scholarly journals Effect of stand structure and aspect on the regeneration of banj oak (Quercus leucotrichophora A. Camus) forest along disturbance in Garhwal Himalaya, Uttarakhand, India

2018 ◽  
Vol 68 (1) ◽  
pp. 33-39
Author(s):  
Vikaspal Singh ◽  
Dhanpal Singh Chauhan ◽  
Sabyasachi Dasgupta

Abstract A study was conducted in an oak forest, to find out the relationship of stand structure, aspect and regeneration of species. Among all disturbance stands the density of banj oak Quercus leucotrichophora A. Camus individuals was peaked at 40–50 cm and 50–60 cm diameter at breast height (DBH) classes and low tree density was observed with the increasing DBH classes. North aspect showed higher density for most of girth classes as compared to south facing aspect. Among all the stands, low seedling density was recorded in undisturbed stand at south facing aspect as compared to the moderately and highly disturbed stands. The tree density of Q. leucotrichophora was higher in the undisturbed stand followed by moderately disturbed and highly disturbed stand. But in case of seedling density the higher density were observed at undisturbed and highly disturbed stand in both of the aspects.

2014 ◽  
Vol 90 (04) ◽  
pp. 489-497 ◽  
Author(s):  
William C. Parker

The relationship of stand structural features with understory light levels, estimated by gap light index (GLI), was investigated in 22 second-growth eastern white (Pinus strobus L.) and red pine (Pinus resinosa Ait.)-dominated stands in central Ontario that encompassed a broad range in density and basal area. Simple, empirical light models were developed to quantify the influence of several stand structural variables on canopy transmittance as estimated by GLI. Models were also derived to facilitate the operational identification of residual basal area, density, and percent canopy closure associated with target understory light levels that optimize the growth of white pine regeneration and its protection from weevil and blister rust when using the uniform shelterwood silvicultural system. Regression models indicated significant negative, nonlinear relationships of GLI with density, basal area, a stand density index, total crown area, and foliar biomass, while GLI was linearly related to percent canopy closure. Application of these models to identify density, basal area, and canopy closure values associated with target light levels for the regeneration and removal cuts of uniform shelterwoods demonstrates the use of this information to help guide management of white pine–red pine forests.


1989 ◽  
Vol 19 (3) ◽  
pp. 392-396 ◽  
Author(s):  
Dan C. Thompson

The relationship of sapwood area to leaf area in lodgepole pine was examined across a variety of habitat types and stand densities in northwest Montana. No statistical differences were found between plots with regard to either habitat type or stand density. A nonlinear relationship was found between leaf area and sapwood area. Increasing amounts of sapwood were associated with a decrease in the leaf area–sapwood area ratio. A large amount of within-plot variation in the sapwood area–leaf area relationship was explained by differences between dominant trees and trees of other crown classes. Leaf area (LA) was best estimated by the equation LA = 0.12 × S − 0.0003 × S2 + 0.06 × S × D, where LA is leaf area, S is sapwood area, and D is the crown class (dominant). Differences between dominant and subdominant trees appear to be related to ring width and its associated permeability. Differences in sapwood area–leaf area equations among different studies may be due in part to differences in stand structure.


1950 ◽  
Vol 3 (4) ◽  
pp. 393 ◽  
Author(s):  
GLA mos ◽  
JW Bisset ◽  
HE Dadswell

A survey has been made of the structure of the wood of Eucalyptusgigantea Hook. f. in relation to growing conditions in the Australian CapitalTerritory. Using the number of cells cut off by the cambium at various intervalsduring the growing season as a measure of growth, mathematical expressionshave been obtained for growth in young trees at ground level, breast height,.and half height; from these, growth rate curves have been derived. The timeof year at which growth commences, the relationship of vessel production tocommencement of growth, the formation of late wood, and the period of dormancyhave all been considered in detail. Variations in fibre dimensions havebeen investigated in relation to growth and it has been shown that in anyonegrowth ring the shortest fibres are found in the early wood and the longest inthe late wood. An intrinsic relationship between growth rate and fibre dimensions�has been established, and, at the junction between late and early wood, asudden change in fibre dimensions occurs corresponding to the discontinuity ingrowth rates. Anomalous woody tissue formed during severe drought conditionsis also described.


Author(s):  
Thomas Asbeck ◽  
Julian Frey

AbstractUnderstanding the relationship of stand structural complexity and forest management is relevant to create desired stand structures by adapting management strategies under changing disturbance scenarios and climatic conditions. To overcome difficulties in differentiating between strict categories of silvicultural practices and to describe the impact of forest management more appropriate, we used a continuous indicator of forest management intensity (ForMI). The ForMI consists of three components including volumes of natural deadwood, non-native tree species and harvested trees. There are a great number of approaches to quantify stand structure; here we used the recently established stand structural complexity index (SSCI) which represents a density-dependent as well as vertical measure of complexity based on the distribution of points in 3D space inventoried by terrestrial laser scanning. The data collection took place in 135 one-hectare plots managed under close-to-nature forest management (CTNFM) located in the Black Forest, Germany. We build generalized additive models to test the relationship of the SSCI with the ForMI. The model results did not prove a significant relationship between the SSCI and the ForMI, but components of the ForMI showed significant relationships to the SSCI. Our results indicate that the relationship between stand structural complexity and forest management intensity is, while plausible, not trivial to demonstrate. We conclude that forest managers have a relatively wide range of choices in CTNFM to adapt forests within a similar range of management intensity as presented here to future challenges, since management intensity does not change the forest structure drastically.


Author(s):  
М.О. Гурьянов ◽  
Д.Э. Раупова

Взаимосвязи между высотами деревьев и диаметрами на высоте груди широко применяются при определении запасов и сортиментной структуры древостоев. Для их описания применяются многочисленные математические модели. Сравнительный анализ точности шести моделей на примере древостоев сосны обыкновенной Учебно-опытного лесничества Ленинградской области показал близкую точность каждой из них. При этом для разных пробных площадей наибольшую точность показывали разные модели. Это обуславливает необходимость дальнейших исследований по данной тематике с целью выявления наиболее применимых для различных древесных пород, возрастов и условий местопроизрастаний математических моделей. В практической деятельности часто используются таблицы, составленные с учетом соотношений высот и диаметров на высоте груди в древостоях, основными из которых являются таблицы объемов стволов по разрядам высот и сортиментные таблицы. В рамках исследования было установлено, что фактические зависимости высот деревьев от диаметров на высоте груди отличаются от приведенных в таблицах, что обусловлено индивидуальными особенностями структуры и условий местопроизрастания древостоев. По этой причине разряды высот, определенные для отдельных ступеней толщины, зачастую отличаются от найденных по средним для древостоя высоте и диаметру на высоте груди. Это приводит к расхождениям в найденных с учетом данных двух подходов запасах древостоев, а также выхода и стоимости сортиментов в них. Несмотря на незначительность различий, их наличие свидетельствует о необходимости дальнейших исследований с целью повышения точности определения таксационных показателей древостоев. The relationships between heights and diameters at breast height of trees are widely used in determining of growing stock and assortment structure of stands. Numerous mathematical models are used to describe them. A comparative analysis of the accuracy of six models on the example of tree stands of Scots pine in the Training and Experimental Forestry of the Leningrad region showed the close accuracy of each of them. For different sample plots, however, the highest accuracy was showed by different models. This necessitates further research on this topic in order to identify the most applicable mathematical models for different tree species, ages and habitat conditions. In practice are often used the tables, compiled taking into account the ratios of heights and diameters at breast height in tree stands, the main of which are tables of volumes of trees by height ranks and assortment tables. Within the framework of the study, it was found that the actual relationships between tree heights and diameters at breast height differ from those given in the tables, which is due to the individual features of the stand structure and habitat conditions. For this reason, the height ranks, determined for individual diameter classes often differ from those found for the average tree stand height and diameter at breast height. This leads to discrepancies in the growing stocks of tree stands, found taking into account these two approaches, as well as the yield and cost of assortments in them. Although the differences are insignificant, they highlight the need for further research in order to improve the accuracy of determining the inventory parameters of tree stands


Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.


Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.


Author(s):  
Leon Dmochowski

Electron microscopy has proved to be an invaluable discipline in studies on the relationship of viruses to the origin of leukemia, sarcoma, and other types of tumors in animals and man. The successful cell-free transmission of leukemia and sarcoma in mice, rats, hamsters, and cats, interpreted as due to a virus or viruses, was proved to be due to a virus on the basis of electron microscope studies. These studies demonstrated that all the types of neoplasia in animals of the species examined are produced by a virus of certain characteristic morphological properties similar, if not identical, in the mode of development in all types of neoplasia in animals, as shown in Fig. 1.


Author(s):  
J.R. Pfeiffer ◽  
J.C. Seagrave ◽  
C. Wofsy ◽  
J.M. Oliver

In RBL-2H3 rat leukemic mast cells, crosslinking IgE-receptor complexes with anti-IgE antibody leads to degranulation. Receptor crosslinking also stimulates the redistribution of receptors on the cell surface, a process that can be observed by labeling the anti-IgE with 15 nm protein A-gold particles as described in Stump et al. (1989), followed by back-scattered electron imaging (BEI) in the scanning electron microscope. We report that anti-IgE binding stimulates the redistribution of IgE-receptor complexes at 37“C from a dispersed topography (singlets and doublets; S/D) to distributions dominated sequentially by short chains, small clusters and large aggregates of crosslinked receptors. These patterns can be observed (Figure 1), quantified (Figure 2) and analyzed statistically. Cells incubated with 1 μg/ml anti-IgE, a concentration that stimulates maximum net secretion, redistribute receptors as far as chains and small clusters during a 15 min incubation period. At 3 and 10 μg/ml anti-IgE, net secretion is reduced and the majority of receptors redistribute rapidly into clusters and large aggregates.


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