53 research outputs found
Wildfire selectivity for land cover type: does size matter ?
Previous research has shown that fires burn certain land cover types disproportionally to their abundance. We used quantile
regression to study land cover proneness to fire as a function of fire size, under the hypothesis that they are inversely
related, for all land cover types. Using five years of fire perimeters, we estimated conditional quantile functions for lower
(avoidance) and upper (preference) quantiles of fire selectivity for five land cover types - annual crops, evergreen oak
woodlands, eucalypt forests, pine forests and shrublands. The slope of significant regression quantiles describes the rate of
change in fire selectivity (avoidance or preference) as a function of fire size. We used Monte-Carlo methods to randomly
permutate fires in order to obtain a distribution of fire selectivity due to chance. This distribution was used to test the null
hypotheses that 1) mean fire selectivity does not differ from that obtained by randomly relocating observed fire perimeters;
2) that land cover proneness to fire does not vary with fire size. Our results show that land cover proneness to fire is higher
for shrublands and pine forests than for annual crops and evergreen oak woodlands. As fire size increases, selectivity
decreases for all land cover types tested. Moreover, the rate of change in selectivity with fire size is higher for preference
than for avoidance. Comparison between observed and randomized data led us to reject both null hypotheses tested
(a = 0.05) and to conclude it is very unlikely the observed values of fire selectivity and change in selectivity with fire size are
due to chance.Funding: This paper was supported by the Fundação para a Ciência e Tecnologia Ph.D. Grant SFRH/BD/40398/2007. JMCP participated in this research under the
framework of research projects ‘‘Forest fire under climate, social and economic changes in Europe, the Mediterranean and other fire-affected areas of the world
(FUME)’’, EC FP7 Grant Agreement No. 243888. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the
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Reassessing global change research priorities in mediterranean terrestrial ecosystems : how far have we come and where do we go from here?
Aim: Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. - Location: Mediterranean terrestrial ecosystems. - Methods: This article revisits the research priorities proposed in a 1998 assessment. - Results: A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. - Main conclusions:(1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with large-scale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use
How expectations became governable: institutional change and the performative power of central banks
Central banks have accumulated unparalleled power over the conduct of macroeconomic policy. Key for this development was the articulation and differentiation of monetary policy as a distinct policy domain. While political economists emphasize the foundational institutional changes that enabled this development, recent performativity-studies focus on central bankers’ invention of expectation management techniques. In line with a few other works, this article aims to bring these two aspects together. The key argument is that, over the last few decades, central banks have identified different strategies to assume authority over “expectational politics” and reinforced dominant institutional forces within them. I introduce a comparative scheme to distinguish two different expectational governance regimes. My own empirical investigation focuses on a monetarist regime that emerged from corporatist contexts, where central banks enjoyed “embedded autonomy” and where commercial banks maintained conservative reserve management routines. I further argue that innovations towards inflation targeting took place in countries with non-existent or disintegrating corporatist structures and where central banks turned to finance to establish a different version of expectation coordination. A widespread adoption of this “financialized” expectational governance has been made possible by broader processes of institutional convergence that were supported by central bankers themselves
Accumulation of Calcium in the Centre of Leaves of Coriander (Coriandrum sativum L.) is Due to an Uncoupling of Water and Ion Transport.
The aim of this study is to understand the parameters
regulating calcium ion distribution in leaves. Accumulation
of ions in leaf tissue is in part dependent on
import from the xylem. This import via the transpiration
stream is more important for ions such as calcium
that are xylem but not phloem mobile and cannot
therefore be retranslocated. Accumulation of calcium
was measured on bulk coriander leaf tissue (Coriandrum
sativum L. cv. Lemon) using ion chromatography
and calcium uptake was visualized using phosphorimages
of 45Ca2+. Leaves of plants grown in hydroponics
had elevated calcium in the centre of the leaf
compared with the leaf margin, while K+ was distributed
homogeneously over the leaf. This calcium was
shown to be localised to the mesophyll vacuoles using
EDAX. Stomatal density and evapotranspiration (water
loss per unit area of leaf) were equal at inner and outer
sections of the leaf. Unequal ion distribution but
uniformity of water loss suggested that there was
a difference in the extent of uncoupling of calcium and
water transport between the inner and outer leaf. Since
isolated tissue from the inner and outer leaf were able
to accumulate similar amounts of calcium, it is proposed
that the spatial variation of leaf calcium concentration
is due to differential ion delivery to the two
regions rather than tissue/cell-specific differences in
ion uptake capacity. There was a positive correlation
between whole leaf calcium concentration and the
difference in calcium concentration between inner and
outer leaf tissue. Exposing the plants to increased
humidity reduced transpiration and calcium delivery to
the leaf and abolished this spatial variation of calcium
concentration. Mechanisms of calcium delivery to
leaves are discussed. An understanding of calcium
delivery and distribution within coriander will inform
strategies to reduce the incidence of calcium-related
syndromes such as tip-burn and provides a robust
model for the transport of ions and other substances
in the leaf xylem
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