Many existing Piedmont hardwood stands are composed of trees that are largely under 45 cm in diameter and contain a desirable oak component, as well as large amounts of undesirable red maple and sourwood. In stands under even-aged silviculture, season of harvest can be used as an effective management tool to favor different species compositions. If oak or other hardwood production is the management objective a dormant season harvest will result in increased sprout vigor of all oak as well as non-oak species. If pine conversion is the objective then a growing season harvest will reduce the vigor of all hardwood species and allow for easier competition control. The higher densities of all classes of regenerants on better sites indicates control will be more difficult. / Master of Science

Através da amostragem de 28 sítios em diferentes estádios de regeneração em uma área de Mata Atlântica contínua, procuramos nesta dissertação contribuir para o entendimento dos mecanismos relacionados às mudanças faunísticas observadas durante o processo de regeneração em florestas tropicais, e, assim, melhor compreender o valor das florestas secundárias para a conservação da biodiversidade tropical. Para isso, na primeira parte da dissertação investigamos a influência da regeneração sobre características de estrutura da floresta e disponibilidade de alimento consideradas importantes para diversos grupos da fauna. Encontramos maior profundidade do folhiço, volume de galhadas e disponibilidade de frutos de uma abundante palmeira de sub-bosque nas florestas mais maduras, enquanto que nas áreas em estádio mais inicial de regeneração encontramos maior conexão da vegetação, biomassa de artrópodes no solo e disponibilidade de frutos no total e da espécie de planta mais abundante no sub-bosque. Essas modificações podem estar relacionadas às mudanças na fauna observadas durante a regeneração florestal. As espécies que dependem de características só encontradas nas matas mais maduras, como espaços abertos para movimentação, maior complexidade do chão da floresta, ou determinados recursos alimentares poderiam encontrar limitações em áreas em estádios mais iniciais de regeneração, ao passo que espécies que não dependem desses recursos poderiam se beneficiar da maior disponibilidade total de alimentos, ou da maior conexão da vegetação para movimentação, encontradas nessas áreas. Na segunda parte do trabalho, avaliamos a influência da regeneração e de características estruturais e de disponibilidade de alimento sobre espécies endêmicas (especialistas de floresta) e não-endêmicas (generalistas de habitat) de pequenos mamíferos terrestres. Como previsto, observamos que um grupo de espécies (generalistas de habitat) prolifera nas áreas mais jovens, enquanto que o outro grupo (especialistas de floresta) foi mais comum, embora de maneira mais sutil, nas áreas mais maduras. Esses padrões foram em parte explicados pelas variáveis mensuradas, principalmente a disponibilidade de recursos alimentares. Aparentemente, as espécies generalistas estão se beneficiando da maior disponibilidade de alimentos encontrada nas áreas em estádio mais inicial de regeneração, enquanto que as especialistas possuem maior capacidade de ocupação das áreas mais maduras, onde esses recursos são mais escassos. Portanto, esses resultados sugerem um compromisso (trade-off) entre capacidade competitiva e capacidade de utilização de recursos 101 abundantes, como prevê o mecanismo de nicho sucessional, proposto inicialmente para explicar a sucessão de espécies vegetais. As características encontradas nas florestas mais jovens favoreceram a proliferação de espécies de pequenos mamíferos terrestres generalistas de habitat. Entretanto, o efeito positivo da regeneração florestal sobre as espécies especialistas, de maior interesse para a conservação, foi menos acentuado, de forma que as florestas secundárias abrigaram uma assembléia de pequenos mamíferos terrestres rica, podendo, portanto, representar um importante instrumento de aumento de área e conectividade em paisagens altamente modificadas, como as encontradas na Mata Atlântica. Entretanto, esses resultados não reduzem o valor das florestas maduras, principalmente em paisagens fragmentadas e para grupos mais sensíveis da fauna. Essas florestas devem ser protegidas, assim como deve ser garantida (e se preciso auxiliada) a regeneração das florestas secundárias, para que possam adquirir em longo prazo as condições necessárias à manutenção das espécies e dos grupos de espécies da fauna mais severamente afetados pela secundarização das florestas tropicais. / By sampling 28 sites in different regeneration stages in a continuous Atlantic forest area, in this master thesis we aimed to contribute to the understanding of the mechanisms associated with the wildlife changes observed during tropical forest regeneration, and thereby better understand the value of secondary forests for the conservation of tropical biodiversity. In the first part of the thesis we investigated the influence of regeneration on aspects of forest structure and food availability considered to be important to several wildlife groups. We found deeper leaf litter, and higher woody debris volume and fruit availability of an abundant understorey palm in the older-growth areas, while in areas in earlier stages we found higher vegetation connection, higher ground-dwelling arthropod biomass, total fruit availability, and availability of fruits of the most abundant understorey plant species. These modifications may be related to the wildlife changes observed during forest regeneration. Species that rely on features only found in older-growth forests, such as open space for movement, higher complexity of the forest floor, or certain food resources, could find limitations in younger forests, whereas species which do not depend on these resources could benefit from the higher total food availability, or higher 102 vegetation connection for movements, found in these areas. In the second part of the study, we assessed the effect of regeneration and of structural attributes and food availability on endemic (forest specialist) and non-endemic (habitat generalist) terrestrial small mammal species. As expected, we found that a group of species (habitat generalists) proliferate in younger areas, while the other group (forest specialists) is more common, although more subtly, in older-growth areas. These patterns were partly explained by the measured variables, especially food availability. Apparently, the generalist species are benefiting from the increased food availability found in younger forests, while specialist species have greater ability to occupy older-growth areas, where these resources are scarcer. Therefore, our data suggest a trade-off between competitive ability and ability to use abundant resources, as predicted by the successional niche mechanism, initially proposed to explain the succession of plant species. The characteristics observed in younger forests favored the proliferation of habitat generalist terrestrial small mammals. However, the positive effect of forest regeneration on specialist species, of more conservation concern, was less pronounced, so that the secondary forests harbored a rich terrestrial small mammal assemblage, and may therefore be an important tool to increase the area and connectivity in highly modified landscapes, such as those found in the Atlantic forest. However, these results do not diminish the value of old-growth forests, especially in fragmented landscapes and for more sensitive wildlife groups. These forests should be protected, as well as the regeneration of the secondary forests should be guaranteed (and assisted, if necessary), so that these areas could acquire in the long term the necessary conditions to maintain the species and the groups of species most adversely affected by the secondarization of the tropical forests.

A abertura de clareiras no dossel das florestas ocorre periodicamente pela queda ou morte de árvores, acarretando a formação de uma paisagem em mosaico de áreas com diferentes idades, condições ambientais e composição florística. A principal modificação que ocorre no ambiente de clareira é o aumento da intensidade de luz, interferindo no estabelecimento, crescimento e sobrevivência de muitos indivíduos. O objetivo desse estudo foi caracterizar a estrutura de habitat e descrever a composição florística de espécies arbustivo-arbóreas de 0,50 a 2m nas clareiras naturais em Floresta de Restinga na parcela permanente localizada no Parque Estadual da Ilha do Cardoso e as acompanhar as modificações na comunidade após um ano. Durante um ano os indivíduos foram acompanhados em relação à sobrevivência, o crescimento e o recrutamento. As espécies foram classificadas em categorias sucessionais com base na literatura. Foram analisadas onze clareiras com áreas entre 30,5 e 398,4m2, das quais 6 foram consideradas pequenas (<150m2) e 5 grandes (>150m2). Foram analisados 1.316 indivíduos pertencentes a 99 espécies arbustivo-arbóreas. O fator determinante do número de espécies e indivíduos encontrados nas clareiras foi o tamanho da área atingida pela abertura do dossel. As espécies mais abundantes foram: Euterpe edulis, Rudgea villiflora, Miconia sp1, Myrcia bicarinata, Dendropanax cuneatum e Astrocaryum aculeatissimum. Apenas Euterpe edulis foi encontrado em todas as clareiras. Do total de plantas amostradas nas clareiras, 42 (3,2%) foram consideradas pioneiras distribuídas em 7 espécies, 579 (46,1%) secundárias iniciais distribuídas em 26 espécies, 419 (33,4%) climáxicas distribuídas em 40 espécies e 215 (17,1%) não classificadas pertencentes a 26 famílias. Nas clareiras consideradas pequenas houve destaque no número de indivíduos pertencentes à categoria clímax (46,3%), enquanto nas clareiras grandes houve predominância das secundárias inicias (52%). Houve diferença na abundância de algumas espécies em relação ao tamanho das clareiras. Nas clareiras pequenas Myrcia bicarinata foi a espécie com maior densidade, já nas clareiras grandes Euterpe edulis foi a espécie de maior densidade. Na remedição dos indivíduos observou-se que apenas 671 indivíduos apresentaram crescimento, os outros indivíduos não apresentaram crescimento, principalmente devido à alta taxa de herbivoria. Euterpe edulis foi a única espécie que apresentou diferença nas taxas de crescimento entre as duas classes de tamanho de clareira. Após um ano foi observada a mortalidade de 84 indivíduos e o recrutamento de 105 indivíduos. Os indivíduos ingressantes pertencem, principalmente, as categorias secundárias iniciais (27%) e clímax (22%). Não há indícios de uma convergência das comunidade presentes nas diferentes clareiras em direção à uma comunidade que fosse típica ou exclusiva de clareira, ao contrário, mostraram-se inicialmente distintas e permaneceram distintas após um ano. / Canopy gap openings periodically occurs when a tree dies or falls, creating a mosaic landscape which result into patches with different ages, environmental conditions and floristic composition. Light enhancement is the main modification within a gap environment, causing modifications on the establishment, development and survival of many individuals. The purpose of this study was to describe shrub and tree species? composition from 0,5 to 2cm height, point out habitat structure and follow community modifications within a year under light gaps in a Restinga Forest, located in a permanent plot at Parque Estadual da Ilha do Cardoso. For an entire year these individuals were studied regarding their survival, growth and recruitment. Species were classified into sucessional categories as suggested by literature. Eleven gaps were analyzed and their total area ranged from 30,5 to 398,4m2, with 6 gaps considered as small (<150m2) and 5 as large (>150m2). The overall number of individuals analyzed in this study was of 1316, representing 99 tree and shrub species. The main factor acting on the species and individuals quantity within a gap was the area size affected by the canopy opening. The most abundant species were: Euterpe edulis, Rudgea villiflora, Miconia sp1, Myrcia bicarinata, Dendropanax cuneatum e Astrocaryum aculeatissimum. The only species sampled in every gap was Euterpe edulis. Regarding sucessional categories, 42 individuals (3,2%) of 7 species were classified as pioneers, 579 individuals (46,1%) of 26 species as early secondary species, 419 individuals (33,4%) of 40 species as climax and 215 individuals remained non-classified (17,1%), representing 26 botanical families. Small gaps presented a remarkable quantity of climax species (46,3%), while on the larger ones early secondary species prevailed (52%). Species abundance varied according to gap size. Myrcia bicarinata showed the highest densities within smaller gaps, while in the larger ones the dominant species was Euterpe edulis. Height measurements indicated growth for only 671 individuals, mainly because of herbivory attacks. Euterpe edulis was the only species with significant growth rate differences between small and large gaps. After a year, 84 individuals were dead, while 105 recruits were accounted. The latter ones were mainly represented by early secondary species (27%) and climax (22%). The communities present in the different sized gaps did not bring any evidence of convergence towards a typical or exclusive gap community. On the contrary, these communities appeared to be dissimilar either on initial phase or after a year.

L’inquiétude au sujet du devenir des forêts tempérées de moyenne montagne va croissant, du fait du changement climatique d’une part, et des difficultés de régénération liées à la pression exercée par les grands ongulés d’autre part. Les populations d’ongulés herbivores connaissent en effet une forte augmentation depuis le milieu du XXème siècle dans l’hémisphère Nord ; et leur abroutissement sélectif, dû à leurs préférences alimentaires, exerce une forte pression sur la régénération, dont l’intensité sur les essences varie selon leur appétence. La réponse de la régénération au changement climatique en termes de survie et de croissance demeure méconnue, mais de premiers résultats suggèrent qu’elle pourrait être encore plus affectée que les arbres adultes, et de manière différentielle également du fait des diverses autécologies des essences. Dans ce contexte de changements globaux, le recours aux forêts mélangées est envisagé comme une option valable de minimisation des risques. Comment caractériser la réponse de la régénération à ces deux pressions de sélection, et quel pourrait être l’avenir d’un peuplement mélangé dans ce contexte ? Notre étude se focalise sur les effets de l’abroutissement par les grands ongulés et du changement climatique sur la régénération du sapin, du hêtre et de l’épicéa en mélange. Nous utilisons pour cela diverses approches. Nous montrons que la germination et l’installation de semis de hêtres n’est pas affectée par l’éclairement au sol plus faible en situation de mélange. Nous mettons en évidence une quasi-inversion d’essences entre sapin et épicéa au niveau de la strate de régénération, bénéficiant à l’épicéa, lorsqu’ils sont soumis à une forte pression d’abroutissement. A l’échelle des traits foliaires, nous trouvons des réponses différentes entre les trois essences aux pressions du climat et de l’abroutissement, le sapin étant le seul à exprimer une réponse claire à l’abroutissement (tissus plus résistants, augmentation du rapport C/N foliaire). Nos résultats démontrent également une diminution de l’abroutissement avec l’augmentation de la température hivernale et un effet plus important de l’abroutissement que de la température printanière sur la croissance des semis de sapin, hêtre, érable. Enfin, via une approche de modélisation, nous avons simulé la dynamique d’un peuplement mélangé de sapin, hêtre et épicéa sur une durée de 100 ans, et montré une modification des seuils de tolérance à la sécheresse par l’abroutissement, et vaildé la possible disparition du sapin dans des scénarios comprenant abroutissement et changement climatique. Ces travaux soulignent l’influence des grands ongulés en interaction avec les conditions climatiques sur la dynamique de la régénération forestière, et l’importance de prendre cette pression en compte dans les protocoles de recherche destinés à étudier l’évolution de la régénération en contexte climatique changeant. / There is growing concern about the future of temperate mountainous forests, because of climate change and of the difficulties in regenerating forests caused by large ungulates pressure. Herbivore ungulate populations have strongly increased since the middle of the XXth century in the northern hemisphere. By their selective browsing due to their dietary preferences, they exert a strong pressure on regeneration, which intensity on each tree species varies with their palatability. The response of regeneration to climate change in terms of growth and survival is still poorly known, but some results suggest it could be affected differentially given the different autecologies of the species. In such a global changes context, mixed forests are considered a valuable option of adaptation. How would the regeneration phase respond to those two pressures, and what could be the future of a mixed stand in such a context? This study focuses on the effects of browsing by large ungulates and climate change on mixed silver fir, Norway spruce and beech stand regeneration. We show that the lower amount of light reaching the ground in mixed stands does not affect beech regeneration germinating. We demonstrate a quasi-substitution of silver fir by Norway spruce saplings when submitted to high browsing pressure. At the finer scale of foliar traits, we find different responses among the three species to varying climate and browsing pressure, silver fir being the only species expressing an answer to browsing (increase in shoot mechanical resistance and in foliar C:N). Our results also demonstrate a decrease in browsing with increasing winter temperature, and a stronger effect of browsing than of spring temperature on saplings growth for silver fir, beech and sycamore maple. Finally, our simulations of the dynamics of a mixed silver fir-Norway spruce-beech stand suggest a shift in tolerance to drought thresholds due to browsing, and confirm the possible eradication of silver fir in scenarios combining browsing and climate change. This work highlights the influence of large ungulates interacting with climate conditions on forest regeneration dynamics, and the importance to consider this pressure in research protocols aiming at studying the behaviour of regeneration in changing climate contexts.

Between October 9, 1991 and October 16, 1991 a fire burned 577 hectares in the Columbia River Gorge near the west end on the Oregon side. All of the area burned consisted of second growth Pseudotsuga menziesii and the accompanying understory. This was the first disturbance of this magnitude in this part of the Columbia River Gorge since 1902. The purpose of this study was to examine the pattern of understory recovery in the first two years following the fire. This study also sought to learn: 1) how Pseudotsuga menziesii seedlings are recruited into the population, 2) how quickly the litter layer is a reforming, and 3) how quickly snags and downed logs are recruited into the understory. Four 800 square meter circular plots were established within the burned area of the Columbia River Gorge. Two plots were designated sun plots since the fire had killed the overstory. The other two were designated shade sites since the canopy over them was still intact. Twenty five randomly placed sample units (20 x 50 centimeters) were placed in each main plot. The plots were then sampled at approximately onemonth intervals from May through September of 1992 and 1993. The frequency and percentage of cover was recorded for all plant species that occurred in each sample unit. The data from 1992 and 1993 were compared by date of visit and type of plot, either (sun or shade) using the Pearson Goodness-of-Fit Test to examine and compare differences in the extent of cover and distribution of understory species. No significant differences were found. An increase in species richness and relative abundance of understory species was noted between pre-fire data collected by the US Forest Service and what I found. However, statistical analysis was not possible because of the limited data collection in the pre-fire sample.

The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old. Early regeneration failures followed slashburning and the planting of unsuitable species. Currently, the most successful and feasible option for reforesting cutovers is natural regeneration with a mix of the three main tree species, but uncertainties remain about the temporal and spatial pattern of regeneration, changes in species composition, and the time required for stand establishment after cutting. Our study addressed these concerns by examining regeneration patterns on 6 sites that were clearcut 11-12 years prior to sampling and left to regenerate naturally. The sites were located at the lower limits of the zone in the Tetrahedron Range, near Sechelt, at elevations from 1060-1100m.

"SELECT CD is a site-specific, decision-support tool for selecting ecologically viable tree species, reproduction cuttings, and regeneration methods in the coastal forest (CDF, CWH, and MH zones). SELECT CD integrates information from several existing guides with new information from literature and recent research into a single, user-friendly resource. SELECT CD also includes a rich library of visuals and an illustrated glossary of technical terms."

The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old. Understanding regeneration patterns in the MH zone has become increasingly important as logging continues towards higher elevations of the zone where snowpacks are deeper.

In BC, it is required that harvested areas be regenerated with a mixture of tree species whenever appropriate to the site. This policy is based upon the assumption that increases in stand productivity, reliability, and/or biodiversity can be achieved in mixed-species stands. However, the knowledge justifying this policy is at best incomplete. Differences in forest productivity of mixed-species stands have been attributed mostly to competition. However, an increasing number of studies are providing evidence to support alternate theories, in which positive plant interactions play a major role. Positive plant interactions are divided into two components: (i) competitive reduction through structural and physiological differences in above and below ground structures, and (ii) facilitation through any positive effect on the growing environment of one plant species by another. These theories have yet to be tested in forest ecosystems. The objectives of this study, with respect to naturally established, unmanaged, second-growth stands of western hemlock (Hw) (Tsuga heterophylla (Raf.) Sarg.), western redcedar (Cw) (Thuja plicata Donn ex D. Don in Lamb.), and their mixtures, were: (1) to review the mechanisms of positive plant interactions and their potential to occur in these mixtures, and (2) to compare the productivity of these three stand types, using relative and absolute yield.

Thesis (M.S.) -- University of Tennessee, Knoxville, 2005. / Title from title page screen (viewed on Feb. 1, 2006). Thesis advisor: David S. Buckley. Vita. Includes bibliographical references.