Reversing borealization as a means to restore biodiversity in Central-European mountainforests – an example from the Krkonoše Mountains, Czech Republic

Forestry in the Central-European mountains is confronted with a severe forest decline, which is attributed to the combined effects of 'borealization', brought about by large scale continued spruce (mainly Picea abies) monocultures, and atmospheric deposition. Borealization is defined as enhanced soil acidification and litter accumulation, retarded nutrient cycling and changed forest climate in such planted coniferous forest ecosystems. An additional effect of borealization is a major decline in biodiversity of the stands. Based on a comparative study of Norway spruce and European beech stands in the Krkonoe National Park (Czech Republic), it is concluded that traditional management should be abandoned and that management should instead focus on regeneration towards broad-leaved or mixed forest stands, to enhance the stability of forest ecosystems and their biodiversity, and to reverse borealization in lower montane zones. Available surveys of forest typology were evaluated for their suitability in regeneration management and were found to be unsuitable, since they reflect the effects of borealization rather than true site conditions. The two main pioneer tree species, birch (Betula pendula) and mountain ash (Sorbus aucuparia), were found to improve soil conditions and reverse borealization. Furthermore, trends in natural vegetation and soil development in declined forests and clear-cuts, and their relevance for forest restoration management were studied, focusing on borealization and plant species diversity. It is concluded that this natural development offers very good possibilities for a more passive, low-cost restoration management.     

Tiller dynamics of Spartina maritima in successional and non-successional mediterranean salt marsh

Tiller demography was compared in two populations of Spartina maritima present at similar elevations in the coastal saltmarshes of Odiel (Huelva, S.W. Spain). The successional population consisted of colonizing tussocks in a littoral lagoon, and the non-successional population comprised a stable sward that had fringed a major channel for 40 years. At both sites S. maritima was replaced by Arthrocnemum perenne at higher elevation, where sediments were less reducing. Rapid, consistent sediment accretion confirmed the successional nature of the lagoon site but there was little net accretion in the stable sward.Census of permanent quadrats at the successional site chronicled moving concentric waves of high tiller density as tussocks expanded. Initially high densities declined after one year to low values at the end of the second year but they had almost recovered after 3 years. The decline represented a combination of reduced numbers of births and increased numbers of deaths. Tiller densities were substantially higher in the stable sward and showed relatively small fluctuations with time. The underlying risk of tiller mortality was similar in the two populations for much of the time but after two years there was increased mortality, mainly associated with flowering, at the successional site; very few tillers flowered in the sward. This mortality contributed to a shift to a younger age structure in the successional population.Data aggregated over consecutive 3-monthly periods were examined for density dependence. None was found in the successional population. In the sward population there was evidence of density-dependent adult and juvenile mortality of tillers, particularly over the first 18 months of the study, when there were compensatory responses to subtle variations in density. The lack of density dependence and relatively low peak density of about 2000 m^-2 near to the leading edges of the expanding tussocks at the successional site suggest that tiller placement there was regulated mainly by physiological mechanisms affecting rhizome growth and bud development in well integrated clones.     

Trends and fluctuations in species abundance and richness in Mediterranean annual pastures

Abstract. Floristic data collected from permanent plots during 14 consecutive years are used to model the frequency of the 62 most abundant species in relation to post-ploughing succession, topography and rainfall in annual Mediterranean grasslands located in a Quercus rotundifolia dehesa. The interannual dynamics of species richness are also analysed. From 1980 to 1993, presence/absence data of grassland species were noted in five 20 cm X 20 cm permanent quadrats placed at random in 1980 in 14 permanent plots on a south-facing slope along the topographic gradient. Weekly autumn rainfall data over the 14 years were analysed using a profile attributes index and Hybrid Multidimensional Scaling to arrange the years according to their autumn rainfall pattern. Generalized Linear Models were used to fit the species richness and species frequency according to topographic position, age since the last ploughing episode, total rainfall in the growing season and autumn rainfall pattern using a forward stepwise procedure. The richness model includes all of these variables, and reveals a relatively high goodness-of-fit (71 %). The fact that the meteorological factors play a key role in modelling richness forces us to include them if we wish to use richness as an indicator of the degree of disturbance in these highly fluctuating annual pastures. Models of species dynamics show that although roughly 33 % of the species have a successional behaviour, the majority are more dependent on temporal heterogeneity associated with rainfall or spatial heterogeneity linked to the topographic gradient.     

The zooplankton of the lower river Meuse, Belgium: seasonal changes and impact of industrial and municipal discharges

Between 1991 and 1993, samples were collected upstream and downstream of the industrial basin and urban centre of Liège. Rotifers and crustaceans (cladocerans and copepods) were identified and counted. Their population dynamics were related to physical and chemical factors (temperature, oxygen, ammonium, nitrates, nitrites, phosphates) and to phytoplankton biomass. The zooplankton was dominated by rotifers; crustaceans (cladocerans and copepods) were less abundant. There was a succession of groups and species, some thriving in the spring and others in summer or autumn. The dominant rotifer species were Brachionus calyciflorus Pallas, Brachionus angularis Gosse, Keratella cochlearis (Gosse) and Synchaeta spp.; B. calyciflorus and B. angularis are spring species. K. cochlearis was present between May and November. Crustacean biomass was important in summer and autumn, but the faunal spectrum and biomass also varied with sampling location. Low spring and summer discharges allowed the phytoplankton to develop significantly. The zooplankton development followed a similar pattern. During low flow, when plankton populations become established, some declines in phytoplankton could only be explained by sedimentation and grazing pressure by zooplankton. Although these factors provided a good explanation of the longitudinal variation, some local conditions (e.g. oxygen deficit, high level of phosphate) also induced changes (e.g. industrial and municipal waste water discharge).     

Field responses to added organic matter, arbuscular mycorrhizal fungi, and fertilizer in reclamation of taconite iron ore tailing

A three season study was conducted to determine the effect of added composted yard waste, arbuscular mycorrhizal (AM) fungi, and fertilizer on plant cover, standing crop biomass, species composition, AM fungal infectivity and spore density in coarse taconite iron ore tailing plots seeded with a mixture of native prairie grasses. Plant cover and biomass, percent seeded species, mycorrhizal infectivity and spore density were greatly increased by additions of composted yard waste. After three seasons, total plant cover was also greater in plots with added fertilizer. Third season plant cover was also greater in plots amended with the higher rate (44.8 Mg ha^{–1) of compost than the moderate rate (22.4 Mg ha-1}). Field inoculation with AM fungi also increased plant cover during the second season and infectivity during the first two seasons. Seeded native species, consisting mostly of the cover species Elymus canadensis, dominated plot vegetation during the second and third seasons. Dispersal of AM fungal propagules into nonmycorrhizal plots occurred rapidly and increased infectivity in compost-amended plots during the third season. In plots with less than 10% plant cover, AM fungal infectivity of inoculated plots was greatly reduced after the second season. The high level of plant cover and the trend of increasing proportion of mycorrhizal-dependent warm-season grasses, along with increases in infectivity, forecast the establishment of a sustainable native grass community that will meet reclamation goals.     

Seed rain,seedling establishment and clonal growth strategies on a glacier foreland

Abstract. Seed production, composition of the seed rain, germination, and seedling mortality, as well as vegetative growth characteristics of common pioneer plant species were studied on the foreland of the retreating Morteratsch glacier in the Swiss Alps. The frequency of diaspores trapped in different successional stages was related to their dispersal mode and was highly skewed towards a few species. Plenty of diaspores well adapted for dispersal by wind are a precondition for the most important pioneer species. Seeds from all pioneer species investigated had a good germination success, provided that the moisture content of the soil was high enough. However, requirement for seedling establishment differed among sites of increasing terrain age and among species. Only specialized pioneers such as Cerastium pedunulatum, Linaria alpina, Oxyria digyna and Saxifraga aizoides tolerate the cold and moist conditions near the glacier. However, these species are restricted to early successional stages. Seedlings of Epilobium fleischeri are affected not only by the cold and moist conditions near the glacier but also by moderately dry conditions on older sites. Availability of safe sites becomes crucial for most species with increasing age of sites and with drier conditions. Most species playing a dominant role during early succession and persisting during later successional stages have a distinctive ability to spread clonally and have a growth form with more or less widely spaced ramets: Achillea moschata. Cerastium pedunculatum. Epilobium fleischeri and Hieraium staticifolium. The growth strategy and demography of the clonal E. fleischeri is presented as an example. The life cycle of this species is characterized in succession by (1) the colonization of safe sites by small seeds adapted for wind dispersal, (2) horizontal spread by clonal growth, and (3) the persistence through phenotypic morphological plasticity in later successional stages. Seedling establishment and clonal growth are thus complementary mechanisms in plant succession on recently deglaciated terrain.     

Mycofloral succession onPinus densiflora needles on a moder site

Mycofloral succession on decaying pine needles in aPinus densiflora forest on a moder site was investigated in Sugadaira, Nagano Pref., central Japan. Dead needles on the tree, fallen needles obtained from two recognizable sublayers of the L layer and the upper sub-layer of the F₁ layer in the organic horizon were examined for their fungal flora using both washing and surface sterilization techniques. The major interior colonizer in freshly fallen needles varied with the season:Chaetopsina fulva in summer andSelenosporella curvispora in the other seasons.Thysanophora penicillioides was a remarkable external colonizer of freshly fallen needles in summer, while soil fungi were external colonizers of such needles in the other seasons. A possible successional change of major fungi with the needle decay was suggested. The observed seasonal alternation of the species colonizing freshly fallen needles was discussed in relation to climatic conditions. Contributions from Sugadaira Montane Research Center, No. 152.     

Comparison of regeneration following burning,clearing or mineral sand mining at Tomago,NSW: I. Structure and growth of the vegetation

Abstract We have begun a long-term ecological research project to address questions about the impact of multiple disturbances on the species richness of communities and whether multiple disturbances are additive or interactive. A protected water catchment area was chosen, which is subjected to fires, sand mining and clearing, and for which detailed records are available. The study area, at Tomago (32°52′S, 151°45′E), has forest, woodland, shrubland and swamp on a sand substrate, with the vegetated dunes forming part of a coastal embayment. Forty-four sites were located in forested areas that had undergone disturbance by either fire, sand mining or clearing. Sites of each disturbance type were grouped into four age classes: less than 1 year since disturbance, nominally 1991; 5 years, nominally 1986; 11 years, nominally 1980; and 17 years, nominally 1974. A set of burned sites, with the time of the last fire matched to the times of the other disturbances, was used as the control response. In this paper we describe the study area and sites, then examine the effects of each single disturbance on vegetation structure. Canopy cover increased with time and type of disturbance, with 17 year old cleared or mined sites similar to the cover of 11 year old burned sites. In the first two years after disturbance, burned sites had significantly more understorey vegetation than cleared or mined sites, but by 5 years all three were similar. The data presented here show that regeneration of mined sites at Tomago is substantially slower than regeneration following disturbance by fire, with the regeneration of cleared sites intermediate but closer to mining than fire. After 17 years regeneration, cleared and sand mined sites had not returned to the vegetation structure of the pre-disturbance state. Understorey height and the amount of vegetation on cleared or mined sites have not achieved the levels in the original forest, although canopy cover did seem to have reached pre-disturbance levels. Current rehabilitation techniques are more sophisticated than those used 17 years ago and continued monitoring of sites currently being rehabilitated may show a faster return to pre-disturbance states. Having established the hierarchy and nature of the response to each single disturbance here, we are now in a position to investigate the impact of multiple disturbances.     

The concept of succession in relation to the spread of sheathing mycorrhizal fungi on inoculated tree seedlings growing in unsterile soils

Summary Repeated annual assessments of the toadstools (fruitbodies) of mycorrhizal fungi associated with a mixed stand ofBetula spp. indicated that they were produced in a pattern ordered in time and space, suggesting a succession with identifiable early-and late-stage fungi. This concept is supported by below-ground observations of mycorrhizas which, however, need to be augmented.Both early- and late-stage mycorrhizal fungi form mycorrhizas on seedlings growing in axenic (aseptic) conditions. In contrast, only early-stage fungi seem able to trigger mycorrhizal formation on seedlings growing in unsterile soils.During axenic propagation, the early-stageHebeloma sacchariolens and the late-stageAmanita muscaria formed similar numbers of mycorrhizas per root system. After being transplanted to a range of unsterile field soils,A. muscaria failed to keep pace with the spread of the developing root system: no moreA. muscaria mycorrhizas were formed. On the other hand the continued development ofH. sacchariolens mycorrhizas precluded, during the first season after transplanting, the development of mycorrhizas by fungi naturally occurring in field soils. In the second season, however, the development ofH. sacchariolens mycorrhizas was restricted in acid peat but not in three other types of soil.The development ofLaccaria mycorrhizas after inoculating Sitka spruce with this fungus was associated, irrespective of soil type, with accelerated tree growth; with heights at the end of the first season being doubled.     

四种国产地衣的化学成分

本文报遣柄果牛皮叶(Sticta henryana),多形树发(Alectoria variabilis),宽瓣肾岛衣漂白变型(Nephromopsis stracheyi f. ectocar pisma)和顶果珊瑚枝(Stereocaulon pomiferum)四种地衣的化学成分。根据光谱数据分析,从中分离得到的18个化合物被鉴定为5-甲基-β-苔黑酚酸甲酯(methyl 5-methy-β-orcinolcarboxylate),苔色酸(orsellinic acid),扁枝衣酸(everainic acid),苔色酸甲酯(methyl orsellinate),赤星衣酸乙酯(ethyl hematommate),β-苔黑酚酸甲酯(methyl β-orcinolcarboxylate),假杯点素A(pseudocyphellarin A),黑茶渍素(atranorin),茶渍酸(lecanoric acid),斑点酸(stictic acid),降斑点酸(norstictic acid),藻纹苔酸(salazinic acid),富马原岛衣酸(fumarprotocetraric acid),左旋和右旋松萝酸(usnic acid),左旋地衣硬酸〔(-)-lichesterinic acid〕,右旋原地衣硬酸〔( )-protolichesterinic acid〕和无羁萜(friedelin)。其中5-甲基-β苔黑酚酸甲酯系首次从植物中得到。分析结果表明,顶果珊瑚枝可作为一种较好的苔香型香原料。