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Intersite Variation (intersite + variation)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

Use of tree rings to study the effect of climate change on trembling aspen in Québec

GLOBAL CHANGE BIOLOGY, Issue 7 2010
MARIE-PIERRE LAPOINTE-GARANT
Abstract In this paper, we present a new approach, based on a mixed model procedure, to quantify the tree-ring-based growth-climate relationship of trembling aspen along a latitudinal gradient from 46 to 54 °N in eastern Canada. This approach allows breaking down the growth response into general intersite and local climatic responses, and analyzing variations of absolute ring width as well as interannual variations in tree growth. The final model also integrates nonclimatic variables such as soil characteristics and the occurrence of insect outbreaks into the growth predictions. Tree level random effects on growth were important as intercepts but were nonsignificant for the climatic variables, indicating that a single climate,growth relationship was justified in our case. The response of tree growth to climate showed, however, a strong dependence on the spatial scale at which the analysis was performed. Intersite variations in tree growth were mostly dependent on variations in the thermal heat sum, a variable that showed low interannual and high intersite variation. When variation for a single site was analyzed, other variables showed up to be important while the heat sum was unimportant. Finally, future growth under six different climate change scenarios was simulated in order to study the potential impact of climate change. Results suggest only moderate growth increases in the northern portion of the gradient and a growth decrease in the southern portion under future climatic conditions. [source]

Comparing tropical forest tree size distributions with the predictions of metabolic ecology and equilibrium models

ECOLOGY LETTERS, Issue 5 2006
Helene C. Muller-Landau
Abstract Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology predicts that tree abundances will scale as the ,2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic predictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of predictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the predictions of metabolic ecology. In most forests, size distributions are much closer to the predictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality. [source]

Compositional analysis of Yayoi-Heian period ceramics from Okinawa: Examining the potential for provenance study

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 8 2006
Scott M. Fitzpatrick
In Okinawa, locally produced pottery dates back to the Initial Jomon period (,6500 14C yr B.P.). Later in time, especially during the Early Yayoi-Heian period (,300 B.C.,A.D. 300), ceramic assemblages appear to contain mainland (Japan) Yayoi pottery. A greater number of these sherds present in Okinawa over time coincide with an increasing amount of interaction with mainland Japan, as evidenced by other exchange items. In this preliminary study, the authors analyzed sherds from several Early Yayoi-Heian period deposits from sites in Okinawa using thin-section petrography and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The objective was to examine the applicability of these techniques for Okinawan ceramic provenance studies, assess intra- and intersite variation in mineralogical and chemical composition, and determine whether some sites exhibited a higher frequency of pottery from one locale versus another that might suggest the importation of pottery from mainland Japan. Results are equivocal, suggesting that the region's geological complexity may inhibit successful provenance study of ceramics using these and possibly other compositional techniques. © 2006 Wiley Periodicals, Inc. [source]

Use of tree rings to study the effect of climate change on trembling aspen in Québec

Flowering phenology of myrtaceous trees and their relation to climatic, environmental and disturbance variables in northern New South Wales

AUSTRAL ECOLOGY, Issue 2 2000
B. Law
Abstract Patterns of flowering phenology, which represent a partial description of food availability for nectarivores, are described for 20 species of myrtaceous trees on the mid-north coast of New South Wales (NSW), Australia. Data were recorded monthly between 1982 and 1992 across 23 sites that comprise a variety of local environmental conditions and disturbance histories. Flowering periodicity and intensity were highly variable between species and sites, ranging from annual flowering to no flowering over the 10-year period. Cool temperatures prior to floral budding was a strong predictor of flowering for nine species. Extraordinary climatic events also influenced flowering. The period of greatest flowering for all species combined occurred 9 months after the highest monthly rainfall recorded in the survey (March 1985). An 18-month extreme drought led to poor flowering in Corymbia variegata, Eucalyptus acmenoides, Eucalyptus grandis and Eucalyptus resinifera, but recovery after the drought broke was rapid. In contrast to climate, few site-based environmental variables explained the intersite variation in flowering performance of the tree species. Site disturbance from logging at two sites during the survey did not influence flowering in the remaining canopy over following years. No species showed a negative correlation with a history of recent logging, and direct comparisons, between large- and medium-sized trees, of the percentage of foliage in flower showed no differences for any species. At the scale of a timber production forest, the negligible effect of tree size (if >10 cm diameter at breast height over bark), and high stem density resulting from selective logging, leave about half of the net harvestable area producing flowers at a similar density to unlogged forest. However, larger trees flowered more frequently than medium-sized trees in C. variegata (medium: every 5.9 years; large: every 2.3 years) and there was a trend in this direction for 13 of 17 species. Low-intensity burns and wildfires caused differing amounts of crown scorch, sometimes resulting in bud loss, but most species flowered at prefire levels 1,3 years after the disturbance. Eucalyptus microcorys and Angophora costata flowered poorly at sites that experienced frequent low-intensity burns. Regionally, blossom shortages occur through a combination of spatial and temporal patchiness in flowering and the clearing of those species that occurred on soils preferred for agriculture. On the north coast of NSW, these shortages commonly occur from late winter to spring. Species that flower reliably in this period include Eucalyptus robusta, Eucalyptus tereticornis and Eucalyptus siderophloia in late winter and E. siderophloia and E. acmenoides in spring. [source]