Effects of clipping or burning on some morphological characteristics of Agropyron spicatum

1980 ◽  
Vol 58 (21) ◽  
pp. 2309-2312 ◽  
Author(s):  
W. Willms ◽  
A. W. Bailey ◽  
A. McLean
Keyword(s):  
Treatment Effect ◽  
Morphological Characteristics ◽  
Douglas Fir ◽  
Plant Weight ◽  
Big Sagebrush ◽  
Bluebunch Wheatgrass ◽  
Agropyron Spicatum ◽  
Tiller Density ◽  
And Control

The effects of fall clipping or burning on the subsequent morphology of bluebunch wheatgrass were studied in both the big sagebrush – bluebunch wheatgrass and Douglas fir – bluebunch wheatgrass communities. Observations were made to the 2nd year after treatment. Burning, in the big sagebrush community, resulted in a larger ratio of plant weight to volume. Burning also increased tiller density by the 2nd year in the big sagebrush community. Plants that were burned had lighter tillers in the 1st year after treatment. They also had a greater proportion of weight distributed near their base. The morphological characteristics of clipped plants were generally intermediate between those of burned and control plants. In general, the treatment effect was less in the Douglas fir community than in the big sagebrush community.

THE EFFECTS OF FALL GRAZING OR BURNING BLUEBUNCH WHEATGRASS RANGE ON FORAGE SELECTION BY DEER AND CATTLE IN SPRING

1980 ◽  
Vol 60 (1) ◽  
pp. 113-122 ◽  
Author(s):  
W. WILLMS ◽  
A. W. BAILEY ◽  
A. McLEAN ◽  
R. TUCKER
Keyword(s):  
Cattle Grazing ◽  
Grazing Pressure ◽  
Douglas Fir ◽  
The Other ◽  
Big Sagebrush ◽  
Effective Barrier ◽  
Other Hand ◽  
Bluebunch Wheatgrass ◽  
Made In

Studies were made in the big sagebrush-bluebunch wheatgrass and Douglas fir-bluebunch wheatgrass communities to examine the effects of fall burning and fall cattle grazing on springtime utilization of bluebunch wheatgrass by both deer and cattle. Deer and cattle displayed greatest preference for forage from the burned treatment and least preference for forage from the control. Grazing pressure by deer was not sufficient to cause the preference rankings among treatments to change. On the other hand, cattle readily switched preferences as availability among treatments changed. Utilization of other species appeared related to the utilization of bluebunch wheatgrass. Dead stubble of bluebunch wheatgrass influenced the height of grazing in spring. Deer were more affected by stubble than were cattle although deer were able to select closer to the height of short stubble and further below the height of long stubble. Dead stubble of small plants was a less effective barrier than that of large plants. This effect was particularly pronounced with cattle.

Effect ofSclerotinia sclerotiorumon the Interference between Bluebunch Wheatgrass (Agropyron spicatum) and Spotted Knapweed (Centaurea maculosa)

1996 ◽  
Vol 10 (1) ◽  
pp. 13-21 ◽  
Author(s):  
James S. Jacobs ◽  
Roger L. Sheley ◽  
Bruce D. Maxwell
Keyword(s):  
Resource Partitioning ◽  
Soil Fungus ◽  
Niche Differentiation ◽  
Species Interaction ◽  
Spotted Knapweed ◽  
Plant Weight ◽  
Bluebunch Wheatgrass ◽  
Chamber Study ◽  
The Common ◽  
Agropyron Spicatum

Effectiveness of the common soil fungusSclerotinia sclerotiorumas a biological control for spotted knapweed and its effect on competitive interactions between spotted knapweed and bluebunch wheatgrass were evaluated in a growth chamber study using addition series methods. Total seeding densities ranged from 2000 to 60 000 seeds/m2. Mean bluebunch wheatgrass plant weight was 3.5 times greater than spotted knapweed weight per plant, respectively. Coefficient ratios estimating species interaction showed bluebunch wheatgrass density had a greater influence than spotted knapweed density on both bluebunch wheatgrass and spotted knapweed weights (2.11 and 0.51, respectively) when not under the influence ofS. sclerotiorum. Niche differentiation ratios indicated a lack of resource partitioning between species (1.11).S. sclerotiorumreduced spotted knapweed density by 68 to 80% without reducing bluebunch wheatgrass density. Spotted knapweed weight per plant also was reduced by the addition of 5.sclerotiorum(1.4 to 1.2 mg) but there was not a corresponding increase in bluebunch wheatgrass weight.S. sclerotiorumdecreased competition between spotted knapweed and bluebunch wheatgrass. This study provides evidence that establishment of bluebunch wheatgrass on spotted knapweed infested rangeland may be improved by combiningS. sclerotiorumwith high grass seeding rates.

scholarly journals Measuring the sensitivity of difference-in-difference estimates to the parallel trends assumption

2021 ◽  
pp. 263208432110613
Author(s):  
Landon Gibson ◽  
Frederick Zimmerman
Keyword(s):  
Sensitivity Analysis ◽  
Treatment Period ◽  
Treatment Effect ◽  
Statistical Tests ◽  
Sensitivity Analyses ◽  
Difference In Difference ◽  
Control Groups ◽  
Pre Treatment ◽  
Background Difference ◽  
And Control

Background. Difference-in-Difference makes a critical assumption that the changes in the outcomes, over the post-treatment period, are similar between the treated and control groups—the parallel trends assumption. Evaluation of this assumption is often done either by graphical examination or by statistical tests in the pre-treatment period. They result in a binary conclusion about the validity of the assumption. Purpose. This paper proposes a sensitivity analysis that quantifies the departure from parallel trends necessary to meaningfully change the estimated treatment effect. Results. Sensitivity analyses have an advantage over traditional parallel trends tests: they use all available data and thereby work even if only one pre-period is available, and they quantify the strength of unobserved confounder(s) required to change the conclusions of a study. Conclusions. We apply the sensitivity analysis metrics developed by Cinelli and Hazlett (2020) and illustrate them on two studies.

scholarly journals Association between the morphological and productive characteristics in the selection of elephant grass clones

2011 ◽  
Vol 40 (3) ◽  
pp. 482-488 ◽  
Author(s):  
Márcio Vieira da Cunha ◽  
Mario de Andrade Lira ◽  
Mércia Virginia Ferreira dos Santos ◽  
Erinaldo Viana de Freitas ◽  
José Carlos Batista Dubeux Junior ◽  
...  
Keyword(s):  
Path Analysis ◽  
Dry Matter ◽  
Morphological Characteristics ◽  
Matter Content ◽  
Dry Matter Production ◽  
Leaf Angle ◽  
Dry Matter Content ◽  
Canonical Correlations ◽  
Matter Production ◽  
Tiller Density

The objectives in this work were to study the association between the morphological and productive characteristics in Pennisetum sp. clones, and to identify the morphological characteristics responsible for the productivity in Pennisetum cp. clones. The canonical correlations were evaluated and the path analysis was made from the simple genotypic correlation matrix between the morphological and productive characteristics of eight Pennisetum sp. clones (Taiwan A-146 2.37, Taiwan A-146 2.27, Taiwan-146 2.114, Merker México MX 6.31, Mott, HV-241, Elefante B and IRI-381). The canonical correlations were significant at 1% probability by the Chi-square test. The first pair of canonic factors, with correlation of 0.9999, related the plants with the highest dry matter content to plants with lower leaf area indexes, light perception and leaf angle. The second pair of canonic factors, with correlation of 0.9999, related the plants with the highest dry matter production to the plants with higher basal tiller density, height, and low green leaf number per tiller. The results of the path analysis indicated that the light interception is determinant in dry matter content expression of Pennisetum sp. clones, while the basal tiller density and plant height are responsible for dry matter production in these clones.

scholarly journals First Report of Colletotrichum truncatum on Alfalfa in Turkey

Plant Disease ◽  
2000 ◽  
Vol 84 (1) ◽  
pp. 100-100 ◽  
Author(s):  
C. Eken ◽  
E. Demirci
Keyword(s):  
Morphological Characteristics ◽  
Conidial Suspension ◽  
Colletotrichum Truncatum ◽  
First Report ◽  
Clear Area ◽  
Granular Cytoplasm ◽  
Symptomatic Tissue ◽  
Medicago Sativa L ◽  
Stem Lesions ◽  
And Control

During the summer of 1997 and 1998, a pathogen identified as Colletotrichum truncatum (Schwein.) Andrus & W.D. Moore was isolated from lesions on stems of alfalfa (Medicago sativa L.) plants in Erzurum, Turkey. Typical symptoms on stems of mature plants were large, sunken, irregularly shaped black lesions. Twenty-eight cultures of C. truncatum were isolated from stem lesions. Acervuli containing spores and dark setae were observed within lesions. Conidia were hyaline, one-celled, falcate to nearly straight with a prominent clear area in the center of highly granular cytoplasm, and measured 16.3 to 20.6 × 3.1 to 4.5 μm. These morphological characteristics were consistent with the description of C. truncatum (1). The pathogenicity of two isolates was determined on alfalfa cv. Bilensoy. Alfalfa seedlings (6-week-old) were inoculated with a conidial suspension of the fungus (1.4 × 107 conidia per ml), incubated in a moist chamber for 3 days, and subsequently transferred to growth chambers maintained at 25°C with a 12-h photoperiod. Ten plants were inoculated with each isolate. Symptoms first appeared on stems 12 days after inoculation. Sunken, irregularly shaped black lesions occasionally girdled stems of plants inoculated with C. truncatum. Symptoms did not appear on stems of control plants inoculated with sterile distilled water. C. truncatum was reisolated from symptomatic tissue. This is the first report of C. truncatum on alfalfa from Turkey. Reference: (1) B. C. Sutton. 1992. Pages 1–27 in: Colletotrichum Biology, Pathology and Control. J. A. Bailey and M. J. Jeger, eds. CAB International, Wallingford, U.K.

Estimating Treatment Effects in the Presence of Noncompliance and Nonresponse: The Generalized Endogenous Treatment Model

2011 ◽  
Vol 19 (2) ◽  
pp. 205-226 ◽  
Author(s):  
Kevin M. Esterling ◽  
Michael A. Neblo ◽  
David M. J. Lazer
Keyword(s):  
Treatment Effect ◽  
Instrumental Variable ◽  
Treatment Effects ◽  
Mean Squared Error ◽  
Principal Stratification ◽  
Squared Error ◽  
Treatment Effect Heterogeneity ◽  
Causal Treatment ◽  
Effect Heterogeneity ◽  
And Control

If ignored, noncompliance with a treatment or nonresponse on outcome measures can bias estimates of treatment effects in a randomized experiment. To identify and estimate causal treatment effects in the case where compliance and response depend on unobservables, we propose the parametric generalized endogenous treatment (GET) model. GET incorporates behavioral responses within an experiment to measure each subject's latent compliance type and identifies causal effects via principal stratification. Using simulation methods and an application to field experimental data, we show GET has a dramatically lower mean squared error for treatment effect estimates than existing approaches to principal stratification that impute, rather than measure, compliance type. In addition, we show that GET allows one to relax and test the instrumental variable exclusion restriction assumption, to test for the presence of treatment effect heterogeneity across a range of compliance types, and to test for treatment ignorability when treatment and control samples are balanced on observable covariates.

Abstract W P20: A Model to Calculate the Expected Treatment Effect in Acute Endovascular Stroke Trials

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Maarten G Lansberg ◽  
Robin Lemmens ◽  
Soren Christensen ◽  
Nishant K Mishra ◽  
Gregory W Albers
Keyword(s):  
Literature Review ◽  
Sample Size ◽  
Endovascular Therapy ◽  
Treatment Effect ◽  
Small Sample Size ◽  
Small Sample ◽  
Absolute Difference ◽  
Sample Size Calculations ◽  
And Control ◽  
Larger Sample

Background: Recent trials have shown no benefit of endovascular therapy. This may, in part, be explained by inaccurate estimates of the treatment effect used in the sample size calculations of these trials. A predictive model which includes variables that modify the expected treatment effect might yield more accurate estimates, and could be valuable in the design of future acute stroke trials. Methods: We conducted a literature review to obtain estimates of parameters that are associated with good functional outcome (GFO) following recanalization. We developed a model to estimate the treatment effect in endovascular stroke trials and applied this model to two recently published endovascular stroke trials. Results: We estimated a 40% absolute difference in the proportion of GFO (mRS 0-2 at 90 days) associated with reperfusion in patients with ICA or M1 occlusions who have a substantial ischemic penumbra at baseline. To estimate the effect size in trials, this value was multiplied by: 1) the proportion of patients undergoing endovascular therapy in the active treatment arm; 2) the proportion of patients with occlusions of the ICA or MCA-M1; 3) the proportion of patients with a substantial penumbra and a DWI lesion <50mL; and 4) the absolute difference in the proportion of patients with reperfusion, defined as TICI 2B-3, between the endovascular treatment and control arms. Based on literature review we assumed a reperfusion rate of 20% in the control arms of IMS III and MR Rescue, a 50% prevalence of patients with substantial penumbra and DWI lesions<50 mL in IMS III, and a 75% prevalence in the penumbral arms of MR Rescue. Based on these model inputs, a 2.2% increase in GFO with endovascular therapy was expected in IMS III, which closely matches the observed 2.1% increase. For MR Rescue, the model predicted a 1.5% increase in GFO with endovascular therapy. Considering the small sample size, this equates to 0.5 additional patients with GFO which closely matches the observed result of 3 fewer patients with GFO. Conclusion: A simple model shows promise for estimating the treatment effect of endovascular stroke trials. It may be useful for the design of future trials and could lead to different inclusion criteria or larger sample sizes compared to the recently conducted studies.

scholarly journals An Evaluation of Dazomet Incorporation Methods on Soilborne Organisms and Pine Seedling Production in Southern Nurseries

2003 ◽  
Vol 27 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Stephen W. Fraedrich ◽  
L. David Dwinell
Keyword(s):  
Morphological Characteristics ◽  
High Rate ◽  
Parasitic Nematodes ◽  
Seedling Production ◽  
Seedling Density ◽  
The North ◽  
Nursery Plant ◽  
Shoot Weight ◽  
And Control

Abstract The use of dazomet as a fall and spring fumigant for pine seedling production and control of soilborne pests was evaluated at two southern nurseries. Dazomet was applied at low (280–325 kg/ha) and high (493–560 kg/ha) rates and incorporated with a rototiller or spading machine. Comparisons were made with methyl bromide/chloropicrin (MBC) fumigation and nonfumigated control treatments. Dazomet incorporation method had no effect on seedling density at either nursery, and often did not affect seedling morphological characteristics. At the Georgia (GA) nursery, seedling density and morphological characteristics did not differ among fumigant treatments except in the spring study area where shoot weight was greater in the MBC treatment than the dazomet or nonfumigated control treatments. In the fall study area at the North Carolina (NC) nursery, seedling density was greater in the high-rate dazomet treatment than the nonfumigated control. Seedlings were generally larger in MBC and dazomet treatments than the control. Seedling density and morphological characteristics did not differ among fumigation treatments in the spring study area. Fumigation with MBC or dazomet generally reduced the percentage of roots withPythium andFusarium spp. compared to controls at the GA nursery and the fall fumigation area in the NC nursery. Plant parasitic nematodes were found infrequently at both nurseries and did not differ among treatments. Nutsedge (Cyperus spp.) was the major problem at the GA nursery and was effectively controlled only with MBC. Compared to the MBC treatment, the abundance of soilborne fungi and the association of certain types ofTrichoderma with roots was often lower in the dazomet treatments. The importance of these differences for long term seedling production and management of soilborne diseases is not known at this time. South. J. Appl. For. 27(1):41–51.

Morphological characteristics of crested wheatgrass populations of diverse origin

2002 ◽  
Vol 82 (4) ◽  
pp. 693-699 ◽  
Author(s):  
A. Mellish ◽  
B. Coulman
Keyword(s):  
Morphological Characteristics ◽  
Agropyron Cristatum ◽  
Crested Wheatgrass ◽  
Crown Diameter ◽  
Crown Width ◽  
Row Width ◽  
Diverse Origin ◽  
One Year ◽  
Tiller Density ◽  
Tiller Angle

In crested wheatgrass, the species Agropyron cristatum includes populations that are diploid and tetraploid, either naturally or artificially induced. The species Agropyron desertorum is tetraploid and there are culitvars that are hybrids between A. cristatum and A. desertorum. The goal of this study was to compare the morphology (height, crown width, tiller density, tiller weight and tiller angle) of populations from the two species and hybrids, including S9240, a recently developed colchicine induced tetraploid A. cristatum. Data were collected in 1999 and 2000 from several different sward-seeded and spaced-planted trials. The four tetraploid crested wheatgrasses (A. cristatum “Kirk” and “S9240”, A. desertorum “Nordan”, and A. desertorum × A. cristatum “CD-II”) were significantly (P < 0.05) taller, narrower in row width, and produced fewer, heavier tillers than the diploid A. cristatum “Parkway”. Among the tetraploid populations, S9240 was significantly (P < 0.05) taller and produced fewer tillers. S9240 also produced significantly (P < 0.05) heavier tillers than CD-II and Nordan, and also than Kirk, one year of two. Row widths were variable among populations, but S9240 generally produced a narrower crown than other populations. Key words: Crested wheatgrass, polyploidy, plant height, crown diameter, tiller characteristics

Early Development of Three Douglas-Fir Stocktypes on a Droughty Skeletal Soil

1989 ◽  
Vol 4 (1) ◽  
pp. 21-24 ◽  
Author(s):  
Stephen D. Hobbs ◽  
Michael S. Crawford ◽  
Beverly A. Yelczyn
Keyword(s):  
Surface Soil ◽  
Morphological Characteristics ◽  
Field Performance ◽  
Douglas Fir ◽  
Root Characteristics ◽  
Relative Growth ◽  
Seedling Root ◽  
Absolute Growth ◽  
Southwest Oregon ◽  
Better Than

Abstract Three stocktypes of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) were planted in a droughty, skeletal soil in southwest Oregon. After 5 years, container-grown plugs and plug-1 transplants survived significantly better than 2-0 bareroots. Seedling root systems were largely confined to the surface soil, with relatively little development upslope or deeper than 15 cm. Stocktype morphology differed significantly at planting. However, annual absolute growth, annual relative growth, and shoot and root characteristics did not differ significantly after 5 years. These results suggest that, on similar sites, seedling morphological characteristics within the range of those measured in this study may not affect growth and that stocktype designation along may not be adequate for predicting field performance. West. J. Appl. For. 4(1):21-24, January 1989.

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