No description available.

Temperate forests are an important carbon sink, yet there is uncertainty regarding land-use history effects on biomass accumulation and carbon storage potential in secondary forests. Understanding long-term biomass dynamics is important for managing forests as carbon sinks and for co-benefits such as watershed protection and biodiversity. However there are many unanswered questions regarding these dynamics in northeastern U.S. forests: How have secondary forests of the U.S. Northeast recovered post nineteenth century agricultural abandonment? How has the region's extensive land-use history influenced long-term structural development and aboveground carbon storage? To answer these questions, we employed a longitudinal study based on twelve years of empirical data (2001-2013) from the Marsh-Billings-Rockefeller (MBR) National Historical Park in Woodstock, VT. MBR Park was the first parcel of land to actively be reforested in the eastern U.S., and as such, its diverse forest mosaic reflects a history of alternate reforestation approaches and varied successional trajectories indicative of secondary forest recovery occurring across the broader northeastern forest landscape. We also used 150 years of documentary data from park management records. This research evaluates the effects of reforestation approaches (planting vs. natural regeneration), management regimes (long-term low-to-intermediate harvest intensities at varied harvest frequencies), and stand development pathways on biomass outcomes. We generated biometrics representative of stand structural complexity, including the H' structural diversity index, and aboveground biomass (live trees, snags, and downed coarse woody debris pools) estimates. Multivariate analyses evaluated the predictive strength of reforestation approach, management history, and site characteristics relative to aboveground carbon pools and stand structural complexity. Classification and Regression Tree (CART) analysis ranked reforestation approach (plantation or natural regeneration) as the strongest predictor of long-term mean total aboveground carbon storage, while harvest frequency, and stand age were selected as secondary variables. CART ranked forest percent conifer (a metric closely associated with reforestation approach) as the strongest predictor of H' index, while harvest intensity, and harvest frequency were selected as secondary variables. Increases in harvest intensity can significantly reduce aboveground carbon storage. Our results suggest that a variety of long-term recovery pathways converge on high levels of aboveground carbon storage, including both conifer plantations and naturally regenerated hardwood stands, but choice of silvicultural management approach can dramatically alter those trajectories. Importantly, total aboveground biomass (i.e., carbon) co-varied with H' (r2 = 0.25), and thus, our dataset showed a positive relationship between forest carbon storage and structural complexity, supporting the concept of multifunctional forestry emphasizing late-successional habitats.

<p>Since the pre-industrial age, the Earth has been warming at unparalleled rates, and this warming is changing climate and weather, creating a more extreme global hydrological cycle. In this dissertation, I explore how these changes to the hydrological cycle may act ecosystem and community level responses of terrestrial plants in the Midwestern United States. In this region, it is projected that mean annual precipitation (MAP) will increase, but precipitation will become more variable across and within seasons. Ecosystem structure and function are vulnerable to changes in hydrologic patterns, including changes in biogeochemical cycles, plant productivity, and plant community structure and function. In this dissertation, I explore how changes in precipitation will alter these processes using two field experiments, and I suggest potential hypotheses that could explain drought-induced community change.</p><p><br></p><p>In chapter 1, I explore how alterations to seasonal precipitation in the winter and summer act ecosystem and community processes in a temperate deciduous forest. Biogeochemical processes and plant communities are sensitive to changes in abiotic conditions, and these conditions will alter forest succession, particularly juvenile woody plant species. Using a fully factorial experiment, I manipulated winter snowfall and summer precipitation to create wet, dry, and control (ambient conditions) treatments and investigated how changes in seasonal precipitation would act mineralization rates, woody plant recruitment, and understory composition. I found that the effects of winter and summer precipitation on these processes acted independently of one another in this system, and the system was resistant to changes in mineralization rates and understory composition. Woody plant recruitment may be more sensitive to altered precipitation, as recruitment of at least one of the four species planted, Lindera benzoin, was impacted by changes in seasonal precipitation. Snow removal treatments reduced germination and increased summer precipitation decreased the relative growth rate of this species. In the short term, slight changes to woody plant recruitment may have little impact on long-term forest succession, but as these changes persist over longer periods of time, they could alter the direction of succession, which could lead to changes in the understory community composition and nutrient cycling.</p> <p><br></p><p>The second and third chapters explore the effects that drought intensification will have on terrestrial plant communities. Numerous studies have investigated the effects of individual droughts on ecosystem and community responses, but the effects that both the timing and duration of drought have on these responses remain largely unknown. To explore this gap in the literature, I conducted a eld experiment using rainout shelters to reduce growing season precipitation, creating dry periods that varied in length and timing. Drought can impact productivity and diversity in this system, and the timing in which the drought occurs influences these effects. Surprisingly, I found that the length of drought did not affect productivity or community composition.</p> <p><br></p><p>The final chapter introduces the Community Response to Extreme Drought framework CRED), which addresses the potential temporal progression of mechanisms and plant-plant interactions that may lead to community changes during and after a drought. The mechanisms for the temporal evolution of community-level drought responses are not fully understood, but plant-plant interactions, both competitive (-) and facilitative (+), are increasingly being recognized as important drivers of community compositional changes. The CRED framework provides hypotheses for the roles that plant-plant interactions have on drought-induced community change. CRED addresses how system-specific variables and the intensity of drought may influence the strength of plant-plant interactions over time, and ultimately the systems resistance and resilience to drought. </p><p><br></p><p>The results from this dissertation work have revealed that more research needs to be done to fully understand how changes in precipitation regimes and patterns will affect terrestrial ecosystems and plant communities. A better understanding of how ecosystems and communities respond to drought timing and length can help improve climate models and restoration strategies.</p>

Os ecossistemas florestais são considerados reservatórios de carbono e têm sido apontados como alternativas para redução de gases do efeito estufa, principais responsáveis pelas mudanças climáticas globais, devido ao acúmulo de biomassa em seus tecidos durante seu desenvolvimento. Assim, surgiu uma grande demanda por pesquisas que quantifiquem o potencial dos ecossistemas florestais - principalmente as florestas secundárias - em sequestrar carbono da atmosfera e por investimentos em recuperação de áreas degradadas. Desta forma, este estudo tem como objetivo comparar florestas do município de Paragominas, Pará, em seis diferentes estágios de desenvolvimento: uma floresta primária e florestas secundárias com 4, 10, 15, 20 e 25 anos de abandono. A comparação entre as florestas se deu por meio da estimativa de carbono e biomassa, de indicadores ecológicos para fins de restauração florestal e de análises espectrais usando imagens de satélite Landsat. Para isso foi realizado um inventário florestal nas regiões de interesse, utilizando 32 parcelas experimentais. Os dados de DAP e altura coletados no inventário foram utilizados no cálculo de biomassa e carbono por meio de equações alométricas. Dados do inventário também foram utilizados para a elaboração dos indicadores para fins de restauração florestal, baseados nas características funcionais e estruturais das florestas estudadas, como diversidade de espécies, cipós, hábitos de vida, incidência de luz, etc. Após alocação das parcelas nas imagens de satélite Landsat e processamento dos dados, foi possível extrair informações quantitativas para comparar espectralmente as florestas. Para avaliar os indicadores para fins de restauração florestal, foi usada uma análise por componentes principais. Esta análise mostrou uma clara distinção entre as diferentes idades de florestas, sendo que a floresta intacta é mais semenhante às florestas secundárias mais maduras. Para a estimativa de biomassa, as análises mostraram que houve diferença estatística entre a floresta primária e todas as outras classes de floresta secundária quanto à biomassa média por hectare calculada por todas as equações utilizadas no estudo. Além disso, houve um aumento de biomassa com a idade das florestas, para todas as equações, ou seja, quanto mais madura a floresta, maior sua biomassa. As análises estatísticas mostraram que é possível distinguir floresta primária da maioria das classes de idade de floresta secundária utilizando um ou uma combinação de dados espectrais avaliados neste estudo. Imagens-fração, GV and shade, foram mais eficientes em diferenciar as florestas. Os resultados mostraram que é possível usar imagens Landsat para monitorar florestas secundárias e mapear classes de idades. / Forest ecosystems are considered carbon sinks and have been pointed as an alternative for reducing the amount of greenhouse gases in the atmosphere, main drivers of global climate changes, due to biomass accumulation in their tissues during growth. Thus, there is great demand for research to quantify the potential of forest ecosystems - especially regrowing secondary forests - in absorbing carbon from the atmosphere and by investments in forest restoration. Therefore, this study aims to compare forests located in Paragominas, Pará, in six different stages: a primary forest and secondary forests with 4, 10, 15, 20 and 25 years of abandonment. The comparison among forests was made by estimating biomass and carbon, ecological indicators for forest restoration and spectral analysis using Landsat satellite imagery. For that purpose, forest inventories were conducted over regions of interest, at 32 experimental plots. The DBH and height data collected in the inventories were used to calculate biomass and carbon using allometric equations. Inventory data were also used to calculate indicators of forest restoration, based on functional and structural characteristics of the studied forests, such as species diversity, lianas, life habits, incidence of light, etc. After allocation of plots in the Landsat imagery and data processing, it was possible to extract quantitative information to compare forests regarding their spectral signature. To assess indicators for restoration purposes, was used a principal component analysis. The results showed a clear distinction among the different ages of forest, in which intact forest is showed more similarity to mature secondary forests then to young secondary forests. For biomass estimation, the analysis showed that there was statistical difference between the primary forest and all other classes of secondary forest considering the average biomass per hectare calculated for all equations used in the study. Furthermore, there was an increase in biomass with age of forests, for all equations, that is, the older the forest, the greater its biomass. The spectral analysis showed that it is possible to distinguish primary forest from most ages of secondary forests using one or a combination of spectral features evaluated in this study. Fraction images, GV and shade, showed more efficient in separating forest types. These results showed that it is possible to use Landsat imagery spectral features to remotely monitor secondary forest and to map age classes.

Os ecossistemas florestais são considerados reservatórios de carbono e têm sido apontados como alternativas para redução de gases do efeito estufa, principais responsáveis pelas mudanças climáticas globais, devido ao acúmulo de biomassa em seus tecidos durante seu desenvolvimento. Assim, surgiu uma grande demanda por pesquisas que quantifiquem o potencial dos ecossistemas florestais - principalmente as florestas secundárias - em sequestrar carbono da atmosfera e por investimentos em recuperação de áreas degradadas. Desta forma, este estudo tem como objetivo comparar florestas do município de Paragominas, Pará, em seis diferentes estágios de desenvolvimento: uma floresta primária e florestas secundárias com 4, 10, 15, 20 e 25 anos de abandono. A comparação entre as florestas se deu por meio da estimativa de carbono e biomassa, de indicadores ecológicos para fins de restauração florestal e de análises espectrais usando imagens de satélite Landsat. Para isso foi realizado um inventário florestal nas regiões de interesse, utilizando 32 parcelas experimentais. Os dados de DAP e altura coletados no inventário foram utilizados no cálculo de biomassa e carbono por meio de equações alométricas. Dados do inventário também foram utilizados para a elaboração dos indicadores para fins de restauração florestal, baseados nas características funcionais e estruturais das florestas estudadas, como diversidade de espécies, cipós, hábitos de vida, incidência de luz, etc. Após alocação das parcelas nas imagens de satélite Landsat e processamento dos dados, foi possível extrair informações quantitativas para comparar espectralmente as florestas. Para avaliar os indicadores para fins de restauração florestal, foi usada uma análise por componentes principais. Esta análise mostrou uma clara distinção entre as diferentes idades de florestas, sendo que a floresta intacta é mais semenhante às florestas secundárias mais maduras. Para a estimativa de biomassa, as análises mostraram que houve diferença estatística entre a floresta primária e todas as outras classes de floresta secundária quanto à biomassa média por hectare calculada por todas as equações utilizadas no estudo. Além disso, houve um aumento de biomassa com a idade das florestas, para todas as equações, ou seja, quanto mais madura a floresta, maior sua biomassa. As análises estatísticas mostraram que é possível distinguir floresta primária da maioria das classes de idade de floresta secundária utilizando um ou uma combinação de dados espectrais avaliados neste estudo. Imagens-fração, GV and shade, foram mais eficientes em diferenciar as florestas. Os resultados mostraram que é possível usar imagens Landsat para monitorar florestas secundárias e mapear classes de idades. / Forest ecosystems are considered carbon sinks and have been pointed as an alternative for reducing the amount of greenhouse gases in the atmosphere, main drivers of global climate changes, due to biomass accumulation in their tissues during growth. Thus, there is great demand for research to quantify the potential of forest ecosystems - especially regrowing secondary forests - in absorbing carbon from the atmosphere and by investments in forest restoration. Therefore, this study aims to compare forests located in Paragominas, Pará, in six different stages: a primary forest and secondary forests with 4, 10, 15, 20 and 25 years of abandonment. The comparison among forests was made by estimating biomass and carbon, ecological indicators for forest restoration and spectral analysis using Landsat satellite imagery. For that purpose, forest inventories were conducted over regions of interest, at 32 experimental plots. The DBH and height data collected in the inventories were used to calculate biomass and carbon using allometric equations. Inventory data were also used to calculate indicators of forest restoration, based on functional and structural characteristics of the studied forests, such as species diversity, lianas, life habits, incidence of light, etc. After allocation of plots in the Landsat imagery and data processing, it was possible to extract quantitative information to compare forests regarding their spectral signature. To assess indicators for restoration purposes, was used a principal component analysis. The results showed a clear distinction among the different ages of forest, in which intact forest is showed more similarity to mature secondary forests then to young secondary forests. For biomass estimation, the analysis showed that there was statistical difference between the primary forest and all other classes of secondary forest considering the average biomass per hectare calculated for all equations used in the study. Furthermore, there was an increase in biomass with age of forests, for all equations, that is, the older the forest, the greater its biomass. The spectral analysis showed that it is possible to distinguish primary forest from most ages of secondary forests using one or a combination of spectral features evaluated in this study. Fraction images, GV and shade, showed more efficient in separating forest types. These results showed that it is possible to use Landsat imagery spectral features to remotely monitor secondary forest and to map age classes.

This thesis is part of Project of the Grant Agency of the Czech Republic No P504/11/1151, focused on the role of plants in the balance of carbon dioxide and the other greenhouse gases produced in the ecosystem of a sedge fen, which is situated on the study site Wet Meadows near Třeboň. The thesis deals with the growth dynamics of the dominant sedge, Carex acuta. The samples were taken using the method of successive harvests near the automatic meteorological station of Czech Globe, Academy of Sciences of the Czech Republic. During the growing season nine harvests were accomplished on 25.3, 15.4, 6.5, 5.6., 9.7., 5.8., 9.9., 21.10., 25.11.. On each date eight replicates were taken, i.e., a total of 72 samples within the vegetation season. The seasonal dynamic of the above ground biomass was compared between C. acuta and the other plant species on the experimental area. Both live and dead biomass, was harvested and subsequently sorted to single botanic species, dried, weighed and the values were processed using the MS Excel tables. The seasonal maximum of aboveground biomass of all plant species (both live and dead parts) was found on 9.7. (1452,72 g.m-2). Among plant species the highest values of aboveground biomass were attained by Calamagrostis canescens (1257,93 g.m-2) and C. acuta (1163,49 g.m-2). C. acuta displayed the highest density of all shoots on 15.4 (300 m-2),and the highest average weight of one shoot. The maximum length of the longest live shoot of Carex acuta was very consistent among the measurememnts.

This thesis is part of Project of the Grant Agency of the Czech Republic No P504/11/1151, focused on the role of plants in the greenhouse gas budget of a sedge fen. The thesis deals with the growth dynamics of the dominant sedge, Carex acuta L., on the study site, Wet Meadows near Třeboň, Czech Republic. The seasonal changes in aboveground biomass were followed using successive harvests during vegetation seasons of 2010 and 2011. The seasonal maximum of aboveground biomass of Carex acuta L. (both live and dead parts) was 321,44 g.m-2 and 357,97 g.m-2 in 2010 and 2011, respectively. The seasonal maximum of total aboveground biomas sof all species was 558,22 g.m-2 and 522,38 g.m-2 in 2010 and 2011, respectively. The seasonal maximum of shoot density was 485 ks.m-2 and 435 ks.m-2 in 2010 and 2011, respectively.

My thesis is a part of the project GACR 206/06/0058 Monitoring of selected heavy metals and risk elements in a wastewater cleaning process in artificial wetlands. The goal is to evaluate temporal and spatial variability of underground biomass of Phragmites australis in the artificial wetland used for wastewater treatment in Slavošovice. The destructive method was used for the sampling. The aboveground biomass was determined from six samples taken at the inflow and six samples at the outflow. The belowground biomass (in 2008) was estimated from two samples taken at the inflow and two samples at the outflow. In 2009, the belowground biomass was determined from six samples taken from the inflow and six samples from the outflow. The analysis of the root structure was determined from 12 samples collected at the inflow and 12 samples of the outflow. The mean total aboveground biomass reached 1039 g.m-2 at the inflow and the 1749 g.m-2 at the outflow. Average total belowground biomass in 2009 reached the inflow 1718 g.m-2 and 1562 g.m-2 at the outflow. The average total length of roots growing from one node to was 284,7 m.m-2 and 324,9 m.m-2 in the inflow and outflow part, respectively. Average specific root length of the inflow was 2589,5 cm.g-1 and the outflow 2956,9 cm.g-1. The average total length of roots reaching the inflow of two kilometers and three kilometers of inflow.

Abstract Plants and soil organisms are closely linked. Plants are the sole source of carbon in the soil and soil organisms are responsible for recycling of nutrients, making them available for plant growth. To understand the function of a system, it is important to understand the interactions between the soil and plants. These interactions have mainly been studied in temperate areas, with few studies in the arctic and subarctic. The aim of this thesis was to investigate the effect of ecological disturbances in sub- and low-arctic grasslands on soil organisms and plant-soil feedback relationships. The effect of removal of vegetation, replanting of a local plant species, and different components of grazing (trampling, defoliation and return of nutrients) on soil decomposer organisms were studied. Whether short term effects of defoliation depended on plant species community was also studied, as well as whether defoliation in the field could create changes in the soil system systems that affect the growth of seedlings. Experiments were conducted under both controlled greenhouse conditions and in field sites. The results showed that physical disturbance (removal of vegetation and trampling) reduced the abundance and diversity of soil biota. Defoliation increased soil decomposer abundance in the short term. Plant species composition did not affect soil biota and only in a few cases did it changes their responses to defoliation. In the long-term, effects of fertilization and defoliation on the soil biota were context-dependent. However, defoliation did create changes in the soil that reduced the growth of seedlings planted into the soil. Furthermore, plant species community and spatial heterogeneity (revealed by blocking) had important effects on the soil communities.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21801号 / 農博第2314号 / 新制||農||1065(附属図書館) / 学位論文||H31||N5173(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 神﨑 護, 教授 北島 薫, 教授 大澤 晃 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM