In many forested ecosystems, the architecture and functional ecology of certain tree species define forest structure and their species‐specific traits control ecosystem dynamics. Such foundation tree species are declining throughout the world due to introductions and outbreaks of pests and pathogens, selective removal of individual taxa, and over‐harvesting. Through a series of case studies, we show that the loss of foundation tree species changes the local environment on which a variety of other species depend; how this disrupts fundamental ecosystem processes, including rates of decomposition, nutrient fluxes, carbon sequestration, and energy flow; and dramatically alters the dynamics of associated aquatic ecosystems. Forests in which dynamics are controlled by one or a few foundation species appear to be dominated by a small number of strong interactions and may be highly susceptible to alternating between stable states following even small perturbations. The ongoing decline of many foundation species provides a set of important, albeit unfortunate, opportunities to develop the research tools, models, and metrics needed to identify foundation species, anticipate the cascade of immediate, short‐ and long‐term changes in ecosystem structure and function that will follow from their loss, and provide options for remedial conservation and management.

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Knowledge of historical fire activity tends to be focused at local to landscape scales with few attempts to examine how local patterns of fire activity scale to global patterns. Generally, fire activity varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesised sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In eastern and western North America and western Europe and southern South America, charcoal records indicate less-than-present fire activity from 21,000 to ~11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greaterthan-present fire activity from ~19,000 to ~17,000 cal yr BP whereas most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ~13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8000 to ~2000 cal yr BP, Indonesia from 11,000 to 4000 cal yr BP, and southern South America from 6000 to 3000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the postglacial period. These complex patterns can be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.

Summary1 Classifying species by shared functional characteristics is important if common functional response groups are to be identified among different taxa. 2 We investigated plant traits that determine the response of forest plant species to land use changes using literature data. Sources from eight European countries and four North-eastern American states, comprising 20 field studies yielded information on 216 forest plant species. For these species, data on 13 life history traits were collected. 3 Trait correlation structure was similar in the European and American data-sets and corresponded well to those described in the literature. The European and American herbs and the European graminoids were clustered into distinct emergent groups based on their plant traits. The profiles of the European and American emergent groups were similar. 4 Herb species belonging to emergent groups characterized by low dispersability (i.e. large seeds, low fecundity, unassisted dispersal) were relatively slow colonizers. Dispersability (and not recruitment) seems to be a key factor limiting the colonization of some forest plant species. The relationship between dispersability and colonizing capacity was less clear for graminoids. 5 A life history trait-based approach offers good opportunities to gain insight into the mechanisms behind species response to land-use change.

Hurricanes represent an important natural disturbance process to tropical and temperate forests in many coastal areas of the world. The complex patterns of damage created in forests by hurricane winds result from the interaction of meteorological, physiographic, and biotic factors on a range of spatial scales. To improve our understanding of these factors and of the role of catastrophic hurricane wind as a disturbance process, we take an integrative approach. A simple meteorological model (HURRECON) utilizes meteorological data to reconstruct wind conditions at specific sites and regional gradients in wind speed and direction during a hurricane. A simple topographic exposure model (EXPOS) utilizes wind direction predicted by HURRECON and a digital elevation map to estimate landscape—level exposure to the strongest winds. Actual damage to forest stands is assessed through analysis of remotely sensed, historical, and field data. These techniques were used to evaluate the characteristics and impacts of two important hurricanes: Hurricane Hugo (1989) in Puerto Rico and the 1938 New England Hurricane, storms of comparable magnitude in regions that differ greatly in climate, vegetation, physiography, and disturbance regimes. In both cases patterns of damage on a regional scale were found to agree with the predicted distribution of peak wind gust velocities. On a landscape there was also good agreement between patterns of forest damage and predicted exposure in the Luquillo Experimental Forest in Puerto Rico and the town of Petersham, Massachusetts. At the Harvard and Pisgah Forests in central New England the average orientation of wind—thrown trees was very close to the predicted peak wind direction, while at Luquillo there was also good agreement, with some apparent modification of wind direction by the mountainous terrain. At Harvard Forest there was evidence that trees more susceptible to windthrow were felled earlier in the storm. This approach may be used to study the effects of topography on wind direction and the relation of forest damage to wind speed and duration; to establish broad—scale gradients of hurricane frequency, intensity, and wind direction for particular regions; and to determine landscape—level exposure to long—term hurricane disturbance at particular sites.