bluuebunny/crossref_metadata_2025 huggingface dataset:
Seed bank patterns in Restionaceae and Epacridaceae after wildfire in kwongan in southwestern Australia
Authors: Meney Kathy A. , Nielssen Georgina M. , Dixon Kingsley W.
Published: May 2006

Abstract. Post‐fire seed germination, seedling mortality and seed banks were investigated in scrub‐heath (kwongan) in SW Australia. Study species included herbaceous and woody, obligate seeders and resprouters in two non‐bradysporous but significant plant families (Restionaceae and Epacridaceae). In all species, seedlings were recruited only in the first autumn‐spring after fire and occurred in similar densities as the estimated germinable annual seed input. Seedlings were absent from unburnt vegetation. Although most species retained some residual seeds after fire, tests (excised embryo culture) indicated that a negligible number of seeds were germinable. Regardless of fire response or species, there appeared to be a large loss of seeds each year and in most cases, only a small proportion of the annual seed production was used in post‐fire recovery of plants. Based on seedling: parent ratios, all species had the capacity to reconstitute parent densities from germinants in the first year after fire, but high seedling mortality and no further recruitment resulted in less seedlings than replacements for four resprouter Restionaceae and three Epacridaceae (all obligate seeders) at the end of the third year after fire.
Post‐burn succession on Brittany heathlands
Authors: Gloaguen J. C.
Published: May 2006

Abstract. Vegetation succession after severe burning of a Brittany heathland was recorded in permanent plots for ten years. Mosses are the first colonizers, soon forming a dense layer which locally prevents establishment of new species. Ten years later, the moss layer is still an important component of the regenerating heathland. After ten years the pattern of species distribution is mosaic‐like with grassy patches (Agrostis), heath patches (Erica, Flex), and wood (Betula). Processes which may be involved in this successional pattern are discussed. They are found to be pluriform: various strategy types, types of response to disturbance and various succession models operate simultaneously.
Semivariograms from a forest transect gap model compared with remotely sensed data
Authors: Weishampel John F. , Urban Dean L. , Shugart Herman H. , Smith Jackson B. Jr.
Published: May 2006

Abstract. A spatially linked version of a forest gap model, ZELIG, parameterized for the H. J. Andrews Experimental Forest, Oregon, was used to generate structural properties (i.e. biomass, leaf area, and maximum tree height) of young (80 yr), mature (140 yr), and old‐growth (450 yr) Pseudotsuga menziesii (Douglas fir) forests. Semivariograms were produced at 10 and 30 m resolution to describe the spatio‐temporal patterns of variation of the simulated structural features along a 5 km transect of contiguous 10 m x 10 m grid cells. These semivariograms from the simulations were compared with semivariograms from matrices of pixel digital values obtained from aerial videography of similarly aged stands. Although autocorrelative spatial patterning was absent from both the remotely sensed imagery (except at < 20 m for the 450 yr stand) and the model output, the pixel‐to‐pixel and plot‐to‐plot variances exhibited similar patterns across the chronosequence at both resolutions. This suggests that gap models are able to capture temporal aspects of landscape dynamics associated with canopy texture of Pacific Northwest forests.
Natural acidophilous Quercus and Pinus forests in the northern Vosges, France, from a geographical perspective
Authors: Muller Serge
Published: May 2006

Abstract. A phytosociological study of forests on Vosges sandstone in the basins of Pays de Bitche (Bitcherland) resulted in the identification of three plant communities: Luzulo‐Quercetum, Leucobryo‐Pinetum, and Vaccinio uliginosi‐Pinetum. The Luzulo‐Quercetum is an association with a typically sub‐continental distribution; the two communities with Pinus sylvestris are clearly more continental. The Luzulo‐Quercetum oak forest represents a climatic climax and the pine forests are considered edaphic climaxes linked to very dry soils (Leucobryo‐Pinetum) or peaty soils (Vaccinio uliginosi‐Pinetum).

These three associations determine a forest sequence that is typical of sub‐continental areas in which Quercus petraea dominates in the climatic climax. In more continental areas, it is gradually replaced by Pinus sylvestris. Thus, the forest sequence in Pays de Bitche represents a remarkable subcontinental link in the transition from Atlantic oak forests to continental pine forests.
On the statistical analysis of vegetation change: a wetland affected by water extraction and soil acidification
Authors: ter Braak Cajo J.F. , Wiertz Jaap
Published: May 2006

Abstract. A case study is presented on the statistical analysis and interpretation of vegetation change in a wetland subjected to water extraction and acidification, without precise information on the environmental changes. The vegetation is a Junco‐Molinion grassland and the changes in vegetation are evaluated on the basis of relevés in 1977 and 1988 of 20 plots in a small nature reserve on moist oligotrophic, Pleistocene sands in the Netherlands. The changes are attributed to water extraction (since 1972) and soil acidification and the effect of the environmental changes on the vegetation is inferred from data on water depth and acidity collected in 1988.

Many species typical of wetlands decreased in abundance, including rare species such as Parnassia palustris, Selinum carvifolia and Ophioglossum vulgatum. Some species increased, notably Anthoxanthum odoratum, Holcus lanatus and Plantago lanceolata. A significant decrease was found in the mean Ellenberg indicator values for moisture and acidity. The mean indicator value for nutrients did not change significantly.

Multivariate analysis of the species data by Redundancy Analysis demonstrated the overall significance of the change in species composition between 1977 and 1988 (P < 0.01, Monte Carlo permutation). The spatial and temporal variation in the species data was displayed in ordination diagrams and interpreted in terms of water depth and pH.

A simple model is developed to infer the change in water depth and pH from the relevé data and recent data on water depth and pH. Because the correlation between water depth and pH made a joint estimation of the changes useless, the change in pH was estimated for a series of likely changes in water depth. For the most likely change in water depth, significant acidification was inferred from the change in vegetation. The model is more generally applicable as a constrained calibration method.
Three levels of floristical variation in the forests of Chaco, Argentina
Authors: Lewis J. P.
Published: May 2006

Abstract. This paper analyses the floristic variation in the southern segment of the Oriental Chaco, known as the Santa Fe Forest Wedge. Floristical variation in Chaco forests is described at three levels of scale. On the coarsest scale there is a gradient of increasing floristic richness towards the north, related to a geographic temperature gradient. At an intermediate scale different types of forests are arranged according to environmental gradients correlated with topographic elevation. At a fine scale many microsites can be discerned with different micro‐environments colonized differentially by species. Microsites arise as the result of site‐physiographic history, development of vegetation and the interaction of both and with animals. Several dimensions of regenerationniche variation are distinguished, including canopy and soil characteristics, and propagule dispersal.
The relation between vegetation and soil chemistry gradients in a ground water discharge fen
Authors: Boeye Dirk , Verheyen Rudolf F.
Published: May 2006

Abstract. The soil chemistry of a headwater valley fen is influenced by local ground water discharge that supplies base cations and alkalinity to the fen. An irrigation canal just upward of the fen is the source of this alkalinity. The ecological consequences of this artificial system are studied both on the soil and vegetation level. Rich‐fen species of the alliance Caricion davallianae are connected to soil water alkalinity and soil base status. They depend directly on the alkaline ground water discharge. In addition, the local input of this water causes a gradient‐rich pattern from poor to rich fen, and it is therefore concluded that it is responsible for the presence of intermediate fen vegetation too. High nutrient levels in the irrigation water have not influenced the fen until now. This case study illustrates the possibility for rich fen restoration after acidification. Irrigation with alkaline water is efficient if excess nutrients can be removed.
Irregular fruiting in Fraxinus excelsior
Authors: Tapper Per‐Göran
Published: May 2006

Abstract. Data of fruit‐set and fruit production of Fraxinus excelsior (ash) at two sites in the archipelago of Stockholm, Sweden, were recorded over six years (1980‐85), with particular emphasis on the fruiting tendency of individual trees. The aim was to determine the grounds for the irregularity of fruiting. There was no support for the assumption that irregular fruiting originates as a consequence of the fruiting tendency being resource limited. The probability of fruiting in a certain year was neither negatively related to previous fruiting years, nor positively related to climatically favourable years. Seeds were infested by the monophagous moth larva Pseudar‐gyrotoza conwagana. An increased seed survival was noted in times of large seed crops, indicating seed predator satiation. Date of leafing the preceding year determined whether individual trees fruited or not. This relationship may have significance in synchronizing the fruit production of ash trees.
Plant colonization of a bare peat surface: population changes and spatial patterns
Authors: Salonen Veikko , Penttinen Antti , Särkkä Aila
Published: May 2006

Abstract. Changes in size and spatial arrangement of plant populations established on an initially bare peat surface were described over a period of 5 yr by following plant individuals on a 1‐cm grid in an area of 10 m x 25 m. The spatial pattern of populations and association between species was analyzed statistically. The study site was very slowly colonized by 14 perennial plant species. The early successional stage was dominated by Carex rostrata, with a clumped spatial distribution, and the homogeneously distributed Eriophorum vaginatum and Pinus sylvestris. Both the growth in size of populations and changes in their spatial distribution were interpreted as a result of species dispersal ability, tolerance to severity of the substrate and pattern of reproduction.
Ecological response surfaces for North American boreal tree species and their use in forest classification
Authors: Lenihan James M.
Published: May 2006

Abstract. Empirical ecological response surfaces were derived for eight dominant tree species in the boreal forest region of Canada. Stepwise logistic regression was used to model species dominance as a response to five climatic predictor variables. The predictor variables (annual snowfall, degree‐days, absolute minimum temperature, annual soil moisture deficit, and actual evapotranspiration summed over the summer months) influence the response of plants more directly than the annual or monthly measures of temperature and precipitation commonly used in response surface modeling. The response surfaces provided estimates of the probability of species dominance across the spatial extent of North America with a high degree of success. Much of the variation in the probability of dominance is apparently related to the species' individualistic response to climatic constraints within different airmass regions.

A forest type classification for the Canadian boreal forest region was derived by a cluster analysis based on the probability estimates. Five major forest types were distinguished by the application of a stopping rule. The predicted forest types showed a high degree of geographic correspondence with the distribution of forest types in the actual vegetation mosaic. The distribution of the predicted types also bears a direct relationship to seasonal airmass dynamics in the boreal forest region.
Phytosociological survey of the tundra vegetation of the Kola Peninsula, Russia
Authors: Koroleva Natalia E.
Published: May 2006

Abstract. A phytosociological survey of the tundra vegetation of the Kola Peninsula, Russia according to the Braun‐Blanquet approach is presented. The areas examined comprise the treeless zones along the shores of the White Sea and the Barents Sea as well as mountain areas above the timberline. Plant communities were assigned to five alliances: Loiseleurio‐Diapension on dry, wind‐swept habitats on summits and wind‐eroded sites in the lowland; Phyllodoco‐Vaccinion myrtilli on well‐drained soils with intermediate snow cover and moisture status, mostly in the lowlands and lower belts of mountain tundra; Nardo‐Caricion bigelowii comprising early snowbed and Salicion herbaceae late snowbed communities; Adenostylion alliariae comprising mesophilous tall‐herb communities along mountain springs and in wind‐protected and well‐drained sites near the sea shore. A DCA‐ordination showed that two major gradients determine the varation in tundra vegetation, altitude and topography, which are connected to variation in snow cover. The syntaxa described are well‐differentiated, although they form a syntaxonomical continuum.
Past and current trends of change in a dune prairie/oak savanna reconstructed through a multiple‐scale history
Authors: Cole Kenneth L. , Taylor Robert S.
Published: May 2006

Abstract. The history of a rapidly changing mosaic of prairie and oak savanna in northern Indiana was reconstructed using several methods emphasizing different time scales ranging from annual to millennial. Vegetation change was monitored for 8 yr using plots and for 30 yr using aerial photographs. A 20th century fire history was reconstructed from the stand structure of multiple‐stemmed trees and fire scars. General Land Office Survey data were used to reconstruct the forest of A.D. 1834. Fossil pollen and charcoal records were used to reconstruct the last 4000 yr of vegetation and fire history.

Since its deposition along the shore of Lake Michigan about 4000 yr ago, the area has followed a classical primary dune successional sequence, gradually changing from pine forest to prairie/oak savanna between A.D. 264 and 1007. This successional trend, predicted in the models of Henry Cowles, occurred even though the climate cooled and prairies elsewhere in the region retreated. Severe fires in the 19th century reduced most tree species but led to a temporary increase in Populus tremuloides. During the last few decades, the prairie has been invaded by oaks and other woody species, primarily because of fire suppression since A.D. 1972.

The rapid and complex changes now occurring are a response to the compounded effects of plant succession, intense burning and logging in the 19th century, recent fire suppression, and possibly increased airborne deposition of nitrates. The compilation of several historical research techniques emphasizing different time scales allows this study of the interactions between multiple disturbance variables.
Effects of fire on long‐unburned Florida uplands
Authors: Abrahamson Warren G. , Abrahamson Christy R.
Published: May 2006

Abstract. The widespread suppression of fire during the 20th century has created extensive areas of fire‐prone ecosystems that are in long‐unburned condition. Plant species of flatwoods and scrubby flatwoods (= oak scrub) in the southeastern USA possess adaptations that facilitate resprouting, clonal spread, or seeding following fire. While the majority of the woody species of these associations can persist for long periods without fire, fire suppression reduces the populations of ephemeral herbs. Long‐unburned (> 35 yr) flatwoods and scrubby flatwoods were burned after five annual vegetation censuses. Both stands were resampled five times over a >8‐yr recovery period. One recently burned (<20 yr) flatwoods and two recently burned scrubby flatwoods were censused prior to fire and were recensused over a 5‐yr or 11‐yr period following fire depending on the stand. In spite of the variety of recovery strategies and time since fire, there were limited changes in the compositions and structures of post‐burn stands compared to their preburn states. Detrended Correspondence Analysis showed that recently burned stands returned to preburn states within 1–2 yr. However, the reintroduction of a single fire to long‐unburned stands did not restore the populations of herbs typical of recently burned stands. Our results suggest that a single fire may not be effective in restoring flatwoods and scrubby flatwoods that have experienced fire suppression to states more characteristic of recently burned stands.
Density regulation during the regeneration of two monocarpic bamboos: self‐thinning or intraclonal regulation?
Authors: Makita Akifumi
Published: May 2006

Abstract. The population dynamics of two monocarpic bamboos, Sasa kurilensis and S. tsuboiana, were studied for more than 10 years after establishment following mass flowering. Both species show vigorous rhizomatous vegetative reproduction after growing up to maturity, but horizontal expansion in the seedling stage was much more vigorous in S. tsuboiana than in S. kurilensis. The pattern of changes in culm density in the two species was strikingly similar: culm densities of both species increased until they reached full‐density states, after which they decreased in accordance with seedling growth. However, the mode of regulation in culm density was different. S. kurilensis seedlings were composed of only a few culms and scarcely extended their rhizomes during the observation period. Such poor lateral expansion resulted in asymmetric competition as observed in many non‐clonal plants, and consequently their culm density decreased as a result of the mortality of genets due to self‐thinning. In S. tsuboiana seedlings, the number of culms per genet increased considerably by frequent tillering and sprouting from rhizomes. However, after reaching full density state, the Bud Utility Ratio (BUR), (the proportion of the rhizome nodes with culms to the total number of rhizome nodes), decreased drastically. In this manner, S. tsuboiana regulated culm density intraclonally as is observed in the stable states of many clonal plants. Hence it is important for the understanding of the regeneration process in clonal species to clarify when and how their seedlings extend rhizomes during their growth.
Patterns of ordination and classification instability resulting from changes in input data order
Authors: Tausch R.J. , Charlet D.A. , Weixelman D.A. , Zamudio D.C.
Published: May 2006

Abstract. Random rearrangement of entry order in three data sets often changed ordination and classification results based on Reciprocal Averaging. Results varied with the data set and method used. Eliminating infrequently occurring species largely reduced, but did not always eliminate, the variability. Overall, results appeared related to data set complexity, the type of data or transformation, and the analysis method used. Detrended Correspondence Analysis had the greatest variability of the ordination methods tested. Results from quantitative data were usually more variable than presence/absence data. Variation in cluster analysis was related to the number of tie values in the similarity matrix. Detailed tests using randomization of entry order of individual data sets with each of the programs to be used are needed to individually assess the effects on the results.; Keywords:; Cluster analysis; DECORANA; Ecological group; Entry order; Environmental gradient; TWINSPAN
Vertical distribution of below‐ground biomass in intensively grazed mesic grasslands
Authors: Rodríguez Miguel A. , Alvarez Javier , Gómez‐Sal Antonio
Published: May 2006

Abstract. Previous work has shown that below‐ground biomass is more concentrated in surface soil layers in intensively grazed mesic grasslands than in moderately grazed grasslands. However, since the mesic grasslands previously studied shared similar compositional traits, the question remained whether grasslands with differing species composition, and intensive defoliation, showed similar biomass distribution patterns. Eight grasslands at four sites distributed along an elevational gradient were investigated. The upper and lower zones of a slope were sampled at each site. Four of these grasslands were grazed by livestock and the other four were grazed and mown. Biomass was divided into above‐ground, root crown and three root layers.

Species composition varied according to management and topography. Annuals and perennial forbs had relatively more above‐ground biomass at the upper part of the slopes, while perennial grasses dominated the lower parts. The above‐ground biomass and root biomass at 4 — 7 cm depth attained maximum values in the lower, potentially more fertile, parts of the slopes. Crown biomass increased with altitude at the upper part of the slopes. Despite their differences in composition and structure, seven out of the eight stands showed a remarkable concentration of the below‐ground biomass near the soil surface, which decreased drastically with soil depth. This pattern is similar to that observed in the intensively grazed mesic communities studied earlier. This similarity was more evident in the more mesic‐like grasslands, since it increased from the upper, potentially drier parts of the slopes, to the lower parts, and, when each topographic position was considered separately, from low to high elevation.
Successional sequences in two Tasmanian valley Sphagnum peatlands
Authors: Whinam Jennifer , Kirkpatrick J.B.
Published: May 2006

Abstract. The sequences of macrofossils in 17 cores from two Tasmanian valley Sphagnum peatlands reveal a wide variety of successional pathways. The most common sequence is from restiad mires to Sphagnum mires to heath. While it is impossible to conclusively separate allogenic and autogenic influences, it seems likely that the rapid rate of change recorded in the upper levels of the cores may, in part, reflect recent climatic change. Most other changes recorded in the core are likely to be predominantly autogenic.
Impact of grazing on vegetation dynamics in former ricefields
Authors: Mesléard F. , Lepart J. , Tan Ham L.
Published: May 2006

Abstract. In the Rhône delta, Juncus gerardi and Scirpus maritimus are often the dominant species in abandoned rice fields which are artificially flooded in early spring to improve forage production. Under these conditions they occur either in mixed communities, or form monospecific stands. Monitoring the vegetation dynamics in quadrats located in six abandoned rice fields artificially flooded from November to April confirmed the important role of grazing.

In ungrazed plots, communities dominated by Scirpus maritimus mixed with Juncus gerardi developed fast. After 42 months of management Scirpus maritimus had established in nearly all quadrats and continued to expand, whereas Juncus gerardi had started to decline.

In grazed plots Juncus gerardi alone dominated and continued to increase in cover up to the 42nd month. Scirpus maritimus established at low densities mainly in quadrats where Juncus gerardi was initially absent. Introduction of seeds of Scirpus maritimus in communities of Juncus gerardi under controlled conditions demonstrated the existence of the phenomenon of preemption.

The increase in cover of Juncus gerardi suggests that the preemption of Juncus gerardi over Scirpus maritimus plays a more pronounced role in the field in the presence of grazing.
Stem demography of Prosopis glandulosa var. torreyana in vegetation arcs and associated bare areas
Authors: López‐Portillo J. , Montaña C. , Ezcurra E.
Published: May 2006

Abstract. Vegetation arcs are characterized by dense patches of up to 100% plant cover surrounded by bare areas where cover is around 5%. These patterns of contracted vegetation have been reported mainly in alluvial fans of arid and semiarid zones (known as bajadas) with gentle slopes (0.2–2%), summer rainfall, and heavy showers that run as sheet‐flow. It has been suggested that run‐off water from bare areas is stopped at the front of the arcs and, depending on the amount of rainfall, may advance superficially into the arc, reaching the downslope limit less often. These dynamics would imply a gradient of water availability inside the arc, higher at the upper edge. We termed this the moisture gradient hypothesis. We indirectly tested this hypothesis by following the demography of a cohort of stems of the honey mesquite Prosopis glandulosa var. torreyana in three vegetation arcs and their corresponding bare areas during a yearly cycle at the Bolsón de Mapimí in the Chihuahuan Desert. We selectively removed different plant life‐forms (trees, shrubs and herbs) in three positions within the arcs; no manipulation was possible in the bare areas due to low plant cover. The results suggested that removal of other plant life‐forms, mainly grasses, affected growth and survival of mesquite low (but not high) stems, making them accessible to medium‐sized mammal browsers (jackrabbits and packrats). These results suggest that, at least for the honey mesquite, water availability in vegetation arcs was not the most strongly limiting factor for shoot performance and demography, and that browsing damage, a biotic constraint, took precedence over resource limitation.
Treefall gap disturbance in an old‐growth beech forest in southwestern Japan by a catastrophic typhoon
Authors: Ida Hideyuki
Published: May 2006

Abstract. In 1991, the catastrophic Typhoon 9119 created many treefall gaps in an old‐growth beech (Fagus crenata) forest on Mt. Garyu, southwestern Japan. In a 3.3‐ha plot, the density and basal area of fatally damaged trunks (DBH ≥ 20 cm) were 29.1 trunks/ha (16.9% of all pre‐typhoon trunks) and 9.1 m2/ha (24.4% of total pre‐typhoon basal area), respectively. Many of the dominant beech were lost and larger trunks were damaged. The pre‐ and post‐typhoon DBH distribution both had an inverse J‐shape. Spatial distribution of living trunks was not random but clustered irrespective of typhoon damage or DBH size, suggesting that the stand structure of the study plot would be an unusual one as compared with the previous study stands in Japanese beech forests. The death of pre‐typhoon trunks, seemed to die standing or to be killed by snap‐off, occurred singly; however, the typhoon fatally damaged many clustered trunks at the same time. Uprooting was the most frequent cause of gaps created by the typhoon. The intermediate DBH size class (40–70 cm) would be more likely to be uprooted than snapped‐off. The DBH distribution of snap‐off may reflect the total pre‐typhoon trunk distribution. Branch‐fall had a flat DBH distribution. Uprooting might have a clustered distribution, while snap‐off and branch‐fall both had random distributions. The smaller trunks of snap‐off and branch‐fall seemed to result from injuries caused by the fall of larger trunks.
The effect of landscape fragmentation and forest continuity on forest floor species in two regions of Denmark
Authors: Graae B.J.
Published: May 2006

Abstract. Forest species composition was recorded in 82 forests in the Himmerland and Hornsherred regions in Denmark and analysed with respect to isolation (distance to other forests and areas of forest), forest continuity (older or younger than 200 yr), soil pH, tree species composition and seed dispersal groups. Continuity and isolation measures were correlated with forest species richness in Hornsherred. Myrmecochorous, autochorous, anemoballistic and endozoochorous species were markedly fewer in recent than in ancient forests. In Himmerland, patterns were much weaker and few significant correlations were found between forest species richness or different seed dispersal groups and continuity or isolation of the forests. Differences between the two regions may result from less intensive land use, a more humid climate and a smaller species pool with less species with short distance dispersal in Himmerland. Landscape fragmentation therefore appears to limit forest species’recolonization more in Hornsherred than in Himmerland.
Riparian vegetation‐environment relationships: complimentarity of gradients versus patch hierarchy approaches
Authors: van Coller Alan L. , Rogers Kevin H. , Heritage George L.
Published: May 2006

Abstract. Two prominent conceptual frameworks, environmental gradients and patch hierarchies, are used in combination to describe vegetation patterns along a riparian corridor in a semi‐arid South African system. We adopt both approaches, since riparian corridors are characterized by both strong environmental gradients above, away from and along the river, as well as a mosaic of patches in the geomorphology at multiple hierarchical scales. Constrained and unconstrained ordinations were used to determine the variability in vegetation pattern accounted for by the gradient and the geomorphic patch hierarchy data sets. The gradient data set consisted of vertical, lateral and longitudinal dimensions of the macro‐channel, while the patch hierarchy data set consisted of substratum type, morphological unit and channel type. Elevation up the macro‐channel bank, of the gradient data set, explained the main variation in vegetation pattern, and alluded to overriding processes of flooding frequency and water availability as determinants of vegetation pattern. Along the fluvially dynamic macro‐channel floor (lower elevation range), patchiness at the scale of the morphological unit best explained vegetation pattern. This relationship with morphological units suggests that the formation of well developed alluvial bars, and the degree of bedrock influence are important processes. The nested hierarchical framework used provided a good basis for identifying scale specific pattern in a relational manner. In systems characterized by strong environmental gradients as well as a patch mosaic at different spatial and temporal scales, the combined use of both perspectives to develop a fuller understanding of vegetation pattern is imperative and is encouraged.
Spatial distribution of Eurya japonica in an old‐growth evergreen broad‐leaved forest, SW Japan
Authors: Manabe Tohru , Yamamoto Shin‐Ichi
Published: May 2006

Abstract. The spatial distribution of Eurya japonica, an evergreen understorey species, was studied on a 4‐ha permanent plot in an old‐growth, temperate, evergreen broad‐leaved forest in southwestern Japan. The pattern of spatial dispersion varied with size class, the environmental heterogeneity produced by tree‐fall gaps and microtopography and the scale of observation. Seedlings (0.05 to < 0.5 m high) had the most clumped distributions, followed by saplings (0.5 to 1.3 m high) and adults (> 1.3 m). Individuals were more clumped at the smallest grid size, 1.56m × 1.56 m, and became less clumped as grid size increased for all size classes. On grids of less than 6.25 m × 6.25 m, no spatial correlations were found between seedlings and larger size classes; positive spatial correlations were found between saplings and adults at this scale. Abundant seedlings appeared in tree‐fall gaps formed by uprooted trees, but seedlings were frequent on ridge tops and upper slopes. Saplings and adults also occurred on upper slopes, but their spatial distribution had little relation to current tree‐fall gaps. The spatial distribution of E. japonica individuals was largely attributed to the distribution of tree‐fall gaps and the differential responses to microtopographic variation by individuals at different size classes.
Small‐scale spatial pattern and size structure of Rubus hirtus in a canopy gap
Authors: Pancer‐Koteja Elżbieta , Szwagrzyk Jerzy , Bodziarczyk Jan
Published: May 2006

Abstract. The response of a Rubus hirtus population to the creation of a new forest gap was analysed. All individuals in two 30‐m2 plots – one in a gap and one with full canopy cover – were mapped and the length of Rubus shoots measured. This was done 1, 2, 3, 4, and 7 yr after creation of the gap. Spatial patterns were analysed using Ripley's K‐method. Although the density of Rubus in the gap increased from 3 to 24 rooting points/m2, the change in spatial pattern of individuals over 7 yr was very limited. During the first four years a clumped pattern appeared at distances of > 0.5 m. After seven years the pattern was random at all distances. Young shoots spread in all directions with equal probability. The expansion was achieved by establishment of new ramets, increase in the number of shoots per rooting point playing a minor role. Individual plants contributed to gap filling very unequally; few of them produced many rooting points. The average size of canes and the proportion of tip‐rooting canes were highest in the second year after the gap formation.
The use of wavelets for spatial pattern analysis in ecology
Authors: Dale M.R.T. , Mah M.
Published: May 2006

Abstract.We investigate the characteristics of the wavelet transform as an approach to analyzing spatial pattern. Compared to the familiar methods of paired quadrat or blocked quadrat variance calculations, the wavelet method seems to offer several advantages. First, when wavelet variance is plotted as a function of scale, the peak variance height is determined by pattern intensity and does not increase with scale and, depending on the wavelet chosen, the position of the variance peak matches the scale exactly. Second, the method produces only faint resonance peaks, if any, and third, by using several different wavelet forms, different characteristics of the pattern can be investigated. Fourth, the method is able to portray very clearly trends in the data, when the pattern is non‐stationary. Lastly, the wavelet position variance can be used to identify patches and gaps in data with random error. We demonstrate these characteristics using artificial data and data from previously published studies for comparison. We show that two versions of the familiar blocked quadrat variance technique are forms of wavelet analysis.
Species associations and nurse plant effects in patches of high‐Andean vegetation
Authors: Nuñez Cecilia I. , Aizen Marcelo A. , Ezcurra Cecilia
Published: May 2006

Abstract. In high‐elevation communities of the southern Andes, plant cover is low due to severe environmental conditions and vegetation occurs mostly as isolated small (< 1 m2) patches. Most patches are dominated by flat cushion plants. We evaluated patterns of plant species co‐occurrence and species affinity for patches with and without cushion plants and different species richness. We mapped and recorded species composition of patches occurring within two 20 m × 20 m plots at the NE slope of Cerro Chall‐Huaco, Nahuel Huapi National Park, Argentina. In these plots, we identified 32 and 24 plant species, and a maximum of 15 and 12 species per patch, respectively. The community was characterized by positive associations between species. Patches in which either of the common cushion plants Mulinum leptacanthum and Oreopolus glacialis occurred sustained richer communities than patches in which they were absent. Patches dominated by different cushion plants did not differ in species composition, but species differed in their affinities for patches with different numbers of species. Because richness increased with patch size and patch size with time, differential affinities of plant species suggest that successional changes take place in the patches. Some small herbaceous species appear to act as late colonizers, mostly restricted to species‐rich patches. Flat cushion plants are considered ‘nurse plants’; they strongly modify micro‐environmental conditions and allow establishment and survival of associated species.
Computerized classification of Mediterranean vegetation using panchromatic aerial photographs
Authors: Carmel Yohay , Kadmon Ronen
Published: May 2006

Abstract.Historical aerial photographs are an important source for data on medium‐ to long‐term (10 ‐ 50 yr) vegetation changes. Older photographs are panchromatic, and manual interpretation has traditionally been used to derive vegetation data from such photographs. We present a method for computerized analysis of panchromatic aerial photographs, which enables one to create high resolution, accurate vegetation maps. Our approach is exemplified using two aerial photographs (from 1964 and 1992) of a test area on Mt. Meron, Israel. Spatial resolution (pixel size) of the geo‐rectified photos was 0.30 m and spatial accuracy (RMS error) ca. 1 m. An illumination adjustment prior to classification was found to be essential in reducing misclassification error rates. Two classification approaches were employed: a standard maximum‐likelihood supervised classifier, and a modification of a supervised classification, which takes into account spectral properties of individual pixels as well as their neighbourhood characteristics. Accuracy of the maximum likelihood classification was 81 % in the 1992 image and 54 % in the 1964 image. The neighbour classifier increased accuracy to 89 % and 82 % respectively. The overall results suggest that computerized analysis of sequences of panchromatic aerial photographs may serve as a valuable tool for the quantification of medium‐term vegetation changes.
Stem demography and post‐fire recruitment of a resprouting serotinous conifer
Authors: Keeley Jon E. , Keeley Melanie B. , Bond William J.
Published: May 2006

Abstract. The contribution of resprouts and seedling recruitment to post‐fire regeneration of the South African fynbos conifer Widdringtonia nodiflora was compared eight months after wildfires in 1990. Stems on all trees were killed by fire but resprouting success was > 90 % at all but one site. A demographic study of burned skeletons revealed that prior to these fires, nearly all plants were multi‐stemmed (4–9 stems/plant) and multi‐aged, indicating continuous sprout production between fires. All stems were killed by these 1990 fires and at most sites > 90 % of the stems were burned to ground level. All diameter stems were susceptible to such incineration as, at most sites, there was no difference in average diameter of stems burned to ground level and those left standing. Individual genets usually had all ramets incinerated to ground level or all ramets charred, but intact, suggesting certain micro‐sites burned hotter, whereas other sites were somewhat protected. Although not true of the 1990 fires, there was evidence that occasionally Widdring‐tonia stems may survive fire. At one site, four of the 16 plants sampled had a burned stem twice as old as the oldest burned stem on the other 12 plants at the site, suggesting some stems had survived the previous fire (ca. 1970) and this conclusion was supported by fire‐scars on these four stems that dated to ca. 1970. Based on the highly significant correlation between stem diameter and cone density left standing after the 1990 fires, we calculated that for most sites > 80 % of the initial cone crop was incinerated by fire. This is important because we observed a strong relationship between size of the canopy cone crop surviving fire and post‐fire seedling recruitment. Under these conditions we hypothesize that sprouting confers a selective advantage to genets when fires cause heavy losses of seed. The infrequent occurrence of sprouting in the Cupressaceae suggests the hypothesis that resprouting is an apomorphic or derived trait in Widdringtonia. Data from this study suggests resprouting provides a selective advantage under severe fynbos fires, which are not only 'stand‐replacing fires,’but also are intense enough to incinerate cone‐bearing stems.
Seed predation, disease and germination on landslides in Neotropical lower montane wet forest
Authors: Myster Randall W.
Published: May 2006

Abstract. Seed mortality (caused by predators and pathogens) and germination were compared between Puerto Rico and Costa Rica on landslides in lower montane wet forest. Seeds of six common species on five Puerto Rican landslides and four common species on two Costa Rican landslides were used with a Cecropia species and a Gonzalagunia species included at both sites. In the Puerto Rican experiments Cecropia schreberiana was the only species to show significant seed predation (which was due to insects), pathogens grew from all species and fewer seeds were lost to predators than pathogens. Also in Puerto Rico mean germination across all species was 57 % before dispersal (filled seeds collected while still on the tree) and 71 % after, with Phytolacca rivinoides seeds germinating most abundantly, followed in descending order by Ocotea leucoxylon, Cecropia spec, Miconia racemosa, Palicourea riparia and Gonzalagunia spicata. In the Costa Rican experiments three species had significant predation: Cecropia polyphlebia and Urera caracasana (both due to insects) and Witheringia coccoloboides (due to mammals); pathogenic disease caused more seed loss than predation, and germination was high (61 % pre‐dispersal, 69 % post‐dispersal).

Similarities between these island and mainland sites included (1) percentage of seeds lost to predation and percentage lost to pathogens (all in the 5–15 % range), (2) generalist pathogens which claimed more seeds than predators and (3) majority germination with a general increase after dispersal. Finally sites were dissimilar only in the number of species with significant predation loss and whether it was by insects or mammals, casting doubt on the traditional island/mainland dichotomy.
Effect of root competition and shading on resprouting dynamics of Erica multiflora L.
Authors: Vilá Montserrat
Published: May 2006

Abstract. Resprouting from underground structures is one of the main regeneration strategies of Mediterranean shrubs after aerial biomass disturbance such as fire or clear‐cutting to reduce fire risk. In order to study the effect of root competition and shading (simulated shoot competition) on Erica multiflora, growth, morphology, flowering performance and sprout size variability during resprouting, a factorial field experiment was conducted in which neighbours around target plants were eliminated and plants were shaded with mesh for two years. Root competition reduced sprout recruitment and sprout density (number of sprouts per unit stump area) more strongly than did shading. The negative effect of root competition on sprout biomass was constant with time, while the reduction due to shading increased with time. There was an interaction between root competition and shading on the biomass of sprouts 22 months after treatment: genets without root competition and shading were four times larger than in any other treatment. Both shading and root competition also decreased percentage branching but did not modify maximum sprout height. Only shading decreased the leaf/shoot biomass ratio and the percentage of flowering genets. One year after resprouting, root competition counteracted the effect of shading on inducing sprout biomass variability within the genet because it decreased sprout density. 22 months after treatment, sprout biomass variability was not affected by any main effect. The results suggest that competition among sprouts within the genet is asymmetric. However, shading by genet neighbours may not always increase sprout biomass variability if root competition is also severe.
BOOK REVIEWS
Authors: Baskin Jerry M.
Published: May 2006

Book reviewed in this article:

Williams, J.E. & Woinarski, J.C.Z. (eds.) 1997. Eucalypt ecology: Individuals to ecosystems. xii + 430 pp. Cambridge University Press, Cambridge. ISBN 0 521 49740 X (hardback). Price USD 150.‐.
Tropical forest diversity, environmental change and species augmentation: After the intermediate disturbance hypothesis
Authors: Sheil Douglas
Published: May 2006

Abstract.It is not simple to predict how environmental changes may impact tropical forest species diversity. Published hypotheses are almost invariably too incomplete, too poorly specified and too dependent upon unrealistic assumptions to be useful. Ecologists have sought theoretical simplicity, and while this has provided many elegant abstract concepts, it has hindered the attainment of more practical goals. The problem is not how to judge the individual hypotheses and arguments, but rather how to build upon and combine the many hard‐won facts and principles into an integrated science.

Controversy is inevitable when the assumptions, definitions and applications of a given hypothesis are unclear. Elegance, as an end in itself, has too often been used to justify abstract simplification and a lack of operational definition. Clarifying and combining hypotheses while avoiding assumptions provides a potentially more useful, if less elegant, standpoint. An appraisal of Connell's intermediate disturbance hypothesis, and its application to long‐term observations from a Ugandan forest illustrates these concerns.

Current emphases encourage ecologists to exclude consideration of environmental instability and non‐pristine ecosystems. In reality, many environmental changes and ecological processes contribute to both the accumulation and erosion of diversity, at all spatial and temporal scales. Site histories, contexts, long‐term processes, species‐pool dynamics, and the role of people require greater emphasis. These considerations reveal that many environmental changes, even those associated with degradation, can lead to a transient rise in species densities. Drawing on related studies, such as forest yield prediction, suggests that the formulation and calibration of simulation models provides the most tractable means to address the complexity of real vegetation. Simulation‐based approaches will become increasingly useful both in unifying the study of vegetation dynamics and in providing improved predictive capacity. Quantification of the processes, scales and sensitivities of the dynamics of tropical forest communities remains a major challenge.
The bootstrapped ordination re‐examined
Authors: Pillar Valério DePatta
Published: May 2006

Abstract. A method is described to determine the number of significant dimensions in metric ordination of a sample. The method is probabilistic, based on bootstrap resampling. An iterative algorithm takes bootstrap samples with replacement from the sample. It finds in each bootstrap sample ordination coordinates and computes, after Procrustean adjustments, the correlation between observed and bootstrap ordination scores. It compares this correlation to the same parameter generated in a parallel bootstrapped ordination of randomly permuted data, which upon many iterations will generate a probability. The method is assessed in principal coordinates analysis of simulated data sets that have varying number of variables and correlation levels, uniform or patterned correlation structure. The results suggest the method is more reliable than other available methods in recovering the true intrinsic dimensionality. Examples with grassland data illustrate utility.