The role of plant resources in forest succession: changes in radiation, water and nutrient fluxes, and plant productivity over a 300-yr-long chronosequence in NW-Germany

In the past insufficient attention has been paid to quantitative measurements of resource fluxes in ecosystems that undergo successional change. In this study, simultaneous changes in seven plant resources (photosynthetically active radiation (PAR), water, nitrogen, phosphorus, calcium, magnesium and potassium) are quantified by a chronosequence approach for a 300-yr-long secondary succession on poor soil from Calluna vulgaris heathland to Fagus sylvatica-Quercus petraea late-successional forest (heathland-to-forest succession).Above-ground net primary production increases sevenfold, and total above-ground phytomass about fortyfold during heathland-to-forest succession. Plant organs that capture resources increase much more slowly (leaf area index: threefold; fine root biomass: 1.3-fold). The increase in productivity is based both on higher absorptivity and conversion efficiency of PAR by the canopies of the successional plants.Accumulation of organic material on the forest floor significantly improves soil water availability. Evapotranspiration losses increase early in succession as the growing vegetation increases in both height and leaf area but tend to decrease again in the late-successional community. Drainage losses are at their minimum at the conifer-dominated pioneer forest stage.Accumulation of available nutrients in the soil is a key process in heathland-to-forest succession that significantly improves plant nutrient availability but leads to only minor changes in carbon/nutrient ratios and humus quality. Litter decomposition rates increase and result in a more rapid nutrient turnover in late successional stages. External nutrient inputs (from the atmosphere and soil weathering) significantly contribute to plant nutrient supply early in succession, whereas the internal cycling of nutrients through litter fall and nutrient mineralisation by far exceeds external inputs at the late stages.Vitousek & Reiners' (1975) ecosystem nutrient loss hypothesis is supported by the heathland-to-forest succession data. Odum's (1969) hypotheses on how nutrient cycles change during the course of succession is, in one part, rejected, in part supported. Tilman's (1988) hypothesis on nutrient limitation early, and light limitation late in primary succession is rejected.     

Spatial-typological differentiation of ecosystems of the West Siberian Plain. Communication V: Terrestrial ecosystems

Results of classification of terrestrial ecosystems using an average similarity matrix are reported for the West Siberian Plain. Initial indices are first calculated separately for four components of an ecosystem. These components (blocks) include the underground block (soil humus, mortmass, and underground phytomass), above-ground vegetation, and invertebrates and vertebrates. Mismatch of boundaries in separate blocks of ecosystems and in comparison with the inhomogeneity of ecosystems in general was demonstrated. These differences are observed in both the typological and typological-chorological analysis. The indicated features of spatial succession within the blocks generate continuity of ecosystems and the conventional character of all the classifications and drawn boundaries.     

Site parameters,species composition,phytomass structure and element stores of a terra-firme forest in East-Amazonia,Brazil

Our objective was to asses site parameters, species diversity, phytomass structure and element stores of a Terra-firme forest prior to subsequent studies on nutrient fluxes during forest conversion. The soil was classified as a Xanthic Ferralsol, with a low effective cation exchange capacity (ECEC), low nutrient status and a deeply weathered solum. On 0.75 ha, including all trees with a DBH >7 cm, we identified 222 tree species belonging to 58 families. The above-ground phytomass was estimated using logarithmic regression analysis on two plots of 0.25 ha each. Despite differences in forest structure and species composition, no major differences were found in terms of total phytomass or overall element stores. The mean living above-ground phytomass (LAGP) was 257 Mg ha^–1, and mean quantity of litter 14 Mg ha^–1, while dead wood contributed between 10 to 17% of total above-ground phytomass (32–56 Mg ha^–1). Element store in LAGP was medium to high compared to other studies on tropical forest systems, while LAGP itself was comparatively low. Comparing 26 humid tropical forest stands recorded in literature, no correlation was found between LAGP and the amount of N and base cations stored in LAGP. However, a correlation between LAGP and P storage in LAGP (R ²=0.76) indicates the important role P may play in phytomass accumulation on zonal tropical soils. More then 60% of C, 20% of total N, 10% of total P and 66–88% of total K, Ca and Mg of the system (including the first meter of soil) were concentrated in the above-ground phytomass, including deadwood and litter. Consequently, phytomass destruction in form of forest conversion will lead to major element losses from the system.     

Pattern and process in above-ground and below-ground components of grassland ecosystems

Abstract. This paper describes patterns of below-ground components in grassland ecosystems. It provides estimates of the contribution of below-ground organs to the total phytomass of the community and of different species to the below-ground phytomass; it describes the distribution of above- and below- ground organs of different species and the spatial and temporal correlation between above-ground and below-ground phyto-mass – both total standing crop and net primary production. 10 Siberian grasslands (meadows and steppes) were investigated during 15 yr. Ca. 70 % of the living phytomass is located in the soil and no less than 70 % of the net primary production is allocated in below-ground organs. Phytomass distribution in the soil layer is more homogeneous than above-ground. For some species the spatial distribution within 1-m² plots of the green and below-ground phytomass is similar, for others it is quantitatively or qualitatively different. According to the dominance-diversity curve, the above-ground size hierarchy is much stronger than the below-ground one. The active growth of above- and below-ground organs of a species may occur at different times of the season and it varies from year to year. Allocation of organic substances to rhizomes and roots occurs simultaneously and with proportional intensity.     

Successions in the forest-steppe under climate changes: a modelling approach

The paper represents an attempt to apply the general principles of modelling vegetation dynamics under climate changes to a study of the long-term vegetation dynamics in the forest-steppe zone of the European territory of Russia, with a purpose to forecast under special climatic scenarios. An original technique is used to construct a Markov chain as a model of vegetation succession. The technique emanated from gebotanic knowledge generalized as a scheme of successional transitions with estimates of the average duration for certain stages of succession. Whenever the knowledge related the stage duration to certain (climate-sensitive) factors of the environment, the fundamental potentiality arises to model the temporal course of succession as a function of a given scenario for how the key factors change. In the formal terms, the model represents a random chain of the Markov kind with a finite number of states and discrete time of transitions by the given scheme. Relative square distributions of succession stages under concern at any time moment (within an adopted scenario) appear as the model outcome (forecasts), as well as estimates of the attainment time for certain states of the vegetation in the territory under study. A method is proposed to describe dynamics of the phytomass production and stores (and the corresponding model trajectories are obtained) for a given scenario.     

Seasonal change in the above-ground phytomass of an Agrostis-with-Festuca grassland in North-east Scotland

Summary

The above-ground standing crop of an Agrostis-with-Festuca grassland near Cabrach, Banff, was measured nine times in a 16-month period by harvesting sample plots. Standing crop peaked in late summer when the weight of live graminoid phytomass reached its seasonal maximum.     

Nutrient supply in undrained and drained Calthion meadows

Abstract. Plant species-rich Calthion meadows on mesotrophic fen peat soil extensively cut for hay are among the endangered semi-natural vegetation types in northwestern Europe. They are often badly affected by lowering the groundwater table (drainage) and fertilization. In a comparative study of an undrained site with a Calthion meadow and an adjacent drained site, availability of N, P and K was biologically assessed under field conditions (for two years) as well as in a greenhouse (for 18 weeks) by measuring shoot responsiveness. Also, experimental wetting of intact turf samples taken from both sites was applied in order to study the interaction between nutrient supply and anaerobic soil conditions. It was concluded that the above-ground phytomass yield in the undrained site was restricted by a major shortage of N-supply and a moderate shortage of K-supply by the fen peat soil. The above-ground phytomass yield of the drained site was only reduced by a strongly limited supply of K by the soil. The extent of K-deficiency was larger for the drained site. No P-deficiency was observed in any of the drained or undrained sites. Rewetting turf samples, taken from the drained site, did not change above-ground phytomass yields, suggesting that nutrient supplies were not affected by rewetting. Leaching has likely resulted in a strong reduction of K-supply in the drained site. It is assumed that a shortage in K-supply from the peat soil may have become an important environmental constraint for characteristic plant species of Calthion meadows. This may hamper the development of this meadow type on drained peat soils after rewetting by groundwater discharge.     

Production and spatial structure of Mediterranean pastures in different stages of ecological succession

The aim of this paper is to describe the changes of Mediterranean pasture phytomass and their dependence on succession, slope geomorphology and herbivore consumption. Four neighbouring slopes of similar aspect and steepness, located in a pasture area of Central Spain, were chosen for sampling. The slopes had not been cultivated for 1, 3, 8 and 40 years respectively. On each slope both the upper, erosion zone and the lower, accumulation zone were sampled during the months of plant growth (April to July), phytomass being recorded in plots where herbivore consumption was avoided with protection cages and in unprotected plots.Results from the protected plots show that the upper and lower parts of slopes undergo a different development during succession. The highest values of phytomass reached, tended to decrease during succession in the upper zones, the same being true for production. However in the lower zones both parameters tended to increase in time. The ratio P/B, widely known in ecology to decrease with time, did not seem to behave as a usual index of succession in the studied ecosystem. In the upper zone this ratio tended to decrease but in the lower zone it increased with succession after the first years.Phytomass consumption by herbivores was progressively concentrated during succession in the slope sectors of greater production, mainly in the lower zone, which increased its productivity as the slope-talweg system became functional. The evolution of the ecological structure of a slope should be interpreted not only as a result of the tolerance of species to phsysico-chemical factors. It may also reveal the existence of an important interaction between the pasture and the grazing behaviour of exploiting animals. Multivariate analysis of phytomass records revealed a trend of temporal variation which should be identified with the progress of succession.     

Vegetation succession and biological turnover on coal-mining spoils

Abstract. This paper describes secondary revegetation and biological turnover development on coal-mining spoils. Qualitative and quantitative changes in species composition, rate of succession, formation of plant bio-mass structure and net primary production are described for revegetation stages with an undisturbed meadow system as a reference. The development of biological turnover in grasslands has four stages. The first stage is characterized by the growth of weedy species, high above-ground standing crop and production and low below-ground production. The second stage includes the establishment of perennial grasses, a decrease in the above-ground plant biomass and production, an increase of the below-ground living and dead root mass, formation of the plant material structure (distribution of plant material among the compartments of the ecosystem) close to steady-state pattern, the approach to the balance between net primary production and organic matter decomposition. During the third stage a mature species composition is formed and below-ground production increases up to the steady-state level. At the fourth stage the humus storage reaches its steady-state value.     

An experimental study of old-field succession in relation to different environmental factors

From 1984 to 1986, old-field succession on sterilized sand and loam was studied under different water- and nutrient regimes. Within one month, moss and phanerogam species appeared on all experimental plots but further succession was rather varied. Salix species established quickly on loam and formed within 3 years a shrub layer up to 3 m in height. On sand, woody plant species were observed only at a high ground-water level. On loam, the well-known old-field succession from short-living therophytes to long-living phanerophytes of clearings and woodlands proceeded very quickly. In contrast, on sand, therophytes, hemicryptophytes and herbaceous chamaephytes of ruderal- and grassland communities were still dominant after three years. A high ground-water level as well as mineral fertilization had sometimes positive, sometimes negative effects on this succession. Periodic estimates of cover, made during the succession were supplemented at the end of the experiment by the measurements of phytomass and bioelement storage. The highest amount of biomass was measured on the three loamy soils where shrub layers were well developed. In comparison with data published elsewhere, the above-ground biomass of 2.2–2.8 kg dry matter m^-2 and the below-ground biomass up to 7.2 kg dry matter m^-2 were both extraordinarily high. Over the three years, the vegetation on sandy soils accumulated between 1.2 and 5.1 g N m^-2 yr^-1 and on loamy soils between 17.1 and 24.7 g N m^-2 yr^-1.     

Phytomass structure of natural plant communities on spodosols in southern Venezuela: the Bana woodland

Bana, or Low Amazon Caatinga is an evergreen sclerophyllous woodland. It occurs on bleached quartz sands in the lowlands of SW Venezuela, where it occupies relatively small ‘islands’ amidst Tall Amazon Caatinga which is exclusively developed on tropaquods. There is an outer vegetation belt about 20 m in width in which trees over 10 m in height occur (Tall Bana); its structure and floristic composition resemble Tall Amazon Caatinga. Low Bana (maximum tree height usually below 5 m) follows next. The central part is occupied by Open Bana in which even lower trees are very widely spaced. Destructive phytomass sampling was carried out for chemical analyses in seven plots along a 150 m line across the zonation. The total dry matter of living plants including roots of Tall Bana (30–32 kg/m²) compares rather well with 41 kg/m² in Tall Amazon Caatinga. This is only 9–14 kg/m² in Low Bana, and 4–6 kg/m² in Open Bana. The average root % of total phytomass increases from 41% in Tall Bana to 63% in Low Bana, and is 88% in Open Bana. Average total dry dead above-ground phytomass (including standing trees and stumps) declines from 1 kg/m² in Tall Bana to 0.2 kg/m² in Open Bana. An accumulation of dead matter in Low and Open Bana, relative to the above-ground phytomass of living plants, is noted and this contrasts with the general absence of raw humus in the soil. Eighty-two species of woody plants (dbh≥1 cm) were recorded on the total plot area (640 m²); 90% of the species are also known to occur in Tall Amazon Caatinga. The species number declines from 59 in Tall Bana to 18 in Open Bana. Mesophylls sensu strictu dominate in Tall Bana, while notophylls are dominant in Low and Open Bana. Herbaceous species are less numerous: most of them belong to the Araceae, Bromeliaceae, Orchidaceae, Droseraceae, Eriocaulaceae and Xyridaceae.     

Fire regimes and phytomass growth dynamics in a Quercus coccifera garrigue

An experiment was set up in a Quercus coccifera garrigue in southern France to analyze the effect of burning frequency and season on phytomass production. Fire regimes consisted of late spring or early autumn burns, every 6 yr, every 3 yr, or every 2 yr. The experiment started in 1969 and lasted for 19 yr. In May 1981 and May 1987, 10 samples, each 1 m², were harvested per treatment. Fire frequency had an effect on the quantity of phytomass which was produced: above-ground phytomass decreased with increasing fire frequency. This was mainly due to the lower biomass of woody plants. In all burning treatments the phytomass of herbs was higher than in the unburned vegetation. Within each burning frequency, the total phytomass of the spring-burned vegetation was always higher than that of the autumn-burned community. Generally, the herb phytomass produced was higher in the autumn-burned plots. There were two fairly distinct phases in the period following fire, each with a different level of annual phytomass production. For the first six years it was about 300 g m^?2 yr^?1, falling thereafter to about 50 g m^?2 yr^?1. This and other studies on Q. coccifera garrigue indicate that this community is very resilient with respect to fire, but possesses a low productive capacity and does not show any sign of degeneration up to 30 yr old.     

Post-logging organic matter recovery in forest ecosystems of eastern Baikal region

The dynamics of organic matter accumulated in the soil and main vegetation elements was analyzed for post-logging forest ecosystem succession series in eastern Baikal region. The phytomass was found to allocate up 63 and 50% of carbon in undisturbed Scots pine and fir stands, respectively. The post-logging phytomass contribution to the total carbon pool appeared to decrease down to 16% in Scots pine and 6% in fir stands. In Scots pine stands, carbon storage was determined to account for almost 70% of the initial carbon 60 years after logging. In 50- to 55-year-old fir stands, carbon recovered its initial pool only by 10%. Soil carbon recorded in recently logged Scots pine and fir sites appeared to be 5 and 16 times that accumulated in the phytomass, respectively. The ratio between phytomass carbon and soil organic matter recovered back to the prelogging level in Scots pine stands by the age of 50–60 years. While phytomass carbon also increased in fir stand of the same age, it did not reach the level of the control stand.     

Effects of herbivorous birds on intertidal seagrass beds in the northern Wadden Sea

During autumn migration (September to December), brent geese (Branta b. bernicla) and wigeon (Anas penelope) feed on the seagrass Zostera noltii in the nearshore, upper tidal zone leeward of the island of Sylt (eastern North Sea). To graze on leaves and shoots above the sediment and on rhizomes and roots below, these birds reworked the entire upper 1 cm layer of sediment eight times within this 3-month period. In addition, brent geese excavated pits 3–10 cm deep by trampling in order to feed on below-ground phytomass. About 12% of the seagrass beds became pitted to an average depth of 4.5 cm. Using net exclosures, it was estimated that birds removed 34 g dry weight m^–2 of above-ground and 28 g of below-ground phytomass. This corresponds to 45% of the phytomass in September. Of the overall loss of phytomass from September to December, 63% was caused by birds. Roughly half of the leaves fell off anyway until December and the other half were taken by the birds. Below the ground, phytomass remained almost constant where birds were excluded, while with birds phytomass of rhizomes and roots was halved. In spite of this strong effect, in the next vegetation period the blade density was lower at former exclosure sites compared to the ambient seagrass bed. The underlying process seems to be a self-inhibition of dense overwintering seagrass by mud accretion. Assuming our experimental results can be scaled up to the entire seagrass bed, we hypothesize that in the sheltered upper intertidal zone, seasonal erosion caused by herbivorous geese and ducks is necessary for the persistence of Z. noltii. Received: 7 January 1999 / Received in revised form: 23 August 1999 / Accepted: 25 August 1999     

Current state of forage resources and feeding of reindeer (<Emphasis Type="Italic">Rangifer tarandus</Emphasis>) and musk oxen (<Emphasis Type="Italic">Ovibos moschatus</Emphasis>) in the arctic tundras of Wrangel Island

The species composition and aboveground biomass of plant and lichens and the composition of reindeer and musk ox diet in the arctic tundra of Wrangel Island were studied in 2004 to 2007. The above-ground phytomass in different areas of the island varied from 1105 to 2100 kg/ha. The composition of plants consumed by reindeer and musk oxen and their proportions in the diet were determined by standard micro-histological analysis of plant remains in their feces. The results showed that, either in winter or in summer, both species obviously preferred feeding on willows (Salicaceae), which comprised almost half of their diet. Moreover, their feeding was highly selective, especially with respect to sedges and rushes (Cyperaceae + Juncaceae) and legumes (Fabaceae). Although the contributions of these plant groups to the total aboveground phytomass were very small (less than 4 and 8%), their proportions in the diet reached 27 and 24%, respectively. Mosses were not a preferred forage: their proportion in the aboveground phytomass reached 40%, but that in the diets of both species was below 10% in summer and increased to 20% only in the winter diet of reindeer. At a high abundance of lichens (up to 20% of the aboveground phytomass), neither of the animals consumed them during the study period.     

Dependence of Phytomass of Herbaceous Cenoses on Weather Factors in Anthropogenically Impacted Areas

This paper is concerned with the phytomass of herbaceous phytocenoses growing in anthropogenically impacted areas in the Middle Urals at different stages of succession along the heavy-metal pollution gradient. Cenoses of young soils of dumps have less resistance and higher sensitivity to changes in weather factors, in contrast to the phytocenoses of the deposits. It is shown by general regression models that the epiterranean and subterranean biomass of cenoses on technozems depends on Selyaninov’s hydrothermic coefficient for September and the amount of precipitation in October–November of the previous year and in January–May of the current year. The degree of this dependence for cenoses under research is determined by edaphic conditions that affect the species diversity and dominance structure.     

Morphological analysis of alpine communities of the north-western Caucasus

The species composition of four alpine communities in the north-western Caucasus was subjected to a morphological analysis. The communities are an alpine lichen heath type (ALH), aFestuca varia grassland type (FVG), aGeranium-Hedysarum meadow type (GHM) and a snowbed community (SBC). Eighty-two species were studied, using the following morphological parameters: vegetative mobility, presence of rosettes, architectural model, life form according toRaunkiaer and life form according toSerebryakov. Representation spectra were calculated on the basis of species presence, above-ground phytomass proportion and species frequency. The results show that most alpine species have a low vegetative mobility; a semi-rosette growth form; a sympodial semi-rosette model of shoot formation and that they are characterised by the prevalence of hemicryptophytes. Differences between the four communities were found in the following features: tap-rooted and short-rhizome plants dominate in ALH and, moreover, dense-tussock plants are dominant in the phytomass; short-rhizome (species presence) and dense- tussock plants (phytomass) are dominant in FVG; short-rhizome and loose-tussock plants dominant in GHM; semi-shrub (phytomass basis) and loose-tussock plants are dominant of SBC. Tuberiferous, bulbiferous and monocarpic plants are not important in any of the communities. *** DIRECT SUPPORT *** A02DO006 00008     

Ecosystem development and carbon cycle on a glacier foreland in the high Arctic, Ny-Ålesund, Svalbard

The Arctic terrestrial ecosystem is thought to be extremely susceptible to climate change. However, because of the diverse responses of ecosystem components to change, an overall response of the ecosystem carbon cycle to climate change is still hard to predict. In this review, we focus on several recent studies conducted to clarify the pattern of the carbon cycle on the deglaciated area of Ny-Ålesund, Svalbard in the high Arctic. Vegetation cover and soil carbon pools tended to increase with the progress of succession. However, even in the latter stages of succession, the size of the soil carbon pool was much smaller than those reported for the low Arctic tundra. Cryptogams contributed the major proportion of phytomass in the later stages. However, because of water limitation, their net primary production was smaller than that of the vascular plants. The compartment model that incorporated major carbon pools and flows suggested that the ecosystem of the later stages is likely to be a net sink of carbon at least for the summer season. Based on the eco-physiological characteristics of the major ecosystem components, we suggest several possible scenarios of future changes in the ecosystem carbon cycle.     

Ecotypic variation in plant characteristics for Origanum vulgare subsp. hirtum populations

Origanum vulgare L. subsp. hirtum (Link) Ietsw. is a polymorphic taxon with respect to essential oil production and glandular trichome density. Here it is examined whether the natural populations that are indigenous in continental Greece may be considered as different ecotypes (i.e. populations with different genetic variation) and whether evidence regarding a fitness cost from essential oil production could be obtained. Samples from 30 different natural populations, differing in climatic conditions, were collected across continental Greece in 1998–2000 and were studied for essential oil production and glandular trichome density. Additionally, individual plants, derived from propagated rhizomes, originated from the natural populations, were transplanted in pots in two gardens that varied in terms of mean temperature and aridity. In these experimental populations, the above-ground phytomass and ratio of leaves and inflorescences to above-ground phytomass were additionally measured. The main findings of the study were (a) a strong positive correlation between essential oil concentration and glandular trichome density, (b) a high positive correlation between natural and experimental populations in essential oil concentration (or glandular trichome density), (c) a negative correlation between essential oil concentration and phytomass and (d) a positive relationship between the essential oil concentration and the factors thermal status and summer drought of the location of origin. Results suggest that the examined populations of O. vulgare subsp. hirtum are different ecotypes, the production of essential oils has a cost to plant growth and that the prime target of selection, by producing these oils, is to increase the resistance to drought and heat stresses.