144 research outputs found
The species diversity × fire severity relationship is hump-shaped in semiarid yellow pine and mixed conifer forests
The combination of direct human influences and the effects of climate change are resulting in altered ecological disturbance regimes, and this is especially the case for wildfires. Many regions that historically experienced low–moderate severity fire regimes are seeing increased area burned at high severity as a result of interactions between high fuel loads and climate warming with a number of negative ecological effects. While ecosystem impacts of altered fire regimes have been examined in the literature, little is known of the effects of changing fire regimes on forest understory plant diversity even though understory taxa comprise the vast majority of forest plant species and play vital roles in overall ecosystem function. We examined understory plant diversity across gradients of wildfire severity in eight large wildfires in yellow pine and mixed conifer temperate forests of the Sierra Nevada, California, USA. We found a generally unimodal hump-shaped relationship between local (alpha) plant diversity and fire severity. High-severity burning resulted in lower local diversity as well as some homogenization of the flora at the regional scale. Fire severity class, post-fire litter cover, and annual precipitation were the best predictors of understory species diversity. Our research suggests that increases in fire severity in systems historically characterized by low and moderate severity fire may lead to plant diversity losses. These findings indicate that global patterns of increasing fire size and severity may have important implications for biodiversity
Climate, snow, and soil moisture data set for the Tuolumne and Merced river watersheds, California, USA
We present hourly climate data to force land surface
process models and assessments over the Merced and Tuolumne watersheds in
the Sierra Nevada, California, for the water year 2010–2014 period. Climate
data (38 stations) include temperature and humidity (23), precipitation
(13), solar radiation (8), and wind speed and direction (8), spanning an
elevation range of 333 to 2987 m. Each data set contains raw data as
obtained from the source (Level 0), data that are serially continuous with
noise and nonphysical points removed (Level 1), and, where possible, data
that are gap filled using linear interpolation or regression with a nearby
station record (Level 2). All stations chosen for this data set were known
or documented to be regularly maintained and components checked and
calibrated during the period. Additional time-series data included are
available snow water equivalent records from automated stations (8) and
manual snow courses (22), as well as distributed snow depth and co-located
soil moisture measurements (2–6) from four locations spanning the
rain–snow transition zone in the center of the domain. Spatial data
layers pertinent to snowpack modeling in this data set are basin polygons
and 100 m resolution rasters of elevation, vegetation type, forest canopy
cover, tree height, transmissivity, and extinction coefficient. All data are
available from online data repositories (https://doi.org/10.6071/M3FH3D).</p
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Warming of Central European lakes and their response to the 1980s climate regime shift
Lake surface water temperatures (LSWTs) are sensitive to atmospheric warming and have previously been shown to respond to regional changes in the climate. Using a combination of in situ and simulated surface temperatures from 20 Central European lakes, with data spanning between 50 and ∼100 years, we investigate the long-term increase in annually averaged LSWT. We demonstrate that Central European lakes are warming most in spring and experience a seasonal variation in LSWT trends. We calculate significant LSWT warming during the past few decades and illustrate, using a sequential t test analysis of regime shifts, a substantial increase in annually averaged LSWT during the late 1980s, in response to an abrupt shift in the climate. Surface air temperature measurements from 122 meteorological stations situated throughout Central Europe demonstrate similar increases at this time. Climatic modification of LSWT has numerous consequences for water quality and lake ecosystems. Quantifying the response of LSWT increase to large-scale and abrupt climatic shifts is essential to understand how lakes will respond in the future
How Close Do We Live to Water? A Global Analysis of Population Distance to Freshwater Bodies
Traditionally, people have inhabited places with ready access to fresh water.
Today, over 50% of the global population lives in urban areas, and water
can be directed via tens of kilometres of pipelines. Still, however, a large
part of the world's population is directly dependent on access to natural
freshwater sources. So how are inhabited places related to the location of
freshwater bodies today? We present a high-resolution global analysis of how
close present-day populations live to surface freshwater. We aim to increase the
understanding of the relationship between inhabited places, distance to surface
freshwater bodies, and climatic characteristics in different climate zones and
administrative regions. Our results show that over 50% of the
world's population lives closer than 3 km to a surface freshwater body, and
only 10% of the population lives further than 10 km away. There are,
however, remarkable differences between administrative regions and climatic
zones. Populations in Australia, Asia, and Europe live closest to water.
Although populations in arid zones live furthest away from freshwater bodies in
absolute terms, relatively speaking they live closest to water considering the
limited number of freshwater bodies in those areas. Population distributions in
arid zones show statistically significant relationships with a combination of
climatic factors and distance to water, whilst in other zones there is no
statistically significant relationship with distance to water. Global studies on
development and climate adaptation can benefit from an improved understanding of
these relationships between human populations and the distance to fresh
water
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From California’s Extreme Drought to Major Flooding: Evaluating and Synthesizing Experimental Seasonal and Subseasonal Forecasts of Landfalling Atmospheric Rivers and Extreme Precipitation during Winter 2022/23
California experienced a historic run of nine consecutive landfalling atmospheric rivers (ARs) in three weeks’ time during winter 2022/23. Following three years of drought from 2020 to 2022, intense landfalling ARs across California in December 2022–January 2023 were responsible for bringing reservoirs back to historical averages and producing damaging floods and debris flows. In recent years, the Center for Western Weather and Water Extremes and collaborating institutions have developed and routinely provided to end users peer-reviewed experimental seasonal (1–6 month lead time) and subseasonal (2–6 week lead time) prediction tools for western U.S. ARs, circulation regimes, and precipitation. Here, we evaluate the performance of experimental seasonal precipitation forecasts for winter 2022/23, along with experimental subseasonal AR activity and circulation forecasts during the December 2022 regime shift from dry conditions to persistent troughing and record AR-driven wetness over the western United States. Experimental seasonal precipitation forecasts were too dry across Southern California (likely due to their overreliance on La Niña), and the observed above-normal precipitation across Northern and Central California was underpredicted. However, experimental subseasonal forecasts skillfully captured the regime shift from dry to wet conditions in late December 2022 at 2–3 week lead time. During this time, an active MJO shift from phases 4 and 5 to 6 and 7 occurred, which historically tilts the odds toward increased AR activity over California. New experimental seasonal and subseasonal synthesis forecast products, designed to aggregate information across institutions and methods, are introduced in the context of this historic winter to provide situational awareness guidance to western U.S. water managers
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