A 10-year evaluation of the functional basis for regeneration habitat preference of trees in an African evergreen forest

The spatial distribution of tree juveniles in relation to light environments may reflect species differences in growth, survival, and functional traits and will shape the nature of forest regeneration. Long-term field experiments are important to evaluate this issue because of the potentially very long juvenile period in trees. Here, we combine a 10-year seedling survival–growth data with the results of community ordination and multivariate analyses of functional traits to ask how observed juvenile light guilds are related to species functional traits and seedling performance. We transplanted seedlings at a standardized height of 11 cm into the shaded understory and quantified their growth and survival for 10-years. Using the community-wide stem distribution data, we categorized 33 species including the focal 11 species to understory vs. gap/edge guilds. Then, we determined differences between the two guilds in seedling survival, growth, as well as seed size, adult height, and a series of leaf traits, including toughness and chemical traits (fiber, protein, phenolics, tannins, alkaloids, saponins). Among the 11 non-pioneer species whose seedlings were planted into the understory, there was no significant difference in 10-year survival between light guilds, but species in gap/edge guild tended to achieve greater height than species in the understory guild. The leaf chemical traits of 33 species did not differ between the two juvenile light guilds, but gap/edge species had smaller seeds, taller adults, and tougher leaves than understory species. We used logistic regression as a complementary approach to assess the extent to which plant traits varied between light guilds and the most parsimonious model based on AIC_c ranking included only leaf toughness and had an Akaike weight of 0.52. In addition, across the 11 species planted as seedlings, these traits were not significantly related to survivorship or growth over 10 years. A Principle Components Analysis illustrated associations among traits. We conclude that light guilds in terms of juvenile stem distribution could not be explained by long-term field performance of post-establishment seedlings alone. Earlier seedling stage or later sapling stage may be more important in differentiation of light guilds. For the species examined difference in growth rates could be linked to seed size and adult stature, but not to the adult leaf chemical traits considered. These results suggest the importance of examining ontogenetic shifts and relationships among functional traits for a better understanding of regeneration strategies of tropical trees.     

Discussions on forest recovery in the burned area in Daxing’anling forest region

The disastrous fire occurred in northern area of Daxing’anling forest region on May 6, 1987, destroyed a large area of forests. The broad-leaved tree species, such as poplar, birch had regenerated in a great quantity after the fire, but the coniferous species such as larch and scotch pine had difficult to regenerate naturally, This paper put forward that the coniferous forest could be recovered by the planting method of effect strip and effect islet based on the principle of borderline effects and by making full use of the condition of broad-leaved trees.     

上海海湾国家森林公园景观林优化改造

在对海湾国家森林公园景观林资源现状调查分析的基础上,根据公园即将向公众开放对林木景观资源的质量和标准要求,针对存在主要问题,提出相应的优化改造措施。通过对本公园人工幼龄林培育过程中,出现的林相单调,密度过大有碍森林赏景、影响森林生态效益的发挥及阻滞森林健康演替等问题提出相应的改造措施,旨在优化提升森林美学等级。       

Post-1935 changes in forest vegetation of Grand Canyon National Park, Arizona, USA: Part 1 - ponderosa pine forest

Vegetation plots originally sampled in Grand Canyon National Park (GCNP), Arizona, USA in 1935 are the earliest-known, sample-intensive, quantitative documentation of forest vegetation over a Southwest USA landscape. These historical plots were located as accurately as possible and resampled in 2004 to document multi-decadal changes in never-harvested Southwestern forests. Findings for ponderosa pine forest (PPF) differed among three forest subtypes (dry, mesic, and moist PPF), indicating that understanding the ecology of PPF subtypes is essential for development of ecologically based management practices. Dry PPF, which is transitional with pinyon-juniper vegetation at low elevation, exhibited no changes from 1935 to 2004. Mesic PPF, the core subtype of PPF, had increased densities of total trees, ponderosa pine (Pinus ponderosa), and white fir (Abies concolor) in the 10-29.9 cm diameter class from 1935 to 2004 that may have induced decreased densities of larger ponderosa pines and total tree and ponderosa pine basal areas. Moist PPF, which is transitional with mixed conifer forest at high elevation, was the most dynamic PPF subtype with decreases from 1935 to 2004 in total density and total basal area that are largely attributable to decreases in quaking aspen (Populus tremuloides). Graphical synthesis of datasets with historical and modern values for density and basal area indicates that overall PPF (all subtypes combined) increased in sapling density of all species combined and conifers with canopy potential and decreased in density of quaking aspen trees since the late 19th century. PPF of GCNP has passed through an accretion phase of forest development with increases in density and, depending on PPF subtype and variable being examined, is at or past the point of inflection to recession of density and basal area. Increases in small diameter ponderosa pine and white fir from 1935 to 2004 portend potential additional accretion, but decreases in total basal area, density and basal area of quaking aspen, basal area of ponderosa pine, and density of larger diameter ponderosa pine indicate PPF has passed the inflection point from accretion to recession. Uncertainties about 19th-century PPF structure and composition and about future ecological and societal environments lead to the conclusion that resource managers of GCNP and other natural areas should consider a change in focus from the objective of achieving desired future conditions to an objective of avoiding undesired future conditions.     

The role of different sources of tree regeneration in the initial stages of natural forest recovery after logging of conifer plantation in a warm-temperate region

We analyzed the role of regeneration type (surviving from advanced regeneration, resprouting from advanced regeneration, or newly recruited seedlings) in determining the quantity and quality of individuals in reestablishing a natural forest following clear-cutting of a conifer plantation. We experimentally clear-cut a plantation and undertook a detailed tree census before and after clear-cutting. After clear-cutting, a species composition partially representing warm-temperate evergreen broadleaf forest was present in the form of surviving and resprouted individuals originating from advanced regeneration that had established in the Chamaecyparis obtusa plantation. On the other hand, seedlings that established after clear-cutting were dominated by pioneer species, and the number of seedlings was far greater than the number of individuals originating from advanced regeneration. Our results suggest that the role of regeneration type would differ in relation to the objectives for forest recovery. When any kind of woody cover of the ground surface after clear-cutting would suffice, we suggest that the contribution of pioneer seedlings originating from buried seeds would be important. If the recovery objective is to form a simple evergreen broadleaf forest, such as a coppice woodland, all three sources of regeneration would play a similar role, provided the understory before clear-cutting was as well developed as the one in this study. If rapid establishment of a lucidophyllous forest with diverse species composition is desired, the role of the surviving and resprouting individuals originating from the advanced regeneration would be much more important.     

Avian studies and research opportunities in the Luquillo Experimental Forest: A tropical rain forest in Puerto Rico

The Luquillo Experimental Forest (LEF) located on the Caribbean island of Puerto Rico has a rich history of ecological research, including a variety of avian studies, and is one of the most active ecological research sites in the Neotropics. The LEF spans an elevational range from 100 to 1075 m over which five life zones and four forest types are found in a warm, humid subtropical climate. A total of 23 bird species breeds here and another 76 species, mostly migrants, are known to occur. The food web of the forest in the lower elevations is especially well studied, which allows an assessment of the role of birds in the food web. The LEF is noted for its high densities of Eleutherodactylus frogs and Anolis lizards, which may depress insect densities thereby contributing to the low species richness and densities of most insectivorous birds. The signature species of the forest is the endangered Puerto Rican Parrot (Amazona vittata) that has been the focus of intensive long-term research and recovery efforts, which have spawned research on associated species, including long-term studies on the Pearly-eyed Thrasher (Margarops fuscatus) and botfly (Philornis spp.) ectoparasitism. Given the frequency of hurricane disturbance to the LEF and studies providing baseline for comparisons, research has made major contributions to an understanding of the effects of hurricanes on forest ecosystems including bird populations and their resources. We summarize these and other studies from the LEF to characterize the avifauna and its environment while noting studies with management implications and identify opportunities for future ornithological studies.     

Effects of topography and management history on natural forest recovery in abandoned forest after clear-cutting in Miyazaki, Japan

We investigated factors limiting the recovery of natural forest in former large-scale conifer plantations abandoned after clear-cutting in southwestern Japan. We analyzed forest recovery status (“recovered” sites covered by evergreen broad-leaved trees, and “unrecovered” sites covered by pioneer community or nonvegetated sites) using aerial photographs and field survey. We applied logistic regression analyses to evaluate the effects of topography, construction of harvesting roads, distance from remnant forest, stand condition before clear-cutting, and prior land-use history on forest recovery. Human factors, i.e., land use and clear-cutting age, were found to affect to forest recovery more than environmental factors such as topography. Harvesting roads had the strongest negative impact on forest recovery. Forest recovery after clear-cutting of young sugi plantations also took longer than after clear-cutting of old sugi plantations or evergreen broad-leaved forests. Furthermore, areas formerly utilized as meadows recovered less successfully than those that had been managed as coppices. The influences of these factors were thought to be promoted by the advance reproduction as the regeneration sources for forest recovery. The influence of stand age before logging suggested an effect of thinning, which might alter the abundance of advanced reproduction in the understory. However, distance from remnant forest appeared to be less important. An influence of topography was also detected, but this could be partly explained by the existence of advance reproduction in the understory in certain topographic positions. Thus, our analysis suggests that regeneration sources originating from advanced reproduction in plantations play a significant role for the recovery of natural forest after clear-cutting.     

Evaluating vegetation recovery following large-scale forest fires in Borneo and northeastern China using multi-temporal NOAA/AVHRR images

This study evaluated whether a normalized difference vegetation index (NDVI), derived from 8-km-resolution National Oceanic Atmospheric Administration (NOAA) Pathfinder AVHRR (advanced very high resolution radiometer) land (PAL) data, is appropriate for monitoring recovery following large-scale forest fires. Recovery processes were examined after fires on the island of Borneo and in northeastern China in 1983 and 1987, respectively. Based on pre- and post-fire NDVI differences (NDVId), six damage classes were established. Post-fire changes in land cover were monitored using (1) the average NDVI of all pixels corresponding to each damage class (A-NDVI) and (2) the ratio of a fire-affected A-NDVI to a non-fire-affected A-NDVI (QNDVI). Burn areas located by an NDVId threshold value were similar to reported burn areas. Both A-NDVI and QNDVI values signaled vegetation recovery, but the QNDVI gave much better results. For both the 1983 Borneo and 1987 northeastern China fires, QNDVI values dropped at the time of the fire and increased for about 4 years afterwards, although a 4-year period is obviously less than the time required for biomass recovery. Trends at the two study sites diverged after this period, however. The QNDVI values for multiple fire events in Borneo (in 1983, 1987, 1991, 1997, and 1998) showed that recovery times varied with the size of the burn area, but not with the damage class of the same event, whereas the severe-class QNDVI values for the fire in northeastern China in 1987 were still lower than the control value 10 years after the fire.     

The effects of cultivation history on forest recovery in fallows in the Eastern Arc Mountain, Tanzania

Using fallows under shifting cultivation systems as a case study, we examined the effects of landuse history (cultivation duration and cropping strategies) on rate and extent of forest recovery. Cultivation duration and five cropping strategies were investigated post facto, indirectly, and with regards to their effect on the structure (basal area, BA and stand complexity, C_HCI) and diversity (Fisher's α) of forests in fallows. Data were generated from vegetation surveys conducted in the Nguru Mountain block of the Eastern Arc Mountains, Tanzania. The surveys were conducted in primary forests, ongoing farms, and fallows that had been out of production for 1-31 years (N = 109, plot size = 0.1 ha). Recovery patterns between lowland (300-800 m) and submontane (800-1600 m) elevations varied substantially. BA and C_HCI recovery levels were consistently higher in submontane fallows. None of the fallows had attained BA and C_HCI levels equivalent to those of primary forests; α in lowland fallows, however, was 124% of primary forest levels. Forest recovery was limited to fallows whose cultivation period was ≤16 years. Recovery was fastest and highest in fallows located within a dense primary/old growth forest matrix. The findings provide a more thorough understanding of how local farming practices affect forest recovery. Improving the recovery outcomes of fallows that are located outside the old growth forest matrix will require (a) more strategic inclusion of remnant trees, (b) drastically shorter cultivation periods, and (c) human intervention through assisted regeneration.     

Lichen diversity in temperate montane forests is influenced by forest structure more than climate

Although the effect of forest management on lichens in temperate forests has been widely examined, little is known about the influence of management-related factors on their biodiversity relative to factors that cannot be altered by management. Here we determined whether forest structure or climate determines lichen diversity in the Bavarian Forest National Park in southeastern Germany, taking spatial variables into account. We investigated 517 single tree stems along 4 transects in 113 pre-stratified plots (8 m in diameter) in this montane forest. We grouped environmental variables into three sets: climate (macroclimate, non-manageable), forest structure (manageable), and space. The explanatory powers of these sets of variables for lichen diversity were compared using variance partitioning for the lichen community, species density, and threatened species density. The relationships of single characteristics of forest structure with lichen species diversity were analyzed using generalized linear models (GLM). Lichen diversity was better explained by stand structures than by climate. Spatial effects influenced the number of species per plot. Among the structural features, the availability of dead wood and sycamore maple as well as forest continuity were most important for the enhancement of lichen diversity. Open canopy structures affected the total diversity positively. Although the availability of large trees was not an influential factor in the GLM at the plot level, high diversity levels were generally associated with large stem diameters at the level of single stems. We provide recommendations for sustainable forest-management practices that aim at specifically enhancing lichen diversity in temperate areas experiencing low levels of air pollution.     

Comparison of statistical tests for habitat associations in tropical forests: A case study of sympatric dipterocarp trees in a Bornean forest

Habitat difference is an important mechanism for maintenance of tree diversity in tropical forests. The first step in studies of habitat difference is to statistically analyze whether the spatial distributions of tree populations are skewed to species-specific habitats; this is called a habitat association test. We propose a novel habitat association test on the basis of the probability of tree occurrence along a continuous habitat variable. The test uses torus shift simulations to obtain a statistical significance level. We applied this test to 55 common dipterocarp species in a 52-ha plot of a Bornean forest to assess habitat associations along an elevation gradient. The results were compared to those of three existing habitat association tests using the same torus shift simulations. The results were considerably different from one another. In particular, the results of two existing tests using discrete habitat variables varied with differences in habitat definitions, specifically, differences in elevation break points, and the number of habitat classes. Thus, definitions of habitats must be taken into account when habitat association tests with discrete habitat variables are used. Analyses of artificial populations independent of habitat showed that all of the tests used were robust with respect to spatial autocorrelation in tree distributions, although one existing test had a higher risk of Type I errors, probably due to the use of multiple tests of significance. Power analysis of artificial populations in which distributions were skewed to certain elevations showed that the novel test had comparable statistical power to the most powerful existing test. Statistical power was affected not by the total number of a given tree but by the number of clumps in a plot, suggesting that >5 clumps were required for a reliable result.     

Effect of recurrent fires on soil nutrient dynamics in a tropical dry deciduous forest of Western Ghats,India

The role of forest fires in the soil dynamics and global carbon cycle has not been comprehensively studied in tropical forests as the effects of fire on tropical forest soils can be extremely variable. This study was aimed to understand how repeated fires affect physical and chemical properties of soil in a tropical dry deciduous forest and alter soil fertility and health. The study was carried out in the dry deciduous forest of Mudumalai Tiger Reserve. Soil samples were collected from unburned (B0) to six-time burned (B6) plots. Samples were collected from each plot from three different depths viz. 0–10 (Top), 10–20 (Middle), and 20–30 cm (Bottom) and analyzed for soil physical and chemical properties. Soil pH, EC, WHC decreased with increasing fire frequencies while bulk density increased. Organic Carbon, Total N, and available P decreased with increasing fire frequencies whereas extractable K initially increased but decreased with the very high frequency of fires. NO₃^?N slightly decreased with high fire frequencies but NH₄^?N decreased significantly with increasing fire frequency. These results provide a new insight regarding the influence of repeated fires on soil that will be valuable to understand the effect of fire on the recovery of soils and nutrient dynamics.     

Windthrow and salvage logging in an old-growth hemlock-northern hardwoods forest

Although the initial response to salvage (also known as, post-disturbance or sanitary) logging is known to vary among system components, little is known about longer term forest recovery. We examine forest overstory, understory, soil, and microtopographic response 25 years after a 1977 severe wind disturbance on the Flambeau River State Forest in Wisconsin, USA, a portion of which was salvage logged. Within this former old-growth hemlock-northern hardwoods forest, tree dominance has shifted from Eastern hemlock (Tsuga canadensis) to broad-leaf deciduous species (Ulmus americana, Acer saccharum, Tilia americana, Populus tremuloides, and Betula alleghaniensis) in both the salvaged and unsalvaged areas. While the biological legacies of pre-disturbance seedlings, saplings, and mature trees were initially more abundant in the unsalvaged area, regeneration through root suckers and stump sprouts was common in both areas. After 25 years, tree basal area, sapling density, shrub layer density, and seedling cover had converged between unsalvaged and salvaged areas. In contrast, understory herb communities differed between salvaged and unsalvaged forest, with salvaged forest containing significantly higher understory herb richness and cover, and greater dominance of species benefiting from disturbance, especially Solidago species. Soil bulk density, pH, organic carbon content, and organic nitrogen content were also significantly higher in the salvaged area. The structural legacy of tip-up microtopography remains more pronounced in the unsalvaged area, with significantly taller tip-up mounds and deeper pits. Mosses and some forest herbs, including Athyrium filix-femina and Hydrophyllum virginianum, showed strong positive responses to this tip-up microrelief, highlighting the importance of these structural legacies for understory biodiversity. In sum, although the pathways of recovery differed, this forest appeared to be as resilient to the compound disturbances of windthrow plus salvage logging as to wind disturbance alone, by most vegetative measures.     

Relationship between annual rainfall and tree mortality in a tropical dry forest: Results of a 19-year study at Mudumalai,southern India

Variability in rainfall is known to be a major influence on the dynamics of tropical forests, especially rates and patterns of tree mortality. In tropical dry forests a number of contributing factors to tree mortality, including dry season fire and herbivory by large herbivorous mammals, could be related to rainfall patterns, while loss of water potential in trees during the dry season or a wet season drought could also result in enhanced rates of death. While tree mortality as influenced by severe drought has been examined in tropical wet forests there is insufficient understanding of this process in tropical dry forests. We examined these causal factors in relation to inter-annual differences in rainfall in causing tree mortality within a 50-ha Forest Dynamics Plot located in the tropical dry deciduous forests of Mudumalai, southern India, that has been monitored annually since 1988. Over a 19-year period (1988–2007) mean annual mortality rate of all stems >1 cm dbh was 6.9 ± 4.6% (range = 1.5–17.5%); mortality rates broadly declined from the smaller to the larger size classes with the rates in stems >30 cm dbh being among the lowest recorded in tropical forest globally. Fire was the main agent of mortality in stems 1–5 cm dbh, elephant-herbivory in stems 5–10 cm dbh, and other natural causes in stems >10 cm dbh. Elephant-related mortality did not show any relationship to rainfall. On the other hand, fire-related mortality was significantly negatively correlated to quantity of rainfall during the preceding year. Mortality due to other causes in the larger stem sizes was significantly negatively correlated to rainfall with a 2–3-year lag, suggesting that water deficit from mild or prolonged drought enhanced the risk of death but only with a time lag that was greater than similar lags in tree mortality observed in other forest types. In this respect, tropical dry forests growing in regions of high rainfall variability may have evolved greater resistance to rainfall deficit as compared to tropical moist or temperate forests but are still vulnerable to drought-related mortality.     

Simulation of the vegetation structure and function in a Malaysian tropical rain forest using the individual-based dynamic vegetation model SEIB-DGVM

An individual-based Dynamic Global Vegetation Model, the SEIB-DGVM, was adapted to a Malaysian tropical rain forest by incorporating formulas and parameters from a gap dynamics model, FORMIX3. After calibration, the model reconstructed forest structure (i.e., size structure, leaf area index, and woody biomass) and carbon fluxes (i.e., gross and net primary productivity) of a dipterocarp forest in Pasoh, Peninsular Malaysia. Sensitivity analysis demonstrated that the model was robust; forest structure and ecosystem functions moderately fluctuated due to changes in parameters and climatic environments. Sensitivity analysis also indicated that the success and decay of a dominant species group that monopolized the canopy layer greatly affected those of a less abundant, shade-intolerant group. This result indicates that even if environmental changes do not exhibit clear effects on dominant canopy species and/or whole forest structure, such changes may still substantially impact the biodiversity of subdominant species. In simulations without gap formation, woody biomass was overestimated and a shade-intolerant species group was eliminated. This finding indicates that incorporating gap formation into the individual-based model is essential for the appropriate simulation of forest biomass and biodiversity in this Malaysian tropical rain forest.     

Effects of undisturbed canopy structure on population structure and species coexistence in an old-growth subalpine forest in central Japan

We investigated structural and compositional characteristics of an old-growth subalpine forest in central Japan, to ascertain forest dynamics and species coexistence. The forest appeared to have been fairly-undisturbed, at least during several recent decades, judging from the maximum occupancy of space by living canopy trees and an unchanged canopy structure between pre- and post-mortality phase. This stable forest showed minimum-scale dynamics that occurred primarily at a single-tree scale. Within this forest, the dominant species were Abies mariesii, A. veitchii and Picea jezoensis var. hondoensis. The two Abies species were abundant and showed advance regeneration, resulting from their high shade-tolerance. On the other hand, Picea showed the greatest basal area, in spite of its lower density. Picea showed steeper initial height-diameter allometric slopes, suggesting that its understorey saplings could increase height more rapidly under sunny conditions. Picea regenerates, given the opportunity of larger disturbances, as approximately even-aged cohorts, and then escapes competition from other shade-tolerant species by attaining the uppermost part of the canopy, resulting from rapid height growth of sapling, longer longevity and emergent attainable height. However, beneath the undisturbed canopy of this forest, in spite of its many seedlings, Picea entirely lacked regenerating individuals, suggesting that its regeneration is in a fairly-limited stage. This suggests that within the undisturbed forest, a demographic trait of Picea, in which the lower mortality of its canopy trees can compensate for its lower recruitment, is not enough to explain its stable coexistence with shade-tolerant Abies spp. Thus, not only the demographic trait, but also the spatial/temporal disturbance magnitude is important for an explanation of the coexistence of Picea with Abies. Consequently, it seems that not only equilibrium process, such as species differences in life-history traits, but also non-equilibrium process, such as disturbances, is crucial for their coexistence in this subalpine forest in central Japan.     

Forest-related partnerships in Brazilian Amazonia: There is more to sustainable forest management than reduced impact logging

There is more to sustainable forest management than reduced impact logging. Partnerships between multiple actors are needed in order to create the institutional context for good forest governance and sustainable forest management and stimulate the necessary local community involvement. The idea behind this is that the parties would be able to achieve more jointly than on their own by combining assets, knowledge, skills and political power of actors at different levels of scale. This article aims to demonstrate by example the nature and variety of forest-related partnerships in Brazilian Amazonia. Based on the lessons learned from these cases and the authors’ experience, the principal characteristics of successful partnerships are described, with a focus on political and socioeconomic aspects. These characteristics include fairly negotiated partnership objectives, the active involvement of the public sector as well as impartial brokers, equitable and cost-effective institutional arrangements, sufficient and equitably shared benefits for all the parties involved, addressing socioeconomic drawbacks, and taking measures to maintain sustainable exploitation levels. The authors argue that, in addition to product-oriented partnerships which focus on sustainable forest management, there is also a need for politically oriented partnerships based on civil society coalitions. The watchdog function of these politically oriented partnerships, their awareness-raising campaigns regarding detrimental policies and practices, and advocacy for good forest governance are essential for the creation of the appropriate legal and political framework for sustainable forest management.     

Long-term spatial dynamics of Acer saccharum during a population explosion in an old-growth remnant forest in Illinois

Species richness and evenness have greatly declined in oak–hickory forests in the central hardwood region in the U.S.A. in the past 100 years due to the rapid population growth of Acer saccharum. This study used a 50-year record of spatial dynamics to examine how demographic processes, particularly recruitment, may have contributed to this increase in an old-growth forest remnant, Brownfield Woods, Urbana, Illinois, U.S.A. The impact of canopy disturbance, including the outbreak of Dutch elm disease, on this increase was also evaluated. Historical maps of trees (≥7.6 cm DBH) from 1951, 1988, and 2001 in a 180 m × 280 m area were used to develop a series of univariate Ripley's L(d) functions to study changes in spatial patterns of three size classes of A. saccharum over time. Bivariate Ripley's L(d) functions were also utilized to evaluate spatial associations between recruitment and canopy disturbance. Our results indicated that A. saccharum was aggregated at most spatial scales up to 80 m during 1951–2001. Such aggregation arose mainly from small individuals. Furthermore, newly recruited individuals were aggregated at multiple spatial scales, and were significantly associated with canopy disturbance in general, as well as gaps created by Ulmus trees killed by Dutch elm disease. The aggregation of the 1951 initial group of small individuals changed via mortality to a random distribution over time. The results indicate that tree deaths caused by disturbances of different scales and types were the main cause of increased recruitment of A. saccharum in Brownfield Woods. The occurrence of Dutch elm disease further accelerated its population increase. This study demonstrated a direct spatial link between recruitment of A. saccharum and disturbance, and provided a long-term case study of a population explosion.