Indicators Of Ecological Change Research Articles

基于多时相Landsat5/8影像的岷江汶川-都江堰段植被覆盖动态监测

PDF HTML阅读 XML下载 导出引用 引用提醒 基于多时相Landsat5/8影像的岷江汶川-都江堰段植被覆盖动态监测 DOI: 10.5846/stxb201409051756 作者: 作者单位: 西南土地资源评价与监测教育部重点实验室,西南土地资源评价与监测教育部重点实验室,西南土地资源评价与监测教育部重点实验室,西南土地资源评价与监测教育部重点实验室,西南土地资源评价与监测教育部重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(41371125) Dynamic monitoring of fractional vegetation cover along Minjiang River from Wenchuan County to Dujiangyan City using multi-temporal landsat 5 and 8 images Author: Affiliation: Key Lab of Land Resources Evaluation and Monitoring in Southwest,Ministry of Education,Sichuan Normal University,Chengdu,Sichuan,Key Lab of Land Resources Evaluation and Monitoring in Southwest,Ministry of Education,Sichuan Normal University,Chengdu,Sichuan,Key Lab of Land Resources Evaluation and Monitoring in Southwest,Ministry of Education,Sichuan Normal University,Chengdu,Sichuan,Key Lab of Land Resources Evaluation and Monitoring in Southwest,Ministry of Education,Sichuan Normal University,Chengdu,Sichuan,Key Lab of Land Resources Evaluation and Monitoring in Southwest,Ministry of Education,Sichuan Normal University,Chengdu,Sichuan Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:植被覆盖度是衡量地表植被状况和指示生态环境变化的一个重要指标。基于像元二分模型,利用Landsat5/8遥感影像和DEM数据,对岷江汶川-都江堰段植被覆盖动态变化进行了监测,并结合高程、坡度和坡向数据,分析了汶川地震前后植被受损与恢复的空间动态格局变化。研究表明:植被覆盖总体良好,大部分区域的植被覆盖度均在中、高度以上,空间格局上呈现由汶川县东部、都江堰市西北部的龙门山区向两侧减少的总体趋势;地震造成植被受损面积达63808.7 hm2,且集中分布于海拔567-4331 m、坡度26-51°的范围以及东坡、北坡、南坡和西坡;震后5a,植被恢复面积17786.47 hm2,主要分布在海拔576-2180 m与3256-3793 m、坡度小于9°和26-51°以及东坡、东南坡和和南坡;高程和坡度对植被损毁与恢复的影响明显高于坡向。 Abstract:The terrestrial ecosystem plays an important role in maintaining the structure, function, and environment of earth systems, and therefore, human survival. Fractional vegetation cover (FVC) is an important indicator of ecological changes in the environment, and an important spatial parameter of land surface vegetation status for various ecological models. It is very important to estimate the changes and patterns of FVC within the fragile ecological system of the Minjiang River, which is located in a transition zone between the Tibetan Plateau and Sichuan basin. FVC information in the arid valley of the Minjiang River was extracted from remote sensing data, DEM, and GIS technology following the dimidiate pixel model. The differentiation characteristics of the spatial and temporal dynamic patterns of FVC, vegetation damage caused by the Wenchuan earthquake, vegetation restoration, elevation, slope, and aspect were also quantitatively studied. The results showed that:(1) the vegetation coverage was generally good during the study period; there were variations in levels of FVC, and the FVC in most areas was above medium and high levels. The overall spatial pattern showed reduced FVC on either side of the Longmen Mountains, in eastern Wenchuan County, and northwestern Dujiangyan City. The FVC change tended to increase first, then decrease with increasing elevation rendering. Above the lower levels, FVC was mainly distributed at elevations of 4331-4869 m, where the FVC decreased with increasing slope. More than 24% of the vegetation coverage was distributed in the area where the slope was less than 9°; there was little or no vegetation coverage in areas where the slope was greater than 51°. The FVC also changed according to aspect. It was mainly distributed on the eastern, western, and southern slopes. (2) The area of vegetation damage caused by the Wenchuan earthquake was 63808.7 hm2. Severe damage to vegetation occurred mainly within the range of 567-4331 m elevation, on slopes of 26-51°, with eastern, northern, southern, or western aspects. (3) After five years of natural regeneration, 17786.47 hm2 of the destroyed areas were recovered. The recovered vegetation area occurred mainly across elevation ranges of 567-2180 m and 3256-3793 m, on slopes of <9° or 26-51°, and eastern, southeastern, and southern aspects. (4) The results also showed that elevation and slope had significantly larger effects than aspect on vegetation damage or restoration. Although there was a certain correlation between the vegetation damage and restoration, the change patterns were complicated. The results provided very useful information for decision-making and policy-planning in the region of the Minjiang River, from Wenchuan County to Dujiangyan City, after the Wenchuan earthquake. Although the natural vegetation recovery is a slow process, some of the areas with earthquake-induced damage can be restored to their original condition through natural succession. Human intervention may not be a good way to address natural vegetation recovery in this area. Thus, vegetation restoration mainly involves closing the areas to promote natural vegetation restoration, or adopting artificial forestation to restore vegetation in a small area. 参考文献 相似文献 引证文献

Testing the Performance of Macroinvertebrate Metrics as Indicators of Changes in Biodiversity After Pasture Conversion in Patagonian Mountain Streams

Conversion of native forest to pastures is a common practice worldwide; it has complex effects on river biota that are related to activity type and intensity. This work was conducted in order to evaluate the effects of cattle grazing on environmental features and to select the most appropriate measures based on the macroinvertebrate community as indicators of ecological changes. Physicochemical features, riparian ecosystem quality, habitat condition, and benthic macroinvertebrates were investigated in streams draining pastures and were compared to reference streams located in nonimpacted native forested catchments. Strong evidence of sediment deposition was observed at pasture streams, which had higher percentage of sand in the streambed but also increased levels of suspended solids. Pasture sites had significantly higher water temperature and conductivity as well as lower dissolved oxygen concentrations than did forested sites. Both riparian quality and in-stream habitat condition were degraded at pasture sites. Among metrics, total richness, Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, Plecoptera richness, Shannon diversity, percentage of dominant taxon, percentage of Chironomidae species, shredder richness, and percentage of predator resulted to be the most consistent measures by displaying stronger responses to impairment. Our results suggest that forest conversion to pasture for livestock practices is diminishing macroinvertebrate biodiversity and potentially changing functioning and dynamics of Patagonian mountain streams as well. Damage prevention on riverine landscapes by restoring riparian ecosystems, replanting missing vegetation in buffer areas, and limiting livestock access to the riverbanks could contribute to enhance the ecological integrity at converted areas. A more extended and comprehensive use of macroinvertebrate metrics could contribute to better understand and evaluate impact effects of these extended land use activities and to promote conservation strategies.

Small mammal responses to environmental change: integrating past and present dynamics

Forecasting the response of species and communities to environmental change is a priority for multiple disciplines in the natural sciences. In looking toward the future, much can be learned from examining faunal response under past episodes of environmental change. Typically, retrospective approaches are limited to one spatial and temporal scale. Here, we illustrate how integrating across spatiotemporal scales can provide powerful insights into faunal response, and can inform conservation and management. To do this we compare paleontological and neontological studies on the small mammal fauna of the Great Basin. Small mammal species and their assemblages have long been recognized as indicators of ecological change and ecosystem health. We use fossil data from two long-term owl roosts to reconstruct patterns of richness and the apportioning of abundance among functional groups across multiple episodes of warming during the Holocene (last 10,000 years). We then use these findings as a climate-only baseline against which to compare changes in richness and abundance in 2 independent mountain ranges over the past century. While the past century has been marked by climate warming, the modern day Great Basin landscape also has been subject to intense human land-use practices and the introduction of nonnative plant species. Our contrast highlights that for Great Basin small mammals, modern-day land-use practices are modifying climate-based expectations.

Roaring counts are not suitable for the monitoring of red deer Cervus elaphus population abundance

The successful management of large herbivores requires the monitoring of a set of indicators of ecological change (IEC) describing animal performance, herbivore impact on habitat and relative animal abundance. Roaring counts during the rut have often been used to assess the abundance of red deer Cervus elaphus populations, but a formal evaluation of this method is still lacking. In this paper, we examined the usefulness of the number of red deer recorded during roaring counts for managing red deer populations. Using standardised spotlight counts applied for the monitoring of red deer at La Petite Pierre, France, as a reference method, we found that roaring counts did not correlate with spotlight counts. Moreover, we did not find any evidence that roaring counts decreased with increasing number of male and female red deer harvested in the reserve during the previous hunting season. We thus conclude that managers should not rely on roaring counts for managing red deer populations.

Benthic meiofauna as indicator of ecological changes in estuarine ecosystems: The use of nematodes in ecological quality assessment

Estuarine meiofauna communities have been only recently considered to be good indicators of ecological quality, exhibiting several advantages over macrofauna, such as their small size, high abundance, rapid generation times and absence of a planktonic phase. In estuaries we must account not only for a great natural variability along the estuarine gradient (e.g. sediment type and dynamics, oxygen availability, temperature and flow speed) but also for the existence of anthropogenic pressures (e.g. high local population density, presence of harbors and dredging activities).Spatial and temporal biodiversity patterns of meiofauna and free-living marine nematodes were studied in the Mondego estuary (Portugal). Both taxonomic and functional approaches were applied to nematode communities in order to describe the community structure and to relate it with the environmental parameters along the estuary. At all sampling events, nematode assemblages reflected the estuarine gradient, and salinity and grain size composition were confirmed to be the main abiotic factors controlling the distribution of the assemblages.Moreover, the low temporal variability may indicate that natural variability is superimposed by the anthropogenic pressures present in some areas of the estuary. The characterization of both meiofauna and nematode assemblages highlighted the usefulness of the integration of both taxonomic and functional attributes, which must be taken into consideration when assessing the ecological status of estuaries.

The oak browsing index correlates linearly with roe deer density: a new indicator for deer management?

Increasing populations of large herbivores during the last decades have had a major impact on vegetation. While several studies have looked for quantifying this impact in terms of plant biomass, plant survival or financial costs, the potential benefit of using the response of the vegetation to changes in browsing pressure by large herbivores to monitor their populations has been poorly investigated. As getting accurate estimates of density in populations of large herbivores is problematic, the use of indicators measuring the intensity of browsing might offer reliable alternative to managers. From the intensive monitoring of a roe deer population subject to an experimental manipulation of density, we looked for assessing the response of oak to changes of roe deer population size. Using a simple browsing index calculated from field data over 10 years, we found that this oak browsing index linearly increased with increasing population size of roe deer. This suggests that such an oak browsing index might be a reliable “indicator of ecological change” for monitoring roe deer populations in oak forests with natural regeneration.

The effects of volcanism on Oligocene-age plant communities from the Ethiopian Plateau, and implications for vegetational resilience in a heterogeneous landscape

Substantial volcanism and associated volcaniclastic sedimentation took place in association with East African Rift formation, and in some cases this would have had substantial ecological impacts. Ethiopian Late Oligocene (27.36 ± 0.11 Ma) fossiliferous volcanogenic strata provide opportunities to evaluate the magnitude of disruptive impact of volcanism on forest communities (before development of the Main Ethiopian Rift), and to assess their resilience. Fine-scale sampling and palynological analyses from the Magargaria River region of the northwestern Ethiopian Plateau tests the hypothesis that volcanism had a regional and significant disrupting effect on forest vegetation. These studies are compared with macrofossil and sedimentological data representing more local conditions previously reported from the same sediments. Results indicate that while some forests gave way to open environments dominated by herbaceous taxa, other communities remained or recovered quickly. Volcanic influences on sedimentary processes altered an existing forest ecosystem by creating a spatially heterogeneous landscape that also varied through time. This study supports the inherent significance of palynological data as indicators of ecological change at a regional scale relative to the more local view that macrofossils can provide, and underscores the importance of both kinds of fossils whenever possible for the study of the ecological dynamics of plant communities. The presence of forest taxa after repeated ashfalls indicates a degree of forest community resilience consistent with relatively limited burial by ash during the studied volcanic episodes. This study also suggests that taphonomic and diagenetic processes strongly affected the composition of palynomorph assemblages, skewing them towards thick-walled individuals, especially fungi.

Are abundance indices derived from spotlight counts reliable to monitor red deer Cervus elaphus populations?

AbstractManagement of large herbivores could be improved by investing less effort in estimating absolute abundance and more effort tracking variation over time of indicators of ecological change (IEC) describing animal performance, herbivore impact on habitat, and relative animal abundance. To describe relative changes in animal abundance, monitoring trends in numbers through indices may constitute a useful and low cost method, especially at large spatial scales. Reliability of indices to detect trends should be evaluated before they are used in wildlife management. We compared population trends estimated from spotlight counts, a standard census method for deer populations, with population size estimates of a red deer Cervus elaphus population monitored using Capture‐Mark‐Recapture (CMR) methodology. We found a strong negative effect of conditions of observation (e.g. rainfall) on both the number of animals (‐24.4%) and the number of groups (‐31.6%) seen per kilometre. After controlling for observation conditions, we found that these two abundance indices were linearly correlated with CMR estimates, with the group‐based index being better correlated (r = 0.75) than the individual‐based index (r = 0.68). These consistent trends between indices and CMR estimates provide support in using standardised spotlight counts as an IEC describing relative changes in abundance for the monitoring and management of red deer populations.

Determination of total antibiotic resistance in waterborne bacteria in rivers and streams in Northern Ireland: Can antibiotic-resistant bacteria be an indicator of ecological change?

Antibiotic resistance (ABR) has now become a major public health issue. Relatively little studies have been published on the incidence of ABR in environmental isolates circulating within the community. A study was performed to determine the diversity of total ABR (intrinsic + acquired resistance) in waterborne bacteria. Surface water from 12 waterways, including 11 rivers/steams and 1 lake, were examined for the presence of ABR phenotypes, using a direct antibiotic susceptibility assay and demonstrated the presence of ABR (in increasing order of resistance), to the following 19 agents: amikacin (17%), gentamicin (17%), ciprofloxacin (33%), colistin (42%), linezolid (42%), tobramycin (42%), vancomycin (42%), ertapenem (67%), erythromycin (75%), meropenem (75%), rifampin (75%), teichoplanin (75%), tetracycline (75%), trimethoprim (75%), fusidic acid (83%), aztreonam (92%), clindamycin (92%), penicillin (92%) and cefoxitin (100%). Multiple resistance to the major classes of antibiotics was noted, which varied from one to six classes, with a mean resistance to 3.7 major antibiotics classes, with diminishing antibacterial effectiveness in the following order: aminoglycosides > fluoroquinolones > glycopeptides > macrolides > tetracyclines > β-lactams. Overall, these data indicate that waterborne bacteria are an important source of ABR determinants and contribute to the mass balance of ABR in the environment, and may be used as an indicator of ecological change in water ecosystems. The waterborne ABR organisms may potentially act as donors in pathogens, which may acquire these through horizontal gene transfer or other genetic exchange events, thus leading to clinically significant cases in both animal and human health. Therefore, environmental bacteria should not be regarded as being devoid of ABR determinants, simply because they are physically removed from clinical settings. Such bacteria have natural intrinsic resistance, as well as having the ability to acquire determinants from agricultural run-off and human wastewater discharge, which may contain ABR organisms, as well as sublethal concentrations of metabolically active antibiotic. The tracking of such organisms to their source may help determine the source of fecal pollution in aquatic ecosystems.

Wetland Eutrophication: Early Warning Biogeochemical Indicators

SL-304, a 3-page illustrated fact sheet by Alan L. Wright, describes the effects of nutrients in the Everglades and identifies sensitive early-warning indicators of ecological changes. Includes references. Published by the UF Department of Soil and Water Science, July 2009. SL 304/SS517: Wetland Eutrophication: Early Warning Biogeochemical Indicators (ufl.edu)

Seasonal exchange of CO2 and δ18O‐CO2 varies with postfire succession in boreal forest ecosystems

Seasonal cycles of atmospheric CO2 and δ18O‐CO2 at high northern latitudes have the potential to serve as indicators of ecological change in response to climate changes. Effective interpretation of these observations requires an understanding of how different species and ecosystems contribute to biosphere‐atmosphere exchange. Here we examined the effect of postfire stand age in boreal forest ecosystems on the seasonal distribution of CO2 and δ18O‐CO2 fluxes. We measured net CO2 fluxes in a 3‐year burn scar, a 15‐year trembling aspen stand, and an 80‐year black spruce stand in interior Alaska using eddy covariance. By combining measurements of the oxygen isotopic composition of ecosystem water pools at each stand with measured CO2 fluxes, we predicted half‐hourly δ18O‐CO2 fluxes and used a one‐box atmosphere model to make relative comparisons of the effect of stand age on the shape and amplitude of the seasonal cycle of CO2 and δ18O‐CO2. A shorter growing season and higher rates of net ecosystem uptake during midsummer at the 15‐year stand resulted in a larger seasonal CO2 amplitude and a delay in the drawdown of atmospheric CO2 as compared with the 80‐year stand. Reduced levels of gross primary production isoforcing from the 15‐year stand during spring and early summer caused atmospheric δ18O‐CO2 to increase more gradually between April and June as compared with fluxes from the 80‐year stand. Our analysis suggests that increased boreal forest disturbance would delay the phase of CO2 drawdown at high northern latitudes, but would advance the phase of δ18O‐CO2 drawdown.

Indicators of ecological change: comparison of the early response of four organism groups to stress gradients

A central goal in monitoring and assessment programs is to detect change early before costly or irreversible damage occurs. To design robust early-warning monitoring programs requires knowledge of indicator response to stress as well as the uncertainty associated with the indicator(s) selected. Using a dataset consisting of four organism groups (fish, macrophytes, benthic diatoms and macroinvertebrates) and catchment, riparian and in-stream physico-chemical variables from 77 mountain and 85 lowland streams we determined the relationships between indicator response and complex environmental gradients. The upper (>75th percentile) and lower (<25th percentiles) tails of principal component (PC) gradients were used to study the early response of the four organism groups to stress. An organism/metric was considered as an early warning indicator if the response to the short gradients was more robust (higher R 2 values, steeper slope and lower error) than the null model (organism response to the full PC gradient). For mountain streams, both fish and macrophyte CA scores were shown to exhibit an early warning response to the upper tail of the 1st PC gradient when compared to the null model. Five of the eight metrics showed better response to the upper tail of the 2nd PC gradient compared to the null model, while only one metric (macrophyte CA scores) showed improvement when compared to the lower tail of the 2nd PC gradient. For lowland streams all four organism-groups showed better response (CA scores) to the upper tail of the PC gradient when compared to the null model. Only one metric (fish CA scores) regressed against the lower tail of the 2nd PC gradient was found to be more robust than the PC2 null model. These findings indicate that the nonlinear relationships of organism/metric response to stress can be used to select potentially robust early warning indicators for monitoring and assessment.

Gradient responses of epilithic diatom communities in the Baltic Sea proper

Diatom communities and assemblages are widely used as indicators of ecological change in aquatic environments and for reconstructing palaeo-environments. Good calibration data sets, directly linking changes in diatom composition to environmental factors, are needed for building reliable gradient models with high indicative value. Such models have a broad applicability because most diatom species have cosmopolitan distributions. This paper presents community analyses of brackish-water diatoms living on submerged stones in four areas of the Baltic Sea proper along the Swedish coast. The communities on the stones were composed of epilithic, epiphytic, epipelic, epipsammic and occasionally some pelagic species. Altogether, 158 quantitative samples were taken at 41 sites between 23 April and 11 May, 1990, and the data set contained 300 diatom taxa belonging to 75 genera. Species data were analysed with principal components analysis (PCA) and environmental factors were fitted passively by multiple regression analysis on the ordination results. Differences in community composition could be explained by variation in salinity (which was correlated with N:P and Si:P ratios and the occurrence of macroalgae on the stones), nutrient concentrations and variation in exposure to wave action (which was correlated to the occurrence of soft bottoms around the stones, water temperature and the occurrence of sand grains and macroalgae on the stones). Separate analyses for small taxa (cell biovolume <1000 μm 3), for large taxa (cell biovolume ≥1000 μm 3) and for small and large diatom taxa together showed that diatoms of different size classes respond differently to environmental variation.

Landscape patterns as indicators of ecological change at Fort Benning, Georgia, USA

This research examined landscape indicators that signal ecological change in both intensely used and lightly used lands at Fort Benning, Georgia. Changes in patterns of land cover through time affect the ecological system by altering the proportion and distribution of habitats for species that these cover types support. Landscape patterns, therefore, are important indicators of land-use impacts, past and present, upon the landscape. This analysis of landscape pattern began with a landscape characterization based on witness tree data from 1827 and the 1830s and remotely sensed data from 1974, 1983, 1991, and 1999. The data from the early 1800s, although coarse, were useful in characterizing the historical range of variability in ecological conditions for the area. The steps for the analysis involved the creation of a land-cover database and a time series of land-cover maps, computation of landscape metrics, and evaluation of changes in those metrics over time as evidenced in the land-cover maps. We focused on five cover types (bare/developed land, deciduous forest, mixed forest, pine forest, and non-forest vegetated land), for they reveal information important to resources management at Fort Benning. An examination of land-cover class and landscape metrics, computed from the maps, indicated that a suite of metrics adequately describes the changing landscape at Fort Benning, Georgia. The most appropriate metrics were percent cover, total edge (km), number of patches, descriptors of patch area, nearest neighbor distance, the mean perimeter-to-area ratio, shape range, and clumpiness. Identification of such ecological indicators is an important component of building an effective environmental monitoring system.

Effect of straws from Bt-transgenic rice on selected biological activities in water-flooded soil

The biochemical properties of soil have often been described as early and sensitive indicators of ecological changes in both natural soil and agroecosystem. In the current study, the impacts of the amendment of Bt-transgenic rice (KMD) straw on biological activities in water-flooded soil were investigated under laboratory conditions and compared with non-transgenic rice (Xiushui 11) straw. The results showed that there were some differences in protease, neutral phosphatase and cellulase activities between soil amended with Bt-transgenic rice straw and non-transgenic rice straw at the early stage of incubation, and none of these differences were persistent. However, differences in dehydrogenase activity, methanogenesis, hydrogen production and anaerobic respiration between soil supplemented with Bt-transgenic rice straw and non-transgenic rice straw were persistent over the course of incubation. Dehydrogenase activity, methanogenesis and anaerobic respiration were considerably lower from sample days 7 to 56, but higher after day 56 in soil amended with Bt-transgenic rice straw. In comparison, the H 2-production in soil containing Bt-transgenic rice straw was significantly lower after day 56. The results demonstrated that the amendment of the Bt-transgenic rice straw altered some important biological properties in water-flooded soil, indicating a shift in microbial populations or a change in the metabolic abilities of the microbial community as a result of substrate availability in soil.

Phytoplankton Photopigments as Indicators of Estuarine and Coastal Eutrophication

Abstract Human development of coastal watersheds has greatly increased nutrient loading and accelerated estuarine and coastal eutrophication. These waters are also affected by climatic perturbations (e.g., droughts, hurricanes, floods), which may be increasing. The ecological effects of these stressors are often most evident at the microbial level, where the bulk of primary production and biogeochemical cycling occurs. Phytoplankton dominate coastal primary production and thus may be indicative of eutrophication and other major perturbations underlying coastal ecosystem change. Using photopigments that are diagnostic for phytoplankton functional groups (chlorophytes, cryptophytes, cyanobacteria, diatoms, and dinoflagellates), we examined the relative responses of these taxonomic groups to nutrient and hydrologic alterations and evaluated their use as indicators of ecological change in the Neuse River Estuary, North Carolina, and Galveston Bay, Texas. Photopigment indicators can be routinely incorporated in water-quality monitoring programs to assess environmental controls on ecosystem structure and function over varying spatial and temporal scales.

Mangrove Rehabilitation and Intertidal Biodiversity: a Study in the Ranong Mangrove Ecosystem, Thailand

The diversity, abundance, biomass and community structure of crustacean and molluscan macrofauna were studied in the Ranong mangrove forest ecosystem on the Andaman Sea coast of southern Thailand. After a history of commercial exploitation the mangroves along the Klong Ngao tidal creek have been assigned conservation status within a new Ranong Biosphere Reserve established in 1997. Over the past 12 years, several areas of mangrove destroyed or degraded by wood harvesting, tin mining and aquaculture, have been rehabilitated on a pilot basis by planting monocultures of mangrove seedlings using four common local species (Rhizophora apiculata, R. mucronata, Bruguiera cyclindrica and Ceriops tagal). These plantation forests with different past management histories were compared with a natural, mixed, mature mangrove forest which has been conserved for about 40 years. Macrofauna were sampled within a 100m2 vegetation quadrat in each study site. Crustaceans were sampled quantitatively by 3×15min timed hand catches per site. Molluscs were sampled in 3×m2 quadrats positioned around three randomly selected trees in each vegetation quadrat. The lowest crustacean and molluscan diversity was recorded from the former tin mining site. The highest diversity was recorded from aRhizophora plantation in the natural mixed forest area for both crustaceans and molluscs. The vegetation community structure was not correlated with the environmental variables measured, or with macrofauna community structure. Of the environmental parameters chosen, the crustacean community structure was best expressed by shore level, while for molluscan diversity and abundance it was soil moisture content. The macrofauna community structure at the tin mining site was significantly different to the other sites, and was dominated by a single species of crab, Metaplax elegans. Grapsid crabs, especially sesarmid species, dominated over ocypodid crabs in the mature forest site, whereas Uca species and other ocypodids were more abundant than grapsids in the degraded concession forest area. Snails of the families Neritidae and Ellobiidae were the most abundant molluscs in the mature forest, whereas Littoriinidae, Assimineidae and Potamidae species were more representative of the younger plantation sites. The findings from this study suggest that some of these well represented families of mangrove macrofauna could be used as indicators of ecological change as part of a long term environmental monitoring programme in Ranong and other areas in Southeast Asia where mangroves are being rehabilitated.

The use of Members of the Family Chydoridae (Anomopoda, Branchiopoda) as an Indicator of Lake Ecological Quality in Ireland

ABSTRACTWe sampled chydorids (Branchiopoda, Anomopoda) from 29 Irish lakes between June 1996 andJuly 1997 in order to assess the usefulness of this group as an indicator of lake ecological quality,as required by the recently published EU Water Framework Directive. The lakes represented awide range of the physicochemical conditions found in Irish lakes. We identified 31 species ofChydoridae from the lakes and used multivariate analysis to elucidate the relationship between thechydorids and their environment. Groups of lakes were found to have distinct chydorid communi-ties, the structure and composition of which depended on environmental variables such as totalphosphorus, total nitrogen, alkalinity, conductivity and lake size. The study highlights the potentialvalue of this group as a biotic indicator of ecological change in Irish lakes.INTRODUCTIONIrish lakes are generally considered to be ofgood quality compared with those in other Eu-ropean countries, and more than 81% of 120 Irishlakes surveyed recently were classed as oligotrophicor mesotrophic (Lucey

Changes in enzyme activities and microbial biomass of tallgrass prairie soil as related to burning and nitrogen fertilization

Microbial biomass and enzyme activities are affected by management practices and can be used as sensitive indicators of ecological stability. Microbial biomass C (MBC), microbial biomass N (MBN) and eight enzyme activities involved in the cycling of C, N, P and S were studied in the surface (0–5 cm) of an Irwin silty clay loam soil (fine, mixed, mesic, Pachic Arguistoll) in a tallgrass prairie ecosystem. Treatments of annual spring burning and N fertilization were initiated in 1986 and encompassed: (1) unburned–unfertilized, (2) burned–unfertilized, (3) burned–fertilized, and (4) unburned–fertilized. Activities of dehydrogenase, β-glucosidase, urease, deaminase, denitrifying enzyme, acid phosphatase, alkaline phosphatase, and arylsulfatase were assayed. Long-term burning and N fertilization of the tallgrass prairie soil reduced MBC and MBN relative to the unburned–unfertilized treatment. The effects of burning and N fertilization varied among the enzymes and the time of sampling. Long-term burning significantly ( P<0.05) increased activities of urease and acid phosphatase, but decreased activities of β-glucosidase, deaminase and alkaline phosphatase. Long-term N fertilization significantly increased activities of β-glucosidase and acid phosphatase but decreased urease activity. This study found that several soil enzyme activities can be used as indicators of ecological changes caused by N fertilization and long-term burning management practices. The relevance of these changes in surface soil to the long-term sustainability of this ecosystem needs further evaluation.