The use of chronosequences in studies of ecological succession and soil development

1. Chronosequences and associated space-for-time substitutions are an important and often necessary tool for studying temporal dynamics of plant communities and soil development across multiple time-scales. However, they are often used inappropriately, leading to false conclusions about ecological patterns and processes, which has prompted recent strong criticism of the approach. Here, we evaluate when chronosequences may or may not be appropriate for studying community and ecosystem development. 2. Chronosequences are appropriate to study plant succession at decadal to millennial time-scales when there is evidence that sites of different ages are following the same trajectory. They can also be reliably used to study aspects of soil development that occur between temporally linked sites over time-scales of centuries to millennia, sometimes independently of their application to shorter-term plant and soil biological communities. 3. Some characteristics of changing plant and soil biological communities (e.g. species richness, plant cover, vegetation structure, soil organic matter accumulation) are more likely to be related in a predictable and temporally linear manner than are other characteristics (e.g. species composition and abundance) and are therefore more reliably studied using a chronosequence approach. 4. Chronosequences are most appropriate for studying communities that are following convergent successional trajectories and have low biodiversity, rapid species turnover and low frequency and severity of disturbance. Chronosequences are least suitable for studying successional trajectories that are divergent, species-rich, highly disturbed or arrested in time because then there are often major difficulties in determining temporal linkages between stages. 5. Synthesis. We conclude that, when successional trajectories exceed the life span of investigators and the experimental and observational studies that they perform, temporal change can be successfully explored through the judicious use of chronosequences

Is 500m2 an effective plot size to sample floristic diversity for Queensland’s vegetation?

Species area curves from 37 sites spanning the diversity of native vegetation in Queensland were examined. For the majority of sites investigated a 500 m2 plot captured about 80–90% of the vascular plant species present at the time of sampling. Floristic data collected for grassland, heathland, acacia shrublands and most eucalypt woodlands using a 500 m2 plot is appropriate for floristic analysis and adequately represent the vascular plants present at the site at the time. Using a larger plot would only slightly increase the species capture at a site but it would generally be more efficient to increase the number of sites sampled to more adequately capture the diversity across the extent of the vegetation type. However for many Queensland rainforest communities, a much larger sample size is required to capture the full species richness of a site

Minimizing Bias in Biomass Allometry: Model Selection and Log‐Transformation of Data

Nonlinear regression is increasingly used to develop allometric equations for forest biomass estimation (i.e., as opposed to the traditional approach of log‐transformation followed by linear regression). Most statistical software packages, however, assume additive errors by default, violating a key assumption of allometric theory and possibly producing spurious models. Here, we show that such models may bias stand‐level biomass estimates by up to 100 percent in young forests, and we present an alternative nonlinear fitting approach that conforms with allometric theory

The Use of Sheep Wool in Nest Construction by Hawaiian Birds

Reports were scanned in black and white at a resolution of 600 dots per inch and were converted to text using Adobe Paper Capture Plug-in.The utilization of sheep wool as a nesting material was examined from 1969 through 1975 on the island of Hawaii. Of the 10 bird species studied, six incorporated wool into their nests. Both introduced and endemic birds use wool, with a significantly greater usage by endemic birds. Use of wool in nest construction appears correlated with the intricacy of the nest that a species builds, with a significant difference between degree of usage in complex and simple nests. Roughly built nests, like those of the Cardinal (Cardinalis cardinalis), contained no wool whereas the complex nest of the Elepaio (Chasiempis sandwichensis) had a great deal of wool. Wool is apparently used by the birds because it is a readily available material in certain areas, and because of its binding quality. The wool is gathered from tufts that snag on branches as the sheep pass or from dried skins on the ground. The amount of wool utilized in each nest varies both interspecifically and intraspecifically, but in all nests only the body of the nest contained wool, the lining always being of other materials. A separate study was conducted to determine if wool is used only when available nearby or is a sought-after material. Only the Elepaio was found to consistently travel distances to procure wool, whereas the other species studied used it only when available within their territories.This work was supported by the Frank M. Chapman Memorial Fund, the International Council for Bird Preservation, NSF grant GB 23230, and The World Wildlife Fund

A survey of selected coastal vegetation communities of Florida

A survey of coastal vegetation around Florida was conducted during 1973 and 1974. Seventeen sites were selected and sampled using the transect method to determine species occurrence, relative densities, and habitat development and structure. Sites were sampled quarterly except where high tides prevented data gathering. Species occurrence was compared within and between sites using Sarensen's Index of Similarity (IS,) as a basis for determining similarity of species inhabiting selected sites. Indices ranged from 4 to 61%, the former representing only one plant common to two sites. Results show environmental factors acting upon species alter species composition in seemingly similar habitats. Instead of the term "community", the term "association" is used to better reflect the concept of a taxonomically unrelated group of plants occupying a particular habitat. (Document has 40 pages.

Nodule Biomass of the Nitrogen-fixing Alien Myrica faya Ait. in Hawaii Volcanoes National Park

Myricafaya forms a nitrogen-fixing symbiosis in which fixation takes place in specialized root nodules. The biomass of these nodules was greater in open-grown than shaded individuals of Myricafaya, and was greater in large than small individuals. All Myricafaya examined, including seedlings and those growing epiphytically, had active nodules. Nitrogen fixation by invading Myrica faya could alter patterns of primary succession in Hawaii Volcanoes National Park

Isolated and vulnerable: the history and future of Pacific Island terrestrial biodiversity

Islands in the tropical Pacific have a rich and unique biota produced by island biogeographic processes and modified by recent anthropogenic influences. This biota has been shaped by four overlapping phases: natural colonization and dynamics (phase 1), impacts of indigenous (phase 2) and non-indigenous (phase 3) settlers, and increasing environmental awareness (phase 4). Island ecosystems are resilient to natural disturbance regimes but highly vulnerable to invasive species and other human-related influences, due to comparatively low alpha diversity, isolated evolution and the absence of certain functional groups. Habitat loss, overexploitation, invasive alien species and pollution continue to threaten terrestrial biodiversity, compounded by limited environmental awareness, minimal conservation funding, project mismanagement, limited local capacity and inadequate and/or unsuitable conservation policies. To achieve effective conservation of terrestrial biodiversity in the region, biophysical threats need to be mitigated with improved scientific, institutional and management capacity

Determination of Ellenberg’s indicator values along an elevational gradient in Central Black Sea Region of Turkey

The Central Black Sea Region has an unique vegetation because different vegetation types occurred. In the present study plant communities (from Mediterranean-type to temperate forests) in the Central Black Sea Region along an elevational gradient was evaluated on Ellenberg’s Indicator Values (EIVs). EIVs were calculated for nutrient availability, pH and temperature variables (nutrient availability (N), pH (R) and temperature (T)) with the help of weighted averages. Additionally, the vegetation of the study area was classified by using two way indicator species analyses (TWINSPAN) method and the interactions among plant species and EIVs were also studied by the help of Canonical Correspondence Analysis (CCA). We found some differences between our data and the previous data which were obtained from similar vegetation types with respect to EIV’s for nutrient availability, pH and temperature. Pteridium aquilinum, Fragaria vesca and Euphorbia amygdaloides var. amygdaloides may be used as an indicator of nutrient availability. There were significant differences among species regarding EIVs for temperature because the study area includes temperate and Mediterranean-type communities