A model to simulate response of plant stomata to environmental conditions

In order to simulate plant transpiration under different field climatic conditions we have developed and verified a semi-empirical model for predicting the stomatal response to solar global radiation, leaf temperature, vapour pressure difference between the leaf and ambient air, ambient air CO₂ concentration and soil water potential. The transpiration and the stomatal relative conductance of a Nicotania Tabaccum var “samsun” plant leaves were measured in a laboratory apparatus and compared to those predicted by the model: good agreement was obtained between them for the different investigated cases. The model was incorporated in a numerical greenhouse microclimate model and its effects on the canopy microclimate are discussed here.     

The response of drought-tolerant sugar beet to salinity stress under field and controlled environmental conditions

Abstract

Thirty-four sugar beet drought-tolerant half-sib families were screened in greenhouse experiment under saline (16?dSm^?1) and normal conditions, and a subset of 10 tolerant genotypes were selected for evaluating of yield-related traits, Na⁺, K⁺, and α-amino-N nitrogen contents under saline field condition (12?dSm^?1). Drought-tolerant genotypes showed a different tolerance level under salt stress. Significant correlation was observed between EP2_s and STIEP2 in greenhouse with root yield (RY) in saline field condition. It should be possible that a simple measurement at 16?dSm^?1 in the greenhouse can be used as main part of sugar beet salt-tolerant breeding program. In total, genotypes SBSI-DR I-HSF14-P.23 (# 16) and 436B-HSF9-P.27 (# 26) were recognized as salt- and drought-tolerant genotypes with low Na⁺ and K⁺ contents in root and high white sugar content (WSC) and RY in field. A larger panel of genotypes to validate this kind of association is necessary.     

Long-term response of spring flora to chronic herbivory and deer exclusion in Great Smoky Mountains National Park, USA

Chronic herbivory by white-tailed deer (Odocoileus virginianus Zimmerman) can have profound impacts on the function and structure of forest ecosystems. We examined the combined influence of intense herbivory associated with a deer population eruption and chronic herbivory by the post eruption population on the spring flora of Cades Cove, Great Smoky Mountains National Park. During the 1970s the deer population reached a peak of 43 deer per km², from which it has slowly declined in recent decades. To examine the influence of intense herbivory, we compared the abundance and flowering rates of early flowering plants in Cades Cove to a nearby reference site with similar bedrock geology, vegetation, and disturbance history but contrasting history of deer abundance. Our results suggest that significant changes (p ? 0.05) in the diversity, evenness, and species richness of the spring flora occurred during the eruptive phase. Trillium spp. and other liliaceous species appeared to be disproportionately impacted. Comparisons between control and exclosure plots established after the deer population eruption indicate that recovery has been largely restricted to species that were able to persist under intense herbivory. These species have increased in number in exclosures, suggesting continued impacts by deer on the plant community outside the exclosures. Little to no recolonization by browse sensitive species was observed. Consequently, to restore the natural diversity of early flowering plants once present in Cades Cove, active restoration may be necessary in addition to maintaining deer densities below current levels.     

The population density of chamois and ibex in the Gran Paradiso National Park,Italy

Starting from the frequently heard claim that the populations of chamois and ibex in the Gran Paradiso National Park are excessive, several factors which influence the populations in the Park are considered, including that of epidemic disease. It is concluded that although some man-made factors favour overpopulation, others act in the opposite direction: on the whole their effect is marginal and there is no need for culling. The only reason which would justify such management would be if the vegetation were showing effects of overgrazing—evidence which is not available at the present time. The claim of overpopulation probably comes about both because a comparison is made with the nearly depopulated surrounding areas (where the numbers are kept artificially very low by hunting and poaching), and because of an emotional evaluation of natural phenomena.     

The response of Phragmites australis to harvesting pressure in the Muzi Swamp of the Tembe Elephant Park,South Africa

Phragmites australis (Cav.) Trin. ex Steud. has been harvested in the Muzi Swamp in Maputaland, South Africa for generations. Over the last ten years, however, a flourishing trade in this reed has developed. Concern has now been expressed that at the current levels of utilization the ecological integrity of the Muzi Swamp is being compromised, and that the current harvesting rates are not sustainable in the long term. The hypothesis was put forward that a degradation gradient exists with the most severe degradation occurring the closest to where community members enter the park, and the least degradation the furthest from this point. The results of this study, however, show no distinct degradation gradient. Yet the overall condition of the reeds in the harvesting area is poorer than in the non‐utilized area. Expansion of the current harvesting area, coupled with adaptive harvesting systems and yearly monitoring will improve the quality of the reeds within the harvesting area without affecting the harvesting quotas. Copyright © 2004 John Wiley & Sons, Ltd.     

Nitrogen mineralization in histosols of the everglades agricultural area

Abstract

A long‐term soil incubation and column nutrient leaching study was conducted to determine nitrogen (N)‐mineralization rates of selected Florida Histosols with drained and intermittent‐flooded conditions. Five surface soils from the Everglades Agricultural Area (EAA) were packed in columns (5‐cm i.d. containing the 0‐ to 15‐cm depth of each soil) and leached with 0.01M CaC12 followed by distilled water every 25 d for 1 yr. Drained columns were treated with a minus‐nitrogen‐phosphorus (NP) solution followed by applying ‐0.97 MPa tension to remove excess solution. Flooded columns received the same minus‐NP solution, but were flooded to a depth of 3 cm. Both treatments were incubated for 25‐d periods, solution sampled, and treatments reapplied. Because flooding conditions could not be maintained during the sampling period, this treatment is referred to as intermittent flooded. The ammonium‐nitrogen (NH₄ ⁺‐N) released from drained soils accounted for less than 6% of the total soluble N released from all soils, compared to more than 30% released from flooded soils. There were no differences in the amounts of soluble organic N from drained and intermittent flooded soils. Total soluble N from the surface 15‐cm of drained soils ranged from 217 to 509 kg‐ha^‐1yr^‐1, with 50 to 67% released as nitrate‐nitrogen (NO₃ ^‐‐N). In contrast, total soluble N released from flooded soils ranged from 168 to 345 kg‐ha^‐1yr^‐1, with less than 3% released as NO₃ ^‐‐N.     

Assessing the utility of stakeholder analysis to Protected Areas management: The case of Corbett National Park, India

This study tests the potential utility of Stakeholder Analysis to Protected Area management. Using Corbett National Park (CNP), India, as a case study, Stakeholder Analysis (SA) was used to identify important stakeholder groups and assess their relationships, relative power and importance. This exercise was undertaken to assist the managers of CNP with future strategy formulation and implementation. The results demonstrate SA to be a simple, yet effective, method that can help PA managers understand the social dimensions of their undertaking, without waiting for long-term policy changes. The results reveal possible stakeholder alliances, and those that may need strengthening to guarantee the welfare of CNP. Divergent opinions on the same issue were also discovered. This underlines that addressing low levels of knowledge and misplaced information may be of strategic importance in reducing conflict against a PA. This research also helps theorize previously unexplored relationships among stakeholders in India, using the framework of Stakeholder Theory. Repeating the exercise on a regular basis could help PA managers monitor stakeholder interactions and political positions over time.     

Wolf population fluctuations in Jasper National Park,Alberta, Canada

Wolves are important components in the northern and western Canadian National Parks. Within Jasper National Park their numbers have undergone wide fluctuations. One cause of these fluctuations can be traced to the predator control programmes in areas adjacent to the National Parks. An examination of the historical records indicates that Wolves were widely persecuted also within the Parks in the past. Such activities have now largely ceased; however, increased human visitation has placed new pressures on these large carnivores. There is a need for public education to gain an acceptance of Wolf predation on ungulates in the Parks, although ungulates are traditionally one of the favoured attractions to North American National Parks.     

The influence of physical soil conditions on the formation of root nodules of Melilotus officinalis in the montane zone of Rocky Mountain National Park

Exotic invasion is a key threat to native biological diversity, second only to habitat degradation. Melilotus officinalis is an exotic species that thrives in areas of anthropogenic disturbances and low nutrient availability. Typically, natural disturbance facilitates native species establishment and maintains species diversity; however, anthropogenic disturbance facilitates exotic species establishment. M. officinalis functions as a competitor in the montane communities because of its symbiosis with Rhizobium bacteria, a symbiosis that allows the plant to acquire nitrogen. Although the ability to fix nitrogen permits M. officinalis to grow in nitrogen depleted soils, the soil must have a microclimate that is favorable to symbiosis and nodulation. We analyzed abiotic soil characteristics in Rocky Mountain National Park to determine if nodulation was related to soil texture, as well as in the mid-range level of soil and temperatures. We found that nodules on plant specimens showed a positive correlation with soil moisture and temperature, and occurred in a specific range of moderate moisture and temperature. Soil texture was not correlated to nodule formation.     

Morphogenetic features of soils in the Cat Tien National Park,southern Vietnam

Morphogenetic features of soils on the selected plots in the Cat Tien National Park in southern Vietnam have been studied with the use of a set of morphological, analytical, and instrumental methods. The lithological factor and topographic position play the leading role in the development of the particular genetic soil features. The soils can be subdivided into four groups according to these factors. The soils developing from volcanic deposits with a predominance of tephra can be classified as thin clayey brown tropical soils (Dystric Skeletic Rhodic Cambisols (Clayic)), and the soils developed from less weathered colluvial derivatives of basalts with some admixture of tephra can be classified as dark-humus clayey tropical soils (Skeletic Greyzemic Umbrisols (Clayic)). Very poor soils developed from the eluvium of argillites are classified as thin weakly developed clayey tropical soils (Dystric Regosols (Clayic)). The soils forming from the alluvial sediments of different textures are classified as alluvial loamy sandy soils (Dystric Fluvisols (Arenic, Drainic)) and as alluvial clay loamy soils (Eutric Fluvisols (Episiltic, Endoclayic)).     

The changing state of Acacia xanthophloea groves in Arusha National Park,Tanzania

Groves of Acacia xanthophloea afford aesthetically satisfying habitats for wildlife in East Africa. In the Arusha National Park, the existing groves vary in their states of succession or decline following disturbances. Methods have been designed to assess the regeneration potential of the groves. The regeneration potential, and the cyclic or seral restoration of the vegetation, have been examined. The degree to which regeneration may be considered natural will depend on the composition and structure of the vegetation as a whole, on the health and age of individual plants, and on their relationship to the environment. The case of the existing groves discloses that imbalances have arisen following a history of animals and fire repressing the course of plant succession. Management depends on a comprehension of the changes occurring. Attainment of its purpose necessitates correction of imbalances arising from disturbances of the environment. In the present instance it is concluded that the cyclic and seral status of the groves is substantially influenced by drainage conditions, and that the regeneration potential is sufficiently vigorous to compensate for the animal impact provided that wildfires are excluded. Nevertheless the situation must be watched and timely action taken if the need arises.     

Chemistry of the Urauchi River Water in Iriomote Island National Park, Okinawa, Japan

The chemical characteristics of the Urauchi River water in Iriomote Island National park, Okinawa, Japan have been studied. Concentrations of PO₄ ^3?, NO₂ ^?, and NH₄ ⁺ were barely detectable. We compared the concentration ratios of Mg²⁺/Na⁺, HCO₃ ^?/Na⁺, and Ca²⁺/Na⁺ in the Urauchi River to those of 60 large rivers in the world and indicated that the chemical composition of the river is most likely formed by the binary mixing of sea salt components and silicate rock weathering components. Although rock weathering in the catchments area is driven by both H₂CO₃ and H₂SO₄, the role of H₂CO₃ is dominant. The percentages of the concentration of each cation in the river water are almost the same as those of other rivers with drainage areas consisting of silicate rock and sandstone. Thus, the Urauchi River shows the typical chemical characteristics of a river in a silicate rock area that includes sandstone.     

Habitat use and spatial dynamics of takhi introduced to Hustai National Park, Mongolia

The successful introduction of captive bred takhi or Przewalski’s horse, Equus ferus przewalskii, into Mongolia in the 1990s is a good example of the benefits of ex situ conservation and one of the few examples of the recovery of an animal after it became extinct in the wild. This is also particularly interesting because virtually nothing was known about how takhi lived before they died out, and the introductions have enabled us to study how they have settled, and their ecology and behaviour within their former natural range. In this paper, we describe the movement, home range size and shape, and habitat use of takhi at one of the release areas, the 570 km² Hustai National Park in Mongolia. Harem home ranges varied between 129 and 2399 ha, with 80% core areas of between 61 and 1196 ha. There was no relationship between range size and harem size, or length of time since release. Initially, harems stayed near their release enclosures, but over time they established home ranges further away. There was little overlap between home ranges of different harems, but neither was there evidence of exclusive range use. The more nutritious vegetation at lower elevations was preferentially selected. Thus the present situation looks good, but, as the population continues to grow, we anticipate that there will be potential problems related to intraspecific competition for water and vegetation resources, and the potential for hybridisation with domestic horses belonging to the local people. We consider the time it may take for takhi to reach carrying capacity within Hustai National Park and emphasise that continual monitoring of the population is essential because interventional management is likely to be required in the future.     

The effect of lime on the response of soils to sodic conditions

The role of CaC0₃ in preventing clay dispersion and losses in hydraulic conductivity (HC) of sodic soils was determined directly by mixing two lime-free soils with 0.5 and 2.0 per cent CaCO₃. Whereas the HC of the lime-free soils dropped sharply when 0.01 n solutions of SAR 20 were displaced with distilled water, mixing the soils with powdered lime prevented both HC losses and clay dispersion. The response of a sandy soil mixed with lime was similar to that of a calcareous sandy soil. The beneficial effect ofCaC0₃ was not so pronounced in soils equilibrated with solutions of SAR 30. The increase in electrolyte concentration, due to CaCO₃ dissolution, was suggested as the mechanism responsible for the beneficial effect of lime.     

Episodic acidification of three streams in Shenandoah National Park,Virginia, USA

Short-term acidification of surface waters in the eastern United States accompanying rainfall and snowmelt events represents an important aspect of the regional acidification problem. The objectives of this field study were to (1) examine the changes in acid-base chemistry during stormflow conditions, (2) understand the hydrological flowpaths that control streamwater acid neutralizing capacity (ANC), and (3) evaluate the contribution of individual ions to the overall changes in streamwater ANC. Three forested mountain streams in Shenandoah National Park (Paine Run, Piney River, and Staunton River) were chosen based on their similar catchment size (11–13 km²) but different bedrock geology and baseflow ANC. Throughout the three-year study, samples were collected at eight-hour intervals (primarily to establish antecedent baseflow conditions), and at two-hour intervals during events until the flow receded. All samples were analyzed for pH, ANC, and all major cations and anions. During storm events, pH and ANC decreases were observed in all streams, with ANC becoming negative several times in Paine Run. Base cation concentrations typically increased in Paine Run and Staunton River, but usually decreased in Piney River. Sulfate and nitrate concentrations generally increased in all streams. Antecedent baseflow ANC was found to be the best predictor of the minimum ANC. The data from more than 40 episodes on these streams (initiated by 25 different storm events) are interpreted to evaluate the relative importance of natural and anthropogenic sources of acidity to these acid-sensitive natural waters.     

Vegetation of roadcut slopes in the tundra of Rocky Mountain National Park,Colorado

Eight study-sites were chosen on road margins in the alpine tundra of Rocky Mountain National Park, Colorado. Seven of the sites were located about the middle of slopes created by filling, below the roads. The remaining site was above the road, and flat on bedrock. Mosaics of pioneer vegetation types are present on roadcut slopes. These appear to be correlated with altitude, exposure, substrate texture, and degree of slope. Forty to fifty years after denudation, succession plays only a minor role on roadcut slopes. Plant coverage after that time is approximately one-half that of cushion-plant communities on natural tundra. The most important pioneer plants under these conditions are ‘bunch type’ Gramineae, especially Agropyron scribneri and Poa fendleriana.     

Factors associated with human-killing tigers in Chitwan National Park, Nepal

Human-killing is the ultimate expression of human-tiger conflict. It is a complex issue that needs to be addressed to maintain support for tiger (Panthera tigris) conservation in areas where human-killing is prevalent. This research was undertaken to investigate the ecological and sociological aspects of human-killing in the central lowlands of Nepal. We used 28 years of data from human-killing events in Chitwan National Park and the surrounding area to: (1) document the geographic distribution of human-killing incidents, (2) examine ecological variables associated with sites where humans were killed, (3) characterize human-killing tigers, and (4) identify human activities that make people vulnerable to attack. Finally, we use this information to recommend strategies to reduce human-tiger conflicts. Data on human-killing incidents and removal of human-killing tigers were obtained from veterinarian and Kathmandu Zoo records and by visiting the location of each kill with a victim’s family member or friend. Thirty-six tigers killed 88 people from 1979 to 2006. Most (66%) kills were made within 1 km of forest edge but equally in degraded and intact forests. An equal number of male and female tigers killed humans and 56% of tigers that were examined had physical deformities. The trend of human deaths increased significantly from an average of 1.2 (±1.2) persons per year prior to 1998 to 7.2 (±6.9) per year from 1998 to 2006. This difference is due primarily to a ten fold increase in killing in the buffer zone since 1998 because of forest restoration. Nearly half the people killed were grass/fodder collectors. Local participation in tiger management and conservation is essential to mitigate human-tiger conflicts. We recommend that villagers be recruited to help radio collar and monitor potentially dangerous tigers, participate in long term tiger monitoring, and attend a tiger conservation awareness program focused on tiger behavior and avoidance of conflict.     

Chemical characterization of several wetlands in Kejimkujik National Park,Nova Scotia

Results are presented from an investigation of wetland chemistry in Kejimkujik National Park, Nova Scotia. Significant differences in the major ionic constituents occurred between wetlands classified as bogs and those classified as fens, indicating the more minerotrophic status of the latter. The fens, however, were categorized as extremely poor, being very low in pH and base cations, indicating almost no buffering capacity. This type of wetland is regarded as transitional to bog and is viewed as highly sensitive to acid deposition by Gorham et al. (1987). Further alkalinity losses may result in abrupt changes in floral assemblages with rapid invasion of carpet forming Sphagnum species.     

蒙山国家森林公园的可持续发展

系统论述了森林风景资源的分布、类型,在以保护自然风貌的前提下,开展森林旅游,通过保护、建设、开发和利用,取得了显著的生态、社会和经济效益。