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Bud burst of birch. Buds in the upper panels are considered closed (-) and buds in the lower panels are considered open (+).
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Phenology can have a profound effect on growth and climatic adaptability of northern tree species. Although the large interannual variations in dates of bud burst and growth termination have been widely discussed, little is known about the genotypic and spatial variations in phenology and how these sources of variation are related to temporal varia...
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... each plantlet, we monitored five buds from the top of the main shoot (the topmost bud not included). The bud was determined as open when the protective bud scales were open and the emerging first leaf was clearly visible (Figure 1). The observations were made on a daily basis during 1992at Yhteislaidun, and during 1993-1996 at Com- mon Garden. ...
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... Such restriction of the basis dimension was used to avoid overfitting. Year and site were used as random effects to account for temporal and spatial dependencies of the data due to site conditions, phenological differences, as well as differences in plasticity, and local adaptations of populations (Marchand et al., 2021;Heer et al., 2018;Housset et al., 2018;Valladares et al., 2014;Rousi and Pusenius, 2005). Smoothing splines were estimated by the generalized cross-validation procedure, which reduces the probability of overfit. ...
... On the other hand, local adaptation of population implies potential for targeted breeding (Jansson et al., 2017(Jansson et al., , 2005. The latitudinal differences of the correlations with meteorological conditions in winter and spring followed local phenology and its shifts (Marchand et al., 2021;Hlasny et al., 2017;Hartmann et al., 2013;Rousi and Pusenius, 2005). Still, considering that local weather-growth relationships were corelative, some of them might be spurious. ...
... A milder positive response to temperature ranging 0-2 • C, which indicates cool spring, might be related to frost damage, particularly as trees are exiting the dormancy (Marchand et al., 2021;Augspurger, 2009;Pearce, 2001). A steeper response to warmer conditions (8-14 • C), in turn, might be explained by extension of growing period, which improves increment (Marchand et al., 2021;Levanič and Eggertsson, 2008;Rousi and Pusenius, 2005). The response of silver birch to temperature in April (Fig. 4C) was similar to that of Scots pine to February temperature (Matisons et al., 2021a), suggesting similar limitation, yet with differing phenology likely to reduce root competition (Baumgarten et al., 2019). ...
Silver birch (Betula pendula Roth.) is a widespread species with a high potential for aiding sustainability and multifunctionality of European forests, as evidenced in Finland and the Baltics. However, under increasing relevance of climate change for tree growth, the meteorological sensitivity of the species is largely unknown, presuming it to be weather tolerant (low sensitivity). Considering local adaptations of populations of widespread species, climatic changes are subjecting trees to extreme conditions, thus testing their adaptability. Accordingly, information on the plasticity (variability) of responses across a gradient of meteorological conditions is crucial for reliable predictions of tree growth. Tree-ring width network was established to assess the plasticity of growth responses of silver birch to meteorological conditions across the eastern Baltic climatic gradient. Time series analysis in combination with generalized additive modelling were applied to assess responses of birch from 21 naturally regenerated conventionally managed stands scattered from southern Finland to northern Germany. Despite the presumed tolerance, explicit meteorological sensitivity of silver birch was estimated. A gradient of local linear weather-growth relationships was estimated, as growth limitation shifted from temperature during the dormancy to water availability during vegetation period in southern Finland and northern Germany, respectively. However, these relationships were nonstationary, as the effect of summer water shortage was intensifying and sensitivity to it has likely been subjected to local adaptation. The regional generalization revealed presence of stationary, yet nonlinear and plastic growth responses, implying disproportional effects of climatic changes. Such responses also explained the nonstationarities, as the local climates shifted along the regional gradient. At the regional scale, summer water shortage was the main driver of increment, while winter conditions had a secondary role; temperature of the preceding vegetation season also had an effect on increment. Accordingly, increased variability of increment of silver birch is expected under changing climate; still, sensitivity and plasticity of increment can be considered as an adaptation to shifting environments.
... Many aspects of plant phenology are known or expected to have a genetic component, including the timing of leafout (Rousi and Pusenius 2005) and flowering (Franks et al. 2007;Volis 2007), as well as interphase duration (i.e., length of time between successive phenological events; Ettinger et al. 2018). In this study, we experimentally manipulated the timing of acorn germination, thereby disrupting any genetic control of germination timing. ...
Seasonal life history events are often interdependent, but we know relatively little about how the relationship between different events is influenced by the abiotic and biotic environment. Such knowledge is important for predicting the immediate and evolutionary phenological response of populations to changing conditions. We manipulated germination timing and shade in a multi-factorial experiment to investigate the relationship between spring and autumn phenology in seedlings of the pedunculate oak, Quercus robur, and whether this relationship was mediated by natural colonization of leaves by specialist fungal pathogens (i.e., the oak powdery mildew complex). Each week delay in germination corresponded to about 2 days delay in autumn leaf senescence, and heavily shaded seedlings senesced 5–8 days later than seedlings in light shade or full sun. Within seedlings, leaves on primary-growth shoots senesced later than those on secondary-growth shoots in some treatments. Path analyses demonstrated that germination timing and shade affected autumn phenology both directly and indirectly via pathogen load, though the specific pattern differed among and within seedlings. Pathogen load increased with later germination and greater shade. Greater pathogen load was in turn associated with later senescence for seedlings, but with earlier senescence for individual leaves. Our findings show that relationships between seasonal events can be partly mediated by the biotic environment and suggest that these relationships may differ between the plant and leaf level. The influence of biotic interactions on phenological correlations across scales has implications for understanding phenotypic variation in phenology and for predicting how populations will respond to climatic perturbation.
... Phenology has a profound effect on plant growth and development patterns (Zhang et al., 2006) and productivity and species distributions (Chuine and Beaubien, 2001;Rathcke and Lacey, 1985)and is used to characterize vegetation types (Opler et al., 1980;Shimwell, 1972). Generally, a phenological shift causes a change in the geographic distribution of species (Walther et al., 2002), which can have positive effects in helping species adapt to changing climates (Rousi and Pusenius, 2005) and increasing productivity (Churkina et al., 2005) and negative impacts by impacting plant fitness (Wookey et al., 1993), species invasion (Chuine, 2010) and reproductive behavior (Hughes, 2000). Moreover, phenology deviation can create asynchrony between interspecific interactions, affecting ecosystem functioning and resulting in biodiversity loss (Roy et al., 2017). ...
Earth's mean air temperature is increasing at an accelerating rate, and forest tree species are sensitive to this changing climate. However, tree species react variably to changing climates across different geographical ranges. Thus, eleven multi-purpose tree species (MPTs), Albizia stipulata, Bauhinia variegata, Celtis australis, Dalbergia sissoo, Gmelina arborea, Grewia optiva, Melia azedarach, Morus alba, Robinia pseudoacacia, Sapindus mukorossi and Toona ciliata, of the mid-hill zone of the northwestern Himalayas were selected to analyse the impact of climatic patterns on their phenological events over two decades (1999- 2017). The results indicated that phenological advancement (in days) was more pronounced from 1999-2006 than from 2006-2017. Specifically, leaf emergence phase advancement ranged from 5 (R. pseudoacacia) to 38 days (M. alba). However, advancement in the flower initiation phase for MPTs was not as prominent. The growth period of M. azedarach was prolonged the most (60 days), followed by those of B. variegata (56 days), D. sissoo (51 days), T. ciliata (48 days), S. mukorossi (46 days), R. pseudoacacia (44 days), G. optiva (41 days), G. arborea (20 days), A. stipulate (15 days), M. alba (10 days) and C. australis (7 days). Increasing growing season duration and rate have implications on future composition, nutrient cycling and carbon sequestration of agro-ecosystems of the mid-hill zone of the north western Himalayas.
... This contrasts with numerous experimental observations of temperate and boreal perennial plants, which have long shown that chilling and photoperiod play a significant role in dormancy release and bud development (e.g. Coville, 1920;Wareing, 1953;Murray et al., 1989;Heide, 1993;Rousi & Pusenius, 2005;Viherä-Aarnio et al., 2006). ...
Microclimatic effects (light, temperature) are often neglected in phenological studies and little is known about the impact of resource availability (nutrient and water) on tree’s phenological cycles. Here we experimentally studied spring and autumn phenology in four temperate trees in response to changes in bud albedo (white‐ vs. black‐painted buds), light conditions (non‐shaded vs. ~70% shaded), water availability (irrigated, control and reduced precipitation) and nutrients (low vs. high availability). We found that higher bud albedo or shade delayed budburst (up to +12 days), indicating that temperature is sensed locally within each bud. Leaf senescence was delayed by high nutrient availability (up to +7 days) and shade conditions (up to +39 days) in all species, except oak. Autumn phenological responses to summer droughts depended on species, with a delay for cherry (+ 7 days) and an advance for beech (‐7 days). The strong phenological effects of bud albedo and light exposure reveal an important role of microclimatic variation on phenology. In addition to the temperature and photoperiod effects, our results suggest a tight interplay between source and sink processes in regulating the end of the seasonal vegetation cycle, which can be largely influenced by resource availability (light, water and nutrients).
... Plant growth is a complex process. In the process of plant ontogenesis growth is observed during the main stages of its life cycle [14][15][16] . Therefore, in further studies it is possible to identify patterns of influence of meteorological parameters on the dynamics of vegetative organs of plants. ...
Factor analysis of annual dynamics from 1879 to 2017 was carried out by the method of identification of stable regularities: maximum, minimum and average air temperature of Central England according to HadCET. The sample capacity was 139 rows. In factor analysis, time is excluded, and it acts only as a system-forming factor that ensures the relationship between the three parameters of climate and weather. Therefore, the adequacy of the dynamics models is taken into account in the diagonal cells of the correlation matrix. In addition to time, different lists of objects are possible in factor analysis. The coefficient of correlation variation, that is, a measure of the functional relationship between the parameters of the system (annual weather at the weather station in Central England) is 0.8230 for trends, 0.8603 taking into account the annual dynamics of the four-membered model obtained from the computational capabilities of the software environment CurveExpert-1.40, and 0.9578 for the full up to the error of measurement wavelet analysis of the dynamics of the values of three factors. In all three methods of factor analysis, the meteorological parameter «average Annual temperature» was in the first place as the influencing variable, the «Maximum temperature» was in the second place, and the «Minimum temperature» was in the third place. As the dependent measure in these areas there are three kind of temperature. The comparison shows that among the binary relations between the three temperatures, the average temperature on the maximum air temperature in the surface layer of the atmosphere has the greatest influence on the correlation coefficient 0.9765. At the same time, all six equations refer to strong connections, so there is a high quantum certainty between the three types of temperature. But when predicting the most meaningful essence showed the maximum temperature.
... Bud break was monitored daily (including weekends), starting before any buds had opened and continuing until all buds had opened. Following the protocol developed by Rousi and Pusenius (2005), buds were considered open once the protective bud scales were clearly separated and the emerging leaf was visible. The day of the year when all monitored buds had opened was considered the start of the growing season for a sapling. ...
Strong seasonality in the subarctic causes unfavorable conditions for plant growth driving strong latitudinal clines in growth onset and cessation related to temperature and photoperiodic cues. Results from controlled experiments indeed show such clines, but results from field experiments seem to indicate that such clines may depend on site characteristics, suggesting that environmental variation, other than temperature and photoperiod, is relevant under climate change. Here, we increase our understanding of the effects of climate change on survival, height growth, and the phenological cycle by investigating their inter‐ and intrapopulation variation using three common gardens and six silver birch (Betula pendula) populations (each represented by up to five cloned genotypes) spanning the Finnish subarctic. We found clinal south–north variation among populations in survival and growth and in spring and autumn phenology to be largely absent. Sapling survival decreased with a transfer of over five degrees of latitude southward, but growth and phenology showed little evidence for adaptation to the local climate. Instead, ample genetic variation and plastic responses were found for all traits studied. Higher soil N availability increased sapling survival and growth, and phenology seemed to be adapted to soil N and day length rather than to temperature. Our results suggest that the climatic conditions predicted for the end of this century may, at least for poor soils, reduce the survival of northern silver birch trees in their early growth. However, those saplings that survive seem to have sufficient phenotypic plasticity to acclimatize to the changing climate. Along with climate, soil fertility plays a significant role and clearly warrants inclusion in the future tests of the effects of climate warming on tree growth and survival.
... The date of the first bud of a plantlet opening was considered as the start of the growing season for that plantlet. A bud was considered open once the protective bud scales were completely separated and the emerging leaf was visible 54 . During the peak growing season, plant performance was estimated two (2017) to three (2018) times by measuring the chlorophyll content of five full-grown topmost leaves in several branches in each plantlet, using the CCM300 non-destructive optical chlorophyll content meter (Opti-Sciences, USA). ...
Climate warming is anticipated to make high latitude ecosystems stronger C sinks through increasing plant production. This effect might, however, be dampened by insect herbivores whose damage to plants at their background, non-outbreak densities may more than double under climate warming. Here, using an open-air warming experiment among Subarctic birch forest field layer vegetation, supplemented with birch plantlets, we show that a 2.3 °C air and 1.2 °C soil temperature increase can advance the growing season by 1–4 days, enhance soil N availability, leaf chlorophyll concentrations and plant growth up to 400%, 160% and 50% respectively, and lead up to 122% greater ecosystem CO2 uptake potential. However, comparable positive effects are also found when insect herbivory is reduced, and the effect of warming on C sink potential is intensified under reduced herbivory. Our results confirm the expected warming-induced increase in high latitude plant growth and CO2 uptake, but also reveal that herbivorous insects may significantly dampen the strengthening of the CO2 sink under climate warming.
... Both species were under significant selection for an extended leaf-out period (Table 4), a trait that was exhibited by the southern ecotype of both species (Fig. 2g). Other studies have found similar results where spring and fall phenology and the length of the growth period were related to plant fitness (Menzel and Fabian 1999, Rousi and Pusenius 2005, Menzel et al. 2006, Ibanez et al. 2010. However, some caution is warranted; ecosystem-level observations (models of CO 2 fluxes and remotely sensed vegetation greenness) indicate that northern terrestrial ecosystems are more likely to lose rather than sequester carbon because of differential impacts on photosynthesis and respiration of spring vs. fall warming (Piao et al. 2008). ...
Boreal forests are experiencing dramatic climate change, having warmed 1‐1.9°C over the last century. Yet forest regeneration practices are often still dictated by a fixed seed zone framework, in which seeds are both harvested from and planted into predefined areas. Our goal was to determine whether seedlings sourced from southern seed zones in Minnesota USA are already better adapted to northerly seed zones because of climate change. Bur oak (Quercus macrocarpa) and northern red oak (Quercus rubra) seedlings from two seed zones (i.e. tree ecotypes) were planted into 16 sites in two northern seed zones and measured for three years. Our hypotheses were threefold: 1) tree species with more southern geographic distributions would thrive in northern forests where climate has already warmed substantially, 2) southern ecotypes of these species would have higher survival and growth than the northern ecotype in northern environments, and 3) natural selection would favor seedlings that expressed phenotypic and phenological traits characteristic of trees sourced from the more southern seed zone. For both species, survival was high (>93%), and southern ecotypes expressed traits consistent with our climate adaptation hypotheses. Ecotypic differences were especially evident for red oak; the southern ecotype had had higher survival, lower SLA, faster height and diameter growth, and extended leaf phenology relative to the northern ecotype. Bur oak results were weaker, but the southern ecotype also had earlier budburst and lower SLA than the northern ecotype. Models based on the fixed seed zones failed to explain seedling performance as well as those with continuous predictors (e.g. climate and geographical position), suggesting that plant adaptations within current seed zone delineations do align with changing climate conditions. Adding support for this conclusion, natural selection favored traits expressed by the more southern tree ecotypes. Collectively, these results suggest that state seed sourcing guidelines should be reexamined to permit plantings across seed zones, a form of assisted migration. More extensive experiments (i.e. provenance trails) are necessary to make species‐specific seed transfer guidelines that account for climate trends while also considering the precise geographic origin of seed sources.
... For provenances it spans the 30-year interval 1969 -1999, for the Joensuu CG it spans the period 2010 -2013 (the experimental years). Tmean, Tmin, Tmax = Mean, minimum, maximum air temperature, Teff = Effective temperature sum (baseline 5°C, suitable for birch phenology (Rousi and Pusenius 2005)), FFD = Frost free days, Tjul, Tjan = July, January air temperature, Cont = Continentality index (difference Tjul-Tjan, e.g. Holowachuk 2001, Rivas-Martínez et al. 2011), Precip = Precipitation, S = Snow depth, Precip Sum = Precipitation sum, S Sum = Snow depth sum, SCD = Snow cover days, Daylength = Sunlight duration for June 1 st at each provenance (from NOAA Sunrise/Sunset and Solar Position Calculators), Elev = Elevation min-mean-max (meters above sea level) is NLS open data (National Land Survey of Finland 2019) for an overview of local geography. ...
Due to its ubiquity across northern latitudes, silver birch (Betula pendula Roth) is an attractive model species for studying geographical trait variation and acclimation capacity. Six birch provenances from 60 to 67°N across Finland were grown in a common garden and studied for provenance and genotype variation. We looked for differences in height growth, photosynthetic gas exchange and chlorophyll content index (CCI), and compared the gas exchange of early and late leaves on short and long shoots, respectively. The provenances stratified into southern and northern groups. Northern provenances attained less height growth increment and had higher stomatal conductance (gs) and lower intrinsic water-use efficiency (WUE, Anet/gs) than southern provenances, whereas net photosynthesis (Anet) or CCI did not show clear grouping. Short shoot leaves had lower gs and higher WUE than long shoot leaves in all provenances, but there was no difference in Anet between shoot types. The separation of the provenances into two groups according to their physiological responses might reflect the evolutionary history of Betula pendula. Latitudinal differences in gas exchange and water use traits can have plausible consequences for global carbon and water fluxes in a warming climate.
... Thanks to the active activity of meristems and photosynthetic activity of leaves, the green plant acquires a number of features that characterize its growth. In the process of plant ontogenesis growth is observed during the main stages of its life cycle [10][11][12]. Therefore, in further studies it is possible to identify patterns of influence of meteorological parameters on the dynamics of vegetative organs of plants, and these patterns to assess the geoecological state of the area. ...
