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In This Issue Emotional signs of approaching depressionComplex systems approaching a tipping point typically experience a period called "critical slowing down, " in which the system's resilience and recovery from perturbations slow prior to a change in state. To assess whether such critical slowdown precedes a shift between healthy and depressed emotional states, Ingrid van de analyzed studies in which volunteers recorded their emotions at random times over 5 or 6 days. The authors focused on reports provided by 535 emotionally healthy and 93 depressed volunteers that monitored four emotions: cheerful, content, sad, and anxious. For volunteers who experienced a change of emotional health after the study, whether into or out of depression, the authors report that previous positive or negative emotions better predicted future similar emotions than for volunteers whose emotional health did not change. Negative emotions appeared to be reinforced in persons progressing toward depression; likewise, positive emotions appeared to be reinforced in persons progressing out of depression. Emotional variance during the study was also high for volunteers approaching a change. The authors suggest that the trends in emotional correlation and variance are indicative of an increase in emotional inertia and critical slowdown leading to a tipping point. Such signs may serve as an early-warning system for the onset of depression, according to the authors. -P.G.

In the northeastern United States, tree declines associated with acid deposition induced calcium depletion have been documented, notably for red spruce (Picea rubens Sarg.) and sugar maple (Acer saccharum Marsh.). There is conflicting evidence concerning whether co-occurring tree species capitalized on these declines or suffered similar growth reductions and on how growth has fluctuated relative to environmental variables. We examined five species along three elevational transects on Mt. Mansfield, Vermont: sugar maple, red spruce, red maple (Acer rubrum L.), yellow birch (Betula alleghaniensis Britton), and balsam fir (Abies balsamea (L.) Mill.). We found baseline differences in growth. Red maple and yellow birch had the highest growth, sugar maple and red spruce had intermediate growth, and balsam fir had the lowest growth. While some year-to-year declines were associated with specific stress events, protracted patterns such as recent increases in red spruce and red maple growth were correlated with increased temperature and cooling degree days (heat index). For most species and elevations, there was a positive association between temperature and growth but a negative association with growth in the following year. Based on our comparisons, for some species, growth at Mt. Mansfield aligns with regional trends and suggests that patterns assessed here may be indicative of the broader region.

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