The effects of environmental variables and human disturbance on woody species richness and diversity in a bamboo–deciduous forest in northeastern Thailand

Variations in species richness and diversity at a local scale are affected by a number of complex and interacting variables, including both natural environmental factors and human-made changes to the local environment. Here we identified the most important determinants of woody species richness and diversity at different growth stages (i.e. adult, sapling and seedling) in a bamboo–deciduous forest in northeast Thailand. A total of 20 environmental and human disturbance variables were used to determine the variation in species richness and diversity. In total, we identified 125 adult, 111 sapling (within fifty 20 × 20-m plots) and 89 seedling species (within one hundred and twenty 1 × 1-m subplots). Overall results from stepwise multiple regression analyses showed that environmental variables were by far the most important in explaining the variation in species richness and diversity. Forest structure (i.e. number of bamboo clumps and canopy cover) was important in determining the adult species richness and diversity (R ² = 0.48, 0.30, respectively), while topography (i.e. elevation) and human disturbance (i.e. number of tree stumps) were important in determining the sapling species richness and diversity (R ² = 0.55, 0.39, respectively). Seedling species richness and diversity were negatively related to soil phosphorus. Based on our results, we suggest that the presence of bamboos should be incorporated in management strategies for maintaining woody species richness and diversity in these forest ecosystems. Specifically, if bamboos cover the forest floor at high densities, it may be necessary to actively control these species for successful tree establishment.     

The effects of disturbance on the population structure and regeneration potential of five dominant woody species – in Hugumburda‐Gratkhassu National Forest Priority Area,North‐eastern Ethiopia

Vast areas of forests in North‐eastern Ethiopia have been replaced by cropland, shrub land or grazing areas. Thus, information about how vegetation composition and structure varies with disturbance is fundamental to conservation of such areas. This study aimed to investigate the effects of disturbance on the population structure and regeneration potential of five dominant woody species within forest where local communities harvest wood and graze livestock. Vegetation structure and environmental variables were assessed in 50 quadrats (20 m × 20 m). In most of both disturbed and undisturbed treatments, Juniperus procera was the highest contributor to the basal area of the forest, while that of Olinia rochetiana was the lowest. Analysis of population structure showed high density at lower Diameter at Breast Height (DBH) and low density at higher DBH classes. Undisturbed forest treatments had 84% canopy cover, 22 m mean vegetation height and a density of 1320 trees of dominant species and 1024 seedlings/saplings ha^?1. In disturbed habitats, canopy cover (73%), mean vegetation height (18 m) and density of dominant trees and saplings were significantly lower than in undisturbed habitats. Thus, to ensure species, survival and maintain species diversity managed use of the protected area is essential.     

Legacy of thinning on woody species composition and structure in southern Appalachian Mountain hardwood forests: restoration implications

In the Appalachian Mountains, Liriodendron tulipifera monocultures are widespread, with these forests lacking both species and structural diversity. In this study, we developed models that described the effects of thinning treatments, conducted almost 60 years ago, on the density, composition, and functional identity of the woody understory in L. tulipifera forests. The woody understory of these thinned L. tulipifera forests was diverse, with the small seedling (<1.4 m), large seedling (≥1.4 m and <2.54 cm dbh), and sapling (≥2.54 and <12.7 cm) layers possessing 38, 32, and 23 species, respectively. Although model performance was low to moderate (r² = 0.05–0.40), we found that legacy effects, alone or in combination with environmental variables, explained, in part, the variability associated with the density, composition, and functional identity of the small seedling, large seedling, and sapling size classes, with the relative influence of legacy versus environmental effects varying by metric and size class. Post-thinning basal area and/or percent of basal area removed were not the primary legacy effects influencing the woody understory. Instead, legacy effects associated with species composition of the overstory before and/or after thinning along with average stem diameter post-thinning, variation in stem diameter post-thinning, and age at the time of thinning were more influential than density or thinning intensity. This study provides evidence that conserving species diversity during forest management activities can have positive long-term effects on composition and function of the woody understory and increase restoration potential.     

Impact of habitat disturbance in the wetland forests of East Usambara,Tanzania

We evaluated habitat characteristics of East Usambara wetland forests. The abundance and species composition in the tree, shrub and herbaceous layers were enumerated in two sets of nested plots, one set in a natural wetland forest and the second in a wetland forest that had been disturbed by small‐scale gold mining activities. Each set had thirty‐six 1 m × 1 m plots for herbs, inside nine 5 m × 5 m plots for shrubs, in three 20 m × 20 m plots for trees. The habitat profile of herbaceous – shrub – tree layers was found to be sharply different from one obtained in previous studies at the surrounding nonwetland forests as were species composition and abundance. Unlike in the nonwetland forests, the herbaceous layer was thick, the shrub layer very thin and the woody species density and richness much lower. Disturbance significantly reduced woody cover and changed species composition in the herbaceous layer. Recovery of the woody vegetation was low. Wetland forests in the East Usambaras form a small fraction of the total area, but they are a unique biodiversity repository, they appear to be an important carbon dioxide sink and to reserve and purify water. They are sensitive to disturbance and need protection.     

Large Sample Area and Size Are Needed for Forest Soil Seed Bank Studies to Ensure Low Discrepancy with Standing Vegetation

A large number of small-sized samples invariably shows that woody species are absent from forest soil seed banks, leading to a large discrepancy with the seedling bank on the forest floor. We ask: 1) Does this conventional sampling strategy limit the detection of seeds of woody species? 2) Are large sample areas and sample sizes needed for higher recovery of seeds of woody species? We collected 100 samples that were 10 cm (length) ×10 cm (width) ×10 cm (depth), referred to as larger number of small-sized samples (LNSS) in a 1 ha forest plot, and placed them to germinate in a greenhouse, and collected 30 samples that were 1 m×1 m×10 cm, referred to as small number of large-sized samples (SNLS) and placed them (10 each) in a nearby secondary forest, shrub land and grass land. Only 15.7% of woody plant species of the forest stand were detected by the 100 LNSS, contrasting with 22.9%, 37.3% and 20.5% woody plant species being detected by SNLS in the secondary forest, shrub land and grassland, respectively. The increased number of species vs. sampled areas confirmed power-law relationships for forest stand, the LNSS and SNLS at all three recipient sites. Our results, although based on one forest, indicate that conventional LNSS did not yield a high percentage of detection for woody species, but SNLS strategy yielded a higher percentage of detection for woody species in the seed bank if samples were exposed to a better field germination environment. A 4 m² minimum sample area derived from power equations is larger than the sampled area in most studies in the literature. Increased sample size also is needed to obtain an increased sample area if the number of samples is to remain relatively low.     

Extant and potential vegetation of an old-growth maritime Ilex opaca forest

The extant and potential (seed bank) vegetation of a rare maritime holly forest on Fire Island, New York was described to assess whether treefall gaps act as a mechanism for the persistence of the species composition of this plant community over time. The Sunken Forest overstory is dominated by Ilex opaca, Amelanchier canadensis and Sassafras albidum. A survey of canopy gaps indicated canopy openings compose 11.3% of the land within the Sunken Forest (16 ha). The composition and density of the seed bank were described using the emergence method. Germination from soil samples placed in the greenhouse was monitored over 2 years. Sixteen species germinated with an average propagule density of 215±41 germinants per square metre. An early successional species (Rhus copallinum) dominated the seed bank, but the late-successional, shade-tolerant I. opaca was also present. Though only one species in the seed bank did not appear in the current vegetation, species abundance differed between vegetation strata. The mean cover and density of the ground-layer flora were higher beneath treefall gaps than closed canopy. Sapling density did not differ between the two canopy conditions, but the dominant species differed with A. canadensis occupying several closed canopy plots and P. serotina saplings appearing more often in gap plots. Most of the dominant canopy species are present in the seed bank and ground layer but are not present in the shrub and sapling layer, with the exception of A. canadensis. Current (2002) sapling density is lower than three decades ago for all species except P. serotina, which is now the dominant woody species in the Sunken Forest understory. The results of this study indicate that if the cause of the sapling reduction is lessened or removed, the characteristic species of the overstory of this unusual plant community may rebound and redevelop a sapling and shrub layer akin to that present before the increase in Odocoileus virginianus on the island.     

Do understorey or overstorey traits drive tree encroachment on a drained raised bog?

• One of the most important threats to peatland ecosystems is drainage, resulting in encroachment of woody species. Our main aim was to check which features – overstorey or understorey vegetation – are more important for shaping the seedling bank of pioneer trees colonising peatlands (Pinus sylvestris and Betula pubescens). We hypothesised that tree stand parameters will be more important predictors of natural regeneration density than understorey vegetation parameters, and the former will be negatively correlated with species diversity and richness and also with functional richness and functional dispersion, which indicate a high level of habitat filtering.
• The study was conducted in the ‘Zielone Bagna’ nature reserve (NW Poland). We assessed the structure of tree stands and natural regeneration (of B. pubescens and P. sylvestris) and vegetation species composition. Random forest and DCA were applied to assess relationships between variables studied.
• Understorey vegetation traits affected tree seedling density (up to 0.5‐m height) more than tree stand traits. Density of older seedlings depended more on tree stand traits. We did not find statistically significant relationships between natural regeneration densities and functional diversity components, except for functional richness, which was positively correlated with density of the youngest tree seedlings.
• Seedling densities were higher in plots with lower functional dispersion and functional divergence, which indicated that habitat filtering is more important than competition. Presence of an abundant seedling bank is crucial for the process of woody species encroachment on drained peatlands, thus its dynamics should be monitored in protected areas.

     

Monsoon rain forest seedling dynamics, northern Australia: contrasts with regeneration in eucalypt-dominated savannas

Aim To explore: (1) the relative influences of site conditions, especially moisture relations, on pathways and rates of monsoon rain forest seedling and sapling regeneration, especially of canopy dominants, in northern Australia; and (2) contrasts between regeneration syndromes of dominant woody taxa in savannas and monsoon rain forest. Location Four monsoon rain forest sites, representative of regional major habitat and vegetation types, in Kakadu National Park, northern Australia. Methods A decadal study involved: (1) initial assessment over 2.5 years to explore within‐year variability in seed rain, dormant seed banks and seedling (< 50 cm height) dynamics; and (2) thereafter, monitoring of seedling and sapling (50 cm height to 5 cm d.b.h.) dynamics undertaken annually in the late dry season. On the basis of observations from this and other studies, regeneration syndromes of dominant monsoon rain forest taxa are contrasted with comparable information for dominant woody savanna taxa, Eucalyptus and Corymbia especially. Results Key observations from the monsoon rain forest regeneration dynamics study component are that: (1) peak seed rain inputs of rain forest taxa were observed in the wet season at perennially moist sites, whereas inputs at seasonally dry sites extended into, or peaked in, the dry season; (2) dormant soil seed banks of woody rain forest taxa were dominated by pioneer taxa, especially figs; (3) longevity of dormant seed banks of woody monsoon rain forest taxa, including figs, was expended within 3 years; (4) seedling recruitment of monsoon rain forest woody taxa was derived mostly from wet season seed rain with limited inputs from soil seed banks; (5) at all sites rain forest seedling mortality occurred mostly in the dry season; (6) rain forest seedling and sapling densities were consistently greater at moist sites; (7) recruitment from clonal reproduction was negligible, even following unplanned low intensity fires. Main conclusions By comparison with dominant savanna eucalypts, dominant monsoon rain forest taxa recruit substantially greater stocks of seedlings, but exhibit slower aerial growth and development of resprouting capacity in early years, lack lignotubers in mesic species, and lack capacity for clonal reproduction. The reliance on sexual as opposed to vegetative reproduction places monsoon rain forest taxa at significant disadvantage, especially slower growing species on seasonally dry sites, given annual–biennial fires in many north Australian savannas.     

Resistance to wildfire and early regeneration in natural broadleaved forest and pine plantation

The response of an ecosystem to disturbance reflects its stability, which is determined by two components: resistance and resilience. We addressed both components in a study of early post-fire response of natural broadleaved forest (Quercus robur, Ilex aquifolium) and pine plantation (Pinus pinaster, Pinus sylvestris) to a wildfire that burned over 6000 ha in NW Portugal. Fire resistance was assessed from fire severity, tree mortality and sapling persistence. Understory fire resistance was similar between forests: fire severity at the surface level was moderate to low, and sapling persistence was low. At the canopy level, fire severity was generally low in broadleaved forest but heterogeneous in pine forest, and mean tree mortality was significantly higher in pine forest. Forest resilience was assessed by the comparison of the understory composition, species diversity and seedling abundance in unburned and burned plots in each forest type. Unburned broadleaved communities were dominated by perennial herbs (e.g., Arrhenatherum elatius) and woody species (e.g., Hedera hibernica, Erica arborea), all able to regenerate vegetatively. Unburned pine communities presented a higher abundance of shrubs, and most dominant species relied on post-fire seeding, with some species also being able to regenerate vegetatively (e.g., Ulex minor, Daboecia cantabrica). There were no differences in diversity measures in broadleaved forest, but burned communities in pine forest shared less species and were less rich and diverse than unburned communities. Seedling abundance was similar in burned and unburned plots in both forests. The slower reestablishment of understory pine communities is probably explained by the slower recovery rate of dominant species. These findings are ecologically relevant: the higher resistance and resilience of native broadleaved forest implies a higher stability in the maintenance of forest processes and the delivery of ecosystem services.     

The influence of macro‐litterfall and forest structure on litterfall damage to seedlings

Abstract Microdisturbance to seedlings is important because it can differentially affect the mortality and recruitment of seedlings of forest tree species and thereby ultimately affect community composition. Microdisturbance due to litterfall has been shown to vary greatly in its influence on seedling survival among and within forests, and yet there have been no previous studies that investigate the cause of these differences. In this study the influence of macro‐litterfall on seedling damage is investigated in five complex temperate forests in New Zealand. Litterfall damage to artificial seedlings in these forests was strongly correlated with macro‐leaf‐fall (leaves > 30 cm × 1.5 cm) dry weight and total macro‐litterfall (leaves and deadwood > 30 cm × 1.5 cm) surface area (R² = 0.99, P < 0.005 for each). Protective vegetation within 2 m of the ground (mostly lianes and woody shrubs) reduced the risk of litterfall damage by up to 84%. Hitherto unexplained differences in litterfall damage to seedlings found among, and within, forests (tropical and temperate) may therefore be due to differences in rates of macro‐leaf‐fall and forest structure. These results are important because they suggest that subtle differences in forest structure, and species composition, may influence regeneration patterns through the litterfall microdisturbance regime.     

Factors Controlling Compositional Changes in a Northern Andean Páramo (La Rusia,Colombia)

In this study, we aimed to assess the processes controlling compositional change in a Northern Andean páramo highly affected by human‐induced disturbances over the last few decades (La Rusia, Colombia). Along the 3000–3800 m asl altitudinal range, we randomly sampled fifty 10 × 10 m plots. Therein, we measured altitude and variables related to soil conditions (i.e., moisture, nutrient contents, bulk density, and texture), occurrence of human‐induced disturbances (i.e., fire, vegetation clearing, potato cultivation, and cattle grazing), and land‐use history. We also recorded richness and abundance of plant species, identifying them as exotic or native. We differentiated four groups of plots according to their species composition. The groups had significant differences in altitude, soil conditions, land‐use history, and particularly, in richness of exotic species and exotic/native cover ratio. They could be ascribed to shrub‐ and grass‐páramo vegetation types based on their relative dominance of woody and herbaceous species; however, these groups were not arranged according to the hypothetical composition of altitudinal belts, but rather formed a mosaic of patches. This mosaic was determined not only by altitude but also by soil conditions and disturbance history of sites. Our results corroborate recent findings which highlight shrub‐ and grass‐páramo vegetation types as patches of contrasting species composition and structure that depend on local environmental variables, as well as human‐induced disturbances as a major determinant of compositional discontinuities in these ‘high mountain’ tropical ecosystems.     

Variation in structural diversity and regeneration potential of tree species in different tropical forest types of Similipal Biosphere Reserve,Eastern India

Understanding the regeneration potential of tree species in natural forest ecosystems is crucial to deliver suitable management practices for conservation of biodiversity. We studied the variation in structural diversity and regeneration potential of tree species in three different tropical forest types, namely: Dry Deciduous forest (DDF), Moist Deciduous forest (MDF) and Semi-evergreen forest (SEF) of Similipal Biosphere Reserve (SBR), Eastern India. Random sample plots were laid for studying the diversity and distribution pattern of tree, sapling, and seedling stages of the tree species. A total of 84 species belong to 73 genera and 35 families were recorded from the study area. The highest species richness was reported for tree (54 species) in DDF, sapling (24 species) in MDF and seedling (22 species each) in SEF and DDF. The overall density of trees with GBH (Girth at Breast Height) ≥ 10 cm was 881 individuals/ha. The regeneration potential of tree species was poor in DDF (39%) where as it was fair in SEF (43%) and MDF (49%). Most of the dominant tree species at each forest type performed good regeneration. The species such as Ehretia laevis Roxb., Bridelia retusa (L.)A.Juss., Mitragyna parviflora (Roxb.) Korth., Terminalia tomentosa Wight & Arn., Terminalia chebula Retz., Terminalia bellirica (Gaertn.) Roxb.etc. had either no regeneration or poor regeneration potential need immediate attention for conservation measures. The diversity of standing trees did not correlate with seedling or sapling diversity in all the cases but there was significant correlation among seedling and sapling diversity found in DDF (r = 0.67, p ≤ 0.05) and SEF (r = 0.83, p ≤ 0.05). Further, the diversity of tree species increased with their age (trees > saplings > seedlings) and the stem density decreased with their age (trees < saplings < seedlings) in all three forest types. The results of our study would be helpful in understanding the structural attributes, diversity and regeneration potential of different tropical forest types of India for their better conservation and management.     

Spatial structure of the abiotic environment and its association with sapling community structure and dynamics in a cloud forest

Analyzing the relationship between the spatial structures of environmental variables and of the associated seedling and sapling communities is crucial to understanding the regeneration processes in forest communities. The degree of spatial structuring (i.e., spatial autocorrelation) of environmental and sapling community variables in the cloud forest of Teipan, S Mexico, were analyzed at a 1-ha scale using geostatistical analysis; after fitting semivariogram models for each set of variables, the association between the two sets was examined through cross-variograms. Kriging maps of the sapling community variables (density, cover, species richness, and mortality and recruitment rates) were obtained through conditional simulation method. Canopy openness, total solar radiation, litter depth, soil temperature and soil moisture were spatially structured, as were sapling density, species richness and sapling mortality rate. Mean range in semivariograms for environmental and sapling community variables were 13.14 ± 3.67 and 12.68 ± 5.71 m (±SE), respectively. The spatial structure of litter depth was negatively associated with the spatial structures of sapling density, species richness, and sapling community cover; in turn, the spatial structure of soil moisture was positively associated with the spatial structure of recruitment rate. These associations of the spatial structures of abiotic and sapling community variables suggest that the regeneration processes in this cloud forest is driven by the existence of different microsites, largely characterized by litter depth variations, across which saplings of tree species encounter a range of opportunities for successful establishment and survival.     

Comparisons of recruitment, survival, and growth in invasive and native saplings on a volcano

We monitored the recruitment, survival, and growth of tree saplings on invasive (Larix kaempferi) versus native species (Betula and Populus) using 16 20 m × 20 m plots established along elevation gradient on the volcano Mount Koma, Japan, for 7 years because the sapling behaviors should determine forest structures. The crowding of overstory consists mostly of Larix decreased with increasing elevation. Larix recruits were conspicuous, particularly at middle elevation where overstory crowding was intermediate, while Betula recruits were least. Larix overstory crowding inhibited the recruitment of all the taxa, although intermediate crowding promoted the recruitment of Larix. The restriction of sapling emergence was conspicuous at lower elevation where the overstory crowding was highest, probably because of shading, and/or competition with overstory trees. Sapling recruitment for all taxa was restricted at higher elevation, due to high stresses derived from direct solar radiation and strong wind without overstory. The survival of saplings was 96% for Larix and Betula, while it was ca. 50% for Populus. Larix overstory decreased the survival and growth of all the taxa, except Larix survival and Betula growth. The results implied that Larix could establish by high survival once the recruits succeeded everywhere and native sapling regeneration was restricted by Larix overstory. Strong recruitment, survival, and growth of Larix, together with resistance to overstory crowding, enables it to dominate and persist in such disturbed areas regardless of the canopy closure.     

祁连山北坡主要木本植物功能性状及其海拔分异

植物功能性状是植物对生境长期适应所形成的可测量特征,受植物遗传特性和环境因子的共同影响。祁连山是我国干旱区的一条重要山脉,北坡海拔介于2000—5000 m,分布着青海云杉、祁连圆柏等10余种木本植物。深入了解祁连山区木本植物功能性状随海拔梯度分异特征对认识山地植物的适应性和植被垂直地带分布具有重要意义。选取祁连山北坡天然分布的11种木本植物,其中灌木9种,分别是金露梅(Potentilla fruticosa)、银露梅(Potentilla glabra)、水栒子(Cotoneaster multiflorus)、猫儿刺(Ilex pernyi)、吉拉柳(Salix gilashanica)、鬼箭锦鸡儿(Caragana jubata)、刚毛忍冬(Lonicera hispida)、高山绣线菊(Spiraea alpina)和鲜黄小檗(Berberis diaphana),乔木2种,分别是青海云杉(Picea crassifolia)和祁连圆柏(Juniperus przewalskii),调查了木质密度、胡伯尔值、叶面积、叶干物质含量、叶含水率和比叶面积6个枝、叶功能性状。结果表明...     

Diversity and composition of understory vegetation in the tropical seasonal rain forest of Xishuangbanna, SW China

Tropical forests vegetation and community research have tended to focus on the tree component, and limited attention has been paid to understory vegetation. Species diversity and composition of the understory of tropical seasonal rain forest were inventoried in a 625 m2 area (for sapling layer) and a 100 m2 area (for herb/seedling layer) in three 1 ha plots. We found 3068 individuals belonging to 309 species, 192 genera and 89 families. The most important family as determined by the Family Importance Value (FIV) was Rubiaceae in both sapling and herb/seedling layers. In terms of Importance Value Index (IVI), the shrub Mycetia gracilis (Rubiaceae) was the most important species in the sapling layer and the pteridophyte Selaginella delicatula (Selaginellaceae) was the most ecological significant species in the herb/seedling layer. Much more vascular plant species were registered in the understory than in the tree layer totaled among the three plots. The species diversity did not differ significantly among the tree layer, sapling layer and herb/seedling layer. Given that we still know little about the understory plant community for growth forms other than trees, the results from the present study indicate that more attention should be paid to the understory vegetation during the decision-making process for biodiversity conservation in the tropical forests.     

The Importance of Ficus (Moraceae) Trees for Tropical Forest Restoration

Forest restoration is an increasingly important tool to offset and indeed reverse global deforestation rates. One low cost strategy to accelerate forest recovery is conserving scattered native trees that persist across disturbed landscapes and which may act as seedling recruitment foci. Ficus trees, which are considered to be critically important components of tropical ecosystems, may be particularly attractive to seed dispersers in that they produce large and nutritionally rewarding fruit crops. Here, we evaluate the effectiveness of remnant Ficus trees in inducing forest recovery compared to other common trees. We studied the sapling communities growing under 207 scattered trees, and collected data on seed rain for 55 trees in a modified landscape in Assam, India. We found that Ficus trees have more sapling species around them (species richness = 140.1 ± 9.9) than non‐Ficus trees (79.5 ± 12.9), and significantly more saplings of shrub and large tree species. Sapling densities were twice as high under Ficus trees (median = 0.06/m²) compared to non‐Ficus (0.03/m²), and seed rain densities of non‐parent trees were significantly higher under Ficus trees (mean = 12.73 ± 3/m²/wk) than other fruit or non‐zoochorous trees (2.19 ± 0.97/m²/wk). However, our regression model found that canopy area, used as a proxy for tree size, was the primary predictor of sapling density, followed by remnant tree type. These results suggest that large trees, and in particular large Ficus trees, may be more effective forest restoration agents than other remnant trees in disturbed landscapes, and therefore the conservation of these trees should be prioritized.     

Relationships between the density of two potential restoration tree species and plant species abundance and richness in a degraded Afromontane forest of Kenya

In recent years, there have been considerable efforts to restore degraded tropical montane forests through active restoration using indigenous tree species. However, little is known about how these species used for restoration influence other species. In this study, two potential restoration species, Albizia gummifera and Neoboutonia macrocalyx, are investigated with regard to the relationship between their density and the abundance and richness of other plant species. The study was conducted in a degraded forest consisting of disturbed transition zones and secondary forest. Our results show positive relationships between the density of A. gummifera and the abundance of tree seedling and sapling richness in the transition zones and in the secondary forest. Shrub richness was negatively related to the density of A. gummifera. Abundance and richness of tree saplings and shrubs were positively related to N. macrocalyx density both in the transition zones and in the secondary forest. Herb species richness declined with N. macrocalyx density in the transition zones but increased with N. macrocalyx density in the secondary forest. The positive relationships between the density of the two tree species and species richness of other woody species suggest that both A. gummifera and N. macrocalyx can be suitable for active restoration of degraded mountain forests within their natural range.     

Slashing Phragmites (Phragmites australis) prior to planting does not promote native vegetation establishment

Phragmites or Common Reed (Phragmites australis) is a tall rhizomatous cosmopolitan grass. While native to Australia, it can be invasive in wetlands, forming dense monocultures and reducing their ecological integrity. We assessed the potential for the cutting of Phragmites reeds prior to planting to promote the establishment of indigenous shrubs that might ultimately outcompete Phragmites. We established ten 5 m × 5 m quadrats in an area dominated by Phragmites, brush‐cut the reeds to ground level in five of them and left five uncut as controls. Within each quadrat, we planted 20 plants (~40 cm tall) of each of five indigenous shrub species, unguarded (4 plants/m²). We surveyed the plants one month after planting and annually for the following four years for survival, height and browsing damage. Browsing damage to plants was common (>50%) and unaffected by cutting. After four years, overall plant survival rates were ~25% and mean plant heights for the five shrub species ranged between 120 and 174 cm. Cutting of Phragmites had no positive effect on plant survival or height. In fact, two Melaleuca species grew taller in the uncut quadrats. Cutting of Phragmites reed beds prior to planting is unlikely to promote the establishment of woody plantings. However, planting within established Phragmites with or without prior brush‐cutting is worthy of further trialling as a potential tool for reinstating native diversity at Phragmites‐dominated sites.     

Disturbance Type and Plant Successional Communities in Bahamian Dry Forests

Different disturbances in similar habitats can produce unique successional assemblages of plants. We collected plant species composition and cover data to investigate the effects of three common types of disturbances—fire, anthropogenic clearing (‘cleared’), and clearing followed by goat grazing (‘cleared‐and‐grazed’)—on early‐successional coppice (dry forest) community structure and development on Eleuthera, Bahamas. For each disturbance type, both the ground layer (<0.5 m height) and shrub layer (>0.5 m height) were sampled in eight patches (>1 ha) of varying age (1–28 yr) since large‐scale mature coppice disturbance. Overall, plant communities differed among disturbance types; several common species had significantly higher cover in the shrub layer of fire patches, and cleared‐and‐grazed patches exhibited higher woody ground cover. Total percent cover in the shrub layer increased in a similar linear fashion along the investigated chronosequence of each disturbance type; however, cover of the common tree species, Bursera simaruba, increased at a notably slower rate in cleared‐and‐grazed patches. The pattern of increase and subsequent decrease in cover of Lantana spp. and Zanthoxylum fagara in the shrub layer was characterized by longer persistence and higher covers, respectively, in cleared‐and‐grazed patches, which also exhibited low peak cover and fast decline of nonwoody ground cover. Our results suggest that goats may accelerate some aspects of succession (e.g., quickly removing nonwoody ground cover) and retard other aspects (e.g., inhibiting growth of tree species and maintaining early‐successional shrubs in the shrub layer). These effects may lead to different successional trajectories, and have important conservation implications.