Effects of grazing and inundation on pasture quality and seed production in a salt marsh

During a six-year period, changes in the composition of dominant plant species of importance to foraging birds in a salt marsh on the Swedish west coast were followed inside and outside exclosures to document effects of grazing on herbage quality and seed production. Since marshes provide an important habitat for foraging geese and ducks, it was of interest to determine how cattle grazing would affect herbage production inAgrostis stolonifera andPuccinellia maritima and seed and root-tuber production inScirpus maritimus. Measurements of cover and height in permanent plots revealed that a wetter weather type favouredAgrostis, probably through reduced salinity, at the expense ofPuccinellia, which was the most favoured food of both cattle and birds.Agrostis out-competedPuccinellia when grazing pressure was low. Seed production inScirpus maritimus was reduced by cattle grazing, particularly whenPhragmites australis formed part of the vegetation. In the absence of cattle grazing, both herbage- and seed producing plants were gradually reduced, andPhragmites increased. Since high herbage consumption and high seed production are mutually exclusive, grazing rotation in combination with mowing is suggested as a management strategy.     

Variability in the chemistry of estuarine plants and its effect on feeding by Canada geese

Summary We investigated the influence of interspecific and seasonal variations in plant chemistry on food choices by adult and gosling Canada Geese, Branta canadensis, on Cape Cod, Massachusetts. The geese fed primarily on the abundant marsh grasses, Spartina spp., and rushes, Juncus gerardi, early in the growing season and switched to a greater dependence on eelgrass, Zostera marina, later. Forbs were generally avoided all season even when growing within patches of abundant species. The avoidance of forbs was related to their low abundance and their high concentrations of deterrent secondary metabolites. Differences in plant chemistry also determined the switch from marsh graminoids to Z. marina during the growing season. Marsh grasses were higher than Z. marina in nitrogen, particularly in the spring when the nitrogen requirement of geese is especially high. Z. marina was a better source of soluble carbohydrates and was the preferred food during the summer when the need to build up energy reserves may be more critical to geese than protein intake. Goslings, which require a diet higher in nitrogen than do adults, fed on marsh graminoids later into the growing season than the adults. The nitrogen content of the diets of goslings was significantly higher than that available to them in the plants, indicating that they selected for introgen. The diets of non-breeding adults in the spring and all geese in mid summer closely reflected the nutrient content of the plants. The diet of breeding adults was more similar to that of their goslings than to that of non-breeding adults. The effects of plant chemistry and the nutritional needs of geese on food choices were modified by the need to select a safe feeding site.     

Changes in ion composition and hexitol content of differentPlantago species under the influence of salt stress

Summary The effect of salinity on the ionic balance and the hexitol content of the halophyteP. maritima L. and the nonhalophytesP. major L. ssp.major, P. lanceolata L., andP. media L. was studied in a culture experiment. In response to salt application the nonhalophilous species increased their internal electrolyte content to a considerably greater extent at high transpiration thanP. maritima. Excessive uptake of Cl and SO₄ following salt-treatment was in most cases compensated by a decline in the total organic anion content in all species under investigation. Na was strongly accumulated in the shoots ofP. maritima when subjected to salt-stress, while the nonhalophytic species tended to exclude this ion from leaf tissue enhancing Mg-uptake for charge balance. Acyclic polyhydric alcohols (sorbitol and mannitol), the dominant soluble carbohydrates in allPlantago species studied, increased, with one exception, in all plants under saline conditions. The results indicate marked physiological differences between the halophyteP. maritima and the nonhalophytic members of the genusPlantago in their reaction to salinity being perhaps partially responsible for differences in the degree of salt tolerance.     

Aggregative responses of brent geese on salt marsh and their impact on plant community dynamics

The aggregative responses and habitat preferences of a generalist herbivore, the dark-bellied brent goose Branta bernicla bernicla, feeding on salt marshes are examined in relation to vegetation community characteristics and the abundances of individual plant species. In the autumn, feeding was strongly concentrated on the low marsh, which had the highest biomass of the preferred food plant, Salicornia europaea. There was a strong aggregative response of the geese to the abundance of S. europaea. A decline in the availability of S. europaea led to an increase in the pattern of aggregation in relation to the two other major food plants on the low marsh, Aster tripolium and Puccinellia maritima. The availability of these food plants, however, reached critically low levels in mid-winter and the geese abandoned the low marsh for the high marsh. Within the high marsh, the plant communities selected tended to be dominated by the inedible species Limonium vulgare. The food plants selected were P. maritima in the winter and P. maritima and Triglochinmaritimum in the spring. On the high marsh, aggregative responses were shown to both P. maritima and T. maritimum, but in both cases, aggregation increased up to a critical level of biomass, and then declined. The prevention of grazing with exclosures for 3 years led to an increase in the abundance of P. maritima on both high and low marshes. This change was slight on high marsh but pronounced on low marsh, where S. europaea showed a decrease in abundance in the exclosures over this time. The implications of the aggregative responses for the population dynamics of P. maritima and S. europaea are discussed. Received: 11 September 1997 / Accepted: 12 December 1997     

Modification of competition between two grass species by a hemiparasitic plant and simulated grazing

Plant parasitism and herbivory are common phenomena in natural grasslands, where they may significantly affect competition between plant species. However, only few studies have simultaneously examined these two processes. We investigated whether the root hemiparasite Odontites litoralis ssp. litoralis affects the outcome of competition between two clonal graminoids, the endangered Puccinellia phryganodes and the common species Agrostis stolonifera, and whether simulated grazing affects the interaction among these three species. This study system simulates the community of early successional stages of the Bothnian Bay salt marsh meadows, which are intensively grazed by greylag geese (Anser anser). We conducted a factorial greenhouse experiment to study the effects of interspecific competition (one or two host species present), hemiparasitic infection (hemiparasite present or not), and simulated grazing (host clipped or not) on Puccinellia and Agrostis. Puccinellia was clearly an inferior competitor to Agrostis, whereas the two species did not differ as hosts for the hemiparasite. Infection by the hemiparasite reduced the aboveground biomass of Puccinellia and Agrostis by 59% and 45%, respectively. Competition with Agrostis decreased the biomass of parasitised Puccinellia by 36% and that of non-parasitised Puccinellia by 56%. Parasitism thus seemed to benefit Puccinellia indirectly by decreasing the relative competitive advantage of Agrostis. Moreover, parasitism increased the relative contribution of Puccinellia to the total aboveground host plant biomass. Simulated grazing decreased the aboveground biomass of Agrostis significantly more than that of Puccinellia and thus increased the competitive ability of Puccinellia. Simulated grazing of the two host species did not affect the performance of Odontites. These results suggest that both hemiparasitic plants and herbivory may play a significant role in the maintenance of plant species diversity by promoting competitively inferior species.     

Movements of wintering diving ducks: new insights from nasal saddled individuals

Flightless moulting Greylag Geese on the Danish island of Saltholm fed on Puccinellia maritima almost exclusively within 150 m of the coastline, despite abundant equivalent food further away. This distribution pattern could theoretically be explained by two alternative (but not necessarily mutually exclusive) explanations: predation risk (since birds take to open water when disturbed) or variation in food quantity/quality. Above ground green parts of this plant showed consistently higher protein and lower fibre content inland than on the coast, hence differences in food quality could not account for the difference in foraging distribution. However, in grazed plots, shoot density was greater at the coast than inland, resulting in an increase of 1.2–2.8 times the available green above-ground biomass. Hence, the greater abundance of Puccinellia at the coast may contribute to the explanation. However, within exclosures at the coast, Puccinellia shoot density was no different to inland areas, suggesting that some function of goose grazing at the coast was involved in enhancing biomass there. It therefore seems likely that the greater food biomass at the coast is a consequence of geese feeding to within 150 m of the coast, though not necessarily the cause. The fact that the Greylag Geese fed throughout the island whilst able to fly but fed exclusively on the coast during flightlessness suggests that a predator escape mechanism could be the most important factor constraining the feeding distribution of moulting geese.     

Lipid Composition of the Roots of Plantago Species: Response to Alteration of the Level of Mineral Nutrition and Ecological Significance

In a study of the adaptation of Plantago species to their specific environment the lipid composition of the roots of several species: Plantago major L. ssp. major, Plantago major L. ssp. pleiosperma Pilger, Plantago lanceolata L., Plantago media L., Plantago maritima L., Plantago coronopus L. was studied as well as the effect of the nutritional regime. Upon exposure to low-salt conditions Plantago major L. ssp. major L. and Plantago maritima L. maintained the level of free sterols in the roots, despite a depressed level of total sterols, and the root lipids were more saturated than under high-salt conditions. Both factors may reduce nutrient leakage from the roots to the low-salt condition. Upon exposure to low-salt conditions, all Plantago species showed a decreased level of galactolipid (exception: Plantago coronopus) and a decreased level of sitosterol (exception: Plantago maritima); the latter being compensated by an elevated level of cholesterol + tocopherol in Plantago major ssp. pleiosperma, Plantago lanceolata and Plantago media. Plantago coronopus was the only species which under low-salt conditions showed an increased level of free sterols, among which cholesterol was the most important; thus indicating a high degree of regulation of membrane permeability under alternating nutritional conditions. The level of sulfolipid was kept constant in all Plantago species, with the highest level observed in Plantago maritima. The role which various lipids may play in maintenance of membrane integrity under alternating nutritional conditions is discussed.     

Hydrology‐driven responses of herbivorous geese in relation to changes in food quantity and quality

East Dongting Lake is a Ramsar site and a particularly important wintering ground for herbivorous geese along the East Asian‐Australasian Flyway. The operation of the Three Gorges Dam has changed the water regime and has a significant impact on wetland ecosystems downstream. We studied the responses of two sympatric herbivorous goose species, the Lesser white‐fronted goose Anser erythropus and Bean goose Anser fabalis, to habitat change by investigating their food conditions, habitat selection, and diet composition in the wintering periods of 2016/2017 and 2017/2018, which had early and late water recession, respectively. It was expected that the contrasting water regimes would result in different food conditions and geese responses. The results showed that the food quality and quantity differed significantly between winters. As responses to the high‐quantity/low‐quality food during 2016/2017, more geese switched to feeding on mudflat and exploited plants such as dicotyledons and moss. The tall swards of Carex spp. (dominant plants in the meadow) that developed during the first growing season decreased the food accessibility during the second growing season and hindered the exploitation of newly generated shoots by the geese, which was further confirmed by our clipping control experiment. Nearly all the geese chose to feed on meadow, and Carex spp. made up the majority of their diet in 2017/2018 when there was more low‐quantity/high‐quality food. Compared with the globally vulnerable Lesser white‐fronted geese, the larger‐sized Bean geese seemed to be less susceptible to winter food shortages and exhibited more stable responses. We concluded that the food quality–quantity condition was the external factor influencing the geese responses, while morphological and physiological traits could be the internal factors causing different responses between the two species. This study enhanced the understanding of the influence that habitat change exerts on herbivorous geese in their wintering site in the context of the Three Gorges Dam operation. We suggested that regulating hydrological regime was important in terms of wetland management and species conservation.     

Diet, fecundity and egg size in some polyphagous predatory carabid beetles

Egg size was measured at different rates of egg laying in three polyphagous carabid species, known to be useful predators of cereal aphids; the small Bembidion lampros Herbst and the medium-sized Pterostichus cupreus L. and P. melanarius Illiger. Variations in fecundity, as well as the ability of the medium-sized species to also build up fat reserves, were obtained when beetles were subjected to different dietary regimes consisting of aphids, or foods with a lower or higher protein content. Egg size was found to be dependent on the rate of egg laying within a species. A diet of cereal aphids appeared to be adequate for egg production in these polyphagous carabids, but female P. cupreus were unable to build up fat reserves when they ingested aphids contaminated with the aphicide pirimicarb. Beetles were able to devote resources to more and larger eggs (B. lampros), or to larger eggs and/or fat reserves (P. melanarius/P. cupreus) when given access to a carbohydrate-rich food with low protein content. The highest rate of egg laying was obtained when female P. cupreus and P. melanarius were given a more varied diet at frequent intervals; including regular shifts between unsprayed aphids, carbohydrate-rich food and protein-rich maggots. Within the varied diet treatment a negative relationship was obtained between egg size and egg number among similar-sized individuals of P. cupreus and P. melanarius; females producing the largest number also laid the smallest eggs. Egg size affected larval survival, since first instars hatching from large eggs were found to survive longer than those hatching from small eggs. The influence of differences in food intake on reproduction, maintenance metabolism, and survival of fieldinhabiting carabids is discussed.     

A preliminary analysis of the diet composition of overwintering Bean geese (Anser fabalis) and greater white-fronted geese (A. albifrons) in Korea using PCR on fecal samples

Bean geese (Anser fabalis) and Greater white-fronted geese (Anser albifrons) are the dominant wintering waterfowl in South Korea. Although they are commonly observed in estuaries and rice fields during the winter, the diet composition of the geese during the winter has rarely been studied. In this study, we provide the results from preliminary analyses on the diet of these two geese species overwintering in Daebu Island of South Korea. We used a total of 13 fecal samples from Bean geese (n?=?4) and Greater white-fronted geese (n?=?9), and performed a BLAST search for the sequences obtained from 87 clones (n?=?36 for Bean geese and n?=?51 for Greater white-fronted geese). The diet of Bean geese consisted of five families of plants: Caryophyllaceae (75.0%), Poaceae (13.9%), Asteraceae (5.5%), Polygonaceae (2.8%) and Cucurbitacea (2.8%). On the other hand, the diet of Greater white-fronted geese consisted of 6 families of plants: Poaceae (74.5%), Caryophyllaceae (9.8%), Solanacea (5.9%), Portulacaceae (3.9%), Lamiaceae (3.9%) and Brassicaceae (2.0%). We found that plants of the rice family (Poaceae) are important in the diet of wintering geese, especially for Greater white-fronted geese. This knowledge can be used to establish conservation strategies of the geese overwintering in South Korea.     

Vegetation growth and a seasonal habitat shift of the barnacle goose (Branta leucopsis)

Summary Barnacle geese (Branta leucopsis) wintering on the island of Schiermonnikoog in the Netherlands abruptly switch all their foraging activities from a dairy pasture (a polder) to an adjacent salt-marsh during the early spring. We present evidence to show that this shift is related to changes in the quality of the diet available in these different habitats. Barnacle geese shift from polder to salt-marsh at the precise time that these are equal in dietary protein availability, which occurs as the food plants on the salt-marsh undergo a sudden spring growth. The dairy pasture undergoes its own spring growth shortly afterwards, and more dietary protein is available there for the rest of the year. We suggest that the salt-marsh is a more preferred habitat, but that low dietary protein during the winter prevents its use by barnacle geese. We hypothesize that the salt-marsh may be more preferred due to a lower level of disturbance which permits geese to graze more slowly, improving the utilization of food plants.     

Nutrient limitation and plant species composition in temperate salt marshes

Addition of inorganic nitrogen, phosphorus and potassium in a factorial design in two ungrazed Wadden-Sea salt marshes at low and high elevations showed that nitrogen was the limiting nutrient. No effects of nutrient addition were detected in the 1st year, probably due to a considerable rainfall deficit during the growing season. In the 2nd year, which was more humid, only nitrogen addition caused significant effects in both the low salt marsh dominated by Puccinellia maritima and the high marsh dominated by Festuca rubra. No two-way or three-way interactions with phosphorus or potassium were found. In the low marsh, nitrogen addition had a negative effect on the biomass of Puccinellia, but a positive effect on the biomass of Suaeda maritima and on the total above-ground biomass. Puccinellia was replaced by Suaeda after nitrogen addition, due to shading. In the high salt marsh, no significant effects of fertilizer application on total above-ground biomass were found, due to the weak response of the dominant species Festuca rubra, which accounted for 95% of total biomass. The biomass of Spergularia maritima increased, however, as a response to nitrogen addition.The shoot length of Festuca was positively affected by nitrogen fertilization. It is suggested that stands of Festuca reached maximal biomass at the study site without fertilization and that its growth was probably limited by self-shading. Received: 22 September 1996 / Accepted: 5 April 1997     

Annual changes in body mass in captive Svalbard ptarmigan: role of changes in locomotor activity and food intake

The influence of changes in the amount of locomotor activity on the annual body mass cycle was investigated in captive Svalbard ptarmigan kept indoors at thermoneutrality and exposed to seasonal changes in daylength or continuous light from the summer onwards. In both groups there was a close correlation between locomotor activity and metabolic rate. Only birds exposed to changes in daylength showed an annual cycle in locomotor activity, with low activity in autumn and mid-winter and a peak in spring. The birds permanently exposed to continuous light had a relatively low activity throughout the year with no systematical changes. Body mass began to increase in both groups in early autumn and the food intake was elevated during most of the following fattening period. It is concluded that elevated food intake is the prime factor involved in autumnal fattening in captive Svalbard ptarmigan. Body mass increased significantly faster under decreasing daylength compared with continuous light, associated with a lower activity as well as a higher food intake. The birds exposed to continuous light maintained a high body mass and a relatively low activity level during spring. In birds exposed to changing daylength, body mass fell from late February onwards, which is about 3 months later than in outdoor caged or free-living Svalbard ptarmigan. In the birds exposed to increasing daylength a fourfold increase in the amount of locomotor activity occurred from February to April. This increased activity was correlated with a negative energy balance and may be casually associated with the fall in body mass in these birds. Under outdoor conditions, elevated locomotor activity in spring may be responsible for a continuation of the decline in body mass commencing in November, despite a slight tendency for an increased food intake towards the end of this period.Abbreviations BM body mass - CE _f caloric equivalent of food - EAE energy assimilation efficiency - EE energy expenditure - FI food intake - LA locomotor activity - LL continuous light - LD simulated annual changes in daylength - MEI metabolizable energy intake - MR metabolic rate - RQ respiratory quotient     

The response of Puccinellia maritima to burial: A key to understanding its role in salt‐marsh dynamics?

Abstract. The plant and sediment dynamics in salt marshes are strongly interrelated, but few data are available to document their interaction. Puccinellia maritima is a perennial grass that occurs widely in salt marshes and this study examines its role in the stabilization or trapping of sediment in the pioneer zone and its response to burial, a characteristic phenomenon in accreting salt marshes. Puccinellia not only appears to limit erosion but also to significantly enhance accretion. The functional role of this species is largely dependent on the local disturbance regime. The response of Puccinellia to burial was studied in a series of burial treatments. Growth performance of Puccinellia was stimulated by burial of 4 mm sediment and reduced by burial of 8 mm/month. Burial under 12 mm of sediment led to high mortality of up to 97%. Response was determined by the instantaneous thickness of sediment rather than by the total quantity. Morphological response to burial consisted mainly of stem elongation. Plants collected from accretion zones in the field also produced tillers with adventitious roots at successive soil layers. The range of burial tolerances found for Puccinellia fits well with its occurrence in locations with up to 8 mm sediment accretion per tidal cycle, a common situation in the salt marsh studied.     

Patch choice of avian herbivores along a migration trajectory–From Temperate to Arctic

Migratory waterfowl species seem to track temporal and spatial pulses of optimal forage availability on their way from temperate wintering to arctic breeding sites. In order to unravel the relative contribution of forage quality and forage biomass to foraging choices in avian herbivores, we experimentally manipulated biomass and quality of main forage plants through fertilisation and grazing exclusion at three sites along the flyway of barnacle geese, Branta leucopsis. Fertilisation increased the nitrogen content of the forage and grazing exclusion increased biomass levels. Manipulated plots were offered to wild geese in a random block experimental design and goose visitation was measured through dropping counts. At all sites there was a trend towards a higher preference of plots with increased quality and average biomass above plots with an average quality and increased biomass. Generally, geese preferred plots with highest standing crop of nitrogen. The numerical response of the geese to forage changes was supported by behavioural observations at the Baltic site. We conclude that for migrating barnacle geese the bottlenecks in the standing crop of nitrogen appear to lie in the limited biomass availability at the Baltic stopover site and the limited nutrient content of food in the Arctic breeding site, restricting the potential nutrient intake on these sites.     

Efflux of Potassium from Wheat Roots Induced by Changes in the Water Potential of the Root Medium

Growth of Plantago major L., ssp. major L. and ssp. pleiosperma Pilger and P. maritime L. was followed at two levels of mineral nutrition (low-salt and high-salt). In addition the response of transfer of plants from low-salt conditions to high-salt conditions and vice versa was studied. Growth of the studied Plantago species was strongly stimulated by high-salt conditions. The Ca²⁺- and Mg²⁺-stimulated ATPase activity of microsomal preparations of the roots was also studied. In P. major ssp. major and P. maritime a major pH optimum was observed at pH 6.5, and in addition a second pH optimum was found at pH 8.0. High-salt plants of these two species were characterized by biphasic stimulation curves for Ca²⁺ and Mg²⁺, whereas P. major ssp. pleiosperma showed a monophasic pattern. The ATPase activity per g dry weight of P. major and P. maritima was highest in high-salt plants. The species investigated here are adapted to relatively nutrient-rich conditions, and the properties of ATPases (K_m, K_max, protein content) and the growth responses are discussed in relation to this ecological property.     

The nature of plant adaptations to salinity stress has trophic consequences

In different ecosystems herbivores highly prefer particular plant species. This is often explained in a stoichiometric framework of nutrient‐based plant adaptations to herbivory. We hypothesize that such super‐palatability can also arise as an evolutionary by‐product of osmoregulatory adaptations of plants to stressful environmental conditions, as salinity, drought and cold. Here, we investigate in a coastal salt marsh why some plant species are highly preferred by migratory brent geese Branta bernicla bernicla in spring while others are avoided. This salt marsh is an important spring staging site for the geese. Sufficient energy storage in a short period is critical to enable their northward migration to Siberia and subsequent reproduction. We test if geese prefer plants that balance their internal osmotic potential with the saline environment through energy‐rich soluble sugars over plant species that use (compartmentalized) salts for this. We find that plant nitrogen and acid detergent fiber content, classic predictors of herbivore preferences, poorly explain which plants the geese prefer. Instead, plant species that are highly preferred by the geese adapt to salinity by high soluble sugar concentrations while avoided species do this by high plant salt concentrations. Thus, the type of osmoregulatory adaptation to stress displayed by different plant species is a good predictor for the food preference of geese on this salt marsh. We suggest that variation in other types of osmoregulation‐based stress adaptations, as plant cold adaptations in tundras and plant drought adaptations in savannas, have similar important consequences for trophic interactions.     

Utilisation of Wadden Sea salt marshes by geese in relation to livestock grazing

To arctic breeding geese, the salt marshes of the International Wadden Sea are important spring staging areas. Many of these marshes have always been grazed with livestock (mainly cattle and sheep). To evaluate the influence of livestock grazing on composition and structure of salt-marsh communities and its consequences for habitat use by geese, a total of 17 pairs of grazed and ungrazed marshes were visited both in April and May 1999, and the accumulated grazing pressure by geese was estimated using dropping counts. Observed grazing pressure was related to management status and to relevant vegetation parameters.The intensity of livestock grazing influences the vegetation on the marsh. Salt marshes that are not grazed by livestock are characterised by stands with a taller canopy, a lower cover of grasses preferred by geese, and a higher cover of plants that are not preferred.Overall goose-dropping densities are significantly lower in ungrazed marshes compared to marshes grazed by livestock. Some ungrazed marshes had comparatively high goose grazing pressure, and these were all natural marshes on a sandy soil, or artificial mainland marshes with a recent history of intensive livestock grazing. Goose grazing is associated with a short canopy. The plant communities with short canopy, dominated by Agrostis stolonifera, Festuca rubra and Puccinellia maritima, together account for 85% of all goose droppings in our data.The sites that were not visited by geese differed very little from those that were visited, in the parameters we measured. This might indicate that there was no shortage of available habitat for spring staging geese in the Wadden Sea, in the study period.     

Interactions between hare and brent goose in a salt marsh system; evidence for food competition?

In this study we accumulate evidence that brown hare competes with brent goose for food resources in a temperate salt marsh. We show that both species overlap in habitat use and share food plants. The two herbivores mainly used the common habitat at different times of the day, with hares active in the dark and geese during the daylight. During the morning and evening, however, the habitat was exploited simultaneously. Food availability was manipulated by excluding brent geese on both small-scale (30 m²) and large-scale (0.96 ha) plots, while hares had free access everywhere. Exclusion of brent geese enhanced the level of utilisation by hares in both Festuca and Puccinellia dominated marshes, which are among the most intensively grazed parts of the salt marsh. The increase in hare grazing pressure following goose exclusion was stronger, when the adjacent control plots had attracted more goose visitation. When geese were excluded, the decrease in Festuca consumption by geese was completely matched by increased hare grazing, while for Puccinellia only part of the `surplus' was harvested. Enhanced levels of hare utilisation were not due to geese interfering directly with hare, nor due to hares avoiding goose droppings. Considering the interaction from the other perspective, hares were observed to disturb geese effectively in every spring. This might have reduced exploitation by geese of the shared resources. On the basis of our experimental results, we conclude that in this salt- marsh system competition for food with brent geese plays a role in the habitat use of hares, and that hares can reduce goose exploitation of shared habitats. Received: 30 March 1998 / Accepted: 6 July 1998     

Kulturverfahren zur Bestimmung der Salz- und Über-flutungsverträglichkeit vonPuccinellia spp. (Gramineae)

In the ecology ofPuccinellia species (P. maritima, P. distans, P. retroflexa andP. limosa of the German flora described to date) two environmental factors seem to be very important: the salinity of the soil or of the tidal sea water and, especially in regard toP. maritima, the periodical inundation during the tidal cycle. The latter species forms an important community (Puccinellietum maritimae) a few decimetres above the middle tide level. The other species seem to be specialized to localities of higher levels. Some 450 natural localities covered withP. maritima on the western coasts of Schleswig-Holstein (W. Germany) have been analysed with respect to the type of plant community, dominance ofP. maritima, frequency of inundations, level above or below middle tide level, and soil factors (for instance: Cl-ion content, electrical conductivity, pH, clay content, etc.). Physiological experiments have been carried out in greenhouses, experimental grounds, and culture-rooms to test the effects onP. maritima (number 57 from the optimal level within the Puccinellietum maritimae of the banks of the River Eider) of soil composition, light intensity and daylength, temperature, inundation, etc.P. maritima grows with long creeping stolons at daylengths of 16 hrs and more; it forms a caespitose tufted plant at daylengths of 12 hrs and less (light intensity: 10,000 lux and more). Optimal growth occurs between 17° and 23° C and under conditions of artificial flooding up to soil surface twice a day (for about 10 minutes) by artificial sea water of 25 ‰ S. Two culture techniques have been developed for testing growth and survival after 8 weeks under greenhouse conditions (20° C or more; 10,000 lux or more; 15 hrs daylength or more, after comparable pre-cultivation over 8 weeks under 12 hrs day and artificial light conditions; sand + 3 % peat). The first technique has been used for testing salt tolerances between 0 and 60 ‰ S (artificial sea water), the second for testing inundation tolerances (0–2.5 hrs inundation twice a day; artificial sea water of 25 ‰ S). Considering different proveniences ofPuccinellia species on German coasts, it became clear thatPuccinellia exhibits broader ecological and morphological than taxonomical variabilities. WithinP. maritima, for example, several ecological types can be separated. This finding indicates the possibility of isolating different ecological types for specific localities in land reclamation areas.