Native Tree Seedlings Research Articles

Effects of soil characteristics and exotic grass cover on the forest restoration of the Atlantic Forest region

The restoration of cattle grazing areas is a significant challenge for tropical forest restoration because of the effects of soil degradation and the competition between native trees and exotic grasses. To identify the major factors that impede forest restoration efforts, we examined the effects of different grass species, soil types and management techniques on the outcome of two species of tree seedlings in abandoned pastures. We compared the initial (12 months) seedling survival rates and growth of a fast-growing tree (Inga edulis) and a slow-growing tree (Campomanesia xanthocarpa), growing in Cambisols and Gleysols, using different management practices (till vs. no-till) and in the presence of two exotic grass species. Soil conditions were the most significant factor for influencing seedling performance, for both species; the grass species used in the pasture was less important. The flooding conditions in Gleysols may have potentially limited the seedling growth by affecting the height and diameter of C. xanthocarpa. Our results support the claim that soil conditions are the primary factors that negatively affect the growth and survival of native tree seedlings in abandoned farmlands. Restoration efforts that employ fast-growing native species should be chosen to increase the chances of restoration success in wet pasture areas.

Dry Forest Restoration and Unassisted Native Tree Seedling Recruitment at Auwahi, Maui

Efforts to restore highly degraded but biologically significant forests draw from a limited toolbox. With less than 10% of their former distribution remaining, Hawaiian dry forests, though critically endangered, remain impor- tant biological and cultural refugia. At restoration onset (1997), vegetation of restoration and control areas of degraded Auwahi dry forest, Maui Island, was similar, dominated by nonnative graminoids (restoration 78.3%; control 75.4%), especially Cenchrus ( Pennisetum) clandestinus. In 2012, unrestored control area vegetation was basically unchanged. In contrast, in the restoration area in 2012, native shrub cover increased from 3.1% to 81.9%, and cover of nonnative gram- inoids declined from 75.4% to 3.3%. In 2012, nonplanted seedlings of 14 of 22 native tree species and six of seven native shrub species were observed in restora- tion plots; the majority (99%) were five native (Dodonaea viscosa, Coprosma foliosa, Osteomeles anthyllidifolia, Chamaesyce celastoides, Nestegis sandwicensis) and one nonnative species (Bocconia frutescens). By 2012, stem counts of native woody plants had increased from 12.4 to 135.0/100 m 2 , and native species diversity increased from 2.4 to 6.6/100 m 2 . By 2012, seven rare dry forest tree species, Charpentiera obovata, Nothocestrum latifolium, Ochrosia haleakalae, Pleomele auwa- hiensis, Santalum ellipticum, S. haleakalae, and Streblus pendulinus, had established seedlings and/or saplings within the restoration site, especially notable because natural reproduction is largely lacking elsewhere. Without development and implementation of appropriate management strategies, remaining Hawaiian dry forest will likely disappear within the next century. Multicomponent restoration incorporating ungulate exclusion, weed control, and outplanting as described here offers one strategy to conserve and restore tracts of high-value but de- graded forests.

Transplanting native tree seedlings to enrich tropical live fences: an ecological and socio-economic analysis

The enrichment of live fences with native tree species has been proposed as a conservation strategy in agricultural landscapes; however, little research has explored ways to do this in tropical areas. This study examines selection of native tree species, effects of damage caused by mammals (mainly cattle) in performance (survival and growth) of transplanted seedlings, and cost-benefit balances as critical steps to enrich tropical live fences. Seven native tree species, with ecological and socio-economic importance, were selected in a Mexican agricultural landscape to grow as seedlings, and six of them were transplanted into live fences of cattle ranches with different levels of cattle activity (none/moderate/high). Costs associated with propagation and seedling protection in the field were calculated, and performance and damage in seedlings were measured over 2 years. We developed an index to identify species with the best performance and lowest costs in sites with cattle activity. Our results showed that damage, caused mainly by cattle, reduced the performance of transplanted seedlings. The effect of this damage varied depending on its severity (level and frequency) and the identity and life history of species. All selected species performed well in the site without cattle access. Dendropanax arboreus was the best species at site with moderate cattle activity, and Trema micrantha and Saurauia scabrida at site with high cattle activity. These species are recommended for enriching live fences because of good cost-benefit balance. This approach could be an important quantitative method to select species useful not only in agroforestry but also in restoration projects, which normally remain under the pressure of domestic and wild animals.

Impact of the invasive shrub Amur honeysuckle (Lonicera maackii) on shrub-layer insects in a deciduous forest in the eastern United States

Invasive Amur honeysuckle (Lonicera maackii) creates a dense shrub layer in deciduous forests in eastern North America that negatively impacts native herbs and tree seedlings. We predicted that higher vegetative cover caused by this shrub would increase abundance and diversity of insects and alter composition of insect assemblages. We used paired plots, one with and one without honeysuckle, in ten forest locations in southwestern Ohio, USA, to sample insects and measure diversity and vertical cover of vegetation in the shrub layer. Vertical cover of this vegetation was higher on honeysuckle-present plots, but diversity of shrub-layer vegetation did not differ between honeysuckle-present and honeysuckle-absent plots. Species diversity of Hexapoda, Coleoptera, and Psocoptera, richness of Hexapoda, Coleoptera, Diptera, Hymenoptera, and Psocoptera, and abundance of Hexapoda, Diptera, Hymenoptera, and Psocoptera were higher on honeysuckle-present than on honeysuckle-absent plots. Evenness did not differ between honeysuckle treatments. Nonmetric multidimensional scaling distinguished taxonomic composition in honeysuckle-present plots from that in honeysuckle-absent plots. Presence of vertical cover explained higher richness of Hexapoda and Coleoptera, and higher abundance of Hexapoda, Diptera, Hymenoptera, and Psocoptera. Attributes of honeysuckle, independent of its contribution to vertical cover, explained increases in richness of Hexapoda, Coleoptera, and Hymenoptera and abundance of Hexapoda, Hymenopera, and Psocoptera. These attributes of honeysuckle could include a more complex vegetative structure, a greater availability of resources such as food, detritus, or shelter, and/or a more favorable cooler and moister microenvironment. To more fully understand the mechanisms causing increased richness and abundance of insects in honeysuckle-present areas, detailed studies on these attributes of honeysuckle would be necessary.

Technical Report on Reclamation of Small Scale Surface Mined Lands in Ghana: A Landscape Perspective

Small scale mining activities which involve surface mining is an acceptable means of mineral exploitation in Ghana but has serious environmental consequences. Although a number of laws and research papers have been written on restoration after a piece of land has been mined, not much detail is provided on the actual processes involved. This review paper attempts a look at the process of restoration with projections on cost of restoration. Although it is based on activities at a predominantly farming community like Akyem Hemang in the Fanteakwa district of the Eastern region of Ghana, the principles involved will be applicable to other mining communities in the tropics. The paper looks at aspects of surface mining popular in rural areas of Ghana and attempt to explain the process of restoration with suggestions on how to measure success and how to involve affected communities to safe guard and ensure the success of the programme. A licensed concession can be as small as 3acres or as large as 25acres and can be mined for 3-5 years after which the land should be reclaimed to a productive state. The reclamation process, after field establishment should last for at least 5years to determine success. Small scale mining is defined as the use of rudimentary implements as well as the more sophisticated mining operating at a relatively low level of production with limited capital investment. It is carried out in rural farming communities and is popular with itinerant poorly educated people and usually results in severe deterioration to the environment, especially, crop land; posing serious health risks to communities in which it is carried out. The deterioration results from the destruction of vegetal cover and excavation of the overburden to assess the mineral bearing soil. Where farm lands or forested lands have been affected, a combination of natural and artificial reclamation is recommended. The process of reclamation should be planned and begins when topsoil at the mined site is removed to store separately from the subsoil and over-burden at the pre-mining stage. Topsoil however cannot be stored for too long as the quality deteriorates with time. Depending on the depth of excavation, restoration should involve importation and replacement of subsoil to a depth of 600mm - 900mm spread in 150mm layers, and left to settle naturally for a period of 3 -6months. When the land is sufficiently settled, topsoil mixed with manure should be laid over the subsoil to a depth of 150mm minimum after settling. This is followed by sowing of nitrogen fixing leguminous green manure by broadcasting to provide the first blanket of vegetative cover to protect the soil from the direct effect of the elements. Although Crotalaria juncea (Sunnhemp) is highly recommended nitrogen fixing leguminous annual with high biomass production for highly degraded land, other area-specific nitrogen fixing plants can be recommended by the area agricultural extension officer. About 60days after sowing of the green manure cover crop, when it is in bloom, it is smothered and worked into the soil. Seedlings of both local and exotic tree plants can then be established on the land after pegging and holing to 563seedlings per acre. The reclaimed land should be maintained and managed by maintaining a balance between introduced exotic tree seedlings and native sprouted tree seedlings by weeding, staking, and occasional pruning for at least 5years before any assessment for the success of the reclamation can be done. The estimated cost for reclamation of 1acre of mined land excavated to a depth of 900mm is about US$ 52,419.33 (Gh¢101,000), inclusive of 2-3% for maintenance.

Phylogenetic ecology applied to enrichment planting of tropical native tree species

Enrichment planting within established plantations or secondary forests is a common strategy to enhance forest recovery, given that later successional forest species tend to have low dispersal and limited recruitment into these sites. It is difficult, however, to predict how species of seedlings will perform when planted under different overstory species. The field of phylogenetic ecology offers tools to help guide the selection of seedlings, drawing on the evolutionary conservatism of important functional traits. We evaluated the survival, growth, foliar disease, and herbivory of various native tropical tree seedlings at different evolutionary distances from monospecific stands of trees beneath which they were planted. We expected that seedlings planted under conspecific overstory trees would have low survival and growth and high percent foliar damage (as predicted by the Janzen–Connell Hypothesis), and that seedling performance would improve steadily with phylogenetic distance between seedling and overstory species. We found that seedlings planted under conspecific canopies had lower survivorship, reduced growth, and greater foliar damage than seedlings planted under canopies of different tree species. An overall increase in seedling performance with greater phylogenetic distance between seedling and overstory species was dominated by the contrast in performance between conspecific pairs and seedlings planted beneath extra-familial overstory species; but lack of available congeneric pairing limited inference about interactions among close relatives. Most pathogenic fungi isolated from enrichment-planted seedlings also caused disease when inoculated on the overstory tree species where the seedlings had been planted; this is consistent with overstory trees being an important reservoir of pathogens that affect seedlings. We conclude that enrichment planting with species more distantly related to those that dominate the canopy should enhance seedling’s performance. Closer analysis at the congeneric level is warranted because of expected strong biotic interactions at close phylogenetic distances.

Performance of established native seedlings in relation to invasive Lantana camara, rainfall and species’ habitat preferences in a seasonally dry tropical forest

Native species' response to the presence of invasive species is context specific. This response cannot be studied in isolation from the prevailing environmental stresses in invaded habitats such as seasonal drought. We investigated the combined effects of an invasive shrub Lantana camara L. (lantana), seasonal rainfall and species' microsite preferences on the growth and survival of 1,105 naturally established seedlings of native trees and shrubs in a seasonally dry tropical forest. Individuals were followed from April 2008 to February 2010, and growth and survival measured in relation to lantana density, seasonality of rainfall and species characteristics in a 50-ha permanent forest plot located in Mudumalai, southern India. We used a mixed effects modelling approach to examine seedling growth and generalized linear models to examine seedling survival. The overall relative height growth rate of established seedlings was found to be very low irrespective of the presence or absence of dense lantana. 22-month growth rate of dry forest species was lower under dense lantana while moist forest species were not affected by the presence of lantana thickets. 4-month growth rates of all species increased with increasing inter-census rainfall. Community results may be influenced by responses of the most abundant species, Catunaregam spinosa, whose growth rates were always lower under dense lantana. Overall seedling survival was high, increased with increasing rainfall and was higher for species with dry forest preference than for species with moist forest preference. The high survival rates of naturally established seedlings combined with their basal sprouting ability in this forest could enable the persistence of woody species in the face of invasive species.

Can hybrid poplar plantations accelerate the restoration of forest understory attributes on abandoned fields?

Multi-functional plantations using fast-growing tree species can potentially be used to accelerate the restoration of forest habitat on abandoned farmland. However, few studies have directly compared the ecological effects of active afforestation using plantations to natural afforestation. The present study compares the effects of the establishment and the first 10years of growth of two different hybrid poplar clones to adjacent abandoned fields and natural second-growth forests, in terms of abiotic attributes and understory vegetation communities. Experimental plantations of a Populus maximowiczii×P. balsamifera (M×B) hybrid and a P. deltoides×P. nigra (D×N) hybrid were established in 2000 on abandoned fields at 8 sites in southern Quebec, Canada. In 2009, soil chemical properties, soil moisture, canopy openness, leaf litter biomass, and understory vegetation communities were sampled in the plantations and in neighboring unmanaged abandoned fields and second-growth woodlots. Canopy development was greatly accelerated by the plantations of both hybrid poplar clones, compared to the unplanted portions of abandoned fields, and in the more productive plantations of both clones, canopy openness and leaf litter biomass were similar to those measured in the woodlots. No difference was detected in soil chemical properties between the abandoned fields and either type of plantation. The plantation soils were drier than those of both the abandoned fields and the secondary forests, possibly due to increased transpiration by the hybrid poplars. The plantations favored the colonization of the sites by native tree seedlings compared to the unmanaged fields, producing a nurse stand effect. Among herbaceous and shrub species, native species richness was slightly higher in the plantations than in the fields. The understories of the fastest growing plantations had species in common with both the fields and the woodlots, while the understory of the slowest growing plantations was very similar to the field vegetation. The plantation understories had lower covers of open-habitat species than the fields, while the M×B plantations had slightly greater covers of native, shade-tolerant species. Plantations of the M×B clone were more distinct from the abandoned fields than were plantations of the D×N clone. In conclusion, hybrid poplar plantations appear capable of accelerating the restoration of certain understory attributes, which in turn favors their colonization by tree seedlings and suppresses competition from light-demanding herbaceous species.

Can perennial dominant grass Miscanthus sinensis be nurse plant in recovery of degraded hilly land landscape in South China?

Perennial C4 grasses, especially Miscanthus sinensis, are widely distributed in the degraded lands in South China. We transplanted native and exotic tree seedlings under the canopy of M. sinensis to assess the interaction (competition or facilitation) between dominant grass M. sinensis and tree seedlings. The results of growth, chlorophyll fluorescence, and ultrastructure showed that negative effects may be stronger in perennial dominant grass M. sinensis. Although M. sinensis buffered the air temperature, improved soil structure, and increased soil phosphorus content, these beneficial effects were outweighed by the detrimental effect, especially overshading. To ensure the establishment of target native species in M. sinensis communities in degraded lands of South China, restoration strategies should include removing aboveground vegetation, planting target species seedlings in openings to reduce the effects of canopy shading, and/or selecting competition-tolerant target species. Also, seedlings of exotic species used in restoration engineering cannot be directly planted under the canopy of M. sinensis.

Braconidae (Hymenoptera) fauna in native, degraded and restoration areas of the Vale do Paraíba, São Paulo state, Brazil

This study sampled the diversity of Braconidae (Hymenoptera) in three different ecosystems: a degraded pasture, a secondary forest and an area in recovery process using native tree seedlings. The objective was to verify the use of those insects as a tool to check the local conservation by examining Shannon's diversity index. Ten subfamilies were identified, and Microgastrinae was predominant in a number of individuals. The diversity index calculated varies among the sampled areas, thus showing a correlation with vegetation cover with the number of individuals collected and number of subfamilies found. The results showed changes in the community of Braconidae, in the recovery area between the first and second year of study, thereby leading to the conclusion that they are indicators of environmental quality.

Evaluating Soil Genesis and Reforestation Success on a Surface Coal Mine in Appalachia

Surface mining poses a significant threat to the Appalachian region via forest loss and fragmentation. Reclamation methods that utilize heavy grading to prevent landslides and erosion create a compacted landscape that is not suitable for forest establishment or growth. Overburden materials derived from differing geologic strata can exhibit large variation in physical, chemical, and mineralogical properties. Determining which strata should be used for creating a rooting medium for successful reforestation is not well established. Twelve 0.2‐ha plots composed of either segregated brown sandstone, gray sandstone, shale, or a sandstone–shale mixture (four treatments; n = 3) were created on a surface mine in eastern Kentucky using a low‐compaction reclamation method. Each plot was planted with native hardwood tree seedlings following the Forestry Reclamation Approach. After two growing seasons, brown sandstone treatments had four times greater extractable P (Mehlich III) and five times greater total N than the other treatments. This helped contribute to greater tree growth on brown sandstone treatments. Spoil settling was faster in the shale treatments due to the loss of carbonate cements. Clay contents and 2:1 minerals were also greater in the whole soil of the shale treatments, leading to greater plant‐available water and a greater cation exchange capacity. Gray sandstone treatments exhibited alkaline conditions (pH = 8.8) that suppressed tree growth. The mixing of brown sandstone and shale overburdens may produce a suitable combination of higher fertility, water holding capacity, and faster settling in reclaimed mine environments.

Restoring a seasonal wetland using woven black plastic weed mat to overcome a weed threshold

SummaryLittle information is available on the use of woven black polypropylene weed control mat in ecological restoration. At a 6.5‐ha area of fertile Vertosol soil ex‐farmland near Perth, Western Australia, concerted efforts to control weed using conventional methods such as herbicides, fire and cultivation proved ineffective. After 5 years, weeds still dominated the site, and native plant establishment was poor. Small‐scale preliminary trials of various weed suppression coverings were then undertaken, with plastic weed mat the most cost‐effective in overcoming the weed threshold, permitting native tree seedling establishment. In a larger‐scale trial of weed mat over the whole site, weeds were controlled and high levels of native plant establishment achieved, with a diverse range of understorey, midstorey and overstorey species providing 56% projected foliage cover. This ensured that completion criteria were finally satisfied. These results suggest that weed mat may be effective for weed control in large‐scale restoration where conventional methods have failed, as long as ultimate removal or decomposition and other issues are addressed.

Landscape-scale relationships between the exotic invasive shrub Lantana camara and native plants in a tropical deciduous forest in southern India

Abstract:Understanding exotic–native plant relationships within the context of landscape-scale environmental factors such as rainfall, topography, disturbance and forest structure, is important for distinguishing the role of invasions in native plant community change. In this study, the relationship between Lantana camara invasion and native forest understorey vegetation was described after accounting for environmental influences. Rainfall, terrain slope, altitude and fire frequency were measured from GIS layers, and tree density, dry above-ground L. camara biomass, and native plant abundance and species richness were measured in nested plots (four 1 × 1-m plots for grass, tree seedlings and L. camara within one 5-m-radius plot for tree saplings and herbs and shrubs within one 10-m-radius plot for trees) at 80 locations distributed across Bandipur Tiger Reserve, a tropical deciduous forest in southern India. Relationships between environmental factors and L. camara abundance were described using a multiple regression. Further, the role of L. camara abundance in explaining residual variation in native vegetation, after accounting for environmental influences, was described using linear models. Lantana camara abundance decreased with increasing tree density, supporting the notion that it thrives in disturbed forest with fewer trees. Whereas native tree seedling and herb and shrub density showed no relationship to L. camara abundance, both tree sapling density and grass volume decreased under L. camara biomass exceeding 2 kg m−2. These data suggest that, by association with grass decline and decreased recruitment of tree saplings, L. camara may be linked to the gradual transition of these tropical deciduous forests into exotic-dominated shrubland, and overall native biodiversity loss.

Woody plant seedling distribution under invasive Lantana camara thickets in a dry-forest plot in Mudumalai, southern India

Abstract:Lantana camara, a shrub of Central and South American origin, has become invasive across dry forests worldwide. The effect of the thicket-forming habit of L. camara as a dispersal and recruitment barrier in a community of native woody seedlings was examined in a 50-ha permanent plot located in the seasonally dry forest of Mudumalai, southern India. Sixty 100-m2 plots were enumerated for native woody seedlings between 10–100 cm in height. Of these, 30 plots had no L. camara thickets, while the other 30 had dense thickets. The frequency of occurrence and abundance of seedlings were modelled as a function of dispersal mode (mammal, bird or mechanical) and affinities to forest habitats (dry forest, moist forest or ubiquitous) as well as presence or absence of dense L. camara thickets. Furthermore, frequency of occurrence and abundance of individual species were also compared between thickets and no L. camara. At the community level, L. camara density, dispersal mode and forest habitat affinities of species determined both frequency of occurrence and abundance of seedlings, with the abundance of dry-forest mammal-dispersed species and ubiquitous mechanically dispersed species being significantly lower under L. camara thickets. Phyllanthus emblica and Kydia calycina were found to be significantly less abundant under L. camara, whereas most other species were not affected by the presence of thickets. It was inferred that, by affecting the establishment of native tree seedlings, L. camara thickets could eventually alter the community composition of such forests.

アズマネザサ、リター、動物による食害が耕作放棄地における自生木本の定着に与える影響

アズマネザサ、リター、動物による食害が耕作放棄地における自生木本の定着に与える影響

Early seedling establishment of two tropical montane cloud forest tree species: The role of native and exotic grasses

Tropical montane cloud forest has been undergoing a drastic reduction because of its widespread conversion to pastures. Once these forests have been cleared exotic grasses are deliberately introduced for forage production. Exotic grass species commonly form monodominant stands and produce more biomass than native grass species, resulting in the inhibition of secondary succession and tree regeneration. The purpose of this study was to assess the effect of native vs. exotic grass species on the early establishment of two native tree seedlings (Mexican alder, Alnus acuminata and Jalapa oak, Quercus xalapensis) on an abandoned farm in central Veracruz, Mexico. Seedling survival and growth were monitored (over 46 weeks) in relation to grass cover and height, and available photosynthetic active radiation (PAR). More seedlings survived in the presence of the native grass Panicum glutinosum than those growing with the exotic grass Cynodon plectostachyus (92% vs. 48%). The causes of seedling mortality varied between species; Q. xalapensis was affected by herbivory by voles but mainly in the exotic grass-dominated stands, whereas A. acuminata seedlings died due to competition with the exotic grass. A. acuminata seedlings increased more in height in the exotic grass-dominated stands (102 ± 7.8 cm) compared to native grass-dominated stands (51 ± 4.7 cm). Grass layer height, cover and available PAR were correlated (Pearson; p < 0.05). In the exotic grass dominated plots, grass layer height was correlated with the relative height growth rates of Q. xalapensis (Pearson; p < 0.05). These results indicate that the exotic grass may be affecting tree regeneration directly (grass competition) and indirectly (higher herbivory). Passive restoration may occur once P. glutinosum dominated pastures are abandoned. However, when C. plectostachyus dominates, introduction of early and mid successional tree seedlings protected against vole damage is needed.

Recuperação Ambiental de Cava com Espécies Nativas Florestais no Norte Fluminense

This paper presents a proposal of evaluation of the development of a revegetation and environmental restoration plan in areas of clay pits in the city of Campos dos Goytacazes. A selection was carried out to identify which tree species were the most suitable to the new environment of low fertility, thus starting an ecological restoration in this area with the purpose of using it as lands set aside for legal reserve in farming properties. Consequently, becoming an interesting and environmental economically option capable of contributing to the CO2 absorption, greenhouse gas reduction and being included in Clean Development Mechanism (CDM) projects. The environmental restoration project was implemented in a clay pit, with 112 native tree seedlings from 12 different species, pioneer and secondary.

Seed rain under tree islands planted to restore degraded lands in a tropical agricultural landscape

Planting native tree seedlings is the predominant restoration strategy for accelerating forest succession on degraded lands. Planting tree "islands" is less costly and labor intensive than establishing larger plantations and simulates the nucleation process of succession. Assessing the role of island size in attracting seed dispersers, the potential of islands to expand through enhanced seed deposition, and the effect of planting arrangements on seed dispersal by birds and bats informs restoration design. Determining the relative importance of local restoration approach vs. landscape-level factors (amount of surrounding forest cover) helps prioritize methods and locations for restoration. We tested how three restoration approaches affect the arrival of forest seeds at 11 experimental sites spread across a gradient of surrounding forest cover in a 100-km2 area of southern Costa Rica. Each site had three 50 x 50 m treatments: (1) control (natural regeneration), (2) island (planting tree seedlings in patches of three sizes: 16 m2, 64 m2, and 144 m2), and (3) plantation (planting entire area). Four tree species were used in planting (Terminalia amazonia, Vochysia guatemalensis, Erythrina poeppigiana, and Inga edulis). Seed rain was measured for 18 months beginning approximately 2 years after planting. Plantations received the most zoochorous tree seeds (266.1 +/- 64.5 seeds x m(-2) x yr(-1) [mean +/- SE]), islands were intermediate (210.4 +/- 52.7 seeds x m(-2) x yr(-1)), and controls were lowest (87.1 +/- 13.9 seeds x m(-2) x yr(-1)). Greater tree seed deposition in the plantations was due to birds (0.51 +/- 0.18 seeds x m(-2) x d(-1)), not bats (0.07 +/- 0.03 seeds x m(-2) x d(-1)). Seed rain was primarily small-seeded, early-successional species. Large and medium islands received twice as many zoochorous tree seeds as small islands and areas away from island edges, suggesting there is a minimum island size necessary to increase seed deposition and that seed rain outside of planted areas is strongly reduced. Planting design was more important for seed deposition than amount of forest cover within the surrounding 100- and 500-m radius areas. Establishing plantations and large islands facilitates the arrival of early-successional tree seeds and represents a broadly applicable strategy for increasing seed rain on abandoned agricultural lands. However, more intensive restoration approaches may be necessary for establishment of dispersal-limited species.

Managing successional trajectories in alien-dominated, novel ecosystems by facilitating seedling regeneration: A case study

Managing novel ecosystems that emerge after strong anthropogenic disturbance and the spread of alien species poses complex problems. As a case example, we discuss efforts on the tropical oceanic island Mahé (Seychelles) to promote the regeneration of native trees in tropical secondary forest dominated by the invasive tree Cinnamomum verum (true cinnamon). We monitored the growth of transplanted and self-sown native and alien tree seedlings in both artificially created forest gaps and in the understorey of closed forest. In the understorey, native species survived but grew very slowly, indicating that any recovery of native tree populations would also be very slow. In larger gaps, seedlings of certain invasive species grew particularly fast, suggesting that these species would rapidly dominate. Nutrient addition had only a minor positive effect on seedling growth, especially in the understorey. Although neither closed canopy conditions nor large gaps are conducive to the recovery of native seedlings, our data indicate that intermediate levels of canopy disturbance, i.e. those attained by felling one or a few trees, provide a combination of below- and aboveground resource limitation of seedling growth that may favour native species over invasive species. Based on these findings, we propose a strategy for restoring native vegetation that entails making small gaps in cinnamon-dominated forest and planting them with native tree species. This study illustrates how management strategies can be improved by combining insights gained from past interventions with the results of field and greenhouse experiments.

Survival and Growth of Tree Species under Two Direct Seedling Planting Systems

Direct tree planting restoration systems are frequently used for recovering degraded tropical landscapes. Although manual planting tends to be more viable economically and logistically over small areas, in large restorations the use of agricultural equipment that optimizes effort is preferable. The aim of this study was to investigate the efficiency of the two native tree species planting systems—manual and mechanized—used in the restoration of Atlantic Forest landscapes that have been converted to pasture. In recently abandoned grazing areas with abundant cover of the exotic grass Brachiaria humidicola, 393 seedlings of 6 species were planted in two treatments: a mechanized planting system (soil prepared with a rotary tiller attached to a tractor; seedlings in polypropylene tubes) and a manual planting system (holes dug with a manual excavator; seedlings wrapped in polyethylene bags). After 12 months, survival (manual: 85%; mechanized: 71%) and growth rates (RGRheight: manual = 0.88 ± 0.06 and mechanized = 0.98 ± 0.06 cm/cm; RGRdiameter: manual = 0.77 ± 0.05 and mechanized = 0.86 ± 0.05 cm/cm) were high in both treatments, but no differences were found between them. Both planting systems proved efficient for planting native tree seedlings in pastures. The excellent results demonstrated in this study by the mechanized planting system are important because this cheap and readily available technique provides a good, but less frequently used, alternative to the manual planting system.