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Antarctica, with its almost pristine conditions and relatively simple vegetation, offers excellent opportunities to investigate the influence of environmental factors on species performance, such information being crucial if the effects of possible climate change are to be understood. Antarctic vegetation is mainly cryptogamic. Cryptogams are poikilohydric and are only metabolically and photosynthetically active when hydrated. Activity patterns of the main life forms present, bryophytes (10 species, ecto- and endohydric), lichens (5 species) and phanerogams (2 species), were monitored for 21 days using chlorophyll a fluorescence as an indicator of metabolic activity and, therefore, of water regime at a mesic (hydration by meltwater) and a xeric (hydration by precipitation) site on Léonie Island/West Antarctic Peninsula (67°36'S). Length of activity depended mainly on site and form of hydration. Plants at the mesic site that were hydrated by meltwater were active for long periods, up to 100 % of the measurement period, whilst activity was much shorter at the xeric site where hydration was entirely by precipitation. There were also differences due to life form, with phanerogams and mesic bryophytes being most active and lichens generally much less so. The length of the active period for lichens was longer than in continental Antarctica but shorter than in the more northern Antarctic Peninsula. Light intensity when hydrated was positively related to the length of the active period. High activity species were strongly coupled to the incident light whilst low activity species were active under lower light levels and essentially uncoupled from incident light. Temperatures were little different between sites and also almost identical to temperatures, when active, for lichens in continental and peninsular Antarctica. Gradients in vegetation cover and growth rates across Antarctica are, therefore, not likely to be due to differences in temperature but more likely to the length of the hydrated (active) period. The strong effect on activity of the mode of hydration and the life form, plus the uncoupling from incident light for less active species, all make modelling of vegetation change with climate a more difficult exercise.

Simple Summary: Temperatures are increasing globally, but polar regions (including Antarctica) are warming much faster than the rest of the globe. Increased temperatures in Antarctica can impact the distribution and performance of plants, the majority of which on this continent are mosses. This study aims to investigate whether Bryum argenteum var. muticum, a moss species found in Antarctica, is capable of acclimation (adjustment of its physiology, specifically photosynthesis and respiration) to increased temperatures. We used short-term warming experiments that mimicked heatwaves and compared them to seasonal rates of photosynthesis and respiration in order to better understand how resilient this important moss species is to climate change. We found that this moss can acclimate very quickly (within 7 days) by increasing its photosynthesis (carbon gain). This shows that B. argenteum is highly resilient, and it may potentially benefit from short- and long-term climatic changes. Climate warming in Antarctica involves major shifts in plant distribution and productivity. This study aims to unravel the plasticity and acclimation potential of Bryum argenteum var. muticum, a cosmopolitan moss species found in Antarctica. By comparing short-term, closed-top chamber warming experiments which mimic heatwaves, with in situ seasonal physiological rates from Cape Hallett, Northern Victoria Land, we provide insights into the general inherent resilience of this important Antarctic moss and into its adaptability to longer-term threats and stressors associated with climate change. Our findings show that B. argenteum can thermally acclimate to mitigate the effects of increased temperature under both seasonal changes and short-term pulse warming events. Following pulse warming, this species dramatically increased its carbon uptake, measured as net photosynthesis, while reductions in carbon losses, measured as dark respiration, were not observed. Rapid growth of new shoots may have confounded the effects on respiration. These results demonstrate the high physiological plasticity of this species, with acclimation occurring within only 7 days. We show that this Antarctic moss species appears to have a high level of resilience and that fast acclimation processes allow it to potentially benefit from both short-term and long-term climatic changes. [ABSTRACT FROM AUTHOR]

Against a changing climate, the development of evidence‐based and progressive conservation policies depends on robust and quantitative baseline studies to resolve habitat natural variability and rate of change. Despite Antarctica's significant role in global climate regulation, climate trend estimates for continental Antarctica are ambiguous due to sparse long‐term in situ records. Here, we present the longest, spatially explicit survey of Antarctic vegetation by harmonizing historic vegetation mapping with modern remote sensing techniques. In 1961, E. D. Rudolph established a permanent survey plot at Cape Hallett, one of the most botanically diverse areas along the Ross Sea coastline, harboring all known types of non‐vascular Antarctic vegetation. Following a survey in 2004 using ground‐based photography, we conducted the third survey of Rudolph's Plot in 2018 using near‐ground remote sensing and methodologies closely mirroring the two historic surveys to identify long‐term changes and trends. Our results revealed that the vegetation at Cape Hallett remained stable over the past six decades with no evidence of transformation related to a changing climate. Instead, the local vegetation shows strong seasonal phenology, distribution patterns that are driven by water availability, and steady perennial growth of moss. Given that East Antarctica is at the tipping point of drastic change in the near future, with biological change having been reported at certain locations, this record represents a unique and potentially the last opportunity to establish a meaningful biological sentinel that will allow us to track subtle yet impactful environmental change in terrestrial Antarctica in the 21st century. Plain Language Summary: In early 2022, record‐breaking high temperatures were recorded all over Antarctica, sparking concerns about the icy continent's future. Although the effects of climate change have been observed in West Antarctica, much less observation is available for East Antarctica, where almost 90% of the Antarctic ice mass is located. It is now, that East Antarctica is at a tipping point for change, and it is now, that we need to establish progressive conservation measures. What is at stake? The vegetation in East Antarctica is distinct. Any organism that managed to survive here has highly specialized traits, and we only find lichens, mosses, cyanobacteria, and green algae. Especially the mosses are used biological sentinels because they live long and with high specificity. However, because they grow so slowly, any attempt to monitor variation in their fitness has to span decades rather than years or even seasons. This constitutes a key problem when trying to understand the natural dynamics of a functional ecosystem in East Antarctica. By applying machine learning and advanced statistics to modern aerial survey data as well as historic vegetation maps (the oldest in Antarctica, from 56 years ago), we created a unique harmonized data set and gained unique ecological insight. This allows us to establish a biological sentinel for change in East Antarctica, just before it is too late. Key Points: The longest plant cover record in Antarctica revealed Cape Hallett, unlike sites around the Peninsula, unaffected by climate changeAntarctic vegetation shows high plasticity, for which most of the changes can be explained by seasonal variation and water availabilityBy harmonizing historic and modern monitoring methodologies we establish a sustainable biological sentinel for change in East Antarctica [ABSTRACT FROM AUTHOR]

During austral summer field seasons between 1999 and 2018, we sampled at 91 locations throughout southern Victoria Land and along the Transantarctic Mountains for six species of endemic microarthropods (Collembola), covering a latitudinal range from 76.0°S to 87.3°S. We assembled individual mitochondrial cytochrome c oxidase subunit 1 (COI) sequences (n = 866) and found high levels of sequence divergence at both small (<10 km) and large (>600 km) spatial scales for four of the six Collembola species. We applied molecular clock estimates and assessed genetic divergences relative to the timing of past glacial cycles, including collapses of the West Antarctic Ice Sheet (WAIS). We found that genetically distinct lineages within three species have likely been isolated for at least 5.54 My to 3.52 My, while the other three species diverged more recently (<2 My). We suggest that Collembola had greater dispersal opportunities under past warmer climates, via flotation along coastal margins. Similarly increased opportunities for dispersal may occur under contemporary climate warming scenarios, which could influence the genetic structure of extant populations. As Collembola are a living record of past landscape evolution within Antarctica, these findings provide biological evidence to support geological and glaciological estimates of historical WAIS dynamics over the last ca. 5 My. [ABSTRACT FROM AUTHOR]

Background and aims: Due to the well-known importance of biocrusts for several ecosystem properties linked to soil functionality, we aim to go deeper into the physiological performance of biocrusts components. Possible functional convergences in the physiology of biocrust constituents would facilitate the understanding of both species and genus distributional patterns and improve the possibility of modelling their response to climate change.Methods: We measured gas exchange in the laboratory under controlled conditions of lichen- and moss-dominated biocrusts from four environmentally different locations in Europe. Field data were used to determine the natural hydration sources that drive metabolic activity of biocrusts.Results: Our results show different activity drivers at the four sites. Within site analyses showed similar C fixation for the different crust types in the three sites without hydric stress whilst light use related parameters and respiration at 15 °C were similar in the between sites analyses. There were significant differences in water relations between the biocrusts types, with moss-dominated crusts showing higher maximum and optimum water contents.Conclusions: The functional type approach for biocrusts can be justified from a physiological perspective when similar values are found in the within and between site analyses, the latter indicating habitat independent adaptation patterns. Our multi-site analyses for biocrusts functional performance provide comparisons of C fluxes and water relations in the plant-soil interface that will help to understand the adaptation ability of these communities to possible environmental changes. [ABSTRACT FROM AUTHOR]

Within Antarctica there are large gradients both in climate and in vegetation which offer opportunities to investigate links between the two. The activity (% total time active) of lichens and bryophytes in hydric and xeric environments was monitored at Livingston Island (62°39'S). This adds a northern site with a maritime, cloudy climate to previous studies in the southern Antarctic Peninsula and the Dry Valleys (78°S). Annual activity increases northwards from less than 1% to nearly 100%. There is a major and consistent difference between hydric sites which, with snow melt, can be 100% active in summer months even in the Dry Valleys, and xeric sites which, depending on precipitation, rarely exceed 80% activity even at Livingston Island. Mosses dominate hydric sites and lichens the xeric sites all along the gradient. Mean temperatures when active are 2-4°C at all sites, as liquid water is required. Light is a potential major stress reaching 880 µmol m-2 s-1 when active in continental sites. The lack of extremes in temperatures and light combined with high activity levels means that summer at Livingston Island is one of the better sites for lichen and bryophyte growth in the world. [ABSTRACT FROM AUTHOR]

Cape Hallett (72°19′S; 170°13′E) lies at the northern end of the western coastline of the Ross Sea region, and, to date, there appears to be no full description of its terrestrial flora despite its probable importance in understanding links between biodiversity and latitude. Here we present information about lichens and mosses from published papers, herbarium collections and personal surveys for Cape Hallett and seven nearby sites. A total of 59 lichen and 11 moss species are reported for these eight sites. Cape Hallett is one of the richest sites for terrestrial biodiversity in the Ross Sea region with about 46 lichen species and nine species of bryophytes. Lichens have their greatest diversity on the upper scree and summit area (30 species, 330 m), the least within the large penguin colony at sea level (one species). The station at Cape Hallett was established in 1957, and some of the earliest ecological and ecophysiological studies in Antarctica were carried out there. Historical comparisons are possible and have revealed considerable changes in vegetation in the lower flush area, a high level of frost heave disturbance, new lichen growth rate estimates for northern Victoria Land and extreme stability of the snow banks on the scree slopes. Cape Hallett represents a very important site for studies on links between terrestrial flora and the environment as well as on possible effects of climate change. [ABSTRACT FROM AUTHOR]

Antarctica has several apparent advantages for the study of biodiversity change along latitudinal gradients including a relatively pristine environment and simple community structures. Published analyses for lichens and mosses show no apparent gradient in biodiversity along the western Ross Sea coast line, the longest ice-free area in Antarctica spanning 14° latitude. One suggestion is that the area remains poorly surveyed. Here, we combine available species lists from four sites along the coast with new own data from two additional sites [Taylor Valley (77°30′S) and Diamond Hill (79°S)]. We show a decline in total terrestrial biodiversity with latitude from Cape Hallett (72°S) to Diamond Hill. However, the southernmost site, the Queen Maud Mountains (84°S), is exceptional with almost the same diversity as Cape Hallett. A categorization of lichens according to their proposed ecology shows the proportion of tolerant species remains relatively constant. However, the absolute number of conformant species declines with latitude, again with a minimum at Diamond Hill. Similarity indices are low and not very different between sites with Diamond Hill being the exception with very few species. We suggest that terrestrial biodiversity best reflects microhabitat water availability rather than macroclimatic temperature changes and use climate data from Taylor Valley and Diamond Hill to support this suggestion. We propose that the importance of microhabitats and landscape location is one of several possible limitations to the application of bioclimatic modeling along the Ross sea coastline. In the absence of a definitive link between macroclimate and the biota, predicting the effects of climate changes will be more challenging. [ABSTRACT FROM AUTHOR]

Bryophyte establishment represents a positive feedback process that enhances soil development in newly exposed terrain. Further, biological nitrogen (N) fixation by cyanobacteria in association with mosses can be an important supply of N to terrestrial ecosystems, however the role of these associations during post-glacial primary succession is not yet fully understood. Here, we analyzed chronosequences in front of two receding glaciers with contrasting climatic conditions (wetter vs drier) at Cordillera Darwin (Tierra del Fuego) and found that most mosses had the capacity to support an epiphytic flora of cyanobacteria and exhibited high rates of N2 fixation. Pioneer moss-cyanobacteria associations showed the highest N2 fixation rates (4.60 and 4.96 µg N g−1 bryo. d−1) very early after glacier retreat (4 and 7 years) which may help accelerate soil development under wetter conditions. In drier climate, N2 fixation on bryophyte-cyanobacteria associations was also high (0.94 and 1.42 µg N g−1 bryo. d−1) but peaked at intermediate-aged sites (26 and 66 years). N2 fixation capacity on bryophytes was primarily driven by epiphytic cyanobacteria abundance rather than community composition. Most liverworts showed low colonization and N2 fixation rates, and mosses did not exhibit consistent differences across life forms and habitat (saxicolous vs terricolous). We also found a clear relationship between cyanobacteria genera and the stages of ecological succession, but no relationship was found with host species identity. Glacier forelands in Tierra del Fuego show fast rates of soil transformation which imply large quantities of N inputs. Our results highlight the potential contribution of bryophyte-cyanobacteria associations to N accumulation during post-glacial primary succession and further describe the factors that drive N2-fixation rates in post-glacial areas with very low N deposition. [ABSTRACT FROM AUTHOR]

Estimates of lichen growth rates based on the measurements of several thalli at any site do not exist for continental Antarctica. However, the very limited existing data suggest that lichen growth rate may be a good indicator of climate change in Antarctica. We present measurements made on thalli of the lichen Buellia frigida Darb. growing in the Dry Valleys, Southern Victoria Land, continental Antarctica, which appear to have some of the slowest radial growth rates yet measured. Photographs of thalli at three different sites were analysed for growth over a 25-year period using nano-GIS techniques. At one site, Mt. Falconer Summit, the lichens had a mean growth rate of 0.0052 mm year with one individual as low as 0.0036 mm year. Thalli at the other two sites had significantly higher mean growth rates, 0.0136 mm year at Mt. Falconer Ridge and 0.0118 mm year at Rhone Bench. Assuming a constant growth rate, thalli at Mt. Falconer Summit had a mean age of 5,367 years, whilst the thalli at the other two sites were much younger, 840-1,026 years. We suggest that the different ages represent the appearance of new substrate for colonisation following climate changes in the Dry Valleys that altered the amount and duration of snow. The results confirm that lichen growth rate differs by almost two orders of magnitude over a latitudinal range of 15 degrees from south to north across Antarctica. [ABSTRACT FROM AUTHOR]

Botany Bay is one of the richest sites for lichen and bryophyte biodiversity in continental Antarctica. A total of 29 lichen, nine moss and one liverwort species have been identified. The most extensive vegetation occurs on a sheltered raised beach terrace. Vegetation associations are described and compared to other continental Antarctic localities that also possess a rich vegetation cover. Ordination analysis clearly indicates the importance of the type of water supply, its regularity, the substrate type, and particularly in Botany Bay, the influence of nutrients derived from the local bird population in governing plant distribution and associations. A vegetation map has been produced and can be used as a baseline to assess vegetation changes over time. [ABSTRACT FROM AUTHOR]

This paper reports on the remapping of a carefully documented vegetation plot at Cape Hallett (72°19'S 170°16'E) to provide an assessment of the rates of vegetation change over decadal time scales. E.D. Rudolph, in 1962, mapped in detail the vegetation of a site approximately 28 m by 120 m at Cape Hallett, Victoria Land, Antarctica. This site was relocated and remapped in January 2004 and changes were assessed using GIS techniques. This appears to be the longest available time period for assessing vegetation change in Antarctica. The analysis indicated that considerable change had occurred in moss and algae distribution patterns and this seems to have been caused by increased water supply, particularly in wetter areas. There was also evidence of some change in lichen distribution. The extent of the change indicates that vegetation cover can be used for monitoring change in areas as extreme as the Ross Sea region. For this analysis to be successful it was important that the mapping techniques used were totally explicit and could easily be replicated. Fortunately, Rudolph had defined his cover classes and the site was also clearly marked. The application of GIS mapping techniques allows the mapping to be more explicitly defined and easily replicated. [ABSTRACT FROM AUTHOR]

Predicting the effects of climate change on Antarctic terrestrial vegetation requires a better knowledge of the ecophysiology of common moss species. In this paper we provide a comprehensive matrix for photosynthesis and major environmental parameters for three dominant Antarctic moss species (Bryum subrotundifolium, B. pseudotriquetrum and Ceratodon purpureus). Using locations in southern Victoria Land, (Granite Harbour, 77°S) and northern Victoria Land (Cape Hallett, 72°S) we determined the responses of net photosynthesis and dark respiration to thallus water content, thallus temperature, photosynthetic photon flux densities and CO2 concentration over several summer seasons. The studies also included microclimate recordings at all sites where the research was carried out in field laboratories. Plant temperature was influenced predominantly by the water regime at the site with dry mosses being warmer. Optimal temperatures for net photosynthesis were 13.7°C, 12.0°C and 6.6°C for B. subrotundifolium, B. pseudotriquetrum and C. purpureus, respectively and fall within the known range for Antarctic mosses. Maximal net photosynthesis at 10°C ranked as B. subrotundifolium > B. pseudotriquetrum > C. purpureus. Net photosynthesis was strongly depressed at subzero temperatures but was substantial at 0°C. Net photosynthesis of the mosses was not saturated by light at optimal water content and thallus temperature. Response of net photosynthesis to increase in water content was as expected for mosses although B. subrotundifolium showed a large depression (60%) at the highest hydrations. Net photosynthesis of both B. subrotundifolium and B. pseudotriquetrum showed a large response to increase in CO2 concentration and this rose with increase in temperature; saturation was not reached for B. pseudotriquetrum at 20°C. There was a high level of variability for species at the same sites in different years and between different locations. This was substantial enough to make prediction of the effects of climate change very difficult at the moment. [ABSTRACT FROM AUTHOR]

Lichens have been used as biomonitors for multiple purposes. They are well-known as air pollution indicators around urban and industrial centers. More recently, several attempts have been made to use lichens as monitors of climate change especially in alpine and polar regions. In this paper, we review the value of saxicolous lichens for monitoring environmental changes in Antarctic regions. The pristine Antarctica offers a unique opportunity to study the effects of climate change along a latitudinal gradient that extends between 62° and 87° S. Both lichen species diversity and thallus growth rate seem to show significant correlations to mean annual temperature for gradients across the continent as well as to short time climate oscillation in the Antarctic Peninsula. Competition interactions appear to be small so that individual thalli develop in balance with environmental conditions and, as a result, can indicate the trends in productivity for discrete time intervals over long periods of time. [ABSTRACT FROM AUTHOR]