Increases in atmospheric C have resulted in concerns about global warming and interest in finding means to sequester atmospheric C through land management strategies. The purpose of this study was to (i) compare changes in mineral soil C after a 30-year interval and (ii) examine the role of inorganic-N, soil texture, and topography in these changes. Soil samples were collected at permanently identified points on the Camp Branch Watershed, a second growth oak forest on the Cumberland Plateau in central Tennessee, in July of 1976 and archived. These points were re-sampled in July of 2006 and both archived and new samples of the 0 to 10 cm increment of the mineral soil were analyzed for C and N using the same procedures. Paired comparisons revealed changes in C and N were distinct to each of the 8 soil series. Comparison of 2006 samples to 1976 samples indicated changes in C concentration ranged from -13.1% to +12.0%. Changes in C mass ranged from -11.3% to +8.3%. Increases in C were most closely associated with increases in the C/total-N ratio. C was positively correlated to exchangeable inorganic-N in 1976 (r2 = 0.387) and 2006 (r2 = 0.107). Regression analysis revealed C increased with increasing azimuth and decreasing elevation in 1976 (r2 = 0.140). C was predicted only by clay content in 2006 (r2 = 0.079) and exhibited a negative relationship. Since topography was no longer a predictor of mineral soil C in 2006, we speculate that changes in forest cover also influenced changes in mineral soil C. / Master of Science

<I>Rhododendron maximum</I> L. (Ericaceae) is an evergreen shrub that grows in dense thickets and currently covers large areas of the understory in the deciduous forests of the southeastern United States. Thickets of R. maximum are inhibitory to recruitment and regeneration of many understory plants including canopy tree seedlings. By effectively lowering the survivorship of woody species trying to establish within thickets, <I>R. maximum</I> could influence stand level regeneration patterns and ultimately the community structure of these deciduous forests. This dissertation outlines research conducted to determine if: 1) below and above ground resources are lower within thickets of <I>R. maximum</I> when compared to forest sites where <I>R. maximum</I> is absent; 2) <I>Quercus rubra</I> and <I>Prunus serotina</I> seedlings growing in thickets have lower mid-day photosynthetic rates; 3) <I>Quercus rubra</I> and <I>Prunus serotina</I> seedlings growing within thickets are low light acclimated when compared to seedlings growing in forest without <I>R. maximum</I>; 4) the presence of <I>R. maximum</I> constrains CO₂ assimilation of <I>Quercus rubra</I> seedlings exposed to light flecks of different durations and intensities; 5) the presence of <I>R. maximum</I> constrains the light fleck responses of <I>Quercus rubra</I> seedlings exposed to eight light flecks in rapid succession; and 6) canopy openness regulates the capacity of <I>Quercus rubra</I> seedlings to assimilate carbon when exposed to eight consecutive light flecks. <I>Rhododendron maximum</I> thickets altered resource availability for seedlings when compared to areas of forest without <I>R. maximum</I>. Diffused photosynthetically active radiation (PAR) averaged less than 5 μmol m⁻² s⁻¹ throughout the growing season in sites with <I>R. maximum</I> in comparison to 10-30 μmol m⁻² s⁻¹ in sites without <I>R. maximum</I>. Soil moisture content, measured using Time Domain Reflectometry was approximately 6% lower in forest sites with <I>R. maximum</I> compared to sites without <I>R. maximum</I> throughout the growing season. Most nutrient concentrations (e.g.,, C, N and most cations) and nitrogen mineralization rates were significantly lower in sites with <I>R. maximum</I>. Temperature and atmospheric relative humidity are slightly lower under thickets of <I>R. maximum</I>. In general, sites with <I>R. maximum</I> are associated with lower resource availability above and below ground in comparison with sites without <I>R. maximum</I>. Attenuation of below canopy PAR by thickets of <I>R. maximum</I> negatively influences the photosynthetic capacity of <I>Quercus rubra</I> and <I>Prunus serotina</I> seedlings as indicated by measurements of mid-day photosynthesis. In 1996, the seasonal mean mid-day photosynthetic rate of first year <I>Q. rubra</I> seedlings growing in <I>R. maximum</I> thickets (1.3 μmol m⁻² s⁻¹) was 62% lower than the seasonal mean mid-day photosynthetic rate (2.1 μmol m⁻² s⁻¹) of seedlings growing in forest sites without <I>R. maximum</I>. For second year seedlings in 1997, seasonal mean mid-day photosynthesis was 183% higher for plants growing outside of thickets (1.7 μmol m⁻² s⁻¹) compared to the mean rate (0.6 μmol m⁻² s⁻¹) for plants located within thicket sites. The mean mid-day PAR available to seedlings located in forest sites without <I>R. maximum</I> during measurements of photosynthesis was 354% higher in 1996 and 257% higher in 1997. First year <I>Prunus serotina</I> seedlings growing in forest without <I>R. maximum</I> also had greater seasonal mean mid-day photosynthesis (0.7 μmol m⁻² s⁻¹) when compared to the mean rate (-0.1 μmol m⁻² s⁻¹) for plants growing within thickets. <I>Prunus serotina</I> seedlings located in the presence of <I>R. maximum</I> received on average 67% less PAR. Photosynthetic acclimation to low light was assessed for <I>Q. rubra</I> and <I>P. serotina</I> seedlings growing under both forest conditions by measuring photosynthetic responses to light <I>in situ</I> using even aged one-year old seedlings. <I>Quercus rubra</I> seedlings growing in forest sites without <I>R. maximum</I> had significantly higher light saturated rates of photosynthesis. For both species, photosynthetic responses to light were otherwise similar irrespective of the presence or absence of <I>R. maximum</I>. The impact of the <I>R. maximum</I> subcanopy on understory PAR and subsequent influence on canopy tree seedling photosynthetic capacity implies that sunflecks are critical for seedling net carbon gain in these forest understory environments. To determine the effect of <I>R. maximum</I> on the photosynthetic response to sunflecks of oak seedlings, light flecks were simulated on 288 randomly chosen, even aged, two-year old seedlings <I>in situ</I>. Half of the seedlings were located within <I>R. maximum</I> thickets. Seedlings were randomly assigned one of four light fleck durations (30, 60, 120, and 300s) and one of three intensities (100, 500, 1000 μmol m⁻² s⁻¹). Half of all seedlings were dark pre-acclimated prior to light fleck simulations by covering with aluminum foil for at least 12 hours, while the remaining seedlings were pre-acclimated under ambient conditions. Analysis of covariance showed that a significant, positive, linear relationship exists between the length of a light fleck and total carbon gain during a light fleck for seedlings in forest sites with and without <I>R. maximum</I> regardless of pre-acclimation status, or light fleck intensity. Furthermore, there was a significant effect of <I>R. maximum</I> on the slope of the relationship such that following ambient pre-acclimation, seedlings located within thickets assimilated significantly less carbon with increasing light fleck length than seedlings located in forest sites without <I>R. maximum</I>. When seedlings were dark pre-acclimated there was no difference in carbon gain with increasing fleck length between seedlings in forest with and without <I>R. maximum</I> except for flecks of 1000 μmol m⁻² s⁻¹. The data lead to the conclusion that under natural conditions the presence of <I>R. maximum</I> likely prohibits <I>Q. rubra</I> seedlings from utilizing sunflecks as effectively as seedlings growing in forest sites where <I>R. maximum</I> is absent. Because sunflecks often occur clustered together during a short period of time during the day, another field study was conducted to further characterize the effect of <I>R. maximum</I> on the photosynthetic response of oak seedlings to eight consecutive light flecks. Within 10 paired sites, (i.e., with and without <I>R. maximum</I>) 3 even aged three-year old <I>Q. rubra</I> seedlings were selected. Over each seedling, a hemispherical canopy photograph was taken and analyzed for percent canopy openness. Each seedling was dark pre-acclimated for 12 hours and then exposed to eight light flecks in rapid succession during which time photosynthesis was logged every two seconds. Each light fleck was 500 μmol m⁻² s⁻¹ in intensity and lasted for 120s. Following each light fleck, leaves were exposed to 10 μmol m⁻² s⁻¹ PAR for 60s before the next light fleck. Mean carbon gain and maximum photosynthesis achieved during each light fleck was significantly lower for seedlings located in the presence of <I>R. maximum</I> for all flecks in an eight-fleck simulation. In addition, seedlings located within thickets generally had significantly lower pre-illumination photosynthesis following the first of eight light flecks. The mean photosynthetic light use efficiency of seedlings located in forest with <I>R. maximum</I> was significantly lower for the first six of eight light flecks in succession. Using regression analysis and analysis of covariance, percent canopy openness was used to explain the variation in carbon gained from all eight light flecks in succession for seedlings under both forest conditions. However, significant relationships failed to exist between under either forest condition and precluded using analysis of covariance. The results from these studies lead to the conclusion that light limitation is a major mechanism responsible for the extirpation of canopy tree seedlings from within thickets of <I>R. maximum</I>. Tree seedlings growing in forest sites with <I>R. maximum</I> receive less solar irradiance, have lower mid-day photosynthesis, fail to acclimate to the lower light conditions within thickets, and utilize sunflecks less effectively as well as less efficiently when compared to plants growing in forest sites without <I>R. maximum</I>. / Ph. D.

A pollen profile from varved lake sediments sampled at 10-year intervals and spanning the past 1000 years is analyzed to understand the effects of climate change and anthropogenic activity on forests in southwestern Quebec. The forests responded rapidly to changes in temperature and precipitation during the Medieval Warm Period and Little Ice Age as well as to land-use changes associated with the European Settlement of the area. The transition into the Little Ice Age was abrupt and had significant impact on the pollen production within a couple of decades. A synthesis of this record with other high-resolution and well-dated pollen data from the conifer-hardwood forest of eastern North America shows consistent results across the whole area, indicating that very-high resolution pollen data can provide insight into multi-decadal climate variability and its impact on forest vegetation. Tree-ring records from the region show inter-annual fluctuations not always consistent between sites, while high-resolution pollen data record multi-decadal to century changes which enable us to interpret climatic effects on plant communities.

Sassafras is a deciduous, hardwood, ring-porous species occurring throughout the eastern United States as far west as the Great Plains, but sassafras is used rarely in dendrochronological studies. Samples from 44 sassafras (Sassafras albidum) trees were crossdated (Crossdating Index 2) within and between two sites in Indiana. Ring-width indices were significantly correlated with a variety of climatic indicators. These results suggest that sassafras can be used for a variety of dendrochronological studies.

No description available.

Submitted by William Justo Figueiro (williamjf) on 2015-07-10T20:59:27Z No. of bitstreams: 1 31b.pdf: 589507 bytes, checksum: 21d8a242d61bcd78e3a38beae332f5bc (MD5) / Made available in DSpace on 2015-07-10T20:59:27Z (GMT). No. of bitstreams: 1 31b.pdf: 589507 bytes, checksum: 21d8a242d61bcd78e3a38beae332f5bc (MD5) Previous issue date: 2009 / CNPQ – Conselho Nacional de Desenvolvimento Científico e Tecnológico / UNISINOS - Universidade do Vale do Rio dos Sinos / Cerca de 50 a 90% das árvores e arbustos tropicais têm suas sementes dispersas por vertebrados. A dispersão zoocórica é fundamental para o processo de regeneração de áreas perturbadas, abertas e/ou abandonadas. Aves e morcegos são considerados como excelentes agentes dispersores em termos de quantidade de sementes, distância de dispersão e por dispersarem a maioria das sementes que consomem. Os objetivos principais deste trabalho foram: avaliar e contrastar o potencial germinativo das sementes e a remoção dos frutos de Solanum granulosoleprosum (Solanaceae) feita por aves e morcegos. O trabalho foi realizado em Frederico Westphalen, norte do Rio Grande do Sul, Brasil, em seis fragmentos de Floresta Estacional Decidual. Observações sobre a fenologia de frutificação de S. granulosoleprosum e observações sobre quais são seus dispersores, através de observações focais e uso de redes de neblina, foram realizadas. Aves e morcegos foram capturados para obtenção de amostras fecais de onde foram separadas sementes de S. granulosoleprosum para ser realizado experimentos de germinação em placas de Petri em laboratório. No experimento foram usadas 120 sementes para cada um dos três tratamentos: aves, morcegos e controle. Frutos de cinco plantas de S. granulosoleprosum foram marcados e monitorados por 30 dias para avaliar a remoção por aves e morcegos. As observações da fenologia de frutificação apontaram um maior número de plantas com frutos maduros no outono e inverno (abril a agosto), com um pico de frutificação ao final do outono. Foram registradas 13 espécies de aves e quatro de morcegos consumindo os frutos de S. granulosoleprosum. As aves (40% de germinação) foram mais eficientes que morcegos (16,7%) e controle (17,5%) na porcentagem de germinação das sementes, enquanto morcegos não diferiram do controle. A velocidade de germinação das sementes que passaram pelas aves foi maior que morcegos e controle, que não diferiram entre si. Ao final do experimento de germinação 41,7% das sementes do tratamento morcegos, 6,7% de aves e 1,7% do controle sofreram ataque de fungos e não germinaram. Dos 667 frutos marcados, 565 (85%) foram removidos. Morcegos removeram 64,5% e aves 35,5%. O presente trabalho ilustra um caso em que aves e morcegos têm efeitos contrastantes na dispersão de sementes: enquanto as aves são mais eficientes que os morcegos do ponto de vista qualitativo, aumentando a germinação das sementes de S. granulosoleprosum, o contrário acontece em relação ao componente quantitativo da dispersão, com os morcegos removendo maior número de sementes que as aves. / Fifty to 90% of the trees and shrubs depend on vertebrates to disperse their seeds in tropical regions, where zoochory is important for the regeneration of disturbed forested areas. In these areas, birds and bats are considered efficient seed dispersers in relation to the quantity and quality of seed dispersal. The aim of this work is to evaluate and contrast the roles of birds and bats in promoting the germination of seeds and fruit removal of Solanum granulosoleprosum (Solanaceae), a pioneer species typical of forest edges, in forest fragments located in south Brazil. The fruiting phenology was monitored, and the frugivores eating the fruits of S. granulosoleprosum were recorded during focal observations and with the aid of mist nets. Seeds ingested by birds and bats were contrasted with seeds extracted from mature fruits (control seeds) in germination trials carried out in laboratory under natural conditions. Fruits from five individuals were marked and monitored at dusk and dawn during a 30-day period to assess the fruit removal by birds and bats. Plants produce mature fruits from Autumn to Winter (April to August), with a peak in late Autumn. Thirteen bird species and fur bat species were recorded eating the fruits. Germination success were higher for bird- (40% of germinated seeds) than batingested seeds (16.7%) or control seeds (17.5%; n = 120 seeds for treatments and control). Similarly, the velocity of seed germination was higher for birds. Bat-ingested seeds did not differ from control seeds neither in germination success nor in the velocity of seed germination. Fungi infestation was noted in 41.7% of the batingested seeds, whereas only 6.7% of the bird-ingested and 1.7% of the control seeds were attacked by fungi which precluded germination. A total of 85% of the 667 marked fruits were removed, mainly by bats (n = 64.5%). The present work illustrates a case where birds and bats have contrasting effects upon seed dispersal: while birds are more efficient than bats in a qualitative way, enhancing the germination of seeds, the opposite is true in the quantitative side of efficiency framework, with bats removing a greater quantity of seeds than birds.

A pollen profile from varved lake sediments sampled at 10-year intervals and spanning the past 1000 years is analyzed to understand the effects of climate change and anthropogenic activity on forests in southwestern Quebec. The forests responded rapidly to changes in temperature and precipitation during the Medieval Warm Period and Little Ice Age as well as to land-use changes associated with the European Settlement of the area. The transition into the Little Ice Age was abrupt and had significant impact on the pollen production within a couple of decades. A synthesis of this record with other high-resolution and well-dated pollen data from the conifer-hardwood forest of eastern North America shows consistent results across the whole area, indicating that very-high resolution pollen data can provide insight into multi-decadal climate variability and its impact on forest vegetation. Tree-ring records from the region show inter-annual fluctuations not always consistent between sites, while high-resolution pollen data record multi-decadal to century changes which enable us to interpret climatic effects on plant communities.

No description available.

A pollen profile from varved lake sediments sampled at 10-year intervals and spanning the past 1000 years is analyzed to understand the effects of climate change and anthropogenic activity on forests in southwestern Quebec. The forests responded rapidly to changes in temperature and precipitation during the Medieval Warm Period and Little Ice Age as well as to land-use changes associated with the European Settlement of the area. The transition into the Little Ice Age was abrupt and had significant impact on the pollen production within a couple of decades. A synthesis of this record with other high-resolution and well-dated pollen data from the conifer-hardwood forest of eastern North America shows consistent results across the whole area, indicating that very-high resolution pollen data can provide insight into multi-decadal climate variability and its impact on forest vegetation. Tree-ring records from the region show inter-annual fluctuations not always consistent between sites, while high-resolution pollen data record multi-decadal to century changes which enable us to interpret climatic effects on plant communities.

Sett över hela landet växer ädellövskog endast på en procent av den produktiva skogsmarken. I det studerade området Dalsland utgörs virkesförrådet uppskattningsvis av tre procent ädla lövträd. Dess förekomst är därför att betrakta som relativt sällsynt. Denna studie hade för avsikt att intervjua markägare som har valt att nyetablera med ädellövskog och genom det förstå vad det är som bidragit till att de föryngrat med dessa trädslag. Undersökningen utfördes genom att sex individer som nyetablerat med ädellövskog intervjuades. Resultatet sammanställdes därefter genom att se på gruppen som en helhet och lyfta fram samtliga påverkande faktorer. Utifrån resultatet kunde 13 faktorer identifieras som bidragande och en förståelse kring dem redogöras för.  Det kan konstateras att ett flertal faktorer påverkat markägarna i valet att plantera ädellövskog.