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The altitudinal distribution of vascular plant species and communities has been intensively studied in neotropical montane forests (e.g., Cleef et al. 1984; Kappelle and Zamora 1995; Kappelle et al. 1995a; Lieberman et al. 1996; Chap. 4). However, still little is known about the population ecology of individual species and their responses to environmental factors along elevational gradients. Population structure studies of single species in relation to environmental factors have proven to be powerful in explaining ecological behavior in temperate regions (Wassen et al. 1990; Oostermeijer et al. 1994; Hegland et al. 2001), but such data are relatively scarce for tropical regions. So far, the main emphasis in the tropics has been on population dynamics of lowland rainforest canopy trees (e.g., Arriaga et al. 1988; Martinez-Ramos et al. 1988; Alvarez-Buylla and Martinez-Ramos 1992; Olmsted and AlvarezBuylla 1995), rather than on non-canopy species (Oyama 1990). Tropical studies directly relating population structure to environmental variables have not received much attention from scientists (Witkowski and Liston 1997; Hicks and Mauchamp 2000). To date, population dynamics of highland forest plant species are even rarer (but see Wesselingh et al. 1999, and Chaps. 14 and 18). In order to gain further insight into environmental factors (e.g., temperature, light availability) that may determine the population structure of vascular plant species on tropical mountains, we studied the relative proportions of different life stages of two tropical montane understory species in response to environmental changes occurring along an altitudinal gradient in Costa Rican montane oak forests.

The current chapter provides some insight into the structure, composition and diversity of Costa Rica’s montane oak forest. It is meant to set the stage on this particularly rich and voluminous forest, in order to better understand its spatial and temporal patterns and processes, and above all, its functioning as an ecosystem. In subsequent chapters (Chaps. 15, 17, 23, 24, 26 and 30), these themes will be dealt with by the author, co-authors and colleagues who have studied the magnificent Talamancan montane oak forest environment over the last two decades.

Tropical montane forests are among the most fragile of all ecosystems on Earth (Stadtmuller 1987; Hamilton et al. 1995; Kappelle and Brown 2001; Schneider et al. 2003). Following clearing, they recover extremely slowly, and it may take one to several centuries before their structure, composition, and function return to the original, pre-disturbance state (Ewel 1980; Hooftman 1998; Kappelle 2004). Southern temperate Nothofagus forest (Gonzalez et al. 2002) and neotropical montane Quercus forests (Kappelle et al. 1994, 1995b, 1996; Ramirez-Marcial et al. 2001; Chaps. 14 and 16) appear to be no exception to this rule. To gain a deeper insight into the patterns and processes of forest recovery and resilience in Central American montane oak forests, we studied changes in structure and diversity in a series of successional vegetation patches along a time sequence, ranging from grazed and recently abandoned pastures to late-successional (35 years old) and old-growth (>200 years old) oak forest stands in the highlands of southern Costa Rica.

A large number of studies on human impact on tropical mountains underline the vast destructive and often irreversible effects that settlements and inappropriate land use practices may have on local forest resources (e.g., Baker and Little 1976; Budowski 1982; Stadel 1986; Churchill et al. 1995; Kappelle 1996, 2004; Kappelle and Brown 2001; Bewket 2002; Benitez 2003). However, still little is known about the impact of man on tropical highland oak forests, the often unsustainable use, and the utilization of native plants by indigenous peoples and locally dwelling peasants (ladino colonists). At many places in Mexico, Central America and Colombia, oak trees have been cut for timber, fuelwood and other uses, and entire oak forests have been converted to pastures and croplands (Kappelle and Juarez 1995; Helmer 2000; Chaps. 16, 17, 21 and 31). In order to gain a better insight into the past and present use of these forests and their vascular plants, we conducted a case study and assessed land use history, changing trends in agricultural practices, and current ethnobotanical knowledge in the montane oak forest zone of Costa Rica’s Talamanca Mountains, with emphasis on the largely cleared Los Santos Forest Reserve, a Human Inhabited Protected Area (HIPA).

Frugivorous birds play an important role in seed dispersal (Levey et al. 2005), especially in the tropics (Stiles 1985; Guevara et al. 1986; Corlett 1998). Their role in lowland rainforest recovery on abandoned pastures has been extensively documented (Debussche et al. 1982; McDonnell and Stiles 1983; Guevara et al. 1986; Gorchov et al. 1993; Guevara and Laborde 1993; MartinezRamos and Soto-Castro 1993; McClanahan and Wolfe 1993; Robinson and Handel 1993; Galindo-Gonzalez et al. 2000). Numerous bird species thrive well in secondary growth tropical lowland habitats where croplands, shrublands and pastures alternate (Estrada et al. 1993; Gorchov et al. 1993). In such patchy landscapes, isolated remnant forest trees may offer protection to birds, and serve as stepping stones during their journey in search for closed old-growth forest fragments (Guevara et al. 1986; McClanahan and Wolfe 1987). In this way, isolated bird-dispersed forest trees may act as ‘seed-trapping’ centers of succession following lowland rainforest clearing (Debussche et al. 1982; McDonnell and Stiles 1983; Guevara et al. 1986; Guevara and Laborde 1993). To date, however, little is known on the ecology of frugivorous birds in human-influenced tropical montane forest landscapes. Neither do we know much about their role in the recovery of cleared upland forest (Stiles 1985; Kappelle et al. 1994; Poulsen 1994; Long 1995; Shiels and Walker 2003). Even less is known on the interaction between frugivorous bird species and specific ornithochorous tree species in relation to montane forest succession (Chap. 25). To further gain insight into these processes, we studied the role of frugivorous, seed-dispersing birds in montane oak forest recovery following clearing, burning and grazing in Costa Rica’s Talamanca highlands.

The preceding chapters of this book discuss scientific research results on natural and managed oak forests growing in the highlands of the American Tropics. Chapter authors highlight evolutionary, ecological and socioeconomic aspects of specific oak forests and identify existing gaps in our understanding. Their work and studies published elsewhere forms the basis for this chapter’s overview of the current state of knowledge on ecological patterns and processes which determine the structure and functioning of these magnificent forests. The increasingly important human use and much needed conservation of these biodiverse and threatened habitats are dealt with as well. Cross-cutting trends and issues are discussed and conclusions drawn. Neotropical montane oak forests are a special type of tropical montane forests (Kappelle 2004), in which tall oak trees (Quercus) dominate a 30to 60-m-high forest canopy, often in pure stands or mixed with pines (Pinus) or other predominant trees. Though Neotropical oak forest history, structure, species diversity, species interactions, ecosystem functioning, post-disturbance recovery, and human use may vary considerably over short geographical ranges, regional trends are now becoming evident. Research presented in this book clearly illustrates these large-scale trends. The following sections in this chapter synthesize our knowledge for each of these trends and themes.