Книги з теми "Tree species effect"

Lacertid lizards have long been a fruitful field of scientific enquiry with many people working on them over the past couple of hundred years. The scope of the field has steadily increased, beginning with taxonomy and anatomy and gradually spreading so that it includes such topics as phylogenetics, behaviour, ecology, and conservation. Since 1992, a series of symposia on lacertid lizards of the Mediterranean basin have taken place every three years. The present volume stems from the 2004 meeting in the Aeolian Islands. In the volume a wide range of island topics are considered, including the systematics of the species concerned, from both morphological and molecular viewpoints, interaction with other taxa, and conservation. The last topic is especially important, as island lizards across the world have often been vulnerable to extinction, after they came into contact with people and the animals they introduced. The volume also has papers on the more positive aspects of human influence, specifically the benign effects of traditional agriculture on at least some reptile species. Olive trees, cork oaks and the banks and walls of loose rocks that crisscross the Mediterranean scene all often contribute to elevated lizard populations. Nor is more basic biology neglected and there are articles on morphology, reproduction, development and thermoregulation. Finally, it is good to see one paper on non-Mediterranean species is included. For, to fully understand the lacertids of this region, it is necessary to appreciate their close relatives in Africa, Asia and the archipelagos of the northeastern Atlantic Ocean. (From Preface by E. Nicholas Arnold & Wolfgang Böhme)

The aim of the study was to determine the influence of different disturbances (both natural and anthropogenic) on species composition and stand structure of old-growth mixed mountain forests in the Western Carpathians. These stands are usually dominated by beech, fir and spruce, mixed in different proportions. The tree main species represent different growth strategies, and they compete against each other. The longevity of trees makes the factors influencing the stand structure difficult to identify, even during longitudinal studies conducted on permanent research plots. That is why dendroecological techniques, based upon the annual variability of tree rings, are commonly used to analyze the disturbance histories of old-growth stands. Dendroecological methods make it possible to reconstruct the stand history over several centuries in the past by analyzing the frequency, intensity, duration and spatial scale of disturbances causing the death of trees. Combining the dendroecological techniques with the detailed measurements of stand structure, snag volume, CWD volume, and the analyses of regeneration species composition and structure allows us to identify the factors responsible for the changes in dynamics of mixed mountain forests. Various disturbance agents affect some species selectively, while some disturbances promote the establishment of tree seedlings of specific species by modifying environmental conditions. Describing the disturbance regime requires a broad scope of data on stand structure, on dead wood and tree regeneration, while various factors affecting all the stages of tree growth should be taken into consideration. On the basis of the already published data from permanent sample plots, combined with the available disturbance history analyses from the Western Carpathians, three research hypotheses were formulated. 1. The species composition of mixed mountain forests has been changing for at least several decades. These directional changes are the consequence of simultaneous conifer species decline and expansion of beech. 2. The observed changes in species composition of mixed mountain forests are the effect of indirect anthropogenic influences, significantly changing tree growth conditions also in the forests that are usually considered natural or near-natural. Cumulative impact of these indirect influences leads to the decrease of fir share in the tree layer (spruce decline has also been observed recently),and it limits the representation of this species among seedlings and saplings. The final effect is the decrease of fir and spruce share in the forest stands. 3. Small disturbances, killing single trees or small groups of trees, and infrequent disturbances of medium size and intensity dominate the disturbance regime in mixed mountain forests. The present structure of beech-fir-spruce forests is shaped both by complex disturbance regime and indirect anthropogenic influences. The data were gathered in permanent sample plots in strictly protected areas of Babia Góra, Gorce, and Tatra National Parks, situated in the Western Carpathians. All plots were located in the old-growth forest stands representing Carpathian beech forest community. The results of the measurements of trees, snags, coarse woody debris (CWD) and tree regeneration were used for detailed description of changes in the species composition and structure of tree stands. Tree ring widths derived from increment cores were used to reconstruct the historical changes in tree growth trends of all main tree species, as well as the stand disturbance history within the past two to three hundred years. The analyses revealed complex disturbance history in all of the three forest stands. Intermediate disturbances of variable intensity occurred, frequently separated by the periods of low tree mortality lasting from several decades up to over one hundred years. The intervals between the disturbances were significantly shorter than the expected length of forest developmental cycle, in commonly used theories describing the dynamics of old-growth stands. During intermediate disturbances up to several dozen percent of canopy trees were killed. There were no signs of stand-replacing disturbances, killing all or nearly all of canopy trees. The periods of intense tree mortality were followed by subsequent periods of increased sapling recruitment. Variability in disturbance intensity is one of the mechanisms promoting the coexistence of beech and conifer species in mixed forests. The recruitment of conifer saplings depended on the presence of larger gaps, resulting from intermediate disturbances, while beech was more successful in the periods of low mortality. However, in the last few decades, beech seems to benefit from the period of intense fir mortality. This change results from the influence of long-term anthropogenic disturbances, affecting natural mechanisms that maintain the coexistence of different tree species and change natural disturbance regimes. Indirect anthropogenic influence on tree growth was clearly visible in the gradual decrease of fir increments in the twentieth century, resulting from the high level of air pollution in Europe. Synchronous decreases of fir tree rings’ widths were observed in all three of the sample plots, but the final outcomes depended on the fir age. In most cases, the damage to the foliage limited the competitive abilities of fir, but it did not cause a widespread increase in tree mortality, except for the oldest firs in the BGNP (Babia Góra National Park) plot. BGNP is located in the proximity of industrial agglomeration of Upper Silesia, and it could be exposed to higher level of air pollution than the other two plots. High level of fir regeneration browsing due to the deer overabundance and insufficient number of predators is the second clear indication of the indirect anthropogenic influence on mixed mountain forests. Game impact on fir regeneration is the most pronounced in Babia Góra forests, where fir was almost completely eliminated from the saplings. Deer browsing seems to be the main factor responsible for limiting the number of fir saplings and young fir trees, while the representation of fir among seedlings is high. The experiments conducted in fenced plots located in the mixed forests in BGNP proved that fir and sycamore were the most preferred by deer species among seedlings and saplings. In GNP (Gorce National Park) and TNP (Tatra National Park), the changes in species composition of tree regeneration are similar, but single firs or even small groups of firs are present among saplings. It seems that all of the analysed mixed beech-fir-spruce forests undergo directional changes, causing a systematic decrease in fir representation, and the expansion of beech. This tendency results from the indirect anthropogenic impact, past and present. Fir regeneration decline, alongside with the high level of spruce trees’ mortality in recent years, may lead to a significant decrease in conifers representation in the near future, and to the expansion of beech forests at the cost of mixed ones.

The aim of the paper was to determine the influence of root systems of chosen tree species found in the Polish Flysch Carpathians on the increase of soil shear strength (root cohesion) in terms of slope stability. The paper's goal was achieved through comprehensive tests on root systems of eight relatively common in the Polish Flysch Carpathians tree species. The tests that were carried out included field work, laboratory work and analytical calculations. As part of the field work, the root area ratio (A IA) of the roots was determined using the method of profiling the walls of the trench at a distance of about 1.0 m from the tree trunk. The width of the. trenches was about 1.0 m, and their depth depended on the ground conditions and ranged from 0.6 to 1.0 m below the ground level. After preparing the walls of the trench, the profile was divided into vertical layers with a height of 0.1 m, within which root diameters were measured. Roots with diameters from 1 to 10 mm were taken into consideration in root area ratio calculations in accordance with the generally accepted methodology for this type of tests. These measurements were made in Biegnik (silver fir), Ropica Polska (silver birch, black locust) and Szymbark (silver birch, European beech, European hornbeam, silver fir, sycamore maple, Scots pine, European spruce) located near Gorlice (The Low Beskids) in areas with unplanned forest management. In case of each tested tree species the samples of roots were taken, transported to the laboratory and then saturated with water for at least one day. Before testing the samples were obtained from the water and stretched in a. tensile testing machine in order to determine their tensile strength and flexibility. In general, over 2200 root samples were tested. The results of tests on root area ratio of root systems and their tensile strength were used to determine the value of increase in shear strength of the soils, called root cohesion. To this purpose a classic Wu-Waldron calculation model was used as well as two types of bundle models, the so called static model (Fiber Bundle Model — FIRM, FBM2, FBM3) and the deformation model (Root Bundle Model— RBM1, RBM2, mRBM1) that differ in terms of the assumptions concerning the way the tensile force is distributed to the roots as well as the range of parameters taken into account during calculations. The stability analysis of 8 landslides in forest areas of Cicikowicleie and Wignickie Foothills was a form of verification of relevance of the obtained calculation results. The results of tests on root area ratio in the profile showed that, as expected, the number of roots in the soil profile and their ApIA values are very variable. It was shown that the values of the root area ratio of the tested tree species with a diameter 1-10 ram are a maximum of 0.8% close to the surface of the ground and they decrease along with the depth reaching the values at least one order of magnitude lower than close to the surface at the depth 0.5-1.0 m below the ground level. Average values of the root area ratio within the soil profile were from 0.05 to 0.13% adequately for Scots pine and European beech. The measured values of the root area ratio are relatively low in relation to the values of this parameter given in literature, which is probably connected with great cohesiveness of the soils and the fact that there were a lot of rock fragments in the soil, where the tests were carried out. Calculation results of the Gale-Grigal function indicate that a distribution of roots in the soil profile is similar for the tested species, apart from the silver fir from Bie§nik and European hornbeam. Considering the number of roots, their distribution in the soil profile and the root area ratio it appears that — considering slope stability — the root systems of European beech and black locust are the most optimal, which coincides with tests results given in literature. The results of tensile strength tests showed that the roots of the tested tree species have different tensile strength. The roots of European beech and European hornbeam had high tensile strength, whereas the roots of conifers and silver birch in deciduous trees — low. The analysis of test results also showed that the roots of the studied tree species are characterized by high variability of mechanical properties. The values Of shear strength increase are mainly related to the number and size (diameter) of the roots in the soil profile as well as their tensile strength and pullout resistance, although they can also result from the used calculation method (calculation model). The tests showed that the distribution of roots in the soil and their tensile strength are characterized by large variability, which allows the conclusion that using typical geotechnical calculations, which take into consideration the role of root systems is exposed to a high risk of overestimating their influence on the soil reinforcement. hence, while determining or assuming the increase in shear strength of soil reinforced with roots (root cohesion) for design calculations, a conservative (careful) approach that includes the most unfavourable values of this parameter should be used. Tests showed that the values of shear strength increase of the soil reinforced with roots calculated using Wu-Waldron model in extreme cases are three times higher than the values calculated using bundle models. In general, the most conservative calculation results of the shear strength increase were obtained using deformation bundle models: RBM2 (RBMw) or mRBM1. RBM2 model considers the variability of strength characteristics of soils described by Weibull survival function and in most cases gives the lowest values of the shear strength increase, which usually constitute 50% of the values of shear strength increase determined using classic Wu-Waldron model. Whereas the second model (mRBM1.) considers averaged values of roots strength parameters as well as the possibility that two main mechanism of destruction of a root bundle - rupture and pulling out - can occur at the same. time. The values of shear strength increase calculated using this model were the lowest in case of beech and hornbeam roots, which had high tensile strength. It indicates that in the surface part of the profile (down to 0.2 m below the ground level), primarily in case of deciduous trees, the main mechanism of failure of the root bundle will be pulling out. However, this model requires the knowledge of a much greater number of geometrical parameters of roots and geotechnical parameters of soil, and additionally it is very sensitive to input data. Therefore, it seems practical to use the RBM2 model to assess the influence of roots on the soil shear strength increase, and in order to obtain safe results of calculations in the surface part of the profile, the Weibull shape coefficient equal to 1.0 can be assumed. On the other hand, the Wu-Waldron model can be used for the initial assessment of the shear strength increase of soil reinforced with roots in the situation, where the deformation properties of the root system and its interaction with the soil are not considered, although the values of the shear strength increase calculated using this model should be corrected and reduced by half. Test results indicate that in terms of slope stability the root systems of beech and hornbeam have the most favourable properties - their maximum effect of soil reinforcement in the profile to the depth of 0.5 m does not usually exceed 30 kPa, and to the depth of 1 m - 20 kPa. The root systems of conifers have the least impact on the slope reinforcement, usually increasing the soil shear strength by less than 5 kPa. These values coincide to a large extent with the range of shear strength increase obtained from the direct shear test as well as results of stability analysis given in literature and carried out as part of this work. The analysis of the literature indicates that the methods of measuring tree's root systems as well as their interpretation are very different, which often limits the possibilities of comparing test results. This indicates the need to systematize this type of tests and for this purpose a root distribution model (RDM) can be used, which can be integrated with any deformation bundle model (RBM). A combination of these two calculation models allows the range of soil reinforcement around trees to be determined and this information might be used in practice, while planning bioengineering procedures in areas exposed to surface mass movements. The functionality of this solution can be increased by considering the dynamics of plant develop¬ment in the calculations. This, however, requires conducting this type of research in order to obtain more data.