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Invasive species are significant drivers of global environmental change, altering the stability and functioning of numerous ecosystems. The exotic shrub Lonicera maackii is an aggressive invader throughout much of the eastern United States. While much is known about its population and community impacts, little is known about effects on ecosystem processes. This dissertation documents changes in ecosystem processes associated with L. maackii growing beneath three native tree species (Fraxinus quadrangulata, Quercus muehlenbergii, Carya ovata) in a savanna in Kentucky. Like many invasive plants, L. maackii litter decomposed and lost nitrogen (N) rapidly, especially in comparison with native tree litter. In comparison to the soils beneath the trees where the exotic shrub was absent, soils beneath L. maackii had a lower bulk density, elevated soil organic matter, C:N, and total soil N and a modified soil microbial community. Inorganic N deposition from spring throughfall was also altered by L. maackii, with higher NO3-N deposition beneath shrubs located beneath the tree canopy relative to canopy locations without L. maackii. While many exotic plant species have been shown to alter ecosystem processes, their impact is often not uniform. This variability is attributed to among-site differences (soil, climate, plant community): within site variability is often ignored. While many of L. maackii’s alterations to ecosystem processes were uniform across the site, several were dependent upon interactions between the exotic and the native tree species. Litter from L. maackii decomposed and lost N more rapidly under C. ovata than under the other native tree species. Soils beneath L. maackii shrubs located under C. ovata also had a greater fungal:bacterial ratio and a greater abundance of the saprophytic fungal lipid biomarker 18:1ω9c. These results demonstrate that L. maackii’s impact extends to ecosystem processes and suggests that invasive plants may have variable effects within a given environment depending on their interactions with the dominant native species. Identifying native species or communities that are more vulnerable to alterations of ecosystem function upon invasion may prove useful to land managers and foster a better understanding of the role that community dynamics play in moderating or enhancing invasive species impacts.

We collected the data for decomposition of spruce litter to determine the limit values of mass loss and to find both chemical and climate factors that influence limit values. Our data contained 28 sequences of spruce which mainly in Sweden and a small part in other places. We choose mean annual temperature (MAT) and mean annual precipitation (MAP) as climate factors and water solubles, lignin, N, P, K, Ca, Mg and Mn as chemical factors. Then we got the estimated limit values by performing a nonlinear model with mass loss and time spots, and found out the influential factors by using another linear mixed model. At the end we knew that linear mixed model is a proper and efficient approach for determining the factors, P and MAP are the significant factors and Species is a good random effect to explain the variance within groups.

Headwaters, which are the most common stream order in the landscape, are mostly dependent on energy produced in the terrestrial system, largely consisting of leaf litter from riparian vegetation. The aim of this study was to investigate the decomposition in headwaters of leaf litter from three native (alder, birch, spruce) and one non-native (lodgepole pine) species and how decomposition responds to changes in the environment. Further, microbial and shredder influences on leaf-litter decomposition and aquatic decomposer ability to adapt to non-native species was investigated. By using field-data from this study, calculations were made to assess if microbes and shredders are resource limited. Litterbags were placed in 20 headwater streams in northern Sweden that varied in water chemistry, stream physical characteristics and riparian vegetation. The results revealed that species litter decomposition of different plant species was affected differently by changes in environmental variables. Alder and birch decomposition were positively associated, whereas lodgepole pine deviated from the other species in decomposition and its relationship with important environmental variables, indicating that the ability of the boreal aquatic systems to decompose litter differs between introduced and native species. When including macroinvertebrates, shredder fragmentation generally increased decomposition, but was not significant for all sites. Resource availability for microbes and shredders was controlled by litter input, and no risk of resource limitations was evident during the study period. These findings highlight a complexity of the decomposition process that needs to be considered when predicting changes due to human activities.

Abstract In northernmost Fennoscandia, grazing by reindeer (Rangifer tarandus L.) has a substantial impact on the vegetation of boreal forests and arctic-alpine tundra heaths, which are reflected in below-ground processes, such as nutrient mineralization and soil organic matter decomposition. In the present thesis, the effects of reindeer grazing on soil nutrient cycling were studied by comparing grazed situation with an ungrazed control area in ten boreal forests and six arctic-alpine tundra heaths. In boreal forests, reindeer grazing reduced microbial respiration in both the oligotrophic and mesotrophic study areas, indicating a deficiency of labile substrates for the soil microbes due to reindeer grazing. Simultaneously, there was heterogeneity in the impact on nitrogen mineralization rates as at some sites, mineralization was enhanced by grazing. The fertilization effect of urine and faeces can therefore be strong enough a factor to outweigh a reduction in quality of soil organic matter. In the oligotrophic forests, low soil moisture content in the grazed areas could sometimes limit the mineralization rates even when the potential for mineralization was enhanced by grazing. In the tundra ecosystems, there was spatial variation in the impact of grazing on microbial respiration and nitrogen mineralization. Low grazing intensity occurring outside the growing season had a retarding impact on nutrient cycling in both unfertilized, nutrient-poor and fertilized, nutrient-rich conditions. In contrast, a relatively high grazing intensity enhanced the mineralization rates in two nutrient-poor and two nutrient-rich tundra heaths. When three different grazing intensities were compared in one oceanic, nutrient-rich and one continental, nutrient-poor tundra heath, the strongest positive effect of grazing on soil nutrient cycling occurred in the heavily grazed areas. The data do not support the assumption that soil nutrient availability regulates whether herbivores enhance or retard nutrient cycling in the soil. Instead, the net effect of grazing is determined by the balance between the underlying mechanisms that may work at opposite directions. The most important of these mechanisms are the grazer-mediated impact on the decomposability of the dominant vegetation and fertilization by urine and faeces. The duration, intensity and seasonal timing of the grazing seem to be important factors that regulate whether reindeer grazing enhances or retards soil nutrient cycling in each specific area. Due to the high spatial and temporal variation in the effects of grazing observed in this study, it is not possible to generalize the overall impact of grazing. Further study is required in order to determine the exact conditions under which grazing enhances or it retards soil nutrient cycling.

In forested ecosystems, salamanders occupy important ecological roles as predator, prey and as potential regulators of ecological processes. The effects of forest management, particularly clearcut harvesting, on salamanders have been well documented; removal of overstory trees negatively affects abundances of salamanders. However, the length of time that salamander populations remain depressed following forest harvesting and factors limiting population recovery have been a source of controversy in the literature and are the goal of this dissertation. As part of the Southern Appalachian Silviculture and Biodiversity (SASAB) project (Chapter 1), a long-term replicated field experiment designed to evaluate a range of silvicultural treatments on biodiversity, I evaluated specific hypotheses related to salamander populations, their prey, and their habitat. First, I examined long-term trends in salamander abundances across a range of silvicultural treatments to determine whether negative effects of forest harvesting persisted for 13-years after harvest (Chapter 2) and to document the effects of multiple harvests on salamanders (Chapter 3). The relative abundances of terrestrial salamanders were quantified in six silvicultural treatments and an unharvested control and on six replicated field sites with night-time, area-constrained searches. Across 13-years of post-harvest data, terrestrial salamander abundances generally were lower in silvicultural treatments with some disturbance to the canopy (group selection harvest through silvicultural clearcut). Further, a comparison of demography of common species of salamanders suggested that differences in habitat quality existed between harvested and unharvested experimental units (EUs). A second harvest in the shelterwood plots to remove overwood had a cumulative negative effect on salamanders at one of two sites studied. Additionally, I conducted a sensitivity and elasticity analysis for eastern red-backed salamanders (Plethodon cinereus) and modeled population growth to evaluate the contribution of demographic parameters to population recovery. These analyses indicated that adult survival was the parameter with the greatest influence on the population growth rate and that >60 years would be required for recovery of salamander populations to preharvest levels even if habitat conditions were restored to preharvest conditions immediately. Next, I quantified the bioenergetics of salamanders across a disturbance gradient to evaluate whether changes to (1) invertebrate prey, (2) energy expenditure for basic maintenance costs, and or (3) an index to body condition could help explain observed changes to abundances or demography of salamanders from forest harvesting (Chapter 4). Although I did not detect a difference in abundances of invertebrates along the disturbance gradient, I determined that salamanders in recently disturbed forest stands expended approximately 33% more energy for basic maintenance costs in an active season and the body condition of salamanders was greater at one of two sites in disturbed EUs. Thus, the bioenergetics of terrestrial salamanders may have been affected by increasing temperatures from silvicultural disturbance and may cause salamanders to allocate less energy to reproduction or growth because of increased maintenance costs. In collaboration with Eric Sucre, Department of Forestry at Virginia Tech, I examined the effects of salamanders on invertebrates and ecosystem processes, specifically leaf litter decomposition. We constructed 12 in situ field mesocosms and I manipulated densities of red-backed salamanders into zero, low, and high density treatments. From June 2006-June 2008, I estimated invertebrate abundances, rates of leaf litter decomposition and food habits of salamanders across treatments. I found that invertebrate abundances were more affected by season than by the density of salamanders and that rates of leaf litter decomposition did not differ among salamander treatments. Salamanders were euryphagic and consumed more (by abundance and volume) herbivorous invertebrates than predators or detritivores. Finally, I modeled habitat relationships of terrestrial salamanders at two spatial scales on the SASAB study sites (Chapter 6). I quantified abundance of salamanders with area-constrained searches during warm rainy nights and measured forest characteristics related to foraging or refugia habitats or that described the overstory and understory of forest stands. At the scale of the 30 m2 transect and the 10 m2 sub-transect, abundance of salamanders was best described by models that incorporated descriptors of canopy cover and woody and herbaceous understory vegetation. Thus, terrestrial salamanders may have responded positively to forest stands with a mature overstory and structurally diverse understory for foraging habitat. Collectively, these data suggest that recovery of salamander populations after forest harvesting will take approximately 60 years, and that life history characteristics (low fecundity, late sexual maturity) and possibly changes to bioenergetics may contribute to the slow recovery. Further, silvicultural practices that retain some canopy trees through a rotation may have a more rapid return of salamander populations to preharvest levels and may encourage development of understory structure for salamander foraging. Although these data fill some gaps in knowledge of relationships between silviculture and terrestrial salamanders, many questions about long-term effects of disturbances on populations and habitats remain. My modeling of recovery of salamander populations depended on estimates of a survival from a congener, and I did not document whether forest harvesting decreases survival of terrestrial salamanders. Lastly, the influence of stochastic events on population dynamics particularly in disturbed stands was not examined in this dissertation. Therefore, future research on the SASAB study sites should continue to track abundances and demography across the disturbance gradient, acquire age-specific estimates of survival, determine whether salamanders exhibit density dependence, develop estimates of entire energy budgets, and use manipulative laboratory experiments to describe the role of plethodontid salamanders in ecosystem functions. / Ph. D.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Inorganic fertilizer applications are common practice in commercial agriculture, yet not much is known regarding their interaction with organic matter and soil biota. Much research has been done on the effect of inorganic N on forest litter decomposition, yet very little research has focused on the effect of inorganic fertilizers on crop litters and, to our knowledge, none on composted organic matter. Furthermore none of the research has been done in South Africa. The main aim of this research project was to determine the effect of inorganic fertilizer applications on the decomposition of selected organic matter sources commonly used in South African agriculture and forestry. Two decomposition studies were conducted over a 3-month period, one on composts and the other on plant litters, using a local, sandy soil. In the first experiment a lower quality compost, compost A (C:N ratio, 17.67), and higher quality compost, compost B (C:N ratio, 4.92) was treated with three commercially used fertilizer treatments. Two were typical blends used for vegetable (tomato and cabbage) production: tomato fertilizer (10:2:15) (100 kg N, 20 kg P, 150 kg K per ha) and cabbage fertilizer (5:2:4) (250 kg N, 100 kg P, 200 kg K per ha). The third fertilizer blend, an equivalent mass application of N and P applied at 150 kg of each element per ha, is more commonly used in pastures. In the second experiment, five commonly encountered crop and forestry litters, namely kikuyu grass, lucerne residues, pine needles, sugar cane trash and wheat straw, were selected to represent the labile organic matter sources. The litters were treated with the tomato and cabbage fertilizer applications rates. Both decomposition experiments were conducted under ambient laboratory conditions at field water capacity. Decomposition rates were monitored by determining CO2 emissions, DOC production, β-glucosidase and polyphenol oxidase activity (PPO). At the start and end of decomposition study, loss on ignition was performed to assess the total loss of OM. Based on the results obtained from these two experiments, it was concluded that the addition of high N containing inorganic fertilizers enhanced the decomposition of both composted and labile organic matter. For both compost and plant litters, DOC production was greatly enhanced with the addition of inorganic fertilizers regardless of the organic matter quality. The conclusion can be made that inherent N in organic matter played a role in the response of decomposition to inorganic fertilizer application with organic matter low in inherent N showing greater responses in decomposition changes. For labile organic matter polyphenol and cellulose content also played a role in the responses observed from inorganic fertilizer applications. / AFRIKAANSE OPSOMMING: Anorganiese kunsmis toedieningss is algemene praktyk in die kommersiële landbou sektor,maar nog min is bekend oor hul interaksie met organiese materiaal en grond biota. Baie navorsing is reeds oor die uitwerking van anorganiese N op woud en plantasiereste se ontbinding gedoen. Baie min navorsing het gefokus op die uitwerking van anorganiese kunsmis op die gewasreste en tot ons kennis, is daar geen navorsing gedoen op die invloed van anorganiese kunsmis op gekomposteer organiese material nie. Verder is geeneen van die navorsing studies is in Suid-Afrika gedoen nie. Die hoofdoel van hierdie navorsingsprojek was om die effek van anorganiese kunsmis toedienings op die ontbinding van geselekteerde organiese materiaal bronne, wat algemeen gebruik word in die Suid-Afrikaanse landbou en bosbou, te bepaal. Twee ontbinding studies is gedoen oor 'n 3-maande-tydperk, een op kompos en die ander op die plantreste, met die gebruik van 'n plaaslike, sanderige grond. In die eerste eksperiment is ‘n laer gehalte kompos, kompos A (C: N verhouding, 17.67), en 'n hoër gehalte kompos, kompos B (C: N verhouding, 4.92) met drie kommersieel anorganiese bemesting behandelings behandel. Twee was tipiese versnitte gebruik vir die groente (tamatie en kool) produksie: tamatie kunsmis (10: 2:15) (100 kg N, 20 kg P, 150 kg K per ha) en kool kunsmis (5: 2: 4) (250 kg N, 100 kg P, 200 kg K per ha). Die derde kunsmis versnit was 'n ekwivalente massa toepassing van N en P van 150 kg van elke element per ha, wat meer algemeen gebruik word in weiding. In die tweede eksperiment was vyf algemeen gewas en bosbou reste, naamlik kikoejoegras, lusern reste, dennenaalde, suikerriet reste en koring strooi, gekies om die labiele organiese materiaal bronne te verteenwoordig. Die reste is met die tamatie en kool kunsmis toedienings behandel. Beide ontbinding eksperimente is uitgevoer onder normale laboratorium toestande by veldwaterkapasiteit. Ontbinding tempo is deur die bepaling van die CO2-vrystellings, opgelosde organiese koolstof (OOK) produksie, β-glukosidase en polifenol oksidase aktiwiteit (PPO) gemonitor. Aan die begin en einde van ontbinding studie, is verlies op ontbranding uitgevoer om die totale verlies van OM te evalueer. Gebaseer op die resultate van hierdie twee eksperimente, was die gevolgtrekking dat die toevoeging van hoë N bevattende anorganiese bemestingstowwe die ontbinding van beide komposte en plant reste verhoog. Vir beide kompos en plantreste word OOK produksie verhoog met die toevoeging van anorganiese bemesting, ongeag van die organiese materiaal gehalte. Die gevolgtrekking kan gemaak word dat die inherente N in organiese materiaal 'n rol gespeel het in die reaksie van ontbinding op anorganiese bemesting toedienings met die grootste reaksie in organiese material laag in inherente N. Vir labiele organiese material het polifenol en sellulose inhoud ook 'n rol gespeel in die reaksie waargeneeming op anorganiese bemesting.

Made available in DSpace on 2015-03-26T13:53:30Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1969812 bytes, checksum: 99b7bd01f7204c8f8b6933b68eb525b3 (MD5) Previous issue date: 2006-10-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In degraded environments biogeochemical cycle following litter decomposition is very important to maintain plant and animal communities. To study the nutrients release coming from leaves of cycling species potentially useful in revegetation programs is fundamental to know the nutrients cycling process, and its sustainability. Organic materials with fast decomposition are sources of nutrients and energy to biota, while more resistant materials remain on the soil, acting as a physical protection. Rapid decomposition of plant materials, in general, shows negative correlation with lignin and cellulose contents, lignin/nitrogen (lig/N), carbon/nitrogen (C/N) and carbon/phosphorus (C/P) ratios; conversely, shows positive correlation with nitrogen (N) and phosphorus (P) contents. Therefore, it was hypothetised that the kinetic decomposition and nutrients release from leaves is function of its chemical composition and environmental conditions, this study aimed to: characterize chemically leaves from 10 native trees species from Mata Atlântica in Viçosa region, Minas Gerais State; evaluate the leaves decomposition in field and greenhouse conditions, relating it with leaves chemical composition, and; evaluate leaves nutrients release. Chemical characterization was carried by the determination of total carbon (C), nitrogen (N), lignin, cellulose, phosphorus (P), sulfur (S), calcium (Ca), magnesium (Mg) and potassium (K) in the leaves. Species were separated into three groups according to estimated leaves speed decomposition (fast, intermediary, and slow), considering C, N, lignin and cellulose contents and C/N and lig/N ratios. Four species were classified with fast decomposition (Senna macranthera, Trema micrantha, Bauhinia forficata, Croton floribundus), three with intermediary (Cassia ferruginea, Zeyheria tuberculosa e Luehea grandiflora), and three with slow decomposition (Aegiphila sellowiana, Schinus terebenthifolius e Mabea fistulifera). Further leaves collection and characterization was performed before the decomposition essay, which was run with 18 litter bags with fresh leaves from each specie and environment (field and greenhouse). In greenhouse, litter bags were inserted in pots with topsoil from a secondary forest, and in field conditions they were placed over the topsoil of the secondary forest. During six months, materials from three litter bags from each specie and environment were taken each 30 days, weighed and analyzed for C, N, P, S, K, Ca and Mg contents. C, N, S, Ca and Mg contents and C/N ratios values varied significantly among species, while K contents were similar. The observed variations are probably due to different leaves maturation stage, environment and genetic variability among individuals of the same specie (different forest fragments) and collection time (season). The accumulated decomposition of leaves varied according with species, chemical composition and environment. In the greenhouse essay only two groups were formed by Scott-Knott test (5 % of probability): Leaves from A. sellowiana, S. terebenthifolius e B. forficata showed fast decomposition, while leaves from the others species (T. micrantha, S. macranthera, M. fistulifera, C. floribundus, Z. tuberculosa, C. ferruginea e L. grandiflora) showed intermediary decomposition. In the field essay, the species formed three groups: fast decomposing material from M. fistulifera, B. forficata, Z. tuberculosa, C. ferruginea, S. macranthera e S. terebenthifoliu intermediary decomposing; from C. floribundus intermediary, and slow decomposing materials for the remaining species. The chemical composition of leaves were not the only factor to explain the decomposition rate, suggesting that physical characteristics, or chemical attributes other than those determined, may also affect it. The biotic influence in the decomposition rate was illustrated by the faster speed observed in the field conditions compared with greenhouse conditions. Nutrients release from the leaves varied as a result of the environment, being more effective in field conditions. In the greenhouse experiment the decomposition time was sufficient to enable significant mineralization of K, Ca, Mg and P for all species, and S for most. / Em ambientes degradados a ciclagem biogeoquímica promovida pela serapilheira é de fundamental importância para o estabelecimento e manutenção de uma comunidade vegetal e animal na área. Estudar o potencial de retorno dos nutrientes por meio do folhedo de espécies aptas a serem utilizadas em programas de revegetação é essencial para o entendimento do processo de ciclagem de nutrientes nestas áreas, e sua sustentabilidade. Materiais que apresentam rápida decomposição atuam diretamente como fonte de nutrientes e energia para a biota, enquanto aqueles materiais mais recalcitrantes permanecem sobre o solo, conferindo-lhe proteção física. A velocidade de decomposição dos materiais vegetais, em geral, se correlaciona negativamente com os teores de lignina, celulose e as relações lignina/nitrogênio (Lig/N), carbono/nitrogênio (C/N) e carbono/fósforo (C/P), e positivamente com os teores de nitrogênio (N) e fósforo (P). Desta forma, trabalhando com a hipótese de que a cinética de decomposição e liberação de nutrientes de folhas das espécies é função de sua composição química e das condições ambientais, este estudo teve como objetivo caracterizar quimicamente as folhas de 10 espécies arbóreas nativas da Mata Atlântica na região de Viçosa MG; avaliar a decomposição das folhas destas espécies em condições de campo e em casa de vegetação, relacionando-a com a composição química das folhas e avaliar o potencial de liberação de nutrientes destas folhas. A caracterização química consistiu da determinação dos teores de carbono (C), nitrogênio (N), lignina, celulose, fósforo (P), enxofre (S), cálcio (Ca), magnésio (Mg) e potássio (K) das folhas de 10 espécies. Estas espécies foram, então, classificadas em três grupos de acordo com a velocidade de decomposição prevista (rápida, intermediária e lenta) de seus materiais foliares, com base nos teores de C, N, lignina e celulose, e relações C/N e Lig/N. Esta classificação foi relativa entre as espécies estudadas, considerando de forma conjunta os fatores citados, sendo quatro espécies classificadas no grupo de rápida decomposição (Senna macranthera, Trema micrantha, Bauhinia forficata, Croton floribundus), três no grupo das intermediárias (Cassia ferruginea, Zeyheria tuberculosa e Luehea grandiflora) e três de decomposição lenta (Aegiphila sellowiana, Schinus terebenthifolius e Mabea fistulifera). Foi feita uma nova caracterização química com os materiais das espécies selecionadas coletados para os ensaios de decomposição. Nos ensaios de decomposição foram utilizados 18 litter bags contendo folhas frescas, para cada espécie em cada ambiente. Os litter bags foram colocados em vasos com solo de uma mata secundária em casa de vegetação, e diretamente no solo de uma mata secundária, sendo retirados três de cada espécie e ambiente a cada 30 dias durante seis meses, para serem pesados e analisados quanto aos teores de C, N, P, S, K, Ca e Mg dos materiais vegetais. Os teores de C, N, S, Ca e Mg, bem como as relações C/N das folhas das diferentes espécies apresentaram variações significativas entre as duas caracterizações. Já os de K mantiveram-se semelhantes e os teores de P apresentaram aumentos significativos. As variações observadas provavelmente se devem ao estágio de maturação dos materiais vegetais coletados, aos ambientes de coleta destes materiais, à variabilidade genética entre os indivíduos da mesma espécie (fragmentos florestais distintos) e à época de coleta (estação do ano). A decomposição acumulada dos materiais foliares em casa de vegetação e no campo variou com a espécie, com sua composição química e com o ambiente. No ensaio em casa de vegetação formaram-se apenas dois grupos, pelo teste de Scott-Knott a 5% de probabilidade. As folhas de A. sellowiana, S. terebenthifolius e B. forficata apresentaram velocidade de decomposição rápida. Os materiais foliares das demais espécies (T. micrantha, S. macranthera, M. fistulifera, C. floribundus, Z. tuberculosa, C. ferruginea e L. grandiflora) apresentaram decomposição intermediária. No ensaio de campo, as espécies foram alocadas em três grupos. As espécies cujos materiais foliares apresentaram rápida decomposição foram M. fistulifera, B. forficata, Z. tuberculosa, C. ferruginea, S. macranthera e S. terebenthifolius. As folhas do C. floribundus apresentaram decomposição intermediária e as das demais espécies apresentaram decomposição lenta. As características químicas utilizadas para predizer a velocidade de decomposição relativa dos materiais foliares estudados não foram suficientes para explicar o comportamento destes, indicando que características físicas, bem como químicas não determinadas, também influem na decomposição destes materiais. A influência da biota na decomposição dos materiais foliares em campo foi evidenciada pelo aumento observado na sua decomposição em relação aos valores encontrados em casa de vegetação. A liberação de nutrientes dos materiais vegetais das espécies variou em função das condições ambientais, sendo mais efetiva em condições de campo, devido à ação da biota mais diversa. No ensaio de casa de vegetação, o período de decomposição dos materiais vegetais possibilitou significativa mineralização de K, Mg, Ca e P para a totalidade das espécies e de S para a maioria destas. Já no ensaio de campo, houve ocorrência de liberação de K, Mg, Ca, P e S para todos os materiais vegetais. Para o material foliar das espécies estudadas, o S seria o nutriente mais limitante do processo de decomposição.

Submitted by GLAUCIA REGINA SANTOS null (glauciaflorestal@gmail.com) on 2016-12-15T11:36:47Z No. of bitstreams: 1 Dissertação_Gláucia_Santos_revfinal.pdf: 2438611 bytes, checksum: 6cb9d42e38327bbdf2a6f7e6841cdfbf (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-15T16:21:16Z (GMT) No. of bitstreams: 1 santos_gr_me_bot.pdf: 2438611 bytes, checksum: 6cb9d42e38327bbdf2a6f7e6841cdfbf (MD5) / Made available in DSpace on 2016-12-15T16:21:16Z (GMT). No. of bitstreams: 1 santos_gr_me_bot.pdf: 2438611 bytes, checksum: 6cb9d42e38327bbdf2a6f7e6841cdfbf (MD5) Previous issue date: 2016-11-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A presença de espécies exóticas em ambientes ripários pode influenciar na quantidade e qualidade de folhas que são realocadas no sistema ecológico. Desse modo, o objetivo deste trabalho foi determinar a influência do Eucalyptus saligna Sm. na dinâmica de produção e decomposição de folhas em três zonas ripárias, cujas hipóteses visam verificar se o estresse hídrico, a densidade e área basal do eucalipto afetam a produção de folhedo, e também constatar se a decomposição de folhas senescentes de eucalipto, em meio aquático e terrestre, ocorre mais lentamente do que das folhas nativas. A pesquisa foi realizada em três microbacias denominadas Forquilha, Monjolinho e Tinga, situadas na Estação Experimental de Itatinga, SP. Apresentam respectivamente 0,4%, 1,2% e 11,9% do total de indivíduos de eucalipto. A avaliação transcorreu durante um ano, e as folhas coletadas foram triadas em eucaliptos e nativas. Avaliou-se a entrada de folhedo por meio de coletores terrestres e verticais, distribuídos sistematicamente por ambas as margens dos rios e também sobre o curso d’água. Para maior caracterização do local, o levantamento dos parâmetros da vegetação foi realizado por meio de parcelas 5x10m e mensuradas as espécies com altura > 1,30 m e DAP ≥ 3,5 cm. Para o estudo de decomposição aquática e terrestre, avaliaram-se um mix de folhas de eucalipto, nativas e eucalipto/nativas (1:1) introduzidas em litter bags. A decomposição em meio aquático foi avaliada ao longo de 112 dias, enquanto que a terrestre passou por um processo de avaliação aos 3, 6, 9 e 12 meses. O remanescente vegetal da microbacia Tinga mostrou maior densidade (n° indivíduos/ha) e área basal (m2/ha) de eucalipto. A vegetação da Forquilha exibiu os maiores valores H (Shannon) e J (Pielou) dentre as áreas estudadas, e menor coleta das folhas de eucalipto. No geral, ocorreu maior deposição de folhedo no final do período que antecede as chuvas. Com exceção da microbacia Monjolinho em ambiente aquático, no geral as folhas de eucalipto apresentaram menor taxa de decomposição. Na microbacia Tinga e Forquilha, as folhas de eucalipto demonstraram quantidades superiores de lignina, celulose, alta relação C/N, baixa concentração de N e Ca. Na microbacia Tinga, verificou-se uma maior deposição das folhas de eucalipto. Em função de uma maior produção das folhas de eucalipto nessa área e por revelarem uma menor taxa de decomposição, sugere-se que neste local ocorre maior acúmulo de folhedo sobre o solo. Portanto o nível de conservação de uma zona ripária pode influenciar nas taxas de decomposição, na manutenção das comunidades decompositoras e nos processos ecológicos, tendo em vista que o desequilíbrio entre maior entrada de folhedo e menor decomposição altera o equilíbrio natural do ambiente. / The presence of exotic species in riparian environments can influence in the quantity and quality of leaves that are relocated in the ecological system. Thus, the aim of this work was to determine the influence of the eucalyptus in the dynamics of production and decomposition of leaves in three riparian zones. The research was done in three micro watersheds named Forquilha, Monjolinho and Tinga located in Estação Experimental de Itatinga in São Paulo. They present respectively 0.4%, 1.2% and 11.9% of the total of eucalyptus individuals. The data collection occurred in a year, and the collected leaves were sorted in eucalyptus and native. The leaf-litter were collected through terrestrial and vertical collectors, systematically distributed on both banks and on the watercourse. For greater characterization of the site, the vegetation parameters were surveyed through 5x10m parcels. For decomposition study, it was evaluated the decomposition of eucalyptus, native and eucalyptus/native (1:1) introduced in litter bags. The decomposition in aquatic environment was evaluated for 112 days, and terrestrial decomposition in 3, 6, 9 and 12 months. The vegetal reminiscent of Tinga watershed showed a higher density (individuals number/ha) and basal area (m²/ha) of eucalyptus. The Forquilha vegetation showed the highest H (Shannon) and J (Pielou) values. In general, leaf-litter decomposition was higher in the end of the dry period. Except for the Monjolinho watershed in the aquatic environment, the eucalyptus leaves had a lower decomposition rate. The eucalyptus leaves, mainly in Tinga and Forquilha watersheds, showed higher quantities of lignin, cellulose, high ratio C/N, low concentration of N and Ca. The forestry fragment of the three watersheds showed significant differences in eucalyptus and native leaves production, where Tinga micro watershed outstanded with the higher eucalyptus deposition. It can be suggested that in this micro watershed, there is a higher leaf-litter amount over the soil. Therefore, the level of conservation of a riparian zone can influence the rates of decomposition, the maintenance of decomposing communities and ecological processes, since the imbalance between greater leaflitter input and less decomposition alter the natural balance of the environment.

abstract: There is a growing consensus that photodegradation accelerates litter decomposition in drylands, but the mechanisms are not well understood. In a previous field study examining how exposure to solar radiation affects decomposition of 12 leaf litter types over 34 months in the Sonoran Desert, litter exposed to UV/blue wavebands of solar radiation decayed faster. The concentration of water-soluble compounds was higher in decayed litter than in new (recently senesced) litter, and higher in decayed litter exposed to solar radiation than other decayed litter. Microbial respiration of litter incubated in high relative humidity for 1 day was greater in decayed litter than new litter and greatest in decayed litter exposed to solar radiation. Respiration rates were strongly correlated with decay rates and water-soluble concentrations of litter. The objective of the current study was to determine why respiration rates were higher in decayed litter and why this effect was magnified in litter exposed to solar radiation. First, I evaluated whether photodegradation enhanced the quantity of dissolved organic carbon (DOC) in litter by comparing DOC concentrations of photodegraded litter to new litter. Second, I evaluated whether photodegradation increased the quality of DOC for microbial utilization by measuring respiration of leachates with equal DOC concentrations after applying them to a soil inoculum. I hypothesized that water vapor sorption may explain differences in respiration among litter age or sunlight exposure treatments. Therefore, I assessed water vapor sorption of litter over an 8-day incubation in high relative humidity. Water vapor sorption rates over 1 and 8 days were slower in decayed than new litter and not faster in photodegraded than other decayed litter. However, I found that 49-78% of the variation in respiration could be explained by the relative amount of water litter absorbed over 1 day compared to 8 days, a measure referred to as relative water content. Decayed and photodegraded litter had higher relative water content after 1 day because it had a lower water-holding capacity. Higher respiration rates of decayed and photodegraded litter were attributed to faster microbial activation due to greater relative water content of that litter. / Dissertation/Thesis / Masters Thesis Biology 2019