Tree Budburst Research Articles

Will climate change have a different impact on different trophic levels? Phenological development of winter moth Operophtera brumata and its host plants

Will climate change have a different impact on different trophic levels? Phenological development of winter moth <i>Operophtera brumata</i> and its host plants

Adaptation of the timing of bud burst of Norway spruce to temperate and boreal climates

The adaptation of the annual cycle of development of boreal and temperate trees to climatic conditions has been seen as a result of stabilizing selection caused by two opposite driving forces of natural selection, i.e. the tolerance of unfavorable conditions during the frost exposed season (survival adaptation) and the effective use of growth resources during the growing season (capacity adaptation). In this study, two theories of the effects of climate on the adaptation of the timing of bud burst of trees were evaluated. This was done with computer simulations by applying a temperature sum model for predicting the timing of bud burst of different Norway spruce genotypes on the basis of air temperature data from various climatic conditions. High geographical variation in the temperature response of bud burst, typical for Norway spruce, was included in the theoretical analyses. The average timing of bud burst and the corresponding risk of occurrence of damaging frost during the susceptible period after bud burst were calculated for each genotype in each climate. Two contrasting theories of the stabilizing selection were evaluated, i.e. the overall adaptedness of each genotype was evaluated either 1) by assuming a fixed threshold for the risk of frost damage, or 2) by assuming a tradeoff between the risk of frost damage and the length of the growing season. The tradeoff assumption produced predictions of between provenance variation in bud burst which correspond more closely with empirical observations available in literature, compared to the fixed threshold assumption.

The role of monoterpenes in resistance of Douglas fir to western spruce budworm defoliation.

We conducted defoliation experiments with 7- to 8-year-old clones of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco var. glauca] to assess the role of monoterpenes as a resistance mechanism to western spruce budworm (Choristoneura occidentalis Freeman) defoliation. The grafted clones were derived from mature trees that showed resistance or susceptibility to budworm defoliation in the forest. All clones were exposed to either budworm defoliation or nondefoliation treatments in 1998 and 1999 under greenhouse conditions. We found that the total concentration of monoterpenes in current-year foliage varied greatly between two consecutive years in clones in the greenhouse and in their corresponding mature trees in the forest. Fractional composition of different monoterpenes was similar between different years and between clones and mature trees, indicating genetic control of this trait. Two different defoliation experiments were conducted to assess the importance of budburst phenology as a factor determining host plant resistance. In the 1998 experiment, budworm feeding was matched to the budburst of each individual plant. Monoterpene concentration was high in 1998, and budworm potential fitness was greater on clones from the resistant mature trees that had lower concentrations of total monoterpenes. In the 1999 experiment, budworm feeding was matched to budburst of the whole population of plants in order to mimic conditions similar to insects feeding on trees in the field. The concentration of monoterpenes was low in 1999, and budworm fitness was not related to monoterpenes. Total monoterpene concentration was negatively related to foliar nitrogen concentration, suggesting that C/N balance may affect monoterpene synthesis in needles. However, tree growth was not related to total monoterpene concentration. We concluded that expression of differences in budworm resistance among Douglas fir genotypes might be caused by interactions among multiple resistance mechanisms such as needle monoterpenes and tree budburst phenology.

A Unified Model for Budburst of Trees

Accurate plant phenology (seasonal plant activity driven by environmental factors) models are vital tools for ecosystem simulation models and for predicting the response of ecosystems to climate change. Since the early 1970s, efforts have concentrated on predicting phenology of the temperate and boreal forests because they represent one-third of the carbon captured in plant ecosystems and they are the principal ecosystems with seasonal patterns of growth on Earth (one-fifth of the plant ecosystems area). Numerous phenological models have been developed to predict the growth timing of temperate or boreal trees. They are in general empirical, nonlinear and non-nested. For these reasons they are particularly difficult to fit, to test and to compare with each other. The methodological difficulties as well as the diversity of models used have greatly slowed down their improvement. The aim of this study was to show that the most widely used models simulating vegetative or reproductive phenology of trees are particular cases of a more general model. This unified model has three main advantages. First, it allows for a direct estimation of (i) the response of bud growth to either chilling or forcing temperatures and (ii) the periods when these temperatures affect the bud growth. Second, it can be simplified according to standard statistical tests for any particular species. Third, it provides a standardized framework for phenological models, which is essential for comparative studies as well as for robust model identification.

WHY DOES EARLY-SEASON HERBIVORY AFFECT SUBSEQUENT BUDBURST?

Delays in budburst in the year following herbivory have previously been attributed to a defensive response to early-season herbivory or localized resource deficien- cies (resource availability hypothesis) limiting bud development. We carried out field ex- periments to test the resource availability hypothesis as well as the crown architecture hypothesis, which attributes changes in the time of budburst in the year following herbivory to changes in the proportion of different bud types. We examined predictions from these hypotheses using a defoliator, Choristoneura fumiferana; a defoliator/stem feeder, Zeira- phera canadensis; and a stem galler, Adelges abietis; on white spruce, Picea glauca. The time of budburst and final leaf size of unexploited midcrown shoots of white spruce were compared to those of adjacent exploited shoots. We also evaluated budburst in a manipulated field study, in which tree growth was reduced through root pruning and increased through fertilization. Partial defoliation by C. fumiferana and Z. canadensis did not affect budburst, but did result in smaller leaves. Almost complete defoliation of shoots by C. fumiferana and galling by A. abietis resulted in delayed budburst. Reductions in leaf size were directly related to the amount of herbivory (i.e., low or high) by C. fumiferana and Z. canadensis. Budburst of trees whose growth rate had been decreased by root pruning or increased by fertilizing occurred later and sooner, respectively, than budburst on unmanipulated trees. The time of budburst was inversely correlated with foliar nitrogen and water content and the length of unexploited shoots. These results supported the resource availability hypothesis. The in- fluence of resource availability on time of budburst was observed at the shoot, branch, and whole-tree levels. When >50% of stems were destroyed by Z. canadensis, budburst occurred earlier or at the same time in the following spring. This was due to the production of basal buds, which burst before all other buds on a shoot. The production of early-bursting basal buds more than compensated, or just compensated, for a small delay in budburst of terminal, distal-lateral, and medial-lateral buds. Thus, changes in the time of budburst in the year following herbivory were due to changes in crown architecture as well as to changes in resource availability. We predict that increased intra-tree heterogeneity in the time of bud- burst should make P. glauca more, rather than less, susceptible to two of the herbivores studied because of the presence of a highly nutritious food source, newly burst buds, for a longer period of time. We suggest that the influence of previous herbivory on the time of budburst in the next growing season is a commonly overlooked factor that may have a large influence on herbivore abundance and distribution.

Air and soil microclimates of deciduous woodland compared to an open site

Forest microclimate has been monitored continuously for more than 3 yr at two sites in deciduous woodland at Wytham Woods, Oxford, UK. Automatic weather stations provided hourly data for wind speed, photosynthetically active radiation (PAR), vapor pressure deficit (VPD) and, in particular, temperature at different heights above the ground and at different depths in the soil. These data were compared with values from an open site at the same location. Air temperatures could be up to 3°C lower under the canopy than at the open site under sunny conditions in summer, but the differences averaged 0.6 and 0.9°C during the summer months and barely differed over winter. Effects of forest cover on soil temperatures were much greater and under the woodland they neither fell below 0°C nor rose above 20°C even at 5 mm depth, in contrast to temperatures under bare earth and grass. The temperature of a grass tussock at the soil surface under the canopy was intermediate between soil and air temperature; in comparison to grassland plants at an open site it experienced a much smaller range of temperatures. The differences between both soil and air temperature under the canopy and in the open were significantly correlated with solar radiation, presence or absence of canopy leaves and wind speed. Soil water content had no significant effect on soil temperature, partly because thermal diffusivity was relatively insensitive to it and partly because soil heat flux was small. Seasonal changes in canopy leaf cover caused a large peak of PAR under the canopy in spring prior to bud burst in trees and a much smaller one in the autumn after leaf fall. Wind speed under the canopy was also affected by the presence of leaves and was proportionally lower in summer and autumn than winter and spring.

Effects of climatic warming on northern trees: Testing the frost damage hypothesis with meteorological data from provenance transfer experiments

According to a hypothesis presented recently the predicted climatic warming will cause premature bud burst of trees in Finnish conditions during mild spells in mid‐winter and heavy frost damage during subsequent periods of frost. The full stocking and high productivity of northern Finnish provenances of Picea abies (L.) Karst. grown in central and southern Finland for several decades seemed to conflict with the frost damage hypothesis, because the increase in the annual mean temperature involved in the most distant provenance transfers exceeded the predicted increase in the annual mean temperature in northern Finland. A calculation method using air temperature data from provenance transfer experiments was developed for testing the frost damage hypothesis. The method was applied with temperature data from Finnish provenence transfer experiments, assuming for northern Finland both (1) a uniform warming scenario of 4.7°C throughout the year and (2) a non‐uniform warming scenario in which the same mean annual...

Gypsy Moth Population Sizes and the Window of Opportunity in Spring

Many outbreaking species of forest Lepidoptera emerge from winter diapause at the time of host budburst. I tested the hypothesis that variable synchrony between insect emergence and tree budburst influences variability in population size of the gypsy moth (Lymantria dispar L.). Since long-term records of insect and plant phenology are not available for testing this hypothesis I constructed models to estimate the timing of insect and leaf emergence in spring. A model of the rate of starvation of newly hatched larvae was also created, to estimate the time between egg hatch and death from starvation. The proportion of larvae alive on days with weather suitable for seeking hosts and on which host leaves were available was estimated for each of 23 years using these models

A variable insect–plant interaction: the relationship between tree budburst phenology and population levels of insect herbivores among trees

Ecological EntomologyVolume 17, Issue 1 p. 91-95 A variable insect–plant interaction: the relationship between tree budburst phenology and population levels of insect herbivores among trees MARK D. HUNTER, Corresponding Author MARK D. HUNTER Pennsylvania State UniversityDr M. D. Hunter, Department of Entomology, Pesticide Research Laboratory, Pennsylvania State University, University Park, PA 16802, U.S.A.Search for more papers by this author MARK D. HUNTER, Corresponding Author MARK D. HUNTER Pennsylvania State UniversityDr M. D. Hunter, Department of Entomology, Pesticide Research Laboratory, Pennsylvania State University, University Park, PA 16802, U.S.A.Search for more papers by this author First published: February 1992 https://doi.org/10.1111/j.1365-2311.1992.tb01046.xCitations: 131AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume17, Issue1February 1992Pages 91-95 RelatedInformation

Does climatic warming increase the risk of frost damage in northern trees?

Abstract. The effect of climatic warming on the timing of bud burst and the subsequent risk of frost damage on trees in central Finland was assessed with the aid of a computer model, 73 years of temperature data and a climatic scenario corresponding to doubled level of atmospheric CO2. In general, climatic warming hastened bud burst, due to ontogenetic development during warm spells in autumn, winter and spring. During the years with the warmest winters in the scenario conditions: (a) bud burst took place during mid‐winter; and (2) depending on the year, the trees were subsequently exposed to temperatures between −27 and −10°C. This finding suggests that the risk of frost damage to trees will be increased if the predicted climatic warming occurs. Because of the assumptions used in the model, the results are not conclusive, but they do point out the importance of further experimental studies on genetic and environmental regulation of timing of bud burst in trees.

Outbreaks of the winter moth on Sitka Spruce in Scotland are not influenced by nutrient deficiencies of trees, tree budburst, or pupal predation.

Since the early 1980s, the winter moth, Operophtera brumata L. (Lepidoptera: Geometridae) has emerged as a serious pest of Sitka Spruce, Picea sitchensis Bong. plantations in southern Scotland. Outbreaks are characterised by susceptible sites within plantations which can occur immediately adjacent to resistant sites. We investigated the level of some nutrients in the trees, the date of budburst of the trees, and the numbers of some potential predators of winter moth pupae. None could satisfactorily explain outbreak patterns. Although foliage analysis demonstrated that many trees were marginal or deficient in phosphorus, nitrogen and potassium, these deficiencies were not related to the susceptibility of a site. Within sites, the numbers and weights of O. brumata were positively related to phosphorus content and negatively related to calcium content of foliage. Other evidence suggests, however, that these correlations may not represent direct effects of phosphorus and calcium on larval growth and survival. Date of budburst, which commonly determines susceptibility of deciduous hosts to O. brumata, was unrelated to density, and pupal predators were more, not less, abundant in susceptible sites. Although it is difficult to distinguish between factors that initiate outbreaks and those that maintain them, these data suggest that nutrient deficiencies of trees, budburst date, and the distribution of pupal predators of the winter moth cannot explain patterns of outbreak of the winter moth on spruce.