Spring Drought (spring + drought)

Distribution by Scientific Domains


Selected Abstracts


Preliminary reconstructions of spring precipitation in southwestern Turkey from tree-ring width

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2003
Ramzi Touchan
Abstract Two reconstructions of spring (May,June) precipitation have been developed for southwestern Turkey. The first reconstruction (1776,1998) was developed from principal components of nine chronologies of Cedrus libani, Juniperus excelsa, Pinus brutia, and Pinus nigra. The second reconstruction (1339,1998) was derived from principal components of three J. excelsa chronologies. Calibration and verification statistics of both reconstructions indicate reasonably accurate reconstruction of spring precipitation for southwestern Turkey, and show clear evidence of multi-year to decadal variations in spring precipitation. The longest period of reconstructed spring drought, defined as consecutive years with less than 80% of normal May,June precipitation, was 4 years (1476,79). Only one drought event of this duration has occurred during the last six centuries. Monte Carlo analysis indicates a less than 33% probability that southwestern Turkey has experienced spring drought longer than 5 years in the past 660 years. Apart from the 1476,79 extended dry period, spring droughts of 3 years in length have only occurred from 1700 to the present. The longest reconstructed wet period, defined as consecutive years with more than 120% of normal May,June precipitation, was 4 years (1532,35). The absence of extended spring drought during the 16th and 17th centuries and the occurrence of extended wet spring periods during these centuries suggest a possible regime shift in climate. Preliminary analysis of links between large-scale climatic variation and these climate reconstructions shows that there is a relationship between extremes in spring precipitation and anomalous atmospheric circulation in the region. Copyright © 2003 Royal Meteorological Society. [source]


Seed size and response to rainfall patterns in annual grasslands: 16 years of permanent plot data

JOURNAL OF VEGETATION SCIENCE, Issue 1 2009
B. Peco
Abstract Question: Are seed size and plant size linked to species responses to inter-annual variations in rainfall and rainfall distribution during the growing season in annual grasslands? Location: A 16-year data set on species abundance in permanent plots 15 km north of Madrid in a Quercus ilex subsp. ballota dehesa. Methods: At species level, a GLM was used to analyse the effects of various rainfall indices (total autumn rainfall, early autumn rainfall and spring drought) on species abundance residuals with respect to time and topography. We also assessed the importance of seed size and plant size in the species responses at community level using species as data points. Seed mass and maximum stem length were used as surrogates for seed size and plant size, respectively. Results: Seed mass and plant size may explain some of the fluctuations in the floristic composition of annual species associated with autumn rainfall patterns. Species that are more abundant in dry autumns have greater seed mass than those species that are more abundant in wet autumns. Early autumn rainfall seems to favour larger plants. Conclusions: Our empirical results support the hypothesis that autumn rainfall patterns affect the relative establishment capacity of small and large seedlings in annual species. [source]


Resilience of a high-conservation-value, semi-arid grassland on fertile clay soils to burning, mowing and ploughing

AUSTRAL ECOLOGY, Issue 4 2010
TOM LEWIS
Abstract In grassland reserves, managed disturbance is often necessary to maintain plant species diversity. We carried out experiments to determine the impact of fire, kangaroo grazing, mowing and disc ploughing on grassland species richness and composition in a nature reserve in semi-arid eastern Australia. Vegetation response was influenced by winter,spring drought after establishment of the experiments, but moderate rainfall followed in late summer,autumn. Species composition varied greatly between sampling times, and the variability due to rainfall differences between seasons and years was greater than the effects of fire, kangaroo grazing, mowing or disc ploughing. In the fire experiment, species richness and composition recovered more rapidly after spring than autumn burning. Species richness and composition were similar to control sites within 12 months of burning and mowing, suggesting that removal of the dominant grass canopy is unnecessary to enhance plant diversity. Two fires (separated by 3 years) and post-fire kangaroo grazing had only minor influence on species richness and composition. Even disc ploughing caused only a small reduction in native richness. The minor impact of ploughing was explained by the small areas that were ploughed, the once-off nature of the treatment, and the high degree of natural movement and cracking in these shrink-swell soils. Recovery of the composition and richness of these grasslands was rapid because of the high proportion of perennial species that resprout vegetatively after fire and mowing. There appears to be little conservation benefit from fire, mowing or ploughing ungrazed areas, as we could identify no native plant species dependent on frequent disturbance for persistence in this grassland community. However, the ability of the Astrebla- and Dichanthium -dominated grasslands to recover quickly after disturbance, given favourable seasonal conditions, suggests that they are well adapted to natural disturbances (e.g. droughts, fire, flooding and native grazing). [source]


Seasonal and annual variation of carbon exchange in an evergreen Mediterranean forest in southern France

GLOBAL CHANGE BIOLOGY, Issue 4 2008
V. ALLARD
Abstract We present 9 years of eddy covariance measurements made over an evergreen Mediterranean forest in southern France. The goal of this study was to quantify the different components of the carbon (C) cycle, gross primary production (GPP) and ecosystem respiration (Reco), and to assess the effects of climatic variables on these fluxes and on the net ecosystem exchange of carbon dioxide. The Puéchabon forest acted as a net C sink of ,254 g C m,2 yr,1, with a GPP of 1275 g C m,2 yr,1 and a Reco of 1021 g C m,2 yr,1. On average, 83% of the net annual C sink occurred between March and June. The effects of exceptional events such the insect-induced partial canopy defoliation that occurred in spring 2005, and the spring droughts of 2005 and 2006 are discussed. A high interannual variability of ecosystem C fluxes during summer and autumn was observed but the resulting effect on the annual net C budget was moderate. Increased severity and/or duration of summer drought under climate change do not appear to have the potential to negatively impact the average C budget of this ecosystem. On the contrary, factors affecting ecosystem functioning (drought and/or defoliation) during March,June period may reduce dramatically the annual C balance of evergreen Mediterranean forests. [source]


Preliminary reconstructions of spring precipitation in southwestern Turkey from tree-ring width

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2003
Ramzi Touchan
Abstract Two reconstructions of spring (May,June) precipitation have been developed for southwestern Turkey. The first reconstruction (1776,1998) was developed from principal components of nine chronologies of Cedrus libani, Juniperus excelsa, Pinus brutia, and Pinus nigra. The second reconstruction (1339,1998) was derived from principal components of three J. excelsa chronologies. Calibration and verification statistics of both reconstructions indicate reasonably accurate reconstruction of spring precipitation for southwestern Turkey, and show clear evidence of multi-year to decadal variations in spring precipitation. The longest period of reconstructed spring drought, defined as consecutive years with less than 80% of normal May,June precipitation, was 4 years (1476,79). Only one drought event of this duration has occurred during the last six centuries. Monte Carlo analysis indicates a less than 33% probability that southwestern Turkey has experienced spring drought longer than 5 years in the past 660 years. Apart from the 1476,79 extended dry period, spring droughts of 3 years in length have only occurred from 1700 to the present. The longest reconstructed wet period, defined as consecutive years with more than 120% of normal May,June precipitation, was 4 years (1532,35). The absence of extended spring drought during the 16th and 17th centuries and the occurrence of extended wet spring periods during these centuries suggest a possible regime shift in climate. Preliminary analysis of links between large-scale climatic variation and these climate reconstructions shows that there is a relationship between extremes in spring precipitation and anomalous atmospheric circulation in the region. Copyright © 2003 Royal Meteorological Society. [source]