Establishment Of Many Species Research Articles

Environmental factors differentially influence species distributions across tree size classes in a dry evergreen forest in Sakaerat Biosphere Reserve, northeastern Thailand

ABSTRACT Plant communities in tropical forests are influenced by multiple environmental variables. For trees, soil and topographic characteristics are key factors that impact the establishment of many species. In this study, the impacts of soil properties and topography on forest structure, species composition, α- and β-diversity, and tree species distribution across size classes were investigated in a dry evergreen forest (DEF) in the Sakaerat Biosphere Reserve, northeastern Thailand. Within a 16 ha permanent plot, all trees with a diameter at breast height (DBH) ≥ 1 cm were recorded. Tree species distributions mostly respected gradients of plot elevation and soil nutrient, including available P; these variables were strongly associated for most size classes. Structural attributes (basal area and tree density) of trees with a DBH of 5–10 cm were highly sensitive to these variables. For trees with a DBH of 2–5 cm, α-diversity was negatively associated with available P while β-diversity was associated with topography and available P. These findings demonstrate the strong influence of topographic and edaphic variables in shaping the DEF. Sensitivity to these variables, particularly elevation and increases in available P, increased with increasing tree size among size classes, as small trees were less sensitive than were larger trees. Our study provides an example of how different environments affect many of the features of tropical forest structure, such as tree size class and species composition.

Long-term, large-scale experiment reveals the effects of seed limitation, climate, and anthropogenic disturbance on restoration of plant communities in a biodiversity hotspot

Ecological restoration is essential for maintaining biodiversity in the face of dynamic, global changes in climate, human land use, and disturbance regimes. Effective restoration requires understanding bottlenecks in plant community recovery that exist today, while recognizing that these bottlenecks may relate to complex histories of environmental change. Such understanding has been a challenge because few long-term, well-replicated experiments exist to decipher the demographic processes influencing recovery for numerous species against the backdrop of multiyear variation in climate and management. We address this challenge through a long-term and geographically expansive experiment in longleaf pine savannas, an imperiled ecosystem and biodiversity hotspot in the southeastern United States. Using 48 sites at three locations spanning 480 km, the 8-y experiment manipulated initial seed arrival for 24 herbaceous plant species and presence of competitors to evaluate the impacts of climate variability and management actions (e.g., prescribed burning) on plant establishment and persistence. Adding seeds increased plant establishment of many species. Cool and wet climatic conditions, low tree density, and reduced litter depth also promoted establishment. Once established, most species persisted for the duration of the 8-y experiment. Plant traits were most predictive when tightly coupled to the process of establishment. Our results illustrate how seed additions can restore plant diversity and how interannual climatic variation affects the dynamics of plant communities across a large region. The significant effects of temperature and precipitation inform how future climate may affect restoration and conservation via large-scale changes in the fundamental processes of establishment and persistence.

Saline gradient drives functional nestedness of polychaete communities in tropical estuaries

Estuarine environmental gradients are strong drivers structuring aquatic metacommunities and may cause an orderly loss or gain of species across sites. Locations with milder environmental conditions may allow the establishment of many species with different functional traits, while stressful sites may restrict the occurrence of a reduced set of species with specific functional traits. This can generate a functional nestedness pattern, where the functional traits present at sites with low functional diversity are subsets of the functional traits present at sites with higher functional diversity. In this study, we evaluated the functional nestedness of polychaete communities along salinity gradients of tropical estuaries, and the effects of seasonal periods on the distribution pattern. Two tropical estuarine ecosystems (Mamanguape and Paraíba do Norte, Northeastern Brasil) were sampled for two years. Three functional traits were considered due to their potential to reflect the species responses to the salinity gradient: maximum body size, life span and fecundity. Functional nestedness was estimated with the traitNODF metric. Subsequently, we used a permutation test to assess whether the nestedness observed along the salinity gradient was distinct from the expected at random. Our results demonstrated that the polychaete communities presented a tendency to functional nestedness along the salinity gradient of estuaries, with observed statistics higher than expected in six of the eight tests performed (2 estuaries * 2 years * 2 seasons). Therefore, the functional diversity of polychaete genera present in the low salinity sites in general were nested subsets of the diversity at high salinity sites. Our results suggest that salinity acted as a strong environmental filter in estuarine ecosystems, causing an orderly loss in the functional traits of polychaete genera along the longitudinal extension of the estuaries. Our results advance in the understanding on how environmental gradients structure polychaete communities and can support future studies aimed to develop conservation strategies for estuarine ecosystems located throughout the world.

The effect of fire on seed germination of campo rupestre species in the South American Cerrado

Fire is an important disturbance in terrestrial ecosystems and plays a key role in the germination process and seedling establishment of many species. In grassland ecosystems, seeds normally tolerate heat-shocks associated with low intensity fires but are negatively affected by higher heat doses. Additionally, smoke-stimulated germination is not commonly recognized as important in neotropical grasslands. This may result from a negative relationship between the ability to resprout after fire and fire-stimulated germination ability, as many species in these grasslands regenerate well after fire by resprouting. To ascertain the role of heat and smoke in the post-fire germination response of campo rupestre vegetation, we exposed seeds of nine species (that regenerate after fire by resprouting) to various treatments related to fire (heat, smoke, and heat plus smoke) and analysed their germination behaviour. Our results suggest that these species have high seed germination in the absence of specific dormancy breaking conditions and/or that stimulated germination triggered by fire-related cues is not common. Additionally, while seeds from some species can withstand temperatures of 80 °C for 5 min without affecting germination, most species are negatively affected by higher heat doses. However, our results suggest an important role of smoke enhancing germination rate (speed) of campo rupestre species. In view of the characteristics of campo rupestre environmental conditions and vegetation, we provide a novel outlook of enhanced germination rate by smoke as an important mechanism for seed regeneration after fire of campo rupestre’s species that resprout, particularly for seeds resulting from post-fire seed dispersion.

Ecosystem engineering through aardvark (Orycteropus afer) burrowing: Mechanisms and effects

Burrowing mammals are often considered to be ecosystem engineers as burrowing disturbs the soil, thereby potentially changing resource availability and affecting habitat conditions for other species. After their excavation, burrows may strongly impact local plant communities through several mechanisms, including resource trapping, altered chemical and physical soil properties, and amelioration of microclimatic conditions. We studied ecosystem engineering by aardvark (Orycteropus afer) burrowing by comparing soil and vegetation characteristics between three microsites (burrow entrances, excavated soil mounds and adjacent control sites). We were able to identify several engineering effects and distinguish between potential mechanisms. Burrow soils were cooler, drier and less compact than the other microsites, with all three microsites representing unique combinations of abiotic conditions. Mean species richness was higher at older burrows than mounds and non-burrowed controls, despite burrows having a smaller seedbank and not differing in soil fertility from mounds and control sites. However, the opposite was observed at fresh burrows and mounds, where control plots contained more species on average than the other two types of microsites. Burrow age and microsite type also affected species composition, although only a small proportion of species were significantly associated with specific microsites and just two species were limited to a single microsite type. We suggest that trampling and the physical digging action at burrow entrances, and burial by deposited soil at mounds, prevents the establishment of many plant species at active burrows. However, once abandoned, burrow entrances provide good physical conditions for seedling survival, allowing the establishment of more species. Therefore, as suggested previously for other ecosystem engineers, it is important to explicitly consider the age and degradation processes of engineered structures. In addition, our results highlight biologically-important differences in engineering impacts between burrow entrances, where soil is removed, and mounds, where soil is deposited. Such microscale differences are important to consider when examining bioturbation or, more generally, ecosystem engineering.

A Ticking Time Bomb: Is the illegal pet trade a pathway for the establishment of Corn Snake (Elaphe guttata) populations in Australia?

ABSTRACT The exotic pet trade may be the principal mechanism for the establishment of invasive reptile species. The escape or deliberate release of captive reptiles has resulted in the establishment of many species globally. In Australia, exposure to this entry pathway has been limited due to long-term legislation preventing the importation and keeping of exotic reptiles by private keepers. Despite this, the corn snake Elaphe guttata is still illegally maintained in many private collections, resulting in occasional reports of released or escaped specimens. We recorded 79 free-ranging corn snakes captured by three wildlife organizations between 2002 and 2014 in the greater Sydney region, Australia. There was an increasing encounter rate over time, suggesting that this is a growing problem and may result in the establishment and spread of this species into Australia. Corn snakes were recorded throughout the Sydney region. No snake clusters were found and this suggests that populations may not have become es...

Vriesea friburgensis: A natural trap or a nurse plant in coastal sand dunes?

Positive interactions between plants play a fundamental role in environments with extreme conditions, such as coastal sand dunes, where the establishment of many species is limited by high temperature, and low availability of water and nutrients in the soil. The ability to store water and enrich the soil with nutrients characterizes bromeliads as potential nurse plants for other species. This study aimed to analyze the potential of the bromeliad Vriesea friburgensis to act as a nurse plant, and to compare this interaction in coastal dunes in herbaceous versus scrub vegetation. The study was performed on Santa Catarina Island in Brazil. Juveniles of other species associated with V. friburgensis were collected within and under bromeliad tanks and on adjacent plots beside each bromeliad. The abundance, species richness and height of juveniles were recorded. We found that abundance and richness of Vf-associated juveniles were lower than those Vf-not associated, in herbaceous vegetation (negative interaction). However, the height of some shrubs species, like Eupatorium casarettoi and Tibouchina urvilleana, was greater when Vf-associated (positive interaction). In scrub vegetation, the abundance and richness of juveniles were not significantly affected by V. friburgensis presence (neutral interaction). However, the height of some shrubs and trees species, like Clusia criuva, Eugenia catharinae, Myrsine parvifolia and Ocotea pulchella, was greater when Vf-associated. Species composition associated with V. friburgensis differed from the assemblage in adjacent plots, indicating that some species interact more with nurse plants, whereas others fail to develop when associated with this bromeliad; the difference between groups in species composition was less evident in scrub vegetation areas. Clusia criuva was considered an indicator species for Vf-associated juveniles in both vegetation types. Despite the fact that these tank bromeliads do not function as nurse plants for some species, there are others that seem to be favoured by this interaction.

Riqueza y composición florística de pteridobiontes en bosque mesófilo de montaña y ambientes asociados en el centro de Veracruz, México

We describe and compare the richness and floristic composition of ferns in natural humid montane forest and disturbed environments associated with different degrees of anthropogenic influence. The study sites were located at the Loma de Santa Rita in the Sierra de Chiconquiaco, central region of Veracruz, Mexico. Furthermore, we made a comparison with other fern inventories from humid montane forests in central Veracruz based on published studies. We established 72 sampling plots of 10×10m each in 6 different environments; natural forest, mature and young secondary forest, shade coffee, Pinus patula plantation, and pasture with remnant trees. We recorded a total of 81 species distributed in 17 families and 36 genera. The results indicate that the natural forest is most species rich, whereas fern diversity decreases with the degree of vegetation disturbance up to 70%. The study highlights the importance of fallows and shade coffee plantations to retain and allow the establishment of many species also found in the forest.

The influence of spring floods on small mammal communities in the Nemunas River Delta, Lithuania

The influence of the annual spring floods on small mammal communities was studied in the Nemunas River Delta, SW Lithuania. The aim of the investigation was to compare the diversity of small mammals inhabiting spring-flooded meadows, meadows not subjected to flooding and spring-flooded forest in years characterized by differing heights and durations of spring flood. In the years of the high flood, the number of species and diversity index were higher, while index of dominance was less than in the years of low flood. Significantly, the highest proportions of Apodemus agrarius were recorded in spring-flooded meadows in years of high flood (41.7%), while Microtus oeconomus occurred in the highest proportions in spring-flooded meadows in years of low flood (66.8%) and in meadows not subjected to flooding (47.1%). In non-flooded areas, M. Oeconomus is not expelled by the floods and outcompetes other species. After high levels of flooding, during the process of re-population, the voles may be outcompeted by A. agrarius. In the absence of dominant species, greater opportunities existed for the establishment of more species (13 species in flooded meadows). Micromys minutus accounted for up to 19.5–30.1% in the years of high flood. We concluded that the annual spring floods in the Nemunas Delta had no long-term negative effects, the number of small mammal species and their abundance had been restored in just a few months. The worst consequences of the high flood were recorded in forest habitat. Spring floods, and especially the higher floods, are natural environmental agents, maintaining the high diversity of small mammals in meadows and reed-beds.

The ecological relationships and demography of restricted ironstone endemic plant species: implications for conservation

We investigated the ecological relationships, reproductive biology and demography of four shrub taxa restricted to ironstone ranges in south-western Australia, to assess the feasibility of post-mining reintroductions. We found that three taxa were restricted to narrow fissures in massive ironstone and the fourth was restricted to fissures and skeletal soils over ironstone. In all taxa, adult plants were the most abundant life stage in populations and produced seeds annually. Newly emerged seedlings were observed in low numbers each winter of three census years, with the highest rates occurring when winter rainfall was above average in the semiarid Mediterranean climate. Mortality was highest and most variable for <1-year-old seedlings (50–93%), 1-year-old seedlings (17–67%), juveniles (21–54%) and vegetative adults (6–50%), and was lowest and least variable for the reproductive adults (2–7%). The restriction of three of our study taxa to narrow fissures excludes the option of using seedlings in reintroductions. Using seeds, although possible, will be both an inefficient and a high-risk strategy for at least three of the four taxa studied. This is because of the low frequency of years when winter rainfall is sufficient to stimulate high rates of seed germination, coupled with the consistently high rates of seedling mortality in most years, and no easy method for determining which rock fissures will be suitable for plant establishment. The more widespread taxa showed reproductive and demographic characteristics similar to those of the taxa restricted to the narrow fissures, indicating that establishment of many species will be difficult in this environment.

Vernon Reynolds. The Chimpanzees of the Budongo Forest: Ecology, Behaviour and Conservation

Vernon Reynolds first studied the chimpanzees of theBudongo Forest, Uganda, in 1962. His study wasinterrupted because of his university teaching positionand the unsafe situation in Uganda. His return to thefield was triggered by a newspaper article about twoinfant chimpanzees that had been smuggled fromUganda to Dubai. These two infants had almost cer-tainly been captured in the Budongo Forest. Reynoldsacquired sufficient funds to return to Uganda andrevisited Budongo in 1990, 27 years after leaving. In1991, he resumed a long-term study of the chimpanzeesliving in the Sonso area, located in the middle of theBudongo Forest, in collaboration with Andy Plumptre,a research director of the Budongo Forest Project.Reynolds and his colleagues have studied the Sonsochimpanzees intensively for 15 years.In his book, Reynolds recounts the history of theBudongo Forest and the work of a large numberof students and senior researchers studying the wildchimpanzees that live there. In five of the twelvechapters of the book he describes the life of the localpeople who live near the Budongo Forest and thehistory of activity to conserve the chimpanzees and theforest; this demonstrates the author’s enthusiasm forchimpanzee conservation and great insight into thecomplex issues concerning wildlife conservation.In Chapter 1 Reynolds outlines the history of theBudongo Forest. Except for forests that are nationalparks, for example Kibale Forest, all forests in Ugandaare ‘‘forest reserves’’ managed by the Ugandan gov-ernment. In these reserves the forest is managed forthe maintenance and use of forest resources, and aneffort has been made to increase the crop of mahoganytrees, which produce valuable timber. In the 1920s, theCynometra trees that dominated the Budongo Forestwere felled because they had no value as timber, andmahogany trees were planted, although without suc-cess. In the 1960s, trees with no commercial value,including Cynometra trees, were treated with a potentarboricide, and the number of Cynometra trees de-creased. Nevertheless, mahogany trees did not increaseas intended, and the treatment resulted in the estab-lishment of more species of non-timber fruiting tress,for example figs. Today, Budongo Forest has a greaterdensities of trees producing fleshy fruits, and of fruit-eating primates, in the logged and arboricide-treatedforest areas than it does in the unlogged, untreatedNature Reserves.The Budongo Forest is a relatively young forest,possibly 300–500-years old, and has changed as a resultof human activity. In this book, Reynolds emphasizesthe importance of practising chimpanzee conservationin such habitats, where most chimpanzees now live.In Chapters 2–8 Reynolds describes the ecology andsocial behavior of the Sonso chimpanzees. He presentsthe results of studies in Budongo and in other chim-panzee study sites, including several sites in Uganda,for example Kibale National Park and Kalinzu Forest.This book provides valuable information on chimpan-zee ecology and behavior, which differ among studysites and communities.In Chapter 2 Reynolds describes demographic andbasic data of the Sonso community, the process ofhabituation of Sonso chimpanzees, and associatedrisks, for example disease transmission and increased

Population dynamics of the shrub Acacia bilimekii in a semi-desert region in central Mexico

Shrubs are important elements of semi-desert vegetation. They provide microhabitats for the establishment of many species under their canopies thus maintaining community structure and diversity. Yet, little is known regarding their population processes and the factors that affect them. In this study, we report an analysis of the population dynamics of the shrub Acacia bilimekii. We followed a population sample ( N = 314 ) for a one-year period (2001–02) and built a projection matrix. We also carried out germination and seedling establishment experiments in two contrasting conditions: a well preserved and an eroded site, and both under the shade of shrubs and in the open. The results of these experiments were used to calculate the fecundity entries for the transition matrix. Germination was not affected by microhabitat (shade vs. open conditions) or site (eroded vs. well-preserved). However, seedling establishment after 7 months was significantly higher under the shade than in exposed conditions. Finite population growth rate was significantly higher than unity ( λ = 1.23 ± 0.173 ). Stasis was the demographic process that contributed mostly to λ (ca. 60%), followed by growth and fecundity. Even with a simulated decrease in fecundity values due to increased erosion, the A. bilimekii population would maintain a high λ-value. Thus, our results suggest that this population has the potential to persist even under relatively high disturbance levels.