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Phenological trends among Australian Alpine species: Using Herbarium records to identify climate-change indicators
Abstract and Figures
Global temperatures are increasing at an unprecedented rate and the analysis of long-term phenological records has provided some of the most compelling evidence for the effect of these changes on species. In regions where systematically collected data on the timing of life-cycle events is scarce, such as Australia, researchers must seek alternative sources of information from which climate-change signals can be identified. In the present paper, we explore the limitations and strengths of using herbarium specimens to detect changes in flowering phenology, to select potential indicator species, and to pinpoint locations for potential monitoring schemes of native plants in Australia's subalpine and alpine zone. We selected 20 species on the basis of a range of selection criteria, including a flowering duration of 3 months or less and the number of herbarium records available in the areas above 1500 m. By the use of gridded temperature data within the study region, we identified an increase in mean annual temperature of 0.74 C between 1950 and 2007. We then matched the spatial locations of the herbarium specimens to these temperature data and, by using linear regression models, identified five species whose flowering response may be sensitive to temperature. Higher mean annual temperatures at the point of collection were negatively associated with earlier flowering in each of these species (a = 0.05). We also found a significant (P = 0.02) negative relationship between year and flowering observation for Alpine groundsel, Senecio pectinatus var. major. This species is potentially a suitable candidate for monitoring responses of species to future climate change, owing to the accessibility of populations and its conspicuous flowers. It is also likely that with ongoing warming the other four species identified (Colobanthus affinis, Ewartia nubigena, Prasophyllum tadgellianum and Wahlenbergia ceracea) in the present study may show the same response.
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... One approach to investigate changes in plant functional traits over a longer time period is to analyse specimens preserved in herbarium records, which can date back many centuries ago. Herbarium specimens supply a baseline source of information on functional traits, from which a wealth of field and observational studies may follow (Gallagher et al., 2009;Heberling, 2022). Herbarium records can be used to better understand the impact that climate change has had on plant communities by studying how the functional traits of specimens have changed over time and in space (Miller-Rushing et al., 2006). ...
... Herbarium records can be used to better understand the impact that climate change has had on plant communities by studying how the functional traits of specimens have changed over time and in space (Miller-Rushing et al., 2006). So far, herbarium records have been used to study plant invasions (Fuentes et al., 2013;Gassó et al., 2009), predict species' distributions (Elith et al., 2006) and determine phenological changes under climate change (Gallagher et al., 2009;Lavoie & Lachance, 2006;Primack et al., 2004). Only rarely have herbarium specimens been used to study traits and shifts in plant trait values over large environmental gradients (although see for example Hill et al., 2015). ...
Climate warming causes upward shifts of plant species distributions, resulting in an influx of species from lower elevations into alpine plant communities. Plant functional trait changes along elevation gradients and over time may reflect these changing conditions. Intraspecific trait variation measured from herbarium records offer a way to observe such changes in trait values over time. We selected four species: Poa alpina and Polygonum viviparum found in alpine grasslands, and Cardamine resedifolia and Ranunculus glacialis found in high‐alpine to subnival scree habitats. We measured several functional traits from (i) herbarium records collected between 1880‐1950 and from (ii) individuals resampled in 2014 along an elevation gradient covering >1500 m within the same study region in the Swiss Alps. By comparing (i) against (ii) for each species separately, we analysed temporal changes in the distribution of traits along the studied elevation gradient. After a century of climate warming, the change in the relationship linking plant functional traits with elevation was species dependent. Size‐related and reproductive functional trait values for P. viviparum increased over time, increasing at lower, but not higher elevations. P. alpina's size‐related traits increased consistently with time along the elevation gradient. Most of C. resedifolia's size‐related and flowering traits decreased over time at lower elevations, and converged at higher elevations. Finally, R. glacialis traits did not respond to time alone ‐ reproductive traits decreased over time at lower, and increased at higher elevations, reversing their historical trait distributions. The negative trend for vegetative trait values with elevation did not change over time, however. In 2014, at lower elevations, all species mainly occurred on their typical microhabitat types, but osccurrence on other microhabitats increased with elevation for all species. Synthesis. Contrasting temporal changes in the distribution of growth and reproductive trait values between alpine grassland and alpine‐subnival scree species, especially at lower elevations, suggest that climate warming effects vary among species. Additionally, species’ physiological constraints and availability of suitable microhabitats may further impact species’ distribution changes. Further warming may confine the distribution of high‐alpine plant species to even higher elevations, or to microclimates currently difficult to colonise by lower‐alpine species.
... Australia's montane biome covers a small proportion of the country's terrestrial surface area (~0.16%, Figure 1) and is a centre of floral endemism in Australia (Crisp et al., 2001). (Gallagher et al., 2009;Green, 2010). ...
... Thus, one would expect greater climate-induced changes in the currently concentrated community flowering periods of Australian Montane or Temperate Forest communities, as they shift towards the longer, more responsive flowering periods of Desert communities (Figure 3). There are already reports that lower and less predictable rainfall is affecting plant community composition through dieback in southwest Australia (Hoffmann et al., 2019), and that higher temperatures are shifting flowering dates in alpine southeast Australia (Gallagher et al., 2009;Hoffmann et al., 2019). ...
Climate shapes the composition and function of plant communities globally, but it remains unclear how this influence extends to floral traits. Flowering phenology, or the time period in which a species flowers, has well‐studied relationships with climatic signals at the species level but has rarely been explored at a cross‐community and continental scale. Here, we characterise the distribution of flowering periods (months of flowering) across continental plant communities encompassing six biomes, and determine the influence of climate on community flowering period lengths. Australia. Flowering plants. We combined plant composition and abundance data from 629 standardised floristic surveys (AusPlots) with data on flowering period from the AusTraits database and additional primary literature for 2983 species. We assessed abundance‐weighted community mean flowering periods across biomes and tested their relationship with climatic annual means and the predictability of climate conditions using regression models. Combined, temperature and precipitation (annual mean and predictability) explain 29% of variation in continental community flowering period. Plant communities with higher mean temperatures and lower mean precipitation have longer mean flowering periods. Moreover, plant communities in climates with predictable temperatures and, to a lesser extent, predictable precipitation have shorter mean flowering periods. Flowering period varies by biome, being longest in deserts and shortest in alpine and montane communities. For instance, desert communities experience low and unpredictable precipitation and high, unpredictable temperatures and have longer mean flowering periods, with desert species typically flowering at any time of year in response to rain. Current climate conditions shape flowering periods across biomes, with implications for phenology under climate change. Shifts in flowering periods across climatic gradients reflect changes in plant strategies, affecting patterns of plant growth and reproduction as well as the availability of floral resources for pollinators across the landscape.
... Similarly, using 216 herbarium specimens, Lavoie and Lachance [71] reported (15-31 days) earlier flowering of Tussilago farfara L.in the twenty-first century than in around 1920. Several herbarium-based studies report earlier flowering in different plants [12,42,72]. The early-spring-flowering species of bluebell, cuckoo flower, coltsfoot, garlic mustard, and wood anemone responded to increasing temperatures by advancing their first flowering day (FFD) [73]. ...
Studies from different parts of the world have generated pieces of evidence of climate change’s effects on plant phenology as indicators of global climate change. However, datasets or pieces of evidence are lacking for the majority of regions and species, including for the climate-sensitive Himalayan biodiversity hotspot. Realizing this gap in information, and the wide-ranging implications of such datasets, we integrated real-time field observations and long-term herbarium records to investigate the changes in the spring flowering phenology of Olea ferruginea Royle, commonly known as the Indian Olive, in response to the changing climate in the western Himalayas. We attempted to create phenological change model using the herbarium records and field observations after recording the current dates of flowering and overall temperature trends from the study area over the last four decades from the five regional meteorological observatories of the Jammu province managed by Indian Meteorological Department (IMD) in Jammu and Kashmir. When considering current flowering dates along with herbarium information (years 1878–2008) for O. ferruginea, our Generalized Additive Model (GAM) showed 15–21 days-early flowering over the last 100 years significantly (p < 0.01). Results of the Mann–Kendall test showed increasing trends of TMin for all seasons significantly (p < 0.05) for Jammu province whereas TMax was only for the spring season. The increasing TMin of spring, summer, and autumn seasons also influenced the flowering phenology of O. ferruginea significantly (p < 0.01). By demonstrating the integrated use of methodological tools for finding long-term phenological changes in response to climate change, this work bridges knowledge gaps in phenological research from the developing world in general and the Himalayas in particular.
... Similarly, using 216 herbarium specimens, Lavoie and Lachance [71] reported (15-31 days) earlier flowering of Tussilago farfara L.in the twenty-first century than in around 1920. Several herbarium-based studies report earlier flowering in different plants [12,42,72]. The early-spring-flowering species of bluebell, cuckoo flower, coltsfoot, garlic mustard, and wood anemone responded to increasing temperatures by advancing their first flowering day (FFD) [73]. ...
Studies from different parts of the world have generated pieces of evidence of climate change’s effects on plant phenology as indicators of global climate change. However, datasets or pieces of evidence are lacking for the majority of regions and species, including for the climate-sensitive Himalayan biodiversity hotspot. Realizing this gap in information, and the wide-ranging implications of such datasets, we integrated real-time field observations and long-term herbarium records to investigate the changes in the spring flowering phenology of Olea ferruginea Royle, commonly known as the Indian Olive, in response to the changing climate in the western Himalayas. We attempted to create phenological change model using the herbarium records and field observations after recording the current dates of flowering and overall temperature trends from the study area over the last four decades from the five regional meteorological observatories of the Jammu province managed by Indian Meteorological Department (IMD) in Jammu and Kashmir. When considering current flowering dates along with herbarium information (years 1878–2008) for O. ferruginea, our Generalized Additive Model (GAM) showed 15–21 days-early flowering over the last 100 years significantly (p < 0.01). Results of the Mann–Kendall test showed increasing trends of TMin for all seasons significantly (p < 0.05) for Jammu province whereas TMax was only for the spring season. The increasing TMin of spring, summer, and autumn seasons also influenced the flowering phenology of O. ferruginea significantly (p < 0.01). By demonstrating the integrated use of methodological tools for finding long-term phenological changes in response to climate change, this work bridges knowledge gaps in phenological research from the developing world in general and the Himalayas in particular.
... Observed impacts in the Australian Alps were projected to continue under future climate change (Zylstra, 2018). The northern Australia savanna (H131) may experience increased rainfall and carbon dioxide due to climate change (Scheiter et al., 2015), and the range of exotic grasses was projected to be reduced under climate warming (Gallagher et al., 2009). In Australian tropical wet forests, ground-living vertebrates may be more sensitive than arboreal species to unstable climates (Scheffers et al., 2017). ...
... Expanded phenological information derived from large numbers of specimens can offer insight into how long-term shifts occur in phenology at a given location over decades or even centuries (Miller-Rushing et al., 2006), how seasonal environmental difference cues phenological shifts (Davis et al., 2015) and to make distribution maps of plant species (L opez and Sassone, 2019). Herbarium records alone or in combination with field observations have been used to show the response of phenological events to changes in climate conditions throughout the entire range of a species (Primack et al., 2004;Gallagher et al., 2009;Davis et al., 2015;Greve et al., 2016). Munson and Sher (2015) used herbarium records to track the phenology of rare and endemic species to determine the changes in flowering over a century and provided evidence for large shifts in the phenology of rare Rocky Mountain plants related to climate (temperature and precipitation). ...
Herbarium specimens are being used as reliable sources for estimating phenological behavior for plant species. Flowering and fruiting periodicity of 520 herbarium specimens, collected between 1948 and 2007 and deposited at the National Herbarium of Ethiopia, were investigated. Scientific names, collection date and locality of specimens were documented to assess the periodicity of phenological events. For the evaluation of periodicity of reproductive phenophases, the presence of flowering and fruiting were visually confirmed from each specimen. Examination of flowering periodicity of Bersama abyssinica, Brucea antidysenterica, Maytenus arbutifolia and Rosa abyssinica showed continuous flowering while Prunus africana, Lobelia rhynchopetalum, Kniphofia foliosa, Solanecio gigas, Buddleja polystachya, Dombeya torrida and Embelia schimperi exhibited seasonal flowering. Although the fruiting period is extended over several months (B. abyssinica, B. antidysenterica, E. schimperi, M. arbutifolia and R. abyssinica), seasonality in fruiting was also observed in K. foliosa, L. rhynchopetalum and P. africana. The highest number of specimens found belonged to M. arbutifolia followed by B. abyssinca and B. antidysenterica, while the highest number of specimens were collected from Shewa Upland followed by Keffa and Bale floristic regions. Surprisingly, Euryops pinifolius, a species endemic to Ethiopia, was represented by only one specimen collected from Gojjam in 1985. The results revealed that herbarium specimens can be used to study flowering and fruiting periodicity of plant species. Therefore, botanists should be encouraged to continue collecting herbarium specimens based on the distribution of species in the flora area to avoid spatial and species biases for future studies.
... niphophila at lower elevations since 1970, which may lead to downhill range shifts in this species (Green & Venn, 2012). Studies have also found changes in species composition including increased shrub cover and decreased graminoid cover with experimental warming in this region (Wahren et al., 2013); as well as observed shifts in species' phenology with a few species flowering earlier in the year than in the past (Gallagher et al., 2009) and increases in the invasion of non-native species (Scherrer & Pickering, 2001). However, our study is the first to test for elevational range shifts across a wide range of Australian alpine plant species. ...
Aim
Alpine plant species’ distributions are thought to have been shifting to higher elevations in response to climate change. By moving upslope, species can occupy cooler and more suitable environments as climate change warms their current ranges. Despite evidence of upslope migration in the northern hemisphere, there is limited evidence for elevational shifts in southern hemisphere plants. Our study aimed to determine if alpine plants in Australia have migrated upslope in the last 2 to 6 decades.
Location
Kosciuszko National Park, NSW, Australia.
Methods
We collated historic occurrence data for 36 Australian alpine plant species from herbarium specimens and historic field observations and combined these historic data with modern occurrence data collected in the field.
Results
Eleven of the thirty‐six species had shifted upslope in mean elevation and four species showed downslope elevational shifts. The rate of change for upslope shifts varied between 4 and 10 m per year and the rate of change for most downslope shifts was between 4 and 8 m per year, with one species shifting downslope at a high rate of 18 m per year. Additionally, some species showed shifts upward in their upper range edge and/or upward or downward shifts in their lower range edge. Five species also showed range contractions in the difference between their lower and upper range edges over time, while two showed range expansions. We found no significant differences in elevational shifts through time among herbaceous dicotyledons, herbaceous monocotyledons and shrubs.
Main Conclusions
Plant elevational shifts are occurring rapidly in the Australian alpine zone. This may allow species to persist under climate change. However, if current warming trends continue, several species within the Australian alpine zone will likely run out of suitable habitat within a century.
... Because most of the collections are dated and geolocated, they constitute a valuable source of information for (i) determining the proven or potential distribution areas of species [21][22][23], whether native or exotic (dynamics of biological invasions), with direct applications in conservation biology [24], and for (ii) determining the reproductive phenological patterns of species (e.g., date and duration of flowering and fruiting periods) [25][26][27][28]. Research in these fields has been particularly stimulated by questions related to climate change and its effect on the range of species distribution [29,30] or their biological rhythms [31][32][33][34][35][36][37][38][39]. More original aspects have been addressed such as changes over time in (i) herbivory [40,41], (ii) the concentration of isotopes (δC13, δO18) related to water use efficiency or photosynthetic efficiency [42], or (iii) the diversity of endophytic fungi present in leaves [43]. ...
A better knowledge of tree vegetative growth phenology and its relationship to environmental variables is crucial to understanding forest growth dynamics and how climate change may affect it. Less studied than reproductive structures, vegetative growth phenology focuses primarily on the analysis of growing shoots, from buds to leaf fall. In temperate regions, low winter temperatures impose a cessation of vegetative growth shoots and lead to a well-known annual growth cycle pattern for most species. The humid tropics, on the other hand, have less seasonality and contain many more tree species, leading to a diversity of patterns that is still poorly known and understood. The work in this study aims to advance knowledge in this area, focusing specifically on herbarium scans, as herbariums offer the promise of tracking phenology over long periods of time. However, such a study requires a large number of shoots to be able to draw statistically relevant conclusions. We propose to investigate the extent to which the use of deep learning can help detect and type-classify these relatively rare vegetative structures in herbarium collections. Our results demonstrate the relevance of using herbarium data in vegetative phenology research as well as the potential of deep learning approaches for growing shoot detection.
... A few years later, Houle (2007) compared the flowering dates of vernal plants in deciduous forests in Quebec and found that they flowered two to six days earlier at the end of the 20th century than at the beginning. More recently, a study in the Australian mountains used herbarium samples to identify alpine (Australian) species whose altered phenology may reflect climate change (Gallagher et al. 2009). ...
... The first is represented by detailed studies of individual species in which the sensitivity to long-term mean climatic conditions and/or to inter-annual variation in climate is estimated, and some report interactions between predictor variables that affect phenological behavior (Robbirt et al. 2011;Gaira et al. 2011Gaira et al. , 2014Matthews and Mazer 2016;Ellwood et al. 2019;Love et al. 2019;Petrauski et al. 2019;Banaszak et al. 2020;Pearson et al. 2021). The second category comprises synthetic studies of multiple species and higher taxa, aiming to detect general similarities and differences among taxa or communities with respect to their phenological responses to climatic factors that vary over time or space (Primack et al. 2004;Miller-Rushing et al. 2006;Houle 2007;Gallagher et al. 2009;Diez et al. 2012;Panchen et al. 2012Panchen et al. , 2017Diskin et al. 2012;Calinger et al. 2013;Li et al. 2013;Mazer et al. 2013;Hart et al. 2014;Park 2014;Davis et al. 2015;Kharouba and Vellend 2015;Rawal et al. 2015;Munson and Long 2017;Park and Schwartz 2018;Jones and Daehler 2018;Mazer 2018, 2019;Berg et al. 2019;Pearson 2019;Kopp et al. 2020;Park, Ramirez Parada, and Mazer 2020;Reeb et al. 2020). A few studies in both categories have begun to investigate sources of intraspecific variation in phenological sensitivity (Matthews and Mazer 2016;Song et al. 2020). ...
To date, most herbarium-based studies of phenological sensitivity to climate and of climate-driven phenological shifts fall into two categories: detailed species-specific studies vs. multi-species investigations designed to explain inter-specific variation in sensitivity to climate and/or the magnitude and direction of their long-term phenological shifts. Few herbarium-based studies, however, have compared the phenological responses of closely related taxa to detect: (1) phenological divergence, which may result from selection for the avoidance of heterospecific pollen transfer or competition for pollinators, or (2) phenological similarity, which may result from phylogenetic niche conservatism, parallel or convergent adaptive evolution, or genetic constraints that prevent divergence. Here, we compare two widespread Clarkia species in California with respect to: the climates that they occupy; mean flowering date, controlling for local climate; the degree and direction of climate change to which they have been exposed over the last 115 yr; the sensitivity of flowering date to inter-annual and to long-term mean maximum spring temperature and annual precipitation across their ranges; and their phenological change over time. Specimens of C. cylindrica were sampled from sites that were chronically cooler and drier than those of C. unguiculata, although their climate envelopes broadly overlapped. Clarkia cylindrica flowers 3.5 d earlier than C. unguiculata when controlling for the effects of local climatic conditions and for quantitative variation in the phenological status of specimens. However, the congeners did not differ in their sensitivities to the climatic variables examined here; cumulative annual precipitation delayed flowering and higher spring temperatures advanced flowering. In spite of significant spring warming over the sampling period, neither species exhibited a long-term phenological shift. Precipitation and spring temperature interacted to influence flowering date: the advancing effect on flowering date of high spring temperatures was greater in dry than in mesic regions, and the delaying effect of high precipitation was greater in warm than in cool regions. The similarities between these species in their phenological sensitivity and behavior are consistent with the interpretation that facilitation by pollinators and/or shared environmental conditions generate similar patterns of selection, or that limited genetic variation in flowering time prevents evolutionary divergence between these species.
Information from natural history collections (NHCs) about the diversity, taxonomy and historical distributions of species worldwide is becoming increasingly available over the Internet. In light of this relatively new and rapidly increasing resource, we critically review its utility and limitations for addressing a diverse array of applications. When integrated with spatial environmental data, NHC data can be used to study a broad range of topics, from aspects of ecological and evolutionary theory, to applications in conservation, agriculture and human health. There are challenges inherent to using NHC data, such as taxonomic inaccuracies and biases in the spatial coverage of data, which require consideration. Promising research frontiers include the integration of NHC data with information from comparative genomics and phylogenetics, and stronger connections between the environmental analysis of NHC data and experimental and field-based tests of hypotheses.
Recent climate warming has been observed at the global scale, but by examining developmental stages of plant species (phenology) that are dependent on local climatic conditions, climate change at the local scale can be detected. There are four gardens in Ireland belonging to the International Phenological Gardens (IPG) network, which has recorded tree phenology for more than 30 years using a common collection of clonal tree species and cultivars. In this analysis two phenological stages were investigated */the beginning of the growing season (BGS) and the end of the growing season (EGS) */ in nine tree cultivars in relation to ambient air temperature. The length of the growing season (LGS) was determined from the number of days between BGS and EGS. Structural time series analysis was used to describe trends in the data. Overall BGS was the most responsive phenophase and was shown to start earlier in more recent years for some species at all sites. It is shown that these observations are due to recent climate change in the form of spring warming, particularly in the south-west of the country. Due to the limited number of observation sites and differences between species responses, we suggest that extrapolation of the results to larger geographical areas should be performed with caution.
The iconic summer tourism destination in the Australian Alps National Parks is the summit area of continental Australia's highest mountain, Mt Kosciuszko. Currently 70,000 people visit the alpine area during the snow-free period each year, and about 21,000 of these take a day-walk to the summit and back. The environmental impacts of summer tourism include: soil compaction and erosion; introduction and spread of weeds; fecal contamination of lakes and creeks; increased feral animals; and vegetation clearance. The principal management responses have been: hardening of tracks; provision of toilets; education, including minimum-impact codes; and restrictions on activities such as camping in the catchment areas of glacial lakes. Currently, only the access tracks and immediate alpine area around the summit of Mt Kosciuszko receive so many visitors in such a small area. The summit area has become a honeypot focusing tourism and its impacts at one site. Effective management is needed to ensure that the summit along with the rest of the Kosciuszko alpine area remains viable for conservation and outdoor recreation.
Delphinium nelsonii is an early-blooming herbaceous perennial of montane western North America, which we studied in dry subalpine meadows in the Colorado Rocky Mountains. We examined the effects of variation in annual snowfall between 1973 and 1989 on the timing and abundance of flowering. During years of lower snow accumulation, D. nelsonii plants experienced colder temperatures between the period of snowmelt and flowering. Also, flowering was delayed, floral production was lower, and flowering curves were more negatively skewed; damage during floral development probably occurred in years of low snowfall. If climate change results in decreased mean annual snowfall for the Rocky Mountains, then the seed production of D. nelsonii will probably be adversely affected. Decreased snowfall may also indirectly lower the seed production of later-blooming species by decreasing populations of bumblebees and hummingbirds that forage on D. nelsonii flowers. Decreased snowfall has the potential to reduce the number and relative proportions of species in the herbaceous flora in our study area.
In China, changes in the timing of plant phenological phases are influenced greatly by monsoonal climate fluctuations, and also vary with species and region. Observations of phenological phases of trees were conducted in the Phenological Observation Network of China from 1963 to 1988. Records of flowering dates of four species (Syringa oblata Lindl., Cercis chinensis Bunge, Robinia pseudoacacia L., Albizzia julibrissin Durazz) at ten sites, together with corresponding climate data, were used to investigate phenophase responses to variation in temperature. The ten sites extend over a wide area, with latitudes ranging from 25°N to 46°N, and altitudes ranging from 17 to 1,922 m a.s.l. Spring temperature was significantly related to flowering date of the trees under the monsoonal climate in the eastern Eurasian Continent. The period during which temperature influences flowering time varies from 60 to 90 days for Robinia pseudoacacia in the south to 30 to 40 days in the north, due to the shorter warm period before flowering in the north. The three other species showed similar trends of changes with latitude in the length of the period of temperature influence. The flowering season for Cercis chinensis in response to a temperature increase 30-60 days prior to flowering advanced from 2.7 to 5.9 days/°C in the low plain, and in response to a temperature increase 60-90 days prior to flowering, advanced from 7.1 to 14.8 days/°C in the Yunnan-Guizhou Plateau. The flowering for Syringa oblata, Robinia pseudoacacia and Albizzia julibrissin, in response to a temperature increase advanced in the range 2.7-4.9, 2.5-6.5, and 2.4-6.0 days/°C in the low plain, respectively. Flowering advanced by 4.7-12.4 days/°C for Robinia pseudoacacia and 13.1 days/°C for Albizzia julibrissin in the plateau.
Herbarium phenology data were evaluated and then applied in a phylogenetically independent contrast study in which flowering times were compared between fleshy and nonfleshy-fruited plants growing in the north-temperate provinces of Uppland and Södermanland, southeastern Sweden (59°-60°N). To evaluate herbarium phenology data, flowering-time information taken from herbarium specimens in the Swedish Natural History Museum (S) was compared with two independent field phenology data sets. Herbarium collections and the field studies were restricted to the province of Uppland. Flowering times derived from herbarium specimens correlated equally well with each of the two field-phenology data sets as the field phenology data sets did to each other. Differences between flowering times derived from field and herbarium collections were not affected by the number of herbarium specimens used. However, these differences in flowering times were affected by flowering season such that herbarium-derived flowering times were later for early spring-flowering species and earlier for late summer-flowering species when compared with flowering times derived from field data. In the phylogenetically independent contrast study of mean flowering times in fleshy- compared with nonfleshy-fruited plants, herbarium data were compiled for 77 species in 17 phylogenetically independent contrasts. Flowering time was found to be earlier for fleshy-fruited taxa, illustrating the evolutionary interdependence between flowering and fruiting phases and the constraining effects of a north-temperate climate on phenology evolution. This study shows that herbaria are reliable and time-saving data sources for comparative phenology studies and allow for studies at large phylogenetic and geographic scales that would otherwise be impossible.
Alpine snowpatch vegetation in Australia is restricted to high mountain areas and occurs in locations where winter snow persists longest into the summer. The timing of annual snowmelt is considered an important determinant of vegetation patterns in alpine areas because it affects the length of the growing season for plant species at landscape scales. There are few studies in Australia that have examined the effects of the date of snowmelt on the performance of plant species at small spatial scales. The phytomass and phenology of three common snowpatch species (Celmisia pugioniformis, Luzula acutifolia, Poa fawcettiae) was examined during one growing season across a natural snowmelt gradient to examine their response to time of snow release. Peak phytomass was significantly higher in early than late-melting zones for L. acutifolia and marginally higher there for C. pugioniformis. P. fawcettiae, however, produced higher mean peak phytomass in late-melting zones where soil was initially wetter in the growing season. Flower buds of L. acutifolia were evident as the snow melted, and flowering occurred at the same time in all areas of the snowpatch. The number of days from the date of snowmelt to the date of the first observed flower bud in C. pugioniformis and P. fawcettiae was 22-25 days shorter in late-melting areas than in early melting areas. For both of these species, flowering and subsequent seed set occurred simultaneously across the snowpatch regardless of the date of the initial snowmelt, suggesting that photoperiod controls flowering in these species. Our study suggests that the predicted declines in snow cover in Australia in coming decades may affect the phytomass of species that are currently constrained by late-lying snow. This, in turn, may affect their long-term patterns of distribution. If plants respond to photoperiod for flowering, as seems to be important here for C. pugioniformis and P. fawcettiae, it is unlikely that the periods following earlier than usual snowmelt will be fully utilised by these species. Any attempts at predicting or modelling future alpine plant distribution on the basis of warming scenarios may therefore need to account for photoperiod constraints on flowering as well changes in phytomass production.
To examine the potential contribution of herbarium material to the description and analysis of tropical tree phenology, flowering times and geographical distribution were graphed for 1673 flowering collections from 18 species native to Neotropical dry forests and phenological differences between species were analysed. These include the timing and duration of flowering as well as morphological differences such as flowering on leafless twigs vs flowering on shoots bearing old or new foliage. Species-specific flowering periods of herbarium collections are similar to those observed in phenological field studies, but are often longer because of the larger geographical and temporal sampling range. Conspecific collections of different geographical origin show distinct differences in flowering periodicity, which are correlated with differences in the timing and intensity of the dry season. Interspecific differences in the timing of phenology relative to the dry season indicate differences in the control of phenology by seasonal drought. Herbaria thus represent a large potential source of phenological information which can either supplement and extend phenological field studies or provide phenological information for dry forest species not studied in the field but well represented in herbarium collections.