Vegetational changes and human presence in the low-alpine and subalpine zone in Val Febbraro,upper Valle di Spluga (Italian central Alps), from the Neolithic to the Roman period

An interdisciplinary palaeoecological study in the low-alpine and subalpine zones of Val Febbraro, upper Valle di Spluga (Italy), between 1830 and 2304 m a.s.l., suggests the temporary presence of early Neolithic groups at about 6000 uncal b.p. Evidence for local woodland clearance and charcoal dust were found. Phases of woodland and treeline disturbances, and indications of increased human presence are evident at about 5500, 5100, and 4000 b.p. A marked increase in disturbance, mainly related to pasturing, is dated to the beginning of the Bronze Age. The last major stage of human impact on the vegetation coincides with the Final Bronze phase and the beginning of the Iron Age, with a small temporary reduction during the Roman period. ¹⁴C dated archaeological sites and finds are broadly concordant with the phases of human impact on the vegetation. A summary figure is presented. No locally significant climatic changes have been traced during the last 6000 years, and if present, they are probably overshadowed by the vegetational changes caused by human activity. Communicated by F. Bittmann     

Growth,chemical composition,and nitrate reductase activity of Rumex species in relation to form and level of N supply

Growth, chemical composition, and nitrate reductase activity (NRA) of hydroponically cultured Rumex crispus, R. palustris, R. acetosa, and R. maritimus were studied in relation to form (NH₄ ⁺, NO₃ ^-, or both) and level of N supply (4 mM N, and zero-N following a period of 4mM N). A distinct preference for either NH₄ ⁺ or NO₃ ^- could not be established. All species were characterized by a very efficient uptake and utilization of N, irrespective of N source, as evident from high concentrations of organic N in the tissues and concurrent excessive accumulations of free NO₃ ^- and free NH₄ ⁺. Especially the accumulation of free NH₄ ⁺ was unusually large. Generally, relative growth rate (RGR) was highest with a combination of NH₄ ⁺ and NO₃ ^-. Compared to mixed N supply, RGR of NO₃ ^-- and NH₄ ⁺-grown plants declined on average 3% and 9%, respectively. Lowest RGR with NH₄ ⁺ supply probably resulted from direct or indirect toxicity effects associated with high NH₄ ⁺ and/or low Ca²⁺ contents of tissues. NRA in NO₃ ^- and NH₄NO₃ plants was very similar with maxima in the leaves of ca 40 μmol NO₂ ^- g^-1 DW h^-1. ‘Basal’ NRA levels in shoot tissues of NH₄ ⁺ plants appeared relatively high with maxima in the leaves of ca 20 μmol NO₂ ^- g^-1 DW h^-1. Carboxylate to organic N ratios, (C-A)/N_org, on a whole plant basis varied from 0.2 in NH₄ ⁺ plants to 0.9 in NO₃ ^- plants. After withdrawal of N, all accumulated NO₃ ^- and NH₄ ⁺ was assimilated into organic N and the organic N redistributed on a large scale. NRA rapidly declined to similar low levels, irrespective of previous N source. Shoot/root ratios of -N plants were 50–80% lower than those from +N plants. In comparison with +N, RGR of -N plants did not decline to a large extent, decreasing by only 15% in -NH₄ ⁺ plants due to very high initial organic-N contents. N-deprived plants all exhibited an excess cation over anion uptake (net proton efflux), and whole-plant (C-A)/N_org ratios increased to values around unity. Possible difficulties in interpreting the (C-A)/N_org ratio and NRA of plants in their natural habitats are briefly discussed.     

The relationship between the digestive enzymes in arctic char,Salvelinus alpinus (Salmonidae,Osteichthyes) and its ability to survive in extreme environments

Digestive enzymes of chars from seven Austrian lakes have been studied. Trypsin activity ml⁻¹ fluid is proportional to body size but inversely proportional to the amount of food in the digestive tract. The pancreas appears to secrete trypsin ± continuously and the activity measureable in the intestinal fluid seems to depend largely on the gut passage rate. There is no seasonal rhythm of enzyme activity. Amylase activity is very weak. Pepsin activity seems to depend mostly on the dilution of the gastric juice. The results indicate that the steering mechanisms of digestive enzymes in salmonidae are well distinct from other families. This work was part of a PH. D. thesis (Reimer, 1984). This work was part of a PH. D. thesis (Reimer, 1984).     

Sacciform cells in the epidermis of the brown trout,Salmo trutta,and the Arctic char,Salvetinus alpinus

Summary Sacciform cells containing an acidophilic, proteinaceous secretion, were identified in the epidermis of the brown trout and Arctic char. This cell type increased in number during the chronic stages of infestation by the ectoparasitic flagellate, Ichthyobodo sp., in immature brown trout, and decreased during sexual maturation in male brown trout and char. It is suggested that the salmonid sacciform cell produces a secretion which protects the fish against infestation or damage by skin parasites.     

Pollen-derived history of timber exploitation from the Roman period onwards in the Romanche valley, central French Alps

The history of forestry in the Romanche river valley, south-east of Grenoble, France, is reconstructed for the past ca. 3000 years on the basis of detailed pollen analysis and AMS¹⁴C dating. Three deforestation phases are recorded during the last two millennia, each phase showing different features and also contrasting woodland succession in the post-clearance period. The first major deforestation is recorded at the Roman time whenAbies alba (fir) was selectively exploited, presumably for use by peoples living downstream of the site. Apart from the deforestation, there appears to have been little human activity in the vicinity of the site at this time. After the clearance fir gradually, and more or less fully, recovered. The second deforestation phase occurred in ca. the 5^th and 6^th century A.D. when there is also substantial evidence for local farming. At this time, both fir and beech (Fagus sylvatica) were non-selectively exploited and probably used locally. Beach subsequently recovers but there is no further regeneration of fir. The third deforestation phase in ca. the 12^th century A.D. is similar to the preceding phase but this time beech does not recover. With the decline in human activity, secondary forest that included spruce (Picea) and pine (Pinus), developed. Forest dynamics were controlled by local human activity and also the economic relationships between the local area and the wider region and especially the region downstream from the site.     

Acid stress in Rumex hydrolapathum (Polygonaceae) and its influence on the phytophage Lycaena dispar (Lepidoptera; Lycaenidae)

Summary The relationship of insect growth to host condition was tested on host plants grown by hydroculture with a standard nutrient solution, but under different acidities, ranging from pH 3.5–7.5. The indirect effect of the host on the development of the phytophage was tested in the pupal stage. The host plant Rumex hydrolapathum had its highest nitrogen content in the range pH 5.5–6.5; pupal weight of Lycaena dispar was correlated with nitrogen concentration, ash weight and water content. There is a remarkable difference in element concentration between young and old leaves of the host, which varies with acidity of the rooting substrate.In this experiment a negative relationship was detected between reproduction of the phytophage and stress of the host.     

Novelties in the Festuca valesiaca group (Poaceae) from the central Alps

Due to their ploidy levels, their morphological and anatomical characters and their distribution the central alpine Festuca stricta subsp. bauzanina (2n = 8x = 56) and Festuca ovina var. guinochetii (2n = 10x = 70), both belonging to the Festuca valesiaca group, are raised to the specific level. As a new subspecies Festuca bauzanina subsp. rhaetica is described here. The taxa of the polyploid Festuca valesiaca group are morphologically, anatomically and chorologically characterised and an identification key for these taxa in the central Alps is presented.     

Reproduction,condition and food of adult arctic charr (Salvelinus alpinus,L.) in Lake Pavin (Massif Central,France)

RésuméTo determine the role and the importance of adult fish predation directly and indirectly in the food web of oligomesotrophic Lake Pavin, reproduction, condition, and feeding activity of the dominant adult chctic charr (Salvelinus alpinus, L.) were studied. Fish were caught by gillnets of different mesh sizes once a month from April to December 1992. The gonad cycle showed that the spawning period occurred between October to December. Relative fecundity is about 2509 ovules per kg of female fish and ovule mean diameter is 4.7 mm ( 0.6 mm). Seasonal variations of the sex-ratio (Max. in April = 2.67 and Min. in October=0.19) indicated the intralake migrations of females and males. The condition coefficients showed higher values for females than males; the maximum was observed in summer for both sexes and the minimum in April and in October for males and females, respectively. Low values of the condition were also observed during the spawning period. High feeding activity was recorded in spring and in December after reproduction; low feeding activity was observed in October during reproduction. Asellus aquaticus was quantitatively the dominant prey from April to September; during the sp awning period, S. alpinus consumed its own eggs, particularly in large quantity in December. Daphnia longispina was numerically the dominant prey all over the studied cycle and the electivity (Ivlev Index) of arctic charr on the latter prey ranged from +s+0.79 to +0.16. During April, more than 15 500 individuals of D. longispina per kg of fish were found in the gut contents. The selective predation of S. alpinus on benthic (A. aquatics) and zooplankton prey (D. longispina) indicated that the fish immigrate during their feeding activity from benthic/littoral to the pelagic area.Afin de d terminer le rôle et l'importance de la prédation directe et indirecte de l'omble chevalier adulte (Salvelinus alpinus, L.) dans le réseau trophique du lac Pavin, milieu oligo- mésotrophe, nous avons étudié la reproduction, deux facteurs de condition et l'activité alimentaire de ce poisson qui est l'espéce dominante dans ce lac. Les poissons ont été capturés par des filets maillants de différent vide de maille selon un pas d'échantillonnage mensuel d'avril á décembre 1992. Le cycle du développement des gonades montre que la période de reproduction se déroule entre octobre et décembre. La fécondité relative calculée est de 2509 ovules par kg de femelles et le diamétre moyen d'un ovule est de 4,7 mm ( 0,6). Les variations saisonniéres du sex-ratio (Max. en avril = 2,67 et Min. en octobre=0,19) indiquent le déplacement actif et successif des femelles et des mâles. Les variations saisonniéres des coefficients de condition indiquent une copulence plus importante des femelles par rapport aux mâles avec des valeurs maximales en été pour les deux sexes et des valeurs minimales en avril et en octobre pour les mâles et les femelles respectivement. De faibles valeurs des facteurs de condition ont été observées pendant la période de reproduction pour les deux sexes. L'activité alimentaire de l'omble chevalier est intense au printemps et au mois de décembre aprés la fraie et faible au mois d'octobre pendant la reproduction. Asellus aquaticus est, en termes de biomasse, la proie dominante d'avril á septembre. Pendant la période de reproduction, S. alpinus se nourrit de ses propres oeufs sur les zones de frayéres et en décembre la quantité d'oeufs consommée par le Salmonidé est importante. Daphnia longispina est, en termes d'abondance, la proie dominante tout au long de cette étude et l'indice d'électivité (Indice d'Ivlev) de l' ombre chevalier vis-á-vis de cette proie varie entre + 0,79 et + 0,16.De plus, au mois d'avril, plus de 15 500 D. longispina par kg de poisson ont été enregistrées dans les contenus stomacaux. La prédation sélective de S. alpinus sur des proies benthiques (A. aquaticus) et zooplanctoniques (D. longispina) indique que le poisson effectue des déplacements en fonction de son activité alimentaire de la zone littorale/benthique á la zone pélagique.     

Induction of somatic embryogenesis and embryo development in Rumex acetosella L.

Axillary buds of the dioecious plant Rumex acetosella L. were isolated and cultured in vitro. The callus tissue which developed at the basal parts of the explants displayed a high capacity for shoot formation. This morphogenetic pattern was predominant on Murashige and Skoog (MS) medium supplemented with 2% sucrose, 2.2 mgl^-1 benzylaminopurine and 0.17 mgl^-1 indole-3-acetic acid. Somatic embryogenesis was induced when the osmolality of the medium was increased by adding 6% sucrose instead of 2%, or hexitols in addition to 2% sucrose. Most of the embryogenic calli were formed on the basal parts of leaf laminae and bracts. Development and maturation was strongly promoted by transferring the tissue to a solid or liquid medium lacking benzylaminopurine and indole-3-acetic acid and supplemented with 10 mgl^-1 gibberellic acid. The embryos germinated and developed into normal rosette plants when transferred to vermiculite moistened with hormone-free, half-strength MS salt solution. The histology of successive embryogenic stages is presented.     

In vitro organogenesis in two dioecious species,Rumex acetosella L. and R. acetosa L. (Polygonaceae)

Callus cultures were established from dioecious plant species Rumex acetosella and R. acetosa, using cotyledons, hypocotyls and stem tips of aseptically germinated seedlings as primary explants. Cultures were also established from male and female R. acetosella adult plants, starting from vegetative lateral buds. Cell division was induced using a high 2,4-D concentration, while bud induction and multiplication were stimulated on a medium with high BAP/IAA ratio. Cotyledon fragments of both species produced only rhizogenic calli. Hypocotyl-derived calli of R. acetosella produced buds, while those of R. acetosa showed no bud forming response under these conditions. Bud multiplication occurred in stem tip cultures of both species and in lateral bud cultures of R. acetosella. Calli derived from male plants produced more buds than those from female. Shoots were easily rooted using IBA, and plantlets were effectively transferred to soil. Flowering was not induced in culture. The sex of regenerated male and female plants was not altered by the culture conditions.     

Middle to Late Holocene vegetation history of the Upper Engadine (Swiss Alps): the role of man and fire

To reconstruct the vegetation and fire history of the Upper Engadine, two continuous sediment cores from Lej da Champfèr and Lej da San Murezzan (Upper Engadine Valley, southeastern Switzerland) were analysed for pollen, plant macrofossils, charcoal and kerogen. The chronologies of the cores are based on 38 radiocarbon dates. Pollen and macrofossil data suggest a rapid afforestation with Betula, Pinus sylvestris, Pinus cembra, and Larix decidua after the retreat of the glaciers from the lake catchments 11,000 cal years ago. This vegetation type persisted until ca. 7300 cal b.p. (5350 b.c.) when Picea replaced Pinus cembra. Pollen indicative of human impact suggests that in this high-mountain region of the central Alps strong anthropogenic activities began during the Early Bronze Age (3900 cal b.p., 1950 b.c.). Local human settlements led to vegetational changes, promoting the expansion of Larix decidua and Alnus viridis. In the case of Larix, continuing land use and especially grazing after fire led to the formation of Larix meadows. The expansion of Alnus viridis was directly induced by fire, as evidenced by time-series analysis. Subsequently, the process of forest conversion into open landscapes continued for millennia and reached its maximum at the end of the Middle Ages at around 500 cal b.p. (a.d. 1450).     

Endogenous cytokinins in the vegetative and reproductive phases of development in the dioecious plant Rumex acetosella L.

The content of endogenous cytokinins has been analysed in leaf and inflorescence extracts of male and female R. acetosella plants, using gas chromatography. Plant parts were extracted at four stages of development: leaves of juvenile plants, leaves of adult plants at the time of flower initiation and in full bloom, and upper internodes of the inflorescence stalks. Cytokinins with characteristics similar to isopentenyl adenine and adenosin, zeatin, zeatin riboside, and a bound form of zeatin, were all found in the extracts. The total amount of cytokinins was higher in female than in male plants during all these stages.Reprint requests     

A Far East Moina,M. weismanni Ishikawa, 1896 found in an Italian ricefield

The study of heleoplankton samples collected in an experimental ricefield in the province of Reggio Emilia (Northern Italy) evidenced a successional pattern of cladoceran species, characterized by the dominance of Moinidae in the early phase the rice cultivation (from May to July). In particular a species new for Italy,Monia weismanni Ishikawa, 1896, typical of Far East ricefields, was found; it was probably introduced into Italy with seeds and constitutes a stable element of the heleoplankton biocoenosis. The population co-occurs withMoina brachiata, Moina affinis, andMoina micrura in the ricefield. In this short noteM. weismanni is described, pointing out the morphological differences with other populations of the same species and with similar species; furthermore, life cycles in Moinidae are analysed in comparison with those of the other dominant cladocerans.     

A genetic contribution to the taxonomy ofOenothera sect.Oenothera (including subsectionsEuoenothera,Emersonia, Raimannia andMunzia)

Based on an analysis of results from experimental hybridization, the plants assigned byMunz toOenothera subg.Oenothera and subg.Raimannia, now divided into approximately 76 species, are referred to a single section,Oenothera. This section is in turn divided into five subsections:Euoenothera, Munzia, Raimannia, Emersonia, and an undescribed group of three species related toOenothera pubescens. Euoenothera is maintained in the traditional sense, and includes about 14 species of North America, widely naturalized elsewhere.Munzia consists of 45 species, comprising three series, and native to South America.Raimannia is restricted to a group of approximately 11 North American species.Emersonia comprises four rather heterogenous species of northern Mexico and southern New Mexico, of whichOenothera macrosceles, O. maysillesii, andO. organensis have been described. Within these four subsections, interspecific hybrids can be made in general, although plastid differentiation often leads to incompatibilities. With varying degrees of difficulty, hybrids were produced in all intersectional combinations involvingEuoenothera, Emersonia, Munzia, andRaimannia, the most difficult being those betweenEmersonia andRaimannia. Based on their habit and distribution,Emersonia species, and especiallyOenothera maysillesii, appear to resemble most closely the common ancestor of the section,Euoenothera andMunzia to have been derived from it or its common ancestor, andRaimannia perhaps to be more closely related to the phylogenetic branch that leads toEuoenothera.     

Climatic signals in tree ring of Picea schrenkiana along an altitudinal gradient in the central Tianshan Mountains, northwestern China

Tree-ring samples of Picea schrenkiana (Fisch. et Mey) were studied along an altitudinal gradient in the central Tianshan Mountains, and ring-width chronologies were developed for three sites at different altitudes: low-forest border (1600–1700 m a.s.l.), interior forest (2100–2200 m a.s.l.), and upper treeline (2600–2700 m a.s.l.). Annual ring-width variations were similar among the three sites but variability was greatest at the low-forest border site. The statistical characters of the chronologies showed that mean sensitivity (MS) and standard deviation (SD) decreased with increasing elevation. In other words, the response of tree growth to environmental changes decreased with increasing altitude. To understand the differing response of trees at different elevations to the environmental changes, response function analysis was used to study the relationships between tree-ring widths and mean monthly temperature and total monthly precipitation from 1961 to 2000. The results showed that precipitation was the most important factor limiting tree radial growth in the arid central Tianshan Mountains, precipitation in August of the prior growth year played an important role on tree's radial growth across the entire altitudinal gradient even at the cold, high-elevation treeline site. It is expected that with increasing altitude air temperature decreased and precipitation increased, the importance of precipitation on tree growth decreased, and the response of tree growth to environmental changes decreased, too. This conclusion may be helpful to understand and research the relationship between climatic change and tree growth in arid and semiarid area.     

A contribution to the explanation of the larch bud moth cycle,the polymorphic fitness hypothesis

Studies of fluctuating insect populations generally discuss the regulating processes at high insect numbers, but very rarely why a cycling population at low densities switches immediately from the declining phase to the increasing phase of the cycle. A long-term study of the larch bud moth (Zeiraphera diniana Gn) has suggested that the key to recovery is assortative mating of specific phenotypes. Z. diniana exhibits distinct host races living either on the deciduous larch or evergreen pines and spruces. As an adaptation to its hosts Z. diniana is necessarily rather polymorphic in its life history parameters, i.e. developmental rate, fertility and survival. Apart from the direct association of the larva with the host tree, the colouration of the mature larva provides the only readily apparent trait by which the host race can be recognised; the larch form is black and the pine or spruce form has a light orange head capsule, anal plate and body colour. Evidence that frequencies of the colour morphs on larch regularly change from an intermediate colour type to black during the increasing phase of the cycle suggests that the combination of traits, such as earliest larval emergence, largest body size and homozygosity, characteristic of the black morph, constitutes the inherent driving force of population increase.     

Plant diversity in Lythrum,Phragmites, and Typhamarshes,Massachusetts, U.S.A.

Concern about colonization of marshesby plant species such as Phragmites australisand Lythrum salicariahas highlighted the needfor management strategies. However, there is a lack ofinformation in the literature on which to base thesedecisions. This study compares the alpha diversity ofmarshes to assess the impact of invasion by Phragmitesand Lythrum. Species occurrence andstem density were measured in marshes dominated by Phragmites, Lythrum, Typhaspp., or otherherbaceous perennials in the Charles River watershedin eastern Massachusetts, USA, and species richness,Shannon's H, Simpson's reciprocal (1/D), and Pielou'sJ were compared among six community types. The threediversity indices had significantly higher values forTypha-Lythrummarshes than for any of the othermarsh types (Tukey test, p< 0.05), with mean values(± s.d.) of H = 2.00 ± 0.74, 1/D = 3.51± 1.68 and J = 0.69 ± 0.1. Marshes dominatedby Phragmiteshad the lowest diversity, with H= 0 and D = 1, i.e. they were monospecific. Typhadominated marshes had the second lowest values,with H = 0.17 ± 0.05, 1/D = 1.05 ± 0.01, andJ = 0.11 ± 0.03. These results support the ideathat a reduction in diversity can be expected inmarshes colonized by Phragmites. However, thehigh diversity found in the Typha-Lythrummarshes contradicts the expectation of lower diversityafter invasion by Lythrum. This information mayalter marsh management decisions.     

A new florally dimorphic hexaploid, Echinocereus yavapaiensis sp. nov. (section Triglochidiatus, Cactaceae) from central Arizona

A florally dimorphic hexaploid (n=33), Echinocereus yavapaiensis M. A. Baker, is newly described and possesses the highest number of chromosomes known within the genus. Populations of E. yavapaiensis occur in central Arizona between 1025 and 1860 m elevation and are associated with volcanic bedrock. Fifty three percent of the individuals studied produce only pollen-sterile flowers, which fail to undergo meiosis within the microspore mother cells, while 47% develop only pollen-fertile flowers. Chromosome determinations are presented for 41 populations of Echinocereus, including E. arizonicus (n=11), E. canyonensis (n=22), E. coccineus (n=22), E. matudae (n=11), E. pacificus (n=22), E. mombergerianus (n=22), E. santaritensis (n=22), and E. yavapaiensis. A phenetic analysis compares morphological variability among populations of E. yavapaiensis to those of its closest allies.     

The relative contribution of symbiotic N2 fixation and other nitrogen sources to grassland ecosystems along an altitudinal gradient in the Alps

The significance of symbiotic N₂ fixation in legumes (Trifolium alpinum L., T. nivale Sieber, T. pratense L., T. badium Schreber, T. thalii Vill., T. repens L., Lotus alpinus [DC.] Schleicher, L. corniculatus L., Vicia sativa L.) and other N sources for the N budget of grassland ecosystems was studied along an altitudinal gradient in the Swiss Alps. The total annual symbiotic N₂ fixation was compared with other sources of N for plant growth of the total plant community (mineralisation and wet deposition). The contribution of symbiotically fixed N to total above-ground N yield of the swards decreased from at least 16% to 9% with increasing altitude where legumes were present. This decrease was due to a decrease in the yield proportion of legumes from 15% at 900 and 1380 m a.s.l. to 5% at 2100 and 2300 m a.s.l. (no legumes were found above 2750 m a.s.l.) and not to a decline in the activity of symbiotic N₂ fixation. With increasing altitude legumes are more patchily distributed. The high symbiotic N₂ fixation of individual plants up to their altitudinal limit is not primarily the result of low mineral N availability since an addition of NH₄ ⁺ or NO₃ ⁻ fertiliser at 2300 m a.s.l. led either to no decrease or only to a minor decrease in symbiotic N₂ fixation. At 1380 m a.s.l., N mineralisation (13.45 g N m⁻² yr⁻¹) appeared to be the main source of N for growth of the sward; N from symbiosis (at least 1.0 g to 2.6 g N m⁻² yr⁻¹) and wet deposition (0.4 g to 0.6 g m⁻² yr⁻¹) was not a significant N source for plant growth at this altitude. At 2100 m a.s.l., the combined amounts of N from symbiotic N₂ fixation (at least 0.1 g N m⁻² yr⁻¹) and wet deposition (0.3 g N m⁻² yr⁻¹) appeared to be similarly important for plant growth as soil N mineralisation (0.47 g N m⁻² yr⁻¹). At high altitudes, wet N deposition and symbiotic N₂ fixation together represent a significant source of N for the grassland ecosystem while at low altitudes these N inputs appear to be much less important. This revised version was published online in June 2006 with corrections to the Cover Date.     

A serological contribution to the systematics of the genusLupinus (Fabaceae)

The immunological comparison of the seed reserve proteins suggests thatLupinus is a natural genus, the American and the Euro-African species belonging to the same stock. Among the Lupines of the Old World, the smooth-seeded and the rough-seeded species from two natural segregates. The genusLupinus is serologically related to the rest of theGenisteae and to the AsiaticSophoreae rather than to AmericanSophoreae andThermopsideae. The data suggest thatLupinus may have originated with the remainder of theGenisteae from primitiveSophoreae of temperate-subtropical Asia. America and the Mediterranean-African region are regarded as secondary centres of speciation.