Amount Of Foliage Research Articles

Variation in the amount of foliage on woody shoots and its effects on water relations parameters derived from pressure–volume curves

The interpretation of pressure–volume curves for woody plant material is complicated by the use of foliated twigs to derive estimates of the water relations parameters of just the foliage. In this study, the ratio of foliage to twig water in shoots of loblolly pine (Pinustaeda) was varied systematically by defoliating twigs to varying degrees prior to constructing pressure–volume curves. Results show that variation in the ratio of foliage to twig water can influence interpretation of the curves. Reducing the amount of foliage causes decreases in the estimates of apoplasmic water content. Estimates of osmotic potential at full turgor and water potential at turgor loss were less affected. When foliated and fully defoliated twigs were compared, foliated twigs had lower water potentials at the same relative water contents. This may partially explain some of the differences in the parameter estimates among the treatments. If care is taken to avoid large differences in relative foliage weight, twigs can be used to estimate water relations characteristics of the foliage. For loblolly pine though, estimates of apoplasmic water content in twigs will be lower than in single fascicles. If single fascicles are used, more samples will have to be taken to obtain the same degree of confidence about the mean as for twigs, since the coefficient of variation is higher.

Use of leaf resources by howling monkeys (Alouatta palliata) and leaf-cutting ants (Atta cephalotes) in the tropical rain forest of Los Tuxtlas, Mexico.

Use of leaf resources by a troop of howling monkeys and two colonies of leaf cutting ants was studied for an annual cycle in the rain forest of Los Tuxtlas, Mexico. Howling monkeys spent half their annual foraging time feeding on leaves; leaf-cutting ants spent at least 80% of their recorded foraging time harvesting leaves. Both herbivores preferred young leaves over nature ones, and chemical analysis showed that the protein: fibre ratio of the leaves used was correlated with these preferences. Howling monkeys used 34 tree species as leaf sources. Leaf-cutting ants used 40 plant species of which 38 were trees. Eighteen species used by Alouatta were also used by Atta; species of Moraceae and Lauraceae were among the most important in their foraging preferences. The plant species used by monkeys and ants occurred at low densities (⩽ 4.0 ind/ha). The seasonal production of leaves, the high density of leaf-cutting ant colonies at the study site, and the high amounts of young foliage harvested by the ants from tree species, and individual trees used by howling monkeys as sources of young leaves suggest that the foraging activities of Atta may represent a significant pressure upon leaf resources available to Alouatta.

Influence of Three Soybean Genotypes on Development of Voria ruralis (Diptera: Tachinidae) and on Foliage Consumption by Its Host, the Soybean Looper (Lepidoptera: Noctuidae)

Foliage consumption of three soybean genotypes (`Davis', D75-10230 and ED73-371) by nonparasitized soybean looper (SBL), Pseudoplusia includens (Walker) (Lepidoptera: Noctuidae), larvae and those parasitized by a South American strain of the tachinid, Voria ruralis Fallen, was investigated under laboratory conditions. Although there were no significant (p>0.05) differences among genotypes, parasitized and non-parasitized SBL larvae reared on the commercial cultivar Davis consumed slightly more foliage than those reared on either breeding line D75-10230 or ED73-371, but larvae reared on ED73-371 consumed the least amount of foliage. Parasitized SBL larvae consumed significantly (p =<0.05) less (ca. 40%) foliage than nonparasitized larvae, regardless of the soybean genotype. Mortality of parasitized SBL larvae (before the successful development of V. ruralis) was greatest (90%) on ED73-371 and least (37%) on D75-10230. The mean number of parasitoid puparia per SBL larva was significantly (p=<0.05) less when larvae were reared on ED73-371.

Relation between size and density in developing stands: A description and possible mechanisms

A description of stand development is presented which incorporates several ecological concepts, including: full-site occupancy; self-thinning; and the relation between the number and average size of plants in the population. Each of these concepts is integrated by a general size-density model. It is suggested that stands which are undergoing self-thinning are those which have achieved an upper limit in the amount of foliage supported. It is postulated that the predictable size-density relations in self-thinning populations can be explained on the basis of regulation and redistribution of a fixed amount of foliage among a declining number of larger individuals.

Tomato Yield Loss as a Result of Simulated Colorado Potato Beetle (Coleoptera: Chrysomelidae) Feeding

Tomato crop losses resulting from feeding by the Colorado potato beetle, Leptinotarsa decemlineata (Say), were estimated. Because of the difficulty in restricting adult beetle movement, feeding was simulated by removing foliage three times a week. The quantity of foliage removed was calculated from a model developed earlier. The effects were measured of foliage removal by the offspring of simulated beetle densities of 0.0006, 0.002, 0.006, 0.017, 0.05, 0.15, 0.45, and 1.35 fertile female beetles per plant at the beginning of the season on fruit weight and number of a determinate and an indeterminate tomato cultivar. Regression equations provided an excellent projection of crop losses. The indeterminate cultivar had significant yield loss above a level of 0.002 initial females per plant, and the determinate cultivar above a level of 0.017 initial females per plant. Yields accumulated over 14 weeks showed when significant yield reduction occurred. For the determinate cultivar at harvest time, the yield was reduced significantly at initial beetle levels of ca. 0.05 females per plant and higher. For the indeterminate cultivar, 0.05 females per plant had no significant effect on yield until week 8 of harvesting.

Tree-crown defoliation measurement from digitized photographs

Sequential color slides of a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) tree were taken over several years to record the progression of crown defoliation by Douglas-fir tussock moth (Orgyiapseudotsugata McDunnough) and foliage recovery. The slides were digitized using a microdensitometer and analysed with a GEMS-300 image analysis system in an effort to detect changes in the amount of crown foliage. Digital images were successfully registered (overlaid) to standardize comparisons of the tree-crown profile in the various photographs. Image analysis algorithms developed for airborne or satellite multispectral scanner data were used to detect changes in crown profiles. The decrease in the amount of defoliation over time after the initial severe insect attack, estimated by a variable threshold technique, was similar to ocular ground-based estimates by well-trained observers. The supervised maximum-likelihood classification technique was found not suitable in this study.

Bunchgrass architecture, light interception, and water-use efficiency: assessment by fiber optic point quadrats and gas exchange.

The bunchgrass growth form, which is very prominent in water-limited environments, can result in considerable self-shading of photosynthetically active foliage. The consequences of this growth form for light interception and water-use efficiency (photosynthesis/transpiration, P/T) were investigated for two Agropyron species which differ in tussock density and degree of self-shading. During the period of most active gas exchange, the tussocks were very compact and photosynthesis of shaded foliage was markedly light-limited. Stomatal control of older shaded foliage was poorly attuned for water-use efficiency. At low light, P/T decreased and intercellular CO2 concentrations increased. Despite differences in architecture and amount of shaded foliage, P/T of whole tussocks under ambient field conditions did not differ between these species. Partial defoliation decreased, rather than increased, P/T, primarily as a result of the poor photosynthetic light harvesting by the remaining foliage. Despite self-shading, the architecture of widely-spaced bunchgrasses provides for interception of as much direct beam solar radiation as is calculated for a rhizomatous grass occupying an area six-fold greater than the ground area underneath the canopy of these bunchgrasses.

Thinning and nitrogen fertilization effects on sapwood development and relationships of foliage quantity to sapwood area and basal area in Douglas-fir

A 24-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand was treated with various levels and combinations of nitrogen fertilization and thinning. Over a period of 5–9 years after treatments, trees were sampled to determine effects on foliage quantity and sapwood characteristics at different stem heights together with their relationships. Sapwood width remained relatively constant up the stem where heartwood was present, but the number of annual rings it contained decreased with height. The sapwood width at breast height (bh) increased with stem diameter; treatments had little effect on percent sapwood at bh. The ratio of foliage mass to sapwood cross-sectional area changed for different portions of the crown and was lower when based on sapwood area at bh than at base of live crown. Significant linear relationships of foliage mass and area to sapwood area at bh were found, but relationships of foliage to basal area (bh) were just as close for all treatments; treatments significantly affected these relationships with control trees having the lowest regression slopes.

Measurement of healthy and diseased haulm area for assessing late blight epidemics in potatoes

The advantages of assessing disease severity by visual grading and by measuring healthy and diseased plant area were compared in four mild to moderate late blight epidemics during spring and in two severe epidemics during autumn in Israel. Disease progress curves obtained through visual grading showed a continuous increase, but the area of lesions tended to fluctuate during the cropping season and often reached a maximum in plots in which the total amount of foliage was also largest. The healthy haulm area differed with disease intensity and undefined seasonal and cultural influences. The decrease in healthy haulm area was not related to expansion of the blighted area only, but also to the breaking of plants at stem lesions. This phenomenon was especially evident in the warm spring season and was not determined by visual grading of disease severity. Each kind of assessment revealed different features of the epidemics and suited different applications. Visual grading enabled the easiest comparison of epidemic patterns. Lesion areas reflected patterns of inoculum potential, while healthy haulm areas reflected the integrated influences of factors affecting the crop and disease and thus provided useful data for simulating epidemics and for estimating yield losses.

Effects of thinning and nitrogen fertilization on growth of Douglas-fir: relative contribution of foliage quantity and efficiency

The aboveground biomass of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and annual production over 7 years was studied in relation to thinning and nitrogen fertilization. Biomass yield of both treatments increased during the first 3–4 years then decreased for fertilization but not with thinning. Treatments doubled biomass production of individual trees over the study period when applied separately and quadrupled it when combined. Annual biomass production per unit of foliage (E) increased during the first 3–4 years, but was at or below control level after 7 years. The increased E accounted for 20, 37, and 27% of the stemwood dry matter response to thinning, fertilization and the combined treatments, respectively; the remainder was attributed to an increase in foliage biomass. Thinning, but not fertilization, influenced distribution of radial growth along the stem, increasing growth only below the top one-third of the stem. This pattern was related to crown development.

Phenolic Compounds in Foliage of Commercial Tomato Cultivars as Growth Inhibitors to the Fruitworm, Heliothis Zea1

Abstract Semi-purifled extracts of phenolics from foliage of tomato (Lycopersicon esculentum Mill.) inhibit larval growth of the fruitworm, Heliothis zea (Boddie), when added to artificial diets for this insect pest. The degree of inhibition of growth (dose-response) is directly related to the quantity of total phenolics in extracts added to diets, whether the extracts are of equivalent amounts of foliage from different cultivars or of foliage pooled from several cultivars added in serial dilution. Dose-responses for extracts were equal to those obtained with pure chlorogenic acid or rutin, major phenolic constituents of tomato foliage. Also, equivalent quantities of phenolics from 5 different cultivars inhibited larval growth equally when added to diets. These 3 sets of observations show that isolated tomato foliar phenolics affect H. zea larvae quantitatively, with no measurable qualitative differences between cultivars. When 2nd instar larvae were reared on excised leaflets from several cultivars of field-grown tomatoes, significant differences in larval growth between cultivars were obtained, which were consistent through two years. However, significant relationships between foliar phenolic content and larval growth were not obtained, partially because of the highly variable nature of phenolic content within and between plants. Our results suggest that phenolics in tomato foliage at the minimum contribute a substantial background level of antibiosis to H. zea.

Grass scorch due to pot ale

SUMMARYGrass scorch sometimes occurs when pot ale, a waste product of malt whisky distilling, is used as a liquid fertiliser. Experiments performed on grass turves show that a high concentration of solids in the pot ale, and a large amount of foliage on the sward result in higher amounts of scorch, as determined by visual assessment. Sward yield is independent of the amount of leaf scorch but appears to be linked to the proportion of dead tillers or plants in the sward. It is suggested that leaf scorch itself does not limit yield, but if the scorching compound runs off foliage and acts against roots then tiller or plant death may occur, accompanied by a yield loss. This interpretation may help to explain some conflicting evidence on scorch effects in the literature.

The role of Douglas-fir stem sapwood and heartwood in the mechanical and physiological support of crowns and development of stem form

The mechanical and physiological support of a tree's crown is the principal function of its bole. A simple model for Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) of different crown classes explains much of the observed differences in stem form development. Sapwood cross-sectional area at any height on the bole of the tree was found to be related linearly to the amount of foliage above that point; however, in large trees the sapwood area needed to supply transpiring foliage with water is insufficient to provide mechanical support. The combination of sapwood and heartwood was found to provide the stem form that would be expected to ensure uniform resistance to bending by the wind.

Comparison of early and late timing of spray applications for control of spruce budworm in Quebec

An experiment was conducted in the Lower St. Lawrence region of Quebec in 1978 to determine (1) the validity of aerial spray applications of aminocarb timed against emerging L2 larvae of the spruce budworm (Choristoneurafumiferana (Clem.)) as well as (2) the relationship of timing spray applications and success of treatment. Two successive applications timed at peak L4–L5 (regime C) gave better results than similar treatment at peak L2 and peak L4 (regime A). Reduction in larval population density, and the amount of foliage saved due to regime C were almost twice that obtained with regime A.

Density and Developmental Stage of Range Caterpillar Hemileuca oliviae Cockerell, as Affected by Topographic Position

Population density and larval development of range caterpillar (Hemileuca oliviae Cockerell) were influenced by topographic position. Larval populations on ridges and upper slopes were in earlier developmental stages and had lower densities than populations on swales and lower slopes. Plant species composition, vegetative productivity, ground cover, and soil surface temperatures were suggested as habitat factors that might explain these differences. The range caterpillar, Hemileuca oliviae Cockerell, is a major insect pest on approximately 7.7 million ha of shortgrass prairie in New Mexico and adjacent areas of Colorado, Oklahoma, and Texas (Ainsley I9 10, Watts and Everett 1976). Blue grama (Bouteloua gracilis (H.B.K.) Lag. ex Steud.), the dominant forage species of these prairies, appears to be the preferred food source of H. oliviae, although it also feeds on other grasses (Capinera 1978, Wildermuth and Caffrey 19 16). Since 1885 there have been at least four major range caterpillar outbreaks. The most recent outbreak was first noticed around 1960 and has been characterized by population fluctuations due to natural mortality factors and insecticide suppression programs (Watts and Everett 1976). The impact of the range caterpillar on rangeland is expressed in three major ways (Huddleston et al. 1976). (1) The larvae, which grow from 5.0 mm to almost 100 mm in 8 to 12 weeks, consume large amounts of foliage. While feeding, larvae waste additional forage when they cut off parts of leaves without eating them. (2) Grass not eaten by the caterpillars is rendered unpalatable to livestock by the irritating spines on the larvae and on their cast skins, which remain attached to the grass throughout the remainder of the growing season and into the winter. (3) The damaged rangeland is subject to soil erosion by wind and water, which has long-term implications. Watts and Everett (1976) suggested that environmental factors such as soil type, plant productivity, effective precipitation, and ground cover affect population density of range caterpillar. Field researchers conjectured that plant species composition, plant productivity and ground cover are related to topographic position in the rolling terrain of east central New Mexico. Field researchers also observed that there were more range caterpillar larvae in swale and lower slope areas than on adjacent ridges and upper slopes. Additionally, larvae in swale and lower slopes were observed to be in later developmental stages than larvae on upper slopes and ridges. This study was designed to confirm these observations Beavis, Owens, Bellows, and Huddleston are with the Department of Entomology and Plant Pathology, New Mexico State University, Las Cruces, New Mexico 88003; Ortiz is with the Department of Experimental Statistics and Ludwig with theDepartment of Biology of the same university. This article was submitted as Journal Article 774, New Mexico Agricultural Experiment Station, Las Cruces, New Mexico. It reports on work supported in part by USDA/SEA/CR Research Grant 801-15-35. Manuscript received June 4, 1980. JOURNAL OF RANGE MANAGEMENT 34(5), September 1981 relating vegetation and range caterpillar populations to topography.

White-Tailed Deer Diets from Pastures in Excellent and Poor Range Condition

A study was initiated in August, 1975, to examine the forage available to and diet composition of white-tailed deer on pastures of excellent and poor range condition at the Sonora Research Station near Sonora, Texas. Grass and forb standing crop and deer feeding time on these two forage classes were considerably higher on the pasture in excellent range condition than that in poor range condition. Browse standing crop and feeding time was greater from the pasture in poor range condition. The Merrill 4-pasture grazing system appeared to increase the availability and use by deer of grass regrowth. Yearly averages of crude protein and phosphorus were higher in diet samples collected from the pasture in excellent range condition. Digestible energy levels were similar between pastures when averaged over the l-year period. Digestible energy levels in diets were, however, higher from the excellent condition pasture in every season except winter. In winter, deer fed primarily on the foliage of oak on excellent condition range; but on the pasture in poor range condition, deer used large amounts of foliage and mast from juniper and dead leaves of persimmon in addition to oak foliage. Juniper and persimmon apparently contributed to the higher digestible energy levels observed on the pasture in poor range condition during the winter season. Energy may be a major nutrient limiting deer production on the Edwards Plateau. In pristine times, the Edwards Plateau of Texas was considered a grassland steppe but has since been invaded by woody perennials (Krebs 1972). It now contains a diverse community capable of supporting many kinds of plants and animals. Among the endemic The authors are assistant professor, Department of Range and Wildlife Management, Texas Tech University, Lubbock 79409, and research associate and professor in charge, Texas Agricultural Experiment Station, Sonora, 76950. At the time of this research Bryant was research assistant, Department of Range Science, Texas AM Reardon et al. 1978), our objectives were to quantify the relationships of excellent vs. poor condition range in terms of quantity of forage available to deer and the botanical composition and nutritional quality of their diets. Study Area and Methods Two 8-ha study sites were selected at the Texas A&M University Agricultural Research Station located 45 km southeast of Sonora, Texas. One study site was selected in a pasture representing excellent range condition and the other poor range condition (Fig. I). The pastures have had different histories of use and manipulation (Table I). Topography of the Sonora Station is rolling with steep breaks along some drainages. Soils are generally stony clays and clay loams. Precipitation averages 61 cm annually with peaks in May and September.

Effects of Earthworm Inoculation Upon the Root Growth of Direct Drilled Cereals

SUMMARY (1) Normal field populations of deep-burrowing or shallow-working earthworms were inoculated into small plots that had been sterilized with dichloropropanedichloropropene (D.D. ?), on a site that had been directly drilled with cereals for six successive years. Inoculation with deep-burrowing species (Lumbricus terrestris and Allolobophora longa) significantly increased barley plant populations and the weight and depth of roots and height and amount of foliage. Most of the straw debris on the soil surface was incorporated into the soil in the earthworm-inoculated plots, compared with very little in plots with no earthworms. Yield was also increased significantly by earthworm inoculation. (2) In box experiments, comparing the influence of natural and simulated earthworm burrows on root growth, it was shown that, although the provision of channels for roots to grow was important, the improved root growth was also partially due to the lining of the burrows with more available nutrients than the surrounding soil. Other experiments demonstrated that the nitrogen from dead earthworms was insufficient to account for increased root growth. Ways of encouraging the build-up of earthworm populations in direct drilled land are discussed.

A Method of Predicting the Defoliation Threat to Pines by the Pine Tree Emperor Moth, Nudaurelia cytherea, by Counting Dead Moths on the Forest Floor

SYNOPSIS A method enabling the early determination of the future defoliation threat to pine trees by larvae of the pine tree emperor moth, Nudaurelia cytherea, is presented. The method is based firstly on the determination of the number of larvae, derived from the number of dead moths present on the forest floor after the termination of their flying season, which can be expected in a particular stand and secondly on the determination of the amount of foliage available as food for the larvae concerned; these data, together with those obtained from earlier studies, are combined in a formula which enables a prediction of the percentage defoliation threat that can be expected in a particular stand. A figure enabling the direct reading of the amount of foliage of Pinus radiata, ranging from 2 to 20 m in height, is given. The method has been tested successfully in some plantations in the Western Cape. It is accepted that with further field experience modifications to the formula may be required.

Movement of Tritiated Water through Young Citrus Plants

Water movement through different organs of 1-2 year old Sour Orange seedlings was studied by using tritium as a tracer injected into the nutrient solution. The activity of the leaf tissue water of plants free to exchange water with the atmosphere reached only 60-70% of the nutrient solution even after long periods exceeding 30 h, whereas in plants exposed to dry air the activity approached equilibrium with the solution. Turnover of water was less rapid in the laminae than in the midveins of the leaves, in both cases the rate being a function of the amount of foliage on the plant. A reduction in transpiration rate effected by plastic covering, silicone coating, or abscisic acid spray was clearly indicated by a lowered level of tritium activity in the plant tissue.

The effects of the date of defoliation of the seed potato crop and the storage temperature of the seed on subsequent growth: 2. Field growth

SummarySix experiments carried out over 3 years investigated the effects of the date of defoliation of the seed potato crop and the storage temperature of the seed on the growth of the subsequent ware crop.Defoliation of the seed crop in July tended to reduce foliage dry weight particularly at later harvests, and in two experiments in 1974 affected the tuber yield. In one of these experiments defoliation in July resulted in a lower yield than from defoliation in August, while in the other experiment it significantly reduced the bulking rate of the ware crop and gave a lower yield of King Edward at the final harvest. Storage of the seed tubers at low temperature (2–3 °C) tended to increase the amount of foliage produced but only in two out of six experiments was there any effect of storage temperature on yield; in both storage at low temperature gave the lowest yield.There was a significant relationship between the effect of storage temperature on tuber yield and its effect on the time to emergence of 50% of the plants. It is suggested that in these experiments a combination of late planting and weather conditions before emergence reduced the effect of storage temperature on the time to 50% crop emergence and therefore reduced its effect on tuber yield.In 1973 when there was a large effect of storage temperature on yield, there was a significant relationship between the tuber yield of the ware crop and the physiological age of the seed measured as accumulated day degrees above 0 °C from dormancy break to planting.