MOISTURE AND TEMPERATURE CONDITIONS IN AFFORESTED AREAS IN ABERDEENSHIRE

1. Soil temperature measurements in a forestry plantation at Birkhall,near Ballater, Aberdeenshire, have been maintained from January1952 onwards, and the present paper extends the results alreadypublished (Quart. J. Roy. Met. Soc. lxxxi (1955), 72) with regardto soil temperature profiles, frost occurrence, and the efficiencyof daily maxima and minima of temperature in the estimationof mean weekly temperatures.
2. Results are given for the interceptionof rain by vegetationalcovers of various types and for thedifferences in moisturestatus that occur between soils in anopen ride and under theforest canopy.
3. The amplitudes of diurnaltemperature fluctuations in the rideand under the forest canopyhave been compared. Over the periodAugust 1954 to December1956, the latter average about 60 percent, of the former; thereare, however, large differences betweenthe results for thedry conditions in 1955 and the wet conditionsin the later monthsof 1956, and consideration is given to thefactors contributingto these differences.
4. The mean temperatures in the ride arehigher than those underthe canopy between April and September;the greatest differences,which are of the order of 1? C., occurin the later part ofthe spring and the earlier part of thewinter.

     

A decade of grey squirrel bark-stripping damage to beech in Lady Park Wood, UK

The scale and distribution of American grey squirrel (Sciuruscarolinensis) bark-stripping damage to beech (Fagus sylvatica)stems was monitored in a mixed broadleaved woodland retainedas a Research Natural Area through the use of permanent transects.During an initial outbreak of debarking damage in 1983 almostone-third of beech individuals 4 cm d.b.h. in stands of 40 years'growth were badly damaged and by 1993 this level of damage hadrisen dramatically to over 50 per cent. One-third of badly damagedindividuals in 1983, including a number of potential canopydominants, died during the decade, but some that survived grewvery vigorously. Throughout squirrels preferentially debarkedintermediate sized (10–25 cm d.b.h.) stems in particularparts of the stands aged 40–50 years, apparently tendingto select stems that were growing rapidly. Other species andstand areas of <100 years' growth remained largely unscathed.Within the 10-year period squirrels had critically affectedthe successional development of the wood.     

SQUIRRELS IN GREAT BRITAIN

The distribution in 1953 and the habits of the two squirrelsSciurus vulgaris leucourus and S. carolinensis are discussedand their control considered.     

Growth and provenance of Norway maple (Acer platanoides) in lowland Britain

The results of an experiment to investigate the early growthand form of ten different provenances of Norway maple (Acerplatanoides L.) are described. Two sites were planted and after8 years survival was 88 per cent and 95 per cent and heightincrement was 402 cm and 201 cm; confirmmg the potential ofNorway maple to be a productive forest tree. Provenances thatperformed well were from Germany, the Netherlands, Denmark andYugoslavia; exact locations were not known for all seed collections.A provenance from Russia was included, material from this fareast has rarely been tested in Britain. However, as expected,its performance was relatively poor. The main constraint tofurther planting of Norway maple is the palatability of thebark to grey squirrels (Sciurus carolinensis Gmelin.). However,it is a useful tree for high pH and heavy soils and as an alternativespecies to sycamore (Acer pseudoplatanus L.).     

Feinde und Parasiten der Weizengallmücken

Ohne Zusammenfassung Weitere Beitr?ge siehe: M. Waede, Bemerkungen zum Auftreten der WeizengallmückenContarinia tritici Kirby undSitodiplosis mosellana Géhin im südlichen Niedersachsen 1954. — Nachrbl. f. d. deutschen Pflanzenschutz.-Dienst. 7, 1955, S. 49–54. — W. Speyer und M. Waede, Eine Methode zur Vorhersage des Weizengallmückenfluges. — Eodem loco, 8, 1956, S. 113–121.     

A Reappraisal of the Importance of Cronartium ribicola on Pinus strobus in Great Britain

Because of the possibility of serious infection by Cronartiumribicola (White pine blister rust), Pinus strobus, the Weymouthpine, is now very rarely planted in British forests. An assessment,in 1962, in a number of experimental forest plots of P. strobusestablished in 1953 and 1954 showed that initial infection ofthe trees while growing in the nursery may be an important factorin causing later damage and losses in the forest. The resultsalso indicated that the risk of infection in plantation cropsas a result of spore dispersal from black currants in the localityis much lower than is generally thought. It is suggested thatif P. strobus is raised in nurseries which are relatively isolatedfrom currants and if protective chemical spraying against thedisease in the nursery is carried out, the incidence of infectionin plantations at least half a mile from the nearest currantsis likely to be low. The disease cannot spread within a pinecrop by direct transmission from tree to tree.     

Damage caused by the American grey squirrel (Sciurus carolinensis) to agricultural crops, poplar plantations and semi-natural woodland in Piedmont, Italy

The incidence of damage caused by grey squirrels in the Turinplain was studied to assess the impact this alien species ishaving on the highly fragmented Piedmont environment, in particularon profitable cereals, poplar plantations and semi-natural woodlands.The survey of damage was conducted both by interviews to localfarmers and growers and by direct assessment using the NearestNeighbour Method on plantations and woodlands, studying randomlychosen plots in the Turin plain to gain a general overview ofthe situation. The results show a low incidence of damage causedby grey squirrels in the area: little or none was found in semi-naturalwoodlands and in agricultural crops, apart from maize whereless than 1 per cent of fields showed damage, and poplar plantationswhere 5 per cent had signs of bark stripping. Damage on maizecrops was random across the plain, but debarking damage to poplarswas mostly concentrated on the western side of the plain, andtended to occur only in particular years. Damage was concentratedclose to streams and rivers surrounding fields and plantations.The introduction of the grey squirrel in Italy has already causedecological damage such as the extinction of the red squirrelin some areas. Nevertheless, little or no information is availableon the damage this species is causing on woodlands or agriculturalareas. This study is a preliminary survey in order to fill thisgap.     

Annual variation in predation and dispersal of Arolla pine (Pinus cembra L.) seeds by Eurasian red squirrels and other seed-eaters

Seed predation and dispersal are key processes in the survival and distribution of plant species. Many animals cache seeds for later consumption, and, failing to recover some of these seeds, act as seed dispersers, influencing post-dispersal seed and seedling survival. Both animal and plant benefit from scatterhoarding and natural selection of seed characteristics and adaptations of seed predators (and dispersers) is one of the most important examples of co-evolution and mutualism. We studied the producer–consumer Arolla pine (Pinus cembra)–red squirrel (Sciurus vulgaris) system in a subalpine forest in the Italian Alps. Arolla pine produced large seed-crops (masting) at irregular intervals, followed by years with poor or moderate seed production. Squirrel density fluctuated in synchrony with the food resource, eliminating the time-lag normally present when resources are produced in pulses. In all years except 2009 (a mast-crop year), all Arolla pine cones were harvested (their seeds consumed and/or cached) by September to late October by different species. Both squirrels and nutcrackers (Nucifraga caryocatactes) fed on seeds, and their relative pre-dispersal predation rates (on cones in the canopy) differed between years. Overall, nutcrackers consumed more seeds between July and October than squirrels, but in 1 year squirrels took the largest number of seeds. Pre-dispersal seed predation by squirrels tended to be lower in years with large seed-crop size and there was a positive correlation, over the entire study period, between density of recovered hoards and Arolla pine seed density of the previous year. We conclude that (i) squirrels and nutcrackers are important pre-dispersal seed predators and seeds dispersers; (ii) squirrels are also post-dispersal seed predators, and (iii) the proportion of cached seeds consumed by squirrels increased with the size of the Arolla pine seed-crop, suggesting that red squirrel is a conditional mutualistic scatterhoarder of Arolla pine seeds.     

CONTROL OF CUTWORM IN FOREST NURSERIES

Larvae of Agrotis segetum Schiff (cutworms) damaged seedlingson a light loam soil at Ken nington Nursery, Oxford. Experimentscarried out in 1955–7 investigated the effect of BHC,DDT, aldrin, and dieldrin on cutworms and their phytotoxicityto Sitka spruce (Picea sitcbensis) seedlings. A spray containing 3 lb. aldrin per acre (as a 30 per cent,miscible oil) or 1? lb. dieldrin per acre (as a 15 per cent,miscible oil) gave excellent control of Agrotis segetum larvaeand did no damage to the seedling crop. Both insecticides wereapplied in 100 gallons water per acre. Immediate control ofcutworm was obtained with applications at time of expected larvalemergence (mid-June) or at time of first visible crop damage(mid-July); applications one month later gave good control after3 days. Stock beds containing seedlings of all the conifers commonlyused in Britain have been sprayed in mid-July with aldrin anddieldrin at half the rate used in the experiments. No specieswas damaged and control of cutworm was good.     

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.     

Die Verbreitung des Hygieneschädlings Braunbandschabe (Supella longipalpa [Fabricius, 1798]) (Blattodea,Blattidae) in Deutschland

The in houses living cockroachSupella longipalpa Fab. was found in Germany for the first time in 1954 (Peters, 1956). A view is given on the localities of findings until 1994/5. From this is to be seen that this pest shows a pronounced insular distribution. For controlling specific measures must be applied.     

Dothistroma pini Hulbary: A New Disease on Pine in Britain

Dothistroma pini Hulbary, not hitherto reported in Britain,is described. Since 1954, and possibly before this date, ithas caused serious defoliation of nursery pine stock, particularlyof Pinus nigra and P. ponderosa. It has been reported only fromtwo nurseries both in the Wareham area, Dorset, but the reasonfor this extremely limited distribution is unknown. Attacksare worst in wet summers. Spore inoculations on potted plantsgave severe infection.     

Chemical components of hardwood barks stripped by the alien squirrel Callosciurus erythraeus in Japan

The Pallas squirrel (Callosciurus erythraeus; common name in Japan: Formosan squirrel) was introduced in the 1950s and has established populations throughout southeastern Kanagawa Prefecture, Japan. Some tree species in natural forests, parks, and gardens in residential areas have been intensively debarked by the squirrels, especially in winter and spring. The amounts of chemical components, such as polyphenols, resins, flavanols, and sugars, in the bark were compared among species and individual trees collected in the forest of Yokohama Nature Sanctuary. Interspecific differences in the extent of stripping were not related to the amounts of the four chemical components. For individual trees, the bark with feeding scars tended to contain more sugar than that without scars.     

Diversifying native pinewoods using artificial regeneration

Little is known about broadleaf establishment within the nativepinewoods of Scotland, yet such information is critical to currentrestoration initiatives. A 2-year field trial was set up toassess the growth and performance of seedlings of four broadleavedspecies within different developmental stages of Pinus sylvestris(Scots pine) woodland in the Scottish Highlands. The developmentalstages included stem initiation (establishment stage), stemexclusion (thicket/pole stage) and canopy break up (old-growthcanopy), providing sites of varying shade and resource availability.It was predicted that differences in establishment between siteswould occur due to species-specific differences in ‘tolerance’of shade, low-nutrient availability and poor soil drainage.Analysis of trial results showed high survival but growth rates(relative stem height and basal diameter growth) declined rapidlyin year two. In year two, Ilex aquifolium achieved the highestmean growth rates in the stem exclusion stands (average 15 percent light) where there was a lower percentage of Phytomyzailicis (holly leaf miner) infection and frost damage. Sorbusaucuparia exhibited generalist behaviour with similar growthand performance across all stand treatments. Betula pubescensmaintained similar growth rates across stand types but was moresusceptible to insect damage in deeper shade. Overall, Alnusglutinosa grew more successfully than the other species andachieved highest mean growth rates in canopy break up (average44 per cent light) and stand initiation (average 71 per centlight) stages. Broadleaf establishment within pinewood standsis challenging on account of acidic nutrient-poor soil regimes,and in places, poor drainage, aggressive understorey competitionand canopies that restrict light availability and insect herbivory.Forest restoration techniques, including matching species tosite, accelerating establishment and using framework species(individuals of high field performance that are able to restoresite productivity and nutrient cycles), are discussed.     

Severely insect-damaged forest: A temporary trap for red squirrels?

Recent insect infestations in the spruce-fir forest in the Pinaleño Mountains of southeastern Arizona provided an opportunity to document response to severe forest disturbance and existence of an ecological trap for an endemic montane isolate, the endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis). From September 2003 to December 2005 we assessed habitat selection and home range dynamics, and monitored potential correlates of fitness (body mass, reproduction, survivorship) in red squirrels living in insect-damaged forest, while drawing comparisons to squirrels inhabiting undamaged mixed-conifer forest. Although Mt. Graham red squirrels demonstrate equal-preference for habitat within insect-damaged forests and reproduce as well as individuals in undamaged forest, poor survivorship and reduced potential to reproduce suggest insect-damaged forest may function as an ecological trap. In addition, areas selected within insect-damaged forest had <69% dead trees, suggesting an upper limit to the extent of tree mortality tolerated by red squirrels. Habitat selection and sensitivity to disturbance will influence use of insect-damaged areas by forest-dwelling species. Although insect-damaged forest may retain habitat patches for a few individuals, low survivorship may generate an ecological trap.     

PICEA OMORIKA IN ITS NATURAL HABITAT

The paper, which is based on a visit to Bosnia in 1954 and onthe literature available, describes in detail ten of the principalsurviving sites or stations of Picea omorika (Pancic) Bollein the Dinaric Alps and discusses the relationship of the treeto its present restricted environment. The main conclusionsare that the spruce, which is a relic in the flora of the BalkanPeninsula, succumbs to competition with other species and ispoorly adapted to its present environment but holds its ownwhen competition is absent as on north-facing cliffs or screesor where it has regenerated itself after fire or exploitation.     

Walnut hoarding by the Japanese wood mouse,Apodemus speciosus Temminck

Walnuts,Juglans ailantifolia Carriere, are large and the shell is difficult to open. Thus, seed predators in Japan are restricted mainly to the Japanese squirrel (Sciurus lis Temminck) and the wood mouse (Apodemus speciosus Temminck), which can shave away the hard shells with their sharp incisors. Previous work indicated that the squirrels are not only predators, but also disperse walnuts. In this study, 95 walnuts in Period1 (September 1996–February 1997) and 80 walnuts in Period 2 (September 1999–February 2000) each attached to a miniature radio transmitter, were placed in a feeding box, and 93 and 53 of them were transported by free-living wood mice in the respective periods. Most of the walnuts provided from September to November were scatter-hoarded in the litter layer, while from December to February, the mice fed immediately and seldom scatter-hoarded on the ground surface. In all, 66 walnuts were hoarded and 80 were eaten soon after discovery, although walnuts were eaten more frequently in Period 1 than in Period 2, which may be related to annual differences in seed crop size in the study site. The mean transport distance of hoarded seeds was 6.2 ± 5.0 m (mean ± SD,n=66). The fate of hoarded walnuts was followed from September 1996 to May 1997; 21 (75%) of the scatter-hoarded walnuts were recovered, but 7 (25%) were left uneaten. Consequently, the Japanese wood mouse also plays a role in seed-dispersion of the walnut, but the transport distance for mice was shorter than that for squirrels.     

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.     

Root anchorage and stem strength of black spruce (Picea mariana) trees in regular and irregular stands

A tree winching experiment was conducted, simulating wind actionand resulting damage, in order to assess mechanical resistanceof black spruce (Picea mariana (Mill.) B.S.P.) trees in standsof regular and irregular structures. The critical bending moment(M_c) of winched trees was determined and the relationship betweenM_c and tree and stand characteristics was investigated throughstatistical analyses. Stem mass (SW), average spacing betweentrees (S) and height:diameter ratio (H/d.b.h.) were initiallyselected by a screening procedure to predict M_c. Potential differencesbetween stand structures were tested in mixed models using differentsubsets of the data. Included fixed effects varied between thedifferent models. SW was the most useful and significant variablein all models and H/d.b.h. was significant only when snappedtrees were included in the analysis. When decayed samples wereexcluded, resistance to uprooting was higher in irregular stands.Decay seemed to play an important role in irregular stands andshould be investigated further. Since no difference was observedin the relationship between stem mass and critical turning momentbetween distant sites, relationships should be applicable acrosswide regions. This study provides some of the basic relationshipsrequired to model windthrow risk in irregular stands. However,the effects of stand structure on wind load for individual treeswill also need to be considered.     

Comparing regional forest policy scenarios in terms of predicted suitable habitats for the Siberian flying squirrel (Pteromys volans)

Forecasting the potential impacts of forest policies on species of special conservation value is a prerequisite for safeguarding forest biodiversity. In this study, regional forest policy scenarios were compared in terms of predicted habitats suitable for the Siberian flying squirrel (Pteromys volans). To derive both patch- and landscape-scale models to predict species presence in a forest stand, species occurrence data from a systematic field survey covering the whole distribution area of the flying squirrel in Finland and Multi-Source National Forest Inventory data were combined. Then, the Finnish forestry model MELA and the derived occupancy models were applied to predict the quantity of suitable habitats for flying squirrels in three different 50-year policy scenarios. The results confirm that increasing the utilization of felling potential from the level of business-as-usual to the level stated as policy targets in regional forest programs decreases the amount of suitable habitat in the future. However, regional forest programs had a less drastic impact on habitats than maximum sustainable removal, except in two regions. It should be noted that the occupancy models seemed to fail on sites that experts deem to be most suitable for the species. Obviously, there are other factors than forest management affecting presence.