Foliage Removal Research Articles

Short-Term Effects of Defoliation by Sawflies (Hymenoptera: Diprionidae) on Above- and Below-ground Growth of Three Ponderosa Pine Genotypes

Diprionid sawflies (Hymenoptera: Diprionidae) feeding on ponderosa pine, Pinus ponderosa Dougl. ex Lawson, divide food resources by feeding at different times during the season and on different aged trees. Whereas some species prefer adult trees, others have specialized on pole-size trees, and yet others on seedlings. Some attempts have been made to determine whether conifer growth compensates in response to herbivore damage as do certain nonwoody plants; however, the impact of defoliation in conifers may depend on the growth stage of trees, The presence or absence of compensatory growth in seedlings is critical because for most pine species, early growth allocation can impact growth in the long term. We induced attacks by Neodiprion gillettei Rohwer on 1-yr-old ponderosa pine seedlings to determine the effect of defoliation on above- and below-ground growth. Three pine half-sib families whose parent trees were either susceptible or resistant to pine sawflies were used in the experiment, Growth was evaluated through destructive sampling. We found no evidence of seedling compensatory growth in response to herbivores. Defoliation reduced both above- and below-ground biomass. Stable root:shoot ratios indicated that foliage removal resulted in an approximately equivalent reduction in below-ground biomass. Differences in growth patterns among genotypes were found as well.

Responses of sap flux and stomatal conductance of Pinus taeda L. trees to stepwise reductions in leaf area

and other hydraulic parameters. Increased gas exchange rates have been commonly observed in response to defoliHerbivory or artificial foliage removal has been shown ation in a range of species (McNaughton, 1983; Gold to affect gas exchange and canopy water relations. In and Caldwell, 1989; Welter, 1989; Reich et al., 1993). this study, canopy architecture and water relations in While defoliation experiments have often focused on response to progressive defoliation were examined in assimilation and growth (Alderfer and Eagles, 1976; a stand of 8-year-old loblolly pine (Pinus taeda L.) Wallace et al., 1984; Belsky, 1986), eVects on g

Foliage Removal Influences Sweetpotato Biomass Yields in Hydroponic Culture

Greenhouse studies were conducted to determine the effect of harvesting sweetpotato [Ipomoea batatas L. (Lam.)] foliage tips (terminal 15 cm) on storage root yield, edible biomass index (EBI), and linear growth rate. Plants were grown hydroponically from 15-cm vine cuttings planted in 0.15 × 0.15 × 1.2-m growth channels using a recirculating nutrient film technique system. Nutrients were supplied from a modified half-strength Hoagland solution with a 1 N: 2.4 K ratio. Foliage tips were removed at 14-day intervals beginning 42 days after transplanting. Final harvest was at 120 days after planting. At the end of the growing season, harvested foliage tips totaled 225 g/plant (fresh mass). Foliage removal significantly reduced storage root yield, shoot biomass, and linear growth rate expressed on a canopy cover basis. The EBI was higher for plants with foliage removed than for the control.

Changes in western wheatgrass foliage quality following defoliation: consequences for a graminivorous grasshopper.

We determined the effects of defoliation by a graminivorous grasshopper on the foliage quality of the C3 plant, western wheatgrass (Pascopyrum smithii [Rydb] A. Love). Additionally, we determined the effects of this defoliation upon the subsequent feeding of the graminivorous grasshopper Phoetaliotes nebrascensis Thomas (Orthoptera: Acrididae). In field and greenhouse studies, graminivorous grasshopper herbivory altered the quality of remaining western wheatgrass foliage. In the greenhouse, severe (50% foliage removal) grasshopper grazing (638 grasshoppers/m2 for 72h) resulted in decreased foliar nitrogen (-12%), carbohydrate (-11%) and water (-2.5%) concentrations, and increased phenolic concentrations (+43%). These changes were associated with decreased adult female grasshopper mass gain, consumption rate, approximate digestibility, and food conversion efficiencies. In the field, moderate (14% foliage removal) grasshopper grazing (20 grasshoppers/m2 for 20 days) led to a 10% reduction in foliar nitrogen concentrations. Foliage quality changes in the field were not associated with any reductions in grasshopper mass gain, consumption rates, food digestibility, or conversion efficiencies. The results presented here are consistent with the hypothesis that defoliation leads to a reallocation of carbon and nitrogen compounds within the plant such that foliage quality for P. nebrascensis is reduced.

Developmental Stage, Light, and Foliage Removal Affect Flowering and Bulb Weight of Easter Lily

Lilium longiflorum Thunb. `Nellie White' plants grown under 1300 μmol·m-2·s-1 maximum photosynthetic photon flux (PPF) in a greenhouse deliberately were completely defoliated when the oldest flower bud was 2, 4, or 7 cm long. Plants were then placed in growth chambers in darkness or in the light (250 μmol·m -2·s-1 PPF, 10 hours) with 25C air, along with intact plants as controls; all were harvested at the completion of flowering. Defoliation at the 2- and 4-cm bud stages resulted in complete flower abortion, with or without light. Plants defoliated at the 7-cm stage and kept in light had 60% of the flower buds develop to anthesis but depleted more scale reserves. Those defoliated at the 7-cm stage and kept in darkness had complete flower abortion; however, bulb weights remained similar to those of the intact plants kept in the light.

Phytophage effects on primary production, nutrient turnover, and litter decomposition of young Douglas-fir in western Oregon

We tested the effect of defoliating and sap-sucking phytophages on young Douglas-fir at the H.J. Andrews Experimental Forest in western Oregon. Experimental trees were subjected to manipulated abundances of a sap-sucking insect at 0–1 insect g −1 foliage or a defoliating insect at 0 –0.06 g −1 foliage. Tree mass, throughfall, litterfall, litter decomposition, and N, K and Ca turnover were measured for each tree over a 3 year period. Herbivore abundance had no effect on calculated tree growth or nutrient content. These data suggest compensatory growth and replacement of lost nutrients. Herbivory also did not significantly affect decomposition rate for exogenous Douglas-fir needle litter. Throughfall volume, N, K and Ca content, and litterfall mass were positively related ( P < 0.05) to defoliator abundance during the early growing season (April–June). At the highest defoliator abundance (causing about 20% foliage removal), turnover of N, K and Ca amounted to 15–25% of the total inputs to litter during this period. Throughfall Ca was significantly related defoliator abundance for the entire growing season (April–September). Sap-sucker feeding significantly influenced K turnover during the growing season. The results of this study support results from an eastern deciduous forest. Our study relates nutrient turnover rates to herbivore abundances, a prerequisite for modeling phytophage effects on nutrient flows.

Litter microarthropod responses to canopy herbivory, season and decomposition in litterbags in a regenerating conifer ecosystem in Western Oregon

The microarthropod community response to season, change in foliage litter quality during decomposition, and manipulated canopy herbivory by insects was measured in litterbags under 10-year-old Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, in western Oregon. Collembola accounted for 35% of the total fauna, oribatid mites for 29%, and fungivorous actinedids for 22%. The community structure was affected by responses to canopy defoliation, season, and changes in litter quality. Of 33 taxa, three were significantly more abundant under trees subject to lepidopteran defoliation (≤20% foliage removal), compared to other treatments, indicating responses to defoliator-induced changes in litter environment. Most taxa (23) showed seasonal fluctuations in abundance related to the seasonal pattern of temperature and precipitation and to the pattern of N and Ca mobilization from litterbags. Five taxa showed significant longterm trends in abundance, indicating responses to changes in litter quality, perhaps a loss of P and K. These data indicate that microarthropod communities respond qualitatively to environmental changes, including canopy defoliation. The qualitative changes can affeet decomposition processes.

The response of western juniper (Juniperusoccidentalis) to reductions in above-and below-ground tissue

Plants are balanced systems that integrate processes of carbon fixation and uptake of water and nutrients to optimize resource acquisition. Response of Juniperusoccidentalis Hook. to reductions in above- and below-ground tissue was measured to determine effects on carbon dioxide assimilation, leaf conductance, intercellular carbon dioxide, xylem water potential, foliage nutrient concentration, aboveground growth, water-use efficiency, and potential photosynthetic nitrogen-use efficiencies. Approximately 50% of the old foliage was removed and lateral roots were severed at the canopy edge in early April 1988; physiological processes were measured during three periods in the summer of 1988. Foliage removal increased rates of carbon dioxide assimilation and photosynthetic nitrogen-use efficiency, but neither increased growth nor improved water status or nitrogen concentration of remaining foliage. Cutting lateral roots reduced assimilation, leaf conductance, foliage nitrogen concentration, branchlet elongation, water-use efficiency, and photosynthetic nitrogen-use efficiency. By late August, juvenile and small-adult J. occidentalis in the cut-top treatment had compensated for foliage removal by reestablishing patterns of water-use efficiencies similar to those of control plants, which may indicate that an overall metabolic control was functioning to regulate the balance between carbon dioxide assimilation and water loss. Cutting lateral roots had a more lasting effect on efficiencies; by late August, juveniles and small adults still had significantly lower water-use efficiencies than controls.

The effects of the spatial pattern of defoliation on regrowth of a tussock grass : III. Photosynthesis, canopy structure and light interception.

The spatial pattern of foliage removal from a tussock grass can influence regrowth through effects on daily carbon gain (CERd). This field study examined the extent to which tussock photosynthetic responses to different defoliation patterns were associated with changes in whole-canopy attributes (e.g., foliage age structure, canopy light microclimate). During the spring growing season, 60% of the green foliage area was removed from individual Agropyron desertorum tussocks with scissors in different spatial patterns. These patterns represented extremes of defoliation patterns that might be inflicted by natural herbivores. Tussock photosynthesis (per unit foliage area) at high light (2000 μmol photons m-2 s-1 between 400 and 700 nm; P2000) increased following clipping with all defoliation patterns. The increases in P2000 were greater when leaves were removed from low in the tussock (older leaves) than if leaves high in the canopy (younger leaves) were removed. These relative changes of P2000 among clipping patterns paralleled the responses of CERd and regrowth from an earlier study. Furthermore, the changes in P2000 corresponded with increases in the proportion of foliage within the tussocks that was directly illuminated at midday. The greater photosynthesis of tussocks after lower-leaf removal was directly related to a higher proportion of younger foliage and a smaller fraction of foliage shaded within the tussock. In a dense canopy, such as these grass tussocks, the influence of defoliation on whole-canopy attributes may be of primary importance to whole-plant photosynthetic responses.

Forage Quality of Winterhardy Lovegrasses

Forage Quality of Winterhardy Lovegrasses

Light Quality as the Environmental Trigger for the Germination of the Fire-promoted Species Sarcopoterium spinosum L.

Summary High germination percentage after fires is usually thought to result from heat scarification or dispersal of seeds. Foliage removal by fire causes changes in light quality and soil temperature fluctuations. Here we show that a change in light quality enhances germination of the fire-promoted species Sarcopoterium spinosum L.: A change in the red to far-red ratio from 0.3 to 1.1 increases the germination percentage ten-fold. The seeds do not have a red light requirement but are inhibited by far-red radiation. Germination of S. spinosum was not enhanced by heat nor by an increase in temperature fluctuations.

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.

The Effect of Post-veneralization Temperature on Seedstalk Elongation and Flowering in Carrots1

Abstract Seedstalk height of carrot (Daucus carota L.) was reduced as the post-vernalization temperature increased from 15/21° to 27/32°C (night/day) with no significant effect on flowering and seed formation. Seedstalks of ‘Royal Chantenay ’ carrot were most affected by the high temperatures and ‘Scarlet Nantes’ were the least affected while ‘Danvers 126’ was intermediate. Few plants had macroscopic seedstalk development 6 weeks after vernalization although the temperature during this period had a permanent influence on ultimate seedstalk height. Carrots grown at 27/32° during the initial 6 weeks following vernalization and then transferred to the optimum 15/21° grew no taller than plants held at 27/32°. Vernalization temperatures of 0°, 5°, and 10° for 10 weeks did not affect the percentage of plants flowered, time of bolting, or rate of seedstalk elongation. Ultimate seedstalk height was reduced only in ‘Royal Chantenay’ vernalized at 10°. Flowering was decreased by post-vernalization temperatures of 27/32° and 2l/27°C when carrots were stored only 5 weeks at 5° but not, after storage for 10 weeks or more. Increasing the vernalization time to 10 weeks hastened the rate of bolting in all three cultivars and increased ultimate seedstalk height in only ‘Royal Chantenay’ and ‘Danvers 126.’ Temperature during the first year of root growth, foliage removal from mature roots prior to storage, and photoperiod following vernalization did not affect seedstalk elongation or flowering.

Soil Moisture Response to Several Levels of Foliage Removal on Two Utah Ranges

Highlight: Range plant clipping studies were conducted at two elevations on Utah's Wasatch Plateau during 1966 and 1967. It was found that extreme clipping treatments (complete denudation) resulted in significantly less soil moisture withdrawal than the unclipped controls at the mid-elevation location. No significant differences were found among clipping treatments at the subalpine location, however.

Foliage Removal Effects on 'Shiraz' Grapevines

All the shoots of mature irrigated 9Shiraz9 grapevines (<i>Vitis vinifera</i>) were cut back to either 2 or 6 leaves above the distal bunch for 3 consecutive seasons at one of 5 phenological stages: 1) during bunch elongation; 2) beginning of fruit set; 3) first rapid growth of berries; 4) lag phase; and 5) véraison. Each vine was cut back only once each season. Slashing to the 2-leaf level gave a lower berry sugar and skin pigmentation than did the 6-leaf level, which was not different from control vines. Response to treatment time was less consistent. Bunch weights were not altered by any time of treatment whereas bunch numbers per vine were highest on vines treated at bunch elongation. The results are interpreted in terms of relative strengths of the sinks and sources for organic nutrients. It is concluded for 9Shiraz9 vines that in general, the 6-leaf treatment is not too severe but the 2-leaf treatment is overly severe, and it is apparent that unslashed vines have more than adequate leaf area.

Foliage Removal Effects on 'Shiraz' Grapevines

All the shoots of mature irrigated 9Shiraz9 grapevines (<i>Vitis vinifera</i>) were cut back to either 2 or 6 leaves above the distal bunch for 3 consecutive seasons at one of 5 phenological stages: 1) during bunch elongation; 2) beginning of fruit set; 3) first rapid growth of berries; 4) lag phase; and 5) véraison. Each vine was cut back only once each season. Slashing to the 2-leaf level gave a lower berry sugar and skin pigmentation than did the 6-leaf level, which was not different from control vines. Response to treatment time was less consistent. Bunch weights were not altered by any time of treatment whereas bunch numbers per vine were highest on vines treated at bunch elongation. The results are interpreted in terms of relative strengths of the sinks and sources for organic nutrients. It is concluded for 9Shiraz9 vines that in general, the 6-leaf treatment is not too severe but the 2-leaf treatment is overly severe, and it is apparent that unslashed vines have more than adequate leaf area.

Root Development of Native Plants Under Three Grazing Intensities

The purpose of this study was to determine the effects of various intensities of grazing upon roots and root systems of plants native to the ponderosa pine zone of the Colorado Front Range. It was designed to ascertain the root characteristics of certain species of the plant community and any changes in root distribution induced by 17 years of moderate and heavy grazing by cattle. The cumulative effects of such grazing are also illustrated. Most studies concerning the effects of plant defoliation show that any cropping (clipping or grazing) reduces plant growth, especially root growth. The initial root and rhizome response to defoliation is the cessation of elongation (Parker and Sampson 1931, Crider 1955). Subsequent reactions to continued defoliation are reduction in root numbers and branching (Jacques 1937, Albertson, Riegel, and Launchbaugh 1953), root diameter (Biswell and Weaver 1933), and depth of soil penetration (Ruby and Young 1953, Cook, Stoddart, and Kinsinger 1958). The amount of reduction is directly related to the severity and frequency of defoliation (Graber 1931, Albertson et al. 1953, Thaine 1954). In general the degree of defoliation is more detrimental to root growth than frequency of defoliation. Crider (1955) showed that apical growth of grass roots stopped within 24 hr after the removal of 40% or more of the foliage in one operation. The time required for roots to resume growth varied directly with the degree of foliage removal. The consequences of overgrazing are apparently carried over from season to season. WVeaver

Problems of Measuring Forage Utilization on Western Ranges

In order to maintain range forage production at its highest level, and restore depletedd ranges, the better forage plants must be used properly. But what is proper use? For the practical range administrator the answer requires a knowledge of the resistance to grazing of several hundred important species which furnish the bulk of the feed and afford most satisfactory watershed protection. However, in a land that requires from 20 to 100 or more acres to support a cow yearlong, the area that can be inspected with necessary frequency by one stockman or forest ranger is so small a proportion of the whole that the actual degree of utilization each season or year is necessarily very difficult to determine. In fact, except on very small study plots or pastures, degree of utilization is comllollnoly based almost entirely on judgment acquired from experience. But when continued productivity or gradual death of a good forage grass may depend upon a difference in foliage removal of as little as 10 per cent, a more accurate measurement of utilization is necessary. That is why the Forest Service, through its Division of Range Research and six western forest and range experiment stations, is initiating a special project to formulate sound utilization standards and simple practical methods of measuring degree of forage utilization. An infinite number of questions must be answered in the setting up of utilization standards for any particular range unit. For example, what are the species that (lo or should furnish most of the forage at different seasons of the year' What are their life histories, and how (lo the different classes of livestock relish them? What is the natural plant succession, how is it affected by varying degrees of grazing, and what stage can or should be maintaine(l under grazing use? Even when proper utilization has been determined for a species or type under one set of conditions, what adjustments are necessary whene the type is depleted severely, and what precautions are necessary for extreme drought or where special land services such as watershed protection, timber production or wildlife are important or dominant? What are the absolute or relative nutritive values or poisonous properties involved ? These problems are especially difficult as a result of the wide variety of the range resource, both as to composition, form, habitat, and in production