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Effects of Experimental Warming on Plant Reproductive Phenology in a Subalpine Meadow
Abstract
Increasing 'greenhouse' gases are predicted to warm the earth by several degrees Celsius during the coming century. At high elevations one likely result is a longer snow-free season, which will affect plant growth and reproduction. We studied flowering and fruiting of 10 angiosperm species in a subalpine meadow over 4 yr, focusing on plant responses to warming by overhead heaters. The 10 species reproduced in a predictable sequence during 3-4 mo between spring snowmelt and fall frosts. Experimental warming advanced the date of snowmelt by almost 1 wk on average, relative to controls, and similarly advanced the mean timing of plant reproduction. This phenological shift was entirely explained by earlier snowmelt in the case of six plant species that flowered early in the season, whereas four later-flowering species apparently responded to other cues. Experimental warming had no detectable effect on the duration of flowering and fruiting, even though natural conditions of early snowmelt were associated with longer duration and greater overlap of reproduction of sequentially flowering species. Fruit set was greater in warmed plots for most species, but this effect was not significant for any species individually. We conclude that global warming will cause immediate phenological shifts in plant communities at high elevations, mediated largely through changes in timing of snowmelt. Shifts on longer time scales are also likely as plant fitnesses, population dynamics, and community structure respond to altered phenology of species relative to one another and to animal mutualists and enemies. However, the small spatial scale of experiments such as ours and the inability to perfectly mimic all elements of climate change limit our ability to predict these longer term changes. A promising future direction is to combine experiments with study of natural phenological variation on landscape and larger scales.
... A few studies have observationally or experimentally examined the separate and combined effects of warming and advanced snowmelt on plant individuals in montane environments over a period of time longer than 4 years. These studies in the Rocky Mountains of Colorado found earlier flowering onset with warming and advanced snowmelt (Dunne et al., 2003;Jabis et al., 2020;Wadgymar et al., 2018), increased floral displays with earlier snowmelt (Inouye, 2008), and extended flowering duration in response to earlier melt (Dunne et al., 2003;Jabis et al., 2020;Price & Waser, 1998), indicating that the phenologies of plant species in this montane ecosystem are tracking climate change. By contrast, Inouye (2008) found reduced floral abundance for three early-spring-flowering perennials (i.e., Delphinium barbeyi, Erigeron speciosus, and Helianthella quinquenervis) associated with earlier snowmelt in a 32-year observational study. ...
... We expected earlier flowering onset with all non-control treatments with the earliest onset occurring in the heating and snow removal treatment in response to earlier light access and warmer spring temperatures (Arft et al., 1999;Fitter & Fitter, 2002;Gezon et al., 2016;Jabis et al., 2020;Kehrberger & Holzschuh, 2019;Steltzer et al., 2009;Wadgymar et al., 2018). We predicted extended flowering durations with snow removal in response to earlier onset and access to light (Dunne et al., 2003;Price & Waser, 1998), but no change with heating and snow removal, as the two treatments could counteract each other (Nagahama et al., 2018). We expected increased maximum floral display with snow removal in response to earlier onset and extended flowering duration, which allows plants to flower longer and potentially produce more flowers (Gezon et al., 2016). ...
... A best-fit line was added to display the relationship between the variables, with bolded lines indicating a significant correlation. temperatures and earlier snowmelt individually lead to advanced flowering onset (Arft et al., 1999;Fitter & Fitter, 2002;Gezon et al., 2016;Jabis et al., 2020;Kehrberger & Holzschuh, 2019;Steltzer et al., 2009;Wadgymar et al., 2018;Wipf, 2010), extended flowering durations (Dunne et al., 2003;Jabis et al., 2020;Price & Waser, 1998), and greater maximum floral displays (Arft et al., 1999;Gezon et al., 2016), but the combined effects of warming and earlier snowmelt on flowering phenology are poorly understood, especially over many consecutive years. Consistent with our predictions, B. sagittata phenology and floral production varied in response to warming via passive heating with experimentally accelerated spring snowmelt across the 7-year study, suggesting that components of climate change interact to affect montane floral populations and community interactions through altered phenology. ...
Climate change is shifting phenology globally, altering when and how species respond to environmental cues such as temperature and the timing of snowmelt. These shifts may result in phenological mismatches among interacting species, creating cascading effects on community and ecosystem dynamics. Using passive warming structures and snow removal, we examined how experimentally increased temperatures, earlier spring snowmelt, and the poorly understood interaction between warming and earlier spring snowmelt affected flower onset, flowering duration, and maximum floral display of the spring‐flowering montane species, arrowleaf balsamroot (Balsamorhiza sagittata), over a 7‐year period. Additionally, potential cumulative effects of treatments were evaluated over the study duration. The combination of heating with snow removal led to earlier flower onset, extended flowering duration, and increased maximum floral display. While there was year‐to‐year variation in floral phenology, the effect of heating with snow removal on earlier onset and maximum floral display strengthened over time. This suggests that short‐term studies likely underestimate the potential for climate change to influence phenological plant traits. Overall, this research indicates that B. sagittata's flowering onset responded more strongly to snow removal than to heating, but the combination of heating with snow removal allowed plants to bloom earlier, longer, and more profusely, providing more pollinator resources in spring. If warming and early snowmelt cause similar responses in other plant species, these patterns could mitigate phenological mismatches with pollinators by providing a wider window of time for interaction and resiliency in the face of change. This example demonstrates that a detailed understanding of how spring‐flowering plants respond to specific aspects of predicted climatic scenarios will improve our understanding of the effects of climate change on native plant–pollinator interactions in montane ecosystems. Studies like this help elucidate the long‐term physiological effects of climate‐induced stressors on plant phenology in long‐lived forbs.
... Observations were made every other day during the growing season to collect observational data on S. breviflora reproductive phenology and phenological period from 2009 to 2019. The phenological phases observed were 0 = spikelet in boot, 1 = spikelet out of boot, 2 = exserted anthers and styles, 3 = developing seed, 4 = all seed dropped (Price and Waser, 1998). First, the species score sequences for different days were analyzed. ...
... January 1st of each year was counted as the first day, and the corresponding day for each phenological event was calculated. An optimal simulation curve was fit to the resulting data on the date and duration of each phenological period by applying the Richard's equation (Price and Waser, 1998): Y = K/(1 + a * exp ( -b*X)) m , where K is the maximum value in the phenology score; a is the startup parameter of the date when observation of the evaluated species began; b is the reproductive phenological rate during the observed period; and m is the curve shape variation parameter. All phenological scores accorded with the Richards equation (R 2 > 0.99). ...
... All phenological scores accorded with the Richards equation (R 2 > 0.99). Four parameters can be determined by equation fitting and substituted into the conversion formula (Price and Waser, 1998): ...
The sensitivity of plant phenology to climate change can be used as the basis for predicting change in plant species' growth and development period as they adapt to gradual increase in atmospheric temperature. However, it is not clear how the reproductive phenology of plants will respond to a continuous increase in temperature gradient, especially when the time series has break points due to interannual change. In this experiment, the flowering phenology of Stipa breviflora, an established species in the desert steppe of Siziwang Banner in northern China, was observed from 2009 to 2019. A no warming treatment and warming treatment (1.3 °C higher than no warming) were applied. Three temperature gradients were defined: the annual average temperature of the 0–10 cm soil layer in the no warming treatment plot from 2009 to 2019 was taken as the average temperature gradient (C2, 5.63 °C ± 1.09); a higher-than-average temperature gradient (C3, 6.93 °C ± 1.34), and a lower than the average temperature gradient (C1, 4.33 °C ± 1.87). The results showed that increasing temperature was an important driving factor that advanced the flowering phenology of S. breviflora. When high temperatures exceed plants’ physiological thresholds (5.63 °C ± 1.09), plants exhibit a temporary delay. Based on a Mann-Kendall test, we found that reproductive phenology was advanced from 2009 to 2015, and delayed by a time break point from 2015 to 2018. After 2018, reproductive phenology continued to be advanced, which once again verified that reproductive phenology would not continue to be advanced in the process of climate warming, but would be temporarily delayed. Therefore, our study reveals the response strategy of S. breviflora to a continuous increase in global atmospheric temperature, and provides a theoretical basis for studying the response mechanism of the desert steppe ecosystem to climate warming.
... Temperature and snow melt timing are important phenological cues in high-elevation and high-latitude plant communities, where climate change is occurring rapidly (Dunne et al., 2003;Jabis et al., 2020;Price & Waser, 1998;Quaglia et al., 2020;Saavedra et al., 2003;Wipf & Rixen, 2010;Ziello et al., 2009). Rising temperatures due to climate change are strongly associated with earlier phenology (Forrest & Miller-Rushing, 2010;Parmesan, 2006;Parmesan & Yohe, 2003;Thackeray et al., 2010). ...
... These effects were exhibited when the warming treatment continued to be significant in the second analysis after ac- although the direction and magnitude were not always the same (Dunne et al., 2003;Li et al., 2016;Sethi et al., 2020). However, several studies have found the duration of phenological stages to be unresponsive to climate change (Jabis et al., 2020;Price & Waser, 1998;Semenchuk et al., 2016). Similarly, we found that the duration of flowering and fruiting of some species did not change significantly under warming and earlier snow melt, whereas other species showed shorter or longer duration of reproductive phases. ...
... show that a single climatic cue-snow melt timing-can have multiple mechanisms for driving phenology. Although there is ample experimental and observational evidence that the timing of snow melt affects flowering phenology (Bjorkman et al., 2015;Høye, Mølgaard Ellebjerg, et al., 2007;Price & Waser, 1998;Steltzer et al., 2009), it has remained unclear whether snow melt simply acts through temperature accumulation or whether it can cue phenological events independently from temperature. This distinction is important because it improves our mechanistic understanding of how snow melt timing acts as a phenological cue. ...
Organisms use environmental cues to align their phenology—the timing of life events—with sets of abiotic and biotic conditions that favor the successful completion of their life cycle. Climate change has altered the environmental cues organisms use to track climate, leading to shifts in phenology with the potential to affect a variety of ecological processes. Understanding the drivers of phenological shifts is critical to predicting future responses but disentangling the effects of temperature from precipitation on phenology is often challenging because they tend to covary. We addressed this knowledge gap in a high‐elevation environment where phenological shifts are associated with both the timing of spring snowmelt and temperature. We factorially crossed early snowmelt and passive warming treatments to (1) disentangle the effects of snowmelt timing and warming on the phenology of flowering and fruiting and reproductive success in three subalpine plant species (Delphinium nuttallianum, Valeriana edulis, and Potentilla pulcherrima) and (2) assess whether snowmelt acts via temperature accumulation or some other aspect of the environment (e.g., soil moisture) to affect phenological events. Both the timing and duration of flowering and fruiting responded to the climate treatments, but the effect of snowmelt timing and warming varied among species and phenological stages. The combined effects of the treatments on phenology were always additive, and the snowmelt treatment often affected phenology even when the warming treatment did not. Despite marked responses of phenology to climate manipulations, the species showed little change in reproductive success, with only one species producing fewer seeds in response to warming (Delphinium, ‐56%). We also found that snowmelt timing can act both through temperature accumulation and as a distinct cue for phenology, and these effects are not mutually exclusive. Our results show that one environmental cue, here snowmelt timing, may act through multiple mechanisms to shift phenology.
... In the arctic, an increase of 1°C and an increased winter snowpack with later trending snowmelt correlated with delayed flowering, while passive warming after snowmelt advanced flowering (Bjorkman et al. 2015). In the subalpine, both earlier snowmelt via snow removal and active warming advanced flowering time (Dunne et al. 2004, Gezon et al. 2016, while earlier snowmelt was associated with extended flowering and greater phenological overlap in co-flowering species (Price and Waser 1998). ...
... Species-specific or functional group strategies prevalent among alpine plants, such as belowground storage and preformation of buds could decouple plant demand from current resource availability and temporarily buffer their sensitivity to changes in climate. Plants active early in the growing season have been more responsive to changes in climatic conditions than later-blooming species (Price and Waser 1998, Dunne et al. 2003, Sherry et al. 2007, Wolkovich et al. 2012, Petraglia et al. 2014. Responses by life-form group have appeared inconsistent, making community shifts hard to predict, graminoids (Oberbauer et al. 2013) and forbs (Smith et al. 2012), are likely to be more sensitive to warming than other community members. ...
... Further, snow addition or removal provides information about sensitivity to snowmelt timing alone but not full effects of warming. Though less commonly used in the subalpine and alpine tundra, active warming (Price and Waser 1998, Dunne et al. 2004, Suonan et al. 2017 both advances snowmelt and warms plants and soils following snowmelt. ...
Large‐scale warming will alter multiple local climate factors in alpine tundra, yet very few experimental studies examine the combined yet distinct influences of earlier snowmelt, higher temperatures and altered soil moisture on alpine ecosystems. This limits our ability to predict responses to climate change by plant species and communities. To address this gap, we used infrared heaters and manual watering in a fully factorial experiment to determine the relative importance of these climate factors on plant flowering phenology, and response differences among plant functional groups. Heating advanced snowmelt and flower initiation, but exposed plants to colder early‐spring conditions in the period prior to first flower, indicating that snowmelt timing, not temperature, advances flowering initiation in the alpine community. Flowering duration was largely conserved; heating did not extend average species flowering into the latter part of the growing season but instead flowering was completed earlier in heated plots. Although passive warming experiments have resulted in warming‐induced soil drying suggested to advance flower senescence, supplemental water did not counteract the average species advance in flowering senescence caused by heating or extend flowering in unheated plots, and variation in soil moisture had inconsistent effects on flowering periods. Functional groups differed in sensitivity to earlier snowmelt, with flower initiation most advanced for early‐season species and flowering duration lengthened only for graminoids and forbs. We conclude that earlier snowmelt, driven by increased radiative heating, is the most important factor altering alpine flowering phenology. Studies that only manipulate summer temperature will err in estimating the sensitivity of alpine flowering phenology to large‐scale warming. The wholesale advance in flowering phenology with earlier snowmelt suggests that alpine communities will track warming, but only alpine forbs and graminoids appear able to take advantage of an extended snow‐free season.
... Here, we highlight the need of incorporating precipitation in the models predicting plant flowering date, particularly in arid and semi-arid regions such as Inner Mongolia. Moreover, the divergent trends of flowering time among species can be attributed to possible different temperature sensitivities of different species (Price and Waser, 1998). It has been reported that flowering time of early-blooming species such as Stipa are more sensitive to temperature changes than that of the late-blooming species such as A. frigida (Price and Waser, 1998;Xia and Wan, 2013), which can support our findings (Fig. 4). ...
... Moreover, the divergent trends of flowering time among species can be attributed to possible different temperature sensitivities of different species (Price and Waser, 1998). It has been reported that flowering time of early-blooming species such as Stipa are more sensitive to temperature changes than that of the late-blooming species such as A. frigida (Price and Waser, 1998;Xia and Wan, 2013), which can support our findings (Fig. 4). Besides, the overall insignificant effect of ASSD (accumulated sunshine duration) indicated that radiation is not a restricted condition on plant growth development shows the average regression intercepts and slopes for the predictors of flowering dates. ...
Under global climate change, particularly warming, plant phenology may vary significantly thereby influencing a series of ecosystem functionalities. However, observational evidences of the variation of plant phenology and its association with climate change in temperate grassland are limited. In this study, we collated plant phenological records during the period from 1982 to 2019 at 26 sites in Inner Mongolian temperate grassland to elucidate the association of plant phenology with a series of environmental variables. The results showed that a trend of warming, particularly during May-September, occurred over the study period. However, this warming did not significantly influence plant phenology (e.g., green-up, flowering and brown-down) of four dominant plant species (i.e., Stipa, L. Chinensis, A. Cristatum and A. Frigida). Rather, multivariate regression considering a series of climatic and edaphic factors revealed that preseason climate predominantly regulates the dynamics of plant phenology. Specifically, heat requirement (HR) and days of precipitation (DOP) during the preseason were the two most influential controls on plant phenology. Our findings highlight the importance of incorporating precipitation as an additional predictor variable in current temperature-based phenology models for application in temperate grassland.
... Major threats identifi ed include: habitat loss and fragmentation (Ricketts 2004 ); habitat isolation (Battacharya et al. 2003 ); agricultural intensifi cation (Kremen et al. 2004 ); agrochemicals (Kearns et al. 1998 ); diseases (Watanabe 1994 ); parasites ; climate change (Price and Waser 1998 ); introduced nonnative plants (Brown et al. 2002 ) and competition with managed pollinators (Paini and Roberts 2005 ). Threats to managed pollinators such as honeybees are documented and in some regions of the world signifi cant losses due to disease and competition with Africanised honeybees have been recorded ). ...
... The timing of phenological events such as fl owering is often related to environmental variables such as temperature. Climate change may also disrupt the synchrony between the fl owering period of plants and the activity season of pollinators (Price and Waser 1998 ;Wall et al. 2003 ). Global warming could disrupt the timing of pollination with serious negative impacts to both plants and pollinators. ...
... Snow cover can affect flowering phenology in alpine and Arctic regions [29,30]. The thickness and duration of snow cover can influence the timing and duration of phenological events [31], and the observed flowering time of early-flowering species is closely associated with the melting date of snow cover [32,33]. However, the snow cover on the QTP may be different from that of the alpine and Arctic regions in Europe and North America because snowfall is quite limited, and the average multiyear mean snow cover days are less than one month on the QTP [34]. ...
... The snow-cover duration (SCD) and snow-cover melt date (SCMD) can influence the timing of flowering phenology in alpine and Arctic regions [31][32][33]. These two snow-cover indices were also used to study the impact of snow cover on the flowering phenology of the QTP. ...
Based on limited controlled experiments, both advanced and delayed shifts in flowering phenology induced by precipitation and snow cover have been reported on the Qinghai–Tibetan Plateau (QTP). To clarify the impact of precipitation and snow cover on flowering phenology, we conducted a comprehensive statistical analysis of the temporal change in flowering phenology and its responses to precipitation and snow cover changes using regression models built on the largest collection of ground phenological observation data on the QTP. We found that first flowering date (FFD) for the early-flowering time series significantly advanced at the rate of −0.371 ± 0.149 days/year (p < 0.001), whereas FFD mid-to-late-flowering time series showed no trend at the rate of 0.158 ± 0.193 days/year (p = 0.108). Cumulative pre-season precipitation regressed with FFD positively for early-flowering time series, with the explained variation ranging from 11.7 to 49.4% over different pre-season periods. The negative impact of precipitation on flowering phenology is unexpected, because an increase in precipitation should not hamper plant growth in the semi-arid and arid environments on the QTP. However, precipitation was found to be inversely correlated with temperature. Thus, it is likely that temperature, and not precipitation, regulated flowering phenology over the study period. No relationship was found between FFD and snow-cover melt date or duration. This result indicated that snow cover may not affect flowering phenology significantly, which may be because plant flowering time was much later than the snow-cover melt date on the QTP. These findings contrast the results of controlled experiments on the QTP, which showed that precipitation regulated flowering phenology, and with other studies that showed that snow-cover melting time determined flowering dates of early-flowering species in high latitude and Arctic zones in Europe and North America, where the low-temperature environment is similar to the QTP. These findings can improve flowering phenology models, assist in the prediction of phenological responses of herbaceous plants to climate change, and forecast changes in the structure and function of the grassland ecosystem on the QTP.
... Snowpack volume is directly correlated with snowmelt date (Ostler et al. 1982;Price and Waser 1998). Shallow snowpacks melt earlier than heavy snowpacks and typically result in an earlier growing season (Price and Waser 1998;Arft et al. 1999;Inouye et al. 2002;Dunne et al. 2003). ...
... Snowpack volume is directly correlated with snowmelt date (Ostler et al. 1982;Price and Waser 1998). Shallow snowpacks melt earlier than heavy snowpacks and typically result in an earlier growing season (Price and Waser 1998;Arft et al. 1999;Inouye et al. 2002;Dunne et al. 2003). Plant phenologies are closely related to snowmelt timing and early season temperature regimes in montane systems (Billings and Bliss 1959;Fareed and Caldwell 1975;Galen and Stanton 1991;Kudo 1992;Walker et al. 1995;Inouye et al. 2002;Totland and Alatalo 2002;Dunne et al. 2003). ...
Regional models of global climate change for the northern Rocky Mountains predict warmer temperatures, and some of the main implications of these changes at a local level involve decreased snowpack, earlier snowmelt, and decreased soil moisture during the growing season. In order to mimic the anticipated effects of climate change, and test the responses from a soil microclimate and plant physiology perspective, open-sided warming chambers and snow removal treatments were applied to 2.44 X 2.44 m plots in a sagebrush steppe meadow within Grand Teton National Park, WY. Four treatments included: (1) control, (2) reduced snowpack, (3) increased temperature, and (4) reduced snowpack with increased temperature. Snow was removed using shovels in early May, and chambers were placed at the same time. The chambers were left on the plots through mid-October. Soil moisture and temperature were measured and recorded at 5 cm, and 25 cm depths using dataloggers set up at the time of snow removal and chamber placement. In addition, surface temperature was measured under each plot and within the study area. Plant physiological data on four plant species, including leaf temperature at dawn and mid-afternoon and water potential, were collected for all of the plots in July. Data are being analyzed to determine whether differences existed between the plots for soil moisture, soil and air temperature, and the plant physiological traits measured.
... In parallel with aboveground productivity, also fine root productivity was expected to increase with warming in cold grasslands, where roots could benefit from longer growing seasons (Price & Waser, 1998) and higher N mineralization rates induced by warming. By contrast, decadal soil warming at our study site decreased fine root production. ...
Below and aboveground vegetation dynamics are crucial in understanding how climate warming may affect terrestrial ecosystem carbon cycling. In contrast to aboveground biomass, the response of belowground biomass to long‐term warming has been poorly studied.
Here, we characterized the impacts of decadal geothermal warming at two levels (on average +3.3°C and +7.9°C) on below and aboveground plant biomass stocks and production in a subarctic grassland.
Soil warming did not change standing root biomass and even decreased fine root production and reduced aboveground biomass and production. Decadal soil warming also did not significantly alter the root–shoot ratio. The linear stepwise regression model suggested that following 10 yr of soil warming, temperature was no longer the direct driver of these responses, but losses of soil N were. Soil N losses, due to warming‐induced decreases in organic matter and water retention capacity, were identified as key driver of the decreased above and belowground production. The reduction in fine root production was accompanied by thinner roots with increased specific root area.
These results indicate that after a decade of soil warming, plant productivity in the studied subarctic grassland was affected by soil warming mainly by the reduction in soil N.
... Early-season species had the biggest acceleration in the studies of Menzel [100], Fitter and Fitter [101], and Sparks and Menzel [102]. These findings were further confirmed in experimental research that showed an acceleration of both flowering and growth [103][104][105], which also found that that early-spring flowering species are affected the most. During 2022, the deviation of phenophases and other flowering events occurred, as well as repeated flowering and fruiting during autumn and early winter 2022/23. ...
The study focuses on describing key events in the flowering phenophases of woody taxa that promote practical landscape sustainability and design planning. Apart from the beginning of flowering, the full development and the duration of phenophases are important for landscape architecture, consumers, and pollination. The phenological patterns of 13 woody taxa were monitored for 16 years through 90,860 phenological observations from the BBCH scale for the period 2007–2022. Growing degree days were determined by combining phenological and climatic data and a linear trend was used to assess phenophase tendencies. Mann–Kendall and Sen’s slope tests and Spearman’s correlation coefficient were used to assess statistical significance. Shifts in flowering indicated warming trends, reflecting various changes in phenology. Early flowering taxa were affected the most, but plants shifted phenophases in both directions (earlier and later in the year). Repeated flowering (and occasionally fruiting) and even third flowering, as seen in 2022, can significantly affect biodiversity and lead to plant–pollinator asynchrony and changes in ecosystem functioning, ecological interaction, and landscape design. A list of native and introduced taxa and their adaptation mechanisms to climate change are provided and can be used for sustainable landscape design and nature-based solutions in landscape architecture.
... Vegetation phenology varies with species and is influenced by environmental factors, such as air temperature, precipitation, soil temperature, soil moisture, and photoperiod (Fu et al., 2019;Meng et al., 2021), which depend on location and time (de Beurs and Henebry, 2008). Experimental studies (Henry and Molau, 1997;Price and Waser, 1998;Menzel and Fabian, 1999;Botta et al., 2000;Fu et al., 2015;Malyshev, 2020) have shown that air temperature is the main driver of phenological changes in northern temperate and highlatitude regions. In addition, precipitation has an impact on the spring phenology of grasslands (Shen et al., 2018;Castillioni et al., 2022). ...
Vegetation phenological models play a major role in terrestrial ecosystem modeling. However, substantial uncertainties still occur in phenology models because the mechanisms underlying spring phenological events are unclear. Taking into account the asymmetric effects of daytime and nighttime temperature on spring phenology, we analyzed the performance of 17 spring phenological models by combining the effects of photoperiod and precipitation. The global inventory modeling and mapping study third-generation normalized difference vegetation index data (1982–2014) were used to extract the start of the growing season (SOS) in the North–South Transect of Northeast Asia. The satellite-derived SOS of deciduous needleleaf forest (DNF), mixed forest (MF), open shrublands (OSL), and woody savannas (WS) showed high correlation coefficients (r) with the model-predicted SOS, with most exceeding 0.7. For all vegetation types studied, the models that considered the effect of photoperiod and precipitation did not significantly improve the model performance. For temperature-based models, the model using the growing-degree-day temperature response had a lower root mean square error compared with the models using the sigmoid temperature response Importantly, we found that daily maximum temperature was most suitable for the spring phenology prediction of DNF, OSL, and WS; daily mean temperature for MF; and daily minimum temperature for grasslands. These findings indicate that future spring phenological models should consider the asymmetric effect between daytime and nighttime temperature across different vegetation types.
... Notably, plant-pollinators interactions may operate as a habitat filter shaping the phenological composition of the community (e.g. the absence of a particular pollinator prevents the establishment of a plant species in a community; Sargent and Ackerly 2008). Flowering time is particularly sensitive to environmental factors such as temperature, moisture, and photoperiod (Rathcke and Lacey 1985;Price and Waser 1998;Sherry et al. 2007;Bisigato et al. 2013). Phenology has thereby received increased attention over the last decades since it has been considered as the most sensitive and easily observable indicator of terrestrial ecosystem response to current climate change (i.e. ...
Background and aims - Plant phenology, defined as the timing of recurring life events like leaf flushing, flowering, or fruiting, is highly sensitive to environmental factors such as photoperiod, temperature, and moisture. Phenological synchrony between interacting species-such as plants and their pollinators-is of major importance to the structure and functioning of ecosystems. Plant phenology might also be affected by changes in edaphic conditions. However, whether former agricultural activities may shift phenological patterns of plant communities remains poorly understood. In this study, we evaluated the impact of past agricultural practices on herbaceous plant community phenology in the protected Mediterranean xeric grassland of La Crau (France).
Material and methods-We compared (1) species composition, and (2) phenological patterns of annuals, perennials, Bromus rubens (annual), and Lobularia maritima (perennial), in formerly-cultivated plots-abandoned for 30 years-and intact native grassland plots (steppe), both subjected to itinerant sheep grazing.
Key results and conclusion - Our results suggest that former agricultural activities can affect species composition of Mediterranean xeric grassland communities with differences visible after 30 years of abandonment, but only altered phenological patterns slightly. We suggest that climatic factors and sheep grazing acted as strong habitat filters constraining community assembly at the phenological level.
... We found no strong evidence that light quality affects the emergence and leaf out of the herbaceous species in our study. Possibly because they are submerged below ground during winter and respond to timing of snowmelt and increases in soil temperature, rather than light quality (Price & Waser, 1998;Rice et al., 2018). However, we monitored herbaceous species less often and on a less detailed scale than A. platanoides, meaning that subtle differences in their phenology could be overlooked in the present study. ...
Forest understorey plants receive most sunlight in springtime before canopy closure, and in autumn following leaf‐fall. We hypothesized that plant species must adjust their phenological and photoprotective strategies in response to large changes in the spectral composition of the sunlight they receive. Here, we identified how plant species growing in northern deciduous and evergreen forest understoreys differ in their response to blue light and ultraviolet (UV) radiation according to their functional strategy. We installed filters in a forest understorey in southern Finland, to create the following treatments attenuating: UV radiation < 350 nm, all UV radiation (< 400 nm), all blue light and UV radiation (< 500 nm), and a transparent control. In eight species, representing different functional strategies, we assessed leaf optical properties, phenology, and epidermal flavonoid contents over two years. Blue light accelerated leaf senescence in all species measured in the understorey, apart from Quercus robur seedlings, whereas UV radiation only accelerated leaf senescence in Acer platanoides seedlings. More light‐demanding species accumulated flavonols in response to seasonal changes in light quality compared to shade‐tolerant and wintergreen species and were particularly responsive to blue light. Reduction of blue and UV radiation under shade reveals an important role for microclimatic effects on autumn phenology and leaf photoprotection. An extension of canopy cover under climate change, and its associated suppression of understorey blue light and UV radiation, may delay leaf senescence for understorey species with an autumn niche. This article is protected by copyright. All rights reserved.
... As I. aggregata generally forms buds after spring frost and does not start blooming until weeks after snowmelt, frost events have little impact on its reproduction. Impacts on phenology are generally smaller for summer blooming species like I. aggregata than for earlier blooming ones (CaraDonna et al., 2014) and were not observed for I. aggregata in one study using experimental warming (Price and Waser 1998). We consider it likely that effects of snowmelt timing are mediated mostly through drought stress. ...
Climate change can impact plant fitness and population persistence directly through changing abiotic conditions and indirectly through its effects on species interactions. Pollination and seed predation are important biotic interactions that can impact plant fitness, but their impact on population growth rates relative to the role of direct climatic effects is unknown.
We combined 13 years of experiments on pollen limitation of seed set and pre‐dispersal seed predation in Ipomopsis aggregata , a subalpine wildflower, with a long‐term demographic study that has documented declining population growth with earlier spring snowmelt date. We determined how pollen limitation and seed predation changed with snowmelt date over 21 years and incorporated those effects into an integral projection model to assess relative impacts of biotic factors on population growth.
Both pollen limitation and the difference in stigma pollen load between pollen‐supplemented and control plants declined over years. Neither pollen limitation nor seed predation changed detectably with snowmelt date, suggesting an absence of indirect effects of that specific abiotic factor on these indices of biotic interactions. The projected biotic impacts of pollen limitation and seed predation on population growth rate were small compared to factors associated with snowmelt date. Providing full pollination would delay the projected date when earlier snowmelt will cause populations to fall below replacement by only 14 years.
Synthesis . Full pollination and elimination of seed predation would not compensate for the strong detrimental effects of early snowmelt on population growth rate, which in I. aggregata appears driven largely by abiotic environmental factors. The reduction over two decades in pollen limitation also suggests that natural selection on floral traits may weaken with continued climate change. These results highlight the value of studying both abiotic factors and biotic interactions to understand how climate change will influence plant populations.
... Plant species may respond differently to warming and soil water supply, depending on their morphological, physiological, and lifecycle characteristics [51][52][53]. In arid and semi-arid ecosystems, warming causes water stress in shallow soils, which reduces shallowroot plant growth and development, allowing plants to make more efficient use of topsoil water [54]. ...
Temperature and precipitation are considered to be the most important indicators affecting the green-up date. Sensitivity of the green-up date to temperature and precipitation is considered to be one of the key indicators to characterize the response of terrestrial ecosystems to climate change. We selected the main grassland types for analysis, including temperate steppe, temperate meadow steppe, upland meadow, and lowland meadow. This study investigates the variation in key meteorological indicators (daily maximum temperature (Tmax), daily minimum temperature (Tmin), and precipitation) between 2001 and 2018. We then examined the partial correlation and sensitivity of green-up date (GUD) to Tmax, Tmin, and precipitation. Our analysis indicated that the average GUD across the whole area was DOY 113. The mean GUD trend was −3.1 days/decade and the 25% region advanced significantly. Tmax and Tmin mainly showed a decreasing trend in winter (p > 0.05). In spring, Tmax mainly showed an increasing trend (p > 0.05) and Tmin a decreasing trend (p > 0.05). Precipitation showed no significant (p > 0.05) change trend and the trend range was ±10 mm/decade. For temperate steppe, the increase in Tmin in March promotes green-up (27.3%, the proportion of significant pixels), with a sensitivity of −0.17 days/°C. In addition, precipitation in April also promotes green-up (21.7%), with a sensitivity of −0.32 days/mm. The GUDs of temperate meadow steppe (73.9%), lowland meadow (65.9%), and upland meadow (22.1%) were mainly affected by Tmin in March, with sensitivities of −0.15 days/°C, −0.13 days/°C, and −0.14 days/°C, respectively. The results of this study reveal the response of vegetation to climate warming and contribute to improving the prediction of ecological changes as temperatures increase in the future.
... Phenological shifts are common responses to climate change for both plants and insects. In plants, warming often advances emergence and flowering dates (Price & Waser, 1998;Wolkovich et al., 2012). However, not all plant species advance their phenology with warming; the phenological response to warming appears to largely depend on plant life history. ...
Throughout the last century, climate change has altered the geographic distributions of many species. Insects, in particular, vary in their ability to track changing climates, and it is likely that phenology is an important determinant of how well insects can either expand or shift their geographic distributions in response to climate change. Grasshoppers are an ideal group to test the hypothesis that phenology correlates with range expansion, given that co-occurring confamilial, and even congeneric, species can differ in phenology. Here, I tested the hypothesis that early- and late-season species should possess different range expansion potentials, as estimated by habitat suitability from ecological niche models. I used nine different modeling techniques to estimate habitat suitability of six grasshopper species of varying phenology under two climate scenarios for the year 2050. My results suggest that, of the six species examined here, early-season species were more sensitive to climate change than late-season species. The three early-season species examined here might shift northward during the spring, while the modeled geographic distributions of the three late-season species were generally constant under climate change, likely because they were pre-adapted to hot and dry conditions. Phenology might therefore be a good predictor of how insect distributions might change in the future, but this hypothesis remains to be tested at a broader scale.
... Most experiments report earlier flowering under warmer temperatures, often associated with increased reproduction (Alatalo & Totland 1997, Cleland et al. 2012, Price & Waser 1998, Stenström & Jonsdottir 1997, Wookey et al. 1993. However, it is unclear whether changes in reproduction reflect shifts in flowering phenology per se or a direct effect of altered climate. ...
When a phenological shift affects a demographic vital rate such as survival or reproduction, the altered vital rate may or may not have population-level consequences. We review the evidence that climate change affects populations by shifting species’ phenologies, emphasizing the importance of demographic life-history theory. We find many examples of phenological shifts having both positive and negative consequences for vital rates. Yet, few studies link phenological shifts to changes in vital rates known to drive population dynamics, especially in plants. When this link is made, results are largely consistent with life-history theory: Phenological shifts have population-level consequences when they affect survival in longer-lived organisms and reproduction in shorter-lived organisms. However, there are just as many cases in which demographic mechanisms buffer population growth from phenologically induced changes in vital rates. We provide recommendations for future research aiming to understand the complex relationships among climate, phenology, and demography, which will help to elucidate the extent to which phenological shifts actually alter population persistence.
Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 52 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... Studies of changes in temporal community composition comprise a large and growing body of research, as such changes can affect resource availability, agriculture, trophic interactions, diversity of associated communities, and ecosystem services [12][13][14][15][16][17]. Phenological studies have traditionally focused on scales of individual organisms and plots, using field observations and experiments [18,19]. More recently, large-scale digitization of natural history collections [20], citizen science programs [21], and the advent of remotely sensed land surface phenology measurements via satellite [22] have facilitated research at more extensive taxonomic, spatial, and temporal scales, some of which integrates multiple methods [23][24][25]. ...
Phenology, or the timing of life history events, can be heterogeneous across biological communities and landscapes and can vary across a wide variety of spatiotemporal scales. Here, we synthesize information from landscape phenology studies across different scales of measurement around a set of core concepts. We highlight why phenology is scale dependent and identify gaps in the spatiotemporal scales of phenological observations and inferences. We discuss the consequences of these gaps and describe opportunities to address the inherent sensitivities of phenological metrics to measurement scale. Although most studies we review and discuss are focused on plants, our work provides a broadly relevant overview of the role of observation scale in landscape phenology and a general approach for measuring and reporting scale dependence.
... The relatively few studies on climate change impacts on fruit production in alpine areas reported contrasting results. For example, a 4-year study on 10 species in a subalpine meadow found that, while fruit production tended to be greater in warmed plots for most species, there was no significant effect for any species (Price and Waser, 1998). Another study found that warming had a negative effect on fruit production by Silene acaulis (Alatalo and Little, 2014). ...
Premise:
Climate change is having major impacts on alpine and arctic regions, and inter-annual variations in temperature are likely to increase. How increased climate variability will impact plant reproduction is unclear.
Methods:
In a 4-year study on fruit production by an alpine plant community in northern Sweden, we applied three warming regimes: (1) a static level of warming with open-top chambers (OTC), (2) press warming, a yearly stepwise increase in warming, and (3) pulse warming, a single-year pulse event of higher warming. We analyzed the relationship between fruit production and monthly temperatures during the budding period, fruiting period, and whole fruit production period and the effect of winter and summer precipitation on fruit production.
Results:
Year and treatment had a significant effect on total fruit production by evergreen shrubs, Cassiope tetragona, and Dryas octopetala, with large variations between treatments and years. Year, but not treatment, had a significant effect on deciduous shrubs and graminoids, both of which increased fruit production over the 4 years, while forbs were negatively affected by the press warming, but not by year. Fruit production was influenced by ambient temperature during the previous-year budding period, current-year fruiting period, and whole fruit production period. Minimum and average temperatures were more important than maximum temperature. In general, fruit production was negatively correlated with increased precipitation.
Conclusions:
These results indicate that predicted increased climate variability and increased precipitation due to climate change may affect plant reproductive output and long-term community dynamics in alpine meadow communities.
... Intraspecific variation in flowering time may affect the pollination success of local populations, reflecting seasonal changes in pollinator activity and availability (Price and Waser 1998;Kameyama and Kudo 2009;Thomson 2010;Kudo et al. 2011). Advances in flowering time due to global warming may disturb plant-pollinator interactions if seasonal activity of pollinators does not follow the phenological shift of plants, i.e., phenological mismatch (Memmott et al. 2007;Forrest 2015;Rafferty et al. 2015). ...
Global warming tends to accelerate flowering phenology of alpine plants, and it may cause a decrease in fruit production due to lower pollinator activity and/or higher risk of frost damage earlier in the season. Because flowering period of alpine plants varies highly depending on snowmelt conditions, the effects of phenological variation on fruit-set success may vary among local populations. I observed the relationship between flowering time and fruit-set success in four populations of a bee-pollinated dwarf shrub, Rhododendron aureum, located in fellfield and snowbed habitats in northern Japan, for 12 or 13 years over the 25 years from 1995 to 2019. Flowering of the fellfield populations usually occurred in June, and flowering of the snowbed populations commonly started after mid-July, although there was considerable yearly variation in actual flowering time within individual populations. Generally, the fruit-set rates of the fellfield populations were low, with large yearly fluctuations, whereas those of the snowbed populations were stable and high. There was a clear trend toward a decrease in fruit-set rates with earlier flowering in the fellfield populations due to pollen limitation and occasional frost damage. The risk of frost damage increased with earlier flowering in the fellfield habitat. These results indicate that the effects of climate change on fruit-set success of alpine plants are strongly site-specific and are greatest early in the growing season.
... In addition to its inland location, Seoul, where Hongneung Arboretum is situated, has higher average spring temperatures than other regions due to its large urban population, various facilities, and the resultant release of artificial heat [37]. Since the greenhouse effect is aggravated by the heat island effect, the FFD of the plants growing in Hongneung Arboretum may have occurred much earlier than the same species growing in other regions [38]. ...
... However, few studies have focused on the effects of the onset of phenology and variation in different phenophases on the carbon cycle. First, phenological duration is determined by the balance between changes in the onset and offset of a given phenophase, and some studies show that the onset of specific phenophases has a greater temperature response than phenological duration (Price and Waser 1998, Post et al. 2008, Haggerty and Galloway 2011, CaraDonna et al. 2014, Wang et al. 2014. Therefore, phenological onset may be a better indicator of the carbon cycle than its duration due to possible uniform advance in phenological onset and non-uniform variation in phenological offset in response to warming. ...
Phenology has a great effect on the carbon cycle. Significant relationships have been well demonstrated between phenology and photosynthesis. However, few studies have been undertaken to characterize relationships between phenology and ecosystem respiration (Re). We conducted a reciprocal transplant experiment among three elevations for two-years to measure Re over six phenological sequences throughout the growing seasons. Our results showed that changes in phenological duration were mainly determined by the onset of phenology, as one day advance of phenological onset could lengthen 0.13 days of phenological duration. Advances in early spring phenophases (i.e., first leaf-out, first bud/boot-set and first flowering) under warming strengthened the temperature sensitivity of Re. However, the late phenophases (i.e., first seeding-set, first post-fruiting vegetation and first leaf-coloring) had non-significant relationships with Re. In total, after pooling all the data, one day advance of phenophases would increase Re by 2.23% under warming. In particular, Re would increase by 29.12% with an advance of phenophases by 8.46 days of under a 1.5 °C warming scenario. Our analysis of the coupling between temperature/moisture–phenology–Re may further supplement evidence that warmer spring temperature increases carbon emission by advancing early phenophases. This points to a faster and easier way to investigate how aboveground functional traits (phenology) affect unseen functional traits (Re) on the Tibetan Plateau.
... The phenological delay induced by snowmelt reported here is consistent with findings from alpine plant phenology studies elsewhere (e.g., Anderson et al. 2012;Price and Waser 1998;Walker et al. 1995) and can be attributed to the need for plants to accumulate a minimum threshold GDD before initiating new spring growth. The later a site melted, though, the shorter the time between melt date and all respective phenophase peaks (lag time). ...
In northeastern North America, alpine snowbank (snowbed) communities are rare, highly diverse plant assemblages. They form in sheltered sites above treeline where late-lying snow provides insulation from late-season frosts and a longer-lasting source of water. We studied the effects of snowmelt timing and cumulative temperature on the vegetative and flowering phenology of seven common, alpine snowbank species on Mt. Washington, New Hampshire. We observed snowmelt date and plant phenology at 14 alpine snowbank sites over one growing season and collected temperature data using automated dataloggers. We used Pearson correlations to analyze the relationships between snowmelt timing and temperature (i.e., growing degree days) and plant phenology. Snowmelt date was positively correlated with the dates of peak phenophases, and lag time (time between snowmelt and peak phenophase) was negatively correlated with snowmelt date. Snowmelt timing consistently delayed the onset of phenological stages, but later snowmelt had a less-pronounced delay. Plants at later-melting sites experienced higher mean daily temperatures and accumulated growing degree days more quickly, leading to a shorter phenological cycle. Continued monitoring of snowmelt timing, temperature, and the phenology of alpine snowbank plants may provide clues to how climate change will affect alpine areas of northeastern North America, especially in terms of diversity, pollination, and abiotic interactions.
... Realizar monitoreo o colectas sistemáticas de especies que se encuentren dentro de áreas naturales protegidas, en especial en comunidades sensibles a los cambios en el clima (como es el caso del páramo de altura) es de suma importancia para entender como el cambio climático está afectando a los ecosistemas y a las plantas distribuidas en el país, ya que como mencionan algunos autores (Price y Waser, 1998;Saavedra et al., 2003;Forrest et al., 2010) los cambios en los patrones de floración y fructificación ocasionados por el cambio climático afectan el éxito reproductivo de las especies, dado que el desfase o la coocurrencia de estas fenofases seguramente afecta las interacciones ecológicas con polinizadores y dispersores. En este contexto, la utilidad real de los ejemplares de herbario esta en proporcionar un punto de referencia histórico el cual sirva de complemento para el contraste de nuevos registros de colecta (Gallagher et al., 2009). ...
... Autumn phenology has been less studied. There is evidence that late season flowering is less sensitive to warming (18,19) and senescence is often delayed by warming (13,15), but not always (7,20). Although we have learned much, there remains considerable uncertainty. ...
Changes in plant phenology associated with climate change have been observed globally. What is poorly known is whether and how phenological responses to climate warming will differ from year to year, season to season, habitat to habitat, or species to species. Here, we present 5 y of phenological responses to experimental warming for 10 subboreal tree species. Research took place in the open-air B4WarmED experiment in Minnesota. The design is a two habitat (understory and open) × three warming treatments (ambient, +1.7 °C, +3.4 °C) factorial at two sites. Phenology was measured twice weekly during the growing seasons of 2009 through 2013. We found significant interannual variation in the effect of warming and differences among species in response to warming that relate to geographic origin and plant functional group. Moreover, responses to experimental temperature variation were similar to responses to natural temperature variation. Warming advanced the date of budburst more in early compared to late springs, suggesting that to simulate interannual variability in climate sensitivity of phenology, models should employ process-based or continuous development approaches. Differences among species in timing of budburst were also greater in early compared to late springs. Our results suggest that climate change—which will make most springs relatively “early”—could lead to a future with more variable phenology among years and among species, with consequences including greater risk of inappropriately early leafing and altered interactions among species.
... have advanced the phenology of sub-shrubs that tended to flower later (Price & Waser, 1998;Xia & Wan, 2012), leading to greater overlap in the growth of sequentially early-flowering perennial forbs, increasing the synchrony between subshrubs and perennial forbs and causing competitive exclusion. Moreover, increased soil temperatures may also negatively affect sub-shrubs growth by enhancing the consumption of carbohydrates in the leaves (Smith, Li, & Dukes, 2019;Zhou, Xu, Hou, Zheng, Chi, & 2018). ...
While most studies account for the effect of total annual precipitation on aboveground net primary productivity (ANPP), few studies have demonstrated how decreased precipitation within specific periods of growing season affect ANPP. Using a precipitation manipulation experiment, we assessed the response patterns and underlying mechanisms of ANPP to decreased precipitation in the early (DEP) and late (DLP) growing seasons on a temperate steppe in northern China. The results showed that both DEP and DLP decreased ANPP by averages of 28.3 and 39.4 g m−2, respectively. The decline of ANPP in DEP was primarily attributed to a 20.7 g m−2 decrease in grass and 4.9 g m−2 decrease in sub‐shrubs, whereas the decrease in ANPP in DLP was due to a 36.6 g m−2 decrease in perennial forbs and an 8.7 g m−2 decrease in sub‐shrubs. The reduction in grass ANPP under DEP was likely due to decreased soil moisture and increased specific leaf area of grass during the early growing season, whereas the reduction in perennial forbs ANPP under DLP was mainly caused by decreased soil moisture during late growing season. The decline of sub‐shrubs ANPP under DEP and DLP could be explained by shallow root length of sub‐shrubs in DEP and by high soil temperature in DLP. Our findings demonstrated how droughts timing affects ANPP at both community and functional group levels. Different responses of functional groups to drought timing indicate that future studies should not neglect the role of precipitation timing in regulating ecosystem productivity. This article is protected by copyright. All rights reserved.
... Realizar monitoreo o colectas sistemáticas de especies que se encuentren dentro de áreas naturales protegidas, en especial en comunidades sensibles a los cambios en el clima (como es el caso del páramo de altura) es de suma importancia para entender como el cambio climático está afectando a los ecosistemas y a las plantas distribuidas en el país, ya que como mencionan algunos autores (Price y Waser, 1998;Saavedra et al., 2003;Forrest et al., 2010) los cambios en los patrones de floración y fructificación ocasionados por el cambio climático afectan el éxito reproductivo de las especies, dado que el desfase o la coocurrencia de estas fenofases seguramente afecta las interacciones ecológicas con polinizadores y dispersores. En este contexto, la utilidad real de los ejemplares de herbario esta en proporcionar un punto de referencia histórico el cual sirva de complemento para el contraste de nuevos registros de colecta (Gallagher et al., 2009). ...
El presente trabajo surgió como respuesta a la inquietud de los ejidatarios por conocer la salud de los bosques, que han estado manejando por un largo tiempo y se realizó con la finalidad de evaluar el grado de infección por muérdago en el Ejido Tonalaco, en el estado de Veracruz. Se realizó un muestreo sistemático en el que se midieron 75 parcelas circulares de 100 m2. Se utilizó la metodología propuesta por Hawksworth para conocer el nivel de infección para copa y se realizó una modificación para medir la infección del tallo de los árboles. Se encontraron 447 árboles de los cuales 373 estaban sanos y 75 presentaron infección, la categoría leve presentó 51 árboles y 23 la categoría moderado. Se muestrearon 75 parcelas de las cuales 12 presentaron infección (3 moderado y 9 leve), la zona de estudio tiene un 3% de infección moderada y un 12% de infección leve, con un 85% de área sin infección. Se realizaron análisis estadísticos para conocer la relación de las variables pendiente, diámetro, exposición de la pendiente, altitud y especies de hospederos. Los análisis de Chi-cuadrada de las variables grado de infección y pendiente fue (P=0.69), para el grado de infección y diámetro se encontró (P=0.009), para la altitud y grado de infestación resultó (P=0.76), para el grado de infección y exposición de la pendiente se encontró (P= 0.31), para el grado de infección y especie de pino se obtuvo (P=0.46), solo la variable diámetros influye de manera significativa sobre el grado de infección. Se puede concluir que los bosques del ejido Tonalaco se encuentran saludables y su infección es leve, esto como resultado del manejo forestal comunal orientado a la selección y corta de árboles infectados.
... In general, the onset of flowering appears to be correlated with the mean temperature in the month of flowering or the months prior to flowering [28], [29]. Also, other potential cues for flowering initiation include photoperiodicity, precipitation, soil humidity and snow melt [30], [31] as well as a particular combination of cues [32]. ...
Changes in temperature, disturbances on rainfall pattern, time of growth, flowering and maturation of plants, or any other environmental variation over the entire season can have serious impact on plants associated biodiversity, which in turn may alter the abundance, diversity and foraging behavior of pollinators. For any successful pollination interactions, there is a need of occurrence of synchronous biological events such as insect emergence, their foraging behavior and date of onset of flowering. In this paper, efforts have been made to review the effects of climate change on the phenology of plants and activities of insect pollinators by compiling the available information from research papers, articles, reports and literature in chronological order.
... Day 65 = March 6 and 230 = August 18. S1-unopened buds; S2-open flowers; S3-old flowers defined as postanthesis; S4-petals gone and initial fruit; S5-expanded fruit; and S6-dehisced fruit (after Price & Waser, 1998). Stages 3 and 5 were not recorded for Scorzoneroides autumnalis in the 7-day flood treatment because they occurred between sampling dates. ...
Global climate change models forecast an increasing frequency and duration of extreme flood events, including during the growing season. In this mesocosm experiment, the survival, growth and flowering of two hydric and two mesic wetland plant species were monitored under two extreme flood regimes, namely repeated 2‐ and 7‐day floods, and compared to unflooded conditions. Plant survival was not significantly affected by flooding but species showed different growth and flowering responses to the flood regimes. The hydric species Cardamine pratensis showed contrasting responses to floods with significantly more flowering stems and longer leaves in the 2‐day regime, but delayed and poorer flowering in the 7‐day regime. Juncus articulatus, the other hydric species, responded most actively to 7‐day flooding, with significantly longer leaves, taller and more abundant flowering stems, and more flowers than in unflooded conditions. The mesic species Ranunculus acris showed variable growth and phenological responses to flooding while Scorzoneroides autumnalis was most affected by the 7‐day flood regime, producing significantly shorter leaves and flowering stems, and fewer flowers earlier in the season, compared to unflooded conditions. Overall, repeated 7‐day floods had a greater impact on plant performance than 2‐day flood events. All four species showed resilience to extreme flooding, irrespective of whether they were classed as hydric or mesic, but there was differential tolerance between species. This suggests that wetlands should be able to sustain vegetation under flooding extremes induced by climate change but community composition, biodiversity, and wetland services will all be affected.
... Only a few research reported climate change impact on medicinal plants community in the Himalayan region. For instance, warming atmosphere is reported to cause phenological shift and advanced the reproduction timing in ten angiosperms in a subalpine meadow (Price and Waser 1998). Ultraviolet-B radiation was observed to increase secondary metabolite (e.g. ...
Himalaya is endowed with a great diversity of medicinal plants, which have been used
extensively for curing a number of ailments since time immemorial. However, climatic
perturbations in the region have imposed severe threat to their survival, status in wild and
production of bioactive metabolites. Changes in climatic conditions include variation in
diferent abiotic (light, water, temperature) and biotic (weed, pathogen) factors, which are
known to play a key role in plant growth and development. Increased global temperature,
erratic monsoon, recurrent drought/fooding events, increased insect-pest attacks, etc., have
negatively afected the phenology, morpho-physiological and biochemical responses of
plants. However, to date, a collective record on the occurrence of various environmental
stresses in the medicinal plants is not available. Thus, this review provides comprehensive
and updated information on this topic to facilitate thorough understanding of response of
Himalayan plants to diferent stress factors. This will help in adapting potential disease
management strategies, identifying resilient accessions and optimum environmental condi-
tions for plant growth and metabolite production. Further, the review will provide valuable
insight to conservation biologists, plant pathologists, plant breeders and biotechnologists
about current disease and stress trends in Himalayan medicinal plants, so that location spe-
cifc management practices can be adopted and/or standardized.
The snowmelt timing is a major factor controlling plant phenology in alpine regions. Presently, the warming is pushing forward snowmelt timing which may influence species’ seasonal cycle throughout the alpine landscape of Himalaya. Nevertheless, very few studies have studied the response of species’ phenology to advanced snowmelt in the Himalayas. The present study investigated different alpine species’ responses to early snowmelt present in different alpine communities. Five communities were identified and two sites were selected in each community (early snowmelt: ES, late snowmelt: LS) with a 50 × 50 m plot marked permanently for species monitoring. The observations for phenophase initiation and durations of all species were recorded fortnightly. Kruskal–Wallis test was performed to examine species-specific differences in phenophase durations. Pairwise differences were tested with Dunn’s post hoc test. The present study hypothesized early snowmelt advances and lengthens phenophases timing and duration in all alpine species. The results showed that phenophases initiations and duration were earlier and longer in ES sites for the majority of species but no significant relationship was found between snowmelt timing and species’ phenophase duration. Many species showed two distinctive phenophases (reproductive and fruiting). The divergence was higher in the reproductive phenophase than in other phenological stages. Hence, it seems that the early snowmelt is an important driver influencing the early spring phenology of herb species, the species-specific effects of already happening phenological adjustment for higher reproductive success in the current warming of alpine meadows points towards other limiting factors too that remain to be better understood.
Plant species are frequently
reported to undergo leaf-out and flowering in a consistent order from 1 year to the next; however, only a limited number of these findings arise from studies encompassing many species or sites. Here, we evaluate the consistency in the order species leafed out in the northeastern United States using observations contributed to the USA National Phenology Network’s Nature’s Notebook platform. We repeated this analysis for flowering, evaluating a total of 132 species across 84 sites. We documented a relatively high degree of consistency in the order of both events among individual plants, with higher consistency in flowering. A small number of species pairs exhibited very high consistency in phenological order across several sites. The majority of species pairs exhibited variability in how consistently they underwent either leaf-out or flowering from site to site, which could be the result of either plastic or locally adaptive responses. Our investigation revealed that neither functional type nor seasonal position played a major role in shaping how consistently species leafed out or flowered in the same order. Instead, we found the number of days separating the events and interannual variability in timing to be the most influential factors driving the consistency in ordering.
Climate warming has the potential to influence plant flowering phenology which in turn can have broader ecological consequences. Herbarium collections offer a source of historical plant data that makes possible the ability to document and better understand how warming climate can influence long-term shifts in flowering phenology. We examined the influence of annual, winter, and spring temperatures on the flowering phenology of herbarium specimens for 36 species collected from 1884–2015. We then compared the response to warming between native and non-native, woody and herbaceous, dry and fleshy fruit, and spring vs summer blooming species. Across all species, plants flowered 2.26 days earlier per 1 °C increase in annual average temperatures and 2.93 days earlier per 1 °C increase in spring onset average temperatures. Winter temperatures did not significantly influence flowering phenology. The relationship of temperature and flowering phenology was not significantly different between native and non-native species. Woody species flowered earlier than herbaceous species only in response to increasing annual temperatures. There was no difference in the phenological response between species with dry fruits and those fleshy fruits for any of the temperature periods. Spring blooming species exhibited a significantly greater phenological response to warming yearly average temperatures than summer blooming species. Although herbarium specimens can reveal climate change impacts on phenology, it is also evident that the phenological responses to warming vary greatly among species due to differences in functional traits such as those considered here, as well as other factors.
Premise of the study:
Changes to flowering time caused by climate change could impact plant fecundity, but studies that compare the individual-level responses of phenologically distinct, co-occurring species are lacking. We assessed how variation in floral phenology affects the fecundity of individuals from three montane species with different seasonal flowering times, including in snowmelt acceleration treatments to increase variability in phenology.
Methods:
We collected floral phenology and seed set data for individuals of three montane plant species (Mertensia fusiformis, Delphinium nuttallianum, Potentilla pulcherrima). To examine the drivers of seed set, we measured conspecific floral density and conducted pollen limitation experiments to isolate pollination function. We advanced the phenology of plant communities in a controlled large-scale snowmelt acceleration experiment.
Key results:
Differences in individual phenology relative to the rest of the population impacted fecundity in our focal species, but effects were species-specific. For our early-season species, individuals that bloomed later than the population peak bloom had increased fecundity, while for our mid-season species, simply blooming before or after the population peak increased individual fecundity. For our late-season species, blooming earlier than the population peak increased fecundity. The early- and mid-season species were pollen-limited, and conspecific density impacted seed set only for our early-season species.
Conclusions:
Our study shows that variation in individual phenology impacts fecundity in three phenologically distinct montane species, and that pollen limitation may be more influential than conspecific density. Our results suggest that individual-level changes in phenology are important to consider for understanding plant reproductive success. This article is protected by copyright. All rights reserved.
The timing of phenological events is highly sensitive to climate change, and may influence ecosystem structure and function. Although changes in flowering phenology among species under climate change have been reported widely, how species‐specific shifts will affect phenological synchrony and community‐level phenology patterns remains unclear. We conducted a manipulative experiment of warming and precipitation addition and reduction to explore how climate change affected flowering phenology at the species‐ and community‐levels in an alpine meadow on the eastern Tibetan Plateau. We found that warming advanced the first and last flowering times differently and with no consistent shifts in flowering duration among species, resulting in the entire flowering period of species emerging earlier in the growing season. Early‐flowering species were more sensitive to warming than mid‐ and late‐flowering species, thereby reducing flowering synchrony among species and extending the community‐level flowering season. However, precipitation and its interactions with warming had no significant effects on flowering phenology. Our results suggest that temperature regulates flowering phenology from the species to community‐level in this alpine meadow community, yet how species shifted their flowering timing and duration in response to warming varied. This species level divergence may reshape flowering phenology in this alpine plant community. Decreasing flowering synchrony among species and the extension of community‐level flowering seasons under warming may alter future trophic interactions, with cascading consequences to community and ecosystem function.
Flowering time is sensitive to climatic conditions and has been a frequent focus of climate change research, yet the implications of phenological shifts for hybridization within plant communities have seldom been explored. Reproductive overlap between interfertile species is a key requirement for the production of hybrid (inter-species) offspring, and climate change may influence the opportunities for hybrid production through changes to species' flowering time, duration, and overlap with other species. To test how climate variation influences flowering overlap between hybridizing species, we analyzed 45 years of flowering phenology data on 2 common plants in the Rocky Mountains of Colorado that are known to produce hybrids (Potentilla pulcherrima and Potentilla hippiana, family Rosaceae). We estimated flowering overlap from flowering distributions in 2 ways that focus on how similar species are in terms of flowering time (symmetric overlap) or relative floral abundance across the season (relative overlap). We found that the 2 species had similar phenological responses to most climate variables. Both flowered earlier in years with warm, dry growing seasons preceded by earlier snowmelt and winters with less snow, and later in cool, wet growing seasons with later snowmelt after winters with heavy snowfall. Precipitation was the best predictor of flowering time overlap. In wetter years, both species flowered later and longer, and reached peak flowering date at a more similar time in the growing season. While our results suggest that precipitation patterns influence the extent of flowering overlap between these 2 species in any given growing season, precipitation has not consistently increased or decreased in this region over the past 45 years, and therefore we do not see a consistent signature of global climate change on flowering overlap. Finally, we found that even though temperature was an important predictor of flowering phenology within each species, it was not a major driver of overlap between species, emphasizing that data on individual species responses cannot necessarily predict how climate change will affect species interactions.
Climatic models indicated that in this century, both average temperatures and extreme events frequency will increase in the Mediterranean basin. These changes are expected to have a great impact on agriculture in general and on crop phenology in particular. Great progress has been made in understanding the responses of plants to abiotic stress. There are inherent physical, morphological, and molecular limitations to the plant’s ability to respond to stress. Plant responses to abiotic stress are dynamic and complex. Among the various abiotic stresses, low temperature adversely affects germination, normal plant growth, development, and phonological events. Consistent with the increasing temperatures, crop development is expected to be faster; thus, phenological stages will be reached early, and the length of the growth period of crops with determinate cycle (i.e., cereals, grapevine, etc.) will be shorter. These impacts, together with the higher risk to have extreme climate events during sensitive phonological phases, may have strong negative effects on final yield and on yield quality. The actual impact of phonological change needs to be assessed for specific crop environment combinations, providing the basis to formulate feasible adaptation options to climate change. In other terms, the simulated changes in phenology cannot be interpreted without considering the environmental context in which a species lives. For winter crops, the effect of predicted prolonged summer drought periods and heat weaves for the next decades may be smoothed or prevented due to the faster development that will allow escaping these and then avoiding reduction in final yields. In contrast, crops, whose growing cycle takes place in summer time, are likely to experience a severe reduction of final yield as the result of increased frequency of extreme climatic events and a reduced time for biomass accumulation to yield.KeywordsChilling and freezing injurySeed germination and seedling growth under low temperatureRoot development in low temperatureGrowth and development under low temperaturePerinea crops and low temperatureMechanism of low-temperature acclimationLow-temperature and phonological developmentTemperature and flower initiationMolecular and genetic aspect of flowering during climate change
Climate warming and extreme hydrological events are threatening the sustainability of wetlands across the globe. However, whether climate warming will amplify or diminish the impact of extreme flooding on wetland ecosystems is unknown. Here, we show that climate warming significantly reduced wetland resistance and resilience to a severe flooding event via a 6-year warming experiment. We first found that warming rapidly altered plant community structure by increasing the dominance of low-canopy species. Then, we showed that warming reduced the resistance and resilience of vegetation productivity to a 72-cm flooding event. Last, we detected slower postflooding carbon processes, such as gross ecosystem productivity, soil respiration, and soil methane emission, under the warming treatment. Our results demonstrate how severe flooding can destabilize wetland vegetation structure and ecosystem function under climate warming. These findings indicate an enhanced footprint of extreme hydrological events in wetland ecosystems in a warmer climate.
Climate warming and management will likely affect carbon (C) fluxes of montane grassland ecosystems. In this study we assessed the effect of simultaneous warming (+2°C) and decreased precipitation (-25%) on carbon exchange of montane grasslands in S-Germany by translocating large intact plant–soil cores from a high altitude to a low altitude site. Cores received two common grassland management regimes: intensive (4-5 cuts and slurry application) and extensive (1-2 cuts and slurry application). Diurnal patterns of net ecosystem exchange (NEE) and total ecosystem respiration (Reco) were measured over 1.5 years in 2-3 weeks intervals during the snow free period. Additional data on environmental controls, i.e. PAR, grass height and soil moisture and temperature, were used to develop empirical models to estimate daily and annual fluxes of gross primary production (GPP) and Reco. Considering the two years period (2014 and 2015), we found that, under warmer and slightly drier conditions, both GPP and Reco significantly (p<0.01) increased (up to 20%) but with a higher temperature sensitivity of Reco, particularly in intensive managed grassland. The higher temperature sensitivity of Reco reduced the net ecosystem exchange (NEE) by 0.7 t C ha-1 yr-1 for both extensive and intensive management, respectively. Considering additional carbon inputs via slurry and exports via harvest (i.e. annual net ecosystem carbon budget: NECB), our results showed that managed grasslands are already a source of C under current climate conditions (1.7-1.8 t ha-1 yr-1) which significantly (p<0.05) increased under climate warming (2.3-2.9 t ha-1 yr-1).
Alpine ecosystems, characterized by cold climates and short growing seasons, are thought to be most vulnerable to climate change. Warmer temperatures and earlier snowmelt extend the growing season length and increase drought stress for alpine plants, resulting in changes to their distribution. Anemone narcissiflora ssp. sachalinensis is a perennial herb that grows in the alpine snow‐meadows of northern Japan. In the last few decades, its distribution has shifted toward later snowmelt habitat in the Taisetsu Mountains of Hokkaido. We recorded demographic data for this species at early, middle and late snowmelt habitats over four years (2009–2012), and constructed transition matrix models to evaluate how demographic parameters and population growth rate vary between local habitats along a snowmelt gradient. The proportion of reproductive plants was low and seed production was limited in the early snowmelt habitat, with drier soil conditions, in comparison to the middle and late snowmelt habitats, with moist soil conditions. Evidence of the transition from small plants to those in the reproductive stage was limited in the early snowmelt habitat, suggesting that growth was inhibited; the local population in this habitat was estimated to be sustained by seed migration from later snowmelt habitats. These results indicate that advancing snowmelt under climate change may decrease the reproductive activity and population growth rate of snow‐meadow plants if seed migration from later snowmelt populations is limited, resulting in the extinction of local populations. In this paper, we analyzed population dynamics of an alpine herb (Anemone narcissiflora) along a snowmelt gradient using transition matrix models and revealed a maintenance mechanism of local populations. Our results suggest that population dynamics varies within a large population responding to local snowmelt conditions and that global warming may cause local extinction of alpine plants in snow‐meadows.
Thermopsis divaricarpa (Fabaceae) is a common wildflower in the montane zone of the Colorado Rocky Mountains, but its reproductive ecology is still largely unknown. Montane meadows are recognized for their relatively high species richness and important ecosystem services. Thus, knowledge of the reproductive ecology of T. divaricarpa is useful when assessing community-level responses to climate change in the montane zone of the Rockies. We investigated the phenology, breeding system, and pollination of this species in the southern Rocky Mountains of Colorado. Our results suggest that T. divaricarpa flowers from early June to mid-July, exhibits a facultative xenogamous breeding system, and may be pollinated by bumble bees. Pollen grains of T. divaricarpa are singular, ellipsoidal, and tricolpate. Beetles consume floral tissue, but their role as pollinators is questionable.
A frequent response of organisms to climate change is altering the timing of reproduction, and advancement of reproductive timing has been a common reaction to warming temperatures in temperate regions. We tested whether this pattern applied to two common North American turtle species over the past three decades in Nebraska, USA. The timing of nesting (either first date or average date) of the Common Snapping Turtle (Chelydra serpentina) was negatively correlated with mean December maximum temperatures of the preceding year and mean May minimum and maximum temperatures in the nesting year and positively correlated with precipitation in July of the previous year. Increased temperatures during the late winter and spring likely permit earlier emergence from hibernation, increased metabolic rates and feeding opportunities, and accelerated vitellogenesis, ovulation, and egg shelling, all of which could drive earlier nesting. However, for the Painted Turtle (Chrysemys picta), the timing of nesting was positively correlated with mean minimum temperatures in September, October, December of the previous year, February of the nesting year, and April precipitation. These results suggest warmer fall, and winter temperature may impose an increased metabolic cost to painted turtles that impedes fall vitellogenesis, and April rains may slow the completion of vitellogenesis through decreased basking opportunities. For both species, nest deposition was highly correlated with body size, and larger females nested earlier in the season. Although average annual ambient temperatures have increased over the last four decades of our overall fieldwork at our study site, spring temperatures have not yet increased, and hence, nesting phenology has not advanced at our site for Chelydra. While Chrysemys exhibited a weak trend toward later nesting, this response was likely due to increased recruitment of smaller females into the population due to nest protection and predator control (Procyon lotor) in the early 2000s. Should climate change result in an increase in spring temperatures, nesting phenology would presumably respond accordingly, conditional on body size variation within these populations. A frequent response of organisms to climate change is altering the timing of reproduction. Over the past three decades, the timing of nesting of the Common Snapping Turtle (Chelydra serpentina) was negatively correlated with mean December maximum temperatures of the preceding year and mean May minimum and maximum temperatures in the nesting year and positively correlated with precipitation in July of the previous year. For the Painted Turtle (Chrysemys picta), the timing of nesting was positively correlated with mean minimum temperatures in September, October, December of the previous year, February of the nesting year, and April precipitation.
Climate change affects communities both directly and indirectly via changes in interspecific interactions. One such interaction that may be altered under climate change is the ant-plant seed dispersal mutualism common in deciduous forests of the eastern US. As climatic warming alters the abundance and activity levels of ants, the potential exists for shifts in rates of ant-mediated seed removal. We used an experimental temperature manipulation at two sites in the eastern US (Harvard Forest in Massachusetts and Duke Forest in North Carolina) to examine the potential impacts of climatic warming on overall rates of seed dispersal (using Asarum canadense seeds) as well as species-specific rates of seed dispersal at the Duke Forest site. We also examined the relationship between ant critical thermal maxima (CT max ) and the mean seed removal temperature for each ant species. We found that seed removal rates did not change as a result of experimental warming at either study site, nor were there any changes in species-specific rates of seed dispersal. There was, however, a positive relationship between CT max and mean seed removal temperature, whereby species with higher CT max removed more seeds at hotter temperatures. The temperature at which seeds were removed was influenced by experimental warming as well as diurnal and day-to-day fluctuations in temperature. Taken together, our results suggest that while temperature may play a role in regulating seed removal by ants, ant plant seed-dispersal mutualisms may be more robust to climate change than currently assumed.
Climate change affects communities both directly and indirectly via changes in interspecific interactions. One such interaction that may be altered under climate change is the ant-plant seed dispersal mutualism common in deciduous forests of the eastern US. As climatic warming alters the abundance and activity levels of ants, the potential exists for shifts in rates of ant-mediated seed removal. We used an experimental temperature manipulation at two sites in the eastern US (Harvard Forest in Massachusetts and Duke Forest in North Carolina) to examine the potential impacts of climatic warming on overall rates of seed dispersal (using Asarum canadense seeds) as well as species-specific rates of seed dispersal at the Duke Forest site. We also examined the relationship between ant critical thermal maxima (CT max ) and the mean seed removal temperature for each ant species. We found that seed removal rates did not change as a result of experimental warming at either study site, nor were there any changes in species-specific rates of seed dispersal. There was, however, a positive relationship between CT max and mean seed removal temperature, whereby species with higher CT max removed more seeds at hotter temperatures. The temperature at which seeds were removed was influenced by experimental warming as well as diurnal and day-to-day fluctuations in temperature. Taken together, our results suggest that while temperature may play a role in regulating seed removal by ants, ant plant seed-dispersal mutualisms may be more robust to climate change than currently assumed.
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Many temperate herbs now flower earlier than a few decades ago. Little is known about other phenological events, despite the importance of life history integration for plant fitness. This study addresses the hypothesis that temporal shifts of multiple phenological events in herbs are concordant with temporal changes in weather. Explicitly showing that changes in timing of annual life cycle events are correlated with changes in weather‐predicting variables provides support for the hypothesis that a phenological shift is concordant with climate change. Observations of six phenological events and five phenophases were made year‐round for 25 yrs for herb species in a deciduous forest fragment, Trelease Woods in Illinois, USA. Dates for 43 species were analyzed by linear mixed‐effects models for events and phenophases, and were compared to weather data from a nearby station. For early species, Emergence was delayed by 1.5 d/decade, while End Expansion advanced by 3.8 d/decade and Begin Dormancy advanced by 2.5 d/decade. For late species, End Expansion advanced by 6.7 d/decade, while Begin Senescence delayed by 17.7 d/decade. Begin Flowering and End Flowering advanced similarly for both seasonal groups, at 3.8 to 4.2 d/decade. Some events showed no temporal change. Species differed greatly in the degree or direction of change, related to seasonality of event or length of phase. Overall, for a given species, most events are advancing (68.4%) and most durations are shortening (74.4%). In 12 of 13 cases, inter‐annual variation in event date was predicted by a temperature event‐season combination variable, but in only six cases did both event date shift and weather variable warm through time. This finding supports the hypothesis that climate change is associated in changes in some, but not all, phenological events. This first long‐term, multi‐phase study of a community of temperate herb species indicates little temporal coherence of responses of multiple phases. Changes in date are event‐specific, phase‐specific, and species‐specific. This complexity of responses among species and uneven responses within a species’ integrated annual cycle events has implications for evolutionary responses and more immediate interactions among plant, animal, and microbe species in this community.
Climate change is driving species’ range shifts, which are in turn disrupting species interactions due to species‐specific differences in their abilities to migrate in response to climate. We evaluated the consequences of asynchronous range shifts in an alpine plant‐pollinator community by transplanting replicated alpine meadow turfs downslope along an elevational gradient thereby introducing them to warmer climates and novel plant and pollinator communities. We asked how these novel plant‐pollinator interactions affect plant reproduction. We found that pollinator communities differed substantially across the elevation/temperature gradient, suggesting that these plants will likely interact with different pollinator communities with warming climate. Contrary to the expectation that floral visitation would increase monotonically with warmer temperatures at lower elevations, visitation rate to the transplanted communities peaked under intermediate warming at mid‐elevation sites. In contrast, visitation rate generally increased with temperature for the local, lower‐elevation plant communities surrounding the experimental alpine turfs. For two of three focal plant species in the transplanted high‐elevation community, reproduction declined at warmer sites. For these species, reproduction appears to be dependent upon pollinator identity such that reduced reproduction may be attributable to decreased visitation from key pollinator species, such as bumble bees, at warmer sites. Reproduction in the third focal species appears to be primarily driven by overall pollinator visitation rate, regardless of pollinator identity. Taken together, the results suggest climate warming can indirectly affect plant reproduction via changes in plant‐pollinator interactions. More broadly, the experiment provides a case study for predicting the outcome of novel species interactions formed under changing climates.
This study investigates the effects of surface vegetation density on the East Asian summer monsoon (EASM). The analysis using observation and reanalysis data reveals that the increase of vegetation drives a dipole pattern in the precipitation anomalies where the precipitation in Northeast Asia tends to increase whereas the precipitation in southern China and East China Sea tends to decrease. The model sensitivity experiments confirm the mechanism of regional monsoon circulation changed by changes in surface vegetation density, in which enhanced vegetation leads to an increase of surface evapotranspiration and a decrease of surface temperature over land. The decrease in precipitation over southern China and East China Sea is attributed to the slow‐down of EASM circulation due to the reduction in thermal contrast between the continent and the ocean. The results suggest that the surface vegetation can change the local thermal conditions and induce the dynamical process in broader scale to change the precipitation response. This article is protected by copyright. All rights reserved.
We assessed the role of growing-season length in regulating absolute and relative cover of six coexisting dominant plant species in an alpine snowbed habitat. To help explain disparity in species-specific responses to growing-season length, we examined the developmental phenology and distribution of each species in relation to natural snow depth variation. Season length varies from approximate to 50 d on early-melting edges of the snowbed to 35 d in the late-melting center, 100 m away. By experimentally altering snowpack, we uncoupled the relationship between spatial location and snowmelt schedule in three consecutive years, imposing the same early dates of snow release in a ''long growing-season'' treatment and the same late dates of snow release in a ''short growing-season'' treatment near the edge and center of the snowbed. Over the course of the experiment, growing-season length had significant effects on absolute and relative cover of the species studied (P < 0.025 and P < 0.005, respectively), and these effects were similar near both the edge and center of the snowbed. Yet, only for the snowbed specialist, Sibbaldia procumbens, were changes in absolute and relative cover under early and late snowmelt schedules predictable from the species' distribution along the historical snow depth gradient. S. procumbens increased in cover under a long growing-season and was more common in historically early-melting portions of the snowbed. Other species (e.g., Ranunculus adoneus, Artemisia scopulorum) were equally common in historically early- and late-melting locations within the snowbed, but showed discordant responses to experimentally imposed changes in snowmelt schedule. That the cover of many species under long- vs, short growing seasons was not predictable from their current distributional affinities in relation to snowmelt pattern likely reflects the disparity between the rates of processes exerting long-term control on species' abundances (colonization, soil development) and more immediate effects of growing-season length on plant growth. Consistent with this view, differences in developmental phenology better predicted species-specific responses to snowmelt schedule than distributional affinities. Species having leaf expansion schedules that are poorly synchronized with snowmelt typically had similar cover under early vs. late schedules of snow release (Geum rossii, Trifolium parryi, and Poa alpina). In contrast, species in which leaf expansion schedules are synchronized with snowmelt responded positively to early snow release (Ranunculus adoneus and Sibbaldia procumbens). We hypothesize that maintaining metabolic ''readiness'' under snowcover provides a mechanism for monopolizing nutrient flushes and competitor-free intervals at snowmelt, and exploiting occasional long intervals for growth in years of little snow accumulation, but incurs a respiratory cost that is manifest as reduced growth and vegetative cover when snowmelt is delayed. Our results suggest that interspecific differences in growth phenology of coexisting species will promote shifts in snowbed plant communities with climate change within generations.
We examined the role of growing season length in regulating percentage cover and seed mass of the alpine snow buttercup, Ranunculus adoneus, in a snowbed habitat. Season length varies from @?50 d in early-melting portions of the snowbed to 35 d in late-melting locations. Percentage cover and seed mass of snow buttercups decrease from early- to late-melting locations. Time available for growth was manipulated experimentally by altering the snowmelt schedule. Advancing snowmelt by 14 d in typically late-melting portions of the snowbed led to a threefold increase in percentage cover of snow buttercups (P < .025). However, delaying snowmelt to the same extent in typically early melting locations had little influence on snow buttercups. These results indicate that time available for growth limits cover of snow buttercups in late-emerging vegetation, whereas other factors regulate cover of snow buttercups in early-emerging vegetation. Perturbation of snowmelt scheduled also had significant effects on seed mass (P < .0055). These effects are probably mediated through changes in time available for seed maturation. Snow manipulation treatment accounted for 71% of the variation in seed maturation interval. Maturation interval, in turn, was correlated with seed mass (P < .01). Reducing or increasing the seed maturation interval by 12 d caused a 33% change in seed mass. These findings show strong direct effects of growing season length on plant performance at diverse life history stages.
Using experimental manipulations, we examined pollen and resource limitations to seed production and their interaction in a natural population of a monocarpic plant, Ipomopsis aggregata. Our design crossed two factors, pollen level (hand-pollinated or control) and resource level (water added, water and fertilizer added, or control). Both hand-pollination and fertilizing during the blooming season increased total seed production, while watering alone had no effect on any component of reproductive success. Hand-pollination boosted number of seeds per flower, with no effect on flower number. In contrast, fertilizing had its primary effect on the number of flowers produced, while also increasing the number Of seeds per mature fruit in hand-pollinated plants. Fertilizing increased nectar volume, but path analysis detected no indirect effect of this increased reward rate on seed production, suggesting instead that fertilizing had a slight, but direct, effect on seeds per flower. These results argue against a strict dichotomy between pollen limitation and resource limitation of female reproductive success in plants.
We used overhead infrared radiators to add a constant increment of â15 W/m², over 2 yr, to the downward heat flux on five 30-m² montane meadow plots in Gunnison County, Colorado, USA. Heating advanced snowmelt by â1 wk, increased summer soil temperatures by up to 3°C, and reduced summer soil moisture levels by up to 25% compared to control plots. Soil microclimate response to heating varied with season, time of day, weather conditions, and location along the microclimate and vegetation gradient within each plot, with the largest temperature increase observed in daytime and in the drier, more sparsely vegetated zone of each plot. Day-to-day variation in the daily-averaged temperature response to heating in the drier zone was negatively correlated with that in the wetter zone. Our experimental manipulation provides a novel and effective method for investigating feedback processes linking climate, soil, and vegetation. 36 refs., 5 figs., 8 tabs.
We developed two sets of regression models for flowering and fruiting of arid zone trees and shrubs, based on (i) rainfall in the current and preceding seasons and (ii) soil moisture lagged over varying time periods combined with mean maximum temperature and daylength in the month prior to phenological observations. Using up to 4 years of flowering and fruiting records, we found that both approaches identified responses matching those reported in two other long-term data sets or in the literature, for some species but not for all. The second approach appeared to provide better correlations than the first but we were unable to predict flowering and fruiting effectively. Flowering and fruiting of central Australian trees and shrubs were least in late summer, creating potential limitations on animal populations dependent on them for food. With better predictive capabilities, there is some scope for managing the trees and shrubs for particular purposes. However, very long-term phenological records are needed to improve predictions.
The authors manipulated light, temperature, and nutrients in moist tussock tundra in Alaska to determine how global changes might affect community and ecosystem processes. Some of these manipulations altered nutrient availability, growth-form composition, net primary production, and species richness in less than a decade, indicating arctic vegetation at this site is sensitive to climatic change. In general, short-term (3-yr) responses were poor predictors of longer term (9-yr) changes in community composition. The longer term responses showed closer correspondence to patterns of vegetation distribution along environmental gradients. Nitrogen and phosphorus availability tended to increase with elevated temperature and in response to light attenuation. Nutrient addition increased biomass and production of deciduous shrubs but reduced growth of evergreen shrubs and nonvascular plants. Light attenuation reduced biomass of all growth forms. Elevated temperature enhanced shrub production but reduced production of nonvascular plants. The contrasting responses to temperature increase and to nutrient addition by different growth forms {open_quotes}canceled out{close_quotes} at the ecosystem level, buffering changes in ecosystem characteristics such as biomass, production, and nutrient uptake. The major effect of elevated temperature was to speed plant response to changes in soil resources and, in long term (9 yr), to increase nutrient availability. Species richness was reduced 30-50% by temperature and nutrient treatments. Declines in diversity occurred disproportionately in forbs and in mosses. During our 9-yr study (the warmest decade on record in the region), biomass of one dominant tundra species unexpectedly changed in control plots in the direction predicted by our experiments and by Holocene pollen records. This suggests that regional climatic warming may already be altering the species composition of Alaskan arctic tundra. 73 refs., 9 figs., 4 tabs.
1 The Marsham phenological data have been 'rediscovered' several times. This unique data set, spanning two centuries, consists of first dates of observation, or 'indications of spring', for 27 phenological events which relate to over 20 species of plants and animals. 2 This paper extends the 1926 appraisal of the data from 1736 to 1925 by adding the 22 years up to 1947, when publication of the record ceased. 3 The Marsham data are examined in relation to Manley's central England monthly temperature data and Craddock's annual rainfall data and are further examined for unexplained trends over time. 4 Most of the phenological variables were significantly related to climatic variables or changed through time. 5 An appraisal of the historical response of flora and fauna to climate was made and allowed us to predict changes in species performance due to climate change in the future. If commonly used climate scenarios are accurate we predict that most or all of the indications of spring noted in the Marsham record will occur earlier in the calendar year.
Variations in growth, flowering, and phenology of two forbs, Acomastylis rossii and Bistorta bistortoides, were compared among six years (1983-1988) and five plant communities (fellfield, dry meadow, moist meadow, wet meadow, snowbed) at an alpine site in the Front Range of Colorado. The purpose was to determine the extent to which the phenological patterns of these species varied among plant communities and how interannual climate variability affects phenology and growth. There were significant differences in growth among communities for both species. In B. bistortoides, there were also significant differences among years, due primarily to the influence of a single year (1983) when leaf length increased by â¼10% and the average number of B. bistortoides leaves nearly doubled. Key phenological events of both species (initiation of growth, date of maximum leaf length, leaf number, and flower number) were related to snowmelt patterns, resulting in differences among communities. There were also significant differences among years, again primarily related to the single year 1983, the year of a major El Nino Southern Oscillation (ENSO) event that produced high snowfall amounts at the site. The increased leaf length in a high snow year is counterintuitive to the commonly accepted notion that alpine species may be limited by season length. We hypothesize that changes in phenology related to changes in snowfall or snowmelt will cause detectable changes in growth, but that these will not be predicted simply from phenology alone. Rather, the timing of snowmelt in relation to nutrient availability, soil moisture, and air temperature will be critical in determining how individual species respond. 90 refs., 7 figs., 3 tabs.
We tested whether the flowering times of animal-pollinated plants are influenced by phylogenetic membership and by life form (e.g., annual, perennial, etc.). We analyzed existing data sets on 2298 animal-pollinated angiosperms of North and South Carolina and 1575 animal-pollinated angiosperms of temperate Japan, and also analyzed a null model based upon the Carolina flora. Our analyses of the complete data sets and of subsets including only the largest families showed that: (1) the floras of the Carolinas and temperate Japan have bimodal distributions of flowering times, with peaks in spring and late summer; (2) within each of these floras, families differ very significantly in flowering time; (3) for most families, flowering times in the Carolinas and in Japan are statistically indistinguishable; (4) the sequences of flowering, ordered by family, are also statistically indistinguishable in the two floras; (5) within each flora, skewness of flowering time differs markedly among families; (6) for a typical family, the skewness of flowering time is the same in the two floras; (7) there is a significant negative correlation between skewness and mean family flowering time; and (8) life forms differ in flowering time, though less markedly than families. These results demonstrate that phylogenetic membership and life form strongly influence a species' flowering time. We argue that seasonal limitations of flowering times are caused by phylogenetic constraints, which may not have changed for millions of years. This study does not provide the degree of resolution needed to determine whether or not there is natural selection for alteration of flowering times in these floras, whether by competition or other mechanisms. However, our results do suggest that competition for pollination does not push species' flowering times beyond seasonal boundaries imposed by phylogenetic constraints. The effects of competition on flowering time are probably limited to small and temporary readjustments of the phenological relationships of competitors. Studies of the flowering times of animal-pollinated plants must consider the strong limits to seasonal displacement imposed by phylogeny and life form, and the probable existence of many alternative modes of escape from competition besides seasonal shifts. We consider the implications of recent paleobotanical studies that suggest that temperate plant communities may not have been sufficiently stable through time for plants to have achieved competitive equilibria. Phylogenetic and life history constraints are likely to influence the evolution of many community characters besides flowering time. The methods we have used and the conclusions we have drawn are relevant to a wide variety of ecological characters in plants and animals.
In a single population of Ipomopsis arizonica (Polemoniaceae), there is a continuum of compensatory responses to vertebrate herbivory. From 1985-1987, the most common response to vertebrate herbivory was equal compensation, whereby grazed plants set numbers of fruits and seeds equal to controls within the same growing season, but there were also cases of significant over- and undercompensation. In 1985 and 1987, overcompensation occurred in vertebrate-grazed plants that were supplemented with nutrients and growing free of competition. These plants produced 33% to 120% more fruit than control, ungrazed plants. Cases of undercompensation occurred in groups where I. arizonica grew in association with grasses or where nutrients were not supplemented. Grazed and clipped plants in these groups produced from 28% to 82% as many fruits as did ungrazed controls. The compensatory response of plants to grazing is probabilistic when 3 external factors are considered. The probability of compensation for herbivory decreases as competition with other plants increases, as nutrient levels decrease, and as the timing of herbivory comes later in the growing season. -from Authors
In experimentally heated plots that each span a soil moisture gradient in a Rocky Mountain meadow, aboveground biomass of
Artemisia tridentata (a sagebrush) increased in the drier habitat and that of Pentaphylloides floribunda (a shrub cinquefoil) increased in the wetter habitat relative to control plots. In contrast, aboveground forb biomass decreased
in the wet and dry habitats of the heated plots. These results, combined with evidence for enhanced sagebrush seedling establishment
rates in the heated plots, suggest that the increased warming expected under an atmosphere with a concentration of carbon
dioxide twice that of pre-industrial levels could change the dominant vegetation of a widespread meadow habitat.
Field tests quantifying the behavioral responses of ants to the seeds of twenty Rocky Mountain species were conducted in Gunnison County, Colorado. The results indicate that Claytonia lanceolata Pursh, Corydalis aurea Willd., C. caseana A. Gray., Delphinium nelsoni Greene, and Viola nuttallii Pursh are myrmecochores. The seeds of these species all bear a conspicuous elaiosome and are selectively removed by three species of ants, Formica podzolica Francoeur, Formica canadensis Francoeur, and Myrmica discontinua Weber. These are the first records of ant dispersal from the Rocky Mountains.
1. A data set of 36 years (1954-1989) of observations on first flowering dates (FFD) of 243 species of angiosperms and gymnosperms in one locality in southern central England is presented and analysed. 2. Individual FFDs ranged from 1 January to 17 August, and species varied considerably in the standard deviation of their FFD. The most variable species were mainly annuals and there was a negative relationship between mean FFD and variability, early-flowering species being the most variable. 3. For 219 of the 243 species, it was possible to fit regression equations for FFD to some set of monthly mean temperatures of the preceding months. These fits were generally best for woody plants and geophytes. February temperature was overall the most important determinant of flowering time. Sixty per cent of species flowering between January and April were affected by temperature 1-2 months before flowering; for summer (May onwards) flowering species, temperatures up to 4 months previously were important. 4. High spring temperatures advanced flowering by a mean of 4 days per degree. In contrast, both spring- and summer-flowering species were retarded in flowering by high temperatures in the previous autumn. 5. These relationships were used to simulate the effects of climatic warming: an overall increase of 1-degree-C in each month would advance flowering in some species and retard others, by as much as 6 weeks. Retarded species were early-flowering, advanced species late-flowering. These results suggest a high degree of dependence of flowering time on temperature, and the variation between species implies that responses to climatic warming may be difficult to predict.
The effects of temperature, precipitation and nutrient perturbations, and their interactions, are being assessed on two contrasting arctic ecosystems to simulate impacts of climate change. One, a high arctic polar semi-desert community, is characterised by a sparse, low and aggregated vegetation cover where plant proliferation is by seedlings, whereas the other, a sub-arctic dwarf shrub heath, is characterised by a complete vegetation cover of erect, clonal dwarf shrubs which spread vegetatively. The developmental processes of seed production were shown to be highly sensitive, even within one growing season, to specific environmental perturbations which differed between sites. At the polar semi-desert site, there was a striking effect of the temperature enhancement treatments on phenology and seed-setting of Dryas octopetala ssp. octopetala, with almost no seed-setting occurring in plots experiencing ambient temperatures. By contrast, there were no significant effects of temperature enhancement alone on fruit production of Empetrum hermaphroditum at the sub-Arctic dwarf shrub heath site, although fruit production was significantly influenced by the application of nutrients and/or water. The response of a dominant high arctic dwarf shrub to increased temperature suggests that any climate warming may stimulate seed-set. This could be particularly important in the high Arctic where colonisation can proceed in areas dominated by bare ground and where genetic recombination may be needed to generate tolerance to predicted changes of great magnitude. In the sub-Arctic, however, the closed vegetation is dominated by clonally-proliferating species and recruitment from seedlings is rare. Plant fitness will increase here in response to any increased vegetative growth resulting from higher nutrient availability in warmer organic soils.
Restricted gene flow and localized selection should establish a correlation between physical proximity and genetic similarity in many plant populations. Given this situation, fitness may decline in crosses between nearby plants (inbreeding depression), and in crosses between more widely separated plants ("outbreeding depression") mostly as a result of disruption of local adaptation. It follows that seed set and offspring fitness may be greatest in crosses over an intermediate "optimal outcrossing distance." This prediction was supported for Ipomopsis aggregata, a long-lived herbaceous plant pollinated by hummingbirds. In six replicate pollination experiments, mean seed set per flower was higher with an outcrossing distance of 1-10 m than with selfing or outcrossing over 100 m. A similar pattern appeared in the performance of offspring from experimental crosses grown under natural conditions and censused for a seven-year period. Offspring from 10-m crosses had higher survival, greater chance of flowering, and earlier flowering than those from 1-m or 100-m crosses. As a result, 1-m and 100-m offspring achieved only 47% and 68%, respectively, of the lifetime fitness of 10-m offspring. Offspring fitness also declined with planting distance from the seed parent over a range of 1-30 m, so that adaptation to the maternal environment is a plausible mechanism for outbreeding depression. Censuses in a representative I. aggregata population indicated that the herbaceous vegetation changes over a range of 2-150 m, suggesting that there is spatial variation in selection regimes on a scale commensurate with the observed effects of outbreeding depression and planting distance. We discuss the possibility that differences in seed set might in part reflect maternal mate discrimination and emphasize the desirability of measuring offspring fitness under natural conditions in assessing outcrossing effects.
Growth and phenology of 26 species of three life forms (12 herbaceous understorey species; six shrub species; eight tree species) were monitored in the Harvard Forest, Massachusetts. Phenology of leaf emergence and flower production in saplings was not affected by soil warming. Mature trees and shrubs leafed out slightly earlier and in larger numbers in heated plots. Trees flowered earlier and in higher proportions in the heated plots in 1993 but not in 1992. Mean area per leaf per plant and leaf expansion rates in 1992 were greatest in control saplings of Acer pensylvanicum and Fagus grandifolia. Vaccinium corymbosum, a shrub, showed reduced leaf sizes under soil heating. Soil warming significantly enhanced relative diameter growth of woody individuals, especially shrubs, in 1992, an effect less pronounced in 1993. Species richness was lower in heated plots in both years. Disturbed but unheated control plots exhibited the lowest species richness overall. Changes in relative abundance of herbaceous species from 1992 to 1993 were highly variable, and not significantly affected by treatment. Total density of herbaceous species was highest in heated plots during April and May, reflecting accelerated emergence of Maianthemum canadense and Uvularia sessilifolia. From June through October control plots exhibited the highest stem densities, as numbers of the early emergents declined. Of all life forms, herbaceous species were most sensitive to soil warming. Their early appearance could influence carbon and nutrient acquisition dynamics under changed climatic conditions in deciduous forests. -from Authors
Evidence is presented indicating that the anthomyiid seed predator, Hylemya sp., of Polemonium foliosissimum Gray (Polemoniaceae) preferentially attacks those plants which receive high numbers of pollinator visits. Seed mortality is high in ovaries which set many seeds (i.e., mortality is density-dependent) during the portion of the flowering season when pollinators are limiting resources and plants compete for pollinator service. The actions of both the seed predator and the pollinators of P. foliosissimum are responsible, in part, for the observed flowering phenology of this species.
During the summers of 1960 and 1961 ten primary phenology stations, representing variations in slope, exposure, elevation, snow cover, and vegetation cover, were established in a 300-acre study area, ranging from 10,600 to 11,200 ft elevation in the northern part of Rocky Mountain National Park, Colorado. At each station approximately 75 plants of various species were observed weekly from early June to late September. Measurements of the physical environment were recorded at least twice a week. June and July were characterized by moderate to strong winds and frequent thundershowers. Air temperature maxima were mostly between 50 degrees and 70 degrees F, and night minima were typically between 30 degrees and 50 degrees F. Soil temperatures at 15-cm depth were commonly 40 degrees-50 degrees F. Precipitation from June 10 to September 10 ranged from 3.5 to 8.9. in. in the 2 years. Initiation of new growth for many species at the relatively snow-free stations occurred in May, and as late as early August in snow-accumulation areas. Most species showed definite signs of dormancy by the middle of September. The duration of phenological phases varied considerably, but the following ranges were common: in bud, 2-5 weeks; in flower, 2-3 weeks; in fruit, 4-5 weeks. There was notable stability in phase duration for a given species, even at quite different sites. Snow cover is considered to be the primary factor influencing phenology. Possible correlations of penology with environmental data are suggested, including the relationship of moisture uptake and consequent development to soil temperature.
Sixteen microclimatic stations with differences in slope, exposure, vegetation cover, and seasonal change were established in a heavily dissected 180-acre Indiana tract. Correlations, based on cumulative air temperature duration-summations, were made between microclimatic differences and variation in phenological events. Nine widespread species of spring wildflowers had a collective mean range in dates of first flowering of 7.2 days for all stations. The maximum range for a single species was 11 days. Flowering dates of nine species of a large gorge were retarded an average of 6.0 days in the north-facing slope with respect to the opposing south-facing slope. This 6.0-day difference between gorge slopes 150 ft apart is equal to the expected to occur in about 110 miles of latitude, assuming standard exposures. Six species of the north-facing slope in a small gorge were retarded an average of 2.8 days with respect to the opposing south-facing slope. Flowering on north-facing gorge slopes was retarded more than in gorge bottoms, and upland stations had earlier than normal flowering dates. Mean flowering dates for the entire area were retarded more at cooler locations than warmer slopes were advanced. Air-temperature sums and flowering dates correlated well in a given microclimate. The results suggest that phenological research could be expedited by making observations in diverse microclimates during a few seasons rather than acquiring long-term phenological records.
Although predispersal seed predation by insects is common, no test exists of its effect on plant recruitment. This study examines seed predation in the population dynamics of a native, temperate shrub, Haplopappus squarrosus H. and A. (Asteraceae), over an elevational gradient in the coastal sage scrub vegetation of San Diego County, California, USA. Frequency and abundance of H. squarrosus increase from coast to mountains. Expected abundance, based on flowers initiated, was highest at the coast and lowest in the interior, the opposite of the observed adult plant distribution. Overall flower and seed predation by insects was high (44-73%) and was greatest at the coast. Insect exclusion experiments at sites along the gradient had three main results. (1) Seedling recruitment was proportional to the number of viable seeds after seed predation. The exclusion plots had significantly higher numbers of seedlings established at all sites than did control plots; the greatest increase was at the coast. (2) Seedling survivorship was independent of both seedling and adult densities. (3) Juvenile recruitment was proportional to seedling establishment. Predation by insects prior to release of seeds played a critical role in the population recruitment of H. squarrosus within and among sites along the gradient. Survivorship of established plants, in addition, was as high at the coast as it was in the interior. These results suggest that indigenous insect seed predators can be a major force controlling the dynamics of a native plant species over its natural distributional range.
A selection experiment to develop reproductive isolation intraspecifically was conducted with maize, Zea mays L. Two populations, a white flint and a yellow sweet maize having different recessive marker genes, were employed. The two populations were planted mixed in the same field, and at harvest all intercrossed kernels could be readily detected since they expressed the two dominant genes. Intracrossed (homogamic) kernels from the ears having the lowest degree of intercrossing (heterogamic) were saved for planting the next generation. The procedure was followed for six generations. A considerable degree of isolation was obtained. Starting from 35.8% and 46.7% intercrossing respectively for the original populations of white flint and yellow sweet maize, after six generations of selection for isolation, the cycleV populations showed a very low per cent of intercrossing--4.9% and 3.4% The progress on a per year basis in decreasing the per cent of intercrossing was 5.9% for the white flint and 8.6% for the yellow sweet maize. The character proved to be easily selected, and thus the realized heritability values were 45.0% and 47.2% respectively for the white flint and for the yellow sweet maize. The mechanisms involved in the isolations were investigated. The data show that the number of days from planting to flowering was probably the main factor. Although the two original populations flowered at the same time, the cycle-IV populations have a difference of 1 week. The white flint became about 5 days earlier and the yellow sweet about 2 days later. Controlled pollinations using pollen mixtures indicated also that the cycle-IV white flint may have gametophyte genes that favor the fertilization from pollen of its own type, against pollen from the other population. The experiment showed that effective reproductive isolation could be obtained through selection in very few generations.
A new set of greenhouse gas emissions scenarios has been produced by the Intergovernmental Panel on Climate Change (IPCC). Incorporating these into models that also include the effects of C02 fertilization, feedback from stratospheric ozone depletion and the radiative effects of sulphate aerosols yields new projections for radiative forcing of climate and for changes in global-mean temperature and sea level. Changes in temperature and sea level are predicted to be less severe than those estimated previously, but are still far beyond the limits of natural variability.
Pollination and seed predation were studied in Silene vulgaris populations during two seasons, one with much lower pollinator abundance than the other. Among the pollinators, noctuid moths of the genus Hadena also acted as seed predators. Nectar-foraging female moths oviposited in flowers, and their larvae consumed flowers and seed capsules.
Despite a lower percentage of pollinated flowers in the year of low pollinator abundance, similar numbers of flowers set fruit in both years, because fewer flower buds and flowers were eaten by Hadena larvae during the year of low pollinator visitation. The number of seed capsules preyed upon was also lower in the year with low pollinator abundance, resulting in a higher seed set. The positive correlation between the percentage of pollinated flowers and the percentage of seed capsules destroyed was also observed when comparing flowers opening in different parts of the season.
Early flowering plant individuals had the same pollination success but suffered higher seed predation than late flowering ones. Selection for maximized pollination success through synchronous flowering, is probably the main reason for the compressed flowering period in 5. vulgaris, but the high level of predation early in the season may further increase the reproductive success of synchronous flowering individuals.
1. The propensity to, and consistency of, flowering of about 340 clones of Saccharum spontaneum collected from six latitudinal belts (from 5⚬ N. to 35⚬ N. in the Indian subcontinent) have been observed at Coimbatore (11⚬ N.) for 6 years. Although all the variants from the three southernmost belts flower at Coimbatore, the number of variants from beyond the twentieth parallel flowering at Coimbatore is inversely related to latitude of origin. This behavior suggests that the clones are bound with respect to flowering to definite photoperiods connected with their native latitudes, and that the limits of latitudinal tolerance which permit them to flower even when displaced vary to some extent among individuals. In regard to consistency, the latitudinally nearer populations flower more consistently (every year or nearly every year) than the farther ones. The tendency is either to flower every year or not to flower at all; the transition from complete readiness to flower to complete inhibition of flowering with...
Theoretical and empirical research on frugivory and seed dispersal has been influenced by concepts derived from the study of pollination. In particular, explicit and implicit analogies between seed dispersal and pollen dispersal have led to the expectation, under certain conditions, of the evolution of obligate, species-specific relationships between fruiting plants and the animals that disperse their seeds. The two systems differ in important respects, however. Plants benefit by directing pollen dispersers to a definite, recognizable "target," a conspecific flower, and they can provide incentives at flowers which serve to attract potential pollinators. In effect, there is "payment upon delivery" of the pollen. In contrast, for seeds the target (an appropriate site for germination and establishment) is seldom readily discernible, and dispersal beneath a conspecific plant may actually be undesirable. Another important difference is that frugivores are "paid in advance." Because of these differences and others, the outcomes of coevolution of fruiting plants and frugivores are expected to be different than those of flowering plants and flower visitors. There are therefore problems with drawing analogies between the two systems and using terminology derived from studies of pollination to design and interpret studies of seed dispersal
This chapter discusses the genetic and environmental factors that influence variability in populations and the implications of variability in plant breeding. Adaptation and adaptability are antagonistic. Success in improving adaptation requires that the population under selection be genetically variable. But high variability tends to be inadaptive because not all the genotypes in variable populations can be optimally fit and the presence of inferior genotypes is expected to reduce the immediate fitness of the population. Thus, successful breeding, insofar as it achieves even higher adaptation, reduces genetic variability and capacity for change. It is suggested that among available breeding methods, mass reservoirs provide the best opportunity for the required recombination to take place. Mass reservoirs are readily set up on a broad genetic base and are then maintained by mass-propagation methods, thus allowing very large populations to be handled with small effort and cost. Hence, it can be used to survey, recombine, and maintain variability on a scale not possible with conventional techniques. Genetically diverse populations are frequently higher yielding over a range of environments than genetically homogeneous populations, and hence, that optimal yield may depend on breeding varieties in which the appropriate compromise is found between the demands for uniformity and the advantages of diversity.
The simultaneous flowering of co—occurring plant species with similar pollinator affinities may result in interspecific pollen transfer and consequent fecundity reductions due to wastage of pollen, stigma surfaces, and effective pollinator visits. In such cases competition for pollination occurs and may lead to or maintain sequential flowering. Two common perennials in the mountains of west—central Colorado, Delphinium nelsoni and Ipomopsis aggregata, flower sequentially in the same meadows and are visited commonly by Broad—tailed Hummingbirds (Selasphorus platycercus). Hummingbirds carry pollen of both species and their exclusion from flowers leads to significant seed set reductions. During the brief period of flowering overlap between D. nelsoni and I. aggregata in natural meadows, hummingbirds visit both species, carry mixtures of their pollen, and appear to cause interspecific pollen transfer. Flowers of both species receptive during this period suffer significant seed set reductions relative to those receptive during nonoverlap periods. Interspecific pollinator flights and pollen transfer also occur in mixtures of potted plants, and seed set reductions consistently occur for both D. nelsoni and I. aggregata in such mixtures relative to single—species controls. Finally, seed set reductions occur for both species following interspecific hand pollination of potted plants. Fecundity reductions in natural and synthetic mixtures of D. nelsoni and I. aggregata indicate that the 2 species compete for hummingbird pollination and suggest that the competitive interaction involves interspecific pollen transfer. The observed reproductive effects represent a selective force sufficient to maintain divergent flowering times of D. nelsoni and I. aggregata in nature.
Concentrating on material published from 1984-1987, examines 1) the impact of insect feeding on different aspects of plant performance, paying particular attention to flowering, fruit production, post-dispersal seed mortality, seedling mortality, defoliation, growth and reproduction, competitive ability, and death rate of established plants; and 2) reviews the impact of insect feeding on plant population dynamics, focusing on the release of specialist insect herbivores against target weed species in classical biological control projects, and the exclusion of insect herbivores from natural plant communities by repeated application of insecticides. -P.J.Jarvis
The International Tundra Experiment (ITEX) was established in late 1990 at a meeting of arctic tundra ecologists as a response to predictions that the human-enhanced greenhouse warming would occur earliest and most intensely at high latitudes. The initial objective of ITEX was to monitor phenology, growth and reproduction in major circumpolar vascular plant species in response to climate variations and environmental manipulations at sites throughout the tundra biome. The manipulations involve passive warming of tundra plots in open-top chambers (OTCs), and manipulating snow depth to alter growing season length. Standard protocols were developed for measurements, experimental design and statistical analyses, and published in an ITEX Manual. The standard methods ensure comparable data are collected at all sites. This special issue of Global Change Biology is based on papers developed from the 6th ITEX Workshop, held at the University of Ottawa, Ottawa, Canada, 7–11 April 1995. The papers compare short-term responses (1–3 years) of common species to climate variations and manipulations at ITEX sites. The OTCs increase mean near-surface temperatures by 1–3°C during the growing season, simulating predictions from global circulation models. All species investigated responded to the temperature increase, especially in phenology and reproductive variables. However, these short-term responses were individualistic, and no general pattern in type or magnitude of response was noted for functional types or phenology class. Responses were generally similar among sites, although the magnitude of response tended to be greater in high Arctic sites. Early snowmelt increased carbon:nutrient ratios in plants. Sustained growth and reproductive responses to warming will depend on nutrient supply, and increased carbon:nutrient ratios in litter could buffer nutrient cycling, and hence plant growth. Ongoing, long-term research at ITEX sites, linked to other global change initiatives, will help elucidate probable effects of climate change at the ecosystems level in arctic and alpine tundra.
In the present study, I examined flowering phenology of dwarf bearded ins, Iris pumila, using naturally occurring clones (three sites, four microsites) and clones transplanted between two sites representing two habitats Naturally occurring clones in contrasting habitats and microsites differed significantly in phenology, with exposition of the site or microsite being the most important Genotypes from more exposed habitats flowered earlier in both habitats and these differences were statistically significant Patterns of between-habitat and between-population differences were stable over years even though years differed markedly in the flowering onset Within-population genetic variability for flowering phenology was also found to be significant Although clones with dark-colored flowers tended to flower earlier in all habitats and microsites I failed to detect statistically significant differences in flowering time among color morphs Flowering phenology in I pumila is highly susceptible to environmental variability, but this factor has not prevented population divergence in flowering time Between-habitat differences in flowering time turned out to be a result of both phenotypic plasticity of individuals and genetic differentiation of populations
Ocotillo, a perennial shrub of Sonoran and Chihuahuan Deserts, produces its red tubular flowers in spring. This timing coincides with northward migration of hummingbirds through desert areas. Observations of visitors, pollen collections, and seed set reductions following exclusion of different flower visitors indicate that both hummingbirds and solitary bees pollinate ocotillo in southern Arizona. Seed sets of flowers on marked plants varied considerably within and between years, and this variation was related to the temporal match between flowering and hummingbird migration. This suggests that selection acts on plants to synchronize flowering with periods of pollinator abundance.
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.
Oviposition choices by a pre-dispersal seed predator (Hylemya sp.). 1. Correspondence with hum-mingbird pollinators and the role of plant size, density, and floral morphology Resource and pollen limitations to lifetime seed production in a natural plant pop-ulation
- A K Brody
Brody, A. K. 1992. Oviposition choices by a pre-dispersal seed predator (Hylemya sp.). 1. Correspondence with hum-mingbird pollinators and the role of plant size, density, and floral morphology. Oecologia 91:56-62. rJune 1998 Campbell, D. R., and K. J. Halama. 1993. Resource and pollen limitations to lifetime seed production in a natural plant pop-ulation. Ecology 74:1043-1051
Phenology of entomophilous flowers
- C. Robertson
Colorado flora: western slope, revised edition
- W. A. Weber
- R. C. Wittmann
Scenarios of global warming
- S. H. Schneider