Alexandre B. Sampaio

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).

Edge effect on tree diversity, composition and structure in a deciduous dry forest in Central Brazil

The effects of edge distance on the structure, composition and diversity of tree community, considering individuals of all size classes, were studied in a well-preserved fragment of deciduous dry forest in northeastern Goias state, Brazil. Plots were systematically established at six distances (0, 40, 80, 160, 280 and 400 m) from the edge, over 10 orthogonal transects on the forest-pasture edge. It was sampled 602 adult individuals/ha, 8,927 saplings/ha and 54,167 seedlings/ha distributed in 58 species. Although the composition of seedlings and adult individuals varied significantly over the forest-pasture gradient, the variation explained by edge distance was below 4%. Among parameters of community structure and tested diversity indexes, there was significant variation only for diversity of seedlings and height of adult trees among forest-pasture edge distances. The dry forest fragment showed only a slight edge effect on the evaluated tree community parameters. This conclusion contrasts with findings from studies on tropical rain forests which indicate sharp differences between edge and interior tree communities in forest fragments.

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

Allelopathy of a native shrub can help control invasive grasses at sites under ecological restoration in the Neotropical savanna

ABSTRACT Background: African C4 grasses threatens newly restored areas in Neotropical savannas. Allelopathy exhibited by some native species may contribute to ecological restoration. Aims: To establish the potential use of Lepidaploa aurea (Asteraceae) in ecological restoration of invaded savannas, we evaluated its allelopathic effects on two invasive grasses, a native grass, and two native trees (one savanna and one riparian forest species). Methods: We tested the allelopathic effects of the leaves and roots of L. aurea in a growth chamber, a greenhouse, and in field experiments. Results: Leaf extracts reduced the growth of all other species in the growth chamber experiment. Root extracts reduced growth in one invasive grass and promoted root growth in the savanna tree. The invasive grass and riparian forest tree were negatively affected when planted in soil where L. aurea had grown, whereas the savanna tree showed increased growth. Lepidaploa aurea litter reduced growth in one invasive grass species and increased root biomass accumulation in the native grass species. Conclusions: Lepidaploa aurea negatively affected the growth of invasive grasses, through plant extracts, litter and through soil. These patterns could explain its ability to colonise abandoned pasturelands and its high success of establishing in restoration areas.

Community-based native seed production for restoration in Brazil - the role of science and policy

Large-scale restoration programmes in the tropics require large volumes of high quality, genetically diverse and locally adapted seeds from a large number of species. However, scarcity of native seeds is a critical restriction to achieve restoration targets. In this paper, we analyse three successful community-based networks that supply native seeds and seedlings for Brazilian Amazon and Cerrado restoration projects. In addition, we propose directions to promote local participation, legal, technical and commercialisation issues for up-scaling the market of native seeds for restoration with high quality and social justice. We argue that effective community-based restoration arrangements should follow some principles: (i) seed production must be based on real market demand; (ii) non-governmental and governmental organisations have a key role in supporting local organisation, legal requirements and selling processes; (iii) local ecological knowledge and labour should be valued, enabling local communities to promote large-scale seed production; (iv) applied research can help develop appropriate techniques and solve technical issues. The case studies from Brazil and principles presented here can be useful for the up-scaling restoration ecology efforts in many other parts of the world and especially in tropical countries where improving rural community income is a strategy for biodiversity conservation and restoration.

Evidence of phytotoxicity in a fast-growing shrub useful for savanna restoration in Central Brazil

Finding fast-growing native species able to interfere in invasive grass species’ growth is essential to restore savannas and grasslands, where native tree growth is rather limited. We tested the phytotoxicity of Lepidaploa aurea (Mart. ex DC.) H.Rob. (Asteraceae), a native shrub from the Brazilian savanna that apparently inhibits the growth of invasive grasses in degraded areas and in areas under restoration process. We performed experiments in Petri dishes and soil conditions using four receiver species: three eudicots: Lactuca sativa L., Raphanus sativus L., Solanum lycopersicum L. and a monocot: Sorghum bicolor L. Moench. These are model species commonly used in phytotoxic studies for their known germination rates and high sensitivity to allelochemicals. We tested the effects of aqueous extracts of L. aurea’s leaves and roots, in four concentrations (10, 5, 2.5, 1.25%) and a control (distilled water). We performed tests in natural versus sterilized soils to identify the influence of soil microbiota in L. aurea’s phytotoxicity. We found phytotoxic effects in all tested conditions. Leaf extracts had more accentuated negative effects on target plants than did root extracts. The growth of receiver plants’ root was more affected than shoot growth. Lepidaploa aurea can be an important ally for the restoration of degraded areas savannas and grasslands. Studies considering species that co-occur with L. aurea in conserved and disturbed are as are necessary to confirm this allelopathic potential.