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Sea-level rise will lead to widespread habitat loss if warming exceeds 2 °C, threatening coastal wildlife globally. Reductions in coastal habitat quality are also expected but their impact and timing are unclear. Here we combine four decades of field data with models of sea-level rise, coastal geomorphology, adaptive behaviour and population dynamics to show that habitat quality is already declining for shorebirds due to increased nest flooding. Consequently, shorebird population collapses are projected well before their habitat drowns in this UNESCO World Heritage Area. The existing focus on habitat loss thus severely underestimates biodiversity impacts of sea-level rise. Shorebirds will also suffer much sooner than previously thought, despite adapting by moving to higher grounds and even if global warming is kept below 2 °C. Such unavoidable and imminent biodiversity impacts imply that mitigation is now urgently needed to boost the resilience of marshes or provide flood-safe habitat elsewhere.

Recent studies suggest that plant roots can avoid competition with other roots of the same plant, but the mechanism behind this behavior is yet largely unclear and their effects on plant performance hardly studied. We grew combinations of two ramets of Trifolium repensin a single pot that were either intact, disconnected for a shorter or longer time, or that belonged to different genotypes. Interconnected ramets developed lower root length and mass than any other combination of ramets, supporting the notion that self/non-self discrimination in T. repenswas based entirely on physiological coordination between different roots that develop on the same plant, rather than biochemical allorecognition. These responses were consistent among eight field-collected genotypes, suggesting that self/non-self discrimination is a common feature in wild populations of white clover. There were no significant treatment x genotype interactions suggesting that genetic variation for self/non-self discrimination may be limited. Self-interactions resulted in lower to similar shoot biomass and number of ramets, but higher flowering probabilities, compared to non-self interactions. Thus, our results demonstrated that the performance consequences of self/non-self discrimination may be more complicated than previously thought.

Abstract: In order to examine whether the translocation of water and nitrogen in clonal plants is interdependent, interramet translocation of these two resources was investigated in the greenhouse. Two-ramet systems of Carex flacca were imposed to different spatial patterns of water and nitrogen supply. The experimental design allowed to examine the effects of water heterogeneity on nitrogen sharing, and, vice versa, the effects of nitrogen heterogeneity on water sharing. Interramet translocation of both water and nitrogen was quantified by stable isotope labelling. If one of the ramets was deprived of water, nitrogen or both resources (parallel resource heterogeneity), resource translocation towards this ramet was markedly enhanced compared to a control treatment in which both ramets received ample water and ample nitrogen. Under these conditions, the amount of water or nitrogen translocated was not significantly affected by the pattern of heterogeneity of the other resource imposed on the two-ramet system. If one of the interconnected ramets was rooted in dry but nitrogen-rich soil and the other ramet was placed in nitrogen-deficient but well-watered soil (reciprocal resource heterogeneity), a significant amount of water was translocated towards the ramet in dry soil, while the low-N ramet hardly received any nitrogen. These results show that little nitrogen is translocated between ramets in a direction opposite to the transpiration stream within the rhizome. However, nitrogen may be translocated independently from water if both are transported in a similar direction within the clonal system. The effects of translocation on ramet performance (in terms of transpiration, nitrogen accumulation, and biomass) were assessed by comparing interconnected ramets with isolated (severed) ramets that were treated identically. Integration enhanced the performance of ramets deficient of one or both of the resources. In case of water translocation, the transpiration and growth of the water exporting (donor) ramets was similar to the transpiration and growth of their isolated counterparts. When nitrogen was heterogeneously supplied, however, nitrogen accumulation and growth of the donor ramet was reduced to the same extent as the performance of the nitrogen-deficient ramet was increased. Water translocation thus enhanced the performance of the whole plant, while nitrogen only reduced the differences in ramet performance within the plant. In the case of the reciprocal heterogeneity treatment, the benefits of translocation were strongly unidirectional towards the ramet in dry soil. The data for this treatment suggested that total nitrogen accumulation was enhanced by the acquisition of nitrogen from the dry pot as a result of “hydraulic lift” and water exudation in the dry soil. We conclude that nitrogen translocation in clonal plants, and the associated benefits in terms of resource utilization and growth, may strongly depend on the pattern of interramet water transport. The implications are discussed for studies of physiological integration in clonal plants and the patterns of interramet resource sharing in the field.

Abstract: We studied the root foraging ability and its consequences for the nutrient acquisition of five grass species that differ in relative growth rate and that occur in habitats that differ widely in nutrient availability. Foraging responses were quantified, based on the performance of the plants in homogeneous and heterogeneous soil environments of the same overall nutrient availability. Although all species tended to produce a significantly higher root length density in a nutrient-rich patch, this response was significant only for the faster-growing species. The increased root length density resulted from small, though not significant, changes in root biomass and specific root length. The effectiveness of root proliferation was determined by quantifying the total amount of nutrients (N and P) accumulated by the plants over the course of the experiment. Plants acquired more N in a heterogeneous environment than in a homogeneous environment, although the total nutrient availability was the same. The ability to acquire nutrients (N or P) in the heterogeneous environment was not related to the ability of species to increase root length density in response to local nutrient enrichment. In contrast to other studies, our results suggest that the role of morphological plasticity of roots in acquiring patchily distributed resources is limited. Possible reasons for this discrepancy are discussed.

The original definition of the guild is reiterated and the concept discussed and placed in the context of related concepts such as resources and competition. From this conceptual framework the current use of guilds in studies of plant community ecology is evaluated. We discuss the criteria with which species are assigned to guilds, the association of guilds with specific communities, the resource classes on which guilds are based, and the competitive relationships between species of a guild. We conclude that the guild is presently applied in a much more loose way as compared to its original definition. In particular, the a priori assignment of species to guilds on the basis of the use of well-defined resource classes is often relaxed. This obscures the insight that the guild structure may provide in the role of resource partitioning and competition in structuring the community. A more strict use of the concept is advocated.

Morphological plasticity in clonal plants has received wide attention because localized plastic changes in spacer length, branching intensity and branching angle may enable clonal plants to place ramets selectively in the more favourable microhabitats within a heterogeneous environment. These responses have been interpreted in terms of foraging behaviour.

As a result of the reconstruction of a dike on the Dutch island of Texel two small areas of the Wadden Sea were embanked in 1977 and 1978. In 1981 both by now blocked brackish waters were investigated for macrofauna and macroflora. The vegetation on these former parts of the Wadden Sea was still in a colonizing state. Many small patches ofRuppia spp. were found, contrary to older brackish waters with more extendedRuppia beds. The striking dominance ofR.maritima agrees with its large seed production enabling to colonize quickly new areas. In one of the ponds, where the maximum salinity of 23‰ Cl− exceeded far the tolerance limit of this species given in the literature (15‰ Cl−),R.maritima was still more numerous thanR.cirrhosa, a species which is more tolerant to salinity fluctuations. Several years after isolation these areas are still inhabited by a few Wadden Sea macrofauna species (e.g. Carcinus maenas, Hydrobia ulvae andCapitella capitata) who managed to survive the drastic environmental changes. In addition, a large number of species characteristic for blocked brackish waters has already colonized the new ponds. One of the two, that has always completely been isolated from other inland water, was inhabited in 1981 by 13 brackish water species. In the future the two new ponds on Texel are expected to loose their pioneer characteristics. There are reasons to expect that most of the Wadden Sea macrofauna relics will soon become extinct. A more extendedRuppia vegetation will probably develop together with a relative increase ofRuppia cirrhosa.

In 1981, 16 brackish inland waters on the Dutch island of Texel were sampled qualitatively for macrofauna. The sampling stations consisted of ditches, small canals and isolated ponds. They were clustered according to their species composition. It appeared that the major fauna differences are closely related to the occurrence of present or past connections of the locality with other water bodies and to the origin and development of a habitat. The distribution of the macrofauna taxa was compared with differences in average chlorinity and variation in chlorinity between the habitats studied. Relations between the number and kind of species and chlorinity were also investigated. It was found that chlorinity cannot be regarded as a master factor affecting the fauna distribution. Hence, it is concluded that, within the range of the mesopolyhalinicum, environmental and historical factors, rather than chlorinity, have to be regarded as the most discriminating abiotic factors determining the species composition in brackish inland waters.