Diversidad de las comunidades de palmas en dos fragmentos de bosque húmedo tropical de Antioquia.

Summary 1. Tropical rainforests are a global conservation priority. Robust arguments supporting rainforest conservation can attract funding and shape land‐use management. However, some popular assertions regarding the value of tropical forests remain largely untested. 2. This study tests the validity of two arguments in support of mature tropical rainforest conservation: first, that these forests should be conserved based on their value as potential sources of medicine. This argument requires mature forests to be better sources of medicine than alternative land‐use types, including secondary forests. Second, secondary forest use may help conserve mature forests by providing sufficient resources to buffer against resource extraction in mature forests. 3. The research was conducted in three communities in the Cordillera Azul, Peru, where 369 individuals from 66 households were surveyed. Participants recorded all flora and fauna collected in mature (>20 years) and secondary forests over 180 days in six use categories (food, medicine, wood, weavings, adornments and ‘other’). Ecological knowledge of secondary and mature forest species was assessed for male and female household heads. 4. Households used 346 folk species (as defined by local classification systems) from 3668 collection events. Individuals had better knowledge of secondary forest species, but more access to mature forests. Participants collected significantly more medicines from secondary than from mature forests. In other major use categories (food, wood, weaving, adornment), secondary forests provided fewer resources than mature forests. Participants collected a different set of species from secondary and mature forests, with only 130 folk species (38%) collected in both secondary and mature forests. 5. Synthesis and applications. The arguments to protect mature rainforests as sources of new drugs may be overstated, because secondary forests can provide more medicinal plant resources than mature forests, and landscapes that incorporate forests of different ages can maximize availability of medicinal plant species. Conservation efforts must take a landscape level approach given the spread of resource use across different forest types. Because of the heterogeneity of resource availability and use among community members, and the dynamic nature of resource use on forest frontiers, conservation should embrace participatory adaptive management approaches that incorporate a variety of resource users.

QuestionsThe effects of agriculture on forest biodiversity and ecosystem properties can persist decades or centuries after abandonment. Many Pacific island nations are experiencing declines in traditional agriculture. Seed dispersal and seedling recruitment are critical to forest regeneration, and this is particularly relevant for Polynesia where native seed disperser diversity is low and species have been extirpated to crisis levels. In this study we asked: are secondary lowland tropical forests converging to mature forest, and are there seedling recruitment and survival differences between forest types?LocationThe Polynesian island of Tutuila, American Samoa, where traditional agriculture has been on the decline since the 1940s and secondary forests comprise 70% of all forest area.MethodsWe surveyed 34 vegetation plots (containing 2,232 adult trees and 6,579 tree seedlings) across mature forest and >50 years old secondary lowland rain forest. We quantitatively compared forest diversity, structure and the 3‐year seedling regeneration dynamics of the tree community.ResultsAlthough species richness and stem densities were similar between mature and secondary forest, most diversity and structure parameters remained distinguishable between the two forest types. Basal area remained significantly higher in mature forest; the diagnostic tree species of mature and secondary forest differed; and community composition (as indicated by NMDS) remained significantly different. However, seedling survivorship did not differ between forest types and seedling recruitment patterns indicated that there remained a suite of effective seed dispersers on Tutuila.ConclusionsWe conclude that (a) community differences between mature and secondary lowland rainforest were driven by the abundance of diagnostic species rather than exclusion of species from a forest type, and (b) there was no evidence of biophysical or ecological barriers to forest recovery of lowland secondary rain forest, or its convergence towards mature lowland rain forest. Nevertheless, more than 50 years after agricultural abandonment, secondary forest remains distinct from mature forest, highlighting that land use legacies are long‐term drivers of forest composition and successional trajectory in post‐agricultural landscapes of Polynesia.

Although primary forests are important for biological conservation, the value of secondary forests for forest-dependent organisms needs to be evaluated when habitat restoration is required. We examined whether flower-visiting insects can use secondary forests as alternative habitats to primary forests. In particular, we compared assemblages of bees (Anthophila) and flower longhorn beetles (Lepturinae: Cerambycidae) in young secondary, mature secondary, and primary forests. Our results showed that more bee species were captured in primary and mature secondary forests than in young secondary forests, and flower longhorn beetle species were captured more frequently in primary forests than in mature and young secondary forests. Ordination showed that the communities in the three forest types were not statistically identical, which indicated that secondary forests cannot provide an absolute alternative habitat to primary forests for bees and flower longhorn beetles. However, the results also suggest that as secondary forests mature, more primary forest species would be able to use secondary forests as habitats. This implies that restoration from other land uses, such as monoculture plantations, to secondary forests could help to promote the faunal biodiversity of primary forests.

Interest in tropical secondary forests has grown as large areas of agriculture have been abandoned in recent decades; yet, there are few long-term studies of post-agriculture vegetation recovery in the tropics. In this study, we compared the vegetation structure and floristic composition of old-growth and 40-year-old secondary riparian forests in the Cordillera Central, Dominican Republic. Canopy height and stem density of woody plants were similar between forest types, but basal area of trees was 27 percent lower in secondary forests. Introduced tree species comprised 20 percent of the basal area and dominated the understory of secondary forests. Life-form diversity was higher in old-growth forests as arborescent ferns, the palm species, and epiphytic bromeliads, orchids, and bryophytes were much more abundant. The number of species of epiphytic orchids and bromeliads, ground ferns, and herbaceous plants was also significantly higher in old-growth forests. The species density of woody plants and vines, however, was comparable between forest types, and vine abundance was significantly higher in secondary forests. The high importance of introduced tree species and the delayed recovery of several plant life-forms have important implications for the conservation of plant diversity in secondary forests in the tropics. The robust regeneration of woody structure despite the long land tenure (ca 60 yr) by farmers is probably due to the nutrient-rich alluvial soils and low-intensity agriculture. This study revealed the potential for the rapid recovery of woody plant diversity and structure in fertile secondary forests adjacent to mature forest seed sources and the more delayed recovery of nonwoody plant diversity and abundance.

While China is promoting the re‐establishment of forests across the country on a globally unprecedented scale, the biodiversity harboured by the resulting secondary and plantation forests remains poorly understood. Here, we assess the carabid diversity at Zhangguangcai Mountains in northeastern China that comprise a unique mosaic of mature forest remnants, secondary forests and forest plantations.We located pitfall traps in five distinct forest types: mature conifer and mature mixed forest, secondary mixed forest, secondary broadleaved forest dominated by birch (Betula platyphylla) and poplar (Populus davidiana), and in larch plantations. We recorded 9073 carabid beetles representing 42 species, with richness, abundance and diversity of ground beetles all peaking in secondary broadleaved forests. Assemblages sampled in larch plantations were least species rich, but species extrapolation curves indicate a potentially high overall species richness.Carabid communities were clearly differentiated according to forest type, with larch plantations and secondary broadleaved forests containing beetle assemblages distinct from the other three forest types, while the mixed secondary and mature forest types harboured similar assemblages.Carabid communities also showed a clear seasonality in all forest types, with the plantation forest communities remaining distinctly different from the clustered communities of the mature and mixed secondary forest types throughout the year. Broadleaved secondary forest assemblages occupy an intermediate position throughout the sampling season.

Effects of an invasive tree on community structure and diversity in a tropical forest in Puerto Rico

Mature tropical forests at agricultural frontiers are of global conservation concern as the leading edge of global deforestation. In the Ituri Forest of DRC, as in other tropical forest areas, road creation associated with selective logging results in spontaneous human colonization, leading to the clearing of mature forest for agricultural purposes. Following 1–3 years of cultivation, farmlands are left fallow for periods that may exceed 20 years, resulting in extensive secondary forest areas impacted by both selective logging and swidden agriculture. In this study, we assessed forest structure, tree species composition and diversity and the regeneration of timber trees in secondary forest stands (5–10 and ∼40 years old), selectively logged forest stands, and undisturbed forests at two sites in the Ituri region. Stem density was lower in old secondary forests (∼40 years old) than in either young secondary or mature forests. Overall tree diversity did not significantly differ between forest types, but the diversity of trees ≥10 cm dbh was substantially lower in young secondary forest stands than in old secondary or mature forests. The species composition of secondary forests differed from that of mature forests, with the dominant Caesalpinoid legume species of mature forests poorly represented in secondary forests. However, in spite of prior logging, the regeneration of high value timber trees such as African mahoganies (Khaya anthotheca and Entandrophragma spp.) was at least 10 times greater in young secondary forests than in mature forests. We argue that, if properly managed and protected, secondary forests, even those impacted by both selective logging and small-scale shifting agriculture, may have high potential conservation and economic value.

The importance of old secondary forests for understory birds in the tropical Andes

ROONEY, T. P. AND W. J. DRESS. (Department of Biology, Indiana University of Pennsylvania, Indiana PA 15705). Patterns of plant diversity in overbrowsed primary and mature secondary hemlock-northern hardwood forest stands. J. Torrey Bot. Soc. 124: 43-51. 1997.-Many studies report that herbaceous species diversity is higher in primary forest than mature secondary forests, but this pattern has not yet been demonstrated in forests overbrowsed by white-tailed deer. We compared the diversity of herbaceous and tree seedling species in 5 primary and 5 mature secondary riparian zone forest stands in northwestern Pennsylvania, a region which has been overpopulated with white-tailed deer for the past 65 years. We sampled study plots with 16 1 -M2 quadrats and recorded herb and tree seedling species presence and abundance. At the -rM2 scale, primary forest sites had significantly more tree seedling species per quadrat but the number of herb species per quadrat in primary and secondary forest sites was not significantly different. At the 2.25 ha scale, primary forest sites had significantly higher herb and tree seedling richness than secondary sites. Herbs and tree seedlings also exhibited significantly greater evenness in primary sites than secondary sites. There was considerable species composition overlap between primary and secondary sites. Tsuga canadensis, Fagus grandifolia, and Oxalis acetosella had a significantly higher frequency of occurrence and significantly greater abundance in primary forest sites, whereas Prunus serotina and Erythronium americanum had a significantly higher frequency of occurrence and significantly greater abundance in secondary forest sites. Acer rubrum was also significantly more abundant in secondary growth sites. We hypothesize that the trend towards greater diversity in primary forest plots is the result of these stands experiencing levels of disturbance closer to the historic disturbance regime.

It is not clear if mature secondary growth coniferous forests can support similar pollinator communities as old growth coniferous forests, or how active management (e.g., retention forestry) in mature secondary growth forests may affect pollinator communities. We compare the native bee community and plant‐bee interaction networks of old growth, naturally regenerating and actively managed (retention forestry) mature secondary growth forests of similar stand age. Old growth forests had a higher bee species richness and Shannon's diversity index, but not Simpson's diversity index, than both actively managed and naturally regenerating mature secondary forests. Forest type (old‐growth, naturally regenerating mature secondary growth, and actively managed mature secondary growth) had a significant effect on bee community composition. Redwood forest bee‐plant interaction networks were small in size and had lower complexity than expected and few connector species. While studies suggest that small‐scale timber harvest may increase bee biodiversity in the short‐term in other coniferous forest habitats, our study suggests that there may be long‐term negative effects of clear‐cutting that lower bee biodiversity in mature secondary growth forests as compared to mature old‐growth forests.

Anthropogenic drivers of headwater and riparian forest loss and degradation in a highly fragmented southern Amazonian landscape

Forest loss, fragmentation, and anthropization threaten the survival of forest species all over the world. Shifting agriculture is one of these threatening processes in Madagascar. However, when its cycle is halted and the land is left to regenerate, the resulting growth of secondary forest may provide a viable habitat for folivorous and omnivorous lemur species. We aimed to identify the response of nocturnal lemurs to different successional stages of regenerating secondary, degraded mature, and mature forest across a mosaic-type landscape. We surveyed four nocturnal lemur species (Avahi laniger, Microcebus cf. simmonsi, Allocebus trichotis, and Daubentonia madagascariensis) in four forest types of varying habitat disturbance in northeastern Madagascar. We estimated densities in mature and regenerating secondary forest for the eastern woolly lemur (Avahi laniger) and mouse lemur (Microcebus cf. simmonsi), two sympatric species with folivorous and omnivorous diets respectively. We did not estimate densities of Allocebus trichotis and Daubentonia madagascariensis owing to small sample size; however, we observed both species exclusively in mature forest. We found higher population densities of A. laniger and M. cf. simmonsi in secondary than in mature forest, showing the potential of regenerating secondary forest for lemur conservation. Several environmental factors influenced the detectability of the two lemur species. While observer and habitat type influenced detection of the eastern woolly lemur, canopy height and vine density influenced detection of mouse lemurs. Understanding how different species with different diets interact with anthropogenically impacted habitat will aid future management decisions for the conservation of primate species.

We examined US scientists’ (1) use of second-growth, mature, and old-growth forest in scientific publication titles, (2) definitions of second-growth, mature, and old-growth forest, and (3) sampling methods in second-growth, mature, and old-growth forest. “Second-growth forest” (55 titles) and “mature forest” (40) experienced the most frequent use in the 2010s. “Old-growth forest” (247) had the most use in the 1990s. Definitions of second-growth forest originated from successional theory and were consistent across scientists. Definitions of mature forest lacked consensus. Definitions of old-growth forest increased in complexity as scientists integrated biological, social, and political factors. Soil was the most frequent abiotic factor measured in mature and old-growth forests. In second-growth forests it was dead organic matter. Trees were the most common life form measured in all forests. The results show that researchers would benefit from a clearer differentiation between second-growth and mature forest and a formal definition for mature forest.

Improving our ability to monitor fragmented tropical ecosystems is a critical step in supporting the stewardship of these complex landscapes. We investigated the structural characteristics of vegetation classes in Ucayali, Peru, employing a co-production approach. The vegetation classes included three agricultural classes (mature oil palm, monocrop cacao, and agroforestry cacao plantations) and three forest regeneration classes (mature lowland forest, secondary lowland forest, and young lowland vegetation regrowth). We combined local knowledge with spaceborne lidar from NASA's Global Ecosystem Dynamics Investigation mission to classify vegetation and characterize the horizontal and vertical structure of each vegetation class. Mature lowland forest had consistently higher mean canopy height and lower canopy height variance than secondary lowland forest (μ = 29.40 m, sd = 6.89 m vs. μ = 20.82 m, sd = 9.15 m, respectively). The lower variance of mature forest could be attributed to the range of forest development ages in the secondary forest patches. However, secondary forests exhibited a similar vertical profile to mature forests, with each cumulative energy percentile increasing at similar rates. We also observed similar mean and standard deviations in relative height ratios (RH50/RH95) for mature forest, secondary forest, and oil palm even when removing the negative values from the relative height ratios and interpolating from above-ground returns only (mean RH50/RH95 of 0.58, 0.54, and 0.53 for mature forest, secondary forest, and oil palm, respectively) (p < .0001). This pattern differed from our original expectations based on local knowledge and existing tropical forest succession studies, pointing to opportunities for future work. Our findings suggest that lidar-based relative height metrics can complement local information and other remote sensing approaches that rely on optical imagery, which are limited by extensive cloud cover in the tropics. We show that characterizing ecosystem structure with a co-production approach can support addressing both the technical and social challenges of monitoring and managing fragmented tropical landscapes.

Concomitant with the rapid loss of tropical mature forests, the relative abundance of secondary forests is increasing steadily and the latter are therefore of growing interest for conservation. We analysed species richness of fruit-feeding nymphalid butterflies in secondary forest fragments of different age and isolation and in mature forest at the eastern margin of the Lore Lindu National Park in Central Sulawesi, Indonesia. From April to August 2001 we collected 2322 individuals of fruit-feeding butterflies, belonging to 33 species. Butterfly species richness increased with succession, but was significantly higher in mature forests than in all types of secondary forest. Isolation of the forest fragments did not have a significant effect on butterfly species richness in the range of distances (up to 1700 m) studied. Rather it appeared to affect only a few species. Species richness of endemic species was higher than of non-endemic species. Although endemic species were most diverse in mature forests, many species captured were restricted to secondary forests. Our results show that mature forest is essential for the conservation of nymphalid butterflies and for the endemic species in this area. However, considering the relatively large number of species found in these rather small habitat islands, secondary forest fragments, especially older successional stages, can be taken into account in conservation efforts and thus contribute to the preservation of tropical biodiversity on a landscape scale.