CO2 efflux from subterranean nests of ant communities in a seasonal tropical forest, Thailand

Many ant species construct subterranean nests. The presence of their nests may explain soil respiration "hot spots", an important factor in the high CO2 efflux from tropical forests. However, no studies have directly measured CO2 efflux from ant nests. We established 61 experimental plots containing 13 subterranean ant species to evaluate the CO2 efflux from subterranean ant nests in a tropical seasonal forest, Thailand. We examined differences in nest CO2 efflux among ant species. We determined the effects of environmental factors on nest CO2 efflux and calculated an index of nest structure. The mean CO2 efflux from nests was significantly higher than those from the surrounding soil in the wet and dry seasons. The CO2 efflux was species-specific, showing significant differences among the 13 ant species. The soil moisture content significantly affected nest CO2 efflux, but there was no clear relationship between nest CO2 efflux and nest soil temperature. The diameter of the nest entrance hole affected CO2 efflux. However, there was no significant difference in CO2 efflux rates between single-hole and multiple-hole nests. Our results suggest that in a tropical forest ecosystem the increase in CO2 efflux from subterranean ant nests is caused by species-specific activity of ants, the nest soil environment, and nest structure

Biodiversity on Broadway - Enigmatic Diversity of the Societies of Ants (Formicidae) on the Streets of New York City

Each year, a larger proportion of the Earth's surface is urbanized, and a larger proportion of the people on Earth lives in those urban areas. The everyday nature, however, that humans encounter in cities remains poorly understood. Here, we consider perhaps the most urban green habitat, street medians. We sampled ants from forty-four medians along three boulevards in New York City and examined how median properties affect the abundance and species richness of native and introduced ants found on them. Ant species richness varied among streets and increased with area but was independent of the other median attributes measured. Ant assemblages were highly nested, with three numerically dominant species present at all medians and additional species present at a subset of medians. The most common ant species were the introduced Pavement ant (Tetramorium caespitum) and the native Thief ant (Solenopsis molesta) and Cornfield ant (Lasius neoniger). The common introduced species on the medians responded differently to natural and disturbed elements of medians. Tetramorium caespitum was most abundant in small medians, with the greatest edge/area ratio, particularly if those medians had few trees, whereas Nylanderia flavipes was most abundant in the largest medians, particularly if they had more trees. Many of the species encountered in Manhattan were similar to those found in other large North American cities, such that a relatively small subset of ant species probably represent most of the encounters humans have with ants in North America

Response of soil microbial functionality and soil properties to environmental plantings across a chronosequence in south eastern Australia

In Australia, environmental plantings using native trees and shrubs have been established to restore agricultural landscapes affected by land degradation. We studied a chronosequence of environmental plantings established between 1993 and 2005, adjacent to pasture and remnant woodland at three study areas on contrasting soil types in New South Wales. Our aim was to assess the effects of environmental plantings on soil properties and microbial attributes and to determine if the recovery to the conditions found under extant remnant woodland were achievable. We examined total organic carbon (TOC), total nitrogen (TN), extractable phosphorus (P), soil pH, electrical conductivity (EC), and changes in microbial functional diversity and activity across the pasture, environmental plantings of different ages and remnant woodlands. Microbial functional diversity, determined using MicroResp™, differed between pasture and environmental plantings, and between environmental plantings and the remnant woodland soil. Ordination distances of microbial functional diversity declined by 7%–36% between environmental plantings and remnant woodland as the age of the environmental planting increased (microbial functionality in plantings becoming similar to that under remnant with increasing age). This result indicated a trajectory of recovery in soil microbial function through time. TOC, TN, P, C:N and EC were positively correlated with microbial activity at all sites. Although TOC and TN levels remained similar under environmental plantings compared to pasture, P levels increased under environmental plantings and with increasing planting age. These results suggest that the environmental plantings had not attained the same functions and nutrient status under their canopies as the remnant woodland soils, but their condition was on a trajectory of change from that of the pasture systems toward that of the remnant vegetation. Therefore, establishment of environmental plantings on degraded lands is an approach that can successfully enhance soil microbial recovery

Spatial distribution of soil microbial activity and soil properties associated with Eucalyptus and Acacia plantings in NSW, Australia

Although much work has been completed in Australia to examine the effects on aboveground ecology of environmental plantings using mixed species of native trees, only limited attention has been focused on their effects on soils and soil microbial population. A study was conducted to determine the spatial distribution of microbial activity, total soil organic carbon (TOC), total nitrogen (TN) and extractable phosphorus (P) in soils under Eucalyptus camaldulensis and Acacia pendula. A 13-year-old environmental planting with mixed native tree species at Gunnedah, New South Wales, was used as a study site. Soil samples were taken from both inside and outside the tree canopy at each of the four compass points (N, S, E and W) at depths of 0-5, 5-10, 10-20, 20-30 and 30-50 cm. The soil was tested for heterotrophic respiration (MicroRespTM), TOC and TN (LECO) and P (Colwell). Microbes were more active inside compared with outside the tree canopy in both A. pendula and E. camaldulensis. The basal respiration rate was significantly higher under A. pendula canopy compared with E. camaldulensis canopy. The relative activity of the microbes and concentrations of TOC, TN and P declined with soil depth. Further, TOC, TN and P contents under the canopy of A. pendula were higher than those of E. camaldulensis and showed a significant positive correlation with basal respiration. However, no difference was detected in the various soil properties measured and microbial activity at four compass points around trees. Changes in soil TOC, TN and extractable P due to the tree plantings were significant only for the 0-5 cm soil depth and changes in microbial activity were mostly confined to the upper 20 cm depth. The improved levels of soil microbial activity and soil nutrients under the tree canopy could be used to measure restoration success of environmental plantings

Community-Friendly Methods for Monitoring Riverside Rehabilitation: A Case Study

Local community groups in their management of rehabilitation projects are often motivated by the goal of creating ecosystems that provide improved habitats for native species. It is important that community groups have the ability to monitor progress towards such a goal, to ensure their hard work and time has not been wasted. Indeed, government funding bodies now require the objectives of rehabilitation projects to be measured in terms of outcomes and reported as such. Terrestrial invertebrates have been recommended as bioindicators because of their abundance, importance in ecosystem function and their sensitivity to environmental change. However, monitoring invertebrates is often not feasible by community groups because of the high costs of both laboratory sorting and storage of specimens. Monitoring invertebrates also requires access to both specialist equipment and taxonomic expertise. Here we present the results of a project to develop indices that: (i) are cost-effective; (ii) limit and/or eliminate laboratory processing and the need for expert help; (iii) can be derived by community groups; (iv) based on processes that invertebrates are responsible for; and (v) are indicative of, and related to, successive stages of riparian rehabilitation. Several simple methods such as scoring insect leaf damage, measuring rates of seed removal by ants and assessing the diversity of web-building spiders (using features of their webs) were developed. These methods and indices were then compared to invertebrate taxa richness and abundance at the same sites estimated from traditional invertebrate sampling techniques such as yellow-pan and pit-fall traps. A set of the simpler methods were subsequently trialled at community attended workshops where we examine observer accuracy, precision and method 'useability'. Quantitative and semi-qualitative collected data from these workshops were used to further refine methods and a number of important outcomes were gained through post-workshop evaluations