Early Development of Soil Microbial Communities on Rehabilitated Quarries

The ecological development of soil microbial communities was studied in terms of microbial composition and structure at different rehabilitated phases on three quarries, namely Turret Hill Quarry (TH), Lam Tei Quarry (LT), and Shek O Quarry (SO), in Hong Kong. Using individual fatty acid methylesters (FAMEs) as biomarkers, Gram^? bacteria dominated at all sites, in which cy19:0 represented more than 15% of the total extracted FAMEs in all soils tested. Redundancy analysis showed that the abundance of Gram^? bacteria and Gram⁺ bacteria correlated significantly with woody species richness, native species richness, organic C, total N, and extractable NO₃‐N. Fungi (18:1w9c and 18:2w6) and arbuscular mycorrhizal (AM) fungi (16:1w5c) decreased in abundance with increasing age in SO and LT, which were positively correlated with grass coverage, soil pH, extractable NH₄‐N, and extractable P. Our study suggested that soil aeration and C availability in soils played a dominant role driving the changes in the composition and structure of Gram^? bacteria and Gram⁺ bacteria communities. Available P was the limiting factor for regulating the fungal and AM fungal communities on our local quarries.     

Plant Recruitment in Early Development Stages on Rehabilitated Quarries in Hong Kong

To understand vegetation development during the ecological succession of rehabilitated quarries, floristic composition and structure were evaluated at different restoration phases on three quarries in Hong Kong that were planted with exotic woody species over the course of 2–14 years. A total of 113 species, of which 82 were woody species, were recorded. Exotic species dominated the overstory, and species number, richness, and diversity increased with age. Some light‐demanding early successional species were becoming dominant in the overstory vegetation at the older phases of revegetation. These species could be potential candidates for early enrichment planting with Acacia spp. Common secondary forest species occurred naturally in the understory vegetation, and were more abundant and dominant after 10 years of ecological development. The most successful restorations were on scree slopes using leguminous Acacia spp. as nurse species.     

Recolonization by Collembola of rehabilitated bauxite mines in Western Australia

Abstract The collembolan faunas of 30 bauxite mines rehabilitated by a range of different methods between 1966 and 1977, and three forest plots were surveyed in the spring and summer of 1978–79 with the aim of studying the restoration of decomposer activity in degraded areas. The rehabilitation methods included seeding and planting with a variety of native or exotic plant species. Physical and botanical parameters of the plots were also measured. Sixty species of Collembola were collected from the rehabilitated areas; nine of the 28 species found in the forest plots were not present on the mined sites. Principal components analysis suggested that the species richness of the collembolan community in rehabilitated areas is positively correlated with plot age. A parametric correlation analysis using a number of collembolan community characteristics revealed that, among other factors, the development of a species rich collembolan fauna is positively correlated with plant species richness and diversity, and also with percentage plant cover. These results provide directions for improving rehabilitation practices.     

Open‐cut mining impacts on soil abiotic and bacterial community properties as shown by restoration chronosequence

Open‐cut mining severely disrupts landforms and soils, preventing or impeding the restoration of preexisting or functional ecosystems because essential properties of the original soils cannot immediately or easily be reinstated. We examined the soil physicochemical and bacterial characteristics of 21 coal‐mined sites in subtropical Queensland, Australia, 3–23 years after establishment of native plant species relative to nonmined analogue sites. Soil disturbance significantly decreased total nitrogen, nitrate nitrogen, and especially total carbon (TC). The TC is projected to take 36 years to recover. Bacterial communities assessed by 16S ribosomal RNA sequencing showed greater species richness and evenness in rehabilitated as compared with nonmined soils, regardless of rehabilitation age. However, bacterial species composition was associated significantly with soil electrical conductivity, the plant density, and total stem cross‐sectional area of woody vegetation. The bacterial communities on rehabilitated sites became progressively more similar to those of nonmined analogue sites over time. This work demonstrates that if topsoils are conserved carefully during mining and supplemented by inorganic fertilizer addition, vigorous plant growth and changes in bacterial community composition can occur soon after plant establishment. This will mitigate the effects of soil disturbance and accelerate the return to the chemical and biological attributes of nonmined analogue soils.     

Comparative Study of Ant Communities of Rehabilitated Mineral Sand Mines and Heathland, Western Australia

We conducted a survey of ants in April 1997 in seven rehabilitated (2- to 20-year-old) and three native heathland reference sites of the Renison Goldfields Corporation (RGC) Mineral Sands operations at Eneabba, Western Australia. We employed a variety of collecting methods, including pitfall trapping, litter and soil sampling, sweeping and beating of vegetation, and collecting by hand in the day and after dark, replicating those used by previous researchers in a similar study conducted in the same area in 1980. We found a total of 96 ant species representing 30 genera in 1997, compared with 46 species from 18 genera in 1980. Ant species richness increased with age of rehabilitation and exceeded that of heath controls by the time it reached 11 years. Ant species richness related to rehabilitation age was represented by a logarithmic curve, and the slope for current rehabilitation was steeper than that for the earlier rehabilitation studied in 1980. This probably reflects improved rehabilitation practices. Ordination of the sites in terms of ant species composition indicated differences between ant species in the rehabilitated sites studied in 1980 and 1997, and also between all rehabilitated sites and heath controls. Classification of the sites in terms of the distribution of ants across functional groups also indicated differences between rehabilitation and heath control sites. According to species composition and functional group profiles from rehabilitated and control sites, we concluded that although the current rehabilitation allows for a rapid return of ant species, even after 20 years the fauna still had not attained the composition of the original heath fauna.     

The roles of biotic resistance and nitrogen deposition in regulating non-native understory plant diversity

Understanding the mechanisms that allow for plant invasions is important for both ecologists and land managers, due to both the environmental and economic impacts of native biodiversity losses. We conducted an observational field study in 2008 to examine the relationship between native and non-native forest understory plant species and to investigate the influence of soil nitrogen (N) on plant community richness and diversity. In 2009, we conducted a companion fertilization experiment to investigate how various forms of N deposition (inorganic and organic) influenced native and non-native species richness and diversity. We found that native species richness and diversity were negatively correlated with 1) non-native species richness and diversity and 2) higher total soil inorganic N. In the deposition experiment, adding organic N fertilizers decreased native richness and diversity compared to inorganic N fertilizers. Together, these results indicate that increasing soil N can be detrimental to native species; however, native species richness and diversity may counteract the N-stimulation of non-native species. Furthermore, the negative effects of organic N deposition on native plants may be just as strong, if not stronger, than the effects of inorganic N deposition.     

Comparison of Post-Mine Rehabilitated and Natural Shrubland Communities in Southwestern Australia

Following mineral sand mining near Eneabba, southwestern Australia, rehabilitation managers have the difficult task of restoring shrubland communities of exceptional plant species richness. Species diversity, composition, structure, and key functional attributes in four mined sites rehabilitated 8 (R8) to 24 (R24) years ago were compared with those of typical nearby natural areas classified on the basis of substrate type (Low and High sand Dunes, shallow sand Swales, sand over Laterite, and sand over Limestone). The rehabilitated sites (except R8) had more species (about 140) than natural sites (about 100) in 40 × 40–m plots, with 12–37% species in common with natural sites. Rehabilitated sites were more similar in composition to each other than they were to the natural sites, with two strong colonizers, the fire-killed Acacia blakelyi and the fire-tolerant Melaleuca leuropoma , universally present. Dendrograms and ordinations based on composition and cover showed that rehabilitated sites grouped with each other before they did with the Dune and Swale sites (physically closest), and last with the Laterite and Limestone sites. Plant densities for R16 and R24 were about half those of the High Dune and Limestone, and about a quarter those of the Swale and Laterite. Fire resprouters were under-represented in the rehabilitated sites. Growth form distribution in rehabilitated sites was most similar to those of the dunes, with some woody shrubs up to 2.5 m tall present. Total iron and soil hardness (penetrability) were the only soil factors consistently different (higher) in the rehabilitated sites.     

豚草入侵对新疆伊犁河谷林下本地草本植物群落结构的影响

为探究外来入侵植物豚草（Ambrosia artemisiifolia）对本地植物群落结构的影响,结合区内林下草本植物调查和室内分析方法,分析了豚草不同入侵压力下（无入侵、轻度入侵、中度入侵、重度入侵）本地草本植物丰富度、盖度等特征,探讨了地形、气候、土壤、光照、人口密度等外部因素与豚草种群特征、本地植物群落结构之间的关系。结果表明：豚草种群盖度与其高度、密度、生物量显著正相关。与对照相比,轻度入侵下本土草本植物Shannon-Wiener多样性指数和Pielou均匀度指数显著增加,丰富度、盖度未出现显著差异。随着豚草入侵程度加剧,本地草本植物物种丰富度、盖度极显著降低,样方Shannon-Wiener多样性指数先升高再降低,本土草本植物Pielou均匀度指数差异不显著。冗余分析（RDA）表明,土壤全氮、与道路距离、土壤全磷、郁闭度对研究区植物群落结构影响最大,土壤全氮含量随豚草盖度和生物量增加而减少,距道路越近或光照越强,豚草盖度和生物量越高。增强伊犁河谷地区交通往来货物豚草检验检疫力度、增加林内植被郁闭度或是抑制区内豚草入侵的有效手段。     

Native and naturalized plant diversity are positively correlated in scrub communities of California and Chile

Abstract. An emerging body of literature suggests that the richness of native and naturalized plant species are often positively correlated. It is unclear, however, whether this relationship is robust across spatial scales, and how a disturbance regime may affect it. Here, I examine the relationships of both richness and abundance between native and naturalized species of plants in two mediterranean scrub communities: coastal sage scrub (CSS) in California and xeric-sloped matorral (XSM) in Chile. In each vegetation type I surveyed multiple sites, where I identified vascular plant species and estimated their relative cover. Herbaceous species richness was higher in XSM, while cover of woody species was higher in CSS, where woody species have a strong impact upon herbaceous species. As there were few naturalized species with a woody growth form, the analyses performed here relate primarily to herbaceous species. Relationships between the herbaceous cover of native and naturalized species were not significant in CSS, but were nearly significant in XSM. The herbaceous species richness of native and naturalized plants were not significantly correlated on sites that had burned less than one year prior to sampling in CSS, and too few sites were available to examine this relationship in XSM. In post 1-year burn sites, however, herbaceous richness of native and naturalized species were positively correlated in both CSS and XSM. This relationship occurred at all spatial scales, from 400 m² to 1 m² plots. The consistency of this relationship in this study, together with its reported occurrence in the literature, suggests that this relationship may be general. Finally, the residuals from the correlations between native and naturalized species richness and cover, when plotted against site age (i.e. time since the last fire), show that richness and cover of naturalized species are strongly favoured on recently burned sites in XSM; this suggests that herbaceous species native to Chile are relatively poorly adapted to fire.     

Using plant functional types to compare vegetation structure of alien-invaded and uninvaded Acacia nilotica savannas

Four plant functional types (PFTs) were used to compare the vegetation structure of an alien-invaded Acacia nilotica savanna with one of negligible invasions. Heights, canopy covers and species richness of three native PFTs (woody plants, grasses and herbs) and one alien PFT (woody plants) were measured in 14, 1-m² quadrats sampled in a stratified-random pattern in a 400-m² plot demarcated in each savanna. In the uninvaded plot, mean heights of native PFTs were stratified. In the invaded plot, the mean height of aliens extended into the native woody stratum with the lower range of native woody PFT heights reduced to the grass stratum. Discriminant analysis of canopy covers and species richness of the four PFTs revealed significant differences in composition between plots with the alien PFT being the most important variable correlated with these differences. Univariate analysis confirmed the dominance of alien woody plants in the invaded plot but also showed significant reductions in the canopy covers and species richness of native herbs and grasses compared to those in the uninvaded plot. These results suggest that PFTs can rapidly measure small-scale, spatial differences in the physiognomy, composition and species richness of A. nilotica savannas when invaded by alien woody plants.     

Floristic diversity of an eastern Mediterranean dwarf shrubland: the importance of soil pH

Questions: Does plant species richness and composition of eastern Mediterranean dwarf shrubland (phrygana) correlate with soil pH? How important is the effect of pH on species diversity in relation to other environmental factors in this ecosystem? What is the evolutionary background of the diversity–pH relationship? Location: Western Crete, Greece. Methods: Species composition of vascular plants, soil and other environmental variables were sampled in 100‐m² plots on acidic and basic bedrock in phrygana vegetation. The relationships between species composition and environmental variables (including climate) were tested using canonical correspondence analysis, and relationships between species richness and environment using correlation and regression analyses. Data were analysed separately for different plant functional types based on life form and life span. Results: Although soil pH varied across a narrow range (5.9‐8.1), species composition changed significantly along the pH gradient within all plant functional types. For most functional types, the effect of soil pH on species composition was stronger than that of other environmental variables. Species richness of annuals, geophytes and suffruticose chamaephytes increased with soil pH, while richness of hemicryptophytes and shrubs was not correlated with pH. Conclusions: The results are consistent with the evolutionary species pool hypothesis. High numbers of calcicole annuals, geophytes and suffruticose chamaephytes may be a result of the evolution of these groups on base‐rich dry soils in the Mediterranean climate. In contrast, hemicryptophytes, a life form typical of the temperate zone, evolved on both acidic and basic soils and therefore their species numbers do not respond to soil pH across the narrow range studied. The lack of a relationship between shrub species richness and pH is difficult to explain: it may reflect the more diverse or older origin of Mediterranean woody species and their conservative niches.     

Factors determining plant species richness in Alaskan arctic tundra

Abstract. We studied the relationship between plant N:P ratio, soil characteristics and species richness in wet sedge and tussock tundra in northern Alaska at seven sites. We also collected data on soil characteristics, above‐ground biomass, species richness and composition. The N:P ratio of the vegetation did not show any relationship with species richness. The N:P ratio of the soil was related with species richness for both vegetation types. Species richness in the tussock tundra was most strongly correlated with soil calcium content and soil pH, with a strong correlation between these two factors. N:P ratio of the soil was also correlated with soil pH. Other factors correlated with species richness were soil moisture and Sphagnum cover. Organic matter content was the factor most strongly correlated with species richness in the wet sedge vegetation. N:P ratio of the soil was strongly correlated with organic matter content. We conclude that N:P ratio in the vegetation is not an important factor determining species richness in arctic tundra and that species richness in arctic tundra is mainly determined by pH and flooding. In tussock tundra the pH, declining with soil age, in combination with Sphagnum growth strongly decreases species richness, while in wet sedge communities flooding over long periods of time creates less favourable conditions for species richness.     

Management intensity affects the relationship between non‐native and native species in subtropical wetlands

Question: Does management intensity affect the association between non‐native and native species and between non‐native species and soil nutrients in wetlands? Location: MacArthur Agro‐Ecology Research Center, Florida, USA. Methods: We evaluated native and non‐native plant richness and relative frequency in 15 1‐m² plots in 40 wetlands across two types of pastures, highly managed (fertilized, ditched, planted, heavily grazed by cattle) and semi‐natural (unfertilized, lightly seasonally grazed). Plant biomass was collected in five 0.25‐m² plots per wetland and sorted to species. Soil cores were collected to analyse soil total nitrogen (N) and phosphorus (P). An information‐theoretic approach was used to compare mixed effects models considering the association of non‐native richness, relative frequency, and biomass with native richness, relative frequency, biomass, C₃ grass relative frequency (a dominant native group), N, P and wetland‐type. Results: Non‐native richness was negatively correlated with native richness in semi‐natural wetlands, but there was no evidence of an association between these variables in highly managed wetlands. Non‐native richness increased with increasing soil N in semi‐natural wetlands, but not in the highly managed wetlands. Soil P was positively related to non‐native frequency in semi‐natural wetlands but negatively related in highly managed wetlands. Non‐native frequency and biomass were negatively related to relative frequency of C₃ grasses in both management types. Conclusions: Our results indicate that management intensity influences relationships between native and non‐native richness. Management intensity interacts with abiotic or biotic factors, such as soil nutrients and composition, in predicting where non‐native species will most likely need control.     

Patterns of woody plant invasion in an Argentinean coastal grassland

Coastal dune grasslands are fragile ecosystems that have historically been subjected to various types of uses and human activities. In Buenos Aires Province (Argentina), these areas are frequently afforested for urban and touristic development. The introduction and subsequent spread of exotic tree species is one of the main threats to conservation of natural grasslands as invasive trees strongly transform their structure and composition. The aim of this study was to identify patterns of woody plant invasion comparing plant communities and environmental variables between invaded and non-invaded areas surrounding the coastal village of Mar Azul, Argentina. Coastal grasslands in this area are being invaded by Populus alba (white poplar) and Acacia longifolia (coast wattle). The height of the saplings and the richness of the accompanying vegetation were evaluated in relation to the distance from the edge of the mature tree patches. Also, the cover, richness and diversity of all species in the invaded and non-invaded areas were measured, as well as soil pH, temperature and particle size. Negative correlations were found between the height of the saplings and distance to mature tree patches in all areas. The richness of the accompanying vegetation was negatively and positively correlated with the distance from the poplar and acacia area, respectively. The most abundant native species was Cortaderia selloana. Less cover, richness and diversity of native plant species and greater soil particle size were found in invaded areas, where the proportion of bare soil was higher. Also, a higher proportion of leaf litter in the invaded areas was registered. The results emphasize the invasive capacity of P. alba and A. longifolia advancing on the native communities and reducing their richness. Knowledge of the impact of invasive woody plants in coastal grasslands is important to design active management strategies for conservation purposes.     

热带森林不同演替阶段蚂蚁巢穴的分布特征及其影响因素

为探明热带森林蚂蚁巢穴的分布特征及其影响因素, 采用样方法研究了西双版纳不同演替阶段热带森林定居巢穴蚂蚁的种类及其巢穴的密度、盖度和空间分布特征, 并分析了土壤理化环境与蚂蚁种类总数、巢穴密度及盖度的相关性。结果表明, 不同演替阶段热带森林蚂蚁种类总数、巢穴的密度及盖度大小顺序为: 小果野芭蕉 (Musa acuminata)群落>白背桐(Mallotus paniculatus)群落>思茅崖豆(Mellettia leptobotrya)群落, 并且热带森林的演替类型显著影响蚂蚁种类总数及巢穴密度, 而对巢穴盖度的影响未达到显著水平; 蚂蚁种类总数、巢穴密度与土壤总有机碳和水解氮显著正相关, 与土壤容重和土壤含水率显著负相关, 但所选择的土壤理化指标与巢穴盖度的相关性均未达到显著水平; 蚂蚁巢穴的空间分布呈随机分布格局。我们的数据表明, 不同演替阶段热带森林所形成的植被类型及土壤环境状况共同影响定居的蚂蚁种类总数与筑巢密度。     

A Comparative Study of Spider (Araneae) Communities of Rehabilitated Bauxite Mines and Surrounding Forest in the Southwest of Western Australia

A study of spider (Araneae) communities was conducted in rehabilitated bauxite mines at the Jarrahdale mine site of Alcoa of Australia Ltd. and in the nearby native jarrah (Eucalyptus marginata) forest in southwest Western Australia. The study was conducted from March to August 1993 in five rehabilitated sites of different age and method of rehabilitation and in two forest sites. A variety of collection methods was used, including pitfall trapping, litter sampling, sweep netting, tree beating, and visual searching. These methods were the same as those carried out in a previous study of some of these areas in 1983. We collected 151 spider species belonging to 102 genera and 34 families. We examined the relationship between various habitat features, including the age and method of rehabilitation, of the spider communities present. It was found that leaf litter depth and cover and vegetation density had a significant positive influence on recolonization by the various spider guilds. The age and method of rehabilitation were found to influence different vegetational and habitat features; these, in turn, influenced the spider communities. Thus, the older a rehabilitated site the greater the species richness of both plants and spiders. We compared these results with those of the 1983 study to determine the spider succession of the aging rehabilitation. The spider communities and guild composition were found to change as the vegetation matured, from a dominance of pioneer species to a community of species requiring less harsh conditions. By comparison with the pre-1983 rehabilitation, the latest method of rehabilitation increased the rate of recolonization by both plants and spiders.     

Ant Community Development on Rehabilitated Ash Dams in the South African Highveld

Ant communities have been widely used as indicators of minesite rehabilitation in Australia and are beginning to play a similar role in other parts of the world. Here we examine ant communities on rehabilitated ash dams associated with a coal‐fired power station on the highveld of South Africa, to improve our understanding of ecosystem development on these substrates. Ants were sampled using pitfall traps at 11 ash‐dam sites, ranging from unrehabilitated to 9‐year‐old rehabilitated sites, as well as two adjacent natural grassland sites. Sampling was conducted on 12 occasions from March 1997 to January 1999. Forty‐nine ant species from 19 genera were recorded during the study. Site species richness was positively correlated with rehabilitation age, ranging from 10 to 25 at ash‐dam sites, compared with 28 and 34 at the two natural grassland sites. There was a humped relationship between total ant abundance and rehabilitation age, with abundance peaking after 5–7 years at levels far higher than those at natural sites. Ordination analysis showed clear separation between ash‐dam and natural sites along the first axis. The unrehabilitated ash‐dam site was also separated from rehabilitated sites along the first axis. Sites of different rehabilitation age were separated along the second axis. Individual ant species showed clear successional patterns across the rehabilitation gradient. Although there was a clear successional trend for the development of ant communities on rehabilitated ash dams, this trend was not toward natural grassland. The lack of convergence toward ant communities of natural grasslands reflects the markedly different substrate and plant composition on ash dams and supports the widely held view that restoration of natural grassland communities is not a realistic goal of ash‐dam rehabilitation. However, the development of species‐rich ant communities, containing at least some late‐successional species, indicates the potential for rehabilitated ash dams to support diverse and complex ecosystems.     

Using Dominance-Diversity Curves to Assess Completion Criteria After Bauxite Mining Rehabilitation in Western Australia

Abstract Dominance‐diversity curves have been previously constructed for a range of ecosystems around the world to illustrate the dominance of particular species and show how their relative abundances compare between communities separated in time or space. We investigate the usefulness of dominance‐diversity curves in rehabilitated areas to compare the floristic composition and abundance of “undisturbed” areas with disturbed areas, using bauxite mining rehabilitation in Western Australia as an example. Rehabilitated pits (11–13 years old) subjected to prescribed fire in autumn and spring were compared with unburned rehabilitated areas and the native jarrah (Eucalyptus marginata) forest. Dominance diversity curves were constructed by ranking the log of the species density values from highest to lowest. Species were categorized according to a variety of functional responses: life form (trees, shrubs, subshrubs, and annuals), fire response syndrome (seeder or resprouter), nitrogen fixing capability, and origin (native or adventive). Exponential functions showed extremely good fits for all sites (r² = 0.939–0.995). Dominance diversity graphs showed that after burning of rehabilitated areas, sites exhibited a more similar dominance‐diversity curve than before burning. This was emphasized in a classification (UPGMA) of the regression equations from the dominance‐diversity curves that showed that sites burned in spring were more similar to the native forest than sites burned in autumn. There was no significant segregation of the nitrogen‐fixing and species origin categories, although the life form and fire response groupings showed significant segregation along the dominance‐diversity curve. Resprouters tended to be over‐represented in the lower quartiles and under‐represented in the upper quartiles of post‐burn sites. It is suggested that using dominance‐diversity curves in the monitoring of rehabilitated areas may be a useful approach because it provides an easily interpretable visual representation of both species richness and abundance relationships and may be further utilized to emphasize categories of plants that are over‐ or under‐represented in rehabilitated areas. This will assist in the post‐rehabilitation management of these sites.     

Post-pastoral changes in composition and guilds in a semi-arid conservation area, Central Otago, New Zealand

Changes in the vegetation of Flat Top Hill, a highly modified conservation area in semi;arid Central Otago, New Zealand, are described four years after the cessation of sheep and rabbit grazing. Unusually moist weather conditions coincide with the four-year period of change in response to the cessation of grazing. Between 1993 and 1997, the average richness and diversity (H') of species increased, and the average proportion of native species decreased significantly. The vegetation was significantly richer in exotic annual and perennial grass species, exotic perennial forbs, exotic woody species and native tussock grasses in 1997 than in 1993. Eight response guilds of species are identified. Most "remnant" native shrubs and forbs were stable, in that they remained restricted to local refugia and showed little change in local frequency. However, taller native grass species increased, some locally, and others over wide environmental ranges. Rare native annual forbs and several native perennial species from "induced" xeric communities decreased, and this may be a consequence of competition from exotic perennial grasses in the absence of grazing. The invasive exotic herb Sedum acre decreased in abundance between 1993 and 1997, but several other prominent exotic species increased substantially in range and local frequency over a wide range of sites. Exotic woody species, and dense, sward-forming grasses are identified as potential threats to native vegetation recovery.