Matching Items (17)

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Dual thinking for scientists

Description

Recent studies provide compelling evidence for the idea that creative thinking draws upon two kinds of processes linked to distinct physiological features, and stimulated under different conditions. In short, the

Recent studies provide compelling evidence for the idea that creative thinking draws upon two kinds of processes linked to distinct physiological features, and stimulated under different conditions. In short, the fast system-I produces intuition whereas the slow and deliberate system-II produces reasoning. System-I can help see novel solutions and associations instantaneously, but is prone to error. System-II has other biases, but can help checking and modifying the system-I results. Although thinking is the core business of science, the accepted ways of doing our work focus almost entirely on facilitating system-II. We discuss the role of system-I thinking in past scientific breakthroughs, and argue that scientific progress may be catalyzed by creating conditions for such associative intuitive thinking in our academic lives and in education. Unstructured socializing time, education for daring exploration, and cooperation with the arts are among the potential elements. Because such activities may be looked upon as procrastination rather than work, deliberate effort is needed to counteract our systematic bias.

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Created

Date Created
  • 2015

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Effect of woody-plant encroachment on livestock production in North and South America

Description

A large fraction of the world grasslands and savannas are undergoing a rapid shift from herbaceous to woody-plant dominance. This land-cover change is expected to lead to a loss in

A large fraction of the world grasslands and savannas are undergoing a rapid shift from herbaceous to woody-plant dominance. This land-cover change is expected to lead to a loss in livestock production (LP), but the impacts of woody-plant encroachment on this crucial ecosystem service have not been assessed. We evaluate how tree cover (TC) has affected LP at large spatial scales in rangelands of contrasting social–economic characteristics in the United States and Argentina. Our models indicate that in areas of high productivity, a 1% increase in TC results in a reduction in LP ranging from 0.6 to 1.6 reproductive cows (Rc) per km[superscript 2]. Mean LP in the United States is 27 Rc per km[superscript 2], so a 1% increase in TC results in a 2.5% decrease in mean LP. This effect is large considering that woody-plant cover has been described as increasing at 0.5% to 2% per y. On the contrary, in areas of low productivity, increased TC had a positive effect on LP. Our results also show that ecological factors account for a larger fraction of LP variability in Argentinean than in US rangelands. Differences in the relative importance of ecological versus nonecological drivers of LP in Argentina and the United States suggest that the valuation of ecosystem services between these two rangelands might be different. Current management strategies in Argentina are likely designed to maximize LP for various reasons we are unable to explore in this effort, whereas land managers in the United States may be optimizing multiple ecosystem services, including conservation or recreation, alongside LP.

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Created

Date Created
  • 2014-09-02

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THE INFLUENCE OF SURFACE ROCK COVER ON WATER AND NUTRIENT AVAILABILITY FOR WINTER ANNUAL PLANTS IN THE SONORAN DESERT

Description

Water is the main driver of net primary productivity (NPP) in arid ecosystems, followed by nitrogen and phosphorous. Precipitation is the primary factor in determining water availability to plants, but

Water is the main driver of net primary productivity (NPP) in arid ecosystems, followed by nitrogen and phosphorous. Precipitation is the primary factor in determining water availability to plants, but other factors such as surface rocks could also have an impact. Surface rocks may positively affect water availability by preventing evaporation from soil, but at higher densities, surface rocks may also have a negative impact on water availability by limiting water infiltration or light availability. However, the direct relationship between rock cover and aboveground net primary productivity (ANPP), a proxy for NPP, is not well understood. In this research we explore the relationship between rock cover, ANPP, and soil nutrient availability. We conducted a rock cover survey on long-term fertilized plots at fifteen sites in the Sonoran Desert and used 4 years of data from annual plant biomass surveys to determine the relationship between peak plant biomass and surface rock cover. We performed factorial ANCOVA to assess the relationship among annual plant biomass, surface rocks, precipitation, and fertilization treatment. Overall we found that precipitation, nutrients, and rock cover influence growth of Sonoran Desert annual plants. Rock cover had an overall negative relationship with annual plant biomass, but did not show a consistent pattern of significance over four years of study and with varying average winter precipitation.

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Created

Date Created
  • 2015-05

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Automated rainfall manipulation system: a reliable and inexpensive tool for ecologists

Description

Water availability is the major limiting factor of the functioning of deserts and grasslands and is going to be severely modified by climate change. Field manipulative experiments of precipitation represent

Water availability is the major limiting factor of the functioning of deserts and grasslands and is going to be severely modified by climate change. Field manipulative experiments of precipitation represent the best way to explore cause-effect relationships between water availability and ecosystem functioning. However, there is a limited number of that type of studies because of logistic and cost limitations. Here, we report on a new system that alters precipitation for experimental plots from 80% reduction to 80% increase relative to ambient, that is low cost, and is fully solar powered. This two-part system consists of a rainout shelter that intercepts water and sends it to a temporary storage tank, from where a solar-powered pump then sends the water to sprinklers located in opposite corners of an irrigated plot. We tested this automated system for 5 levels of rainfall, reduction-irrigation (50–80%) and controls with N = 3. The system showed high reduction/irrigation accuracy and small effect on temperature and photosynthetically active radiation. System average cost was $228 USD per module of 2.5 m by 2.5 m and required low maintenance.

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Created

Date Created
  • 2013-02

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Enhanced precipitation variability effects on water losses and ecosystem functioning: differential response of arid and mesic regions

Description

Climate change will result in increased precipitation variability with more extreme events reflected in more frequent droughts as well as more frequent extremely wet conditions. The increase in precipitation variability

Climate change will result in increased precipitation variability with more extreme events reflected in more frequent droughts as well as more frequent extremely wet conditions. The increase in precipitation variability will occur at different temporal scales from intra to inter-annual and even longer scales. At the intra-annual scale, extreme precipitation events will be interspersed with prolonged periods in between events. At the inter-annual scale, dry years or multi-year droughts will be combined with wet years or multi-year wet conditions. Consequences of this aspect of climate change for the functioning ecosystems and their ability to provide ecosystem services have been underexplored. We used a process-based ecosystem model to simulate water losses and soil-water availability at 35 grassland locations in the central US under 4 levels of precipitation variability (control, +25, +50 + 75 %) and six temporal scales ranging from intra- to multi-annual variability. We show that the scale of temporal variability had a larger effect on soil-water availability than the magnitude of variability, and that inter- and multi-annual variability had much larger effects than intra-annual variability. Further, the effect of precipitation variability was modulated by mean annual precipitation. Arid-semiarid locations receiving less than about 380 mm yr[superscript −1] mean annual precipitation showed increases in water availability as a result of enhanced precipitation variability while more mesic locations (>380 mm yr[superscript −1]) showed a decrease in soil water availability. The beneficial effects of enhanced variability in arid-semiarid regions resulted from a deepening of the soil-water availability profile and a reduction in bare soil evaporation. The deepening of the soil-water availability profile resulting from increase precipitation variability may promote future shifts in species composition and dominance to deeper-rooted woody plants for ecosystems that are susceptible to state changes. The break point, which has a mean of 380-mm with a range between 440 and 350 mm, is remarkably similar to the 370-mm threshold of the inverse texture hypothesis, below which coarse-texture soils had higher productivity than fine-textured soils.

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Created

Date Created
  • 2015-07-01

The imprint of crop choice on global nutrient needs

Description

Solutions to meet growing food requirements in a world of limited suitable land and degrading environment focus mainly on increasing crop yields, particularly in poorly performing regions, and reducing animal

Solutions to meet growing food requirements in a world of limited suitable land and degrading environment focus mainly on increasing crop yields, particularly in poorly performing regions, and reducing animal product consumption. Increasing yields could alleviate land requirements, but imposing higher soil nutrient withdrawals and in most cases larger fertilizer inputs. Lowering animal product consumption favors a more efficient use of land as well as soil and fertilizer nutrients; yet actual saving may largely depend on which crops and how much fertilizer are used to feed livestock versus people. We show, with a global analysis, how the choice of cultivated plant species used to feed people and livestock influences global food production as well as soil nutrient withdrawals and fertilizer additions. The 3 to 15-fold differences in soil nutrient withdrawals per unit of energy or protein produced that we report across major crops explain how composition shifts over the last 20 years have reduced N, maintained P and increased K harvest withdrawals from soils while contributing to increasing dietary energy, protein and, particularly, vegetable fat outputs. Being highly variable across crops, global fertilization rates do not relate to actual soil nutrient withdrawals, but to monetary values of harvested products. Future changes in crop composition could contribute to achieve more sustainable food systems, optimizing land and fertilizer use.

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Created

Date Created
  • 2014-08-01

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Differential sensitivities of grassland structural components to changes in precipitation mediate productivity response in a desert ecosystem

Description

In arid and semi-arid ecosystems, there are legacies of previous-year precipitation on current-year above-ground net primary production. We hypothesized that legacies of past precipitation occur through changes in tiller density,

In arid and semi-arid ecosystems, there are legacies of previous-year precipitation on current-year above-ground net primary production. We hypothesized that legacies of past precipitation occur through changes in tiller density, stolon density, tiller growth, axillary bud density and percentage of viable axillary buds. We examined the sensitivity to current- and previous-year precipitation of these grassland structural components in Bouteloua eriopoda, the dominant grass in the northern Chihuahuan Desert.
We conducted a rainfall manipulation experiment consisting in −80% reduced precipitation, ambient, +80% increased precipitation treatments that were subjected to one of five precipitation levels in the previous two years (−80% and −50% reduced precipitation, ambient, +50% and +80% increased precipitation). The first two years preconditioned the experimental plots for year three, in which we created wet-to-dry and dry-to-wet transitions. Measurements were taken in year 3.
We found that stolon density was the most sensitive to changes in precipitation and that percent-active buds were insensitive.
We also found that past precipitation had a significant legacy on grassland structural components regardless of the precipitation received in the current year, and that the legacy occurs mostly through changes in stolon density.
Here, we showed that there is a differential sensitivity of structural components to current and past precipitation and supported previous findings that vegetation structure is one of the controls of productivity during precipitation transitions.

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Agent

Created

Date Created
  • 2014-10-01

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Climate change will increase savannas at the expense of forests and treeless vegetation in tropical and subtropical Americas

Description

Transition areas between biomes are particularly sensitive to environmental changes. Our understanding of the impacts of ongoing climate change on terrestrial ecosystems has significantly increased during the last years. However,

Transition areas between biomes are particularly sensitive to environmental changes. Our understanding of the impacts of ongoing climate change on terrestrial ecosystems has significantly increased during the last years. However, it is largely unknown how climatic change will affect transitions among major vegetation types.
We modelled the distribution of three alternative states (forest, savanna and treeless areas) in the tropical and subtropical Americas by means of climate-niche modelling. We studied how such distribution will change by the year 2070 by using 17 downscaled and calibrated global climate models from the Coupled Model Intercomparison Project Phase 5 and the latest scenarios provided by the 5th Assessment Report of the IPCC.
Our results support the savannization of the tropical and subtropical Americas because of climate change, with an increase in savannas mainly at the expense of forests.
Our models predict an important geographical shift in the current distribution of transition areas between forest and savannas, which is much less pronounced in the case of those between savannas and treeless areas. Largest shifts, up to 600 km northward, are predicted in the forest–savanna transitions located in the eastern Amazon.
Our findings indicate that climate change will promote a shift towards more unstable states: the extent of the transition areas will notably increase, and largely stable forest areas are predicted to shrink dramatically.
Synthesis. Our work explores dimensions of the impact of climate change on biomes that have received little attention so far. Our results indicate that climate change will not only affect the extent of savanna, forest and treeless areas in the tropical and subtropical Americas, but also will: (i) promote a significant geographical shift and an increase of the extent of transition areas between biomes and (ii) decrease the stability of the equilibrium between forest, savanna and treeless areas, yielding a more unpredictable system.

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Agent

Created

Date Created
  • 2014-11-01

Soil animal responses to moisture availability are largely scale, not ecosystem dependent: insight from a cross-site study

Description

Climate change will result in reduced soil water availability in much of the world either due to changes in precipitation or increased temperature and evapotranspiration. How communities of mites and

Climate change will result in reduced soil water availability in much of the world either due to changes in precipitation or increased temperature and evapotranspiration. How communities of mites and nematodes may respond to changes in moisture availability is not well known, yet these organisms play important roles in decomposition and nutrient cycling processes. We determined how communities of these organisms respond to changes in moisture availability and whether common patterns occur along fine-scale gradients of soil moisture within four individual ecosystem types (mesic, xeric and arid grasslands and a polar desert) located in the western United States and Antarctica, as well as across a cross-ecosystem moisture gradient (CEMG) of all four ecosystems considered together. An elevation transect of three sampling plots was monitored within each ecosystem and soil samples were collected from these plots and from existing experimental precipitation manipulations within each ecosystem once in fall of 2009 and three times each in 2010 and 2011. Mites and nematodes were sorted to trophic groups and analyzed to determine community responses to changes in soil moisture availability. We found that while both mites and nematodes increased with available soil moisture across the CEMG, within individual ecosystems, increases in soil moisture resulted in decreases to nematode communities at all but the arid grassland ecosystem; mites showed no responses at any ecosystem. In addition, we found changes in proportional abundances of mite and nematode trophic groups as soil moisture increased within individual ecosystems, which may result in shifts within soil food webs with important consequences for ecosystem functioning. We suggest that communities of soil animals at local scales may respond predictably to changes in moisture availability regardless of ecosystem type but that additional factors, such as climate variability, vegetation composition, and soil properties may influence this relationship over larger scales.

Contributors

Created

Date Created
  • 2014-08-01

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Physiological Response to Environmental Stress in Drylands Ecosystems: Examining Prosopis velutina Seedling Responses to Temporal Water Availability Gradients

Description

Climate change is increasing global surface temperatures, intensifying droughts and increasing rainfall variation, particularly in drylands. Understanding how dryland plant communities respond to climate change-induced rainfall changes is crucial for

Climate change is increasing global surface temperatures, intensifying droughts and increasing rainfall variation, particularly in drylands. Understanding how dryland plant communities respond to climate change-induced rainfall changes is crucial for implementing effective conservation strategies. Concurrent with climate change impacts on drylands is woody encroachment: an increase in abundance of woody plant species in areas formerly dominated by grasslands or savannahs. For example, the woody plant, Prosopis velutina (velvet mesquite), has encroached into grasslands regionally over the past century. From an agricultural perspective, P. velutina is an invasive weed that hinders cattle forage. Understanding how P. velutina will respond to climate change-induced rainfall changes can be useful for management and conservation efforts. Prosopis velutina was used to answer the following question: Is there a significant interactive effect of mean soil water moisture content and pulse frequency on woody seedling survival and growth in dryland ecosystems? There were 256 P. velutina seedlings sourced from the Santa Rita Experimental Range in southern Arizona grown under four watering treatments where mean and pulse frequency were manipulated over two months. Data were collected on mortality, stem height, number of leaves, instantaneous gas exchange, chlorophyll fluorescence, biomass, and the leaf carbon to nitrogen (C:N) ratio. Mortality was low across treatments. Pulse frequency had less impact across response variables than the mean amount of water received. This may indicate that P. velutina seedlings are relatively insensitive to rainfall timing and are more responsive to rainfall amount. Prosopis velutina in the low mean soil moisture treatments lost a majority of their leaves and had greater biomass allocation to roots. Prosopis velutina’s ability to survive in low soil moisture conditions and invest in root biomass can allow it to persist as drylands are further affected by climate change. Prosopis velutina could benefit ecosystems where native plants are at risk due to rainfall variation if P. velutina occupies a similar niche space. Due to conflicting viewpoints of P. velutina as an invasive species, it’s important to examine P. velutina from both agricultural and conservation perspectives. Further analysis on the benefits to P. velutina in these ecosystems is recommended.

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Agent

Created

Date Created
  • 2020