Tree architecture is an important component of forest community dynamics - taller trees with larger crowns often outcompete their neighbors, but they are generally at higher risk of wind-induced damage. Yet, we know little about wind impacts on tree architecture in natural forest settings, especially in complex tropical forests. Here, we use airborne light detection and ranging (LiDAR) and 30 yr of forest inventory data in Puerto Rico to ask whether and how chronic winds alter tree architecture. We randomly sampled 124 canopy individuals of four dominant tree species (n = 22-39). For each individual, we measured slenderness (height/stem diameter) and crown area (m2) and evaluated whether exposure to chronic winds impacted architecture after accounting for topography (curvature, elevation, slope, and soil wetness) and neighborhood variables (crowding and previous hurricane damage). We then estimated the mechanical wind vulnerability of trees. Three of four species grew significantly shorter (2-4 m) and had smaller crown areas in sites exposed to chronic winds. A short-lived pioneer species, by contrast, showed no evidence of wind-induced changes. We found that three species' architectural acclimation to chronic winds resulted in reduced vulnerability. Our findings demonstrate that exposure to chronic, nonstorm winds can lead to architectural changes in tropical trees, reducing height and crown areas. La arquitectura de los & aacute;rboles es un componente importante de la din & aacute;mica de la comunidad forestal: los & aacute;rboles m & aacute;s altos con copas m & aacute;s grandes suelen sobrepasar a sus vecinos, pero por lo general corren m & aacute;s riesgo de sufrir da & ntilde;os inducidos por el viento. Sin embargo, es poco lo que se sabe sobre el impacto del viento en la arquitectura de los & aacute;rboles en entornos forestales naturales, sobre todo en bosques tropicales complejos. En este caso, utilizamos LiDAR y 30 a & ntilde;os de datos de campo en Puerto Rico para preguntarnos si los vientos cr & oacute;nicos alteran la arquitectura de los & aacute;rboles. Se tom & oacute; una muestra aleatoria de 124 individuos del dosel de cuatro especies arb & oacute;reas dominantes (n = 22-39). De cada individuo, medimos la esbeltez (altura/di & aacute;metro) y el & aacute;rea de la copa (m2) y evaluamos si la exposici & oacute;n a vientos cr & oacute;nicos influ & iacute;a en la arquitectura teniendo en cuenta la topograf & iacute;a (curvatura, elevaci & oacute;n, pendiente, humedad del suelo) y las variables del vecindario (aglomeraci & oacute;n y da & ntilde;os previos por huracanes). Luego, estimamos la vulnerabilidad mec & aacute;nica de los & aacute;rboles al viento. En los lugares expuestos a vientos cr & oacute;nicos, tres de las cuatro especies crecieron mucho menos (2-4 m) y tuvieron & aacute;reas de copa m & aacute;s peque & ntilde;as. Cecropia schreberiana, en cambio, no mostr & oacute; indicios de cambios inducidos por el viento. La aclimataci & oacute;n arquitect & oacute;nica de tres especies a los vientos cr & oacute;nicos llevaba a una reducci & oacute;n de la vulnerabilidad. Nuestros hallazgos demuestran que la exposici & oacute;n a vientos cr & oacute;nicos puede provocar cambios arquitect & oacute;nicos en los & aacute;rboles tropicales, reduciendo su altura y la superficie de sus copas.

In the Low Arctic, a warming climate is increasing rates of permafrost degradation and altering vegetation. Disturbance associated with warming permafrost can change microclimate and expose areas of ion-rich mineral substrate for colonization by plants. Consequently, the response of vegetation to warming air temperatures may differ significantly from disturbed to undisturbed tundra. Across a latitudinal air temperature gradient, we tested the hypothesis that the microenvironment in thaw slumps would be warmer and more nutrient rich than undisturbed tundra, resulting in altered plant community composition and increased green alder (Alnus viridis subsp. fruticosa) growth and reproduction. Our results show increased nutrient availability, soil pH, snow pack, ground temperatures, and active layer thickness in disturbed terrain and suggest that these variables are important drivers of plant community structure. We also found increased productivity, catkin production, and seed viability of green alder at disturbed sites. Altered community composition and enhancement of alder growth and reproduction show that disturbances exert a strong influence on deciduous shrubs that make slumps potential seed sources for undisturbed tundra. Overall, these results indicate that accelerated disturbance regimes have the potential to magnify the effects of warming temperature on vegetation. Consequently, understanding the relative effects of temperature and disturbance on Arctic plant communities is critical to predicting feedbacks between northern ecosystems and global climate change.