Alison Macalady

• Ph.D. Geography, University of Arizona
• Senior Water Security Advisor at United States Agency for International Development (USAID)

Central Italy has been a cradle of geology for centuries. For more than 100 years, studies at the Umbria and Marche Apennines have led to new ideas and a better understanding of the past, such as the Cretaceous-Paleogene (K-Pg) boundary event, or the events across the Eocene-Oligocene transition from a greenhouse to an icehouse world. The Umbria-Ma...

Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing unce...

Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere–atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing unce...

In 1999 the National Academies of Sciences, Engineering, and Medicine released a landmark report, Our Common Journey: A Transition toward Sustainability, which attempted to “reinvigorate the essential strategic connections between scientific research, technological development, and societies’ efforts to achieve environmentally sustainable improveme...

A National Academies of Sciences, Engineering, and Medicine committee was tasked with developing a strategy to increase the nation's scientific capability for research on sub-seasonal to seasonal prediction of weather and climate over the coming decade. The Committee's report (released in the fall of 2015) discusses the advancement of S2S predictio...

Climate change is expected to drive increased tree mortality through drought, heat stress, and insect attacks, with manifold impacts on forest ecosystems. Yet, climate-induced tree mortality and biotic disturbance agents are largely absent from process-based ecosystem models. Using data sets from the western USA and associated studies, we present a...

I. II. III. IV. V. VI. References SUMMARY: Recently, widespread piñon pine die-off occurred in the southwestern United States. Here we synthesize observational studies of this event and compare findings to expected relationships with biotic and abiotic factors. Agreement exists on the occurrence of drought, presence of bark beetles and increased mo...

We related measurements of annual burned area in the southwest United States during 1984–2013 to records of climate variability. Within forests, annual burned area correlated at least as strongly with spring–summer vapour pressure deficit (VPD) as with 14 other drought-related metrics, including more complex metrics that explicitly represent fuel m...

In 2011, exceptionally low atmospheric moisture content combined with moderately high temperatures to produce record-high vapor-pressure deficit (VPD) in the southwestern United States (SW). These conditions combined with record-low cold-season precipitation to cause widespread drought and extreme wildfires. Although interannual VPD variability is...

The processes leading to drought-associated tree mortality are poorly understood, particularly long-term predisposing factors, memory effects, and variability in mortality processes and thresholds in space and time. We use tree rings from four sites to investigate Pinus edulis mortality during two drought periods in the southwestern USA. We draw on...

Model–data comparisons of plant physiological processes provide an understanding of mechanisms underlying vegetation responses to climate. We simulated the physiology of a piñon pine–juniper woodland ( Pinus edulis–Juniperus monosperma ) that experienced mortality during a 5 yr precipitation‐reduction experiment, allowing a framework with which to...

Background/Question/Methods Drought and insects such as bark beetles frequently interact to produce widespread tree mortality in forest ecosystems. However, our ability to project future forest dynamics is strongly limited because the processes and thresholds leading to tree death are poorly constrained. Tree allocation to defense may be a key el...

The creation of chronologies from intra-annual features in tree rings is increasingly utilized in dendrochronology to create season-specific climate histories, among other applications. A conifer latewood-width network has recently been developed for the southwestern United States, but considerable uncertainty remains in understanding site and spec...

As the climate changes, drought may reduce tree productivity and survival across many forest ecosystems; however, the relative influence of specific climate parameters on forest decline is poorly understood. We derive a forest drought-stress index (FDSI) for the southwestern United States using a comprehensive tree-ring data set representing AD 100...

To test the hypothesis that drought predisposes trees to insect attacks, we quantified the effects of water availability on insect attacks, tree resistance mechanisms, and mortality of mature piñon pine ( Pinus edulis ) and one‐seed juniper ( Juniperus monosperma ) using an experimental drought study in New Mexico, USA. The study had four replicate...

Background/Question/Methods Few studies have experimentally manipulated water availability to mature trees and measured changes in insect resistance mechanisms, insect attacks, and subsequent tree survival to address the role of drought in predisposing woodlands to insect-induced mortality. Our objectives were to quantify insect attacks and tree...

Indicators are vital in everyday life, such as tracking blood pressure to assess your health or monitoring the nation's economy using unemployment rates. Tracking the state of the environment in a uniform and integrated manner requires simple and broadly-applicable indicators of year-to-year variability and change. For example, indices such as the...

Droughts in the early 1950s and early 2000s significantly accelerated tree mortality rates in the Southwestern United States. During the early 2000s, forest inventory data indicate that the proportion of dead piñon pine, ponderosa pine, and Douglas-fir trees doubled in the Southwest. The 2000s drought peaked in 2002 and was the most severe drought...

Detailed physical and chemical studies of trees that die and survive during drought provide insight into the historic conditions and physiological mechanisms that underpin episodes of tree mortality. We seek to deduce key physiological parameters that influenced the mortality and survival of piñon pine (Pinus edulis) during relatively warmer (2000'...

Spatial and temporal patterns of variability in spring onset are identified across western North America using a spring index (SI) model based on weather station minimum and maximum temperatures (Tmin and Tmax, respectively). Principal component analysis shows that two significant and independent patterns explain roughly half of the total variance...

One of the greatest uncertainties in global environmental change is predicting changes in feedbacks between the biosphere and atmosphere that could present hazards to current earth system function. Terrestrial ecosystems, and in particular forests, exert strong controls on the global carbon cycle and influence regional hydrology and climatology dir...

One of the greatest uncertainties in global environmental change is predicting changes in feedbacks between the biosphere and the Earth system. Terrestrial ecosystems and, in particular, forests exert strong controls on the global carbon cycle and influence regional hydrology and climatology directly through water and surface energy budgets [ Bonan...

Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with climate change could fundamentally alter the composition, structure, and biogeography of forests in many regions. Of particular concern are pot...

Almost 20 years ago, a post-1976 step change was identified in a host of physical and biological time series in the eastern Pacific and western Americas (Ebbesmeyer et al. 1991). The shift was linked to decadal changes in Pacific SST, and lately to external forcing, as well. More recently, a similar step change ~1984 has become evident in springtim...

Background/Question/Methods The climatologies underlying interannual variations and secular trends in spring onset are poorly understood. Spring onset can have important hydrological and ecological consequences, including changes in the timing of snowmelt and snowmelt runoff, in timing of plant and animal phenologies and their interactions, in eco...

Background/Question/Methods Recent and large-scale tree die-off in the southwestern U.S. highlights the importance of understanding the underlying processes of tree mortality in order to predict the impacts of climate variability and change on forest ecosystems. The severe droughts and associated pulses of tree mortality in the Southwest during th...

The Oligocene represents an important time period from a wide range of perspectives and includes significant climatic and eustatic variations. The pelagic succession of the Umbria-Marche Apennines (central Italy) includes a complete and continuous sequence of marly limestones and marls, with volcaniclastic layers that enable us to construct an inte...

A combination of satellite imagery, meteorological station data, and the NCEP/NCAR reanalysis has been used to explore the spatial and temporal evolution of the 2003 heat wave in France, with focus on understanding the impacts and feedbacks at the land surface. Vegetation was severely affected across the study area, especially in a swath across cen...

We use a combination of satellite imagery, meteorological station data, and the NCEP/NCAR reanalysis to explore the spatial and temporal evolution of the 2003 heatwave in France, with a focus on understanding impacts to vegetation and energy fluxes at the land surface. Vegetation was severely affected across the study area, especially in a swath ac...