G. Londo

Bio: G. Londo is an academic researcher. The author has contributed to research in topics: Quadrat & Scale (ratio). The author has an hindex of 2, co-authored 2 publications receiving 855 citations.

The decimal scale for releves of permanent quadrats

Abstract: For vegetation analyses of permanent quadrats the author formerly used a modified scale of Braun-Blanquet with smaller intervals than in the original. For calculations of difference- and change quotients etc., on the basis of coverage, the symbols of this scale have to be converted to values proportional to the real coverage percentages. A conversion in simple terms is not possible; so the calculations are inconvenient. For an efficient analysis of permanent quadrats a scale is needed that fulfils some requirements. The decimal scale fulfils these. For the analysis of small sub-quadrats of a permanent quadrat a coarse scale is proposed. This scale is directly comparable with the finer decimal scale.

The decimal scale for relevés of permanent quadrats

Abstract: For vegetation analyses of permanent quadrats the author formerly used a modified scale of Braun-Blanquet with smaller intervals than in the original. For calculations of difference- and change quotients etc., on the basis of coverage, the symbols of this scale have to be converted to values proportional to the real coverage percentages. A conversion in simple terms is not possible; so the calculations are inconvenient. For an efficient analysis of permanent quadrats a scale is needed that fulfils some requirements. The decimal scale fulfils these. For the analysis of small sub-quadrats of a permanent quadrat a coarse scale is proposed. This scale is directly comparable with the finer decimal scale.

Transformation of Cover-Abundance Values in Phytosociology and its Effects on Community Similarity

Abstract: The numerical treatment of phytosociological data is often based on estimates of cover and/or abundance according to the Braun-Blanquet and Domin scales. Since Schwickerath (1931, 1938, 1940) and Tuxen & Ellenberg (1937) published their transformations there has been discussion on the way the scale values should be used in calculations Qualitative approaches, i.e. based on presence and absence have also been favoured (e.g. Williams & Lambert 1959, van der Maarel 1966) Dagnelie (I960) proposed a pseudoqualitative basis for various calculations by means of a ‘coupure’. A coupure includes the deletion of lower values, usually according to a fixed criterion, e.g. the number of occurrences in a phytosociological table to be remained should be as close as possible to 50%. Dagnelie’s approach remained largely unknown and apparently it has never been tested.

Assessing biodiversity by remote sensing in mountainous terrain: the potential of LiDAR to predict forest beetle assemblages

Abstract: Summary 1. Effective biodiversity management can only be implemented if data are available on assemblage–environment relationships. The level of detail needs to be relevant to the scale of planning and decision making. A number of remote-sensing methods are available, but there are few studies that link information collected at both landscape and local scales. This is particularly true for arthropods even though these organisms are ecologically very important. 2. We assessed the predictive power of habitat variables measured by airborne laser scanning (light detection and ranging; LiDAR) to model the activity, richness and composition of assemblages of forest-dwelling beetles. We compared the results with data acquired using conventional field methods. We sampled beetles with pitfall traps and flight-interception traps at 171 sampling stations along an elevation gradient in a montane forest. 3. We found a high predictive power of LiDAR-derived variables, which captured most of the predictive power of variables measured in ground surveys. In particular, mean body size and species composition of assemblages showed considerable predictability using LiDAR-derived variables. The differences in the predictability of species richness and diversity of assemblages between trap types can be explained by sample size. We expect predictabilities with R2 of up to 0·6 for samples with 250 individuals on average. 4. The statistical response of beetle data and the ecological interpretability of results showed that airborne laser scanning can be used for cost-effective mapping (LiDAR : field survey : beetles 15 : 100 : 260 € ha−1) of biodiversity even in remote mountain areas and in structurally complex habitats, such as forests. 5. Synthesis and applications. The strong relationship between characteristics of beetle assemblages to variables derived by laser scanning provides an opportunity to link data from local ground surveys of hyperdiverse taxa to data collected remotely at the landscape scale. This will enable conservation managers to evaluate habitats, define hotspots or map activity, richness and composition of assemblages at scales relevant for planning and management. In addition to the large area that can be sampled remotely, the grain of the data allows a single tree to be identified, which opens up the possibility of planning management actions at local scales.

Use of visual cover assessments as quantitative estimators of some british woodland taxa

Abstract: SUMMARY (1) Ten observers made visual estimates of plant cover on a series of 4 m2, 50 m2 and 200 m2 quadrats in a woodland. (2) Mean cover values from the ten observers corresponded reasonably closely with point quadrat estimates of cover for most species in the 4 m2 quadrats. (3) For all taxa, significant differences occurred between the estimates of different observers at all quadrat sizes. Using an observer drawn at random, 90% confidence intervals were in the range + 10-20% cover. The corresponding range for an individual repeating an estimate on the same quadrat was + 5-15% cover. (4) Variability between observers was usually lowest when estimating broad-leaved species and highest with fine-leaved species and bryophytes. (5) Observers differed in the consistency with which they tended to under- or over-estimate cover in relation both to species and to quadrat size; this consistency was not correlated with experience. (6) The biases of different observers for a particular species and quadrat size were sufficiently consistent that the use of mean bias correction factors brought about clear gains in the precision of cover estimates for most species.