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Extensive network of tile drains present in the Midwest USA accelerate losses of nutrients to receiving ditches, rivers and eventually to the Gulf of Mexico. Nutrient inputs from agricultural watersheds and their role in affecting water quality have received increased attention recently; however, benthic sediment-nutrient interactions in tile-fed drainage ditches is still a matter of active research in consideration to nutrient discharge from tile drains. In this study, phosphorus (P) and nitrogen (N) contents and variability of nutrient retention ability of benthic sediments upstream and downstream from tile drain outlets were evaluated in managed agricultural drainage ditches in Indiana. Sediment samples were collected every three months upstream and downstream from selected tile drains in three ditches in northwest Indiana. Sediment equilibrium P concentrations (EPC0) were measured to examine P adsorption-desorption and equilibrium characteristics of benthic sediments in the ditches. P sorption index (PSI), exchangeable P (ExP), and exchangeable NH4+-N (ExN) were measured to evaluate nutrient retention ability and readily available nutrient content of benthic sediments. Results indicated a dynamic interaction between benthic sediment and overlying water column where sediments were acting as a sink or a source of P. There were no differences in nutrient retention ability between sediments collected upstream and sediments collected downstream from the selected tile drains. While the data, except for ExN, was comparable to reported values by previous studies in Indiana’s drainage ditches, there was no particular seasonal pattern in the content of exchangeable nutrient content in sediments at all three sites. This study also suggested that nutrient uptake by benthic sediments in these drainage ditches is not always efficient; therefore watershed management should focus on minimizing the delivery of nutrients into ditches while maintaining their drainage functionality.

2007/2008 Il Golfo di Trieste, localizzato nella parte più settentrionale ed orientale del bacino Adriatico, rappresenta un’area peculiare per le sue caratteristiche geomorfologiche, oceanografiche e biologiche. In quest’area, in particolare, insistono diverse attività economiche che vanno dalla maricoltura al turismo e pertanto i problemi legati alla qualità ambientale sono oltremodo diversificati: da un lato è importante che la trofia del sistema supporti lo sviluppo e la crescita dei molluschi allevati e dall’altro la fruizione delle acque per la balneazione richiede requisiti di qualità precisi e stabiliti dalle normative europee. Alla base di qualsiasi approccio gestionale all’ambiente marino costiero è comunque necessario conoscere la dinamica dei composti che stanno alla base della rete alimentare e che rappresentano anche importanti segnali di apporti antropici al sistema. I nutrienti, siano essi nella forma inorganica o in quella organica, regolano le dinamiche trofiche dell’ecosistema costiero e sono oltremodo concentrati in prossimità di scarichi urbani o nelle acque a bassa salinità frutto del mescolamento tra fiume e mare. Nonostante i numerosi e approfonditi studi sull’ecosistema del Golfo di Trieste, la dinamica dei nutrienti è stata poco approfondita, soprattutto in relazione alla frazione organica. La ricerca svolta nell’ambito di questo dottorato ha avuto come obiettivi principali: La valutazione delle dinamiche spaziali e temporali della concentrazione dei macronutrienti, nella forma inorganica ed organica, nelle acque del Golfo di Trieste La verifica del ruolo degli apporti fluviali e antropici sulla loro disponibilità La comprensione dell'importanza delle attività microbiche di rimineralizzazione sulla disponibilità degli stessi. Il protocollo sperimentale ha previsto l'analisi di campioni d'acqua prelevati mensilmente in 9 stazioni del Golfo, nel periodo 2004-2008. Nella stazione storica C1 il campionamento è stato intensificato per meglio valutare le dinamiche temporali esplorando la variabilità giornaliera e quella a scala oraria. Poiché il Golfo è soggetto a notevoli apporti fluviali, è stato valutato il ruolo dell’Isonzo, il fiume più importante, e, a partire dal 2006, è stato considerato anche il Timavo. Per evidenziare il ruolo degli scarichi antropici sono stati considerati i dati provenienti dal Monitoraggio delle acque costiere predisposto dalla Regione FVG (2002-2005). L’imponente lavoro analitico ha permesso di confermare la scarsa disponibilità di fosforo nelle acque del Golfo anche in periodi di limitata utilizzazione biologica. L’apporto dei fiumi arricchisce le acque delle forme particellate ma non incide sulla frazione disciolta mentre gli scarichi urbani non influenzano significativamente la disponibilità. Importante risulta, invece, il ruolo della degradazione enzimatica della sostanza organica. Sia il fitoplancton che il batterioplancton producono, infatti, notevoli quantità di fosfatasi alcalina, enzima in grado di recuperare fosforo da molecole organiche. Attraverso la produzione di enzimi, i microrganismi riescono a sopperire alla scarsa disponibilità di molecole inorganiche, più facilmente utilizzabili ma estremamente meno abbondanti. Questi risultati sono oltremodo importanti per l’organizzazione dei futuri piani di monitoraggio degli ambienti marini costieri caratterizzati da forti input di acqua dolce sia di origine antropica che fluviale. La trofia del sistema, infatti, non è sostenuta soltanto dai Sali inorganici disciolti di azoto, fosforo e silicio ma è fortemente dipendente dal pool di organico sia disciolto che particellato. L’attività degradativi dei microrganismi su queste matrici consente loro di ottenere le sotanze essenziali per la crescita e la duplicazione. XIX Ciclo 1966

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Coombabah Lake is a sub-tropical, semi-urbanised, shallow lagoon in southern Moreton Bay (Australia), recognised nationally and internationally as an important conservation and habitat zone. However, significant increases in urban development have occurred within the lagoon catchment in recent times, raising concerns over the sustainability of the lagoon ecosystem. This is typical of many estuarine environments which are ecologically and economically important waterways that often become surrounded by urban development and therefore experience degradation of water and sediment quality. The processes controlling the distribution of organic matter and nutrients in estuaries are especially important in understanding their chemical cycling. Consequently, the assessment and understanding of biogeochemical processes and other influential factors is essential for the effective management of estuaries. This study is a multi-disciplinary investigation of biological, physical, and biogeochemical processes occurring in the surface sediments and overlying waters of Coombabah Lake and the adjoining creek. The primary aim of this study was to investigate physico-chemical and biogeochemical processes occurring over various patial and temporal scales and improve the understanding of Coombabah Lake and similar shallow sub-tropical systems. Spatial variability of physico-chemical surface sediment variables and the sources and distribution of surface sediment organic matter were investigated to provide an understanding of the physico-chemical and ecological processes driving the lagoon system. Lagoon sediments were characterised by generally fine sediments with predominantly sandier sediments occurring within the northern region and muddier sediments occurring within the southern region. Although some sediment locations had elevated nutrient concentrations in comparison to adjacent lagoon sediments, nutrient concentrations within the lagoon were generally typical of Australian estuarine environments. Comprehensive analysis of biomarkers indicated that the lagoon received organic matter from a variety of autochthonous and allochthonous sources including terrestrial vascular plants (i.e. surrounding mangroves), diatoms, and benthic bacteria with the fringing mangroves potentially playing an important role in the lagoon food web. The intratidal variability of hydrological and physico-chemical variables were measured and the filterable nutrient and chlorophyll-a transport loads entering the lagoon determined. Instrumental measurements and hourly water collections provided the first account of intratidal variability within the system and indicated the lagoon and adjoining creek was characterised by a mixed tidal regime with cyclic and temporal variations in physico-chemical variables, suspended solids, and chl-a concentrations. Both dissolved oxygen and turbidity values exceeded regulatory guideline values for the region. Nutrient concentrations were typical of local and Australian estuarine environments and exceeded regulatory guideline values for the region. Nutrients sourced externally from the Coombabah Lake-Creek system resulted in increased transportation rates during flood events indicating a potential for increased nutrient loadings and enrichment within the lagoon and associated wetland environment...

Reducing decomposition and mineralization of organic matter by increasing groundwater levels is a common approach to reduce plant nutrient availability in many peat meadow restoration projects. The soil community is the main driver of these processes, but how community composition is affected by peat meadow restoration is largely unknown. Furthermore, it is unclear whether restoration induced changes could lead to altered decomposition and mineralization rates. We determined soil community composition in restored peat meadows with different groundwater levels and soil pH. This composition was subsequently used in food web model calculations of C and N mineralization rates to assess whether differences in soil community composition may have contributed to differences in decomposition and mineralization rates observed between these meadows. Community composition of micro-organisms, Collembola and Enchytraeidae differed considerably between meadows and were correlated with differences in groundwater levels and soil pH. Collembolan and enchytraeid species from wet and neutral environments were more abundant at meadows with higher groundwater levels. Lower fungal to bacterial PLFA ratios and higher numbers of protozoa indicated an increased importance of the bacterial part of the food web at meadows with higher groundwater levels. Food web model calculations suggested that the observed changes in community composition would lead to higher rates of C and N mineralization at meadows with high groundwater levels. Results from modeling were consistent with field measurements of C mineralization, but not with measurements of N mineralization. We conclude that understanding changes in soil community composition in response to specific restoration measures may help us to better understand ecosystem responses to wetland restoration schemes, especially regarding soil biogeochemical processes. © 2009 Elsevier Ltd. All rights reserved.

Decomposition of senescent leaves of Castanea sativa (CS), and needles of Pinus pinaster (PP), Pinus nigra (PN) and Pseu- dotsuga menziesii (PM) was studied during 3.1 to 3.5 years through weight loss and nu- trient concentration evolution, using the litter bag technique, whereas the variation of chemical structural compounds was followed during 391 to 518 days. The highest contents of N were measured in PM and CS (respectively 14.5 and 12.1 g kg-1), which showed lower C/N ratio (39.0, 46.8) than PN and PP (122.2 and 147.7, respectively). Highest contents of Ca (9.1 g kg-1) and of alcohol and water soluble compounds (384 against 95 to 160 g kg-1 to other species) were measured in PM needles, which also showed the lowest contents of holocelulose (253 g kg-1 against about 500 g kg-1 in the other species). The lignin Klason/N ratio decreased according to PP>PN>PM>CS, (71.2, 58.3, 20.5 and 20.3 respectively), and the holocelulose/lignin ratio ranged from 0.9 (PM) to 1.9-2.1 in the other species. Annual decay rates, according to the negative exponential model, were ordered according to CS>PN>PM>PP (respectively -0.35, -0.27, -0.19 and -0.16), but with higher values during the first year for CS (-0.60) and PM (0.31). Soluble compounds and hemicelulose strongly decreased during the decomposition period, while lignin and cellulose amounts showed a low variability, mainly in PP and PM needles. Nutrient amounts decreased during the decomposition process, but remaining quantities for N (41 to 121 %) and P (33 to 104 %) were higher than those estimated for K, Ca and Mg (respectively 17 to 65%, 30 to 60 % and 18 to59%). A strong decreasing of C/N ratio was observed especially for PP and PN, where reached 53.2 and 47.1.

Laboratory mesocosm incubations were undertaken to investigate the influence of natural densities of the thalassinidean shrimp, Trypaea australiensis (marine yabby) on sediment oxygen demand (SOD), inorganic nutrient fluxes, and the N-cycle processes of nitrification, denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Mesocosms (~ 0.1 m 2 × 55 cm deep) of sieved, natural T. australiensis inhabited sands were continually flushed with fresh seawater and pre-incubated for two weeks prior to being assigned to one of three treatments; control (no additions), low yabby density (40 T. australiensis m − 2 ) or high yabby density (80 T. australiensis m − 2 ). Thereafter, SOD and sediment–water column inorganic nutrient fluxes were determined periodically over a 38 day period. On the final day rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were also determined using the 15 N-isotope pairing technique. Yabbies consistently and significantly ( p − 2 day − 1 for control, low and high density treatments, respectively). The increased organic matter mineralisation rates greatly enhanced nitrogen regeneration rates in the sediment and fuelled significantly higher effluxes of dissolved inorganic nitrogen with NH 4 + and total DIN effluxes in the low and high density treatments respectively, being 617 and 1534%, and 269 and 565% higher than those in the controls, despite sediment bioavailable (porewater + exchangeable) NH 4 + pools being approximately 2 and 4-fold lower in the low and high density yabby treatment sediments compared to the controls, measured at the end of the 37 day experiment. Mass balance calculations based on the final day nutrient flux and nitrate reduction rate data demonstrated that yabbies stimulated benthic nitrification rates by 31 and 46% in the low and high density treatments. However, somewhat surprisingly T . australiensis population density had no effect on rates of denitrification and DNRA despite the higher rates of nitrification and higher equilibrium water column nitrate concentration. Indeed, nitrate reduction processes became an increasingly unimportant element with increasing yabby density with for example, N 2 generated by coupled nitrification–denitrification representing 11.5, 5.2 and 2.8% of the total inorganic-N recycled to the water column in the control, low density and high density yabby treatments, respectively. Overall, the major influence of T. australiensis in the studied low organic matter content, sandy sediments was to enhance coupling between the benthic and pelagic systems through increased rates of inorganic nitrogen regeneration in the sediment and enhanced export of this nitrogen to the water column. Our results also suggest that the influences of organisms such as T. australiensis which form deep, extensive and complex burrow systems where irrigation rates differ greatly between different burrow sections, may be more complex than those recorded for infauna which form simple U-shaped burrows. Additionally, there may be a strong interaction between faunal effects and the sediment physical and biological environment and thus the same species may have contrasting influences in different sediment types.

Mangrove ecosystems are considered vulnerable to climate change as coastal development limits the ecosystem services and adaptations important to their survival. Although they appear rather simple in terms of species diversity, their ecology is complex due to interacting geophysical forces of tides, surface runoff, river and groundwater discharge, waves, and constituents of sediment, nutrients and saltwater. These interactions limit developing a comprehensive framework for science-based sustainable management practices. A suite of models have been developed independently by various academic and government institutions worldwide to understand the dynamics of mangrove ecosystems and to provide ecological forecasting capabilities under different management scenarios and natural disturbance regimes. The models have progressed from statistical tables representing growth and yield to more sophisticated models describing various system components and processes. Among these models are three individual-based models (IBMs) (FORMAN, KIWI, and MANGRO). A comparison of models' designs reveal differences in the details of process description, particularly, regarding neighbor competition among trees. Each model has thus its specific range of applications. Whereas FORMAN and KIWI are most suitable to address mangrove forest dynamics of stands, MANGRO focuses on landscape dynamics on larger spatial scale. A comparison of the models and a comparison of the models with empirical knowledge further reveal the general needs for further field and validation studies to advance our ecological understanding and management of mangrove wetlands. (C) 2008 Elsevier B.V. All rights reserved.

9 páginas, 4 figuras, 4 tablas., Soil ecosystem engineers such as termites and ants are able to modify physico-chemically the surrounding environment through the production of biogenic structures, thus affecting the availability of trophic and spatial resources for other organisms. The aim of this study was to assess the concentrations of Corg, NH4+ and NO3− in the biogenic structures produced by a soil-feeding termite (Spinitermes sp.; Termitinae) and a fungus-grower ant species (Atta laevigata; Myrmicinae; tribe Attini) and the surrounding soil in the Colombian “Llanos”. We tested the hypothesis that higher concentrations occur in the biogenic structures compared to control soil and that deposition of new building material at the top of the biogenic structures also increases nutrient concentrations. Sampling was conducted along a transect, at regular intervals proportional to the size of the biogenic structure. Average Corg and NH4+ concentrations were significantly higher in termite mounds than in ant nests and the control soil, whereas NO3− concentrations were similar. For both types of biogenic structures, the highest difference in nutrient concentrations was found between the top centre of the biogenic structure and the control soil, but significant differences were only reported for Spinitermes mounds and the control soil. No significant effect of land use on nutrient concentrations in the biogenic structures produced by either species was observed. We conclude that the activities of soil ecosystem engineers contribute to the variability of nutrient concentrations through the formation of biogenic structures., Financial support was provided by the Soil, Water and Nutrient Management systemwide programme of the CGIAR and through the IBOY-DIVERSITAS programme.

Seasonal variation patterns of aboveground and belowground biomass, net primary production, and nutrient accumulation were assessed in Atriplex portulacoides L. and Limoniastrum monopetalum (L.) Boiss. in Castro Marim salt marsh, Portugal. Sampling was conducted for five periods during 2001–2002 (autumn, winter, spring, summer, and autumn). This study indicates that both species have a clear seasonal variation pattern for both aboveground and belowground biomass. Mean live biomass was 2516 g m22 yr21 for L. monopetalum and 598 g m22 yr21 for A. portulacoides. Peak living biomass, in spring for both species, was three times greater in the former, 3502 g m22 yr21, than in the latter, 1077 g m22 yr21. For both the Smalley (Groenendijk 1984) and Weigert and Evans (1964) methods, productivity of L. monopetalum (2917 and 3635 g m22 yr21, respectively) was greater than that of A. portulacoides (1002 and 1615 g m22 yr21, respectively). Belowground biomass of L. monopetalum was 1.7 times greater than that of A. portulacoides. In spite of this, the root:shoot ratio for A. portulacoides was greater throughout the year. This shows that A. portulacoides allocates more biomass to roots and L. monopetalum to aerial components. Leaf area index was similar for both species, but specific leaf area of A. portulacoides was twice that of L. monopetalum. The greatest nutrient contents were found in leaves. Leaf nitrogen content was maximum in summer for both species (14.6 mg g21 for A. portulacoides and 15.5 mg g21 for L. monopetalum). Leaf phosphorus concentration was minimum in summer (1.1 mg g21 in A. portulacoides and 1.2 mg g21 in L. monopetalum). Leaf potassium contents in A. portulacoides were around three times greater than in L. monopetalum. Leaf calcium contents in L. monopetalum were three times greater than in A. portulacoides. There was a pronounced seasonal variation of calcium content in the former, while in the latter no clear variation was registered. Both species exhibited a decrease in magnesium leaf contents in the summer period. Manganese content in L. monopetalum leaves was tenfold that in A. portulacoides. Seasonal patterns of nutrient contents in A. portulacoides and L. monopetalum suggest that availability of these elements was not a limiting factor to biomass production.

In the Oxisols of the eastern plains of Colombia, the large native anecic earthworm Martiodrilus sp. is an abundant ecosystem engineer producing long-lasting casts and burrows. Casts deposited in the soil by this species have been estimated at several tonnes per hectare per year. The physical and chemical processes occurring in these casts have never been studied. In this study, we compared the dynamics of water content (WC), total C (Ctot), and available N (Navail) contents, and the distribution in size of aggregates in ageing below-ground casts of this species and in the bulk soil. In a native herbaceous savannah and a sown grass/legume pasture (Brachiaria humidicola, Arachis pintoi, Desmodium ovalifolium and Stylosanthes capitata), fresh surface casts were experimentally injected into artificial burrows of 1 cm O and 10 cm depth and sampled at different dates during a total period of 120 days. The injection procedure used resulted in a 34% decrease in WC of the casts from the sown pasture and reduced the mean mass diameter (MMD) of the aggregates of casts from the savannah by 19%. Other properties were not significantly affected by the procedure. For injected casts in both grasslands, MMD and Ctot were stable during cast ageing while WC and Navail were initially at levels several times higher than the bulk soil and decreased to similar bulk soil values with ageing. The Ctot was twice and one third higher in casts compared with the bulk soil in the pasture and the savannah, respectively. Overall means for cast MMD (8.3 and 7.4 mm) were twice as high as those in the bulk soil (3.8 mm) in the savannah and the pasture, respectively. However, MMD was not significantly different between the casts and the bulk soil in two occasions in the pasture. Available nitrogen (Navail) in injected casts was initially greater than bulk soil levels, reaching maximum levels just after injection (116 and 93 mg kg−1) and remained significantly greater during 1–2 weeks, in the savannah and the pasture, respectively. In conclusion, the tonnes of casts deposited in the soil profile by Martiodrilus sp. each year are likely to contribute greatly to plant nutrition and to the regulation of the soil structure. For each anecic earthworm species, the ecological impact of its below-ground casts is likely to be as important as its surface casts.

Entre 1999 i 2003 es va desenvolupar un projecte Life de restauració a la maresma de La Pletera, afectada per un pla urbanització, i a la llacuna del Ter Vell, amb un elevat grau d'eutròfia (aiguamolls del Baix Ter, NE Península Ibèrica). L'objectiu d'aquesta tesi és establir el funcionament d'ambdós ecosistemes, analitzar-ne la problemàtica ambiental i avaluar els efectes de la restauració. A la maresma de la Pletera, es va analitzar el paper de la hidrologia en la composició i dinàmica dels nutrients i del zooplàncton en cinc llacunes, tres de les quals havien estat creades dins el projecte de restauració com a nous refugis per una espècie de peix amenaçada (Aphanius iberus). La hidrologia es va caracteritzar per un llarg període de confinament sense entrades d'aigua, interromput de manera irregular per inundacions puntuals. La dinàmica del nitrogen inorgànic es va relacionar amb les entrades d'aigua, mentre que la del fòsfor, del nitrogen total i de la matèria orgànica es va relacionar amb els processos d'acumulació i reciclatge intern durant el confinament. El zooplàncton es va analitzar mitjançant la combinació d'aproximacions taxonòmiques i de mides. L'estructura de mides de la comunitat es va veure més afectada per les interaccions tròfiques (depredació i competència) mentre que l'estructura taxonòmica va ser més sensible a factors abiòtics (nutrients). El ràpid creixement de la població A. iberus en les noves llacunes va suggerir que aquestes havien proporcionat l'hàbitat adequat per a l'espècie, almenys a curt termini. Les actuacions de restauració a la llacuna del Ter Vell es van centrar en la millora de la qualitat de l'aigua mitjançant (1) la construcció d'uns aiguamolls per depurar l'aigua d'entrada i (2) el dragat del sediment en diversos punts. Simultàniament a la restauració, però de forma independent, la gestió agrícola de l'aigua va reduir dràsticament el cabal d'entrada d'aigua dolça a la llacuna, provocant un canvi en el règim hídric. Es van analitzar els efectes a curt termini d'aquest canvi sobre la limnologia i el zooplàncton de la llacuna. Abans del canvi, la hidrologia era artificial ja que s'havia prolongat l'entrada d'aigua dolça d'acord amb la demanda agrícola, i per tant la llacuna presentava una elevada taxa de renovació de l'aigua i majors concentracions de nutrients. Després del canvi, la hidrologia va dependre més del clima, es van reduir les entrades d'aigua i es va allargar el període de confinament. La composició y dinàmica dels nutrients va tendir a assemblar-se a l'observada a les llacunes de la maresma, mentre que la comunitat del zooplàncton no ho va fer. L'estat ecològic de la llacuna va millorar després del canvi en el règim hídric., Between 1999 and 2003, a restoration Life project was developed in La Pletera salt marshes, affected by an urbanisation plan, and in the Ter Vell lagoon, a highly eutrophic lagoon (Baix Ter Wetlands, NE Iberian Peninsula). The aim of this thesis is to establish the natural functioning of both ecosystems, analyze their environmental problematic and also to evaluate the effects of the restoration measures.In La Pletera salt marshes, the role of the hydrological regime in the nutrient and zooplankton composition and dynamics was analysed in five brackish lagoons. Three of them were created in the framework of the restoration project as new refuges for an endangered fish species (A. iberus). The hydrology was determined by a prolonged period of confinement without water inputs, irregularly interrupted by sudden flooding events. While the dynamics of inorganic nitrogen depended on the water inputs variability, dynamics of phosphorus, total nitrogen and organic matter was related more to the cumulative mechanisms and internal recycling during the confinement periods. The zooplankton community structure was analysed by means of the combination of taxon- and size-based approaches. Whereas the community size structure was more affected by trophic interactions (predation and competition), the taxonomic structure appeared to be more sensitive to abiotic factors (nutrients). The fast growth of the size population of A. iberus in the new lagoons suggested that they had provided a suitable refuge for this species, at least in the short-term.Restoration actions in the Ter Vell lagoon were focused on the improvement of the water quality by means of (1) wetlands construction to reduce nutrient inputs and (2) sediment dredging. Simultaneously, but independent of the restoration activities, water management in agriculture drastically reduced the freshwater inflow to the lagoon and, therefore, changed the hydrological regime. The short-term effects of this hydrological change on the limnological characteristics and the zooplankton of the lagoon were analysed. Before the change, the hydrology was artificial since the freshwater flooding period was prolonged due to the high agricultural demand. As a result, the lagoon showed a high water turnover rate and high nutrient concentrations. After the change, hydrology was climate-dependent, with scarce water inputs and prolonged confinement periods. Then, the nutrient composition and dynamics tended to be more similar to those observed in the salt marsh lagoons. However, zooplankton did not tend to resemble to that of the salt marsh lagoons. The ecological status of the Ter Vell lagoon was improved after the hydrological change.

A study was conducted to assess nutrient dynamics of soils under old and young cocoa, coffee and cashew plantations and the leaf nutrient contents of the crops at Uhonmora, Edo State, Nigeria for proper cultural and soil fertility management of the plantations. Soil and crop leaf samples were collected from each plantation using a random sampling technique. The samples were analyzed using standard procedures for sand, silt, clay, pH (H2O), electrical conductivity (EC), total N, available P, K, Ca, Mg, Na, and Effective Cation Exchange Capacity (ECEC). Leaf samples were analyzed for N, P, K, Ca, Mg and Na. Data were compared with the corresponding soil and foliar critical nutrient values for each crop. Results indicated that the soils were texturally sandy clay loam and acidic. The soils varied in their nutrient contents, with soil P for the old cocoa, young coffee and cashew plantations far below critical values. The young cashew plot was low in N content but adequate for other plots. However, the soil ECEC increased with the increasing of calcium contents. Leaf N was below critical for all the crops. Leaf K was low for cocoa and coffee plants, leaf Ca was low for the young cashew plants, while leaf Mg was low for the young cocoa and old cashew. The high soil Mg/K ratio of 8.7- 22.3 as against the established value of 2.0 might have resulted in gross nutrient imbalance which must have affected the absorption and utilization of other nutrients. Hence, adequate soil N did not translate the same availability to the crops. The ECEC showed that the soil needs to be improved upon for sustainable productivity. Soil nutrient content variation across the plantations with age of establishment will necessitate the need for consistent routine soil nutrient assessment for proper and balanced soil nutrient supply to the crops, for healthy crop growth and optimum yield. Management practices of soil surface mulching using organic wastes and cover crops under compatible cropping systems are needed for successful plot establishment and better growth performance of the young seedlings.Key words: Nutrient dynamics, plantation crops, rehabilitation, soil fertility management [How to Cite: Rotimi RI and JS Ogeh. 2014. Soil Nutrient Dynamics under Old and Young Cocoa, Coffee and Cashew Plantations at Uhonmora, Edo State, Nigeria. J Trop Soils 19(2): 85-90. Doi: 10.5400/jts.2014.19.2.85] [Permalink/DOI: www.dx.doi.org/10.5400/jts.2014.19.2.85]

This is a preliminary assessment of the relative contributions of the major driving forces related to climate change on nutrient dynamics in the Po catchment-North Adriatic Sea continuum has been performed adopting the Driver-Pressure-State-Impact-Response (DPSIR) approach. In the DPSIR analysis, major driving forces included both human and pseudo-natural drivers (not properly natural because they are of anthropogenic origin) (see Table VI.C.1). The nutrient loads (i.e. environmental 184 Pressures) deriving from these Drivers are reported (see Table VI.C.2) (ABP, 1999) in terms of "Potential" and "Effective" loads for both nitrogen and phosphorous. Table-2 suggests that the contribution of diffuse sources is higher (69%) than point sources (31%) for nitrogen, whereas for phosphorous point sources contribute with 62% of the total and diffuse sources with the remaining 38%.

The Northern German Wadden Sea is characterized as a natural eutrophic system, which is subjected to an additional anthropogenic nutrient input deriving mainly from the discharge of the Elbe river through its seaward border. Information about the distribution and transport of the nutrients near to the coast is still insufficient, since most of the previous measurements were restricted to the tidal inlets only. The aim of the present study is to set up a nutrient dynamic model which takes into account the main Wadden Sea specific processes governing the dissolved inorganic nutrient distribution in the shallow area. Investigations were carried out in a semi-enclosed tidal flat area known as the Meldorf Bight. The hydrodynamics in the area is mainly dominated by tidal forcing with the mean tidal range of about 3.5m. During low tide the tidal flat area is dry and it is flooded during high tide. First, seasonal nutrient gradients and their transport patterns were evaluated. The seasonal cycle of dissolved inorganic nitrogen compounds corresponds to the usual pattern in temperate seas with maxima in winter and minima in spring and summer. In the case of phosphate, high concentrations prevailed also in late summer, which is a result of remobilization from the temporary iron hydroxide sediment buffer. Nutrient concentrations during ebb tide were slightly higher than the concentrations during flood tide indicating the importance of local sources near the coast. Due to a strong tidal mixing, the vertical variation of nutrient concentrations was found to be insignificant. Computed net transports of nutrients were found to be slightly different for spring, summer and winter. Export of phosphate was observed in late summer. Results from small scale spatial measurements and from tidal nutrient cycles were used as a data basis to set-up the nutrient dynamic model. The Delft3D modelling system (Delft Hydraulics, The Netherlands) was employed for the numerical analysis of the flow and nutrient dynamics. The model was set-up for the simulation of nitrate, ammonium and phosphate gradients. Measured nutrient concentrations at the model open sea boundaries were used as input data. A sensitivity analysis with respect to the model parameters such as the dispersion coefficient was carried out. Due to the complexity of the natural processes, only the seasonal dominant ones were selected for the calibration. The model results were compared to the measured data. There is a good agreement in winter when the nutrients are conservative and biological processes are minimal. During spring the influence of local freshwater discharge deriving from the hinterland drainage was found to be significant. The model is capable of capturing the impact due to the freshwater releases. Main nutrient trends are relatively well estimated, especially for nitrate and phosphate. In summer, denitrification of nitrate as well as ammonification and phosphorus remineralisation were accounted for in the model calibration. Although the trends in ammonium are well predicted by the model, some discrepancies between the measured and computed concentrations are still significant. However, the results of model validation confirm the ability of the calibrated model in predicting the short term nutrient distribution in the investigation area. keine dt.-spr. Zusammenfassung vh.

Six seasonal measuring campaigns were performed in the period December 2000 to December 2001 in order to investigate the effects of anthropogenic nutrient enrichment on the seasonal dynamics of phytoplankton biomass and production in 3 Indonesian embayments subjected to a different degree of anthropogenic pressure. Jakarta Bay receives the highest riverine nutrient load (21260 t DIN/y), when compared to those of Lampung (5003 t DIN/y) and Semangka Bay (1378 t DIN/y). These high loads resulted in high concentrations of dissolved nitrogen, phosphate and silicate in the bay, with annual averages of 20 µM N, 5 µM P and 45 µM Si. In keeping with this, mean levels of chl-a and annual primary production were considerably higher than in the two other bays under investigation, accounting for 13 µg/l and 223 g C m^2 y^-1, respectively. Lampung Bay exhibited mean chl-a levels of 4 µg/l and an annual primary production of 89 g C m^2 y-1, whereas in the less nutrified Semangka Bay they were only 0.8 µg/l and 25 g C m^2 y^-1. The phytoplankton community was dominated by diatoms in all of the bays. The occurrence of dinoflagellates, chlorophyceae and cyanophyceae was mainly restricted to the river mouths and their surrounding waters. Evaluation of the trophic state (Marine Trophic Index TRIX) revealed that Jakarta Bay was the most eutrophied system, followed by Lampung and Semangka Bay. However, within each bay, distinct areas with different trophic levels could be distinguished, being highest near the coast. In total, spatial variability of parameters were much more pronounced than temporal variability, which is in keeping with the moderate meteorological fluctuations typical for tropical regions.

In shallow lakes, macrophytes have important effects on food webs, community structure and nutrient dynamics. For this reason they play a significant role in the restoration of degraded systems. Particularly when present with large coverage, they establish mechanisms favoring low phytoplankton biomass and a decrease of nutrient concentration in the water column. Even if these effects are documented from a number of systems, little evidence comes from shallow mountain lakes. In this study, we report temporal patterns of phytoplanktonic chlorophyll a and nutrient concentration in six eutrophic mountain ponds showing contrasting macrophyte coverage. Six ponds, situated in the Italian Apennines at altitudes ranging from 1164 to 1604 m, were monitored from March to November 1997. Four subsurface water samples were collected at each pond on every visit and analysed for chlorophyll a and nutrients following standard methods. Ponds were divided into two groups: vegetated (VP) and unvegetated (UP) according to their summer macrophyte coverage (respectively > 30% and < 30% of pond area). A nested ANOVA was used to detect macrophyte coverage, season and date (nested within season) effect on phytoplanktonic chlorophyll a concentration, dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP). Chlorophyll a was affected by coverage (P < 0.01) and by season (P < 0.05). In both groups chlorophyll a concentration increased from spring to summer, but differences were higher in UP than in VP. DIN was affected by coverage and season but temporal pattern was not consistent among UP and VP (interaction among coverage and season was significant, P < 0.01). SRP was not affected by coverage (P = 0.158) and season (P = 0.169). Our results on mountain ponds are consistent with those of similar lowland systems. We conclude that managing the presence of macrophytes can be an effective tool for the restoration of eutrophic shallow lakes also in mountain areas.

Neste trabalho, foram comparadas as características dos solos de áreas de floresta e áreas de pastagens, considerando quatro diferentes idades de instalação, em três sítios, no estado de Rondônia. Os sítios foram escolhidos com o auxílio de imagens do sensor TM/Landsat, obtidas entre 1987 e 1997, sendo dois em Argissolo Vermelho-Amarelo (PVA) e um em Luvissolo Crômico (TC). Amostras de solo foram colhidas na camada de solo a 20 cm e submetidas à análise de fertilidade e granulométrica, obtendo-se os dados de pH, bases trocáveis, fósforo disponível, saturação por alumínio e por bases e carbono orgânico. Para o solo distrófico e de baixa fertilidade natural (PVA), a adição de cinza proveniente da queima da floresta e os restos vegetais nos primeiros anos de implantação de pastagem influenciaram bastante a dinâmica de solo. Para os dois sítios de PVA, o nível de saturação por bases manteve-se superior na área de pastagem, mesmo com mais de 10 anos de uso, ao encontrado na área de floresta. Já o alumínio mostrou baixo nível após a implantação de pastagem em todas as classes de idade estudadas. O fósforo disponível sofreu queda rápida após atingir o valor de pico e, após um período de mais de 10 anos de uso com pastagem, apresentou valor praticamente igual ao original, nos dois tipos de solo estudados. No caso do solo eutrófico (TC), o efeito da cinza, em geral, foi de menor intensidade em relação ao do solo distrófico (PVA), mostrando alta perda de nutrientes no tempo, decorrente de fatores associados ao baixo teor de argila do solo e ao relevo local mais acentuado. In the State of Rondônia, Brazil, soil characteristics of forest and converted pasture areas were compared (four age classes). Adjacent areas of undisturbed natural forest were also surveyed for comparison. Based on the analysis of TM/LANDSAT images obtained between 1987 and 1997, three sites were selected for soil sampling. Two of these sites belong to the class "Argissolo Vermelho-Amarelo" (PVA - Ultisol), and the other to the "Luvissolo Crômico" (TC - Alfisol). The soil samples were collected at a depth of 20 cm, and fertility and texture analyses were carried out to obtain data on pH, exchangeable bases, available phosphorus, aluminum and base saturation, and organic matter values. Soil fertility in the dystrophic soil of low natural fertility (PVA) was strongly influenced by the incorporation of ashes derived from the burning of the primary forest and by the remaining vegetation in the first years after pasture implantation. Base saturation was higher in the two PVA pasture areas than in the forest, even after more than 10 years of use. On the contrary, the aluminum rate was lower in pastures after conversion in all investigated age classes. The values of available phosphorus dropped quickly after reaching a peak and returned to practically the original level after over 10 years of pasture utilization in both studied soil types. The eutrophic soil (TC) was less influenced by the effect of the ashes than the distrophic soil (PVA) and presented elevated nutrient leaching, due to factors related to the low clay content and the marked local topography.

As increased nutrient availability due to drainage is considered a major cause of eutrophication in wetlands rewetting of drained wetlands is recommended as a restoration measure. The effect of soil drying and rewetting on the contribution of various nutrient release or transformation processes to changed nutrient availability for plants is however weakly understood. We measured effects of soil drying and re-wetting on N mineralization, and denitrification, as well as on release of dissolved organic nitrogen (DON), phosphorus, and potassium in incubated soil cores from a wet meadow in southern Sweden. Additionally, the impact of re-wetting with sulphate-enriched water was studied. Soil drying stimulated N mineralization (3 times higher) and reduced denitrification (5 times lower) compared to continuously wet soil. In the wet cores, denitrification increased to 20 mg N m(-2) d(-1), which was much higher than denitrification measured in the field. In the field, increased inorganic-N availability for plants due to drainage seemed primarily to be caused by increased N mineralization, and less by decreased denitrification. Soil drying also stimulated the release of DON and K, but P release was not affected. Re-wetting of dried soil cores strongly stimulated denitrification (up to 160 mg N m(-2) d(-1)), but N mineralization was not significantly decreased, neither were DON or K release. In contrast, the extractable P pool increased upon soil wetting. Re-wetting with sulphate-enriched water had no effect on any of the nutrient release or transformation rates. We conclude that caution is required in re-wetting of drained wetlands, because it may unintendently cause internal eutrophication through an increased P availability for plants.

A three-year study was carried out in Las Tablas de Daimiel National Park, a Spanish semi-arid wetland, to describe eutrophication patterns and the responses of the main primaryproducers in contrasting inundation years. Total and dissolved nitrogen and phosphorus, phytoplankton chlorophyll-a(monthly) and emergent macrophyte cover (yearly) were measured together with water levels. Water balances were taken to assessphosphorus and nitrogen annual nutrient budgets. The wetland could be termed hypertrophic. Nutrients displayed distinct seasonality because nitrogen peaked both in winter and summer,whereas phosphorus did so in late spring and early summer. A reduction in both total nitrogen and phosphorus in humid yearsdue to higher water levels was also observed. An important spatial heterogeneity in nutrient content occurred throughout the study, part of which could be ascribed to hydrological fluctuations since the input site showed higher mean values in rainy years. Mass balances suggested that sedimentation played a key role in nutrient dynamics, with macrophyte leaching and waterfowl additions being minor sources. Internalloading was much higher than external loading in this wetland,thereby being responsible for higher sedimentation rates.Phytoplankton chlorophyll-a displayed seasonality, withpeaks in late summer, when macrophyte activity was decreasing.No relationship between either chlorophyll-a and nutrients or hydrological conditions could be ascertained formost sampling stations and years of study. However, the waterlevel-dependent, emergent macrophyte sawgrass (Cladium mariscus) presented a statistically significant relationship with both nitrogen and phosphorus. Our results demonstrate thatmacrophytes must be taken into account in wetland eutrophicationmodels. A conceptual model comparing the responses of primary producers to eutrophication in lakes and wetlands is outland, This research was funded by the Spanish Ministry of the Environment

Water flow through a plastic tunnel (1OL x 0.80W x 0.30H m) was used to determine nutrient retention and release rates over two substrates (with and without oysters) in a natural oyster bank at the northeastern end of the Cienaga Grande de Santa Marta. In general terms, nutrient fluxes are inversally related to the water flow. Values obtained over the substrate without oysters were higher than those observed over the substrate with oysters. Such differences can be explained by the low oyster density in the area and the great microbial activity and typical sediment diffusion processes in this estuarine ecosystem.Un flujo de agua a través de un túnel plástico (10 L x 0.80 W x 0.30H m) fue utilizado para determinar las tasas de liberación-retención de amonio y fosfatos sobre dos tipos de sustratos (con y sin ostras) en un banco de ostras en el sector nororiental de la Ciénaga Grande de Santa Marta. En general se observa que los flujos de amonio y fosfatos son inversamente proporcionales al caudal de agua, y que los valores obtenidos en el sustrato sin ostras son mayores comparados a los obtenidos en el sustrato con ostras. Estas diferencias entre los sustratos pueden haberse debido a la baja densidad de ostras en el área (7.5 ostras/ m2) y a la gran actividad microbiana y procesos de difusión de los sedimentos característicos de este ecosistema estuarino.

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2000, Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2000, Bu çalışma ile lagün sistemlerinde besi maddelerinin çevrimleri ile fiziksel kimyasal ve biyolojik dönüşümlerin daha iyi anlaşılması ve bu şekilde modelleme için gerekli mekanizmaların ortaya konması amaçlanmıştır. Bu yolla, Dalyan Lagünü’nün sürdürülebilir yönetim ve kirletici kaynakların kontrolü çalışmalarına katkıda bulunulması hedeflenmiştir. Dalyan Lagün sistemi, kanal sistemleri ve bu kanallara bağlı iki gölden; Sülüngür Gölü ve Alagöl oluşmaktadır. Hidrodinamik farlılıklar göz önüne alındığında kanallar ve göller ayrı ayrı değerlendirilmiştir. Nutirent çevrimlerini daha iyi anlayabilmek için, bölgeye yapılan 3 seferde, 16 izleme istasyonundan, yüzey ve dip olmak üzere iki farklı derinlikten su numuneleri alınmıştır. Temelde azot ve fosfor türleri ve çözünmüş reaktif silikat, klorofil-a ve partikül organik karbon ölçümleri yapılmıştır. Yapılan hidrodinamik değerlendirmeler sonucunda sistemde iki tabakalı akımın oluğunu ve tuzluluğun zamana ve mekana göre değişiklik gösterdiği görülmüştür. Baharda su kolonunda önemli ölçüde karışım olmakta ve sisteme tatlı su girdileri artmaktadır. Ölçülen kirletici konsantrasyonlarda büyük çalkalanmalar olmakta ve karasal kaynaklı kirletici yükleri artmaktadır. Sülüngür gölü dip sularında oksijenin ölçüm limitlerinin altında oluşu ve toplam azot ve toplam fosfor parametrelerindeki önemli artışlar, sedimentten suya nütrient salınımı olduğunu göstermektedir. Diğer taraftan, lagün sularının kalite sınıflandırması olmadığından, Dalyan Lagünü su kalitesi parametreleri mevcut ulusal standartlarla karşılaştırılmıştır., The aim of this study is to better understand the nutrient cycles together with their physical, chemical and biological transformations and thus to set the required mechanisms for modelling. In this manner, it is aimed to make contributions to the sustainable management and control of pollutant resources in Dalyan lagoon. Dalyan Lagoon system consists of channel systems and of two lakes; Sülüngür, Alagöl, joined to these channels. Considering the hydrodynamic differences, channels and lakes were evaluated separately. In order to understand the nutrient cycles, water samples were taken from two different depths in the form of surface and bottom water samples, at 16 monitoring stations along the channel system and lakes, during the 3 Cruises arranged to the region. Mainly nitrogen and phosphorus species, dissolved reactive silicate, chlorophyll-a and particulate organic carbon were analyzed. Hydrodynamic evaluations lead to the conclusion that, there existed a 2 layer flow in the system and variable salinity values prevail in the lagoon spatially and temporally. During spring period a significant mixing in water column occurs and the freshwater entering to the system increases. Therefore, big fluctuations in the measured concentrations occur and pollutant loads carried to the lagoon system from land increases. Dissolved oxygen concentrations below detection limit and significantly high concentrations of Total Nitrogen and Total Phosphorus, that found in Sülüngür Lake bottom waters indicate nutrient release from sediments. On the other hand, as there is no classification for lagoon waters, Dalyan Lagoon water quality parameters are compared with the existing national standards., Doktora, PhD