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National Science FoundationNational Science Foundation (NSF) [DBI-0735191, DBI-1265383]; National Oceanic and Atmospheric Administration's Regional Integrated Sciences and Assessments (RISA) program [NA17OAR4310288]; Climate Assessment for the Southwest program at the University of Arizona

National Oceanic and Atmospheric Administration's Regional Integrated Sciences and Assessments (RISA) program [NA17OAR4310288]; Climate Assessment for the Southwest program at the University of Arizona; National Science FoundationNational Science Foundation (NSF) [DBI-0735191, DBI-1265383]

Understanding the patterns and relationships between vegetation productivity and climatic conditions is essential for predicting the future impacts of climate change. Climate change is altering precipitation patterns and increasing temperatures in the Southwest United States. The large-scale and long-term effects of these changes on vegetation productivity are not well understood. This study investigates the patterns and relationships between seasonal vegetation productivity, represented by Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI), and the Standardized Precipitation Evapotranspiration Index (SPEI) across the Mojave, Sonoran, and Chihuahuan Deserts and the Apache Highlands of the Southwest United States over 16 years from 2000 to 2015. To examine the spatiotemporal gradient and response of vegetation productivity to dry and wet conditions, we evaluated the linear trend of different SPEI timescales and correlations between NDVI and SPEI. We found that all four ecoregions are experiencing more frequent and severe drought conditions in recent years as measured by negative SPEI trends and severe negative SPEI values. We found that changes in NDVI were more strongly correlated with winter rather than summer water availability. Investigating correlations by vegetation type across all four ecoregions, we found that grassland and shrubland productivity were more dependent on summer water availability whereas sparse vegetation and forest productivity were more dependent on winter water availability. Our results can inform resource management and enhance our understanding of vegetation vulnerability to climate change.

International audience; With contributions from the global natural product (NP) research community, and continuing the Raw Data Initiative, this review collects a comprehensive demonstration of the immense scientific value of disseminating raw nuclear magnetic resonance (NMR) data, independently of, and in parallel with, classical publishing outlets. A comprehensive compilation of historic to present-day cases as well as contemporary and future applications show that addressing the urgent need for a repository of publicly accessible raw NMR data has the potential to transform natural products (NPs) and associated fields of chemical and biomedical research. The call for advancing open sharing mechanisms for raw data is intended to enhance the transparency of experimental protocols, augment the reproducibility of reported outcomes, including biological studies, become a regular component of responsible research, and thereby enrich the integrity of NP research and related fields.

Briarellins, a subset of C2-C11 cyclized cembranoids, were proposed to contain a C3-C14 ether or lactone bridge, similar to asbestinins. However, the total synthesis of the proposed structure of briarellin J revealed a misassignment. We revisited briarellins, computationally, with the help of a recently developed hybrid DFT/parametric method, DU8+, and revised the structures of briarellin C14-C3 e-lactones to new structural types containing either a C14-C11 or C14-C12 lactone bridge. The original structures of briarellin and asbestinin ethers were confirmed.

The authors acknowledge financial and programmatic support from the Howard Hughes Medical Institute. Program and institutional staff who assisted with data collection and program operation are acknowledged in the supplementary materials

Farmers, ranchers, and forest landowners across the USA make weather- and climate-related management decisions at varying temporal and spatial scales, often with input from local experts like crop consultants and cooperative extension (CE) personnel. In order to provide additional guidance to such longer-term planning efforts, we developed a tool that shows statistically downscaled climate projections of temperature and precipitation consolidated to the county level for the contiguous US. Using the county as a fundamental mapping unit encourages the use of this information within existing institutional structures like CE and other U.S. Department of Agriculture (USDA) programs. A “quick-look” metric based on the spatial variability of climate within each county aids in the interpretation of county-level information. For instance, relatively higher spatial variability within a county indicates that more localized information should be used to support stakeholder planning. Changes in annual precipitation show a latitudinal dipole where increases are projected for much of the northern US while declines are projected for counties across the southern US. Seasonal shifts in county-level precipitation are projected nationwide with declines most evident in summer months in most regions. Changes in the spatial variability of annual precipitation for most counties were less than 10 mm, indicating fairly spatially homogenous midcentury precipitation changes at the county level. Annual and seasonal midcentury temperatures are projected to increase across the USA, with relatively low change in the spatial variability (

The synthesis of the briarane-brianthein A core has been accomplished utilizing an extension of the dianionic Ireland-Claisen rearrangement to establish the C1 quaternary carbon and the adjacent C10 ring juncture stereocenters. Two sequential ring-closing metathesis reactions were exploited to construct the 6-10 trans fused ring system.

For more than a decade, the Four Corners Region has faced extensive and persistent drought conditions that have impacted vegetation communities and local water resources while exacerbating soil erosion. These persistent droughts threaten ecosystem services, agriculture, and livestock activities, and expose the hypersensitivity of this region to inter-annual climate variability and change. Much of the intermountainWestern United States has sparse climate and vegetation monitoring stations, making fine-scale drought assessments difficult. Remote sensing data offers the opportunity to assess the impacts of the recent droughts on vegetation productivity across these areas. Here, we propose a drought assessment approach that integrates climate and topographical data with remote sensing vegetation index time series. Multisensor Normalized Difference Vegetation Index (NDVI) time series data from 1989 to 2010 at 5.6 km were analyzed to characterize the vegetation productivity changes and responses to the ongoing drought. A multi-linear regression was applied to metrics of vegetation productivity derived from the NDVI time series to detect vegetation productivity, an ecosystem service proxy, and changes. The results show that around 60.13% of the study area is observing a general decline of greenness (p

Monitoring drought conditions in arid and semiarid regions characterized by high levels of intra- and interannual hydroclimatic variability is a challenging task. Typical drought-monitoring indices that are based on monthly-scale data lack sufficient temporal resolution to detect hydroclimatic extremes and, when used operationally, may not provide adequate indication of drought status. In a case study focused on the Four Corners region of the southwestern United States, the authors used recently standardized World Meteorological Organization climate extremes indices to discern intra-annual hydroclimatic extremes and diagnose potential drought status in conjunction with the simple metric of annual total precipitation. By applying data-reduction methods to a suite of metrics calculated using daily data for 1950–2014, the authors identified five extremes indices that provided additional insight into interannual hydroclimatic variability. Annual time series of these indices revealed anomalous years characterized by shifts in the seasonal distribution of precipitation and in the intensity and frequency of individual events. The driest 4-yr intervals over the study period, characterized by similar annual and interval total precipitation anomalies, represent dramatically different assemblages of index values, which are interpreted as different “flavors” of drought. In turn, it is expected that varying drought impacts on ecosystems, agricultural systems, and water resources would emerge under these different flavors of drought. Results from this study indicate that operational drought monitoring and historical drought assessments in arid and semiarid regions would benefit from the additional insight that daily-based hydroclimatic extremes indices provide, especially in light of expected climate change–driven changes to the hydrologic cycle.

Organic Chemistry is a required course for programs in chemistry, biology, and many health science careers. It has historically been considered a highly challenging course with significant failure rates. As with many science disciplines, the teaching of Organic Chemistry has traditionally focused on unstructured exposition-centered delivery of course material. This report details efforts to transform the teaching of a large section of Organic Chemistry to a more student-centered approach through the use of a highly structured, active learning format. In this study, the authors examine student performance data on homogeneous examinations and course grades for two groups of students at a large public university for comparison between those that received highly structured active learning pedagogy and those that received traditional, unstructured, lecture pedagogy in Organic Chemistry. Data consist of repeated cross sections over 4 different years, with a total sample size n = 766. Regression and propensity s...

On the Ground•Seasonal climate predictions, based largely on the status of the El Niño-Southern Oscillation, are one such tool but need to be used with prudence, understanding when and where they perform the best.•Advance planning and preparation for drought includes finding the right place for uncertain climate predictions in management decision making, as well as working to reduce overall exposure to drought risks.

Mining, agriculture, and deforestation are important energy-intensive activities that impact economies and at the same time directly and indirectly cause soil, air, and land pollution. Mining produces vast quantities of almost sterile and structureless geologic materials (crushed rock) that often contain significant amounts of toxic metals, such as lead, arsenic, and cadmium in the form of primary minerals such as metal sulfides, and secondary minerals such as calcium, magnesium, and metal sulfates and carbonates. Mine overburden and tailings are often stockpiled next to large open pit excavations. Modern agricultural production requires the use of large quantities of commercial fertilizers and pesticides, and produces animal wastes, all of which can pollute land, air, and water. Land deforestation indirectly affects the quality of land and water by increasing the rates of soil erosion and sediment transport, and accelerating the loss of the nutrient-rich soil surface. Invasive exotic plant species also have a significant impact on the quality of our lands by creating soil conditions that may be toxic to other plants and by increasing fire hazards. All of these activities in turn can affect soil salinity and acidity of surrounding land areas by releasing or concentrating unwanted metals, salts, and acid or acid-forming minerals. These materials can also be released into air or water sources.

The droughts striking the Colorado Plateau, where the Hopi Tribe and Navajo Nation Native American reservation lands are located, and their impacts have appeared slowly and relatively unnoticed in conventional national drought monitoring efforts like the National Drought Monitor. To understand the effect of drought-based drivers on vegetation productivity in the Hopi Tribe and Navajo Nation reservation lands, an assessment approach was developed integrating climate, land cover types, and topographical data with annual geospatially explicit normalized difference vegetation index (NDVI)-related productivity from 1989 to 2014 derived from 15-day composite multi-sensor NDVI time series data. We studied vegetation–environment relationships by conducting multiple linear regression analysis to explain the driver of vegetation productivity changes. Our results suggest that the interannual change of vegetation productivity showed high variability in middle elevations where needleleaf forest is the dominant vegetation cover type. Our analysis also shows that the spatial variation in interannual variability of vegetation productivity was more driven by climate drivers than by topography ones. Specifically, the interannual variability in spring precipitation and fall temperature seems to be the most significant factor that correlated with the interannual variability in vegetation productivity during the last two and a half decades.

Earlier four brominated sesquiterpenes, aldingenins A–D, were isolated from the red algae Laurencia aldingensis, and their structure elucidated by spectroscopic methods including NMR. Total syntheses of the proposed structures of aldingenin B (Org. Lett. 2012, 14, 2168) and aldingenin C (J. Org. Chem. 2014, 79, 9373) have demonstrated that the structures are misassigned. Koshino has proposed aldingenins C and D to be caespitol and 5-(S)-acetoxycaespitol. Computational evidence presented in this Letter and based primarily on the computed proton spin–spin coupling constants (but also including 13C NMR chemical shifts) leads to the conclusion that the remaining two aldingenins A and B are also halogenated sesquiterpenes of the same caespitol family. Aldingenin A is assigned the structure of 5-(S)-hydroxycaespitol 1, and aldingenin B—hemiacetal 2 of a related 8-oxo compound.

Severe freeze events have been identified as a primary limiting factor for the saguaro cactus at high elevations in the southwestern United States. With the observed increase in minimum temperatures, it may be expected that saguaros will expand their elevational range. To better understand the factors influencing potential range expansion, we developed a logistic regression model to help explain saguaro presence along its current uppermost elevation. We find that the occurrence of fire decreases the odds of saguaro presence by 78 percent. While less frequent freeze events could allow saguaros to push their current elevational limit, our model suggests that increased fire activity related to the establishment and spread of invasive species could inhibit this range expansion.

The drylands of the US Desert Southwest (SW) are dependent on precipitation stored as soil moisture for aboveground productivity. Availability of soil moisture in dryland systems is a function of climate and soil physical properties; however, we lack accurate understanding of how soil physical properties modulate regional patterns of aboveground productivity responses to climate forcing in the SW. We used established regional soil, vegetation, and climate datasets to quantify differences in vegetation productivity attributable to soil texture and climate forcing. Subsurface soil texture accounted for significant variation in aboveground productivity in the winter and fore-summer months, but not during the summer monsoon. Subsurface soil texture differences were more important in the Mojave and Sonoran Deserts, which receive significant winter precipitation. Subsurface soil texture is a significant determinant in modulating aboveground productivity, linked to winter precipitation storage as soil moisture, suggesting that drying winters may lead to increased dryland ecosystem stress.

In light of global climate change, adaptation will be necessary at all levels of social organization. However, the adaptation literature emphasizes that because the impacts of climate change and vulnerability are locally specific, adaptation is inevitably local. In this paper, in order to inform the design of institutions that can encourage and support effective local-level adaptation, the authors derive principles for their design theoretically and use a case study to explore how these principles could be practically implemented. Ten design principles are synthesized from principles derived from reviews of the literatures on local-level adaptation, usable science, and boundary organizations. Bringing these three literatures together highlights the characteristics of boundary organizations that make them particularly valuable for addressing the challenges of local-level adaptation. The case study then illustrates how an existing boundary organization, The University of Arizona Cooperative Extension, of the U.S. Cooperative Extension System (CES), implements these principles in its organizational structure and in the daily practice of Extension professionals. It also highlights the significance of the CES’s existing social networks and social capital for facilitating their implementation. From the case study it is concluded that the CES is uniquely positioned to serve an important role in a national adaptation strategy for the United States in supporting local-level adaptation in urban and rural communities across the country.

With contributions from the global natural product (NP) research community, and continuing the Raw Data Initiative, this review collects a comprehensive demonstration of the immense scientific value of disseminating raw nuclear magnetic resonance (NMR) data, independently of, and in parallel with, classical publishing outlets., Covering: up to 2018 With contributions from the global natural product (NP) research community, and continuing the Raw Data Initiative, this review collects a comprehensive demonstration of the immense scientific value of disseminating raw nuclear magnetic resonance (NMR) data, independently of, and in parallel with, classical publishing outlets. A comprehensive compilation of historic to present-day cases as well as contemporary and future applications show that addressing the urgent need for a repository of publicly accessible raw NMR data has the potential to transform natural products (NPs) and associated fields of chemical and biomedical research. The call for advancing open sharing mechanisms for raw data is intended to enhance the transparency of experimental protocols, augment the reproducibility of reported outcomes, including biological studies, become a regular component of responsible research, and thereby enrich the integrity of NP research and related fields.

A dianionic Ireland-Claisen rearrangement of chiral, nonracemic α-methyl-β-hydroxy allylic esters has been developed that proceeds with high diastereoselectivity and provides products containing three contiguous stereogenic carbons, including a quaternary center. The potential utility of the rearrangement for complex molecule synthesis is also demonstrated.

The infiltration of stormwater runoff for use by urban trees is a major co-benefit of green infrastructure for desert cities with limited water resources. However, the effects of this passive irrigation versus regular, controlled moisture inputs, or active irrigation, is largely unquantified. We monitored the ecohydrology of urban mesquite trees (Prosopis spp.) under these contrasting irrigation regimes in semiarid Tucson, AZ. Measurements included soil moisture, sap velocity, canopy greenness, and leaf-area index. We expected both irrigation types to provide additional deep (>20 cm) soil moisture compared to natural conditions, and that trees would depend on this deep moisture for transpiration and phenological activity. Results show that active irrigation supported higher soil moisture throughout the study than passive irrigation. Passive irrigation only provided additional deep moisture when green infrastructure features received impervious runoff from a city street. Sap velocity and greenness were similar under both irrigation types, outside of isolated periods of time. These differences occurred during the extremely wet summer 2017 when passively irrigated trees exhibited a greenness peak, and the dry conditions of spring when actively irrigated trees had higher sap flow and relative greenness. Finally, it was not determined that deep soil moisture had a stronger relationship with mesquite productivity than shallow moisture, but both relationships were stronger in the spring, before summer rains. This study aims to contribute empirical observations of green infrastructure performance for urban watershed management.

As adaptation has come to the forefront in climate change discourse, research, and policy, it is crucial to consider the effects of how we interpret the concept. This paper draws attention to the need for interpretations that foster policies and institutions with the breadth and flexibility to recognize and support a wide range of locally relevant adaptation strategies. Social scientists have argued that, in practice, the standard definition of adaptation tends to prioritize economic over other values and technical over social responses, draw attention away from underlying causes of vulnerability and from the broader context in which adaptive responses take place, and exclude discussions of inequality, justice, and transformation. In this paper, we discuss an alternate understanding of adaptation, which we label “living with climate change,” that emerged from an ethnographic study of how rural residents of the U.S. Southwest understand, respond to, and plan for weather and climate in their daily lives, and we consider how it might inform efforts to develop a more comprehensive definition. The discussion brings into focus several underlying features of this lay conception of adaptation, which are crucial for understanding how adaptation actually unfolds on the ground: an ontology based on nature–society mutuality; an epistemology based on situated knowledge; practice based on performatively adjusting human activities to a dynamic biophysical and social environment; and a placed-based system of values. We suggest that these features help point the way toward a more comprehensive understanding of climate change adaptation, and one more fully informed by the understanding that we are living in the Anthropocene.

To make decisions about drought declarations, status, and relief funds, decision makers need high-quality local-level drought impact data. In response to this need in Arizona the Arizona DroughtWatch program was created, which includes an online drought impacts reporting system. Despite extensive and intensive collaboration and consultation with the intended public participants, Arizona DroughtWatch has had few consistent users and has failed to live up to its goal of providing decision makers or the public with high-quality drought impacts data. Based on an evaluation of the DroughtWatch program, the authors found several weaknesses in the public-participation reporting-system model including that participation was reduced because of participants' over-commitment and time constraints, consultation fatigue, and confusion about the value of qualitative impact reports. Based on these findings, the authors recommend that professional resource agency personnel provide the backbone of drought impacts monitoring to ensure that decision makers receive the high-quality, consistent information they require. Public participation in impacts monitoring efforts can also be improved using this model. Professional observers can help attract volunteers who consider access to high-quality data an incentive to visit the Arizona DroughtWatch site and who may be more likely to participate in impacts monitoring if they see examples of how the information is being used by decision makers.

The demand for regional climate information is increasing and spurring efforts to provide a broad slate of climate services that inform policy and resource management and elevate general knowledge. Routine syntheses of existing climate-related information may be an effective strategy for connecting climate information to decision making, but few studies have formally assessed their contribution to informing decisions. During the 2010–11 winter, drought conditions expanded and intensified in Arizona and New Mexico, creating an opportunity to develop and evaluate a monthly regional climate communication product—La Niña Drought Tracker—that synthesized and interpreted drought and climate information. Six issues were published and subsequently evaluated through an online survey. On average, 417 people consulted the publication each month. Many of the survey respondents indicated that they made at least one drought-related decision, and the product at least moderately influenced the majority of those decisions, some of which helped mitigate economic losses. More than 90% of the respondents also indicated that the product improved their understanding of climate and drought, and that it helped the majority of them better prepare for drought. The results demonstrate that routine interpretation and synthesis of existing climate information can help enhance access to and understanding and use of climate information in decision making, fulfilling the main goals for the provision of climate services.

The semiarid southwestern United States is an area of rapid population growth. Urban development is encroaching upon many ecosystems, including riparian areas. Because most stream miles in the southwestern United States occur along ephemeral streams, recognizing how these ecosystems are affected by increasing urban land covers is imperative. In this study, we recorded air temperature at 30 cm above the ground surface within riparian ecosystems along nine ephemeral stream reaches in three levels of housing density: High Density (HD: >13 houses/hectare); Moderate Density (MD: 4–8 houses/hectare); Low Density (LD

Synthesis of the C1-C6 and C7-C23 fragments of the proposed structure of iriomoteolide 1a has been accomplished. Key steps include a cross metathesis to form the C15-C16 E olefin and a chelation controlled Grignard addition to form the tertiary alcohol at C14. Notably, 7 of the 9 stereocenters of the proposed structure have been set using various aldol reactions employing metallo enolates of thiazolidinethiones.

Shifts in species phenology in response to climate change have wide-ranging consequences for ecological systems. However, significant variability in species responses, together with limited data, frustrates efforts to forecast the consequences of ongoing phenological changes. Herein, we use a case study of three North American plant communities to explore the implications of variability across levels of organisation (within and among species, and among communities) for forecasting responses to climate change. We show how despite significant variation among species in sensitivities to climate, comparable patterns emerge at the community level once regional climate drivers are accounted for. However, communities differ with respect to projected patterns of divergence and overlap among their species phenological distributions in response to climate change. These analyses and a review of hypotheses suggest how explicit consideration of spatial scale and levels of biological organisation may help to understand and forecast phenological responses to climate change.

Climate change effects on wildfire occurrence have been attributed primarily to increases in temperatures causing earlier snowpack ablation and longer fire seasons. Variability in precipitation is also an important control on snowpack accumulation and, therefore, on timing of meltwater inputs. We evaluate the correlation of total area burned and area burned severely to snowmelt-induced streamflow timing and total annual streamflow metrics across the Pacific Northwest region from 1984-2005. Principal component scores on total annual water year flow and date of 50th percentile flow (PC1T) in the Pacific Northwest were used as predictors of satellite-inferred area burned and area burned severely in forested settings. Both annual area burned and burned severely are significantly correlated with mean annual flow and streamflow timing. PC1T alone explains 24% of the variability in annual area burned. Path analysis suggests that a substantial amount of the variability in annual area burned, previously attributed solely to temperature effects on melt timing, may be primarily driven by trends in precipitation and total annual streamflow. Principal component analysis scores on mean annual streamflow explain as much as 46% of the variability in annual area burned from 1984-2005. Thus, although streamflow timing may be a better single correlate of annual wildfire activity, timing is, in turn, strongly dependent on precipitation. These results suggest that recent fire activity in forests of this region are influenced more by precipitation variability than temperature-induced shifts in snowmelt timing, with significant implications for our ability to predict wildfire activity in the future. Published in 2011. This article is a US Government work and is in the public domain in the USA.

The formal synthesis of (+)-sorangicin A was completed by two independent routes. Both approaches feature a cross metathesis reaction to form the C29-C30 bond to arrive at the bicyclic ether/tetrahydropyran fragment. Formation of the C15-C16 olefin to unite the dihydropyran fragment with the rest of the molecule was achieved by either a cross metathesis reaction or a Julia-Kocienski olefination.

We have utilized a spiroketal template in an approach to the C1–C16 fragment of bryostatin. The stereoselective construction of an exocyclic enoate at C13 and insertion of a vinyl group on C15 were accomplished by using Peterson–Yamamoto olefination and copper-catalyzed addition of vinyl magnesium bromide, respectively.

An approach towards the stereoselective synthesis of the bottom half fragment of bryostatin 11 is described. Key steps include asymmetric aldol and Saksena-Evans reduction reactions to construct multiple stereogenic centers and thioketalization-lactonization reactions to form the thioketal-protected C-ring.

A formal synthesis of the top half fragment of bryostatin 11has been developed. Stereoselective construction of the B ring wasachieved by using a ring-closing metathesis reaction in conjunctionwith asymmetric glycolate alkylation. Furthermore, the C1-C9fragment was synthesized by Brown allylation, chelation-controlledaldol condensation, and Saksena-Evans reduction to constructall stereogenic centers.

Accurate, fine spatial resolution predictions of surface air temperatures are critical for understanding many hydrologic and ecological processes. This study examines the spatial and temporal variability in nocturnal air temperatures across a mountainous region of Northern Idaho. Principal components analysis (PCA) was applied to a network of 70 Hobo temperature loggers systematically distributed across 2 mountain ranges. Four interpretable modes of variability were observed in average nighttime temperatures among Hobo sites: (1) regional/synoptic; (2) topoclimatic; (3) land surface feedback; (4) canopy cover and vegetation. PC time series captured temporal variability in nighttime temperatures and showed strong relationships with regional air temperatures, sky conditions and atmospheric pressure. PC2 captured the topographic variation among temperatures. A cold air drainage index was created by predicting PC2 loadings to elevation, slope position and dissection indices. Nightly temperature maps were produced by applying PC time series back to the PC2 loading surface, revealing complex temporal and spatial variation in nighttime temperatures. Further development of both physically and empirically based daily temperature models that account for synoptic atmospheric controls on fine-scale temperature variability in mountain ecosystems are needed to guide future monitoring efforts aimed at assessing the impact of climate change.

The enantioselective total synthesis of spirofungins A (1) and B (2) is reported in 14 steps over the longest linear sequence. Key steps include the use of thiazolidinethione-mediated aldol reactions to assemble the major fragments and installation of the C1-C6 side chain using a cross metathesis reaction.

Summary 1. Many studies have documented advancement in spring plant phenology; however, studies in dry climates, where water, rather than temperature, is the limiting factor, are rare. To better understand how plants of a water-limited environment may respond to predicted changes in climate, we used a species-rich 20-year data set collected in a semi-arid ecosystem to determine species’ relationships with precipitation and temperature for seasons coincident with and previous to flowering. Our data were collected across a 1200-m elevation gradient, allowing us to explore the consistency in relationships with climatic variables from desert scrub to pine forest. A second objective was to document evidence of changes in the onset of spring flowering over this 20-year period. 2. Onset of spring flowering for species at the lowest elevations was most commonly driven by temperature and precipitation conditions of the previous autumn. In contrast, onset of spring flowering for species in high-elevation communities was more often associated with spring temperatures, a pattern consistent with communities of higher latitudes. Despite these coarse patterns, species’ relationships to climate variables were highly variable and individualistic. 3. Approximately 10% of species showed a significant trend in changes in first flowering date over the period 1984–2003; most trends were in the direction of later onset. The decrease in autumn precipitation observed over the study period appears to explain the delay in onset observed for many of the species across the elevation gradient. Other species’ delays in spring flowering appear to be related to the slight decrease in spring temperature observed over the study period. 4. Synthesis. The south-western USA is expected to become warmer and drier. Climate relationships documented in this study suggest divergent, individualistic changes in the onset of spring flowering. Low-elevation plants may exhibit delayed spring flowering due to changes in the timing or amount of precipitation or insufficient chilling. High-elevation species may show advancement in spring flowering due to warming temperatures. The highly individualistic responses to climate change may result in significant changes in the diversity, composition and abundance of plants in flower. Variable changes in phenology such as these have major implications for species population dynamics and ecosystem functioning.

Low-frequency changes (decades to years) in precipitation related to the El Nino-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) are known to influence wildfire variability across the southwest United States. Little work has been done to identify whether daily fire weather variability, also important to wildfire activity, is influenced by these same climatic phenomena. This study identifies the synoptic climatological conditions associated with extreme fire weather events in the Southwest and constructs an extreme fire weather frequency data set for the period of 1958–2003 using a logistic regression technique. Interannual changes in extreme fire weather day frequencies are not linearly correlated with either ENSO or PDO, but do show significant deviations from expected values when grouped by PDO phase (positive or negative) and further subgrouped by ENSO state (La Nina, El Nino or neutral). A higher number of extreme fire weather days occur during the negative phase of the PDO, especially when accompanied by a La Nina event. Copyright © 2010 Royal Meteorological Society