An indicator species approach for result-orientated subsidies of ecological services in grasslands - A study in Northwestern Germany

Agri-environmental subsidies for grasslands of high conservation interest are usually associated with fairly strict management rules, but have not always been successful in terms of the preservation of species. A new approach now links the subsidies paid to the ecological value of a grassland site: the farmers are paid for keeping up a high plant species richness, and they can control the species richness of their sites by using vascular plants as indicator species. The method was tested in different grassland communities in six regions of Lower Saxony in Northwestern Germany, mainly addressing the question whether the number of selected indicator species was correlated with the total species richness of vascular plants and with the number of endangered species.Field work was carried out in 2004. Total species richness of vascular plants was recorded in all grassland sites, and the number of indicators was counted along two transects, usually being the diagonals of a rectangular site. Each transect was divided into three segments in which all indicators growing within 1 m distance from the transect line were recorded. In total 43 indicators were selected, mostly representing species that are fairly easy to recognise.The number of indicators was significantly positively correlated with the total number of species in all regions, also when correcting for autocorrelation (except in one region). When using grassland area as a co-variable, the same results were obtained, supporting the low significance of grassland size for the predictive ability of the method. In all regions but one, the mean number of indicators per segment was also significantly positively related to the number of red-listed and near-threatened species in the grasslands. Grassland size and transect length were found to be of minor importance for the application of the method.In conclusion, the study shows that the indicator approach is suitable for identifying those grassland sites that have a high plant species richness and a high number of endangered species. It may thus form the basis for result-orientated subsidies in grasslands.     

Declines of the gopher tortoise on protected lands

We compared two assessments of the status of gopher tortoise populations at 10 protected sites in Florida, taken about a decade apart. We assessed status indirectly, using surveys of burrows along belt transects. Transect placement and timing were identical between surveys. We compared numbers of burrows, relative numbers of burrows of different activity conditions, and size distributions of burrows between surveys. The comparisons indicated that populations had declined at as many as eight of the sites. We found no strong connection between population decline and decline in habitat quality, as reflected in decreased ground cover and/or increased canopy cover between surveys. The response of a population to decline in habitat quality may depend on initial habitat structure, the degree of change in habitat structure, the period of time over which change is measured, the amount of habitat involved, and the level of habitat management.     

Cost-effective abundance estimation of rare animals: Testing performance of small-boat surveys for killer whales in British Columbia

Top predators are often rare, subject to anthropogenic mortality, and possess life-history traits that make them inherently vulnerable to extinction. IUCN criteria recognise populations as Critically Endangered when abundance is <250 mature individuals, but estimating abundance of rare species can be more challenging than for common ones. Cost-effective methods are needed to provide robust abundance estimates. In marine environments, small boats are more widely accessible than large ships for researchers conducting sightings surveys with limited funds, but studies are needed into efficacy of small-boat surveys. This study compares line transect and mark-recapture estimates from small-boat surveys in summer 2004 and 2005 for ‘northern resident’ killer whales in British Columbia to true population size, known from censuses conducted by Fisheries and Oceans Canada. The line transect estimate of 195 animals (95% CI 27-559) used model averaging to incorporate uncertainty in the detection function, while the mark-recapture estimate of 239 animals (CI 154-370) used a simple two-sample Chapman estimator. Both methods produced estimates close to the true population size, which numbered 219 animals in 2004 and 235 in 2006, but both suffered from the small sample sizes and violations of some model assumptions that will vex most pilot studies of rare species. Initial abundance estimates from relatively low-cost surveys can be thought of as hypotheses to be tested as new data are collected. For species of conservation concern, any cost-effective attempt to estimate absolute abundance will assist status assessments, as long as estimates are presented with appropriate caveats.     

Waterfowl-habitat associations during winter in an urban North Atlantic estuary

Coastal habitats near urban centres in North Atlantic estuaries often support substantial numbers of wintering waterfowl, but little is known of the effects of landscape setting and urbanisation on habitat use. We conducted surveys of waterfowl at 32 wintering sites in Narragansett Bay, Rhode Island, to identify characteristics that may influence habitat use. Sites were chosen along a gradient of urbanisation and reflected the dominant habitat types used by waterfowl in the Bay. Mean waterfowl abundance was 206.7 ± 209.5 birds per site, and sites in the inner part of the estuary had higher overall waterfowl abundances (r² = 0.40, p = 0.021). Species richness ranged from 3.2 to 13.0 and decreased with increasing hunting activity (r² = 0.36, p = 0.040). Hunting activity and habitat characteristics (e.g., latitude, shoreline configuration, prey density) explained 13-27% of the variation in waterfowl abundance and species richness among sites, but landscape characteristics (e.g., surrounding residential development, vegetated land, or wetland surrounding the sites and the extent of wetland edge) explained an additional 1-26%. The landscape characteristics extent of adjacent residential development and vegetated upland were the most common variables entering into the models; most species were more abundant at sites with more adjacent vegetated upland and less adjacent residential development. Our results suggest that landscape setting may be influencing the distribution of wintering waterfowl, and should be considered when developing strategies for the conservation for these species in urban North Atlantic estuaries.     

Bats in a fragmented landscape: Species composition, diversity and habitat interactions in savannas of Santarém, Central Amazonia, Brazil

Species response to forest fragmentation may strongly vary according to ecological requirements, shape, spatial configuration and connectivity of fragments, and the structure of the surrounding matrix. Bats are natural candidates for studies on forest fragmentation. However, the conclusions of such studies are often contradictory. We present the results of a study on the effects of forest fragmentation on bat communities in Alter do Chão, Santarém area, in Central Amazonia, Brazil, an area composed by forests and fragments surrounded by savanna-like vegetation. We compared the species composition between habitats, tested the effect of size, shape and density of trees of forested areas on the presence species and their relative frequency of captures, and investigated the savannas as an ecological barrier for the dispersion of bats. With an effort of 5678 mistnet-hours, we captured 3740 bats (64 species). Multidimensional Scaling indicated no strong separation between the habitats sampled, however, savanna sites were grouped distinctly of fragments and forest sites. Multiple linear regressions indicated no significant correlation between the number of bat species recorded and the size, shape or tree density in forest sites and fragments. There was a significant correlation between the number of captures and the variables tested, explained by the shape of the sites, but not by size or tree density. In general, sites with bigger shape indices had fewer captures. Ten of the 20 most captured species showed no significant difference between the three habitats. The bat communities in Alter do Chão were not strongly affected by forest fragmentation, and the savannas did not appear to act as an ecological barrier to bats.     

Clonal diversity and morphometry in the parthenogenetic earthworm Eiseniella tetraedra (Sav.) as affected by habitat characteristics including radioactive pollution

Eiseniella tetraedra (Sav.) is a cosmopolitan earthworm reproducing by obligate parthenogenesis. Here, we examined whether habitat characteristics affected the clone pool diversities and morphometric variability of the stenotopic riparian species E. tetraedra along a west–east transect from the Scandinavian mountains to lowland habitats of the Swedish east coast through Finland and to Russia (the Komi Republic) near the Ural Mountains. The transect comprised a geographical distance that cuts through the maritime to continental climatological zones within the boreal forest belt. It terminated in the Komi Republic, thus adding habitat (soil) characteristics to the factor of radioactive pollution. We found that mountain brooks in Sweden hosted the lowest numbers of clones, but in the lowland samples the clone pool diversities decreased in general from Sweden through Finland and Russia, i.e. from west to east. Nevertheless, high levels of clonal variability were observed within the countries, so that even monomorphic pools were found. However, no clones were shared between the countries. The fresh body weights and posterior body lengths of adult earthworms decreased from west to east. The numbers of posterior segments did not, however, differ between the countries, due to decreased segment size. The location of the clitellum, tubercula pubertatis and male pores showed no clear-cut morphometric clines along the W–E gradient, but the tubercula pubertatis and male pores were more clearly demarcated in adults of the Russian material than in those from the West. Eiseniella adults from the Swedish mountains carried spermatophores considerably more often than those from the other localities. E. tetraedra from localities with radioactive pollution in Russia (the Komi Republic) showed no clear-cut clone pool diversities in comparison to the clone pools of the other sites within the area. Monomorphic clone pools were recorded in localities with low as well as high levels of long-term ionizing radiation and exposure to heavy metals. We found no morphological malformations, such as dislocations of characters, in comparison to individuals from sites with lower levels of environmental radiation.     

Butterflies and diurnal moths along road verges: Does road type affect diversity and abundance?

Roadsides form potential habitats for several grassland species adapted to regular mowing management. We studied the communities of butterflies and day-active moths in 51 sites along the verges of the three road types, i.e., highways, urban roads and rural roads. Despite different traffic densities and widths of the road and verge, the groups were rather similar with regard to soil properties, vegetation structure and mowing intensity. The species richness and total abundance of butterflies (53 species, 5964 individuals) and diurnal moths (46 species, 4626 individuals) were also rather similar in each road type, although a preference for wider verges was observed. Butterfly diversity increased (but not significantly) from the verges of narrow rural roads to wider highways. The highest numbers of meadow species were recorded along highways and the total abundance, especially of diurnal moths, decreased in accordance with the road size. High nectar abundance was the most important factor increasing the numbers of meadow butterflies along road verges, while meadow moths were mostly favoured by shelter provided by tall vegetation. Verges surrounded by cultivated fields were generally related to low numbers of both Lepidoptera groups, whereas adjacent forests increased the total number of all species and favoured several butterflies inhabiting forest edges. The adjacent environment inflicted compositional differences on the Lepidoptera fauna of the three road types. The results indicate that road verges should be considered an important reserve for species dependent on semi-natural grasslands in Finland. A growing interest in accommodating current roadside management for conserving biodiversity is likely to benefit Lepidoptera communities in the verge habitats.     

Anatidae in eastern China during the non-breeding season: Geographical distributions and protection status

Eastern China’s Anatidae are globally important, occurring in large numbers and exhibiting very high diversity; however populations have declined greatly since the 1950s due to habitat loss and degradation, and poaching. To meet the urgent need for up-to-date conservation information, we conducted extensive surveys of the region’s inland and coastal wetlands to collect data on current Anatidae numbers, distributions and key sites. This paper provides information on the non-breeding distributions of 27 species and how these have changed during the last 30 years, and discusses the protection status afforded to Anatidae and their habitats. About 80% of eastern China’s Anatidae occur at inland wetlands, predominantly within the Yangtze River floodplain. Current distributions of most species are different to those of the late-1970s; range contraction, range shift and northward expansion have occurred. Approximately 45% of the total Anatidae population, and high proportions of five globally threatened species populations, were located within National Nature Reserves; coverage could be increased to ca. 65% by inclusion of additional important Anatidae sites within the National Reserve system. However, a number of important issues, such as management skilling and control of land use within reserves, need to be addressed if National Nature Reserves are to provide satisfactory protection for Anatidae. It is also highly desirable that the China National List of Protected Animals include all the relevant Anatidae species on the IUCN Red List to provide a high level of protection for globally threatened species.     

Commonness and rarity in plants with special reference to the Sheffield flora Part I: The identity,distribution and habitat characteristics of the common and rare species

By reference to extensive vegetation surveys the habitats of common and rare herbaceous plants and small (<1 m) woody species have been compared for the Sheffield region of Central England.Common species are frequent at sites of high fertility, are strongly represented in habitats which are heavily disturbed or of recent origin and generally have a wide geographical and ecological range in the Sheffield region and within Britain as a whole.Many of the rare species are restricted to the lowland half of the region and most of the species which have become extinct from the region in the recent past were associated with lowland agricultural areas where the pressures of changing land use are greatest. Rare species are concentrated within less fertile sites, particularly those with calcareous soils, and they are often present in species-rich vegetation in ancient habitats. Many rare species have a narrow ecological range, some appear restricted to ‘intermediate’ habitats (either ecoclines or ecotones) and a high proportion are near the northern limit of their geographical range.No single ecological characteristic is totally diagnostic of either common or rare species. Most of the differences between common and rare species in the Sheffield region may be interpreted in terms of the availability of suitable habitats within the region with common species occupying common, and rare species less common, habitats.     

Pesticide use on cereal crops and changes in the abundance of butterflies on arable farmland in England

A survey of butterfly numbers on two plots of arable farmland in southern England in 1984 was carried out using the transect method of Pollard et al. (1975). On one plot the field edges were left unsprayed with pesticides (herbicides, fungicides and insecticides) from 1 January and on the other all fields were fully sprayed in accordance with normal farming practice. Sprayed and unsprayed transect sections were paired up according to adjacent field boundary habitat type.A total of 868 butterflies were recorded on the unsprayed plot compared to 297 on the sprayed plot. Of the 17 species recorded on more than one survey section, 13 were significantly more abundant on the unsprayed treatment. Butterfly species whose larval host plants occurred in unsprayed field edges showed slightly larger differences in number between treatments than species less able to breed in weedy cereal crops.The results suggest that pesticide use on cereal crops may reduce butterfly numbers and that arable farmland is a habitat in need of further study for butterfly conservation.     

The hydroecological controls and conservation value of beetles on exposed riverine sediments in England and Wales

There are large numbers of records of uncommon beetles from exposed riverine sediments (ERS) (gravel, sand and silt shoals) in the UK. However, systematic surveys of their occurrence in relation to environmental controls are seldom undertaken. Data are presented here from a survey of 69 shingle ERS across England and Wales and used to establish which factors were important in constraining species assemblages. Over 480 species of Coleoptera were collected by a combination of pitfall trapping, hand searching and excavation techniques. A total of 81 species with conservation status of Vulnerable, Rare or Nationally Scarce were recorded during the work and this includes six species on the United Kingdom Biodiversity Action Plan (BAP) lists. A subset of 42 of these rare species can be classified as ERS specialists. The data were analysed using TWINSPAN, redundancy analysis (RDA), single factor ANOVA, general linear modelling (GLM) and correlation to examine the importance of selected environmental variables and their relationships with the species assemblages. The results indicate that: (i) ERS sites with large numbers of species that are either rare or exhibit strong fidelity to the sediments have a markedly western distribution in the UK and are found on unregulated rivers in Wales and a number of rivers in the south west of England, (ii) the type of substrate, habitat heterogeneity, the percentage of shade from trees, the percentage of fine sediments on the ERS, the amount of trampling and ERS size are important in determining invertebrate communities and (iii) ERS provide valuable and important habitats for rare beetles species in the UK. The importance of river regulation, engineering and trampling by stocking for ERS invertebrates is discussed.     

Tolerance of frugivorous birds to habitat disturbance in a tropical cloud forest

In view of the continued decline in tropical forest cover around the globe, forest restoration has become a key tool in tropical rainforest conservation. One of the main - and least expensive - restoration strategies is natural forest regeneration. By aiding forest seed influx both into disturbed and undisturbed habitats, frugivorous birds facilitate forest regeneration. This study focuses on the tolerance of a frugivorous bird community to anthropogenic habitat disturbance within the broader context of natural forest regeneration with conservation purposes. It was carried out in the tropical cloud forest of Costa Rica’s Talamanca Mountains. Bird community response and tolerance to habitat disturbance was assessed by comparing bird presence and densities along a disturbance gradient, ranging from open pastures to closed mature forests. Birds were censused along nine transects applying the variable width line transect procedure. Forty relevant frugivorous bird species were observed during 102 h of survey time. Densities were calculated for 33 species; nine species responded negatively to increasing level of disturbance and nine others positively. Results indicate that large frugivores are generally moderately tolerant to intermediate, but intolerant to severe habitat disturbance, and that tolerance is often higher for medium and small frugivores. It appears that moderately disturbed habitats in tropical cloud forests are highly suitable for restoration through natural regeneration aided by frugivorous birds. Due to a lack of large forest seed dispersers, severely disturbed habitats appear less suitable.     

Conservation of non-game wildlife in California: A model programme

Public interest prompted the California State Legislature to provide needed authority and precedent-setting mandates for the management and protection of its non-game wildlife resources. Newly established activities and regulations include: research and field surveys on species-specific problems; the introduction of protective categories for threatened or unique species; bag limits and seasons on the taking of any unprotected animal; a moratorium on mountain lion hunting; measures to promote increases in the numbers of the rare Tule elk; curtailment of imported wildlife; a ban on the trade in endangered species; protective measures for intertidal organisms; and land acquisition of areas with important habitats. These constitute a comprehensive programme that merits wider adoption in the USA.     

A comparative analysis of decline in the distribution ranges of orchid species in Estonia and the United Kingdom

National databases were interrogated to analyse and compare proportional alterations in the distribution ranges of orchid species between two surveys in the UK (surveys completed in 1969 and 1999) and in Estonia (surveys completed in 1970 and 2004). Nearly every species declined between the surveys in both countries, and two species may have become extinct in the UK. Mean decline in distribution range for 49 species in the UK was 50% (range 14-100%), and 23 species declined by over 50%. The mean decline for 33 orchid species in Estonia was 25% (range 0-62%), and three species declined by over 50%. These results corroborate serious range declines recently reported for orchids in other regions of Europe (the Netherlands and Flanders, Belgium). In contrast with these other regions, we found that species associated with calcareous grassland and woodland habitats had suffered greater mean contractions in range than species of wet grassland habitats. Greater decline was recorded for species found on drier soils, and for species characteristic of open habitats. In addition, greater decline was found in species with short inflorescences, and in species that were short-lived, and clonal. Our results suggest that levels of decline shown both by groups of species associated with specific habitat types, and by particular species of orchid, depend strongly on local policies and specific conservation action, and indicate the habitat types on which conservation efforts may need to be concentrated in the future. The results suggest that grazing and mowing of competing vegetation, and avoidance of substrate disturbance, will produce the greatest rewards for the most vulnerable species.     

Abundance, body size and movement patterns of a tropical treefrog in continuous and fragmented forests in the Brazilian Amazon

Phyllomedusa tarsius is a hylid frog that breeds in ponds located in a range of habitats from continuous forests to severely disturbed matrix habitats in Central Amazon. During three reproductive seasons, we followed the movement patterns, measured body size and registered abundance and residency time of this species in five habitats: pasture, Vismia regrowth, Cecropia regrowth, 1 and 10 ha forest fragments, and continuous forest. The frog captures were strongly correlated with rainfall in all disturbed habitats, but not in continuous forest, probably because individuals respond more directly to rainfall patterns in more open habitats. Males in disturbed habitats were smaller than those found in continuous forest, perhaps as a result of differences in habitat quality. Males remained at sites for longer periods in fragments and continuous forest compared to matrix habitats. Here again, the quality and suitability of breeding sites in matrix habitats may be lower than in continuous forest resulting in the need for more movement. We found bigger subpopulations in matrix habitat ponds and a higher percentage of individuals moving among them when compared to continuous forest ponds. Constant movement of individuals among disturbed subpopulations decreases population isolation and increases interbreeding among different subpopulations. No movement between individuals from continuous forest ponds and disturbed habitats was observed. This suggests that the disturbed habitat subpopulations are not acting as sink subpopulations for continuous forest populations. The maintenance of individuals in fragments is more dependent on local conditions for reproduction and on subpopulations in the matrix habitat than on recruitment of individuals from populations in continuous forest.     

Are indices reliable for assessing conservation value of natural areas? An avian case study

Bird censuses in two wetland habitats (bogs and wet meadows) in SW Sweden were used to test the applicability of five conservation indices suggested for birds. The censused sites were first evaluated and ranked by the authors, then ranked according to each of the indices. Two indices based on species diversity (H′ or Λ) showed a poor agreement with our evaluation; we suggest that they should not be used for ranking of sites of ornithological interest. Three indices based on rarity showed a better agreement with our evaluation, but were influenced by the size of the geographical area for which rarity was assessed. None of the five indices takes into account all of the relevant aspects for an evaluation of the bird fauna at the different sites. Before constructing further indices, conservationists must reach agreement on which evaluation criteria to use, and how to use them. It may, however, not be feasible to construct a single index; a better strategy might be to construct indices only for single evaluation criteria.     

The impact of data realities on conservation planning

Conservation planning decisions are typically made on the basis of species distribution or occurrence data, which ideally would have complete spatial and taxonomic coverage. Agencies are constrained in the data they can collect, often pragmatically prioritising certain groups such as threatened species, or methods, such as volunteer surveys. This mismatch between goals and realities inevitably leads to bias and uncertainty in conservation planning outputs, yet few studies have assessed how data realities affect planning outputs. We conducted a sensitivity analysis on the Protection Index, a method for assessing conservation progress and priorities, using an extensive dataset on species occurrences and distributions derived from the Florida Natural Areas Inventory. Analyses revealed a high proportion of occurrence records for threatened species and certain taxonomic groups, reflecting the agencies’ priorities. We performed a sensitivity analysis on conservation planning outputs, simulating a ‘data poor’ scenario typical of many real situations; we deleted increasing amounts of data in both a biased (exaggerating patterns observed) and unbiased (random) manner. We assessed the effects of data paucity and bias on the value of potential conservation sites, and planning priorities. Certain high value sites with only a few important species occurrences were more sensitive to data depletion than those with many occurrences. Data bias based on taxonomic bias was more influential to site value than threat rank. To maximise benefit from surveys from a planning perspective, it would be better to focus on poorly surveyed areas rather than adding occurrences in already well represented sites. This study demonstrates the importance of sensitivity analysis in conservation planning, and that the effects of uncertainty and data quality on planning decisions should not be ignored.     

Habitat management of little terns in Japan’s highly developed landscape

The little tern (Sterna albifrons) is a species of shorebird that nests in colonies on sandy beaches and riverbanks with little vegetation cover. In Japan, the natural breeding habitats of the terns have decreased drastically, and the species is listed under the category “vulnerable” in the Red List of the Government of Japan. To reduce the effects of habitat loss on the terns, conservationists are attempting to create and manage artificial colony sites in highly developed landscapes, such as reclaimed lands located in Tokyo Bay, central Japan. We present the factors that contribute to breeding success for this species and the habitat characteristics related to nest-site selection in the artificial colony sites along Tokyo Bay. Our data show that around 3 ha of a building rooftop without vegetation cover could sustain more than 2000 little tern nests. We found a strong positive relationship between colony size and hatching success, observing that a colony size of more than 100 lowered predation rates of eggs. On sites built upon white crushed-concrete, nest densities were high and predation rates of eggs were low. We also found that feeding rates were affected by foraging habitats, of which the best types were the shoreline of sandy beaches and mud flats. The 40 km dispersal range of the breeding terns, inferred from distribution data, should be considered when establishing a network of the multiple colony sites.     

Relating bat species presence to simple habitat measures in a central Appalachian forest

We actively sampled the bat community at 63 sites using detection and non-detection metrics on the Fernow Experimental Forest (FEF) in the central Appalachians of West Virginia using Anabat acoustical equipment May-June 2001-2003 to relate species presence to simple habitat measures such as proximity to riparian areas, forest canopy cover, forest canopy gap width, and forest canopy height. We acoustically detected eight species on the FEF, including the endangered Myotis sodalis. The presence of Lasiurus cinereus, M. lucifugus, M. sodalis, and Pipistrellus subflavus was associated more with riparian areas than upland areas. Both univariate comparisons and multiple logistic regression modeling showed that the probability that clutter-adapted foraging species such as M. septentrionalis and M. sodalis would be detected was greater as forest canopy cover increased or forest canopy gap size decreased, whereas the opposite was true for open-adapted foraging species such as Eptesicus fuscus and L. cinereus. The overall proportion of unidentifiable bat echolocation sequences to those identified to species was related to upland sites with increasing forest canopy cover indicating some sampling bias between cluttered and uncluttered habitats. However, given sufficient sample points, bat community surveys using acoustical detection show the ability to quickly develop generalized habitat associations for rugged areas such as the central Appalachians where traditional mist-net survey efforts often are logistically difficult and are lacking in scope. Moreover, these acoustical surveys also could lend themselves to species-specific predictive mapping of foraging habitat as well as allowing researchers to formulate testable hypotheses about detailed bat habitat relationships to be definitively tested with radio-telemetry techniques.     

Assessing the variability of soil surface characteristics in row-cropped fields: The case of Mediterranean vineyards in Southern France

Spatial patterns of soil surface characteristics (SSC) are important factors for heterogeneity in runoff and infiltration processes in row-cropped fields. The objective of this paper is to analyse the spatial heterogeneity of SSC in the case of a vineyard in order to propose an adequate sampling strategy. A preliminary field survey was carried out to obtain a quantitative assessment of SSC. The experimental layout consisted of 3 wire-trained vine subplots with 3 different soil treatment. 60 observations per subplot were conducted using the line transect method. Their locations were determined according to a stratified sampling design conceived in accordance with the geometric structure of the vineyard system, defined by the alignment of vine rows and the direction of the main slope. The spatial heterogeneity of SSC was analysed at intra-transect and inter-transect levels using measurements of structural crust, sedimentary crust, grass and organic litter. The characterization of intra-transect heterogeneity, using join-count statistics, allowed patches of homogeneous units of attributes to be detected and hence an appropriate sampling resolution and an adequate transect length to be determined. A sampling resolution of 10 cm on a 1.25 m length transect was found to be appropriate for the observation of homogeneous units of attributes. Analysis of inter-transect heterogeneity, using non-spatial statistics, revealed considerable variability between rows and inter-rows that must be accounted for during field surveys. The role of site topography on spatial patterning of SSC attributes across the plot and the need to stratify the plot into areas with homogeneous slope were also demonstrated. Finally, the t-test procedure indicated that the minimum sample size was found to be 200 transect/ha for a minimum precision rate of 80% in the values of SSC attributes.