Questions: Are there any sustainable or vulnerable habitats in which beech (Fagus crenata) forests could survive in Japan under 110 hypothetical climate change scenarios?Location: Six islands of Japan on which beech grows naturally.Methods: An ecological habitat model was used to simulate the potential habitat shifts of beech forests under 110 climate change scenarios. The amount of suitable habitat loss and gain was calculated with three migration options and risk surfaces. Vulnerable and sustainable habitats were identified to evaluate the potential risks and survival of beech forests.Results: The total areas of potential suitable habitats differed considerably depending on the future temperature and precipitation changes. Some areas on the Sea of Japan (SOJ) side showed higher probability of maintaining suitable habitats, whereas there were wider areas in which suitable habitats could not persist under any of the 110 climate change scenarios.Conclusions: The risk surfaces of the suitable habitats showed that decreases in precipitation along with increases in temperature reduced the total areas of suitable habitats. Increases in precipitation with increases in temperature of more than or equal to 2°C always reduce the areas of suitable habitats. Under increased precipitation with a temperature increase of <2°C, the areas of suitable habitats showed an increase, maintenance of the status quo or a decrease, depending on the size of the increase in precipitation. Beech forests in western Japan are predicted to be vulnerable to climate change, whereas some mountains on the SOJ side are predicted to be possible future refugia.
Question: Did the composition of the herb layer of a deciduous forest on loamy soils sensitive to soil acidification change between 1954 and 2000? How are these change related to the abandonment of traditional coppice-with-standards forest management and increased soil acidification?
Location: Central Belgium (Europe).
Methods: Twenty semi-permanent phytosociological quadrats from an ancient deciduous forest (Meerdaal forest) were carefully selected out of a total of 70 plots dating from 1954 and were revisited in 2000. Species composition and soil pH H2O were recorded using an analogous methodology. The studied period coincides with a period of forest conversion from coppice-with-standards towards a high forest structure and with an increase in acidifying and eutrophying deposition.
Results: Between 1954 and 2000, species composition of the herb layer changed significantly. Redundancy analysis pointed to increased shade resulting from shifts in cover and species composition of the shrub and tree layer as the main driving force. Soil acidity increased and the majority of plots entered the aluminium buffer range, which potentially affected herb layer composition. Observations at the species level, especially a strong decrease in cover of the vernal species Anemone nemorosa supported this hypothesis.
Conclusions: Our results show significant shifts in the forest herb layer in less than five decades. These shifts were related to an alteration in the traditional forest management regime and increased soil acidity. Whereas the effect of a changed management regime can be mitigated, soil acidification is less reversible. Testing the generality of these patterns on more extensive data sets is certainly needed.
Questions: What is the effect of the 19th century (pre-industrialization) landscape pattern on the recovery of climax forests in cool-temperate mountain areas dominated by Fagus crenata (Japanese beech)?
Location: Secondary forests on Mt. Daisen, western Japan.
Methods: Vegetation patterns before and after industrialization were obtained from maps drawn in 1898 and 1979. Tree measurements were made in 12 plots in 1997. Correlation between current Fagus crenata dominance and forest edge in the 19th century was analysed using an S-shaped regression curve. Fagus juvenile density was counted in the plots, and distances from each plot to the five nearest mother trees were measured to determine the dispersal kernel.
Results: Secondary grassland covered a substantial area in 1898, whereas forest covered most of the area in 1997. Fagus was dominant in places in the interior forest 100 years ago, and mature Fagus trees were absent in secondary forests that had been grasslands in 1898. The expected number of juveniles decreased to one individual per 100 m2 at 43.5 m from the mother tree.
Conclusions: The pre-industrialization landscape greatly affected recovery of Fagus forest. Forests found on the 1898 vegetation map might have acted as refugia for Fagus. The limited dispersal ability of Fagus suggests that it would take many generations (several hundred years) for Fagus forests to recover at the centre of what had been grasslands in the 19th century.
Question: How rapidly has the sandy beach and maritime forest vegetation on Phuket recovered and regenerated after the impact of the major Indian Ocean tsunami of 2004? What are the characteristics of sandy beach species for regenerating their populations and the invasion patterns of originally non-sandy beach species or other newcomers after the tsunami?
Location: Phuket Island, southern Thailand.
Methods: Species composition of beaches was studied on the same research plots 6 months before and 9 months after the tsunami. The changes in individual species cover before and after the tsunami were determined by χ2 tests. Change in community composition was analysed by detrended correspondence analysis. The relationship between species and environmental factors was analysed by canonical correspondence analysis.
Results: The sites disturbed by the tsunami were often invaded by annuals, especially grasses and asteraceous plants, rather than by perennials. In contrast, species with clonal growth by stolons decreased significantly. Factors determining the species habitat differences were soil hardness (penetration resistance of sandy soil), per cent silt content, soil water content and beach management. Habitat differences among originally non-sandy beach herbaceous species that expanded their population or moved to the coast after the disaster were defined by sand accretion or erosion caused by the tsunami. Many sandy beach herbaceous communities changed into Dactyloctenium aegyptium communities because of the tsunami were originally constituted by non-sandy beach D. aegyptium with Cenchrus echinatus. Although the forest floors of most maritime forests were invaded by originally non-sandy beach Tridax procumbens, Eleusine indica or D. aegyptium because of the tsunami, this did not result in a change in the vegetation unit, because species' loss was restricted to the understorey. In time, these forests will recover their previous community composition.
Conclusions: Our results suggest that originally non-sandy beach native species invaded the disturbed beaches rapidly after the tsunami but their habitats differ. Sites where sand accumulated on a beach because of the tsunami were invaded by D. aegyptium and E. indica, whereas soil erosion permitted invasion by Digitania adscendens. Tridax procumbens establishes rapidly on wet sites with hard soil, high per cent silt content and low beach management pressure. Sandy beach species with subterranean long rhizomes are strongly tolerant of such disasters. We concluded that the species composition of the beaches disturbed by a temporary large disaster is determined by dormancy and growth forms, with radicoid form being influential.
Motivation: The Buell-Small Succession Study (BSS) is the longest running study of post agricultural succession in North America. To honor this program, a symposium at the Ecological Society of America meetings was organized to explore the state of succession theory and its contribution to the field of ecology and its application to restoration. The BSS was originally motivated by two controversies in the literature during the 1950's. The first was between a community versus and individual basis of secondary succession. The second was the validity of the Initial Floristic Composition hypothesis.
Location: Hutcheson Memorial Forest, Somerset, New Jersey, USA
Methods: Vegetation composition and cover has been continuously quantified in permanent plots established in 10 old fields.
Continued Research Motivation: The rich data set has documented population and community dynamics and the spatio-temporal controls and historical contingencies that influence those dynamics. The regulation of community dynamics continues to be a line of inquiry as does the application of results to restoration and understanding the dynamics of non-native species.
Conclusions: Long term vegetation studies are uncommon in ecology yet they are uniquely valuable for understanding system dynamics – particularly if the studies capture periodic events or system shifts such as droughts and invasions by non-native species. Resilient long term studies, of which the BSS is an example, maintain methods and data structure while allowing motivating questions to evolve along side advancements in the theoretical and conceptual realms of the field. Succession continues to serve as a basic tenet of ecology which is demonstrated by the papers making up this special issue.
Eleven years of abandonment of a species-rich fen-meadow under undisturbed environmental conditions resulted in transformation into areas with tall herb-, sedge- and rush-dominated communities and areas with Alnus thicket. Species cover was measured in permanent plots in both community types and succession was monitored during 14 yr of restoration following reintroduction of management. The annual increase in accumulated species number followed a log-log-time linear regression during 10 yr of grazing management. The expected number of years taken before this annual rate was equal to annual extinction, i.e. a stable situation according to species density, was up to six. The response of 64 species to management was evaluated through paired statistical tests of changes in cover and frequency over time. In total, 55 species could each be allocated to one unique response model (monotone or non-monotone, concave models) independently of the importance value used (cover or frequency) and type of management (grazing following felling or mowing and mowing without grazing). Species which increased in response to grazing had the most persistent seed banks and CR-strategies, while species decreasing in response to grazing had less persistent seed banks and CS-strategies. Some of the species which increased due to grazing followed a model with a local maximum in cover and frequency. The results are discussed in relation to management of species with high cover value during restoration succession.
Questions: Which factors influence the persistence of vascular grassland plants in long-abandoned (at least 50 yr) arable fields and meadows? What might be the implications of current levels of species richness on abandoned arable fields and meadows for future restoration?
Location: Forested highlands of Kilsbergen, south central Sweden.
Methods: The abundance of all vascular plant species was investigated in three habitat types: former arable fields, hay meadows and outlands (pastures) at 27 farms, abandoned for either approximately 50 yr or 90 yr. Time since abandonment, tree cover, soil depth, degree of soil podsol development, size of the infield area and two measures of connectivity were used as predictors for species richness and species composition.
Results: Former outland had denser tree cover, fewer species and fewer grassland species than former arable fields and hay meadows, irrespective of time since abandonment. Former hay meadows and arable fields with a longer time since abandonment were less rich in species, more wooded and had greater podsolization than meadows and fields abandoned at a later stage. Species richness was higher in hay meadows and arable fields at farms with larger infield area and deeper soils compared with farms with smaller infield area and shallower soils. The greatest richness of species and most open habitat were former arable fields at larger farms abandoned 50 yr before the study. Former arable fields had the highest number of grassland species.
Conclusion: After 50 yr of abandonment, former arable fields were the most important remnant habitats for grassland species and may be a more promising target for restoration than formerly managed grasslands.
Questions: Could the seed bank increase biodiversity during restoration of abandoned, species-poor, formerly cultivated vegetation? Is it possible to identify how climate, soil and former and present management and vegetation affected the seed bank?Location: The study sites were eight abandoned grasslands, four in Orkdal, central Norway and four in Gaular, western Norway.Methods: 144 seed bank samples were collected from three depths. Each sample was sown and placed in a greenhouse. After three months, the trays were dried and stored at 4°C in a dry place for two months. This was repeated twice.Results: There was a separation of the two regions along the first DCA axis in both the seed bank and in the vegetation analysis and also a clear separation of the seed bank from the vegetation along the second axis. These results are caused by differences in former management as well as temperature, precipitation and soil type between Gaular and Orkdal. We found more annuals, short-lived species and species demanding light open conditions in the seed bank than in the vegetation probably because these species have the capacity for producing persistent seeds. Most of the species found only in the seed bank were found in very few samples and with few individuals.Conclusion: These results suggest that it may be difficult to increase vegetation biodiversity through restoration of grasslands such as those investigated if the natural soil seed bank is the main seed source.
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.
Sheep grazing was investigated as an alternative to traditional management of meadows in the Krkonoše Mts. Until the second World War these meadows were mown in mid-summer and grazed by cattle for the rest of the season. Subsequent abandonment of the meadows has resulted in decreasing species richness. Degradation phases of the former communities have been replacing the original species-rich vegetation. Significant changes were apparent six years after the introduction of sheep grazing. In grazed plots the proportion of dominant herbs (Polygonum bistorta and Hypericum maculatum) decreased and grasses (Deschampsia cespitosa, Festuca rubra, Agrostis capillaris, Anthoxanthum alpinum) increased. The increase in grasses was positively correlated with an increase in several herbs. The proportion of some herbs increased despite being selectively grazed (Adenostyles alliariae, Melandrium rubrum, Veratrum lobelianum). Any losses caused by grazing of mature plants were probably compensated by successful seedling establishment. Cessation of grazing resulted in significant changes in vegetation within three years. The cover of nitrophilous tall herbs and grasses (e.g. Rumex alpestris, Holcus mollis, Deschampsia cespitosa, Geranium sylvaticum) increased in the abandoned plots. In the plots grazed for nine years cover of species-rich mountain meadow species increased (e.g. fine-leaved grasses, Campanula bohemica, Potentilla aurea, Viola lutea, Silene vulgaris). The main conservation risk is the expansion of a competitive species with low palatability, Deschampsia cespitosa. This species can be suppressed by a combination of grazing and mowing. In order for grazing to be effective, the number of sheep should be proportional to meadow production. This may be difficult to maintain as production is variable and is impossible to predict at the beginning of a growing season. A large part of the biomass may thus remain intact in some years. Negative effects of grazing may be, at least partly, eliminated by a combination of cutting and grazing.
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.
Secondary succession and seed bank formation was studied in a formerly grazed, abandoned, eastern Hungarian sandy steppe-meadow (Pulsatillo-Festucetum). The vegetation was sampled at different elevations of a sand dune which became partly invaded by the tree Robinia pseudo-acacia ca. 10 yr ago. Pre-abandonment vegetation records were used as historic references. Though composition of the non-invaded grassland only changed moderately, dominance of tall grasses (Elymus hispidus, Poa angustifolia) increased significantly at the cost of annuals and low stature perennials. In the stand invaded by Robinia most grassland species were lost and replaced by nitrophytes. Vertical position influenced species abundance, but affected the composition only moderately. Fine-scale zonation of the vegetation also changed with time. Species richness of the above-ground vegetation and the seed density of soil samples at the lower elevation were slightly greater than at the higher sites.Seed banks of sensitive grassland specialists (e.g. Pulsatilla pratensis subsp. hungarica) disappeared during grass encroachment. Following extinction from above-ground vegetation, restoration must rely on dispersal from adjacent areas. In contrast, several annuals and perennials, which survived this degradation stage in the above-ground vegetation, possessed seed banks. Many of these species became extinct from the vegetation during the Robinia invasion but left viable persistent seeds. This fact is promising for restoration of the Potentillo-Festucetum sandy pasture. Competitive weedy species and sprouting Robinia can, however, limit seedling establishment.
Until the 1960s, species-rich vegetation on minero-trophic peaty soüs (fen sites) were characteristic of the alluvial plains in Schleswig-Holstein (Northwest Germany). Today, many of these habitats undergo successional changes due to abandonment. Vegetation development after abandonment can be characterized as a sequence of different successional stages and described in terms of a successional model. Successional stage I includes grazed, mown and recently abandoned sites without dominants. Stages II and III are characterized by the dominance of highly competitive herbaceous species whüe stage IV consists of woody vegetation.Ca. 3000 phytosociological relevés were assigned to the respective successional stages. Mean cover values were calculated for 250 species of the regional fen flora and assigned to successional categories according to their changes in cover in the successional series. According to our results 141 species decrease during succession, while 100 species were restricted to early successional stages and 85 species increased. Abandonment of all fen sites in Schleswig-Holstein will probably lead to the regional loss of 23 species of the fen flora.To identify mechanisms underlying successional change, the successional categories were correlated with life history traits and ecological requirements of the species. Results indicate that both light competition and limitation of sexual reproduction of small-seeded species might play a major role in the decrease and extinction of species during succession.Finally, conservation strategies for endangered species in a cultural landscape are discussed.
We compared the plant species composition, productivity and canopy structure of seven mown sites to a chronosequence of 20 abandoned calcareous fens in northeastern Switzerland. Cessation of mowing led to an 18% decline in overall plant species richness and the diversity of most functional groups. Abandonment did not lead to marked increases of above-ground productivity, but rather selectively favoured certain functional groups. On abandoned fens biomass of grasses increased nearly threefold, at the expense of biomass of Cyperaceae and Juncaceae, which declined by 30% compared to mown fens, while forb biomass remained unaffected. Litter mass increased more than 15-fold in fallows, while canopy height increased by 50%. The foliage in abandoned fens was oriented more horizontally and had a lower overall cover. However, these successional changes were never dependent upon the age of the fallow. Furthermore, nearly all traits differed significantly on regional and local spatial scales, suggesting that floristic and (meso-)climatic differences obscure or override successional trajectories in these species-rich wetlands.
Question: Our knowledge of secondary old-field succession in Mediterranean environments is extremely poor and is non-existent for restrictive soil conditions. How these ecosystems, such as those on semi-arid gypsum outcrops, recover seems a priority for managing change and for ensuring conservation of specialized and endangered biota. We tested whether reinstallation of gypsum vegetation after cropland abandonment requires: (1) soil physical restructuring and (2) chemical readjustment to enable growth and survival of specialized gypsophilous vegetation, and more specifically how time from abandonment drives such environmental change.
Location: We sampled a complete set of old fields on gypsum soils (1–60 yr since abandonment) in Villarrubia de Santiago (Toledo, Spain).
Methods: Generalized linear models and model comparisons were used to analyse the effect of several environmental parameters on species abundance and richness. Ordination methods (canonical correspondence analyses and partial canonical correspondence analyses) were undertaken to evaluate compositional variation among the sampled fields.
Results: Secondary old-field succession on semi-arid Mediterranean gypsum soils was controlled by a complex set of factors acting relatively independently. Surprisingly, time since abandonment explains only a small proportion of compositional variation (3%). Conversely, soil chemical features independently from time since abandonment are important for explaining differences found in old-field composition.
Conclusions: Secondary succession on specialized Mediterranean soils does not follow the widely described “amelioration” process in which soil features and composition are closely related over time. Restrictive soil conditions control both structure and functioning of mature communities and also secondary succession.
We studied the effects of abandonment on two common fen plant species. In mown and a chronosequence of abandoned fen meadows spanning 35 yr, we measured fitness traits of the sedge Carex davalliana and the forb Succisa pratensis. Cessation of mowing had little effect on fitness traits and seed production of C. davalliana, but seedling density decreased more than threefold. Population density of S. pratensis decreased with increasing community biomass, but was not affected by the cessation of mowing. However, flowering frequency increased threefold and seed production was 20% higher in fallow meadows. Consequently, seedling density of S. pratensis increased nearly threefold after abandonment. However, these changes were not dependent on the age of the fallow. In a common garden and germination experiment, we found no differences in either species between plants from fallows and mown fen meadows, except for the height of the flowering stalk of S. pratensis. The combined results from the common garden experiment and the field studies indicate that changes in fitness traits observed in fallows were mostly phenotypic and likely to be reversible. If other species react in similar ways, there is a high potential for re-establishing traditional fen meadow communities from fallows by mowing.
Question: What are the consequences of grazing abandonment on the Stipa lessingiana dominated steppe-like grasslands? What is the relative importance of management and environmental factors in causing variation in species composition and abundance in the continuously grazed and abandoned grassland stands?
Location: Transylvanian Lowland, Romania.
Methods: Repeated vegetation mapping of a grassland stand, where grazing was abandoned 35 years ago; re-sampling six grassland stands surveyed 29–57 years ago. For revealing long-term changes in species composition and rank abundance PCoA ordination was applied. The relative importance of management and environmental factors in structuring vegetation were explored by CCA ordination. Diversity, evenness and the relative number and abundance of red-listed species were compared between managed and abandoned stands.
Results: Our results pointed out that grasslands which were formerly grazed and dominated by S. lessingiana, in the long-term absence of grazing, have been transformed into a S. pulcherrima dominated type. Management, probably by creating bare surfaces and preventing litter accumulation, had the strongest effect on the species composition and abundance in the grasslands. Abandoned grassland stands had lower diversity and evenness compared to continuously grazed stands. While at the same time, the relative number of threatened, rare species did not differ between managed and abandoned sites.
Conclusion: Maintaining extensively grazed, as well as un-managed, Stipa dominated grasslands would be important in order to create various habitat conditions for plant species, especially threatened and rare species, and promote diversity on the landscape scale.
Questions: What are the short-term effects of restoration treatments, including fire and/or partial cutting with dead wood creation, on seedling density and distribution among microsites, and do they differ between upland and paludified biotopes?
Location: Mature managed Picea abies-dominated stands in southern Finland.
Methods: The restoration treatments consisted of four levels of cutting, with and without fire: uncut, low-CWD (partial cutting leaving 50 m3 ha−1 of standing retention trees and 5 m3 ha−1 of down retention trees, DRT), intermediate-CWD (as previous but with 30 m3 ha−1 of DRT), and high-CWD (as previous but with 60 m3 ha−1 of DRT).
Results: The cutting treatment alone did not affect seedling density. Fire had an immediate effect, both by itself in upland biotopes (decreasing effect on P. abies density) and in combination with cutting in paludified biotopes (increasing effect on Betula spp. density). The density of other deciduous species (Sorbus aucuparia, Populus tremula, and Salix spp.) was not affected. Before treatments, seedlings grew predominantly on level ground and mounds. After treatments, more Betula, but fewer P. abies and other deciduous species, grew on these microsites. More Betula and other deciduous species grew next to CWD and under a fallen crown; more P. abies grew under a fallen crown in unburned stands.
Conclusion: The post-treatment tree seedling density and distribution among microsites can be affected by restoration treatments. However, knowledge of local site characteristics and their interaction with different restoration treatments is needed to achieve the goals set for restoration at the stand and landscape levels.
The effects of reduction and cessation of sheep grazing on salt-marsh vegetation were studied on a formerly intensively grazed salt marsh in northern Germany. Plant species cover was recorded in 45 permanent plots from 1992 to 2000. In 1995, physical and chemical soil parameters were analysed. Results of Redundancy Analysis (RDA) indicated that salinity and the depth of anoxic conditions below the surface were the most important soil factors related to the spatial vegetation pattern. Furthermore, plant species distribution was influenced by present and past grazing intensity, by soil grain size and nitrogen content.
Vegetation changes over 9 yr were analysed by non-linear regression. The cover of Aster tripolium, Atriplex portulacoides, and, to a lesser extent, Artemisia maritima and Elymus athericus increased due to reduced grazing pressure, whereas the cover of Salicornia europaea decreased. After a strong increase in the first years Aster decreased 2 to 6 yr after abandonment. In the mid salt-marsh zone Puccinellia maritima was replaced by Festuca rubra. The cover of Puccinellia, Festuca, Suaeda maritima, Glaux maritima and Salicornia fluctuated strongly, probably due to differences in weather conditions and inundation frequency. Species richness per 4 m2 generally increased while vegetation evenness decreased during the study period. Only in the high salt marsh abandoned for 9 yr did the number of species decrease slightly. Thus far, cessation of grazing did not lead to large-scale dominance of single plant species.
Question: Has the vegetation of Sphagnum bogs been affected by more than 200 years of human activities?
Location: Bas-Saint-Laurent region, southeastern Québec, Canada.
Methods: Data (species assemblages, abiotic and spatio-historical variables) were collected in 16 bogs ranging from 2 to 189 ha, and incorporated in a geographical information system. Major gradients in vegetation composition were identified using DCA. CCA was used to relate vegetation gradients to abiotic and spatio-historical variables.
Results: A clear segregation of species assemblages was observed, from open and undisturbed bogs to forested and highly disturbed sites. Among abiotic factors, tree basal area, water table level and peat thickness had a significant influence on plant species composition. Among spatio-historical factors, disturbance level, area loss and fire were the most influential factors. Variance partitioning between these groups of factors suggests that spatio-historical factors had a major influence on peatlands, representing 22% of the variation observed in the plant species assemblages while abiotic factors represent only 17% of the variation.
Conclusions: The results highlight the influence of agricultural and other anthropogenic activities on plant assemblages and suggest that even wetlands apparently resistant to disturbances, such as peatlands, can be severely affected by anthropogenic factors. Plant species assemblages of ombrotrophic peatlands of the Bas-Saint-Laurent region were, and still are, largely influenced by human activities.
Question: Does experimental warming, designed to simulate future warming of the Arctic, change the biomass allocation and mycorrhizal infection of tundra plants?
Location: High Arctic tundra near Barrow, Alaska, USA (71°18′N 156°40′W).
Methods: Above and below ground plant biomass of all species was harvested following 3–4 yr of 1-2°C of experimental warming. Biomass allocation and arbuscular mycorrhizal infection were also examined in the two dominant species, Salix rotundifolia and Carex aquatilis.
Results: Above-ground biomass of graminoids increased in response to warming but there was no difference in total plant biomass or the ratio of above-ground to below-ground biomass for the community as a whole. Carex aquatilis increased above-ground biomass and proportionally allocated more biomass above ground in response to warming. Salix rotundifolia increased the amount of above- and below-ground biomass allocated per leaf in response to warming. Mycorrhizal infection rates showed no direct response to warming, but total abundance was estimated to have likely increased in response to warming owing to increased root biomass of S. rotundifolia.
Conclusions: The community as a whole was resistant to short-term warming and showed no significant changes in above- or below-ground biomass despite significant increases in above-ground biomass of graminoids. However, the patterns of biomass allocation for C. aquatilis and S. rotundifolia did change with warming. This suggests that long-term warming may result in changes in the above-ground to below-ground biomass ratio of the community.
Question: How does above-ground net primary production (ANPP) differ (estimated from remotely sensed data) among vegetation units in sub-humid temperate grasslands?
Location: Centre-north Uruguay.
Methods: A vegetation map of the study area was generated from LANDSAT imagery and the landscape configuration described. The functional heterogeneity of mapping units was analysed in terms of the fraction of photosynthetically active radiation absorbed by green vegetation (fPAR), calculated from the normalized difference vegetation index (NDVI) images provided by the moderate resolution imaging spectroradiometer (MODIS) sensor. Finally, the ANPP of each grassland class was estimated using NDVI and climatic data.
Results: Supervised classification presented a good overall accuracy and moderate to good average accuracy for grassland classes. Meso-xerophytic grasslands occupied 45% of the area, Meso-hydrophytic grasslands 43% and Lithophytic steppes 6%. The landscape was shaped by a matrix of large, unfragmented patches of Meso-xerophytic and Meso-hydrophytic grasslands. The region presented the lowest anthropic fragmentation degree reported for the Rio de la Plata grasslands. All grassland units showed bimodal annual fPAR seasonality, with spring and autumn peaks. Meso-hydrophytic grasslands showed a radiation interception 10% higher than the other units. On an annual basis, Meso-hydrophytic grasslands produced 3800 kg dry matter (DM) ha−1 yr−1 and Meso-xerophytic grasslands and Lithophytic steppes around 3400 kg·DM·ha−1·yr−1. Meso-xerophytic grasslands had the largest spatial variation during most of the year. The ANPP temporal variation was higher than the fPAR variability.
Conclusions: Our results provide valuable information for grazing management (identifying spatial and temporal variations of ANPP) and grassland conservation (identifying the spatial distribution of vegetation units).
This paper presents a new and simple technique to derive quantitative estimates of green or dry biomass using colour information from digital pictures. This pixel-counting technique is based on the association of particular plant material with a representative region on a two-dimensional colour space, and applies to cases of non-overlapping canopies. The efficacy of the method is demonstrated using sets of samples obtained from both field and laboratory studies. It is shown that application of the proposed approach results in a highly linear relationship between pixel count and foliar area for both green and non-green material [r= 0.99 (p < 0.001)]. Analysis of images from a short-grass steppe shows a high correlation between pixel count and measured values of green biomass [r= 0.95 (p < 0.001)]. The method outlined here allows for a substantial improvement in the speed of sample evaluation to estimate biomass both in the field and in the laboratory. It also provides a non-destructive alternative to monitor plant cover and biomass in open canopies.
Questions: How does recreational disturbance (human trampling) affect soil characteristics, the performance of the understorey vegetation, and the density and species composition of the soil seed bank in Fagus sylvatica forests?Location: Suburban forests near Basel, northwestern Switzerland.Methods: We compared various soil characteristics and the performance of the understorey vegetation in six beech forest areas frequently disturbed by recreational activities with those in six undisturbed control areas, in spring 2003. In the same forest areas, the soil seed bank was investigated using the seedling emergence method. Samples were obtained from soil cores in January 2003.Results: We found substantial changes in soil compaction, above-ground vegetation and in the soil seed bank due to recreational activities. In frequently visited areas, soil compaction was enhanced which caused a decrease in cover, height and species richness of both herb and shrub layers. Compared with control areas, the number of trampling-tolerant species of the seed bank was significantly higher in disturbed areas, and total species richness tended to be higher in disturbed than in control areas. Furthermore, the similarity in species composition between the above-ground vegetation and seed bank was significant lower in disturbed than in control areas.Conclusions: The intensive use of suburban forests for recreational activities, mainly picnicking, affects the vegetation of natural beech forests. Our study indicates that a restoration of degraded forest areas from the soil seed bank would result in a substantial change of the vegetation composition.
Questions: How does disturbance and successional age influence richness, size and composition of the soil seed bank? What is the potential contribution of the soil seed bank to the plant community composition on sites differing in their successional age or disturbance intensity?
Location: Experimental Botanical Garden of Göttingen University, central Germany.
Methods: Above-ground vegetation and soil seed bank were studied on formerly arable fields in a 36-year-old permanent plot study with five disturbance intensities, ranging from yearly ploughing via mowing to long-term uninterrupted succession. We compared species compositions, seed densities and functional features of the seed bank and above-ground vegetation by using several methods in parallel.
Results: The seed bank was mainly composed of early successional species typical of strongly disturbed habitats. The difference between seed bank composition and above-ground vegetation decreased with increasing disturbance intensity. The species of greatest quantitative importance in the seed bank was the non-native forb Solidago canadensis.
Conclusions: The ability of a plant community to regenerate from the soil seed bank dramatically decreases with increasing time since abandonment (successional age) and with decreasing disturbance intensity. The present study underlines that plant species typical of grasslands and woodlands are limited by dispersal capacity, owing to low capacity for accumulation of seeds in the soil and the fact that most species do not build up persistent seed banks. Rare and target species were almost absent from the seed bank and will, after local elimination, depend on reintroduction for continuation of their presence.
Question: To what extent are environmental factors the main determinants of species abundance in Mediterranean coastal marshlands?
Location: The Llobregat delta, Barcelona, Spain.
Methods: Vegetation relevés were performed and a set of water table and soil variables were periodically monitored in 43 sampling points randomly distributed in four marsh areas (sites) along a coastal–inland gradient. A canonical correspondence analysis (CCA) was performed to identify the primary water and soil correlates of species cover, after considering the effect of site and point spatial location. The realized niches of dominant species were modeled through GLMs performed on the first two axes of CCA. Niche overlapping among these species was compared with their coexistence, assessed through pairwise correlations of relative species cover in each sampling point.
Results: Water and soil variables explained more of the variation in species' abundance than site and spatial position. Mean water table level, maximum water conductivity and sodium adsorption ratio (SAR), summarized in the two first CCA axes, explained 23.8% of the variability in species' cover. Arthrocnemum fruticosum, Phragmites australis subsp. australis, Juncus acutus, Spartina versicolor and Juncus maritimus dominated the vegetation stands. Niches obtained from GLM response curves showed moderate overlapping among all these species except for A. fruticosum. However, pairwise correlations were mainly negative or non-significant, indicating low coincidence, and even segregation, between species' cover.
Conclusions: The abundance of dominant plants in Mediterranean marshes is only partly explained by the environmental gradients summarized in niche models. The role of other factors such as facilitation or competition between species and random recruitment should be explored.
Questions: Is the introduced timber species Fraxinus uhdei invasive in Hawai'i? Has logging disturbance facilitated the spread of Fraxinus and other alien species?Location: Windward Mauna Kea, island of Hawai'i.Methods: We surveyed 29 plots which were established before selective logging of the native tree Acacia koa in 1971 to determine if Fraxinus spread beyond the borders of an existing plantation and if other alien species increased. We created gaps in the canopy of the Fraxinus plantation and measured seed rain and regeneration, and we sampled foliar and soil nutrients inside and around the plantation.Results: Basal area of Fraxinus increased from 0.7 m2.ha-1in 1971 to 10.8 m2.ha-1 in 2000. Fraxinus was not found in plots that were located more than 500 m from those where it occurred in 1971 except along a road. Basal area of Acacia koa decreased after logging but subsequently recovered. Occurrence of the alien vine Passiflora tarminiana and alien grass Ehrharta stipoides decreased. Seedling regeneration of Fraxinus was prolific in gaps but did not occur under the canopy. Basal area of Fraxinus did not correlate with soil nutrient concentrations.Conclusions: Fraxinus was able to regenerate following logging more rapidly than native tree species. Basal area growth of Fraxinus was great enough to offset a decline in native trees and cause an increase in forest productivity. If the Fraxinus plantation is harvested, managers should plan ways of favoring regeneration of the native Acacia which is more valuable both for timber and for conservation.
Questions: The formerly overgrazed Inner Mongolia steppe was subject to retrogressive succession. Today, Artemisia frigida and Potentilla acaulis are two dominant species in different phases of successive degradation. To investigate the impact of grazing intensity on spatial community structure, we investigated the small-scale spatial association between A. frigida and P. acaulis at zero, light, medium and heavy sheep grazing, and proposed factors involved in the spatial associations between these two species along a grazing intensity gradient.
Question: To establish a habitat classification based on functional group co-occurrence that may help the drawing up of conservation plans.
Location: Riverine forest fragments in the Grand-duché de Luxembourg, Europe.
Methods: Forest fragments were surveyed for their abundance of vascular plants. These were clustered into emergent groups according to 14 life-traits related to plant dispersal, establishment and persistence. Forest fragments were classified according to similar distribution of the identified emergent groups. Environmental factors were related to the emergent group richness in each forest type using generalized linear models.
Results: Contrary to former species centred classifications, only two groups of forests, each with clearly different emergent group composition and conservation requirements, were detected: (1) swamp forests characterized by anemogamous perennials, annuals and hydrochorous perennials and (2) moist forests characterized by barochorous perennials, small geophytes and zoochorous phanerophytes. From a conservation point of view, priority should be given to large swamp forest with intact flooding regimes. This is in accordance with the high wind and water dispersal capacities of their typical emergent groups. For the moist forests, conservation priorities should be high forest connectivity and historical continuity since dispersal and establishment of their characteristic emergent groups are highly limited.
Conclusions: The described methodology, situated at an intermediate integration level between the individual species and whole community descriptors, takes advantage of both conservation plans built for single species and the synthetic power of broad ecological measures.
Question: Can the seed bank play a significant role in the restoration of plant communities of dry acidic dune grassland where fire has destroyed Ulex europaeus scrub?
Location: Northern French Atlantic coast.
Methods: One year after the fire, the seed bank and vegetation were sampled in 1 m × 1 m plots along three transects from the oldest scrub vegetation towards the grassland. Differences in species richness, seed density and contribution of ecological groups in the seed bank and vegetation along the transects were analysed.
Results: Seed density and species richness in the seed bank decreased significantly from the grassland towards the centre of the scrub vegetation; 50% of the seed bank consisted of core species of the target plant community, such as Carex arenaria, Aira praecox, Rumex acetosella and Agrostis capillaris. Seeds of these species were also found in the deeper soil layers beneath the oldest scrub vegetation, indicating that they can be considered to be long-term persistent. Beneath the youngest scrub vegetation, seeds of rare satellite target species also occurred. However, no target species were established on the burned site after one year, resulting in a large discrepancy between seed bank and vegetation.
Conclusions: Although the seeds present in the soil indicate that restoration of the acidic grassland based on the seed bank is possible, additional management actions such as mowing and soil disturbance may be necessary to restrict resprouting of Ulex and to stimulate the germination of seeds of target species in the deeper soil layers.
Questions: (1) Does soil acidification in calcareous sandy grasslands lead to loss of plant diversity? (2) What is the relationship between the soil content of lime and the plant availability of mineral nitrogen (N) and phosphorus (P) in sandy grasslands?
Location: Sandy glaciofluvial deposits in south-eastern Sweden covered by xeric sand calcareous grasslands (EU habitat directive 6120).
Methods: Soil and vegetation were investigated in most of the xeric sand calcareous grasslands in the Scania region (136 sample plots distributed over four or five major areas and about 25 different sites). Environmental variables were recorded at each plot, and soil samples were analysed for exchangeable P and N, as well as limestone content and pH. Data were analysed with regression analysis and canonical correspondence analysis.
Results: Plant species richness was highest on weakly acid to slightly alkaline soil; a number of nationally red-listed species showed a similar pattern. Plant species diversity and number of red-listed species increased with slope. Where the topsoil had been acidified, limestone was rarely present above a depth of 30 cm. The presence of limestone restricts the availability of soil P, placing a major constraint on primary productivity in sandy soils.
Conclusions: Acidification of sandy grasslands leads to reduced abundance of desirable species, although the overall effect is rather weak between pH 5 and pH 9. Slopes are important for high diversity in sandy grasslands. Calcareous soils cannot be restored through shallow ploughing, but deep perturbation could increase the limestone content of the topsoil and favour of target species.
Minsmere is a large nature reserve in East Anglia UK, owned and managed by the Royal Society for the Protection of Birds (RSPB). Two blocks of land, which were farmed commercially until 1990, have been bought in an attempt to link existing patches of heathland and acid grassland, thus creating a larger area for conservation. This paper discusses methods for the creation of acid grasslands. Previous studies of the arable soils in these fields identified three constraints -a depauperate seed bank, a high pH and vigorous growth of ruderal species after the fields were abandoned. Accordingly, experiments were set up to test the effects of (1) adding seed of species typical of acid grasslands and (2) adding amendments (elemental sulphur, litter of Pteridium aquilinum and pine chippings) to acidify the soil. The results confirmed that ruderal growth was high on unamended plots, but this could be reduced by addition of acidic amendments. Where the cover of ruderals was reduced, the cover of the sown species increased. The sown species colonized adjacent unsown subplots naturally and this was most pronounced where the acidity had been reduced by treatment. The most effective treatment was 21 S/ha, which gave the optimal reduction in soil pH, controlled ruderal growth and provided a reasonable cover of the sown species. The addition of Pteridium litter or pine chippings gave good establishment of sown species, but control of the ruderals was less effective.
Question: Does grazing by large herbivores affect species composition or community-wide variation in plant functional traits?Location: Dune grasslands at the Belgian coast. Methods: Plant cover and soil data were collected in 146 plots that were randomly selected at 26 grazed and ungrazed grassland sites. Plant community composition was assessed by Detrended Correspondence Analysis and mean values of plant trait categories were calculated across the plots.Results: Differentiation of plant composition and community-wide plant trait characteristics was largely determined by grazing, soil acidity and their interaction. In ungrazed situations, a clear floristic distinction appears between acidic (non-calcareous) and alkaline (calcareous) grasslands. In grazed situations, these floristic differences largely disappeared, indicating that grazing results in a decrease of natural variation in species composition. At higher soil pH, a larger difference in plant community composition and community-wide plant traits was observed between grazed and ungrazed plots. In ungrazed situations, shifts in plant functional traits along the acidity gradient were observed.Conclusions: Grazing is responsible for shifts in plant community composition, and hence a decrease in plant diversity among grasslands at opposing acidity conditions in coastal dune grasslands. Therefore, care should be taken when introducing grazing as a system approach for nature conservation in dune grasslands as it may eliminate part of the natural variation in plant diversity along existing abiotic gradients.
Plant traits which may give an indication of a plant's strategy for nutrient acquisition and regeneration are known for numerous grassland species. This study aimed to establish whether there is any relationship between two plant traits: specific leaf area (SLA) and number of reproductive tillers, and sward structural characteristics which influence herbage intake by grazers (bulk density and digestibility, leaf:stem ratio). Comparison is made for nutrient-rich (Dactylis glomerata) and nutrient-poor (Festuca rubra) grass species. We hypothesized that these traits are responsive to environmental gradients and also act on the processes of the ecosystem. Both grasses were compared with two P-fertilizer rates in two localities (200 and 1300 m a.s.l.) which differed in their temperature:radiation ratios. For the vegetative phase SLA was well correlated with sward characteristics: D. glomerata, which has the higher SLA, has the lower bulk density and higher digestibility. The values of SLA and vegetation bulk density varied according to growing conditions (P-rate and temperature:radiation ratio), but the ranking of the species remained the same because the phenotypic plasticity that exists for plant traits was also observed for sward structure and composition. That suggested the possibility of grouping natural grassland species for their relevant characteristics for grazers according to SLA values. Over the reproductive phase, the proportion of stems was well correlated to the percentage of reproductive tillers. However, the percentage of reproductive tillers was a very plastic trait for both species, depending on the growing conditions, and resulting in a density-dependent effect, particularly for F. rubra. The species studied were too plastic and too similar in their regenerative strategy so that there is no unique relationship between percentage of reproductive tillers and stem proportion, regardless of the species and the growing conditions. The number of reproductive tillers is not a suitable plant trait which could be used to rank species for leaf and stem proportions in the sward.
QuestionHow does large-scale context affect native and alien species richness across different habitat types?LocationCatalonia, NE Spain.Methods
We analysed a set of 5309 vegetation plots from the BDBC (Biodiversity Data Bank of Catalonia) database, organized following the UTM (Universal Transverse Mercator) 10 km × 10 km grid. Plots were assigned to the first or second hierarchy of EUNIS (European Nature Information System) habitat classification. For each plot, the number of native plants (including archaeophytes, i.e. alien plants introduced before 1500 ad) and neophytes (alien plants introduced after 1500 ad) was recorded. Neophytes were classified according their Raunkiaer's life form. For each UTM we selected eight predictors related to land cover composition, anthropogenic context and climate. The association of neophyte and native species richness with these predictor variables was explored by generalized linear mixed models for each terrestrial habitat type after controlling for plot area.ResultsA total of 77 different neophyte species were found distributed among the eight habitat types with fitted models. Minimum adequate models on both neophyte and native species richness were highly variable. In general, native species richness responded more to climatic variables, while neophyte species richness was associated more with human landscape factors such as distance to main roads and, secondarily, cropland cover.Conclusions
Context factors defined on a large scale (10 km) have a significant effect on local native and neophyte species richness for many habitat types in Catalonia. Our results highlight the major influence of climatic context on native species richness and the influence of human landscape context on neophyte species richness in the study region. The inconsistency of results between habitat types suggests that this large-scale effect might be highly idiosyncratic and dependent on species ecology and life form.
Question: Do low or high intensity fires affect micro-organism activity in the upper soil layer of Mediterranean maquis?
Location: 600 m from the sea in the Nature Reserve of Castel Volturno (Campania, southern Italy, 40°57’N; 13°55’E).
Methods: Soil respiration was measured in situ on intact soil; enzyme activity (cellulase, xylanase, invertase, trehalase and protease) and ATP content were measured on soil samples collected under three species of maquis vegetation: Phillyrea angustifolia L., Myrtus communis L. and Cistus incanus L.
Results: Soil microbial respiration showed no significant differences in CO2 flux in treated and untreated plots, but the ATP content in the soil under C. incanus and M. communis was lower in the treated plots for most of the study period. In the soil under Ph. angustifolia, ATP content was low only for one week after fire. The reduction was more marked in the samples from ‘high fire intensity’ than from ‘low fire intensity’ plots. Soil respiration and ATP content exhibited seasonal variations linked to soil water content. Among the enzyme activity measured in the soil under the three plant covers, only invertase declined in burned plots throughout the study period, particularly in the ‘high fire intensity’ plots. Activity of the enzymes cellulase, xylanase, trehalase and protease had a different sensitivity depending on the respective shrub cover.
Conclusions: Impact of fire on soil microbial activity is largely dependent on vegetation mosaic and species identity.
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.
Question: Does forest vegetation community structure reflect legislative land use designations?Location: Adirondack Park, New York, USA.Methods: The Adirondack Park, located in northern New York State, is a mixture of public and private lands, with state-owned Forest Preserve lands comprising ca. 42% of the 2.4 million ha, on which timber harvesting and many other forms of anthropogenic disturbance are prohibited. A survey of vegetation communities was conducted in eighteen upland catchments with differing land use history (managed and Forest Preserve), including overstory, understory, and dead wood (snags and downed woody debris) using randomly placed plots.Results: Mean overstory density and basal area were not significantly different between land uses, although mean overstory tree size was greater in Preserve catchments. Sapling densities were greater in managed catchments, while mean herb/shrub coverage was not affected by land use. Densities of 25% of common species were affected by land use, determined by GIS coverages constructed using an Inverse Distance Weighted estimation procedure. Discriminant Analysis of per-plot plant community data correctly classified 89% of both managed and Preserve plots.Conclusion: The success of the Discriminant Analysis in classifying land uses based on vegetation communities indicates its potential utility of this method in comparing forest vegetation to a reference condition in this and other areas. The analysis suggests that at least 85 years is required for Adirondack up-land catchments to recover following harvesting. Uncertainty in classification was related to heterogenous management and disturbance patterns within catchments.
Questions: Do invasions of P. halepensis (Aleppo pine) from plantations into adjacent natural communities occur in the Mediterranean region, where the species is native? What are the spatio-temporal processes involved in pine invasions in contrasting Mediterranean and semi-arid climatic regions?
Location: Mediterranean and semi-arid regions of Israel.
Methods: The density of invading Pinus was measured in relation to the distance from the plantation edge. Plants were categorized by age, height, basal stem girth and developmental stage, their spatial distribution was also recorded.
Results: Analysis of plant age distribution indicates that the invasion process started when the plantations were 20–25 years old. Most invading plants were found within 20 m from the plantation edge, but a few individuals reached distances up to 100 m and became new invasion foci. Plant density declined sharply with distance from adult trees, data showing a better fit to a power model than to a negative exponential model. Invading Pinus began to produce cones earlier in the semi-arid than in the Mediterranean region (9 vs 12 years to 50% reproductive plants). In both regions, higher densities of invading plants were found on the west side of the plantation, the opposite direction to the hot winds that prevail during seed release.
Conclusion: The frontal advance of P. halepensis from plantations is relatively slow, but the populations also expand by a saltation process, creating spreading ‘islands’ of pine trees in the natural vegetation. Spatial pattern of recruits with distance from the source population was remarkably similar to the pattern of seed dispersal in the same region (Nathan et al. 1999). This implies that the probability of a dispersed seed developing into a plant is independent of the distance from the forest edge.
Question: Does clear-felling influence forest herb colonization into post-agricultural forest?
Location: A stand of poplar cultivars with a dense understorey of Acer pseudoplatanus in Muizen forest (northern Belgium), planted in 1952 on farmland adjacent to ancient forest and clear-felled in 1997.
Methods: Shade-tolerant forest herbs were surveyed in 112 grid-based sample plots: just before clear-felling, and 5 and 10 yr afterwards. Shade-tolerant herbs were subdivided into ancient forest species (AFS) and other shade-tolerant species (OSS). Effects of clear-felling on species number per plot, total cover per plot and colonization rate of species groups were compared using non-parametrical tests. Species number per plot was modelled by means of generalized linear mixed models (GLMMs), with inventory time, distance to the nearest parcel edge, and cover of light-loving species (LS) as explanatory variables. The C-S-R signature (competitive, stress-tolerant and ruderal strategies, respectively) shift of sample plots was calculated on the selected shade-tolerant species.
Results: Frequency of most species increased during the 10-yr period. Number of OSS increased more and faster than that of AFS. OSS increased to the level of the adjacent forest, but was lower where LS cover remained high. There was a positive correlation between the change of the colonization rate and the competitive plant strategy.
Conclusions: We assume that clear-felling stimulated generative reproduction of shade-tolerant herbs, whereas quickly emerging woody species controlled competitive exclusion by LS. Succession of dark and light phases, such as provided by an understorey managed as a coppice, could promote colonization of shade-tolerant herbs into post-agricultural forest.
Piper aduncum is a neotropical invasive species which has spread throughout Papua New Guinea over the past three decades. It has become a most successful alien woody plant in New Guinea, occurring from sea level up to 2000 m a.s.l. The species prefers initial stages of forest succession and is particularly common in recently abandoned gardens representative of a system of swidden agriculture. It often attains high cover, suppresses other pioneer species and becomes the absolute dominant species in these habitats. The species is now also spreading into naturally disturbed habitats far from direct human influence, such as natural tree-fall gaps, landslides and frequently flooded stream banks. It has, however, never been found in a closed primary forest. The species germinates from faeces of mammal and bird species, and we conclude that dispersal through endozoochory contributes to this species’ extraordinary success in Papua New Guinea. A similar invasion behaviour has been documented over a large geographic area, from Malaysia to Fiji. Piper aduncum has attributes which are common amongst successful invasive species: (1) a large native geographic range; (2) aggressively colonizing disturbed habitats in its native area; (3) relatively small seeds; (4) a short juvenile period; (5) a large seed production every year.
Question: Recognizing water table dynamics in wetlands is crucial for understanding species-environment relationships, ecosystem function and changes during restoration. The PVC tape discolouration method enables spatially and temporally extensive studies of reductive conditions associated with long-term water table dynamics in peat soils. The reliability of the method has been verified only for ombrotrophic bogs, even though wide usage can be expected in minerotrophic fens.
Location: Třreboň basin, Czech Republic.
Methods: Using data from 49 plots in six poor and moderately rich fens, we correlated the directly measured lowest, highest and mean water table depths and the same variables indicated by discolouration of PVC tape attached to green bamboo stakes installed vertically in the soil profile.
Results: The depth to the first sign of PVC discolouration was highly correlated with the directly measured position of the highest water table, the correlation between the depth of complete discolouration and the directly measured position of the lowest water table was poorer. The accuracy of the minimum water table measurement depended on the depth of the peat layer. Surprisingly, the depth at which the green bamboo stakes turned brown correlated highly with the minimum water table.
Conclusions: The PVC tape discolouration method reliably indicates water table maxima in fens, but minima are not accurately indicated. The depth of the green bamboo discolouration is suggested as a new alternative indicator of the minimum water table, even in fens and mineral soils. Combining both methods enables efficient monitoring of water table dynamics at a large number of mire sites.
Question: To what extent can aerial photography be used for taxonomic identification of Amazonian tree crowns?Objective: To investigate whether a combination of dichotomous keys and a web-based interface is a suitable approach to identify tree crowns.Location: The fieldwork was conducted at Tiputini Biodiversity Station located in the Amazon, eastern Ecuador.Methods: High-resolution imagery was taken from an airplane flying at a low altitude (600 m) above the ground. Imagery of the observable upper layer of the tree crowns was used for the analysis. Dichotomous identification keys for different types of crowns were produced and tested. The identification keys were designed to be web-based interactive, using Google Earth as the main online platform. The taxa analysed were Iriartea, Astrocaryum, Inga, Parkia, Cecropia, Pourouma, Guarea, Otoba, Lauraceae and Pouteria.Results: This paper demonstrates that a combination of photo-imagery, dichotomous keys and a web-based interface can be useful for the taxonomic identification of Amazonian trees based on their crown characteristics. The keys tested with an overall identification accuracy of over 50% for five of the ten taxa with three of them showing accuracy greater than 70% (Iriartea, Astrocaryum and Cecropia).Conclusions: The application of dichotomous keys and a web-based interface provides a new methodological approach for taxonomic identification of various Amazonian tree crowns. Overall, the study showed that crowns with a medium-rough texture are less reliably identified than crowns with smoother or well-defined surfaces.
A technique for fine-scale vegetation mapping with the aid of low-altitude aerial photography was developed. The procedure is as follows: 1. The site is divided into a lattice pattern - in case the site is too large to fit into a single photograph with satisfactory resolution. The coordinates of every lattice point are surveyed to be used as control points for geometric correction. A photograph of each block of the lattice is taken using a remote-controlled camera system lifted by a captive helium balloon. 2. The vegetation is classified on the basis of a phytosociological survey. 3. The shapes and locations of vegetation patches appearing in the photographs are entered into a computer, using a digitizer. A geometric correction is carried out through coordinate transformation referring to the coordinates of the control points and subsequently a draft vegetation map is produced. Finally, discrepancies are corrected and the map is coloured to produce the final version of the vegetation map.This technique was applied to vegetation mapping at a bar, 500 m wide and 2 km long, in the river Yoshino in Shikoku, Japan. A fine-scale vegetation map was obtained and used to analyse the influence of plants on geomorphic processes and community-specific hydrogeomorphic conditions on the bar.
Conservation management has significant gaps between (1) collection and storage of biological data, (2) data analysis, and (3) application of results. In order to improve management decision-making, it is necessary to bridge these gaps. One of the most promising approaches uses computer-based decision support systems (DSS): interactive models of the system in question—for example, a nature reserve. One kind of DSS is scenario modeling: spatially-based models which (1) use expert opinion and data on vegetation, geology, hydrology, and management, (2) to project changes in landscape through time, (3) on the basis of changes in driving environmental factors. Scenario models are essentially graphic hypotheses, predicting changes in landscape with a specified change in driving factors, which can then be verified or falsified by monitoring.This paper presents an application of this approach to an Israeli nature reserve, the En Afeq Reserve in western Galilee. Our project tests the possibility of improving Israeli conservation management by using methods now standard for nature reserves in the Netherlands.
Succession, changes in the distribution pattern of forest vegetation, and Pinus forest survival following pine wilt disease were clarified based on phytosociological analysis and vegetation maps. Survival of Pinus forests was restricted to the early successional stages, which were located on ridges and the upper part of slopes. Subsequent to pine wilt disease, the succession progressed from early to late substages of Pinus forest, mixed deciduous and evergreen Quercus, to evergreen Quercus forest. Succession occurs in abandoned pine forests which apparently are in a bad state and are vulnerable to attacks by pine wilt disease.
Question: Are growth form and dispersal-mode replacement during vegetation succession in semi-arid Mediterranean conditions affected by the starting quality of the substrate and by site aspect?
Location: Central-western Spain.
Methods: We monitored successions on three waste materials left after uranium mining: unbroken waste, broken waste and wastes amended with a sandy material (Arkoses); both north and south aspects were also studied on each substrate.
Results: The substrate starting quality had the greatest influence on spontaneous succession, separating the poorer quality substrates (broken and unbroken wastes) from the better ones (Arkoses) and two reference communities (Topsoil and Dehesa). The importance of aspect was confirmed then within each substrate type. Most species with a short life span (mostly annuals and a few biennials), together with some woody species on Arkoses, showed no response to age (years following the deposition of new soil). Others short-lived species declined over time on the poorer wastes but not on the better Arkoses. There was a tendency for life form replacement (from thero-phytes to hemicryptophytes) during succession only on the poorer-quality substrates. No dispersal-mode replacement sequence was found.
Conclusion: Improving the abiotic conditions of the substrate had a great effect on vegetation succession, but this effect was modified by aspect. Aspect took longer to induce differences in floristic composition on the poorer substrates, where succession was slower. Some trends in species responses to successional change were found by considering species traits, particularly life-form.
Question: Does management intensity affect the association between non-native and native species and between non-native species and soil nutrients in wetlands?
Location: MacArthur Agro-Ecology Research Center, Florida, USA.
Methods: We evaluated native and non-native plant richness and relative frequency in 15 1-m2 plots in 40 wetlands across two types of pastures, highly managed (fertilized, ditched, planted, heavily grazed by cattle) and semi-natural (unfertilized, lightly seasonally grazed). Plant biomass was collected in five 0.25-m2 plots per wetland and sorted to species. Soil cores were collected to analyse soil total nitrogen (N) and phosphorus (P). An information-theoretic approach was used to compare mixed effects models considering the association of non-native richness, relative frequency, and biomass with native richness, relative frequency, biomass, C3 grass relative frequency (a dominant native group), N, P and wetland-type.
Results: Non-native richness was negatively correlated with native richness in semi-natural wetlands, but there was no evidence of an association between these variables in highly managed wetlands. Non-native richness increased with increasing soil N in semi-natural wetlands, but not in the highly managed wetlands. Soil P was positively related to non-native frequency in semi-natural wetlands but negatively related in highly managed wetlands. Non-native frequency and biomass were negatively related to relative frequency of C3 grasses in both management types.
Conclusions: Our results indicate that management intensity influences relationships between native and non-native richness. Management intensity interacts with abiotic or biotic factors, such as soil nutrients and composition, in predicting where non-native species will most likely need control.
Question: What is the impact of grazing and/or afforestation on grassland diversity, species composition and cover parameters?Location: Semi-arid Mediterranean grasslands of Jordan.Methods: Vegetation, litter, bare soil and rock cover were compared among four management types – free grazing and protected from grazing with three levels of tree cover. Species composition, plant cover, species richness and evenness were used to evaluate differences in vegetation among management types. Species composition differences among management types were also investigated.Results: Semi-arid Mediterranean grasslands harbour appreciable levels of plant biodiversity. Grazing did not affect plant diversity, indicating the high resilience against and adaptation to grazing; however,grazing affected species composition and cover parameters. Afforestation seems to protect soil through higher litter cover but its impact on plant biodiversity was negative and markedly affected species composition.Conclusions: Neither protection from grazing or massive afforestation alone are sufficient for conserving biodiversity in this system. A management model is suggested where the landscape should be maintained as a mosaic of four management types: complete protection from grazing, grazing rotation, planting sparse trees in eroded areas and revegetating degraded areas using native, herbaceous and grazing tolerant species.
Question: Is Opuntia stricta more frequent, and its patches larger, under trees suitable for baboon roosting? If so, does it mean that baboons are major dispersal agents and that plants established under these trees are important foci of Opuntia stricta spread?
Location: Skukuza, Kruger National Park, South Africa.
Method: We surveyed an area invaded by Opuntia stricta in the Skukuza region of KNP. The survey included plots under potential baboon roosting trees,plots under trees unlikely to support baboons,and paired randomly located open sites.
Results: The null hypothesis -tree-Opuntia spatial independence – can be rejected for Acacia nilotica, but not for Spirostachys africana. Opuntia plants are positively associated with Acacia trees suitable for baboon roosting. However, there is no significant difference between frequency of Opuntia under Acacia trees suitable and unsuitable for baboon roosting.It appears that all Acacia trees can serve as nurse trees for Opuntia. Compared to plots under Acacia trees, frequencies of old and robust Opuntia plants are significantly higher in open areas and under dead trees.
Conclusions: While baboons may be responsible for long distance Opuntia dispersal (over km),their role is not detectable at a local scale.On the other hand, elephants seem to contribute substantially to the local vegetative propagation of this species. Opuntia establishment and growth are more influenced by micro-habitat than previously thought.