Coastal Grassland Research Articles

Effects of nitrogen and salinity on growth and competition between a native grass and an invasive congener.

Numerous studies show that an increase in the availability of limiting resources can increase invasion by non-native plants into natural communities. One possible explanation is that the ability of natives to compete with non-natives tends to decrease when resource availability is increased. We tested this hypothesis in a competition experiment using two closely matched plant species and two environmental factors related to limiting resources in a coastal grassland system on Bodega Head in northern California. We grew the native grass Bromus carinatus and the non-native grass B. diandrus together and apart at different levels of soil nitrogen crossed with different levels of soil salinity. Both species are abundant in the grassland and previous work suggested that the abundance of B. carinatus is lower and the abundance of B. diandrus is higher on soil that has been enriched with nitrogen. Salinity has been shown to be negatively associated with invasion by B. diandrus into another California grassland, and to vary significantly over short distances in the grassland at Bodega Head, where it could affect water availability, which strongly limits plant growth during the dry season. Contrary to our prediction that low resource availabilities would increase the relative competitive ability of the native, the ability of B. carinatus to compete with B. diandrus was not greater when nitrogen availability was lower or when soil salinity was higher. Instead, high salinity increased the relative competitive ability of the non-native, and low nitrogen had little effect on competition. This suggests that preventing resource enrichment will not suffice to control invasion by non-native plant species in this grassland.

Patterns of invasion within a grassland community

Summary Relatively few studies have looked for patterns of invasion by non‐native species within communities. We tested the hypotheses that: (i) some types of microhabitats within a community are more invasible than others; (ii) microhabitat types that differ in invasion also differ in resource availability; and (iii) invasibility is mediated by effects of these resources on competition between native and non‐native species. To test the first two hypotheses, we measured plant cover and soils in a coastal grassland in northern California. Consistent with these hypotheses, cover of non‐native plants was consistently high where nitrogen‐fixing shrubs had recently grown, in the bottoms and sides of gullies and on deep soils, and these microhabitats tended to have relatively high nitrogen or water availability. Cover and number of native species tended to be lower where cover of non‐native species was higher, indicating that non‐native species as a group negatively affected native species. However, the number of non‐native species also tended to be lower where the total cover of non‐natives was higher. This suggests that a few non‐native species excluded natives and other non‐natives alike. To test the third hypothesis, we grew a common non‐native, the annual grass Lolium multiflorum, and a common native, the perennial grass Hordeum brachyantherum, at different levels of water and nitrogen. The relative competitive ability of the native was higher at lower nitrogen availability but not at lower water availability. When 10‐week‐old native plants were grown with non‐native seedlings and nitrogen was relatively low, the native out‐competed the non‐native. However, the non‐native out‐competed the native at all resource levels when species were both grown as seedlings. Competition between native and non‐native grasses in this system may thus help prevent invasion by non‐natives in microhabitats where nitrogen availability is low, but invasion may be relatively irreversible.

Effect of flooding and draw‐down disturbance on germination from a seashore meadow seed bank

Abstract. The objective of this study was to investigate the effects of flooding and draw‐down on the germination from the coastal grassland seed banks and to determine whether the effect of flooding varies between the delta and the seashore. Seed bank samples were collected from three shore transects in SW Finland, two on the shore of the Baltic Sea and one on the delta of River Kokemäenjoki. Samples were germinated in non‐flooded and flooded conditions for over a month, after which both treatments were maintained in non‐flooded conditions. A total of 9267 seedlings of 47 species germinated and mean density of seeds in the soil was ca. 84 000/m2. Most of the seedlings were monocots (98%) and perennials (98%). Ca. 30–40% of the species found in the above‐ground vegetation had a seed bank including the majority of the most abundant species. The number of seeds and species richness increased as the organic layer became thicker. The organic layer was thicker in the seashore samples and the seed bank was significantly larger than in the delta. The flooding and draw‐down treatment significantly increased the number of germinating seedlings in the seashore and also increased species richness in two transects, one in the delta and the other in the seashore. Two species, Schoenoplectus tabernaemontani and Typha latifolia, had significantly higher germination in the flooded treatment than in the non‐flooded. Apparently, many species in these coastal grasslands have adapted to flood disturbance and for seeds of some species flooding may work as a positive signal, possibly breaking dormancy.

Intraspecific competition and subterranean herbivory: individual and interactive effects on bush lupine

High mortality of plants growing in dense monospecific stands (i.e. self‐thinning) usually results from intense intraspecific competition. However, inconspicuous below‐ground insect herbivory might be a potent but overlooked source of mortality within dense stands of plants, particularly if crowding limits a plant's ability to compensate for herbivore damage. Here I ask how high conspecific density influences a plant's ability to cope with heavy below‐ground insect herbivory. I manipulated conspecific density and exposure to an abundant root‐borer, the ghost moth (Hepialus californicus), and examined the impacts on the fecundity, growth, and survival of bush lupine (Lupinus arboreus), a fast‐growing shrub that grows in dense monospecific stands in coastal grasslands. Both herbivory and intraspecific competition affected seed production, size, and mortality of bush lupine over the two years of the experiment. Plants consistently produced fewer seeds when growing at high versus low density and ghost moth herbivory also significantly reduced seed production. The negative effects of herbivory on plant fecundity were similar, regardless of plant density. In contrast, plant survival was affected by both competition, herbivory, and the interaction of these factors. In high density plots, plant survival was uniformly low (averaging 0.45–0.50); plants exposed to herbivores died from heavy herbivory, and plants protected from herbivores died due to intense intraspecific competition that compensated for losses due to herbivory. In low density plots, ghost moth herbivory similarly reduced lupine survival, from an average survival probability of 0.94 in plots protected from these herbivores to 0.55 in plots exposed to herbivory. Thus, results show that regardless of plant density, below‐ground herbivory can be a potent source of mortality.

Broad-toothed rat, Mastacomys fuscus (Rodentia, Muridae), found in alpine heathland in Tasmania.

THE broad-toothed rat Mastacomys fuscus is a native, herbivorous rodent that occurs in New South Wales, Victoria and Tasmania. On the Australian mainland the species has been recorded in several habitats at altitudes ranging from sea level to 1800 m. In alpine and sub-alpine areas of New South Wales and Victoria it has been recorded in heathlands, open eucalypt woodlands and wet sedgelands (Calaby and Wimbush 1964; Dixon 1971; Seebeck 1971; Bubela et al. 1991). At lower altitudes in Victoria, it has been recorded in wet sclerophyll forests with a dense undergrowth, coastal heathland, coastal grassland and in a pine plantation (Seebeck 1971; Wallis et al. 1982; Warneke 1960). In Tasmania, M. fuscus has been previously recorded only in buttongrass moorlands of western Tasmania at altitudes ranging from sea level to 900 m (Finlayson 1933; Andrews 1968; Green 1968, 1984; Hocking and Guiler 1983; Driessen and Comfort 1991; Slater 1992; Driessen 1998). Buttongrass moorland (also referred to as sedgeland) is a treeless vegetation typically dominated by Gymnoschoenus sphaerocephalus (buttongrass) that covers more than a million hectares in Tasmania, predominantly in the western part of the State (Jarman et al. 1988). Buttongrass moorland is a very variable vegetation group and not all communities recognised within buttongrass moorland provide habitat for M. fuscus (Driessen and Comfort 1991; Slater 1992; Driessen 1998). The purpose of this note is to report the results of a survey for M. fuscus in alpine heathland, a habitat in which the species has not been previously recorded in Tasmania. This finding has significant implications for the conservation status of this species.

Effects of invasion by the indigenous shrub Acacia sophorae on plant composition of coastal grasslands in south-eastern Australia

Invasion of natural ecosystems by weeds is often associated with increasing levels of disturbance. However, there is substantial evidence that cessation of disturbance can also lead to plant invasions, especially of woody species. In some coastal grasslands in south-eastern Australia, removal of grazing and burning appears to have triggered invasion by the indigenous shrub, Acacia sophorae. To quantify the impacts of such invasions on plant diversity, this study focussed on the coastal grasslands in Eurobodalla National Park, NSW. Analysis of aerial photographs indicated that 96 ha of the 479 ha study area (20%) was invaded by Acacia between 1944 and 1994, with the most rapid expansion from the late 1970s when grazing was removed. Vegetation sampling demonstrated a strong negative correlation between Acacia cover and plant species richness. A linear regression between the species richness of each quadrat and the number of growth rings on the largest Acacia branch showed an average loss of 7.5 species (38% of species) after 10 years of Acacia invasion and 15 species (76%) after 20 years. Long-term invasion favoured just a small group of shade tolerant, rhizomic grasses and sedges. Without active ecosystem management, grassland plant diversity should continue to decline and the nationally threatened herb, Thesium australe, is likely to disappear. An adaptive management program should be implemented promptly to assess the effects of different management regimes on Acacia abundance and plant diversity at ENP.

The influence of plant and corolla size on pollen deposition and seed set in Geranium sanguineum (Geraniaceae)

In a coastal grassland area the influence of plant and corolla size on insect visitation rate, pollen deposition on stigmas and seed set was measured in a natural population of Geranium sanguineum. Visits by bumble bees, the primal pollinators, were significantly affected by plant size measured as the number of flowers, and differences in visit rates among plants were explained by size differences among these. On average, larger plants had bigger corollas. The mean corolla area affected pollen deposition positively whereas deposition did neither affect seed set (number per flower) nor seed weight. Insects reaction to corolla size was dependent on plant size, and thus we found the effect of corolla size on pollen deposition to decline with plant size. Instead pollen deposition per plant seemed to be correlated to overall floral display. We argued that resource status of the individual plants could explain corolla size and seed set variation. The finding of some plant setting seeds while other plant with comparable size did not set any seeds could not be explained satisfactory by resource limitation.

Carbon Addition as a Countermeasure Against Biological Invasion by Plants

Increased nitrogen availability is known to favor invasion by non-native plants into natural grasslands. This suggests that decreasing nitrogen availability might serve as a countermeasure against invasion. One way to at least temporarily decrease nitrogen availability to plants is to increase microbial nitrogen uptake by adding carbon to the soil, and sawdust is a carbon source whose low cost could make it a practical conservation tool. To test whether adding sawdust to soil can counter the tendency of nitrogen enrichment to promote invasions by non-native plants, we hand-tilled 1.5 kg sawdust/m2 into the upper soil of the bare, nitrogen-rich patches left by dead shrubs of the nitrogen-fixing shrub Lupinus arboreus in two nearby areas with contrasting levels of invasion in a coastal grassland in northern California. After two years, in both areas, patches with sawdust had 40% less biomass of non-native plants than patches without sawdust, whereas biomass of native plants was not affected by sawdust addition. The more negative effect of sawdust on non-native species was specifically due to an effect on non-native grasses; adding sawdust increased the frequency of both native and non-native forbs. Results suggest that adding carbon as sawdust to soil can help counter invasion of grassland by non-native plants when invasion is being promoted by increased nitrogen availability, especially when the major invasive species are grasses.

Effects of Burning and Grazing on a Coastal California Grassland

AbstractWe tested the effects of fall burning and protection from livestock grazing as management to enhance native grasses on a coastal grassland in central California. Plants from the Mediterranean, introduced beginning in the late 1700s, have invaded and now dominate most of California's grasslands. Coastal grasslands are generally less degraded than those inland and have higher potential for restoration and conservation. Productivity of the experimental plots varied annually and declined over the course of the study because of rainfall patterns. Foliar cover of the native Danthonia californica (California oatgrass) increased more under grazing than grazing exclusion and did not respond to burning. Two other natives, Nassella pulchra (purple needlegrass) and Nassella lepida (foothill needlegrass), responded variably to treatments. The response of N. pulchra differed from that reported on more inland sites in California. Restoring these grasslands is complicated by differing responses of target species to protection from grazing and burning. The current practice of managing to enhance single species of native plants (e.g., N. pulchra) may be detrimental to other equally important native species.

Vegetation of the Sileza Nature Reserve and neighbouring areas, South Africa, and its importance in conserving the woody grasslands of the Maputaland Centre of Endemism

An analysis of the plant communities of the Sileza Nature Reserve and surrounding areas (± 4 124 ha) is presented. The study area falls within the Maputaland Centre o f Endemism, which is part ot the Maputaland-Pondoland Region, a centre of plant diversity rich in endemic plants and animals. A TWINSPAN classification, refined by Braun-Blanquet procedures, revealed 12 distinct, mainly grassland plant communities. A hierarchical classification, description and ecological interpretation ot these communities are presented. The level o f the water table, either directly, or indirectly through its role in soil formation, is the deciding factor in defining plant communities on the geologically young sandy substrate. Fire is an essential factor, particularly in maintaining the woody grasslands, a rare vegetation type rich in geoxylic suffrutices. and unique to the Maputaland Centre. A comparison between the endemic complement in the subtropical coastal grasslands of Maputaland and the high-altitude Afromontane grasslands of the Wolkberg Centre of Endemism shows marked differences in grow th form and vegetation type partitioning between the two centres. This can probably be ascribed to the relative youth (Quaternary) of the Maputaland coastal plain and its associated plant communities. Notable for their richness in Maputaland Centre endemic/near-endemic taxa. the conservation of sand forest and woody grasslands should receive high priority. Afforestation with alien trees is the most serious threat to the biodiversity of the Maputaland coastal grasslands, not only because of habitat destruction, but also through its expected negative effect on the hydrology of the region

Home range and spatial organisation of stoats (Mustela erminea), ferrets (Mustela furo) and feral house cats (Felis catus) on coastal grasslands, Otago Peninsula, New Zealand: Implications for yellow‐eyed penguin (Megadyptes antipodes) conservation

This radio‐tracking study reports the home range and spatial organisation of 12 stoats (Mustela erminea), 21 feral ferrets (Mustela furo) and 11 feral house cats (Felis catus) in coastal grasslands surrounding yellow‐eyed penguin (Megadyptes antipodes) breeding colonies, Otago Peninsula, South Island, New Zealand. Fully revealed ranges averaged 133 (±52 SD) ha for 6 male stoats; 83 (±73 SD) ha for 2 female stoats; 163 (± 50 SD) ha for 6 male ferrets; 135 (±44 SD) ha for 10 female ferrets; 207 (±99 SD) for 7 male cats; and 148 (± 63 SD) ha for 3 female cats. Males had larger ranges than females, and the larger predators ranged over greater areas than the smaller predators. Mustelids did not have intrasexual territorial spacing systems. Similarly, mustelid and cat ranges overlapped extensively, though stoats may avoid ferrets and/or cats by using different micro‐habitats. An example on how the logic of this argument applies to protect yellow‐eyed penguins threatened by stoats or ferrets and cats follows: based on minimum home range size, control stations should be placed less than 638 and 964 m apart respectively to ensure all individual predators are at risk of being killed. Investigation of the number of control stations per home range to ensure all trappable predators are killed would allow improved cost‐effectiveness of control programmes. As an interim protocol we recommend control stations spaced 286 and 432 m apart on trapping grids to control stoats and ferrets/cats repectively.

Nitrous oxide production by denitrification and nitrification in temperate forest, grassland and agricultural soils

SummaryNitrous oxide is produced in soils by biological denitrification and nitrification. To improve the fundamental understanding of the processes leading to N2O fluxes from soils, the production of N2O from denitrification and nitrification in spruce forest, beech forest, riparian grassland, coastal grassland and an agricultural field were studied. Samples were taken at a high and a low position along a topographic gradient in each site in the spring and autumn when the largest N2O fluxes were expected. They were incubated after being amended with N, and C2H2 was used as biological inhibitor to distinguish nitrification and denitrification.The N2O production in the low landscape position varied between 32 and 121 ng N cm−3 h−1 in the riparian grassland. 9 and 26 ng N cm−3 h−1 in the coastal grassland, and 135 and 195 ng N cm−3 h−1 in the agricultural field which was 10–100 times more than in the high positions where rates ranged between 3 and 5 ng N cm−3 h−1, 0.3 and 0.4 ng N cm−3 h−1, and 7 and 10 ng N cm−3 h−1, respectively. These differences almost certainly arose because the soil in the low positions was wetter and contained more organic matter. In the two forests N2O production was less than 1 ng N cm−3 h−1, strongly inhibited by O2, and not influenced by landscape position. Nitrification contributed to more than 60% of total N2O production in the riparian grassland. In the agricultural field nitrification produced 13–74% of the total N2O in the low position, and 10–88% in the high position. Denitrification was the dominant source of N2O in the coastal grassland except at the low position in the autumn where nitrification produced 60% of the total N2O. In the two forests where the soil had small nitrification potentials denitrification was the only source of N2O. In the other sites nitrification and denitrification potentials were large and of identical magnitude. The results emphasize the need to separate nitrification and denitrification at the process level and to recognize topography at the field scale when modelling N2O effluxes from soil.

Systematics and Morphologic Variation in Two Chromosomal Forms of the Agile Kangaroo Rat (Dipodomys agius)

Morphologic variation between two chromosomal forms of Dipodomys agilis was analyzed by use of external, cranial, and bacular characters. Significant morphologic differences were evident between chromosomal forms. Discriminant-function analysis followed by examination of specimens from the Los Angeles Basin, California, suggested a broad zone of sympatry between the two chromosomal forms, primarily delineated by habitat and elevation. Animals with a diploid chromosomal number of 2n = 62 generally were collected in mesic woodland and coniferous forests at higher elevations in the San Gabriel, San Bernardino, and coastal Santa Monica mountains. Conversely, the southern chromosomal form (2n = 60) inhabits a mosaic of environments ranging from coastal grassland and chaparral in southern California to arid desert and conifer forests in Baja California. These two chromosomal forms appear to represent two distinct species.

Effect of seed predation on seed bank size and seedling recruitment of bush lupine (Lupinus arboreus).

Whether seed consumers affect plant establishment is an important unresolved question in plant population biology. Seed consumption is ubiquitous; at issue is whether seedling recruitment is limited by safe-sites or seeds. If most seeds inhabit sites unsuitable for germination, post-dispersal seed consumption primarily removes seeds that would otherwise never contribute to the population and granivory has minimal impacts on plant abundance. Alternatively, if most seeds ultimately germinate before they lose viability, there is greater potential for seed consumption to affect plant recruitment. Of the many studies on seed consumption, few ask how seed loss affects seedling recruitment for species with long-lived seed banks. We examined post-dispersal seed predation and seedling emergence in bush lupine (Lupinus arboreus), a woody leguminous shrub of coastal grasslands and dunes in California. We followed the fate of seeds in paired experimental seed plots that were either protected or exposed to rodent granivores in grassland and dune habitats. Significantly more seeds were removed by rodents in dunes than grasslands. In dunes, where rodent granivory was greatest (65% and 86% of seeds removed from plots by rodents in two successive years), there is a sparse seed bank (6.6 seeds m-2), and granivory significantly reduced seedling emergence (in the same two years, 18% and 19.4% fewer seedlings emerged from exposed versus protected plots), suggesting seed rather than safe-site limited seedling recruitment. In contrast, rodents removed an average of 6% and 56% of seeds from grassland plots during the same two years, and the grassland seed bank is 43-fold that of the dunes (288 seeds m-2). Even high seed consumption in the second year of the study only marginally influenced recruitment because seeds that escaped predation remained dormant. Burial of seeds in both habitats significantly reduced the percentage of seeds removed by rodents. Results suggest that granivores exert strong but habitat-dependent effects on lupine seed survival and seedling emergence.

Distinguishing between the hair fibres of the rabbit and the mountain hare in scats of the red fox

Irish mountain hare and rabbit hair fibres were examined for differences in microstructure. Obvious and significant differences were found in the widths of the cortex in the shield and shaft regions of the dorsal guard hairs. Other less obvious differences were also noted in scale overlap and patterns. These findings were applied in the examination of a small number of fox scats collected from a coastal grassland habitat. Mammals were by far the most important prey item of the fox; rabbit remains were present in 83% of scats examined. Hare remains were present in 15% of the scats with significantly more hare remains occurring in the scats during winter.

Demographic change and microhabitat Variability in a Grassland Endemic, Silene Douglasii Var. oraria (Caryophyllaceae)

Variable spatial and temporal environments are known to affect the population dynamics of plants, but studies of local scale variability and its relationship to demographic change within a population remain limited. Using mapped plants, we examined the population dynamics of a coastal grassland endemic, Silene douglasii var. oraria, in two habitats over 10 yr. We hypothesized that ecological differences between rocky and grassy habitats might influence demographic parameters, including adult survival, growth, and density. Soil pH, soil moisture. and other abiotic variables differed little between habitats, but microsite differences in light, soil depth. and vegetation height were related to variation in Silene density and plant circumference. We also found significantly higher population densities, lower adult mortality, and more juvenile recruitment in rocky areas. Finite rates of population growth varied across years and habitats (lambda = 0.82-1.12). with different patterns evident in the two habitats. In both, observed population sizes in 1992 were similar to matrix projections using 1982-1985 data. Populations declined in size in some years despite high adult survivorship and variable recruitment. More intensive study of seedlings is needed, including experimental evaluation of the role of light and competition. However, the habitat-specific differences we observed imply that ecological studies and conservation plans developed for rare plants should consider the effect of local scale variability on demography.

The effect of solar UV radiation on four plant species occurring in a coastal grassland vegetation in The Netherlands

During the summer of 1992, growth and some physiological parameters of four native plant species occurring in a coastal grassland in The Netherlands, were studied after reduction of solar UV irradiance using different cut‐off filters. Biomass production, morphology and photosynthesis of all species tested were unaffected by the different treatments. Litter production of Plantago lanceolata was increased in the absence of the total UV waveband, indicating a possible role for this waveband in plant senescence. Depletion of the total UV waveband from sunlight resulted in alterations in biomass allocation in Calamagrostis epigeios and Urtica dioica while no changes were observed in P. Ianceolata and Verbascum thapsus. In C. epigeios an increase in the specific leaf area was observed, whereas in U. dioica root weight per total plant weight was decreased resulting in an increase in the shoot/root ratio. Both photosynthetic and UV‐absorbing pigment concentrations were altered by the different filter applications. When compared to control plants receiving full sunlight, depletion of UV‐B resulted in a significant increase in chlorophyll concentration in U. dioica leaves, this however did not affect photosynthetic rate. The presence of UV‐B radiation enhanced the UV‐absorbance of leaf extracts of all species except P. lanceolata. Optical characteristics of the leaves were also changed. Both the quantity (P. lanceolata and U. dioica) and the quality (all species) of radiation transmitted by the leaves was affected by the different treatments.

The effect of solar UV radiation on four plant species occurring in a coastal grassland vegetation in The Netherlands

The effect of solar UV radiation on four plant species occurring in a coastal grassland vegetation in The Netherlands

Secondary poisoning of stoats (Mustela erminea), feral ferrets (Mustela furo),and feral house cats (Felis catus) by the anticoagulant poison, brodifacoum

Abstract A poisoning operation using Talon 20P™, active ingredient brodifacoum, targeting rabbits (Oiyctolagus cuniculus) in coastal grasslands on the Otago Peninsula, New Zealand, also killed stoats (Mustela erminea), ferrets (Mustela furo), cats (Felis catus), and mice (Mus musculus) and probably possums (Trichosurus vulpecula), hedgehogs (Erinaceus europaeus), rats (Rattus rattus), hares (Lepus europaeus occidentalis), and chaffinches (Fringilla coelebs). A new immigrant ferret also died 41 days after poisoning. If repeated in other habitats such as tussock grasslands and forests this method could greatly assist in restoration of mainland ecosystems and mitigation of bovine tuberculosis (Mycobacterium bovis) by controlling a variety of pests/ Tb carriers in one operation. The removal of small mammalian predators following poisoning operations could decrease immediate predation pressure on native wildlife. However, the efficacy of this multi‐species pest control method and unwanted side‐effects must be researched before its routine use. This research also demonstrates the potential threat of second‐generation anticoagulant poisons such as brodifacoum to small mammalian carnivores with high conservation value in their native countries.

Influence of overstory composition on understory colonization by native species in plantations on a degraded tropical site

Abstract. Patterns of understory colonization by native and naturalized trees and shrubs were evaluated in 4.5‐year‐old plantations of three exotic tree species, Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala, on a degraded coastal grassland site with reference to overstory composition and understory environmental conditions. 19 secondary forest species were established in the plantation understories (with a total area of 0.52 ha), while no natural regeneration occurred in unplanted, though protected, control areas. The majority of these species (90 %) and the total seedling population (97 %) were zoochorous, indicating the importance of frugivorous bats and particularly birds as facilitators of secondary forest species colonization. Understory species richness and seedling densities were affected significantly by overstory composition, the most abundant regeneration occurring beneath Leucaena and least under Casuarina. Understory colonization rates within mixed‐species stands were intermediate between those of single‐species stands of the trees comprising their overstories. Significant negative correlations were found between understory species richness and seedling density, and forest floor depth and dry mass, especially for small‐seeded ornithochorous species. Higher colonization rates near the peripheries of plantation plots relative to plot interiors were due in part to roosting site preferences by frugivores, particularly bats.The study results indicate that overstory species selection can exert a significant influence on subsequent patterns of colonization by secondary forest species and is an important consideration in the design of plantations for ‘catalyzing’ succession on deforested, degraded sites.