Integrated synusial phytosociology: some notes on a new,multiscalar approach to vegetation analysis

Abstract. The integrated synusial approach of the vegetation is based on the differentiation of several spatio-temporal organization levels. A phytocoenosis (community of the second level) is considered as a complex of synusiae (communities of the first level) and is characterised by a strong tendency to self-organization. At each level, a typology of the communities can be performed. Ecological indicator values as well as different diversity indices are calculated for each vegetation unit. They are useful for understanding the spatial and temporal organization of the phytocoenoses. As an example. this approach is applied to wooded meadows.     

Influence of tree cover on the diversity of herbaceous communities in subalpine wooded pastures

Abstract. The relationships between several diversity indices and tree cover in subalpine wooded pastures with Larix de-cidua were analysed at two spatial scales: phytocoenoses (2500-m² plots) and herbaceous synusia (1-m² quadrats). Diversity indices have a non-linear relationship to Larix cover; the best fit was obtained with Gaussian regressions. Species richness was influenced by Larix cover more than evenness. At the phytocoenosis level, the optimum for species and synusial richness in the herb layer was near 25 % tree cover. At the synusia level, species richness of the herb layer showed an optimum when mean distance to the four nearest Larix trees was ca. 30 m, or when the potential number of sunshine hours between April and September was close to 1250 h. Canonical Correspondence Analysis confirmed the influence of Larix cover on the composition of phytocoenoses and herbaceous synusiae, but included also the role of altitude, slope and aspect.     

Succession secondaire et perte de diversité végétale après réduction du broutage dans un paturage boisé des Alpes centrales suisses

Freléchoux F., Meisser M. and Gillet F. 2007. Secondary succession and loss in plant diversity following a grazing decrease in a wooded pasture of the central Swiss Alps. Bot. Helv. 117: 37 – 56. Reduced cattle grazing pressure in the Alps has caused the reforestation of many subalpine pastures during the last decades. To understand the dynamics of natural reforestation and to evaluate how this change affects plant species diversity, we described the vegetation of a wooded pasture in the central Swiss Alps (Sembrancher, Valais) using the integrated synusial method. Based on stratified vegetation relevés in 27 plots,we defined 11 community types at the synusial level (two tree-layer, five shrub-layer, and four herb-layer synusiae), and four community types at the phytocoenosis level (pasture, tall forbs and scrub, wooded pasture and forest). The spatial distribution of these four phytocoenoses suggests that they represent successional stages after abandonment, and that the pathway of vegetation succession depends on the aspect. We suppose that on northern oriented, cool and shady locations, abandoned pastures first develop towards tall-forb meadows and scrub with Alnus viridis, and then to a preforested stage with Picea abies and Larix decidua. In contrast, on western oriented, warm and sunny location, Larix decidua (mainly) and Picea abies directly colonize the abandoned pastures, but further succession finally leads to the same pre-forested stage as on northern slopes. Plant species richness was highest in open areas and decreased by 25% as tree cover increased from 6% to 65%. According to our successional model, plant species diversity is lost more rapidly on northern slopes (with species-poor green alder scrub) than on western slopes (with species-rich young larch forests), suggesting that northern slopes most urgently need an appropriate grazing management. Manuscrit accepté le 28 mars 2007     

A critical evaluation of minimum area concepts

Various types of and modern Braun-Blanquet school viewpoints on homogeneity and heterogeneity of vegetation and their causes are discussed. A distinction is made between methodological minimum areas, MMA's (divided into qualitative and quantitative MMA's) and biological minimum areas, BMA's, divided into space, resistance and regeneration minima. Various definitions of the qualitative MMA are reviewed and some methods of analysis are discussed. It was found that the species-area curve of sample plots almost invariably follows the Fisher model, however with superimposed oscillations, which are regarded to represent a number of relative MMA's for each phytocoenosis (stand). These relative MMA's probably correspond to the elements of the compound mosaic pattern of which vegetation normally consists.A method to investigate the various biological minimum areas is expounded and results obtained in chalk grasslands, juniper scrub, oak woods and oligotrophic heath pools are briefly discussed. The species/area curve of BMA's appeared to follow either the Goodall or the Fisher or the Preston model. No saturation of the species number was obtained, not even in the largest stands examined (9 ha). Species numbers of stands were analysed in relation to size and age of the stands and to their degree of isolation. The value of the exponent z of the Preston formula appeared to be an unsuitable measure for the degree of isolation of these habitat islands. This z value was calculated for all species, for various taxonomic groups, including bryophytes and fungi, and for various dissemination types. There is no relation between size of stand, degree of isolation and number of dyschorous resp. eurychorous plants. Species numbers of phytocoenoses are obviously governed mainly by size, age and habitat quality (degree of disturbance).Abbreviations BMA = Biological minimum area - GMA = Regeneration minimum area - MMA = Methodological minimum area - RMA = Resistance minimum area - SMA = Space minimum area Communication no. 372 of the Biological Station Wijster of the Agricultural University Wageningen, The Netherlands.     

The oligotrophic peatlands of Western Siberia-the largest peino-helobiome in the world

Summary The paper summarizes the vegetation pattern of the largest swamp (peat bog) area in the world. The core area covers about 800×1800 km (NS x EW) in West Siberia between the Ural mountains and the river Yenisey. The core area is one gigantic oligotrophic swamp (Peino-Helobiome acc), the new classification suggested in Walter 1976, see also summary in Vegetatio 32, 1976, pp. 75–81. A map of the entire area is presented.Intensive recent field studies were executed by the geobotanical-soil science faculty of the University of Moscow and the first five publication under the editorship of A. I. Popov (1971–1975) are the basis for this paper. The original papers are in Russian, still unavailable for most western scientists.The bog genetics was stratigraphically analyzed. The analysis revealed that the majority of the Northern bogs started in taiga forests. The peat in these areas is now 4–7 m deep. About 60% of the peat consists of the mixed (Sphagnum) fuscum type deposit. Peat type profiles are shown in Figure 4. The figure illustrates the different peat deposits in relation to depth as well as to surface pattern of strings and hollows.The surface vegetation shows the pattern typical for many northern peat bogs on very slightly inclined land: parallel strings of peat moss and Pinus trees alternating with hollows filled with rain water and hydrophytic Sphagna (Sph. dusenii, Sph. balticum). A cross section through this vegetation pattern is given in Figure 5. Details of the pattern: strings and hollows are given in Chapter 4 of the paper.The second chapter of this paper deals with regression phenomena in the vegetation development due to excessive water logging caused by the development of the strings. Under such conditions black water lakes are formed which grow in size through the erosive action of wind and waves on the expense of the peat moss surface.Bog development in the middle and northern Taiga zone of the biome are discussed in Section 3. The hydrology of this area is ruled by the seasonal fluctuation of water level. The amplitude of the Ob river amounts to 12 m with the amplitude of the tributaries ranging around 4–6 m. The annual flood is aggravated in spring by huge ice packages. The entire area is for extended periods one great lake which dissects into hundreds of thousands of little lakes during the low water season.In some parts of this area local drainage is responsible for the development of small forest patches. The crown cover in this forest is reported up to 50%; the species composition changes from Pinus sibirica, P. sylvestris, Picea spec. near the drainage creeks to Pinus sylvestris f. willkommii and Betula in the drained upland portions.In this area the general peat bog is eutrophic because of the high influence of the flood. The local development of oligotrophic raised bogs is frequent, however. These bogs are obviously a successional stage in series that leads eventually to a boreal forest.Section 5 deals with the vegetation typology of the entire area. Three different subdivisions of the Helobiome are distinguished, with several regional subdivisions in each. The principle for the biome division is the environmental change from oligotrophic water on the northern lower end of the watershed to the eutrophic water condition further south in the forest steppe zone. In the area of the southern eutrophic biome are forest islands Ryami and even the first salt soil patches noticeable especially in the northern steppe zone. This indicates the regional transition to the Halo-Helobiome. Some vegetational and floristic details for the subdivisions are summarized in this chapter.Supplement to H. Walter: The vegetation of Eastern Europe, North and Central Asia, 1974.Translated by: Stephen S. Talbot, Forest Management Institute, 396 Cooper Street, Ottawa, Ontario, Canada K1A OH3, and Runhild E. Eessell, 54 Spindle Road Hicksville, New York 11801, USA.

---

     

Effect of habitat fragmentation on levels and patterns of genetic diversity in natural populations of the peat moss Polytrichum commune

Peat bogs represent unique ecosystems that are under particular threat from fragmentation due to peat harvesting, with only 38% of the original peatland in Europe remaining intact and unaffected by peat cutting, drainage and silviculture. In this study, we have used microsatellite markers to determine levels and patterns of genetic diversity in both cut and uncut natural populations of the peat moss Polytrichum commune. Overall diversity levels suggest that there is more genetic variation present than had previously been assumed for bryophytes. Despite this, diversity values from completely cut bogs were found to be lower than those from uncut peatlands (average 0.729 versus 0.880). In addition, the genetic diversity was more highly structured in the cut populations, further suggesting that genetic drift is already affecting genetic diversity in peat bogs subjected to fragmentation.     

Conservation of bog plant species assemblages: Assessing the role of natural remnants in mined sites

Abstract. Bogs, economically valuable wetlands, are subjected to exploitation in southern Canada. We addressed plant conservation within bogs mined for peat, in which small undisturbed remnants are left, mostly at the margins of the mined areas. The main goal of the study was to test whether these remnants act as refuges for plants which could recolonize areas that are planned for restoration after mining is completed. Mosses, lichens and vascular plants were sampled in remnants of 24 mined bogs in southeastern Canada during the summer of 1997. The vegetation was also sampled at the margins and centres of 24 nearby natural bogs in plots similar in size to these remnants. Using similarity analysis and ordination techniques, we found that plant species assemblages in remnants of mined bogs differ from those near the margins of natural bogs, and that certain species are associated with the centre of natural bogs, due to the presence of pools. We also showed that water conditions of remnants are affected by drainage due to peat mining. Sphagnum moss showed itself to be a key indicator of mining effects on vegetation. Implications for peat resource management and bog conservation are discussed.     

Persistent versus transient tree encroachment of temperate peat bogs: effects of climate warming and drought events

Peatlands store approximately 30% of global soil carbon, most in moss‐dominated bogs. Future climatic changes, such as changes in precipitation patterns and warming, are expected to affect peat bog vegetation composition and thereby its long‐term carbon sequestration capacity. Theoretical work suggests that an episode of rapid environmental change is more likely to trigger transitions to alternative ecosystem states than a gradual, but equally large, change in conditions. We used a dynamic vegetation model to explore the impacts of drought events and increased temperature on vegetation composition of temperate peat bogs. We analyzed the consequences of six patterns of summer drought events combined with five temperature scenarios to test whether an open peat bog dominated by moss (Sphagnum) could shift to a tree‐dominated state. Unexpectedly, neither a gradual decrease in the amount of summer precipitation nor the occurrence of a number of extremely dry summers in a row could shift the moss‐dominated peat bog permanently into a tree‐dominated peat bog. The increase in tree biomass during drought events was unable to trigger positive feedbacks that keep the ecosystem in a tree‐dominated state after a return to previous ‘normal’ rainfall conditions. In contrast, temperature increases from 1 °C onward already shifted peat bogs into tree‐dominated ecosystems. In our simulations, drought events facilitated tree establishment, but temperature determined how much tree biomass could develop. Our results suggest that under current climatic conditions, peat bog vegetation is rather resilient to drought events, but very sensitive to temperature increases, indicating that future warming is likely to trigger persistent vegetation shifts.     

Persistence of tree cavities used by cavity-nesting vertebrates declines in harvested forests

An abundant supply of cavity-bearing trees is important for maintaining wildlife communities in harvested forests. During harvesting, suitable trees and cavities are directly removed, and the longevity of cavities in retained trees may be reduced by increased exposure to wind and other disturbance factors. We examined patterns of cavity survival in retained trembling aspen (Populus tremuloides) trees in harvested stands compared with those in unharvested mature stands by monitoring the persistence of individual cavities. We followed 930 cavities in 3 harvest treatments for up to 17 years in pre-cut and uncut forest, and up to 13 years post-harvest (reserve patches and dispersed retention), in temperate-mixed forests of interior British Columbia, Canada. Average annual cavity loss rates were 5.6% in pre-cut and uncut forest, 7.2% for cavities in trees retained in reserves, and 8.1% for cavities in retained trees dispersed throughout cuts. Correspondingly, median cavity longevity was 15 years for cavities in pre-cut and uncut forest, 10 years for cavities retained in reserves, and 9 years for those in dispersed retention. Risk of loss increased most for cavities in living trees (factor of 2.17), but we found no detectable difference for cavities in recently dead trees and trees with advanced decay. We suggest retention of a range of aspen size and decay classes to allow for future cavity-tree recruitment in harvested stands. Inclusion of wildlife reserves as part of an overall forest management plan will also help to mitigate the effects of windthrow and maintain long-lived cavity resources required by a large portion of forest wildlife. © 2013 The Wildlife Society     

South Patagonian ombrotrophic bog vegetation reflects biogeochemical gradients at the landscape level

Question: Which environmental variables affect the floristic composition of south Patagonian bog vegetation along a gradient of climate and biogeochemical changes with increasing distance from the Pacific ocean? Location: Trans‐Andean transect (53° S), southern Patagonia Material and Methods: Floristic composition, peat characteristics (water level, decomposition, pH, total nitrogen, total carbon, ash content and plant available P, K, Na, Ca, Mg, Fe, Mn, Zn, and Al) and climatic constraints of ombrotrophic peat‐lands were measured at 82 plots along a gradient of increasing distance from the Pacific Ocean. Results: Climatic constraints and biogeochemical peat characteristics significantly change with increasing distance from the Pacific. Peatland vegetation shifted from hyperoceanic blanket bogs dominated by cushion forming vascular plants to the west to Sphagnum bogs to the east. Climatic and biogeochemical variables explained a large proportion of the floristic variation along the first DCA axis. The second axis represented a water level gradient. When ‘distance to the Pacific’ was defined as a covariable in partial CCA, the proportion of variance explained declined for most other variables, especially in the case of annual precipitation and exchangeable base cations and related traits. The differences in biogeochemical characteristics related to peat were mainly attributed to the input of sea‐borne cations. Conclusions: While variation in vegetation composition along a longitudinal gradient crossing the southern Andes was attributed to climatic constraints as expected, vegetation composition was also strongly affected by the biogeochemical characteristics of peat. Sea spray was of high ecological importance to peat chemistry and, consequently, to floristic composition. Presumably, south Patagonian peat bogs represent a glimpse of pre‐industrial environments, so that these peat bogs may act as reference systems with respect to atmospheric inputs in mire ecology research.     

Changes in Biomass, Aboveground Net Primary Production, and Peat Accumulation following Permafrost Thaw in the Boreal Peatlands of Manitoba, Canada

Permafrost thaw resulting from climate warming may dramatically change the succession and carbon dynamics of northern ecosystems. To examine the joint effects of regional temperature and local species changes on peat accumulation following thaw, we studied peat accumulation across a regional gradient of mean annual temperature (MAT). We measured aboveground net primary production (AGNPP) and decomposition over 2 years for major functional groups and used these data to calculate a simple index of net annual aboveground peat accumulation. In addition, we collected cores from six adjacent frozen and thawed bog sites to document peat accumulation changes following thaw over the past 200 years. Aboveground biomass and decomposition were more strongly controlled by local succession than regional climate. AGNPP for some species differed between collapse scars and associated permafrost plateaus and was influenced by regional MAT. A few species, such as Picea mariana trees on frozen bogs and Sphagnum mosses in thawed bogs, sequestered a disproportionate amount of peat; in addition, changes in their abundance following thaw changed peat accumulation. ²¹⁰Pb-dated cores indicated that peat accumulation doubles following thaw and that the accumulation rate is affected by historical changes in species during succession. Peat accumulation in boreal peatlands following thaw was controlled by a complex mix of local vegetation changes, regional climate, and history. These results suggest that northern ecosystems may show responses more complex than large releases of carbon during transient warming. Received 8 August 2000; accepted 12 January 2001.     

Raised peat bog development and possible responses to environmental changes during the mid- to late-Holocene. Can the palaeoecological record be used to predict the nature and response of raised peat bogs to future climate change?

Palaeoecological analyses of raised peat bog deposits in northwest Europe show the naturalness, antiquity and robust response of these ecosystems to environmental changes from c. 7800 years ago to the present. A review of the techniques used to identify these long-term features is presented and the role of climate change, autogenic change processes and human disturbance is discussed. Millennial records of vegetation changes recorded in peat deposits demonstrate the response (often rapid) of raised peat bog vegetation to climatic changes during the mid-Holocene, Bronze Age/Iron Age transition and the Little Ice Age. Greenhouse warming scenarios exceed the reconstructed Holocene record of climatic changes (c. the last 11, 500 years), and bog-water tables may fall considerably. A combination of centennial palaeoecological analyses of bogs affected by human disturbance and experimental manipulations have been used as analogues for the potential response of raised peat bog vegetation to these changes. These show that possible greenhouse gas climate forcing scenarios may exceed the ability of Sphagnum- dominated raised peat bogs to respond to projected increases in summer temperature and decreases in summer precipitation. In combination with increasing N deposition, a loss of their Sphagnum-rich vegetation and increases in the abundance of vascular plants could occur on decadal timescales.     

Patterns of plant species and community diversity at different organization levels in a forested riparian landscape

Abstract. Integrated synusial phytosociology combined with traditional measures of diversity is used to describe the structure of vascular vegetation diversity along the forested riparian landscape of the upper Oise valley (Belgium and France). The two dimensions (longitudinal and lateral) of the geomorphological complex are examined at four scales: synusia, phytocoenosis, tesela and catena. The results support the following hypotheses: (1) the environmental gradients observed, particularly the lateral ones, are very complex; (2) there is a clear lack of coupling between the tree, shrub and herb layers, which indicates a differential response to the underlying influence of environmental controls; (3) moderate flooding‐induced disturbance enhances herb species richness; (4) stressful environments support a low plant species diversity but a high synusial richness; (5) natural factors (substrate, climate, disturbance) are more important at the synusia and phytocoenose scales, but (6) anthropogenic disturbances, mainly through forest and river management, are more important at the landscape level. By considering plant communities as structural‐dynamic entities of ecosystems in a landscape context, integrated synusial phytosociology provides a basis for decomposing a complex system since the different hierarchical levels are both nested and thus strongly relational and process‐based.     

The Auchenorrhyncha fauna of peat bogs in the Austrian part of the Bohemian Forest (Insecta,Hemiptera)

The first overview on the Auchenorrhyncha fauna of peat bogs of the Austrian Bohemian Forest is presented. Seven oligotrophic peat bog sites were studied in 2011 by suction sampler (“G-Vac”) and 93 Auchenorrhyncha species (with 7465 adult specimens) were recorded. Eleven species (about 18 % of the individuals) are tyrphobiontic or tyrphophilous. The relative species abundance plot is not very steep; the six most abundant species represent 50 % of the individuals. The most common species is Conomelus anceps (17 % of the individuals). Compared to the whole Austrian Auchenorrhyncha fauna, the fauna of peat bogs comprises distinctly more univoltine species and more species hibernating in nymphal stage. Densities of adult Auchenorrhyncha in peat bogs are low in spring (about 10–60 individuals per m²) and high in July, with up to 180 (±50) individuals per m². Disturbed peat bogs have higher species numbers and higher Auchenorrhyncha densities in total, but lower numbers and densities in peat bog specialists.     

Scots pine growing on forested mires in Abernethy Forest,Strathspey, Scotland

Summary

A substantial proportion of the Abernethy Forest Reserve has Scots pine (Pinus sylvestris) growing on the surfaces of a variety of mires. The hydrology of the mires has been affected by drainage and peat cutting but this area is unusual in having had a long period of protection from grazing by domestic stock. There are three main types of pine populations found on these mires. Woodland bog comprises predominantly bog vegetation with abundant pine seedlings due to the heavy seed rain from the surrounding woodland. Only a few very small trees survive, which are stunted, heavily diseased and have very low seed production. Wooded bog also comprises predominately bog vegetation but there are scattered mature trees of a moderate height with an open canopy. The trees are fertile and can form uneven aged stands with regeneration. Bog woodland is a predominantly woodland vegetation with tall, dense tree cover on deep peat. The trees are well grown with a dense canopy. A few remnants of bog vegetation remain in the ground flora although most have been replaced by woodland bryophytes and shrubs. Each of these three types is described and their development is discussed.     

Development of ombrotrophic raised bogs in North-east Germany 17?years after the adoption of a protective program

The present study reports on the development of ombrotrophic raised bogs in NE Germany after the adoption of a protective program with a focus on the hydrological and floristic changes in two simultaneously restored cut-over bogs as a reference for all other bogs. At the moment, four fifths of the bogs area is dominated by woody vegetation forms and <5?% is characterized by typical raised bog vegetation. The trend of increasing areas with woody vegetation forms and decreasing areas with vegetation typical for ombrotrophic raised bogs could not be prevented despite increasing the portion of revitalized areas. The reason for the negative developments is founded in the different types of raised bogs in NE Germany, which differ in regard to the historical lagg area and the original grown up raised peat body. This as well as the kind and intensity of anthropogenic use have significant implications for the possibilities of revitalization and protection. Except for those bogs where no peat remnants remain, the revitalization of cut-over raised bogs in NE Germany can succeed if an almost closed hydrological protection zone (HPZ which is equal to the historical lagg area) is established so that the gradient of entire lateral water flow between the higher lying peat remnant and the lower lying surrounding area is reduced. The attainment of a lateral water flow gradient comparable to the original state and of a water-saturated peat body succeeds in turn in the precondition for growing Sphagnum species, which readjust the system??s self regulation. The comparison of two bogs with similar preconditions concerning location, climate, and anthropogenic transformation has shown that an incompletely closed HPZ is one important reason for the decreasing portion of intact raised bogs with their typical vegetation. The influence of climate change on current hydrological and floristic changes in NE German ombrotrophic raised bogs has less influence on the success of revitalization than the historic grown type of bog and the intensity of anthropogenic use.     

Breeding habitat use and the future management of the critically endangered Southern Corroboree Frog

Summary   The Southern Corroboree Frog ( Pseudophryne corroboree ) is one of Australia's most critically endangered frog species. The species occurs entirely within Kosciuszko National Park, which has a history of cattle grazing (up to the 1970s). A consequence of cattle grazing has been a significant reduction in the extent of montane and sub-alpine peat-bog systems that the species uses as breeding habitat. Furthermore, climate change and associated increased wildfire frequency is expected to further reduce the extent and quality of peat bogs throughout the Australian Alps. In this study, we investigated habitat selection for breeding pools and nest sites within peat-bog systems in order to inform the conservation management of the species and guide other management practices being undertaken in peat bogs where this species occurs. Occupancy of breeding males at bog pools was found to be positively associated with increasing pool area, water depth and mid-day temperature, and negatively associated with extent of bare substrate. The majority of breeding pools identified were ephemeral. Nest sites within vegetation where males call and where females deposit their eggs were located at mid-elevations in a range of vegetation types, with the majority of nests being within moss and sedge dominated by Sphagnum cristatum and Empodisma minor . We also found that male nest sites were not randomly distributed within the edges of pools, but were more often located in areas of loose vegetation. These results highlight the potential sensitivity of the Southern Corroboree Frog to predicted changes in peat-bog systems resulting from climate change such as earlier drying and a possible reduction in the size of bog pools. A monitoring programme focused on key features of the breeding habitat should be undertaken to provide a basis for developing and assessing management actions implemented in peat bogs occupied by this species.     

Methanotrophic Bacteria of Acidic Sphagnum Peat Bogs

Acidic Sphagnum peat bogs cover a considerable part of the territory of Russia and are an important natural source of biogenic methane, which is formed in their anaerobic layers. A considerable portion of this methane is consumed in the aerobic part of the bog profile by acidophilic methanotrophic bacteria, which comprise the methane filter of Sphagnum peat bogs and decrease CH₄ emission to the atmosphere. For a long time, these bacteria escaped isolation, which became possible only after the elucidation of the optimal conditions of their functioning in situ: pH 4.5–5.5; temperature, from 15 to 20°C; and low salt concentration in the solution. Imitation of these conditions and rejection of earlier used media with a high content of biogenic elements allowed methanotrophic bacteria of two new genera and species—Methylocella palustris and Methylocapsa acidiphila—to be isolated from the peat of Sphagnum peat bogs of European northern Russia and western Siberia. These bacteria are well adapted to the conditions in cold, acidic, oligotrophic Sphagnum peat bogs. They grow in a pH range of 4.2–7.5 with an optimum at 5.0–5.5, prefer moderate temperatures (15–25°C) and media with a low content of mineral salts (200–500 mg/l), and are capable of active dinitrogen fixation. Design of fluorescently labeled 16S rRNA–targeted oligonucleotide probes for the detection of Methylocella palustris and Methylocapsa acidiphila and their application to the analysis of sphagnum peat samples showed that these bacteria represent dominant populations of methanotrophs with a density of 10⁵–10⁶ cells/g peat. In addition to Methylocella and Methylocapsa populations, one more abundant population of methanotrophs was revealed (10⁶ cells/g peat), which were phylogenetically close to the genus Methylocystis.     

The mating system in natural and shelterwood stands of Douglas-fir

Summary Mating systems in two pairs of old-growth uncut and adjacent shelterwood stands of Douglas-fir (Pseudotsuga menziesii var. menziesii) were compared by estimating the proportions of viable progenies due to outcrossing (t) with both single-locus and multilocus techniques. Single-locus population estimates (_s), ranging from 0.41 to 1.16, were significantly (P<0.05) heterogeneous among loci in three of four stands; mean single-locus estimates for shelterwoods were not significantly different from those for uncut stands. Multilocus population estimates (_m) ranged from 0.94 to 1.00; again, estimates for shelterwoods were not significantly different from those for uncut stands. Multilocus estimates were slightly higher than mean single-locus estimates for uncut stands but were nearly equivalent for shelterwoods, suggesting that related matings other than selfs may be associated with uncut stands, but not shelterwoods. Individual-tree outcrossing rates (_{m i}), estimated for six trees in each shelterwood, ranged from 0.90 to 1.10 and were significantly heterogeneous among trees at one of the two shelterwoods. Outcrossing was high (> 0.90) in both uncult and shelterwood stands, and no evidence indicated that low parent-tree density had affected stand outcrossing rates.FRL 1918, Forest Research Laboratory. Oregon State University, Corvallis, USA