Litter Mats Research Articles

A Preconditioning Paradox: Contrasting Effects of Initial Phyllosphere and Early Leaf Decomposer Microfungi on Subsequent Colonization by Leaf Decomposing Non-Unit-Restricted Basidiomycetes.

Fungal interactions during leaf decomposition can facilitate or inhibit other fungi. This experiment focused on whether preconditioning of leaf litter by microfungi that were confined to one leaf (Unit-Restricted) made leaf litter less likely to be colonized and decomposed by basidiomycetes that bind litter into mats (Non-Unit-Restricted) than non-preconditioned litter. Leaves of Manilkara bidentata in litterbags were preconditioned by incubating them for 0, 1, 2 or 3 months in flat litter/seed rain baskets 10 cm above the forest floor to avoid colonization by basidiomycete fungi. Preconditioned and non-preconditioned leaves were transferred to 5 replicate basidiomycete fungal mats of Gymnopus johnstonii for 6 weeks. Both attachment by basidiomycete fungi and percent mass loss after 6 weeks decreased significantly with increasing preconditioning time. In non-preconditioned leaves, gamma irradiation did not affect mass loss or percent white-rot despite having significantly increased numbers of basidiomycete fungal connections as compared to non-irradiated leaves. In non-preconditioned leaves, more basidiomycetes attachmented to non-irradiated than irradiated leaves suggest facilitation by phyllosphere microfungi. While basidiomycete colonization was initially facilitated by phyllosphere fungi, we inferred that degradation of resource quality led to fewer fungal attachments and less mass loss after 1–3 months of preconditioning by microfungi. The date suggest there is a 1-month time window for basidiomycete fungi to incorporate fallen leaves into their litter mats.

Disturbance reduces fungal white‐rot litter mat cover in a wet subtropical forest

AbstractFungi that bind leaf litter into mats and produce white‐rot via degradation of lignin and other aromatic compounds influence forest nutrient cycling and soil fertility. Extent of white‐rot litter mats formed by basidiomycete fungi in Puerto Rico decreased in response to disturbances—a simulated hurricane treatment executed by canopy trimming and debris addition in 2014, a drought in 2015, a treefall, and two hurricanes 10 days apart in September 2017. Percent fungal litter mat cover ranged from 0.4% after Hurricanes Irma and Maria to a high of 53% in forest with undisturbed canopy prior to the 2017 hurricanes, with means mostly between 10% and 45% of fungal litter mat cover in undisturbed forest. Drought decreased litter mat cover in both treatments, except in one control plot dominated by a drought‐resistant fungus, Marasmius crinis‐equi. Percent fungal litter mat cover sharply declined after hurricanes, a treefall, and a simulated hurricane treatment. Solar radiation was significantly inversely correlated with relative humidity (RH) and percent litter mat cover within each of the four climatic seasons. Solar radiation was also directly correlated with prior month litterfall, while RH was moderately correlated with throughfall, rain, and litter wetness. However, rainfall was inversely correlated with litter mat cover, possibly due to erosion or saturation during high rainfall events. Canopy opening reduced leaf fall and litter mat cover but these variables were not correlated except in winter. The main factor inhibiting basidiomycete fungi that bind leaf litter into mats was likely lower litter moisture associated with drought and increased solar radiation from canopy opening but secondary compounds in green litterfall may have contributed. Although higher litterfall likely increases fungal mat cover under closed canopy, changes in environmental factors apparently had a stronger inhibitory effect following canopy disturbances. Drought tolerance of some basidiomycete fungal litter mat species provided some resilience to drought.

Small mammal controls on the climate‐driven range shift of woody plant species

Climate change is resulting in shifts in species’ ranges as species inhabit new climatically suitable areas. A key factor affecting range‐shifts is the interaction with predators. Small mammals, being primary seed predators and dispersers in forest ecosystems, may play a major role in determining which plant species will successfully expand and the rate at which range‐shifts will occur. Plants dispersing seeds beyond the species’ current range limits will encounter seed predators to which these seeds are novel; however, empirical studies of seed predator–novel seed interactions are lacking. The aims of our study were to: 1) quantify seed selection by small mammals presented with ‘novel’ seeds; 2) quantify the post‐selection fate of ‘novel’ seeds; and 3) identify seed traits that affect seed selection and post‐selection seed fate.We designed a field experiment exposing small mammal communities to novel seeds produced by plants expected to shift their ranges in response to climate change. We matched novel seeds with reference ‘familiar’ seeds and studied key steps defining interactions between small mammals and novel seeds.We found that the probability of selection of a novel seed varied among species and was, at times, higher than the selection probability of familiar seeds. Key traits that affected seed selection and the distance a seed was dispersed for caching were shell hardness and seed mass. We also found that 33% of dispersed seeds were cached in optimal germination sites (e.g. within fallen logs and buried under the leaf litter mat). Through seed emergence trials we found that emergence was higher for larger seeds, suggesting that the role of small mammals may be modulated by emergence rates.Our results suggest that the interaction between small mammals and novel seeds may have cascading effects on climate‐induced plant range shifts and community composition.

Modification of furnished cages from conventional cages for laying hens: which do hens like a nest mat or a litter mat for the nest area?

Modification of furnished cages from conventional cages for laying hens: which do hens like a nest mat or a litter mat for the nest area?

Tall-statured grasses: a useful functional group for invasion science

Species in the grass family (Poaceae) have caused some of the most damaging invasions in natural ecosystems, but plants in this family are also among the most widely used by humans. Therefore, it is important to be able to predict their likelihood of naturalisation and impact. We explore whether plant height is of particular importance in determining naturalisation success and impact in Poaceae by comparing naturalisation of tall-statured grasses (TSGs; defined as grass species that maintain a self-supporting height of 2 m or greater) to non-TSGs using the Global Naturalised Alien Flora database. We review the competitive traits of TSGs and collate risk assessments conducted on TSGs. Of the c. 11,000 grass species globally, 929 qualify (c. 8.6%) as TSGs. 80.6% of TSGs are woody bamboos, with the remaining species scattered among 21 tribes in seven subfamilies. When all grass species were analysed, TSGs and non-TSGs did not differ significantly in the probability of naturalisation. However, when we analysed woody bamboos separately from the other grasses, the percentage of TSGs that have naturalised was 2–4 times greater than that of non-TSGs for both bamboos and non-bamboo groups. Our analyses suggest that woody bamboos should be analysed separately from other TSGs when considering naturalisation; within the ≥ 2 m height class they do not naturalise at the same rate as other TSGs. Rapid growth rate and the capacity to accumulate biomass (a function of height) give many TSGs a competitive advantage and allow them to form monospecific stands, accumulate dense and deep litter mats, reduce light availability at ground level, and alter fire and nutrient-cycling regimes, thereby driving rapid ecosystem transformation. While the height distribution in grasses is continuous (i.e. no obvious break is evident in heights), the 2 m designation for TSGs defines an important functional group in grasses that can improve predictive modelling for management and biosecurity.

Limbless geckoes hanging on? Lessons in exploiting arid-zone unpredictability from an elusive habitat-specialist pygopod

Context The study of threatened species is often challenged by their rarity and secretive life-history traits. Species adapted to extreme environments prone to stochastic conditions present further challenges because of fluctuating populations and patchy distributions. We employed a variety of methods to gather records and habitat information on the bronzeback legless lizard (Ophidiocephalus taeniatus), an endemic, nationally vulnerable monotypic pygopod reptile that is poorly understood because of fossorial, cryptic behaviour and remote distribution in the stony deserts of inland Australia. Aims Our aim was to determine foundational information on the distribution and landscape parameters relevant to this species and its disturbance-prone habitat and to formulate conceptual models to guide understanding, future research and management of threats. Methods We used multiple data sources, including targeted field surveys with Antakarintja traditional land owners across ~5000 km2 of previously unsurveyed habitat, sampled the catch of uncapped mine shafts with community volunteers, trialled artificial refuge substrates and elicited public opportunistic sightings. Key results We gathered 30 new records of the species from leaf litter mats of six shrub species, across four land systems. Examination of these records in the context of land system boundaries demonstrated a continuous distributional link between previously known areas of habitat and suggested large tracts of potential habitat that remain unsurveyed for the species. This information in combination with other published data was used to create conceptual models of habitat preference, population and disturbance, in which we suggest that O. taeniatus favours microhabitats that are prone to severe and long-lasting disturbance in some parts of the landscape, exacerbated by human land use practices. Conclusions Our study suggests that O. taeniatus distribution is unlikely to be severely fragmented, as had previously been suggested. Its total extent of occurrence may be greater than previously thought, despite a very low area of occupancy within this. Implications This study emphasises the value of using multiple, innovative data sources when studying rare and cryptic species. Further distributional surveys in identified areas of potential habitat in combination with testing and refinement of our conceptual model of habitat and population drivers are needed to fully assess the distribution, conservation status and ecological drivers of O. taeniatus.

The lizard fauna of litter mats in the stony desert of the southern Northern Territory

The formation of Australia’s stony deserts 2–4 million years ago will have reduced the availability of suitable habitat for lizards extant at that time, particularly for fossorial species. For such taxa, mats of litter, which form underneath woody vegetation, may offer the only suitable refuge sites in a greater matrix of unsuitable stony and compacted clay habitat. The integrity of litter mats in Australia’s stony deserts is potentially threatened by trampling by large introduced herbivores and by surface flows during flood events. Here we assess the importance of litter mats as habitat for lizards in these stony deserts and determine the suitability of the mats in relation to disturbance regimes. We surveyed 85 sites in the stony desert in the extreme south of the Northern Territory, using hand-raking as the sampling technique. We located 85 individuals of eight lizard species from three families, including 18 individuals of the nationally vulnerable monotypic pygopodid Ophidiocephalus taeniatus, establishing the significance of this limited microhabitat. Lizards were located underneath mats produced from the litterfall of four species of Acacia shrubs, though were not evenly distributed across these four mat types. Our results also provide the first evidence of the impact of large introduced herbivores on the suitability of litter mats. Although this was not statistically significant, lizards were more likely to be located at sites without disturbance from large herbivores, and were located only under individual mats that exhibited no sign of disturbance.

Production performance and proportion of nest eggs in layer hybrids housed in different designs of furnished cages

The aim of the study was to compare use of nests, production performance, and egg quality in 4 designs of furnished cages (FC) housing 8 (T8), 10 (T10), 20 (T20), or 40 (T40) layers. The FC housing 8 and 10 hens were commonly used in commercial egg production in Sweden, whereas the cages housing 20 and 40 hens constituted new designs, at present not allowed in Sweden. The FC also differed in design and location of litter facilities. The study comprised 2 full production cycles (20-72 wk of age). Trial 1 included 588 Hy-Line White W98 and 460 Hy-Line Brown layers, and trial 2 used 572 Lohmann Selected Leghorn and 588 Lohmann Brown layers. In accordance with Swedish prohibition, beak treatment was not conducted. In both trials production parameters and mortality were considered normal and levels were unaffected by cage design. Deaths attributable to cannibalistic pecking were rare. Overall, exterior egg quality was superior in T8 compared with T20 and T40, whereas T10 generated intermediate results. Genotype differences were found in production performance, exterior egg quality, and use of nests. In T8 and T10 at least 95% of the eggs were laid in nest whereas in T20 and T40 a considerable percentage of eggs were laid on the litter mat, constituting the litter facility in those cage models. Additional lighting of litter mats (trial 2) had no effect on layers' choice of site for egg laying. Dividing T40 cages in 2 identical cage halves by a rear partition with pop holes had no effect on any of the traits measured. In conclusion, housing larger groups of non-beak-treated hens together in FC is possible, with acceptable levels of production and mortality, provided that cannibalism does not develop. The inferior egg quality in T20 and T40, likely caused by the large proportions of misplaced eggs, needs to be considered in the further development of those cage designs.

Estimation Procedures for Understory Biomass and Fuel Loads in Sagerrush Steppe Invaded by Woodlands

Regression equations were developed to predict biomass for 9 shrubs, 9 grasses, and 10 forbs that generally dominate sagebrush ecosystems in central Nevada. Independent variables included percent cover, average height, and plant volume. We explored 2 ellipsoid volumes: one with maximum plant height and 2 crown diameters and another with live crown height and 2 crown diameters. Dependent variables were total, live, leaf, and dead biomass. Simple, multiple, linear, and power equations were investigated. Models were chosen based on scatter plots, residual plots, and R2 and SEE values. In general, simple power equations provided the best-fit regressions. For shrubs, the ellipsoid volume computed with maximum plant height best predicted total plant weight, and the ellipsoid volume computed with the live crown height best predicted shrub foliage weight. In addition to regression equations for biomass, ratios for division of that biomass into 1-, 10-, 100-, and 1000-hour fuels were derived for common large shrubs. Regression equations were also derived to relate litter mat sizes of major shrub species to litter weights. The equations in this paper could be used to predict biomass in other areas of the Great Basin if training data were taken to validate or adjust these models.

Persistence of Western Juniper (Juniperus occidentalis) Resource Islands Following Canopy Removal

Western juniper (Juniperus occidentalis Hook.) encroachment has altered the spatial distribution of soil nutrients and plants in semi-arid systems of the northern Great Basin, forming nutrient enriched ‘resource islands’ under tree canopies. Our goal was to determine the persistence of resource island characteristics after restoration treatment (tree cutting). The study site was a privately owned grazing allotment in eastern Oregon where trees had been cut eight and fifteen years ago. In each age class and in uncut western juniper woodlands, juniper stumps or trees were randomly selected for sampling. At each bole three radial transects, set at 120° from each other, were marked and soil cores were collected to 5-cm depth at distances of 50, 100, 150 and 300-cm from the bole then combined to a single composite sample per distance class. Samples were analyzed for total C and N, soluble P, K, Ca, Fe, Al, Mg and Na and pH. Despite increases in shrub, forb and grass crops in the fifteen-year old cut treatment, western juniper resource island effects were still evident for most soil variables measured; tree island soils were significantly higher in Ctot, Ntot, P, K and Ca compared to inter-island soils. Resource island persistence was attributed to litter mats beneath relic canopies. Management efforts may be more successful at preventing establishment of undesired annuals by focusing on young juniper stands where resource islands are less developed.

Biophysical controls on accretion and elevation change in Caribbean mangrove ecosystems

Habitat stability of coastal ecosystems, such as marshes and mangroves, depends on maintenance of soil elevations relative to sea level. Many such systems are characterized by limited mineral sedimentation and/or rapid subsidence and are consequently dependent upon accumulation of organic matter to maintain elevations. However, little field information exists regarding the contribution of specific biological processes to vertical accretion and elevation change. This study used biogenic mangrove systems in carbonate settings in Belize (BZ) and southwest Florida (FL) to examine biophysical controls on elevation change. Rates of elevation change, vertical accretion, benthic mat formation, and belowground root accumulation were measured in fringe, basin, scrub, and dwarf forest types plus a restored forest. Elevation change rates (mm yr − 1) measured with Surface Elevation Tables varied widely: BZ-Dwarf (−3.7), BZ-Scrub (−1.1), FL-Fringe (0.6), FL-Basin (2.1), BZ-Fringe (4.1), and FL-Restored (9.9). Root mass accumulation varied across sites (82–739 g m −2 yr −1) and was positively correlated with elevation change. Root volumetric contribution to vertical change (mm yr − 1) was lowest in BZ-Dwarf (1.2) and FL-Fringe (2.4), intermediate in FL-Basin (4.1) and BZ-Scrub (4.3), and highest in BZ-Fringe (8.8) and FL-Restored (11.8) sites. Surface growth of turf-forming algae, microbial mats, or accumulation of leaf litter and detritus also made significant contributions to vertical accretion. Turf algal mats in fringe and scrub forests accreted faster (2.7 mm yr −1) than leaf litter mats in basin forests (1.9 mm yr −1), but similarly to microbial mats in dwarf forests (2.1 mm yr −1). Surface accretion of mineral material accounted for only 0.2–3.3% of total vertical change. Those sites with high root contributions and/or rapid growth of living mats exhibited an elevation surplus (+2 to +8 mm yr −1), whereas those with low root inputs and low (or non-living) mat accumulation showed an elevation deficit (−1 to −5.7 mm yr −1). This study indicates that biotic processes of root production and benthic mat formation are important controls on accretion and elevation change in mangrove ecosystems common to the Caribbean Region. Quantification of specific biological controls on elevation provides better insight into how sustainability of such systems might be influenced by global (e.g., climate, atmospheric CO 2) and local (e.g., nutrients, disturbance) factors affecting organic matter accumulation, in addition to relative sea-level rise.

Herbaceous Succession After Burning of Cut Western Juniper Trees

The expansion of western juniper (Juniperus occidentals spp. occidentalis Hook.) in the northern Great Basin has resulted in the wide-scale conversion of sagebrush-steppe communities to juniper woodlands. Prescribed fire and mechanical cutting are the 2 main methods used to remove juniper and restore sagebrush steppe. Mechanical treatments commonly leave cut juniper on site. Disadvantages of leaving cut juniper are the increased fuel hazard and the potential for increased establishment and growth of invasive species. This study evaluated the response of herbaceous plants to winter burning of cut western juniper. Vegetation response was compared among 2 burning treatments (burning trees the first winter after cutting and burning the second winter after cutting), a control (cut-unburned juniper), and the interspace between cut trees. To minimize fire impacts to herbaceous perennials, cut trees were burned in the winter when soils and ground litter were frozen and/or soils were at field capacity. Only felled trees were burned, as fire did not carry into interspaces or litter mats around western juniper stumps. We hypothesized that winter season burning would increase herbaceous perennials and would reduce cheatgrass establishment when compared to the cut-unburned control. After 10 years, total herbaceous and perennial grass cover was 1.5- to 2-fold greater, respectively, in burned treatments compared to cut-unburned controls. Perennial grass density was 60% greater in the burned treatments than in the cut-unburned treatment and the interspace. Cheatgrass cover was twice as great in the control than in the 2 burn treatments and the interspace. We concluded that burning cut western juniper when soils were wet and frozen in winter enhanced community recovery of native perennials compared to leaving cut juniper unburned.

Variation of soil respiration at three spatial scales: Components within measurements, intra-site variation and patterns on the landscape

Soil respiration is an important component of terrestrial carbon cycling and can be influenced by many factors that vary spatially. This research aims to determine the extent and causes of spatial variation of soil respiration, and to quantify the importance of scale on measuring and modeling soil respiration within and among common forests of Northern Wisconsin. The potential sources of variation were examined at three scales: [1] variation among the litter, root, and bulk soil respiration components within individual 0.1 m measurement collars, [2] variation between individual soil respiration measurements within a site (<1 m to 10 m), and [3] variation on the landscape caused by topographic influence (100 m to 1000 m). Soil respiration was measured over a two-year period at 12 plots that included four forest types. Root exclusion collars were installed at a subset of the sites, and periodic removal of the litter layer allowed litter and bulk soil contributions to be estimated by subtraction. Soil respiration was also measured at fixed locations in six northern hardwood sites and two aspen sites to examine the stability of variation between individual measurements. These study sites were added to an existing data set where soil respiration was measured in a random, rotating, systematic clustering which allowed the examination of spatial variability from scales of <1 m to 100+ m. The combined data set for this area was also used to examine the influence of topography on soil respiration at scales of over 1000 m by using a temperature and moisture driven soil respiration model and a 4 km 2 digital elevation model (DEM) to model soil moisture. Results indicate that, although variation of soil respiration and soil moisture is greatest at scales of 100 m or more, variation from locations 1 m or less can be large (standard deviation during summer period of 1.58 and 1.28 μmol CO 2 m −2 s −1, respectively). At the smallest of scales, the individual contributions of the bulk soil, the roots, and the litter mat changed greatly throughout the season and between forest types, although the data were highly variable within any given site. For scales of 1–10 m, variation between individual measurements could be explained by positive relationships between forest floor mass, root mass, carbon and nitrogen pools, or root nitrogen concentration. Lastly, topography strongly influenced soil moisture and soil properties, and created spatial patterns of soil respiration which changed greatly during a drought event. Integrating soil fluxes over a 4 km 2 region using an elevation dependent soil respiration model resulted in a drought induced reduction of peak summer flux rates by 37.5%, versus a 31.3% when only plot level data was used. The trends at these important scales may help explain some inter-annual and spatial variability of the net ecosystem exchange of carbon.

LONG-TERM VEGETATION DYNAMICS IN A CUT WESTERN JUNIPER WOODLAND

Abstract Western juniper (Juniperus occidentalis spp. occidentalis Hook.) expansion in the northern Great Basin has reduced shrubsteppe productivity and diversity. Chainsaw cutting of western juniper woodlands is commonly applied to remove tree interference and restore sagebrush plant communities. Studies assessing understory response following cutting have been limited to early successional stages and have not evaluated the effects of western juniper debris on plant succession. Cutting western juniper produces a large amount of debris which is commonly left on site, occupying a significant portion of treated areas. This study evaluated successional dynamics spanning 13 years after western juniper cutting. Four 0.45-ha blocks were selected on Steens Mountain in southeastern Oregon. Western juniper cover averaged 26% and mature tree density averaged 250 trees · ha−1. Blocks were cut in late summer 1991. Understory standing crop, cover, and density were compared among 3 locations: old canopy litter mats (ca...

Species-specific effects of grass litter mass and type on emergence of three tall grass prairie species

:Because the mat of dead grass stems and leaves, or litter, is a conspicuous feature of grasslands and has been shown to affect various plant processes, I performed a growth chamber experiment on the effect of both grass litter mass (density) and type (species mixes) on emergence of three common prairie grass species. I found that (1) switchgrass (Panicum virgatum) emergence decreased significantly at the highest litter density, but different types of litter had no effect; (2) little bluestem (Schizachyrium scoparium) emergence decreased significantly at the highest litter density and with those litter types that included switchgrass litter; and (3) indiangrass (Sorghastrum nutans) emergence increased significantly at medium density and decreased significantly under its own litter. The results show that the smallest-seeded species had reduced emergence through the litter mat and that amount of litter was more important than type of litter. In conclusion, the full range of litter effects occurred: (1) two species were inhibited by density while the other species was facilitated, and (2) one species was inhibited by litter from another species, one species was inhibited only by its own litter, and one species was unaffected by the species composition of the litter. Finally, the results indicate a potential for grass litter of different species to differentially influence regeneration of tall grass prairie species.

Acidification of Soil Solution in a Chestnut Forest Stand in Southern Switzerland: Are There Signs of Recovery?

In a previous study, a rapid acidification of soil solution was observed between 1987 and 1997 in a cryptopodzolic soil in southern Switzerland despite a reduction in acidic deposition. The molar ratio of base nutrient cations to aluminum (BC/Al) in the soil solution was used to assess acidification. The monitoring of the soil solution chemistry was continued at the same site between 1998 and 2003 to find out how long the delay in reaction to reduced deposition would last and whether the BC/Al ratios would recover. The reevaluation of all data collected during the 16-year observation period showed no clear improvement in the BC/Al ratios, except below the litter layer where the ratios greatly increased after 1998. Initial signs of recovery were also detected in the mineral horizons, the ratios stabilizing in the second part of the observation period. Sulfate concentrations decreased significantly below the litter mat in response to decreased S deposition. BC concentrations markedly declined below the litter layer and in the mineral horizons, which was attributed to the depletion of the BC exchangeable pool as a result of continued acidic deposition.

Recruitment in a Mediterranean annual plant community: seed bank, emergence, litter, and intra‐ and inter‐specific interactions

A small‐scale field study was conducted to explain seedling emergence and recruitment of reproductive individuals in a four‐year‐old Mediterranean annual plant community. The analyzed levels were populations, functional types, and total number of individuals in the community. We hypothesized that the number of germinable seeds positively affects the number of emerged seedlings, which positively affects the number of reproductive individuals. We hypothesized as well that litter mass, biomass of established adults, and number of non‐conspecific emerged seedlings negatively affect the numbers of emerged seedlings and reproductive individuals. The results supported our multivariate causal explanation of plant recruitment, although concordances with the initial hypotheses were more frequent at the community level. The effect of the number of germinable seeds on the number of emerged seedlings was found to be robust only at the community level. At the population level, this relationship did not have a consistent tendency and depended on species identity and range of seed density experienced. Litter had negative effects on total number of individuals in the community, and usually non‐significant effects at the population level. Litter effects were found to be inversely related to seed mass, and sharper cotyledons did not improve seedling emergence likely by favoring litter mat penetration. Interactions among plant species appeared not to have any effect on seedling emergence and survival, and had positive effects on certain populations. Biomass of established adult plants exerted no influence on seedling emergence and survival, probably due to their low abundance in this community during the germination period. Results permitted the inference of the main stages in the recruitment process and causal factors. They provided evidence for the greater importance of germination and emergence in comparison with seedling survival to insure reproductive recruitment in this community.

Nitrogen mass balance in deep litter during the pig fattening cycle and during composting

For welfare reasons, fattening pigs on organic farms are raised on deep litter in the open with simple, flexible climate tents for shelter. Within this system, the nitrogen (N) flow both during fattening of the pigs from 17 to 100 kg liveweight in winter and during composting of the deep litter from the enclosures in summer was studied. During the fattening period, the pigs were provided with barley straw at four daily rates (0·67, 1·21, 1·32 and 1·87 kg) per kg increase in liveweight. During the summer period, N balances from four enclosures receiving straw at around the 1·32 kg rate were examined. Temperatures in the deep litter mat and in the compost heap were determined, as well as concentrations of ammonia (NH3) and nitrous oxide (N2O) in the compost heaps. The temperature increased after 4 weeks to between 40 and 70 °C in the deep litter mats receiving &gt; 1·21 kg straw; the highest temperatures were observed in the mats with the highest straw rate. Temperatures exceeded 50 °C in all compost heaps. In the deep litter mats and compost heaps the highest temperatures were recorded for the longest periods in the material containing the most straw. The initial concentration of NH3 in the gas phase of the compost heaps was &gt; 10 mg NH3-N/m3, which dropped to zero within 1 month. After the NH3 concentration had fallen, the amount of N2O increased significantly for a period in the two heaps with 1·21 and 1·32 kg straw. Over 120 days in summer, an average of 16·3±6% N was lost from the four enclosures strawed at a rate of 1·32 kg (±0·2 kg) straw per kg increase in liveweight. During the winter 12–24% of the N excreted was lost during a fattening period of 119–134 days, and 15–42% of the N stored was lost during the following composting period of 143 days. In total, 29–54% of the N added to the deep litter mat in excretion and straw was lost during the fattening period (119–134 days) and subsequent storage (143 days). The lowest loss was recorded from deep litter strawed daily with 1·32 kg straw per kg increase in pig liveweight.

A new method to estimate accumulation rates of lignites in the Eocene Buchanan Lake Formation, Canadian Arctic

Exceptionally well-preserved Eocene plant fossils occurring in leafy litter mats from the Buchanan Lake Formation, Canadian Arctic, make it possible to estimate the accumulation rate of the lignite. This method is based on the assumption that the projected leaf-surface area of individual tree species per unit of ground-surface area (leaf-area index) is more or less constant. The calculated accumulation rate of 1.6 mm/year has been corrected to the minimum accumulation rate of 0.8 mm/year by considering the effects of organic decomposition. Since the compaction ratio of the leaf lignite is difficult to estimate, correct comparison with accumulation rates of modern and Quaternary peats that have been determined by using 14C ages is impossible. However, the accumulation rate calibrated in the peat stage of coalification by using the compaction ratio of woods embedded in the leaf lignite is within the range of accumulation rates determined for modern and Quaternary peats.

Lizards, Snakes, and Amphisbaenians from the Quaternary Sand Dunes of the Middle Rio Sao Francisco, Bahia, Brazil

Lizards, Snakes, and Amphisbaenians from the Quaternary Sand Dunes of the Middle Rio Sao Francisco, Bahia, Brazil