Ground-level ozone in China: distribution and effects on crop yields

Rapid economic development and an increasing demand for food in China have drawn attention to the role of ozone at pollution levels on crop yields. Some assessments of ozone effects on crop yields have been carried out in China. Determination of ozone distribution by geographical location and resulting crop loss estimations have been made by Chinese investigators and others from abroad. It is evident that surface level ozone levels in China exceed critical levels for occurrence of crop losses. Current levels of information from ozone dose/response studies are limited. Given the size of China, existing ozone monitoring sites are too few to provide enough data to scale ozone distribution to a national level. There are large uncertainties in the database for ozone effects on crop loss and for ozone distribution. Considerable research needs to be done to allow accurate estimation of crop losses caused by ozone in China.     

Private Actions and Preferences for Coordinated Groundwater Conservation in Colorado's Republican River Basin

Conservation of groundwater resources is critical for maintaining the future productivity of irrigated land in the Ogallala Aquifer Region and beyond. This research explores motivations and behavior related to groundwater conservation among agricultural producers in the Colorado portion of the Republican River Basin, which is part of the Ogallala Aquifer. The empirical modeling uses data from a recently conducted survey to analyze how a common set of producer, farm, and resource characteristics influence groundwater values, concern for future groundwater availability, private conservation actions, and support for coordinated conservation efforts. We find two factors, producer age and land owner status, are consistently correlated with the key conservation‐related outcomes we evaluate. More generally, the results suggest considerable similarities in the characteristics that drive private conservation actions and support for coordinated conservation. This knowledge could be used to better target and incentivize future groundwater conservation efforts in the region. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Atmospheric ozone: formation and effects on vegetation

Ozone (O(3)) is present both in the troposphere and the stratosphere. Troposphere O(3) is predominantly produced by photochemical reactions involving precursors generated by natural processes and to a much larger extent by man's activities. There is evidence for a trend towards increasing tropospheric O(3) concentrations. However, tropospheric O(3) is known to account for only 10% of the vertical O(3) column above the earth's surface. The stratosphere accounts for an additional 90% of the O(3) column. There is evidence to suggest that there are losses in the stratospheric O(3) due to the updraft of O(3) destroying pollutants generated by both natural processes and by human activity. Such a loss in stratospheric O(3) can result in alterations of incidence in the ultraviolet (UV) radiation to the earth's surface. Tropospheric O(3) is known to be highly phytotoxic. Appropriate exposures to O(3) can result in both acute (symptomatic) and chronic (changes in growth, yield or productivity and quality) effects. Chronic effects are of great concern in terms of both crops and forests. A number of experimental techniques are available to evaluate the chronic effects of O(3) on plants. There are limitations attached to the use of these techniques. However, results obtained, with such techniques are valuable if interpreted in the appropriate context. Among all field evaluation techniques, open-top chambers are the most frequently used method for evaluating the chronic effects of O(3) on crops. The National Crop Loss Assessment Program (NCLAN) of the United States is the largest such effort. However, given the limitations of the open-top chambers and the experimental aspects of NCLAN, its results must be interpreted with caution. On the other hand, acute effects can be evaluated with less complexity through the use of biological indicator plants. The numerical modelling of such effects are also far less complicated than establishing numerical cause and effects relationships for chronic effects. Confounding the acute or chronic responses of plants to O(3), is the presence of other kinds and forms of pollutants in the ambient atmosphere and the incidence of pathogens and pests. The resulting complex interactions and joint effects on plants are poorly understood. Future research must address these issues. In the final analysis we have re-emphasized the fact that plant health is the product of its interaction with the physical and chemical climatology and pathogens and pests. What we have described in this context is the importance of tropospheric O(3) within the chemical climatology of our environment and its effects on vegetation.     

Responses of sensitive and tolerant bush beans (Phaseolus vulgaris L.) to ozone in open-top chambers are influenced by phenotypic differences, morphological characteristics, and the chamber environment

Responses of bush bean (Phaseolus vulgaris L.) lines 'S156' (O(3)-sensitive) and 'R123' (O(3)-tolerant), and cultivars 'BBL 290' (O(3)-sensitive) and 'BBL 274' (O(3)-tolerant) to ambient ozone (O(3)) were investigated during the 2001 and 2002 growing seasons. Seedlings were grown in pots inside open-top chambers (OTCs), with charcoal filtered (CF) and non-filtered (NF) ambient air, and in non-chambered ambient air (AA) plots. Growth parameters from individual plants were evaluated after harvests at the end of vegetative (V(4)) and reproductive (R(10)) growth phases. Results at V(4) indicated that CF did not provide additional benefits over NF in 'S156' in 2001 and 2002. In contrast, exposure to CF significantly impaired the growth of 'R123'. At the end of R(10), 'S156' produced more pods, most of which remained immature, and contained fewer seeds or were more frequently aborted, whereas pods produced in 'R123' reached pod maturation and senescence more consistently. Despite increased seed weights inside the OTCs, as observed in 'S156', differences between the two lines were insignificant when grown outside OTCs. Results from the 'BBL 290'/'BBL 274' pair, especially at V(4) phase, remained inconclusive. Plant morphological characteristics, variabilities in environmental conditions, and 'chamber effects' inside OTCs were influential in determining plant response to ambient O(3).     

Recreation and river type: Social-environmental relationships

Recreation use was studied on a diverse state river system to test the hypothesis that recreation use patterns vary systematically by river type. River segments were classified into representative river types through application of a two-fold classification system. The first classification factor, generalized geomorphology, defines and groups the dominant resource bases of which rivers are comprised. The second classification factor, cultural setting, defines the land use and settlement patterns in which each river type is found. Significant differences were found among resulting river types with respect to the nature and intensity of recreation activity, desired use density, and user perceived problems and conflicts. Management recommendations were developed, based on study findings, for each river type. It is concluded that when both environmental attributes and cultural setting are taken into account, regularities appear with respect to the way in which river resources are used and perceived by recreationists. Further exploration and expansion of such recreation-resource relationships to other activities and environments may hold substantial implications for the allocation and management of outdoor recreation resources.     

Dose-response studies with ethylenediurea (EDU) and radish

There is some concern that the antiozonant ethylenediurea (EDU), used for crop loss assessment due to ambient ozone (O3) may per se affect plant growth and yield. In view of this, and to provide knowledge for later field experiments, dose-response studies with EDU and O3 were carried out in greenhouses in winter and spring 1989, using radish (Raphanus sativus L.) cv. 'Cherry Belle' and 'Red Prince', grown in two different substrates. EDU was applied as a single or repeated soil drench in concentrations ranging from 300 to 800 mg litre(-1) in the first, and from 100 to 400 mg litre(-1) in the second trial. In the second experiment, plants were exposed to a chronic level of O3, mimicking ambient patterns, or to filtered air after the EDU-treatment. When applied in concentrations above 300 mg litre(-1), EDU reduced growth, thereby affecting the development of the thickened hypocotyl far more than the shoot growth that was partially stimulated by lower doses of EDU. Phytotoxic symptoms on the leaves, attributable to EDU, were observed at concentrations above 200 mg litre(-1), but complete protection from visible O3-injury was provided by a single application of EDU at a concentration as low as 100 mg litre(-1). Significant interactions on growth characters measured between O3-exposure and EDU application were observed only in one of the substrates. While these results demonstrate the need for careful dose-response studies prior to field assessments, they also provide evidence of a dosage that is effective in protecting radish from O3 damage without interfering with plant growth itself.     

IMPACTS OF RECREATION ON RIPARIAN SOILS AND VEGETATION1

ABSTRACT: The seemingly magnetic attraction of water resources for recreation has direct implications for proximate land resources which are needed to provide access and support facilities. This paper reviews and synthesizes the literature dealing with the impacts of recreation use on riparian soils and vegetation. Part one of the paper sets forth the major negative impacts of recreation use on soils and vegetation. A seven-step soil impact cycle is identified, beginning with the scuffing away of leaf litter and other organic material and working through the soil erosion and sedimentation process. Four major kinds of impacts of recreation use on vegetation are then outlined, and the‘Vicious circle” relationship between impacts on soil and vegetation is demonstrated through a Soil/Vegetation Impact Diagram. Part two identifies several spatial and temporal patterns of environmental impact caused by recreation use. The node and linkage pattern of recreation use, campground and trail expansion, ground cover response and succession, rates of soil compaction, and resource response to various intensities of recreation use are important aspects. The final part of the paper deals with measuring environmental impacts caused by recreation use. Management implications of the research findings are considered throughout the paper.     

Potential climate change impacts on Atlantic cod (Gadus morhua) off the northeastern USA

We examined the potential impacts of future climate change on the distribution and production of Atlantic cod (Gadus morhua) on the northeastern USA’s continental shelf. We began by examining the response of cod to bottom water temperature changes observed over the past four decades using fishery-independent resource survey data. After accounting for the overall decline in cod during this period, we show that the probability of catching cod at specified locations decreased markedly with increasing bottom temperature. Our analysis of future changes in water temperature was based on output from three coupled atmosphere–ocean general circulation models under high and low CO₂ emissions. An increase of <1.5°C is predicted for all sectors under the low emission scenario in spring and autumn by the end of this century. Under the high emission scenario, temperature increases range from ～2°C in the north to >3.5°C in the Mid-Atlantic Bight. Under these conditions, cod appear vulnerable to a loss of thermal habitat on Georges Bank, with a substantial loss of thermal habitat farther south. We also examined temperature effects on cod recruitment and growth in one stock area, the Gulf of Maine, to explore potential implications for yield and resilience to fishing. Cod survival during the early life stages declined with increasing water temperatures, offsetting potential increases in growth with warmer temperatures and resulting in a predicted loss in yield and increased vulnerability to high fishing mortality rates. Substantial differential impacts under the low versus high emission scenarios are evident for cod off the northeastern USA.     

Carrying capacity as "Informed Judgment": the values of science and the science of values

Contemporary park and wilderness carrying capacity frameworks rely on formulation of standards of quality, which are defined as minimum acceptable resource and social conditions. Formulation of standards of quality involves elements of both science and values, and both of these elements must be integrated into informed judgments on the part of park and wilderness managers. That is, managers must ultimately make value-based judgments about the maximum acceptable level of visitor-caused impacts to the resource base and the quality of the visitor experience. However, such judgments should be as informed as possible by scientific data on the relationships between visitor use and resulting impacts and the degree to which park and wilderness visitors and other interest groups judge such impacts to be acceptable. Such information represents the “values of science” to managing carrying capacity in parks and wilderness. A growing body of literature has begun to address the corresponding “science of values,” and how this type of information might be integrated in park and wilderness management. Visitor-based research has employed normative theory and techniques to explore the acceptability of a range of resource and social impacts related to visitor use, and findings from these studies are being integrated into a body of knowledge and applied in management decision-making. Conceptual and methodological extensions of the normative approach are currently being explored in a variety of park and wilderness contexts, and new theoretical and empirical approaches are being adapted to address trade-offs inherent in carrying capacity. In these ways, the science of values is progressing to meet the opportunities and challenges of the values of science to park and wilderness management. The concept of carrying capacity, along with the theoretical and methodological approaches described in this paper, can be extended to a large number of natural resource and environmental issues.