Stratified Random Sampling Plan Research Articles

A Taxonomic Baseline to Monitor Retreating Arctic Biota: The Marine Invertebrate Collection of the Icelandic Institute of Natural History (IINH)

The IINH collection comprises ~5.3 million specimens of marine invertebrates, collected within 758,000 km2 of the 200-mile Exclusive Economic Zone (EEZ) of Iceland, which is a significant part of the greater Arctic-Boreal biogeographic boundary in the northern Atlantic. The oldest collected specimen is from 1871, but most of the specimens (4.7 million) were collected during the BIOICE project between 1991 and 2004. The program objective is to build a museum collection, reflecting the geographical distribution and morphological variation of benthic species. Over 1,390 zoological samples were collected following a stratified random sampling plan with 579 stations at a depth range of 20 to 3,000 m, and temperatures from −1°C to over +9°C. The material is sorted to about 50 higher taxonomic groups, and 3,007 benthic species, of which fifty-one are new to science. The collection offers a baseline to monitor changing biodiversity at the Arctic-Boreal boundary, with rising temperature, salinity, and acidification.

AREA ESTIMATION OF MULTI-TEMPORAL GLOBAL IMPERVIOUS LAND COVER BASED ON STRATIFIED RANDOM SAMPLING

Abstract. Estimating area of impervious land cover is the most useful and one of the ecological assessment indexes of urban and regional environment. Global land cover maps are inevitably misclassified, which affects the quality and application of the data. Statistical approach for assessing the accuracy is critical to understand the global change information and area estimation is usually based on sample data with a probability-based estimator. However, research on evaluation of multi-temporal global impervious land cover maps has not been implemented. In this study, spatial characteristics of the data are considered to assess the thematic map accuracy with a two-stage stratified random sampling plan. The first stage of stratification is determined by the global urban ecoregion and the second one is determined by land cover classes. Additionally, sample size of both map stage and pixel stage are calculated using a probability sampling model. A response design is constructed for a per-pixel accuracy assessment and blind interpretation is implemented using sample pixels and its surrounding area. Our method is applied to the multi-temporal global impervious land cover maps between 2000 and 2010 with a time interval of 5 years and the estimated area in different epoch are listed in detail. The main contribution of our research is illustrating the details for calculating the proportion area of impervious land cover and corresponding confidence intervals based on the reference classification. The experimental results show that the increasing area of the impervious surface according to the sample unit shows good agreement with the urbanization and descriptive accuracy assessments by user’s, producer’s and overall accuracy are shown respectively.

Soil surveyor knowledge in digital soil mapping and assessment in Australia

In the last three decades, land resource assessment and soil survey has shifted from an expert-driven qualitative soil-landscape paradigm to a quantitative, correlative environmental modelling approach now commonly referred to as ‘digital soil mapping and assessment’ (DSMA). The role of soil surveyors in producing spatial soil and land suitability assessments under an operational paradigm of digital soil mapping is discussed using the recently completed Northern Australia Water Resources Assessment (NAWRA) project as a case study. Real world DSMA problems are presented, and pragmatic solutions suggested. In NAWRA, a stratified random sampling plan for data collection on ~500 new sites in the field was produced using conditioned Latin hypercube sampling using 30-m resolution environmental data layers that each represented a factor of soil formation but had low correlations between them. Some free survey sites were added in soil-landscapes that were under-represented in the stratified random sampling plan in the judgment of the soil surveyors. Predictive random forest models and gridded maps for soil classes and continuous soil attributes (and their prediction uncertainty) were produced at 90-m resolution in an iterative process that enabled the identification of issues, particularly in the legacy data included for model training. As a consequence errors in data entry in the state soil databases have been corrected. Another stratified random sampling plan using the prediction uncertainties was produced to select sites for field validation. Soil surveyors played a key role in all aspects of the DSMA workflow including identifying soil-landscapes that need to be mapped accurately and applying expert knowledge to the selection of final maps of soil classes and attributes necessary to implement land suitability rules.

Estimation of fish consumption rates based on a creel angler survey of an urban river in New Jersey, USA

A one-year angler intercept survey was conducted on the lower 17 miles of the Passaic River, an urban industrialized river that flows through Newark, New Jersey. The purpose of the survey was to collect data about anglers’ behaviors and fish consumption habits in order to calculate exposure factors for a human health risk assessment of the Study Area. This paper focuses on estimating site-specific fish consumption rates for LPRSA anglers that consume their catch. The study design included on-site interviews and counts (angler enumeration). Forty survey locations were included in the stratified random sampling plan; interviews were conducted on 136 days and counts on 164 days. After matching intercepts with the same angler, a total of 294 anglers were interviewed, of which 25 reported consuming their catch. LPRSA fishing trips ranged from 2 to nearly 50 annual trips for anglers who reported consuming their catch. Species caught and reported to be consumed included carp, catfish, white perch, smallmouth bass, and eel. The estimated mean and 90th percentile consumption rates for the population of consuming anglers are 5.0 and 8.8 g/day, respectively. Based on sensitivity analyses, the 90th percentile fish consumption rates range from approximately 4 to 18 g/day.

Near-miss crashes and other predictors of motorcycle crashes: Findings from a population-based survey

Objective: Crash and injury surveillance studies have identified a range of rider-related factors, including age, sex, licensure, training and experience, as being associated with motorcycle crash risk. The aim of this study was to establish whether these previously identified factors were associated with crash involvement in an Australian-based population.Methods: Data obtained from motorcyclists recruited from road authority licensing offices in a population-based survey design were analyzed. In addition to descriptive analysis, survey logistic regression was used to examine predictors of self-reported motorcycle crashes.A statewide population prevalence study of motorcyclists in New South Wales, Australia, was conducted using a multistage stratified random sampling plan. Participants (n = 503) represented 47% of eligible riders invited to participate. The distribution of responses was weighted to represent the population based on motorcycle registrations as a proxy for active motorcyclists, adjusted for age, sex, and variations in sample size and population density between survey sites.Results: This analysis investigated factors associated with having crashed in the past 12 months. The key predictors of increased crash risk included frequent near-crash experiences (6–10) in the past year (adjusted odds ratio [ORadj] = 5.3; 95% confidence interval [CI], 1.3–21.8), having 4 or more riding demerit points (ORadj = 4.1; 95% CI, 1.1–14.7), and motorcycle type and riding purpose. Sports (ORadj = 2.8; 95% CI, 1.1–7.3) and commuter motorcycles (ORadj = 4.0; 95% CI, 1.1–15.3) were associated with higher odds of crashes compared to cruiser/touring motorcycles.Those whose purpose for riding frequently involved commuting, high-speed roads, or motorcycle sports had higher odds of being involved in a crash compared to riders who rarely took part in such activities. Rider age, license type, and time holding a motorcycle license were not predictive of crash involvement when other factors were taken into account.Conclusions: These findings provide important population-level information and insights about risk exposure for motorcyclists. Taking a more tailored approach to data collection meant that factors associated with crash involvement were identified that are not commonly observed in studies relying on administrative data. In particular, the study highlights the importance of near-crash experiences as warnings to riders and the need to use such experiences as learning opportunities to improve their riding style and safety.

Spatial modelling and mapping of female genital mutilation in Kenya

BackgroundFemale genital mutilation/cutting (FGM/C) is still prevalent in several communities in Kenya and other areas in Africa, as well as being practiced by some migrants from African countries living in other parts of the world. This study aimed at detecting clustering of FGM/C in Kenya, and identifying those areas within the country where women still intend to continue the practice. A broader goal of the study was to identify geographical areas where the practice continues unabated and where broad intervention strategies need to be introduced.MethodsThe prevalence of FGM/C was investigated using the 2008 Kenya Demographic and Health Survey (KDHS) data. The 2008 KDHS used a multistage stratified random sampling plan to select women of reproductive age (15–49 years) and asked questions concerning their FGM/C status and their support for the continuation of FGM/C. A spatial scan statistical analysis was carried out using SaTScan™ to test for statistically significant clustering of the practice of FGM/C in the country. The risk of FGM/C was also modelled and mapped using a hierarchical spatial model under the Integrated Nested Laplace approximation approach using the INLA library in R.ResultsThe prevalence of FGM/C stood at 28.2% and an estimated 10.3% of the women interviewed indicated that they supported the continuation of FGM. On the basis of the Deviance Information Criterion (DIC), hierarchical spatial models with spatially structured random effects were found to best fit the data for both response variables considered. Age, region, rural–urban classification, education, marital status, religion, socioeconomic status and media exposure were found to be significantly associated with FGM/C. The current FGM/C status of a woman was also a significant predictor of support for the continuation of FGM/C. Spatial scan statistics confirm FGM clusters in the North-Eastern and South-Western regions of Kenya (p < 0.001).ConclusionThis suggests that the fight against FGM/C in Kenya is not yet over. There are still deep cultural and religious beliefs to be addressed in a bid to eradicate the practice. Interventions by government and other stakeholders must address these challenges and target the identified clusters.

Mapping spatial resources with GPS animal telemetry: foraging manatees locate seagrass beds in the Ten Thousand Islands, Florida, USA

Turbid water conditions make the delineation and characterization of benthic habitats difficult by traditional in situ and remote sensing methods. Here, we develop and validate modeling and sampling methodology for detecting and characterizing seagrass beds by analyzing GPS telemetry records from radio-tagged manatees. Between October 2002 and October 2005, 14 manatees were tracked in the Ten Thousand Islands (TTI) in southwest Florida (USA) using Global Positioning System (GPS) tags. High density manatee use areas were found to occur off each island facing the open, nearshore waters of the Gulf of Mexico. We implemented a spatially stratified random sampling plan and used a camera-based sampling technique to observe and record bottom observations of seagrass and macroalgae presence and abundance. Five species of seagrass were identified in our study area: Halodule wrightii, Thalassia testudinum, Syringodium filiforme, Halophila engelmannii, and Halophila decipiens. A Bayesian model was developed to choose and parameterize a spatial process function that would describe the observed patterns of seagrass and macroalgae. The seagrasses were found in depths <2 m and in the higher manatee use strata, whereas macroalgae was found at moderate densities at all sampled depths and manatee use strata. The manatee spatial data showed a strong association with seagrass beds, a relationship that increased seagrass sampling efficiency. Our camera-based field sampling proved to be effective for assessing seagrass density and spatial coverage under turbid water conditions, and would be an effective monitoring tool to detect changes in seagrass beds.

Study of spatiotemporal variation of atmospheric mercury and its human exposure around an integrated steel plant, India

Abstract. Mercury release by coal combustion has been significantly increased in India. Mercury content in coal has been analyzed to 0.272 ppm by Central Pollution Control Board. Toxicological effects of elemental Hg (Hg0) exposure include respiratory and renal failures, cardiac arrest, and cerebral oedema, while subclinical exposure may induce kidney, behavioral, and cognitive dysfunctions. The present work is focused on dispersion pattern and inter-phase exchange phenomena of ambient mercury between air-particulate matter evaluations of alongwith dominance of various major routes of human exposure-dose response using regression analysis around an integrated steel plant in central India. Source-downwind type stratified random sampling plan using longitudinal study design has been adopted for ambient monitoring of total mercury, while representative sampling plant has been adopted for persona exposure-dose response study In space-time framework. Control sites and subjects have been chosen from uncontaminated area (100 km away from any industrial activities). 06 ambient air monitoring stations and 17 subjects from workers, non-workers but local residents' categories and from controlled sites have been chosen for the study. Samples of mercury biomarkers (blood, breast milk and urine) have also been collected from same subjects in each month during sampling period. The sampling period was March 2005 to February 2006 . Samples of 30% acidified KMnO4 for air-Hg absorption, PM10, RPM and biological samples were analyzed for total mercury by ICP-AES using standard methods. Local soils and ground water were also monitored for total mercury content during the sampling period. Results have shown that mercury concentration is very high compared to prescribed limits in all receptors. Results of exchange phenomenon have shown the higher transfer of mercury from air to particulate during combustion in steel plant environment due to presence of huge amount of iron particles, in contrast to results obtained in other industrial locations earlier. Plant workers have shown 1.5 to 2.5 times higher personal RPM-Hg levels compared to Category 2 and 20–30 times higher than Category 3. All biomarkers have shown higher Hg presence compared to prescribed standards. Regression analysis between exposure routes and bio-receptors has been investigated. Dominance status of selected routes of bio-accumulation has been varied from category to category.

Geospatial Methods for Monitoring a Vegetative Treatment Area Receiving Beef Feedlot Runoff

A vegetative treatment area (VTA) offers alternative solutions to traditional feedlot runoff holding ponds, but the distribution of nutrients is not easily defined. Methods for monitoring salt accumulations in soils have been demonstrated at the United States Salinity Laboratory, Riverside, CA. This study was conducted to determine if methods developed to inventory saline soils can be used to inventory a VTA designed to control feedlot runoff. A soil conductivity map was generated at a VTA site using electromagnetic induction equipment (Dualem-1S) and global positioning satellite. The ESAP software package, developed by the United States Salinity Laboratory at Riverside, CA, was used to determine a representative set of (n = 20) soil sampling locations for estimating the chloride distribution in the VTA (Cl(-): selected as an indicator ion to track feedlot runoff). An additional set of (n = 20) stratified random sampling (SRS) locations were selected for comparison. The ESAP-generated, prediction-based sampling plan exhibited better design optimality criteria than the SRS plan. Statistical validation tests confirmed that the regression model estimated from the ESAP-generated sample data was capable of producing accurate and unbiased predictions of the natural log (Cl(-)) levels at the independently chosen SRS sites. The combination of geo-referenced soil conductivity, directed soil sample data, and regression modeling provides a cost-effective tool to observe and manage liquid flow patterns in a VTA.

A quantitative analysis of factors contributing electronic data interchange adoption among Bruneian SMEs

PurposeThe primary purpose of this research is to examine and explore quantitatively the determining factors that contribute electronic data interchange (EDI) adoption among Brunei's small and medium enterprises (SMEs) not addressed previously.Design/methodology/approachThe study is based upon survey approach to collect the primary data from 50 SMEs in Brunei Darussalam based upon stratified random sampling plan. A one stage normative model that is associative in nature was developed based upon reviewing the previous researches and further in line with the research objectives. The model elicits six factors that are grouped in three categories, namely, organizational, environmental and technological.FindingsThe findings based upon regression analysis indicate that factors such as perceived benefits, government support and management support are significant determinants of EDI adoption. The 35 percent of the total variance is explained by these three factors.Research limitations/implicationsThe small market size as well small sample size is one of the research limitations in addition that only 20 percent of the SMEs have adopted EDI. The inclusion of some more variables such as external pressure and competitive pressure will not only increase the shared variance, but will also bring broader perspective to the research. However, findings support similar other regional Asia‐Pacific studies.Practical implicationsThe study has practical significance as it provides help to the management of the SMEs with the factors contributing towards EDI adoption. In case, these SMEs have to capitalize on EDI adoption, the management with the government support should not only take a supporting role, but also act proactively and competitively. The management focusing on the potential benefits could further trigger the adoption.Originality/valueThis pioneering study adds value to the existing knowledge and supports previous work. It further provides a platform for the future research. The EDI adoption among Brunei's SMEs could further be geared up by considering the factors mentioned above.

Stratified random sampling for estimating billing accuracy in health care systems

This paper presents a stratified random sampling plan for estimating accuracy of bill processing performance for the health care bills submitted to third party payers in health care systems. Bill processing accuracy is estimated with two measures: percent accuracy and total dollar accuracy. Difficulties in constructing a sampling plan arise when the population strata structure is unknown, and when the two measures require different sampling schemes. To efficiently utilize sample resource, the sampling plan is designed to effectively estimate both measures from the same sample. The sampling plan features a simple but efficient strata construction method, called rectangular method, and two accuracy estimation methods, one for each measure. The sampling plan is tested on actual populations from an insurance company. Accuracy estimates obtained are then used to compare the rectangular method to other potential clustering methods for strata construction, and compare the accuracy estimation methods to other eligible methods. Computational study results show effectiveness of the proposed sampling plan.

Academic Counselling

The study investigates the relationship between cognitive and affective outcomes of the quality of teacher–student interaction at different business schools in Pakistan. As early as 1936, Kurt Lewin recognized that the environment was a determinant of human behaviour and performance. Following Lewin's work, Murray proposed a Needs-Press model in which situational variables found in the environment account for a degree of behavioural variance. Attempts were also made to study situational variables found in the environment that affect the learning process, on the one hand, and students’ professional performance, on the other. A multistage stratified random sampling plan was used to select a sample from business schools at Lahore, Islamabad, Multan and Karachi. Stratification was done first at the ownership level, where the two strata consist of public and private sector schools. At the second stage, three strata were made according to the students’ background, where students coming from English-medium schools, semi-English-medium schools and vernacular-medium schools were placed in three strata. In the third stage, the stratification was done on a gender basis. In the final stage, students were selected using systematic sampling. Such a multi-stage stratification plan permitted us to do an in-depth analysis of the whole process of teacher–student interaction. The study identifies the types of interactions that are most likely to enhance students’ progress in business administration courses. It also identifies the important factors inhibiting or encouraging, teacher–student interaction. Further, it provides suggestions to enhance this interaction process.

Workplace Monitoring of Refractory Ceramic Fiber in the United States

This paper summarizes data from a comprehensive workplace exposure monitoring program for refractory ceramic fiber (RCF) conducted since 1990, including data collected under a 5-year consent agreement (1993–1998) between the U.S. Environmental Protection Agency and the Refractory Ceramic Fibers Coalition. It presents additional data and analyses, which complement an earlier article published in this journal (L. D. Maxim et al., 1997, Regul. Toxicol. Pharmacol. 26, 156–171). As part of this exposure monitoring program, data were collected at plants operated by RCF manufacturers and at customer facilities. Beginning in 1993, at least 720 samples (each sample consisting of one or more cassettes) were collected annually, distributed according to a stratified random sampling plan. The strata consisted of workers in eight functional job categories (FJCs) at manufacturing and customer plants. Time-weighted average (TWA) and task length average data were gathered and analyzed using phase contrast optical microscopy and (for a subset of samples) transmission electron microscopy methods. Data on respirator usage (by type) were also collected. Statistical analysis indicates that there are significant differences in TWA fiber concentrations (exposure) among FJCs (installation, finishing, and removal categories have the highest average concentrations), that workplace concentration data are approximately lognormally distributed, and that weighted average fiber concentrations decreased over the period from 1990 to 1998—although trend curves leveled out as exposures have decreased and further improvements became more difficult. Material differences exist in exposure between RCF manufacturers and their customers (largely because the mix of jobs differ), but these differences have narrowed over the years. Respirator usage varies with exposure. Respirator data are used to derive improved estimates of actual worker exposure. Alternative criteria for selecting FJCs for control efforts are defined and illustrated. Lessons learned for future monitoring efforts are summarized.

Nonlinear integer programming for optimal allocation in stratified sampling

A stratified random sampling plan is one in which the elements of the population are first divided into nonoverlapping groups, and then a simple random sample is selected from each group. In this paper, we focus on determining the optimal sample size of each group. We show that various versions of this problem can be transformed into a particular nonlinear program with a convex objective function, a single linear constraint, and bounded variables. Two branch and bound algorithms are presented for solving the problem. The first algorithm solves the transformed subproblems in the branch and bound tree using a variable pegging procedure. The second algorithm solves the subproblems by performing a search to identify the optimal Lagrange multiplier of the single constraint. We also present linearization and dynamic programming methods that can be used for solving the stratified sampling problem. Computational testing indicates that the pegging branch and bound algorithm is fastest for some classes of problems, and the linearization method is fastest for other classes of problems.

The Occurrence of Agricultural Chemicals in Illinois' Rural Private Wells: Results from the Pilot Study

AbstractWater samples from 240 private wells in rural Illinois were collected over one year and analyzed for 39 agricultural chemicals. Sampling was conducted to provide preliminary information to refine a plan for a statewide survey of the agricultural chemical contamination of rural private wells. Wells were sampled according to a stratified random sampling plan that included four classes of depth lo the uppermost aquifer material and two classes of well type. Depth lo uppermost aquifer material was defined as the depth from ground surface to a geologic material that, if saturated, could he used as an aquifer.Occurrence, defined as the presence of one or more target analytes in a well water sample above some specified concentration, was shown to be higher in large‐diameter bored or dug wells than in small‐diameter drilled wells. For small‐diameter wells, occurrence generally decreased as the depth to the uppermost aquifer material increased, In addition, depth to the uppermost aquifer material could be used to predict the occurrence of some individual agricultural chemicals, such as nitrate and atrazine, but could not be used to predict the occurrence of pielorarn or pesticides in small‐diameter wells.Of the 39 target analytes, 10 were detected at concentrations exceeding their respective minimum reporting levels. Nitrate and atrazine were the only compounds found at concentrations exceeding their respective maximum contaminant levels (MCLs) or U.S. EPA lifetime health advisory limits (HAI.s).A nonparametric statistical technique, contingency table analysis, identified factors associated with the occurrence of agricultural chemicals in three of the file study areas. Elevated specific conductance (&gt;500 μmhos/cm) of the sampled water was strongly associated with the occurrence of agricultural chemicals. This association was common to all three study areas analyzed. Identification of the source of the specific conductance could help identify the dominant pathway for transport of agricultural chemicals to ground water.

INTRA- AND INTER-CROWN DISTRIBUTION OF THE EASTERN SPRUCE GALL ADELGID, ADELGES ABIETIS (L.), ON YOUNG WHITE SPRUCE

AbstractIntra- and inter-crown distribution of eastern spruce gall adelgid, Adelges abietis (L.) (Homoptera: Adelgidae), on young white spruce, Picea glauca (Moench) Voss., was studied at three sites in New Brunswick, Canada. Within a branch, the majority of galls were found on lateral shoots. Similar distributions of galls within trees were observed regardless of whether 20 or 30 lateral shoots or all shoots on a branch were sampled. Gall densities were highest on mid-crown branches of open-grown trees 1–4 m tall and were not influenced by cardinal direction. After crown closure, most galls were found in the upper crown, above the point of branch overlap. In all circumstances, gall distributions were strongly clumped within trees. Inter-tree distribution of A. abietis galls differed significantly from a Poisson but not a negative binomial distribution, indicating a high degree of aggregation among trees. Therefore, a stratified random sampling plan using 20 lateral shoots of a mid-crown branch as a sampling unit would be adequate for monitoring A. abietis populations. If the mid-crown branches are undergoing crown closure, we suggest sampling in the lowest open-grown branch above the point of crown overlap.

First-Generation Parasitism of the Mimosa Webworm (Lepidoptera: Plutellidae) by Elasmus albizziae (Hymenoptera: Eulophidae) in an Urban Forest

Elasmus albizziae Burks is a parasitoid of the mimosa webworm, Homadaula anisocentra Meyrick. Honeylocust foliage samples containing first-generation mimosa webworm cocoons were collected in Ames, Iowa, by using a stratified random sampling plan during 1985, 1986, and 1987. Survey objectives were to determine the percentage of parasitized first-generation webworm prepupae and to assess the potential of E. albizziae in an integrated pest management program. Conservative determinations of first-generation parasitism of mimosa webworm prepupae by E. albizziae were 44,39, and 47% for 1985, 1986, and 1987, respectively. Precise effects of this parasitism on webworm populations have not been determined. Mortality levels imposed by E. albizziae should, however, be taken into account when management practices are considered. The parasitoids are exposed during host-seeking activity and would be vulnerable to broad-spectrum insecticides applied when first-generation webworm larvae were spinning cocoons on honeylocust foliage. When insecticidal treatment is warranted for management, it is recommended that Bacillus thuringiensis insecticides be adopted as the treatment of choice over broad-spectrum insecticides to minimize damage to the parasitoid complex.

Identifying chronic affective disorders in outpatients: validation of the General Behavior Inventory.

The validity of the General Behavior Inventory (GBI) in screening outpatients for chronic unipolar and bipolar affective conditions was evaluated. The GBI was administered to 492 consecutive patients at a university clinic and a community mental health center. Using a stratified random sampling plan, 167 patients were selected and administered blind structured diagnostic interviews. In addition, unipolar depressives were followed up 6 months after the initial evaluation. Overall, the GBI exhibited fair-to-good positive predictive power and good-to-excellent negative predictive power. In addition, GBI scores in the case range were consistently associated with poor outcome at the 6-month follow-up. These findings suggest that the GBI may provide an economical means of screening for chronic unipolar and bipolar affective conditions in outpatient settings.

La végétation forestière du secteur nord-ouest de la vallée du Saint-Laurent, Québec

The forest vegetation of the north-west section of the St. Lawrence Valley in Quebec was sampled within 68 quadrats. The location of the quadrats was selected by means of a stratified random sampling plan. Ordination (detrended correspondence analysis) and cluster analysis (TWINSPAN) allowed the identification of 11 forest community types. The ecological factors most closely associated with the distribution of these communities are soil drainage and richness. These two factors are strongly related to the types of surface deposits. Communities dominated by Acer saccharum are found on well drained and nutrient-rich moraines. On the contrary, communities dominated by Acer rubrum and the majority of coniferous forests are found on poorly drained and nutrient-poor soils. Two floristically distinct community types, the Fraxinus – Tilia americana forests and the Tsuga canadensis – Acer saccharum forests, are found on poorly drained marine deposits with edaphically identical lower horizons. However, the pH and major cation concentrations of the upper soil horizons are much lower under the cover of the hemlock forests than under the cover of the ash – basswood forests.

Response of woody species to site factors in Maryland, USA: Evaluation of sampling plans and of continuous and binary measurement techniques

A detailed analysis of sample plots quantifying woody vegetation and environment in the Piedmont and Coastal Plain of Maryland, USA, shows (1) that sample sites must be selected according to some formal design, and (2) that binary (presence or absence) measurement of species serves equally well as continuous measurements of importance value or percent cover in identifying significant species-environment relationships. A comparison of data from a set of samples located at the discretion of the investigators with a set chosen according to a predetermined stratified random sampling plan shows that each set produces different results. The samples located at the investigators' discretion show a larger number of significant species-environment relationships, and in addition, the outcomes of many individual species-environment tests differ between the two sets of samples. Binary and continuous measurements were compared within the random stratified samples, and nearly all species showed similar environmental trends whether analyzed by continuous or binary techniques. The differences between outcomes of binary and continuous techniques are of the magnitude which can be expected from random variation. These results suggest that where an area containing great floristic variation is to be sampled to identify species-environment relationships, the best sample plan would involve many species taken according to a carefully divised random sampling plan.