Ecosystem Demand Research Articles

Foreste, boschi, arboricoltura da legno

In protected areas the forest ecosystem management is directed to define the best approaches with high protection levels from ecological, historical, anthropological and landscape point of view. The conservation purposes have to be taken in consideration to not disturb the natural and functional processes, and therefore any forest human activity has to be done. Through a detailed analysis of the relations among functionality, stability, productivity and genetic diversity, the statement of the reasons for application of close-to-nature silviculture is described and discussed. Some specific silvicultural systems are illustrated on the basis of very large quantity of data and information originated from researches carried out for long time. A major challenge facing modern silviculture is to reconcile the traditional objectives of timber production with the demand for multifunctional forest ecosystems which arises from the society. The preservation of the functionality is strictly related to the forest genetic pool which is the basis of biodiversity, as it represents the basis for adaptation and survival of species and individual.

On effects of trawling, benthos and sampling design

The evidence for the wider effects of fishing on the marine ecosystem demands that we incorporate these considerations into our management of human activities. The consequences of the direct physical disturbance of the seabed caused by towed bottom-fishing gear have been studied extensively with over 100 manipulations reported in the peer-reviewed literature. The outcome of these studies varies according to the gear used and the habitat in which it was deployed. This variability in the response of different benthic systems concurs with established theoretical models of the response of community metrics to disturbance. Despite this powerful evidence, a recent FAO report wrongly concludes that the variability in the reported responses to fishing disturbance mean that no firm conclusion as to the effects of fishing disturbance can be made. This thesis is further supported (incorrectly) by the supposition that current benthic sampling methodologies are inadequate to demonstrate the effects of fishing disturbance on benthic systems. The present article addresses these two erroneous conclusions which may confuse non-experts and in particular policy-makers.

Response of the herbaceous layer of forest ecosystems to excess nitrogen deposition

SummaryThis review brings into focus what is known about the response of the herbaceous layer of forest ecosystems to increasing nitrogen deposition. The emphasis on forests in general is important for two reasons. First, forests often occupy areas receiving high rates of atmospheric deposition of N. Second, compared with herb‐dominated communities, about which much is known regarding response to excess N, forests generally display greater biological and structural complexity. The more specific focus on the herbaceous layer – here defined as all vascular (herbaceous and woody) plants ≤ 1 m in height – is warranted because most of the species diversity of forests occurs in the herb layer.Most responses of forest ecosystems to N saturation, defined here as ecosystem supply of N exceeding ecosystem demand for N, can be characterized by two complementary hypotheses, each emphasizing different facets of ecosystem structure and function. One focuses on ecosystem processes, such as net primary productivity, whereas the other addresses seasonal patterns of concentrations ofin stream water. Although neither hypothesis considers the effects of chronically elevated N deposition on forest herbs, both share a prediction – a dramatic increase in availability of– that is relevant to forest herb response. Such a shift towardsdominance has important implications for changes in herbaceous layer dynamics. For example, increases in soilpools can increase invasibility by exotic species. Also, because preferential use ofvs.can be highly species‐specific among forest herbs, predominance ofavailability can bring about further changes in herb layer species composition. Also important to forest herbs is the tendency for enhanced mobility ofto increase mobility and decrease availability of essential cations, such as Ca2+.The response of plant species of the herbaceous layer of forest ecosystems to excess N availability can arise from N‐mediated changes in several processes. Here I identify six – competition, herbivory, mycorrhizal infection, disease, species invasions and exotic earthworm activity – and discuss how they respond to excess N and how this response affects the herb layer of forests. With the exception of the activity of exotic earthworms (which is correlated with, but not necessarily caused by, high N deposition), there is compelling evidence that all processes respond sensitively to N deposition and that this response generally leads to drastic shifts in species composition and decreases in biodiversity of forest herb communities.A hypothesis is suggested – the nitrogen homogeneity hypothesis – that predicts loss of biodiversity in forest ecosystems experiencing chronically elevated N deposition. This hypothesis is based on the decrease in spatial heterogeneity of N availability that is typically high in forest soils under N‐limited conditions.

Integration of approaches to increasing water use efficiency in rice-based systems in southeast Australia

Australian rice growers are under considerable pressure to increase water use efficiency to remain profitable and avoid soil salinisation. In particular, profitability is threatened by decreasing water availability and certainty of supply and by increasing water price, as a result of environmental and National Competition Policy agendas. Field irrigation water productivity has more than doubled in the past 20 years from an average of around 0.34 g paddy rice per kg water to around 0.77 g kg −1, largely due to increased yield from the development and adoption of improved varieties and management strategies, and to a lesser degree due to the introduction of rice water use and soil suitability policies. Future increases in rice field water productivity will come from greater yields through breeding for increased cold tolerance, precision agriculture and improved crop establishment, and from reduced water use due to reduced duration of ponding. A key challenge of the next decade will be to increase cold tolerance to the extent that deep water ponding for low temperature protection is no longer required, possibly allowing a complete shift away from ponded culture and reducing irrigation water requirement. While increasing the water productivity of rice is important, water productivity and profitability of the entire cropping system is of ultimate importance. Growing winter crops after rice and permanent bed systems offer potential benefits of increased productivity of crops traditionally grown in rotation with rice and increased cropping diversity and flexibility. Irrigation water productivity is also being improved through on-farm and regional technologies such as on-farm recycling systems and automatic data acquisition and control systems in irrigation supply systems. To increase water use efficiency and achieve sustainability of rice-based farming systems in Australia, irrigation communities are implementing a range of on-farm and regional technologies and policies. An integrated approach is required to evaluate options, prioritise investments, maximise economic returns, guide policy and balance the environmental demands of river ecosystems with the needs of irrigated agriculture and its dependent regional communities. Significant progress is being made, through the development and application of farm and irrigation area hydrologic models linked with production models and economics, combined with strong stakeholder participation. The progress in integrating science, people and policy makers was recognised in 2002 by the award of the first “Reference” catchment status to the lower Murrumbidgee catchment, a major Australian rice-growing region, under the UNESCO/WMO HELP (Hydrology for Environment, Life and Policy) program.

The effect of elevated atmospheric CO2 and drought on sources and sinks of isoprene in a temperate and tropical rainforest mesocosm

AbstractIsoprene is the most abundant volatile hydrocarbon emitted by many tree species and has a major impact on tropospheric chemistry, leading to formation of pollutants and enhancing the lifetime of methane, a powerful greenhouse gas. Reliable estimates of global isoprene emission from different ecosystems demand a clear understanding of the processes of both production and consumption. Although the biochemistry of isoprene production has been studied extensively and environmental controls over its emission are relatively well known, the study of isoprene consumption in soil has been largely neglected.Here, we present results on the production and consumption of isoprene studied by measuring the following different components: (1) leaf and soil and (2) at the whole ecosystem level in two distinct enclosed ultraviolet light‐depleted mesocosms at the Biosphere 2 facility: a cottonwood plantation with trees grown at ambient and elevated atmospheric CO2 concentrations and a tropical rainforest, under well watered and drought conditions. Consumption of isoprene by soil was observed in both systems. The isoprene sink capacity of litter‐free soil of the agriforest stands showed no significant response to different CO2 treatments, while isoprene production was strongly depressed by elevated atmospheric CO2 concentrations. In both mesocosms, drought suppressed the sink capacity, but the full sink capacity of dry soil was recovered within a few hours upon rewetting. We conclude that soil uptake of atmospheric isoprene is likely to be modest but significant and needs to be taken into account for a comprehensive estimate of the global isoprene budget. More studies investigating the capacity of soils to uptake isoprene in natural conditions are clearly needed.

Snowshed Contributions to the Nooksack River Watershed, North Cascades Range, Washington

Meltwater contributes to watershed hydrology by increasing summer discharge, delaying the peak spring runoff, and decreasing variability in runoff. High‐elevation snowshed meltwater, including glacier‐derived input, provides an estimated 26.9 percent of summer streamflow (ranging annually from 16 to 40 percent) in the Nooksack River Basin above the town of Deming, Washington, in the North Cascades Range. The Nooksack is a major spawning river for salmon and once was important for commercial, recreational, and tribal fishing, and in the past its flow met the demands of both human and aquatic ecosystems. But the river is already legally overallocated, and demand is rising in response to the rapidly growing human population. Variability in snowshed contributions to the watershed is considerable but has increased from an average of 25.2 percent in the 1940s to an average of 30.8 percent in the 1990s. Overall stream discharge shows no significant increase, suggesting that the glaciers are melting, and/or precipitation levels (or other hydrologic factors) are decreasing at about the same rate. If glaciers continue to recede, they may disappear permanently from the Cascades. If that occurs, their summer contribution to surface‐water supplies will cease, and water‐management policies will need drastic revision.

Climate‐driven changes in spring plankton dynamics and the sensitivity of shallow polymictic lakes to the North Atlantic Oscillation

Climate is increasingly recognized as a major factor driving long‐term changes in plankton communities in both marine and limnetic ecosystems. In a shallow and polymictic lake, marked changes in the dynamics of phytoplankton and in the timing of distinctive successional events in spring were observed during two recent decades. We studied whether and how these changes were linked to a series of uncommonly warm winter and spring seasons, focusing on the predictive power of a macroscale atmospheric circulation pattern, the North Atlantic Oscillation (NAO). In the warm period 1988‐1998, phytoplankton developed about 1 month earlier than in the cool period 1979‐1987, and high total phytoplankton biomass was recorded in early spring. These changes were significantly related to the NAO, which explained about 35% of the variance, and can be attributed to a shortening or lack of ice cover periods in winter. Zooplankton (Keratella, Bosmina, Daphnia) developed about 2 weeks earlie in the warm period, consequently leading to an early establishment of the clearwater phase. The shift in the timing of the daphnid peak and of the clearwater phase required an additional warming trend in late April and early May and was not significantly correlated with the winter situation. The memory effect of the NAO was restricted to a rather short postwinter period and was overtaken by the prevailing weather in April. Our results suggest that assessments of potential impacts of climate warming on biological processes in freshwater ecosystems demand basic knowledge about the relationships between global climate indices, local meteorological conditions, and the thermal response of various lake type .

Vertebrate frugivory and seed dispersal of a Chihuahuan Desert cactus

Vertebrate frugivory of fleshy-fruited plants may be very important for the recruitment of sexually derived seedlings if it represents the main mechanism of primary seed-dispersal.Opuntia rastrera produces fleshy fruits rich in water and sugars that are attractive to vertebrate frugivores. However, there is a very low rate of seedling recruitment in natural conditions. One of the causes that can influence this low recruitment is an insufficient seed dispersal due to a low fruit removal even under different resource (fruits) availability. To test this prediction, we studied the production and consumption of fruits in two consecutive years in two vegetation types: nopaleras (dense Opuntia-dominated scrublands) and grasslands with sparse populations of O. rastrera. Plant cover, fruit production and removal, and frugivore identity were recorded within each vegetation type in four randomly selected circular plots (7854 m2). Fruit production per area was higher in nopaleras in both years whereas per cladode production did not differ between vegetation types but differed between years in response to variation in precipitation. Fruit consumption by vertebrates was high (100%) and independent of spatial and temporal fruit availability. The intensity of fruit removal was inversely related to resource availability: it was faster in the less dense community (grassland) and in the driest year. Contrary to other studies with similar cacti, fruit removal by small mammals was insignificant whereas main consumers were birds and large mammals. Vertebrate frugivory represents the only mechanism of primary dispersal of seeds as all fruits are removed in about one month. Despite the high quantity of viable seeds (more than one million per ha in nopaleras and a tenth of that in grasslands) that are dispersed by frugivores after the consumption of about 300 kg of fruit per ha in nopaleras and a tenth of that in grasslands, the rare establishment of seedlings (about one seedling per three million of seeds produced) reported in the literature indicates that the interaction between O. rastrera and the disperser guild is indeed very asymmetrical. We speculate that the harsh conditions for cactus establishment found in this ecosystem demand a high investment in disperser rewards (fleshy fruits) to allow a very modest rate of sexually-derived seedling establishment.

Bioindication of Different Stresses in Forest Decline Studies in Slovenia

Determination of the stresses operating on a forest ecosystem demands the use of several bioindication methods. Air quality indicators were assessed from an inventory of forest decline based on the assessment of tree crowns and epiphytic lichens. Photosynthetic pigments, ascorbic acid and major macronutrients were studied in Norway spruce needles as indicators of physiological and biochemical stress. Analyses were carried out on selected forest plots in polluted areas (Zasavje district, vicinity of thermal power plants) and predominantly unpolluted areas (Triglav National Park, Julian Alps, Slovenia). For some bioindication methods, there was good agreement with measured air quality and climatological parameters. The best agreement was found between total foliar sulphur in needles and epiphytic lichens, especially in more polluted areas. Agreement with forest decline inventories and analyses of some needle stress physiological/biochemical parameters was less convincing. The strength of agreement was further decreased by soil characteristics and climatic parameters, influenced also by biotic parameters and forest stand history and management. It was concluded that there is no simple bioindication method available to evaluate the vitality of a forest.

Biomonitoring the Health of Coastal Marine Ecosystems – The Roles and Challenges of Microscale Toxicity Tests

Coastal marine ecosystems in many parts of the world are under unrelenting stress caused by urban development, hazardous or toxic substances, overfishing, habitat destruction, the introduction of exotic species and natural toxins. Biomonitoring plays a vital role in governmental and industrial strategies to identify, assess, control and reduce these problems. Sensitive and practical techniques in biomonitoring are needed in all of the strategic approaches – from toxic chemical rating and classification, to pollution source control, status and trends monitoring, and assessments of “marine ecosystem health”. Due to the shear magnitude and scope of the challenge, biomonitoring coastal ecosystems demands new and innovative approaches that are relatively easy and cheap to deploy and that provide timely and accessible information to environmental managers and policy makers. This paper explores recent developments in microscale toxicity testing – a branch of aquatic toxicology involving the discovery and application of small-scale, innovative, sensitive, practical, inexpensive and frequently automated biological techniques. Highlights of a recent unique synthesis (Wells et al., 1998) are given, describing microscale tests at various biological and phylogenetic levels. Many of these tests are marine and focus on gametes, embryos and other young life stages. They can be utilized in the field ( in vivo), with field collected samples, and in the laboratory. Their low cost, sensitivity, practicality and speed are their strengths, and commercial test kits have been developed as a result. But being largely “single-species” and sub-individual-level biomonitors, do such microscale tests provide information directly useful to protecting vital ecosystem processes? Indeed, how can this question be addressed? The needs and challenges of matching the most promising of the microscale tests with higher level (population, community, ecosystem) measurements to protect habitats and biodiversity are discussed. Improving marine biomonitoring and protecting coastal ecosystem health demands such new techniques within the context of new paradigms and rigorous approaches for their application.

Derivation of acceptable concentrations for the protection of aquatic organisms

Derivation of quality standards to protect aquatic ecosystems demands a minimum set of toxicity data to allow the risk assessor to take some account of: (1) variable responses to toxicants; (2) variable environmental characteristics; (3) interactions between duration of exposure and effects; and (4) ecological significance of impacts. Extrapolation from limited experimental data to predict a concentration protective in diverse ecosystems can employ either statistical models (consistent but rather rigid and may not protect all species) or empirical factors (more flexible and possibly more protective, but require expert judgment in their application). However derived, quality standards must be tailored to the specific conditions of release and environmental fate which influence a chemical's impact in aquatic ecosystems. It must also be recognised that protection of all individuals and even of all aquatic species may not be achievable or necessary to maintain a healthy ecosystem. Some possible future advances in the determination of water quality standards are suggested.

Ecological resources for conservation and development in Wadi Allaqi, Egypt*

PULFORD, I. D., MURPHY, K. J., DICKINSON, G., BRIGGS, J. A. & SPRINGUEL, I., 1992. Ecological resources for conservation and development in Wadi Allaqi, Egypt. The creation of Lake Nasser behind the Aswan High Dam on the River Nile has brought about significant environmental changes in Upper Egypt. A multidisciplinary project was started in 1987 to assess the environmental changes associated with periodic inundation in desert ecosystems. The data presented here provide a baseline for studies aimed at assessing the potential for, and ecological impacts of, sustainable development in the target area, and may act as a blueprint for wider-scale development. Soil, water, vegetation, animal and human resources are being monitored. There has been a major increase in plant communities dominated by riverain species, at the expense of the original desert wadi vegetation. The water has attracted human settlement, with some 200-250 people now living in the wadi. The inherent high fertility of the soil has allowed them to grow a range of crops in small plots, using a system of shifting cultivation dictated by the lake water level. While this degree of development may be sustainable, larger-scale development of the fragile wadi ecosystem demands a full assessment of appropriate management techniques.

World survey of climatology volume 1A heat balance climatology

The Zoige wetland, located in the eastern edge of Qinghai-Tibet Plateau, is highly sensitive to global climate change for its high elevation and cold environment. As one of the major components in the hydrological cycle, evapotranspiration (ET) affects regional water balance and ecosystems in alpine wetlands. To identify the impact of the changes of wetland eco-environment on ET, and to indicate the relation between the real ET and the potential ET, a comparative study on the hourly real ET measured by weighting lysimeters and the hourly potential ET, calculated by the FAO Penman-Monteith equation, has been carried out at three blocks with different surface water levels during three vegetation growth stages in the Zoige wetland. Results show that the hourly potential ET is generally higher than the real ET during the studied period. The hourly ET changed with the variation of the vegetation growth stage, the water level and vegetation characteristics. The hourly potential ET is the largest in the peak growth stage, and the least during the last growth stage for each water level. The real ET is the least at the highest water level for all growth stages. The results suggest that future wetlands management strategies should emphasize the protection of a reasonable vegetation pattern and the basic water demands of ecosystems for improving the wetland ecosystem health in the Zoige wetland.