Effects of distinct types of disturbance on seed rain in the Atlantic forest of NE Brazil

In disturbed sites, some groups of seeds might be excluded from the seed rain due to their dispersal modes or seed size, and some groups might be successful as a result of disturbance effects. In the present study, we examined the seed rain in natural treefall gaps and in an area of regenerating forest following an accidental burning, which occurred 4 years before this study. Both of these disturbed areas were compared with nearby forest understorey. The number of seeds, number of species, and proportion of wind-dispersed seeds were compared between these disturbed and undisturbed areas. The treefall gaps have received lower numbers of seeds and species than the nearby understorey, but the number of wind-dispersed seeds did not differ between these areas. The lowest seed number observed in treefall gaps can be attributed to a lower number of animal-dispersed seeds, suggesting that animals may be avoiding treefall gap areas. A higher number of seeds and a lower number of species were observed in the burned area when compared to the adjacent understorey. The high number of small-sized seeds and of wind-dispersed seeds in the burned area was almost surely a consequence of the local production of the pioneer plants established after the burning. In this study, substantial differences were observed in the characteristics of the seed rain at disturbed sites, when compared with undisturbed understorey. However, these two distinct types of disturbance showed quite differing patterns, as treefall gaps received lower number of seeds while the burned area received a higher number of seeds, with a greater proportion of wind-dispersed seeds. The exception was for species richness, which was quite low at both these disturbed sites.     

Seeds and seedlings of two neotropical montane understory shrubs respond differently to anthropogenic edges and treefall gaps

Edges resulting from forest clear-cutting and treefall gaps can affect plant populations and consequently the distribution of species across landscapes. These two types of disturbance might interact to exacerbate or ameliorate “edge effects”, a rarely tested possibility. We focused on the effects of distance from forest edge (0–10, 30–40, 60–70, and 190–200 m) and habitat within forest fragments (treefall gaps and intact forest) on the early stages of development of Palicourea gibbosa and Faramea affinis, two common shrubs of montane forests in southwest Colombia. Seed germination and seedling growth did not change with distance from forest edge. Within forest fragments, however, seed germination and seedling growth were higher in treefall gaps than in intact forest understory for both species. In contrast, seed predation was influenced by distance from forest edge and in P gibbosa it depended on habitat. Seed predation was highest in the forest interior (190–200 m from forest edge) and in P. gibbosa this was true only in treefall gap habitats. These results suggest that animal mediated processes such as post-dispersal seed predation are more likely than physiological processes to be affected by anthropogenic edges. Our results provide some evidence that treefall gaps may interact with “edge effects”, however, they are inconclusive as to whether they exacerbate or ameliorate them. Received: 31 August 1998 / Accepted: 18 February 1999     

Tree seed germination and seedling establishment in treefall gaps and understorey in a subtropical forest of northeast India

Abstract Seed germination, and survival and growth of seedlings of four dominant tree species, Quercus dealbata, Quercus griffithii, Quercus glauca and Schima khasiana were studied in the treefall gaps and forest understorey of an undisturbed mature-phase humid subtropical broadleaved forest in northeast India. Three important microenvironmental factors namely photosynthetically active radiation (PAR), soil moisture and litter depth, were also measured in the forest understorey and gaps and correlated with seedling mortality. Seed germination of S. khasiana was significantly higher in the treefall gaps than in the understorey; among the tree species studied, it had the highest germination. Quercus seedlings were abundant in the understorey and small gaps, while S. khasiana seedlings were more numerous in the large gaps. The survivorship curves for the seedling populations revealed that the three Quercus species survived better in the understorey, while S. khasiana did so in the gaps. PAR and soil moisture were positively correlated with tree seedling mortality, which occurred mainly during the winter months. The Quercus seedlings grew better in the forest understorey and small gaps and S. khasiana seedlings in the large gaps. The differential performance of the tree seedlings to the conditions prevailing in the understorey and gaps of two sizes indicates that different species were adapted to different light environments depending upon their optimum requirements. This could be an effective mechanism for promoting species coexistence in the forest community.     

Effects of Treefall Gap Disturbances on Ant Assemblages in a Tropical Montane Cloud Forest

The study of gap dynamics and the effects of gaps on diversity has been at the center of tropical ecology for decades. While most studies have focused on the responses of plant species and communities to gap formation, in this study, we consider the effects of treefall gap disturbances on leaf litter ant assemblages in a Neotropical montane cloud forest. We sampled leaf litter ant assemblages and estimated a suite of abiotic parameters in 12 large (>80‐m²) treefall gaps across a chronosequence and in 12 paired adjacent intact forest sites in the Monteverde Cloud Forest Preserve in Costa Rica. No species were more common in gaps than in intact forests, and in fact, species that were common in gaps were also among the most common in forests. The Chao2 estimate of species richness, however, was higher in gap sites than in intact forest sites. In addition, ant assemblages in gap sites did not become more similar to those in adjacent intact sites as gaps aged. In contrast to other studies, our work demonstrates that ant assemblages in the Monteverde Cloud Forest Preserve are weakly affected by the formation of treefall gaps. Together, these results indicate that treefall gap dynamics probably play little role in promoting ant diversity at more regional scales, or coexistence among species at more local scales.     

Effect of treefall gaps on the patchiness and species richness of Neotropical ant assemblages

Natural formation of treefall gaps plays an integral role in the ecological and evolutionary dynamics of many tropical forests, affecting the spatiotemporal distribution of plants and the animals that interact with them. This study examines the impact of treefall gaps on the spatial and temporal patchiness of ant assemblages in a moist lowland forest in Panama. Using pitfall traps and honey baits, we compared ant assemblages in five 1 to 2-year-old treefall gaps (ca 100 m²) and five adjacent plots (ca 100 m²) in undisturbed forest understory at three different times of year (late wet season, late dry season, and early wet season). We found little evidence that ant assemblages respond dramatically to the formation of treefall gaps and the differences in habitat qualities they produce. Ant abundance, species richness, species composition, and rates of resource discovery did not differ between gaps and forest understory. However, we did find significant differences in numerical abundance related to forest stratum (ground vs vegetation) and resource type in pitfall traps (oil-cockroach vs honey), and significant differences in ant species richness and rates of resource discovery across seasons. While habitat effects by themselves were never statistically significant, habitat and seasonal differences in species richness interacted significantly to produce complex, season-dependent differences among gap and forest habitats. These results suggest that the formation of natural treefall gaps has less of an effect on Neotropical ant assemblages compared to other groups of organisms (e.g., plants, birds) or other causes of patchiness (e.g., ant mosaics, moisture availability, army ant predation). The results of our study also have important implications for the underlying causes of habitat differences in the distribution of ant-defended plants. Received: 3 February 1998 / Accepted: 7 April 1998     

Seed shadow, seedling recruitment, and spatial distribution of Buchenavia capitata (Combretaceae) in a fragment of the Brazilian Atlantic forest.

Here we describe the seed shadow, seedling recruitment, ontogenetic structure and spatial distribution of Buchenavia capitata (an emergent canopy tree) in a 380-ha fragment of the Atlantic forest in northeast Brazil. In particular, we examine seed distribution around 10 parental trees and both seedling recruitment and mortality, during an 18 month period beneath and around parental trees. Moreover, we describe: (1) B. capitata occurrence within treefall gaps; (2) population structure in terms of ontogenetic stages for the whole site; and (3) spatial distribution of adults within an area of 51 hectares. 99% of seeds were found beneath parent crowns (n = 4,236) and seed density reached 14.6 +/- 29.9 seeds/m2 (0-140 seeds/m2). 49% of all seeds germinated but seedling mortality reached 100% after an 18 month period. In addition, saplings of B. capitata were not found in forest understory and within 30 treefall gaps (94-2,350 m2). The adults showed an average DBH of 69.3 +/- 22.1 cm, were 19.2 +/- 2.9 m tall and presented a clumped spatial distribution. B. capitata matched some of the features presented by shade intolerant trees or large-gap specialists, and we hypothesize that low rates or even lack of long distance seed dispersal events may be reducing the probability of B. capitata seeds reaching suitable habitats for successful seedling recruitment and growth. Because of that (1) seedlings face high levels of early mortality; (2) there is no sapling recruitment at the study site; and (3) local population faces senility and it is threatened by local extinction.     

Seed Dispersal and Demography of Pioneer Trees: The Case of Hortia arborea

Abstract: This study investigates the relationships among seed dispersal, patterns of seedling recruitment and the spatial distribution of a pioneer tree (Hortia arborea, Rutaceae) in the Brazilian Atlantic forest. The study was carried out at Dois Irmãos Reserve, a 387.4 ha reserve in northeastern Brazil. Fruit shadow concentrated beneath parental trees (74.6 % < 6 m distant) and fruit removal averaged 5.6 % (0 ‐ 25.5 %). Agoutis (Dasyprocta prymnolopha, Rodentia) ate fruits in the forest and in captivity and were the only vertebrates recorded feeding on Hortia fruits. Agoutis, however, destroyed 86.7 % of the seeds they ingested. In addition, only one seed from an expected number of 1980 germinated in a treefall gap after it passed through the digestive tract of agoutis. Both seed germination and seedling recruitment were restricted to gaps, and occurred among seeds manually released from the pulp or among those from fruits that naturally rotted in gaps. Moreover, exposed seedlings were taller than those covered by plants in a gap. H. arborea appears to self‐maintain populations in the same patches of forest, which are delimited by a pool of old and newly created gaps. More specifically, there is successful recruitment in patches occupied by parents, resulting in dense clumps of H. arborea.     

Short dry spells in the wet season increase mortality of tropical pioneer seedlings

Variation in plant species performance in response to water availability offers a potential axis for temporal and spatial habitat partitioning and may therefore affect community composition in tropical forests. We hypothesized that short dry spells during the wet season are a significant source of mortality for the newly emerging seedlings of pioneer species that recruit in treefall gaps in tropical forests. An analysis of a 49-year rainfall record for three forests across a rainfall gradient in central Panama confirmed that dry spells of ≥10 days during the wet season occur on average once a year in a deciduous forest, and once every other year in a semi-deciduous moist and an evergreen wet forest. The effect of wet season dry spells on the recruitment of pioneers was investigated by comparing seedling survival in rain-protected dry plots and irrigated control plots in four large artificially created treefall gaps in a semi-deciduous tropical forest. In rain-protected plots surface soil layers dried rapidly, leading to a strong gradient in water potential within the upper 10 cm of soil. Seedling survival for six pioneer species was significantly lower in rain-protected than in irrigated control plots after only 4 days. The strength of the irrigation effect differed among species, and first became apparent 3–10 days after treatments started. Root allocation patterns were significantly, or marginally significantly, different between species and between two groups of larger and smaller seeded species. However, they were not correlated with seedling drought sensitivity, suggesting allocation is not a key trait for drought sensitivity in pioneer seedlings. Our data provide strong evidence that short dry spells in the wet season differentially affect seedling survivorship of pioneer species, and may therefore have important implications to seedling demography and community dynamics.     

Extant and potential vegetation of an old-growth maritime Ilex opaca forest

The extant and potential (seed bank) vegetation of a rare maritime holly forest on Fire Island, New York was described to assess whether treefall gaps act as a mechanism for the persistence of the species composition of this plant community over time. The Sunken Forest overstory is dominated by Ilex opaca, Amelanchier canadensis and Sassafras albidum. A survey of canopy gaps indicated canopy openings compose 11.3% of the land within the Sunken Forest (16 ha). The composition and density of the seed bank were described using the emergence method. Germination from soil samples placed in the greenhouse was monitored over 2 years. Sixteen species germinated with an average propagule density of 215±41 germinants per square metre. An early successional species (Rhus copallinum) dominated the seed bank, but the late-successional, shade-tolerant I. opaca was also present. Though only one species in the seed bank did not appear in the current vegetation, species abundance differed between vegetation strata. The mean cover and density of the ground-layer flora were higher beneath treefall gaps than closed canopy. Sapling density did not differ between the two canopy conditions, but the dominant species differed with A. canadensis occupying several closed canopy plots and P. serotina saplings appearing more often in gap plots. Most of the dominant canopy species are present in the seed bank and ground layer but are not present in the shrub and sapling layer, with the exception of A. canadensis. Current (2002) sapling density is lower than three decades ago for all species except P. serotina, which is now the dominant woody species in the Sunken Forest understory. The results of this study indicate that if the cause of the sapling reduction is lessened or removed, the characteristic species of the overstory of this unusual plant community may rebound and redevelop a sapling and shrub layer akin to that present before the increase in Odocoileus virginianus on the island.     

Community dynamics of evergreen broadleaf forests in southwestern Japan. I. Wind damaged trees and canopy gaps in an evergreen oak forest

The rates of treefall and canopy opening in the evergreen oak forest in southwestern Japan were determined by studying the number and size distribution of overstory trees, wind damaged trees, and canopy gaps in a belt transect in the Kasugayama Forest Reserve in Nara City. Thirty three percent of the overstory trees wereCastanopsis cuspidata. The total area of canopy gaps was about 20% of the total land area in the study area. The ages of the gaps were determined by counting the annual rings of various kinds of trees growing in gaps. By comparing gap ages with meteorological data, it became evident that gap formation was mainly caused by strong typhoons. The mean time interval between strong typhoons visiting the forest reserve, 6.57 years, was determined by applying the MNY method to the meteorological data. The treefall rate and the mean area of canopy openings per year were 0.84 overstory trees/ha·year and 55.6 m²/ha·year, respectively. The mean residence time of the forest canopy was about 180 years.     

Influence of gap size and soil properties on microbial biomass in a subtropical humid forest of north-east India

We examined the effects of treefall gap size and soil properties on microbial biomass dynamics in an undisturbed mature-phase humid subtropical broadleaved forest in north-east India. Canopy gaps had low soil moisture and low microbial biomass suggesting that belowground dynamics accompanied changes in light resources after canopy opening. High rainfall in the region causes excessive erosion/leaching of top soil and eventually soil fertility declines in treefall gaps compared to understorey. Soil microbial population was less during periods when temperature and moisture conditions are low, while it peaked during rainy season when the litter decomposition rate is at its peak on the forest floor. Greater demand for nutrients by plants during rainy season (the peak vegetative growth period) limited the availability of nutrients to soil microbes and, therefore, low microbial C, N and P. Weak correlations were also obtained for the relationships between microbial C, N and P and soil physico–chemical properties. Gap size did influence the microbial nutrients and their contribution to soil organic carbon, total Kjeldhal nitrogen and available-P. Contribution of microbial C to soil organic carbon, microbial N to total nitrogen were similar in both treefall gaps and understorey plots, while the contribution of microbial P to soil available-P was lower in gap compared to the understorey. These results indicate that any fluctuation in microbial biomass related nutrient cycling processes in conjunction with the associated microclimate variation may affect the pattern of regeneration of tree seedlings in the gaps and hence be related with their size. This revised version was published online in June 2006 with corrections to the Cover Date.     

Legacy effects of canopy gaps on liana abundance 25 years later in a seasonal tropical evergreen forest in northeastern Thailand

Lianas require host trees to reach and stay in the forest canopy, but as seedlings and juveniles, they benefit from canopy gaps created by treefalls. Here, we evaluated the relative importance of these two aspects, that is, the availability of potential hosts vs. the legacy effect of past treefall gaps, on the local abundance of liana stems in a seasonal tropical evergreen forest in the Sakaerat Biosphere Reserve in northeastern Thailand. Within a 2.5-ha plot for forest dynamics monitoring, canopy height was measured in 1993 and 2018 at 5-m intervals to distinguish areas of mature (canopy height ≥ 20 m), building (10–20 m), and gap phases (< 10 m). In 2017–2018, we surveyed all liana stems ≥ 1 cm in diameter at breast height within 50 subplots (10 m × 10 m each) and recorded their diameter and the diameter of the host tree. Of a total of 445 liana individuals, 242 could be identified at least to the family level, while the others had clear morphological traits of climbing mechanisms. The number of liana stems was higher in areas that had been at the building/gap phase than those at the mature phase in 1993. When this 25-year-old legacy of past gap locations was considered, there was a positive association of local abundance between lianas and trees in areas at the mature phase in 2018. In conclusion, liana abundance reflected a long-term legacy of past treefall gaps more than 25 years earlier in this seasonal evergreen forest.     

Postdispersal survivorship of north Queensland rainforest seeds and fruits: Effects of forest,habitat and species

Abstract Diaspore (seed and/or fruit) survivorship of 12 species of North Queensland rainforest trees was monitored over a 4 week period in two rainforests on the Atherton Tableland, north Queensland, Australia, with replicated sites in forest interiors, canopy gaps, forest edges and adjacent pastures. General linear modelling was used to estimate the relative importance of forest site, habitat, species and diaspore type on survival. The probability of survival varied significantly among species, between habitat, forest and diaspore types. Survival averaged 41.2% at day 28, was greater in one forest (Curtain Fig, 56.1%) than the other (Lamins Hill, 25.3%) and was apparently inversely related to the abundance of rodents. In both forests, survival declined in the order: pasture ≥ forest edge ≥ forest interior = canopy gap. A lack of significant difference between the forest interior and canopy gap is consistent with findings in other rainforest sites within Australia, but contrasts with most results from other continents. The study also indicated that diaspore weight was an important intrinsic variable affecting survival, the predators (mostly rodents) taking small to moderately large diaspores rather than the very large ones.     

A comparison of 12 tree species of Amazonian caatinga using growth rates in gaps and understorey, and allometric relationships

1. The relative growth rate of saplings of 12 species from an oligotrophic lowland rain forest were measured in treefall gaps and understorey. Mean relative height growth ( R _H) within treefall gaps was found to be slowest for tall-tree species with branched saplings, intermediate for subcanopy trees and fastest for tall-tree species with unbranched saplings. Most species had similar R _H within the understorey. R _H values were not related to leaf mass per unit area (LMA) or foliar N concentrations.
2. Allometric relationships between the total leaf area (TLA) and height were dependent upon light conditions; in general saplings of a given height had a greater TLA in treefall gaps than in understorey. The species with the largest estimated TLA values in gaps tended to have the greatest R _H values in gaps; no such trend emerged in the understorey. The values of the allometric coefficients were not related to foliar properties.
3. The relationship between stem diameter and height was only weakly dependent on light conditions and the relationship between the growth rates in these dimensions was also weak. The lack of plasticity may reflect the fact that the height–diameter relationship has little bearing on a sapling's tolerance of shade.
4. One way of accommodating the dependence of allometry upon irradiance is to add R _H as a covariate. We derive a relationship between growth rates from this resource-dependent allometric equation and show that it reasonably describes measurements taken in the caatinga forest.     

Spatial Variation and Dynamics of Flooding,Canopy Openness,and Structure in a Neotropical Swamp Forest

Temporal changes and spatial variation of soil drainage and understory light availability in 2001 and 2002, small stem (5 ≤ dbh (diameter at breast height) < 10 cm) density, forest successional phase and large stem (dbh ≥ 10 cm) spatial distribution were investigated in 1 ha of tropical swamp forest in southeastern Brazil. Building patches and treefall gaps comprised, respectively, 69.75 and 7.5% of the area in 2002. Semivariograms indicated spatial segregation of successional phases, with mature areas predominating in the North and gaps aggregated into the South. Exclusion of outliers showed large unpredictability of background variation in canopy openness, but patches with high canopy openness values concentrated along the South and East plot borders. Overall canopy openness increased from 2001 to 2002, and was locally autocorrelated between years. In 2001, well-drained and flooded sites comprised 46.75 and 38.19% of the study area, respectively, and were not spatially autocorrelated. In the study period, the number of flooded sites decreased by 40.4%. Canopy openness and small stem density were independent from drainage and were not correlated. Large trees aggregated at scales larger than 40 m, while arborescent palms were aggregated at all scales. Our findings suggest that tropical swamp forests have architectural characteristics similar to that of young, secondary forests and treefall gaps in old-growth forests. Patterns at larger scales pointed to the occurrence of widespread forest degradation, which seems to be particularly advanced in some forest sectors.     

The effects of treefall gaps on understory vegetation in New York State

Abstract. Treefalls are a common form of disturbance in northeastern United States forests. The resultant gaps contribute to a high degree of environmental heterogeneity in the understory of these forests. Plant density, plant cover, and species richness in understory plant communities were monitored for three years during the growing season, May - September. Differences between treefall gap and closed canopy vegetation were less pronounced early in the growing season for plant density and leaf cover. Species richness was significantly greater within treefall gaps during the entire growing season. Eight species were found in greater abundance within treefall gaps (i.e., gap-phase species), while one species was found more commonly under closed canopy. Ordination results suggest that time since gap creation and treefall gap size marginally affect the species composition of vegetation found within treefall gaps.     

Treefall gap characteristics and regeneration in the laurel forest of Tenerife

Abstract. We conducted a study in the laurel forest of Tenerife (Canary Islands, Spain) to describe the characteristics of natural gaps and to assess the role of treefall gaps in forest dynamics. Very little is left of the natural laurel forest with i.a. Laurus azorica, Ilex canariensis and Prunus lusitanica. We looked for treefall gaps in 80 randomly located 2500 m² plots. These plots represented ca. 1% of the remaining and protected laurel forest of Tenerife. We recorded the characteristics of the species causing the gaps, gap architecture and gap age in all observed gaps larger than 10 m². We inventoried the regeneration in each gap and in a neighbouring control plot with the same topography. Large gaps (>75 m²) were not common in the laurel forest. The absence of large gaps could be due to the physiognomy of the vegetation, the mild weather or the rarity of disturbances. Instead of forming gaps, many trees decompose in place and branches from neighbouring trees and suckers from the decomposed trees occupy the free space. Also, the high rate of asexual regeneration could contribute to the fast closing of the gap. The number of gaps created by Prunus lusitanica was higher than expected (based on canopy composition) while Ilex canariensis and Laurus azorica created fewer gaps. In this evergreen forest, differences between gap and non-gap conditions are not as distinct as in other forest types. Only 0.4% of the canopy is in the gap phase (0.6% including gaps smaller than 10m²). No differences were found in patterns of regeneration between gap and non-gap phases in the forest. Gaps do not explain the persistence of pioneer species in the laurel forest.     

Factors affecting post-dispersal seed survival in a tropical forest

Summary Using the subcanopy tree Faramea occidentalis in Panama, I studied post-dispersal seed survival as a function of five characteristics describing seed locations. By simultaneously considering distance from a conspecific adult, size of the nearest conspecific adult, leaf litter quantity, proximity to logs or tree trunks, and whether or not the seed was in a gap, I was able to analyze the influences of individual factors, as well as the interactions among factors. Seed survival was significantly less in treefall gaps than in the forest understory. Seed survival was also influenced by the size of the nearest adult but in a complex interaction with distance to an adult. For seeds beneath adults, survival decreased with increasing tree size, while for seeds away from adults, survival was independent of the size of the nearest conspecific adult. Distance did not directly affect seed survival, nor did the quantity of leaf litter or the proximity to a tree trunk or a log. In a separate analysis, the relationship between distance and seed survival was consistent over four years, suggesting that single cohort studies may provide accurate insights into the consequences of dispersal. In contrast, the spatial locations of surviving seeds were not consistent over the four-year period. Transects with high survival one year did not tend to have high survival in other years, and the locations of surviving seeds in any particular year could not be predicted from the knowledge of where seeds survived in other years. While survival is patchy within a year, the locations of patches shift from year to year.     

Rapid colonization and turnover of birds in a tropical forest treefall gap

Ecological disturbance is an important factor that influences the abundance and distribution of species. Treefalls are a prominent source of disturbance in tropical forests, but robust characterization of community change after treefalls requires baseline data that are often not available. We capitalized on 25 yr of avian mark–recapture data from a lowland moist forest in central Panama to investigate the timescale of colonization and persistence of birds in a newly formed treefall gap. We compared bird species assemblages pre- and post-treefall to explore how the disturbance affected specific foraging guilds and overall assemblage structure (abundance and alpha diversity). We documented rapid colonization (i.e., within five months post-treefall) of the treefall gap by birds. Abundance and alpha diversity increased following the treefall, but both remained relatively constant in a nearby control plot. At the guild level, frugivores spiked in abundance and nectarivores (i.e., hummingbirds) increased in alpha diversity following the treefall. These results are in agreement with those of previous spatial studies of gap dynamics and suggest that certain tropical frugivores and nectarivores have a remarkable ability to rapidly find and exploit preferred resources and microhabitats embedded in a landscape matrix. Assemblage abundance and alpha diversity decreased back to pre-treefall levels within 1 and 4 yr of the treefall, respectively. Thus, even large gaps may provide only ephemeral benefits, highlighting the importance of periodic disturbance for landscape-level persistence of species that use gaps.     

Distribution and abundance of Tillandsia spp. (Bromeliaceae) in the Zapotitlán Valley,Puebla, México

Seed germination of woody species was studied in treefall gaps in NewZealand to assess how environmental heterogeneity affects regeneration fromseed. Gaps were created in a relictual Pinus radiataplantation destined for restoration to native forest. Seeds of the nativespecies Alectryon excelsus, Macropiperexcelsum, and Fuchsia excorticata, and theinvasive alien species Cytisus scoparius andBerberis darwinii were sown in sites differing inexposure,with and without 3 cm of pine litter. Litter promoted germinationof Alectryon and Macropiper,independent of site. Without litter, percent germination ofMacropiper was negatively correlated with percent open skyoverhead. Germination of Fuchsia was significantly higherin treefall gaps than in the forest understory, with litter having littleeffect. Cytisus germinated most successfully in sitesexposed to direct solar radiation, with or without litter. Percent germinationof Berberis was high in all sites, and was consistentlypromoted by litter. Glasshouse trials for each species showed the same effectsof litter cover as found in the field. These results suggest thatmicroenvironmental heterogeneity can be an important influence on the speciescomposition of regenerating vegetation within and around treefall gaps.