Trees In Pastures Research Articles

Conservation of Epiphyte Diversity in an Andean Landscape Transformed by Human Land Use

Epiphytes are diverse and important elements of tropical forests, but as canopy-dwelling organisms, they are highly vulnerable to deforestation. To assess the effect of deforestation on epiphyte diversity and the potential for epiphyte conservation in anthropogenically transformed habitats, we surveyed the epiphytic vegetation of an Ecuadorian cloud forest reserve and its surroundings. Our study was located on the western slopes of the Andes, a global center of biodiversity. We sampled vascular epiphytes of 110 study plots in a continuous primary forest; 14 primary forest fragments; isolated remnant trees in young, middle-aged, and old pastures; and young and old secondary forests. It is the first study to include all relevant types of habitat transformation at a single study site and to compare epiphyte diversity at different temporal stages of fragmentation. Epiphyte diversity was highest in continuous primary forest, followed by forest fragments and isolated remnant trees, and lowest in young secondary forests. Spatial parameters of habitat transformation, such as fragment area, distance to the continuous primary forest, or distance to the forest edge from inside the forest, had no significant effect on epiphyte diversity. Hence, the influence of dispersal limitations appeared to be negligible or appeared to operate only over very short distances, whereas microclimatic edge effects acted only in the case of completely isolated trees, but not in larger forest fragments. Epiphyte diversity increased considerably with age of secondary forests, but species assemblages on isolated remnant trees were impoverished distinctly with time since isolation. Thus, isolated trees may serve for recolonization of secondary forests, but only for a relatively short time. We therefore suggest that the conservation of even small patches of primary forest within agricultural landscape matrices is essential for the long-term maintenance of the high epiphyte diversity in tropical cloud forests.

¿Las cercas vivas ayudan a la conservación de la diversidad de mariposas en paisajes agropecuarios?

In Central America, natural forests have been transformed into agriculture production areas, generating forest fragmentation, desertification, erosion and loss of biodiversity, among other concerns. Different tree cover compositions are kept on these agricultural landscapes, including scattered trees in pastures, live fences, fragments of secondary forests, and riparian forests. These can help in biodiversity conservation because they generate shelter, feeding and reproduction areas, among others. We studied the composition, richness and abundance of diurnal butterflies on two types of live fences in a landscape where pastures are predominant in Costa Rica's Central Pacific Region. Transects (120 x 5 m) were observed for an hour (two days/habitat) in five multi-strata fences (with several plant species, strata and canopy width) and five simple fences (with smaller and pruned trees). A total of 2,782 butterflies were observed (75 species). The most abundant species were Anartia fatima, Eurema daria, Eurema nise, Hermeuptychia hermes, Junonia evarete and Phoebis philea. Multi-strata fences had more species and can help maintain 56% of the total species observed in secondary and riparian forests. This type of live fence can play an important role in butterfly conservation in livestock areas, and its benefits are influenced by the manner in which farmers manage their land.

Dispersal limitation in epiphytic bromeliad communities in a Costa Rican fragmented montane landscape

Abstract:Transformation of tropical forests is likely to affect seed-dispersal patterns and influence the composition of epiphytic plant communities in human-altered habitats. We tested this hypothesis by carrying out a comparative study of seed influx, survival and growth of transplanted seedlings of epiphytic bromeliads among isolated trees in six pasture areas, six forest edges and six forest sites in a montane area in Costa Rica. In total, 72 traps trapped 1285 seeds over a 2-mo period in the dry season of 2003. For all four investigated bromeliad genera, Catopsis, Guzmania, Tillandsia and Werauhia, the number of trapped seeds in each habitat followed a pattern similar to the number of fruiting individuals in the vicinity of the traps. Traps in forest edges (30) were 1.9 times more likely to collect seeds than traps at forest interiors (30) and pasture trees (12), the latter showing similar probabilities of catching seeds. After 1 y, survival and growth of 3660 transplanted seedlings from three bromeliad species was significantly higher in forest interiors, providing no explanation for the lower abundance of fruiting adults in that habitat. These results suggest that the successful establishment of epiphytic bromeliads in forest interiors is mainly dispersal-limited. If corroborated, differences in abundance among species at each habitat are likely related to differences in growth rates and reproductive success. Further studies on the growth and mortality of seedlings up to the flowering stage, however, are needed.

Influence of pasture understoreys and tree management on soil moisture under a young New Zealand stand of Pinus radiata

Soil moisture content (SMC) and throughfall were monitored along transects between rows of radiata pine (Pinus radiata D. Don) planted at 7 m row spacing and grown with ryegrass/clover or lucerne pastures or with no understorey. SMC was recorded to 1 or 2 m depths for years 2–6 or 4–6, respectively. The predominant rainfall from the south–south–west (SSW) direction created rain shadows (60% of open pasture) on the northern sunny side of the trees. The rain shadows increased as the trees grew but their position were modified by stand pruning and thinning in years 4 and 5. SMC in the top meter showed strong positional effects with the lowest SMC under the tree crowns and on the northern side. There were strong seasonal patterns driven by high spring and summer evapotranspiration, modified by rain shadows and stand age. For the no-understorey treatment, SMC remained high midway between tree rows until the trees were 4 years old and started utilizing this moisture. For the two pasture understoreys, the difference in SMC between the north and south sides decreased with time after trees were thinned and pruned. In the no-understorey there was little difference between the two aspects. Understorey evapotranspiration and fine rooting patterns also helped explain soil moisture use patterns. No difference was detected between two contrasting radiata pine tree types. The effective rooting depth of the ryegrass/clover understorey was <0.7 m while that of lucerne and trees were deeper. Alternative tree planting practices may reduce some of the negative effects of tree-understory moisture competition.

Effect of sewage sludge and liming on productivity during the establishment of a silvopastoral system in north‐west Spain

Silvopastoral systems are recognised as a sustainable means of increasing forest land through recovery of abandoned agricultural land. Establishment of agroforestry systems is currently promoted by the new EU regulations through direct farmer payments. This can fulfil Agenda 21's economic, cultural and social principles better than simply planting forest. An interesting fertilisation option for silvopastoral systems is sewage sludge, in view of the need to manage this product in environmentally acceptable ways. The present study aimed to evaluate the effect of three sewage sludge application rates (0, 160 and 320 kg ha‐1 per year of total N) and two liming rates (0 and 2.5 t ha‐1 of CaCO3) on pasture production and tree growth in a Populus x euramericana silvopastoral system, during the 5 years from planting. The silvopastoral system was established in autumn 2001, in Lugo (north‐west Spain), on a piece of abandoned agricultural land. A pasture mixture (25 kg ha‐1 of Dactylis glomerata var. ‘Artabro’ and 4 kg ha‐1 of Trifolium repens var. ‘Huia') was sown and Populus × euramericana saplings were planted at a density of 400 trees ha‐1. Liming (main plots) was applied before pasture was sown in autumn 2001, and sewage sludge (subplots) was applied homogeneously in the spring of 2002 and 2003. The results indicate that there was a significant liming × fertilisation interaction, and that initial pasture production could limit tree growth. The high sewage sludge rate when no lime was applied and the low sewage sludge rate after liming increased tree height and diameter because of the soil pH increment 6 years after establishment.

Pollen dispersal and genetic structure of the tropical tree Dipteryx panamensis in a fragmented Costa Rican landscape

In the face of widespread deforestation, the conservation of rainforest trees relies increasingly on their ability to maintain reproductive processes in fragmented landscapes. Here, we analysed nine microsatellite loci for 218 adults and 325 progeny of the tree Dipteryx panamensis in Costa Rica. Pollen dispersal distances, genetic diversity, genetic structure and spatial autocorrelation were determined for populations in four habitats: continuous forest, forest fragments, pastures adjacent to fragments and isolated pastures. We predicted longer but less frequent pollen movements among increasingly isolated trees. This pattern would lead to lower outcrossing rates for pasture trees, as well as lower genetic diversity and increased structure and spatial autocorrelation among their progeny. Results generally followed these expectations, with the shortest pollen dispersal among continuous forest trees (240 m), moderate distances for fragment (343 m) and adjacent pasture (317 m) populations, and distances of up to 2.3 km in isolated pastures (mean: 557 m). Variance around pollen dispersal estimates also increased with fragmentation, suggesting altered pollination conditions. Outcrossing rates were lower for pasture trees and we found greater spatial autocorrelation and genetic structure among their progeny, as well as a trend towards lower heterozygosity. Paternal reproductive dominance, the pollen contributions from individual fathers, did not vary among habitats, but we did document asymmetric pollen flow between pasture and adjacent fragment populations. We conclude that long-distance pollen dispersal helps maintain gene flow for D. panamensis in this fragmented landscape, but pasture and isolated pasture populations are still at risk of long-term genetic erosion.

Conventional and genetic measures of seed dispersal for Dipteryx panamensis (Fabaceae) in continuous and fragmented Costa Rican rain forest

The effects of habitat fragmentation on seed dispersal can strongly influence the evolutionary potential of tropical forest plant communities. Few studies have combined traditional methods and molecular tools for the analysis of dispersal in fragmented landscapes. Here seed dispersal distances were documented for the tree Dipteryx panamensis in continuous forest and two forest fragments in Costa Rica, Central America. Distance matrices were calculated between adult trees (n = 283) and the locations of seeds (n = 3016) encountered along 100 × 4-m transects (n = 77). There was no significant difference in the density of seeds dispersed &gt; 25 m from the nearest adult (n = 253) among sites. There was a strong correlation between the locations of dispersed seeds and the locations of overstorey palms favoured as bat feeding roosts in continuous forest and both fragments. Exact dispersal distances were determined for a subset of seeds (n = 14) from which maternal endocarp DNA could be extracted and matched to maternal trees using microsatellite analysis. Dispersal within fragments and from pasture trees into adjacent fragments was documented, at a maximum distance of 853 m. Results show no evidence of a fragmentation effect on D. panamensis seed dispersal in this landscape and strongly suggest bat-mediated dispersal at all sites.

Environmental quality improvement of agricultural lands through silvopasture in southeastern United States

We hypothesized that, because of the ability of trees to sequester carbon (C) in the deep soil profile and remove excess nutrients from soils, the silvopastoral agroforestry system could enhance the environmental quality of the agricultural lands. To test this hypothesis, two sets of experiments were conducted in two soil orders in Florida, Spodosols and Ultisols, with two major objectives: i) determining the soil C accumulation and tracing the plant sources of C in soil fractions, and ii) quantifying water soluble phosphorus (WSP) and estimating the Soil P Storage Capacity (SPSC). Total C in both soil orders was greater under silvopasture than in treeless pastures, particularly at lower depths. Stable-isotope signature analysis suggested that C3 plants (in this case, slash pine, Pinus elliotii) contributed to a more stable C fraction than C4 plants (in this case, bahiagrass, Paspalum notatum) at soil depths up to 1 m. WSP was consistently higher in treeless pastures, while the remaining SPSC was lower in this land-use system, suggesting the greater likelihood of P moving out of the soil under treeless pasture than in silvopasture. Thus, the presence of trees in pastures contributed to more stable C within the soil profiles, lower WSP, and greater SPSC, indicating more environmental benefits provided by silvopastoral systems as compared to treeless pastures under similar ecological settings.

Composición florística en potreros de Los Tuxtlas, Veracruz, México

Se hizo un inventario de especies de plantas fanerógamas y pteridofitas en potreros en áreas desprovistas de árboles, en la zona del volcán San Martín Tuxtla, en Los Tuxtlas, Veracruz. Con el fin de tener la composición florística más completa posible, se realizaron muestreos durante la temporada seca y la de lluvia del año de 1992, en dos localidades: el ejido Balzapote y la colonia agrícola-ganadera La Palma. En cada localidad se seleccionaron cinco potreros dominados por especies de pastos nativas (conocidos como potreros de grama) y cinco en que prevalece la gramínea introducida Cynodon plectostachyus (llamados potreros de estrella). En cada potrero, dentro de una hectárea se ubicaron al azar 10 cuadros fijos de 2 x 2 m en los que se registró a toda planta presente y se estimó su cobertura, además de medir la altura de la vegetación dentro de cada cuadro. El resultado arrojó un total de 200 especies de angiospermas y 14 de pteridofitas, pertenecientes a 55 familias. Las familias con 10 especies o más fueron Asteraceae, Euphorbiaceae, Poaceae y Leguminosae (sensu lato). Las plantas con cobertura mayor de 10% del área muestreada fueron C. plectostachyus, Axonopus spp., Paspalum conjugatum (Poaceae), Hyptis atrorubens (Lamiaceae) y Mimosa pudica (Leguminosae: Mimosaceae). La mayoría de las especies encontradas en potreros fueron malezas y pastos; sin embargo, también se registraron plántulas de árboles y arbustos.

Farmers and the Forest: Can Agroforestry Actually Conserve Biodiversity?

Farmers and the Forest: Can Agroforestry Actually Conserve Biodiversity?

Methods for conservation outside of formal reserve systems: The case of ants in the seasonally dry tropics of Veracruz, Mexico

Like most ecosystems of the world, tropical dry forests of the central coast of the Gulf of Mexico are inadequately preserved. Given that reserve expansion is unlikely, it is imperative that the conservation capacity of the matrix surrounding reserves is enhanced. Here, we examine the habitat value of isolated pasture trees and patches of secondary regrowth in terms of their terrestrial and arboreal ant assemblages in both a wet and dry season. These simplified wooded systems increase species densities within the agricultural matrix and provide habitat for some forest ant species. Estimated species richness of arboreal ants was particularly low on isolated trees, highlighting an important limitation. This was not the case for terrestrial ants, which were particularly species rich under isolated trees. We also found that the inter-site variations in species densities and similarity to the forest ant assemblage for terrestrial and arboreal strata were not correlated, suggesting that responses to restoration may not be as uniform as often thought. This has important implications for the use of indicator taxa in suggesting the response of other taxa. In terms of species composition, neither secondary regrowth nor isolated trees were appropriate replacements for forest fragments, even though the studied forest fragments were small (13–32ha). The ant assemblages did not exhibit a seasonal change in composition. However, season influenced the contrast between habitats, with isolated trees being more distinct from pasture, and regrowth more closely resembling forests, during the wet season. Microclimatic variables indicate that the forests were least affected by the tropical dry season, and this may contribute to their characteristic fauna. We conclude that even small forest patches make a unique contribution to landscape conservation and that, where reserves are limited, conscientious management of the landscape matrix may provide some species with sufficient new habitat to survive outside of reserve systems. These conclusions are influenced by both season and strata studied.

A Survey of Small-Scale Farmers Using Trees in Pastures in Herrera Province, Panama

Herrera province in Panama has suffered extensive deforestation due to cattle ranching. Scientific knowledge of tree species use in Herreran pastures is limited and baseline information is necessary for the development of viable silvopastoral systems. The present study employed surveys to describe the current use of trees in Herreran pastures. The Ministry of Agricultural and Livestock Development (MIDA) and Panama Peace Corps identified eight informants who were interviewed in order to develop a semi-structured interview. The developed interview was then administered to 45 randomly selected small-scale (< 20 hec) Herreran pasture owners, with stratification by informant gender and farm ecozone. Nine different tree uses were identified. There were differences in the popularity and perceived species richness of these uses. Sørensons's similarity index indicated that percent similarity between uses ranged from 0-51%. Abundance-diversity curves for uses were steep with only a few dominant species. Native species (e.g., Byrsonima crassifolia, Guazuma ulmifolia, Cordia alliodora) tended to receive the highest multipurpose tree priority ratings. Protein banks were not used and are likely inappropriate for most small-scale farmers. However, fodder trees (e.g., Guazuma ulmifolia, Enterolobium cyclocarpum) were often retained in pastures and agricultural by-products (stover, immature fruits) were commonly used as feed supplements. Trees provide a number of products and services in Herreran pastures and require further research, with special attention to native species.

A Review of the Agroforestry Systems of Costa Rica

SUMMARY This review aims to summarize some of the studies in the agroforestry systems of Costa Rica from the 1970s to date. From the 1970s to the mid 1980s, agroforestry systems were characterized by a dominance of the association of indigenous trees from natural regeneration with coffee, cacao, and pastures. However, in the mid-1980s, a number of trials with native species started in Costa Rica, which identified several promising species for reforestation or agroforestry (i.e., Vochysia ferruginea, V. guatemalensis, Terminalia amazonia, Hyeronima alchorneoides, and others). In the 1990s to date, there has been a diversification in the types of agroforestry systems used, and an increase in research on these systems (i.e., taungya, improved fallows, multipurpose trees in pastures, alley cropping, and home gardens). Current research not only focuses on the benefits of trees to the systems, but it also studies the proper combinations of crops-trees to attain more profitable yields and to avoid risk, and highlights the environmental services provided by the systems.

Foraging preferences of Swift Parrots on Tasmanian Blue-gum: tree size, flowering frequency and flowering intensity

The Swift Parrot (Lathamus discolor), is a migratory species that forages primarily on Blue-gum (Eucalyptus globulus) during its Tasmanian breeding season. We investigated the foraging preferences of Swift Parrots for Blue-gum trees of different sizes and the effect of tree size on flowering frequency and flowering intensity over three seasons (1998, 1999, 2001). Swift Parrots showed a clear preference for larger Blue-gum trees: Blue-gum trees in which Swift Parrots foraged were ∼40% larger than surrounding (non-forage) trees, while the size-class distribution of forage trees was significantly skewed towards larger tree-size compared with surrounding non-forage trees. The mean flowering intensity of forage trees was also significantly greater than the mean flowering intensity of non-forage trees. Both flowering frequency and flowering intensity increased with tree size, although there was a trend for both flowering frequency and intensity to decline in the largest tree size-classes. Past clearing has resulted in the loss of over 50% of the original (pre-European) grassy Blue-gum forest in Tasmania. Remnant grassy Blue-gum forest as well as artificially planted Blue-gum trees typically occur in small patches of <1 ha, including many solitary and scattered trees in pasture, parkland and gardens. These isolated patches of Blue-gum frequently include trees of large stature, making them an important food resource for the endangered Swift Parrot.

Arboreal Ant Species Richness in Primary Forest, Secondary Forest, and Pasture Habitats of a Tropical Montane Landscape1

ABSTRACTCanopy invertebrates may reflect changes in tree structure and microhabitat that are brought about by human activities. We used the canopy fogging method to collect ants from tree crowns in primary forest, secondary forest, and pasture in a Neotropical cloud forest landscape. The total number of species collected was similar in primary forest (21) and pasture (20) habitats, but lower in secondary forest (9). Lower diversity in secondary forest was caused by lower species density (no. of species per sample). Rarefaction curves based on number of species occurrences suggest similar community species richness among the three habitats. This study has implications for conservation of tropical montane habitats in two ways. First, arboreal ant species density is reduced if secondary forest replaces primary forest, which increases the chance of extinction among rare species. Second, pasture trees may serve as repositories of primary forest ant communities due to similar tree structure.RESUMENLos disturbios antropogénicos sobre la estructura de los árboles y microhabitat afectara la diversidad de invertebrados del dosel. Se usó la técnica de fumigación para colectar hormigas de las copas de los árboles en tres ambientes en un bosque nuboso Neotropical; bosque primario, bosque secundario, y pastizal. La cantidad total de especies colectadas fue similar entre el bosque primario (21) y el pastizal (20), pero menor en el bosque secundario (9). La baja riqueza en el bosque secundario fue consequencia de menor densidad de especies (cantidad de especies por muestra). Las curvas de rarefacción basada en presencia/ausencia de especies sugieren que la riqueza a nivel de la comunidad es similar entre los tres tipos de hábitat. Estos resultados puede aportar a la conservación de los hábitat tropicales nubosos de dos maneras. Primero, sugieren que la densidad de especies de hormigas es baja cuando un bosque primario es reemplazado por un bosque secundario. Segundo, los árboles grandes de pastizales pueden servir como refugios para las comunidades de hormigas, debido a que presentan similitud con la estructura de un bosque primario.

Small-footprint lidar estimation of sub-canopy elevation and tree height in a tropical rain forest landscape

Meso-scale digital terrain models (DTMs) and canopy-height estimates, or digital canopy models (DCMs), are two lidar products that have immense potential for research in tropical rain forest (TRF) ecology and management. In this study, we used a small-footprint lidar sensor (airborne laser scanner, ALS) to estimate sub-canopy elevation and canopy height in an evergreen tropical rain forest. A fully automated, local-minima algorithm was developed to separate lidar ground returns from overlying vegetation returns. We then assessed inverse distance weighted (IDW) and ordinary kriging (OK) geostatistical techniques for the interpolation of a sub-canopy DTM. OK was determined to be a superior interpolation scheme because it smoothed fine-scale variance created by spurious understory heights in the ground-point dataset. The final DTM had a linear correlation of 1.00 and a root-mean-square error (RMSE) of 2.29 m when compared against 3859 well-distributed ground-survey points. In old-growth forests, RMS error on steep slopes was 0.67 m greater than on flat slopes. On flatter slopes, variation in vegetation complexity associated with land use caused highly significant differences in DTM error distribution across the landscape. The highest DTM accuracy observed in this study was 0.58-m RMSE, under flat, open-canopy areas with relatively smooth surfaces. Lidar ground retrieval was complicated by dense, multi-layered evergreen canopy in old-growth forests, causing DTM overestimation that increased RMS error to 1.95 m. A DCM was calculated from the original lidar surface and the interpolated DTM. Individual and plot-scale heights were estimated from DCM metrics and compared to field data measured using similar spatial supports and metrics. For old-growth forest emergent trees and isolated pasture trees greater than 20 m tall, individual tree heights were underestimated and had 3.67- and 2.33-m mean absolute error (MAE), respectively. Linear-regression models explained 51% (4.15-m RMSE) and 95% (2.41-m RMSE) of the variance, respectively. It was determined that improved elevation and field-height estimation in pastures explained why individual pasture trees could be estimated more accurately than old-growth trees. Mean height of tree stems in 32 young agroforestry plantation plots (0.38 to 18.53 m tall) was estimated with a mean absolute error of 0.90 m ( r 2=0.97; 1.08-m model RMSE) using the mean of lidar returns in the plot. As in other small-footprint lidar studies, plot mean height was underestimated; however, our plot-scale results have stronger linear models for tropical, leaf-on hardwood trees than has been previously reported for temperate-zone conifer and deciduous hardwoods.

Considerations for Establishing and Managing Silvopastures

Silvopasture managers deliberately integrate trees, forages, and livestock to take advantage of their beneficial interactions. Correctly managed, production of each component can be greater than in traditional forestry and forage-livestock systems. Silvopasture systems also support greater biological and economic diversity and provide environmental benefits. In this review, the authors discuss establishment and management of trees in pastures and potential benefits to system productivity, primarily in relation to hardwood species.

Arboreal Ant Species Richness in Primary Forest, Secondary Forest, and Pasture Habitats of a Tropical Montane Landscape1

Canopy invertebrates may reflect changes in tree structure and microhabitat that are brought about by human activities. We used the canopy fogging method to collect ants from tree crowns in primary forest, secondary forest, and pasture in a Neotropical cloud forest landscape. The total number of species collected was similar in primary forest (21) and pasture (20) habitats, but lower in secondary forest (9). Lower diversity in secondary forest was caused by lower species density (no. of species per sample). Rarefaction curves based on number of species occurrences suggest similar community species richness among the three habitats. This study has implications for conservation of tropical montane habitats in two ways. First, arboreal ant species density is reduced if secondary forest replaces primary forest, which increases the chance of extinction among rare species. Second, pasture trees may serve as repositories of primary forest ant communities due to similar tree structure.

Spider Assemblages in Costa Rican Cloud Forests: Effects of Forest Level and Forest Age

We investigated spider assemblages in trees at three cloud forest sites and in trees isolated in pasture habitat in Monteverde, Costa Rica. Spiders were collected from two forest types (primary and secondary) within each forest site, and at two different levels (canopy and understory) within forest types and the pasture. They were identified to family or genus level and assigned to morphospecies. Araneidae and Linyphiidae were the most commonly collected families at all locations. Although spider abundance and morphospecies richness did not differ between forest types, perhaps due to their close proximity, these parameters were generally lower in the forest canopy than in the understory. Relative abundances of nearly all common spider families also differed between canopy and understory levels within forests, suggesting that distinct sub-assemblages exist. However, spider abundance and morphospecies richness did not differ between canopy and understory in pasture trees. Spiders were generally more abundant and more diverse in the pasture than the forest, possibly due to its lower elevation or its greater habitat complexity in the form of vascular epiphytes.

Pollen dispersal of tropical trees (Dinizia excelsa: Fabaceae) by native insects and African honeybees in pristine and fragmented Amazonian rainforest

Tropical rainforest trees typically occur in low population densities and rely on animals for cross-pollination. It is of conservation interest therefore to understand how rainforest fragmentation may alter the pollination and breeding structure of remnant trees. Previous studies of the Amazonian tree Dinizia excelsa (Fabaceae) found African honeybees (Apis mellifera scutellata) as the predominant pollinators of trees in highly disturbed habitats, transporting pollen up to 3.2 km between pasture trees. Here, using microsatellite genotypes of seed arrays, we compare outcrossing rates and pollen dispersal distances of (i) remnant D. excelsa in three large ranches, and (ii) a population in undisturbed forest in which African honeybees were absent. Self-fertilization was more frequent in the disturbed habitats (14%, n = 277 seeds from 12 mothers) than in undisturbed forest (10%, n = 295 seeds from 13 mothers). Pollen dispersal was extensive in all three ranches compared to undisturbed forest, however. Using a twogener analysis, we estimated a mean pollen dispersal distance of 1509 m in Colosso ranch, assuming an exponential dispersal function, and 212 m in undisturbed forest. The low effective density of D. excelsa in undisturbed forest (approximately 0.1 trees/ha) indicates that large areas of rainforest must be preserved to maintain minimum viable populations. Our results also suggest, however, that in highly disturbed habitats Apis mellifera may expand genetic neighbourhood areas, thereby linking fragmented and continuous forest populations.