Academic literature on the topic 'Soils – Tropics – Composition'
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Journal articles on the topic "Soils – Tropics – Composition"
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van der Velden, Nic, J. W. Ferry Slik, Yue-Hua Hu, Guoyu Lan, Luxian Lin, XiaoBao Deng, and Lourens Poorter. "Monodominance of Parashorea chinensis on fertile soils in a Chinese tropical rain forest." Journal of Tropical Ecology 30, no. 4 (June 23, 2014): 311–22. http://dx.doi.org/10.1017/s0266467414000212.
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Abstract:Monodominance in the tropics is often seen as an unusual phenomenon due to the normally high diversity in tropical rain forests. Here we studied Parashorea chinensis H. Wang (Dipterocarpaceae) in a seasonal tropical forest in south-west China, to elucidate the mechanisms behind its monodominance. Twenty-eight 20 × 20-m plots were established in monodominant and mixed forest in Xishuangbanna, Yunnan province. All individuals ≥1 cm stem diameter and 16 soil variables were measured. Parashorea chinensis forest had a significantly higher mean tree dbh compared with mixed forest. Diversity did not differ significantly between the two forest types. However, within monodominant patches, all diversity indices decreased with an increase in P. chinensis dominance. Floristic composition of P. chinensis forest did differ significantly from the mixed forest. These differences were associated with more fertile soils (significantly higher pH, Mn, K and lower carbon pools and C:N ratio) in the P. chinensis forest than the mixed forest. In contrast to current paradigms, this monodominant species is not associated with infertile, but with fertile soils. Parashorea chinensis seems to be especially associated with high manganese concentrations which it can tolerate, and with edaphic conditions (water, K) that allow this tall and exposed emergent species to maintain its water balance. This is in contrast with most previous studies on monodominance in the tropics that found either no effect of soil properties, or predict associations with nutrient-poor soils.
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Oliveira, Luiz Antônio de. "CARACTERIZAÇÃO DOS LATOSSOLOS DA CHAPADA DE ARAGUARI: MINERAIS ARGILOSOS, GRANULOMETRIA E EVOLUÇÃO." Caminhos de Geografia 4, no. 8 (February 28, 2003): 20–37. http://dx.doi.org/10.14393/rcg4815302.
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The mineralogical composition of the latosols in the study area as determined by X-ray diffraction. Kaolinite and goethite is the dominant mineral in all profile (dark red, red-yellow and lateritic soils). Gibbsite is a common mineral present in the upper part of the profile (dark red and redyellow soils), while in the lateritic soil occur only in the "matriz� fraction. Hematite happens in the topsoils (dark red and red-yellow soils). Quartz dominates the coarse fraction in all materials and shows a higher variability in sizes, although it is predominantly fine sand-size. Anatase were also detected in the topsoil. The mineralogical composition of the materials indicates a high degree of weathering of the parent material, wich caracteristic for oxisols in the humid tropics.
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Salawu, M. B., T. Acamovic, C. S. Stewart, F. D. DeB. Hovell, and R. L. Roothaert. "Chemical composition and in vitro degradability of different parts of Calliandra calothyrsus from Kenya." Proceedings of the British Society of Animal Science 1997 (1997): 72. http://dx.doi.org/10.1017/s1752756200595131.
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Calliandra calothyrsus is a promising tropical leguminous browse, native to South America, but now planted in most parts of the tropics and subtropics. It is a fast growing plant, rich in proteins and can do well on poor soils (NRC, 1983). Its high content of condensed tannins has however limited its use as a feed for ruminants. The chemical composition and degradability in vitro in a consecutive batch culture (CBC) system were studied.
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Lyon, Steve W., Benjamin M. C. Fischer, Laura Morillas, Johanna Rojas Conejo, Ricardo Sánchez-Murillo, Andrea Suárez Serrano, Jay Frentress, Chih-Hsin Cheng, Monica Garcia, and Mark S. Johnson. "On the Potential of Biochar Soil Amendments as a Sustainable Water Management Strategy." Sustainability 14, no. 12 (June 8, 2022): 7026. http://dx.doi.org/10.3390/su14127026.
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Biochar has been put forward as a potential technology that could help achieve sustainable water management in agriculture through its ability to increase water holding capacity in soils. Despite this opportunity, there are still a limited number of studies, especially in vulnerable regions like the tropics, quantifying the impacts of biochar on soil water storage and characterizing the impacts of biochar additions on plant water composition. To address this critical gap, we present a case study using stable water isotopes and hydrometric data from melon production in tropical agriculture to explore the hydrological impacts of biochar as a soil amendment. Results from our 10-week growing season experiment in Costa Rica under drip irrigation demonstrated an average increase in volumetric soil moisture content of about 10% with an average moisture content of 25.4 cm3 cm−3 versus 23.1 cm3 cm−3, respectively, for biochar amended plots compared with control plots. Further, there was a reduction in the variability of soil matric potential for biochar amended plots compared with control plots. Our isotopic investigation demonstrated that for both biochar and control plots, there was a consistent increase (or enrichment) in isotopic composition for plant materials moving from the roots, where the average δ18O was −8.1‰ and the average δ2H was −58.5‰ across all plots and samples, up through the leaves, where the average δ18O was 4.3‰ and the average δ2H was 0.1‰ across all plots and samples. However, as there was no discernible difference in isotopic composition for plant water samples when comparing across biochar and control plots, we find that biochar did not alter the composition of water found in the melon plant material, indicating that biochar and plants are not competing for the same water sources. In addition, and through the holistic lens of sustainability, biochar additions allowed locally sourced feedstock carbon to be directly sequestered into the soil while improving soil water availability without jeopardizing production for the melon crop. Given that most of the expansion and intensification of global agricultural production over the next several decades will take place in the tropics and that the variability of tropical water cycling is expected to increase due to climate change, biochar amendments could offer a pathway forward towards sustainable tropical agricultural water management.
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Piperno, Dolores R., and Peter Becker. "Vegetational History of a Site in the Central Amazon Basin Derived from Phytolith and Charcoal Records from Natural Soils." Quaternary Research 45, no. 2 (March 1996): 202–9. http://dx.doi.org/10.1006/qres.1996.0020.
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AbstractAnalysis of phytoliths and macroscopic charcoal from natural soils near Manaus, Brazil shows that the central Amazonian terra firme forest has not been stable during the Holocene. Phytolith taxonomic composition and radiocarbon ages indicate that a closed forest has continuously existed in the area since at least 4600 yr B.P., but that forest composition and species abundance changed significantly sometime during the Holocene Epoch. There is no evidence that the vegetation experienced swidden cultivation. The distribution and dates of the charcoal in the soils indicate that forest fires between 1795 and 550 yr B.P. burned an area of about 200 hectares. Vegetational changes and fires appear to be a result of climatic drying that may have affected large areas of the Amazon Basin over the past 5000 to 7000 years. Soil phytolith analysis is a promising tool for the study of environmental history in the humid tropics and may reduce the previous dependence on lake and swamp sediments, at least for the Holocene Epoch.
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Foran, BD, G. Bastin, and B. Hill. "The pasture dynamics and management of two rangeland communities in the Victoria River District of the Northern Territory." Rangeland Journal 7, no. 2 (1985): 107. http://dx.doi.org/10.1071/rj9850107.
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The use of destocking as a means of promoting pasture recovery was evaluated on two important rangeland types of the semi-arid tropics of north west Australia. Recovery on eroded calcareous red soils was substantial within five years. Standing biomass and species composition, particularly the contribution of the major forage grass Enneapogon spp., was then similar to areas in good condition. However, an exotic shrub, Calotropls procera, invaded the area during the study. Grazing limited its increase to 200 bushes ha-1 compared to unstocked areas where it increased to 1,000 bushes ha-1. Destocking had no effect on cracking clay soils in good condition, dominated by Chrysopogon fallax and Iseilema fragile. An index based on similarity measures of herbage standing biomass, followed closely the course of recovery of the eroded calcareous soil during the period. There is a need for range condition assessment and the development and application of appropriate pasture management strategies for the whole district.
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Nadel, R. L., M. C. Scholes, and M. J. Byrne. "Slash burning, faunal composition, and nutrient dynamics in a Eucalyptus grandis plantation in South AfricaThis article is one of a selection of papers published in the Special Forum on Towards Sustainable Forestry — The Living Soil: Soil Biodiversity and Ecosystem Function." Canadian Journal of Forest Research 37, no. 2 (February 2007): 226–35. http://dx.doi.org/10.1139/x06-287.
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The sustainability of exotic commercial plantations is dependent on the conservation of soil nutrients, especially on the ancient, leached soils of the tropics, particularly when limited fertilization is practiced. In Eucalyptus grandis W. Hill ex Maid. plantations in South Africa, the site is usually burned following harvest and prior to replanting, potentially causing a disruption of soil faunal function and losses of nutrients associated with burning and removal of slash residues. The aim was to study the effect of fire on nutrient dynamics and invertebrate faunal composition. The in situ nitrogen and phosphorus mineralization rates and invertebrate faunal composition were measured in six randomly located plots — three burned and three unburned — prior to and after a low-intensity fire. Results indicate that within the burned plots, phosphorus availability was enhanced 10-fold within the first month following the fire. Invertebrate faunal diversity was low both prior to and after burning, with ants constituting the highest number. Invertebrate faunal composition was more markedly influenced by season than by the fire, with millipedes present in the majority of plots in spring and ants dominating in summer.
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Albuquerque, A. G. B. M., T. O. Ferreira, G. N. Nóbrega, R. E. Romero, V. S. Souza Júnior, A. J. A. Meireles, and X. L. Otero. "Soil genesis on hypersaline tidal flats (apicum ecosystem) in a tropical semi-arid estuary (Ceará, Brazil)." Soil Research 52, no. 2 (2014): 140. http://dx.doi.org/10.1071/sr13179.
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Wetland soils, especially those under a semi-arid climate, are among the least studied soils in the tropics. The hypersaline tidal flats on the north-eastern Brazilian coast, locally named apicum, are coastal wetland ecosystems in the peripheral portions of semi-arid estuaries. Despite their great ecological importance, they have been highly impacted by anthropogenic activities. Morphological and analytical data of six soil profiles, representative of the different coastal compartments (mangroves, apicum and coastal tablelands) of the north-eastern Brazilian coast, were examined to better understand the pedogenesis of apicum soils. The hypersaline tidal flat soils were classified as Typic Fluvaquents and Typic Sulfaquents with the following main characteristics: predominance of sand fraction (62–77%); presence of high-activity clays (>24 cmolc kg–1 clay); clay fraction comprising kaolinite, illite, smectite and an interstratified smectite/illite; exchangeable complex dominated by Na+ (ESP ≥15%); elevated levels of salinity (electrical conductivity, EC 25–44 dS m–1); alkaline pH values (7.5–9.5). The sandy texture and quartz-dominated composition of the hypersaline, tidal flat soils indicate a pedogenesis associated with the superficial addition of mineral material. This upbuilding process would have lowered the watertable (relatively to the ground level) and decreased the flooding frequency by the tides, favouring salinisation and solonisation processes at the hypersaline tidal flats. Furthermore, the still-existing hydromorphism would have promoted the maintenance of gleisation and sulfidisation. The presence of pyrite on the hyper-saline tidal flat soils further corroborates the formation of apicum soils from/over buried mangroves.
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Pereira-De-Oliveira, Luiz, Lucio Macedo, José Neto, Dellane Santos, and Hugo Silva. "Viability of lateritic soil as alkaline activated precursor." MATEC Web of Conferences 274 (2019): 01004. http://dx.doi.org/10.1051/matecconf/201927401004.
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This study investigates the disposal of lateritic soil available in the state of Maranhao, Brazil, to be used as a natural precursor of alkaline activated material. Lateritic soils are formed in the tropics through weathering processes that favour the formation of iron, aluminium and may contain a large amount of quartz and kaolinite. The quality of laterite for this application may vary significantly depending on both geographic location and depth of a quarry. The identification of quarry locals was carried out in this work, together with a disposal volume estimation considering economic issues about exploration techniques. A comparison of the chemical composition of the lateritic soil of the state of Maranhao with those related in the literature is used to outline the feasibility of using this natural material as precursor of alkaline activated cements. It is concluded that the lateritic soil availability, as well as their characteristics, can enable the development of alkaline activated materials as a future local building material and environmentally friendly.
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Williams, J. E., M. P. Scheele, P. F. J. van Velthoven, J. P. Cammas, V. Thouret, C. Galy-Lacaux, and A. Volz-Thomas. "The influence of biogenic emissions from Africa on tropical tropospheric ozone during 2006: a global modeling study." Atmospheric Chemistry and Physics Discussions 9, no. 2 (April 28, 2009): 10367–427. http://dx.doi.org/10.5194/acpd-9-10367-2009.
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Abstract. We have performed simulations using a 3-D global chemistry-transport model to investigate the influence that biogenic emissions from the African continent exert on the composition of the tropopause in the tropical region. For this purpose we have applied two recently developed biogenic emission inventories provided for use in large-scale global models (Granier et al., 2005; Lathiére et al., 2006) whose seasonality and temporal distribution for isoprene, biogenic NO and biogenic volatile organic compounds is markedly different. The use of the climatological values for biogenic emissions provided by Lathiére et al. (2006) results in an increase in the amount of nitrogen sequestrated into longer lived reservoir compounds which contributes to the reduction in tropospheric ozone burden in the tropics. The associated re-partitioning of nitrogen between PAN, HNO3 and organic nitrates also results in a ~5% increase in the loss of nitrogen by wet deposition. At a global scale there is a reduction in the oxidizing capacity of the model atmosphere which increases the atmospheric lifetimes of CH4 and CO by ~1.5% and ~4%, respectively. By the use of sensitivity studies we show that the release of NO from soils in Africa accounts for between ~5–45% of tropospheric ozone in the African troposphere, ~10% in the upper troposphere and between ~5–20% of the tropical tropospheric ozone column over the tropical Atlantic Ocean. The subsequent reduction in OH over the source regions allows enhanced transport of CO out of the region. For biogenic volatile organic C1 to C3 species released from Africa the effects on tropical tropospheric ozone are rather limited, although this source contributes to the global burden of VOC by between ~2–4% and has a large influence on the organic composition of the troposphere over the tropical Atlantic Ocean. Comparisons against a range of different measurements indicate that applying the climatology of Lathiére et al. (2006) improves the performance of TM4 for 2006 in the tropics.
Dissertations / Theses on the topic "Soils – Tropics – Composition"
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Kedi, Atolé Brice. "Fonctionnement des phosphatases dans les sols tropicaux : influence de la composition organo-minérale sur l'expression de l'activité enzymatique." Thesis, Montpellier, SupAgro, 2011. http://www.theses.fr/2011NSAM0049/document.
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La prédiction de l'activité des phosphatases fongiques dans l'amélioration de la nutrition phosphatée doit prendre en compte les facteurs qui influencent leur fonctionnement dans les sols. L'objectif de cette thèse a été d'étudier divers facteurs qui pouvaient influencer l'efficacité des phosphatases de champignons ectomycorhiziens dans les sols. L'adsorption et l'activité à l'état adsorbé des phosphatases de Suillus collinitus et de Hebeloma cylindrosporum ont été étudiées avec plusieurs fractions de différents sols tropicaux. La persistance de l'activité de ces enzymes immobilisées sur les sols a également été étudiée. Ces phosphatases ont montré une diversité d'affinité avec les colloïdes des sols, liée surtout à leur origine et leurs caractéristiques. En outre, aucune relation n'a été établie entre l'adsorption et l'activité catalytique résultante, car il n'y avait généralement pas de perte d'activité à l'état adsorbé. L'une des enzymes qui à montré une dégradation rapide en solution suivant le temps d'incubation, a été protégée par les sols ferrallitiques mais pas par les vertisols. Des essais de purification et de caractérisation ont été faits sur ces échantillons de phosphatases fongiques. Les fractions de phosphatases de S. collinitus purifiées et retenues sur une colonne hydrophobe de chromatographie ont montré une activité en contact avec des argiles fortement supérieure à celle en solution. L'hypothèse d'une dimérisation produite à la surface des argiles a été avancée pour expliquer l'amplification inattendue d'activité catalytique à l'état adsorbé des fractions purifiéesThe role of catalytic activity of fungal phosphatases in the improvement of the phosphorus nutrition cannot be reliably predicted without taking into account the factors which influence their behaviour in the soil. The objective of this thesis was to study various factors which could influence the effectiveness of ectomycorrhizal fungal phosphatases in soils. Adsorption and the activity in the adsorbed state of phosphatases produced by Suillus collinitus and Hebeloma cylindrosporum were studied in contact with several fractions of various tropical soils. The persistence of the activity of these enzymes immobilized on the soils was also studied. These phosphatases showed a diversity of affinity for soil colloids, due to their origin and their characteristics. Moreover, no relation was found between adsorption and the resulting catalytic activity; there was generally no loss of activity in an adsorbed state. One of the enzymes which underwent rapid degradation in solution was protected by the presence of ferrallitic soils but not by the vertisols. These fungic phosphatase samples were purified and partially characterized. The fractions of S. collinitus phosphatases retained on hydrophobic chromatography column showed enhanced activity in contact with mineral clays with respect to solution. The hypothesis of dimeerisation on the clay surfaces was advanced to explain the unexpected enhancement of catalytic activity in an adsorbed state of the purified fractions
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Setiari, Marwanto. "Study on decomposition characteristics of peat soils under oil palm plantation in Riau and West Kalimantan, Indonesia." Kyoto University, 2018. http://hdl.handle.net/2433/233851.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第21312号
農博第2297号
新制||農||1065(附属図書館)
学位論文||H30||N5146(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 舟川 晋也, 教授 縄田 栄治, 教授 北山 兼弘
学位規則第4条第1項該当
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Ngo, Thi Phuong. "Effets des amendements organiques exogènes sur la composition de la matière organique et le stockage du carbone d'un sol dégradé par l'érosion dans le Nord du Vietnam." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066152/document.
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Une stratégie pour améliorer durablement la fertilité des sols dégradés par érosion au Nord du Vietnam consiste à apporter des amendements organiques exogènes (AOEs). L'application du lisier de buffle, son compost et lombricompost, ainsi que le biochar permettraient à faible coût d’améliorer la qualité des sols et la croissance des plantes en réduisant l'utilisation d'engrais, mais également de séquestrer du carbone. L’objective de cette thèse est d’évaluer (1) l’utilité des quatre AOEs seuls ou en association pour séquestrer du carbone, et (2) l’effet de l’apport des quatre substrats organiques seuls ou en association sur la quantité et qualité des matières organiques d’un sol agricole tropical dégradé typique du Nord du Vietnam. Pour répondre à cet objectif, nous avons effectué des incubations au laboratoire, en sachet de litière dans des conditions de terrain et suivi pendant trois ans une expérience en mesocosme avec ajouts des AOEs au sol cultivé en conditions de terrain.Nos résultats montrent que le compostage en présence de vers de terre conduit à une plus forte transformation de la matière organique issue du lisier de buffle par rapport au compostage traditionel. Le lombricompost était enrichi en composés azotés et appauvri en polysaccharides, et se caractérisait par une altération plus importante des lignines en comparaison avec le compost. La stabilité biologique de ces AOEs a été liée à leur teneur en carbone soluble, diminuant suivant l’ordre : lisier de buffle > compost > lombricompost, alors que leur réactivité chimique était similaire. Le biochar, constitué de carbone aromatique, se caractérisait par une très forte stabilité biologique et chimique. L’association du biochar avec les autres AOEs a influencé leur stabilité chimique et biologique, en protégeant la matière organique labile contre l'oxydation chimique et la dégradation biologique.Notre expérience de trois ans en mésocosmes en conditions naturelles a montré que tous les AOEs ont un effet positif sur le stockage du carbone dans le sol ainsi que sur la qualité de la matière organique de sol. L’association de biochar et de lombricompost en augmenttant l’abondance des composés dérivés de la lignine ainsi que la teneur en sucre provenant des plantes et des microorganismes, semble montrer un effet synergique de cette association sur la fertilité des sols (activité microbienne, prospection racinaire). Comparé aux résultats d’incubation en sachet de litières, ces résultats indiquent un effet significatif et contrasté des AOEs sur la croissance des plantes en particulier sur l’apport racinaire. En conclusion, l’association de biochar et de lombricompost semble la meilleure solution pour améliorer la qualité de sol dégradé par l'érosion dans le Nord du Vietnam. Ces résultats devront être confirmés par des études à long terme, tant du point de vue de la qualité physicochimique que biologique des sols amendés par ces AOEsIntensification of agricultural use of tropical soils in Northern Vietnam leads to acidification associated with organic matter loss, rapid decline of their fertility and high erosion rates. Such negative effects may be counteracted by exogenous organic amendments (EOMs). The application of buffalo manure, its compost and vermicompost and biochar alone or in mixture with other EOMs is promising to improve at low cost soil quality, plant growth and carbon sequestration. The aims of this study were to evaluate (1) the usefulness of the four EOM alone or in mixture to sequester carbon and (2) the effect of these amendments on quantity and quality of soil organic matter of a tropical soil degraded by erosion. To anwer to this objective we carried out incubations in the laboratory, in litterbags under field conditions and we monitored a mesocom experiment, where the EOM were added and subjected during three years to cultivation and natural rainfall conditions. Our results showed that composting in the presence of earthworms led to stronger transformation of buffalo manure than regular composting. Vermicompost was enriched in N-containing compounds and depleted in polysaccharides. It further contained stronger modified lignin compared to regular compost. Biological reactivity of these AOEs was related to their soluble organic matter content, which decreased in the order buffalo manure > compost > vermicompost, whereas their chemical reactivity was similar. Bamboo biochar was enriched in aromatic carbon and characterized by a high biological and chemical recalcitrance. The presence of biochar influenced the biological as well as chemical reactivity of the other organic amendments. It led to a protection of organic matter against chemical oxidation and changed their susceptibility to biological degradation. Our experience with mesocosmes during 3 year under the natural conditions showed that all organic amendments had a positive effect on soil carbon storage and significantly influences soil organic matter quality. Biochar could increase the soil carbon sequestration potential, when applied in mixture with vermicompost. The presence of biochar increased lignin derived compounds abundance as well as both plant and microbial sugar content of soil amended with vermicompost but it had no effect in the case of control soil. Compared to our litterbag experiment these results show that EOM have a strong contrasting effect on plant growth, in particular root litter input. In conclusion, the incorporation of biochar and vermicompost seems to be the best solution to improuve the quality of degraded soil in Northem Vietnam. More studies about the impacts of this amendment on soil physico-chemical and biological properties in long-term are needed to comfirm these results
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Violette, Aurélie. "Processus et bilans d'altérations en milieu tropical (bassin versant de Mule Hole, Inde du sud) : sensibilité à la composition minéralogique et au climat." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1199/.
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L'objectif de cette thèse est d'améliorer les connaissances sur les processus et les facteurs de contrôle des flux d'altération chimiques à l'échelle d'un petit bassin versant tropical (Mule Hole, Inde du Sud). Le rôle de la minéralogie et du climat est étudié grâce à la modélisation. Dans la première partie du travail, les sols (fersialsols, vertisols) et la roche mère (gneiss) sont caractérisés minéralogiquement et chimiquement afin de procéder, dans la seconde partie, à la modélisation des processus. Le modèle géochimique est couplé avec un modèle hydrologique. Premièrement, les processus actuels sont étudiés. Le modèle est calibré grâce à la composition chimique du ruisseau et de la nappe. Les flux d'altération à l'échelle du bassin sont reproduits. Ils mettent en évidence le rôle prépondérant de l'altération des smectites (5% volumique dans les sols) sur le bilan d'altérationThe objective of this thesis is to improve our understanding of the chemical weathering processes and of the control factors at a small experimental watershed scale in the Tropics (Mule Hole, South India). Relying on the numerical modelling method, it focuses particularly on the sensitivity to the mineralogy and climate. The first part of this work concerns the mineralogical and chemical descriptions of the soils (chromic luvisol, vertisol) and the bedrock (gneiss). The second part deals with the coupled modelling between a geochemical and a hydrological model. On the first hand, current processes at play in the catchment are investigated. The model is calibrated with both stream and groundwater measured chemical compositions. The results show that the chemical weathering fluxes are mainly supplied by the dissolution of authigenic smectites in soils (5 vol. %) and not by the dissolution of the primary minerals. On the second hand, sensitivity tests to the mineralogical composition and climate are performed
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Solis, Michael Jay L. [Verfasser]. "Leaf-inhabiting fungal endophytes of F. benjamina, F. elastica, F. religiosa from Philippine tropical forests and German botanical greenhouses : assessment of diversity, community composition and bioprospecting perspective / Michael Jay L. Solis." Greifswald : Universitätsbibliothek Greifswald, 2016. http://d-nb.info/1098171217/34.
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Marian, Franca [Verfasser], Stefan [Akademischer Betreuer] [Gutachter] Scheu, and Mark [Gutachter] Maraun. "Altitude, litter quality and availability of root derived resources as determinants of decomposition processes and soil microarthropod community composition in tropical montane rainforests in Southern Ecuador / Franca Marian ; Gutachter: Stefan Scheu, Mark Maraun ; Betreuer: Stefan Scheu." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://d-nb.info/1117908585/34.
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Dahlsjö, Cecilia A. L. "Termite assemblage structure and function : a study of the importance of termites in lowland equatorial forests." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:28a37283-4013-4c5a-be2e-aac26d97f838.
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Termites are important ecosystem engineers in tropical and sub-tropical terrestrial regions where they influence ecosystem processes by altering the physical and chemical structure of the habitat. Termites affect nutrient availability by decomposition and comminution (shredding) of organic matter and act as agents of bioturbation as they re-work substrates during the construction of nests, tunnels and runways. At present we have a relatively good understanding of termite diversity patterns in the tropics through the extensive use of the standardised transect sampling protocol by Eggleton et al. (1995). These diversity data suggest that there is a functional difference in termite assemblage structure, and potentially in termite abundance and biomass, among comparable habitats across continents. However due to the lack of comparable abundance and biomass data from South America this has not previously been confirmed. In this thesis I, therefore, collected extensive data on termite taxonomic and functional assemblage structure in a South American site in Peru. The data were used to compare termite abundance and biomass from two comparable sites in Africa (Cameroon) and south east Asia (Malaysia) in order to gain better understanding of the role termites play in ecosystem processes. I found that there was an intercontinental difference in the abundance and biomass of termite feeding-groups mainly due to the dominance of soil-feeding termites in Cameroon and the absence of fungus-growing termites from Peru. The impact of certain lineages on the intercontinental differences suggests that the differences may be due to biogeographical evolution. Moreover, Eggleton et al. (1998) show that larger-bodied soil-feeding termites in Cameroon process more energy per unit area than predicted by their body size. Due to the need for an examination of the allometric relationships in termite assemblages outside Africa and the development of a more sophisticated feeding-group classification I explore the findings in Eggleton et al. (1998) further using population density - body mass relationships in three termite feeding-groups among the three continental sites in Cameroon, Peru and Malaysia. I found that large-bodied soil-feeding termites in Cameroon and large-bodied wood-feeding termites in Peru had higher population densities than expected by their body masses. As the population density - body mass relationship is inverse to that of the energy - body mass relationship the results suggest that the two feeding-groups also use more energy than expected by their body masses. Further, we have a relatively good understanding of the role termites play as ecosystem engineers e.g. in nutrient cycling and distribution, however, compared with our understanding of wood and litter decomposition in tropical forests quantitative data on the impact of termites in soil processes is poorly understood. In this thesis I conducted, to our knowledge, the first in situ soil macrofauna exclusion experiment using translocated soil in Peru to examine the impact of termites on soil C and N loss. I found that termites promote soil C and N loss which may be linked to the increase in microbial activity due to the passage of soil through the termite gut as well as the affect termites have on bioturbation and nutrient distribution. To conclude, in this thesis I present the first intercontinental comparison of abundance and biomass as well as the first in situ soil macrofauna exclusion experiment to date. The link between termite ecology, biogeography and evolution is discussed as well as the contribution of this thesis to the field of termite ecology.
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Azevedo, Luiz Otavio Roffee. "Infra-Red Spectrophotometry and X-Ray Diffractometry as Tools in the Study of Nickel Laterites." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/231213.
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Nickel silicate laterite deposits developed on ultra-mafic rocks are similar in many general respects but they vary considerably in detail. The mineralogy of these surficial deposits is very complex and difficult to determine because of the fine grained nature and solid solution characteristics of the hydrous secondary minerals and because many of the phases are actually mineraloids that are poorly ordered or amorphous. To try some new approaches toward clarification of these phases, 24 samples from New Caledonia and Puerto Rico ranging from the ophiolite-ultramafic olivine-pyroxene-chromite-serpentine substrate rocks upward through intermediate phases of weathering to the final oxide -hydroxide iron cap phase were analyzed with the infrared spectrophotometer (IR -10) and with the automated X –ray diffractometer. Four limonite samples were also mineralogically analyzed. Goethite, secondary quartz, cryptomelane, hematite, chromite, talc, thuringite, and garnierite have been identified in various samples as weathering profile products.
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Grunberger, O. "Étude géochimique et isotopique de l'infiltration sous climat tropical contrasté : massif du Piton des neiges, île de la Réunion." Paris 11, 1989. http://elgebar.univ-reunion.fr/login?url=http://thesesenligne.univ.run/H/Orsay_Grunberger.pdf.
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L'étude chimique et isotopique des éléments dissous des eaux de pluie, de l'eau du sol et des eaux souterraines permet la mise en évidence des caractères principaux du cycle hydrique sur une île volcanique tropicale à climat contrasté comme la Réunion (21°7S, 52°32W). La variation des teneurs chimiques dans les pluies montrent une influence marquée de la présence marine qui diminue avec le relief. La répartition des teneurs isotopiques des précipitations montre une distribution similaire en situation "normale" et fortement perturbée lors de la forte dépression tropicale Clotilda où les teneurs sont très appauvries. Cette variation naturelle des teneurs, due aux pluies à forte ascendance, constitue un signal que l'on s'est efforcé de retrouver dans l'eau des profils de sols et dans les points d'eau. L'examen des teneurs des eaux dans les sols montre, qu'en bas de pente, dans le secteur aride de l'île, se produit une évaporation irréductible alimentée par les nappes libres. Plus haut, sur les versants, il se produit une infiltration que l'on a pu également quantifier. Les analyses chimiques et isotopiques des eaux souterraines montrent que la minéralisation globale est bien représentée, loin de l'océan, par la minéralisation carbonatée essentiellement d'origine biogénique. La composition cationique des eaux reflète les compositions chimiques des roches qu'elles ont lessivées. D'autre part, les circulations souterraines ne suivent pas obligatoirement la pente générale du volcan. Les aquifères côtiers montrent une hydrochimie où l'influence marine est prédominante mais où apparaît un pôle de minéralisation carbonaté et sulfaté. L'analyse des isotopes du carbone et des sulfates a permis de mettre en évidence une influence non négligeable de la culture de la canne à sucre et des temps de transit des aquifères probablement inférieurs à 35 ans. Les aquifères de la côte ouest sont peu protégés de la pollution de bas de versant et toute mise en valeur de cette côte devra tenir compte de la sensibilité des aquifères aux sources de pollutionReunion Island is located in the Indian ocean (21° 7 S, 52 °32 W) in the intertropical zone. Chemical and isotopic natural contents in rain waters, soil waters and groundwaters allow to study the water cycle upon the "Piton des Neighs" massif, which is an inactive strato-volcano. Chemical contents in rain show a marine influence pondered by effects of the relief. Isotopic abundances of 180 and 2H have similar distributions which are strongly disturbed during the tropical hurricanes. These natural variations determine an "input" function and can be found in soils and aquifers. The distribution of the abundances of 180 in soil water in the west part of the island allows to quantify the evaporation rate from the groundwater table at a steady state. At higher altitude infiltration occurs and has also been quantified. Groundwaters chemical analysis show that global salinity is related to the carbonate mineralization from biogenic C02. Cation contents can be related to the geochemistry of weathered lavas. Groundwater flow patterns do not necessary follow the general slope of the volcano. Chemical contents of ground water from costal aquifers not only show marine influence but also a carbonated and sulfated source of mineralization. Carbone and sulfate isotopic contents illustrate the influence of cane sugar cultivation. The mean transit times are probably less than 35 years. All developing managements to come should take into account that western costal aquifers are not protected from pollution
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涂惠珠. "Effects of Different Fertilizers on Nitrification Activities and the Compositions of Nitrifying Bacterial Polulations of Tropical Soils." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/66969943901854233361.
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碩士東吳大學
微生物學研究所
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Nitrification is the process of converting ammonium to nitrate by way of nitrite. This process will not only reduce the toxic effect of high concentration of ammonium against plant growth but also increase the fertilitiy of soils. However, this process can also cause soil acidification. Nitrate carrying negative charge is easily been repelled by the clay particles, so it can move rapidly through the soil profile. Therefore, it can move into groundwater by simple leaching process and cause great harm to our health if ingested, in order to estimate the nitrifying activity of soil samples, one can obtain the information by multiplying the numbers of the nitrifying bacteria to the measured nitrifying potential of that soil. In this study, the methed of most probable number (MPN) was used to estimate the numbers of ammonium-oxidizing bacteria and nitrite-oxidizing bacteria in soils receiving chemical or organic fertilizer. At the same time, we had also measured the effects of different fertilizers on the short-term nitrifying activities of Taiwan clay and sandstone shale and slate alluvial soil. The results indicate that in soils samples without the addition of ammonium sulfate, we had detected little or no accumulation of both nitrite and nitrate. On the other hand, when ammonium sulfate was added, we observed an increase in the concentration of nitrate while no nitrite accumulation was been detected. Generally speaking, in all the treatments the amount of nitrate been accumulated was the lowest in sandstone shale and slate alluvial soil amended with chemical fertilizer. The results also indicated that in both Taiwan clay and sandstone shale and slate alluvial soil, the rates of nitrification varies with seasons. However it is clear that the above rate is faster in soils receiving organic fertilizer. Besides soils' physical and chemical properties, the compositions of nitrifying bacterial population may also play an important role. When NaClO3 was used to inhibt the conversion of nitrite to nitrate, we observed that the inhibitory results varied with soils and with seasons. However, in soils receiving organic fertilizer usually has high NO2--N accumulation than soils receiving chemical fertilizers. Although the numbers of ammonium-oxidizing bacteria is generally higher than the numbers of nitrite-oxidizing bacteria, no direct relationship could be established between the numbers of nitrifying bacteria and soils' nitrifying activities. Nevertheless, from the results obtained from those experiments involving the usage of nitrification inhibitors, it is clear that the compositions of nitrifying bacterial population varied not only with soils but also with seasons. Antiserum against Nitrosomonas europaea was also prepared in this study which was to be used for the identification purpose in future experiment.
Book chapters on the topic "Soils – Tropics – Composition"
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Martinelli, L. A., M. C. Piccolo, A. R. Townsend, P. M. Vitousek, E. Cuevas, W. Mcdowell, G. P. Robertson, O. C. Santos, and K. Treseder. "Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests." In New Perspectives on Nitrogen Cycling in the Temperate and Tropical Americas, 45–65. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4645-6_3.
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Sposito, Garrison. "The Composition of Soils." In The Chemistry of Soils. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190630881.003.0005.
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Soils are porous media created at the land surface through weathering processes mediated by biological, geological, and hydrological phenomena. From the point of view of chemistry, soils are open biogeochemical systems containing reactive solids, liquids, and gases. That they are open systems means they exchange both matter and energy with the surrounding atmosphere, biosphere, and hydrosphere. That they are biogeochemical systems means their development over time is a result of chemical transformations of earth materials linked to the life cycles of the soil biota and plant roots. Soils are the central feature of the life-supporting Critical Zone, which extends from the top of the vegetation canopy to the bottom of the groundwater aquifer in a terrestrial ecosystem. The Critical Zone provides essential ecosystem services (outputs of food, fiber, fuel, and water, including their quality) that sustain the biosphere. Other earth materials than soil may occur in the Critical Zone (for example, weathered rock [saprolite]), but soils are unique in showing a distinctive vertical stratification, the soil profile (Fig. 1.1), created by percolating water under the combined influence of parent material, topography, climate, living organisms, and pedogenic time—the five factors of soil formation. Analogous to biomes, which classify terrestrial ecosystems according to similar climate and vegetative cover, orders classify soils according to similar climate, parent material, or pedogenic time. With respect to climate, for example, Oxisols reflect tropical conditions, whereas Mollisols reflect temperate conditions. Spodosols and Gelisols reflect mainly boreal conditions (Table 1.1). Andisols, Histosols, and Vertisols, on the other hand, are not defined by climatic region, but instead by parent material (volcanic ash, organic litter, or swelling clay, respectively), whereas Entisols and Inceptisols reflect pedogenic time being insufficiently long for significant A or B horizon development, respectively. Biomes are basic classification units of the aboveground biosphere useful for characterizing its ecosystem services, whereas orders are basic classification units of the pedosphere useful for the same purpose. The natural capitalof soils is the set of assets that allows them to function beneficially as providers of ecosystem services.
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Juo, Anthony S. R., and Kathrin Franzluebbers. "Soil Physics." In Tropical Soils. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195115987.003.0007.
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Soil physics deals with physical properties of soils such as soil texture, porosity, soil water, soil aeration, soil temperature, soil structure, and the influence of these properties on plant growth. Soil texture refers to the particle-size distribution of soils. The primary soil particles are arbitrarily divided into different size classes. The International Society of Soil Science defines soil particles larger than 0.02 mm and smaller than 2 mm as sand, those larger than 0.002 mm but smaller than 0.02 mm as silt, and those smaller than 0.002 mm as clay. Soil particles larger than 2 mm, such as gravel and stones, are called coarse fragments and are not part of the soil itself, to which the term soil texture applies, but can have considerable influence on soil properties and plant growth. Sand particles (0.02-2 mm) can be further divided into fine sand (0.02-0.2 mm) and coarse sand (0.2-2 mm). Sand particles can be rounded or angular, and are noncohesive. They usually consist of a single mineral, usually quartz (SiO2) or other primary silicate, and may appear brown, yellow, or red as a result of Fe-oxide coatings. Due to its mineral composition, sand has a smaller plant-nutrient content than finer soil particles. Sand particles have large voids between them which promote drainage of water and entry of air into the soil. Due to their low specific surface area, sand particles can hold little water, therefore rain needs to be received at short intervals to enable plant growth on sandy soils. Silt particles (0.002-0.02 mm) do not feel gritty when rubbed between fingers and are not visible to the unaided eye as sand particles are. Quartz is generally the dominant mineral. However, when silt is composed of weatherable minerals, the release of plant nutrients can be significant. The pores between silt particles are smaller and more numerous than those in sand, and silt therefore retains more water than sand, which helps to sustain plant growth. Silt itself does not exhibit much stickiness or plasticity and is therefore easily washed away by water. If silt fractions have some cohesion and adsorptive capacity, it is due to a film of adhering clay particles.
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Seligson, Kenneth E. "Fields." In The Maya and Climate Change, 69—C4.P89. Oxford University PressNew York, 2023. http://dx.doi.org/10.1093/oso/9780197652923.003.0004.
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Abstract This chapter explores the agricultural adaptations that sustained gradual population growth in the Maya lowlands up through the demographic explosion of the Late Classic Period. At the heart of Maya agriculture is a cultivated field system known as the milpa that incorporates several crops at once. Traditional milpa systems were supplemented by a wide range of land-modification strategies that included extensive terrace networks and wetland raised-field systems. Underpinning these intensification strategies was an in-depth knowledge of all aspects of the natural environment and how they could best sustain growing human populations. Farmers developed intimate understandings of precipitation and growth cycles, plant and animal roles, and soil compositions. They knew which species grew well together at which points of the rainy season, in which types of soils, and with which types of fertilization. The question of how Classic Maya communities sustained such high populations for so many centuries in such a challenging tropical environment no longer perplexes researchers. The multitude of techniques that farmers used to sustainably and efficiently manage food production across the mosaic of lowland microenvironments for over seven centuries are becoming increasingly clear through the application of paleoenvironmental, paleobotanical, and lidar-based analyses.
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Dias-Filho, Moacyr B., and Eric A. Davidson. "Linking Biogeochemical Cycles to Cattle Pasture Management and Sustainability in The Amazon Basin." In The Biogeochemistry of the Amazon Basin. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195114317.003.0009.
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Pasture development has become the largest anthropogenic disturbance of forest land in the Amazon basin (Skole et al. 1994, Serrão and Toledo 1990). The area of forests converted to cattle pasture in Amazonia is currently estimated at approximately 20 million hectares. In the Brazilian Amazon basin, most of the conversion of forest land to pasture began during the early 1960s to the late 1980s, as a consequence of the opening of Amazon highways and government policies aimed at regional development (Hecht 1982, Nepstad et al. 1991, Serrão et al. 1979). Pasture productivity and longevity in the Amazon basin seem to be closely related to soil fertility and nutrient cycling (e.g., Dias Filho and Serrão 1987, Serrão et al. 1979). Thus, understanding the major biogeochemical cycles that influence soil fertility under pasture is vital for predicting the consequences of continued conversion of tropical forests to cattle pastures. This understanding is also important for devising management technologies that enhance the sustainability of these areas and thus slow further deforestation. Although during the first three to five years after establishment, the productivity of pastures is often good, after that period a rapid decline in productivity of the planted grasses associated with an increased presence of herbaceous and woody invaders is generally observed (reviewed by Serrão and Toledo 1990). If left uncontrolled, these invader species slowly become dominant and lead to “pasture degradation,” a condition characterized by a complete dominance of the weedy community. If left to secondary succession, forest vegetation usually becomes reestablished on these degraded pasture lands in the Amazon, although the species composition is usually different than that of the primary forest (Nepstad 1989). The nutrient status of the degraded pasture soils is among the factors that affect the rate of regrowth of the secondary forests. One of the first attempts to study soil nutrient dynamics under cultivated pastures in the Amazon basin was conducted in the early 1970s by Falesi (1976). The results of that chronosequence study in different soil types suggested that soil nutrient cycling in pastures differed from that of the traditional slash-and-burn agriculture.
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M. Mejía-Ortíz, Luis, Peter Sprouse, Juan C. Tejeda-Mazariegos, Jair Valladarez, Oscar Frausto-Martínez, Alejandro L. Collantes-Chavez-Costa, Guillermo Ruíz-Cancino, and German Yáñez. "Tropical Subterranean Ecosystems in Mexico, Guatemala and Belize: A Review of Aquatic Biodiversity and Their Ecological Aspects." In Natural History and Ecology of Mexico and Central America. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97694.
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The subterranean ecosystems in tropical areas of Mexico, North of Guatemala & Belize are very abundant because the karstic soil that allow these formations are the main composition in the Yucatán Peninsula and several mountains systems in these countries; also, they have a strong relationship with tropical forest adjacent where the main energy into the caves have an alloctonous origin. In these three countries there are three different cave conditions: a) freshwater semi-dry caves, b) flooded freshwater systems and c) anchialine systems. Mainly crustaceans and freshwater fishes are the major representative group in the aquatic diversity in these systems because the anchialine members are restricted to Yucatán Peninsula and Islands adjacent. Around 5000 entries to subterranean world there are among these countries, where the Yucatan Peninsula is the area with major caves or cenotes in comparison with southern of Mexico, North of Guatemala and Belize. Into these systems are possible found crustaceans and fishes from different families. The objective of this paper is present a review of these systems according with each karstic areas and show the current map including the location of each systems; as well their subterranean aquatic biodiversity and, finally discuss the relationships among these different areas using their biological aquatic richness in consideration with ecological subterranean conditions.
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Nadkarni, Nalini M., and Robert O. Lawton. "Ecosystem Ecology and Forest Dynamics." In Monteverde. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195095609.003.0015.
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The earth’s surface supports living organisms and their environments to form the biosphere, a thin film of life around the planet. Organisms participate in interacting systems or communities, and these communities are coupled to their environments by the transfer of matter and energy and by movements of air, water, and organisms. Human activities in Monteverde and elsewhere can drastically alter forest ecosystems. Textbooks on ecosystem ecology typically include such topics as community structure and composition (including plant growth forms, vertical structure, niche space, species diversity), communities and environments (species distributions along environmental gradients, community classification, succession), production (food chains and webs, decomposition and detritus, photosynthesis), and nutrient cycling (mineral nutrition of organisms, soil development, biogeochemistry). Our understanding of tropical ecosystem ecology generally falls short of what we know of other aspects of tropical biology. There are far more studies concerning population biology, autecology, and life history of tropical organisms than nutrient cycling, productivity, and landscape ecology. This pattern is true in Monteverde and in such well-studied tropical forests as La Selva, Barro Colorado Island (BCI), and the Luquillo National Forest (Lugo and Lowe 1995, McDade et al. 1994). Logistical blocks to ecosystem research exist because collaborating teams of scientists are typically needed to tackle the multiple disciplines that ecosystem-level questions require, which demands a large infrastructure and budget. Temporal problems exist because ecosystem-level phenomena (e.g., tree mortality and forest regeneration) may involve time scales longer than the life of a single granting period or lifetime of a researcher. A strong academic base for ecosystem ecology is lacking because the pool of existing studies is too small to draw patterns and extrapolate trends. These obstacles have not often been overcome in Monteverde. No Monteverde institution has provided the infrastructure to support ecosystem research (e.g., laboratory facilities, meteorological station, technical library). Some community members have negative feelings about experimental manipulations and destructive sampling sometimes needed to answer ecosystem ecology questions. From the 1970s to the 1990s, Organization for Tropical Studies (OTS) courses were in Monteverde and in such well-studied tropical forests as La Selva, Barro Colorado Island (BCI), and the Luquillo National Forest (Lugo and Lowe 1995, McDade et al. 1994).
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Denevan, William M. "Pre-European Human Impacts on Tropical Lowland Environments." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0025.
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The topic of early human impacts on New World environments, including Amazonia, is controversial as to degree and extent (Balée, 1989; Cleary, 2001; Denevan, 1992b; Gómez-Pompa and Kaus, 1992; Hayashida, 2005; Krech, 1999; Stahl, 1996; Vale, 2002). Certainly, whenever and wherever people were present, even sparse populations, there was some change in the landscape. People cannot live on the land and use plants and animals for subsistence and other needs without changing that land and the plants and animals present. Human-induced changes may involve equilibrium in which the natural ecosystem basically recovers, even though composition is changed, or in which the human ecosystem is sustainable; or the changes may involve disequilibrium in which the regenerative capacities (i.e., biological diversity and productivity) of either system are retarded or destroyed (i.e., degradation) (Sponsel, 1992). These changes may have been intentional or not, ephemeral or long lasting, localized or regional, onetime events or cumulative, highly visible or not readily apparent. Vegetation is the most widespread focus of change; other impacts have been on wildlife, soil, river patterns, microclimate, and the land surface itself. The forces of change are settlement, cultivation, grazing, hunting and gathering (foraging), burning, and various earthworks and river works. All of these impacts and forces were present in pre- European South America. Furthermore, native people “recognize that human beings, past and present . . . have affected the distribution of the biota and the formation of the landscape” (Balée, 2003: 285–286). “Far from being a wild world . . . the forest is perceived as a superhuman garden” by the Achuar in Ecuador (Descola, 1994: 324). Lacking written records, it is difficult to reconstruct early indigenous impacts, and any attempt to do so involves speculation and inference. Some alterations have persisted to the present, but most have been masked by either landscape recovery or by human destruction. Furthermore, nature and culture merge, the dichotomy being artificial, conceptual (Descola, 1994: 1–6). And some human disturbances that seem old are actually recent, but the reverse is also true. The distinction may be difficult to ascertain.
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Milchunas, Daniel G., and William K. Lauenroth. "Effects of Grazing on Abundance and Distribution of Shortgrass Steppe Consumers." In Ecology of the Shortgrass Steppe. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195135824.003.0022.
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Although livestock are the most obvious consumers on the shortgrass steppe, they are certainly not the only consumers. However, livestock may influence the other consumers in a number of different ways. They may directly compete for food resources with other aboveground herbivores. There is behavioral interference between livestock and some species of wildlife (Roberts and Becker, 1982), but not others (Austin and Urness, 1986). The removal of biomass by livestock alters canopy structure (physiognomy) and influences microclimate. Bird, small-mammal, and insect species can be variously sensitive to these structural alterations (Brown, 1973; Cody, 1985; MacArthur, 1965; Morris, 1973; Rosenzweig et al., 1975; Wiens, 1969). There are both short- and long-term effects of grazing on plant community species composition, primary production, and plant tissue quality. Belowground consumers can also be affected by the effects of grazing on soil water infiltration, nutrient cycling, carbon allocation patterns of plants, litter accumulation, and soil temperature. The overall effects of livestock on a particular component of the native fauna can be negative or can be positive through facilitative relationships (Gordon, 1988). In this chapter we assess the effects of cattle grazing on other above- and belowground consumers, on the diversity and relative sensitivity of these groups of organisms, and on their trophic structure. We first present some brief background information on plant communities of the shortgrass steppe and on the long-term grazing treatments in which many of the studies reported herein were conducted. Details on the plant communities are presented by Lauenroth in chapter 5 (this volume), grazing effects on plant communities by Milchunas et al. in chapter 16 (this volume); and grazing effects on nutrient distributions and cycling by Burke et al. in chapter 13 (this volume). The physiognomy of the shortgrass steppe is indicated in its name. The dominant grasses (Bouteloua gracilis and Buchloë dactyloides), forb (Sphaeralcea coccinea), and carex (Carex eleocharis) have the majority of their leaf biomass within 10 cm of the ground surface. A number of less abundant midheight grasses and dwarf shrubs are sparsely interspersed among the short vegetation, but usually much of their biomass is within 25 cm of the g round. Basal cover of vegetation typically totals 25% to 35%, and is greater in long-term grazed than in ungrazed grassland. Bare ground (more frequent on grazed sites) and litter-covered ground (more frequent on ungrazed sites) comprise the remainder of the soil surface (Milchunas et al., 1989).
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Seyler, Patrick T., and Gerald R. Boaventura. "Trace Elements in the Mainstem Amazon River." In The Biogeochemistry of the Amazon Basin. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195114317.003.0019.
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Measurements of trace metals in rivers are of substantial interest for researchers examining basic scientific questions related to geochemical weathering and transport and to scientists involved in pollution control evaluation. Trace metals in natural waters include essential elements such as cobalt, copper, zinc, manganese, iron, molybdenum, nickel, which may also be toxic at higher concentrations, and nonessential elements, which are toxic, such as cadmium, mercury and lead. Recent findings indicate that iron and, to a lesser extent, zinc and manganese play an important role in regulating the growth and ecology of phytoplankton (Martin et al. 1991), while in contrast, cadmium, arsenic, and mercury have long been recognized as poisonous to living organisms (see Pfeiffer et al. 1993, for a description of mercury problem in the Amazon basin). The release of potentially large quantities of these toxic metals, particularly in the river systems of industrialized countries, but also in tropical rivers, is an acute problem of great environmental concern. An understanding of the weathering and transport processes controlling the fate and flux of trace metals in pristine environments is important in evaluating the capacity of receiving waters to accommodate wastes without detrimental effects. The Amazon River system, which is relatively free of industrial and agricultural interference, represents an ideal case for the investigation of the origin and transport of trace metals. This understanding may also provide a scientific basis for the anticipated development of the Amazon basin. With regard to trace metals, Amazon River is still poorly documented. Martin and Meybeck (1979) and Martin and Gordeev (1986) presented a global tabulation of trace metal concentrations in particulate matter of major rivers including the Amazon, and Palmer and Edmond (1992) measured dissolved Fe, Al, and Sr concentrations in the Amazon mainstream and a number of its tributaries. Boyle et al. (1982) and Gordeev et al. (1990) published some data on Cu, Ni, Cd, and Ag dissolved concentrations at the mouth of the Amazon River and in its oceanic plume. Konhauser et al. (1994) reported the trace and rare earth elemental composition of sediments, soils and waters, mainly in the region of Manaus.
Conference papers on the topic "Soils – Tropics – Composition"
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Gordienko, T. A., R. A. Sukhodolskaya, D. N. Vavilov, and Yu A. Lukyanova. "SUSTAINABILITY OF PEDOBIONT MEADOW COMMUNITIES UNDER ANTHROPOGENIC LOAD." In V International Scientific Conference CONCEPTUAL AND APPLIED ASPECTS OF INVERTEBRATE SCIENTIFIC RESEARCH AND BIOLOGICAL EDUCATION. Tomsk State University Press, 2020. http://dx.doi.org/10.17223/978-5-94621-931-0-2020-12.
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Studies of the soil mesofauna were carried out in Tanaev meadows of the «Nizhnyaya Kama» National Park in natural and disturbed areas. The abundance of pedobionts and herpetobionts in natural areas significantly exceeded the abundance in disturbed areas. However, the taxonomic composition and trophic structure were similar. In general, communities structure indexes in natural sites indicate a stable ecosystem of floodplain meadows. The observance of pipe laying technology during further restoration of disturbed areas, high soil moisture and a small width of the disturbed soil layer contribute to the preservation and rapid restoration of the structure and population of large soil and litter invertebrates of meadow phytocenosis.
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Dechang Han, Siwei Jiang, and Jing An. "Trophic-groups composition of nematode community in petroleum-contaminated soil of Liaohe Oilfield." In 2011 International Conference on Remote Sensing, Environment and Transportation Engineering (RSETE). IEEE, 2011. http://dx.doi.org/10.1109/rsete.2011.5966307.
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Hesterberg, Dean, Talita Ferreira, Carla Pólo, Renata Rabelo, Hélio Tolentino, Carlos Pérez, Leandro Gonzaga, et al. "Micro- and Nano-Pore Structure and Composition of Microaggregates from a Tropical Soil." In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.12510.
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Li, Yutian, Changchun Wu, Xiaokai Xing, Mingliang Yue, and Yun Shang. "Testing and Analysis of the Soil Thermal Conductivity in Tropical Desert and Grassland of West Africa." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90291.
Full textAbstract:
Thermal conductivity is one of the basic thermal properties of soil. For a buried pipeline, the thermal conductivity of the surrounding soil is the most important factor determining the overall heat transfer from the pipeline, and plays an important role in assessing the safety and energy consumption of pipeline operation. For providing reliable basic data for the commissioning and the operation of a waxy crude oil pipeline stretching in southwest Sahara Desert, six phases of thermal conductivity testing were performed along the pipeline route, respectively in February, March, April, May, July and September, 2011. The pipeline is 462.5km long and 323.9mm outside diameter. The pipeline route crosses tropical desert and grassland. Test points are located at roughly equal spaces along the pipeline route, and additional test points are located in seasonal river beds and rugged terrains. The soil temperature and thermal conductivity were tested simultaneously at a depth of about130cm below soil surface, which is also near to the pipeline centerline. The test equipment used was a field thermal needle system FTN01 for thermal conductivity made in Holland. For a given location along the pipeline route, the soil thermal conductivities have different values in dry season and rainy season. The average soil thermal conductivities for the pipeline route between two stations ranges from 0.5 to 1.1W/(m·°C) in rainy season, and from 0.4 to 0.8 W/(m·°C) in dry season. The test results show that the change of soil moisture content has significant impact on soil thermal conductivity. Because other properties of the tested soil along the pipeline route such as soil mineral composition, particle size distribution and density have no significant change, these factors have little effect on soil thermal conductivity.