Search
Search Results
-
11. [Article] Factors influencing the herbicidal activity of dimethyl 2,3,5,6-tetrachloroterephthalate
Studies were conducted to determine the site of DCPA toxicity on annual ryegrass. This was done by means of a technique which used pyrex tubing and a vapor barrier to separate exposure of coleoptile and ...Citation Citation
- Title:
- Factors influencing the herbicidal activity of dimethyl 2,3,5,6-tetrachloroterephthalate
- Author:
- McKinley, James Raleigh
Studies were conducted to determine the site of DCPA toxicity on annual ryegrass. This was done by means of a technique which used pyrex tubing and a vapor barrier to separate exposure of coleoptile and roots of emerging grass seedlings to various concentrations of DCPA. Coleoptiles that emerged through treated soil were completely killed, but when only roots were exposed to treated soil, little shoot reduction was attained. The toxicity exerted through the roots was investigated by exposing only roots to DCPA-treated soil at concentrations ranging from 0 to 128 ppm. There was no significant shoot reduction when roots were exposed to concentrations as high as 128 ppm. Root growth, however, was greatly reduced when roots grew in soils treated with DCPA at concentrations of 4 ppm and greater. There was a direct correlation between phytotoxicity and the depth of treated soil through which the coleoptile emerged, which might indicate greater efficiency would result from shallow incorporation under field conditions. There was also a direct relationship between the extent of phytotoxicity and the concentration of DCPA in the soil through which the coleoptile emerged. These two correlations indicate that the toxicity exerted was directly related to a given quantity of DCPA absorbed. The lethal dosage could be accumulated either by long exposure to low DCPA concentrations or short exposure to high concentrations. DCPA seems to be an inhibitor of normal mitotic cell division. Enlargements occurred in all areas of meristematic tissue. The swollen area appeared to be due to excessive cell proliferation. DCPA at sub-lethal doses served as a growth stimulator causing in creased growth in both roots and shoots. Optimum growth stimulation occurred at a 72°F. temperature. The influence of soil temperature on DCPA toxicity to annual ryegrass was investigated by means of a temperature-controlled water bath in the greenhouse. DCPA was slightly more toxic at 84°F. and 60°F. temperature levels as compared to a medium temperature of 72°F. which would indicate a variation in plant-chemical response rather than chemical property differences. Plants growing in warm soil treated at 2 parts per million were able to overcome early evidence of toxicity better than those growing in cooler soils. Studies conducted on DCPA degradation in the soil indicated that DCPA was broken down faster at 90°F. than at 70°F. There was no detectable breakdown at the 50°F. temperature level. The halflife of DCPA at 90°F. was 105 days, and 155 days at 70°F.
-
Applications of ethofumesate in Oregon have been observed from previous research and from commercial use to be less effective when applied to dry soils, even if subsequent precipitation occurred within ...
Citation Citation
- Title:
- Effect of a pre-irrigation period on the activity of ethofumesate applied to dry soil
- Author:
- McAuliffe, David
Applications of ethofumesate in Oregon have been observed from previous research and from commercial use to be less effective when applied to dry soils, even if subsequent precipitation occurred within a few days. Two field studies were established in the summer of 1979 using sweet corn (Zea mays L. 'Jubilee') and winter wheat (Triticum aestivum L. 'Stephens') as bioassay species to determine the effect of dry soil on ethofumesate efficacy. Applications of various rates of the herbicide were made to soils of approximately 2 and 30% w/w soil moisture. After 2 to 4 days, all soils were irrigated for stand establishment and maintained at a high moisture level. Ethofumesate, at most rates, was significantly less effective on both corn and wheat when applied to dry soil than to wet soil. Two greenhouse studies were conducted using spring wheat (Triticum aestivum L. 'Fielder') bioassays. One employed five soil moisture levels, 2, 5, 9, 15, and 36%, and all soils were wetted to field capacity 4 days after herbicide application. The other study used 2 and 12% moisture contents and soils were wetted 0, 2, and 4 days following herbicide application. The first study showed a general decrease in herbicide activity with decreasing water content with a greater than expected drop in activity at 15% moisture. This drop in herbicide activity is believed to be the result of the soil surface drying after application. The second study showed substantially greater herbicide activity at 12% moisture than at 2% moisture. The ethofumesate was incorporated in this study, eliminating the effect of surface drying. An increase in herbicidal activity was apparent as the length of time between herbicide application and wetting increased from 2 to 4 days for the 2% moisture soils. The reason for this effect is not clear. Soil samples (50 g, air-dried equivalent) at 2 and 20% soil moisture were treated with 484 pg of ethofumesate. The herbicide was extracted from the soils with hot methanol 0, 2, 4, 6, and 12 days after application. A gas chromatography analysis for ethofumesate revealed no loss in the amount of herbicide applied to wet soil over the 12-day period while in the dry soil, the amount extracted after 12 days was 10% of the amount extracted at 0 days. These data suggest chemical degradation of ethofumesate as the most likely mechanism for the activity loss in dry soil.
-
HOE 23408 [methyl 2-[ 4-( 2, 4- dichlorophenoxy )phenoxy]propanoate] is a herbicide used to selectively-control Italian ryegrass (Lolium muitiflorum Lam.) and wild oats (Avena fatua L.) in wheat. The objective ...
Citation Citation
- Title:
- Foliar vs. root uptake of the herbicide Hoe 23408 in Italian ryegrass and wild oats
- Author:
- West, Geralyn Marie
HOE 23408 [methyl 2-[ 4-( 2, 4- dichlorophenoxy )phenoxy]propanoate] is a herbicide used to selectively-control Italian ryegrass (Lolium muitiflorum Lam.) and wild oats (Avena fatua L.) in wheat. The objective of this research was to compare the relative importance of foliar and root uptake of the herbicide in these two weed species. Factors such as plant biotype, stage of plant growth, soil type, irrigation type, and amount of soil moisture were examined. Plants were grown in plastic pots in the greenhouse with a 12- hour day, 12-hour night schedule. HOE 23408 (38% a.i. emulsifiable concentrate) was applied using an overhead variable-speed sprayer calibrated to deliver 309 L/ha. The herbicide was applied at three placement sites: foliage only, soil only, and foliage plus soil. Foliar placement was accomplished by protecting the soil with a 1.5 cm layer of perlite prior to spraying. This layer was removed when dry. Soil only application was administered by pouring a 25 ml solution of the herbicide directly onto the soil. The combination treatment was sprayed with neither area protected. Symptoms developed within 2 to 4 weeks from the day of treatment. Fresh weights, visual ratings of injury, and dry weights were obtained to assess injury. Fresh weights gave the best injury estimate and were converted to percent fresh weight reduction prior to analysis. Five replications were used in each experiment. Both foliar only and soil only applications of the herbicide caused injury to both species. Italian ryegrass was more sensitive to HOE 23408 than wild oats. HOE 23408 was applied at rates of .56, 1.12, 1.68, and 2.24 kg/ha. Injury increased with increasing rate in all placement treatments. The effect of the herbicide on ryegrass and wild oats was examined under conditions of New Zealand and western Oregon. In New Zealand, the high organic matter Canterbury Plains silt loam greatly reduced soil activity of the herbicide. 'Tama' ryegrass, a rapidly growing New Zealand variety, was found to be more sensitive to foliar application than the western Oregon biotype. Ryegrass was slightly more susceptible to the herbicide at the one- to two-leaf stage than at the three- to four-leaf stage. Ryegrass and wild oats were grown in western Oregon using Woodburn silt loam (3.5% 0.M.), Newberg sandy loam (1.7% O.M.), and silica sand (0.5% O.M.). Injury from a 1.12 kg/ha application of the herbicide decreased with increasing organic matter content. No differences were noted for foliar applications of the herbicide in the different soil types. Placement effects were examined under two irrigation types: subsurface and overhead. No placement x irrigation interaction was noted. Plants subjected to subsurface irrigation grew more rapidly, and consequently, the overall injury was greatest in these plants. Two studies were conducted with ryegrass grown under various soil moisture conditions: 120% Field Capacity (F.C.), 96% F.C., 60% F.C., and 32% F.C. Neither foliage only nor soil only placements were affected by soil moisture. However, HOE 23408 activity in the combination treatment was significantly reduced under low soil moisture conditions. Ryegrass and wheat were grown in quart size glass Mason jars filled with nutrient solution. The objective of this study was to determine if root inhibition could be caused by either placement of HOE 23408. The herbicide was applied either to the foliage or to the nutrient solution. Measurements of the longest root were taken daily. Root growth was severely inhibited only when the roots were exposed to the herbicide, not when the foliage was treated.
-
Equipment for strip-till planting is under development in wheat-fallow rotations in the Columbia Basin of Oregon. This involves the absence of tillage during the fallow season. At planting time, the strip-till ...
Citation Citation
- Title:
- Factors influencing metribuzin use in strip-planted wheat
- Author:
- Zeghida, Ali
Equipment for strip-till planting is under development in wheat-fallow rotations in the Columbia Basin of Oregon. This involves the absence of tillage during the fallow season. At planting time, the strip-till planter creates a narrow band into which the wheat seed is placed. The area between the rows is undisturbed except for the deposition of a 2-cm thick layer of soil displaced from the tilled area. Chemical weed control is required between the rows. Preliminary work has shown that metribuzin [4-amino-6-tert-butyl-3- (methylthio)-as-triazin-5(4H)-one] is a promising herbicide for this purpose. Factors influencing the application, effectiveness, and selectivity of metribuzin used in conjunction with strip-till planting were investigated in the laboratory and greenhouse. Application of metribuzin in combination with liquid fertilizer would be convenient and economical. Laboratory experiments were conducted to determine the physical compatibility of four liquid fertilizers: Solution 32 at 56 kg N/ha, 10-34-0 at 45 kg P₂0₅/ha, 0-0-15 at 22 kg K/ha, and 11-0-0-26 at 22 kg S/ha, with three metribuzin formulations each of Sencor and Lexone at 112 g a.i./ha. Wettable powder, flowable, and dispersible granule formulations of both Sencor and Lexone were tested. Only the wettable powder formulations were sufficiently compatible with the liquid fertilizers tested to be recommended for practical commercial use. Large differences were seen between the other formulations. Their use with liquid fertilizers might require the addition of compatibility agents or mixing them with water first, before adding them to the fertilizers. When compatibility is obtained after mixing them with water first, continuous agitation might be required to maintain the suspension. No major differences were observed between comparable formula tions of Sencor and Lexone. Greenhouse experiments were conducted to determine the biological compatibility of Solution 32 and metribuzin on downy brome (Bromus teetorum LJ, the effect of Solution 32 on downy brome and wheat emergence, the effect of soil layer on metribuzin effectiveness for downy brome control, and the effect of banding width over the wheat row and wheat seeding depth on metribuzin phytotoxicity to wheat. More effective downy brome control was obtained when metribuzin was mixed with Solution 32 than when it was used alone. Solution 32 was used at 0, 36, 54, and 79 kg N/ha, and metribuzin at 0, 14, 28, 56, and 112 g a.i./ha. Solution 32 itself had some phytotoxic effects on downy brome at the high rates. Wheat was not affected as severely as downy brome. Application of metribuzin to the surface of the newly deposited soil layer was more effective in controlling downy brome than when the herbicide was applied and then covered with the soil layer. Results suggested that better downy brome control could be obtained with metribuzin applied after the strip-tiller had deposited the soil layer between the rows, especially if adequate rainfall is expected. Under such rainfall conditions, metribuzin covered with a soil layer may leach deeper out of the root zone and less effectiveness could result. Both seeding depth of wheat and width of the unsprayed area were factors influencing metribuzin phytotoxicity to wheat. Greater wheat injury was observed when the herbicide was applied on top of, or too close to, the seed row, particularly when wheat was planted shallow. The results suggested that wheat should be planted 3 cm deep or deeper when the unsprayed band is 15 cm wide, and at least 5 cm deep when the unsprayed band is 10 cm wide.
-
15. [Article] Effects of three herbicides on yields of five cultivars of winter wheat (Triticum aestivum L. em Thell)
With the development of new selective herbicides and the frequent change in commercial wheat cultivars, information is needed as to the possible interaction between cultivars and herbicides. The responses of ...Citation Citation
- Title:
- Effects of three herbicides on yields of five cultivars of winter wheat (Triticum aestivum L. em Thell)
- Author:
- Yahyaoui, Amor
With the development of new selective herbicides and the frequent change in commercial wheat cultivars, information is needed as to the possible interaction between cultivars and herbicides. The responses of five genotypically diverse wheat cultivars (Bezostaya, Daws, Maris Hobbit, Stephens and Yamhill) to diuron [3-(3,4-dichloropheny1)-1,1- dimethylurea], diclofop methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate and 2,4-D (2,4-dichlorophenoxy acetic acid) herbicides were compared under field and greenhouse conditions during the 1979-80 growing season. Grain yield was considered as a measure of herbicide injury when compared to the control plots for each cultivar. Effect on components of yield, plant height and grain protein content also were investigated. Differences in yield performance and related agronomic characters could be attributed to specific herbicides, designated rates and growth stages at the time of application. The lower (1.4 kg/ha) rate of diuron, diclofop and 2,4-D reduced yields less than the higher rate (2.8 kg/ha). Diuron and diclofop applied at the earlier (three to to five leaf) growth stage caused greater yield reductions than when applied at the later (five to six tiller) growth stage. Differential yield responses were found among and within the five winter wheat cultivars. The higher rate of diuron (2.8 kg/ha) caused the most injury in all of the cultivars tested. Major injury from diclofop occurred on the cultivar Maris Hobbit with minor effects on the other four cultivars. The primary reduction in yield from application of 2,4-D was to the cultivar Bezostaya. Among the five wheat cultivars tested in this experiment, Daws was the most tolerant to the three herbicides tested. Among the yield components (number of spikes per unit area, kernels per spike and 1000 kernel weight), number of kernels per spike accounted for most of the variation in yield. The data showed a direct relationship between kernel number and grain yield. Grain protein percentage of Daws, Maris Hobbit, Stephens and Yamhill significantly increased at the higher rate of diuron; whereas a similar increase was noted only in Bezostaya at the lower rate of 2,4-D. These increases in protein were associated with significant decreases in yield. Yield reductions due to herbicide treatments were generally lower than those due to weed competition. Reductions in yield and corresponding changes in the other agronomic characteristics observed in this experiment were the result of concentrations which are higher than those normally used in spraying wheat for weed control. This high chemical dosage was chosen for each herbicide to assure a greater differential response among and within the wheat cultivars. It also provided information for the plant breeder as to which cultivars had higher levels of tolerance. Such information is important when making hybrid combinations for the development of future varieties if higher levels of tolerance to specific herbicides are required.
-
The use of CIPC (isopropyl N-(3-chlorophenyl) carbamate) to control dodder (Cuscuta spp.) in alfalfa is an established practice. A rate of six pounds per acre applied to moist soil has given good dodder control ...
Citation Citation
- Title:
- The effects of CIPC vapors on dodder (Cuscuta spp.) seedlings
- Author:
- Slater, Clarence Harold
The use of CIPC (isopropyl N-(3-chlorophenyl) carbamate) to control dodder (Cuscuta spp.) in alfalfa is an established practice. A rate of six pounds per acre applied to moist soil has given good dodder control lasting from four to six weeks. The purpose of this study was to determine the effect of CIPC vapors on dodder seedlings. In order to obtain a relatively high percent germination of dodder seeds, the seeds were scarified with concentrated sulfuric acid and planted in sterile soil. Since dodder is a parasitic plant it was necessary to find a suitable host plant. Alfalfa and carrots were used in initial experiments and toothpicks were substituted for the host plants in later experiments. It was found that dodder seedlings would wrap around toothpicks and haustoria would develop. Control of dodder seedlings was measured by counting the number of wrapped or attached dodder seedlings on a suitable host. Dodder seedlings were exposed to CIPC vapors in a closed plastic vapor trap system. Twenty percent granular CIPC at six pounds per acre was applied to moist soil within the vapor trap. Exposure of dodder seedlings to CIPC vapors for 2, 4, 8, 16, 32, and 64 hours indicated that at least 16 hours exposure was necessary to prevent seedlings from wrapping. A similar experiment was carried out using CIPC at six pounds per acre on dry soil. Complete control of dodder seedlings was obtained in each experiment. Dodder seedlings were grown in 12 x 75 mm test tubes. They were then exposed to CIPC vapors released from CIPC granules in the open greenhouse. The test tubes provided assurance that all contact between CIPC and the dodder must have been as a vapor. In all cases the seedlings failed to wrap around the toothpicks. Data from a field experiment using the test tube method and alfalfa as a host showed positive dodder control as a result of CIPC vapor toxicity. An attempt was made to determine whether CIPC in the soil solution or CIPC vapors were most active in controlling dodder seedlings. In all cases seedlings were isolated from CIPC in soil solution. The vapors released did prevent wrapping of dodder seedlings on the toothpicks. A suitable method was not found which would assure only exposure of dodder seedlings to CIPC in the aqueous form. The evidence collected shows that CIPC vapors are important in the control of dodder seedlings.
-
The physical and chemical properties of soils greatly affect the toxicity of bromacil and picloram. Consequently, a knowledge of the parameters which influence the soil inactivation of these herbicides is ...
Citation Citation
- Title:
- Surfactant effects on bromacil and picloram adsorption by Oregon soils
- Author:
- Gaynor, John Donald
The physical and chemical properties of soils greatly affect the toxicity of bromacil and picloram. Consequently, a knowledge of the parameters which influence the soil inactivation of these herbicides is necessary to determine proper application rates for good weed control. Enhancement in phytotoxicity with the addition of surfactants or surface active agents in the spray volume has been observed for these chemicals; however, little is known concerning the effects of these additives on picloram and bromacil adsorption. The objectives of this research are: 1) to evaluate the effects of cation saturation on bromacil adsorption by montmorillonite, 2) to determine the effects of pH and organic matter on the adsorption of bromacil and picloram by soils and 3) to determine the effects of dilute solutions of four surfactants on the adsorption of bromacil and picloram by soils. The adsorption of 2-¹⁴C-labeled bromacil on Ca²⁺, Cu²⁺ and Al³⁺ saturated montmorillonite was determined after equilibration a. 0° and 25°C. Seven concentrations of 2-¹⁴C-labeled bromacil and ¹⁴C-carboxyl labeled picloram were equilibrated without surfactant with nine Oregon soils at 25°C. Labeled bromacil and picloram at 5 ppm and 10 ppm concentration in 1% and 10% surfactant solution were also equilibrated at 25°C with eight of the above soils. After equilibrium the montmorillonite and soil samples were centrifuged and analyzed on a liquid scintillation counter for bromacil and picloram remaining in solution. The adsorption of bromacil at 25° and 0°C for each cationic saturated montmorillonite and at 25°C by the nine Oregon soils increased with concentration according to the Freundlich equation, Bromacil adsorbed on the montmorillonite increased with cation saturation in the order Ca²⁺ < Cu²⁺ < Al³⁺. The overall adsorption of bromacil was reduced when the temperature was increased to 25°C. Bromacil adsorbed on the cation saturated rnontmorillonite may occur by complexation of the Cu²⁺ or Al³⁺ cations with the ring N at the one position of the bromacil or by induction through a pH effect. The increased adsorption at the lower temperature may be due to a change in water solubility or adsorption energy. The equilibration of bromacil with the nine Oregon soils indicated organic matter was the most important parameter affecting adsorption. A highly significant correlation coefficient of 0.913 was calculated between the Freundlich K value for bromacil adsorption and organic matter. Bromacil adsorption in the low organic matter soils appeared to be directly correlated with an increase in exchangeable aluminum or pH as observed in the montmorillonite study. However, the wide range in organic matter at the intermediate level limited the opportunity to correlate bromacil adsorption with aluminum or pH. The adsorption of bromacil increased in the presence of the 1% cationic and anionic surfactants and decreased in the presence of the 1% nonionic surfactant solution compared to that without surfactant. Regardless of surfactant type the 1% surfactant solutions greatly decreased the variable effects of organic matter on bromacil adsorption in the Minam and Kinney soil series but not the Woodcock soil series. Bromacil adsorption from the 10% concentration of each surfactant type was greatly reduced compared to adsorption from the 1% surfactant solution. Strangely, the adsorption of bromacil from surfactant solution was always less in the Woodcock soil series than in the Minam and Kinney soil series. Picloram adsorption increased with concentration on the nine soils according to the Freundlich equation. A significant negative correlation coefficient of 0.667 was calculated between the Freundlich K value for picloram adsorption and pH; however, the interaction between pH and exchangeable aluminum could not be isolated. Complexation of picloram with exchangeable aluminum and adsorption of the molecular species by organic matter appeared to be the principle modes of adsorption. The adsorption of picloram by soils increased in the presence of the 1% cationic and nonionic surfactant solutions and decreased in the 1% anionic surfactant solution compared to that without surfactant. Adsorption in the presence of 1% cationic surfactant solution occurred from the molecular and ionic species as indicated by equal adsorption in the Minam (pH = 7) and Kinney (pH = 5) soil series. The 10% cationic surfactant solution decreased adsorption from that in the 1% surfactant solution; however, an inverse relationship between organic matter and adsorption was evident in the Minam and Kinney soil series. Adsorption from the nonionic surfactant solution was independent of surfactant concentration but decreased as pH increased. The 1% anionic surfactant solution effectively competed with picloram for adsorption sites. However, the 10% surfactant solution increased adsorption from that in the 1% surfactant solution possibly due to the creation of adsorption sites for picloram by the adsorbed surfactant. Increased phytotoxicity of bromacil and picloram has been observed by others when a nonionic surfactant was introduced into the spray solution. The results of this study indicate that part of the increased toxicity may be due to reduced soil adsorption of the chemicals in anionic and nonionic surfactant solutions. The addition of a cationic surfactant, on the other hand, may increase adsorption and provide poor weed control at recommended rates. Further investigation is required to determine if the herbicides adsorbed by the surfactant are available for root uptake and if the soil applied surfactant is phytotoxic.
-
18. [Article] Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird
Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions ...Citation Citation
- Title:
- Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird
- Author:
- Jones, Kristin N.
Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions and phenology driven by climate change are well-documented, yet we lack a strong understanding of how climate change will influence the demographic rates of animal populations, which directly determine the likelihood of species persistence. Land cover change, an agent of global change that is increasing in extent and intensity to meet the needs of a growing human population, can combine with climate change to stress animal populations by altering microclimatic conditions, as well as changing the availability of resources such as food and cover from predators. Thus, identifying the individual and combined effects of climate and land management practices is essential to accurately predict the responses of animal populations to global change. Intensive forest management results in land cover change by suppressing the growth of competing plant species in favor of commercial species and altering the abundance and composition of forest vegetation. In turn, changes in the abundance and composition of forest vegetation can modify local air temperatures. I hypothesized that herbicide application would alter the thermal environment for early-seral forest organisms (Chapter 2). If this were the case, then air temperature could be expected to increase in magnitude and variability along a gradient of herbicide treatment intensity. To test this hypothesis, I used iButton dataloggers to monitor air temperature at 160 nest boxes on 20 intensively managed early-seral forest stands (10.4 - 18.9) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I also measured the amount and composition of vegetation cover to test for herbicide effects on vegetation among application intensities. Using linear mixed models, I compared three measures of air temperature (mean daily minimum, mean, and maximum) and their associated coefficients of variation (CVs). Additionally, I used linear mixed models to confirm differences in total vegetation and broadleaved vegetation cover. Although mean total vegetation cover generally decreased, it did not significantly differ among herbicide treatments; in contrast, mean broadleaved vegetation cover was significantly reduced in the moderate and intensive treatments. Herbicide treatment was a significant predictor of maximum and mean temperatures, but minimum temperatures did not differ with herbicide treatment. Although there was an effect of herbicide treatment on air temperature, corrected pairwise comparisons indicated no significant differences among treatments. I note that though my power to detect statistical differences among treatments was limited, these differences were quite small (< 0.5°C) and confidence intervals were generally relatively narrow (< 1.5°C), suggesting that temperature did not differ among herbicide treatments in biologically meaningful ways. Furthermore, I did not detect an effect of herbicide treatment on temperature variability. Estimated differences in temperature variability among treatments were small (< 0.5%) and confidence intervals covered a relatively broad range of values, indicating that I did not have enough statistical power to detect effects. I found no uniform pattern in the direction (positive or negative) of the effect of herbicide treatment on temperature or CVs among treatment intensities. Daily air temperatures can strongly influence the reproductive output of early-seral songbirds if temperatures exceed physiological tolerances of offspring, decreasing physiological performance (e.g., excessively high and low temperatures can alter metabolic rates) and survival. Moreover, the abundance and composition of early-seral forest vegetation can influence songbird reproductive output through changes in nest predator communities, food resources, or both. Thus, I further hypothesized that intensive forest management practices could combine with intraseasonal air temperatures to impact reproductive output in an insectivorous cavity-nesting songbird, the House Wren (Trogolodytes aedon) (Chapter 3). If this were the case, then House Wren nest survival, the number of offspring produced, and the quality of those offspring would decline with greater management intensity and increasing air temperatures. To test these predictions, I monitored 283 nests on 24 intensively managed early-seral forest stands (8.6 - 18.9 ha) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I used data from Chapter 2 to test for combined effects of air temperature and herbicide-driven vegetation changes on House Wren reproductive output. Using linear mixed models within a model selection framework, I did not find support for combined effects of temperature and herbicide treatment on nest survival. After accounting for the effects of herbicide-driven vegetation changes on reproductive output, air temperature effects were negligible. My results suggest that post-harvest vegetation management likely does not influence the number of young produced nor their quality (as indicated by body condition) in intensively managed early-seral forests, but may influence nest survival. However, nest survival did not decline along a gradient of herbicide intensity as I expected. Instead, mean nest survival was greatest in the control and most intensively managed stands (failure was greatest in the light treatment); however, these effects were so variable as to not be statistically significant. My results suggest that post-harvest vegetation management in intensively managed forests may be linked to minor changes in microclimatic air temperatures, but that there is high variation in these effects and effects are likely small. Therefore, there appears to be limited potential for vegetation control strategies through herbicides to buffer expected climate change effects on organisms in early-seral forest. My results also suggest that the potential for combined effects of herbicide application and air temperature on early-seral cavity-nesting songbirds is limited. Under current local climate patterns, air temperature appears to exert negligible effects on House Wren reproductive output after accounting for changes in vegetation cover. The effects of herbicide-driven vegetation changes on early-seral songbirds may be large, though highly variable, and not an increasing function of herbicide intensity. These effects may be primarily predator-mediated, as indicated by the large effects of herbicide treatment on House Wren nest survival but not the number of offspring produced nor their quality. My finding of limited temperature effects on House Wren reproductive output compared to the effects of forest management intensity supports predictions that, despite increasing concerns over the impacts of advancing climate change on animal populations, land cover change driven by anthropogenic land use will continue to be the primary global change driver impacting animal populations in the near future.