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The gopher tortoise is a familiar turtle species across the southeastern Coastal Plain, but its population has declined significantly over several decades. A principal reason is that much of its primary habitat – sparse, open stands of mature pine – has been replaced by development or agriculture, or has become degraded through the suppression of low‐intensity, forage‐producing ground fires. The gopher tortoise is a “keystone” species, meaning that its disappearance from the landscape would negatively impact many other species that make use of its underground burrows. Out of concern over its decline and its important role in the ecosystem, the gopher tortoise is being considered for listing under the federal...
A field experiment was established to quantify the effects of different amounts of rainfall on root growth and dry mass of belowground plant parts in three types of grassland ecosystems. Mountain (Nardus grassland), highland (wet Cirsium grassland), and lowland grassland (dry Festuca grassland) ecosystems were studied in 2006 and 2007. Roofs constructed above the canopy of grass stands and gravity irrigation systems simulated three climate scenarios: (1) rainfall reduced by 50%, (2) rainfall enhanced by 50%, and (3) the full natural rainfall of the current growing season. Experimentally reduced amounts of precipitation significantly affected both yearly root increments and total root dry mass in the highland grassland....
Current climate models predict a shift to warmer, drier conditions in the southwestern US. While major shifts in plant distribution are expected to follow these climate changes, interactions among species and intraspecific genetic variation rarely have been incorporated into models of future plant distributions. We examined the drought-related mortality of pinyon pine (Pinus edulis) in northern Arizona focusing on trees that showed genetically-based resistance or susceptibility to a nonlethal herbivore, the shoot-boring moth, Dioryctria albovittella. Because moth resistant trees have outperformed susceptible trees during 20 years of study, and herbivory has been shown to increase drought related mortality, we expected...
Riparian cottonwood (Populus deltoides) forests form the one of the most extensive deciduous forest ecosystems in arid regions of the western United States. However, cottonwood populations are threatened by flow alteration and channel degradation caused by dams, water diversions, and groundwater pumping. We developed a stochastic, density-dependent, population model to (1) consolidate information concerning cottonwood population dynamics in a conceptual and analytical framework, (2) determine whether complex forest stand dynamics can be predicted from basic cottonwood vital rates and river hydrology, and (3) aid in planning prescribed floods by projecting how altered flow regimes might affect populations. The model...
Seeds from northern (Idaho) and southern (New Mexico and Texas) populations of broom snakeweed (Gutierrezia sarothrae) were germinated in a greenhouse and the seedlings grown in a soil mixture in 30-cm deep (19-1) plastic pots for 50 days. The pots were then fastened onto the top of similar pots and the seedling root systems were allowed to grow into the lower pots for 4 weeks through punctures in the bottoms of the upper pots. Soil water extraction from four different depths was measured using time domain reflectometry (TDR) 2 weeks after roots had begun to grow into the lower pots. The two New Mexico populations (Jornada and Mountainair) and a population from Plains, Texas extracted more water from deeper (greater-or-equal,...
1 Precipitation in arid regions is temporally variable with much of it arriving in discrete, unpredictable pulses. Climate change models predict an increase in the variation of precipitation, with longer droughts and larger rainfall events, in addition to increased temperatures. 2 A life table response experiment (LTRE) was conducted with the herbaceous arid-land perennial Cryptantha flava (Boraginaceae) from 1997 to 2000, in order to determine how variation in precipitation affects asymptotic population growth (l) and vital rates. Variation in precipitation took two forms, through rainout shelters erected just before and during the 1999 spring growing season, and through naturally occurring variation over the 4...
Although tropical Pacific islands are generally perceived as having wet climates, they are vulnerable to periodic episodes of drought. This literature review strives to establish a base of information relating to such drought events in the U. S.- affiliated Pacific Islands (USAPI), a vast expanse of the oceanic Pacific larger than the North American continent, spanning five time zones and the International Date Line roughly between the southern Tropic of Capricorn across the equator to the northern Tropic of Cancer. The USAPI include the Territories of American Samoa and Guam, Commonwealth of the Northern Mariana Islands, and the Freely Associated States of the Republic of Palau, Federated States of Micronesia,...
Abstract (from http://journal.frontiersin.org/article/10.3389/fpls.2014.00785/abstract): Fire is a key ecological process affecting vegetation dynamics and land cover. The characteristic frequency, size, and intensity of fire are driven by interactions between top-down climate-driven and bottom-up fuel-related processes. Disentangling climatic from non-climatic drivers of past fire regimes is a grand challenge in Earth systems science, and a topic where both paleoecology and ecological modeling have made substantial contributions. In this manuscript, we (1) review the use of sedimentary charcoal as a fire proxy and the methods used in charcoal-based fire history reconstructions; (2) identify existing techniques...
Water laws and drought plans are used to prioritize and allocate scarce water resources. Both have historically been human-centric, failing to account for non-human water needs. In this paper, we examine the development of instream flow legislation and the evolution of drought planning to highlight the growing concern for the non-human impacts of water scarcity. Utilizing a new framework for ecological drought, we analyzed five watershed-scale drought plans in southwestern Montana, USA to understand if, and how, the ecological impacts of drought are currently being assessed. We found that while these plans do account for some ecological impacts, it is primarily through the narrow lens of impacts to fish as measured...
With our colleagues at the USGS, we are creating a new paradigm for drought planning that gives ecological impacts a seat at the table. Our approach recognizes the importance of considering human water use as a driver of ecological responses, and provides mechanisms for identifying feedback loops and situations where the ecological water availability thresholds for nature and people (via key ecosystem services) may differ within a given geography. Teasing apart these and other components of addressing drought risks is helping update natural resource planning and conservation strategy development as the frequency and intensity of droughts continue to increase in the US.
Abstract (from Ecosphere): In semi‐arid mountainous regions across the western United States, the distribution of upland aspen (Populus tremuloides) is often related to heterogeneous soil moisture subsidies resulting from redistributed snow. As temperatures increase, interactions between decreasing snowpack and future trends in the net primary productivity (NPP) of aspen forests remain uncertain. This study characterizes the importance of heterogeneously distributed snow water to aspen communities in the Reynolds Creek Critical Zone Observatory located in southwestern Idaho, USA. Net primary productivity of three aspen stands was simulated at sites spanning elevational and precipitation gradients using the biogeochemical...
Abstract (from ScienceDirect): Improved coastal stratocumulus (Sc) cloud forecasts are needed because traditional satellite cloud motion vectors (CMV) do not accurately predict how Sc clouds move or dissipate in time, which often results in an underprediction of irradiance in the morning hours. CMV forecasts assume clouds move in the direction of the average regional wind field, which is not necessarily the case for Sc clouds. Sc clouds over the land form at night and typically reach their maximum coverage before sunrise. During the day, heating from solar radiation at the surface and entrainment of dry and warm air from above causes Sc clouds to dissipate. A Sc cloud edge forecast using Geostationary Operational...
Abstract (from https://dl.sciencesocieties.org/publications/sssaj/abstracts/81/3/490): In situ soil moisture measurements have the potential to improve wildfire danger assessments, which often rely on the Keetch–Byram Drought Index (KBDI) as a soil moisture surrogate. However, the relative merits of measured soil moisture and KBDI as indicators of wildfire danger are unknown. Therefore, our objectives were to (i) identify relationships between drought indices (KBDI or fraction of available water capacity, FAW) and wildfire size for 34,939 growing and dormant-season wildfires, (ii) compare relationships between each drought index and wildfire probability for 501 large (≥ 405 ha) growing-season and dormant-season...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/2014GL062803/abstract): Observations from the main mountain climate station network in the western United States (U.S.) suggest that higher elevations are warming faster than lower elevations. This has led to the assumption that elevation-dependent warming is prevalent throughout the region with impacts to water resources and ecosystem services. Here we critically evaluate this network's temperature observations and show that extreme warming observed at higher elevations is the result of systematic artifacts and not climatic conditions. With artifacts removed, the network's 1991–2012 minimum temperature trend decreases from +1.16°C decade−1 to +0.106°C decade−1...
"Motivation": The motivation for this briefing is to examine the large inhomogeneity (step shift) in the observed temperature record at the SNOw TELemetry (SNOTEL) stations in the Intermountain West—Colorado, Utah and Wyoming—and its implications for climate, hydrology and ecological research in the region. This issue impacts the entire SNOTEL network across the 11 Western states, as demonstrated by Jared Oyler of the University of Montana and his colleagues in Oyler et al. (2015). Here we build on that work by performing finer-grained analyses, and identifying the implications for climate studies that have incorporated SNOTEL temperature data. In doing so, we intend to promote a broader awareness of this issue...
Abstract (from http://link.springer.com/article/10.1007/s00382-015-2692-0/fulltext.html): The future rate of climate change in mountains has many potential human impacts, including those related to water resources, ecosystem services, and recreation. Analysis of the ensemble mean response of CMIP5 global climate models (GCMs) shows amplified warming in high elevation regions during the cold season in boreal midlatitudes. We examine how the twenty-first century elevation-dependent response in the daily minimum surface air temperature [d(ΔTmin)/dz] varies among 27 different GCMs during winter for the RCP 8.5 emissions scenario. The focus is on regions within the northern hemisphere mid-latitude band between 27.5°N...
This 2-pager describes the Evaporative Demand Drought Index (EDDI), which is a drought index that can serve as an indicator of both rapidly evolving “flash” droughts (developing over a few weeks) and sustained droughts (developing over months but lasting up to years).