Predicted changes in the synchrony of larval emergence and budburst under climatic warming

Summary The impact of climatic warming on the synchrony of insect and plant phenologies was modelled in the case of winter moth (Operophtera brumata) and Sitka spruce (Picea sitchensis) in the Scottish uplands. The emergence of winter moth larvae was predicted with a thermal time requirement model and the budburst of Sitka spruce was predicted from a previously published model (Cannell and Smith 1983) based on winter chilling and thermal time. The date of emergence of winter moth larvae was predicted to occur earlier under climatic warming but the date of budburst of Sitka spruce was not greatly changed, resulting in decreased synchrony between larval emergence and budburst. The general question of how a change of climate might affect phenological synchrony and insect abundance is discussed.     

The use of ion exchange resin bags to assess N availability beneath pure spruce and larch + spruce stands growing on a deep peat soil

Summary Mineral N accumulation by ion exchange resins placed beneath the forest floor layer of pure spruce and mixed larch + spruce stands indicated greater N availability in the presence of larch. Findings were in qualitative agreement with those of previous incubation experiments.     

Chemoreception of amino acids by female fourth- and sixth-instar larvae of the spruce budworm

An electrophysiological approach was used to record the responses of maxillary styloconic sensilla of fourth- and sixth-instar larvae of the spruce budworm Choristoneura fumiferana to 14 amino acids. One cell in the lateral styloconic sensillum was identified as an amino acid-sensitive neuron. All of the amino acids tested, except l-proline and l-arginine, were detected by this cell. Arginine did not evoke a response from either the medial or lateral styloconic sensilla. Proline evoked responses from a cell in the medial styloconic sensillum. It is known from previous behavioural work that l-proline is a phagostimulant and l-valine inhibits feeding in Choristoneura; we thus further characterized the responses to these two amino acids. For both instars, l-proline was detected as low as 0.001 mmol/l and the maximal response was at 50 mmol/l. Stimulation of fourth- and sixth-instar larvae with l-valine showed that the maximum firing frequency was obtained at 1 mmol/l. Above and below this concentration, firing frequency decreases. Sensory responses to the amino acids stimuli did not correlate with known behavioral responses to similar stimuli.     

Air temperature,tree growth,and the northern and southern range limits to Picea mariana

Abstract. Many models that simulate the long-term response of forests to climatic change use the assumption that northern and southern range limits are caused by the deleterious effects of cold and hot air temperatures, respectively, on individual tree growth and that growth declines symmetrically with air temperatures above and below some optimal value in between these extremes. To test the validity of this assumption, we combined physiological data for black spruce, Picea mariana, growing near the treeline in subarctic Quebec with a model of the biophysical and biochemical effects of temperature on photosynthesis. The physiological conditions allow black spruce to grow over a wider range of air temperatures than is reflected in its geographic distribution. In particular, the physiological data suggest that the northern range limit of black spruce is not caused by the direct effects of cold growing-season air temperatures on tree growth and that growth is optimal, with respect to temperature, at the southern range limit. While pollen data indicate large geographic changes in spruce abundance with past climatic changes, the current analyses suggest that the direct effect of air temperature on individual tree growth has not caused these changes. Until we better understand the effects of air temperature on ecological processes, the efficacy of climatic change analyses must be evaluated in terms of model assumptions.     

Possibilities and constraints in the regeneration of trees from cotyledonary needles of Picea abies in vitro

Although use of embryonic or seedling tissues for mass clonal micropropagation in vitro in conifer reforestation programmes is questionable, there is a potential application in the regeneration of plants from scarce and costly seed derived from controlled pollination. In addition, in vitro culture shortens considerably the lag phase in numbers during the initial stages of vegetative propagation via rooted cuttings. Successive steps of the present technique are described whereby cotyledonary needles (secondary explants) were subcultured on a hormone-free medium after administration of cytokinin or auxin to 14-day-old seedling (primary) explants of Picea abies. For bud induction, N⁶-benzyladenine (BA) was applied either as a short-duration (3 h), high-concentration (125 μM) pulse or by vacuum infiltration and incubation in a BA-containmg (5 μM) infusion medium. Induced adventitious shoots were elongated with the aid of far-red light and rooted in vivo after a long-duration (12 h), high-concentration (625 μM) application of indolebutyric acid. Pulse and infusion treatments resulted in the induction of greater numbers of adventitious buds (average of 12 per needle) over a three to four week shorter culture period than was the case with the conventional inclusion of growth regulators in the agarified medium. No exogenous auxin was required in the bud-induction programme; its inclusion even at nanomolar levels promoted histo- rather than morphogenesis. In cotyledonary needles, to the primary explants of which BA was applied as a pulse or by infusion, the cell divisions which gave rise to the meristemoids from which adventitious buds were produced, appeared to commence mainly in undifferentiated hypodermal layer cells but also in the mesophyll immediately below. By contrast, where BA was incorporated in the agarified medium the first divisions occurred mainly in cells of the epidermal layer. A number of factors affected plantlet regeneration, for instance seed variability, age of seedlings, and mode of application of growth substances. It should also be accepted that the xeromorphic nature of the conifer leaf might impose physiological and morphological constraints on its culture in vitro that could militate against easy morphogenic manipulation. It is deemed essential that the current mean ratio of regenerated plants to cotyledonary needles of 1:1 be increased 10 to 20 fold in order to approach commercial feasibility.     

Evidence of a spatial auto‐correlation in the browsing level of four major European tree species

1. The contribution of spatial processes to the spatial patterns of ecological systems is widely recognized, but spatial patterns in the ecology of plant‐herbivore interactions have rarely been investigated quantitatively owing to limited budget and time associated with ecological research. Studies of the level of browsing on various tree species reported either no spatial auto‐correlation or a small effect size. Further, the effects of disturbance events, such as hurricanes, which create large forest openings on spatial patterns of herbivory are not well understood.
2. In this study, we used forest inventory data obtained from the federal state of Baden‐Württemberg (Southern Germany) between 2001 and 2009 (grid size: 100 × 200 m) and thus, after hurricane Lothar struck Southern Germany in 1999. We investigated whether the browsing level of trees (height ≤ 130 cm) in one location is independent of that of the neighborhood.
3. Our analyses of 1,758,622 saplings (187.632 sampling units) of oak (Quercus), fir (Abies), spruce (Picea), and beech (Fagus) revealed that the browsing level is characterized by a short distance spatial auto‐correlation.
4. The application of indicator variables based on browsed saplings should account for the spatial pattern as the latter may affect the results and therefore also the conclusions of the analysis.

     

Influence of young black spruce plantations on moose winter distribution

Logging in the boreal forest may benefit moose by increasing food availability. However, the influence of tree plantations on moose behavior, especially on moose spatial ecology, is poorly understood. We assessed the impacts of black spruce plantations on moose winter distribution at a landscape scale in the Bas-Saint-Laurent region (Québec, Canada). We used winter aerial surveys to examine relationships among plantation characteristics and other habitat variables known to affect moose distribution. The total area of plantations positively influenced moose abundance, but highly aggregated plantations resulted in fewer moose. Moose abundance was also positively associated with food availability and the density of edges between stands providing cover and stands offering high food availability, but moose abundance was negatively associated with road density. Although plantation characteristics were less influential than habitat variables related to foraging and predator avoidance, we demonstrate that the area of black spruce plantations and their configuration should be considered in moose management. We conclude that an integrated management strategy is needed to find a balance between overdeveloped road networks (needed to join homogeneously distributed plantations) and agglomerated plantations in order to mitigate impacts on moose winter distribution. © 2012 The Wildlife Society.