Weakening warming on spring freeze-thaw cycle caused greening Earth's third pole.

The Tibetan Plateau, recognized as Earth's third pole and among the most responsive regions to climate shifts, profoundly influences regional and even global hydrological processes. Here, we discerned a significant weakening in the influence of temperature on the initiation of surface freeze-thaw cycle (the Start of Thawing, SOT), which can be ascribed to a multitude of climatic variables, with radiation emerging as the most pivotal factor. Additionally, we showed that the diminishing impact of warming on SOT yields amplified soil moisture within the root zone. This, in turn, fosters a greening third pole with increased leaf area index and solar-induced chlorophyll fluorescence. We further showed that current Earth system models failed to reproduce the linkage between weakened sensitivity and productivity under various shared socioeconomic pathways. Our findings highlight the dynamic shifts characterizing the influence of climate warming on spring freeze-thaw process and underscore the profound ecological implications of these changes in the context of future climate scenarios.

Widespread decline in winds delayed autumn foliar senescence over high latitudes.

The high northern latitudes (>50°) experienced a pronounced surface stilling (i.e., decline in winds) with climate change. As a drying factor, the influences of changes in winds on the date of autumn foliar senescence (DFS) remain largely unknown and are potentially important as a mechanism explaining the interannual variability of autumn phenology. Using 183,448 phenological observations at 2,405 sites, long-term site-scale water vapor and carbon dioxide flux measurements, and 34 y of satellite greenness data, here we show that the decline in winds is significantly associated with extended DFS and could have a relative importance comparable with temperature and precipitation effects in contributing to the DFS trends. We further demonstrate that decline in winds reduces evapotranspiration, which results in less soil water losses and consequently more favorable growth conditions in late autumn. In addition, declining winds also lead to less leaf abscission damage which could delay leaf senescence and to a decreased cooling effect and therefore less frost damage. Our results are potentially useful for carbon flux modeling because an improved algorithm based on these findings projected overall widespread earlier DFS than currently expected by the end of this century, contributing potentially to a positive feedback to climate.

Fine particulate matter (PM2.5) trends from land surface changes and air pollution policies in China during 1980-2020.

High levels of fine particulate matter (PM2.5) pose a severe air pollution challenge in China. Both land use changes and anthropogenic emissions can affect PM2.5 concentrations. Only a few studies have addressed the long-term impact of land surface changes on PM2.5 in China. We conducted a comprehensive analysis of PM2.5 trends over China using the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) during 1980-2020. The monthly mean PM2.5 concentrations of MERRA-2 were evaluated across mainland China against independent surface measurements from 2013 to 2020, showing a good agreement. For the trend analysis, China was subdivided into six regions based on land use and ambient aerosols types. Our results indicate an overall significant PM2.5 increase over China during 1980-2020 with major changes in-between. Notwithstanding continued urbanization and associated anthropogenic activities, the PM2.5 reversed to a downward trend around 2007 over most regions except for the part of China that is most affected by desert dust. Statistical analysis suggests that PM2.5 trends during 1980-2010 were associated with urban expansion and deforestation over eastern and southern China. The trend reversal around 2007 is mainly attributed to Chinese air pollution control measures. A multiple linear regression analysis reveals that PM2.5 variability is linked to soil moisture and vegetation. Our results suggest that land use and land cover changes as well as pollution controls strongly influenced PM2.5 trends and that drought conditions affect PM2.5 particularly over desert and forest regions of China. This work contributes to a better understanding of the changes in PM2.5 over China.

Winter warming offsets one half of the spring warming effects on leaf unfolding.

Winter temperature-related chilling and spring temperature-related forcing are two major environmental cues shaping the leaf-out date of temperate species. To what degree insufficient chilling caused by winter warming would slow phenological responses to spring warming remains unclear. Using 27,071 time series of leaf-out dates for 16 tree species in Europe, we constructed a phenological model based on the linear or exponential function between the chilling accumulation (CA) and forcing requirements (FR) of leaf-out. We further used the phenological model to quantify the relative contributions of chilling and forcing on past and future spring phenological change. The results showed that the delaying effect of decreased chilling on the leaf-out date was prevalent in natural conditions, as more than 99% of time series exhibited a negative relationship between CA and FR. The reduction in chilling linked to winter warming from 1951 to 2014 could offset about one half of the spring phenological advance caused by the increase in forcing. In future warming scenarios, if the same model is used and a linear, stable correlation between CA and FR is assumed, declining chilling will continuously offset the advance of leaf-out to a similar degree. Our study stresses the importance of assessing the antagonistic effects of winter and spring warming on leaf-out phenology.

Varying temperature sensitivity of bud-burst date at different temperature conditions.

The relationship between the rate of development (DR) of bud-burst and temperature may be nonlinear, which could lead to varying temperature sensitivity (TS) of budburst date under different climate conditions. In order to determine the functional form between DR/TS and temperature, we gathered twigs with flower buds of five woody plants (Malus halliana, Forsythia suspense, Crataegus pinnatifida, Prunus cerasifera F. atropurpurea, and Berberis thunbergii var. atropurpurea Chenault) in early spring of 2017 at Beijing, and placed them in six growth chambers at same daylength but different temperature conditions (5, 10, 15, 20, 25, and 30 °C). The proportion of bud- burst was recorded every 2 or 3 days for each species at each temperature condition. The results showed that the proportion of bud-burst followed the logistic function over time at a given temperature. Subsequently, we developed a mathematical model to simulate the proportion of bud-burst at any temperature and date. The DR and TS were parameterized using a differential method. The simulation results showed that the DR increased monotonically with the rise in temperature, but only two species could reach the maximum value at 30 °C. The TS decreased with the increase in temperature, but this effect was weak when the temperature was high enough. These findings suggested that the predicted warming in the future may result in a slowdown in the advance of spring phenology of woody plants.

Comparison of chilling and heat requirements for leaf unfolding in deciduous woody species in temperate and subtropical China.

Climate warming has advanced the spring phenology of many plant species by accelerating heat accumulation. However, delayed phenophases due to insufficient chilling have also been reported. Based on phenological observation data (1963-2010), we compared the effects of preseason chill and heat accumulation on leaf unfolding dates of four deciduous woody species (Lagerstroemia indica, Robinia pseudoacacia, Sophora japonica, and Ulmus pumila) in temperate and subtropical regions of China. Daily chill and heat accumulation were calculated by two chilling models (the Positive Utah Model and the Dynamic Model) and the Growing Degree Hour (GDH) Model. We determined the temporal trends in chill and heat accumulations for leaf unfolding of the four species. The results showed that there were shorter chilling periods in the subtropics than in temperate sites because the chilling period typically started later and ended earlier. There was no significant difference in the length of the forcing period in the different regions. The chilling requirements for leaf unfolding were higher in temperate regions (1344.9-1798.9 chilling units (CU) or 64.7-79.4 chilling portions (CP)) than in the subtropics (1145.9-1828.1 CU or 47.9-75.2 CP). Plants in the subtropics needed higher forcing temperatures (4135.8-10084.8 GDH) than those in temperate regions (3292.0-8383.6 GDH). The earlier-leafing species (e.g., U. pumila) had a lower heat requirement for leaf unfolding than the later-leafing species (e.g., L. indica). A significant increase in heat accumulation was found at all sites except Guiyang, while chill accumulation only increased in Beijing.

Assessing the adaptability of maize phenology to climate change: The role of anthropogenic-management practices.

Phenology has been regarded as an essential bio-indicator of climate change widely. Quantifying the crop phenological changes caused by climate change and anthropogenic-management practices can help formulate effective climate change adaptation strategies. In this study, the effects of climate change and anthropogenic-management practices on maize phenology (spring, summer, and intercropping maize) in China were distinguished based on historical meteorological and phenological data (1981-2010) of 114 stations using the first-order difference regression method. Our results show: (1) The vegetative growing period of spring and intercropping maize was extended, whereas that of summer maize was shortened. The reproductive growing periods of spring, summer, and intercropping maize were extended. (2) Isolated impacts of climate change shortened the vegetative growing period of spring maize, summer maize, and intercropping maize by 0.19, 1.06, and 3.12 d decade-1, respectively, while the reproductive growing period was extended by 0.19, 0.74, and 3.47 d decade-1, respectively. (3) The contribution of temperature to maize phenology was greater in the northwest inland maize zone and north spring maize zone than in other regions, whereas the contribution of sunshine hours was higher in Huang-Huai Plain intercropping maize zone and the southwest mountain hills maize zone. (4) The effects of anthropogenic-management practices on maize phenological stages such as sowing, emergence, and maturity were generally greater than that of climate change, which has delayed the phenological stages of summer and intercropping maize and extended the growing period of spring maize. The focus should be paid to the emergence, jointing, and milky stages to increase the water use efficiency in the northwest inland maize zone. The findings provide a scientific basis for improving the adaptability of agricultural systems in climate change.

The optimization of wheat yield through adaptive crop management in a changing climate: evidence from China.

BACKGROUND: Adaptive crop management is critical to food security in a changing climate, but the respective contributions of climate change and crop management to yields remain unclear. Thus, we distinguished and quantified the respective contribution of climate change and crop management on wheat yield between 1981 and 2018 in China, using first-difference multivariate regression model. RESULTS: Wheat production in China has increased over the past four decades. Under the sole impact of climate change, wheat yield generally decreased (-5.45 to +1.09% decade-1 ). Crop management increased the wheat yield from 7.11 to 19.94% decade-1 . Sensitivities of wheat yield to climatic variables (average temperature, accumulated sunshine hours, accumulated precipitation) were spatially heterogeneous; notably, in spring-wheat planting areas, wheat yield was more susceptible to the negative impact of warming. In terms of relative contribution, the contribution of climate change to spring wheat yield was -24.08% to -5.41%, and the contribution to winter wheat was -4.98% to +34.69%. Crop management had a positive contribution to all wheat-growing areas (65.31-96.84%). CONCLUSION: Crop management had a greater effect on wheat yield than climate change did. Among the three climatic variables investigated, average temperature had the dominant effect on wheat yield change; the impact of precipitation was minimal but mostly negative. The results provide insight regarding the contribution of climate change and crop management to wheat yield; adaptation measures may be more effective in planting areas where crop management contributes more, which will help stakeholders optimize crop management and adaptation strategies. © 2020 Society of Chemical Industry.

Trends in maize (Zea mays L.) phenology and sensitivity to climate factors in China from 1981 to 2010.

Changes in crop phenology may reflect crop responses and adaptation to climate change. In this study, we used observational data (1981-2010) of maize (Zea mays L.) phenology from agricultural meteorological stations in the major maize-growing regions of China to examine spatiotemporal changes in the phenologies and growth periods and associated sensitivities to changes in major climatic factors. The results showed that, during the study period, sowing, tasseling, and maturity dates for maize were delayed in most maize growth regions. The lengths of vegetative growth period (VGP, from emergence to tasseling) were increased in spring and spring-summer maize growth regions and decreased in summer maize growth regions; the lengths of the maize reproductive growth period (RGP, from tasseling to maturity) and whole growth period (WGP, from emergence to maturity) were mostly extended (except NWMR_SU). Overall, sensitivity of maize VGP, RGP, and WGP was negatively related to average temperature (P < 0.01) and positively related to precipitation and sunshine hours (P < 0.01); there were variations in sensitivity among regions and data station locations. Precipitation was a driver of growth period length in the northwest inland maize region, whereas mean temperature and sunshine hours were drivers in the southwest hilly region.

Changes in flowering phenology of woody plants from 1963 to 2014 in North China.

Existing evidence demonstrates that the first flowering date (FFD) of most plant species became earlier in response to temperature increase over the past several decades. However, the studies on changes in flowering duration (FD) were limited. By using the non-parametric Theil-Sen estimator, this study investigated the temporal trends in 127 time series of FFD, end of flowering date (EFD), and FD of 97 woody plants from 1963 to 2014 at three sites (Harbin, Beijing, and Xi'an) in North China. The relationship between flowering phenophases and temperature was analyzed using two phenological models. The results showed that most of FFD and EFD time series exhibited an apparent advancing trend. Among them, trends of 52.0% (40.9%) of FFD (EFD) time series were significant (P < 0.05). FFD and EFD time series (95.3 and 89.8%, respectively) responded negatively and significantly to preseason temperature (P < 0.05). The direction of FD changes varied among sites and species. On average, a shortening trend of FD was observed at Harbin (-0.51 days decade-1), with 7.5% of species significantly. However, FD on average extended by 0.42 and 0.93 days decade-1 at Beijing (24.5% significantly) and Xi'an (28.9% significantly), respectively. The regression models could simulate the interannual changes in FFD and EFD with the mean goodness of fit (R2) ranging from 0.37 to 0.67, but fail to simulate the changes in FD accurately (R2 ranging from 0.09 to 0.18). The growing degree day model could improve the R2 for simulating FFD and EFD except for FD. Therefore, more phenological models need to be tested, and more drivers of FD need to be further investigated.

Variations in the temperature sensitivity of spring leaf phenology from 1978 to 2014 in Mudanjiang, China.

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.

Impacts of global warming on phenology of spring leaf unfolding remain stable in the long run.

The impact of spring temperature forcing on the timing of leaf unfolding of plants (temperature sensitivity, ST) is one important indicator of how and to what degree plant species track climate change. Fu et al. (Nature 526:104-107, 2015) found that ST has significantly decreased from the 1980-1994 to the 1999-2013 period for seven mid-latitude tree species in Europe. However, long-term changes in ST over the past 60 years are still not clear. Here, using in situ observations of leaf unfolding for seven dominant European tree species, we analyze the temporal change in ST over decadal time scales extending the data series back to 1951. Our results demonstrate that ST shows no statistically significant change within shifting 30-year windows from 1951 to 2013 and remains stable between 1951-1980 and 1984-2013 (3.6 versus 3.7 days °C-1). This result suggests that the significant decrease in ST over the past 33 years could not be sustained when examining the trends of phenological responses in the long run. Therefore, we could not conclude that tree spring phenology advances will slow down in the future, and the ST changes in warming scenarios are still uncertain.

Predicting the responses of forest distribution and aboveground biomass to climate change under RCP scenarios in southern China.

In the past three decades, our global climate has been experiencing unprecedented warming. This warming has and will continue to significantly influence the structure and function of forest ecosystems. While studies have been conducted to explore the possible responses of forest landscapes to future climate change, the representative concentration pathways (RCPs) scenarios under the framework of the Coupled Model Intercomparison Project Phase 5 (CMIP5) have not been widely used in quantitative modeling research of forest landscapes. We used LANDIS-II, a forest dynamic landscape model, coupled with a forest ecosystem process model (PnET-II), to simulate spatial interactions and ecological succession processes under RCP scenarios, RCP2.6, RCP4.5 and RCP8.5, respectively. We also modeled a control scenario of extrapolating current climate conditions to examine changes in distribution and aboveground biomass (AGB) among five different forest types for the period of 2010-2100 in Taihe County in southern China, where subtropical coniferous plantations dominate. The results of the simulation show that climate change will significantly influence forest distribution and AGB. (i) Evergreen broad-leaved forests will expand into Chinese fir and Chinese weeping cypress forests. The area percentages of evergreen broad-leaved forests under RCP2.6, RCP4.5, RCP8.5 and the control scenarios account for 18.25%, 18.71%, 18.85% and 17.46% of total forest area, respectively. (ii) The total AGB under RCP4.5 will reach its highest level by the year 2100. Compared with the control scenarios, the total AGB under RCP2.6, RCP4.5 and RCP8.5 increases by 24.1%, 64.2% and 29.8%, respectively. (iii) The forest total AGB increases rapidly at first and then decreases slowly on the temporal dimension. (iv) Even though the fluctuation patterns of total AGB will remain consistent under various future climatic scenarios, there will be certain responsive differences among various forest types.

Reply to communications by Fu et al. international journal of biometeorology.

Temperature sensitivity of plant phenology (ST) is a determining factor of as to what degree climate change impacts on plant species. Fu et al . (Int J Biometeorol 60:1611-1613, 2016) claimed that long long-term linear trends mask phenological shifts. However, the decreased and increased ST was both found in warming scenarios. The conceptual scheme telling the nonlinear relationship between spring temperature and leaf unfolding date proposed by Fu et al . (Int J Biometeorol 60:1611-1613, 2016) cannot be supported by observation data across Europe. Therefore, linking declined ST to climate warming is misleading, and future ST changes are more uncertain than they suggested.

Phenological response to climate change in China: a meta-analysis.

The change in the phenology of plants or animals reflects the response of living systems to climate change. Numerous studies have reported a consistent earlier spring phenophases in many parts of middle and high latitudes reflecting increasing temperatures with the exception of China. A systematic analysis of Chinese phenological response could complement the assessment of climate change impact for the whole Northern Hemisphere. Here, we analyze 1263 phenological time series (1960-2011, with 20+ years data) of 112 species extracted from 48 studies across 145 sites in China. Taxonomic groups include trees, shrubs, herbs, birds, amphibians and insects. Results demonstrate that 90.8% of the spring/summer phenophases time series show earlier trends and 69.0% of the autumn phenophases records show later trends. For spring/summer phenophases, the mean advance across all the taxonomic groups was 2.75 days decade(-1) ranging between 2.11 and 6.11 days decade(-1) for insects and amphibians, respectively. Herbs and amphibians show significantly stronger advancement than trees, shrubs and insect. The response of phenophases of different taxonomic groups in autumn is more complex: trees, shrubs, herbs and insects show a delay between 1.93 and 4.84 days decade(-1), while other groups reveal an advancement ranging from 1.10 to 2.11 days decade(-1) . For woody plants (including trees and shrubs), the stronger shifts toward earlier spring/summer were detected from the data series starting from more recent decades (1980s-2000s). The geographic factors (latitude, longitude and altitude) could only explain 9% and 3% of the overall variance in spring/summer and autumn phenological trends, respectively. The rate of change in spring/summer phenophase of woody plants (1960s-2000s) generally matches measured local warming across 49 sites in China (R=-0.33, P<0.05).

Early millet use in northern China.

It is generally understood that foxtail millet and broomcorn millet were initially domesticated in Northern China where they eventually became the dominant plant food crops. The rarity of older archaeological sites and archaeobotanical work in the region, however, renders both the origins of these plants and their processes of domestication poorly understood. Here we present ancient starch grain assemblages recovered from cultural deposits, including carbonized residues adhering to an early pottery sherd as well as grinding stone tools excavated from the sites of Nanzhuangtou (11.5-11.0 cal kyBP) and Donghulin (11.0-9.5 cal kyBP) in the North China Plain. Our data extend the record of millet use in China by nearly 1,000 y, and the record of foxtail millet in the region by at least two millennia. The patterning of starch residues within the samples allow for the formulation of the hypothesis that foxtail millets were cultivated for an extended period of two millennia, during which this crop plant appears to have been undergoing domestication. Future research in the region will help clarify the processes in place.

Geographical pattern in first bloom variability and its relation to temperature sensitivity in the USA and China.

Advance in spring plant phenology over the last several decades has been found in all continents of the Northern Hemisphere. Compared to the studies detecting phenological trends, the studies investigating the geographical pattern of phenological variability (including mean date and magnitude of variability) are rather limited. In this study, we analyzed spatial pattern of mean date and standard deviation (SD) of first bloom date (FBD) time series (≥15 years) for black locust (Robinia pseudoacacia) at 22 stations in China, common lilac (Syringa vulgaris) at 79 stations in the Western US and Chinese lilac (Syringa chinensis) at 45 stations in the Eastern US. Subsequently, the impact of geographical factors (latitude, longitude, and altitude) on the mean date and SD was quantified by using the multiple regression analysis method. Meanwhile, the relationship between FBD variability and temperature sensitivity of FBD was examined. Results showed that the mean FBD highly depended on geographical factors for all the three species. Compared to the mean date, the dependence of SD of FBD time series on geographical factors was weaker. The geographical factors could only explain 13 to 31 % of spatial variance in SD of FBD. The negative regression coefficients of latitude (P < 0.05 except black locust) indicated that FBD is more variable at lower latitude. At most of stations, significant and negative correlations between FBD and preseason temperature on interannual scale were found, but the temperature sensitivity varied among different stations. The magnitude of temperature sensitivity decreased with increasing latitude. In general, the locations at lower latitude had earlier and more variable spring phenophase and showed stronger phenological response to climate change than the locations at higher latitude.

CERES-Maize model-based simulation of climate change impacts on maize yields and potential adaptive measures in Heilongjiang Province, China.

BACKGROUND: Climate change would cause negative impacts on future agricultural production and food security. Adaptive measures should be taken to mitigate the adverse effects. The objectives of this study were to simulate the potential effects of climate change on maize yields in Heilongjiang Province and to evaluate two selected typical household-level autonomous adaptive measures (cultivar changes and planting time adjustments) for mitigating the risks of climate change based on the CERES-Maize model. RESULTS: The results showed that flowering duration and maturity duration of maize would be shortened in the future climate and thus maize yield would reduce by 11-46% during 2011-2099 relative to 1981-2010. Increased CO2 concentration would not benefit maize production significantly. However, substituting local cultivars with later-maturing ones and delaying the planting date could increase yields as the climate changes. CONCLUSION: The results provide insight regarding the likely impacts of climate change on maize yields and the efficacy of selected adaptive measures by presenting evidence-based implications and mitigation strategies for the potential negative impacts of future climate change.

Simulating changes in the leaf unfolding time of 20 plant species in China over the twenty-first century.

Recent shifts in phenology reflect the biological response to current climate change. Aiming to enhance our understanding of phenological responses to climate change, we developed, calibrated and validated spatio-temporal models of first leaf date (FLD) for 20 broadleaved deciduous plants in China. Using daily meteorological data from the Chinese Meteorological Administration and the Community Climate System Model, version 3 (CCSM3) created using three IPCC scenarios (A2, A1B and B1), we described the FLD time series of each species over the past 50 years, extrapolating from these results to simulate estimated FLD changes for each species during the twenty-first century. Model validation suggests that our spatio-temporal models can simulate FLD accurately with R² (explained variance) >0.60. Model simulations show that, from 1952 to 2007, the FLD in China advanced at a rate of -1.14 days decade⁻¹) on average. Furthermore, changes in FLD showed noticeable variation between regions, with clearer advances observed in the north than in the south of the country. The model indicates that the advances in FLD observed from 1952-2007 in China will continue over the twenty-first century, although significant differences among species and different climate scenarios are expected. The average trend of FLD advance in China during the twenty-first century is modeled as being -1.92 days decade⁻¹ under the A2 scenario, -1.10 days decade⁻¹ under the A1B scenario and -0.74 days decade⁻¹ under the B2 scenario. The spatial pattern of FLD change for the period 2011-2099 is modeled as being similar but showing some difference from patterns in the 1952-2007 period. At the interspecific level, early-leafing species were found to show a greater advance in FLD, while species with larger distributions tended to show a weaker advance in FLD. These simulated changes in phenology may have significant implications for plant distribution as well as ecosystem structure and function.

The spatial pattern of leaf phenology and its response to climate change in China.

Leaf phenology has been shown to be one of the most important indicators of the effects of climate change on biological systems. Few such studies have, however, been published detailing the relationship between phenology and climate change in Asian contexts. With the aim of quantifying species' phenological responsiveness to temperature and deepening understandings of spatial patterns of phenological and climate change in China, this study analyzes the first leaf date (FLD) and the leaf coloring date (LCD) from datasets of four woody plant species, Robinia pseudoacacia, Ulmus pumila, Salix babylonica, and Melia azedarach, collected from 1963 to 2009 at 47 Chinese Phenological Observation Network (CPON) stations spread across China (from 21° to 50° N). The results of this study show that changes in temperatures in the range of 39-43 days preceding the date of FLD of these plants affected annual variations in FLD, while annual variations in temperature in the range of 71-85 days preceding LCD of these plants affected the date of LCD. Average temperature sensitivity of FLD and LCD for these plants was -3.93 to 3.30 days °C(-1) and 2.11 to 4.43 days °C⁻¹, respectively. Temperature sensitivity of FLD was found to be stronger at lower latitudes or altitude as well as in more continental climates, while the response of LCD showed no consistent pattern. Within the context of significant warming across China during the study period, FLD was found to have advanced by 5.44 days from 1960 to 2009; over the same period, LCD was found to have been delayed by 4.56 days. These findings indicate that the length of the growing season of the four plant species studied was extended by a total of 10.00 days from 1960 to 2009. They also indicate that phenological response to climate is highly heterogeneous spatially.