Continental-scale tree-ring-based projection of Douglas-fir growth: Testing the limits of space-for-time substitution.

A central challenge in global change research is the projection of the future behavior of a system based upon past observations. Tree-ring data have been used increasingly over the last decade to project tree growth and forest ecosystem vulnerability under future climate conditions. But how can the response of tree growth to past climate variation predict the future, when the future does not look like the past? Space-for-time substitution (SFTS) is one way to overcome the problem of extrapolation: the response at a given location in a warmer future is assumed to follow the response at a warmer location today. Here we evaluated an SFTS approach to projecting future growth of Douglas-fir (Pseudotsuga menziesii), a species that occupies an exceptionally large environmental space in North America. We fit a hierarchical mixed-effects model to capture ring-width variability in response to spatial and temporal variation in climate. We found opposing gradients for productivity and climate sensitivity with highest growth rates and weakest response to interannual climate variation in the mesic coastal part of Douglas-fir's range; narrower rings and stronger climate sensitivity occurred across the semi-arid interior. Ring-width response to spatial versus temporal temperature variation was opposite in sign, suggesting that spatial variation in productivity, caused by local adaptation and other slow processes, cannot be used to anticipate changes in productivity caused by rapid climate change. We thus substituted only climate sensitivities when projecting future tree growth. Growth declines were projected across much of Douglas-fir's distribution, with largest relative decreases in the semiarid U.S. Interior West and smallest in the mesic Pacific Northwest. We further highlight the strengths of mixed-effects modeling for reviving a conceptual cornerstone of dendroecology, Cook's 1987 aggregate growth model, and the great potential to use tree-ring networks and results as a calibration target for next-generation vegetation models.

Sampling bias overestimates climate change impacts on forest growth in the southwestern United States.

Climate-tree growth relationships recorded in annual growth rings have recently been the basis for projecting climate change impacts on forests. However, most trees and sample sites represented in the International Tree-Ring Data Bank (ITRDB) were chosen to maximize climate signal and are characterized by marginal growing conditions not representative of the larger forest ecosystem. We evaluate the magnitude of this potential bias using a spatially unbiased tree-ring network collected by the USFS Forest Inventory and Analysis (FIA) program. We show that U.S. Southwest ITRDB samples overestimate regional forest climate sensitivity by 41-59%, because ITRDB trees were sampled at warmer and drier locations, both at the macro- and micro-site scale, and are systematically older compared to the FIA collection. Although there are uncertainties associated with our statistical approach, projection based on representative FIA samples suggests 29% less of a climate change-induced growth decrease compared to projection based on climate-sensitive ITRDB samples.

Disturbance and productivity interactions mediate stability of forest composition and structure.

Fire is returning to many conifer-dominated forests where species composition and structure have been altered by fire exclusion. Ecological effects of these fires are influenced strongly by the degree of forest change during the fire-free period. Response of fire-adapted species assemblages to extended fire-free intervals is highly variable, even in communities with similar historical fire regimes. This variability in plant community response to fire exclusion is not well understood; however, ecological mechanisms such as individual species' adaptations to disturbance or competition and underlying site characteristics that facilitate or impede establishment and growth have been proposed as potential drivers of assemblage response. We used spatially explicit dendrochronological reconstruction of tree population dynamics and fire regimes to examine the influence of historical disturbance frequency (a proxy for adaptation to disturbance or competition), and potential site productivity (a proxy for underlying site characteristics) on the stability of forest composition and structure along a continuous ecological gradient of pine, dry mixed-conifer, mesic mixed-conifer, and spruce-fir forests following fire exclusion. While average structural density increased in all forests, species composition was relatively stable in the lowest productivity pine-dominated and highest productivity spruce-fir-dominated sites immediately following fire exclusion and for the next 100 years, suggesting site productivity as a primary control on species composition and structure in forests with very different historical fire regimes. Species composition was least stable on intermediate productivity sites dominated by mixed-conifer forests, shifting from primarily fire-adapted species to competition-adapted, fire-sensitive species within 20 years of fire exclusion. Rapid changes to species composition and stand densities have been interpreted by some as evidence of high-severity fire. We demonstrate that the very different ecological process of fire exclusion can produce similar changes by shifting selective pressures from disturbance-mediated to productivity-mediated controls. Restoring disturbance-adapted species composition and structure to intermediate productivity forests may help to buffer them against projected increasing temperatures, lengthening fire seasons, and more frequent and prolonged moisture stress. Fewer management options are available to promote adaptation in forest assemblages historically constrained by underlying site productivity.

Tree Morphologic Plasticity Explains Deviation from Metabolic Scaling Theory in Semi-Arid Conifer Forests, Southwestern USA.

A significant concern about Metabolic Scaling Theory (MST) in real forests relates to consistent differences between the values of power law scaling exponents of tree primary size measures used to estimate mass and those predicted by MST. Here we consider why observed scaling exponents for diameter and height relationships deviate from MST predictions across three semi-arid conifer forests in relation to: (1) tree condition and physical form, (2) the level of inter-tree competition (e.g. open vs closed stand structure), (3) increasing tree age, and (4) differences in site productivity. Scaling exponent values derived from non-linear least-squares regression for trees in excellent condition (n = 381) were above the MST prediction at the 95% confidence level, while the exponent for trees in good condition were no different than MST (n = 926). Trees that were in fair or poor condition, characterized as diseased, leaning, or sparsely crowned had exponent values below MST predictions (n = 2,058), as did recently dead standing trees (n = 375). Exponent value of the mean-tree model that disregarded tree condition (n = 3,740) was consistent with other studies that reject MST scaling. Ostensibly, as stand density and competition increase trees exhibited greater morphological plasticity whereby the majority had characteristically fair or poor growth forms. Fitting by least-squares regression biases the mean-tree model scaling exponent toward values that are below MST idealized predictions. For 368 trees from Arizona with known establishment dates, increasing age had no significant impact on expected scaling. We further suggest height to diameter ratios below MST relate to vertical truncation caused by limitation in plant water availability. Even with environmentally imposed height limitation, proportionality between height and diameter scaling exponents were consistent with the predictions of MST.

An update in options for the treatment of pain: a review of new opioid formulations.

In the past 2 decades, there has been a significant increase in the use of opioids for the management of chronic nonmalignant pain. This increase in usage has led to concerns of misuse and abuse of opioids. Also, many of the available opioid options were previously only available as oral tablets or capsules, further limiting treatment options for health care providers. Several new opioid formulations have been developed to address and prevent the misuse and abuse of opioids via tampering in the United States. In addition, alternative delivery systems have been developed to provide physicians with more options to provide adequate pain management for those with chronic pain. This article reviews new opioid options for the treatment of pain management and requirements of the Risk Evaluation and Mitigation Strategies program.

Treatment options for osteoarthritis: considerations for older adults.

Osteoarthritis (OA) is the most common form of arthritis and the leading cause of disability among older adults in the United States. Treatment options such as acetaminophen and nonsteroidal anti-inflammatory drugs are the most widely used agents to manage mild-to-moderate pain. Treatment with tramadol or opioids is usually reserved for severe pain associated with OA. These agents do not come without risk, especially for older adults. Patient-specific parameters and comorbid conditions must be considered when evaluating treatment options for older adults. This article reviews pharmacological and nonpharmacological approaches to the management of OA in older adults.

Osteoarthritis: a review of treatment options.

Osteoarthritis (OA) is the most common form of arthritis and the leading cause of disability in the United States, especially among older adults. Treatment options have primarily focused on alleviating the pain often associated with this condition. Acetaminophen and nonsteroidal anti inflammatory drugs (NSAIDs) are often employed for relief of mild-to moderate pain associated with OA. NSAIDs are typically more effective than acetaminophen; however, because of adverse effects associated with long-term use of NSAIDS, acetaminophen is considered first-line therapy. Safety concerns of traditional pharmacotherapeutic agents used in the management of OA, such as NSAIDs and opioids, have led healthcare professionals to seek other options. Trials of disease modulating agents that focus on preventing further damage to the joints have the potential to change how this disease state is managed. This article reviews nonpharmacologic and pharmacologic approaches to management of OA of the knee and hip.

Management strategies for premenstrual syndrome/premenstrual dysphoric disorder.

OBJECTIVE: To evaluate the current nonpharmacologic and pharmacologic treatment options for symptoms of premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD). DATA SOURCES: Literature was obtained through searches of MEDLINE Ovid (1950-March week 3, 2008) and EMBASE Drugs and Pharmacology (all years), as well as a bibliographic review of articles identified by the searches. Key terms included premenstrual syndrome, premenstrual dysphoric disorder, PMS, PMDD, and treatment. STUDY SELECTION/DATA EXTRACTION: All pertinent clinical trials, retrospective studies, and case reports in human subjects published in the English language were identified and evaluated for the safety and efficacy of pharmacologic and nonpharmacologic treatments of PMS/PMDD. Data from these studies and information from review articles were included in this review. DATA SYNTHESIS: Selective serotonin-reuptake inhibitors (SSRIs) have been proven safe and effective for the treatment of PMDD and are recommended as first-line agents when pharmacotherapy is warranted. Currently fluoxetine, controlled-release paroxetine, and sertraline are the only Food and Drug Administration-approved agents for this indication. Suppression of ovulation using hormonal therapies is an alternative approach to treating PMDD when SSRIs or second-line psychotropic agents are ineffective; however, adverse effects limit their use. Anxiolytics, spironolactone, and nonsteroidal antiinflammatory drugs can be used as supportive care to relieve symptoms. Despite lack of specific evidence, lifestyle modifications and exercise are first-line recommendations for all women with PMS/PMDD and may be all that is needed to treat mild-to-moderate symptoms. Herbal and vitamin supplementation and complementary and alternative medicine have been evaluated for use in PMS/PMDD and have produced unclear or conflicting results. More controlled clinical trials are needed to determine their safety and efficacy and potential for drug interactions. CONCLUSIONS: Healthcare providers need to be aware of the symptoms of PMS and PMDD and the treatment options available. Treatment selection should be based on individual patient symptoms, concomitant medical history, and need for contraception.

Therapeutic options for sleep-maintenance and sleep-onset insomnia.

Insomnia, defined as difficulty falling asleep, staying asleep, and/or experiencing restorative sleep with associated impairment or significant distress, is a common condition resulting in significant clinical and economic consequences. Many options are available to treat insomnia, to assist with either falling asleep (sleep onset) or maintaining sleep. We searched MEDLINE for articles published between January 1996 and January 2006, evaluated abstracts from recent professional meetings, and contacted the manufacturer of the most recent addition to the pharmacologic armamentarium for insomnia treatment (ramelteon) to gather information. Nonpharmacologic options include stimulus control, sleep hygiene education, sleep restriction, paradoxical intention, relaxation therapy, biofeedback, and cognitive behavioral therapy. Prescription and over-the-counter drug therapies include benzodiazepine and nonbenzodiazepine sedative-hypnotic agents; ramelteon, a melatonin receptor agonist; trazodone; and sedating antihistamines. Herbal and alternative preparations include melatonin and valerian. Before recommending any treatment, clinicians should consider patient-specific criteria such as age, medical history, and other drug use, as well as the underlying cause of the sleep disturbance. All pharmacotherapy should be used with appropriate caution, at minimum effective doses, and for minimum duration of time.