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Plant phenology refers to cyclic plant growth events, and is one of the most important indicators of climate change. Integration of plant phenology information is crucial for understanding the ecosystem response to global change and modeling the material and energy balance of terrestrial ecosystems. Utilizing 24 552 in situ phenological observations of 24 representative woody plant species from the Chinese Phenology Observation Network (CPON), we have developed maps delineating species phenology (SP) and ground phenology (GP) of forests over China from 1951 to 2020. These maps offer a detailed spatial resolution of 0.1 ∘ and a temporal resolution of 1 d. Our method involves a model-based approach to upscale in situ phenological observations to SP maps, followed by the application of weighted average and quantile methods to derive GP maps from the SP data. The resulting SP maps for the 24 woody plants exhibit a high degree of concordance with in situ observations, manifesting an average deviation of 6.9 d for spring and 10.8 d for autumn phenological events. Moreover, the GP maps demonstrate robust alignment with extant land surface phenology (LSP) products sourced from remote sensing data, particularly within deciduous forests, where the average discrepancy is 8.8 d in spring and 15.1 d in autumn. This dataset provides an independent and reliable phenology data source for China on a long-time scale of 70 years, and contributes to more comprehensive research on plant phenology and climate change at both regional and national scales. The dataset can be accessed at 10.57760/sciencedb.07995 (Zhu and Dai, 2023). [ABSTRACT FROM AUTHOR]

Spring warming could induce earlier leaf-out or flowering of temperate plant species, and decreased chilling in winter has a delaying effect on spring phenology. However, the relative contribution of the decreased chilling and increased forcing on spring phenological change is unclear. Here, we analyzed the experimental data for 14 temperate woody species in Beijing, China and quantified the forcing requirements (FR) of spring phenology and chilling sensitivity (the ratio of the FR at the low chilling condition to the FR at the high chilling condition) for each species. Furthermore, using species-specific functions between the amount of chilling and FR, we established a phenological model to simulate the annual onset dates of spring events during the past 69 years (1952–2020) and in the future (2021–2099) under RCP 4.5 and RCP 8.5 climate scenarios. We also developed a novel method to quantitatively split the predicted phenological change into the effects caused by changes in forcing and those caused by changes in chilling. The results show that the FR of spring events decreased with the increase in the amount of chilling, and this relationship could be described as an exponential decay function. The basic FR (the FR at the high chilling condition) and chilling sensitivity varied greatly among species. In the 1952–2020 period, the advancing effect of increased forcing was stronger than the effect of chilling, leading to earlier spring events with a mean trend of −1.96 days/decade. In future climate scenarios, the spring phenology of temperate species would continue to advance but will be limited by the decreased chilling. The species with lower chilling sensitivities showed stronger trends than those with high chilling sensitivities. Our results suggested that the delaying effect of declining chilling could only slow down the spring phenological advance to a certain extent in the future. [ABSTRACT FROM AUTHOR]

Continuous long-term temperature sensitivity (ST) of leaf unfolding date (LUD) and main impacting factors in spring in the period 1978–2014 for 40 plant species in Mudanjiang, Heilongjiang Province, Northeast China, were analyzed by using observation data from the China Phenological Observation Network (CPON), together with the corresponding meteorological data from the China Meteorological Data Service Center. Temperature sensitivities, slopes of the regression between LUD and mean temperature during the optimum preseason (OP), were analyzed using 15-year moving window to determine their temporal trends. Major factors impacting ST were then chosen and evaluated by applying a random sampling method. The results showed that LUD was sensitive to mean temperature in a defined period before phenophase onset for all plant species analyzed. Over the period 1978–2014, the mean ST of LUD for all plant species was − 3.2 ± 0.49 days °C−1. The moving window analysis revealed that 75% of species displayed increasing ST of LUD, with 55% showing significant increases (P < 0.05). ST for the other 25% exhibited a decreasing trend, with 17% showing significant decreases (P < 0.05). On average, ST increased by 16%, from − 2.8 ± 0.83 days °C−1 during 1980–1994 to − 3.30 ± 0.65 days °C−1 during 2000–2014. For species with later LUD and longer OP, ST tended to increase more, while species with earlier LUD and shorter OP tended to display a decreasing ST. The standard deviation of preseason temperature impacted the temporal variation in ST. Chilling conditions influenced ST for some species, but photoperiod limitation did not have significant or coherent effects on changes in ST. [ABSTRACT FROM AUTHOR]

Autumn phenology can regulate climate-biosphere interactions and net primary production within the ecosystem. However, studies modeling spatiotemporal variations in leaf coloring date (LCD) remain limited, especially for species-specific phenology on a continental scale. Aiming to simulate spatiotemporal variations in LCD in three widespread tree species ( Ulmus pumila , Fraxinus chinensis, and Robinia pseudoacacia ) across China, we used phenological observation records acquired from the China Phenology Observation Network (CPON) during 1963–2010 to establish and compare three LCD models (multiple regression (MA), temperature-photoperiod (TP), spring-influenced autumn (SIA)). Subsequently, we simulated the mean LCD of the three species using the most effective model and examined the effect of geographical factors (i.e., latitude, longitude, and altitude) on LCD through multiple regression analysis. Empirical Orthogonal Function (EOF) analysis was applied to identifying the most extensive and influential spatial modes of LCD variability and how they changed with time. The results showed that: (1) The LCD of F. chinensis was fitted better with the statistical model using monthly temperature as the independent variables (MR model). The LCD of F. chinensis was delayed by a temperature rise in August and September, but advanced by a temperature rise in May and June. The LCD of U. pumila and R. pseudoacacia was fitted better with the TP and SIA models, in which the photoperiod determined the date when the cold temperature started to accumulate. (2) The simulated mean LCD of U. pumila , F. chinensis, and R. pseudoacacia was October 6, October 16 and October 22, respectively. Latitude, longitude, and altitude had a significant influence on mean LCD of the three tree species. With increasing latitude and altitude, the LCD of all three species became earlier. However, the impact of longitude on the mean LCD varied among species. (3) For all the three species, the first EOF mode presented a consistent pattern of LCD variability across space, suggesting that an earlier or later LCD occurred simultaneously in the whole China. Meanwhile, the second EOF mode exhibited contrary signals of LCD variability in the north and south for F. chinensis and R. pseudoacacia . Over the past 50 years, the LCD of all the three species has delayed. The delaying trend revealed by the first EOF mode was 1.25 ( p < 0.01), 0.21 ( p < 0.01), and 0.53 days/decade (not significant) for U. pumila , F. chinensis and R. pseudoacacia , respectively. These results provide the basis for a better understanding of the phenology process in autumn and how it responds to climate change. [ABSTRACT FROM AUTHOR]

We selected widely distributed and well observed plant species Fraxinus chinensis to study the formation mechanism of geographical distribution of the plant phenophase changes and revealed their spatiotemporal dynamics in China. Based on the first leaf date (FLD) data at 12 sites derived from Chinese Phenological Observation Network (CPON) and related meteorological data, we developed and validated the process-based model of FLD for Fraxinus chinensis. After reconstructing data series of FLD for Fraxinus chinensis over the study area from 1952 to 2007, we analyzed different spatiotemporal patterns of phenophase changes of this species. The results suggested that the process-based model was able to simulate the FLD accurately for Fraxinus chinensis on large spatial and temporal scales, because of the consideration of different budding rate responded to the air temperatures during the dormancy and the quiescence in accordance with the physiological mechanism of plants. The geographical distribution of the spring phenology in temperate regions was determined by the spatial pattern of daily average air temperature. The changes of FLD for Fraxinus chinensis revealed significant phenological advances in most areas. However, it showed delayed trends in a few sites. The overall average change trend was −1.1 days/decade. This result was consistent with the advanced trend in other regions of the North Hemisphere. The changes of FLD showed a noticeable regional variation with clearer advance in the north than in the south. The FLD in northern China showed an average advance as high as −2.0 days/decade ( P<0.01). And the advance in northeastern and northwestern China was respectively −1.5 and −1.4 days/decade ( P<0.01). Furthermore, eastern and central regions showed a minor trend, which was −1.0 days/decade ( P<0.05). The smallest and non-significant advance appeared in southwestern and southern China. [ABSTRACT FROM AUTHOR]

Confirming the results of previous regional studies on changes in first bloom dates (FBD) in China, this study provides evidence that complements conclusions drawn from studies of phenological changes in other dynamic climate systems in the Northern Hemisphere. Furthermore, increased occurrences of yearly second blooms (YSB) further reinforce results derived from other studies indicating a recent trend of generalized climate warming across China. Additionally, ascertaining changes in FBD and YSB against a recent background not only provides a hitherto poorly formulated autumnal equivalent to the well-studied shifts in FBD, but also formulates both spring and autumn flowering changes in recent years. Data in this study are derived from observations made from 1963 to 2006 by the Chinese Phenological Observation Network (CPON)-a nationwide system of monitoring stations that has made observations of over 173 species from across China since 1963. At each site, the mean value of each species' annual deviation and spring mean surface temperatures were calculated. For each species, years and locations were also recorded for species in which second blooms (YSB) occurred. Of the 46 FBD samples, 31 showed advances from the mean, blooming earlier over the course of the study period. Notably, although only 8 of the 46 FBD samples showed significance levels of 0.1 or better, the average FBD did advance by 5.3 days. After the 1980s, the frequency of YSB occurrence remained steady, declining a little from the peak in the 1980s, but still exhibiting occurrences far more than were observed earlier. The data from this study clearly indicate that both the phenological advance of FBD in spring and the increased occurrence of YSB are consistent with climate warming. [ABSTRACT FROM AUTHOR]

• Spring phenological traits of plant species in Northeast China are analyzed. • Spring phenological traits of plants are phylogenetically conserved. • Reproductive phenology is more phylogenetically conserved than vegetative phenology. • Native climate has a stronger effect than phylogeny on spring phenological traits. The effects of climate change on plant phenology have been widely recognized around the world. However, the effect of plant internal factors (such as phylogeny) on the variations in phenology among plant species remains unclear. In this study, we investigated the phylogenetic conservatism in spring phenological traits using phylogenetic signal and evolutionary models, including Brownian motion (BM) model, Ornstein–Uhlenbeck (OU) model and white noise (WN) model, based on the phenological data of 48 temperate plant species in Northeast China. We also explored the relative contributions of phylogeny and adaptation to native climate (i.e., the climate in native range of species) to the variations in the phenological traits among species using phylogenetic eigenvector regression and variance partitioning analysis. The results showed thatspring phenological traits conformed to the OU model, indicating thatspring traits were phylogenetically conserved. The effect of phylogeny on flowering traits was stronger than that on leaf-out traits. Additionally, the adaptation to native climate contributed more to the variations in spring phenological traits among species than phylogeny, and adaptation to native climate explained more variations in leaf-out traits than in flowering traits. Our results suggested that the spring phenological traits were constrained by both phylogeny and adaptation to native climate. However, the adaptation to native climate had a stronger effect on the variations in phenological traits than phylogeny. Therefore, the degree of similarity in spring phenological traits across closely related species depends on the degree of similarity in the environmental conditions where these close relatives are distributed. [ABSTRACT FROM AUTHOR]