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Climate Variation and Disturbance Regime Affect Stand Composition and Structure of the Boreal Forests in Southwest Yukon of Canada  [PDF]
Shyam K. Paudel, Suzanne W. Simard, Craig R. Nitschke, John L. Innes
Open Journal of Forestry (OJF) , 2015, DOI: 10.4236/ojf.2015.54029
Abstract: The cold and dry boreal forests of the Southwest Yukon are dominated by white spruce (Picea glauca), trembling aspen (Populus tremuloides) and balsam poplar (Populus balsamifera), and the variability in structure and composition of stands depends on the favourability of disturbance, climate and site conditions for stimulating regeneration. In this study, we investigated relationships between stand structure and ecological, climatic and disturbance factors in the southwest Yukon. We found that white spruce dominates mature forests across the landscape, but it is regenerating proportionately less than trembling aspen. Nevertheless, regeneration of all the three species was abundant following any type or severity of disturbance. Height and diameter of both species varied with several environmental variables, particularly site physiography. Mixed stands of aspen and white spruce were more productive than pure stands of aspen or spruce. However, overall productivity in mixed stand decreased when density of aspen was more than 1000 stems/ ha. These results suggested that mixed stands of deciduous and coniferous species where appropriate should be promoted maintaining aspen density below 1000 stems/ha as the productivity declined beyond this threshold. Similarly, we suggest carrying out selection harvesting of co-dominant trees and regular thinning of intermediate trees to promote the height and diameter growth of the remaining trees.
Silviculture's Role in Managing Boreal Forests  [cached]
Russell T. Graham,Theresa B. Jain
Ecology and Society , 1998,
Abstract: Boreal forests, which are often undeveloped, are a major source of raw materials for many countries. They are circumpolar in extent and occupy a belt to a width of 1000 km in certain regions. Various conifer and hardwood species ranging from true firs to poplars grow in boreal forests. These species exhibit a wide range of shade tolerance and growth characteristics, and occupy different successional positions. The climate is subarctic, with short growing seasons, and the soils are shallow. Both wildfires and timber harvesting play an important role in shaping the structure and composition of boreal forests. Both uneven-aged and even-aged silvicultural systems can be used to produce commercial harvests, but systems can also be designed to meet a variety of other forest management objectives. Wildlife habitat maintenance, water production or conservation, and fire hazard reduction are only some of the objectives for which silvicultural systems can be designed. Coarse wood debris, snags, shrubs, canopy layers, and species composition are examples of forest attributes that can be managed using silvicultural systems. Systems can be designed to sustain predator habitat, yet provide a continual production of wood products. Uneven-aged systems tend to favor the regeneration and development of shade-tolerant species, whereas even-aged systems tend to favor shade-intolerant species. These systems and all of their permutations can create and maintain a suite of different stand compositions and structures that can be used to meet a wide variety of management objectives.
Changes in structure and composition of evergreen forests on an altitudinal gradient in the Venezuelan Guayana Shield
Lionel Hernández,Nelda Dezzeo,Elio Sanoja,Leandro Salazar
Revista de Biología Tropical , 2012,
Abstract: There have been several ecological studies in forests of the Guayana Shield, but so far none had examined the changes in structure and composition of evergreen forests with altitude. This study describes and analyzes the structure, species composition and soil characteristics of forest stands at different altitudinal zones in Southeastern Venezuelan Guayana, in order to explain the patterns and the main factors that determine the structure and composition of evergreen forests along the altitudinal gradient. Inventories of 3 948 big (>10cm DBH) and 1 328 small (5-10cm DBH) woody stems were carried out in eleven plots, ranging from 0.1 to 1.0ha, along a 188km long transect with elevations between 290 and 1 395masl. It has been found that 1) hemiepihytes become more dominant and lianas reduce their dominance with increasing altitude and 2) the forest structure in the study area is size-dependent. Five families and 12 genera represented only 9% of the total number of families and genera, respectively, recorded troughout the gradient, but the two groups of taxa comprised more than 50% of the Importance Value (the sum of the relative density and the relative dominance) of all measured stems. Moreover, the results suggest that low species richness seems to be associated with the dominance of one or few species. Stand-level wood density (WD) of trees decreased significantly with increasing elevation. WD is an indicator of trees’life history strategy. Its decline suggests a change in the functional composition of the forest with increasing altitude. The Canonical Correspondence Analysis (CCA) indicated a distinction of the studied forests on the basis of their altitudinal levels and geographic location, and revealed different ecological responses by the forests, to environmental variables along the altitudinal gradient. The variation in species composition, in terms of basal area among stands, was controlled primarily by elevation and secondarily by rainfall and soil conditions. There are other interacting factors not considered in this study like disturbance regime, biological interactions, productivity, and dispersal history, which could affect the structure and composition of the forests in the altitudinal gradient. In conclusion, it appears that the structural and floristic variability observed in the studied transect is produced by a combination of different climates and randomly expressed local processes interacting across a complex physical landscape A pesar de los diversos estudios ecológicos realizados en los bosques del Escudo de Guayana, ninguno de ell
Relationships between Structure, Composition, and Dynamics of the Pristine Northern Boreal Forest and Air Temperature, Precipitation, and Soil Texture in Quebec (Canada)  [PDF]
Louis Duchesne,Rock Ouimet
International Journal of Forestry Research , 2009, DOI: 10.1155/2009/398389
Abstract: This study reports on the contemporary structure, composition, and dynamics of the pristine northern boreal forest in Quebec, Canada, associated with air temperature, precipitation, and soil texture, using 147 permanent sample plots located at the limit of continuous forest in Quebec. The results show that tree species composition of stands is associated with stand age, soil texture, air temperature, and precipitation regime. After establishment of the pioneer cohort, the postsuccessional stand dynamics differed among temperature and precipitation regimes, probably because of their influence on tree growth. Our results support the hypothesis that shifts in forest composition related to stand dynamics and the subsequent senescing phase associated with the old growth stage generally occur sooner and proceed faster on more fertile sites due to quicker growth and the subsequent earlier mortality of pioneer species. This study suggests that climate warming should accelerate the successional dynamics of these ecosystems through its positive influence on tree growth.
A COMPARISON OF THE COMPOSITION AND STRUCTURE OF TWO OAK FORESTS IN MARSHALL AND POTTAWATOMIE COUNTIES
Bruce A. Smith
Oklahoma Native Plant Record , 2012,
Abstract: In October 2011, high school students from McLoud High School sampled an oak forest in Earlsboro, Pottawatomie County. In July, 2012, students in the Pre-collegiate Field Studies Camp at the University of Oklahoma Biological Station sampled the Marshall County forest at the Buncombe Creek camp ground, located approximately 100 miles south of the Earlsboro forest and 1 mile north of the University of Oklahoma Biological Station. One component of each botany course was to study the composition and structure of an oak forest. These 2 forests were chosen to compare because of their similarity in composition and physical distance apart. They found 10 hardwood species in the Marshall County forest and 9 in the PottawatomieCounty forest, with 6 species common to both. Quercus stellata was most important in both forests and most frequent in the Pottawatomie forest where the total density was 0.141/m2. Quercus stellata and Ulmus alata were most frequent in the Marshall County forest where the total density was 0.107/m2.
Forest Typification to Characterize the Structure and Composition of Old-growth Evergreen Forests on Chiloe Island, North Patagonia (Chile)  [PDF]
Jan R. Bannister,Pablo J. Donoso
Forests , 2013, DOI: 10.3390/f4041087
Abstract: The Evergreen forest type develops along the Valdivian and North-Patagonian phytogeographical regions of the south-central part of Chile (38° S–46° S). These evergreen forests have been scarcely studied south of 43° S, where there is still a large area made up of old-growth forests. Silvicultural proposals for the Evergreen forest type have been based on northern Evergreen forests, so that the characterization of the structure and composition of southern Evergreen forests, e.g., their typification, would aid in the development of appropriate silvicultural proposals for these forests. Based on the tree composition of 46 sampled plots in old-growth forests in an area of >1000 ha in southern Chiloé Island (43° S), we used multivariate analyses to define forest groups and to compare these forests with other evergreen forests throughout the Archipelago of North-Patagonia. We determined that evergreen forests of southern Chiloé correspond to the North-Patagonian temperate rainforests that are characterized by few tree species of different shade tolerance growing on fragile soils. We discuss the convenience of developing continuous cover forest management for these forests, rather than selective cuts or even-aged management that is proposed in the current legislation. This study is a contribution to forest classification for both ecologically- and forestry-oriented purposes.
Ecological Sustainability of Birds in Boreal Forests  [cached]
Gerald Niemi,JoAnn Hanowski,Pekka Helle,Robert Howe
Ecology and Society , 1998,
Abstract: We review characteristics of birds in boreal forests in the context of their ecological sustainability under both natural and anthropogenic disturbances. We identify the underlying ecological factors associated with boreal bird populations and their variability, review the interactions between boreal bird populations and disturbance, and describe some tools on how boreal bird populations may be conserved in the future. The boreal system has historically been an area with extensive disturbance such as fire, insect outbreaks, and wind. In addition, the boreal system is vulnerable to global climate change as well as increasing pressure on forest and water resources. Current knowledge indicates that birds play an important role in boreal forests, and sustaining these populations affords many benefits to the health of boreal forests. Many issues must be approached with caution, including the lack of knowledge on our ability to mimic natural disturbance regimes with management, our lack of understanding on fragmentation due to logging activity, which is different from permanent conversion to other land uses such as agriculture or residential area, and our lack of knowledge on what controls variability in boreal bird populations or the linkage between bird population fluctuations and productivity. The essential role that birds can provide is to clarify important ecological concerns and variables that not only will help to sustain bird populations, but also will contribute to the long-term health of the boreal forest for all species, including humans.
Floristic Composition, Diversity and Stand Structure of Tropical Forests in Popa Mountain Park  [PDF]
Yu Ya Aye, Savent Pampasit, Chanin Umponstira, Kanita Thanacharoenchanaphas, Nophea Sasaki
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.517150
Abstract: Safeguarding biodiversity is an important component of the REDD+ scheme of the United Nations Framework Convention on Climate Change. Information on tree species and their distribution is therefore needed for successful implementation of forestry carbon projects. Forest inventory data were collected in four natural forests located in Popa Mountain Park, Myanmar. Based on the data from 4-ha sample plots, average stem density ranges from 1293 trees ha-1 in dry dipterocarp forest to 804 tree ha-1 in dry evergreen forest. According to the Jackknife estimator for species richness (trees with DBH ≥ 5 cm), the highest number of species was recorded in dry mixed deciduous forest—74 species ha-1, and the lowest number of species recorded in dry forest—40 species ha-1. Dry mixed deciduous forest occupied the highest value on the Shannon-Wiener index and Simpson diversity index while the lowest was in dry forest, indicating that dry mixed deciduous forest is the most complex whereas dry forest is the simplest community. Not only does this study provide useful information on the current status of vegetation type but the information is important for designing forestry management systems that could result in biodiversity conservation and carbon emission reductions.
Does the amount of trees retained at clearfelling of temperate and boreal forests influence biodiversity response?
Katja Fedrowitz, Lena Gustafsson
Environmental Evidence , 2012, DOI: 10.1186/2047-2382-1-5
Abstract: The overall aim of our review will be to provide forest practitioners and conservationists in temperate and boreal forests with more detailed recommendations regarding the amount of trees that should be retained in order to achieve positive effects for biodiversity compared to traditional clear-cutting.Intensive forestry has modified forest landscapes worldwide, with a decrease in global forest extent (habitat loss) and an increase in habitat fragmentation, resulting in negative effects for biodiversity [1,2].Industrial forestry is common in different parts of the world, with more or less intense forest management and harvest for the purpose of producing pulp, timber and bioenergy. Clear-cutting is a traditional method of logging, i.e. the complete removal of the tree layer and a subsequent regeneration of even-aged stands. This practice has been controversial due to the simplification of forest structure and composition [3], and the type and intensity of disturbance that occur under industrial forestry can deviate dramatically from natural disturbance processes [4]. The resulting lack of complexity in managed stands and across forest landscapes feeds back on ecosystem processes and carries high risks of reducing several key environmental services [e.g. [5].A new forest management model – “retention forestry” – was introduced in northwestern North America about 25?years ago as a response to the rapid ongoing transformation and simplification of forests, and the need to create greater balance between wood production and biodiversity [6]. Retention forestry spread rapidly and was adapted to conditions in various regions of the world [7]. Prescriptions can vary in a multitude of ways with large variation in type, amount, and spatial distribution of retained trees to achieve different ecological outcomes. The primary goal is to provide for continuity in ecosystem structure, function, and composition between forest generations. Legacies, such as large old trees and dead
Structure and Composition of Natural Gmelin Larch (Larix gmelinii var. gmelinii) Forests in Response to Spatial Climatic Changes  [PDF]
Jingli Zhang, Yong Zhou, Guangsheng Zhou, Chunwang Xiao
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0066668
Abstract: Background Many theoretical researches predicted that the larch species would decrease drastically in China under future climatic changes. However, responses of the structural and compositional changes of Gmelin larch (Larix gmelinii var. gmelinii) forests to climatic changes have rarely been reported. Methodology/Principal Findings Field survey was conducted to examine the structures and compositions of natural Gmelin larch forests along a climatic gradient. Stepwise linear regression analyses incorporating linear and quadratic components of climatic and non-climatic factors were performed on the structural and compositional attributes of those natural Gmelin larch forests. Isothermality, Max Temperature of Warmest Month (TempWarmestMonth), Precipitation of Wettest Month (PrecipWettestMonth), Precipitation Seasonality (PrecipSeasonality) and Precipitation of Driest Quarter (PrecipDriestQuarter) were observed to be effective climatic factors in controlling structure and composition of Gmelin larch forests. Isothermality significantly affected total basal area of larch, while TempWarmestMonth, PrecipWettestMonth and PrecipSeasonality significantly affected total basal area of Mongolian pine, and PrecipDriestQuarter significantly affected mean DBH of larch, stand density of larch and total basal area of spruce and fir. Conclusions/Significance The summer and winter temperatures and precipitations are all predicted to increase in future in Northeast China. Our results showed the increase of total basal area of spruce and fir, the suppression of regeneration and the decrease of stand density of larch under increased winter precipitation, and the decrease of total basal area of larch under increased summer temperature in the region of current Gmelin larch forest. Therefore, we suggest that larch would decrease and spruce and fir would increase in the region of future Gmelin larch forest.
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