Factors influencing patch occupancy and within‐patch habitat use in an apparently stable population of Willow Tits Poecile montanus kleinschmidti in Britain

Capsule Birds selected younger woodland patches with fewer conifers and higher soil moisture content; within these patches, they selected areas with higher vegetation cover at 2–4 m, and less bracken.

Aims For an apparently stable population, to investigate habitat differences between occupied and unoccupied woodland patches and habitat selection within occupied woodlands.

Methods We surveyed woodland patches for breeding Willow Tits in April 2006 in an area with an apparently stable population. Habitat was measured at points spread throughout each woodland patch and at points where Willow Tits were located. We compared habitat between occupied and unoccupied sites. In addition, within occupied sites, we examined habitat differences between Willow Tit locations and the points spread throughout the wood.

Results We surveyed 65 woodland patches, of which 29 were occupied. Willow Tits were more likely to be found in deciduous woodland that was younger and had higher levels of soil moisture. Probability of occupancy fell from 60% for woods aged 20–25 years to only around 15–30% for woods aged over 80 years. Within occupied woods, Willow Tits were more likely to be found in areas with more vegetation cover at the 2–4 m level and in areas with less bracken.

Conclusions Habitat management for Willow Tits should involve provision of young woodland patches with moist soils. Changes to the age structure and/or the soil moisture content of woods may be implicated in the dramatic decline of Willow Tits in Britain.     

Biodiversity and ecology of the invertebrates of Atlantic Oakwoods

Summary

Woodland in general supports the richest invertebrate fauna of any habitat in Britain. The number of species depends on the structure of the wood and the age of the trees within it. The greatest biodiversity is associated with oaks although the difference between the communities found on the two oak species is not clearly understood, the Sessile Oak woods have been less well studied than their lowland equivalents, particularly so in Scotland. A number of minor habitats within the wood are important for many invertebrates and the presence of many of these may be due to past management. Every part of the oak tree, the leaves, flowers, acorns, bark and wood, supports invertebrates, herbivores, predators and parasites, and the fallen leaves and deadwood provides habitat for a complex of detritus feeders. Within the woodland the other trees, the fungi and the ground flora all have characteristic woodland invertebrates. Only a few studies, on beetles and spiders, have looked at which invertebrates are particularly associated with acidic oakwoods and there have been no specific studies of Atlantic oakwoods. It is known that there are some rare and local invertebrate species associated with western woods on ancient sites, including some recently discovered suggesting that the biodiversity of these sites and their management for invertebrates might be more important than currently thought.     

Seasonal activity patterns of Ixodes pacificus nymphs in relation to climatic conditions

Abstract In western North America, the tick Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) is the primary vector to humans and domestic animals of the disease agents causing Lyme disease and granulocytic ehrlichiosis. We examined the seasonal activity patterns of I. pacificus nymphs over a 4‐year period, including the wet and cold El Niño winter/spring of 1998, in a dry oak/madrone woodland, and for one year in a cooler and moister redwood/tanoak woodland in Mendocino County, California. Linear regressions were used to estimate when nymphal densities first exceeded and then fell below 25, 50 and 75% of the recorded yearly peak densities. In oak/madrone woodland, nymphs typically were active by mid‐March, reached 50% of their yearly peak densities in early to mid‐April, peaked by early May, fell below 50% of their peak densities by early to mid‐June, and were absent by late July to mid‐August. The lengths of the periods with nymphal densities exceeding 50 and 75% of the recorded yearly peaks in oak/madrone woodland were associated positively with rainfall and negatively with maximum air temperatures during April–May. Moreover, nymphal numbers typically reached 50% of their peak 10–15 days later, remained at levels above 50% of the peak 1.3–1.5 times longer, and started declining 4–6 weeks later under cooler, moister climatic conditions (oak/madrone woodland in 1998 and redwood/tanoak woodland in 2000) relative to warmer, drier conditions (oak/madrone woodland in 2000–2001). In oak/madrone woodland, nymphal densities typically started to decline when mean maximum daily air temperatures exceeded 23°C. Nymphal densities were higher in dry oak/madrone relative to moist redwood/tanoak woodland from mid‐March to late May 2000, similar in both habitat types in early June, but higher in redwood/tanoak woodland from late June onwards. We conclude that large‐scale studies of the density of I. pacificus nymphs in California need to consider spatial variation in the length of nymphal activity periods and select temporal sampling regimens that yield representative data for all included habitat types.     

Timing of breeding and nestling diet of Wood Warbler Phylloscopus sibilatrix in relation to changing food supply

Capsule Wood Warblers did not match their reproduction to the caterpillar peak

Aims To study the timing of Wood Warblers’ breeding and nestling diet in relation to caterpillar abundance under primeval conditions in the Bia?owie?a National Park, Poland.

Methods Observations of food brought by parents. Inter‐year and seasonal changes in availability of folivorous caterpillars were assessed by direct counts and caterpillar frass collection.

Results Maximum food requirements occurred two weeks after the peak of caterpillar abundance. The mismatch had no effect on nestlings’ development. Diet varied little across years and habitats, but varied strongly within a season. Following the decline of ‘green’ caterpillars, their proportion in the Wood Warbler diet strongly declined. Caterpillars were replaced by winged insects. Small nestlings received more spiders than older ones.

Conclusion Timing of Wood Warbler breeding in Bia?owie?a National Park was constrained by the females’ arrival time. Birds did not match their reproduction to the caterpillar peak. ‘Green’ caterpillars were the preferred food for nestlings; birds responded to the caterpillar decrease by feeding smaller proportions of them and switching to alternative prey, namely winged insects.     

Assessing breeding success in common woodland birds using a novel method

Capsule Repeated counts of fledged broods can provide a useful estimate of breeding success for most common woodland birds.

Aims To assess the efficacy of comparing fledged-brood survey data with territory mapping using simple mark–recapture analysis techniques to provide an estimate of breeding success for common woodland birds that does not involve finding nests.

Methods Three observers undertook territory mapping surveys of adults, followed by counts of fledged broods four times a week during May–July 2007 in two 15 ha woods each, both in southern England. Using known fledging to maturity periods, these counts were used to calculate daily detection probabilities for broods of ubiquitous species. These enabled fledged brood territory occupancy probabilities (i.e. brood to territory ratios) to be estimated that take account of the possibility that broods were present but missed by surveys.

Results Of the 19 species found in all six woods, mean daily detection probability estimates for fledged broods of 17 species ranged from 0.17 to 0.50 with significant variation between woods for 12 species, but within region/observer for four species. The mean probability of detecting a brood at least once was over 75% using four visits per week and over 50% using two visits. Only for Great Spotted Woodpeckers Dendrocopos major and Garden Warblers Sylvia borin was the fledging period too short and the daily detection probability too low to provide a reasonable estimate of the territory occupancy probability.

Conclusion Daily detection probabilities for fledged broods of most common woodland birds were sufficiently high to enable useable estimates of fledged-brood territory occupancy probabilities to be made based on a survey programme involving two or three visits per week between late May and the end June. The method used may have application as a means of providing a relatively easily derived productivity index for woodland bird monitoring programmes or for research studies.     

The pattern of Dunlin Calidris alpina distribution and abundance in relation to habitat variation in the Flow Country of northern Scotland

Capsule Folivorous caterpillars constituted the majority of nestlings’ food in a primeval forest. Blue Tit broods only partially matched the caterpillar peak, and the mismatch did not affect food composition or nesting success.

Aims To describe factors influencing the timing of reproduction in Blue Tits under primeval conditions (Bia?owie?a National Park, Poland) and to check whether they schedule breeding so as to synchronize broods with a seasonal caterpillar peak.

Methods We gathered information on phenology of leaf development, seasonal availability of folivorous caterpillars (frass collection), timing of Blue Tit breeding, composition of its nestling food, and nest fate over a three-year period.

Results Caterpillars constituted c. 74% of nestling diet, but only 17–65% of broods matched the caterpillar peak in any season. Neither total nest loss, nor frequency of brood reduction depended on the level of mismatch. Caterpillar availability was probably adequate every year, regardless of the amount of mismatch, and no selective advantage of precise matching was detectable. Phenological events at all trophic levels occurred earlier in warmer springs. Egg-laying coincided with tree bud burst and appearance of caterpillars, but was not critically dependent on their timing.

Conclusion The observations are consistent with the view that Blue Tits under primeval conditions in Bia?owie?a National Park, Poland, breed as early as possible, rather than synchronizing their breeding with the caterpillar peak later in the season.     

Lichens — the biodiversity value of western woodlands

Summary

The Atlantic broad-leaved woodlands of Britain are of international renown for their lichen floras. They are inhabited by 517 lichens, representing 28.3% of the total lichen flora and 73.2% of all British woodland lichens, and they are the main habitat for 165 species. Of these, 31 have a marked southern distribution and do not reach Scotland, whereas 26 species are found in Scotland, but not England or Wales. Their British Red-listed species are outnumbered by the 86 species for which Britain has International Responsibility.

Within the Atlantic broad-leaved woodlands, only 30 lichens show a preponderance for oak. With the exception of some ancient oakwoods in southern England, a high lichen biodiversity is rarely dependent on a dominance of oak in the woodland canopy, more usually it is the result of a long ecological continuity, often a varied tree and shrub composition, a varied canopy density, and good air quality. Consequently, the oak stands within former ‘industrial’ woodlands have a much lower lichen biodiversity compared with woodlands that have a history as ‘pasture woodland’ or, as with some ravine woodlands, have otherwise escaped intensive management.

The life-history of an oak tree is considered in relation to the niches it provides for lichen colonisation with time. Some management scenarios are provided with the enhancement of the lichen interest of former ‘industrial’ oakwoods as an objective.     

Breeding season habitat associations and population declines of British Hawfinches Coccothraustes coccothraustes

Capsule At both landscape and local scales, breeding persistence in a declining Hawfinch population was greatest where broadleaved woodland cover was high, while at a fine scale, nest sites were associated with openings in the woodland canopy.

Aims To assess which components of habitat are associated with Hawfinch occupancy at landscape (10-km), local (tetrad) and fine (nest) spatial scales, during a period of population decline and range contraction.

Methods Bird Atlas 2008–11 data were used to determine areas of Hawfinch loss and persistence over 20 years. Current habitat was measured and compared to look for correlates that helped explain the differing status at both 10-km and tetrad scales. Fine scale habitat data collected at nest sites were compared with random locations to investigate within-wood nest site selection.

Results At both 10-km and tetrad scales, Hawfinch persistence is more likely where woodland cover is greater. Recent woodland management was less evident in tetrads where the species persisted. At the nest site scale, the only relationship detected was for nests to be close to canopy openings.

Conclusions Maintaining and increasing broadleaved woodland area is likely to benefit Hawfinch. Within woods, maintenance and creation of open areas may enhance nesting opportunities.     

Willow Warbler Phylloscopus trochilus habitat in woods with different structure and management in southern England

Capsule Use of Light Detection and Ranging (LiDAR) data identified suitable Willow Warbler habitat based on mean vegetation height. This habitat model provided maps of distribution and occupation of suitable habitat.

Aims To identify habitat associations in woods with different vegetation structure and management systems during a period of low Willow Warbler populations.

Methods Locations of all Willow Warblers were mapped during the breeding season in three woods of contrasting management; recent low intervention, actively coppiced woodland and high forest with clear‐fells. Height profile models of each wood were derived from airborne LiDAR. The mean vegetation height at locations with Willow Warblers and a sample from the rest of the wood were used to produce models of optimum habitat and breadth of habitat occupied in each wood. The habitat model was then used to produce maps of suitable habitat.

Results The habitat models did not differ between woods, with highest probability of Willow Warbler occurrence in mean vegetation heights of 3.7–5.3 m. Habitat of heights 6–11 m appeared less suitable, being only partly occupied. Habitat maps showed that habitat of suitable height was only occupied when it occurred as large patches; smaller patches (mostly <0.5 ha) and edges along rides and fields were not used.

Conclusion The use of LiDAR derived measures of vegetation height identified areas of suitable habitat for Willow Warblers. Willow Warblers occupied areas of low mean vegetation height either as early successional or open canopy woodland in all woods. Height‐based habitat maps can identify areas of suitable habitat within larger expanses of heterogeneous woodland and are a potentially useful tool in assessing changes in extent of what are often temporary patches of habitat.     

National‐scale analyses of habitat associations of Marsh Tits Poecile palustris and Blue Tits Cyanistes caeruleus: two species with opposing population trends in Britain

Capsule Marsh Tits were strongly associated with both the amount and species diversity of woodland understorey; Blue Tits were associated with large trees and deadwood.

Aims To gather quantitative information on the habitat requirements of Marsh Tits, in comparison with those of Blue Tits, across a large number of sites in England and Wales, and secondly to evaluate the range of habitat conditions likely to encourage the presence, and increase the abundance of, each species.

Methods Counts of birds were made at each of 181 woods across England and Wales, and habitat data were collected from the same locations in each woodland. Marsh Tit and Blue Tit presence and abundance were related to habitat characteristics, interspecific competition and deer impact.

Results Shrub cover and species diversity were important for the presence and abundance of Marsh Tits, across their geographical range in Britain. Blue Tits were associated with large trees and deadwood.

Conclusion Our results support the hypothesis that changes in woodland management, leading to canopy closure and a decline in the understorey available, could have had an impact on Marsh Tits, and may have led to the observed population decline. These same changes were also consistent with population increase in Blue Tits.     

Structure and utilisation of the early oakwoods

Summary

The paper explores whether any of the familar range of current oakwood structures in the west of Scotland can be used as realistic analogues for the prehistoric oakwoods. Even for the early historic oak woodlands we have no detailed knowledge of previous structures and composition.

The structure of today's oak woodlands, and to some extent even the legacy of species within that habitat, are a type of biocultural heritage. The oak woodlands that we see today are the product of a long interaction: between man's use of the woodlands and the ongoing natural processes within the oakwood ecosystem.

Grazing animals, especially domestic cattle and red deer, have played a key part in determining oak woodland structure in historic times, and perhaps have a future role too. Are there lessons to be drawn from knowledge of past management and regeneration of oak which are relevant to the present day, when most managers are finding it difficult to regenerate oak woodlands on any scale?

Understanding past utilisation and structure of oak woodlands is valuable mainly as a guide to future management. Indeed one might ask which models and structures are relevant for managing an oak woodland resource now regarded mainly as a wildlife habitat?     

Seasonal variation in diet quality: antioxidants,invertebrates and blue tits Cyanistes caeruleus

Breeding success is often dictated by the degree to which parents can synchronize the maximum food requirements of offspring to the peak in abundance of invertebrate prey. Less studied is how the nutritional quality of individual diet items impacts on breeding. In the present study, we assessed the abundance and antioxidant concentrations of arboreal arthropods from oak woodland and provisioning behaviour of the blue tit Cyanistes caeruleus. Dietary antioxidants are important during development because they defend against oxidative stress. Operophtera caterpillars, Erannis caterpillars, and spiders contained significantly different levels of individual carotenoids and α‐tocopherol. Concentrations of lutein and β‐carotene in Operophtera caterpillars did not vary seasonally, although concentrations of zeaxanthin declined and α‐tocopherol increased with date. Blue tit broods hatched later in the season received significantly fewer caterpillars and more spiders per chick compared to earlier broods. Reflecting changes in prey composition, blue tit nestling plasma showed decreases in zeaxanthin and increases in α‐tocopherol with date. Thus, processes that shift the timing of breeding in birds and/or prey composition are likely to alter antioxidant intake and thus potentially influence the oxidative stress status of animals. The data obtained in the present study suggest a mechanism by which environmental change as a result of human activities could influence the health and fitness of individuals in natural populations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 708–717.     

The effect of woodland area on avian community composition in a fragmented southern UK landscape and associated management recommendations

ABSTRACT

Capsule: Smaller woodlands not only support fewer species but also show different avian community composition due to loss of woodland interior and an increase in edge habitat.

Aims: To use observed community composition changes, rather than traditional total species richness-area relationships, to make area-specific management recommendations for optimizing woodland habitat for avian communities in fragmented landscapes.

Methods: 17 woodlands were selected in Oxfordshire, UK, with areas between 0.2 and 120 ha. Three dawn area searches were conducted in each woodland between 1st April and 28th May 2016 to record encounter rates for each species. The impact of internal habitat variation on woodland comparability was assessed using habitat surveys.

Results: Woodlands with area less than 3.6 ha showed a significant positive relationship between total avian species richness and woodland area. Woodlands with area over 3.6 ha were all consistent with a mean (± se) total richness of 25.4?±?0.6 species, however the number of woodland specialists continued to increase with woodland area. Woodland generalists dominated the total encounter rate across the area range, however the fractional contribution of woodland specialists showed a significant positive correlation with woodland area, while the fractional contribution of non-woodland species significantly decreased. Non-woodland species numbers peaked in mid-sized woodlands with enhanced habitat heterogeneity.

Conclusions: Community composition analysis enabled more targeted recommendations than total species richness analysis, specifically: large woodlands (over 25?ha) in southern UK should focus conservation efforts on providing the specific internal habitats required by woodland specialists; medium-sized woodlands (between approximately 4 and 25?ha) should focus on promoting internal habitat variety, which can benefit both woodland species and non-woodland species of conservation concern in the surrounding landscape; small woodlands (under 4?ha) should focus on providing nesting opportunities for non-woodland species and on improving connectivity to maximize habitat for woodland generalists and facilitate movement of woodland specialists.     

Oak as a commercial crop in the eighteenth and nineteenth centuries

Summary

The main period of the exploitation of the Atlantic oakwoods lasted from around 1700 –1900, and was intense only from 1750–1850, though it had been preceded by a long period of anthropogenic interference of which medieval boatbuilding at least had the potential to alter the character of the woods. The Irish were pioneers when they began to search the coast from the Solway to the Great Glen for fresh supplies of oak bark for their tanning industry, and early in the 18th century this involved an attempt to buy large swathes of Argyll oakwoods, and also to create iron works at Glen Kinglas to utilise local charcoal. This failed, but by mid-century English ironmasters had followed them at Bunawe and Craleckan, works ambitious enough to draw fuel from most of the area within reach of the sea, and this led to greater care being taken of the woods involving the exclusion of stock, systematic rotational coppicing and apparently species selection in favour of oak. Management for tanbark by Scots to supply Scottish markets outpaced charcoaling before 1800, however, and affected areas like Loch Lomondside and Perthshire far from the sea, with similar consequences.

A crisis developed when the tanbark and charcoal markets collapsed, notably after 1840, but it took another generation of owners to adapt. Before the end of the century, coppice was largely abandoned, though in places where there were pyroligneous acid works or opportunities to sell spoke wood, the practice lingered on. Generally, however, stock were readmitted, and the woods converted to high forest or game coverts.     

The Quercus cerris woods of the alliance Carpinion orientalis Horvat 1958 in Italy

Abstract

A phytosociological study of the alliance Carpinion orientalis in the hilly and subcoastal areas of the Italian peninsula is presented. These woods are included in the suballiances Laburno-Ostryenion and Lauro-Quercenion; the distinction between these two suballiances is not always easy also because of the conservation status of these forest ecosystems. The hilly and subcoastal Turkey oak woods of the alliance Carpinion orientalis are mainly distributed on the Adriatic side of the Italian peninsula, where they are found on neutro-basic substrata to which these coenoses are linked. The Turkey oak woods of the alliance Teucrio siculi-Quercion cerridis are strongly linked to the acidic substrata typical of the Tyrrhenian side, but are sporadically found on the Adriatic side within small enclaves with more acidic substrata. A numerical analysis allowed us to rearrange the lower hierarchical levels of the associations of Turkey oak woods of the alliance Carpinion orientalis. In particular, the association Lonicero xylostei-Quercetum cerridis is included in the alliance Carpinion orientalis, and the new subassociation festucetosum exaltatae is proposed. The subassociation rosetosum arvensis is proposed for the association Daphno laureolae-Quercetum cerridis, and the new subassociation cytisophylletosum sessilifolii of the association Aceri obtusati-Quercetum cerridis is described.     

Argyll oakwoods: Use and ecological change, 1000 to 2000 AD — a palynological-historical investigation

Summary

This paper explores the relationship between ecological change and human use in Atlantic oakwoods during the last millennium. Information on vegetation change derived from high resolution pollen analytical studies can sometimes be satisfactorily linked with localised documentary evidence of historical woodland management. Key findings based on this approach using case studies of individual woods in Lorn are presented. Relatively diverse woods, probably containing old-growth, were transformed in the medieval period into disturbed open stands used for pasturage and local domestic wood supply. Around or prior to 1700 AD commercial management began and modes of exploitation changed so that, for a period until the late 19th or early 20th century, stands were cropped intensively. In the most recent 100 years or so, use of the woods has been relatively minor except as a grazing resource. The consequences of this history for the development of the current condition and character of Atlantic oakwood resources are discussed with reference to elements of woodland biodiversity such as arboreal species composition and Atlantic bryophyte assemblages.     

Regional variation in the origin,extent and composition of Scottish Woodland

Summary

Results from the Nature Conservancy Council's Inventory of Ancient Woodland show regional variations in the extent, origin and composition of Scottish woods and the degree to which they are recognized as important sites for nature conservation. Around 14.5% of Scotland is forested but not more than 2% of the land area is ancient woodland. Nearly half of the ancient area has been replanted, mainly with introduced conifers. Thus the area retaining ancient semi-natural woodland covers just 1 % of Scotland. Woodland within Sites of Special Scientific Interest or nature reserves covers 38,154 ha. The majority of this is ancient semi-natural woodland, but 68% of the total ancient semi-natural woodland area is not so protected. The value for nature conservation of many ancient sites has declined because of the extent of replanting and overgrazing. Recent beneficial changes in land use policies and practices need to be continued to prevent further decline in the nature conservation value of these important woods.     

Interactions of temperature and dietary protein concentration in growth and feeding of Manduca sexta caterpillars

Abstract .Temperature and the protein content of food affect rates of consumption and growth in herbivorous insects in different ways: reduced temperature typically reduces both consumption and growth rates, whereas reduced dietary protein typically increases consumption rate but either reduces or has no effect on growth rate. The interactions between temperature and dietary protein concentration in affecting consumption, growth and efficiency in fifth-instar caterpillars of Manduca sexta were studied, using both short-term (4 h) and long-term (duration of fifth stadium) experiments. The short-term experiments examined constant temperatures between 14 and 42°C, whereas the long-term experiments examined constant temperatures between 18 and 34°C; both experiments considered two levels of dietary protein. In both experiments, caterpillars had significantly higher consumption and frass production rates on low-protein compared with high-protein diets at each test temperature between 18 and 34°C, thereby compensating for the lower diet quality. In contrast, at more extreme temperatures (14 and 42°C) in the short-term studies, consumption and frass production rates were lower on low-protein compared with high-protein diets. As a result, there were substantial interactions between temperature and dietary protein for consumption and frass production rates in the short-term experiments, but not in the long-term experiments. These results suggest that interactions between temperature and dietary protein may emerge because of the failure of compensatory feeding responses at low and high temperatures. It is hypothesized that the failure of compensatory responses is more likely to occur under diurnally fluctuating temperatures than under a constant temperature with the same mean, and it is proposed that interactions between temperature and dietary protein for consumption are relevant to M. sexta and other caterpillars that experience wide diurnal fluctuations in temperature in the field.     

Are changes in breeding habitat responsible for recent population changes of long-distance migrant birds?

Capsule: The direction and magnitude of changes in structure of UK woodlands since the 1980s, are inconsistent with them playing a causative role in the declines of four migrant bird species in upland oak woods.

Aims: To investigate whether changes in woodland structure were a possible cause of population changes of four Afro-Palearctic migrants (Wood Warbler Phylloscopus sibilatrix, Tree Pipit Anthus trivialis, Pied Flycatcher Ficedula hypoleuca and Common Redstart Phoenicurus phoenicurus) in the upland oakwoods of western and northern Britain.

Methods: Bird population estimates and measures of woodland structure were recorded in two time periods 1982–85 and 2003–04 across six regions of the UK. We modelled the effect of habitat change and initial habitat state on population changes between the two time periods. The predicted effects of habitat change on populations were then compared with observed population changes across the different regions.

Results: All four species underwent population declines; there were also significant increases in ground cover and understorey cover. The number of birds in 2003–04 was influenced by habitat structure at this time in addition to showing regional differences. Change in bird numbers varied between regions and was affected by both the initial habitat state and change in habitat structure, with regional variation in the effect of habitat change. There was however no relationship between the predicted effect of change in habitat structure on population size and observed regional population changes.

Conclusions: Changes in woodland structure are unlikely to be the main driver of population change in these four migrant bird species, and large-scale factors affecting demographics in other parts of their breeding range or in their wintering areas are likely reasons for local population declines.     

L'evoluzione della cerchia legnosa in Quercus Pubescens W. Ein Quercus Ilex L. nel clima di Firenze

Summary

The evolution of the wood ring in Quercus pubescens W. and in Quercus Ilex L. in Florence (from June 1946 to June 1947).

The present study deals with the anatomical characters of the wood ring of Q. pubescens and of Q. Ilex. In both the specimens the wood of the stem and of the young branch has been investigated.

In both plants studied the cambial tissue of the stem starts dividing at the end of April, reaching its maximum activity from May to June.

On the contrary the cambium of the branch differentiates in Q. pubescens a month earlier (18 March-18 April) than in Q. Ilex (18 April-18 May). While in the branch of Q. Ilex a false ring can be seen corresponding to the autumn months, nothing of the kind is found in the branch of Q. pubescens; though it presents a false ring in the stem.

It is difficult to date clearly the period when the cambium stops its activity, but probably it happens at the end of August in the samples of the stem.

The leaf buds of Q. pubescens and of Q. Ilex open during April-May and the young branch is completely developed at the end of June. In both oaks some buds open in autumn, but the small branches are prevented to develop because of the cold.

No comparison can be made between the opening of the buds and the beginning of the cambial activity in the stem and in the branch.

Considering the evolution of these woods and their relationship to climatic factors, we can see that the cambial activity starts during a period of remarkable rainfall and of regular increase of temperature, and stops almost completely at the end of July, when temperature and dryness reach their highest values.

The autumn rainfall would favour again a cambial activity, but the values of the temperature, regularly decreasing, do not allow it.