Sampling forests with terrestrial laser scanning

Background and AimsTerrestrial laser scanners (TLSs) have successfully captured various properties of individual trees and have potential to further increase the quality and efficiency of forest surveys. However, TLSs are limited to line of sight observations, and forests are complex structural environments that can occlude TLS beams and thereby cause incomplete TLS samples. We evaluate the prevalence and sources of occlusion that limit line of sight to forest stems for TLS scans, assess the impacts of TLS sample incompleteness, and evaluate sampling strategies and data analysis techniques aimed at improving sample quality and representativeness.MethodsWe use a large number of TLS scans (761), taken across a 255 650-m² area of forest with detailed field survey data: the Harvard Forest Global Earth Observatory (ForestGEO) (MA, USA). Sets of TLS returns are matched to stem positions in the field surveys to derive TLS-observed stem sets, which are compared with two additional stem sets derived solely from the field survey data: a set of stems within a fixed range from the TLS and a set of stems based on 2-D modelling of line of sight. Stem counts and densities are compared between the stem sets, and four alternative derivations of area to correct stem densities for the effects of occlusion are evaluated. Representation of diameter at breast height and species, drawn from the field survey data, are also compared between the stem sets.Key ResultsOcclusion from non-stem sources was the major influence on TLS line of sight. Transect and point TLS samples demonstrated better representativeness of some stem properties than did plots. Deriving sampled area from TLS scans improved estimates of stem density.ConclusionsTLS sampling efforts should consider alternative sampling strategies and move towards in-progress assessment of sample quality and dynamic adaptation of sampling.     

Spatial variability of throughfall chemistry and selected soil properties as influenced by stem distance in a mature Norway spruce (Picea abies,Karst.) stand

Our aims were to investigate the spatial variability of throughfall chemistry and soil parameters as influenced by stem distance and to evaluate the implication of the observed systematic and random patterns for the sampling strategy.One hundred throughfall samplers with a sampling area of 106 cm² each were established in a systematic grid around 5 trees in a mature Norway spruce; site of the Fichtelgebirge (Germany). One hundred soil cores were taken with an auger of 50 cm² next to the throughfall samplers. Soil samples were stratified according to genetic soil horizons and analysed for pH, exchangeable NH₄ ⁺, SO₄ ^2– and total-S. Throughfall samples were collected over a period of 6 months. For each sampler an aliquod sample was mixed over the observation period and analysed for major ions.The spatial variability of the element concentrations in throughfall, expressed by the coefficient of variance, was 21–164%, depending on the element considered. For precipitation volume, the coefficient of variance was only 3%. The distance to the stem influenced most element concentrations in throughfall with increasing concentrations approaching the stem. Steepest gradients were observed in case of SO₄ ^2– and H⁺.The spatial variability of the investigated soil parameters was also very high with the exception of pH. The SO₄ ^2– content of the forest floor reflected the gradients observed in throughfall, while for the other investigated soil parameters and soil horizons no significant relations to stem distance were found.To determine site representative throughfall concentrations and soil properties with the sample volumes and time intervals we used, the number of samples required to get a statistical error of less than 10% (with 95% probability) can be very high. In case of throughfall, more than 100, and in case of the soil parameters, more than 300 replicates would be required.     

Density and productivity of breeding Skylarks Alauda arvensis in relation to crop type on agricultural lands in western France

Capsule Small field size and the maintenance of set-aside and lucerne are important to ensure high breeding pair densities and productivity.

Aims To investigate the effects of crop types and their attributes on density and productivity of breeding Skylark.

Methods At each of four selected study sites in western France, territory density, vegetation height, vegetation cover and field size was estimated by field and attempts were made to find nests. Crop types included winter and spring cereals, oilseed rape, sunflower, maize, grass, lucerne, set-aside, and bare ground.

Results About 80% of Skylark territories included more than one crop type. Birds preferred small fields and territory density decreased with increasing field size. Density was highest in crops with low vegetation height and cover. Set-aside, lucerne and grass supported highest territory density. Fledging productivity was highest in set-aside and lucerne, and was zero on bare ground. Skylark density decreased throughout the breeding season (-26% in 1999 and -29% in 2000), suggesting an instability in territory distribution or activity in intensive farmland.

Conclusions Farming systems that decrease field size and increase set-aside and lucerne instead of oilseed rape, maize and sunflower will benefit Skylark and other declining farmland species.     

Root growth of potato crops on a marine-clay soil

Summary In 1982 and 1983 root samples were taken by auger from potato crops grown on marine clay in the Flevo-Polder. The roots increased their penetration depth throughout the periods of measurement, and ultimately reached depths between 80 cm and 100 cm below the hills. Between 50 and 60 days after emergence, decay of roots commenced, starting in the upper horizons. In the hill mean root length densities varied between 1 and 2 cm cm⁻³. Below the hills root density rarely exceeded 1 cm cm⁻³. The random variation in root density was equivalent to a coefficient of variation of 50%. There were significant effects of the position of sampling (relative to the centre of the plant) on root density; densities were usually lowest beneath the furrow. Depending on season and sampling date, total root length varied between 3.4 and 7.1 km m⁻², and root dry mass varied between 33 and 77 g m⁻². Representative figures for specific root length were 100–120 m g⁻¹ dry weight. About 90% of the root diameters were smaller than 0.44 mm; the most frequent class (35%) were roots with diameters between 0.12 and 0.20 mm.     

Nitrogen fertilization and sex expression affect size variability of fibre hemp (Cannabis sativa L.)

Mechanical harvesting and industrial processing of fibre hemp (Cannabis sativa L.) require uniformity of stem length and weight. In 1991 and 1992 we carried out field experiments to investigate the effects of soil nitrogen level (80 and 200 kg ha^-1N) and row width (12.5, 25 and 50 cm) on the variability of weight and height in hemp plants. The crops were sampled 5 times between early June and early September. Row width did not affect size variability. At final harvest coefficients of variation (CV) of both weight and height were about 1.5 times higher at 200 than at 80 kg ha^-1N. Distributions of dry weight were positively skewed at all sampling dates except the first, with skewness larger at 200 than at 80 kg ha^-1N. Distributions of height were negatively skewed at all sampling dates except the first at 80 kg ha^-1N. At 200 kg ha^-1N they changed from negative skewness during the first part of the growing season to negative kurtosis in the second part of the growing season. More suppressed plants were present at 200 than at 80 kg ha^-1N. Contrary to most published results, we did not find a reduction of CV of weight nor of CV of height at the onset of self-thinning. Suppressed hemp plants can survive relatively well in the low-light environment under the canopy. Sexual dimorphism contributed to variability of height and weight, but the effects were smaller than those of nitrogen fertilization. The ratio of female to male plants was higher at 200 than at 80 kg ha^-1N, as a result of a shift in sex-ratio within the population of suppressed plants. As suppressed plants were much more slender than dominating plants, self-thinning eliminated the most slender individuals in a hemp crop. However, the presence of many more heavy individuals of low slenderness at 200 than at 80 kg ha^-1 N was probably the major cause of the difference in slenderness between 200 and 80 kg ha^-1 N.     

Leaf area estimation in a sugar beet cultivar by linear models

An indirect method of leaf area measurement for Rizor sugar beet cultivar was tested. Leaves were sampled during two growing seasons in a Randomised Complete Block Design experiment. For 2002 samplings, leaf area [cm²] was linearly correlated with maximum leaf width [cm] using all leaf samples (r ² = 0.83, p < 0.001) or using the means of the 8 sampling occasions (r ² = 0.97, p < 0.001). Correlations between leaf area and leaf mid vein length [cm] were weaker (r ² = 0.75, p < 0.001 and r ² = 0.93, p < 0. 001, respectively). For 2003 samplings, the area estimated by the equations was highly correlated to the measured leaf area.     

Allometric Biomass,Biomass Expansion Factor and Wood Density Models for the OP42 Hybrid Poplar in Southern Scandinavia

Biomass and biomass expansion factor functions are important in wood resource assessment, especially with regards to bioenergy feedstocks and carbon pools. We sampled 48 poplar trees in seven stands with the purpose of estimating allometric models for predicting biomass of individual tree components, stem-to-aboveground biomass expansion factors (BEF) and stem basic densities of the OP42 hybrid poplar clone in southern Scandinavia. Stand age ranged from 3 to 31 years, individual tree diameter at breast height (dbh) from 1.2 to 41 cm and aboveground tree biomass from 0.39 to 670 kg. Models for predicting total aboveground leafless, stem and branch biomass included dbh and tree height as predictor variables and explained more than 97 % of the total variation. The BEF was approaching 2.0 for the smallest trees but declined with increasing tree size and stabilized around 1.2 for trees with dbh >10 cm. Average stem basic density was more than 400 kg m^?3 for the smallest trees but declined with increasing tree height and stabilized around 355 kg m^?3, at a tree height of about 20 m. Existing biomass functions from the literature all underestimated the measured sample tree biomass. Possible explanations include not only differences in competition among trees in the examined stands and site conditions but also differences in sampling procedures. We observed that basic density increased with height above the ground. This trend may have led to the observed underestimation by existing biomass functions including only few samples from the lower end of the stems.     

Capture efficiency of insect natural enemies from tall and short vegetation using vacuum sampling

Experiments were conducted in lucerne to determine the efficiency of vacuum sampling of insects and whether this was affected by the height of vegetation sampled. Three insects of significance as predators of pests in Australian lucerne were studied: transverse ladybird beetle (Coccinella transversalis Fabricius), pollen beetle (Dicranolaius bellulus (Guérin-Méneville)), and spined predatory shield bug (Oechalia schellembergii (Guérin-Méneville)). In a preliminary experiment comparing a commercially harvested area of lucerne with an unharvested area within the same crop, the proportions of released insects recaptured from unharvested lucerne were significantly lower than recoveries from the shorter, harvested lucerne. Resampling the tall lucerne after it was cut by hand gave cumulative recapture proportions which did not differ from those observed for the harvested lucerne. A second experiment with a randomised replicated design re-tested the hypotheses of the preliminary experiment for two insect species. Very similar results were obtained. This verification showed that recapture efficiencies from tall lucerne ranged between 0.60 and 0.74 but that resampling after hand cutting gave cumulative recapture proportions in excess of 0.86 which did not differ from recapture proportions from short lucerne.     

Fibrous carrot root responses to irrigation and compaction of sandy and organic soils

Field experiments were performed in Southern Finland on fine sand and organic soil in 1990 and 1991 to study carrot roots. Fall ploughed land was loosened by rotary harrowing to a depth of 20 cm or compacted under moist conditions to a depth of 25–30 cm by three passes of adjacent wheel tracks with a tractor weighing 3 Mg, in April were contiguously applied across the plot before seed bed preparation. Sprinkler irrigation (30 mm) was applied to fine sand when moisture in the 0–15 cm range of soil depth was 50% of plant-available water capacity. For root sampling, polyvinyl chloride (PVC) cylinders (30 × 60 cm) were installed in the rows of experimental plots after sowing, and removed at harvest. Six carrot plants were grown in each of in these soil colums in situ in the field.Fine root length and width were quantified by image analysis. Root length density (RLD) per plant was 0.2–1.0 cm cm^-3 in the 0–30 cm range. The fibrous root system of one carrot had total root lengths of 130–150 m in loose fine sand and 180–200 m in compacted fine sand. More roots were observed in irrigated than non-irrigated soils. In the 0–50 cm range of organic soil, 230–250 m of root length were removed from loosened organic soils and 240–300 m from compacted soils. Specific root surface area (surface area divided by dry root weight) of a carrot fibrous root system averaged 1500–2000 cm² g^-1. Root length to weight ratios of 250–350 m g^-1 effectively compare with the ratios of other species.Fibrous root growth was stimulated by soil compaction or irrigation to a depth of 30 cm, in both the fine sand and organic soils, suggesting better soil water supply in compacted than in loosened soils. Soil compaction increased root diameters more in fine sand than it did in organic soil. Most of the root length in loosened soils (fine sand 90%, organic soil 80%) and compacted soils (fine sand 80%, organic soil 75%) was composed of roots with diameters of approximately 0.15 mm. With respect to dry weight, length, surface area and volume of the fibrous root system, all the measurements gave significant resposes to irrigation and soil compaction. Total root volumes in the 0–50 cm of soil were 4.3 cm³ and 9.8 cm³ in loosened fine sand and organic soils, respectively, and 6.7 cm³ and 13.4 cm³ in compacted sand and organic soils, respectively. In fine sand, irrigation increased the volume from 4.8 to 6.3 cm³.     

Effect of remained stem height on yield,quality of Inula helenium I. and on soil water content

To explore the reason causing low yield, poor quality of Inula helenium I., this paper investigated the influence of different remained stem heights on the yield, quality and water consumption of Inula helenium I. in Gannan plateau area using field single factor randomized block method. Research results showed that Inula helenium I. which was cut before blooming period in the last ten-day of July with remained stem height of 25?cm had the lowest water consumption, the best underground root traits (including main root length, root diameter, and root dry weight per plant), and the highest yield which was higher that control group by 18.73% (P?<?.01) Moreover, Inula helenium I. with remained stem height of 25?cm had the lowest ash content while the highest alantolactone content, therefore its quality was the best. The water use efficiency (WUE) of Inula helenium I. with remained stem height of 35?cm at September was the highest (1.12?kg?h?m^?2?mm^?1). However, in terms of biological yield WUE and economic yield WUE, Inula helenium I. with remained stem height of 15?cm was the highest. Therefore, it can be concluded that remained stem height from 15 to 25?cm is an ideal solution, which can not only save water, but also improve yield and quality of Inula helenium I.     

Growth and mortality of trees in Amazonian tropical rain forest in Ecuador

Abstract. Structural changes are analysed in four samples representing 4 ha, two line transects and two hectare plots, of Amazonian tropical lowland rain forest in northern Ecuador. Only trees with a DBH ≥ 10 cm were included. A sample of floodplain forest in Añangu represents the largest turnover found in tropical forests (stand half-life = 23 yr). The line transect and hectare plot both of tierra firme forest in Añangu have the same turnover (37 yr) and were balanced for death and in-growth of both individuals and wood (basal area). The 1-ha tierra firme sample in Cuyabeno had a turnover of 67 yr and was in a growing phase. The floodplain line transect in Añangu was in a phase of structural breakdown. However, the floodplain line transect had the largest growth of basal area per tree (23.4 cm²/yr). The tierra firme samples had a growth of 9.6, 10.1, and 13.6 cm²/yr. Most of the dead trees fell with some uprooting in three of the four samples. However, no significant difference in the distribution of mode of death was found between the four samples. Death was independent of topography and the dead trees were randomly distributed. As the trees grow up they occupy more space and larger trees (DBH ≥ 15 cm) become more uniformly distributed, whereas smaller trees (DBH ≤ 15 cm) were randomly distributed. Our study confirms that plots of 1 ha are not sufficient to include representative samples of different stages of forest structure.     

Evaluation of Sample Recovery Efficiency for Bacteriophage P22 on Fomites

Fomites are known to play a role in the transmission of pathogens. Quantitative analysis of the parameters that affect sample recovery efficiency (SRE) at the limit of detection of viruses on fomites will aid in improving quantitative microbial risk assessment (QMRA) and infection control. The variability in SRE as a function of fomite type, fomite surface area, sampling time, application media, relative humidity (rH), and wetting agent was evaluated. To quantify the SRE, bacteriophage P22 was applied onto fomites at average surface densities of 0.4 ± 0.2 and 4 ± 2 PFU/cm². Surface areas of 100 and 1,000 cm² of nonporous fomites found in indoor environments (acrylic, galvanized steel, and laminate) were evaluated with premoistened antistatic wipes. The parameters with the most effects on the SRE were sampling time, fomite surface area, wetting agent, and rH. At time zero (the initial application of bacteriophage P22), the SRE for the 1,000-cm² fomite surface area was, on average, 40% lower than that for the 100-cm² fomite surface area. For both fomite surface areas, the application medium Trypticase soy broth (TSB) and/or the laminate fomite predominantly resulted in a higher SRE. After the applied samples dried on the fomites (20 min), the average SRE was less than 3%. A TSB wetting agent applied on the fomite improved the SRE for all samples at 20 min. In addition, an rH greater than 28% generally resulted in a higher SRE than an rH less than 28%. The parameters impacting SRE at the limit of detection have the potential to enhance sampling strategies and data collection for QMRA models.     

Utilisation of a packed-bed biofilm reactor for the determination of the potential of biofilm accumulation in water systems

Abstract

An experimental system has been developed that allows the monitoring of biofilm development on supports exposed to water of different characteristics. The system consists of a series of packed-bed reactors filled with glass beads, and by periodically removing biofilm attached to these beads for off-line analyses this provides a means for monitoring biofilm development. Despite its reduced dimensions (6.9 cm long and 1.58 cm in diameter), the experimental system used has a sampling surface of 90.3 cm² (including only the surface of the glass beads). This allows reproducible and representative samples to be taken from different water systems, providing a reliable and economic method for evaluating in situ the formation of biofilms from different environments. The set-up of the entire experimental system was constructed to meet the demands of field experiments in a well-defined hydrodynamic environment and to allow easy removal of samples for biomass quantification and microscopic observation. Data obtained using this device can be used as an indicator of the risk of biofilm formation in different water systems. This indicator, “the biofilm accumulation potential”, represents an effective and representative tool for the monitoring of biofilm development in an integrated antifouling strategy, in order to help keep biofouling, scaling and microbial risks under control. According to the experiments with the packed-bed reactors used with a high flow regime, the ratio TCN/HPC could provide an indication of the state of the biofilm, and lower ratios could indicate a higher biofilm accumulation potential.     

Characterisation of grids of point detectors in maximum skin dose measurement in fluoroscopically-guided interventional procedures

PurposePoint detectors are frequently used to measure patient's maximum skin dose (MSD) in fluoroscopically-guided interventional procedures (IP). However, their performance and ability to detect the actual MSD are rarely evaluated. The present study investigates the sampling uncertainty associated with the use of grids of point detectors to measure MSD in IP.MethodChemoembolisation of the liver (CE), percutaneous coronary intervention (PCI) and neuroembolisation (NE) procedures were studied. Spatial dose distributions were measured with XR-RV3 Gafchromic^® films for 176 procedures. These distributions were used to simulate measurements performed using grids of detectors such as thermoluminescence detectors, with detector spacing from 1.4 up to 10 cm.ResultsThe sampling uncertainty was the highest in PCI and NE procedures. With 40 detectors covering the film area (36 cm × 44 cm), the maximum dose would be on average 86% and 63% of the MSD measured with Gafchromic^® films in CE and PCI procedures, respectively. In NE procedures, with 27 detectors covering the film area (14 cm × 35 cm), the maximum dose measured would be on average 82% of the MSD obtained with the Gafchromic^® films.ConclusionThermoluminescence detectors show good energy and dose response in clinical beam qualities. However the poor spatial resolution of such point-like dosimeters may far outweigh their good dosimetric properties. The uncertainty from the sampling procedure should be estimated when point detectors are used in IP because it may lead to strong underestimation of the MSD.     

Micro- and Nanoforaminifera from Abyssal Northeast Atlantic Sediments: A Preliminary Report

Rose Bengal stained benthic foraminifera which pass through a 63 μm mesh (microforaminifera and nanoforaminifera) have been extracted by handsorting the fine sieve residues (> 45 μm, 31 μm, 28 μm, 20 μm, 15 μm) of abyssal sediment samples. The samples were collected using a multiple corer in four areas of the northeast Atlantic between 31° N and 59° N. The abundance of these minute foraminifera varied from 2 specimens per 1 cm² (Madeira Abyssal Plain) to > 110 per 1 cm² (BIOTRANS area). They include a variety of taxa, the most common being certain rotaliid species, hormosinaceans and other multilocular agglutinated forms, the unilocular agglutinated genus Lagenammina, soft-bodied agglutinated sphaeres and flasks (saccamminids and psammosphaerids) and allogromiids. Some specimens are < 63 μm in maximum dimension but others belonging to elongate taxa are longer. Two samples taken 10 cm apart on the Porcupine Abyssal Plain suggest that minute foraminifera may be patchily distributed on a small scale. One sample, which was overlain by substantial amounts of phytodetritus, contained > 100 stained specimens (> 30 per 1 cm²) while the other, in which much less phytodetritus was present, yielded only 10 specimens (2.9 per 1 cm²). This observation suggests that some micro- and nanoforaminifera may flourish in the presence of decaying organic matter, perhaps consuming the associated bacteria. The presence of phytodetritus may also explain why two of our samples from the Madeira Abyssal Plain (MAP) contained an order of magnitude more stained tiny foraminifera than two other MAP samples in which phytodetritus was absent.     

The influence of leaf area on the rooting physiology of leafy stem cuttings of Terminalia spinosa Engl.

Summary The effect of different leaf areas on the rooting of Terminalia spinosa Engl. cuttings in an non-mist propagation system in glasshouses at Edinburgh was investigated by trimming the leaves to 0, 7.5, 15 and 30 cm² before cuttings were severed from stockplants. Cuttings were taken to a standard length of 5 cm from the lateral shoots of previously pruned stockplants grown in a tropicalised glasshouse. During the rooting period, photosynthetic rate, stomatal conductance, water potential and relative water content of the cuttings were assessed at regular intervals. It was found that (i) removal of the entire leaf area prevented rooting; (ii) cuttings with a 7.5 cm², 15 cm² and 30 cm² leaf all achieved 80% rooting after 3 weeks; (iii) an increase in leaf area from 7.5 cm² to 30 cm² increased the rate of rooting and the length of the longest root after 2 weeks, but also increased the number of original leaves abscised after 6 weeks; and (iv) the greatest number of new leaves were produced by cuttings with 7.5 cm² and 15 cm² leaf area per cutting. All leafy cuttings actively photosynthesized during the propagation period, with a mean rate of 2 mol CO₂ m^-2 s^-1 with an irradiance of 100 mol m^-2 s^-1. Cuttings with 30 cm² leaf area had lower relative water contents, lower stomatal conductances and lower photosynthetic rates per unit leaf area than those with a 7.5 cm² and 15 cm² leaf. It was concluded that T. spinosa cuttings are easy to root, provided the cuttings have leaves to produce current assimilates.A member of the Edinburgh Centre for Tropical Forests     

Temporal analyses of the distribution and diversity of Salmonella in natural biofilms

The diversity and distribution of salmonellae in freshwater biofilms were analyzed at a fine scale (i.e. in 20 locations from a 324 cm² area) for two sites in San Marcos, TX. A concrete storm water overflow channel (City Park) was sampled 4 times and a concrete surface in the spring-fed headwaters of the San Marcos River (Spring Lake) 5 times between April and September 2009, and each biofilm sample analyzed by a combination of traditional enrichment methods and molecular techniques. PCR detection of the invA gene, that encodes a protein of a type III secretion system present in salmonellae, after semi-selective enrichment of salmonellae was achieved in biofilms from all 20 locations at the City Park site, with locations generally being positive 2-3 times out of 4 sampling times for a total of 59% positive samples. InvA gene fragment detection in biofilms was less frequent for the 5 sampling times and 20 locations from the Spring Lake site (18% of all samples), with 1 sampling time being entirely negative and 8 locations remaining negative throughout the study. Rep-PCR fingerprinting of 491 Salmonella isolates obtained from both sites resulted in 30 distinct profiles, with 26 and 7 profiles retrieved from City Park and Spring Lake samples, respectively, and thus with 3 profiles present at both sites, and multiple strains frequently obtained from single locations at both sites. The composition of Salmonella strains in the area analyzed changed in time with large differences between early (April, June) and late sampling times (September) within and among sites, except for one strain (S12) that was present at almost all sampling times at both sites, though often at different locations within the area analyzed. These results demonstrate the presence of salmonellae in natural biofilms and a significant micro-heterogeneity with differences in diversity and persistence of salmonellae.     

Quantification of diatoms in biofilms: Standardisation of methods

Abstract

Benthic diatoms, which often dominate marine biofilms are mostly pennate along with a few centric species that have an attached mode of life. Even though the range of diatoms in biofilms is diverse, their ecology is poorly understood because of the difficulty in sampling and enumeration. Scraping or brushing are the traditional methods used for removal of diatoms from biofilms developed on solid substrata. The method of removal is the most critical step in enumerating the biofilm diatom community structure. In this study, a nylon brush and ceramic scraper were used as tools for the removal of diatoms from 1 – 4-day-old biofilms developed on fibreglass coupons and glass microscope slides. Standardisation of methods showed that the sample volume used in the analyses had the least influence on the quantification, whereas the method of removal was critical. The nylon brush was more efficient at recovering diatoms compared to a ceramic scraper. Direct microscopic enumeration of the community in the case of glass slides indicated that scraping resulted in between 30–50% underestimation. Heterogeneity in diatom community structure between replicate samples is one possible reason for such underestimation.     

Production of Metarhizium anisopliae spores using nutrient‐impregnated membranes and its economic analysis

Metarhizium anisopliae spores were produced on nutrient‐impregnated membranes (NIMs). The NIM system involved wetting the membrane with a spore and nutrient suspension, followed by harvesting the spores produced after incubation. The cost efficiency of spore production was assessed for a range of nutrient sources and membrane types. Skim milk powder (20 g l^‐1) was found to be the most cost‐effective nutrient source of the nine nutrients examined. Yield was 5.7 × 10⁶ spores/cm² after 28 days incubation on a paper membrane. Supplementation of the skim milk with either sucrose (2 g l^‐1) or dextrose + KNO₃ maximized yield. Superwipe, an absorbent fibrous material, was the most efficient of 16 membranes tested which ranged from fibreglass mesh to paper and cloth. A series of small pilot plants were built, but the cost efficiency of spore production decreased as the size of the membrane increased from 24 × 24 cm to 270 × 15 cm and up to 100 × 80 cm. Yield on the two smaller pilot plants was over 10⁷spores/cm², but the cost (nutrient and membrane only) of producing 10¹³ spores (standard dose required per hectare) was around $A37 and was found not to be competitive with spore production on grain.     

Structure of Anogeissus leiocarpa Guill., Perr. natural stands in relation to anthropogenic pressure within Wari‐Maro Forest Reserve in Benin

The present study focused on the analysis of the structure of the Anogeissus leiocarpa dominated natural stands in the Wari‐Maro forest reserve which are under high and minimal anthropogenic pressures. These stands were considered for forest inventories after carrying out a random sampling scheme of 40 sample units of 30 m × 50 m. In each level pressure stand, the dbh and tree‐height of identified tree‐species were measured in each plot. Data analyses were based on the computation of structural parameters, establishment of diameter and height distributions and the floristic composition of the two types of stands. Results obtained showed higher values for the overall basal area (9.78 m² ha^?1), mean height (22.37 m) and mean diameter (36.92 cm) for A. leiocarpa in low‐pressure stands. In high‐pressure stands, some species like Afzelia africana had lower Importance Value Index and the frequency of A. leiocarpa trees in the successive diameter classes dropped rapidly and the value of the logarithmic slope of the height–diameter relationship was lower (9.77) indicating a lanky shape. Results obtained suggest that effective conservation is needed for A. leiocarpa stands under high pressure by limiting human interference and developing appropriate strategy for restoration purposes.