Foliar and shoot allometry of pollarded black locust, Robinia pseudoacacia L.

Browse of multipurpose tree species such as black locust could be used to broaden grazing options, but the temporal distribution of foliage has not been adequately studied. Our objective was to determine effects of harvest date, P fertilization (0 and 600 kg ha⁻¹ yr⁻¹), and pollard height (shoots clipped at 5-, 50-, and 100-cm above ground) on foliar and shoot allometry of black locust. The experiment was conducted on a naturally regenerated 2-yr-old black locust stand (15,000 trees ha⁻¹). Basal shoot diameter and foliar mass were measured monthly in June to October 2002 and 2003. Foliar and shoot dry mass (Y) was estimated from basal shoot diameter (D) by the function Y = aD ^b , with regression explaining ≥95% of variance. Allometry of foliar mass was affected by harvest date, increasing at a greater rate with D in September than in June or July, but not by P fertilization or pollard height. Foliar mass was predicted best by month-specific equations for the June to October growth interval. Allometry of shoot dry mass was unaffected by harvest date, P fertilization, or pollard height. These equations could be used as a first approximation of foliar and shoot mass for pollarded black locust.     

Variation in damage by terminal shoot insects among jack pine families

The susceptibility of jack pine, Pinus banksiana Lamb., to damage by the white pine weevil, Pissodes strobi (Peck) and the eastern pine shoot borer, Eucosma gloriola Heinrich, was examined over a three-year period (1994–1996) in a 400-family genetic test near New Liskeard, Ontario. Of the 7180 trees examined, white pine weevil damaged 1041 and eastern pine shoot borer damaged 1913 trees, yielding damage frequencies of 14.5% and 26.6%, respectively. Thirty families of jack pine never sustained weevil damage during the study period, while only one family escaped damage by the shoot borer. The expected, and observed, damage rates were significantly different for the weevil, but not for the shoot borer. There was no discernible spatial pattern in the incidence of shoot damage by either insect species, based on the geographic location of the parent trees. The data suggest that there is a basis for pursuing further studies to evaluate genetic resistance in tree improvement programs.     

A Study on the Mode of Infection of Pinus sylvestris L. by Peridermium pint (Pers.) Lev.

Inoculations by Peridermium pini (Pers) Lev. aeciospores ofscalpel wounds 2 mm deep on current year's Pinus sylvestrisL. shoots gave more numerous infections than shallower wounds.Some lesions resulting from these infections developed pycnidialdroplets and a few also produced aecial blisters within thefirst year after infection. Infection of P. sylvestris by P.pini can take place by direct stomatal penetration. This wasobserved only inside the needle sheaths of trees with previousnatural infections and was not observed on healthy trees. Thehyphae that developed from these penetrations passed intercellularlythrough the mesophyll to the vascular tissue where they proliferated.     

Resistance levels of Spanish conifers against Fusarium circinatum and Diplodia pinea

Pitch canker, caused by Fusarium circinatum, and Diplodia shoot blight, caused by Diplodia pinea, are both damaging to pines (Pinus spp.) grown in plantations throughout the world, including Spain. To assess the potential for interspecific differences in susceptibility to contribute to the management of pitch canker and Diplodia shoot blight in the Atlantic region of Spain, the present study was undertaken to characterize the susceptibility of six pine species (P. sylvestris, P. nigra, P. pinaster, P. radiata, P. halepensis and P. pinea) and Douglas‐fir (Pseudotsuga menziesii) to F. circinatum and D. pinea. Based on inoculations of 2‐year‐old trees, Ps. menziesii, P. pinea and P. nigra were the most resistant to F. circinatum, with lesion lengths ranging from 3.7 to 21.5 mm, 2.2 to 12.6 mm and 2.8 to 30.9 mm, respectively. At the other extreme, Pinus radiata was the most susceptible, sustaining lesions that ranged from 8.5 to 74.8 mm in length. Pinus sylvestris, P. pinaster and P. halepensis showed an intermediate response to F. circinatum. Broadly similar results were observed in inoculations with D. pinea, with Ps. menziesii being relatively resistant and P. radiata being highly susceptible. Consistent with these results, field surveys revealed no pitch canker in stands of Ps. menziesii and low severity of Diplodia shoot blight, whereas P. radiata was severely affected by both diseases. Our findings suggest that selection of appropriate species can greatly reduce the risk of damage from two important canker diseases affecting pine plantations in the Atlantic region of Spain. Furthermore, intraspecific variation in susceptibility implies that selection may allow for the enhancement of resistance in otherwise susceptible species.     

Relative susceptibility of selected pure and hybrid pines to Fomes annosus (Fr.) Cke.

Eight strains of Fomes annosus (Fr.) Cke. were grown on malt and potato dextrose agar to determine their growth rates. Pine wood from several locations in P. resinosa trees was tested to ascertain which sample area was best-suited for fungal growth studies. Fifteen pines were ranked according to relativc susceptibility to two strains of F. annosns. Pinus densiflora Sieb. and Zucc. and P. rigida × radiata were most “resistant” and “susceptible” respectively.     

Decay in Norway Spruce Caused by Stereum sanguinolentum Alb. & Schw. ex Fr. Developing from Extraction Wounds

In two stands of Norway spruce (Picea abies (L.) Karst.), plantedin 1952 and 1929 in Yair Hill Forest and Glentress Forest, BordersRegion, two per cent of the trees examined in 1983 had extractiondamage on stems and superficial roots. Extraction wounds were4 and 8 years old respectively and ranged in size from 52 to1099 cm². Infection frequency of the damaged trees was 47 percent and 54 per cent respectively. Stereum sanguinolentum wasthe most common fungus isolated, accompanied by Trichodermaviride Fr; Chaetomium cochlioides Palliser and Heterobasidionannosum (Fr.) Bref. The frequency of isolation of S. sanguinolentumincreased progressively in samples taken from the outside ofstems inwards, whereas the other microorganisms present showedthe opposite pattern. In four trees, T. viride overgrew S. sanguinolentumin the the decay columns. Positive correlations were demonstratedbetween surface area of wounds and vertical extension of decay,tree volume and decay volume, and diameter of stem at breastheight (DBH) and decay volume; whereas a negative correlationoccurred between number of growth rings per 5 cm (measured inwardsfrom the outside of the bole) and radial penetration of decay.The results confirm the importance of S. sanguinolentum as awound pathogen.     

Growth of Young Sitka Spruce (Picea sitchensis (Bong.) Carr.) and the Effect of Simulated Browsing, Staking and Treeshelters

Sitka spruce (Picea sitchensis (Bong.) Carr.) 1 + 1 transplantswere grown at 1 x 1 m for 3 years with 100 per cent chemicalweed control on a very fertile site. Treatments were control,firm staking, staked with 15 cm diameter netting with simulatedbrowsing, staked with simulated browsing to 15 cm diameter crown,1.2 m treeshelter, 1.2 treeshelter with holes and no browsing.No leaders were browsed. Trees were assessed for annual heightgrowth, stem diameter at 0.5 m and 1.0 m, total above and belowground biomass, root:shoot ratio, root plate diameter, rootdepth and root volume. No 3-year heights were significantlydifferent but third-year increments were; the greatest finalheight was in the control at 200.7 cm. All other tree parametershad significant treatment differences demonstrating the needto select carefully the criteria of success in experiments.Treatments which restricted the horizontal development of thecanopy either physically or by simulated browsing seriouslyreduced stem diameter and root development. The controls hada root:shoot ratio of 0.418; treeshelter treatments had thesmallest root:shoot ratio of 0.238; staked trees were 0.379while staked browsed trees had the highest value at 0.447. Acceptanceof browsing or use of shelters or guards to protect trees frombrowsing may seriously reduce growth.     

Plasticity of shoot and needle morphology and photosynthesis of two Picea species with different site preferences in northern Japan

We compared shoot and needle morphology and photosynthesis in Picea glehnii (Friedr. Schmidt) M.T. Mast. and Picea jezoensis (Sieb. et Zucc.) Carr. trees planted on immature volcanic ash and well-developed brown forest soils to investigate whether species differences in morphological and physiological plasticity affected tree growth on different soil types. Height growth of P. glehnii was reduced by about 10% on volcanic ash compared with forest soil, whereas that of P. jezoensis was reduced by more than 60%. Needle morphology of P. glehnii was unaffected by soil type. In contrast, needles of P. jezoensis trees growing on volcanic ash were shorter, narrower and thicker, with less dry mass and area, than those of trees growing on forest soil, and specific needle area was lower, indicating lower foliar light-interception efficiency. In both species, changes in needle morphology with increasing irradiance were similar in trees growing on both soil types, indicating that plasticity of needle morphology was unaffected by soil type. In both species, shoot mass and shoot silhouette area were lower and needle mass per unit shoot mass was higher in trees growing on volcanic ash than in trees growing on forest soil. Trees of both species had more needles per unit shoot length, lower shoot silhouette to projected needle area ratios and lower shoot silhouette areas per unit shoot mass (SAM) on volcanic ash than on forest soil, indicating lower shoot-level light-interception efficiency. For P. glehnii, the response of shoot morphology to increasing irradiance was similar on both soil types, with the exception of SAM, which showed lower plasticity in trees growing on volcanic ash. In contrast, shoot-level morphological plasticity of P. jezoensis was reduced in trees growing on volcanic ash. Light-saturated maximum photosynthetic rate (P(max)) of P. glehnii was unaffected by soil type, whereas mass-based P(max) of P. jezoensis was lower in trees growing on volcanic ash than in trees growing on forest soil. In P. jezoensis trees growing on forest soil, area-based P(max) increased with increasing irradiance, but this response was not observed in trees growing on volcanic ash. As a result, area-based P(max) at the top of the canopy was 39 to 54% lower in trees growing on volcanic ash than in trees growing on forest soil. Our results indicate that constraints on morphological acclimation to high irradiances may contribute to reduced height growth of P. jezoensis on volcanic ash.     

Evidence for the occurrence of induced resistance to pitch canker,caused by Gibberella circinata (anamorph Fusarium circinatum), in populations of Pinus radiata

Pitch canker, caused by Gibberella circinata, was discovered in California in 1986. Although initially quite damaging to Monterey pines (Pinus radiata), the severity of pitch canker has moderated in areas where the disease was first observed and some trees appear to have recovered completely. The absence of symptoms on trees that were once severely affected implies they have become more resistant to the disease. Experimental work has shown that P. radiata can manifest systemic induced resistance (SIR) in response to infection by the pitch canker pathogen and observations of disease remission may indicate that SIR is operative under natural conditions as well. As a test of this hypothesis, the susceptibility of trees in remission was assessed by inoculating them with G. circinata and recording the extent of lesion development. In addition, randomly selected trees in areas that differed in residence time of pitch canker were inoculated to determine if trees with a longer period of exposure to the pathogen were more resistant to the disease. The results of these tests showed that 89% of trees observed to be in remission sustained very limited lesion development, consistent with resistance to pitch canker. Furthermore, trees in areas where pitch canker was well established tended to be more resistant than trees in areas where the disease was of more recent occurrence. In sum, these findings support the view that SIR occurs in P. radiata and is contributing to a moderation of the impact of pitch canker under natural conditions.     

Variation in shoot water status of Picea abies (L.) Karst. trees with different life histories

Daily dynamics of the shoot water potential (ψ) in Norway spruce [Picea abies (L.) Karst.] depending on soil water availability and atmospheric evaporative demand was studied on originally freely-grown trees and suppressed trees exposed to full sunlight after clear-cutting. The base water potential (ψ_b) was significantly correlated (R² = 0.73) with the available soil water storage (W_tr) at a depth of 20–40 cm. ψ_b was relatively constant at high soil water status and decreased sharply if W_tr dropped below 14 mm. Among the atmospheric factors observed, the vapour pressure deficit (VPD) proved to be the most relevant variable in predicting diurnal changes in ψ. The leaf water status was more sensitive to VPD at sufficient soil water storage. With soil drying, the daily amplitude of ψ diminished, testifying to the more efficient stomatal control under soil drought. For predicting the daily course of ψ from VPD and ψ_b (taken as a measure of the soil water availability) an empirical model was derived, which described 78–80% of the total variatin in the shoot water potential. In contrast to values of ψ_b, the daily values of ψ differed significantly (P < 0.05) between the trees with different life histories. The newly exposed trees demonstrated substantially lower values of ψ with increasing atmospheric evaporative demand at the same soil water availability. Dynamic water stress is considered one of the main causes of the continuing growth retardation in suppressed spruce trees after their release from overstorey.     

The impact of forest fertilization on growth of mature Norway spruce affected by Sirococcus shoot blight

The effects of forest fertilization and Sirococcus shoot blight on growth of mature Norway spruce (Picea abies (L.) Karst.) were studied in a field experiment. The single tree fertilization experiment was established with 144 sample trees in the year 2000. These trees were selected among the dominant and co-dominant trees of the stand in a way that half of the trees exhibited symptoms of Sirococcus shoot blight and the other half did not. One-third of the sample trees were fertilized with dolomitic lime, one-third with kieserite and gypsum and one-third were left unfertilized as control. The treatments were randomly assigned to the sample trees. As the experimental design became unbalanced due to tree mortality caused by bark beetle infestation final analyses were performed with the volume growth data of 125 sample trees only. An analysis of covariance was used to evaluate the effect of fertilization and Sirococcus shoot blight on volume growth. The average volume increment of the period 1977–1980 was used as a covariate attribute, assuming that during this period growth was not yet affected by Sirococcus shoot blight. Indeed an effect of Sirococcus shoot blight on growth turned out to start after 1980 and the analysis revealed that over the whole period 1981–2006 trees with shoot blight symptoms had a significantly lower increment. The increment reduction of the nonfertilized trees by Sirococcus   was 7.46±2.90$7.46\pm 2.90$% in 1981 and was continuously increasing with time to 37±3.78$37\pm 3.78$% by the year 2000. A significant positive effect of fertilization was only found for the kieserite+gypsum$\text{kieserite}+\text{gypsum}$ variant from 2002 to 2006, with the highest surplus increment in 2004 with 31.6±15.2$31.6\pm 15.2$%, calculated as average over the diseased and healthy group. However, a mitigation of the Sirococcus-caused increment loss via fertilization with kieserite and gypsum was statistically significant only for the year 2003. A moderate relationship between basal area increment and disease severity was found, indicating decreasing basal area increment with increasing disease severity.     

Stand structure and dynamics of four native Scots pine (Pinus sylvestris L.) woodlands in northern Scotland

Stands in four native pinewoods (Glenmore, Black Wood of Rannoch,Glen Garry and Glen Affric) dominated by Scots pine (Pinus sylvestrisL.) with contrasting management histories and climates wereassessed for differences in age, structure and dynamics. Treeage, height, diameter at breast height (d.b.h.), basal area,stem density and x, y coordinates were used to compare the recruitmentof trees (>1.3 m height, >7 cm d.b.h.), saplings (>1.3m height, <7 cm d.b.h.) and seedlings (<1.3 m) followingdisturbance events and protection from browsing. There was a20-year lag between localized intensive cultivation and treerecruitment on sites that were protected from deer browsing(Glenmore and Glen Garry). Recruitment was low in sites withdisturbance but no protection (Black Wood of Rannoch). The oldestpopulation, Glen Affric, showed signs of initial intense recruitmentfollowed by a long period of nil recruitment. Abundant standingdead trees were recorded only in Glen Affric, and prolific birchand rowan only in Glen Garry. Managers should consider localizedintense cultivation in conjunction with a complete reductionin browsing pressure for rapid seedling recruitment and increasedstructural diversity.     

Variation in the ratio of shoot silhouette area to needle area in fertilized and unfertilized Norway spruce trees

We compared the range and variation in shoot silhouette area to projected leaf area ratio (SPAR) in fertilized and unfertilized (control) Norway spruce (Picea abies (L.) Karst.) trees. We measured SPAR for several view directions of 169 shoots at different depths in the crown of fertilized and control trees. There was an increase in SPAR with depth in the crown in both control and fertilized trees. In the fertilized trees, however, mean SPAR was larger overall, the increase with depth in the crown was steeper, and there was a larger variation in SPAR with inclination and rotation angle of the shoot (relative to the view direction). In particular, shoots in the lower crown of fertilized trees were rotationally asymmetrical ("flat") and had high values of the maximum ratio of shoot silhouette area to projected leaf area (SPAR(max)). Differences in SPAR between fertilized and control trees were explained by changes in shoot structure in response to fertilization and shading. Shoots of fertilized trees were larger and had more needle area than shoots of control trees. However, the ratio of needle area to shoot size was smaller in fertilized trees than in control trees, implying less within-shoot shading and, consequently, a larger SPAR. Also, the increase in SPAR with increased shading (depth in the crown) could be explained by a decrease in the ratio of needle area to shoot size. In addition, because fertilized trees had more needle area than control trees, the effect of shading at a given depth in the crown was more pronounced in fertilized trees than in control trees.     

Development of Thaumetopoea pityocampa schiff. (Lepidoptera: Thaumetopoeidae) in relation to food consumption

T. pityocampa is the most harmful needle-eating insect of the Greek pine forests. Field trials in the Thessaloniki area of N. Greece showed that the development of young larvae which were enclosed in cloth bags on trees of the experimental site was greatly influenced by the kind of food the larvae consumed. Food consisted of needles from five pine species: Pinus brutia Ten., P. pinea L., P. maritima Lam., P. halepensis Mill., and P. radiata D. Don. Larvae had greatest weight gain and rate of development when fed on leaves of P. radiata, and least when fed on those of P. pinea.     

The lack of persistence of Ophiostomataceae fungi in Pinus radiata 3 years after damage by the bark beetle Hylastes ater,and the subsequent colonisation by Sphareopsis sapinea

A survey established in 2002 of 1-year-old Pinus radiata seedlings in New Zealand confirmed the presence of a number of members of the Ophiostomataceae family within the seedlings following damage. The persistence of fungi in P. radiata trees for extended periods following prior damage to the seedlings by the bark beetle Hylastes ater was studied subsequently as is reported herein. A random selection of the remaining P. radiata trees from the original sites were destructively sampled in 2005, approximately 3 years after the initial study. The diameter of each tree was measured, visual observations of any damage to tree were noted and any potential sapstaining fungal species were isolated. Sphareopsis sapinea was isolated from 6 to 16% of trees, despite not being isolated from any trees in the first study. With the exception of Ophiostoma setosum isolated from a single tree, no members of the Ophiostomataceae family were isolated this second time from the trees. The present study highlights that Ophiostoma species initially inhabited P. radiata seedlings following bark beetle attack, but their presence was not sustained over the three year period, showing that they were not endophytes in P. radiata. The asymptomatic persistence of S. sapinea in seedlings and larger P. radiata trees, however, is of significant concern for the forest industry.     

Environmentally induced changes in the distribution of disease susceptibility phenotypes in Pinus radiata

Pinus radiata (Monterey pine) is highly susceptible to Fusarium circinatum, the cause of pitch canker, but heritable variation in resistance to this disease has been documented in P. radiata. In this study, the distribution of susceptibility phenotypes (=lesion lengths) was assessed by inoculating P. radiata trees with a spore suspension of F. circinatum. The results show the distribution of susceptibility phenotypes in naïve seedlings to be normally distributed, both in a breeding population and in a population established from seed collected in a native forest. This pattern aligns with expectations for a quantitatively inherited trait. However, after 2.5 years of growth in a forest, variation in susceptibility is no longer normally distributed but rather is positively skewed. Thus, exposure to the forest environment results in a distribution that is enriched for relatively resistant individuals. A similarly skewed distribution is observed in standing trees in a native population of P. radiata. The observed change in distribution cannot be attributed to ontological effects on resistance to pitch canker, because tree age accounts for almost none of the variation in susceptibility. We hypothesize that the change in distribution of susceptibility phenotypes is due primarily to infections and infection attempts by the microbiota resident in the forest.     

Needle nutrient status of Sirococcus shoot blight‐diseased and healthy Norway spruces

In this study the needle nutrient status of Sirococcus shoot blight‐diseased and healthy Norway spruces (Picea abies) was investigated. Element contents were determined in the current year and 3‐year‐old needles collected in December 2000 from 72 mature trees randomly distributed in the investigated stand. Half of the trees were severely affected by Sirococcus conigenus and had a reduced crown whereas the other trees were unaffected and vigorous. Compared with the uninfected trees, contents of Mg, Ca, P and Mn were significantly lower in the current year and 3‐year‐old needles of diseased trees. Furthermore, analyses of the nutrient contents of needles from severely affected trees revealed insufficient Mg and Ca supply and enhanced N/Mg and N/Ca ratios, when compared with threshold values. The results of this study suggest that imbalanced tree nutrition either has a significant impact on the expression of Sirococcus disease symptoms or fungal infection itself is affecting needle nutrient contents.     

The Timing of Canopy and Epicormic shoot growth in Quercus robur L.

The sequence and timing of shoot development from buds on thebranches and trunk of Quercus robur were observed over 2 years.Shoots on crown branches began development before those on existingepicormic branches but both stopped growing at about the sametime. Epicormic buds on the trunk began expanding 3–4weeks after crown buds, and finished growth 3 weeks later. Theseobservations do not support previous claims that new epicormicshoots grow before development of the canopy.     

Nitrogen fixation in L. leucocephala L. as affected by rooting volume and competition with E. camaldulensis

Fast growing trees, in particular nitrogen fixing trees, are essential for the establishment of sustainable agroforestry practices by resource-poor and/or environmentally conscious aarmers. An important selection factor for trees is therefore high N₂ fixing capability. This study was conducted to examine biological nitrogen fixation (BNF) in Leucaena leucocephala L., as affected by growth in pots containing 4, 10, 15 and 30 kg soil and when grown together with Eucalyptus camaldulensis. BNF was measured by the ¹⁵N isotope dilution technique. Leucaena and Eucalyptus were grown either sole (SL, SE) or in two mixtures (1:1 - L1:E1 and 1:2 - L1:E2) for a period of 6 months. Planting pattern influenced (P < 0.05) dry matter and N content of shoot and roots of Eucalyptus, as the sole planted trees gave the highest yield. Dry matter, N content and total amount of N fixed by Leucaena significantly decreased with decreasing rooting volume. Also, the smaller the rooting volume (or soil weight), the higher was the proportion (%) of N derived from the atmosphere (%Ndfa) by leucaena. For each rooting volume, the sole or mixed planting pattern did not significantly influence either the proportion (%) or amount of N fixed by leucaena. For these trees, therefore, rooting volume rather than cropping pattern influenced the proportion and amount of nitrogen fixed.     

Frost damage on the terminal shoot as a risk factor of fork incidence on common beech (Fagus sylvatica L.)

Forking is a frequent flaw in beech which can adversely affect the formation of high quality logs. Even though the hypothesis that late frosts increase forking is widely accepted by forest managers, it remains to be proved and quantified experimentally. Damage caused by a late frost on 15 May 1995 to young beech trees in an experimental site at Lyons-La-Forêt (France) and the consequences on the development of forking were analysed. The beech trees were 17 years old with heights between 1.5 and 9 m. Of all the plantation densities tested only the lowest density (625/ha) showed various and severe frost damage. Three levels of immediate damage to the growing terminal shoot were observed, with increasing intensity from: (1) no trace of frost damage, (2) reddened leaves and (3) frost-nipped shoots. The intensity of visible damage to the terminal shoot appeared to be very dependent on the height of the plant which justified our original experimental approach, based on an evaluation of the damage for each individual. Almost all of the beech trees less than 4 m high suffered frost damage and all those taller than 7 m were unaffected. Three-year-old forks due to frost which occured in May 1995 were recorded at the end of 1997 using an objective definition based on dendrometric and age criteria. The worst frost damage resulted in a significant increase in the risk of fork emergence (71.7% of the plants were forked). With a risk related to forking in the presence of frost-nipped shoots equal to 2.15 and a fraction of the attributed risk of 0.36 it was concluded that the late frost observed played a significant role in the degradation of the shape of the beech affected by frost and the overall quality of the stand.