Spatio-temporal analysis of alpine ecotones: A spatial explicit model targeting altitudinal vegetation shifts

There is general agreement in literature that Alpine vegetation belt ecotones have shown a trend of upward migration in the last few decades. Despite the potential of such shifts as indicators of global change effects in mountain ecosystems, there are relatively few works focused on their assessment in a systematic and spatially explicit way. In this work our aim is to quantify the altitudinal shifts and analyse the spatial pattern dynamics of mountain ecotones. We developed a novel procedure to delineate the current and former state of three characteristic mountain ecotones, which we formalised as forest, tree and tundra lines. Our approach is based on the recognition of altitudinal extreme outposts identified with ecotone locations at a slope scale. The integration of multi-temporal datasets allows the identification and quantification of altitudinal advances and retreats in the outpost locations for a given period. We tested the method in a section of the Italian Alps for the period 1957-2003. Results show a general trend of an increase in altitude for the three ecotones, despite the occurrence of occasional decreases. We estimate decadal altitude increments of 25 m for forest line, 13 m for treeline and 11 m for tundra line. We also identified changes in ecotone spatial morphology between the two dates, with significant implications in connectivity and colonisation dynamics.     

Social monogamy in the shrimp Pontonia margarita, a symbiont of Pinctada mazatlanica, off the Pacific coast of Panama

A previous study predicted the evolution of monogamy in symbiotic crustaceans inhabiting scarce, relatively small hosts in tropical environments where predation risk away from hosts is high. This prediction was tested in the shrimp Pontonia margarita, which inhabits the pearl oyster Pinctada mazatlanica. A total of 68 oysters were collected from the intertidal and shallow subtidal at two islands (Islas Secas [N 27° 55′, W 82° 03′] and Isla de La Coiba [N 27° 50′, W 97° 03′]) off the eastern tropical Pacific coast on 15 and 17 March 2007, respectively. The population structure, distribution, male-female association pattern, and relative growth of the major claw and pleura of the second abdominal segment of each shrimp retrieved were examined. Shrimps were found as heterosexual pairs in the mantle cavity of hosts more frequently than would be expected by chance alone. Males occurred with females in the same host, independent of the reproductive condition of the female or the stage of development of brooded embryos. This observation, and strong correlations between the host and shrimp body size in both males and females suggest a long-term association between males and females in each host. Sexual dimorphism in body size was minor, with males being just slightly smaller than females. In agreement with predictions for monogamous species, the major claw of males did not display positive allometry, which has been generally reported for polygamous shrimps. In turn, the pleura of the second abdomen presented negative allometry in males but positive allometry in females. All available information suggests that Pontonia margarita has a socially monogamous mating system with males and females forming exclusive pairs in their hosts.     

Assessment of groundwater quality by means of self-organizing maps: application in a semiarid area

The Kohonen neural network was applied to hydrochemical data from the Detritic Aquifer of the Lower Andarax, situated in a semiarid zone in the southeast of Spain. An activation map was obtained for each of the sampling points, in which the spatial distribution of the activated neurons indicated different water qualities. To extract the information contained in the activation maps, they were divided into nine quadrats. Cartesian coordinates were assigned to each quadrant (x, y), and for each sampling point, three derived variables were selected, which were assigned the values x and y of the corresponding quadrat. A classification was defined based on this simple matrix system which allows an easy and rapid means of evaluating the water quality. This assessment highlights the various processes that affect groundwater quality. The method generates output that is easier to interpret than from traditional statistical methods. The information is extracted from the activation maps without significant loss of information. The method is proposed for assessing water quality in hydrogeochemically complex areas, where large numbers of observations are made.     

Roadside habitats: a missing link in the conservation agenda

Roadside habitats in Brazil have been and remain major suppliers of biological diversity and plant genetic resources to society. If the ultimate demise of these habitats is to be avoided, their inclusion in conservation policy planning is mandatory.     

Heavy metal accumulation by the halophyte species Mediterranean saltbush

To identify Cd- and Zn-accumulating plants exhibiting a high growth rate, seeds from the halophyte species Mediterranean saltbush (Atriplex halimus L.) were collected on a heavy-metal-contaminated site in southeastern Spain (Llano del Beal, Cartagena). Seedlings from this ecotype were exposed for 3 wk to 0.1 mM Cd or Zn in a nutrient solution in a fully controlled environment. All plants remained alive and no significant growth inhibition was recorded until the end of the experiment. Mean Cd and Zn accumulation in aerial parts was 830 and 440 mg kg(-1), respectively, and the rate of metal translocation even increased with the duration of stress exposure. Resistance to heavy metals in this species may be partly linked to precipitation of Cd in oxalate crystals in the stems. A Cd-induced decrease in glutathione concentration also suggests that phytochelatins overproduction may occur in these conditions. We conclude that Mediterranean saltbush, which is able to produce up to 5 Mg dry matter ha(-1) yr(-1), may be an effective species for phytoextraction and should be tested for this purpose in field conditions.     

Root growth and metal uptake in four grasses grown on zinc-contaminated soils

Depth and area of rooting are important to long-term survival of plants on metal-contaminated, steep-slope soils. We evaluated shoot and root growth and metal uptake of four cool-season grasses grown on a high-Zn soil in a greenhouse. A mixture of biosolids, fly ash, and burnt lime was placed either directly over a Zn-contaminated soil or over a clean, fine-grained topsoil and then the Zn-contaminated soil; the control was the clean topsoil. The grasses were 'Reliant' hard fescue (Festuca brevipila R. Tracey), 'Oahe' intermediate wheatgrass [Elytrigia intermedia (Host) Nevski subsp. intermedia], 'Ruebens' Canada bluegrass (Poa compressa L.), and 'K-31' tall fescue (Festuca arundinacea Schreb.). Root growth in the clean soil and biosolids corresponded to the characteristic rooting ability of each species, while rooting into the Zn-contaminated soil was related to the species' tolerance to Zn. While wheatgrass and tall fescue had the strongest root growth in the surface layers (0-5 cm) of clean soil or biosolids, wheatgrass roots were at least two times more dense than those of the other grasses in the second layer (5-27 cm) of Zn-contaminated soil. When grown over Zn-contaminated soil in the second layer, hard fescue (with 422 mg/kg Zn) was the only species not to have phytotoxic levels of Zn in shoots; tall fescue had the highest Zn uptake (1553 mg/kg). Thus, the best long-term survivors in high-Zn soils should be wheatgrass, due to its ability to root deeply into Zn-contaminated soils, and hard fescue, with its ability to effectively exclude toxic Zn uptake.     

Testing soils and cornstalks to evaluate nitrogen management on the watershed scale

High nitrate (NO3-N) concentrations in Iowa rivers have been linked to areas of intensive row crop production, but they have not been experimentally linked to specific management practices used during row crop production. This study demonstrates how the late-spring test for soil NO3-N and the end-of-season test for cornstalk NO3-N can be used to measure N sufficiency levels across many fields and how the results can be used to evaluate management practices within a watershed. More than 3200 soil and cornstalk samples were collected over a 12-yr period from fields planted to corn (Zea mays L.) and already fertilized by farmers using their normal practices. Results showed that early-season rainfall and associated N losses were major factors affecting N concentrations in soils and cornstalks. Evidence for NO3-N movement from fields to rivers was provided by an inverse relationship between annual means for NO3-N concentrations in soils and rivers. Because these losses can be avoided by delaying N applications, the practice of applying N several weeks or months before plants grow was linked to inefficient use of fertilizer and manure N by crops. Results of the study demonstrate how aggregate analyses of soil and cornstalk samples collected across many farms and years make it possible to identify the major factors affecting N management outcomes and, therefore, N management practices that are likely to produce the best outcomes within a watershed or region. This approach seems to have unique potential to interrelate the management practices of farmers, the efficiency of N fertilization, and NO3-N concentrations in rivers.     

Manatee Mortality in Puerto Rico

Trichechus manatus ) in Puerto Rico is mortality due to human activities. We assessed 90 cases of manatee strandings in Puerto Rico based on historical data and a coordinated carcass salvage effort from 1990 through 1995. We determined patterns of mortality, including type of event, condition of carcasses, spatial and temporal distribution, gender, size/age class, and the cause of death. The spatial distribution of stranding events was not uniform, with the north, northeast, and south coasts having the highest numbers. Six clusters representing the highest incidence included the areas of Fajardo and Ceiba, Bahía de Jobos, Toa Baja, Guayanilla, Cabo Rojo, and Rio Grande to Luquillo. The number of reported cases has increased at an average rate of 9.6%/yr since 1990. The seasonality of stranding events showed a bimodal pattern, from February through April and in August and September. Most identified causes of death were due to human interaction, especially captures and watercraft collisions. Natural causes usually involved dependent calves. From 1990 through 1995, most deaths were attributed to watercraft collisions. A reduction in anthropogenic mortality of this endangered species can be accomplished only through education and a proactive management and conservation plan that includes law enforcement, mortality assessment, scientific research, rescue and rehabilitation, and inter- and intraagency cooperation.     

An inverse approach for piping networks monitoring

Spills and leakages of hazardous fluids from piping networks may pose a significant safety risk to population, industrial plants and the environment. Therefore in fluid distribution the problem of monitoring the network status in order to identify abnormal conditions and locate leakages arises. In the paper an inverse approach resorting to a multi-layer perceptron back-propagation Artificial Neural Network (ANN) is proposed, in order to locate leakages based on pressure and flow rate information. Strategies for generating input data and for correlating by ANN such data to the fluid distribution system status are presented. A two-level architecture is selected, composed by a main ANN at the first level and several branch-specific second-level ANNs in cascade to the main one. The branch in which the leakage occurs is identified, resorting to the ANN operating at the first level, while the specific second-level ANN is activated to estimate accurately the magnitude and location of the leakage in the selected branch.