This research aimed to: estimate the inputs of litterfall; model the decomposition process and assess the rates of litter decay and turnover; study the litter decomposition process and dynamics of nutrients in old chestnut high forests. This study aimed to fill a gap in the knowledge of chestnut decomposition process as this type of ecosystems have never been modeled and studied from this point of view in Portugal. The study sites are located in the mountains of Marão, Padrela and Bornes in a west-to-east transect, across northern Portugal, from a more-Atlantic-to-lessmaritime influence. This research was developed on old chestnut high forests for quality timber production submitted to a silviculture management close-to-nature. We collected litterfall using littertraps and studied decomposition of leaf and bur litter by the nylon net bag technique. Simple and double exponential models were used to describe the decomposition of chestnut litterfall incubated in situ during 559 days. The results of the decomposition are discussed in relation to the initial litter quality (C, N, P, K, Ca, Mg) and the decomposition rates. Annually, the mature chestnut high-forest stands (density 360-1,260 tree ha–1, age 55-73 years old) restore 4.9 Mg DM ha–1 of litter and 2.6 Mg ha–1 yr–1 of carbon to the soil. The two-component litter decay model proved to be more biologically realistic...

Leaf decomposition is a basic ecosystem process in low order streams, mainly carried out by a particular group of fungi, aquatic hyphomycetes (AH), and invertebrate detritivores. In this thesis, the main goal was to investigate how and to what extent fungal diversity species relates to the stream’s key functional parameter: leaf decomposition. In Chapter 2, I tested the relative importance of substrate quality in the establishment of AH assemblages and their ability to decompose leaves at different temperatures. I assessed the decomposition rate of alder and oak leaves preconditioned in the stream at four constant temperatures (5, 10, 15 and 20° C) in the lab. Oak leaves were colonized by a lower number of AH and decomposition rates increased with temperature. In contrast, alder leaves were colonized by a greater number of AH species and decomposition was not affected by temperature increases. Under the tested temperature regimes, the substrate was more important than temperature for AH. In Chapter 3, I investigated if rich fungal assemblages are functionally better buffered against temperature fluctuations than poor assemblages. A microcosm experiment was run to test the effect of AH diversity (single species and manipulated mixtures of three or eight species) on oak leaf decomposition under constant (5...

Litter decomposition, a fundamental ecosystem process in woodland streams, is potentially affected by the predicted increase in water temperature. Here, we assessed the effects of experimental and seasonal warming on oak litter decomposition and on the relative contributions of microbes and invertebrates to this process. Experimental warming (*3 C) stimulated litter decomposition in the coldest, but not in the warmest, months. This may be attributed to (1) higher temperature sensitivity of decomposition at lower ambient temperature due to temperature limitation of enzymatic activity, (2) higher relative temperature increase in winter than in warmer months, (3) existence of a previous warming period in winter, and (4) stronger stimulation of the activity of detritivores by warming in winter due to the prevalence of earlier (smaller) instars than in warmer months. The low response of litter decomposition to warming may have been due to the low nutrient availability in the study stream. The 30-day litter decomposition was stimulated over the seasonal gradient (monthly mean temperature: 6–16 C), which may be attributed to a stimulation of metabolic activities by warming and to changes in detritivore life history over the seasons. The stimulation of litter decomposition with temperature suggests that the rate of CO2 release from freshwaters will increase under global warming. However...

1. Litter decomposition recycles nutrients and causes large fluxes of carbon dioxide into the atmosphere. It is typically assumed that climate, litter quality and decomposer communities determine litter decay rates, yet few comparative studies have examined their relative contributions in tropical forests. 2. We used a short-term litterbag experiment to quantify the effects of litter quality, placement and mesofaunal exclusion on decomposition in 23 tropical forests in 14 countries. Annual precipitation varied among sites (760-5797 mm). At each site, two standard substrates (Raphia farinifera and Laurus nobilis) were decomposed in fine- and coarse-mesh litterbags both above and below ground for approximately 1 year. 3. Decomposition was rapid, with >95% mass loss within a year at most sites. Litter quality, placement and mesofaunal exclusion all independently affected decomposition, but the magnitude depended upon site. Both the average decomposition rate at each site and the ratio of above- to below-ground decay increased linearly with annual precipitation, explaining 60-65% of among-site variation. Excluding mesofauna had the largest impact on decomposition, reducing decomposition rates by half on average, but the magnitude of decrease was largely independent of climate. This suggests that the decomposer community might play an important role in explaining patterns of decomposition among sites. Which litter type decomposed fastest varied by site...

Decomposition was studied in a reciprocal litter transplant experiment to examine the effects of forest type, litter quality and their interaction on leaf decomposition in four tropical forests in south-east Brazil. Litterbags were used to measure decomposition of leaves of one tree species from each forest type: Calophyllum brasiliense from restinga forest; Guapira opposita from Atlantic forest; Esenbeckia leiocarpa from semi-deciduous forest; and Copaifera langsdorffii from cerradao. Decomposition rates in rain forests (Atlantic and restinga) were twice as fast as those in seasonal forests (semi-deciduous and cerradao), suggesting that intensity and distribution of precipitation are important predictors of decomposition rates at regional scales. Decomposition rates varied by species, in the following order: E. leiocarpa > C. langsdorffii > G. opposita > C. brasiliense. However, there was no correlation between decomposition rates and chemical litter quality parameters: C:N, C:P, lignin concentration and lignin:N. The interaction between forest type and litter quality was positive mainly because C. langsdorffii decomposed faster than expected in its native forest. This is a potential indication of a decomposer`s adaptation to specific substrates in a tropical forest. These findings suggest that besides climate...

We examined the effects of soil mesofauna and the litter decomposition environment (above and belowground) on leaf decomposition rates in three forest types in southeastern Brazil. To estimate decomposition experimentally, we used litterbags with a standard substrate in a full-factorial experimental design. We used model selection to compare three decomposition models and also to infer the importance of forest type, decomposition environment, mesofauna, and their interactions on the decomposition process. Rather than the frequently used simple and double-exponential models, the best model to describe our dataset was the exponential deceleration model, which assumed a single organic compartment with an exponential decrease of the decomposition rate. Decomposition was higher in the wet than in the seasonal forest, and the differences between forest types were stronger aboveground. Regarding litter decomposition environment, decomposition was predominantly higher below than aboveground, but the magnitude of this effect was higher in the seasonal than in wet forests. Mesofauna exclusion treatments had slower decomposition, except aboveground into the Semi-deciduous Forest, where the mesofauna presence did not affect decomposition. Furthermore...

A atividade de decomposição constitui-se em importante indicador do padrão funcional dos ecossistemas, pois controla processos básicos relacionados à disponibilidade de nutrientes e produtividade. Salienta-se a importância das características climáticas, edáficas, da qualidade da serapilheira e da fauna do solo como determinantes no processo de decomposição. No entanto, a importância de cada um destes fatores varia em escalas de tempo e espaço. O objetivo deste trabalho foi avaliar a importância de alguns fatores determinantes na decomposição em trechos representativos dos principais ecossistemas florestais do Estado de São Paulo. Para tanto foram conduzidos dois experimentos independentes. O primeiro, aqui denominado Experimento Exóticas, examinou os efeitos do tipo florestal e da fauna do solo sobre a decomposição de folhas de uma espécie exótica (Laurus nobilis L.) em duas florestas úmidas (Floresta de Restinga do Parque Estadual da Ilha do Cardoso e Floresta Atlântica de Encosta do Parque Estadual Carlos Botelho) e uma floresta estacional (Floresta Estacional Semidecidual da Estação Ecológica de Caetetus). Os efeitos destes fatores foram testados em duas situações: acima e abaixo da superfície simulando então o ambiente de decomposição de folhas e raízes respectivamente. O tipo florestal apresenta efeito superior à fauna acima da superfície...

Foram sintetizados, purificados e caracterizados os peróxidos cíclicos: peróxido de difenoíla (1), dimetil-1,2-dioxetanona (2), e spiro-adamantil α-peróxi lactona (3), e determinados seus parâmetros de quimiluminescência. Foram redeterminados os rendimentos quânticos singlete na decomposição catalisada de 1 e 2 em condições análogas as utilizadas anteriormente na literatura, obtendo-se valores várias ordens de grandeza menores que os inicialmente relatados para estes sistemas padrão para a formulação do mecanismo Luminescência Iniciada Quimicamente por Troca de Elétron (Chemically Initiated Electron Exchange Luminescence - CIEEL). O efeito de gaiola de solvente, utilizando-se o sistema binário tolueno/difenilmetano, sobre o rendimento quântico na decomposição de 1 catalisada por rubreno, mostrou-se consideravelmente menor para este sistema intermolecular do que o observado no sistema intramolecular da decomposição induzida de 1,2-dioxetanos fenóxi-substituidos. Foram determinados pela primeira vez os parâmetros de quimiluminescência na decomposição unimolecular e catalisada da spiro-adamantil α-peróxi lactona (3), mostrando que esta é a α-peróxi lactona mais estável sintetizada e estudada até o momento. Este peróxido é sujeito à decomposição catalisada por ativadores adequados...

This study dealt with the decomposition and nutrient release from the halophytes Atriplex portulacoides, Arthrocnemum macrostachyum, Limoniastrum monopetalum, and Spartina densiflora, the dominant species in the Castro Marim salt marsh, Portugal. Environmental effects on decomposition were also assessed. The study was carried out for one year using the in situ litterbag technique. S. densiflora showed a lower decomposition rate (k = 0.003 day−1) than the other study species (k = 0.005–0.009). Study species showed similar decomposition patterns, that is, the weight loss mostly occurred during the autumn–winter period (study beginning in November). This indicates that temperature in this period did not hamper the decomposition process. The decomposition rate was positively affected by the initial N concentration (r2 = 0.87, P < 0.05) and negatively by the C:N ratio (r2 = 0.86, P < 0.05) in decomposing materials. At the end of the study, S. densiflora and L. monopetalum, the species with lower initial N concentrations, retained much higher proportion of initial N (89–109%) than the others (5–14%). Also, S. densiflora with the lowest P concentration retained higher proportion of initial P (48%) than the others (5–20%). Release of K and Mg were also slower from S. densiflora and was associated with their initial low concentration in this species. The lowest Mn release was observed from A. macrostachyum and also in relation to the lowest initial concentration. Our study supports the hypothesis that decomposition patterns of marsh species are mostly associated with differences regarding their morphology and chemical composition. Given the higher resistance of S. densiflora to decomposition...

The decomposition kinetics of four synthetic alkaline earth metal carbonates (MgCO3, CaCO3, SrCO3 and BaCO3) was studied under non-isothermal conditions from thermo-gravimetric measurements as compared to. The integral approximation method of Coats and Redfern was used to determine the kinetic parameters for the decomposition processes. The decomposition reactions followed mostly first order kinetics and the activation energy of the decomposition reactions increased with the increase in the molecular mass of the carbonates. The change in enthalpy for the decomposition processes was also calculated and compared with the activation energies for the decomposition processes. The activation energy of the decomposition process for all the carbonates was higher than the enthalpy of the reaction excepting SrCO3.

We studied the contribution of oribatid mites in the dynamics of litter decomposition in an experiment using litterbags of three different mesh sizes (20 µm, 250 µm, and 1 cm). The experiment was carried out at a primary forest (FLO), a secondary forest (SEC), and at two polyculture systems (POA and POC). We compared the weight loss of the leaves of Vismia guianensis and the changes of the oribatid mite species community. We processed the samples after 26, 58, 111, 174, 278, and 350 days from the beginning of the experiment by using the Berlese-Tullgren to extract the animals. We hypothesized that: 1. the abundance and diversity of oribatid mites would exert an influence in the decomposition process; 2. there would be a successional changing of the species during decomposition; and 3. there would be differences in the colonization of species in relation to the mesh size of the litterbags. A total of 95 species of oribatid mites was found. The biomass data was the first registered for the Amazon region. The great dominance of oribatid mites did not exert an influence in the decomposition process. There was not a successional changing of the species during the course of the decomposition process, unlike those shown by results obtained in the temperate forest...

Les milieux humides remplissent plusieurs fonctions écologiques d’importance et contribuent à la biodiversité de la faune et de la flore. Même s’il existe une reconnaissance croissante sur l’importante de protéger ces milieux, il n’en demeure pas moins que leur intégrité est encore menacée par la pression des activités humaines. L’inventaire et le suivi systématique des milieux humides constituent une nécessité et la télédétection est le seul moyen réaliste d’atteindre ce but. L’objectif de cette thèse consiste à contribuer et à améliorer la caractérisation des milieux humides en utilisant des données satellites acquises par des radars polarimétriques en bande L (ALOS-PALSAR) et C (RADARSAT-2). Cette thèse se fonde sur deux hypothèses (chap. 1). La première hypothèse stipule que les classes de physionomies végétales, basées sur la structure des végétaux, sont plus appropriées que les classes d’espèces végétales car mieux adaptées au contenu informationnel des images radar polarimétriques. La seconde hypothèse stipule que les algorithmes de décompositions polarimétriques permettent une extraction optimale de l’information polarimétrique comparativement à une approche multipolarisée basée sur les canaux de polarisation HH...

This project is focussed on the thermsLl decomposition of t-butyl hydroperoxide and sec-butyl hydroperoxide at 120°C to 160°C in three alcohol solvents. These are methanol, ethajiol and isopropyl alcohol. The aim of the project was to examine the process of induced decomposition. Thermal decomposition of t-hutyl hydroperoxide and sec-butyl hydroperoxide indicate that these reactions have first-order kinetics with activation energies on the order of 20 to 28 K cal/mole, Styrene was used as a free radical trap to inhibit the induced decomposition. The results permitted calculation of how much induced decomposition occurred in its absence. The experimental resvilts indicate that the induced decomposition is important for t-butyl hydroperoxide in alcohol solvents, as shown by both the reaction rate suid product studies. But sec-butyl hydroperoxide results show that the concerted mechanism for the interaction of two sec-butylperoxy radicals occurs in addition to the induced decomposition. Di-sodium E.D,T.A. was added to reduce possible effects of trace transition metal ion .impurities. The result of this experiment were not as expected. The rate of hydroperoxide decomposition was about the same but was zero-order in hydroperoxide concentration.

Kinetics and product studies of the decompositions of allyl-t-butyl peroxide and 3-hydroperoxy- l-propene (allyl hydroperoxide ) in tolune were investigated. Decompositions of allyl-t-butyl peroxide in toluene at 130-1600 followed first order kinetics with an activation energy of 32.8 K.cals/mol and a log A factor of 13.65. The rates of decomposition were lowered in presence of the radical trap~methyl styrene. By the radical trap method, the induced decomposition at 1300 is shown to be 12.5%. From the yield of 4-phenyl-l,2- epoxy butane the major path of induced decomposition is shown to be via an addition mechanism. On the other hand, di-t-butYl peroxyoxalate induced decomposition of this peroxide at 600 proceeded by an abstraction mechanism. Induced decomposition of peroxides and hydroperoxides containing the allyl system is proposed to occur mainly through an addition mechanism at these higher temperatures. Allyl hydroperoxide in toluene at 165-1850 decomposes following 3/2 order kinetics with an Ea of 30.2 K.cals per mole and log A of 10.6. Enormous production of radicals through chain branching may explain these relatively low values of E and log A. The complexity of the reaction is indicated a by the formation of various products of the decomposition. A study of the radical attack of the hydro peroxide at lower temperatures is suggested as a further work to throw more light on the nature of decomposition of this hydroperoxide.

14; Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 431S to 681N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates...

97-4; 1. descomposición de la hojarasca recicla los nutrientes y provoca grandes flujos de dióxido de carbono a la atmósfera. Se asume generalmente que las comunidades de clima, calidad de la cama y descomponedores determinan las tasas de descomposición de basura, sin embargo, pocos estudios comparativos han examinado sus contribuciones relativas de los bosques tropicales. 2. Se utilizó un experimento de hojarasca corto plazo para cuantificar los efectos de la calidad de la cama, la colocación y la exclusión mesofauna en descomposición en 23 bosques tropicales en 14 países. La precipitación anual varía entre los sitios (760-5797 mm). En cada sitio, dos sustratos estándar (Raphia farinifera y Laurus nobilis) se descompusieron en bolsas de basura Fine- y grueso de malla por encima y por debajo de la tierra durante aproximadamente 1 año.3. La descomposición fue rápida, con> 95% de pérdida de masa dentro de un año en la mayoría de los sitios. Calidad de la cama, la colocación y la exclusión mesofauna todas afectadas de forma independiente la descomposición, pero la magnitud dependían sitio. Tanto la tasa de descomposición promedio en cada sitio y la relación de anteriormente a la caries por debajo del suelo aumentaron linealmente con la precipitación anual...

Proper management of soil organic matter (SOM) contributes to increasing plant productivity and reducing dependency on mineral fertilizers. Organic matter is widely regarded as a vital component of a healthy soil as it plays an important role in soil physical, chemical and biological fertility. Plant residues are the primary source of SOM. Therefore, proper SOM management requires a better understanding of plant residue decomposition kinetics in order to synchronize nutrient release during decomposition and plant uptake and prevent nutrient losses. In natural and managed ecosystems, residues are added frequently to soil, in the form of dead roots and litter fall of plant species with different C/N ratios. However, in most studies on residue decomposition, residues with different C/N ratios are added once and the effect of the presence of plants on residue decomposition is rarely investigated. In this project, four experiments were carried out with different objectives in order to close these knowledge gaps. The aim of the first experiment was to investigate the effect of frequent wheat residue addition on C mineralization and N dynamics. The experiment consisted of five treatments with different frequency of residue addition (2% w/w of wheat residues in total): once (100%W)...

Plant residues added to soil are a source of nutrients for plants and soil organisms and increase soil organic matter which has an important role in improving soil structure and fertility, hence maintaining soil quality for sustainable agriculture. In order to utilize plant residues for increasing soil organic matter more effectively, it is necessary to understand the mechanisms of plant residue decomposition. Soil organic matter decomposition is influenced by several factors such as plant residue quality, temperature, water availability, soil structure and soil texture, particularly clay content. The interaction of clay and decomposition of organic matter has been studied in the past. Nevertheless, many studies investigated this interaction in natural soil or under field conditions over long periods of time. Variation in environmental factors may influence the interaction of clay and decomposition of organic matter, thus in most previous studies their effect cannot be separated from the direct effect of clay on decomposition. To study the direct effect of clay on organic matter decomposition, four experiments with different objectives were carried out using isolated natural clay, under controlled conditions (e.g. temperature and organic matter input) and a short incubation period (approximately one month). All experiments were carried out using a sand matrix to which different clay types...

The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government.; Determining the best base stationing for military units can be modeled as a capacitated facility location problem with sole sourcing and multiple resource categories. Computational experience suggests that cross decomposition, a unification of Benders Decomposition and Lagrangean relaxation, is superior to other contemporary methods for solving capacitated facility location problems. Recent research extends cross decomposition to pure integer prograrnming problems with explicit application to capacitated facility location problems with sole sourcing; however, this research offers no computational experience. This thesis implements two cross decomposition algorithms for the capacitated facility location problem with sole sourcing and compares these decomposition algorithms with branch and bound methods. For some problems tested, cross decomposition obtains better solutions in less time; however, cross decomposition does not always perform better man branch and bound due to the time required to obtain the cross decomposition bound that is theoretically superior to other decomposition bounds.

A decomposição da serapilheira é um processo fundamental, que influencia o armazenamento de carbono (C) no solo e a disponibilidade de nutrientes para as plantas e os microrganismos, afetando assim a distribuição de espécies em um ecossistema. A Floresta Ombrófila Densa, conhecida popularmente como Mata Atlântica localiza-se ao longo da costa brasileira e é caracterizada pela elevada diversidade e endemismo. Dentre as diversas famílias botânicas presentes neste ecossistema, a família Fabaceae apresenta grande importância, tanto pela sua abundância e ampla distribuição, como por desempenhar um papel importante no ciclo do nitrogênio (N) terrestre. O objetivo deste estudo foi investigar as taxas de decomposição e mudanças na composição inorgânica e orgânica da serapilheira ao longo desse processo em duas fisionomias de florestas (Terras Baixas vs. Montana) localizadas em diferentes altitudes (100 m vs. 1000 m). Levantamentos realizados em diferentes formações vegetais da Floresta Ombrófila Densa ao longo de um gradiente altitudinal indicam diferenças significativas na disponibilidade de N nos solos em diferentes altitudes, além de diferenças contrastantes na temperatura do ar. Essas diferenças podem influenciar na composição das folhas...