The impact of community-based forest management on timber treeregeneration in north-eastern Honduras,with specific reference tobig-leaf mahogany (Swietenia macrophylla)

Reduced-impact logging is used to minimise the negative effects of selective logging. However, it has been suggested that low-impact logging may create too little disturbance for the regeneration of the light-demanding timber tree species, hence compromising forest productivity. This study evaluates the impact of low-intensity, non-mechanised, certified community forest management on timber tree regeneration. Particular attention was paid to big-leaf mahogany (Swietenia macrophylla), which has a regeneration pattern linked with large-scale disturbances. Logging gaps were compared to natural treefall gaps of an unlogged forest. There were more species of the light-demanding timber trees, but fewer individuals of the shade-tolerant timber species in the certified forest logging gaps, compared to unlogged forest treefall gaps. Furthermore, significant differences were found in the environmental characteristics of the logging and natural treefall gaps, although these only partially explained the differences in timber regeneration. Mahogany was found in over half of the logged forest gaps, whilst being nearly absent in the natural treefall gaps. However, all mahoganies in the established logging gaps were seedling-sized, indicating that regeneration may be hampered due to competing vegetation. The results of the study suggest that low-impact forest management may, at least in the short term, favour light-demanding species over the shade-tolerant ones, similarly to conventional forest management.     

Resilience of stand structure and tree species diversity in subtropical forest degraded by clear logging

Subtropical forests in the Ryukyu Islands have been degraded by silvicultural practices, and thus their structural attributes are being shifted to other states dominated by a few tree species. This study clarified the mechanisms of the change, and examined the effect of clear logging on the resilience of a subtropical forest. Sprouting regeneration and typhoon disturbance were introduced into an individual-based model, SEIB-DGVM, for describing stand development and succession. The regeneration dynamics from young secondary to old-growth stands were reproduced fairly well with the model. Sprouting recruitment produced high stem density at the beginning of stand development, which caused a self-thinning trajectory following the −3/2 power law. In the late development stage after 70 years, tree species diversity fluctuated because of the regenerative response of sprouting species and the facilitatory effect of typhoon disturbance on the coexistence of subordinate species. The death of canopy trees because of typhoon disturbances reduced the dominance of Castanopsis sieboldii, and depressed its dominance in the understory. Consequently, the understory species could establish by virtue of fallen canopy trees, and tree species diversity increased at the stand level. Clear logging experiments in the model revealed that species diversity deteriorated, especially in the stand dominated by sprouting species. Resilience of subtropical forests was determined by initial species composition before clear logging. Our simulation results suggest that repeated logging drives subtropical forests with high species diversity to a stand monopolized by C. sieboldii.     

Response of ground beetles (Coleoptera: Carabidae) to forest gaps formed by a typhoon in a red pine forest at Gwangneung Forest,Republic of Korea

In Korea, damaging typhoons related to climate change have increased steadily since the 1990s. Red pine (Pinus densiflora) forests in Gwangneung Forest were greatly disturbed by typhoon Kompasu in 2010. A survey was carried out to clarify differences in ground beetle (Coleoptera: Carabidae) communities between forest gaps and undamaged forests. Ground beetles were sampled using pitfall traps from early May to late October 2011. Vegetation changes, litter layer, organic matter layer, and soil conditions were also measured. A total of 1035 ground beetles of 32 species were collected. Contrary to our expectation, species richness, abundance, and community structure of the ground beetles in forest gaps were similar to those in undamaged forests. Species richness and abundance of habitat type were also similar. However, species diversity and estimated species richness in forest gaps were significantly higher than in undamaged forests. These findings suggest that forest gaps formed by a typhoon did not lead to great change in ground beetle communities.     

Timber tree regeneration along abandoned logging roads in a tropical Bolivian forest

Sustainable management of selectively logged tropical forests requires that felled trees are replaced through increased recruitment and growth. This study compares road track and roadside regeneration with regeneration in unlogged and selectively logged humid tropical forest in north-eastern Bolivia. Some species benefited from increased light intensities on abandoned logging roads. Others benefited from low densities of competing vegetation on roads with compacted soils. This was the case for the small-seeded species Ficus boliviana C.C. Berg and Terminalia oblonga (Ruiz & Pav.) Steud. Some species, e.g. Hura crepitans L., displayed patchy regeneration coinciding with the presence of adult trees. Our results suggest that current management practices could be improved by intensifying logging in some areas to improve regeneration of light demanding species. Sufficient seed input in logged areas should be ensured by interspersing large patches of unlogged forest with logged areas. This may also assist regeneration of species that perform poorly in disturbed areas.     

Regeneration dynamics of a mixed Mediterranean pine forest in the absence of fire

The aim of this study is to determine the competing regeneration and expansion patterns of two co-occurring pine species (Pinus brutia, Pinus nigra ssp. pallasiana), in a transitional montane Mediterranean zone. We measured the regeneration density of all woody species in 102 randomly located stands along an altitudinal gradient on the island of Lesbos, Greece. Individuals of pines were assigned to different size classes. Topographic factors (altitude, aspect, and soil depth) and light availability (through hemispherical photographs) were measured for each stand. Statistical analyses were applied to explore the effect of each factor on recruitment density of the competing pine species, and to elucidate patterns of interaction. Canopy openness was the most important parameter controlling the recruitment of P. brutia, while the regeneration density of P. nigra was mainly related to canopy openness and heat load. An idiosyncratic response of the recruitment vigour of the two species was identified along gradients of shade and drought stress. The decline in P. nigra recruitment density with drought conditions underlines threats to its population maintenance even in the absence of fire. On the other hand P. brutia seems to be a stronger invader in transitional zones. The studied species could be considered typical representatives of the two most widely distributed pine functional types across the Mediterranean basin, and our results agree with the theoretical ability of such species to maintain and expand their populations.     

Tree recruitment in gaps of various size,clearcuts and undisturbed mixed forest of interior British Columbia,Canada

Tree seedling recruitment was monitored after various types of logging in mixed conifer and deciduous forests of northern British Columbia, Canada. Predicting tree seedling recruitment after disturbance is fundamental to understanding forest dynamics and succession and is vital for forest management purposes. Seedling recruitment success in multi-species northern latitude forests varied as a function of mature tree canopy cover, gap size and position in a gap. Recruitment was abundant within canopy gaps across a wide range of gap sizes (20–5000 m²), but recruit numbers dropped off rapidly under the closed forest canopy and in the open conditions of clearcuts. Inside canopy gaps, recruitment was similar by gap position in small gaps (<300 m²) but, in these northern latitude forests, exhibited a trend of increasing density from the sunny north to shady south end of larger gaps. This was true for all tree species regardless of their shade tolerance ranking. There was no evidence of gap partitioning by any of the tree species during the regeneration phase suggesting that adaptation to the subtleties of gap size during early recruitment are not well developed in these tree species. Favorable locations for emergence and early establishment of germinants were less favorable for growth and survival of established seedlings, i.e. the regeneration niches in these forests were discordant. Tree abundance and species diversity appears to be controlled more by differentiation among growth and survival niches than by the regeneration niches. From the perspective of forest management, abundant natural regeneration of all the dominant tree species of these mixed-species forests can be obtained after partial cutting.     

Does the herb Acanthus pubescens and/or elephants suppress tree regeneration in disturbed Afrotropical forest?

As a result of extensive deforestation, the survival of many tropical forest species may depend on disturbed forests. However, recent studies demonstrate that tree regeneration following logging can be slow, decreasing the conservation value of disturbed forests. Here we test whether the dominating herb, Acanthus pubescens, in the understory of logged forest, suppresses tree regeneration in Kibale National Park, Uganda. We compare the establishment, growth, and survival of tree seedlings over 2.5 years between sites cleared of A. pubescens and controls. We also consider the role of elephants (Loxodonta africana) in inhibiting tree regeneration. Seedling abundance and species richness was greater in cleared than control plots at the start of the study. Seedling abundance decreased over the study, but remained greater in cleared than control plots. Species richness did not vary over the study. However, species composition of the cleared plots was marginally different from control plots at the start, but converged on the composition of control plots by the end of the study. This suggests a common regeneration assemblage derived from reorganisation of species, rather than recruitment of new species. There was no difference in recruitment rates between cleared and control plots. These findings suggest no strong direct effects of the herb on tree regeneration in this disturbed forest. However, when we modelled (i.e., removed) the effect of elephants on regeneration, the abundance of seedlings increased in both plot types and remained reasonably constant over time. The decline in density of regenerating stems over the study was most likely caused by elephants visiting the plots. We conclude that elephants have a far greater effect in suppressing tree regeneration at Kibale than the herb stratum and are ultimately responsible for arresting succession in disturbed forest. However, as intensive logging creates conditions favourable for A. pubescens, which is eaten by elephants, the best management intervention is to constrain logging intensities to below levels above which widespread establishment of A. pubescens is promoted, thus limiting elephant activity in regenerating areas.     

Nitrogen nutrient mechanism in secondary succession process of the mixed broad-leaved/Korean pine (Pinus koraiensis) forest

Chemical and biochemical analysis methods were used to monitor the variations of nitrogen nutrient among the dominance trees species in secondary succession process of the mixed broad -leaved/Korean pine forest on Changbai Mountains, Northeast China. Amounts of total nitrogen, ammonium and NRA in soils of virgin broad-leaved/Korean pine forest which is in climax were higher than those ofsecondary birch forests those are in succession stage. The amount of nitrate was in the other hand. In climax, dominance trees species are tolerant mesophytic trees such asPinus Koraiensis, Tilia amurensis, Acer mono and alsoFraxinus mandshurica, they are all ammonium + nitrate adapted species, but they show a preference for the ammonium rather than those of the pioneer trees species in secondary birch forest, such asPopulus davidiava andBetula platyphylla. Because they have more ammonium in their leaves and roots, especiallyPinus koraiensis. Populus davidvana andBetula platyphlla are intolerant trees, amounts of nitrate and total nitrogen is higher in their leaves and roots and also NRA in their leaves, so they preference for the nitrate rather than the others. In secondary birch forest, the regeneration trees species adapt their nitrogen nutrient to the variation of nitrogen nutrient situation in soil, finally they could survival well and the secondary birch forest would succession to climax. In climax, dominance trees species adapt their Nitrogen nutrient to the situation in soil and there are not strong competition in nitrogen nutrient among them, so they can coexist well and keep the climax as stable vegetation.     

Thinning after selective logging facilitates floristic composition recovery in a tropical rain forest of Central Africa

In the Congo Basin where most timber species are light-demanding, the low logging intensities commonly implemented (1-2 trees harvested ha⁻¹) do not provide sufficient canopy gaps to ensure species regeneration. The regeneration of light-demanding timber species may therefore benefit from more intensive logging, or from post-harvest treatments such as thinning by poison girdling that increases light penetration. Little is known of the impact of post-harvest treatments on the floristic composition of tropical moist forests. This study therefore aimed to assess the effects of low and high selective logging (?2.33 and 4.73 trees harvested ha⁻¹, and ?4.96 and 9.16 m² ha⁻¹ of basal area removed (logging + damage), respectively) - followed or not by thinning (?21.14 trees thinned ha⁻¹, and ?6.57 m² ha⁻¹ of basal area removed) - on the floristic composition of a tropical moist forest in the Central African Republic, from 7 to 23 years after logging.We analyzed abundance data for 110 tree genera recorded every year for 14 years in 25 one-hectare permanent subplots. We used multivariate analysis to detect floristic variations between treatments and we assessed changes in floristic composition throughout the period. We compared floristic composition recovery between thinned and unthinned subplots, using unlogged subplots as a reference characterizing the pre-logging floristic composition.Logging and thinning had little impact on the floristic composition of the subplots as quantified 7 to 23 years later, though they did increase the proportion of pioneer species. Surprisingly, additional thinning at both logging levels failed to further distance floristic composition from that of the unlogged subplots, though it did increase disturbance intensity. Floristic composition recovery appeared to be facilitated when thinning was associated with logging. Thinning seemed to favor the growth and survival of non-pioneer species, to the detriment of pioneer species. These non-pioneer species could either be non-pioneer light demanders or shade-bearers. One explanation for this is that thinning by tree-poison girdling increased light availability without causing major damage to the forest, and thus increased the growth and survival of advance regeneration. The resulting enhanced competition then reduced the survival of pioneer species.     

Individual-scale responses of five dominant tree species to single-tree selection harvesting in a mixed forest in Hokkaido, northern Japan

We investigated the individual-scale responses of five dominant species (Abies sachalinensis, Acer mono, Tilia japonica, Quercus crispula, and Betula ermanii) to single-tree selection harvesting in a conifer–broadleaved mixed forest in Hokkaido, northern Japan. Using data from stems with a diameter at breast height of ≥12.5 cm, collected during 20 years of monitoring a 6.7-ha stand, we analyzed the effects of harvesting in the neighborhood on tree recruitment and the growth (diameter class transition) and mortality of the residual trees. The effects of harvesting varied considerably among tree sizes and species. Harvesting improved the recruitment of A. mono and B. ermanii, and moderated the negative effect of the initial basal area of the surrounding canopy trees on the recruitment of Q. crispula. Conversely, harvesting limited the recruitment of A. sachalinensis by offsetting the positive effect of the initial basal area of the surrounding canopy trees. The growth of A. sachalinensis and Q. crispula decreased with the initial basal area of the surrounding canopy trees. Harvesting in the neighborhood resulted in an improvement in the growth of the trees of these species only in the smaller size classes. With increasing local harvesting intensity, the mortality of smaller A. sachalinensis trees decreased, whereas the mortality of larger trees increased. These results suggest that differences in the local harvesting intensity, spatial patterns of harvesting, and initial stand structures influence the stand-scale dynamics in response to partial harvesting in the mixed forests of this region.     

Dynamics of the vegetation eco-boundary under climate warming in Northeast China

I "trod notionClimate warming is one of the most serious environment problems. It is sure that the present elevation of COZ and other greenhouse gases such as CH4,NzO, Of induced by human activities were makingglobal climate to go through inexperienced changes(Zhao et al. 1998i Wu 1989). The ecosystems distributed in high latitude area were likely to experiencemuch bigger change according to some previous researches (Shetwood 1983). This is the main reasonthat we focus on effects of possi…     

The influence of gap creation on the regeneration of Pinus tabuliformis planted forest and its role in the near-natural cultivation strategy for planted forest management

It remains unclear whether or not creating gaps in planted forests can increase the plant species composition, structure, and biodiversity, and also whether it can be helpful for restoring planted forests (to a more natural state). Based on a comparison of species composition and structure among forest patches, small gaps (4-25 m²), medium gaps (25-150 m²) and large gaps (150-450 m²), we found that (1) creating gaps enhanced vascular plant diversity. Both the species richness and Shannon diversity indices of small, medium and large gaps were significantly higher than in the understory. The pattern of increasing diversity of vascular plants with gap creation could be partly attributed to the emergence of novel shade intolerant species in gaps. (2) Creating gaps favored the colonization and regeneration of native species. Gap size influenced not only the emergence and density of individuals of different species, but also the emergence of different life form types. Small gaps promoted the regeneration of some shrub species, such as Ostryopsis davidiana, Rosa hugonis, and Forsythia suspense, leading to these species becoming canopy dominants early on in succession. The medium and large gaps favored the growth of tree species, such as Populus davidiana and Betula platyphylla (early successional stage), and Quercus liaotungensis and Pinus tabulaeformis (later successional phase). (3) The canonical correspondence analysis showed that plant species composition and distribution were mainly influenced by gap size and slope aspect, and that the recorded plant species could be divided into three life forms (trees, shrubs and herbs) on the biplot diagram. (4) Finally, creating gaps provided opportunities not only for native pioneer species in the early successional stage, but also for climatic climax species to grow to canopy dominants in later successional phases, suggesting that a more natural forest will develop with plant succession. Gap size plays an important role in plant regeneration, and it could be used to produce desired successional communities in near natural management for planted forests.     

Influence of typhoon disturbances on the understory light regime and stand dynamics of a subtropical rain forest in northeastern Taiwan

In 1996 and 1997 we examined the effects of typhoon disturbance on the understory light environment and sapling dynamics of the Fu-shan Experimental Forest, a subtropical rain forest in northeastern Taiwan. Mean understory light levels were approximately 30% of those in the open immediately following the two 1996 typhoons which affected the forest, yet in 1997, following two more typhoons, mean understory light levels were 10%–20% of those in the open. The decline of understory light levels to those present prior to the typhoons was more rapid in 1996 than in 1997, even though the two typhoons in 1996 were more intense than those in 1997. This difference might be the result of the timing of the typhoons. In 1996 the typhoons occurred earlier in the growing season, before August 1 rather than the middle and end of August in 1997. The regular defoliation caused by the frequent typhoons that impact Fu-shan (average of 1.4 per year) and the low stature of the forest (mean canopy height of 10.6m), results in much higher light levels beneath the canopy (9%–30% of levels in the open) than those found in most tropical and temperate forests. As a result, understory light levels are not limiting the distribution of canopy tree saplings within the forest and there is no evidence that canopy gaps play an important role in canopy tree regeneration within the Fu-shan Experiment Forest. This is in contrast with the pattern reported for some tropical forests. With frequent typhoons impacting northeastern Taiwan, the forests of this region are perpetually recovering from wind disturbances.     

Twenty-three years of stand dynamics in an old-growth Chamaecyparis forest in central Japan

Structures and dynamics of old-growth coniferous stands are affected by several types of disturbances including typhoons. We report the forest dynamics of four old-growth Chamaecyparis stands in central Japan that differ in the disturbance history of typhoons over a period of 23 years. The stem number, basal area and mortality were examined. In a predominant stand of C. obtusa (Sieb. et Zucc.) Endl., 24 % of the C. obtusa canopy trees died, mainly as a result of the severe damage of a strong typhoon that caused a single tree-fall gap and the following gap enlargements. In this stand, the total basal area decreased to 76.5 % of the initial value, although the mortality declined in recent years. In contrast, the other three stands decreased only slightly in the stem numbers (0.0–5.6 %) and increased in the basal areas of C. obtusa canopy trees. It is confirmed that the stand-level ingrowths of 300-year-old C. obtusa canopy trees could contribute to the increase in the stock of each stand. Our results support an idea that the dynamics of old-growth Chamaecyparis forests were greatly affected by typhoons. The stand structures will be gradually changed (with the processes of gap dynamics) and C. obtusa will continue to be dominant, potentially over hundreds of years.     

Characteristics of a 20-year-old evergreen broad-leaved forest restocked by natural regeneration after clearcut-burning

? To elucidate the application of natural regeneration to the restocking of evergreen broad-leaved forests in the subtropics, the characteristics of a 20-year-old evergreen broad-leaved forest restocked by natural regeneration after clearcut-burning were studied in Okinawa, Japan. Within a 0.87 ha clearcut area with four 10 m × 10 m sampling plots, two burned and two unburned ones, the tree composition, tree species diversity and vegetation changes were investigated.

? The results showed that the species diversity, basal area and density of woody stems ? 1.0 m in height differed significantly among phanerophyte types, while they were not significantly different between the burned and unburned treatments. A vegetation census also revealed no obvious differences between the treatments.

? The primary dominant species, Castanopsis sieboldii, continued to dominate the secondary forest with a broad height distribution.

? The structural complexity and high tree species diversity of the regenerating forest after clearcut-burning provides no evidence of degeneration. We can predict that the regeneration forest may gradually develop into stands similar to pre-clearcut primary forest, and that natural regeneration may restore the high tree species diversity of the evergreen broad-leaved forests in Okinawa.

     

Secondary forest regeneration under fast-growing forest plantations on degraded Imperata cylindrica grasslands

Natural regeneration of native tree species in the understoreys of fast-growing plantation tree species (Acacia mangium, Gmelina arborea and Paraserianthes falcataria) and in adjacent natural riverine forest and non-cultivated grassland areas were studied on Imperata cylindrica grassland sites in Riam Kiwa plantation area, South Kalimantan, Indonesia. Seedling and sapling densities as well as species composition and richness were assessed in a total of 35 ha by a systematic line plot survey.Floristic composition was similar in A. mangium and P. falcataria stands which differed distinctly from G. arborea stands and Imperata grassland area. Riverine forest was characterized by later successional species. In A. mangium and P. falcataria stands, a total of 63 species from 24 families were recorded. Seedling stock consisted merely of pioneer and secondary species, but also several fairly commonly occurring primary forest species. Euphorbiaceae was the most common family representing 42% of sapling and 29% of seedling densities. The most abundant regeneration occurred in A. mangium stands (4,706 seedling/sapling ha^-1), followed by P. falcataria (2,242 ha^-1) and G. arborea (554 ha^-1). Seedling recruitment was significantly lower in plots dominated by grass vegetation than those dominated by no vegetation or shrub vegetation. Breast height diameter and basal area of canopy trees as well as coverage and height of ground vegetation did not explain seedling/sapling density. Results show that plantation establishment with suitable fast-growing tree species facilitates recruitment of a variety of native tree species. This provides potential for rapid restoration of forest ecosystem and for further development of the mixed stands of fast-growing exotics and naturally regenerated native species.     

Community structure and regeneration types of Betula dahurica forest in Badaling forest center of Beijing

Using plant community analysis methods, we analyzed the floristic characteristics, species composition, community structure, population structure, and spatial distribution patterns of a Betula dahurica forest on the “1238” mountain of Badaling in Beijing, China. The results show that: 1) There are 33 plant species in the B. dahurica community, including 18 woody plant spe- cies. The B. dahurica forest is a monodominant community with 75.9% dominance. 2) Based on diameter at breast height (DBH) size class distribution, the population structure of B. dahurica and Acer mono—two heliophyllous and pioneer tree species—is cascade-type, with both in an increasing stage. The population structure of Tilia mandshurica and T. mongolica, two shade-tolerant tree species, is inverse-J type, and they have more young seedling individuals and regenerate more stably. They are associated species of the pioneer tree species. The population structure of Quercus mongolica, as the associated species of climax species in the community, is sporadic, and its regeneration is fluctuating and random. Fraxinus rhynchophylla is a shade-tolerant tree species which has a unibar population structure and climax characteristics of pioneer tree species. The relative frequency of young seedlings reached 0.4. 3) The dominant species B. dahurica is still in an increasing stage, and the regeneration of other species is steady or partly influences the community, putting the community in the pioneer species stage. From the population structure and distribution frequency of F. rhynchophylla, the B. dahurica forest will approach to a climax state in the future.     

Light-dependent development of two competitive species (Rubus idaeus, Cytisus scoparius) colonizing gaps in temperate forest

Forest regeneration can be inhibited by competition for environmental resources (water, nutrients, light) between tree seedlings and some competitive species that are generally light-demanding species developing in gaps. The study’s aim was to quantify the development of two competitive species (Rubus idaeus and Cytisus scoparius) present in the chaîne des Puys, France, relatively to light in gaps inside Picea abies stands. On 29 transects linking the stand to the gap centre (223 points), light intensity was measured (0–80% of relative light) and floristic measurements (cover and height of the different species) were done. Development of both competitive species is positively connected to light, with a bell-shaped curve with a maximum of 40–50% for R. idaeus and a quite constant increase to 80% (maximum of light recorded in the experimentation) for C. scoparius. These results are discussed relatively to understorey vegetation management in order to favour forest regeneration.     

Stand structure and establishment process of an old-growth stand in the mixed deciduous broadleaf/conifer forest of Mt. Moiwa Forest Reserve, central Hokkaido, Northern Japan

Stand structure of an old-growth forest was studied by tree (≥4.0 cm in DBH) census in a main plot of 1.3 ha and 8 additional plots (0.525 ha in total) located in the Mt. Moiwa Forest Reserve, central Hokkaido, northern Japan. Major tree species with ≥1.0% of the relative basal area and of relative number of trees (Acer mono, A. mono var.mayrii, Kalopanax pictus, Magnolia kobus var.borealis, M. obovata, Prunus ssiori, Tilia japonica, andUlmus laciniata) have positive values of skewness in DBH, which shows the abundance of smaller-sized stems. All stems over 1.3 m high in the main plot were mapped to clarify the relationship between stem densities and canopy states. Although advances from sapling (>1.3 m tall and <4.0 cm DBH) to small tree (10.0 cm ≤ DBH <25 cm) for all major component species, exceptP. ssiori andU. laciniata, were independent of canopy states, those ofP. ssiori andU. laciniata depended on canopy gaps.Betula spp. was the most abundant gap makers, butT. japonica andA. mono (including var.mayrii) were dominant species in the main plot. This suggests the shift of dominant species in the forest of the study site. Historical records of disturbance demonstrated that selective cuttings of conifers during the late 19th century were responsible for the dominance ofBetula spp. and the subsequent shift of dominant species. This fact suggests that artificial disturbance plays an important role in the establishment ofTilia japonica-Acer mono forest considered to be a climax of the mixed deciduous broadleaf/conifer forests.     

Influence of forest structure and environmental variables on recruit survival and performance of two Mediterranean tree species (<Emphasis Type="Italic">Quercus faginea</Emphasis> L. and <Emphasis Type="Italic">Q. suber</Emphasis> Lam.)

We investigated the regeneration requirements of the two dominant tree species in a mixed-oak forest of SW Portugal: Quercus suber (cork oak, evergreen) and Q. faginea (Portuguese oak, winter-deciduous). We hypothesized that (1) recruits of different oak species are differentially influenced by soil and overstory variables and (2) different factors explain the recruitment occurrence and performance of the same species. We sampled the recruits’ height and diameter, and several environmental and forest structure variables of their microsites. Both recruitment occurrence and performance were modeled using generalized linear models. Our final models predicted the probability of occurrence of recruits of Q. faginea and Q. suber with 74 and 82% of accuracy, respectively, and explained about 50% of the variance of their recruitment performance. The recruits of Q. faginea tended to occur in microsites with higher canopy height, canopy density and litter cover, and closer to both conspecific and heterospecific adults, while the opposite was true for recruits of Q. suber. The performance of recruits of Q. suber was favored by the higher litter cover (a good surrogate for N and P availability), but negatively affected by the higher litter depth. We concluded the following: (1) there were significantly different regeneration niches for each species (Q. faginea and Q. suber); (2) the factors explaining the recruitment occurrence differed from those explaining the recruitment performance; (3) the overstory plays a complex and important role in the regeneration process; (4) different variables apparently related with the same environmental factor (e.g. litter cover and litter depth) could affect recruits in an opposite way; (5) sensitive trade-offs must be considered for delineating management actions, since they could favor the regeneration of Q. suber, but, at the same time, negatively affect the regeneration of Q. faginea.