bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in forest understorey vegetation in Norway related to long‐term soil acidification and climatic change
Authors: Økland Tonje , Bakkestuen Vegar , Økland Rune Halvorsen , Eilertsen Odd 
Published: February 2009

Abstract:Question: Does the understorey vegetation of Norwegian boreal forests change in relation to broad‐scale, long‐term changes?Location: Norway.Methods: Permanently marked 1‐m2 vegetation plots from 17 monitoring reference areas in forests dominated by Picea abies (11 areas, 620 plots) and Betula spp. (six areas, 300 plots) were analysed twice, at the start in 1988–1997 and 5 yr later (1993–2002). Species subplot frequency data were analysed separately for each area by univariate and multivariate statistical methods; 5‐yr changes in single species abundances, species number per plot and species composition were tested.Results: Two distinct patterns of change were found: 1. Abundance of several vascular plant species decreased in SE Norwegian Picea forests, most noticeably of species with a preference for richer soils, such as Oxalis acetosella. 2. Abundance of many bryophyte species as well as bryophyte species number per plot increased in forests of both types over most of Norway.Conclusions: The pattern of vascular plant changes is probably a time‐delayed response of long‐lived, mainly clonal, populations to acidified soils resulting from deposition of long‐distance airborne pollutants. The pattern bryophyte changes, with reference to the close link between climatic conditions for growth and abundance changes for Hylocomium splendens established in previous demographic studies, is related to climatic conditions favourable for bryophyte growth. We conclude that many forest understorey plants are sensitive indicators of environmental change, and that the concept used for intensive monitoring of Norwegian forests enables early detection of changes in vegetation brought about by broad‐scale, regional, impact factors.
Influence of historical, geographical and environmental variables on understorey composition and richness in Danish forests
Authors: Graae B.J. , Økland R.H. , Petersen P.M. , Jensen K. , Fritzbøger B. 
Published: February 2009

Abstract:Question: What is the relative influence of forest continuity, environmental differences and geographical context on vegetation and species richness in ancient and recent forests?Location: Himmerland and Hornsherred in Denmark.Methods: Lists of forest species from deciduous forests were subjected to CCA with variation partitioning to quantify the relative amount of variation in species composition attributable to historical, present geographical and environmental variables. GLM was used to estimate the importance of the variables to species richness.Results: The importance of temporal forest continuity in one region was negligible but was considerable in the other. The variation in species composition explained by geographical, environmental and historical variables showed little overlap in both regions, particularly at the fine scale.Conclusions: This paper does not support the idea that differences in the flora between ancient and recent forests is mainly caused by environmental differences. Furthermore, species richness seemed unaffected by isolation and forest connectivity.
Population dynamics of four understorey shrub species in beech forest
Authors: Hara M. , Kanno H. , Hirabuki Y. , Takehara A. 
Published: February 2009

Abstract:Question: In the population dynamics of four understorey shrub species (Hp, Hydrangea paniculata Sieb, et Zucc.; Lu, Lindera umbellata Thunb. var. membranacea (Maxim.) Momiyama; Ms, Magnolia salicifolia (Sieb, et Zucc.) Maxim.; Vf, Viburnum furcatum Blume ex Maxim.), (1) What is the relative importance of seedling regeneration versus vegetative growth? (2) Can these shrubs persist stably for a long time in the understorey? (3) What kind of variation in demographic features is observed among these shrubs?Location: 780m a.s.l., north‐eastern Japan.Methods: Population dynamics were analyzed by using stage‐classified matrix models. Models were mainly constructed from five years stem‐census data, including current‐year seedlings and sprouts.Results: Current‐year sprouts emerged every year in every species. Current‐year seedlings emerged every year in Lu and Vf, but densities were very low. In every species, population growth rate (A) was close to the equilibrium value 1.0 and no statistical difference was found among species. The stable stage‐distribution predicted from the matrix model was similar to the observed distribution for Lu, Ms and Vf, but much different for Hp. Elasticity matrix was also similar among Lu, Ms and Vf, but was quite different for Hp.Conclusions: Lu, Ms and Vf were considered as climax shrubs that can regenerate and maintain their population stably in the understorey, even if canopy gaps form infrequently. Hp is a pioneer shrub that require more frequent formation of canopy gaps for long‐term persistence in the understorey.
Vertical seed distribution in the soil constrains regeneration of Bromus pictus in a Patagonian steppe
Authors: Rotundo José L. , Aguiar Martín R. 
Published: February 2009

Abstract:Question: What is the effect of vertical seed distribution (i.e. seeds on soil surface or buried) and the relative importance of vertical and horizontal seed distribution (i.e. seeds near established vegetation or near bare soil) for seedling emergence?Location: Patagonian arid steppe.Methods: To evaluate the effect of vertical seed distribution on seedling emergence, four sowing treatments were used in field and greenhouse experiments. Vertical vs. horizontal seed distribution and the occurrence of seedlings were analysed in the field. Effects of trampling and mechanical drilling on seedling emergence were investigated experimentally in the field.Results: In field and glasshouse experiments buried seeds showed a higher emergence and larger seedling size than seeds lying on the soil surface. The observational field study indicated that natural emergence was not associated with particular microsites or plant cover (horizontal distribution), but that most seedlings emerged from buried positions (vertical distribution). Buried seeds represented less than 10% of the sampled seed cohort but account for almost 60% of the seedlings. The trampling/drilling experiment showed that sheep trampling and mechanical drilling increased seedling emergence compared to non‐treated controls.Conclusions: The population dynamics of Bromus pictus is strongly constrained by the vertical position of seeds, which largely affects emergence, and seed horizontal distribution, which largely affects seedling survival. Our results showed that sheep trampling after seed dispersal may be a low‐input technique for increasing grass recruitment.
Relationship between topographic heterogeneity and vegetation patterns in a Californian salt marsh
Authors: Morzaria‐Luna Luna , Callaway J.C. , Sullivan G. , Zedler J.B. 
Published: February 2009

Abstract:Questions: Are species richness and species abundances higher in the presence of tidal creeks? Do species richness and species abundances vary with plot size?Location: Intertidal plain of Volcano Marsh, Bahia de San Quintin, Mexico.Methods: We analysed vegetation patterns in large areas (cells) with tidal creeks (+creek) and without (‐creek). We surveyed vegetation cover, microtopography, habitat type, and distance to creeks in nested plots of five sizes, 0.1, 0.25, 1, 2.5, and 10 m2.Results: Species richness, frequency, cover, and assemblages differed between ±creek cells. Richness tended to be higher in +creek cells, and cover and frequency of individual species differed significantly between ±creek cells. We found consistent patterns in vegetation structure across plot sizes. We encountered 13 species that occurred in 188 unique assemblages. The most common assemblage had six species: Batis maritima, Frankenia salina, Salicornia bigelovii, S. virginica, Salicornia spec. and Triglochin concinna. This assemblage occurred in ±creek cells and at all spatial scales. Of the most common assemblages all but one were composed of multiple species (3–9 species/plot).Conclusions: The persistence of vegetation patterns across a 100‐fold range in spatial scale suggests that similar environmental factors operate broadly to determine species establishment and persistence. Differences in assemblage composition result from variation of frequency and cover of marsh plain species, particularly Suaeda esteroa and Monanthochloe littoralis. The recommendation for restoration of Californian salt marshes is to target (and plant) multi‐species assemblages, not monocultures.
Distribution of plant species at a biome transition zone in New Mexico
Authors: Kröel‐Dulay György , Ódor Péter , Peters Debra P. C. , Hochstrasser Tamara 
Published: February 2009

Abstract:Question: Is there a difference in plant species and life form composition between two major patch types at a biome transition zone? Are subordinate species associated with different patch types at the shortgrass steppe — Chihuahuan desert grassland transition zone? Is this association related to differences in soil texture between patch types and the geographic range of associated species?Location: central New Mexico, USA.Methods: Patches dominated by either Bouteloua gracilis, the dominant species in the shortgrass steppe, or Bouteloua eriopoda, dominant species in the Chihuahuan desert grasslands, were sampled for the occurrence of subordinate species and soil texture within a 1500‐ha transitional mosaic of patches.Results: Of the 52 subordinate species analysed, 16 species were associated with B. gracilis‐dominated patches and 12 species with B. eriopoda‐dominated patches. Patches dominated by B. gracilis were richer in annual grasses and forbs, whereas patches dominated by B. eriopoda contained more perennials forbs and shrubs. Soils of B. gracilis‐dominated patches had higher clay and lower rock contents compared with soils of B. eriopoda‐dominated patches. Differences in species characteristics of the dominant species as well as differences in soil texture between patch types contribute to patch‐scale variation in composition. The association of species to patch types was not related to their geographic range and occurrence in the adjacent biomes.Conclusions: Patch types at this biome transition zone have characteristic life‐form and species composition, but species are associated to patch types due to local constraints, independently from their affinity to the adjacent biomes.
Chance versus determinism in canopy gap regeneration in coastal scarp forest in South Africa
Authors: Obiri John A. F. , Lawes Michael J. 
Published: February 2009

Abstract:Question: Is tree regeneration in canopy gaps characterized by chance or predictable establishment.Location: Coastal scarp forests, Umzimvubu district, Eastern Cape Province, South Africa.Methods: Estimation of richness of gap‐filling species across canopy gaps of different size. Data are compared with regeneration under the canopy. Probability of self‐replacement of gap forming species is calculated.Results: Forest area under natural gap phase was 7.8%, caused mostly by windthrow (54%). The abundance and average size of gaps (87.8 m2) suggests that species diversity may be maintained by gap dynamics. However, only four of 53 gap‐filler species displayed gap size specialization and these were pioneer species. An additional 13 species were more common in larger gaps but there was no gradient in composition of gap‐filler species across gap size (p= 0.61). Probabilities of self‐replacement in a gap were low (< 0.3) and common canopy species were equally abundant in gaps and the understorey. Species composition in gaps showed no pattern of variation, i.e. was unpredictable, which suggests absence of a successional sequence within tree‐fall gaps. There was also only a slight increase in species richness in gaps at intermediate levels of disturbance.Conclusions: Coastal scarp forest appears not to comprise tightly co‐evolved, niche‐differentiated tree species. Unpredictable species composition in gaps may be a chance effect of recruitment limitation of species from the species pool. Chance establishment slows competitive exclusion and may maintain tree diversity in these forests. These data suggest that current levels (≤ 3 gaps per ha) of selective tree harvesting may not cause a reduction in species richness in this forest.
The value of stress and limitation in an imperfect world: A reply to Körner
Authors: Lortie Christopher J. , Brooker Rob W. , Kikvidze Zaal , Callaway Ragan M. 
Published: February 2009

Abstract:A recent perspective paper offered by Körner essentially argued that ‘limitation’ and ‘stress’ are functionally useless terms for ecology except perhaps within limited contexts such as plant physiology or agriculture. We strongly disagree, and to this end argue that, although stress is not as precise as other concepts in ecology and is probably more difficult to apply to communities than to individuals, if ecologists want to communicate in a meaningful and interesting way about the distribution and abundance of species, we have to use multi‐purpose terminology that allows us to scale from reductionistic, strictly quantifiable levels of analysis to more general conceptual levels. Here, we revisit the main arguments presented against these concepts and use three lines of counter‐argument to support our conclusion that limitation and stress are necessary concepts for organizing and integrating general ecological inquiry. We discuss (1) the role of interactions between individuals in changing the limitation experienced by a species, (2) the importance of delineating whether stress is being applied to individuals or to the community, and (3) the evolutionary argument that fitness is never perfect since even adapted species are likely limited to some degree by the environment.
Individuals have limitations, not communities — A response to Marrs, Weiher and Lortie et al.
Authors: Körner Christian 
Published: February 2009

Abstract:A reply is presented on the comments by Marrs, Weiher, and particularly Lortie et al. on an earlier Forum paper. The main point is that adapted alpine plants are not stressed, which follows, i.a., from their productivity which is equal to that in tropical systems when the length of the growing season is taken into account. Another point is that individual‐based and community‐based considerations should not be confused.
Light as an environmental filter in fen vegetation
Authors: Kotowski Wiktor , van Diggelen Rudy 
Published: February 2009

Abstract:Questions: 1. To what extent does light availability differ among fen plant communities? 2. To what extent does light coincide with productivity and moisture gradients? 3. Does light act as an important environmental filter in natural and transformed riparian landscapes?Location: Current data from the Biebrza Valley, NE Poland; literature data from the Třeboň area, Czech Republic and four sites in the western and southern Netherlands.Methods: Relative light intensity (RLI) was measured in vertical profiles, next to vegetation relevés accompanied by measurements of above‐ground biomass, summer groundwater level, N and P content in vegetation, pH and soil redox potential. Data derived from literature included profiles of RLI, biomass and vegetation records. Relationships between RLI and biomass and between species distribution, RLI and other variables were examined by regression analysis and CCA. Four traits were analysed: ability to spread clonally, seed weight, maximum height of adults and time of commencement of flowering.Results: RLI at ground level varied from < 1% in reed beds and tall herb meadows to > 60% in sedge‐moss communities and litter meadows. RLI was largely determined by the standing crop and explained a large part of variation in species occurrence. The combinations of analysed functional traits were constrained by the communities’ light profiles.Conclusion: Light availability is related more closely to site fertility than to hydrological regime. This confirms that hydrological regime and productivity should be analysed separately with regard to their effect on species distribution in wetlands. Limited light availability seems the major environmental control of the distribution of low growing and late flowering species.
Probability distributions, vulnerability and sensitivity in Fagus crenata forests following predicted climate changes in Japan
Authors: Matsui Tetsuya , Yagihashi Tsutomu , Nakaya Tomoki , Taoda Hirosi , Yoshinaga Shuichiro , Daimaru Hiromu , Tanaka Nobuyuki 
Published: February 2009

Question: How much is the probability distribution of Fagus crenata forests predicted to change under a climate change scenario by the 2090s, and what are the potential impacts on these forests? What are the main factors inducing such changes?Location: The major islands of Japan.Methods: A predictive distribution model was developed with four climatic factors (summer precipitation, PRS; winter precipitation, PRW; minimum temperature of the coldest month, TMC; and warmth index, WI) and five non‐climatic factors (topography, surface geology, soil, slope aspect and inclination). A climate change scenario was applied to the model.Results: Areas with high probability (> 0.5) were predicted to decrease by 91%, retreating from the southwest, shrinking in central regions, and expanding northeastwards beyond their current northern limits. A vulnerability index (the reciprocal of the predicted probability) suggests that Kyushu, Shikoku, the Pacific Ocean side of Honshu and southwest Hokkaido will have high numbers of many vulnerable F. crenata forests. The forests with high negative sensitivity indices (the difference between simulated probabilities of occurrence under current and predicted climates) mainly occur in southwest Hokkaido and the Sea of Japan side of northern Honshu.Conclusion: F. crenata forest distributions may retreat from some islands due to a high WI. The predicted northeastward shift in northern Hokkaido is associated with increased TMC and PRS. High vulnerability and negative sensitivity of the forests in southern Hokkaido are due to increased WI.
Cover‐weighted averaging of indicator values in vegetation analyses
Authors: Käfer Jos , Witte Jan‐Philip M. 
Published: February 2009

Abstract:Question: How should species cover be weighted when calculating average indicator values of vegetation relevés?Location: The Netherlands.Method: Various weighting methods were statistically investigated with 188 relevés from The Netherlands for which accurate groundwater levels were available. For each method the correlation between average Ellenberg indicator value for moisture and mean spring groundwater level was calculated. A permutation test on correlation coefficients revealed whether differences between methods were significant or not.Results: Optimization of a general weighting function did not produce a significantly higher correlation than disregarding cover and calculating the average as the arithmetical mean of indicator values. Giving a higher weight to species at both ends of the indicator scale and using indifferent species as indicators of mediocre conditions did improve the correlation significantly. Weighting species proportionate to their cover yielded a significantly lower correlation than the correlation obtained with the method that disregards cover. A significantly lower correlation was also established when taking into account the fact that cover is related to the growth strategy of species.
More efficient estimation of plant biomass
Authors: Bråthen Kari Anne , Hagberg Oskar 
Published: February 2009

Abstract:Question: The optimal use of the point intercept method (PIM) for efficient estimation of plant biomass has not been addressed although PIM is a commonly used method in vegetation analysis. In this study we compare results achieved using PIM at a range of efforts, we assess a method for calculating these results that are new with PIM and we provide a formula for planning the optimal use of PIM.Location: Northern Norway.Methods: We collected intercept data at a range of efforts, i.e. from one to 100 pins per 0.25 m2 plots, on three plant growth forms in a mountain meadow. After collection of intercept data we clipped and weighed the plant biomass. The relationship between intercept frequency and weighed biomass (b) was estimated using both a weighted linear regression model (WLR) and an ordinary linear regression model (OLR). The accuracy of the estimate of biomass achieved by PIM at different efforts was assessed by running computer simulations at different pin densities.Results: The relationship between intercept frequency and weighed biomass (b) was far better estimated using WLR compared to the normally used OLR. Efforts above 10 pins per 0.25 m2 plot had a negligible effect on the accuracy of the estimate of biomass achieved by PIM whereas the number of plots had a strong effect. Moreover, for a given level of accuracy, the required number of plots varied depending on plant growth form. We achieved similar results to that of the computer simulations when applying our WLR based formula.Conclusion: This study shows that PIM can be applied more efficiently than was done in previous studies for the purpose of plant biomass estimation, where several plots should be analysed but at considerably less effort per plot. Moreover, WLR rather than OLR should be applied when estimating biomass from intercept frequency. The formula we have deduced is a useful tool for planning plant biomass analysis with PIM.
Plant species and community responses to sand burial on the machair of the Outer Hebrides, Scotland
Authors: Owen Nia W. , Kent Martin , Dale M. Pamela 
Published: February 2009

Abstract:Question: Is there a critical depth of burial by sand beyond which species and communities fail to recover, and does repeated incremental burial have a greater impact than a single large deposition?Location: The machair on the calcareous sand dunes on South Uist, in the Outer Hebrides of Scotland, UK.Methods: Eight turves were collected from each of four machair sub‐community types. After acclimatization in an unheated polythene tunnel, they were buried with sterilized machair shell sand, either by one single burial to 5 cm or by five applications of 1 cm of sand at approximately seven‐week intervals. Species response was recorded on five occasions.Results: Within machair sub‐communities, burial by sand reduced the abundance (local rooted frequency) of plants more than it reduced species richness. Intermittent burial was more damaging than a single burial event. Those species with the highest pre‐burial frequencies tended to dominate recovery in the sub‐community as a whole. Species occurring across all four sub‐community types exhibited varying responses to community burial between the differing types. Samples from slack sub‐communities had distinctly different response characteristics from those of foredunes and unploughed and three‐year fallow dune grassland.Conclusions: The perennial life‐form of many machair species has been evolutionarily selected for and dominates throughout the machair habitat. Account needs to be taken of competitive interaction between species in relation to burial response. The results of the investigation show that the hypotheses of Gilbertson et al. and Kent et al. on ‘machair stratification’ require refinement in that frequency of shallow burial can be as important as overall burial depth.