Restoration of Araucaria Forest: The Role of Perches, Pioneer Vegetation, and Soil Fertility Lessandra Zanini 1 and Gislene Ganade 1,2 Abstract The Araucaria forest is Brazil’s highly threatened sub- tropical forest ecosystem that has been disappearing in recent decades. Restoration programs involving this forest type are scarce, and there is a lack of scientific information on how ecological processes such as competition, facilita- tion, and seed dispersal influence natural forest restora- tion. This work aims to investigate how use of perches to attract seed dispersers and the influence of pioneer vege- tation and soil fertilization could affect the colonization of woody species in a degraded area. An experiment was conducted in an abandoned field where the natural estab- lishment of seeds and seedlings of woody species was monitored under factorial combinations of the following treatments: (1) pioneer vegetation (presence and absence); (2) soil fertility (addition of NPK and control); and (3) perches (presence and absence). Seed and seedling abun- dance, seed and seedling species richness, and seedling mortality were recorded monthly during 12 months. Seed abundance and species richness were significantly greater in places with perches than in control plots. These results were consistent over the year and more pronounced when the surrounding forest produced a higher amount of fruit. Species richness and abundance of seedlings were signifi- cantly greater in places with perches than in control plots, and in places with vegetation than without. Soil fertility did not influence seedling establishment. Facilitation and seed dispersal are important factors affecting the coloniza- tion of woody species in this subtropical area. Nutrient availability neither regulates the facilitation process nor in- fluences species replacement during the early stages of Araucaria forest succession. Key words: bird seed dispersal, Brazil subtropical forest, early successional processes, facilitation, nutrient competi- tion, seed predation, seedling establishment. Introduction The Araucaria forest is a subtropical forest located within the fourth most important conservation hot spot of the world (Myers et al. 2000). This forest has been extensively exploited since the nineteenth century (IBGE 1986). In the southern limit of its distribution, the Araucaria forest has lost about 95% of its native cover (Gorgonio 1992; Secretaria Estadual do Meio Ambiente 2001). Although this forest has been highly threatened, programs of forest restoration are scarce, and there is a lack of scientific information on how ecological processes may influence natural forest regrowth. The rates of arrival of forest seeds in degraded areas can influence the speed of forest restoration. Seed arrival greatly depends on the abundance and behavior of dis- persal agents such as birds, bats, and wind (Nepstad et al. 1990; Janzen & Va ´ squez-Yanes 1991; Ganade 2001). Stud- ies have shown that seeds of the majority of tropical forest tree species are dispersed by birds (Howe & Smallwood 1982). Nevertheless, activity of seed-dispersing bird spe- cies in pasture areas is low, and their movements are limited and dependent upon the availability of fruit or branches for perching (Guevara et al. 1986; McClanahan & Wolfe 1993; Robinson & Handel 1993; Silva et al. 1996). Because arrival of forest bird species in pastures oc- curs very slowly, lack of seed dispersal becomes an impor- tant barrier for forest restoration (McDonnel & Stiles 1983; Uhl et al. 1988; Nepstad et al. 1990, 1991; Aide & Cavalier 1994). Many studies have shown that the use of perches increases the arrival of seeds dispersed by birds in degraded areas (McDonnel & Stiles 1983; McDonnel 1986; McClanahan & Wolfe 1993; Miriti 1998). Seed num- ber can be 150 times larger under perches, increasing woody plant colonization (McClanahan & Wolfe 1993). Therefore, the use of perches would be an important procedure to stimulate forest regeneration (McDonnel & Stiles 1983). The presence of pioneer vegetation could affect the establishment of late-successional species in degraded areas by altering some microclimatic conditions such as light, water, and nutrient availability that may facilitate or inhibit the establishment of seedlings of late-successional species (Connell & Slatyer 1977; Callaway & Walker 1997). Furthermore, the presence of pioneer vegetation could attract or deter seed predators and seedling herbivores, altering the chances of seedling establishment and as a con- sequence, affecting the balance between facilitation and competition in early successional systems (DeSteven 1991; Gill & Marks 1991; Hammond 1995; Ganade 1996; Callaway & Walker 1997). A large number of vegetation 1 Laborato ´ rio de Ecologia da Restaurac xa ˜ o, Biologia, Universidade do Vale do Rio dos Sinos—UNISINOS, CP 275, CEP 93022-000, Sa ˜ o Leopoldo, Rio Grande do Sul, Brazil. 2 Address correspondence to G. Ganade, email gganade@unisinos.br Ó 2005 Society for Ecological Restoration International SEPTEMBER 2005 Restoration Ecology Vol. 13, No. 3, pp. 507–514 507