Increase In Basal Area Research Articles

Effects of associating Quercus robur L. and Alnus cordata Loisel. on plantation productivity and water use efficiency

Mixed-species plantations containing non-nitrogen (N)-fixing species and N-fixing species have the potential to increase the productivity and the ecophysiological performance of the target tree species in comparison to monoculture. However, there are few and conflicting data on the effects of fixed N transfer on species water use efficiency in the short, medium and long term. In this paper, we evaluate the productivity and intrinsic water use efficiency (WUEi), i.e., the ratio of photosynthesis (A) to stomatal conductance (gs), in Quercus robur L. (pedunculate oak) stands growing in monoculture and in combination with Alnus cordata Loisel. (Italian alder) in a ratio of 25% (stand F25%) and 50% (stand F50%). We analyzed δ13C in tree rings as a proxy of the inter-annual changes in WUEi, while the influence of the stomatal conductance was explored through δ18O data. Our results indicate a considerable increase in cumulative basal area (BAI) and in WUEi in the two mixed stands during the period 1990–2002, largely resulting from an increase in N availability, due to the N-fixing species that induced an enhancement of A. After 2002, the differences between the three stands in terms of N% in tree rings, BAI and WUEi leveled off, when natural mortality or management practices decreased the competitive ability of Italian alder. Our study shows the importance of intercropping with a suitable N-fixing species to ensure high levels of productivity and water use efficiency of the target tree species in a Mediterranean-type agroforestry system, but also the need to understand how species interaction changes in time and space with a view to setting the management criteria to maximize tree performance.

Sprouting capacity of Persea borbonia and maritime forest community response to simulated laurel wilt disease

There are numerous examples of how exotic insect pests and pathogens have altered the dominance of native tree species. Changes to the structure of associated communities will depend on whether the affected species survives and if so, the degree to which it is diminished. In the southeastern USA, Persea borbonia, a common tree found in many coastal plain habitats, is the primary host of laurel wilt disease (LWD); infection rates and main-stem mortality are catastrophically high (>90%) in invaded populations. We simulated the effects of LWD prior to its arrival in coastal Mississippi by girdling and then removing the main stems of P. borbonia trees. Over a 2-year period, we monitored P. borbonia persistence via basal resprouts, understory light availability, and community structure. Removal of P. borbonia main stems resulted in a 50% increase in light transmission (measured at 1 m above ground level). All treated individuals produced basal resprouts, the size and number of which were positively related to initial tree girth. Post-treatment increases in basal area were greatest for the sub-canopy species, Ilex vomitoria, and were significantly higher in treatment versus control plots. Woody seedlings and herbaceous plants showed no significant trends in composition and abundance over time or between control and treatment plots. Our results suggest that removal of P. borbonia and subsequent resprouting causes shifts in P. borbonia size class frequencies and sub-canopy species dominance but has negligible impacts on understory plant community dynamics.

Influence of reproduction cutting methods on structure, growth and regeneration of longleaf pine forests in flatwoods and uplands

Though longleaf pine (Pinus palustris Mill.) forests have been primarily managed with even-aged methods, interest is increasing in uneven-aged systems, as a means of achieving a wider range of stewardship goals. Selection silviculture has been practiced on a limited scale in longleaf pine, but difficulty with using traditional approaches and absence of an evaluation across a range of site types has left managers in doubt concerning its suitability. This study was conducted to quantify the effects on stand dynamics of applying single-tree selection, group selection, irregular shelterwood and uniform shelterwood in longleaf pine forests on flatwoods and uplands of the southeastern United States. Selection treatments reduced stand basal area to ∼11.5m2ha−1 and shelterwood treatments left a basal area of ∼5.8m2ha−1. In spite of initial decreases in tree density and standing volume, growth rates were normal in all stands (1–5% per year), as were subsequent increases in basal area and tree density. Despite the continuing abundance of saw-palmetto (Serenoa repens W. Bartram) cover and absence of prescribed fire during the eight post-treatment years, significant increases in pine regeneration were observed in all treated stands in the flatwoods. Because of a multi-year drought in the uplands, pine seedling numbers dramatically declined, no matter which reproduction approach was employed. Although seedling numbers eventually began to recover, they were again precipitously depressed by a wildfire in 2013. Even with such losses, sufficient pine seedlings remained in each treatment to foster successful stand regeneration. Single-tree selection produced less overall change in the forest ecosystem than group selection, which caused less alteration than shelterwood treatment. Single-tree selection appears to be an effective way for achieving stand regeneration, while maintaining a continuous canopy cover that aids in the control of woody competitors and supports an array of resource values. Selection silviculture seems to be a lower risk approach for guiding forests along a trajectory of gradual improvement, with adjustments provided by frequent surface fires and periodic tree harvest. Long-term observation will be required to verify that selection can sustain forest ecosystems on sites characterized by differing environments.

Climate changes and wildfire alter vegetation of Yellowstone National Park, but forest cover persists

AbstractWe present landscape simulation results contrasting effects of changing climates on forest vegetation and fire regimes in Yellowstone National Park, USA, by mid‐21st century. We simulated potential changes to fire dynamics and forest characteristics under three future climate projections representing a range of potential future conditions using the FireBGCv2 model. Under the future climate scenarios with moderate warming (>2°C) and moderate increases in precipitation (3–5%), model simulations resulted in 1.2–4.2 times more burned area, decreases in forest cover (10–44%), and reductions in basal area (14–60%). In these same scenarios, lodgepole pine (Pinus contorta) decreased in basal area (18–41%), while Douglas‐fir (Pseudotsuga menziesii) basal area increased (21–58%). Conversely, mild warming (<2°C) coupled with greater increases in precipitation (12–13%) suggested an increase in forest cover and basal area by mid‐century, with spruce and subalpine fir increasing in abundance. Overall, we found changes in forest tree species compositions were caused by the climate‐mediated changes in fire regime (56–315% increase in annual area burned). Simulated changes in forest composition and fire regime under warming climates portray a landscape that shifts from lodgepole pine to Douglas‐fir caused by the interaction between the magnitude and seasonality of future climate changes, by climate‐induced changes in the frequency and intensity of wildfires, and by tree species response.

Habitat Use and Avoidance by Foraging Red-Cockaded Woodpeckers in East Texas

Picoides borealis (Red-cockaded Woodpecker) is an endangered bird endemic to the Pinus (pine) ecosystems of the southeastern US. Mature pine savannahs with a minimal midstory and lush herbaceous groundcover represent high-quality habitat. This study examines the foraging-habitat patterns of Red-cockaded Woodpeckers in East Texas. We present a logistic regression model that best differentiates between foraged and non-foraged habitat. Increases in hardwood-midstory basal area have the greatest negative impact on the probability of Red-cockaded Woodpeckers selecting a habitat patch for foraging. Five additional variables negatively impact foraging probability: shrub height, diameter at breast height (DBH) of pine midstory, canopy closure, density of pine midstory, and density of hardwood midstory. Our model shows a high degree of accuracy as to the probability of habitat-patch selection for Red-cockaded Woodpeckers foraging in East Texas forests composed of different pine species.

Allometric projections of time-related growth trajectories of two coexisting dipterocarp canopy species in India

Background: The Western Ghats of India contain the westernmost dipterocarp forests of Asia. However, only a few dipterocarp tree species actually coexist in the forest canopy among which Vateria indica and Dipterocarpus indicus are the most common. The mechanisms contributing to the coexistence of these phylogenetically closely related species have not been identified.Aims: We investigated the time-related growth trajectories in diameter, height and crown size of these two species in the Uppangala Permanent Sample Plot to determine if trade-offs in their three-dimensional developmental strategies could contribute to their long-term coexistence.Methods: From annual diameter growth data of 692 trees >9.55 cm in diameter at breast height over a 21-year period, we developed time-related diameter growth models for the two species, accounting for local density-dependent competition effects and topography. Combining the diameter growth models with static stem and crown allometries, we projected time-related tree growth trajectories in height and crown size.Results: While both species can reach similar dimensions, V. indica grows much faster, or at least as fast as D. indicus in diameter, height and crown size in all the observed situations. Both species respond similarly to topography, but V. indica appears to be more responsive to local density-dependent competition than D. indicus. Finally, V. indica shows higher mortality and recruitment rates and a greater basal area increase than D. indicus.Conclusions: These results refute our hypothesis that D. indicus coexists with the outperformer V. indica by a growth strategy allowing selected individuals in favourable conditions to reach the canopy more quickly than their competitors. The current coexistence of the two dipterocarp species at Uppangala appears not to be at a static equilibrium; V. indica probably being in a phase of canopy stand colonisation.

Age estimation of large trees: New method based on partial increment core tested on an example of veteran oaks

Knowledge about tree age is critical to forestry, nature conservation and ecological studies. Direct age determination of large diameter trees through increment cores is complicated by various obstacles, primarily because of rot and insufficient borer length. Here, we aim to (1) test the accuracy of various methods (tree-ring width, basal area increment, age-size relationship) for tree age estimation, (2) select the most accurate approach and (3) enable age estimation of large individuals of Quercus robur. This was done through increment cores collected in an alluvial forest in the Czech Republic. We achieved 75 age estimates for each tree, including our novel approach, which reduces the effect of decreasing tree-ring width and increasing basal area increment during tree life. The extrapolation of mean ring width to missing radius generally overestimates the number of missing rings (by up to 27.5% of actual age) and the level of overestimation increases with decreasing partial core length, while the application of basal area increment largely underestimates the age estimation (by up to 20.5%). Thus, to eliminate the over- and underestimation caused by natural tree ring width decrease and basal area increase during the tree senescence and increasing size, we averaged the number of estimated rings by these two methods. This technique obtained the most reliable age estimates, with an error up to 3.5%. Thus it is suggested here that this technique provides a relatively accurate age estimate for trees where it is impossible to directly determine the age; at least for light-demanding species. Moreover, the proposed technique does not require complicated analysis and is not time consuming. However, future research should test the applicability of this technique for tree species with various ecological strategies, i.e. shade-tolerant species. Finally, we estimate that the age of large oaks in our study area does not exceed 400years. Due to such fast growth, it is possible to keep the continuity of these keystone structures in a given landscape and thus preserve the associated biodiversity.

Temporal Changes in Tree Species and Trait Composition in a Cyclone-prone Pacific Dipterocarp Forest

Our understanding of the effects of tropical cyclones on species composition and dynamics of forest communities is mainly derived from studies that have considered single cyclonic events. Here we examined changes in the tree species and functional trait composition in an 8-ha Dipterocarp forest at Palanan in the northeastern Philippines that is subject to a high frequency of cyclonic disturbance (1–4 cyclones annually). The plot has been censused four times over a 16-year interval allowing us to consider the medium-term forest dynamics in response to repeated cyclones. We hypothesized that as the forest community in Palanan has been selected under frequent disturbance by cyclones, it should show little functional change across the census intervals. We analyzed changes in demography, species composition, and community-weighted functional traits (specific leaf area, leaf area, wood density, and specific growth rate) across the censuses and compared these against cyclone intensities during the census intervals. Demographic changes across census years suggest that the community responded to cyclonic disturbances through substantial turnover in the small- and medium-size individuals, and that there has been an increase in plot-level stem density and basal area across the measured period. Trait compositional changes from 1994 to 2010 were mostly small, but indicate a shift towards species with larger leaves and faster growth rates—traits that are associated with fast recovery after disturbance. These changes all coincide with a large intense cyclone between the second and third censuses, suggesting that cyclone strength, more than cyclone frequency, affects this forest.

Evaluating the Influence of Elevation and Impact of Hurricane Katrina on Radial Growth in Slash Pine (Pinus elliottiivar.elliottiiEngelm) on Cat Island, Mississippi, U.S.A.

ABSTRACT Funderburk, W.R.; Carter, G.A., and Anderson C.P., 2016. Evaluating the Influence of elevation and impact of hurricane Katrina on radial growth in slash pine (Pinus elliottii var. elliottii Engelm) on Cat Island, Mississippi, U.S.A. Hurricane Katrina heavily affected the Mississippi barrier islands, in the northern Gulf of Mexico, on 29 August 2005. On Cat Island, Mississippi, field observations of geographic patterns in poststorm survival of slash pine (Pinus elliottii var. elliottii Engelm) suggested that its growth and resiliency to storm impact may depend substantially on ground elevation. This hypothesis was tested by evaluating the lifetime mean radial growth rate (in millimeters per year), stem (trunk) diameter (in centimeters), the percentage of change in the radial growth rate for the initial 5-y period after the storm (2006–10) vs. the 5-y period before the storm (2001–05), and the yearly percentage increase in stem radius and basal area for 2001–10 with respect to high-accuracy GPS mea...

Did early logging or changes in disturbance regimes promote high tree densities in river red gum forests?

Density of woody plants is thought to have increased in many ecosystems in Australia since European colonisation. Globally, there has been much debate as to whether this phenomenon is driven by the process of post-disturbance recovery – whereby historical logging resulted in the replacement of large, mature trees with smaller, younger trees – or by the process of encroachment – whereby cessation of disturbance events reduced the mortality of seedlings and saplings. We examined the extent to which historical changes in forest structure are compatible with each of these models. The study was conducted in river red gum Eucalyptus camaldulensis Dehnh. floodplain forest on the River Murray at Millewa Forest, southern New South Wales. We compared ‘historical’ (~1860s) stand structure to ‘current’ structure in 45 one-hectare quadrants randomly stratified between three forest productivity classes. Historical trees were determined by stumps or stags likely to have been cut during the late 1800s. Size and position of each historical and current tree was recorded, and used to calculate stem density, basal area, canopy cover and the area of the ‘zone of influence’ (the peripheral extent of the root zone). Current stand structure was vastly different from historical structure. Stem density has increased 9-fold, from a mean of 17 (historical) to 147 (current) trees ha–1. However, basal area increased only slightly, from 13.0 to 15.3 m2 ha–1. Canopy cover increased substantially from 22.1 to 33.5% cover, as did zone of influence, from 55 to 81% cover. Evidence for both the post-disturbance recovery and encroachment hypotheses was found. The 9-fold increase in stem density between historical and current stands was attributable largely to the replacement of large trees with small trees, because basal area had increased only slightly (by 18%). However, the increase in basal area was associated with a substantial increase in canopy cover and area of the zone of influence, supporting the encroachment hypothesis. Regardless, the post-disturbance recovery hypothesis accounts for the bulk of changes in this river red gum forest.

Higher survival drives the success of nitrogen-fixing trees through succession in Costa Rican rainforests.

Trees capable of symbiotic nitrogen (N) fixation ('N fixers') are abundant in many tropical forests. In temperate forests, it is well known that N fixers specialize in early-successional niches, but in tropical forests, successional trends of N-fixing species are poorly understood. We used a long-term census study (1997-2013) of regenerating lowland wet tropical forests in Costa Rica to document successional patterns of N fixers vs non-fixers, and used an individual-based model to determine the demographic drivers of these trends. N fixers increased in relative basal area during succession. In the youngest forests, N fixers grew 2.5 times faster, recruited at a similar rate and were 15 times less likely to die as non-fixers. As succession proceeded, the growth and survival disparities decreased, whereas N fixer recruitment decreased relative to non-fixers. According to our individual-based model, high survival was the dominant driver of the increase in basal area of N fixers. Our data suggest that N fixers are successful throughout secondary succession in tropical rainforests of north-east Costa Rica, and that attempts to understand this success should focus on tree survival.

Partial harvesting in boreal mixedwoods: A case for planned heterogeneity in industrial silvicultural prescriptions

In large areas of the boreal mixedwoods of eastern Canada, conventional forestry practices dominated by large-scale clearcutting have led to an increase in early-successional trembling aspen (Populus tremuloides Michx.) stands and a decrease in late-successional mixedwood stands. Partial harvesting provides an alternative practice that could promote a return to mixedwood composition with greater potential economic returns. Our objective was to identify the stand attributes that have an effect on trembling aspen regeneration following industrial harvest operations. Ninety plots were surveyed immediately before and five years after partial harvesting, to collect information on harvested trees (stumps), residual cover and pre- and post-harvesting regeneration. Using zero-inflated beta regression models, we found that the transition probabilities (projected relative abundance) of trembling aspen were positively influenced by an increase in removal percentage and by an increase in initial basal area of trembling aspen in the overstory. Abundant balsam fir advance growth had a strong negative influence on trembling aspen transition probabilities. This information could be incorporated into silvicultural prescription decision tools to suggest optimal local basal area removal targets that would limit the regeneration success of trembling aspen. Using these results, we propose a new approach that consists of deliberately introducing heterogeneity within partial cutting prescriptions in order to limit deciduous encroachment and to promote the recruitment of coniferous regeneration in eastern Canadian boreal mixedwoods.

On the relationship between saplings and ingrowth in northern hardwood stands

We used long-term data collected from 22 study sites in northern hardwood stands comprised of sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), and American beech (Fagus grandifolia Ehrh.) to establish relationships between sapling abundance and tree ingrowth. After 10years, postharvest sapling density in the 6cm diameter class (5.1–7.0cm) showed linear relationships with ingrowth. Proportion of variation explained (r2) varied from 36% to 83% depending upon tree species and silvicultural treatment (partial cutting vs. uncut control). After 20years, linear relationships were also established (r2=24–65%) between ingrowth and sapling density in the 2cm diameter class (1.1–3.0cm). From a wide pool of variables related to stand species composition, climate, physiography, and soil nutrients, postharvest sapling density was most strongly correlated to merchantable tree density (r=0.43–0.75). Sugar maple sapling density was also positively correlated with base saturation and calcium saturation of the B horizon (r=0.56 and 0.58). Over a 30-year period, the increase in American beech sapling basal area was substantial compared to mitigated increases found in sugar maple and yellow birch depending upon treatment. Our results provide useful information on integration of sapling data into forest management.

Post-fire dynamics of the woody vegetation of a savanna forest (Cerradão) in the Cerrado-Amazon transition zone

Fire can change the species composition, diversity, and structure of savanna vegetation, thus altering growth and mortality rates. Such changes in the woody vegetation of burned savanna forest were evaluated over four years in comparison to unburned savanna forest. All woody plants with a diameter at breast height > 10 cm were measured in 100 permanent plots. Six months later, 38 of these plots were burned. Three and a half years later, all surviving individuals were re-sampled. Species richness, diversity, and the number of individuals did not change in the burned plots, although they had significantly higher (p < 0.05) increases in basal area and mortality rates (5.1% year-1) than the unburned plots (3.0% year-1).Tachigali vulgarishad the greatest post-fire increase in basal area (53%). The results indicate that fire alters the dynamics and structure of the savanna forest, excluding the less fire-tolerant species and smaller individuals (? 15cm). Tachigali vulgaris is a key species for the recovery of savanna forest biomass due to its considerable post-fire gains in basal area, at least over the short term due to its short life cycle. It follows that frequent burning of savanna forest would result in a marked change in the species composition and structure of its woody vegetation.

Does Tree Species Composition Affect Productivity in a Tropical Planted Forest?

AbstractWith growing pressure on primary forests from destructive land uses, increasing the diversity of native species plantations can increase ecosystem service provision, such as timber production or carbon sequestration, thus better supporting sustainable livelihoods. Understanding the effects of tree species composition on productivity can inform plantation design and ecological restoration strategies. However, tree species composition effects have been neglected in experimental biodiversity‐ecosystem function (BEF) research. This study uses a 10‐yr data set from one of the first tropical planted forest experiments established with native species and designed forBEFresearch at scales relevant to forest management. At our site in Sardinilla, Panama, we established plots containing 6 species from a pool of 18, in four combinations, to investigate how composition affects species and plot productivity. We used basal area as a proxy for productivity through time, measured annually, and summed this at species and plot levels for analysis. We found that plots that differed in species composition appeared to differ in temporal rate of basal area increase, but did not differ inBAafter 10 yr. Species were generally consistent in size between compositions, and composition performance was correlated with the size of component species, suggesting that species identities were most important in determining plot productivity. Our results suggest that species choice can be based on preferences for individual species, as species performance was consistent across composition contexts. We make recommendations for the use of particularly productive species that also provide multiple services such asGuazuma ulmifolia, Spondias mombin, andAnacardium excelsum.

Tree species composition affects the abundance of rowan (Sorbus aucuparia L.) in urban forests in Finland

Recent studies have shown a considerable increase in the abundance of rowan (Sorbus aucuparia) saplings in urban forests in Finland, yet the reasons for this increase are not well understood. Here we investigated whether canopy cover or tree species composition, i.e., the basal areas of different tree species in Norway spruce dominated urban forests, affects the abundances of rowan seedlings, saplings and trees. Altogether 24 urban forest patches were investigated. We sampled the number of rowan and other saplings, and calculated the basal areas of trees. We showed that rowan abundance was affected by tree species composition. The basal area of rowan trees (≥5 cm in diameter at breast height, dbh) decreased with increasing basal area of Norway spruce, while the cover of rowan seedlings increased with an increase in Norway spruce basal area. However, a decrease in the abundance of birch (Betula pendula) and an increase in the broad-leaved tree group (Acer platanoides, Alnus glutinosa, Alnus incana, Amelanchier spicata, Prunus padus, Quercus robur, Rhamnus frangula and Salix caprea) coincided with a decreasing number of rowans. Furthermore, rowan saplings were scarce in the vicinity of mature rowan trees. Although it seems that tree species composition has an effect on rowan, the relationship between rowan saplings and mature trees is complex, and therefore we conclude that regulating tree species composition is not an easy way to keep rowan thickets under control in urban forests in Finland.

Woody vegetation dynamics in a floodplain campo de murundus in central Brazil

Campos de murundus (grasslands dotted with knolls that are covered with savanna-like woody vegetation) are a common landscape in central Brazil. In this study, we assessed for the first time the dynamics of the vegetation in a floodplain campo de murundus, describing changes in composition and structure of the woody vegetation. In 2005, we established 16 permanent 25 × 25 m plots, where we identified and mapped individuals with a trunk diameter at the base ≥ 2.86 cm, as well as measuring the height of those individuals. In 2008 (after two fire events), we resampled the plots. In 2005, we had registered 4.54 m² ha-1 of basal area, 430 individuals, 42 species, 36 genera and 24 families. In 2008, we found an increase in basal area (to 4.65 m² ha-1) and a decrease in numbers of individuals (to 399), species (to 41), genera (to 35) and families (to 23). Species diversity did not differ between the two surveys. Mortality exceeded recruitment (2.68% year-1 vs. 1.29% year-1). Nevertheless, the community showed a gain in basal area owing to the growth of surviving individuals and, particularly, to the rise in the number of basal sprouts. We argue that the small floristic turnover may be related to the great resilience of the woody vegetation, whereas the structural changes might reflect the effects of the burnings in the area.

Simplification of the composition, diversity and structure of woody vegetation in a semi-arid African savanna reserve following the re-introduction of elephants

Elephant populations at high density commonly transform their habitat, but a low density population would not be expected to have a marked impact. Re-introduction of elephants into the Venetia-Limpopo Nature Reserve (320km2) in the early 1990s established a low density population for the period of survey (0.16–0.33 individuals km−2). Accordingly, their impact on the composition and structure of the woody vegetation of three riparian and nine dryland vegetation types was measured between 1997 and 2010 using 148 permanent transects. Riparian habitat showed a greater change in composition and diversity, and also a greater decline of species richness, density of tall trees or total basal area, than dryland habitat. Change of dryland Commiphora Woodland was comparable to changes of riparian types. These conspicuous changes were a consequence primarily of severe use by elephants. Some species within these vegetation types declined markedly in abundance. Vegetation types dominated by Colophospermum mopane showed an increase in total basal area and relatively minor change in composition or structure, resulting mainly from the impact of moisture stress. Vegetation types that were severely impacted by elephants constituted <10% of reserve area; lightly impacted dryland C. mopane types constituted >70% of area. Some uncommon, selected dryland species were heavily impacted by elephants. A number of species may therefore be trending toward local extirpation. It was concluded that the coexistence of elephants and some plant species in this medium-sized, contained reserve was not possible.

Quantifying the impact of an extreme climate event on species diversity in fragmented temperate forests: the effect of theOctober 1987 storm onBritish broadleaved woodlands

SummaryWe report the impact of an extreme weather event, theOctober 1987 severe storm, on fragmented woodlands in southernBritain. We analysed ecological changes between 1971 and 2002 in 143 200‐m2plots in 10 woodland sites exposed to the storm with an ecologically equivalent sample of 150 plots in 16 non‐exposed sites. Comparing both years, understorey plant species‐richness, species composition, soilpHand woody basal area of the tree and shrub canopy were measured.We tested the hypothesis that the storm had deflected sites from the wider national trajectory of an increase in woody basal area and reduced understorey species‐richness associated with ageing canopies and declining woodland management. We also expected storm disturbance to amplify the background trend of increasing soil pH, aUK‐wide response to reduced atmospheric sulphur deposition. Path analysis was used to quantify indirect effects of storm exposure on understorey species richness via changes in woody basal area and soil pH.By 2002, storm exposure was estimated to have increased mean species richness per 200 m2by 32%. Woody basal area changes were highly variable and did not significantly differ with storm exposure.Increasing soil pHwas associated with a 7% increase in richness. There was no evidence that soil pHincreased more as a function of storm exposure. Changes in species richness and basal area were negatively correlated: a 3.4% decrease in richness occurred for every 0.1‐m2increase in woody basal area per plot.Despite all sites substantially exceeding the empirical critical load for nitrogen deposition, there was no evidence that in the 15 years since the storm, disturbance had triggered a eutrophication effect associated with dominance of gaps by nitrophilous species.Synthesis. Although the impacts of the 1987 storm were spatially variable in terms of impacts on woody basal area, the storm had a positive effect on understorey species richness. There was no evidence that disturbance had increased dominance of gaps by invasive species. This could change if recovery from acidification results in a soil pHregime associated with greater macronutrient availability.

Mortality, recruitment and growth of the tree communities in three forest formations at the Panga Ecological Station over ten years (1997-2007)

The area evaluated in this study was a continuous stretch comprising three vegetation formations: gallery forest, semideciduous seasonal forest and cerradão (woodland savanna). The aim of this study was to examine the tree community dynamics in a forest gradient-from gallery forest to cerradão-at Panga Ecological Station, in the city of Uberlandia, located in the state of Minas Gerais, Brazil. The study was based on data from a previous inventory of the continuous forest conducted in 211 permanent 10 × 10 m sample plots in eight parallel transect running perpendicular to Panga Creek. Trees with a diameter at breast height > 4.77 cm were sampled in 1997, 2002 and 2007. With the exception of the cerradão, there was a net reduction in tree density over the studied period of ten years, because mortality rates were higher than the recruitment rates. The basal area increased during the period of the study, especially at cerradão. The mean mortality rate in the studied area was 2.64%.yr-1 and 3.36%.yr-1 for the 1997-2002 and 2002-2007 periods, respectively, whereas the mean recruitment rate was 1.76%.yr-1 and 1.97%.yr-1, respectively. In general, mortality rates and recruitment rates have increased during the two successive periods of measurement and showed an imbalance in favor of mortality for the semideciduous seasonal forest and the gallery forest. This fact, added to the low density and high basal area, suggest that there was a process of thinning in the tree community. However, at cerradão, there was an imbalance in favor of recruitment, with a consequent increase in density and basal area, indicating that the cerradão is in a construction phase, which was further favored by a decrease in the occurrence of fire and other anthropogenic disturbances. When the turnover rates are taken into consideration, the global dynamics of the study area over the ten years evaluated can be expressed as cerradão > semideciduous seasonal forest > gallery forest.