bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumor volume of colon carcinoma is related to the invasive pattern but not to the expression of cell adhesion proteins
Authors: HAHN‐STRÖMBERG VICTORIA , EDVARDSSON HENRIK , BODIN LENNART , FRANZEÉN LENNART
Published: February 2009

Tumor volume increases during growth and due to tumor progression various mutations appear that may cause phenotypic changes. The invasive pattern may thus be affected resulting in a more disorganized growth. This phenomenon might be due to mutations in the genome of the adhesion proteins, which are responsible for the structural integrity of epithelial tissue. Tumor volume was assessed in whole mount sections of 33 colon carcinomas using Cavalieri's principle. Images from the entire invasive border were captured and used for calculating the irregularity of the border (Complexity Index). The expression of the adhesion proteins E‐cadherin, β‐catenin, Claudin 2 and Occludin was assessed after immunohistochemical staining of two randomly selected areas of the invasive front of the tumor. Statistical significance for differences in volume was obtained for tumor Complexity Index, tumor stage (pT) and lymph node status (pN). Expression of adhesion proteins was significantly perturbed in the tumors compared with normal mucosa but only infrequently correlated to tumor differentiation or invasive pattern. The results show that when tumor volume increases the invasive pattern becomes more irregular which is compatible with tumor progression. A direct contribution of adhesion protein derangement to this process appears to be insignificant.
High individual repeatability and population differentiation in stable isotope ratios in winter‐grown collared flycatcher Ficedula albicollis feathers
Authors: Hjernquist Mårten B. , Veen Thor , Font Laura , Klaassen Marcel
Published: February 2009

For migrants, we often lack complete information of their spatial distribution year round. Here, we used stable carbon, nitrogen and hydrogen isotope ratios extracted from feathers grown at the wintering sites of the long‐distance migratory collared flycatcher Ficedula albicollis, to study how individuals from different breeding populations are distributed at the wintering sites. A sub‐sample of birds was also sampled in two consecutive years to test for the repeatability of isotope ratios. Birds from the same breeding populations had more similar isotope ratios compared to birds from other nearby populations (10–100 km apart). Furthermore, isotope repeatability within individuals was high, implying that the observed pattern of isotope variation is consistent between years. We put forward two hypotheses for these patterns; 1) strong wintering site philopatry and migratory connectivity, suggesting that migratory connectivity may potentially be found on a much smaller spatial scale than previously considered, and 2) consistent interpopulation differentiation of feeding ecology at their wintering site.
The role of competition and rarity in the restoration of a dry grassland in Finland
Authors: Tikka Päivi M. , Heikkilä Tuula , Heiskanen Mira , Kuitunen Markku
Published: February 2009

Abstract. Semi‐natural grasslands have become scarce throughout Europe. Preservation of their plant species requires either the maintenance of the existing grasslands or the creation of new ones. To study the establishment and regeneration ability of plant species typical of dry grasslands we laid out an experiment on a former arable field in central Finland. We compared the success of 13 grassland species both in a theoretical situation with minimal competition and in competition with weeds. More than half of the species used were regionally rare. As a group, grassland plants reached the highest cover in the experimental plots in which outside competition was minimised by weeding. However, the total cover achieved by their sward remained as low as 60% in the third growing season. The ability of grassland plants to regenerate and disperse on a small scale was therefore considered to be moderately poor. The short‐living species that were rare in the region where the study took place also had the greatest difficulties in establishment and survival in the experimental field. The preservation of rare species ‐ i.e. those species in the most urgent need of protection ‐ therefore appears to be difficult to achieve by habitat creation. Efforts should primarily be directed towards the maintenance of those habitats into which they have spread and become established naturally.
Management impacts on vegetation dynamics of hyper‐eutrophicated fields at Berlin, Germany
Authors: Rebele Franz
Published: February 2009

Abstract. This paper reports on vegetation dynamics on terrestrial, temperate grassland sites at the upper range of the productivity scale, i.e. on abandoned sewage fields (fields once used for waste water disposal) at Berlin‐Blankenfelde, Germany. I studied regeneration and the influence of different management practices (removal of top soil and mowing in late summer). Changes in species composition and cover were followed on permanent plots of 2m × 2m size through five years of vegetation development. At the outset of the experiment the abandoned fields were dominated by dense Urtica dioica /Elymus repens stands. Species richness was 7 species/ 4m2, and it remained low on unmanaged plots during the time of observation (7.6 species/plot in year 5). Removal of 20 cm of top soil caused a severe decline of Urtica and a large increase in species richness (21 species in year 1 after disturbance). Mowing was slightly higher compared with unmown plots on both initially excavated and unexcavated plots. Total cover was always near 100 % (except immediately after top soil removal). Colonization of bare soil was very rapid and in late summer of the first year after disturbance cover already increased towards 100%. On all plots the vegetation was mostly dominated by perennial herbs and grasses. Winter season gaps are occupied by Galium aparine, a large‐seeded annual scrambling climber. Monocarpic perennials behaved as winter annuals in most cases. Woody species were inhibited by dense above‐ground biomass and litter cover. The paper questions whether succession on abandoned sewage fields may proceed towards a woodland stage and advises how vegetation of such hyper‐eutrophicated sites can be managed towards higher diversity.
Succession during the re‐creation of a flood‐meadow 1985‐1999
Authors: McDonald Alison W.
Published: February 2009

Abstract. The study site, Somerford Mead, is located on the river Thames floodplain and was a species‐rich flood‐meadow in the 1950s. In the 1960s and 1970s it was subjected to intensive grassland management with regular NPK additions and occasional herbicide treatment. In 1981 Somerford Mead was ploughed for the first time and converted to arable land. Seeds of an Alopecuruspratensis‐Sanguisorba officinalis flood‐meadow community (MG4; Rodwell 1992) were sown onto prepared soil in the autumn of 1986, and botanical records were made from 1985 to 1999. From 1989 to 1999, three replicates of three treatments: cow‐grazing, sheep‐grazing and no‐grazing were introduced after hay‐cutting. Analysis successfully separated the establishment phase from the experimental phase and showed a significant difference between the grazed and ungrazed treatments. Abiotic and biotic factors which might contribute to successional trends are discussed. A convoluted pattern for each treatment could be attributed in part to intrinsic‘cycles’of perennial hemicryptophytes behaving as short‐lived species and in part to the percentage frequency of many species which was reduced in 1990 and 1995/1996, years of drought. After the initial inoculation of MG4 seed and the disappearance of arable therophytes, recruitment of new species was very slow. Coefficients for Somerford Mead matched against MG4 (Rodwell 1992) produced an equilibrium within three years. It subsequently fluctuated over a 10‐yr period well below the level of Oxey Mead, the donor site.

Land managers should ensure that their proposed site has the right soils and hydrology for MG4 grassland and that traditional management of hay‐cutting and aftermath grazing is practised. Only one cut a year in July could lead to a reduction in percentage frequency of most species except Arrhenatherum elatius.
Light distribution in mesic grasslands: Spatial patterns and temporal dynamics
Authors: Derner Justin D. , Wu X. Ben
Published: February 2009

Abstract.Spatial patterns and temporal dynamics of light distribution were investigated using lacunarity analysis, a multi‐scale measure of spatial heterogeneity, in three mesic grasslands with different disturbance regimes. Frequency distributions of relative light intensity (RLI) were similar for the two non‐disturbed grasslands, despite different composition (forbs vs. caespitose grass) resulting from different historical disturbance regimes prior to 1985, and different from the annually disturbed grassland. Spatial heterogeneity of light distribution was greater at all scales in the native, annually disturbed grassland than in the two non‐disturbed grasslands. The disturbance regime affected temporal dynamics of the spatial patterns of light distribution in each grassland. The annually disturbed grassland exhibited a dramatic decrease in lacunarity (heterogeneity) from early to late April, likely the result of considerable growth of a cool‐season grass. A general decrease in lacunarity occurred in the native, non‐disturbed grassland, although the magnitude was much less than in the annually disturbed grassland. The reverted, non‐disturbed grassland did not exhibit an appreciable change in lacunarity until later in the growing season, and then only at smaller scales. Combining the frequency distribution of RLI and the lacunarity curves provided an effective approach to assess relationships between the dynamics of spatial pattern of light distribution and ecological processes as influenced by different disturbance regimes. Integrating lacunarity analysis with more traditional measurements of grassland ecosystems (plant spatial distribution and arrangement and plant species composition and architecture) may be an effective way to assess functional consequences of structural changes in grassland ecosystems.
Effect of time on the natural regeneration of salt marsh
Authors: Onaindia Miren , Albizu Isabel , Amezaga Ibone
Published: February 2009

Abstract. The effect of time on natural regeneration of two salt marshes was studied in relation to plant and edaphic factors. The study was carried out in two naturally restoring salt marshes, differing in restoration time, in Txingudi (Bay of Biscay). After 20 yr, the younger salt marsh had the same plant species richness and high species similarity as a 35 yr old salt marsh (17 and 16, respectively, similarity index = 0.9), but both sites had lower species richness and similarity than a nearby natural salt marsh (36 plant species and similarity indices of 0.45 with the 35 yr old marsh and 0.46 with the 20 yr old marsh). Plant species present in the two recovering salt marshes followed a similar distribution pattern in relation to organic matter, conductivity and moisture content although this zonation differed from the natural salt marsh. The range of edaphic factors measured was also similar, but differed from those in the natural salt marsh. The process of plant species recolonization and spatial distribution might be delayed by a low probability of species arrival and by the time need for the restoration of hydrologic and edaphic factors. This study supports the necessity of long‐term monitoring in measuring coastal salt marsh restoration.
Do life history traits predict responses to defoliation in co‐occurring prairie grasses?
Authors: Teague W.R. , Dowhower S.L.
Published: February 2009

Abstract. This study examines whether competition between the unpalatable grass Hilaria mutica and three co‐occurring, palatable grasses in a Texan mixed prairie is altered by non‐selective or selective defoliation. In this four‐year study, plants were grown in monoculture or in combination with the unpalatable Hilaria in a replacement design.

Under no defoliation, the unpalatable Hilaria had a lower growth potential than Bouteloua curtipendula and Nassella leucotricha that were of equal stature, and produced only as much as the shorter grass, Buchloe dactyloides. Bouteloua had the highest growth potential under no‐defoliation and was defoliation tolerant, except when defoliated at ground level. Nassella was more productive than the unpalatable Hilaria, since the ability to grow earlier in the year enabled it to compete successfully with Hilaria. These results indicate that with adequate deferment Bouteloua and Nassella should compete successfully with Hilaria and Buchloe should be able to maintain itself in the presence of Hilaria.

Under non‐selective defoliation, Hilaria was able to compete successfully only with Buchloe. Hilaria was sensitive to defoliation, despite being rhizomatous, and competed less successfully with Buchloe after non‐selective defoliation than it did when not defoliated. This indicates that the management practice of burning and stocking heavily with livestock until Hilaria is avoided, resulting in non‐selective defoliation, will not cause Hilaria to be more competitive with the more palatable Bouteloua, Buchloe or Nassella.

Hilaria was able to compete most successfully under selective defoliation when it was not defoliated. Under selective defoliation, by avoiding herbivory, Hilaria is able to compete strongly with at least Buchloe and Nassella. The reaction of Nassella and Buchloe to selective defoliation indicates that they may have been displaced by Hilaria in the past. In contrast, under the short‐term and non‐limiting growth conditions of this study, Bouteloua competed successfully with Hilaria even under selective defoliation. These results do not rule out the possibility that, through selective defoliation, Hilaria may have displaced other grasses including Bouteloua in the past.
Vegetation change in a man‐made salt marsh affected by a reduction in both grazing and drainage
Authors: Esselink Peter , Fresco Latzi F.M. , Dijkema Kees S.
Published: February 2009

Abstract. In order to restore natural salt marsh in a 460‐ha nature reserve established in man‐made salt marsh in the Dollard estuary, The Netherlands, the artificial drainage system was neglected and cattle grazing reduced. Vegetation changes were traced through two vegetation surveys and monitoring of permanent plots over 15 yr after the management had been changed. Exclosure experiments were started to distinguish grazing effects from effects of increased soil waterlogging caused by the neglect of the drainage system.

Both vegetation surveys and permanent plots demonstrated a dichotomy in vegetation succession. The incidence of secondary pioneer vegetation dominated by Salicornia spp. and Suaeda maritima increased from 0 to 20%, whereas the late‐successional (Phragmites australis) vegetation from 10 to 15%. Grazing intensity decreased towards the sea. The grazed area contracted landward, which allowed vegetation dominated by tall species to increase seaward.

Grazing and increased waterlogging interacted in several ways. The impact of trampling increased, and in the intensively grazed parts soil salinity increased. This can probably be explained by low vegetation cover in spring.

Framework Ordination, an indirect‐gradient‐analysis technique, was used to infer the importance of environmental factors in influencing changes in species composition. Many changes were positively or negatively correlated with soil aeration and soil salinity, whereas elevation was of minor importance. Grazing accounted for only a few changes in species frequency. Changes in permanent plots were greater during the first than during the second half of the study period. In exclosures that were installed halfway through the study period, there was a relatively rapid recovery of previously dominant species that had decreased during the first half of the study period.

Species richness per unit area in the reserve increased. At the seaward side of the marsh, the altered management allowed succession to proceed leading to establishment of stands of Phragmites australis, whereas on the landward side, the combination of moderate grazing with neglect of the drainage system appeared an effective measure in maintaining habitats for a wider range of halophytic species.
Effects of long‐term cutting in a grassland system: perspectives for restoration of plant communities on nutrient‐poor soils
Authors: Bakker J.P. , Elzinga J.A. , de Vries Y.
Published: February 2009

Abstract. The upper courses of brook valley systems harbour Nardo‐Galion saxatilis communities characteristic of oligo‐trophic soils under low‐intensity farming. Most of these communities have disappeared under intensified farming i.e. application of fertilizers. We studied the possibilities of restoration i.e. re‐establishment of the former plant community by adopting various cutting regimes after the cessation of fertilization in 1972. The various cutting regimes revealed different effects after 25 yr. Regimes with cutting every second year with or without removal of the swath, and complete abandonment deviated from the other regimes that included annual haymaking with different frequency and timing. The latter group of cutting regimes came closer to the community of an adjacent field where fertilization stopped in 1967. This field in turn harboured several Nardo‐Galion species after 25 yr of annual cutting, and showed more resemblance with a local reference community (at a distance of 500 m) that had not been fertilized since the 1940s. The local reference still does not match poorly developed Nardo‐Galion saxatilis communities found in the region of ca. 50 km around the study area, and is far from well developed Nardo‐Galion communities in the same region.

The study site still harbours several species characteristic of eutrophic soil and few species characteristic of oligotrophic soil after 25 yr of annual cutting and removal of the swath. The soil seed bank harbours only few target species. Although species characteristic of oligotrophic soil are present in an adjacent field and Nardo‐Galion saxatilis species occur at 500 m, they have not (yet) established in the target area.
Response to cutting of Larrea divaricata and L. cuneifolia in Argentina
Authors: Martinez Carretero E. , Dalmasso A.
Published: February 2009

Abstract. The response of Larrea divaricata and L. cuneifolia to cutting stems 0–20 cm above the ground was studied in the arid piedmont area west of Mendoza, Argentina. The species occur at different elevations and in vegetation zones: L. cuneifolia < 1250 m; L. divaricata between 1250 and 2500 m. Four treatments with 10 replicates were analysed in randomly chosen plants: cut at ground level with lopping shears; cut at ground level with a pick; cut at 10 cm with lopping shears; and cut at 20 cm with lopping shears. The initial and final height, volume, and dry matter (above‐ and below‐ground) were determined. The relation between volume and initial and final dry matter and height was analysed through a factorial MANOVA (p < 0,05), and the functional relation between volume, dry matter and height was estimated by adjusting a regression model. In both species, maximum recovery was reached when cut with shears, and predicted recovery (turnover) was 17‐18 yr. In the two last treatments height was a useful predictor of dry matter. L. divaricata‐dominated plots have a lower biomass, growth rate, and allocation to stems and root than L. cuneifolia‐dominated plots. Regrowth following clipping on an area of 3–10 ha, is sufficient to support the annual needs (cooking and heating) of one family.
A landscape‐scale model for optimal management of sheep grazingin the Magellanic steppe
Authors: Cingolani Ana M. , Anchorena Juan , Stoffella Susana L. , Collantes Marta B.
Published: February 2009

Abstract. Effective management of rangelands requires the development of landscape‐scale models for predicting spatial and temporal variability of forage. In the Magellanic tussock steppes, as in other cold‐temperate regions, grazing capacity is dependent on the winter season. To develop a management tool for the region, we analysed links between winter forage availability, weather, stocking rate and vegetation structure. We studied four paddocks over five years with a range of stocking rates from 0 to 1.53 sheep.ha‐1. We sampled forb and non‐tussock graminoid biomass, vegetation structure and faecal pellet abundance at the end of each summer. Daily temperature and rainfall data were also recorded. A regression model explained the amount of winter forage as a positive function of graminoid cover, spring minimum temperature, annual precipitation and a negative function of dwarf shrub canopy, bare soil and stocking rate (R2= 0.59). Interactions of structural variables with precipitation and stocking rate were detected, indicating strong fluctuations of forage availability in lawn communities dominated by short graminoids. The most probable causes of this response would be higher utilisation and lack of canopy structure. Our results illustrate how maps of vegetation structure, obtainable from satellite images, with weather and stocking rate data could be used for predicting optimal stocking rates in large, heterogeneous sheep paddocks.ed.
Species introduction through seeds from an old, species‐rich hay meadow: Effects of management
Authors: Losvik M.H. , Austad I.
Published: February 2009

Abstract.A local seed mixture from plants growing in a species‐rich, traditionally managed hay meadow site at Varaldsoy, Hardanger, western Norway, where many endangered hay meadow species of the region are growing, was sown in a newly harrowed experimental field 1 km from the source meadow in order to increase the habitat area for the endangered species. Of 25 endangered species recorded in the source meadow, only one (Holcus lanatus) was present in the target meadow. After sowing, 16 of the endangered species in addition toHolcus lanatuswere recorded in the new site. Six species were only present in sown plots and seven others were more frequent there, while three species might have arrived by chance or originated from the seed bank. Replacing the traditional management regime, including one late cut and grazing in spring and in autumn, with three cutting times and the creation of gaps in the sward, resulted in a higher number of endangered species in plots which were only cut, possibly because the grazing was too intensive in the small enclosures.
The effects of cutting and herbicide treatment on Pteridium aquilinum encroachment
Authors: Pakeman R.J. , Thwaites R.H. , Le Due M.G. , Marrs R.H.
Published: February 2009

Abstract. Pteridium aquilinum (bracken) encroachment is an important factor in the loss of certain habitats in the United Kingdom. However, no information exists as to whether prevention of encroachment is a cost‐effective strategy for Pteridium management. Conventional methods for the control of Pteridium (cutting, asulam application) were tested at one site (Levisham) to quantify their ability to prevent or delay encroachment and to affect the vigour of the Pteridium at the edge of the stand. The effects of encroachment and asulam application on the vegetation present were monitored at a second site (Ramsley), where techniques commonly used for moorland restoration were employed in combination with asulam application.

Cutting once per year or a single application of asulam delayed the advance of the Pteridium front. At Levisham, the untreated front advanced 2.7 m in 5 yr, while in the same period the cut front advanced 0.88 m and the sprayed front was 1.5 m behind its initial position. At Ramsley, the untreated front invaded 1.8 m in 5 yr, and the sprayed front was again 1.5 m behind its starting position. Both spraying and cutting reduced frond biomass, frond cover and rhizome biomass. Herbicide spraying prevented the loss of Calluna vulgaris, though the restoration treatments had little effect. The merits of a balanced targeting of control on encroaching fronts or Pteridium at the stand level are discussed for different situations.
Classification and ecology of the mid‐seral Picea mariana forests of British Columbia
Authors: Klinka K. , Krestov P.V. , Chourmouzis C.
Published: February 2009

Abstract. We sampled vegetation and soils of, and classified mid‐seral, even‐aged, fire‐origin, upland Picea mariana ecosystems in the Boreal White & Black Spruce and Sub‐boreal Spruce zones of British Columbia, Canada. We applied multi‐variate and tabular methods to analyse and synthesize the data from 121 plots according to the methods of biogeoclimatic ecosystem classification. We delineated seven basic vegetation units and described their vegetation and environmental features. However, the delineated units could not be related to neither of the taxonomies proposed for the North American boreal forest communities. Although species‐poor, the under‐storey vegetation in the sampled ecosystems provided for a sufficient floristic differentiation, which matched well the major edaphic differences between the units. The classification of mid‐seral boreal ecosystems may be more useful that based on old‐growth stands that are infrequent or lacking in the landscape due to wildfires.
The impact of site conditions and seed dispersal on restoration success in alluvial meadows
Authors: Donath Tobias W. , Holzel Norbert , Otte Annette
Published: February 2009

Abstract. We studied the restoration success of flood plain meadows in the northern Upper Rhine valley, where between 1988 and 1992, 35 ha of arable land was converted into grassland and subsequently managed for nature conservation.

Remnant populations of typical alluvial meadow species were found in old meadows and along drainage ditches that dissect the whole area. We analysed the site conditions and phytosociological relevés in old and new meadows. Small differences in site parameters between old and new meadows contrasted with a clear floristic differentiation between the two meadow types. The vegetation of old meadows was much more differentiated along prevailing environmental gradients than the vegetation of new meadows. Despite the favourable site conditions for the re‐establishment of species‐rich meadows on the former arable land, restoration success was limited to the vicinity of remnant stands. In contrast to old meadows, indicator species of new grassland were still typical species of regularly disturbed ruderal and arable habitats, often capable of building up a persistent seed bank.

The precise mapping of 23 target species revealed that even wind dispersal predominantly leads to re‐establishment in the close circumference of parent plants. We found no indication that regular flooding, hay‐making and autumnal grazing had an impact on recolonization of newly created grassland. Even under favourable conditions for the re‐establishment of target species, restoration success in alluvial meadows proved to be strongly dispersal limited. We discuss the implications of our findings for future restoration management in grasslands.
Simulated effects of herb competition on planted Quercus faginea seedlings in Mediterranean abandoned cropland
Authors: Rey Benayas , José M. , Espigares Tíscar , Castro‐Díez Pilar
Published: February 2009

Abstract. We tested simulated effects of herb competition on the performance of planted seedlings of Quercus faginea ssp. faginea in Mediterranean abandoned cropland. We produced three types of environment with respect to herb competition: absence of competition (AC), below‐ground competition (BGC), and total competition (TC). We assessed the performance of Q. faginea seedlings in each treatment in five ways: (1) seedling mortality, (2) leaf length and total plant leaf area, (3) water potential, (4) total biomass and biomass allocation, and (5) non‐structural carbohydrate storage in different plant organs. We also measured (6) soil moisture at different depths and (7) biomass production of herbs. The TC treatment reduced water availability more than the BGC treatment, in agreement with the most pronounced water stress in seedlings under TC conditions. BGC and TC treatments showed a high and similar seedling mortality, which was one order of magnitude higher than that in the AC treatment. Competition treatments affected glucose concentration in both shoots and roots, and followed the rank TC > BGC > AC. Q. faginea seedlings might compensate a lower water availability through glucose accumulation in leaves to reduce the osmotic potential. There was a maximum starch concentration in the BGC treatment that hints that a moderate resource limitation would limit tissue growth but not carbon assimilation. We conclude that the negative effects of herbs on Q. faginea seedlings are mostly a result of competition for water, and that this competition is noticeable since the earliest stages of the establishment. Complete weed removal is a technique that would strongly improve seedling survivorship.
Effect of burning and mowing on grass and forb diversity in a long‐term grassland experiment
Authors: Fynn Richard W.S. , Morris Craig D. , Edwards Trevor J.
Published: February 2009

Abstract. Disturbance may be an important determinant of plant community composition and diversity owing to its effects on competitive interactions, resources, dominance and vigour. The effect of type, timing and frequency of disturbance on grass and forb species richness was examined using data from a long‐term (> 50 yr) grassland burning and mowing experiment in KwaZulu‐Natal, South Africa.

Grass species richness declined considerably (> 50%) in the absence of disturbance, whereas forb species richness was unaffected. Annual burning in sites not mown in summer tended to increase grass species richness relative to triennial burning (22% increase) with the reverse being true in sites mown twice in summer (37% decline). Forb species richness declined by 25% in sites mown twice in summer relative to sites mown in early summer only. Disturbance was necessary to achieve maximum grass species richness presumably by removing litter and increasing the availability of light. The interaction of time of mowing in summer (early versus late) and time of burning during the dormant period (spring versus winter) had the most dramatic effect on species richness. Time of burning had no effect on richness in sites mown in early summer, but winter burning resulted in a dramatic decline (27–42%) in richness in sites mown in late summer. This effect may be related to possible greater soil desiccation with this combination of disturbances.
Sapling survival and growth of coniferous and broad‐leaved trees in successional highland habitats in Mexico
Authors: Quintana‐Ascencio Pedro Francisco , Ramírez‐Marcial Neptalí , González‐Espinosa Mario , Martínez‐Icó Miguel
Published: February 2009

Abstract. We assessed survival and growth of transplanted saplings of understory broad‐leaved trees (Oreopanax xalapensis, Rapaneajuergensenii, Rhamnus sharpii and Tern‐stroemia lineata) and canopy conifers (Abies guatemalensis, Pinus ayacahuite and P. pseudostrobus) into Grassland (GR), Mid‐Successional Oak Forest (MS), and Old‐Growth Oak Forest (OF) stands in the central highlands of Chiapas, Mexico. A total of 727 plants were monitored over eight years. The results suggest habitat preferences of the studied species that should be considered for their conservation oriented management. Conifers had highest survival and growth in GR, while broad‐leaved trees survived better under sparse canopy in MS, but grew tallest in full light. Saplings of all species in dense canopy sites in OF were smaller, and the survival of conifers was lower. An integrated response index (IRI) calculated for each species with survival and relative growth rates showed similar trends. Re‐introduction of the endangered A. guatemalensis is possible in open habitats if fire, trampling and grazing are suppressed. Open habitats in current man‐made landscapes in the highlands of Chiapas may limit the establishment of understory trees requiring partial shade. Inclusion of such species in restoration programs has not been usual so far; yet, local and global interest in native species for such programs is increasing. Information on the response of these kind of species in contrasting habitats may help to incorporate them in the management of high‐diversity forests that may follow pine plantations.
Year‐to‐year changes in water level drive the invasion of Vochysia divergens in Pantanal grasslands
Authors: Nunes da Cunha C. , Junk W.J.
Published: February 2009

Abstract. In recent decades, cattle ranchers of the Pantanal of Mato Grosso, Brazil, have pointed to the accelerated spread of several herbaceous and woody plant species that invade natural and artificial pastures (campos). It has been speculated that overgrazing by an increasing number of cattle, lack of grazing in abandoned areas, or large‐scale changes in environmental conditions may be the reason for this invasion. This study focuses on ecological and ecophysiological aspects of Vochysia divergens (cambará), a flood‐tolerant tree that began spreading in the Pantanal during the last 30 years and is considered a very aggressive invasive plant. The study shows that the spread of cambará can be related to natural multi‐years wet periods. During multi‐years dry periods the species is reduced by the increasing impact of fires in the Pantanal. This points to the great importance of multi‐years climatic events on the vegetation cover of the Pantanal and indicates a very dynamic development in plant communities.
Nutrient limitation in boreal rich‐fen vegetation: A fertilization experiment
Authors: Øien Dag‐Inge
Published: February 2009

Abstract. Rich‐fen vegetation influenced by hay‐making in the Sølendet Nature Reserve, Central Norway, was fertilized with N, P and K in a full‐factorial fertilization experiment to investigate the nutrient limitation of plant growth at both community and species levels. Above‐ground biomass, shoot density and nutrient concentration were measured in several species and groups of species at three sites after two years of fertilization. At the community level, the results indicate multiple limitation by N and P in the two least productive rich‐fen communities: one characterized by small sedges and herbs, and the other by high abundance of Menyanthes trifoliata and tall sedges. Increased nutrient availability had no effect on a more highly productive, tall‐growing, spring‐influenced community, indicating no nutrient limitation. The results at the species level correspond well with those at the community level, indicating multiple limitation by N and P in most of the dominant and sub‐dominant species. However, P seems to limit growth more than N in Succisa pratensis, and N seems to limit growth more than P in Carex panicea. Furthermore, Eriophorum angustifolium seems to be limited by K. The results did not show which nutrient limits the growth of Carex dioica, C. lasiocarpa and Trichophorum cespitosum. Indications that growth in low‐productive, boreal rich‐fen communities is generally limited by P was not confirmed.
Effects of re‐introducing fire to a central Florida sandhill community
Authors: Reinhart Kurt O. , Menges Eric S.
Published: February 2009

Abstract. A southern ridge sandhill site in central Florida, USA, was burned in 1989, 1991, and 1995 after 63 years of fire‐suppression to simulate a pre‐settlement fire regime. Fire changed species abundance and vegetation structure but caused only minimal changes in species turnover and diversity. There was a general trend for an increase in the cover of herbs following fire but this was a statistically significant effect for only one species, Liatris tenuifolia var. tenuifolia. Aristida beyrichiana increased, litter cover and litter depth were significantly reduced, and ground lichens were eliminated in response to burning. Scrub oaks and palmettos in the ground cover and small shrub layers (height ≤ 1 m) either increased or did not respond to burning, reflecting strong post‐fire resprouting. Diversity in the ground cover and small shrub layers were not affected by fire. Scrub oaks and palmettos in the large shrub and overstorey layers (height > 1 m) were reduced in density, basal area, and longest canopy measurements in response to fire. Species diversity also decreased within these layers following fire. Some Pinus elliottii var. densa survived fire, but their density was reduced. All Pinus clausa were eliminated by fire. Periodic burning can suppress the dominance of shrubs (Quercus spp.) while increasing the cover of grasses and herbs in southern ridge sandhill vegetation.
Seedling recruitment on agriculturally improved mesic grassland: the influence of disturbance and management schemes
Authors: Hofmann Martina , Isselstein Johannes
Published: February 2009

Question: Are the recruitment patterns of deliberately introduced wildflower species influenced by cutting frequencies and disturbance treatments? To what extent do these different treatments affect productivity and sward structure of an agriculturally improved grassland?

Location: A mesic lowland grassland near Göttingen, Lower Saxony, Germany.

Methods: Recruitment success of eight sown wildflower species was studied in a permanent grassland treated by a factorial combination of different pre‐sowing cutting intervals (1, 3 or 9 wk), post‐sowing cutting intervals (1,3 or 9 wk) and disturbance (control, harrowing, removal of sward). Seedling emergence and survival, biomass production and sward structure were followed over two years.

Results: For most species seedling emergence was highest in the harrowing treatment. The complete sward removal did not further increase seedling emergence. Seedling survival was strongly influenced by the post‐sowing cutting frequency with highest mortality in the 9 wk cutting interval compared to one and 3 wk cutting intervals. Annual dry matter yield varied between 4.4, 5.9 and 9.4 t.ha‐1 in the 1,3 and 9 wk pre‐sowing cutting treatment, respectively. In June, when the seeds were sown, the tiller number of the 1 wk cut plots was twice as high as for the 9 wk cut plots and five times higher than in the harrowing treatment.

Conclusions: Disturbance by harrowing provided the optimal environmental cues to trigger germination, whereas seedling survival was facilitated by increased light penetration due to frequent cutting. The investigation revealed the overriding importance of frequent standing crop removal in the early phase of seedling establishment on agriculturally improved grassland.
Large herbivores as mobile links between isolated nature reserves through adhesive seed dispersal
Authors: Couvreur Martine , Christiaen Bart , Verheyen Kris , Hermy Martin
Published: February 2009

Question: Do large herbivores contribute to the dispersal of plant seeds between isolated habitats by epizoochory?

Location: Nature reserves in Flanders, Belgium.

Methods: Epizoochory was studied by brushing plant seeds from the fur of 201 domesticated large herbivores (Galloway cattle, donkeys and horses), grazing in 27 Flemish nature reserves. Several herbivores were examined after transport between different nature reserves as part of the seasonal grazing system in Flanders, allowing detection of seed dispersal both within and between reserves. The seedling emergence method was used to identify the dispersed plant species.

Results: In total, 6385 epizoochorous seeds from 75 species germinated, yet the real seed quantity was underestimated by the seedling emergence method. A wide variety of seed morphology, seed weights and plant heights was represented among the dispersed species, many of which had a transient seed bank. There was a gradual turnover in epizoochorous species composition in the course of the vegetation season, and seed dispersal occurred both within and between different nature reserves.

Conclusions: Domesticated large herbivores, as models for wild mammals in the present and the past, are important dispersers of many plant species. Through seasonal grazing, the herbivores function as ‘mobile link organisms’, connecting isolated nature reserves through seed dispersal, possibly influencing vegetation development and long‐term survival of plant populations. As such, large herbivores are important instruments in ecological restoration, especially in fragmented ecosystems.
Temporal and spatial patterns of ecosystem functioning in protected arid areas in southeastern Spain
Authors: Paruelo José M. , Piñeiro G. , Escribano P. , Oyonarte C. , Alcaraz D. , Cabello J.
Published: February 2009

We characterized the spatial variability and temporal dynamics of the photosynthetic active radiation absorbed (APAR) by the canopy, a descriptor of ecosystem functioning, in Cabo de Gata – Níjar Natural Park (CGNNP) (Spain). Ecosystem functioning was characterized for five landscape classes using the Normalized Difference Vegetation Index (NDVI) derived from NOAA/AVHRR LAC (1 km × 1 km) images. We also used a 19‐year time series of NDVI PAL data (8 km × 8 km) to analyse the relationship APAR‐precipitation inside and outside the park.

The vegetation of CGNNP absorbed less than 20% of the incoming radiation. Plains intercepted 37% and hills 14% less photosynthetic active radiation than mountains, the most productive landscape of the park. CGNNP showed a well‐defined growing season with a unique peak of APAR. Plains and piedmont, covered by annual vegetation displayed an earlier development of the leaf area index than the shrublands and grasslands typical of the other landscapes. APAR had a significant relationship with the sum of the precipitation of the current and two previous growing seasons, except for the plains. We found that the APAR of the areas more modified by humans (outside the park) showed a lower sensitivity to changes in precipitation than those under protection. The differences were higher if the accumulated precipitation of the previous three growing seasons was considered. The description of such differences in the response of absorbed PAR to water availability are proposed as the base of a monitoring system for semi‐arid and arid areas.
Seedling recruitment in flood‐meadow species: The effects of gaps, litter and vegetation matrix
Authors: Hölzel Norbert
Published: February 2009

Question: Is the failure of establishment of rare flood‐meadow species in habitat restoration primarily due to seed or microsite limitation? How do sown species respond to artificially created gaps and added litter at two neighbouring sites with similar physical conditions but contrasting vegetation matrix (young arable fallow field vs species‐poor meadow sward)?Location: Upper Rhine valley, southwestern Germany, 85 m a.s.l.

Methods: Seeds of six typical flood‐meadow species were sown in four treatment combinations of the factors gap creation and litter addition. Seedling recruitment was monitored for three years.

Results: Five of the six species established successfully at both sites largely irrespective of treatments, indicating seed limitation. Only in the small‐seeded Arabis nemorensis, which was revealed to be strictly gap‐dependent at the meadow site, could an obvious microsite limitation be shown. The non‐significance of gap treatments in all other species at the relatively high productive meadow site is probably due to biomass removal by mowing in early summer. Only at the extremes of the seed size spectrum did the results meet predictions of plant ecological theory, such as the strict gap dependence of small‐seeded species in closed swards or the positive to neutral response of large‐seeded species to litter layers.

Conclusions: Species identity was revealed to be the major factor influencing differences in recruitment. Due to the lack of a general trend in the response towards treatments the results support conceptual models that describe the interplay of facilitation and interference as a highly dynamic equilibrium, driven by variable abiotic and biotic marginal conditions.
Experimental assessment of initial revegetation on abandoned paths in temperate deciduous forest
Authors: Roovers Pieter , Gulinck Hubert , Hermy Martin
Published: February 2009

Question: Do soil treatments and addition of seed facilitate rapid vegetation restoration on forest paths excluded from trampling?

Location: Six mesophilic mixed deciduous Querco‐Fagetea forests in Flanders, northern Belgium.

Methods: Enclosures on paths were excluded from trampling by fencing. In a full factorial design, plots were subjected to seeding, soil scarification, addition of organic material and inoculum. The following two years, seedling establishment and growth were sampled during spring and summer. Soil treatments and seeding effect was tested and seedling occurrence was analysed in relation to species' origin.

Results: Spontaneous re vegetation was significant in all plots since fencing. Throughout the observation period seedling cover and height continued to increase. Seeding had an overall effect on seedling density, cover and height. Some soil treatment interactions significantly enhance re vegetation, although each individual soil treatment had no significant effect. Regardless of the seeded individuals, invading species mostly originated from the surrounding area and the seed bank.

Conclusion: The preliminary results of this experiment imply that seeding is the only treatment which has a positive effect on re vegetation success in all circumstances, provided that the exclusion from trampling is effective.
Population size and fire intensity determine post‐fire abundance in grassland lichens
Authors: Johansson P. , Reich Peter B.
Published: February 2009

Questions: What is the variability in abundance of lichens on grassland soil between and within fields after prescribed fire? Is post‐fire lichen abundance an effect of pre‐fire population size?

Location: Cedar Creek Natural History Area, Minnesota, USA.

Methods: Lichen abundance, estimated as ground cover and dominated by Cladonia spp., was mapped in plots in two fields before prescribed burning on 06.10.2003 and 15.10.2003 for the first time since abandonment in the 1950s. The plots were resurveyed one year post‐fire.

Results: Post‐fire cover of Cladonia spp. varied strongly between the fields, most likely due to different weather conditions between the burn events, which resulted in different fire intensities, one of low and one of high intensity. In the field that experienced the low intensity fire, post‐fire cover of Cladonia spp. was still relatively high, and showed a positive relationship with pre‐fire cover, while no such relationship was found after the high intensity fire. In that field Cladonia spp. experienced high mortality rates irrespective of pre‐fire cover.

Conclusions: This study provides an example of how species response to disturbance can be a function of population size, but that this relationship can be non‐linear; lichens in grassland can survive a low intensity fire proportionally to pre‐fire population size, but experience high mortality rates above a fire intensity threshold. The applications of these results are that fire intensity matters to species response to prescribed fire, and that the persistence of climax lichen communities and biodiversity in the study system needs a broad range of fire intervals.