Heathland Plant Communities Research Articles

Burnt wood management enhances soil multifunctionality at the medium term after a large wildfire in north-west Spain

Background Mulching and burnt wood treatments are commonly applied to prevent the loss of soil quality and erosion, but their effect on soil multifunctionality remains unexplored. Aims We filled this gap by assessing the medium-term (4 years) effects of these treatments on soil multifunctionality after a large wildfire in NW Spain. Methods Straw mulching (SM) and cut plus lopping (CpL) treatments were applied in high-severity affected areas of heathland plant communities. CpL areas had been afforested with Scots pine 15 years before the fire. We considered four soil functions estimated in treated and burned control plots 4 years after fire: (1) carbon regulation; (2) water regulation; (3) soil fertility; and (4) nutrient cycling. The functions were integrated into a multifunctionality index and linear models were used to evaluate treatments effect. Key results SM had no impact on individual functions and multifunctionality. Conversely, CpL with burnt Scots pine wood was able to sustain higher levels of multiple functions simultaneously than control areas. Consistent trade-offs between soil functions emerged in control areas for both treatments. Conclusions Burnt wood could ensure long-lasting effects to promote soil multifunctionality in Mediterranean ecosystems. Implications We recommend using a multifunctionality approach to avoid biases in treatment success.

Heathland plant species composition and vegetation structures reflect soil‐related paths of development and site history

AbstractQuestionsTo improve our knowledge on how environmental conditions determine the development of high‐value Calluna vulgaris heathland habitats, we studied the floristic and structural characteristics of heathland plant communities across North Germany and how they are influenced by edaphic, climatic and management factors. We ask how heathland development is related to these factors and what are the implications for conservation management and restoration.LocationNorth German Plain.MethodsWe collected 350 relevés in 18 dry Calluna heathland areas. Plant communities were classified using Isopam, and Redundancy Analysis (RDA) determined effects of environmental conditions. Potential pathways of development and the nature conservation status of the communities were identified on a multifactorial basis.ResultsWe found nine floristically and structurally distinct heathland plant communities. Heathland vegetation showed distinct patterns along Calluna age development stages and environmental conditions. Soil conditions and related effects of long‐term site history and recent management turned out to be the predominant factors influencing species composition and diversity, resulting in three potential heathland succession pathways. Mosaic‐like communities with particularly high taxonomic diversity and conservation value occurred on early‐successional inland dunes or as regeneration stage growing on nutrient‐poor sandy soils without humus accumulation.ConclusionsThe study reveals fundamental differences between historically farmed heathland in the oceanic Northwest and former military training areas mainly in northeastern Germany with consequences for restoration ecology. Present nature conservation criteria turned out to be insufficient in predicting habitat quality, as lichens are frequently disregarded. Our findings highlight the need for intense soil disturbance to maintain early‐stage soil conditions and a diverse Calluna growth‐phase composition, as these factors essentially determine species richness in lowland heaths.

Barriers to restoration: Soil acidity and phosphorus limitation constrain recovery of heathland plant communities after sod cutting

AbstractQuestionsSod cutting has been used extensively as an effective measure in removing excess N and restoring dwarf shrub dominance in heathlands affected by increased nitrogen deposition. However, recovery of other plant species is often very limited. One barrier is high soil acidity following sod cutting, which results in soil aluminium (Al3+) and ammonium (NH4+) reaching toxic concentrations. Sod‐cutting management also removes most of the major nutrients from the system, so intensified nutrient limitation could be an additional barrier to the recovery of species‐rich communities. Soil phosphorus (P) is of special interest as research indicates sod‐cutting management can shift the system to P limitation.LocationHoge Veluwe National Park, The Netherlands.MethodsWe set up a full‐factorial experiment in sod‐cut heathland formerly encroached by Molinia caerulea, adding phosphate (P+) and lime (Ca+) and over the next three growing seasons, we recorded soil chemistry and plant responses.ResultsSoil inorganic N, especially soil NH4+, strongly declined after liming compared to the control situation, confirming that liming alleviates NH4+ toxicity. Addition of P resulted in a similar decline, also suggesting a role for soil phosphate availability in this process. Acid‐sensitive plant species richness increased significantly in both Ca+ and P+ treatment, whereas acid‐insensitive plant species richness only increased significantly as a result of P+ treatment. Mean vegetation relative growth rate increased significantly in both Ca+ and P+ treatments.ConclusionsExcessive P removal due to sod cutting constitutes a second barrier to restoration in addition to soil acidity. We discourage the large‐scale use of sod cutting to reduce soil N availability in heathlands and propose to use interventions that leave the soil nutrient balance intact, such as burning and grazing, mowing or litter removal, in combination with measures that restore the soil buffer capacity.

Constructing more informative plant-pollinator networks: visitation and pollen deposition networks in a heathland plant community.

Interaction networks are widely used as tools to understand plant–pollinator communities, and to examine potential threats to plant diversity and food security if the ecosystem service provided by pollinating animals declines. However, most networks to date are based on recording visits to flowers, rather than recording clearly defined effective pollination events. Here we provide the first networks that explicitly incorporate measures of pollinator effectiveness (PE) from pollen deposition on stigmas per visit, and pollinator importance (PI) as the product of PE and visit frequency. These more informative networks, here produced for a low diversity heathland habitat, reveal that plant–pollinator interactions are more specialized than shown in most previous studies. At the studied site, the specialization index was lower for the visitation network than the PE network, which was in turn lower than for the PI network. Our study shows that collecting PE data is feasible for community-level studies in low diversity communities and that including information about PE can change the structure of interaction networks. This could have important consequences for our understanding of threats to pollination systems.

Soil Seed Bank in Nantucket's Early Successional Communities: Implications for Management

ABSTRACT: Globally rare sandplain grassland and coastal heathland plant communities of Nantucket Island, Massachusetts, merit high conservation priority because they support many rare and endangered species. Management (brush-cutting, grazing, and prescribed fire) has been effective in maintaining these communities, but less successful in transforming overgrown native scrub oak shrubland to diverse grassland. These scrub oak (Quercus ilicifolia Wangenh.) communities may lack a seed bank of grassland species in their soil. To examine this on Nantucket, we used the seedling emergence method to compare the soil seed bank of grassland, heathland, and scrub oak sites. We classified seedlings by growth form (graminoid, forb, or woody) and identified them to genus and species when possible. We observed that seedling density declined along a successional gradient, with the highest total density and highest graminoid density at grassland sites and the lowest at one of the scrub oak sites. A nMDS ordination grouped...

Effects of invasion by introduced versus native conifers on coastal heathland vegetation

AbstractQuestionsWhat are the effects of conifer invasion on plant species composition and richness of coastal heathlands; do effects differ between heathlands invaded by introduced or native coniferous tree species?LocationThreatened coastal Calluna heathlands, western Norway.MethodsWe compared the effects of invasion by introduced Sitka spruce (Picea sitchensis (Bong.) Carr.) and native Scots pine (Pinus sylvestris L.) on heathland plant communities by focusing on the local impacts of single coniferous tree canopies. For each of 58 target coniferous trees (2–4‐m tall), 2‐m transects were laid out in a north and south orientation from the tree stem to beyond the tree canopy, and control transects were laid out in open heathland adjacent to the target trees. Vascular plants and bryophytes were recorded within 0.0625 m2 contiguous quadrats along the transects. Principal response curves (PRC) and generalized linear mixed models (GLMMs) were used to investigate tree canopy effects on species composition and richness.ResultsInvasion by coniferous trees induced considerable changes in the coastal heathland vegetation: distinct microcommunitites developed beneath the canopies of relatively young, single coniferous trees in the heathlands. There was a marked difference in subcanopy species composition under the introduced Sitka spruce relative to the native Scots pine; forest floor species had colonized to a greater extent under Sitka spruce, replacing the light‐demanding species characteristic of the coastal heathland vegetation.ConclusionOur study showed that conifer invasion induces considerable and rapid changes in heathland vegetation, and that the effects were stronger under the introduced conifer. This suggests that Sitka spruce invasion may pose a more immediate threat to the characteristic coastal heathland vegetation and flora than succession based on native conifers. The open coastal heathlands along the Atlantic coast of Western Europe are a threatened landscape of high conservation value, and our results suggest that the spread of Sitka spruce into these landscapes should be controlled, especially in heathlands that are targeted for conservation.

Colonization Credit in Restored Wet Heathlands

Although human‐driven landscape modification is generally characterized by habitat destruction and fragmentation, it may also result in the creation of new habitat patches, providing conditions conducive to spontaneous colonization. In this article, we propose the concept of “colonization credit” (i.e., the number of species yet to colonize a patch, following landscape changes) as a framework to evaluate the success of colonization, in terms of species richness, in new/restored habitats, taking into account the spatial structure of landscapes. The method mirrors similar approaches used to estimate extinction debt in the context of habitat fragmentation, that is, comparisons, between old and new habitat patches, of the relationships among spatial patch metrics and patch species richness. We applied our method to the case of spontaneous colonization of newly created habitat patches suitable for wet heathland plant communities in South Belgium. Colonization credit was estimated for the total species richness, the specialist species richness, and the species richness of three emergent groups (EGs) of specialist species, delineated on the basis of dispersal traits. No significant colonization credit was identified either in patches created 25–55 years ago or in those created within the past 25 years, with the exception of species from our first EG (mostly anemochorous species with long‐term persistent seed bank). However, the differential response of species in that first EG could not be explained through their characteristic life history traits. The results of this study are encouraging and suggest that deliberate, directed restoration activities could yield positive developments in a relatively short period of time.

Estimating plant competition coefficients and predicting community dynamics from non-destructive pin-point data: a case study with Calluna vulgaris and Deschampsia flexuosa

A method is proposed for estimating plant competition coefficients and predicting the dynamics of herb and grassland plant communities from non-destructive pin-point measurements. The method is applied to inter-specific competition in a natural heathland community with relatively few interacting species. The study shows that the dynamics of the heathland plant community may be thought of as essentially a two-species system of Calluna vulgaris and Deschampsia flexuosa. There were significant competitive interactions between C. vulgaris and D. flexuosa. D. flexuosa affected both the cover and compactness of C. vulgaris individuals as a function of the compactness the previous year, whereas C. vulgaris significantly affected only the compactness of D. flexuosa. There was a significant negative effect of drought on the compactness of both C. vulgaris and D. flexuosa individuals, whereas night warming had no significant effects on either species. The predicted long-term outcome of the competitive interaction between C. vulgaris and D. flexuosa was that of unstable equilibrium, where the more dominant of the two will outcompete the other. However, when both species are found at relatively high plant covers the two species are predicted to co-exist for a long time period relatively to the time scale of the ageing process of C. vulgaris. Direct analyses of the inter-specific competitive interactions in natural plant communities with non-destructive measurements can provide important new insight into the processes that determine the composition of plant communities.

Biotic and abiotic edge effects in highly fragmented heathlands adjacent to cropland and forest

The aims of this study were to examine how adjacent land use, in this case cropland and forest, affects the heathland plant community and soil chemical composition, and whether potential edge effects differ according to adjacent land use type or edge orientation. Therefore mixed modeling was applied on vegetation and soil data gathered from 20 heathland edges adjacent to cropland or forest. Plant community composition showed a clear gradient across the heathland edge, both for cropland and forest as adjacent land use. Heathland soil nutrient content also varied with edge distance. No effects of heathland orientation with respect to forest could be found. For both types of adjacent land use, edge effects were limited in their extent to a zone of ca. 8 m into the heathland patch. Within this zone however, eutrophicating effects of cropland on the heathland vegetation and soil were more pronounced than the effects of the presence of an adjacent forest. From these results, it could be concluded that heathland flora and soil were significantly altered in a zone of ca. 8 m from the heathland edge. Eutrophication was the driving force behind this change, both for heathland adjacent to cropland and heathland adjacent to forest. Especially in the heathland-cropland edges this eutrophication has resulted in an almost complete replacement of the characteristic dwarf shrub vegetation by grasses and species typical for nutrient-rich habitats.

Harvested heather shoots as a resource for heathland restoration

Large quantities of woody stems bearing seed capsules can be cut readily from heathland in the autumn and winter. Unlike other sources of heathland propagules, harvested shoots are a renewable resource which can be collected as part of routine conservation management. A study on heathland in Dorset, England compared the regeneration capacity of harvested heather shoots on both abandoned farmland and mineral wastes. Harvested shoots contained large numbers of seed of heather species. Seed of other heathland plant species was present, but in a smaller proportion to that of intact vegetation. Variations in the amount of biomass and seed collected from different sites were due to differences in vegetation age and composition, management history and topography, as well as the time of year when collected. Adequate reinstatement of the heathland plant community could be achieved using as little as 0·6 kg m −2 of harvested shoots, and it is possible to restore between two and five times the area harvested. It is likely that the woody stems provided suitable microsites for the germination and survival of heathland species and acted as a mulch, conserving moisture on skeletal mineral wastes and suppressing weed growth on farmland. The depth of harvested shoots applied to the substrate was found to have a critical effect on heather seedling germination and recruitment at the small scale.

A Comparison of Techniques for Restoring Heathland on Abandoned Farmland

1. Recent changes in agricultural policies have reduced the extent of cultivated farmland. This has provided opportunities to restore heathland vegetation on lowland sites where it once occurred. 2. Between December 1988 and April 1990 large-scale replicated experiments were established on abandoned farmland in southern Britain to compare the effectiveness of four treatments for heathland restoration : (i) the application of herbicide ; (ii) the addition of harvested heather shoots ; (iii) the addition of heathland topsoil ; and (iv) the translocation of heathland turves. 3. The number of seedlings of heathland plant species on each treatment was counted in December 1990 and 1991, and the shoot frequency of these species was recorded in January 1993. 4. The grassland soil had a significantly higher pH and contained greater concentrations of extractable phosphorus and exchangeable calcium than that of the adjacent heathland. Despite this, the controls showed that there was some natural regeneration of heathers within the grassland. 5. Herbicide treatment inhibited the regeneration of heathland plants. Cultivation followed by the application of harvested heather shoots increased the number of seedlings of heathland plant species, but some key species were missing. All the components of the heathland plant community occurred in greater numbers on the plots where heathland topsoil had been applied, and on the parts of transferred heathland turves which had died from drought. 6. The large-scale translocation of heathland turf appeared to be feasible and instantly recreated the mature heathland plant community. However, some changes in the plant community occurred which probably resulted from differences in soil drainage characteristics between the donor and recipient sites. Of the different sources of heathland plant propagules, harvested heather shoots were a renewable resource, whereas the collection of heathland topsoil and turves involved the destruction of existing heathland.