366 research outputs found
Droughts and the ecological future of tropical savanna vegetation
1. Climate change is expected to lead to more frequent, intense and longer droughts in the future, with major implications for ecosystem processes and human livelihoods. The impacts of such droughts are already evident, with vegetation dieback reported from a range of ecosystems, including savannas, in recent years.
2. Most of our insights into the mechanisms governing vegetation drought responses have come from forests and temperate grasslands, while responses of savannas have received less attention. Because the two life forms that dominate savannasâC3 trees and C4 grassesârespond differently to the same environmental controls, savanna responses to droughts can differ from those of forests and grasslands.
3. Droughtâdriven mortality of savanna vegetation is not readily predicted by just plant droughtâtolerance traits alone, but is the net outcome of multiple factors, including droughtâavoidance strategies, landscape and neighborhood context, and impacts of past and current stressors including fire, herbivory and interâlife form competition.
4. Many savannas currently appear to have the capacity to recover from moderate to severe shortâterm droughts, although recovery times can be substantial. Factors facilitating recovery include the resprouting ability of vegetation, enhanced flowering and seeding and postâdrought amelioration of herbivory and fire. Future increases in drought severity, length and frequency can interrupt recovery trajectories and lead to compositional shifts, and thus pose substantial threats, particularly to arid and semiâarid savannas.
5. Synthesis. Our understanding of, and ability to predict, savanna drought responses is currently limited by availability of relevant data, and there is an urgent need for campaigns quantifying droughtâsurvival traits across diverse savannas. Importantly, these campaigns must move beyond reliance on a limited set of plant functional traits to identifying suites of physiological, morphological, anatomical and structural traits or âsyndromesâ that encapsulate both avoidance and tolerance strategies. There is also a critical need for a global network of longâterm savanna monitoring sites as these can provide key insights into factors influencing both resistance and resilience of different savannas to droughts. Such efforts, coupled with siteâspecific rainfall manipulation experiments that characterize plant traitâdrought response relationships, and modelling efforts, will enable a more comprehensive understanding of savanna drought responses
Convergence of bark investment according to fire and climate structures ecosystem vulnerability to future change
Fire regimes in savannas and forests are changing over much of the world. Anticipating the impact of these changes requires understanding how plants are adapted to fire. Here we test whether fire imposes a broad selective force on a key fire-tolerance trait, bark thickness, across 572 tree species distributed worldwide. We show that investment in thick bark is a pervasive adaptation in frequently burned areas across savannas and forests in both temperate and tropical regions where surface fires occur. Geographic variability in bark thickness is largely explained by annual burned area and precipitation seasonality. Combining environmental and species distribution data allowed us to assess the vulnerability to future climate and fire conditions: tropical rainforests are especially vulnerable, whereas seasonal forests and savannas are more robust. The strong link between fire and bark thickness provides an avenue for assessing the vulnerability of tree communities to fire and demands inclusion in global models
Ground deformation analysis at Campi Flegrei (Southern Italy) by CGPS and tide-gauge network
Campi Flegrei caldera is located 15 km west of the
city of Naples, within the central-southern sector of a
large graben called Campanian Plain. It is an active
volcanic area marked by a quasi-circular caldera
depression, formed by a huge ignimbritic eruption
occurred about 37000 years ago. This caldera was
generated by several collapses produced by strong
explosive eruptions (the last eruption, occurred in
1538, built an about 130 m spatter cone called Mt.
Nuovo). Campi Flegrei area periodically experiences
significant deformation episodes, with uplift
phenomena up to more than 3.5 m in 15 years (from
1970 to 1984), which caused during 1983-84 the
temporary evacuation of about 40000 people from the
ancient part of Pozzuoli town.
The deformation field obtainable by CGPS and tidegauge
stations plays an important role for the
modelling and interpretation of volcanic phenomena,
as well as for forecasting purposes.
The structural complexity of the Campi Flegrei area,
together with the evidence of a strong interaction
between magmatic chamber and shallow geothermal
system, calls for a detailed characterization of the
substructure and of magma-water interaction
processes.
The incoming experiment of deep drilling, down to
about 4 km, will give detailed structural and physical
constraints able to resolve the intrinsic ambiguities of
geophysical data and in particular geodetic ones.
In this poster we describe the recent ground
deformations at Campi Flegrei area by means of GPS
technique and tide gauge stations, discussing the
possible interpretations also in light of further
constraints likely coming from the next CFDDP
(Campi Flegrei Deep Drilling) deep drilling experiment
The importance of monsoon precipitation for foundation tree species across the semiarid Southwestern U.S.
Forest dynamics in arid and semiarid regions are sensitive to water availability, which is becoming increasingly scarce as global climate changes. The timing and magnitude of precipitation in the semiarid southwestern U.S. (âSouthwestâ) has changed since the 21st century began. The region is projected to become hotter and drier as the century proceeds, with implications for carbon storage, pest outbreaks, and wildfire resilience. Our goal was to quantify the importance of summer monsoon precipitation for forested ecosystems across this region. We developed an isotope mixing model in a Bayesian framework to characterize summer (monsoon) precipitation soil water recharge and water use by three foundation tree species (Populus tremuloides [aspen], Pinus edulis [piñon], and Juniperus osteosperma [Utah juniper]). In 2016, soil depths recharged by monsoon precipitation and tree reliance on monsoon moisture varied across the Southwest with clear differences between species. Monsoon precipitation recharged soil at piñon-juniper (PJ) and aspen sites to depths of at least 60 cm. All trees in the study relied primarily on intermediate to deep (10-60 cm) moisture both before and after the onset of the monsoon. Though trees continued to primarily rely on intermediate to deep moisture after the monsoon, all species increased reliance on shallow soil moisture to varying degrees. Aspens increased reliance on shallow soil moisture by 13% to 20%. Utah junipers and co-dominant ñons increased their reliance on shallow soil moisture by about 6% to 12%. Nonetheless, approximately half of the post-monsoon moisture in sampled piñon (38-58%) and juniper (47-53%) stems could be attributed to the monsoon. The monsoon contributed lower amounts to aspen stem water (24-45%) across the study area with the largest impacts at sites with recent precipitation. Therefore, monsoon precipitation is a key driver of growing season moisture that semiarid forests rely on across the Southwest. This monsoon reliance is of critical importance now more than ever as higher global temperatures lead to an increasingly unpredictable and weaker North American Monsoon
Encapsulation of 2-amino-2-methyl-1-propanol with tetraethyl orthosilicate for CO2 capture
Carbon capture is widely recognised as an essential strategy to meet global goals for climate protection. Although various CO2 capture technologies including absorption, adsorption and membrane exist, they are not yet mature for post-combustion power plants mainly due to high energy penalty. Hence researchers are concentrating on developing non-aqueous solvents like ionic liquids, CO2-binding organic liquids, nanoparticle hybrid materials and microencapsulated sorbents to minimize the energy consumption for carbon capture. This research aims to develop a novel and efficient approach by encapsulating sorbents to capture CO2 in a cold environment. The conventional emulsion technique was selected for the microcapsule formulation by using 2-amino-2-methyl-1-propanol (AMP) as the core sorbent and silicon dioxide (SiO2) as the shell. This paper reports the findings on the formulated microcapsules including key formulation parameters, microstructure, size distribution and thermal cycling stability. Furthermore, the effects of microcapsule quality and absorption temperature on the CO2 loading capacity of the microcapsules were investigated using a self-developed pressure decay method. The preliminary results have shown that the AMP microcapsules are promising to replace conventional sorbents.Engineering and Physical Sciences Research Council (EPSRC
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