daily ET was overestimated, the seasonal cumulative ET was also overestimated at all sites by both models with the exception of R-METRIC over Tonzi. Surface and evaporative fluxes retrieved from the two models were also inter-compared over the different land cover types in the scenes. As both schemes were specifically developed for use over agricultural lands, they agree reasonably well with measurements when used over that land cover type. When applied over other land covers, specifically forests, grassland and shrubs, the daily ET showed greater discrepancies. The results of this study suggest that the current version of the Fusion scheme estimates much higher ET than actually occurs at all three tower locations at both instantaneous and daily scales. This likely results from the ALEXI processing step in which the air temperature for input into DisALEXI is found. Though relatively easy for the user to implement this model, until that step is debugged, it remains unclear how accurate it may be over non-agricultural environments. R-METRIC shows good agreement at the instantaneous scale but more discrepancy at the daily scale. Unlike the Fusion scheme, R-METRIC requires user discretion in order to calibrate it to the study site and is therefore subject to user bias. Though both models have proven their utility over agricultural fields, the water stressed conditions at both sites present a challenging yet important environment that needs improved accuracy in both models.
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Alnus rubra (Bong. ) seedlings were grown in sand culture and irrigated with nutrient solution containing CdCl₂ ranging from 5 μg to 100 mg per liter. Treatment of A. rubra seedlings for 4 weeks with 50 ...
Citation Citation
- Title:
- The effects of cadmium on the nitrogen fixation system in Alnus rubra
- Author:
- Wickliff, Carlos
Alnus rubra (Bong. ) seedlings were grown in sand culture and irrigated with nutrient solution containing CdCl₂ ranging from 5 μg to 100 mg per liter. Treatment of A. rubra seedlings for 4 weeks with 50 and 100 mg CdCl₂ per liter of nitrogen-free nutrient solution decreased in situ nitrogenase activity 93 and 99%, respectively, when compared to controls. Nitrogen fixation was decreased 32 and 65% at CdCl₂ concentrations of 50 and 100 mg per liter, respectively. Growth was decreased to about the same extent as nitrogen fixation. Cadmium concentrations in the organs of A. rubra increased with increasing CdCl₂ concentrations in the nutrient solution and increasing duration of treatment. Treatment of A. rubra seedlings for 11 weeks with CdCl₂ - concentrations ranging from 0.1 to 25 mg per liter of nitrogen-free nutrient solution decreased in situ nitrogenase activity 25 to 89% when compared to controls. These treatments resulted in nitrogen fixation decreases of 23 to 98% and the number of nodules per plant decreased 29 to 74%. Similar reductions were observed in plant growth. Treatment with lower cadmium concentrations (0.01 to 0.1 mg CdCl₂ per liter) decreased nitrogenase activity 6 to 31%. Nitrogen fixation was not significantly reduced in the 0.01 to 0.1 mg CdCl₂ per liter treatment range and treatments in this range resulted in an increased number of nodules formed. Cadmium concentrations in the plant organs decreased with increasing CdCl₂ concentration in the nutrient solution. Either the Mo-Fe or the Fe protein component of nitrogenase was pre-incubated with CdCl₂ and then combined with the other nonincubated component to reconstitute the enzyme. Pre-incubation of the Mo-Fe protein with 136 μM CdCl₂ decreased in vitro nitrogenase activity to a minimum of 45% of the control assay without cadmium. Incubation of the Fe protein with cadmium non-specifically increased activity up to 175% (at 27 μM CdCl₂), Activity then decreased to 70% of control at 136 μM CdCl₂. When the two proteins were combined and then pre-incubated with CdCl₂ the results were similar to those obtained by pre-incubating the Fe protein. A. rubra seedlings without nodules were inoculated at the start of the experiment. The growth period prior to apparent nodulation increased from 5 to 8 weeks as the CdCl₂ concentration increased from 10 to 100 μg per liter of nitrogen-free nutrient solution. Nitrogen fixation decreased 52 and 89%, when compared to control plants, at 10 and 20 μg CdCl₂ per liter, respectively. No detectable nitrogen fixation was observed at higher cadmium concentrations. Decreases in plant growth from CdCl₂ treatment were roughly parallel to de-creases in nitrogen fixation. When seedlings without nodules were given 12 mM NH₄NO₃ nitrate reductase activity in the roots decreased 22 to 25% as the CdCl₂ concentration increased from 10 to 100 μg per liter. Nitrogen gain and growth were not decreased from this range of CdCl₂ treatments. When the seedlings were given 6mM concentrations of either NH₄NO₃ or Ca(NO₃)₂ nitrate reductase activity decreased 22 and 24%, respectively, at 100 μg CdCl₂ per liter. Nitrogen gain and growth were decreased in plants supplied with Ca(NO₃)₂ and 50 and 100 μg CdCl₂ per liter. Cadmium concentrations in the plant organs increased as CdCl₂ in the nutrient solution increased. The ultrastructure of root and nodule cells was investigated by electron microscopy. Spaces lacking cristae were observed in mitochondria and endophyte resorption advanced as the cadmium concentration increased. The number of starch grains in root xylem parenchyma cells increased as the CdCl₂ concentration increased from 20 to 100 μg per liter. Nucleoli increased in prominence and mitochondrial cristae became less well defined over the same range of CdCl₂ concentrations. These results indicate that cadmium in nutrient media inhibits nitrogenase activity, and therefore nitrogen fixation in Alnus rubra. Growth, modulation, and nitrate reductase activity were inhibited by the element. Observations of root and nodule cell ultrastructure suggest that cadmium exerts a portion of its effect by influencing the structure of organelles.
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Streamflow forecasts are essential to the optimal operation of hydroelectric and irrigation reservoirs in the Pacific Northwest. Satellite snow cover observations would aid in these streamflow forecasts by ...
Citation Citation
- Title:
- An investigation into modeling snow cover elements at Crater Lake National Park and surrounding environs as an improved "ground truth" method for satellite snow observations
- Author:
- Hamilton, William L.
Streamflow forecasts are essential to the optimal operation of hydroelectric and irrigation reservoirs in the Pacific Northwest. Satellite snow cover observations would aid in these streamflow forecasts by providing snow cover data at regular time intervals. Unfortunately, satellite capability to remotely sense mountain snow cover conditions is indeterminate due to lack of "ground truth." This study focuses on the development of a mountain snow cover model capable of generating snow cover data at a scale useful as "ground truth" for operational satellite snow cover observations. The study area used to develop the snow cover model was Crater Lake National Park and its surrounding environs. Both the physiography (topography and vegetation) and snow climate of the study area were analyzed and found to be quite dynamic. In order to take into account the affects of the dynamic snow climate and physiography upon snow cover conditions, multiple regression analysis was used to create the Crater Lake Snow Model. Forty-five snow core sites were located within the study area. Snow depth and snow water equivalent values were recorded at each site. Eighteen sites located within Crater Lake National Park were sampled on a weekly basis for the 1977-1978 snow year. An additional 16 sites were sampled at high elevations in the Park on a weekly basis from April through June, 1978. The remaining 11 sites comprised the historical snow core data set collected by Soil Conservation Service (S.C.S.) on a monthly basis, January through June, 1948 through 1978. These data sets were statistically reduced using the quasi-constant ratio theory to synthesize values for missing data to temporally unify the data sets. Also the physiographic elements of slope, aspect, elevation, percentage of forest canopy cover, and regional aspect were recorded for each snow core site. The physiographic elements (independent variables) were regressed against the snow core data (dependent variables) to produce snow model equations. Three different Temporal-Spatial Situations (T.S.S. 1, 2, 3) of data were entered into regression analysis. T.S.S. 1 and 2 models were generated from the 11 S.C.S. snow core sites, T.S.S. 1 from 1978 data and T.S.S. 2 for 1948 -1978 data. The T.S.S. 3 model was generated from the 45 snow core site data for 1978. Using the theory of the quasiconstant ratio it was possible to combine the T.S.S. 1, 2, and 3 sets of regression equations to produce a T.S.S. 4 snow model ( a model based upon the 45 sites for the 1948-1978 snow seasons). Subsequently the T.S.S. 1 and 2 snow models were utilized with this derived T.S.S. 4 snow model to produce T.S.S. 3 snow cover models for any month of any year for the 1948 through 1978 period. Validity testing of the model indicates that it has an average error of ± 15.7" for modeled snow depth values and ± 8.2" for modeled snow water equivalent values. The Crater Lake Snow Model has a combined spatial, annual, and long term resolution unequaled in previous snow cover models. The Model's combined high resolving properties give it capabilities of generating mountain snow cover "ground truth." Current studies are being conducted to couple dynamic snow meteorology and LANDSAT digital data to the Model to increase its accuracy and reduce its dependency on snow core data. Also, output of the Model can be used for studies on snow cover affect upon wildlife movement and survival and the determination of source regions of relative runoff from snow melt.
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684. [Article] Interaction of ethofumesate with dry soil
Previous studies have shown loss of ethofumesate activity when the herbicide was applied to dry soil (2% w/w moisture content) in both field and greenhouse studies, even when rainfall or irrigation was ...Citation Citation
- Title:
- Interaction of ethofumesate with dry soil
- Author:
- McAuliffe, David
Previous studies have shown loss of ethofumesate activity when the herbicide was applied to dry soil (2% w/w moisture content) in both field and greenhouse studies, even when rainfall or irrigation was received within a few days. Laboratory studies were conducted to determine the mechanism for this activity loss. Dry soils (Woodburn silt loam, 2% moisture) were treated with 20 ppmw radiolabeled ethofumesate and were either wetted immediately to 35% moisture or remained dry for 4 days before wetting. After equilibration, the soil samples were centrifuged to extract the soil solution for analysis. Radiolabeled ethofumesate and degradation products in the soil solution were separated by thin-layer and column chromatography and assayed by liquid scintillation. Ethofumesate and metabolites also were extracted with methanol 4 days after herbicide application from both dry and wetted soils. After extraction, the soil samples were oxidized to determine the quantity of radioactivity remaining in the soil. Ethofumesate degradation, as affected by soil moisture, pH, temperature, and the length of time soils remained dry after herbicide application, was studied in a Woodburn soil. Several soil moisture levels were maintained between 0.7 and 6.7% (w/w) by placing soil samples in desiccators at various relative humidities. To ascertain the effect of pH, the soil reaction was adjusted to 3.9, 4.9, 7.0, 8.0, and 9.0 prior to drying and treatment. The influence of soil temperature on degradation was determined by incubating dry soil samples at temperatures from 20 to 50 C and constant relative humidity. The time period between ethofumesate application and soil wetting was varied between 0 and 8 days to study the rate of ethofumesate degradation. To determine the effect of soil type, the herbicide was applied to air-dried Woodburn, Dayton, Madras, and Agency soils. All soil samples were treated with 20 ppmw ethofumesate. Ethofumesate applied to soil that remained dry for 4 days degraded in significant quantities to two metabolites, while little ethofumesate degraded in soils wetted immediately. The major metabolite accounted for more than 80% of the degradation products and was identified by gas chromatography and mass spectroscopy to be an oxidation product, 2, 3- dihydro- 3,3- dimethyl- 2- oxo -5- benzofuranyl methanesulfonate. The second metabolite was not identified. The percentage of applied ethofumesate that was tightly adsorbed, not extracted with methanol, was at least 5% greater for applications to soils that remained dry than for soils that were wetted immediately.. Soil moisture levels substantially influenced metabolite formation. Increasing moisture contents to greater than 3% (w/w) reduced degradation to negligible levels. Rapid ethofumesate degradation occurred at soil moisture levels between 1 and 3%. Metabolites were detected 1 day after application to soils at 2% moisture content and as much as 18% of the ethofumesate was degraded in 4 days. Degradation was four to five times greater in soils of pH 4.9 or 7.0 than in more acid or more alkaline soils and ethofumesate metabolite formation increased 6-fold as soil temperature increased from 20 to 50 C. Of the soil characteristics correlated with ethofumesate degradation, percent clay and the level of soluble salts were best correlated with degradation (r = .89 and -.95, respectively). Ethofumesate adsorption studies were conducted in four soils comparing a batch equilibrium technique with a centrifuge extraction technique. Madras and Agency soils and two Woodburn soils were treated with 1 to 20 ppmw ethofumesate. The batch technique had a water-to-soil ratio of 5:1 while the ratio for the centrifuge technique was 0.35:1. The quantity of ethofumesate adsorbed with the centrifuge method was approximately twice that adsorbed with the batch method for a given amount of applied ethofumesate. For a given equilibrium concentration, the batch technique adsorbed more ethofumesate; i.e., the Freundlich K values were higher for the batch method. At least 24 hours were required for equilibrium to be established with the batch technique while the equilibrium concentration was established in a few hours with the centrifuge technique. Ethofumesate degrades rapidly in dry soils to two metabolites. The herbicide also is tightly adsorbed in greater amounts in dry soil than in wet soil. Ethofumesate degradation and increased adsorption results in the activity loss of ethofumesate on dry soil. Soil moisture content is critical in determining the extent of degradation. Moisture levels below 1% or above 3% reduce degradation substantially. Metabolite formation is optimal for soilt of moderately acid to neutral reaction (4.9 to 7.0) and the degradation rate also depends on temperature, increasing linearly as temperature increases. Metabolite formation is influenced by the chemical and physical properties of the soil; clay content and soluble salts are most highly correlated with degradation.
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Sulfur-coated urea (SCU), a slow release nitrogen fertilizer, may be economically competitive with conventional fertilizers, but little is known of the mechanism of urea release from SCU and the environmental ...
Citation Citation
- Title:
- Urea release from sulfur-coated urea and nitrogen utilization by tall fescue
- Author:
- Pettygrove, G. Stuart
Sulfur-coated urea (SCU), a slow release nitrogen fertilizer, may be economically competitive with conventional fertilizers, but little is known of the mechanism of urea release from SCU and the environmental factors which affect the urea release rate. Objectives of this thesis were: (1) to determine factors which affect the rate of nitrogen release from SCU; (2) to compare nitrogen utilization by tall fescue (Festuca arundinacea Schreb. ), fertilized with urea or SCU. The rate of urea release from SCU surface-applied to soil was determined during incubation for periods of up to five months under a range of temperatures (5 to 35 C) and soil water potentials (-5 to -30 bars). Three SCU fertilizers with different seven-day urea release percentages and sealants were studied: SCU 4 (wax sealant); SCU 25 (polyethylene-oil sealant, 30:70 w/w); and SCU 23 (no sealant). Ina four-year field experiment (1972-1976), the dry matter and nitrogen yields of irrigated tall fescue fall-fertilized with 200, 400, 600, or 800 kg N/ha/yr as urea, SCU 30, or SCU 4, were measured. Also, urea was applied in five equal increments in the fall and at the first four cuttings each year at annual rates of 980 kg N/ha (1972- 1973), 700 kg N/ha (1973-1974), and 800 kg N/ha (1974-1975). Cumulative nitrate leaching losses from tall fescue plots were estimated by analysis of soil solution samples. Urea release from sealed SCU was slowed by soil sterilization. The rate of urea release from SCU without sealant was unaffected by soil sterlization. After a lag period of 25 days, wax-sealed SCU applied to non-sterile soil at 25 C and -5 bars water potential released urea at a rate of 1.0%/day. In sterile soil, after an initial release of about 10%, no further release occurred. At -15 and -30 bars water potential in non-sterile soil, release took place at 0. 5% /day, with a lag period of up to 60 days. SCU sealed with polyethylene-oil released urea at a slightly faster rate at -30 bars that at -5 and -15 bars. Urea release from wax-sealed SCU was more sensitive to temperature than was urea release from the other SCU materials. Following an initial release of 10%, urea release rates from wax-sealed SCU at 35, 25, 15, and 5 C were 1. 5, 0. 71, 0, and 0%/day, respectively. The urea release pattern from multi-granule samples of SCU 4, 23, and 25 was shown to correspond to the coating thickness distribution. The coating thickness distribution can be rapidly determined and is a better indicator of the long-term urea release pattern than the conventional seven-day release test. In the field experiment, over a four-year period, tall fescue fall-fertilized with SCU produced about 20% more dry matter than fescue fall-fertilized with urea, e.g. , 61 mtons /ha versus 50mtons /ha at the 800-kg N /ha/yr rate. Fall application of SCU and split application of urea resulted in the same dry matter yield. Residual nitrogen resulted in higher yields by SCU-fertilized tall fescue during the second, third, and fourth years. Four -year nitrogen recoveries by tall fescue receiving fall applications of 800 kg N/ha/hr as urea, SCU 30, or SCU 4 were 43, 58, and 61% respectively. Over a two-year period nitrate-nitrogen leaching losses from plots fertilized with urea (400 kg N/ha/yr), SCU 4 (400 or 800 kg N/ha/yr) or urea in a split application (average of 800 kg N/ha/yr) were estimated at 65, 20, 19, and 126 kg N/ha, respectively. Nitrate-nitrogen leaching losses were < 10% of the total nitrogen applied.
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The following paper is an objective view on the viability of growing the truffle Tuber melanosporum in the Willamette Valley. Included in this study are the history of the truffle, biological cycle, habitat ...
Citation Citation
- Title:
- Black truffle economics : evaluating the costs and returns of establishing and producing Tuber melanosporum in the Willamette Valley, Oregon.
- Author:
- Alvis, Heather E.
The following paper is an objective view on the viability of growing the truffle Tuber melanosporum in the Willamette Valley. Included in this study are the history of the truffle, biological cycle, habitat description, method of cultivation and an enterprise budget for commercial production in the Willamette Valley. The truffle, a fungus that grows naturally underground, has long been a delicacy in European culture and it continues to appear in expensive restaurants around the world. The cultivation of T melanosporum was established first in Europe, but is gaining popularity in other parts of the world. Farms are appearing in Israel, Australia, The United States, New Zealand, and other nations. North Carolina and California also have operating truffle farms. Several species are currently cultivated in Europe, but the most prevalent and the only species cultivated outside of Europe is the Perigord (Black) truffle, Tuber melanosporum. Truffles are the fruiting bodies of various fungi. Spores produced within fruiting body germinate into tiny hair-like filaments (mycelia) that eventually attach themselves to the root tips of a host species and form mycorrhiza. After about six years, secondary mycelia emanating from the mycorrhizae grow together into a knot and form the fruiting body or carpophore. Host trees vary according to the location and species of truffle, however oak and hazelnut trees are most commonly used. Host trees that have been mycorrhized with truffles can be purchased from reputable growers for about $15 each. The climatic characteristics of the Willamette Valley are similar to those of major truffle growing regions in Europe. In addition, soils in the Willamette Valley may have an advantage because potentially competitive ectomycorrhizal fungi are adapted to acidic soils. T. melanosporum is grown in soils with high pH. Raising the soil pH for T. melanosporum could reduce the competition from native fungi adapted to acidic soils. Although few attempts have been made to cultivate truffles in Oregon, the Willamette Valley could be an ideal habitat for growing Tuber melanosporum. Establishment of a truffle farm takes 7 to 12 years depending on the species and the condition of the plot. Land must be free of plants that support ectomycorrhizal fungi, have evenly mixed sand, silt and clay (or well drained soils) and have an alkaline pH. An irrigation system should be installed in case of drought. After the trees are planted, maintenance of the truffle plot involves tilling the soil once a year, liming to maintain pH and pruning the host trees. Production typically begins after about six years and full production after about 10 years. Yields are difficult to estimate because truffle production is heavily influenced by weather conditions. In Europe, typical yields range from 50-150 kg per hectare (50-150 pounds per acre) in different plantations. The enterprise budget for a truffle farm in the Willamette Valley considers the costs and returns for a newly established farm. The budget is, by design, only a guide and does not consider individual differences among farmers. For example, it is expected that truffle cultivation will be an enterprise added to an existing farm, however the included budget includes costs of renting machinery for tilling. For a farmer that already owns his/her machinery, the budget must be altered accordingly. Truffles are expensive to produce. Profit and loss depend greatly on yield and price per pound. Also, commercial cultivation of truffles has not been achieved in Oregon and results are unpredictable. In good years, however some farms yield more than 100 kg per hectare (100 pounds per acre). Market prices fluctuate and may depend heavily on reputation as well as quality of truffles. In 2001, fresh truffles of the variety Tuber melanosporum were available on the Internet for about $225/kg ($500/pound). Other truffle species such as T. magnatum sell for about $765/kg ($1700/pound). The truffle industry is virtually unexplored in Oregon and there is potential to grow T. melanosporum in the Willamette Valley. This is a high risk crop due to the initial investment, a 10 year establishment period and fluctuations in yield and market values. Still, truffles are a low maintenance crop, can be sold worldwide and are highly acclaimed among gourmets. Also, truffle supply is limited, resulting in extreme high price. Socially and economically it appears that Tuber melanosporum could be a viable enterprise in the Willamette Valley.
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A major constraint to the production of self-rooted wine grapes (Vitis vinifera) in eastern Washington is plant-parasitic nematodes. Plant-parasitic nematodes can impact grape productivity by limiting ...
Citation Citation
- Title:
- Facilitating plant-parasitic nematode management decisions for Washington Vitis vinifera growers : determining the spatial distribution of plant-parasitic nematodes and the host status of Vitis spp. to Meloidogyne hapla
- Author:
- Howland, Amanda
A major constraint to the production of self-rooted wine grapes (Vitis vinifera) in eastern Washington is plant-parasitic nematodes. Plant-parasitic nematodes can impact grape productivity by limiting water and nutrient uptake, educing physiological changes, and extracting plant nutrients from roots, thereby reducing root biomass, plant vigor, and yield. The most commonly encountered plant-parasitic nematodes in Washington V. vinifera vineyards are Meloidogyne hapla, Mesocriconema xenoplax, Pratylenchus spp., Xiphinema americanum, and Paratylenchus sp.; however, little is known about their biology, distribution, and pathogenicity in this production system. Therefore, the objectives of this study were to 1) determine the spatial distribution of plant-parasitic nematodes in eastern Washington V. vinifera vineyards, and 2) determine the host status of V. vinifera varieties and clones predominantly grown in Washington, and several Vitis spp. rootstocks to M. hapla. For the first objective, two vineyards in eastern Washington were sampled over a two-year period to determine the horizontal and vertical distribution of plant-parasitic nematodes. To achieve the second objective, V. vinifera varieties and clones and Vitis spp. rootstocks were inoculated with M. hapla, grown in the greenhouse, and destructively harvested to determine nematode reproduction. Results from the spatial studies showed that, in general, populations of M. hapla and M. xenoplax were aggregated under irrigation emitters and that population densities of these nematodes decreased with soil depth. While Pratylenchus spp. population densities also decreased with depth, populations of these nematodes were concentrated along the alley ways between vine rows. Paratylenchus sp. and X. americanum were random in both their vertical and horizontal distributions within the vineyards. We also found that soil moisture plays a dominant role in the distribution of fine roots and plant-parasitic nematodes within semi-arid vineyards. Where soil moisture was the highest, fine root biomass and population densities of M. hapla and M. xenoplax were also the highest. The opposite was true for Pratylenchus spp., with higher population densities of this nematode in drier areas of the vineyard. There was no relationship of X. americanum and Paratylenchus sp. population densities with soil moisture. These results show there is potential to only treat a 60 cm area around the vine row when targeting M. hapla and M. xenoplax; however, this strategy would not be effective against X. americanum or Paratylenchus sp. It also appears that Pratylenchus spp. are not parasites of V. vinifera in this production system and that there may not be a need to consider these nematodes from a management perspective. In our host status trials with M. hapla, all of the V. vinifera varieties and clones were excellent hosts for M. hapla, but the magnitude of increase in population size of M. hapla on white (Chardonnay and Riesling) compared to red (Cabernet Sauvignon, Merlot, and Syrah) varieties was significantly greater. White varieties had higher M. hapla eggs/g root and an almost 40% higher reproduction factor value than red varieties. All the Vitis spp. rootstocks screened (Salt Creek, Freedom, Harmony, St. George, Riparia Gloire, 101-14, 3309C, 110R, and 420A) allowed very little or no M. hapla reproduction, and therefore are considered non-hosts. This research will provide Washington grape growers with the knowledge to select appropriate planting material to minimize the impact of M. hapla on grapevines. The results of both studies greatly expand the knowledge of the spatial distribution of plant-parasitic nematodes in semi-arid Washington V. vinifera vineyards as well as the host status of commonly planted V. vinifera varieties to M. hapla.
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California's Central Valley agricultural landscapes provide several important wintering regions for Pacific Flyway sandhill crane (Grus canadensis) populations; however, the value of those regions is being ...
Citation Citation
- Title:
- Comparative wintering ecology of two subspecies of sandhill crane : informing conservation planning in the Sacramento-San Joaquin River Delta region of California
- Author:
- Ivey, Gary L.
California's Central Valley agricultural landscapes provide several important wintering regions for Pacific Flyway sandhill crane (Grus canadensis) populations; however, the value of those regions is being compromised by urban expansion, other developments, and conversions to incompatible crop types. Greater (G. c. tabida) and lesser sandhill cranes (G. c. canadensis) both have special conservation status in California; the greater is listed as threatened and the lesser as a bird species of conservation concern by the state. However, basic information about their wintering ecology has been lacking to design biologically sound conservation strategies to maintain their wintering habitats. My study of sandhill cranes focused on one major Central Valley wintering region, the Sacramento-San Joaquin River Delta (Delta). I compared daily movements and winter site fidelity between the two sandhill crane subspecies, evaluated the timing of crane arrival and departure from the region, assessed foraging habitat choices, measured abundance and distribution in the Delta, documented the characteristics of roost sites, and developed habitat conservation models and decision tools for managers to facilitate habitat conservation and management. Both crane subspecies showed strong fidelity to my Delta study area. Foraging flights from roost sites were shorter for greaters than lesser (1.2 ± 0.4 km vs. 3.1 ± 0.1 km, respectively) and consequently, mean size of 95% fixed kernel winter home ranges was an order of magnitude smaller for greaters (1.9 ± 0.4 km² vs.21.9 ± 1.9 km², respectively). The strong site fidelity of greaters to roost complexes within landscapes in the Delta indicates that conservation planning targeted at maintaining and managing for adequate food resources around traditional roost sites can be effective for meeting sandhill crane habitat needs, while the scale of conservation differs by subspecies. I recommend that conservation planning actions consider all habitats within 5 km of a crane roost as a sandhill crane conservation "ecosystem unit." This radius encompasses 95% and 69% of the flights from roosts to foraging location (commuting flights) made by greaters and lessers, respectively. For lessers, a conservation radius of 10 km would encompass 90% of the commuting flights. Management, mitigation, acquisition, easement, planning, and farm subsidy programs intended to benefit cranes will be most effective when applied at these scales. Within these radii, conservation and management of wintering habitats should include creating both new roost and feeding areas to ensure high chances of successful use. Sandhill cranes used major crops and habitat types available in the landscapes surrounding their roost sites and focused most of their foraging in grain crops. They generally avoided dry corn stubble, selected dry rice stubble early in the season, and rarely used dry wild rice stubble. Tilled fields were also usually avoided but were occasionally used shortly after tillage. Mulched corn ranked high in comparison to other corn treatments while mulched rice use was used similarly to dry rice stubble. Both subspecies often highly favored cropland habitats when they were initially flooded. Cranes were attracted to new plantings of pasture and winter wheat. One important difference between the subspecies was that lessers used alfalfa which was generally avoided by greaters. Dry corn stubble was avoided while dry rice stubble was favored early in winter. If wildlife managers want to encourage winter field use by cranes they could provide incentives for favorable practices such as production of grain crops, reduction or delaying tillage and flooding of grain fields, provision of irrigations to some crop types, and increasing the practice of mulching of corn stubble. Of the 69 crane night roosts I identified, 35 were flooded cropland sites and 34 were wetland sites. I found that both larger individual roost sites and larger complexes of roost sites supported larger peak numbers of cranes. Water depth used by roosting cranes averaged 10 cm (range 3-21 cm, mode 7 cm) and was similar between subspecies. Roosting cranes avoided sites that were regularly hunted or had high densities (i.e., > 1 blind/5 ha) of hunting blinds. Roost site design and management should consider providing and maintaining large roost complexes (100 - 1000 ha) ideally in close proximity (< 5 km) to other roost sites, with large individual sites (> 5 ha) of mostly level topography, dominated by shallow water (5-10 cm depths). The fact that cranes readily use undisturbed flooded cropland sites makes this a viable option for creation of roost habitat. Because hunting disturbance can limit crane use of roost sites I suggest these two uses should not be considered compatible. However, if the management objective of an area includes waterfowl hunting, limiting hunting at low blind densities (i.e., < 1 blind/60 ha) and restricting hunting to early morning may be viable options for creating a crane-compatible waterfowl hunt program. Radio-marked sandhill cranes arrived in the Delta beginning 3 October, most arrived in mid-October, and the last radio-marked sandhill crane arrived on 10 December. Departure dates ranged from 15 January to 13 March. Mean arrival and departure dates were similar between subspecies. From mid-December through early-February in 2007-2008, the Delta population ranged from 20,000 to 27,000 sandhill cranes. Abundance varied at the main roost sites during winter, likely because sandhill cranes responded to changes in water and foraging habitat conditions. Sandhill cranes used an area of approximately 1,500 km² for foraging. Estimated peak abundance in the Delta was more than half the total number counted on recent Pacific Flyway midwinter surveys, indicating the Delta region is a key area for efforts in conservation and recovery of wintering sandhill cranes in California. Based on arrival dates, flooding of sandhill crane roost sites should be staggered with some sites flooded in early September and most sites flooded by early October. Maintaining flooding of at least some roost sites through mid-March would provide essential roosting habitat until most birds have departed the Delta region on spring migration. Not all 5-km radius ecosystem units are equal in their value to greater sandhill cranes, and the relative foraging value of a particular parcel within an ecosystem unit depends on the numbers of cranes using the focal roost site, the habitat choices they make, and the probability that they will fly to a particular parcel. Additionally, some ecosystem units overlap, and in these overlap zones, the probability of crane use is higher, because of additive effects. To provide a tool to allow managers to further refine management plans, I developed a model which allows more specific focus of crane conservation, mitigation and habitat management, using what my study revealed about greater sandhill cranes. This model considers the abundance of greaters at individual roost sites and the probability that they would fly to a given location. Sites closer to roosts had a higher probability of crane use. I calculated the probability that greaters would fly to a parcel within concentric 1-km intervals as a product of the proportion of commuting flights of individuals that reached that interval, and the proportion of all commuting flights that reached that interval. Within crane ecosystem units, it is important to protect the existing habitat from further loss and optimize foraging conditions for cranes. I provide a decision matrix to assist with plans to enhance existing crane landscapes, create new crane habitat areas or mitigate habitat losses. This matrix provides a framework for decision-making regarding enhancing sandhill crane foraging and roost site habitats. Wildlife managers could employ a variety of tools to conserve and manage crane habitats, including fee title acquisitions, private conservation easements, and specific cropland management actions to maintain crane-compatible conditions and high food values for cranes (possibly including providing unharvested food plots). My study has demonstrated that most cranes use a relatively small landscape surrounding their traditional roost sites and that they favor certain crops and post-harvest crop management practices for foraging. However, we need a better understanding of the actual carrying capacity for cranes in these crane management zones to ensure that managers can maintain these sites for cranes in the future.