Different Species Of Trees Research Articles

Tree life history strategies: the role of defenses

Analysis of energy partitioning between defensive investments and growth in woody plants indicates that increasing a tree's life-span should require increased energy investment in protective measures such as thick bark and defensive chemicals. Increased investment in such defenses, however, logically must slow down the growth rate, thereby raising the mortality rate for juveniles in competition for height growth. Early reproduction should also reduce the growth rate. It is hypothesized that rapid growth can substitute for these defenses, but the consequence is rapid decline upon reaching maturity. These predictions are tested with data compiled from the literature for 159 species of North American trees. Data analysis supports predictions. Longevity of angiosperms, but not of gymnosperms was correlated with increased investment in defenses as measured by volumetric heat content of the wood. Wood density was not as good a measure. Longevity of gymnosperms was predicted by resistance to wood decay. For both taxa there was a negative correlation between growth rate and longevity, supporting the hypothesis of growth trade-offs. Age of sexual maturity was closely predicted by longevity in angiosperms. There was no such relationship for conifers as a whole, though there was for pines. The lack of relationship for all conifers might be explained by (i) variation in reproductive opportunities for young trees of different species, or (ii) variation in growth rates of young trees in certain adverse habitats occupied by conifers.

Fruit‐Size, Gape Width, and the Diets of Fruit‐Eating Birds

In most animals, especially those that must swallow food items whole, prey size is related to predator size. This paper examines gape limitation and the influence of fruit size on diet in fruit—eating birds, drawing on data gathered over a 5—yr period on 70 bird species and 171 plant species in the lower montane forests of Monteverde, Costa Rica. The results suggest that fruit—eating birds face many of the constraints imposed on other gape—limited foragers, but have an unusual minimum—size relationship with their food because of the unique characteristics of fruits. Fruit—eating birds with broad gapes consumed more lauraceous fruit species and a larger mean and maximum size of fruits overall than narrow—gaped birds. However, the size of the smallest fruits eaten was not correlated with gape width; large—gaped species commonly fed on diminutive fruits. Birds effectively selected among individual fruits within a tree on the basis of fruit size, dropping bulky fruits beneath the tree. Effective size selectivity also occurred among trees of different species in the same family and among plant species in various families. The diet of broad—gaped birds was not comprised differentially of large fruit species. For example, Three—wattled Bellbirds favored medium—sized fruits, whereas Long—tailed Manakins took individual fruits in the same proportions as they took fruit species of different mean fruit diameters. Gape limitations and effective size selectivity have obvious consequences for seed dispersal patterns: Plants with large fruits attracted fewer species of birds than plants with small fruits. Moreover, the broad—gaped bird species on which large—fruited plants specialized were those with the most generalized diets.

Some Distance-Based Tests of Independence for Sparsely-Sampled Multivariate Spatial Point Patterns

Summary Methods for the statistical analysis of spatial point patterns can be divided into two categories, according to whether or not a complete map of the underlying pattern is available. This paper is concerned only with methods for the analysis of data extracted from a pattern in situ by a 'sparse sampling' method involving the measurement of distances from sampling origins to neighbouring points of the pattern. The paper first gives a brief review of sparse sampling methods for univariate patterns and then discusses the problem of testing for independence between two or more patterns. Some new tests are described and power comparisons are presented. The methods are illustrated on two sets of forestry data, where the patterns are formed by the locations of trees of different species.

Some Observations on the Epiphytic Moss Flora of Trees in Argyll

THE, purpose of this investigation, carried out in July 1934, was the comparative study of the moss flora on different species of trees growing under different environmental conditions. The locality chosen, Achnacloich in Argyll, is very favourable for the study of epiphytic bryophytes and lichens on account of the oceanic conditions, cool winds and heavy rainfall, which persist through most of the year, as the prevailing moisture-carrying west winds come in from the Atlantic. The district round Achnacloich is very well wooded, extensive plantations being in existence on the Achnacloich estate, as well as much wood which appears natural. The state forest (Fearnoch Forest) is slightly to the south-east of Achnacloich. The great amount of free water in the neighbourhood, in the form of lochs, rivers and burns of all sizes, and the dense wood, allied to and correlated with the heavy rainfall make a remarkably suitable habitat for mosses on the trees. The moss covering is in some cases quite extraordinary, and on some of the oaks moss and lichen together cover the entire bark, from quite small twigs down to the base of the trunk. The results of the investigation given below are for mosses only. Specimens of lichens and leafy liverworts were taken at the same time, and statistics as to their occurrence and frequency obtained in similar detail to those for mosses, but these results have not yet been worked out. Trees of different species were chosen, and an attempt was made to study them in different habitats. Detailed observations were made for each individual tree studied, including the average height and diameter, the altitude (as shown

Effect of covercrops on the soil solution at different depths under orchard conditions

Abstract does not appear. First page follows. Two earlier papers(4), (5) have presented progress reports concerning changes in concentration of the more important ions in the soil solution under a variety of covercrop treatments and with different species of trees. These results were obtained from the orchard of the Pomology Division of the California Agricultural Experiment Station at Davis. The crop history has been given(4) in a former paper and is not essential for consideration of the data given here. The plot treatments were alfalfa sod (Medicago sativa); a summer covercrop of mat bean (Phaseolus aconitifolius), which was superseded by Dolichos lablab in the seasons 1931 and 1932; and winter covercrops of rye (Secale cereale) and of Melilotus indica. These were all compared with three clean-cultivated checks. The treatments were duplicated. They ran in strips across the species plantings of pears, prunes, apples, Japanese plums, cherries, apricots, and peaches as shown in figure 1. The method used in obtaining the soil solution has been described elsewhere(3), and is essentially a displacement rather than an extraction with an excess of water.

Mosquito Control

THE Report for 1930 of the British Mosquito Control Institute, Hayling Island, Hampshire, is a record of two and a half years' work, the previous Report having been presented in June 1928. The Institute, it may be added, was built and equipped in 1925 by Mr. John F. Marshall, who has since occupied the position as director without remuneration. It was incorporated by licence of the Board of Trade in February 1927 and, by a deed executed at the same time, the building and its equipment were leased to trustees for a term of years. No financial aid is received from any official funds, and the income of the Institute is derived solely from the results of its own activities and from subscriptions and donations. Funds are greatly needed in order to enable the work to become more self-supporting, since the present income falls a long way short of covering expenditure. The activities of the Institute have markedly increased since the issue of the last Report, and the interest shown by the outside public in this work is borne out by the fact that more than 1400 visitors (scientific and others) inspected the museum and laboratory during 1930. Advisory work relating to mosquitoes, their identification and control, is carried out by means of inspection and by correspondence. Inspections are generally undertaken by the director's assistant at a pre-arranged charge which includes the submission of a report and the recommendation of remedial measures. Various ’lines of investigation have been carried out during the period under review, including tests of fly-killing preparations and of cresol-containing larvicides, at the request of commercial firms. A study has also been commenced with regard to the breeding of arboreal mosquitoes in cavities (natural and artificial) in sawn-off parts of trees of different species.

The History of the London Plane

IN an article on “The Artificial Production of Vigorous Trees,” an abstract of which was pub lished in NATURE, January 7, 1915, p. 521, Prof. Augustine Henry directed attention to certain well-known trees, like the Lucombe oak, Huntingdon elm, cricket-bat willow, and black Italian poplar, which owe their vigour and botanical characters to the fact that they are of hybrid origin. Such hybrids arose as chance seedlings due to cross-pollination of two trees of different species growing together. The introduc tion into Europe during the seventeenth centurv of North American trees which grew alongside similar, but distinct, European species in parks and gardens was the occasion of considerable hybridisation. Trees like the black Italian poplar and the London plane, which have never been seen anywhere in the wild state, are intermediate in botanical characters between an American and a European species in each case, and are undoubtedly first-crosses.