Daniel L. M. Vieira

Tropical dry-forest regeneration from root suckers in Central Brazil

Seed dispersal, predation, desiccation and seedling survival are strong bottlenecks that impede tropical forest recovery on abandoned agricultural lands (reviewed in Holl 2002). The ability to resprout after disturbances overcomes these barriers, as those individuals bypass the seed stage and have more vigorous shoots than seedlings (Bond & Midgley 2001, Kammesheidt 1999, Kennard et al . 2002). Resprouting is a particularly important recovery mechanism in tropical dry forests (reviewed in Vieira & Scariot 2006). There are a number of reasons why resprouting may be more important in dry forests than in rain forests, including slower decay rates of trunk bases (Ewel 1980), or adaptation of plants to drought (Bond & Midgley 2001, Sampaio et al . 1993).

Síndromes de dispersão de espécies arbustivo-arbóreas em cerrado sensu stricto do Brasil Central e savanas amazônicas

O objetivo deste trabalho foi identificar as proporcoes das sindromes de dispersao de sementes em areas de cerrado sensu stricto do Brasil Central, comparando-as com as de areas isoladas de savanas amazonicas. Foram utilizadas listas de especies de nove areas de cerrado e cinco areas de savanas amazonicas. Determinou-se a similaridade floristica entre as areas. As sindromes de dispersao de especies ocorrentes nestas areas foram determinadas a partir de dados da literatura. Utilizou-se o teste Qui-quadrado (c2) a fim de detectar possiveis diferencas nas proporcoes de zoocoria e anemocoria entre as areas de cerrado e entre as areas de savanas amazonicas. As medias entre as duas regioes foram comparadas pelo teste t. Nao foram encontradas diferencas significativas para as duas analises (p > 0,05). A media das proporcoes de zoocoria para o cerrado sensu stricto foi de 56,7% ± 5,4 DP e para as savanas amazonicas 55,6% ± 11,7 DP, e a media das proporcoes de anemocoria no cerrado sensu stricto foi de 39,7% ± 6,2 DP e para as savanas amazonicas 44,4% ± 11,7 DP. No cerrado sensu stricto, a autocoria variou de 1,4 a 5%, porem nao se verificou a presenca de especies autocoricas nas savanas amazonicas. A autocoria e uma estrategia de dispersao raramente encontrada no cerrado e sua ausencia nas areas de savanas amazonicas pode estar relacionada a sua baixa eficiencia em colonizar areas isoladas.

Environmental variables and tree population structures in deciduous forests of central Brazil with different levels of logging

Population structures of six tree species in three fragments of intact seasonal deciduous forest and three fragments disturbed by logging were studied in the northeastern Goias. Forty random 400 m2 plots were allocated in each fragment to survey plant population structures, number of stumps, cattle feces, burnt logs, and canopy openness. Soil cover by life forms was estimated in 1m2 sub-plots. Lianas were abundant in intermediately logged fragments and invasive herbs in the most disturbed fragment. Cattle avoided dense herbaceous strata, such as liana tangles. Cavanillesia arborea, Eugenia dysenterica and Swartzia multijuga trees occurred at very low densities in all the fragments and their seedlings were practically absent, which might endanger their future populations in these fragments. Myracrodruon urundeuva, Tabebuia impetiginosa and Astronium fraxinifolium, the most logged species, had high density of seedlings in all the fragments. However, the highest density of saplings and juvenile individuals occurred in the most disturbed fragment.

Recruitment of Dry Forest Tree Species in Central Brazil Pastures

Despite its importance as a wealthy source of unique biodiversity (Janzen 1988) and that it covers 42% of the tropical vegetation worldwide (Murphy and Lugo 1995), the dry forest is the most endangered terrestrial ecosystem and one of the least protected (Scariot and Sevilha 2005). In Central America for example, less than 1% of the original 500,000 km2 is preserved in conservation units (Janzen 1988, Sanchez-Azofeifa et al. 2003). In Brazil, the seasonal deciduous forests—a type of dry forest—covers 27,367,815 ha (3.21%) of the territory, from which 1,072,946 ha (3.9%) are protected by conservation units. Among conserved areas of deciduous dry forest, only 117,980 ha (0.43%) are in conservation units of restricted use as national parks and biological reserves. Most of the conservation units (402,456 ha or 1.47%) allow limited economic use of the land and natural resources. There is no information of the conservation unit assigned in official database for 552,509 ha (2.02%) of dry forests (Sevilha et al. 2004). Dry forests occur in many soil classes. In Brazil they occur in at least 13 soil classes of the Brazilian Soil Classification (Scariot and Sevilha 2005), but deciduous dry forests occur predominantly in rich soils. There are many valuable trees used for timber. These forests are the main targets of farmers, who log the trees and sell the timber to acquire financial resources to establish farms. In Central Brazil, where some of the most important remnants of dry forests of the country occur (Fig. 11.1), most of the area originally occupied by dry forests has been replaced by pasture composed by exotic grass in extensive farmlands on rich soils. Recommendations have been made for the creation of new conservation units, but given the high degree of landscape fragmentation any new conservation unit will contain significant proportion of its area covered by pasture and forest fragments with different levels of disturbance caused by logging, cattle grazing, fire and invasive species. Thus, in this scenario it is fundamental to understand the mechanisms of tree regeneration in pasture fields to address vegetation recovery and use this information to facilitate forest regeneration. There are four to five times more studies on the natural regeneration of rainforests than on dry forests, and even less on restoration (Vieira and Scariot 2006a). Taking into account the threat level, the lack of conservation units, the lack of information