Nature Precedings - Tag feed for climate change

A Comparative Study of the Magnitude, Frequency and Distribution of Intense Rainfall in the United Kingdom

Mon, 12 Oct 2009 07:56:27 UTC

During the 1960s, a study was made of the magnitude, frequency and distribution of intense rainfall over the UK, employing data from more than 120 daily-read rain gauges covering the period 1911 to 1960. Using the same methodology, that study was recently updated utilizing data for the period 1961 to 2006 for the same gauges, or from those nearby. This paper describes the techniques applied to ensure consistency of data and statistical modelling. It presents a comparison of patterns of extreme rainfalls for the two periods and discusses the changes that have taken place. Most noticeably, increases up to 20% have occurred in the north west of the country and in parts of East Anglia. There have also been changes in other areas, including decreases of the same magnitude over central England. The implications of these changes are considered.

Resin duct density and size predicts mortality in ponderosa pine trees of Northern Arizona

Jeffrey M. Kane — Wed, 09 Sep 2009 23:15:55 UTC

In the presence of herbivores, plants must allocate a portion of their accumulated carbon towards defense to survive. For example, trees susceptible to bark beetle attack are primarily reliant on resin production for protection. Tree mortality may be reflected by individual differences in the ability of plants to produce defensive structures and compounds. We compared the radial growth rates, resin duct production, density, and size between living and dead ponderosa pine trees in northern Arizona using standard dendrochronology techniques. As a result, we found four main findings: 1) living ponderosa pines had 33% more resin ducts than dead pines (t = 2.97, P < 0.003); 2) resin duct size was 13% larger in living than in dead pines (t = 3.00, P < 0.003); 3) both resin duct density and size were predictive of mortality (Wald’s Z = 1.9, P < 0.05); and 4) resin duct production was positively correlated with growth rate. Our results suggest dendrochronology can quantify defense structure production and predict tree mortality in ponderosa pine forests in northern Arizona.

The effect of drought and subsequent precipitation pulse on productivity, species composition, and carbon fluxes of the herbaceous understorey in a cork oak woodland

Marjan Jongen — Wed, 02 Sep 2009 09:34:27 UTC

In the Iberian Peninsula, the cork oak woodlands are of great ecological and socio-economic importance. These savanna-type woodlands are characterized by an herbaceous understorey, dominated by C3 annual species. The productivity and related ecosystem processes of this understorey are highly dependent on timing and magnitude of precipitation events. Climate change scenarios for the Iberian Peninsula suggest not only increasing air temperatures, but also the possibility of decreasing spring precipitation, accompanied by an increase in the interval between precipitation events, which might cause drought conditions to occur, with more severe effects on productivity and ecosystem processes. An experiment was carried out in southern Portugal to assess the effect of a drought treatment, with a subsequent extreme precipitation event, on the herbaceous component of managed cork oak woodland. The facility consisted of five plots with rainout shelters (2.5×2.5 m), which exclude normal rainfall inputs (drought treatment), and five non-sheltered control plots (control treatment). In the drought treatment, 193 mm of precipitation was excluded in the period from mid March to mid May, with a subsequent precipitation pulse of 50 mm in the middle of May. Variables measured included productivity, plant community composition, soil respiration and soil microbial activity.

Moisture availability influences the effect of ultraviolet-B radiation on leaf litter decomposition

William K. Smith — Tue, 18 Aug 2009 07:55:48 UTC

Altered surface ultraviolet-B (UV-B) radiation resulting from a combination of factors that include changes in stratospheric ozone concentrations, cloud cover, and aerosol conditions may affect litter decomposition and, thus, terrestrial nutrient cycling on a global scale. Although litter decomposition rates vary across biomes, patterns of decomposition suggest that UV-B radiation accelerates litter decay in xeric environments where precipitation is infrequent. However, under more frequent precipitation regimes where litter decay rates are characteristically high, the effect of UV-B radiation on litter decomposition has not been fully elucidated. To evaluate this association between moisture regime and UV-B exposure, a litter decomposition experiment was designed for aspen (Populus tremuloides) leaf litter, where conditions that influence both abiotic (photodegradation) and biotic (microbial) processes could be manipulated quantitatively. We found that experimentally increasing UV-B exposure (0, 7.4, and 11.2 kJ m-2 d-1, respectively) did not consistently increase litter decomposition rates across simulated precipitation frequencies of 4-, 12-, and 24-days. Instead, a UV-B exposure of 11.2 kJ m-2 d-1 resulted in a 13% decrease in decomposition rates under the 4-day precipitation frequency, but an increase of 80% under the 24-day frequency. Furthermore, the same UV-B dose increased litter decomposition rates under the 24-day precipitation frequency by 78% even in conditions where microbial activity was suppressed. Therefore, under more xeric conditions, greater exposure to UV-B radiation increased decomposition rates, presumably through photodegradation. In contrast, when decomposition was not moisture-limited, greater UV-B exposure slowed decomposition rates, most likely from the resulting inhibition of microbial activity. Ultimately, these experimental results highlight UV-B radiation as a potential driver of decomposition, as well as indicate that both the direction and magnitude of the UV-B effect is dependent on moisture availability, a factor that may change according to future patterns in global precipitation.

Can global models reproduce the current increase in Western United States Wildfires and project a reliable future trend?

Dominique Bachelet — Mon, 17 Aug 2009 09:07:52 UTC

Background/Question/Methods:Wildfires in the western U.S. are generally thought to have increased since the 1980s. Many factors have contributed to this increase such as fire suppression, livestock grazing, and urban sprawl. Fires have also been associated with variations in sea surface temperatures and described by indices such as El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Atlantic Multidecadal Oscillation (AMO). Recent analyses have also shown that we may have entered a new fire regime starting with a climate shift in 1998 and are currently entering years of combined long-term warm AMO phase with cool ENSO and PDO phases usually associated with increased drought-induced fires in the interior West. Moreover, while the increase in atmospheric CO2 is likely increasing water use efficiency and thus reducing drought stress in western ecosystems, it may also have enhanced fuel build-up as warm temperatures enhance growth and thus contribute to larger fires during extreme drought conditions. Results/Conclusions:We have run our dynamic vegetation model MC1 in the conterminous United States at various spatial resolutions (grain) and documented the relative importance of climate and CO2 on historical fires (1895-2006) using continental (2500km2 pixels), regional (100km2 pixels), and local (0.64km2) climate and soil datasets. We will present some of our results at those various scales, compare them to observations, and discuss scaling issues.

The Effects of Climate Change on the Phenological Interactions of Plants and Pollinators

David W. Inouye — Mon, 10 Aug 2009 16:27:35 UTC

Symposium title: Interdisciplinary Canary: Linkages between Ecology and Sustainable Decision Making in a Dynamic Environment1) Background/Question/MethodsThe responses of pollinators to climate change could include changes in phenology of migratory pollinators and in the routes or destinations for their migration, changes in the phenology and distribution of non-migratory species, and changes in the host plants they visit for nectar and pollen. Plants face similar challenges with regard to changes in their distributions, their reproductive phenology, and interactions with both co-flowering species and pollinators (competition, facilitation, etc.). Unless pollinators and their host plants are responding similarly to changing environmental cues that affect their phenology, their historical patterns of interaction, both mutualistic and competitive, are likely to change. Long-term data are essential to investigating which if any of these potential outcomes are occurring. A 36-year record of abundance and phenology of flowering of 90+ wildflower species, surveys of the altitudinal distribution of bumble bees in the 1970s and the past few years, and data from a long-term Malaise trap sampling program, all near the Rocky Mountain Biological Laboratory (West Elk mountains, Colorado) are used for this investigation. 2) Results/ConclusionsAlthough the flowering phenology of all species examined to date is affected by a single environmental event, disappearance of the winter snowpack (range 22 April -19 June since 1975), either their responses to that single cue are not uniform, or different species respond to additional cues in addition to snowmelt (e.g., growing degree days). Thus the community of co-flowering species varies temporally and quantitatively among years; differential sensitivity to frost damage is an example of an environmental variable that generates the quantitative variation among years, and is in turn affected by date of snowmelt. Arrival dates of migratory Broad-tailed Hummingbirds are significantly correlated with the amount of snow remaining on 30 April, and with the day of first flowering of Erythronium grandiflorum (glacier lily), the first flower that they visit at this site in the spring. Altitudinal distributions of at least some bumble bee species, and of the flowers they feed on, are also changing, with one bee species occurring about 600m higher than it did 30 years ago and one wildflower (Mertensia cilata) disappearing from lower altitudes where it was historically common. As these communities of plants and pollinators respond to environmental changes with changes in phenology and distribution, new interactions will be created and old ones will be lost.

The importance of decadal-scale climate variability to wind-driven modulation of hypoxia in Chesapeake Bay

Malcolm E. Scully — Wed, 03 Jun 2009 16:36:32 UTC

Millions of dollars are spent annually to reduce nutrient loading to Chesapeake Bay, with a fundamental goal of reducing the extent and severity of low dissolved oxygen (hypoxia) during the summertime months1. Yet despite recent reductions in nutrient loading, large volumes of the Bay continue to be impacted by hypoxia and anoxia during the summer months2-3. One obstacle to assessing efforts to improve water quality in the Bay and other estuarine systems is a complete understanding of the physical processes that modulate dissolved oxygen and the long-term variability of these processes. Here I analyze a 58-year data set of estimated hypoxic volume in the Bay2 and demonstrate the importance that wind direction plays in controlling the extent and severity of summertime hypoxia. This analysis indicates that wind direction explains a greater percentage of the observed inter-annual variation in hypoxic volume than estimates of nutrient loading. The implication is that physical processes play a dominant role in modulating hypoxia and that much of the increased hypoxia observed since the early 1980s can be attributed to changes in wind forcing that are the result of decadal-scale climate variability. These findings emphasize the importance of understanding the physical processes that modulate dissolved oxygen in coastal and estuarine systems and highlight the potential impact that climate change may have on water quality in Chesapeake Bay and other estuarine systems.

Projected Climate Change Impacts on Grape Growing in the Okanagan Valley, British Columbia, Canada

Sierra Rayne — Fri, 24 Apr 2009 19:20:12 UTC

A statistical analysis was conducted on long-term climate records in the Okanagan Valley wine grape growing region of British Columbia, Canada. No observable trends for average annual temperatures were found in the region. Analyses of monthly mean and extreme temperatures show wide spatial and temporal heterogeneity, indicating that future studies using downscaling of global climate models for this region will require resolutions on the order of several kilometers. Mean winter temperatures are increasing throughout the valley, and extreme minimum temperatures are also increasing during the winter at the central and northern sites which have historically presented the most risk of winter damage to grapevines. Only the most southern and northern sub-regions are expected to see significant changes in their heat unit accumulations during the growing season. Over the coming century, the southern end of the valley will likely move from Winkler heat unit region 1 to 2. All regions of the Okanagan will continue to have latitude-temperature indices among the lowest of the world’s fine table wine producing regions over the coming century. Growing season and dormant season average temperatures are expected to change by only a modest amount by 2100. Current climate maturity groupings for ripening grape varieties will likely stay constant at cool (central and southern areas) and intermediate (south-central) for all sites except Osoyoos (south). The climate trendings at Osoyoos suggest it will transition from an intermediate to a warm grouping by about 2050. The early to mid-season ripening capacity of the region may improve due to climate changes, but there is a risk of the asymmetric late season increases in minimum daily temperatures lowering the daily temperature range at some sites, possibly leading to difficulties in maintaining a balanced between sugar and sensory profiles as wine grapes approach maturity. The projected warming at the southern end of the valley should favor improved and increased Merlot production, will require Chardonnay production to shift northwards, and will allow growing of warmer climate wine grape varieties currently inaccessible because of low winter temperatures and a lack of growing season heat units. Increasing winter temperatures throughout the region are expected to result in increased risk of pests such as Pierce’s disease.

Global warming affected some morphological characters of Pistachio trees (Pistacia vera L.)

Amanollah A. Javanshah — Tue, 02 Dec 2008 16:07:36 UTC

Pistachio is one of the main horticulture crops in Iran where have the first cultivation and exportation position in the world. Climate change has already affected species distribution shifts in many parts of the world and more impacts are expected for the future, yet few studies have aimed for a general understanding of the regional basis for species vulnerability. In this research meteorology data of four months (December, January, February and March) from 1991 to 2008 and Phenology data of six pistachio cultivars that ranked in 3 groups: early flowering (Kalehghoochi and Ahmadaghaei), mid flowering (Momtaz and Amiri) and late flowering (Akbari and Shahpasand) during summer of 1997, 2001-5, and 2007 were studied in Kerman province. The evaluated factors included leaf area, normal and abnormal leaves. The results showed the mean of temperature on March has significant increasing during 1991 to 2008 and fluctuations between years increased after 1999 in December, January and February. Phenological characters including leaf area and number of normal and abnormal leaves were different each year that abnormality leaves in early and late flowering cultivars had negative correlation with mean temperature of December and mid flowering cultivars had positive correlation with mean temperature of February. The level of leaf area changing in Ahamadaghaei cultivar was less than other cultivars but kallehghoochi and Akbari had the highest range which can probably be a good marker for determining the effects of temperature changes in winter on production level.

Increasing Insect Reactions in Alaska: Is this Related to Changing Climate?

Jeffrey Demain — Fri, 07 Nov 2008 11:05:29 UTC

During the summer of 2006, Fairbanks Alaska experienced its first two known cases of fatal anaphylaxis as a result of Hymenoptera stings, presumably from yellowjackets. An increase in insect bites and stings has been observed throughout the state.Has there been an increased incidence of medical visits due to insect bites and stings in Alaska in recent years? We conducted a retrospective review of three independent patient databases in Alaska to identify trends of patients seeking medical care for adverse reactions following insect bites and stings. For each database, an insect bite or sting episode warranting medical care was defined as a claim for the Clinical Modification of the International Classification of Diseases, Ninth Revision (ICD-9-CM), codes E905.3 (venomous insect; Hymenoptera); E906.4 (bite; non-venomous arthropod), and 989.5 (toxic effect; venom). Increases in bite and sting events in each region were compared to temperature changes in the same region. Each database revealed a statistically significant trend in patients seeking care for reactions to insect bites and stings. Fairbanks Memorial Hospital Emergency Department reported a four-fold increase in patients in 2006 compared to previous years (1992-2005). The Allergy Asthma and Immunology Center of Alaska reported a three-fold increase in patients from 1999 – 2002 to 2003- 2007. A retrospective review of the Alaska Medicaid database between 1999 and 2006 showed increases in billings for insect bites and stings among all regions, with the largest percentage increases occurring in the most northern areas. Alaska has experienced an increase in insect bites and stings, most dramatically indicated by two anaphylaxis deaths due to Hymenoptera stings. Statistically significant increases in patients seeking medical care for insect bite and sting related events are observed throughout the state, with 5 of the 6 regions experiencing at least a 6 degree Fahrenheit increase in winter temperature since 1950.