Publications by authors named "Junhu Dai"

21 Publications

  • Page 1 of 1

A new method for broad-scale modeling and projection of plant assemblages under climatic, biotic, and environmental cofiltering.

Conserv Biol 2021 Jun 15. Epub 2021 Jun 15.

Environmental Science Center, Qatar University, Doha, P.O. Box 2713, Qatar.

There is increasing interest in broad-scale analysis, modeling, and prediction of the distribution and composition of plant species assemblages under climatic, environmental, and biotic filtering, particularly for conservation purposes. We devised a method (broad-scale analysis & modeling of plant assemblages under climatic-biotic-environmental co-filtering, BAM-PACC) for reliably predicting the impact of climate change on arbitrarily large assemblages of plant communities, while also considering competing biotic and abiotic factors. When applied to a large set of plant communities in the Swiss Alps, BAM-PACC explained presences/absences of 175 plant species in 608 plots with >87% cross-validated accuracy, predicted decreases in α, β, and γ diversity by 2040 under both moderate and extreme climate scenarios, and identified plant species likely to be favored/disfavored by climate change. BAM-PACC also revealed the importance of topography and soil in determining the distribution of plant species and their response to climate change, and showed the overriding importance of temperature extremes rather than averages. BAM-PACC was able to address a number of challenging research problems, such as scaling to large numbers of species, exploiting species relationships, dealing with species rarity, and overwhelming proportion of absences in the presence/absence matrix. By handling hundreds/thousands of plants and plots simultaneously over large areas, BAM-PACC can help broad-scale conservation of plant species under climate change, as it allows species that require urgent conservation planning and policies (assisted migration, seed conservation, ex-situ conservation) to be detected and prioritized. BAM-PACC can also increase the practicality of assisted colonization of plant species, by helping to prevent ill-advised introduction of plant species with limited future survival probability in a certain area. This article is protected by copyright. All rights reserved.
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http://dx.doi.org/10.1111/cobi.13797DOI Listing
June 2021

Effects of ambient climate and three warming treatments on fruit production in an alpine, subarctic meadow community.

Am J Bot 2021 03;108(3):411-422

Department of Plant and Environmental Sciences, University of Gothenburg, P.O. Box 461, SE-405 30, Gothenburg, Sweden.

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.
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http://dx.doi.org/10.1002/ajb2.1631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8251864PMC
March 2021

Overestimation of the effect of climatic warming on spring phenology due to misrepresentation of chilling.

Nat Commun 2020 10 2;11(1):4945. Epub 2020 Oct 2.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China.

Spring warming substantially advances leaf unfolding and flowering time for perennials. Winter warming, however, decreases chilling accumulation (CA), which increases the heat requirement (HR) and acts to delay spring phenology. Whether or not this negative CA-HR relationship is correctly interpreted in ecosystem models remains unknown. Using leaf unfolding and flowering data for 30 perennials in Europe, here we show that more than half (7 of 12) of current chilling models are invalid since they show a positive CA-HR relationship. The possible reason is that they overlook the effect of freezing temperature on dormancy release. Overestimation of the advance in spring phenology by the end of this century by these invalid chilling models could be as large as 7.6 and 20.0 days under RCPs 4.5 and 8.5, respectively. Our results highlight the need for a better representation of chilling for the correct understanding of spring phenological responses to future climate change.
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http://dx.doi.org/10.1038/s41467-020-18743-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7532433PMC
October 2020

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

Int J Biometeorol 2021 Mar 2;65(3):393-403. Epub 2020 Sep 2.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 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.
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http://dx.doi.org/10.1007/s00484-020-02007-7DOI Listing
March 2021

Phenological changes in herbaceous plants in China's grasslands and their responses to climate change: a meta-analysis.

Int J Biometeorol 2020 Nov 30;64(11):1865-1876. Epub 2020 Jul 30.

State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.

Plant phenological events are sensitive indicators of climate change, and their change could markedly affect the structure and function of ecosystems. Previous studies have revealed the spatiotemporal variations in the phenological events of woody plants. However, limited studies have focused on the phenophases of herbaceous plants. In this study, by using a meta-analysis method, we extracted information about the phenological changes in herbaceous plants in China's grasslands from existing studies (including the period, station, species, phenophases, phenological trends, and climatic determinants) and analyzed the patterns manifested in the dataset. The results showed that the spring phenophases (e.g., first leaf date and first flowering date) of the herbaceous plants mainly advanced over the past 30 years, but a large difference existed across grassland types. The spring phenophases of forages (species from the Cyperaceae, Gramineae, and Leguminosae families) became earlier in the desert steppe and alpine steppe but showed no apparent trends in the alpine meadow and even became later in the meadow steppe and typical steppe. In most cases, the increase in spring temperatures and precipitation promoted the greening up of herbaceous plants, while sunshine duration was positively correlated with the green-up date of herbaceous plants. For the autumn phenophases, the proportions of the earlier and later trends were very close, but the trends varied among the grassland types. The leaf coloring dates of the forages were delayed in the meadow steppe and alpine steppe but showed no distinct pattern in the typical steppe or alpine meadow and even became earlier in the desert steppe. In most cases, the increase in growing season temperature led to an earlier leaf coloring date of the herbaceous plants, but the increase in the preseason precipitation delayed the leaf coloring date. Our results suggested that the phenophases of herbaceous plants have complicated responses to multiple environmental factors, which makes predicting future phenological changes difficult.
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http://dx.doi.org/10.1007/s00484-020-01974-1DOI Listing
November 2020

Responses of Autumn Phenology to Climate Change and the Correlations of Plant Hormone Regulation.

Sci Rep 2020 06 3;10(1):9039. Epub 2020 Jun 3.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing, 100101, China.

Current understanding of autumn phenological responses to climate change in deciduous tree species remains limited, mainly due to the difficulties in defining autumn events and the lack of knowledge about its mechanism. Here we applied a method based on measuring chlorophyll A (Chla) content in leaf tissue during the entire autumn senescence processes to appropriately quantify autumn phenological processes. Beginning of leaf coloring could be defined as when about 50% of the Chl was lost. End of leaf coloring could be defined as when about 95% of the Chl was lost. Then the mechanism behind the timing of autumn senescence responses to climate change through hormone regulation was studied for the first time. Four dominate deciduous tree species with representative senescence type (Salix babylonica, Ginkgo biloba, Acer mono, Cotinus coggygria) were chosen as the subject of study. Variations in climate factors (temperature, day length, precipitation, humidity) were recorded and nine major endogenous hormones (IAA, IPA, ZR, DHZR, GA, GA, ABA, MeJA, BR) in leaf tissues were monitored during the entire autumn senescence processes. The experimental results verified temperature and day length are the major climate factors affecting autumn phenology. Low temperature and short day length could result in the decrease of ZR level and the increase of ABA level in leaf tissue, which directly trigger/promote senescence. Meanwhile, low temperature and short day length could cause the decrease of MeJA level and the increase of GA and GA level, which regulate the timing of autumn senescence indirectly through ZR, ABA, and IAA. Our study improves the understanding of autumn phenological response to climate change in deciduous trees.
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http://dx.doi.org/10.1038/s41598-020-65704-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7270090PMC
June 2020

The Interactive Effects of Chilling, Photoperiod, and Forcing Temperature on Flowering Phenology of Temperate Woody Plants.

Front Plant Sci 2020 16;11:443. Epub 2020 Apr 16.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.

The effects of winter chilling, spring forcing temperature, and photoperiod on spring phenology are well known for many European and North American species, but the environmental cues that regulate the spring phenology of East Asian species have not yet been thoroughly investigated. Here, we conducted a growth chamber experiment to test the effects of chilling (controlled by different lengths of exposure to natural chilling conditions), forcing temperature (12, 15, or 18°C) and photoperiod (14 or 10 h) on first flowering date (FFD) of six woody species (three shrubs and three trees) native to East Asia. The three-way analysis of variance (ANOVA) separately for each species showed that the effects of chilling and forcing temperature were significant for almost all species ( < 0.05). Averaged over all chilling and photoperiod treatments, the number of days until FFD decreased by 2.3-36.1 days when the forcing temperature increased by 3°C. More chilling days reduced the time to FFD by 0.7-26 days, when averaged over forcing and photoperiod treatments. A longer photoperiod could advance the FFD by 1.0-5.6 days, on average, but its effect was only significant for two species (including one tree and one shrub). The effects of forcing temperature and photoperiod interacted with chilling for half of the studied species, being stronger in the low chilling than high chilling treatment. These results could be explained by the theory and model of growing degree-days (GDD). Increased exposure to chilling coupled to a longer photoperiod reduced the GDD requirement for FFD, especially when plants grew under low chilling conditions. However, shrubs (except ) had lower chilling and heat requirements than trees, suggesting that, by leafing out sooner, they engage in a more opportunistic life strategy to maximize their growing season, especially before canopy closure from trees' foliage. Our results confirmed the varying effects of these three cues on the flowering phenology of woody species native to East Asia. In future climate change scenarios, spring warming is likely to advance the spring phenology of those woody species, although the reduced chilling and shorter photoperiod may partly offset this spring warming effect.
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http://dx.doi.org/10.3389/fpls.2020.00443DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7176907PMC
April 2020

Plant phenology and global climate change: Current progresses and challenges.

Glob Chang Biol 2019 06 1;25(6):1922-1940. Epub 2019 Apr 1.

Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong.

Plant phenology, the annually recurring sequence of plant developmental stages, is important for plant functioning and ecosystem services and their biophysical and biogeochemical feedbacks to the climate system. Plant phenology depends on temperature, and the current rapid climate change has revived interest in understanding and modeling the responses of plant phenology to the warming trend and the consequences thereof for ecosystems. Here, we review recent progresses in plant phenology and its interactions with climate change. Focusing on the start (leaf unfolding) and end (leaf coloring) of plant growing seasons, we show that the recent rapid expansion in ground- and remote sensing- based phenology data acquisition has been highly beneficial and has supported major advances in plant phenology research. Studies using multiple data sources and methods generally agree on the trends of advanced leaf unfolding and delayed leaf coloring due to climate change, yet these trends appear to have decelerated or even reversed in recent years. Our understanding of the mechanisms underlying the plant phenology responses to climate warming is still limited. The interactions between multiple drivers complicate the modeling and prediction of plant phenology changes. Furthermore, changes in plant phenology have important implications for ecosystem carbon cycles and ecosystem feedbacks to climate, yet the quantification of such impacts remains challenging. We suggest that future studies should primarily focus on using new observation tools to improve the understanding of tropical plant phenology, on improving process-based phenology modeling, and on the scaling of phenology from species to landscape-level.
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http://dx.doi.org/10.1111/gcb.14619DOI Listing
June 2019

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

Int J Biometeorol 2019 May 16;63(5):569-577. Epub 2017 Dec 16.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.

Continuous long-term temperature sensitivity (S) 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 S 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 S of LUD for all plant species was - 3.2 ± 0.49 days °C. The moving window analysis revealed that 75% of species displayed increasing S of LUD, with 55% showing significant increases (P < 0.05). S for the other 25% exhibited a decreasing trend, with 17% showing significant decreases (P < 0.05). On average, S increased by 16%, from - 2.8 ± 0.83 days °C during 1980-1994 to - 3.30 ± 0.65 days °C during 2000-2014. For species with later LUD and longer OP, S tended to increase more, while species with earlier LUD and shorter OP tended to display a decreasing S. The standard deviation of preseason temperature impacted the temporal variation in S. Chilling conditions influenced S for some species, but photoperiod limitation did not have significant or coherent effects on changes in S.
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http://dx.doi.org/10.1007/s00484-017-1489-8DOI Listing
May 2019

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

Int J Biometeorol 2019 May 25;63(5):579-590. Epub 2017 May 25.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 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), with 7.5% of species significantly. However, FD on average extended by 0.42 and 0.93 days decade 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 (R) ranging from 0.37 to 0.67, but fail to simulate the changes in FD accurately (R ranging from 0.09 to 0.18). The growing degree day model could improve the R 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.
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http://dx.doi.org/10.1007/s00484-017-1377-2DOI Listing
May 2019

Comment on "Outburst flood at 1920 BCE supports historicity of China's Great Flood and the Xia dynasty".

Science 2017 03;355(6332):1382

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.

Wu (Reports, 5 August 2016, p. 579) reported geological and archaeological evidence about an earthquake-induced landslide dam outburst flood around 1920 BCE and claimed a support to the historicity of China's legendary Great Flood and Xia dynasty. We argue that the physical evidence is unreliable and their arguments are unconvincing.
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http://dx.doi.org/10.1126/science.aal1278DOI Listing
March 2017

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

Int J Biometeorol 2016 Dec 23;60(12):2005-2007. Epub 2016 Nov 23.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.

Temperature sensitivity of plant phenology (S) 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 S 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 S to climate warming is misleading, and future S changes are more uncertain than they suggested.
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http://dx.doi.org/10.1007/s00484-016-1264-2DOI Listing
December 2016

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

Int J Biometeorol 2017 Feb 28;61(2):287-292. Epub 2016 Jul 28.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.

The impact of spring temperature forcing on the timing of leaf unfolding of plants (temperature sensitivity, S) 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 S 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 S 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 S over decadal time scales extending the data series back to 1951. Our results demonstrate that S 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). This result suggests that the significant decrease in S 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 S changes in warming scenarios are still uncertain.
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http://dx.doi.org/10.1007/s00484-016-1210-3DOI Listing
February 2017

Parameterization of temperature sensitivity of spring phenology and its application in explaining diverse phenological responses to temperature change.

Sci Rep 2015 Mar 6;5:8833. Epub 2015 Mar 6.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences. Beijing, China.

Existing evidence of plant phenological change to temperature increase demonstrates that the phenological responsiveness is greater at warmer locations and in early-season plant species. Explanations of these findings are scarce and not settled. Some studies suggest considering phenology as one functional trait within a plant's life history strategy. In this study, we adapt an existing phenological model to derive a generalized sensitivity in space (SpaceSens) model for calculating temperature sensitivity of spring plant phenophases across species and locations. The SpaceSens model have three parameters, including the temperature at the onset date of phenophases (Tp), base temperature threshold (Tb) and the length of period (L) used to calculate the mean temperature when performing regression analysis between phenology and temperature. A case study on first leaf date of 20 plant species from eastern China shows that the change of Tp and Tb among different species accounts for interspecific difference in temperature sensitivity. Moreover, lower Tp at lower latitude is the main reason why spring phenological responsiveness is greater there. These results suggest that spring phenophases of more responsive, early-season plants (especially in low latitude) will probably continue to diverge from the other late-season plants with temperatures warming in the future.
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http://dx.doi.org/10.1038/srep08833DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4351518PMC
March 2015

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

Int J Biometeorol 2015 Aug 14;59(8):961-9. Epub 2014 Oct 14.

Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A, Datun Road, Chaoyang District, Beijing, 100101, People's Republic of 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.
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http://dx.doi.org/10.1007/s00484-014-0909-2DOI Listing
August 2015

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

Glob Chang Biol 2015 Jan 24;21(1):265-74. Epub 2014 Jun 24.

Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.

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).
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http://dx.doi.org/10.1111/gcb.12648DOI Listing
January 2015

Spatiotemporal analysis of ground-based woody plant leafing in response to temperature in temperate eastern China.

Int J Biometeorol 2014 Sep 20;58(7):1583-92. Epub 2013 Nov 20.

Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.

The analysis of woody plant leafing in response to regional-scale temperature variation using ground-based phenology is usually limited by the sparse coverage and missing data of ground observation. In this study, a station-based multispecies method was proposed to generate spatiotemporal variation of woody plant leafing date using ground observations from the Chinese Phenological Observation Network during 1974-1996. The results show that the leafing date had slightly insignificant advance (-0.56 day decade(-1)), and the Arctic Oscillation (AO) index could explain 36% variance of the spring leafing date anomaly. The leafing date had been substantially delayed (4 days) when AO shifted from an extreme high index state (2) in 1989-1990 to a relatively low state (0.1) in 1991-1996. The canonical correlation analysis (CCA) was used to demonstrate the temporal evolutions and spatial structures of interannual variations of the spring temperature and leafing date anomalies. The three CCA spatial patterns of leafing date anomaly are similar to those of spring temperature anomaly. The first spatial pattern shows ubiquitous warming, which is consistent with the ubiquitous advance in leafing date across the study area. The second and third spatial patterns present the regional differences featured by advanced (delayed) leafing associated with high (low) temperature. The results suggest that the spring leafing date anomaly is spatiotemporally coherent with the regional-scale temperature variations. Although we focus here on woody plant leafing in a historical period in temperate eastern China, our station-based multispecies method may be applicable to analysis of the ground-based phenology in response to regional-scale climatic variation in other regions.
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http://dx.doi.org/10.1007/s00484-013-0762-8DOI Listing
September 2014

Chilling and heat requirements for flowering in temperate fruit trees.

Int J Biometeorol 2014 Aug;58(6):1195-206

Climate change has affected the rates of chilling and heat accumulation, which are vital for flowering and production, in temperate fruit trees, but few studies have been conducted in the cold-winter climates of East Asia. To evaluate tree responses to variation in chill and heat accumulation rates, partial least squares regression was used to correlate first flowering dates of chestnut (Castanea mollissima Blume) and jujube (Zizyphus jujube Mill.) in Beijing, China, with daily chill and heat accumulation between 1963 and 2008. The Dynamic Model and the Growing Degree Hour Model were used to convert daily records of minimum and maximum temperature into horticulturally meaningful metrics. Regression analyses identified the chilling and forcing periods for chestnut and jujube. The forcing periods started when half the chilling requirements were fulfilled. Over the past 50 years, heat accumulation during tree dormancy increased significantly, while chill accumulation remained relatively stable for both species. Heat accumulation was the main driver of bloom timing, with effects of variation in chill accumulation negligible in Beijing’s cold-winter climate. It does not seem likely that reductions in chill will have a major effect on the studied species in Beijing in the near future. Such problems are much more likely for trees grown in locations that are substantially warmer than their native habitats, such as temperate species in the subtropics and tropics.
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http://dx.doi.org/10.1007/s00484-013-0714-3DOI Listing
August 2014

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

Int J Biometeorol 2014 May 4;58(4):521-8. Epub 2013 Jun 4.

Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, A 11, Datun Road, Chaoyang District, Beijing, 100101, People's Republic of 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.
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http://dx.doi.org/10.1007/s00484-013-0679-2DOI Listing
May 2014

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

Int J Biometeorol 2014 May 22;58(4):473-84. Epub 2013 May 22.

Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, A 11, Datun Road, Chaoyang District, Beijing, 100101, People's Republic of China.

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.
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http://dx.doi.org/10.1007/s00484-013-0671-xDOI Listing
May 2014

Multiple phenological responses to climate change among 42 plant species in Xi'an, China.

Int J Biometeorol 2013 Sep 1;57(5):749-58. Epub 2012 Nov 1.

Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, A11 Datun Road, Chaoyang District, Beijing 100101, People's Republic of China.

Phenological data of 42 woody plants in a temperate deciduous forest from the Chinese Phenological Observation Network (CPON) and the corresponding meteorological data from 1963 to 2011 in Xi'an, Shaanxi Province, China were collected and analyzed. The first leaf date (FLD), leaf coloring date (LCD) and first flower date (FFD) are revealed as strong biological signals of climatic change. The FLD, LCD and FFD of most species are sensitive to average temperature during a certain period before phenophase onset. Regional precipitation also has a significant impact on phenophases of about half of the species investigated. Affected by climate change, the FLD and FFD of these species have advanced by 5.54 days and 10.20 days on average during 2003-2011 compared with the period 1963-1996, respectively. Meanwhile, the LCD has delayed by 10.59 days, and growing season length has extended 16.13 days. Diverse responses of phenology commonly exist among different species and functional groups during the study period. Especially for FFD, the deviations between the above two periods ranged from -20.68 to -2.79 days; biotic pollination species showed a significantly greater advance than abiotic pollination species. These results were conducive to the understanding of possible changes in both the structure of plant communities and interspecific relationships in the context of climate change.
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http://dx.doi.org/10.1007/s00484-012-0602-2DOI Listing
September 2013
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