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Peguero G.,Autonomous University of Barcelona | Lanuza O.R.,National Autonomous University of Nicaragua, Managua | Save R.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Espelta J.M.,Autonomous University of Barcelona
Plant Ecology | Year: 2013

Secondary succession after land abandonment in tropical dry forests has been suggested to be favoured by the facilitation effects for seedling establishment exerted by pioneer trees isolated in these savannah-like landscapes. However, it has also been noticed that these pioneer species may sometimes have an encroaching effect and arrest succession for several decades. We investigated in this study whether allelopathy can play a role in limiting seedling establishment of co-occurring tree species under the canopy of Acacia pennatula by means of lab bioassays and field experiments in north-west Nicaragua. Leaf extracts of A. pennatula did not affect seed germination but reduced the general growth and especially the development of the root compartment in seedlings, shifting their biomass allocation model to a reduced root/shoot ratio. Survival of planted seedlings under the canopy of A. pennatula was about 20-30% lower than outside, and this reduction was particularly pronounced as the dry season progressed, despite the milder conditions (e. g. higher soil moisture) being experienced in the inner positions under the canopy. Altogether, our results suggest that, rather than facilitating, A. pennatula may inhibit the establishment of seedlings under its canopy probably by means of an allelopathic interference in the development of the root system with critical negative consequences for young seedlings in terms of overcoming the dry season. This article warns about overemphasizing the nucleation effect that remnant and isolated trees may have to facilitate secondary succession in these highly disturbed savannah-like tropical dry forests. © 2011 Springer Science+Business Media B.V. Source


Munoz-Antoli C.,University of Valencia | Pavon A.,National Autonomous University of Nicaragua, Managua | Marcilla A.,University of Valencia | Toledo R.,University of Valencia | Esteban J.G.,University of Valencia
Tropical Biomedicine | Year: 2011

A cross-sectional study of cryptosporidiosis was carried out in Nicaragua. The prevalence of Cryptosporidium infection was determined in 272 (110 boys and 162 girls) schoolchildren, aged between 4 to 15 years from department of Rio San Juan. The total percentage obtained for Cryptosporidium (35.7%) was one of the highest reported so far. Cryptosporidium appeared in 94.8% of multiparasitism cases. No significant statistical differences were detected in the cryptosporidiosis prevalence between loose/watery (22.2%) and soft/formed (36.7%) stool samples. No significant age and sex differences were observed. This is the first report to identify Cryptosporidium in Nicaragua at species level, providing a preliminary molecular characterization of all positive samples, such as Cryptosporidium parvum (genotype 2). The high prevalence of C. parvum suggests that animals may be potential sources of infection for human cryptosporidiosis, although C. parvum infections may have originated from humans themselves. The human health problem caused by Cryptosporidium in this region may be related to the poor human hygiene/sanitation and contamination of the environment, food, or water supplies. Continuous exposure to the parasite could have been protective against development of symptoms in the children examined. Source


Calderon H.,National Autonomous University of Nicaragua, Managua | Uhlenbrook S.,Technical University of Delft
Hydrological Sciences Journal | Year: 2016

The water balance dynamics and runoff components of a tropical forested catchment (46 km2) on the southwestern Pacific coast of Nicaragua were studied combining hydrometry, geological characterization and hydrochemical and isotopic tracers (three-component hydrograph separation). The climatic water balance was estimated for 2010/11, 2011/12 and 2012/13 with net values of 811 mm year-1, 782 mm year-1 and –447 mm year-1, respectively. Runoff components were studied at different spatial and temporal scales, demonstrating that different sources and temporal contributions are controlled by dominant landscape elements and antecedent rainfall. In forested sub-catchments, permeable soils, stratigraphy and steep slopes favour subsurface stormflow generation contributing 50% and 53% to total discharge. At catchment scale, landscape elements such as smooth slopes, wide valleys, deeper soils and water table allow groundwater recharge during rainfall events. Groundwater dominates the hydrograph (50% of total discharge) under dry prior conditions. However, low soil infiltration capacity generates a larger surface runoff component (42%) under wet prior conditions which dominates total discharge. Our results show that forested areas are important to reduce surface runoff and thus soil degradation, which is relevant for the design of water management plans.EDITOR D. KoutsoyiannisASSOCIATE EDITOR D. Gerten © 2016 IAHS Source


Flores K.E.,Brooklyn College | Flores K.E.,American Museum of Natural History | Skora S.,ETH Zurich | Martin C.,American Museum of Natural History | And 3 more authors.
International Geology Review | Year: 2015

The Siuna Serpentinite Mélange (SSM) is a subduction-zone-related complex that contains diverse blocks of igneous and sedimentary origin, overprinted by various metamorphic conditions. The SSM is located at the southern border of the Chortís block and marks the boundary between continental and oceanic crusts in the western margin of the Caribbean Plate. The serpentinite matrix mainly consists of lizardite/chrysotile, Cr-rich spinel, and relict orthopyroxene that suggest a harzburgitic protolith and an upper mantle supra-subduction zone origin. Blocks within the southern and central regions range from Jurassic pelagic sediments to mafic/intermediate igneous rocks that are metamorphosed to various degrees, ranging from prehnite-pumpellyite/greenschist to likely blueschist facies (e.g. riebeckite-bearing metashale) conditions. In contrast, the northern section encloses almost exclusively epidote-amphibolite facies metabasite blocks, and minor mica- and chlorite-rich rocks of metasomatic origin, respectively. Some of the epidote-amphibolite blocks contain relic garnet-rich zones embedded in an amphibole-rich matrix. The garnets appear to record two generations of growth and contain mineral inclusions such as amphibole, apatite, titanite, aegirine-augite, and quartz. Thermobarometric estimates for the garnet-rich zones and epidote-amphibolite-rich matrix suggest a prograde blueschist facies at ~1.2 GPa and 400-450°C, an eclogite facies metamorphic peak at 1.5-1.7 GPa and 565-614°C, and a post-peak epidote-amphibolite facies metamorphism. These pressure and temperature estimates indicate a classical clockwise PT path that has been observed in many palaeo-subduction zone environments worldwide. Phengite Ar-Ar dating of mica-rich rock yields 140 Ma and suggests an Early Cretaceous exhumation along the southern edge of the continental Chortís block. © 2015 © 2015 Taylor & Francis. Source


Hilmo O.,Norwegian University of Science and Technology | Gauslaa Y.,Norwegian University of Life Sciences | Rocha L.,National Autonomous University of Nicaragua, Managua | Lindmo S.,Norwegian University of Science and Technology | Holien H.,Nord-Trondelag University College
Botany | Year: 2013

All specimens of three foliose lichens (Lobaria pulmonaria (L.) Hoffm., n = 725; Lobaria scrobiculata (Scop.) DC., n = 6613; Pseudocyphellaria crocata (L.) Vain., n = 1237) and two pendulous lichens (Alectoria sarmentosa (Ach.) Ach., n = 441; Ramalina thrausta (Ach.) Nyl., n = 990) were collected from 160 random Picea abies (L.) H. Karst. branches (2-15 m above the ground) in three spruce-dominated boreal rainforests in Norway. Maximum diameter (foliose lichens), length (pendulous lichens), and reproductive structures were quantified in each thallus. The effects of measured tree and branch variables on abundance and reproduction were tested by generalized linear mixed models with binomial errors (binomial GLMM) and zero-altered (over-dispersed) Poisson generalized linear mixed models (ZAPGLMM). Lobaria pulmonaria, P. crocata, and R. thrausta occurred predominantly in the lower canopy, whereas the remaining species were also common at higher levels. The portions of thalli producing soredia and (or) isidia were 60%, 22%, and 14% for P. crocata, L. scrobiculata, and L. pulmonaria, respectively. Isidiate and (or) sorediate L. pulmonaria thalli occurred mainly on low, dead branches, whereas sorediate L. scrobiculata and P. crocata occurred at all heights. The occurrence of small P. crocata, <5 mm, decreased by branch height and small L. scrobiculata, <5 mm, increased with branch length and decreased with tree age. Upper branches supported a significant part of the total populations of studied lichens and are, thus, important when evaluating epiphyte conservation status. Source

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