An Experiment to Control Fomes annosus in Second Rotation Pine Crops

Stump removal was found to singnificantly reduce killing byFomes annosus in second rotation crops of pine. Poisoning andgirdling of trees prior to felling and also stump poisoningfailed to control the disease. In this experiment no significantdifferences were detected in the susceptibility of Scots andCorsican pine to attack. Increasing periods of delay beforereplanting resulted in less mortality. An equation is presented,based on factors of the first rotation crop which may be usedto predict losses likely to occur when a site is replanted.Root attack by F. annosus results in reduced growth and yieldas well as mortality. The results from the experiment are discussed in trems of themangement of pine crops attacted by F. annosus in Theford Chase.     

Some Consequences of the 1975-1976 Drought for Dutch Elm Disease in Southern England

During the exceptionally hot, dry summer of 1976 the large elmbark beetle, Scolytus scolytus, was able to invade and successfullybreed in apparently healthy, undiseased elms. A conspicuousfeature was the clustering of wasps, bees and ladybirds on thestems, attracted by sap exudation. The trees were probably sufferingfrom drought, although many showed no symptoms. The phenomenonoccurred mainly on shallow soils over limestone; trees on chalkwere not generally affected. In 1976, and to some extent in 1975, the downward developmentof Ceratocystis ulmi through the tree was less than in previousyears, and only a low proportion of the numerous maturationfeeding wounds became infected. However the drought does notappear to have significantly influenced the course of the epidemic. The attacks by S. scolytus on undiseased trees are discussedin respect of 19th Century reports of attacks on elms, and itis concluded that the ability of S. scolytus to assume a moreprimary role may have been underestimated.     

Infection by Armillaria mellea and some Factors Affecting Host Resistance and the Severity of Disease

Infection by A. mellea in Britain occurs by means of rhizomorphs;the transfer of mycelium at root contacts is probably not importantas a means of spread. Following the initial phase of rhizomorphpenetration, established infection in the cambium is precededby ectotrophic spread of mycelium in the bark scales. Field investigation confirmed reports in the literature thatin susceptible conifers the greatest number of deaths generallyoccurs approximately 6–8 years after planting. However,attacks can also occur in much older crops and the reasons forthis are discussed. Inoculation experiments showed that suppressed trees and thoseexperiencing conditions of reduced light intensity are moresusceptible to infection than dominant trees and trees in fulllight. Species susceptibility in a variety of soils was studiedby inoculation of trees 20–30 cm tall. Of the coniferstested Pseudotsuga menziesii and Abies grandis were more resistantthan Picea abies, P. sitchensis, Larix kaempferi and Pinus sylvestris.Quercus robur and Fagus sylvatica were more resistant than allthe conifers except A. grandis. Soil type influenced diseasedevelopment and the proportion of trees infected was higherin an acidic sand soil than in an alkaline clay soil.     

Infection of Picea sitchensis and Pinus contorta stumps by basidiospores of Heterobasidion annosum

Infection of Pinus contorta and Picea sitchensis stumps by basidiospores of Heterobasidion annosum is extremely variable, both within and between sites, but in general P. sitchensis stumps are less sus-ceptible than those of P. contorta. Measurement of the cross-sectional area occupied by H. annosum on each stump provides a more sensitive test of species susceptibility than assessment of the proportion of stumps infected. P. sitchensis stumps become infected on a variety of soils but there is evidence to suggest that infection may be reduced by high rainfall. In some infected stumps, H. annosum is confined to the lower stump tissues. Its absence from the upper portion of the stump may be due to replacement by other micro-organisms or, alternatively, physical conditions in the upper stump tissues may prevent its continued survival after infection has taken place. In both species, but more commonly in P. sitchensis, some stumps remain alive for at least two years after felling, particularly on peat soils, due to the presence of root grafts with neighbouring trees. Results for P. sitchensis suggest that infection occurs more readily in living stumps than in those which die rapidly after felling. The viability of H. annosum basidiospore suspensions can be determined more accurately and more rapidly on a selective agar medium than on conifer stem sections.     

Early regeneration of Fraxinus rhynchophylla in the understorey of Larix kaempferi stands in response to thinning

The effects of thinning were investigated on naturally regeneratedFraxinus rhynchophylla Hance (Korean ash) grown in the understoreyof a Larix kaempferi (Lamb.) Carr. plantation, established ona site that previously supported old growth hardwood forests.The regeneration characteristics were evaluated after thinningof the plantation (about 60 per cent of relative density wasremoved). In the naturally regenerated and mixed stands, Quercusmongolica Fisch. was the most abundant tree species in the overstorey,but the understorey of the thinned plantations was dominatedby F. rhynchophylla with six other minor tree species. Fraxinusrhynchophylla was regenerated by four propagation types includingnatural seedling, stump sprout, root sprout and layering. Beforethinning, the difference of average height growth for each regenerationtype was insignificant. One year after thinning, the stump sproutsshowed the fastest growth among the regeneration types. Heightgrowth of advance regeneration was slow in the year followingthinning but then increased rapidly surpassing the other regenerationtypes 5 years after thinning. Thinning had an effect on thecomposition of regenerated trees also by seedling, stump sprout,root sprout and layering in the understorey. Advance regenerationsoccupied the upper understorey at 5 years after thinning. Alarge number of stump sprouts emerged in the plots 1 year afterthinning, while at 5 years after thinning the occupation ofstump sprouts decreased. Root sprouts and layers faded away.Considering the early growth and the composition of understoreyF. rhynchophylla, its advance regeneration has a high potentialto develop into overstorey trees at this site.     

Soils, Forests, and Pastures in South Wales

Marginal upland soils may be used for forestry or sheep grazing.In the State Forests of South Wales a study of selective plantingshows the greatest volume yield is generally obtained from Sitkaspruce (Picea sitchensis) planted in ridge-crest soils. Yieldsfrom Sitka spruce on ridge-flank soils are reduced by the presenceof Ericaceae on upper slopes and the dryness of the soils onlower slopes. Contrary to this trend, the nutritional valueof the pasture for sheep is lowest on ridge crests and increasesdownslope, being greatest on the Agrostis pastures of lowerslopes. Further, reclamation is most economically accomplishedon ridge flanks where they are not too steep. Although profitcomparisons are very difficult to make, ridge slopes might bemore usefully allocated to sheep grazing and ridge crests toSitka spruce forests. To be economically viable, a forest mustbe large, but within any new forestry acquisitions the largerareas occupied by slope soils might be reclaimed or utilizedas sheep pastures.     

Comparison of ground disturbance of frozen peatland during stump harvesting using a stump drill and rake

ABSTRACT

Tree stumps could be a source of renewable energy, contributing to a reduced dependence on fossil fuels. In Finland, stumps are currently harvested when the ground is not frozen to avoid co-removal of large amounts of soil and stones. Hence, the machinery used for stump extraction is not operated year-round. On peatlands, stumps could potentially be harvested when the ground is frozen. However, peatlands are highly sensitive to ground disturbance. There is, therefore, a need to identify equipment that causes low ground disturbance. In this study, peatland ground disturbance at stump level caused by stump harvesting using either a stump drill or a conventional stump rake was evaluated and compared in winter conditions. Results show that the stump drill caused up to 90% less ground disturbance per harvested stump than the conventional stump rake, but harvested 32–53% of the stump wood. Additionally, the size and shape of the disturbed areas changed between the harvesting year and following year, indicating that frost heaving plays a role in filling holes caused by stump extraction. The stump drill also consumed similar time to the conventional stump rake when harvesting Scots pine stumps on mineral soils, but far more when harvesting Norway spruce stumps.     

The Ecology of Armillaria mellea Vahl (ex Fries) in the Indigenous and Exotic Woodlands of Rhodesia

A. mellea is the cause of severe killing in young plantationsof Pinus elliottii in Rhodesia. P. patula is more resistantthough it may act as a carrier of the fungus; its resistancemay be overcome when planted in conditions of high inoculumconcentration such as clear-felled areas of P. elliottii whichhave a previous disease history. The source of infection isthe stumps of felled indigenous trees. Subsequent spread inthe pine is from tree to tree by root contact. The rate of increasein the incidence of the disease up to thirteen years from plantinghas been plotted. An initially logarithmic increase of killingshows a significant decline when the plantation is eight toten years of age. Viable basidiospores of A. mellea are presentin the air spora but little evidence of their importance inthe spread of A. mellea could be found.     

Fomes annosus (Fr.) Cke. and other Root-rotting Fungi in Conifers on ex-Hardwood Sites

The development of root rot and butt rot caused by Fomes annosusin conifer crops planted on ex-hardwood ground is slower thanthat in second-rotation conifer plantations. This is apparentlydue to competition from other fungi, notably Artnillaria mellea.Excavations on ex-hardwood sites showed that F. annosus waspresent in conifer thinning stumps, and that transference ofinfection occurred, causing butt rot. The investigations confirmedthe need for stump protection of all conifer crops planted onex-hardwood sites. Short accounts are given of the activityof A. mellea and Polyporus schweinitzii, the other two importantroot-rotting fungi on these sites.     

Use of stump diameter to estimate diameter at breast height and tree volume for major pine species in El Salto, Durango (Mexico)

Foresters may require to estimate the diameter at breast height(d.b.h.) and the volume of trees that have been cut, and mayonly have available the stumps as an indicator of the size ofthe trees. In the present study, equations for predicting bothd.b.h. and volume from stump diameter inside bark were developedfor major pine species in the forest region of El Salto, Durango(Mexico). The d.b.h. was estimated with relatively high accuracywith a simple linear model. The tree volume was also estimatedwith high precision by use of an allometric equation. Weightedlinear and non-linear least squares methods were used to takeinto account the problem of heteroscedasticity observed in thevolume–stump diameter relationships. The results of thenon-linear extra sum of squares method and of the F tests indicatedthat species-based equations for estimating both d.b.h. andvolume from stump diameter are required.     

Responses to Pathogen-induced Disturbance: Decomposition, Nutrient Availability, and Tree Vigour

In the Oregon subalpine zone, extensive dieback occurs in relativelypure stands of 150 to 250-year-old mountain hemlock growingon very infertile soils. Tree death is caused by a root-rotfungus, Phellinus weirii. Young trees that become establishedfollowing death of the original forest are apparently not reinfectedby the pathogen until 80–140 years later. whereon mortalityoccurs again. We examined the effects.of this natural disturbanceand subsequent regrowth on a number of ecosystem characteristics. Decomposition rates and nitrogen availability measured by insitu exchange resins increased in the zones of young regrowth,but dropped to values common for old growth as the forest agedand the canopy closed. Phosphorus and potassium accumulationon exchange resins showed trends opposite to nitrogen, and mayhave been associated with changes in biomass. Increased nitrogenconcentrations and decreased lignin concentrations in fine rootsin the zone of young regrowth suggested improved tree nutritionunder conditions of higher N availability and lower leaf areaindex. Tree vigour, estimated as wood production per unit leafarea, also was significantly increased in the zones where youngforests grew. Circumstantial evidence suggests that increasesin nutrient availability and light following death of the matureforest improved photosynthesis leading to increased resistanceof young trees against infection by the pathogen.     

Significance and Control of Attack by the Ambrosia Beetle Trypodendron lineatum (Oliv.) (Col. Scolytidae) in Argyllshire Forests

Following damage to saw-logs in Argyllshire forests methodsof controlling attack by the ambrosia (pinhole borer) beetleTrypodendron lineatum (Oliv.) have been studied. Attack beginsin April, reaches a peak in May but then declines rapidly, beingof negligible importance after August. Trees felled betweenNovember and January are more susceptible but few logs leftat stump are attacked. Damage is much more widespread in logsstacked in the forest or at the milt. Good protection can be provided economically by spraying stackedtimber with an emulsion of 0?75 per cent, gamma BHC. A freshtreatment is advisable if logs are restacked or the outsideones removed from a stack between April and August. These treatments,combined with rapid extraction and conversion of logs duringthe summer, should reduce the incidence of damage. Suspensionof felling during this period appears unjustified if these measuresare followed; moreover, freshly felled timber is less susceptibleto attack. Although the Lymexylid beetle Hylecoetus dermestoides L. isalso widespread, damage is less apparent due to the absenceof associated staining. The control measures recommended forTrypodendron appear suitable for Hylecoetus.     

Norway or Sitka Spruce?

The deep and wide continental range and climate occupied bythe European species Picea abies is contrasted with the long,narrow, and humid coastal strip which the American species Piceasitchensis inhabits. Norway is the more plastic spruce and cansuffer thinner soils and much more drought, but neither spruceis a shallow rooter where soils are good and deep. Of the two,the litter of Sitka is less harmful to the soil. To date thereis no evidence that height for height Norway is more stableunder high wind pressures, but the belief that it is less sensitiveto frost than Sitka is well established. Sitka is far superiorto Norway for planting at high altitudes and in exposed placesand on Molinia peatlands in Britain, which accounts for thevast preponderance of the American species used in the westand north of the British Isles. The present popularity of Norwayspruce with foresters and timber merchants is admitted, butthe point is made that in planting it where Sitka could growwell, only some 75 per cent, of the volume will be secured.Finally, the types of site which each spruce requires and alsowhich each cannot take are considered in detail. A plea is madefor mixtures in certain circumstances, and the belief expoundedthat only deeper and better cultivation of the hardpacked materialunder-lying thin soils will make it possible to extend considerablyour acreage of really stable crops of these high-volume producers.     

NOTE ON THE FIRST BRITISH OCCURRENCE OF IPS CEMBRAE HEER (COL. SCOLYTIDAE)

During 1955 the larch bark beetle, Ips cembrae Heer, was discoveredin twenty-nine localities in Moray, Nairn, Banff, and Inverness.These are the first British records for this species. It isassumed that I. cembrae entered the country in post-war shipmentsof German timber and has persisted in small numbers until thedamage to woodlands caused by the gale in 1953 provided favourableconditions for its increase. A conspicuous feature of attackis the twig tunnelling of the adult beetles which produces crownpruning. In one locality I. cembrae succeeded in breeding inand killing standing European larch of some 45 years of age.     

Achieving food and nutritional security through agroforestry: a case of <Emphasis Type="Italic">Faidherbia albida</Emphasis> in sub-Saharan Africa

Faidherbia albida is an ideal agroforestry tree commonly intercropped with annual crops like millet and groundnuts in the dry and densely populated areas of Africa. With its peculiar reverse phenology, it makes growth demands at a different time from that of crops. In addition, it deposits great amount of organic fertilizer on food crops. Leaves entering soils are comparable to fertilization of almost 50 t·ha 1 ·year 1 of manure in dense stands of 50 large trees per ha. These nutrients help maximize agricultural production and reduce the need for a fallow period on poorer soils. Research has shown that millet grown under F. albida yielded 2.5 and 3.4 fold increases in grain and protein, respectively. Animals eat pods which contain mean amounts of crude protein of 20.63% and carbohydrate of 40.1% in seeds. Moreover, the continued existence of F. albida in agroforestry parklands as in Ethiopia and Mali signifies the success of traditional conservation measures. Modern scientists have also developed much interest in the role of agroforestry in maintaining long-term biological balance between agriculture and livestock production systems. To ensure food security, which still remains a major challenge in sub-Saharan Africa, and concurrently minimize environmental degradation, promotion of agroforestry that specifically involves indigenous trees is crucial. We discuss the prospective role of F. albida in alleviating poverty while simultaneously protecting the environment from factors associated with, for example, deforestation and loss of biodiversity. The overall aim is to promote wide-scale adoption of F. albida as a valuable tree crop in farming systems, particularly in those areas where it remains unexploited.     

Establishment of the Second Rotation in the Jutland Heath Plantations

The paper describes briefly the silvicultural methods used toregenerate stands of pure Norway spruce (Picea abies Karst.)or Norway spruce mixed with a small proportion of Silver fir(Abies alba Mill.) on the poor heath soils of Jutland. Regenerationafter clear felling, uniform shelterwood, and shelterwood stripfelling is described. The last method has advantages over theother two.     

Optimizing the management of a Picea abies stand under risk of butt rot

A simulation model was developed to predict the growth of a Norway spruce stand under risk of butt rot caused by Heterobasidion annosum stump infection and logging injuries. The simulation model was distance‐dependent; tree growth was predicted with a distance‐dependent model, and the spread of butt rot through root contacts depended on tree location. Infection of stumps and injured trees, and the spread of butt rot in the stand were stochastic processes whereas tree growth and mortality were treated as deterministic processes. The simulation model was used with the nonlinear optimization algorithm of ooke and J eeves (J. Assoc. Comput. Mach, 8, 212–229, 1961) to find the most profitable management schedule for an even‐aged, young stand. Optimization used four different stump infection rates and two spreading capacities from infected stumps. The profitability was evaluated by the expected soil expectation value (SEV) at a 3% interest rate. Two thinnings, both in winter‐time, and hence without H. annosum infections, resulted in the highest SEV. If any stump infection by H. annosum occurred, only one thinning and a shortened rotation were suggested. The optimal thinning rate tended to decrease but also large trees were removed with the increasing infection rate. With one thinning during a rotation, stump treatment was profitable above a stump infection rate of 10%     

The Incidence of Root-Surface Fungi on Naturally Regenerated Picea sitchensis Seedlings in Southeast Alaska

The root-surface fungi were examined from naturally regeneratedSitka spruce obtained from recently exposed glacial outwashand mature upland soils where spruce had grown alone and inmixture with alder. Roots from the poorest trees on least fertilesoil had a high incidence of Mortierella and few other fungibut as growth and soils improved the numbers and genera of otherfungi increased The same genera occurred on roots from glacialdrift and upland soils and were the same as those found on intensivelygrown seedlings from acid heathland soil at Wareham forest nurseryin Dorest, England.     

THE GROWTH OF SITKA SPRUCE ON SHALLOW SOILS IN RELATION TO ROOT-DISEASE AND WIND-THROW

The paper considers in detail the evidence from the examinationof some Sitka spruce (Picea sitcbensis Carr.) 35 to 50 yearsold, and old enough therefore to begin to reflect the potentialitiesof the sites occupied which are normally considered suitablefor the species. The examination was made to ascertain whatfactors other than parasitic infestations or infections wereacting to cause the thinning of crowns, the death of trees,and the susceptibility to wind-throw. In these shallow soils,factors of fundamental importance are those which determinethe regularity of the supply of water and air, and it is consideredthat where, as in the cases examined, the soils are mainly intractable,early development of disease and of wind-throw will have tobe expected.     

An Analysis of Peridermium Stem Rust of Scots Pine in Thetford Forest in 1984 and 1985

The status of stem rust (Peridermium pini or (Pers.) Lev.) inScots pine (Pinus sylvestris L.) in the central block of Thetfordforest, East Anglia was determined by means of detailed analysisof freshly felled trees. A total of 935 trees was examined,these comprising c. 100 from each of nine compartments plantedbetween 1922 and 1933. Lesions in all stages of development were found; from thosein their first year of sporulation on young twigs to those whichhad been established for many years on the trunk and main branches.Death of cambium occurred typically on lesions on shoots thatwere more than five years of age. Downward growth of the funguswas estimated to average between 4.7 and 5.6 cm per year, whenbased on the length of sporulating tissue on young twigs, and6.3 cm per year when based on cambial killing in trunk lesions.The average rate of circumferential killing of trunk lesionsaveraged 4.3 crn per year (i.e. 2.2 cm in each direction). Therewas no evidence that wounds provided a significant infectioncourt. A strong association was found between the presence of the ‘purplemould’ (Tuberculina maxima) and an absence of sporulationby the rust fungus. However, there was no evidence for lesioninactivation by T. maxima. Data are presented on the distribution of disease between sitesand between trees. Five per cent of the total sample of treeswere dead and an additional 12 per cent had crown symptoms associatedwith girdling trunk lesions. Among the 775 trees with predominantlyhealthy crowns, it is estimated that 9 per cent would have diedwithin 5 years, 15 per cent within 10 years and 22 per centwithin 20 years. By contrast 66 per cent had no disease at all,probably for genetic reasons. It is concluded that, althoughthe disease situation is serious, there is no requirement fora major change to be made in the felling programme for the pre-warScots pine in Thetford.