The inselberg flora of Atlantic Central Africa. I. Determinants of species assemblages

Aims To identify the relative contributions of environmental determinism, dispersal limitation and historical factors in the spatial structure of the floristic data of inselbergs at the local and regional scales, and to test if the extent of species spatial aggregation is related to dispersal abilities. Location Rain forest inselbergs of Equatorial Guinea, northern Gabon and southern Cameroon (western central Africa). Methods We use phytosociological relevés and herbarium collections obtained from 27 inselbergs using a stratified sampling scheme considering six plant formations. Data analysis focused on Rubiaceae, Orchidaceae, Melastomataceae, Poaceae, Commelinaceae, Acanthaceae, Begoniaceae and Pteridophytes. Data were investigated using ordination methods (detrended correspondence analysis, DCA; canonical correspondence analysis, CCA), Sørensen's coefficient of similarity and spatial autocorrelation statistics. Comparisons were made at the local and regional scales using ordinations of life‐form spectra and ordinations of species data. Results At the local scale, the forest‐inselberg ecotone is the main gradient structuring the floristic data. At the regional scale, this is still the main gradient in the ordination of life‐form spectra, but other factors become predominant in analyses of species assemblages. CCA identified three environmental variables explaining a significant part of the variation in floristic data. Spatial autocorrelation analyses showed that both the flora and the environmental factors are spatially autocorrelated: the similarity of species compositions within plant formations decreasing approximately linearly with the logarithm of the spatial distance. The extent of species distribution was correlated with their a priori dispersal abilities as assessed by their diaspore types. Main conclusions At a local scale, species composition is best explained by a continuous cline of edaphic conditions along the forest‐inselberg ecotone, generating a wide array of ecological niches. At a regional scale, these ecological niches are occupied by different species depending on the available local species pool. These subregional species pools probably result from varying environmental conditions, dispersal limitation and the history of past vegetation changes due to climatic fluctuations.     

Reproductive phenology of coastal plain Atlantic forest vegetation: comparisons from seashore to foothills

The diversity of tropical forest plant phenology has called the attention of researchers for a long time. We continue investigating the factors that drive phenological diversity on a wide scale, but we are unaware of the variation of plant reproductive phenology at a fine spatial scale despite the high spatial variation in species composition and abundance in tropical rainforests. We addressed fine scale variability by investigating the reproductive phenology of three contiguous vegetations across the Atlantic rainforest coastal plain in Southeastern Brazil. We asked whether the vegetations differed in composition and abundance of species, the microenvironmental conditions and the reproductive phenology, and how their phenology is related to regional and local microenvironmental factors. The study was conducted from September 2007 to August 2009 at three contiguous sites: (1) seashore dominated by scrub vegetation, (2) intermediary covered by restinga forest and (3) foothills covered by restinga pre-montane transitional forest. We conducted the microenvironmental, plant and phenological survey within 30 transects of 25 m × 4 m (10 per site). We detected significant differences in floristic, microenvironment and reproductive phenology among the three vegetations. The microenvironment determines the spatial diversity observed in the structure and composition of the flora, which in turn determines the distinctive flowering and fruiting peaks of each vegetation (phenological diversity). There was an exchange of species providing flowers and fruits across the vegetation complex. We conclude that plant reproductive patterns as described in most phenological studies (without concern about the microenvironmental variation) may conceal the fine scale temporal phenological diversity of highly diverse tropical vegetation. This phenological diversity should be taken into account when generating sensor-derived phenologies and when trying to understand tropical vegetation responses to environmental changes.     

Forest classification in an Amazonian rainforest landscape using pteridophytes as indicator species

Habitat classification systems are poorly developed for tropical rainforests, where extremely high plant species richness causes numerous methodological difficulties. We used an indicator species approach to classify primary rainforest vegetation for purposes of comparative wildlife habitat studies. We documented species composition of pteridophytes (ferns and fern allies) in 635 plots (2×100 m) along 8 transects within a continuous rainforest landscape in northeastern Peruvian Amazonia. Considerable floristic variation was found when the data were analyzed using multivariate methods. The obtained forest classification was interpreted with the help of indicator value analysis and known soil preferences of the pteridophyte species. The final classification included four forest types: 1) inundated forests, 2) terrace forests, 3) intermediate tierra firme forests and 4) Pebas Formation forests. This rapid and relatively simple vegetation classification technique offers a practical, quantitative method for large-scale vegetation inventory in complex rainforest landscapes.     

西双版纳森林植被研究

西双版纳是世界生物学多样性保护的关键和热点地区,倍受国际学术界的关注。笔者依据30多年来对西双版纳植被的调查,结合植物群落生态学与植物区系地理学研究,并参考世界类似热带植被的研究成果,对西双版纳植被的分类、物种组成、群落生态表现和植物区系特征等作了系统探讨,还进一步分析比较了其与世界类似热带森林植被的关系。结果显示,西双版纳的森林植被共包括32个较为典型的群系,且分属于7个主要的植被型,即热带雨林、热带季节性湿润林、热带季雨林、热带山地(低山)常绿阔叶林、热带棕榈林、暖热性针叶林和竹林。本文对西双版纳植被进行的全面记录和系统归纳,可为科学研究、生物多样性保护和自然保护区的管理提供参考。     

Plant Species Diversity in the Southern Part of the Taï National Park (Côte d’Ivoire)

Plant species diversity is surveyed in the southern part of the Taï National Park (TNP), Côte d’Ivoire. This park is the largest remaining tract of pristine forest in the West African rainforest biodiversity hotspot. Plant assemblages and environment factors were surveyed in 39 temporary 625-m² plots within three areas. The species list was completed thanks to itinerant prospections. TWINSPAN classification and detrended correspondence analysis were applied to the 39 relevés. We recorded a total of 916 plant species, including 169 West African endemics, that rises the floristic richness of TNP in 1233 species. Most plant species recorded were Guineo-Congolian species (90.9%) among which 8% were ‘Sassandrian species’, i.e. endemics of the extreme southwest Côte d’Ivoire. Eight of these endemics were exclusive of the southern part of TNP. The forest is very species-rich, particularly in Rubiaceae, Leguminosae and Euphorbiaceae. Most of the sampled species (59.5%) were erect phanerophytes with a dbh≤10 cm. We distinguished 7 plant community types, mainly determined by geomorphology and disturbance history. Lowland forests were typical dense evergreen forests with different degrees of maturity related to historical human impact. Inselbergs and swampy depressions provide an original azonal vegetation. We conclude that the southern part of TNP contributes significantly to the regional biodiversity hotspot since it includes the last remnants of primary evergreen rainforest and contains species assemblages from both higher rainfall biomes on moist soils derived from schist parent material and lower rainfall biomes on inselberg slopes and top. As anthropogenic disturbance clearly reduces biodiversity, these last remnants should be integrally protected.     

Vegetation composition,structure and soil properties across coastal forest–barren ecotones

Coastal barrens support rare plant species but may be threatened by forest encroachment. We determined whether trees spread into coastal barren habitat from forest patches and assessed plant species composition and soil properties across the forest–barren ecotone. We quantified tree age and height, soil properties, and vascular plant, bryophyte and lichen species composition along transects perpendicular to the edges of tree patches within the forest–barren ecotone in coastal Nova Scotia. Randomization tests assessed whether the vegetation and environmental characteristics were significantly different in the transition zone compared to one or both adjoining ecosystems. We used ordination to examine trends in species composition across the ecotone and the relationship to environmental variables. Tree age and height decreased continuously from the forest towards the edge of the forest patches. There were also trends in vegetation composition and structure from the forest into the open barrens. Many species were most abundant within the transition zone, although not always significantly. Soil properties were relatively uniform across the ecotone. The structure and vegetation of the forest–barren ecotone suggests that forest patches act as nuclei for forest expansion on barrens with a typical successional pathway where coastal barren vegetation is gradually replaced by forest species. This encroachment may pose a threat to rare barrens communities. While landscape factors such as salt spray and wind exposure may determine the general locations where forest can establish, biotic processes of growth and dispersal appear to govern the fine-scale expansion of tree patches.     

Nitrogen input by cyanobacterial biofilms of an inselberg into a tropical rainforest in French Guiana

Inselbergs are isolated rock outcrops displaying high heterogeneity in both soil formation and microclimatic condition with high variation in plant biodiversity. Vegetation patterns on inselbergs in the humid tropics range from rocks covered with dense biofilms predominated by cyanobacteria to high forest on deep soils. Along a similar transect, we investigated N supply to the vegetation using element and isotopic analyses of soil and biofilm samples from an inselberg in French Guiana. An increase in N content related to total dry weight (N%) in soils from the inselberg peak to surrounding habitats was related to changes in stable isotope composition (δ¹⁵N). At the inselberg peak cyanobacterial biofilms on bare rocks and soils within small vegetation islands had similar δ¹⁵N values of −1.9‰ and −1.3‰ while δ¹⁵N of soils progressively increased towards the primary rainforest up to 6‰. From the peak towards the base of the inselberg, the density of higher plants and soil depth increased. Hence, soil N cycling and N losses to the environment resulted in a progressive increase of soil δ¹⁵N. The distribution of N%, δ¹⁵N and δ¹³C values suggest that the main N supply for soils at and nearby the inselberg is derived from cyanobacterial N₂ fixation through leaching processes.     

Land-use history affects understorey plant species distributions in a large temperate-forest complex,Denmark

In Europe, forests have been strongly influenced by human land-use for millennia. Here, we studied the importance of anthropogenic historical factors as determinants of understorey species distributions in a 967 ha Danish forest complex using 156 randomly placed 100-m² plots, 15 environmental, 9 spatial, and 5 historical variables, and principal components analysis (PCA), redundancy analysis (RDA) as well as indicator species analysis. The historical variables were status as ancient (1805 AD) high forest, reclaimed bogs, ≤100 m from Bronze Age burial mounds, or former conifer plantation, and stand age. The PCA results showed that the main gradients in species composition were strongly related to the explanatory variables. Forward variable selection and variation partitioning using RDA showed that although modern environment was the dominant driver of species composition, anthropogenic historical factors were also important. The pure historical variation fraction constituted 13% of the variation explained. The RDA results showed that ancient-forest status and, secondarily, reclaimed bog status were the only significant historical variables. Many typical forest interior species, with poor dispersal and a strong literature record as ancient-forest species, were still concentrated in areas that were high forest in 1805. Among the younger forests, there were clear floristic differences between those on reclaimed bogs and those not. Apparently remnant populations of wet-soil plants were still present in the reclaimed bog areas. Our results emphasize the importance of historical factors for understanding modern vegetation patterns in forested landscapes.     

A multivariate approach to identify vegetation belts: Gallery forest and its surrounding savanna along the river Kota in north Benin

Abstract

The floristic composition and spatial structure of a West African riverine forest in north-western Benin were studied in order to identify vegetation zones and their arrangement and composition. Data were collected on five continuous belt transects and were analysed using multivariate methods. A total of 133 tree taxa from 34 plant families were identified, with Rubiaceae and Leguminosae-Papilionoideae as the most frequent families. Fifteen homogeneous transect sections were documented. Near-river sections were dominated by water-demanding species (Syzygium guineense, Garcinia ovalifolia, Berlinia grandiflora, Breonardia salicina) (=gallery forest), whereas uphill sections were characterised by savanna species (Terminalia laxiflora, Hymenocardia acida, Detarium microcarpum, Burkea africana) (= savanna). The shift from gallery forest to savanna was reflected by a floristic turnover and the different physiognomy of the vegetation, although diversity values for gallery forest and savanna were very similar. In the Principal Co-ordinates Analysis (PCoA), gallery forest and savanna sections did not overlap. Parallel sections at both sides of the river could be linked by isolines following the topography parallel to the river, resulting in a continuous gallery forest belt (width between 10 and 30 m) flanked by savanna. Tree species typical for gallery forests have wider areas of distribution than savanna species.     

Are landscape attributes a useful shortcut for classifying vegetation in the tropics? A case study of La Amistad International Park

Effective vegetation classification schemes identify the processes determining species assemblages and support the management of protected areas. They can also provide a framework for ecological research. In the tropics, elevation‐based classifications dominate over alternatives such as river catchments. Given the existence of floristic data for many localities, we ask how useful floristic data are for developing classification schemes in species‐rich tropical landscapes and whether floristic data provide support for classification by river catchment. We analyzed the distribution of vascular plant species within 141 plots across an elevation gradient of 130 to 3200 m asl within La Amistad National Park. We tested the hypothesis that river catchment, combined with elevation, explains much of the variation in species composition. We found that annual mean temperature, elevation, and river catchment variables best explained the variation within local species communities. However, only plots in high‐elevation oak forest and Páramo were distinct from those in low‐ and mid‐elevation zones. Beta diversity did not significantly differ in plots grouped by elevation zones, except for low‐elevation forest, although it did differ between river catchments. None of the analyses identified discrete vegetation assemblages within mid‐elevation (700–2600 m asl) plots. Our analysis supports the hypothesis that river catchment can be an alternative means for classifying tropical forest assemblages in conservation settings.     

Biodiversity and vegetation of small-sized inselbergs in a West African rain forest (Taı, Ivory Coast)

The vegetation of small granitic rock outcrops (geomorphologically small-sized inselbergs) which do not reach the canopy was studied in the Taı rain forest (southwestern Ivory Coast) under aspects of species diversity and phytogeographical affinities. Rock outcrops form edaphically arid (due to absent or very sparse soil cover) and microclimatologically xeric (i.e. low air humidity, temperature regularly exceeding 50°C) islands with cryptogamic crusts, succulents and poikilohydric vascular plants as characteristic elements of their vegetation which differs totally from the surrounding forest. Altogether sixty-six species of vascular plants out of twenty-nine families occur, the number of species correlates positively with inselberg size. Compared with large inselbergs the microclimatic attributes of small-sized rock outcrops are less pronounced. This is accompanied by a decrease of typical inselberg taxa (i.e. species mainly occurring on inselbergs). Low beta diversity between inselbergs indicates deterministic influences as important regulators of species composition. Annual Poaceae and Cyperaceae are richly represented. It can be hypothesized that inselbergs may represent natural growing sites of widely distributed tropical weeds today. Inselbergs might provide habitat resources for savanna elements in rain forest zones.     

Avian Composition Co‐varies with Floristic Composition and Soil Nutrient Concentration in Amazonian Upland Forests

Spatial heterogeneity in the plant species composition of tropical forests is expected to influence animal species abundance and composition because vegetation constitutes the primary habitat feature for forest animals. Floristic variation is tied to variation in soils, so edaphic properties should ultimately influence animal species composition as well. The study of covariation in floristic and faunistic turnover has been hindered by the difficulty of completing coordinated surveys in hyperdiverse tropical communities, but this can be overcome with the use of a few plant taxa that function as surrogates for general floristic turnover. We used avian and plant transect surveys and soil sampling in a western Amazonian upland (terra firme) forest landscape to test whether spatial variation in bird community composition is associated with floristic turnover and corresponding edaphic gradients. Partial Mantel tests and Non‐metric Multidimensional Scaling showed floristic distinctiveness between two forest types closely associated with differences in soil cation concentrations, and differences in both floristic composition and cation concentrations were further linked to compositional differences in avian species, independent of geographic distances among sites. Ten percent of bird species included in Indicator Species Analyses showed significant associations with one of the two forest types. The upland forest types that we sampled, each corresponding to a different geological formation, are intermediate relative to edaphically extreme environments in the region. Models of avian diversification should take into account this environmental heterogeneity, as should conservation planning approaches that aim to represent faunal diversity. Abstract in Spanish is available in the online version of this article.     

Woody plant communities of isolated Afromontane cloud forests in Taita Hills,Kenya

In the Taita Hills in southern Kenya, remnants of the original Afromontane forest vegetation are restricted to isolated mountain peaks. To assess the level of degradation and the need for forest restoration, we examined how forest plant communities and their indicator species vary between and within remnant patches of cloud forest. We used ordinal abundance data to compare plant communities in eight forest fragments. We also analyzed data on the diversity and abundance of trees in 57 0.1 ha plots to compare tree communities within and between the largest two of these fragments, Ngangao (120 ha) and Mbololo (220 ha). The extant vegetation of the Taita Hills at landscape scale consists of secondary moist montane to intermediate montane forest. There was a high species dissimilarity between fragments (69%). Variation in species composition coincided with an abiotic gradient related to elevation. At plot level, secondary successional species and species of forest edges were most abundant and most frequent. Inferred clusters of plots almost entirely coincided with the two forest fragments. Indicator species associated with forest margins and gaps were more frequent in the smaller of the two forest fragments, while indicators for the larger fragment were more typical for less disturbed moist forest. Abiotic site variability but also different levels of disturbance determine site-specific variants of the montane forest. Conservation efforts should not only focus on maintaining forest quantity (size), but also on forest quality (species composition). Late-successional rainforest species are underrepresented in the woody plant communities of the Taita Hills and assisting restoration of viable populations of cloud forest climax tree species is urgently needed.     

Spatial distribution and floristic composition of trees and lianas in different forest types of an Amazonian rainforest

A quantitative inventory of trees and lianas was conducted (1) to compare floristic composition, diversity and stem density variation between three different forest types (tierra firme, floodplain and swamp), and (2) to analyse the relationships between floristic similarity and forest structure in two regions ~60 km apart in Yasuní National Park, Amazonian Ecuador. A total of 1,087 species with a diameter at breast height ≥ 2.5 cm were recorded in 25 0.1-ha plots. Tierra firme was the habitat with the highest number of species and stem density for trees and lianas, followed by floodplain and swamp in both regions. Two hypotheses that have been independently proposed to describe plant distribution in tropical rain forests, together explain species spatial distribution in this study. The fact that the 30 most important species per forest type (totalling 119 species) accounted for 48.2% of total individuals supports the oligarchy hypothesis. Likewise, 28 out of these 119 species are reported as restricted to a single forest type, which supports the environmental-determinism hypothesis. In general, both canopy and understorey trees and lianas showed rather similar floristic patterns across different forest types and regions.     

Interactive effects of vegetation structure and composition describe bird habitat associations in mixed broadleaf–conifer forest

The effects that changes in forest structure and composition have on wildlife have often been considered independently, such that the potential for interactive effects has received relatively little attention. We investigated the importance of vegetation structure, floristic composition, and their interaction for predicting bird distribution in mixed broadleaf–conifer forest. We collected vegetation and bird data at 979 stations in a watershed in southern Oregon in the spring of 2001. At each station, we described the vegetation using measures of structure (total vegetation volume) and of floristic composition (broadleaf–conifer composition). We then used logistic regression to model the probability of occurrence of bird species as a function of these 2 variables, their quadratic terms, and their interaction. Using stepwise model selection we identified the best model for each species and used area under the curve (AUC) scores to evaluate model performance. Of the 44 bird species we investigated, 20 had models with AUC scores ≥0.70. Of the best models for these 20 species, 1 included vegetation composition alone, 12 included just the main effects of vegetation composition and structure, and 7 included both the main effects and interaction terms. In summer of 2001 a wildfire burned 2,500 ha of the study area, resulting in substantial changes in the vegetation structure and composition. We used 4 yr of postfire bird and vegetation surveys to test the predictive performance of the habitat models for 9 species that occurred at >15% of the burned stations. Models for 3 of these species performed poorly (AUC < 0.7) in all 4 yr. For the other 6 species, predictive performance was low in the first year after fire and improved during subsequent years, suggesting a lagged response to changes in vegetation structure and composition. Quantifying the interactive effects of vegetation structure and composition improves our understanding of how birds respond to forest management and large-scale disturbances, such as wildfires. © 2011 The Wildlife Society.     

Rainforest expansion reduces understorey plant diversity and density in open forest of eastern Australia

The expansion of rainforest pioneer trees into long‐unburnt open forests has become increasingly widespread across high rainfall regions of Australia. Increasing tree cover can limit resource availability for understorey plant communities and reduce understorey diversity. However, it remains unclear if sclerophyll and rainforest trees differ in their competitive exclusion of understory plant communities, which contain most of the floristic diversity of open forests. Here, we examine dry open forest across contrasting fire histories (burnt and unburnt) and levels of rainforest invasion (sclerophyll or rainforest midstorey) to hindcast changes in understorey plant density, richness and composition. The influence of these treatments and other site variables (midstorey structure, midstorey composition and soil parameters) on understorey plant communities were all examined. This study is the first to demonstrate significantly greater losses of understorey species richness, particularly of dry open‐forest specialists, under an invading rainforest midstorey compared to a typical sclerophyll midstorey. Rainforest pioneers displaced over half of the understorey plant species, and reduced ground cover and density of dry forest specialists by ~90%. Significant understorey declines also occurred with increased sclerophyll midstorey cover following fire exclusion, although losses were typically less than half that of rainforest‐invaded sites over the same period. Understorey declines were closely related to leaf area index and basal area of rainforest and wattle trees, suggesting competitive exclusion through shading and potentially belowground competition for water. Around 20% of displaced species lacked any capacity for population recovery, while transient seed banks or distance‐limited dispersal may hinder recovery for a further 68%. We conclude that rainforest invasion leads to significant declines in understorey plant diversity and cover in open forests. To avoid elimination of local native plant populations in open forests, fires should occur with sufficient frequency to prevent overstorey cover from reaching a level where shade‐intolerant species fail to thrive.     

Cryptogams on decaying wood in old-growth forests of southern coastal British Columbia

Abstract. We studied the floristic composition of lignicolous cryptogams (i.e. bryophytes and lichens inhabiting decaying wood) in the old-growth coniferous forests of southern coastal British Columbia. The composition of the cryptogams was related to forest communities (described by vegetation units using forest floor cryptogams and vascular plants) and regional climates (described by biogeoclimatic zones). The study is based on a total of 247 sample plots, each of 0.04 ha in size. The plots were located in three different biogeoclimatic zones and were classified into 12 alliances and four orders in a previous study. We used indicator species analysis to determine cryptogam indicator species for each vegetation unit and biogeoclimatic zone, and used similarity analysis and multi-variate analyses (discriminant analysis and detrended correspondence analysis) to detect differences in the floristic composition of the cryptogams among sample plots, vegetation units, and biogeoclimatic zones. Most of the cryptogams in this study had a narrow distribution, and only < 5% of the species were present across all the vegetation units and biogeoclimatic zones. The overall means of Jaccard coefficients between two sample plots from the same vegetation unit (alliance or order) or biogeoclimatic zone were significantly higher (P < 0.05) than those from different vegetation units or biogeoclimatic zones. The difference in the mean Jaccard coefficients within- and between-units was highest for zones. The results of detrended correspondence analysis and discriminant analysis suggest that the composition of lignicolous cryptogams changes with the change in the floristic composition of forest floor vegetation. When the first axes of detrended correspondence analysis were compared, the Pearson's correlation coefficients between the first axes of lignicolous cryptogams and forest floor vascular plants and between the first axes of lignicolous cryptogams and forest floor cryptogams were 0.78 and 0.87, respectively. The degree of correspondence in the composition of lignicolous cryptogams and forest floor vegetation increased from alliance to order to biogeoclimatic zone. This trend suggests that the floristic composition of lignicolous cryptogams is influenced at the community level mainly by edaphic conditions and at the regional level by climatic conditions.     

滇东南热带雨林种子植物区系的初步研究

通过对滇东南地区热带雨林植被的初步调查 ,统计滇东南热带雨林种子植物区系有种子植物 119科 ,378属 ,6 73种 (包括变种和亚种 )。种子植物分布区类型组成是主产热带和亚热带的科占 82 .35% ;热带分布属占非世界属数的 93.87% ;典型热带分布种占总种数的 75.93%。热带分布属中以亚洲热带分布属最多 ,占非世界属数的 4 0 .2 7% ;典型热带分布种中以热带亚洲分布及其变型越南 (印度支那 )至云南 (华南 )分布占比例最高 ,分别为 71.4 7%和 16 .34 %。分布区类型分析表明滇东南热带雨林种子植物区系具有热带亚洲区系的特点 ,属于古热带植物区中的马来亚森林植物亚区之中的北部湾区系。进一步分析表明此区系具热带北缘的性质。分布区类型的组成也表明此区系古特有种丰富。     

Vegetation,fire and soil feedbacks of dynamic boundaries between rainforest,savanna and grassland

At fine spatial scales, savanna‐rainforest‐grassland boundary dynamics are thought to be mediated by the interplay between fire, vegetation and soil feedbacks. These processes were investigated by quantifying tree species composition, the light environment, quantities and flammability of fuels, bark thickness, and soil conditions across stable and dynamic rainforest boundaries that adjoin grassland and eucalypt savanna in the highlands of the Bunya Mountains, southeast Queensland, Australia. The size class distribution of savanna and rainforest stems was indicative of the encroachment of rainforest species into savanna and grassland. Increasing dominance of rainforest trees corresponds to an increase in woody canopy cover, the dominance of litter fuels (woody debris and leaf), and decline in grass occurrence. There is marked difference in litter and grass fuel flammability and this result is largely an influence of strongly dissimilar fuel bulk densities. Relative bark thickness, a measure of stem fire resistance, was found to be generally greater in savanna species when compared to that of rainforest species, with notable exceptions being the conifers Araucaria bidwillii and Araucaria cunninghamii. A transect study of soil nutrients across one dynamic rainforest – grassland boundary indicated the mass of carbon and nitrogen, but not phosphorus, increased across the successional gradient. Soil carbon turnover time is shortest in stable rainforest, intermediate in dynamic rainforest and longest in grassland highlighting nutrient cycling differentiation. We conclude that the general absence of fire in the Bunya Mountains, due to a divergence from traditional Aboriginal burning practices, has allowed for the encroachment of fire‐sensitive rainforest species into the flammable biomes of this landscape. Rainforest invasion is likely to have reduced fire risk via changes to fuel composition and microclimatic conditions, and this feedback will be reinforced by altered nutrient cycling. The mechanics of the feedbacks here identified are discussed in terms of landscape change theory.     

Understory vegetation as an indicator for floodplain forest restoration in the Mississippi River Alluvial Valley,U.S.A.

In the Mississippi River Alluvial Valley (MAV), complete alteration of river‐floodplain hydrology allowed for widespread conversion of forested bottomlands to intensive agriculture, resulting in nearly 80% forest loss. Governmental programs have attempted to restore forest habitat and functions within this altered landscape by the methods of tree planting (afforestation) and local hydrologic enhancement on reclaimed croplands. Early assessments identified factors that influenced whether planting plus tree colonization could establish an overstory community similar to natural bottomland forests. The extent to which afforested sites develop typical understory vegetation has not been evaluated, yet understory composition may be indicative of restored site conditions. As part of a broad study quantifying the ecosystem services gained from restoration efforts, understory vegetation was compared between 37 afforested sites and 26 mature forest sites. Differences in vegetation attributes for species growth forms, wetland indicator classes, and native status were tested with univariate analyses; floristic composition data were analyzed by multivariate techniques. Understory vegetation of restoration sites was generally hydrophytic, but species composition differed from that of mature bottomland forest because of young successional age and differing responses of plant growth forms. Attribute and floristic variation among restoration sites was related to variation in canopy development and local wetness conditions, which in turn reflected both intrinsic site features and outcomes of restoration practices. Thus, understory vegetation is a useful indicator of functional progress in floodplain forest restoration.