Ecology and management of mahogany (Swietenia macrophylla King) in the Chimanes Forest, Bed, Bolivia

Mahogany ( Swietenia macrophylla King) regenerates in areas of erosion on high terraces and in forest killed by flooding and deposition of alluvial sediments in the Chimanes Forest, Bolivia. These hydrological disturbances are patchy, and only one of five stands of mahogany that we inventoried was regenerating. Mahogany survives these disturbances significantly better than the common tree species. The long time between disturbances appears to favour late maturation. Mahogany trees allocate little photosynthates to reproduction until they are very large emergents, at least 80 cm in diameter. The episodic nature of the regeneration sites means that mahogany stands are composed of one or a few cohorts, which are vulnerable to overharvesting, particularly with the current use of a minimum cutting diameter to regulate harvest. The delayed onset of fecundity means that the small trees that escape harvest are not very fecund, resulting in minimal seed input to logged forest. Only 7–9% of the gaps created by logging contain natural regeneration after 20 + yr. A successful management plan for mahogany would entail a monocyclic harvest, with a rotation age of 100 + years, the estimated time that it takes for trees to achieve commercial size in natural forest. Since the number of seed trees that will be left is small, they should be concentrated in sites that are likely to be conducive to natural regeneration, such as near rivers and flood damaged forest. Seed production will be maximized for a given basal area (opportunity cost to loggers) if trees c. 110 cm dbh are selected as seed trees. The mahogany stocks in the Chimanes Forest are nearly exhausted, but the findings of this study could be used to help rebuild the mahogany populations, or to design management plans for the commercial species that have similar ecologies to mahogany.     

Factors Limiting Post‐logging Seedling Regeneration by Big‐leaf Mahogany (Swietenia macrophylla) in Southeastern Amazonia,Brazil, and Implications for Sustainable Management1

Post‐logging seedling regeneration density by big‐leaf mahogany (Swietenia macrophylla), a nonpioneer light‐demanding timber species, is generally reported to be low to nonexistent. To investigate factors limiting seedling density following logging within the study region, we quantified seed production rates, germinability, dispersal patterns, and seed fates on the forest floor through germination and the first seedling growing season in southeastern Amazonia, Brazil. Fruit production rates were low by three logged and one unlogged populations compared to reports from other regions. Commercial‐sized trees (>60 cm diameter) were more fecund than noncommercial trees (30–60 cm diameter) at two sites, averaging 14.5 vs. 3.9 fruits/tree/year, respectively, at Marajoara, a logged site, over 8 yr. Fruit capsules contained an average of 60.3 seeds/fruit, 70 percent of which appeared viable by visual inspection. Sixty‐seven to 72 percent of apparently viable seeds germinated in nursery beds 2.5 mo after the dispersal period, when wet season rains began. Dry season winds blew most seeds west‐northwest of parent trees, with median dispersal distances of 28 and 9 m on west and east sides of parent trees, respectively. Nearly 100 percent of seeds fell within an area of 0.91 ha. On the forest floor beneath closed canopies, mammals, invertebrates, and fungal pathogens killed 40 percent of apparently viable seeds, while 36 percent germinated. Nine months after seedling establishment—midway through the first logging season following seed dispersal—14 percent of outplanted seeds survived as seedlings, representing 5.8 seeds/fruit. We conclude that seedlings are likely to survive in logging gaps at appreciable densities only in rare cases where previous year fruit production rates by logged trees were high (4–12.5% of commercial‐sized trees/year at Marajoara) and where tree crowns were felled in west or northwest directions.     

Cordia millenii: on the risk of local extinction?

Selective logging of valuable tropical timber trees is a conservation concern because it threatens the long-term sustainability of forests. However, there is insufficient information regarding the postlogging recovery of harvested species. Here, I assessed the seed dispersal patterns, recruitment and abundance of Cordia millenii , a valuable timber tree in two Ugandan tropical rain forests that have been subjected to varying disturbance regimes. The aim was to determine the vulnerability of Cordia in these forests. The rate of seed dispersal was lower in the heavily disturbed Mabira Forest compared with the less disturbed Budongo Forest. Frugivores in Mabira were small-bodied individuals that spat seeds beneath fruiting trees, whereas 90% of the fruit in Budongo was consumed by large-bodied chimpanzees that disperse seeds over long distances. Juveniles of Cordia were not found in the closed forest, although they were found in forest gaps in Budongo but not Mabira. Mature tree density was higher in Budongo compared with Mabira. Lack of effective seed dispersal coupled with the inability of seedlings of Cordia to establish under closed canopy account for the arrested recruitment in Mabira. Enrichment planting in felling gaps is necessary to avoid local extinction of Cordia in forests without large vertebrates.     

Impacts of Selective Logging and Agricultural Clearing on Forest Structure, Floristic Composition and Diversity, and Timber Tree Regeneration in the Ituri Forest, Democratic Republic of Congo

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

The importance of tree size and fecundity for wind dispersal of big-leaf mahogany

Seed dispersal by wind is a critical yet poorly understood process in tropical forest trees. How tree size and fecundity affect this process at the population level remains largely unknown because of insufficient replication across adults. We measured seed dispersal by the endangered neotropical timber species big-leaf mahogany (Swietenia macrophylla King, Meliaceae) in the Brazilian Amazon at 25 relatively isolated trees using multiple 1-m wide belt transects extended 100 m downwind. Tree diameter and fecundity correlated positively with increased seed shadow extent; but in combination large, high fecundity trees contributed disproportionately to longer-distance dispersal events (>60 m). Among three empirical models fitted to seed density vs. distance in one dimension, the Student-t (2Dt) generally fit best (compared to the negative exponential and inverse power). When seedfall downwind was modelled in two dimensions using a normalised sample, it peaked furthest downwind (c. 25 m) for large, high-fecundity trees; with the inverse Gaussian and Weibull functions providing comparable fits that were slightly better than the lognormal. Although most seeds fell within 30 m of parent trees, relatively few juveniles were found within this distance, resulting in juvenile-to-seed ratios peaking at c. 35-45 m. Using the 2Dt model fits to predict seed densities downwind, coupled with known fecundity data for 2000-2009, we evaluated potential Swietenia regeneration near adults (≤30 m dispersal) and beyond 30 m. Mean seed arrival into canopy gaps >30 m downwind was more than 3× greater for large, high fecundity trees than small, high-fecundity trees. Tree seed production did not necessarily scale up proportionately with diameter, and was not consistent across years, and this resulting intraspecific variation can have important consequences for local patterns of dispersal in forests. Our results have important implications for management and conservation of big-leaf mahogany populations, and may apply to other threatened wind-dispersed Meliaceae trees.     

Growth Ecology of Carapa nicaraguensis Aublet. (Meliaceae): Implications for Natural Forest Management1

The probability of achieving a sustainable tropical logging operation is increased if the growth of surviving trees is maximized after logging. This research examined the growth ecology of seedlings and trees of the Neotropical timber species, Carapa nicaraguensis (Meliaceae). Shadehouse experiments, field plantings, and growth rate analyses tested the hypothesis that Carapa seedlings and trees experience higher growth rates in high light levels (recently formed logging gaps or logged forest plots) than in low light levels (old logging gaps or undisturbed forest plots). Consistently poor seedling growth rates under low light conditions suggest that seedlings establishing in newly formed gaps will be more successful than those establishing in building-phase gaps. Thus, the first year after logging is a critical time for gap recolonization by Carapa, and seed casting into gaps after logging is recommended. Growth of Carapa trees was significantly faster in logged forest than in undisturbed forest, and was positively associated with light availability. The results provide evidence that harvest models can be both diameter- and illumination-based. Crown illumination was not significantly higher in logged forest than in undisturbed forest, indicating that the illumination scale for this study was not sensitive enough to detect increases in light availability brought about by selective logging. Potential silvicul-tural methods (particularly poison-girdling) that maintain adequate forest light levels in Carapa swamps without significantly altering long-term tree diversity or allowing invasion of secondary species should be explored.     

Fine-scale genetic structure and gene flow within Costa Rican populations of mahogany (Swietenia macrophylla)

Fine-scale structure of genetic diversity and gene flow were analysed in three Costa Rican populations of mahogany, Swietenia macrophylla. Population differentiation estimated using AFLPs and SSRs was low (38.3 and 24%) and only slightly higher than previous estimates for Central American populations based on RAPD variation (20%). Significant fine-scale spatial structure was found in all of the surveyed mahogany populations and is probably strongly influenced by the limited seed dispersal range of the species. Furthermore, a survey of progeny arrays from selected mother trees in two of the plots indicated that most pollinations involved proximate trees. These data indicate that very little gene flow, via either pollen or seed, is occurring between blocks of mahogany within a continuous or disturbed forest landscape. Thus, once diversity is removed from a forest population of mahogany, these data suggest that recovery would be difficult via seed or pollen dispersal, and provides an explanation for mahogany's apparent susceptibility to the pressures of logging. Evidence is reviewed from other studies of gene flow and seedling regeneration to discuss alternative extraction strategies that may maintain diversity or allow recovery of genetic resources.     

Impacts of selective logging on inbreeding and gene flow in two Amazonian timber species with contrasting ecological and reproductive characteristics

Selective logging in Brazil allows for the removal of up to 90% of trees above 50 cm diameter of a given timber species, independent of a species’ life history characteristics or how quickly it will recover. The genetic and demographic effects of selective logging on two Amazonian timber species (Dipteryx odorata Leguminosae, Jacaranda copaia Bignoniaceae) with contrasting ecological and reproductive characteristics were assessed in the same forest. Genetic diversity and gene flow were characterized by genotyping adults and seed sampled before and after logging, using hypervariable microsatellite markers. Overall, there were no short‐term genetic impacts on the J. copaia population, with commercial application of current Brazilian forest management regulations. In contrast, for D. Odorata, selective logging showed a range of genetic impacts, with a 10% loss of alleles, and reductions in siring by pollen from trees within the 546‐ha study area (23–11%) and in the number of pollen donors per progeny array (2.8–1.6), illustrating the importance of the surrounding landscape. Asynchrony in flowering between D. odorata trees led to trees with no breeding partners, which could limit the species reproduction and regeneration under current regulations. The results are summarized with other published studies from the same site and the implications for forest management discussed. The different types and levels of impacts associated with each species support the idea that ecological and genetic information by species, ecological guild or reproductive group is essential in helping to derive sustainable logging guidelines for tropical forests.     

Gap characteristics and regeneration in Bwindi Impenetrable National Park, Uganda

Before Bwindi Impenetrable forest, Uganda, became a national park in 1991, there was a high level of human activity in much of the forest, especially cutting of large trees for timber by pitsawyers. This created extensive gaps in this tropical Afromontane rain forest. We quantified and compared tree regeneration in three sites that were logged at different intensities. Gap sizes in Bwindi, even under fairly natural conditions are very large (mean =4460.1 m²). Logging further enlarged the gap sizes and had a negative impact on tree regeneration. The study shows the strong role of logging disturbance in promoting an alternative successional pathway, where the large gaps created by logging are in a low‐canopy state dominated by a dense tangle of herbs, shrubs, and herbaceous or semi‐woody climbers. We recommend periodic monitoring of gap size and tree regeneration in the gaps to ascertain the trend of recovery from past logging disturbance.     

Effects of Light Gaps and Litter Removal on the Seedling Performance of Six African Timber Species1

Valuable timber tree species frequently show poor regeneration after selective logging in tropical forests. Small size of logging gaps, lack of soil disturbance, and limited seed availability have each been blamed for observed regeneration failures. We investigated seed germination and seedling performance using a split‐plot factorial design involving light availability and litter removal for six Central African timber tree species, hypothesizing that canopy gaps and litter removal would improve seedling establishment, and that less shade‐tolerant species would show stronger responses to both factors. Contrary to our expectations, significantly more germinants established on intact litter than on exposed mineral soil 3 mo after seeding. After 18 mo, seedling survival, height and diameter growth, leaf area, and rooting depth were all much higher in gap plots than in the understory for all species, with the exception of Gilbertiodendron dewevrei, a highly shade‐tolerant species whose survival was higher in the understory. Leaf production was negatively influenced by litter removal in the least shade‐tolerant species, Nauclea diderrichii, with weak or positive effects in other species. G. dewevrei, while displaying a low‐light threshold for growth, exhibited a surprisingly high growth response to increasing light comparable to more shade‐intolerant species, a response that may help explain its local competitive dominance in the region. Due to the rapid closure of small gaps, we suggest that shade‐intolerant species such as N. diderrichii, Khaya anthotheca, and Entandrophragma utile might benefit from more intensive silvicultural practices that create larger canopy gaps.     

Responses of native and invasive plant species to selective logging in an Acacia koa‐Metrosideros polymorpha forest in Hawai'i

Questions: Is the introduced timber species Fraxinus uhdei invasive in Hawai'i? Has logging disturbance facilitated the spread of Fraxinus and other alien species? Location: Windward Mauna Kea, island of Hawai'i. Methods: We surveyed 29 plots which were established before selective logging of the native tree Acacia koa in 1971 to determine if Fraxinus spread beyond the borders of an existing plantation and if other alien species increased. We created gaps in the canopy of the Fraxinus plantation and measured seed rain and regeneration, and we sampled foliar and soil nutrients inside and around the plantation. Results: Basal area of Fraxinus increased from 0.7 m².ha^‐1in 1971 to 10.8 m².ha^‐1 in 2000. Fraxinus was not found in plots that were located more than 500 m from those where it occurred in 1971 except along a road. Basal area of Acacia koa decreased after logging but subsequently recovered. Occurrence of the alien vine Passiflora tarminiana and alien grass Ehrharta stipoides decreased. Seedling regeneration of Fraxinus was prolific in gaps but did not occur under the canopy. Basal area of Fraxinus did not correlate with soil nutrient concentrations. Conclusions: Fraxinus was able to regenerate following logging more rapidly than native tree species. Basal area growth of Fraxinus was great enough to offset a decline in native trees and cause an increase in forest productivity. If the Fraxinus plantation is harvested, managers should plan ways of favoring regeneration of the native Acacia which is more valuable both for timber and for conservation.     

Documenting Biogeographical Patterns of African Timber Species Using Herbarium Records: A Conservation Perspective Based on Native Trees from Angola

In many tropical regions the development of informed conservation strategies is hindered by a dearth of biodiversity information. Biological collections can help to overcome this problem, by providing baseline information to guide research and conservation efforts. This study focuses on the timber trees of Angola, combining herbarium (2670 records) and bibliographic data to identify the main timber species, document biogeographic patterns and identify conservation priorities. The study recognized 18 key species, most of which are threatened or near-threatened globally, or lack formal conservation assessments. Biogeographical analysis reveals three groups of species associated with the enclave of Cabinda and northwest Angola, which occur primarily in Guineo-Congolian rainforests, and evergreen forests and woodlands. The fourth group is widespread across the country, and is mostly associated with dry forests. There is little correspondence between the spatial pattern of species groups and the ecoregions adopted by WWF, suggesting that these may not provide an adequate basis for conservation planning for Angolan timber trees. Eight of the species evaluated should be given high conservation priority since they are of global conservation concern, they have very restricted distributions in Angola, their historical collection localities are largely outside protected areas and they may be under increasing logging pressure. High conservation priority was also attributed to another three species that have a large proportion of their global range concentrated in Angola and that occur in dry forests where deforestation rates are high. Our results suggest that timber tree species in Angola may be under increasing risk, thus calling for efforts to promote their conservation and sustainable exploitation. The study also highlights the importance of studying historic herbarium collections in poorly explored regions of the tropics, though new field surveys remain a priority to update historical information.     

Multiple stages of tree seedling recruitment are altered in tropical forests degraded by selective logging

Tropical forest degradation is a global environmental issue. In degraded forests, seedling recruitment of canopy trees is vital for forest regeneration and recovery. We investigated how selective logging, a pervasive driver of tropical forest degradation, impacts canopy tree seedling recruitment, focusing on an endemic dipterocarp Dryobalanops lanceolata in Sabah, Borneo. During a mast‐fruiting event in intensively logged and nearby unlogged forest, we examined four stages of the seedling recruitment process: seed production, seed predation, and negative density‐dependent germination and seedling survival. Our results suggest that each stage of the seedling recruitment process is altered in logged forest. The seed crop of D. lanceolata trees in logged forest was one‐third smaller than that produced by trees in unlogged forest. The functional role of vertebrates in seed predation increased in logged forest while that of non‐vertebrates declined. Seeds in logged forest were less likely to germinate than those in unlogged forest. Germination increased with local‐scale conspecific seed density in unlogged forest, but seedling survival tended to decline. However, both germination and seedling survival increased with local‐scale conspecific seed density in logged forest. Notably, seed crop size, germination, and seedling survival tended to increase for larger trees in both unlogged and logged forests, suggesting that sustainable timber extraction and silvicultural practices designed to minimize damage to the residual stand are important to prevent seedling recruitment failure. Overall, these impacts sustained by several aspects of seedling recruitment in a mast‐fruiting year suggest that intensive selective logging may affect long‐term population dynamics of D. lanceolata. It is necessary to establish if other dipterocarp species, many of which are threatened by the timber trade, are similarly affected in tropical forests degraded by intensive selective logging.     

Spatial and temporal patterns of rowan (<Emphasis Type="Italic">Sorbus aucuparia</Emphasis> L.) regeneration in West Carpathian subalpine spruce forest

Non-random seed shadows are commonly seen in plant species whose seeds are dispersed by animals, in particular by birds. The behaviour of birds can influence the spatial pattern of seed dispersal and, consequently, the entire regeneration process of fleshy-fruited trees. This study examined regeneration patterns in a fleshy-fruited tree species, rowan (Sorbus aucuparia L.), growing in West Carpathian subalpine spruce forests, focussing on two problems: the temporal relationship between rowan regeneration and gap formation, and the spatial relationship between rowan regeneration and stand structure. It was found that rowan seedlings and saplings were recruited in advance of gap formation. Establishment of new rowan individuals in gaps was infrequent, but gaps enhanced their regeneration nearby under spruce canopy, where they occurred densely in a narrow belt about 15 m wide. Inside spruce stands, the highest density of young rowans was directly under crowns, especially near trunk bases. Few rowan saplings were found growing under mature rowan trees. The presence of a rowan seedling and sapling bank determines whether rowans fill spruce stand gaps. Dense rowan groves can develop mainly in extensive but slowly expanding gaps.     

Evaluation of the extent of genetic variation in mahoganies (Meliaceae) using RAPD markers

Despite the economic importance of mahoganies (Meliaceae) little is known of the pattern of genetic variation within this family of tropical trees. We describe the application of a polymerase chain reaction (PCR)-based polymorphic DNA assay procedure random amplified polymorphic DNAs (RAPDs) to assess the extent of genetic variation between eight mahogany species from four genera. Pronounced genetic differentiation was found between the species and genera. There was a clear separation of Cedrela odorata from the other species, with 95% of the variable amplification products differing, whereas Lovoa trichilioides, Khaya spp. and Swietenia spp. were more closely grouped. These results are consistent with the current taxonomic viewpoint. A number of markers were found to be diagnostic for particular species, which could be of value in determining the status of putative hybrids. The application of RAPDs to the study of genetic variation in mahoganies is discussed in the context of developing genetic conservation and improvement strategies for these species.     

Nitrogen aboveground turnover and soil stocks to 8 m depth in primary and selectively logged forest in southern Amazonia

Extensive areas of Amazonia undergo selective logging, modifying forest structure and nutrient cycles. Anthropogenic‐accelerated rates of nitrogen (N) turnover could increase N loss and affect regeneration, carbon sequestration and timber production. We quantified leaf area reduction, canopy opening and downed biomass and resultant N flux from reduced impact logging (RIL) activities. We compared canopy reduction, surface soil moisture and nitrate to 8 m depth between logged gaps and intact primary forest to determine if logging activities increase subsoil nitrate. To test long‐term logging effects, we evaluated surface N stocks along a 12‐year postlogging chronosequence. At the harvest rate of 2.6 trees ha^?1, total N additions in logging gaps, including leaves and wood from felled crowns (24.8 kg N ha^?1) and other killed trees (41.9 kg N ha^?1), accounted for over 80% of the total N addition to aboveground necromass from all logging activities (81.9 kg N ha^?1). Despite this N turnover by logging, belowground nitrate storage to 8 m depth did not differ between logging gaps and primary forest at the low harvest rate and disturbance intensity of this study. Soil water depletion also did not differ between gaps and primary forest over 1 year, indicating the impact on belowground inorganic N was low. Compared with primary forest, nitrate concentrations to 8 m depth in logging gaps were only significantly higher at 60–100 cm, suggesting some N redistribution beyond the bulk of the fine roots in logging gaps. Extrapolated to the Amazon Basin scale, we provide a conservative estimate that logging damage and bole export under RIL would turn over 0.14 ± 0.07 to 0.23 ± 0.12 Tg N yr^?1 based on 1999–2002 selective logging rates. Greater damage during conventional selective logging would cause higher N turnover throughout the Amazon Basin than our results based on RIL.     

Recruitment dynamics of two low-density neotropical multiple-use tree species

In the present study, we describe the temporal and spatial variability in recruitment, growth, and mortality rates of seedlings and saplings of two low-density neotropical tree species, Dipteryx odorata and Copaifera reticulata in Eastern Amazonia, Brazil. As both species have important timber and non-timber uses, for each species we compare regeneration parameters among different management scenarios (sites used for timber logging, non-timber product extraction, and undisturbed forests). Results suggest that both species share similar natural regeneration characteristics. These include temporally and spatially asynchronous germination, existence of individuals that have more abundant and frequent fruit production than the average of the population and a positive influence of the mother tree crown on seedling and sapling density. The management activities analyzed did not influence the regeneration parameters of both species, which suggests that timber logging the way it was performed and current rates of D. odorata seed gathering and C. reticulata tapping at the study site are not sufficiently intense to threaten species population. However, some species characteristics, such as their reproductive strategies, light-demanding syndromes, low-dispersal ranges, and high-mortality rates of seedlings make both species vulnerable to exploitation.     

Biological control of the fruit‐spotting bug Amblypelta lutescens using weaver ants Oecophylla smaragdina on African mahoganies in Australia

• 1 African mahogany Khaya senegalensis is a high‐value timber tree. Pilot plantings showed that the fruit‐spotting bug Amblypelta lutescens causes severe damage of the tree in the wet–dry tropics of northern Australia. The weaver ant Oecophylla smaragdina is an efficient biocontrol agent in some horticulture crops. To investigate whether the ants control this pest, field experiments were conducted from April 2006 to January 2009 at two study sites in the Darwin area, Australia. A laboratory experiment was carried out in March 2007 at Berrimah Farm.
• 2 During the experimental period, in the weaver ant treatments, the overall percentage of trees damaged by the pest was 0–8% at both sites, and the damaged trees were attacked once only. In the treatments without weaver ants, however, the damage level was > 80% at Berrimah Farm and 31–100% at Howard Springs, and the damaged trees were attacked more than once.
• 3 The mean percentage of trees damaged per monitoring occasion was 0–2.6% in the weaver ant treatments at both sites, whereas, in the treatments without the ants, the damage percentages were 14.2–27.0% at Howard Springs and 28.2–48.6% at Berrimah Farm.
• 4 Extrafloral nectar of African mahoganies is attractive to weaver ants. Fruit‐spotting bugs only damage the tender parts of flushing shoots and growing tips. Weaver ants live on sugar solution and meat, and they frequently harvest extrafloral nectar on growing shoots, on which they catch nymphs of the pest for their meat supply. The aggressive behaviour of the ants also repels the pest away from flushing shoots.
• 5 The data suggest that weaver ants were effective biocontrol agents of fruit‐spotting bugs, and the ants can be used to manage the pest on African mahoganies.
• 6 The present study demonstrates that the introduced African mahogany comprises another major host of the fruit‐spotting bug.

     

Floristic composition and structure of a rainforest area 25yr after logging

In 1949 an area of undisturbed warm temperate rainforest (simple notophyll vine forest) in mid-north coastal New South Wales, Australia was studied in terms of both floristics and structure (Burges A. & Johnston R. D. J. Ecol. 41, 72-83, 1953). During 1955-56, the area in which the transect was located was logged. Over 90% of the upper closed canopy trees adjacent to the creek and on the lower slope and about 35% of canopy trees on the upper slope were removed. The area was reassessed in terms of floristics and structure in 1981. The greatest impact of logging in the study area was structural and largely confined to the flat adjacent to the creek and to the lower slope. With the exception of the remaining gaps covering 6% of the area, structural recovery time is estimated at 140-190 yr. In the gaps structural recovery may take up to 250 yr. All flowering plants, ferns and mosses previously recorded were present 25 yr after logging. The two alien plant species on the site are short lived intolerant species and gradually disappearing with canopy closure of the regenerating forest. The regeneration of the original tree species is healthy and vigorous with most regeneration resulting from the growth of advance regeneration present at the time of logging or the germination of new seedlings. Eleven per cent of the regeneration is attributable to coppicing. The importance of remnant canopy trees as a source of propagules for the trees and epiphytes is recognised. The larger openings are slower to recover as a result of lack of protection from frost. The stability of floristic composition of this area of warm temperate rainforest following heavy logging is demonstrated.     

Effects of Natural and Human-Assisted Regeneration on Landscape Dynamics in a Korean Pine Forest in Northeast China

Improper forest harvesting can potentially degrade forest ecosystem functions and services. Human-assisted regeneration (e.g., planting) is often used to increase the rate of forest recovery and thereby reduce regeneration failure. Seed dispersal is a fundamental ecological process that can also influence spatio-temporal patterns of forest regeneration. In this study, we investigated the relative contribution of planting and seed dispersal on forest regeneration at landscape scales. Because such influences can be further complicated by timber harvest intensity and seed availability within and around harvested area, we also evaluated the effects of those factors on forest landscape dynamics. We used the forest landscape model LANDIS to simulate the dynamics of Korean pine-broadleaf mixed forests in Northeast China. We considered three factors: timber harvest intensity (3 levels), seed dispersal and whether or not planting was used. The results showed that planting was more important in maintaining the abundance of Korean pine (Pinus koraiensis), a climax keystone species in this region, under the high-intensity harvesting option during early succession. In contrast, seed dispersal was more important during late succession. Korean pine can be successfully regenerated through seed dispersal under low and medium harvest intensities. Our results also indicated that effective natural regeneration will require protecting seed-production trees (seed rain). This study results provide a basis for more effectively managing Chinese temperate forests and possibly other similar ecosystems.