We assessed if the relative importance of biotic and abiotic factors for plant community composition differs along environmental gradients and between functional groups, and asked which implications ...this may have in a warmer and wetter future. The study location is a unique grid of sites spanning regional-scale temperature and precipitation gradients in boreal and alpine grasslands in southern Norway. Within each site we sampled vegetation and associated biotic and abiotic factors, and combined broad- and fine-scale ordination analyses to assess the relative explanatory power of these factors for species composition. Although the community responses to biotic and abiotic factors did not consistently change as predicted along the bioclimatic gradients, abiotic variables tended to explain a larger proportion of the variation in species composition towards colder sites, whereas biotic variables explained more towards warmer sites, supporting the stress gradient hypothesis. Significant interactions with precipitation suggest that biotic variables explained more towards wetter climates in the sub alpine and boreal sites, but more towards drier climates in the colder alpine. Thus, we predict that biotic interactions may become more important in alpine and boreal grasslands in a warmer future, although more winter precipitation may counteract this trend in oceanic alpine climates. Our results show that both local and regional scales analyses are needed to disentangle the local vegetation-environment relationships and their regional-scale drivers, and biotic interactions and precipitation must be included when predicting future species assemblages.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In theory, canopy openings can influence tree species establishment and resulting distributions over environmental gradients, but evidence concerning the magnitude and direction of such effects ...remain scarce. In this study we examine how canopy openings influence seedling persistence and growth and resulting elevation range limits. We transplanted 1360 seedlings of eight woody species (trees Trichilia habanensis, Persea caerulea, Cedrela tonduzii, Cornus disciflora, Quercus salicifolia, Q. bumelioides, Q. costaricensis and the shrub Hypericum irazuense) under the forest canopy and in open areas with understorey vegetation removed in a replicated design along a 2900 m elevation gradient in Costa Rica. We recorded survival, stem diameter and height over 18 months. We used hierarchical generalized additive models to examine relationships of seedling survival and growth with elevation and treatment (inside forest versus open area). We found a clear effect of open versus forest conditions on survival across the elevation gradient for six species. Species planted into open areas with full light exposure survived 100–1000 m below (~ 0.5–5°C warmer), and in one case 300 m above (~ 1.8°C colder) their observed ranges. Above 2900 m, survival of all species was markedly greater under the forest canopy versus open sites, suggesting facilitation from the forest, as frost occurred in open areas above this elevation. The resulting upper range increased between 200 and 1160 m (~ 1–6°C colder) compared to their observed range. At lower elevations, severe insect herbivory occurred on some species likely influencing lower range limits. Open areas influenced how seedling survival and growth varied with elevation for all the studied species. All species survived and grew outside the elevation ranges where they are typically observed. We suggest that the influence of forest gaps and clearings over extended gradients offers novel insights into tree range dynamics, limits and conservation.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
1 I examined the role of species interactions on the population dynamics of the herb Thalictrum alpinum and the sedge Carex vaginata by removing the dwarf shrub Dryas octopetala over four growing ...seasons at Finse, in the alpine region of south Norway, Furthermore, by increasing temperature (open top chambers) and nutrient availability (nutrient addition), I assessed the effects of climate warming on biotic interactions. 2 Dryas removal increased the number of Thalictrum and Carex leaves, and flowering frequency of Carex. Flower stems and leaf stalks of Thalictrum, and the leaves of Carex, became significantly shorter following Dryas removal. Warming and nutrient addition increased vegetative plant growth, whereas warming alone had positive effects on sexual reproductive effort of the target species. My results suggest that there is both competition for nutrients, and a facilitative shelter effect of Dryas on its neighbours. 3 Species interactions affected population dynamics of Thalictrum and Carex. Interactions between the impacts of Dryas removal and abiotic factors on leaf production, suggested that interactions between Dryas and neighbouring species might be modified if temperature and, in particular, nutrient availability increase under global warming. 4 This study shows that both biotic interactions and abiotic environmental conditions may affect alpine plant population dynamics. Furthermore, it shows that climate change may modify species interactions. 5 Species interaction effects should be included in climate change experiments and in future models predicting plant community changes under global warming.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
Question: How will warming and increased nutrient availability affect individual alpine plant species abundances (non-vascular and vascular) and community composition? Location: Dryas octopetala ...heath at alpine Finse, southern Norway. Methods: Four years with experimental warming (open top chambers) and nutrient addition. Detrended Correspondence Analysis and Redundancy Analysis were used to examine changes in community composition. GLM-ANOVA was used to examine treatment effects on individual species. Results: Warming alone decreased the abundance of some Carex and bryophyte species, but did not affect community composition. Nutrient addition and warming combined with nutrient addition increased the abundance of high stature species, such as grasses (Festuca spp., Poa alpina) and some forbs (e.g. Cerastium alpinum, Potentilla crantzii). Low stature forbs (e.g. Tofieldia pusilla), a lycophyte (Selaginella selaginoides) and most bryophytes and lichens decreased in abundance. After four years of warming combined with nutrient addition 57% of the mosses, 57% of the liverworts and 44% of the lichens had completely disappeared. Community composition changed significantly, with the largest shift when warming and nutrient addition was combined. Conclusions: Tall species may expand at the expense of low stature species in the alpine region if temperature and soil nutrient content increase. Contrasting responses between grasses and sedges, and species-specific responses within forbs, sedges and shrubs, within and across alpine and arctic sites, suggest that the use of functional types in environmental change research may mask important information on individual species responses. The response of one species within a functional type cannot predict the response of another. Nomenclature: Lid & Lid (1994) for vascular species; Hallingbäck & Holmåsen (1995) for bryophytes; Krog et al. (1994) for lichens.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NMLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Understanding the degree to which plant communities are open to seedling recruitment is key to predicting how they will be impacted by climate change. We experimentally assessed whether communities ...assembled under colder climates were inherently more open to recruitment than warmer‐climate communities, after controlling for differences in the current climate under which the communities were growing. We then tested whether variation in openness to recruitment could be explained by community biomass or by the plant functional traits of the community.
The study was conducted in a climate grid of twelve grassland sites across southern Norway, differing systematically in temperature and precipitation. Along a 2000 mm precipitation gradient, we transplanted turfs with intact plant communities from alpine and sub‐alpine sites into 2°C warmer sites, and measured natural seedling emergence in these transplanted turfs versus locally replanted control turfs at the transplant destination sites. Mixed effect models were used to assess the effect of origin (cold versus warm climate), biomass, and functional trait composition of the communities on seedling emergence. We further assessed variation in these effects across different climatic contexts (the temperature and precipitation gradients).
Communities originating from colder climates were consistently more open to recruitment, with on average 44% more seedlings emerging, than the locally replanted control communities. The higher rates of seedling emergence in colder‐climate communities were attributable to systematic differences in plant functional traits, but not in biomass. The colder‐climate communities were composed of species with smaller leaves and lower maximum plant heights; traits that may make these communities less effective at excluding new recruits. These trait‐related responses were not significant in the warmest sites and did not very across the precipitation gradient.
Our results suggest that alpine species lack the competitive effect traits required to make their communities resistant to invasion by novel competitors under climate change.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
•We evaluate the influence of forest certification on conserving biodiversity.•Biodiversity indicators are higher in certified forests than non-certified forests.•Forest certification appears to have ...positive influence on conservation.•Forest certification may be a good policy option to conserve forest biodiversity.
Forest certification management standards aim at maintaining forest ecosystem integrity, including forest biodiversity conservation. However, studies from the Amazon and Congo basin find that forest certification may not protect forest biodiversity and ecosystems, and may therefore be unsustainable. This study evaluates the influence of forest certification on conserving biodiversity. Specifically, we (a) estimate tree (adult and seedling) species richness, diversity and density among different forest management regimes; (b) assess the relationship between environmental and human forest use variables, and species richness, diversity and density among the forest management regimes; and (c) assess the influence of forest governance of villages adjacent to the forests on tree (adult and seedling) species richness, diversity and density among the forest management regimes. This is achieved in a comparative study of Forest Stewardship Council certified community forests, non-certified open access forests, and non-certified state forest reserves in the Kilwa District in Tanzania.
Our results show that forest certification standards and implementation processes are positively related to biodiversity conservation. There are significantly higher tree (adults) species richness, diversity, and density in certified community forests than in open access forests and state forest reserves. These findings suggest that forest certification may be a good policy option to conserve biodiversity. The present study is one of the first studies in tropical Africa, which contributes to the limited data on the influence of forest certification on conserving biodiversity. Our results may also serve as baseline for further research on the contribution of certified forests in conserving biodiversity at both temporal and spatial scales.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Soil temperature and moisture are important regulators of a broad range of biotic and abiotic processes in terrestrial ecosystems. Vegetation can, in turn, play a role in regulating soil ...microclimate, which creates potential for powerful and interactive feedbacks from soil and vegetation on the atmosphere. Although the regulatory effect of vegetation on soil microclimatic conditions has been quite extensively and empirically assessed, most studies have determined the net effect of intact woody vegetation versus bare ground. However, for other plant functional groups we lack a clear understanding of their role and any climate‐context dependency in controlling microclimatic conditions.
We investigated the role of three major plant functional groups – graminoids, forbs and bryophytes – in regulating soil microclimate in semi‐natural alpine grasslands. Using a fully factorial above‐ground biomass removal experiment, we assessed the role of these plant functional groups in regulating soil temperature amplitude, soil moisture, and number of freezing days. The experiment was replicated across orthogonal temperature and precipitation gradients in Norway to assess whether the effects of functional group abundance varied with climate.
The effect of plant biomass on soil microclimate varied among functional groups across the climatic gradients. Bryophytes reduced growing season soil temperature, whereas graminoids and forbs did not (0.5ºC compared to 0ºC), and with a stronger effect in colder climates at higher elevations and on days with high solar radiation. Bryophyte biomass further reduced the number of soil freezing days at boreal and sub‐alpine sites. Finally, graminoid biomass partly explained variation in soil moisture: soils dried more under graminoids at drier sites.
Our findings highlight that functional group identity plays a key role in regulating soil microclimate in alpine grasslands across seasons. The strong effect of bryophytes on soil temperature points to their importance in the plant community for a variety of ecosystem functions, some of which may be indirectly vulnerable to future warming via biomass reductions of bryophytes.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The determinants of local species richness in plant communities have been the subject of much debate. Is species richness the result of stochastic events such as dispersal processes, or do local ...environmental filters sort species into communities according to their ecological niches? Recent studies suggest that these two processes simultaneously limit species richness, although their relative importance may vary in space and time. Understanding the limiting factors for species richness is especially important in light of the ongoing global warming, as new species establish in resident plant communities as a result of climate-driven migration. We examined the relative importance of dispersal and environmental filtering during seedling recruitment and plant establishment in an alpine plant community subjected to seed addition and long-term experimental warming. Seed addition increased species richness during the seedling recruitment stage, but this initial increase was cancelled out by a corresponding decrease in species richness during plant establishment, suggesting that environmental filters limit local species richness in the long term. While initial recruitment success of the sown species was related to both abiotic and biotic factors, long-term establishment was controlled mainly by biotic factors, indicating an increase in the relative importance of biotic interactions once plants have germinated in a microhabitat with favourable abiotic conditions. The relative importance of biotic interactions also seemed to increase with experimental warming, suggesting that increased competition within the resident vegetation may decrease community invasibility as the climate warms.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Soil seed banks offer plants the possibility to disperse through time. This has implications for population and community dynamics, as recognised by ecological and evolutionary theory. In contrast, ...the conservation and restoration literature often find seed banks to be depauperate, weedy and without much conservation value or restoration potential. One explanation for these contrasting views might lie in a systematic bias in the sampling of seed banks versus established plant communities. We use the species–area relationship as a tool to assess and compare the per‐area species richness and spatial structuring of the diversity of the established plant community versus soil seed banks. To allow this direct comparison we extensively survey the species–area relationship of the vegetation and underlying seed bank of a grassland community across twelve sites spanning regional bioclimatic gradients. We also compile a global dataset of established vegetation and seed banks from published sources. We find that seed banks have consistently higher intercepts and slopes of the relationship, and hence higher diversity at any given spatial scale, than the vegetation both in the field and literature study. This is consistent across habitat types, climate gradients, and biomes. Similarity indices are commonly used to compare vegetation and seed bank, and we find that sampling effort (% of the vegetation area sampled for seed bank) was the strongest predictor of vegetation–seed bank similarity for both the Sørensen (R² = 0.70) and the Raup–Crick (R² = 0.25) index. Our study suggests that the perception that seed banks are intrinsically less diverse than established plant communities has been based more on inadequate sampling than on biological reality. Across a range of ecosystems and climatic settings, we find high diversity in seed banks relative to the established community, suggesting potentially important roles of seed banks in population dynamics and diversity maintenance.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In a rapidly changing climate, alpine plants may persist by adapting to new conditions. However, the rate at which the climate is changing might exceed the rate of adaptation through evolutionary ...processes in long-lived plants. Persistence may depend on phenotypic plasticity in morphology and physiology. Here we investigated patterns of leaf trait variation including leaf area, leaf thickness, specific leaf area, leaf dry matter content, leaf nutrients (C, N, P) and isotopes (δ
C and δ
N) across an elevation gradient on Gongga Mountain, Sichuan Province, China. We quantified inter- and intra-specific trait variation and the plasticity in leaf traits of selected species to experimental warming and cooling by using a reciprocal transplantation approach. We found substantial phenotypic plasticity in most functional traits where δ
N, leaf area, and leaf P showed greatest plasticity. These traits did not correspond with traits with the largest amount of intraspecific variation. Plasticity in leaf functional traits tended to enable plant populations to shift their trait values toward the mean values of a transplanted plants' destination community, but only if that population started with very different trait values. These results suggest that leaf trait plasticity is an important mechanism for enabling plants to persist within communities and to better tolerate changing environmental conditions under climate change.
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