Inconclusive Predictions and Contradictions: A Lack of Consensus on Seed Germination Response to Climate Change at High Altitude and High Latitude

Climate change directly affects arctic-alpine plants and acute responses to increased temperatures may be seen in their reproductive fitness and germination ability. However, uncertainties prevail in predicting whether a future warmer climate favors or hampers seed germination in high latitude and high altitude soils and seed germination research in such systems has not been able to provide generalizable patterns of response. The available literature on this subject has been conducted at various locations contributing to difficulties in predicting the response of arctic-alpine seeds to climate change. Here, we show that discrepancies in seed collection, dormancy breaking treatments, and germination conditions found in the published literature are possible reasons for our inability to draw large scale conclusions. We explore how these factors influence the results and highlight the fact that many of the previous investigations have reported the effects of warmer temperature, rather than a warmer climate and all the associated complex environmental interactions, on seed germination. We recommend that long-term monitoring of seed response to treatments that mimic the present and future alpine climate is likely to produce more ecologically meaningful insights and suggest several practical steps that researchers can take that would facilitate greater coherence between studies

The importance of donor population identity and habitat type when creating new populations of small Melampyrum sylvaticum from seed in Perthshire, Scotland

Small cow-wheat Melampyrum sylvaticum, a nationally scarce annual identified as a priority species in the UK Biodiversity Action Plan, was the focus of a translocation attempt aiming to establish new populations within the extent of its former Scottish range. Seeds were collected (from wild Scottish populations) in three phases (in the years 2005, 2006 and 2008) and sown at six receptor sites where the species was absent but habitat seemed suitable. Each phase used increasing numbers of seed after the results of the first phase (89 to 103 seeds sown per site) suggested that many more than 100 seeds are needed to establish the species (at least in the short-term) at a site. Comparisons of the suitability of seed from three different wild populations showed that one resulted in higher germination rates. This donor population was associated with environmental conditions more similar to those at the receptor sites than those of the other donors. Receptor sites also differed in their suitability; those that were climatically and edaphically more similar to sites supporting wild populations appear to be more favourable to M.sylvaticum longer-term survival. Together, these can be seen to suggest that future seed translocation should be to sites that are ecologically similar to the donor population and within sites that fall into the cooler and wetter range of environmental conditions currently supporting Scottish populations of M. sylvaticum

Towards an Understanding of Factors Controlling Seed Bank Composition and Longevity in the Alpine Environment

The ability of seeds to regenerate from soil seed banks has long been recognized as a key survival strategy for plants establishing new niches in highly variable climates of alpine environments. However, the fundamental aspects of evolutionary/selective forces for seed bank development in alpine ecosystems are largely unknown. Here, we developed a model that describes dormancy, a high temperature requirement and a specific light/darkness regime at the time of seed shedding can preclude autumn germination, thus contributing to seed persistence until the next growing season. The benefits of these factors synchronising germination with the growing season are reviewed. Additionally, the importance of climatic variations of maternal environment affecting some of these factors is also discussed. It is suggested that the environmental conditions during the growing season partly control the seed persistence and seeds that fail to germinate are carried over to the next season. Species that have small (<3 mg) and round-shaped seeds tend to persist more easily in soil for over five years, than do the large or flat seeds. However, some large-seeded species also have the potential to establish short-term persistence bank. A literature survey reveals 88% of the alpine seeds have a mass <3 mg. Seed size has only a weak relationship with mean germination timing (MGT) indicating that reduced persistence in large-seeded species cannot be counteracted by quicker germination, but combined effects of other factors stimulating germination remain an open area to be studied. It is proposed that long distance dispersal (LDD) is limited in most-but not all-species, primarily due to the absence of specialized dispersal structures. However, among numerous dispersal modes, most species tend to be dispersed by wind. Thus, spermatophytes of alpine environments have a greater tendency to establish seed banks and spread the risk of germination to many years, rather than being dispersed to other micro-climates

Are reintroductions an effective way of mitigating against plant extinctions? CEE review 07-008 (SR32)

Re-introductions are considered by some conservation practitioners to be a controversial management option for mitigating threatened plant declines. The use of translocations (including re-introductions) has been criticised for the lack of monitoring and central recording, inappropriateness of the action due to genetic considerations, a lack of knowledge of the demography of the donor populations and inadequate information on the habitat requirements of the species. Despite these arguably justified criticisms, re-introductions are growing in use as practitioners see no other option for meeting management plan targets. Re-introductions have been proposed as options for overcoming habitat loss, habitat fragmentation and reproductive isolation. An extension of this increasingly interventionist approach, often termed assisted colonisation, is being considered as a potential method for preventing extinctions due to climatic shifts too rapid to allow corresponding species‟ distribution changes. This review evaluates the effectiveness of re-introductions as a conservation tool by using the available evidence to determine in what context plant translocations have improved the status of threatened species

Physically, physiologically and conceptually hidden: improving the description and communication of seed persistence

Seed persistence is a trait that is difficult to observe or measure and consequently, has remained conceptually obscure for 40 years since Grubb’s influential description of the regeneration niche. Seed persistence is the ability of seeds to persist in a viable state post-dispersal and is relevant to current research in plant community dynamics and conservation. However, categorisations of seed persistence as transient, short-term or long-term persistent do not acknowledge the variation in persistence times as a result of deterministic processes and are difficult to apply in a predictive capacity. Consequently, a more robust understanding of seed persistence is needed in niche descriptions that are temporally explicit and in predicting the distributional changes of species in the current and future climate. We surmise an alternative to the categorizations of seed persistence on the basis of seed bank type and argue that it is best expressed as a continuous variable. We review the methods available for estimating seed persistence in situ and provide a number of testable hypotheses to contribute to the development of this important research topic. We maintain that seed persistence has not been incorporated adequately into niche theory and highlight that it can make several contributions including properly defining metapopulation niche, population growth definition. This holistic approach by integrating seed persistence into niche theory would allow us to better predict the survival of plants in a changing environment

Ex situ seed banks and the IUCN Red List.

Extinct, or just extinct in the wild? Plants lost from in situ habitat, but represented in seed banks, are labelled extinct despite the potential for restoration. A change in the International Union for Conservation of Nature Red List definition of extinct in the wild is needed to improve the status and prospects of threatened plant species

Identifying factors associated with the success and failure of terrestrial insect translocations

Translocation is increasingly used as a management strategy to mitigate the effects of human activity on biodiversity. Based on the current literature, we summarised trends in terrestrial insect translocations and identified factors associated with success and failure. As the authors’ definitions of success and failure varied according to the individual sets of goals and objectives in each project, we adopted a standardised species-specific definition of success. We applied generalised linear models and information-theoretic model selection to identify the most important factors associated with translocation success. We found literature documenting the translocation of 74 terrestrial insect species to 134 release sites. Of the translocations motivated by conservation, 52% were considered successful, 31% were considered to have failed and 17% were undetermined. Our results indicate that the number of individuals released at a translocation site was the most important factor associated with translocation success, despite this being a relatively infrequent perceived cause of failure as reported by authors. Factors relating to weather and climate and habitat quality were the most commonly perceived causes of translocation failure by authors. Consideration of these factors by managers during the planning process may increase the chance of success in future translocation attempts of terrestrial insects

Seed Survival at Low Temperatures: A Potential Selecting Factor Influencing Community Level Changes in High Altitudes under Climate Change

In alpine ecosystems, imbibed seeds are often exposed to temperatures as low as −35 °C, challenging their survival in the soil. Here, we show that seeds have mechanisms to survive cold climate prevalent in alpine ecosystems and have identified three such mechanisms from existing literature, including two forms of freezing avoidance (the presence of water impermeable seed coats, and the supercooling of seed tissues) and one form of freezing tolerance (by extracellular-freezing). Experimentally-derived published data on the lowest temperature recorded at which 50% of a seed sample survived (i.e., lethal temperature; LT50) was used to generate a dataset of 24 species across low altitude, boreal and alpine environments. We assumed that the ability of seeds to maintain viability at very low temperatures would increase in species associated with higher altitudes conferring a competitive advantage that would be lost under projected climate change. However, our results reveal to underpin that seeds from boreal species survive relatively better at lower temperatures than those of alpine species. Paradoxically, a warming climate could lead to alpine seed death due to extremes of cold at the soil surface resulting from snow cover loss, whilst the declining snow cover may facilitate boreal forest colonization above the current treeline

Small cow-wheat. Version 1.0

Small cow-wheat (Melampyrum sylvaticum) is a hemi-parasitic annual herb with bright yellow, nodding flowers in pairs up the main stem and side branches (Fig. 1). It is found in remnants of upland broadleaved woodland where birches (Betula spp.) are typically the dominant tree species

Nutrient additions three decades on: potential interactions of nutrients and climate in the recovery of a high latitude serpentine system

Nutrient addition experiments initiated in 1980 on the Keen of Hamar, Shetland Isles, have produced a unique dataset of long-term vegetation response to amendments of major plant growth nutrients (N, P, NP, NPK and NPKCa). Previous studies have reported the notable impact of phosphorus on the ‘serpentine debris’ community, and the negligible effect of nitrogen. However, a survey in 2010 provided our first indication that the experimentally-induced phosphorus effect was weakening and this was consolidated by further surveys of vegetation cover and community composition. This community shift might have been different had the local climate acted synergistically with phosphorus additions: in the last few years of the study the Shetland Isles experienced particularly low spring rainfall – the dry spell may have been a well-timed environmental filter driving community recovery rather than a permanent change of state to heathland on an organic soil. The longevity of our investigation is a unique opportunity to explore vegetation response to the key drivers of global environmental change, namely climate change, eutrophication as a result of agricultural intensification, and the potential for invasion of species as new resource-rich niches become available