Estado actual del conocimiento y la conservación de los moluscos continentales de Costa Rica

Feeding Ecology and Development of Juvenile Black Ducks in Maine

Over the last decades, the application of calcitic materials to soil to restore the vigor of Sugar Maple (Acer saccharum Marsh) trees has increased in northeastern North America. However, few studies have evaluated how this treatment affects other ecosystem components, especially over several years. In Sugar Maple stands, the Eastern Red-backed Salamander (Plethodon cinereus Green, 1818) is one of the most abundant vertebrates and an important terrestrial species for key ecological processes. Because the species commonly serves as an indicator of forest disturbances, it is important to know how anthropogenic disturbances, such as soil liming, might affect it. The goal of this study was to evaluate the medium-term (5-year) effects of liming on body condition in a wild population of P. cinereus in Quebec, Canada. Lime (CaCO3) was spread by helicopter on a declining Sugar Maple forest growing on an acidic and base-poor soil. The results of this study, combined with those of previous published works, show that liming has no short- or medium-term effects on the body condition of the Eastern Red-backed Salamander. This study adds to those on other species in Europe and northeastern North America that report that liming has no major effect on amphibians when it is used as a treatment to restore acidified forest ecosystems. This should help foresters decide whether or not liming treatments are compatible with conservation, ecological, and management objectives.

Plant-soil interactions and soil carbon dynamics are an essential part of soil function. Land-use change can affect the soil’s ability to accumulate and store carbon. Deforestation and conversion to croplands has decreased tree species cover and diversity in the tropics resulting in degraded and secondary forests becoming the dominant forested habitat. Understanding the effects of forest degradation on soil carbon dynamics is vital if we are to remediate these ecosystems under climate change. The overarching aim of this thesis was understanding how changes in tree and plant species composition at different levels of degradation affect soil carbon dynamics and litter decomposition in the old and neo-tropics using litter transplant experiments in the field. Malaysia is one of the two biggest producers of palm oil in the world with Indonesia. Borneo is a biodiversity hotspot, but this ecosystem is decreasing at an alarming rate. Sabah, in norther Malaysian Borneo is converting its tropical forest to oil palm plantations resulting in vast expanses of oil palm monocultures containing secondary forest fragments at various degrees of degradation. In Central America, the tree cover is also dominated by secondary forests and timber plantations; in Panama, only 21 % of the tree cover classified as intact forest and there are remediation projects in place to encourage reforestation of degraded landscapes into plantations using native timber species. The level of degradation in the habitats changed the microclimate which affected soil properties, microbial activity and litter decomposition. Litter properties also had an effect on the rate of litter decomposition and microbial activity. The loss of tree cover in the deforested habitats and monocultures resulted in lower microbial activity and decomposition rates whereas the secondary forests has similar microbial activity and decomposition rates as the old growth forests. Overall, my results suggest that mixed litter inputs are crucial for maintaining soil function and that tropical forest soils might be more resilient to change than expected.

Biodiversity is the term given to the variety of life on Earth and the natural patterns it forms. The biodiversity we see today is the fruit of billions of years of evolution, shaped by natural processes and, increasingly, by the influence of humans. It forms the web of life of which we are an integral part and upon which we so fully depend. Biological resources are the pillars upon which we build civilizations. Nature's products support such diverse industries as agriculture, cosmetics, pharmaceuticals, pulp and paper, horticulture, construction and waste treatment. The loss of biodiversity threatens our food supplies, opportunities for recreation and tourism, and sources of wood, medicines and energy. It also interferes with essential ecological functions. While the loss of individual species catches our attention, it is the fragmentation, degradation, and outright loss of forests, wetlands, coral reefs, and other ecosystems that poses the gravest threat to biological diversity. While loss of species has always occurred as a natural phenomenon, the pace of extinction has accelerated dramatically as a result of human activity. Ecosystems are being fragmented or eliminated, and innumerable species are in decline or already extinct. In this context this study has tried to bring out an assessment of the biodiversity in the Ratapani Forests block of Dungarpur range. Pure stand of Tectona Grandis can be seen in Dungarpur district where it dominates the vegetation but in varied degree of degradation due to biotic influence. Associated trees seen in the area are Diospyros melanoxylon, Aegle marmelos, Anogeissus latifolia(which is the most common), Bauhinia racemosa, Soymida febrifuga, Mitragyna parvifolia and Terminalia tomentosa. Undergrowth plant varieties cover Nyctanthes arbor-tristis, Carissa opaca etc. The present study found that the increasing pressure of both human and livestock population is taking a heavy toll on the biodiversity of the area particularly in terms of rapid falling of trees and excessive grazing of livestock. On the flat plateau and ridges of the hills most of the fertile soil has been washed away due to serious erosion and these areas are not capable for good teak growth. It is therefore suggested that as the soil of hilly and plateau tracks is fragile and has a thin horizon so these areas must be monitored very closely so that the soil erosion due to removal of vegetation cover can be checked by planting of new saplings which can bind the soil in short term and then these areas too can be made viable to support the teak vegetation as they were supporting prior to the deterioration conditions were set in. The study also suggests various ways and means to arrest the degradation of biodiversity in the area and to regenerate the forest cover on the patches which are rendered barren due to manmade practices.

Land use change is one of the major challenges currently facing the worlds many forests and a major threat to the availability of ecosystem services and sustainable development. These land uses include changing forested lands to agricultural land. Most of the indigenous forests in Kenya are located on mountains. These forests include: Elgon, Kenya, Aberdares, Cherangani and the Mau. The forests provide the country with essential ecosystem services which include being a catchment to Kenya’s major rivers. The Kenya’s indigenous mountain forests are highly vulnerable to the impacts of unsustainable land use changes and this is evidenced by many disasters that have afflicted the forests and the local communities over the recent past. Demographic, institutional, economic and socio cultural factors play a critical role of being drivers of these land use changes. It is expected that land-use management should successfully address these challenges and ensure risk reduction. Unfortunately this is lacking. Drawing upon the available literature and field research, this paper synthesizes the factors responsible for the vulnerability of Kenya’s major forest resources and the impacts of land use change on ecosystem services in the 21st Century in Kenya. Achieving sustainable development in our environment will requires planned change to the way in which the land bordering the forest and forest resources are utilized. Referred to as the ‘water towers of the world’, mountain forest ecosystems cover about twenty seven (27%) of the world’s land surface and directly support twenty two (22%) of the world’s population and provide the freshwater needs for more than half of humanity (Convention on Biological Diversity 2010). Most of the indigenous forests in Kenya are located on mountains. These forests include: Elgon, Kenya, Aberdares, Cherangani and the Mau. These forests are biologically diverse and contain numerous local endemic plant and animal species. Similarly Kenya's hydrology is characterized by four major rivers (the Tana, Mara, Yala and Nzoia river basins); all originating from these forested water towers.

Effects of grassland management on plants and invertebrates in Transylvania, Romania : a threat to local biodiversity hotspots

The relationship between plant biodiversity and soil chemical fertility has been widely investigated in temperate forests and agroecosystems, but there is lack of information about the correlation between these two variables in tropical forests. In this study, the relationship between plant biodiversity and soil chemical fertility was analyzed in a mature tropical forest in Costa Rica. Soil samples were collected in 9 sampling plots (5 m by 25 m) in order to identify the concentration level of P, K, Ca, Mg, Fe, Zn, Mn, and Cu, the soil fertility index, the CEC, and the C/N ratio. Furthermore, species richness, Shannon-Wiener and Simpson’s species diversity, structural richness, and structural diversity were determined for each of the 9 sampling plots. Simple linear regression analysis was used to determine if there was a significant relationship between any of the different variables of plant biodiversity and soil chemical fertility. Tree species richness was inversely related to concentration levels of K, Ca, and P, CEC, and soil fertility index. These results agree with the few studies that were done in tropical ecosystems. Higher tree species richness tended to be found in sites with lower soil fertility. Shannon-Wiener tree species diversity was positively correlated to C/N ratio. This is a new discovery and it seems that there is less N stored in organic matter compared to C in sites with higher species diversity. Herb structural richness was positively related to soil fertility index and P concentration. The herb community may be able to grow taller in soil with higher P content and soil fertility leading to higher structural richness because P is the main soil factor limiting growth in tropical ecosystems. There was a positive relationship between herb structural diversity and Mn concentration in the soil. Therefore, structural diversity is not affected much by soil fertility. No relationship was found among any of the other variables. This study gives important insights on the ecological relationship between plant biodiversity and soil chemical fertility in primary tropical forest stands.

Ecological impact of phytoinvasions in Ukraine

Motorized trawl fishing is considered highly predatory due to the accidental capture of numerous organisms. Based on the context and due to the need for knowledge about the malacofauna associated with industrial fishing in the Amazonian Platform, the present study aims to characterize the accompanying malacofauna. The samples were collected in 2016, 2017 and 2018, 250 trawls were monitored. 30 and 80 meters in 22 fisheries, 4,834 molluscs were collected, distributed in five classes (Bivalvia, Cephalopoda, Gastropoda, Polyplacophora and Scaphopoda), and 81 species. The class that presented the greatest diversity was the gastropod followed by the bivalves in relation to abundance. The species that stood out were the cephalopods Doryteuthis sp. e Lolliguncula brevis, the gastropods Hydatina physis; Marsupina bufo; Tonna galea; Turbinella laevigata; Stigmaulax cayenensis; Calyptraea centralis; Conasprella janowskyae and Polystira coltrorum, the abundance model that characterizes the region and the geometric type, where few species are dominant and the other rare species. The area studied is important in terms of conservation of marine biodiversity given the presence of species of economic interest and the existence of a wide diversity of species. Keywords: mollusk, diversity, invertebrates, amazonian platform.

Literature is replete with evidence of deforestation of the tropical forest. In Nigeria, studies on deforestation also abound. This report, which is built on the government forests in South West Nigeria attempts to provide a basic linkage between deforestation and endangered indigenous tree species. Endangered indigenous forest trees in South West Nigeria are further threatened by lack of commitment and business as usual. Deforestation is highly severe and this continues unabated. The stock of the forest is depleted by agents such as saw millers and fuel wood gatherers. They constitute 42% of the agents of deforestation. On the scale of threat, Miliciaspecies comes first with a level of 26, followed by Triplochyton scleroxylon with 20 on the threat incident scale while Khaya species and Mansonia species comes next with a threat incident level of 17. The ratio of regeneration in general is, one cut to two replenishment but the replenishment is based on coppicing, which limits the power of the forest to replace lost volumes. Deforestation apart from its direct effect on endangered indigenous tree species impacts negatively on food supply, soil and landscape of South West Nigeria. For improvement to be engendered in the Zone, more Education is needed for the entire citizenry on the need to conserve the endangered species as well as making sure that forest policies are well fashioned out and followed to the latter, to safeguard the tree species from extinction. Key words: Deforestation, endangered species, non-timber forest products, greenhouse, depletion.

The functioning and services of Central European forests are threatened by global change and a loss of biodiversity. Nutrient cycling as a key forest function is affected by biotic drivers (e.g., dominant tree species, understory plants, soil organisms) that interact with abiotic conditions (e.g., climate, soil properties). In contrast to grassland ecosystems, evidence for the relationship of nutrient cycles and biodiversity in forests is scarce because the structural complexity of forests limits experimental control of driving factors. Alternatively, observational studies along gradients in abiotic conditions and biotic properties may elucidate the role of biodiversity for forest nutrient cycles. This thesis aims to improve the understanding of the functional importance of biodiversity for nutrient cycles in forests by analyzing water-bound fluxes of nitrogen (N) and phosphorus (P) along gradients in biodiversity in three regions of Germany. The tested hypotheses included: (1) temperate forest canopies retain atmospheric N and retention increases with increasing plant diversity, (2) N release from organic layers increases with resource availability and population size of decomposers but N leaching decreases along a gradient in plant diversity, (3) P leaching from forest canopies increases with improved P supply from recalcitrant P fractions by a more diverse ectomycorrhizal fungal community. In the canopies of 27 forest stands from three regions, 16 % to 51 % of atmospheric N inputs were retained. Regional differences in N retention likely resulted from different in N availability in the soil. Canopy N retention was greater in coniferous than in beech forests, but this was not the case on loessderived soils. Nitrogen retention increased with increasing tree and shrub diversity which suggested complementary aboveground N uptake. The strength of the diversity effect on canopy N uptake differed among regions and between coniferous and deciduous forests. The N processing in the canopy directly coupled back to N leaching from organic layers in beech forests because throughfall-derived N flushed almost completely through the mull-type organic layers at the 12 studied beech sites. The N release from organic layers increased with stand basal area but was rather low (< 10 % of annual aboveground litterfall) because of a potentially high microbial N immobilization and intensive incorporation of litter into the mineral soil by bioturbation. Soil fauna biomass stimulated N mineralization through trophic interactions with primary producers and soil microorganisms. Both gross and net leaching from organic layers decreased with increasing plant diversity. Especially the diversity but not the cover of herbs increased N uptake. In contrast to N, P was leached from the canopy. Throughfall-derived P was also flushed quickly through the mull-type organic layers and leached P was predominantly immobilized in non directly plant-available P fractions in the mineral soil. Concentrations of plant-available phosphate in mineral soil solution were low and P leaching from the canopy increased with increasing concentrations of the moderately labile P fraction in soil and increasing ectomycorrhiza diversity while leaf C:P ratios decreased. This suggested that tree P supply benefited from complementary mining of diverse mycorrhizal communities for recalcitrant P. Canopy P leaching increased in years with pronounced spring drought which could lead to a deterioration of P supply by an increasing frequency of drought events. This thesis showed that N and P cycling in Central European forests is controlled by a complex interplay of abiotic site conditions with biological processes mediated by various groups of organisms, and that diverse plant communities contribute to tightening the N cycle in Central European forests and that diverse mycorrhizal communities improve the limited P availability. Maintaining forest biodiversity seems essential to ensure forest services in the light of environmental change.

DEVELOPMENT OF SOIL AND LITTER ARTHROPOD ASSEMBLAGES IN RAINFOREST RESTORATION

Stratégies villageoises pour la gestion des paysages forestiers du Menabe Central, Madagascar

ObjectiveThe objectives of this paper were to review and synthesizes the research programs which were conducted in the field of change of forest vegetation and the evolution of soil erosion in Southeast Asia, and to discuss the effectiveness of improved conservation practices on managing soil erosion and sediment yield at catchment scale. MethodsThe forest vegetation change countermeasures at different spatial and temporal scales were analyzed according to data from countries in Southeast Asia. This paper focused on an extensive range of methodologies at different spatial and temporal scales. The research area was the region selected for the implementation of watershed management in Thailand. The efficacy and practicality of passive and active erosion control strategies were expounded. Results① Forest loss in Southeast Asia had remained at high levels during the period from 2000 to 2005, accumulating to an annual deforestation rate of about 2.76×106 ha. However, forest cover has increased in the recent years due to the establishment of forest plantations. ② Southeast Asian haze was a large-scale air pollution problem that occurs regularly. The haze was largely caused by illegal agricultural fires. ③ Soil erosion control strategies for manage soil erosion in Southeast Asia include alley cropping, contouring, strip cropping, grass barriers, conservation tillage, minimum tillage and hedgerow inter-cropping. Despite the role of conservation practices being well established in reducing water runoff at the plot scale, extrapolation to a large scale, it has been less understood and verified. The potential impact of soil conservation on yield may be a key factor that affects the value of soil conservation investments. ConclusionThe challenge of forest vegetation change in Southeast Asia is real and urgent. Regional prevention and control mechanisms should be constructed to decrease forest fire and haze. To decrease soil erosion, we should keep a sustainable forestry and sustain terrestrial biodiversity. Selection of appropriate soil conservation methods for low income smallholder farmers is critical to reduce the rate of soil erosion as well as to increase crop productivity.

1. Land set aside for preservation of biodiversity often has low productivity. As biodiversity generally increases with productivity, due to higher or more diverse availability of resources, this implies that some of the biodiversity may be left unprotected. Due to a lack of knowledge on the species diversity and conservation value of low-productivity habitats, the consequences of the biased allocation of low-productivity land for set-asides are unknown. 2. We examined the conservation value of boreal low-productivity forests (potential tree growth < 1 m3 ha-1 year-1) by comparing assemblages of tree- and deadwood-dwelling lichens and forest stand structure between productive and low-productivity forest stands. We surveyed 84 Scots pine-dominated stands in three regions in Sweden, each including four stand types: two productive (managed and unmanaged) and two low-productivity stands (on mires and on thin, rocky soils). 3. Lichen species richness was highest in low-productivity stands on thin soil, which had similar amounts and diversity of resources (living trees and dead wood) to productive unmanaged stands. Stands in low-productivity mires, which had low abundance of living trees and dead wood, hosted the lowest lichen richness. Lichen species composition differed among stand types, but none of them hosted unique species. The differences in both species richness and composition were more pronounced in northern than in southern Sweden, likely due to shorter history of intensive forestry. 4. Synthesis and applications: Boreal low-productivity forests can have as high conservation value as productive forests, which should be reflected in conservation strategies. However, their value is far from uniform, and conservation planning should acknowledge this variation and not treat all low-productivity forests as a uniform group. Some types of low-productivity forest (e.g. on thin soil) are more valuable than others (e.g. on mires), and should thus be prioritized in conservation. It is also important to consider the landscape context: low-productivity forests may have higher value in landscapes where high-productivity forests are highly influenced by forestry. Finally, although low-productivity forests can be valuable for some taxa, productive forests may still be important for other taxa.