Seasonal Volatile Emission Patterns of the Endemic New Zealand Shrub Dracophyllum subulatum on the North Island Central Plateau

Volatile organic compounds (VOCs) produced by plants are essential indicators of their physiological response to environmental conditions. But evidence of natural variation in VOC emissions and their contributing factors is still limited, especially for non-cultivated species. Here we explored the natural volatile emissions of Dracophyllum subulatum Hook.f., an endemic shrub to the North Island Central Plateau of New Zealand, and determined some environmental factors driving the plant’s emissions. Volatile emissions of D. subulatum were measured on four separate occasions from December 2017 to September 2018 using the “push-pull” headspace sampling technique and analyzed using gas chromatography-mass spectrometry (GC-MS). D. subulatum was classified based on the volatiles measured on each sampling occasion using linear discriminant analysis (LDA). On each sampling occasion, we also recorded and compared ambient air temperature, herbivory damage, total soil nitrogen (N), available phosphorus (P), potassium (K), and soil moisture content. The relationship between environmental variables that differed significantly between sampling occasions and volatile emissions were estimated using generalized linear models (GLMs). Based on VOCs measured on each sampling occasion, we were able to distinguish different chemical profiles. Overall, we found that total emission and the relative proportions of all major chemical classes released by D. subulatum were significantly higher during summer. The GLMs reveal that differences in environmental factors between the four sampling occasions are highly associated with changing emissions. Higher temperatures in summer had a consistently strong positive relationship with emissions, while the impacts of soil moisture content, P and K were variable and depended on the chemical class. These results are discussed, particularly how high temperature (warming) may shape volatile emissions and plants’ ecology.

Removal modelling in ecology: A systematic review

Removal models were proposed over 80 years ago as a tool to estimate unknown population size. More recently, they are used as an effective tool for management actions for the control of non desirable species, or for the evaluation of translocation management actions. Although the models have evolved over time, in essence, the protocol for data collection has remained similar: at each sampling occasion attempts are made to capture and remove individuals from the study area. Within this paper we review the literature of removal modelling and highlight the methodological developments for the analysis of removal data, in order to provide a unified resource for ecologists wishing to implement these approaches. Models for removal data have developed to better accommodate important features of the data and we discuss the shift in the required assumptions for the implementation of the models. The relative simplicity of this type of data and associated models mean that the method remains attractive and we discuss the potential future role of this technique.

Removal modelling in ecology

Removal models were proposed over 80 years ago as a tool to estimate unknown population size. Although the models have evolved over time, in essence, the protocol for data collection has remained similar: at each sampling occasion attempts are made to capture and remove individuals from the study area. Within this paper we review the literature of removal modelling and highlight the methodological developments for the analysis of removal data, in order to provide a unified resource for ecologists wishing to implement these approaches. Models for removal data have developed to better accommodate important feature of the data and we discuss the shift in the required assumption for the implementation of the models. The relative simplicity of this type of data and associated models mean that the method remains attractive and we discuss the potential future role of this technique.Author summarySince the introduction of the removal in 1939, the method has being extensively used by ecologists to estimate population size. Although the models have evolved over time, in essence, the protocol for data collection has remained similar: at each sampling occasion attempts are made to capture and remove individuals from the study area. Here, we introduce the method and how it has been applied and how it has evolved over time. Our study provides a literature review of the methods and applications followed by a review of available software. We conclude with a discussion about the opportunities of this model in the future.

Using visual encounter data to improve capture-recapture abundance estimates

Capture-recapture studies are widely used in ecology to estimate population sizes and demographic rates. In some capture-recapture studies, individuals may be visually encountered but not identified. For example, if individual identification is only possible upon capture and individuals escape capture, visual encounters can result in failed captures where individual identities are unknown. In such cases, the data consist of capture histories with known individual identities, and counts of failed captures for individuals with unknown identities. These failed captures are ignored in traditional capture-recapture analyses that require known individual identities. Here we show that if animals can be encountered at most once per sampling occasion, failed captures provide lower bounds on population size that can increase the precision of abundance estimates. Analytical results and simulations indicate that visual encounter data improve abundance estimates when capture probabilities are low, and when there are few repeat surveys. We present a hierarchical Bayesian approach for integrating failed captures and auxiliary encounter data in statistical capture-recapture models. This approach can be integrated with existing capture-recapture models, and may prove particularly useful for hard to capture species in data-limited settings.

The impact of experimental forest fire on collembolan communities

Our study was carried out in fresh pine mixed forest, Biala Forest, near Warsaw (52°59’ N, 21°46’ E and 52°79’ N, 21°89’ E, Eastern Poland). Three experimental plots, 1m2 size, were chosen at random and burnt in June. The material was collected: just after the experimental fire (in June ), 30, 60, and 90 days after fire (respectively: in July, August, and September). On every sampling occasion 10 soil samples of an area of 10cm2 and a depth of 5 cm were taken in each sampling plots: burnt plots, in the border of burnt plots, and in surroundings of burnt plots. We found that experimental fire influenced on collembolan densities (Kruskall-Wallis test, H=8.29, P=0.01). Just after the experimental fire we found no collembolans in burnt plots. In a period of 90 days following the experimental fire densities of springtails of burnt and surroundings were similar. Euedaphic springtails were the dominating group in burnt plots and contrary to the border of burnt plots and surroundings, we noticed no epigeic springtails. Contribution of epigeic, hemiedaphic and euedaphic species in collembolan communities of investigated areas could point to different defense strategies of these invertebrates. Immature individuals of Collembola were the most numerous in burnt plots and at the border of burnt plots and this phenomenon is probably crucial for the reconstruction of collembolan communities after the fire.

Soil Heterotrophic Respiration Potential and Maximum Respiration Rate of Differently Managed Meadows

In this study were compared heterotrophic respiratory potential (VDS/VMAX) expressing an increase in C mineralisation rate after drying and re-wetting the soil to 60% soil water content (v/w)(VDS) in relation to maximum respiration rate (VMAX) after glucose addition, and VMAX in organomineral soil (Ah horizon) of mod­erately mown and for 11 years abandoned mountain meadows in Moravian-Silesian Beskids Mts. VDS/VMAX and VMAX were assessed in soil samples taken in 30-day intervals throughout the period of May–September 2004. The results obtained showed higher VDS/VMAX on the abandoned meadow throughout the whole experiment except the last sampling occasion, and higher VMAX throughout the whole experiment. Significantly (P < 0.05) higher VDS/VMAX on the abandoned meadow was found in May and July, VMAX was significantly higher on the same meadow (P < 0.05) only in September. From the parameters studied, the time of sampling had no significant (P > 0.05) effect on VMAX when the data from the moderately mown meadow were evaluated. On the abandoned meadow, VMAX found was significantly (P < 0.05) different when the samples from May and September or July and September were compared. A significant (P < 0.05) effect of the sampling time on VDS/VMAX on the moderately mown meadow was presented by differences between May and other sampling times, on the abandoned meadow differences between September and other times of sampling except May were significant (P < 0.05).

Sources of variation of Escherichia coli concentrations in bivalve molluscs

Bivalve molluscs can concentrate contaminants, including pathogenic microorganisms, from the water column during their normal filter-feeding activity. In the European Union, the risk of human and animal faecal contamination in bivalves is estimated by determining the concentration of Escherichia coli in time-series samples from production areas. A structured field study was undertaken to determine the extent to which such concentrations varied between sites, sampling occasions and shellfish species and to determine the residual variability of the method. E. coli was enumerated in three species of bivalve mollusc (Crassostrea gigas, Mytilus spp. and Pecten maximus) co-located in each of three geographically separate commercial shellfisheries. The data were subjected to analysis of variance (ANOVA). This showed that the effects of site, sampling occasion, species and site/sampling occasion interaction were all significant. The proportion of variation due to site was markedly greater than that due to other factors. Post-ANOVA analysis showed that the concentration of E. coli in P. maximus was significantly higher than in the other two species. Mytilus spp. and C. gigas exhibited comparable levels of E. coli. The observed standard deviation of the most probable number method in the study was 0.33 log10.

Spatial variation of five co-existing siluriformes in an atlantic rain forest drainage

Five species of Siluriformes were registered in the Ubatiba system. Pimelodella lateristriga was the dominant one, followed by Hypostomus gr. punctatus, Rineloricaria sp., Callichthys callichthys and Rhamdia sp. Simple correlation analysis between species density and habitat parameters indicated that hydrology explained density patterns of four species. Pimelodella densities were negatively correlated with pools, Callichthys and Hypostomus densities were positively correlated with runs and Rhamdia densities were positively correlated with riffles; Rineloricaria densities did not respond to any hydrological parameter. Substrata were an important factor to all species, but specific preferences were observed. Marginal vegetation was positively correlated only to Pimelodella densities. Sorensen dissimilarity analysis indicated that site groups, based on both species composition and habitat parameters, were very similar and corroborated the correlation analysis suggesting that Siluriformes composition should be explained by many habitat parameters. Analysis of co-variation of species densities at each sampling occasion showed to be statistically similar in at least all (100%) analysed cases indicating that Siluriformes composition was strongly persistent in time.

Spatial distribution of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) larvae in three scales

The spatial distribution of larvae of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), the citrus leaf miner, in leaves, shoots, and tree crowns of Montenegrina tangerine (Citrus deliciosa Tenore) and Murcott tangor (Citrus sinensis L. Osbeck x Citrus reticulata Blanco) was determined. Fortnightly samplings from July/2001 to June/2003, in orchards located in Montenegro (29º 68’ S and 51º 46’ W), RS, Brazil, were carried out. At each sampling occasion eighth shoots randomly selected were collected. The spatial distribution pattern of P. citrella larvae between tree crowns and in the shoots was aggregated in most sampling occasions in both citrus species. Nevertheless, on the leaves, this pattern followed a random distribution, as indicated by the indices I, Idelta and k parameter.

Contrasting occurrence of Chromobacterium violaceum in tropical drinking water springs of Uganda

Occurrence of Chromobacterium violaceum in six protected drinking water springs in Uganda was investigated. C. violaceum showed a contrasting occurrence, which was independent of human impact as assessed by faecal pollution indicators. It was isolated from two springs (S1 and S2) that were located close to each other (3 km) but not in the rest. In S1 C. violaceum was continuously detected, in concentrations ranging from 6 to 270 cfu 100 ml−1, while in S2 it was detected on only one sampling occasion. C. violaceum was never detected in the investigated upper soil layers (down to 15 cm) in the immediate surroundings (50 m radius) of the springs, despite continued isolation of faecal indicators. The results of the study indicate that C. violaceum may not be ubiquitous in spring water, but could occur in significant numbers in particular potable groundwaters as an autochthonous member.