Percent Soil Moisture Research Articles

Microhabitat Segregation of Two Utah Sand Dune Tiger Beetles (Coleoptera: Cicindelidae)

The Coral Pink Sand Dunes tiger beetle (Cicindela limbata albissima) exists only within the Coral Pink Sand Dunes in southwestern Utah. It is currently a candidate for listing as an endangered species. Cicindela tranquebarica occurs throughout the southwestern United States, including the Coral Pink Sand Dunes. We examined microhabitat differences between C. l. albissima and C. tranquebarica. Results of June 1999 adult counts and measurements of percent soil moisture and salt content in 53 interdune swales indicated a significant negative correlation between soil moisture and an index of the relative number of adult C. l. albissima to C. tranquebarica, and a significant positive correlation between soil moisture and direct counts of adult C. tranquebarica. The index of relative number of adults of the 2 species was unrelated to salt content. The relative ratio of larvae of the 2 species in a given swale was significantly correlated to the relative ratio of adults of the 2 species. The cause of the observed microhabitat differences for relatively moist or dry soil could be due to a number of as yet unstudied factors including oviposition preference by the females and larval competition.

Spatial and Temporal Patterns of Xylem Water Potential in Juniperus ashei Seedlings

Juniperus ashei woodlands are found extensively throughout the Edwards Plateau of central Texas. Prior studies indicate that seed germination and seedling survival in J. ashei was greatest under the canopy whereas growth was greatest at the canopy edge. To investigate the cause of these spatial differences, measurements of percent soil moisture and plant predawn xylem water potential (ψ p ) for J. ashei seedlings were made along transects from under a woodland canopy into an intercanopy patch. A soil moisture gradient was detected, with soil moisture highest under the woodland canopy and decreasing into the intercanopy patch. Soil moisture was lowest during the summer drought along this gradient. Mean soil moisture was highest at 68.4 ′ 7.0% (′SE) under the Juniperus canopy in May 1997 and lowest at 12.5 ′ 1.9% in the intercanopy patch during July 1997. Seedling ψ p under the Juniperus canopy ranged from values of -0.51 ′ 0.02 MPa in May to -6.59 ′ 0.00 MPa in August Plant ψ p at the canopy edge was -0.72 ′ 0.03 MPa in May and -6.50 ′ 0.00 MPa in August. No seedlings were found in the intercanopy patch. Spatial and temporal differences in seedling ψ p between the Juniperus woodland and canopy edge did exist, but differences were small (<0.20 MPa). Temporal decreases in soil moisture were followed by more negative seedling ψ p values. Differences in observed ψ p along this woodland to intercanopy patch gradient probably cause reductions in photosynthesis and growth rates in J. ashei, and are likely due to an interaction of several abiotic factors, including soil temperature, soil depth, soil moisture, surface light levels, and soil organic content.

The potential of organic and inorganic soil amendments, and a biological control agent (Trichoderma sp.) for the management of Phytophthora root rot of papaw in far northern Queensland

Non-chemical options for the management of Phytophthora palmivora on papaw in far northern Queensland were evaluated in pot and field experiments. In pots, sawdust (150 m3/ha) + urea (600 kg/ha) reduced root rot, increased plant growth and reduced Phytophthora inoculum to undetectable levels. The addition of filterpress (400 m3/ha) and mill ash (200 m3/ha), reduced the damage caused by P. palmivora, but amendment with chicken manure (4% v/v), MinPlus(4.5 t/ha) and Trichodry (1.0 kg/m3) plus Trichoflow (5.0 kg/ha) failed to reduce root damage. In a second pot experiment, growing brassica (Bioquire Mulch) as a green manure significantly (P < 0.05) reduced Phytophthora inoculum levels and root rot severity, whereas the incorporation and composting of soybean, brachiaria, banana and sugar-cane failed to reduce the severity of root rot in papaw compared to a bare fallow. In a field crop of papaw grown for 46 weeks on 0.75 m high mounds, the suppressive effects of sawdust (150m3/ha) + urea (600 kg/ha), filterpress (400 kg/ha), molasses (100 L/ha/week for 20 weeks), brassica (Bioquire Mulch, 4.5 kg/ha), soybean (cv. Leichardt, 40 kg/ha) and gypsum (5 t/ha) were compared. Soil amended with sawdust + urea had the lowest incidence of root rot. Soil amended with filterpress or molasses had the highest incidence of root rot and the highest populations of P. palmivora. Cumulative totals of percentage soil moisture were greatest in soil amended with filterpress or molasses, and this was evidence of the influence soil moisture retention has on root rot development.

The impact of soil disturbance on root development in woodland communities in Western Australia

The impact of soil disturbance of the Banksia woodland soil profile and particularly the effect of different reconstructed soil profiles (overburden profile, white profile and yellow profile) and soil ripping within rehabilitation sites, was investigated in terms of root development and architecture for eight species that are key structural elements in Banksia woodland. The aim was to determine the soil environment best suited for root development and architecture likely to contribute to high seedling survival in post-mined sites. Root development and architecture differed significantly between native woodland, and rehabilitation sites. In general, roots were longer in native woodland with low lateral root production (for all species studied) compared to rehabilitation sites where the roots were shorter, tended to divide or lose geotrophy and consisted of numerous laterals. When comparing the different soil profiles in the rehabilitation sites, the commonly reconstructed profile of ‘topsoil over overburden’ (overburden profile) was the least favourable for root development and architecture. Ripping of the soil to 80 cm depth had a positive effect on root growth. There were differences between native woodland and rehabilitation sites, in soil impedance, soil bulk density, soil moisture percentage and organic carbon content. In general, reconstructed soils in rehabilitation sites have (1) soil impedance and soil bulk density values likely to seriously impede root development and architecture, (2) soil moisture percentages higher than those in undisturbed woodland during all months of monitoring and at most depths down to 40 cm and (3) lower organic carbon content than native woodland. When comparing the different soil profiles in rehabilitation sites, the overburden profile (a) had the highest impedance values, (b) was one of the profiles with the highest bulk density values and (c) had the highest soil moisture percentages during most months and at most depths examined. Ripping the soil decreased soil impedance and soil moisture contents. The major conclusion from this study is that soil impedance, which influences water movement, is a key characteristic of soil conditions that are not conducive to the development of deep penetrating root systems. These deep root systems may be directly linked to survival.

Soil response to canopy position and feral pig disturbance beneath Quercus agrifolia on Santa Cruz Island, California

We assessed the effects of canopy position and feral pig disturbance on soil moisture, pH, and inorganic nitrogen concentrations beneath canopies of Quercus agrifolia and surrounding grasslands on Santa Cruz Island, California. Percent soil moisture, pH, nitrate-N, and total inorganic nitrogen varied significantly with canopy position. Soil moisture decreased, and pH increased along transects from the subcanopy trunk position to the open grassland outside the canopy. Nitrate and total nitrogen increased from the trunk position to midcanopy and then decreased from midcanopy to the open grassland position. The ratio of nitrate to ammonium varied with canopy position, even after controlling for the effects of soil moisture and pH, both of which strongly influence rates of nitrogen mineralization. Temporally, soil pH, soil moisture, nitrate-N, and total carbon all varied significantly between drought and non-drought years. Soils from fenced exclosures that removed feral pig disturbance did not exhibit significant differences in any soil property compared to control plots where pig access was permitted. The results of our analysis suggest that the primary factors influencing spatial and temporal variability in oak woodland soils on Santa Cruz Island were subcanopy position and climate variability, respectively. Biotic disturbance by feral pigs did not cause a significant cause in soil properties over the spatial and temporal domains examined in this study.

An investigation of marginal habitat and macrophyte community enhancement on the River Torne, UK

During floodbank raising work as part of a major capital flood defence scheme on the River Torne between 1985 and 1990, selected reaches of the main trapezoidal channel were enhanced. By winning spoil from the channel margins and from borrow pits in the floodplain, a more varied marginal zone was created which maximised the potential habitat for wetland plant communities and their associated fauna. Enhancement comprised bank re-profiling to create narrow wetland shelves (berms), shallow bays, channel margins of varying shape and depth and linear still ponds from the borrow pits. The 1990 planting programme comprised 11 macrophyte species and a total of 7740 individual plants. This paper reports on an initial study to evaluate the marginal habitat enhancements on the River Torne 5 years after completion of the project. Lack of pre-scheme data necessitated a space-time substitution; enhanced river margins were compared with neighbouring reaches that had undergone conventional floodbank repair and remained as trapezoidal channel sections planted with a standard, low maintenance seed mix. Marginal vegetation was surveyed and supported by measurements of the physical habitat at 10 enhanced and 10 conventionally-engineered reaches. The macrophyte surveys and the results from the cluster analysis and polar ordination indicate that enhanced and conventionally-engineered reaches are floristically distinct and that the enhanced reaches have a more varied macrophyte community. The results from the Mann–Whitney U-tests show that enhanced reaches have significantly higher values of wetland species diversity and equitability, percentage of wetland species, bank width and soil moisture and significantly lower bank angles. However, the correlation and linear regression analyses did not show any strong associations between the physical habitat and plant parameters. Copyright © 2000 John Wiley & Sons, Ltd.

Effects of increased nitrogen deposition on soil nematodes in alpine tundra soils

Summary Because of anthropogenic activities, atmospheric deposition of nitrogen has increased on some high elevation ecosystems in North America. On Elk Mountain in SE Wyoming, USA, we found that ice, formed by the impaction of supercooled cloud droplets, contains nitrogen levels (NH 4 + = 58 ± 47 μmole/1, NO 3 − = 52 ± 40 μmole/1) significantly higher than snow (NH 4 + = 7 ±5 μmole/1, NO 3 − = 14 ± 7 μmole/1). At this site the impaction process (riming) occurs on krummholz and is an important mechanism of water and nutrient deposition. We sampled nematodes in alpine soil for two seasons under this rime ice deposition and in adjacent meadow and krummholz soil with only snow deposition. No significant difference was found in nematode density and trophic composition between snow and rime ice deposition zones in krummholz; and nematode densities were significantly higher in meadow soil than in the krummholz rhizosphere. Densities of active nematodes were highest immediately after snow melt and a positive correlation was found between nematode density and percent soil moisture. With subsequent soil drying, nematodes gradually entered anhydrobiosis and this process began earlier in the exposed meadow than under the krummholz canopy. In a subsequent microcosm experiment we exposed nematodes in two alpine soils to four different nitrogen treatments [ammonium nitrate (NH 4 NO 3 ) at 0, 20, 40 and 80 kg N/ha/yr] and two temperatures (5 and 25°C). None of the three variables had a significant effect on nematode density. But at the first sampling (1 month) the interaction between soil type and nitrogen level was significant, and at the second and final sampling (6 months) the interaction between soil type and temperature was significant. Nematode response to increasing nitrogen deposition rates varied in a complex way with soil type and temperature. Under the microcosm conditions, nematode community composition shifted to opportunistic rhabditid species. Our work indicates that higher levels of nitrogen deposition (>80 kg N/ha/yr) were necessary to produce detectable effects on nematode density in this alpine region.

Patterns and controls of ecosystem function in longleaf pine - wiregrass savannas. II. Nitrogen dynamics

The productivity of many temperate forests is nitrogen limited. Controls on N availability are particularly important in fire-maintained ecosystems such as longleaf pine - wiregrass (Pinus palustris Mill. - Aristida stricta Michx.) forests of the Coastal Plain of the southeastern United States, where periodic burning can result in substantial N losses. This study quantifies variation in net N mineralization across a complex ecological gradient for longleaf pine - wiregrass forests, from dry sandhills to wet-mesic sites adjacent to wetlands, for the first year after burning. Net N mineralization was consistently higher for the xeric site and declined as soil moisture status increased. Higher N availability was primarily due to higher rates of net nitrification in these plots, suggesting possible substrate-induced influences. Temperature was positively related to net N mineralization, while percent soil moisture was inversely correlated to net N mineralization. The greater N availability on dry sites may reflect greater quality organic matter inputs resulting from a significant hardwood (Quercus laevis Walt. predominately) component, and (or) it may reflect microclimate differences (warmer soil) that accelerate decomposition of detritus in soil.

180 Cover Crops Improve Soil Quality in Strawberry Production

Improving soil quality and suppressing weeds are two challenges facing strawberry growers. Cover crops, such as perennial ryegrass (Lolium perenne) and sorghum-sudangrass (Sorghum sudanense), have been used in rotation with strawberry in the Midwest. The objective of the field study was to investigate the effects of various cover crops on soil quality and weed populations for strawberry production. The experiment was established in 1996 at the Iowa State Univ. Horticulture Station, Ames, in plots that previously were planted continuously in strawberry for 10 years. Nine treatments were arranged in a randomized complete-block design with three replications. Treatments included cover crops of Indian grass (Sorghastrum avenaceum), switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), black-eyed susan (Rudbeckia hirta), marigold (Tagetes erecta `Crackerjack'), sorghum-sudangrass, perennial ryegrass, strawberry (Fragaria ×ananassa `Honeoye'), and bare soil (control). Data from 1998 showed that both annual and perennial cover crops were established more readily (higher treatment-plant populations and less weed populations) than in 1997. Water infiltration rates were highest in bare soil plots and lowest in P. virgatum plots. Bare soil plots and S. sudanense plots had the lowest percent soil moisture.

Pecan Weevil (Coleoptera: Curculionidae) Emergence in a Range of Soil Types

The pecan weevil, Curculio caryae (Horn), can injure pecan from kernel initiation in August until dehiscence of the involucre 2-3 mo later. Prevention of injury requires killing adults after they emerge from soil cells but before they oviposit within developing nuts. The adult emergence period is typically from mid-August to late September, but a portion of the population can be delayed in emerging because of drought hardened soils. Emergence was delayed in this study when soil penetrability was >65 kg/cm2. Soil penetrability as a function of percent soil moisture, clay, and sand can be predicted by the following equation: y = 137.713−8.965 x 1+3.463 x 2−1.190 x 3. Changes in soil penetrability caused by rainfall can be calculated by first determining the change in percent soil moisture as a function of percent soil moisture before rainfall, rainfall (centimeter), and percent sand: y = −18.358−0.607 x 1+0.458 x 2+2.342 x 3 and then solving the previous equation with the new value to update the status of pecan weevil emergence. These findings can be combined with data on soils and new weather monitoring technologies like Doppler radar to predict weevil emergence status initially and then update that status across wide regions on a near real-time basis to aid in making decisions with regard to pecan weevil management. These predictions would be based on county-wide rainfall data and growers would need to take into account their own irrigation programs before making any decision regarding pecan weevil control.

Precision Planting for sh2 Sweet Corn Stand Establishment

The impact of soil type and planting depths on the emergence of three hybrids of shrunken 2 sweet corn with varying seed vigor was investigated. Two field trials were completed (planted on 18 Sept. 1996 and 6 May 1997) in a field containing Crosby and Kokomo soil types in Columbus, Ohio. Three sh2 hybrids (`Starship', `Skyline', and `Confection') were planted at 1.3-, 2.5-, and 5.1-cm depths with six replications on each of the two soils in the fall study. The same hybrids were planted the following spring with an adjustment to 2-, 4-, and 6-cm planting depths over the same soil types, and the addition of a transition soil. The use of data loggers in 1997 allowed for continual monitoring of soil temperatures at each of the planting depths throughout the field, and calculation of soil heat units throughout the emergence period. There were no significant differences between depths for average temperatures or soil heat units. Minimum temperatures were significantly colder on the lighter color soil and had a linear relationship with emergence counts. Soil tests were carried out at all sites for P, K, Mg, and Ca. Although significant differences were found with the Kokomo soil having higher nutrient levels than the transition or Crosby soil, levels throughout the field were more than adequate for emergence. Compaction and soil moisture measurements were taken with a neutron probe. Dry density was significantly higher on the lighter color soils, while soil moisture percentage climbed from 18% on Crosby to 25% on the Kokomo. In both years, there were significant differences in emergence indices based not only on hybrid and planting depth but also on location. Emergence ranged from below 50% to nearly 100% depending on the treatment and field location. Each of the 108 sampling points was located with a GPS receiver and the use of ArcView software allowed for data layers to be stored and mapped so that prescriptions could be made for best stand establishment.

Quantitative estimates of water tables and soil moisture in Holocene peatlands from testate amoebae

Changes in surface wetness on Holocene ombrotrophic mires have principally been estimated from plant macrofossils and humification. Testate amoebae (Protozoa: Rhizopoda) provide an additional technique and have the potential to provide improved quantitative estimates of water-table depths and soil moisture. The relationship between hydrology and testate amoebae assemblages from 163 samples on nine British mires is explored using canonical correspondence analysis (CCA). Mean annual water-table depth and percentage soil moisture are two of the most important environmental variables related to the distribution of testate amoebae within peat. Transfer functions for these variables are developed using four underlying models; weighted aver aging (WA), tolerance downweighted weighted averaging (WA-Tol), weighted averaging partial least squares (WA-PLS) and partial least squares (PLS). In ‘jack-knifed’ validation, WA produced the lowest prediction errors for water table, but was outperformed by WA-Tol for percentage moisture. WA and WA-Tol based transfer functions are then applied to a fossil data set from Bolton Fell Moss, Cumbria. This methodology offers a new technique for reconstructing surface wetness changes on British ombrotrophic and oligotrophic mires and provides data in terms of a meaningful environmental parameter. The cosmopolitan distribution of testate amoebae species suggests that the technique has a much wider geographical potential.

Composting of Fish Waste with Wood By-Products and Testing Compost Quality as a Soil Amendment: Experiences in the Patagonia Region of Argentina

Composting experiments of fish processing wastes and wood by-products were conducted in the Andean-Patagonian Region. Fish wastes were mixed with sawdust + wood shavings (3:1 ratio by weight) with two replicates. Materials were mixed and placed in 220-liter PVC reactors. After 20 days, materials were remixed and reloaded in the reactors. Samples were taken at 20, 30, 40, 60, 80 and 100 day intervals and chemical analyses were made to assess predictors of compost stability. Thermophilic temperatures over 55°C were sustained long enough to satisfy the EPA requirements for pathogen reduction (72 hours). The decrease of NH4+-N, water soluble carbon and the ratio of water soluble carbon to total nitrogen appeared to be the best parameters for predicting compost stability. Mature compost (CMP) and an organic commercial product, Lombriquen (LQN) were incubated with an Andisol and a Xeric Mollisol at a rate of lOg/kg for 16 weeks (20 to 30 percent soil moisture, 25°C) in order to estimate nitrogen and phosphorus release. Soils amended with LQN retained more P than CMP-amended soils (80 percent vs 60 percent of added Olsen-P in the Andisol and 50 vs 35 percent in the Xeric Mollisol). While N mineralization rates of LQN were variable (three to 11 percent of added total N), CMP showed constant rates for both types of soils (12 percent) and released more available N than LQN.

Mortality of Eastern Subterranean Termites (Isoptera: Rhinotermitidae) Exposed to Four Soils Treated with Termiticides

Termite survivorship was affected by soil type and termiticide tested in constant-exposure bioassay. Four soil types were tested at the same percentage soil moisture (15% wt:wt). Soil pH values were between 5.4 and 5.5 with organic matter contents ranging from <0.07 to 3.75%. Soils tested included a sand, sandy loam, sandy clay loam, and sandy clay. Six termiticide formulations were tested including chlorpyrifos (Dursban TC), fenvalerate (Tribute), cypermethrin (Prevail FT, Demon 2 EC), and permethrin (Dragnet FT, Torpedo). Estimated lethal concentrations for all termiticides were at least 7 times lower in sand compared with sandy loam or sandy clay loam soils. However, soil type alone could not be used to predict termite mortality with the termiticides tested.

Effect of soil moisture and crop cover in remote sensing

An investigation with moist soil covered by narrow leaf crop at different stages of growth for establishing relation with scattering/reflection coefficient for both like polarizations (i.e. HH-pol and VV-pol) has been done. There is a linear relationship between crop covered soil moisture with scattering/reflection coefficient. Using linear relationship a theoretical model was proposed. The results from the model have been compared with the observed values. In this model, scattering/reflection coefficient was taken as dependent variable and percentage soil moisture (PSM) as independent variable. Regression parameters were obtained using the regression analysis which show that the brightness temperature at X-band depends significantly on the polarization that is chosen for receiving channel. The VV-pol is more sensitive to changes in the soil moisture, whereas, the contribution of crop morphology was more dominant near nadir for HH-pol. The calculated values show that the scattering increases as the PSM increases, whereas, observed values show no significant trend worth any conclusion.

`Pinot noir' and `Riesling' Grapevines Respond to Water Stress Duration and Soil Water-holding Capacity

Glasshouse-grown `Pinot noir' and `Riesling' grapevines (Vitis vinifera L.) were subjected to one of four water stress durations [no water deficit (control); and water deficits imposed postbloom, lag phase, and veraison] in combination with three soil water-holding capacities (0%, 26%, and 52% gravel, by volume). Vines subjected to increasing water stress duration had less cumulative lateral shoot length and lower shoot count, leaf size, and berry weights than those not stressed. Soluble solids concentration (SSC) during maturation and pH at harvest also increased with increasing water stress duration, but titratable acidity was not affected. Transpiration and stomatal conductance also were reduced with increased water stress duration, but soil water increased, reflecting the larger leaf surface on vines with veraison-imposed deficits. Reducing water-holding capacity (by increasing the percentage of gravel in the soil) tended to increase berry weight and SSC but reduced lateral shoot growth. The 52% gravel treatments increased transpiration rate and stomatal conductance for `Riesling' but reduced them slightly in `Pinot noir'. Percentage of soil moisture was reduced linearly with reduced water-holding capacity. These results indicate that early irrigation deficits may advance fruit maturity of wine grapes with concomitant reductions in vegetative growth. Differential responses of these cultivars to soil water-holding capacity also should help to identify suitable wine grape cultivars as the wine grape industry expands into areas with low water-holding capacity soils.

A Simplified Model for Estimating Nitrogen Mineralization in Paddy Soil.

The estimation of available nitrogen in paddy soil is important in order to evaluate rice productivity and to improve fertilizer management. In this study, a simplified model is proposed for estimating nitrogen mineralization in paddy soil based on incubation experiments. The main factors considered are soil moisture percentage on dry weight basis before submergence (θ) and temperature (T). Soil samples were collected from an experimental paddy field (Alluvial, SL) at Kyoto University. Incubation experiments were conducted for wet and air dried soil under four different temperatures of 15°, 20°, 25° and 30°C. To investigate the effect of preflooding soil moisture on N mineralization, we set eight levels of soil moisture before submergence, after which samples were subjected to a similar incubation experiment. Mineralized N in wet soil (NW) increased linearly, while the drying effect (ND), defined as a difference in N mineralized between air-dried soil and wet soil, was found to have an equal ceiling value over the incubation temperature conditions, though the rate toward the asymptote varied with temperature. We employed the following equations to express the N mineralization rate :dN/dt=dNW/dt+dND/dt dNW/dt=KW dND/dt=KDNOexp(-KDt) where, KW and KD are temperature dependent rate constants expressed by the Arrhenius' equation, of which the apparent activation energy was 24, 803 and 14, 058 cal·mol-1, respectively. No is the maximum effect of soil drying expressed as a function of θ before submergence as follows : NO=7.171-0.66θ+0.015θ2, θl19.56% =0 θ>19.56% The present model was able to estimate satisfactorily the amount of NH4-N mineralized under specific conditions. Increasing the model generality is a subject for further study.

Soil Moisture, Native Revegetation, and Pinus lambertiana Seedling Survival, Growth, and Mycorrhiza Formation Following Wildfire and Grass Seeding

AbstractGrass seeding is widely used for erosion control, but its consequences for soil and regeneration following fire have been measured only infrequently. This study investigates the effect of grass seeding on the type and extent of plant cover; soil moisture percentage; and moisture stress, survival, growth, and root‐tip and mycorrhiza formation of Pinus lambertiana (sugar pine) seedlings in a clearcut intensely burned by wildfire. One‐year‐old containerized sugar pine seedlings were planted in seeded and nonseeded areas in Spring 1988 and 1989 in the Longwood Fire area of southwest Oregon. In 1988, tree seedlings in grass‐seeded plots experienced intense competition from the grass, reduced root‐tip and mycorrhiza formation, low levels of soil moisture to meet evapotranspirational demand, high levels of mortality, and reduced growth. In 1989, however, the opposite was true: tree seedlings in nonseeded plots experienced competition from invading native annuals and perennials, low levels of soil moisture in summer, and higher levels of mortality. The studies we report here further indicate that, in an area characterized by extended summer drought, annual ryegrass impeded regeneration of sugar pine during the first season following the fire. Native species cover and richness have been significantly reduced in the seeded area and may affect long‐term soil stability, productivity, and conifer restoration. Seeding of annual ryegrass at high rates under these conditions would seem ill advised.

Willow Planting Success as Influenced by Site Factors and Cattle Grazing in Northeastern California

In recent years there has been an increasing emphasis on reestablishment of woody vegetation in degraded riparian zones. In this study we evaluated the influence of grazing and selected site factors on survival and leader growth of planted Geyer willow (Salix geyeriana Anderss.) cuttings. Three grazing treatments (early summer, late summer, and non-use) were evaluated on each of 3 streams in broad, low-gradient meadows with silt loam soils in the northern Sierra Nevada. The streams were perennial with terraces often 1.0 to 1.5 m above streambottom. Unrooted Geyer willow cuttings were planted to 30-cm soil depth in early May 1987 at 3 streamchannel locations (streambottom, streambank, and stream terrace) within each of the grazing treatments. Survival, associated community type, and cover class were determined for 2,700 plantings. Leader length and grazing intensity were measured for 694 surviving cuttings in 1988. Percent soil moisture and water table depth were determined for a subset of the willow cuttings. There was no significant (P>0.05) effect of grazing treatment on either willow survival or growth despite 3.5 to 5 times more defoliation use of the willow cuttings in the grazed pastures. Streamchannel location did significantly (P?0.05) affect willow survival (streambottom = 83%, streambank = 34%, and stream terrace = 3%) but not individual plant leader length. Survival of willow cuttings for Carex nebrascensis/Juncus nevadensis, bareground, Deschampsia caespitosa/Carex nebrascensis, and A rtemisia sp. dominated sites was 76, 60, 44, and 2%, respectively. However, leader length was significantly (P?0.05) greater for bareground sites than for sites supporting vegetation. Cover class was not a good indicator of survival, but as might be expected from the results on the bareground sites, leader length for the 0-5% class was 1.8 times the length of the next class. There was a clear relationship between water table depth, soil moisture, and willow planting survival but not between moisture measurements and leader length. Once the water table has declined to the point that A rtemisia sp. can survive on a site, the chances of successfully replanting willows are minimal. However, even during the drought years of this study (<50% of average annual precipitation) a survival rate of 60% or greater was achieved by planting into Carex nebrascensis communities or bareground in the streamchannel.

Soil temperature, moisture and penetrometer resistance under zero and conventional tillage in central Alberta

A 5-year study of zero vs. conventional tillage was conducted at Lacombe, Joffre, Blackfalds and Crestomere in central Alberta. After a 5-year period, soil temperature and percent moisture in soil (w/w basis) were determined only at Lacombe, while mechanical resistance to penetration readings were taken at all sites. Soil temperatures in the spring at 2.5- or 5.0-cm depth were generally lower under zero than conventional tillage. On the average of 10 recording dates over 3 years, soil temperature at a depth of 2.5 cm under zero tillage was 2.8°C lower than under conventional tillage. Percent soil moisture in the surface layer (0–15 cm), on the average of 5 years was 7.2% greater on zero-tillage plots than on conventional-tillage plots. Mechanical resistance to penetration was consistently greater on zero-tillage plots than on conventional-tillage plots. Depth of resistance to penetration owing to zero tillage was 3.5 cm at Lacombe, 7.0 cm at Joffre and 10.5 cm at Blackfalds and Crestomere.