The effects of climate change on plant phenological events such as flowering, leaf flush, and leaf fall may be greater in steep river basins than at the horizontal scale of countries and continents. ...This possibility is due to the effect of temperature on plant phenology and the difference between vertical and horizontal gradients in temperature sensitivities. We calculated the dates of the start (SGS) and end of the growing season (EGS) in a steep river basin located in a mountainous region of central Japan over a century timescale by using a degree-day phenological model based on long-term, continuous, in situ observations. We assessed the generality and representativeness of the modelled SGS and EGS dates by using phenological events, live camera images taken at multiple points in the basin, and satellite observations made at a fine spatial resolution. The sensitivity of the modelled SGS and EGS dates to elevation changed from 3.29 days (100 m).sup.-1 (-5.48 days °C.sup.-1) and -2.89 days (100 m).sup.-1 (4.81 days °C.sup.-1 ), respectively, in 1900 to 2.85 days (100 m).sup.-1 (-4.75 days °C.sup.-1) and -2.84 day (100 m).sup.-1 (4.73 day °C.sup.-1) in 2019. The long-term trend of the sensitivity of the modelled SGS date to elevation was -0.0037 day year.sup.-1 per 100 m, but the analogous trend in the case of the modelled EGS date was not significant. Despite the need for further studies to improve the generality and representativeness of the model, the development of degree-day phenology models in multiple, steep river basins will deepen our ecological understanding of the sensitivity of plant phenology to climate change.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Spatiotemporal prediction of the response of planted forests to a changing climate is increasingly important for the sustainable management of forest ecosystems. In this study, we present a ...methodology for estimating spatially varying productivity in a planted forest and changes in productivity with a changing climate in Japan, with a focus on Japanese cedar (Cryptomeria japonica D. Don) as a representative tree species of this region. The process-based model Biome-BGC was parameterized using a plant trait database for Japanese cedar and a Bayesian optimization scheme. To compare productivity under historical (1996-2000) and future (2096-2100) climatic conditions, the climate scenarios of two representative concentration pathways (i.e., RCP2.6 and RCP8.5) were used in five global climate models (GCMs) with approximately 1-km resolution. The seasonality of modeled fluxes, namely gross primary production, ecosystem respiration, net ecosystem exchange, and soil respiration, improved after two steps of parameterization. The estimated net primary production (NPP) of stands aged 36-40 years under the historical climatic conditions of the five GCMs was 0.77 ± 0.10 kgC m-2 year-1 (mean ± standard deviation), in accordance with the geographical distribution of forest NPP estimated in previous studies. Under the RCP2.6 and RCP8.5 scenarios, the mean NPP of the five GCMs increased by 0.04 ± 0.07 and 0.14 ± 0.11 kgC m-2 year-1, respectively. The increases in annual NPP were small in the southwestern region because of the decreases in summer NPP and the small increases in winter NPP under the RCP2.6 and RCP8.5 scenarios, respectively. Under the RCP2.6 scenario, Japanese cedar was at risk in the southwestern region, in accordance with previous studies, and monitoring and silvicultural practices should be modified accordingly.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The epithelial-mesenchymal transition (EMT) is a crucial morphological event that occurs during the progression of epithelial tumors. EMT can be induced by transforming growth factor β (TGF-β) in ...certain kinds of cancer cells through the induction of Snail, a key regulator of EMT. We have previously found that TGF-β remarkably induces Snail expression in cooperation with Ras signals; however, the underlying mechanism of this synergism has not yet been determined. Here, we demonstrate that signal transducer and activator of transcription 3 (STAT3) acts as a mediator that synergizes TGF-β and Ras signals. The overexpression of STAT3 enhanced Snail induction, whereas siRNA-mediated knockdown of STAT3 inhibited it. The STAT3-YF mutant, which has Tyr 705 substituted with Phe, did not enhance Snail induction. Several STAT3 mutants lacking transcriptional activity also failed to enhance it; however, the putative STAT3-binding elements in the Snail promoter regions were not required for STAT3-mediated Snail induction. Protein inhibitor of activated STAT3 (PIAS3) inhibited the enhanced Snail promoter activity induced by TGF-β and Ras. The interaction between PIAS3 and STAT3 was reduced by TGF-β in cells harboring oncogenic Ras, whereas TGF-β promoted the binding of PIAS3 to Smad3, a crucial mediator of TGF-β signaling. Therefore, these findings suggest that STAT3 enhances Snail induction when it is dissociated from PIAS3 by TGF-β in cooperation with Ras signals.
The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial carbon dioxide fluxes in Asia. In this study, we developed such a ...standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem carbon dioxide exchange (NEE). Data-driven estimation was conducted by using a machine learning algorithm: support vector regression (SVR), with remote sensing data for 2000 to 2015 period. Site-level evaluation of the estimated carbon dioxide fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8 days are reproduced (e.g., r (exp 2) =0.73 and 0.42 for 8 day GPP and NEE). Evaluation of spatially estimated GPP with Global Ozone Monitoring Experiment 2 sensor-based Sun-induced chlorophyll fluorescence shows that monthly GPP variations at subcontinental scale were reproduced by SVR (r (exp 2)=1.00, 0.94, 0.91, and 0.89 for Siberia, East Asia, South Asia, and Southeast Asia, respectively). Evaluation of spatially estimated NEE with net atmosphere-land carbon dioxide fluxes of Greenhouse Gases Observing Satellite (GOSAT) Level 4A product shows that monthly variations of these data were consistent in Siberia and East Asia; meanwhile, inconsistency was found in South Asia and Southeast Asia. Furthermore, differences in the land carbon dioxide fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land carbon dioxide fluxes. These data-driven estimates can provide a new opportunity to assess carbon dioxide fluxes in Asia and evaluate and constrain terrestrial ecosystem models.
We propose reservoir computing (RC), a framework for constructing recurrent neural networks (RNNs) with simple training rule, using ferroelectric tunnel junction (FTJ) crossbar array. Not only the ...weights of connection between reservoir layer and output layer need to be trained, but also random fixed weights within reservoir layer can be realized by the conductance of FTJs. Random weights within reservoir layers have optimal variability, which is dependent not on the type of the distribution but on the reservoir size. Optimal variability can be attained by device-to-device variability in FTJs together with analog converters on the wordlines and the bitlines. Analog resistive switching characteristics in FTJs can also realize the weights connected to output layer, which need to be trained. Furthermore, device-to-device variability in HfFormula OmittedZrxO2 (HZO) FTJ is extensively investigated. Taking into account the low current operation in FTJs, RC with FTJ crossbar array is a potential candidate for neuromorphic computing system with low power consumption.
In Japan, the geographical distribution of the first date of flowering (FFD) of Yoshino cherry trees (
Cerasus
×
yedoensis
) in 2020, a year when temperatures were mild during the previous December ...and March, was different from the average FFD, which progresses northward along a latitudinal gradient. We hypothesized that global warming may have changed the average geographical pattern of the FFD. To test this hypothesis, we examined the relationship between the observed FFD and latitude at 42 sites during the period 1953–2020. We found that the correlation between FFD and latitude had decreased since 1980. This decrease may have been caused by a rise of temperatures in winter that delayed dormancy release and the subsequent FFD in areas where the annual mean temperature is high. Our results suggest that the correlation between FFD and latitude will decrease further as the climate warms in the future.
To achieve a sustainable society and solve the problems caused by climate change and socioeconomic activities, it is necessary to monitor the spatial and temporal variability of ecosystem functions, ...services, and biodiversity at both regional and global scales. During the last decade, we have seen rapid and significant improvement in satellite and near‐surface remote‐sensing technologies. In this review, we describe how remote‐sensing observations are being used to effectively evaluate the spatial and temporal variability of land use and cover types and of plant phenology in East Asia. We discuss the current status, uncertainties, problems, and future perspectives for terrestrial ecosystem and biodiversity monitoring, and we address the multidisciplinary research by incorporating in situ and satellite observations for East Asia. Recent satellites with advanced optical sensors, such as MultiSpectral Instrument/Sentinel‐2A/2B, Advanced Himawari Imager/Himawari‐8, and PlanetScope, and satellites with synthetic aperture radar, such as Advanced Land Observing Satellite‐2, allow detailed monitoring of land use and cover type changes and plant phenology. These satellite sensors can provide images with high spatial (3–10 m) and high temporal (10 min to 5 days) resolution, at both large (≥1 km2) and small (<1 km2) scales. In particular, researchers are expected to develop discrimination techniques that will enable these advanced satellite technologies to detect evergreen broadleaf trees and ways to estimate the geographic distribution of leaf traits. We encourage more collaborations among ecologists, engineers, and remote‐sensing scientists to share their abundant knowledge and experience and thereby improve the monitoring capabilities.
In this review paper, to encourage multidisciplinary research that combines in situ and satellite observations for terrestrial ecosystem and biodiversity monitoring in East Asia, we review the use of remote‐sensing observations that focused on land cover changes and plant phenology in East Asia.
In Japan, cherry blossoms are an important tourism resource and provide many cultural ecosystem service benefits. Under future warming conditions, we will require adaptions such as changing the ...timing of flower festivals to account for changes in the flowering phenology. In this study, we evaluated the coincidence between the flowering phenology of cherry blossoms and the associated festival periods in two Japanese cities under past, recent, and future climate conditions. We examined the situation in Shinhidaka, where the flower festival period changes every year, and Takayama, where the festival period is fixed to coincide with a shrine’s annual spring festival. Currently, the average dates of beginning of flowering (more than four or five flowers open in an index tree; ~BBCH60) and full bloom (equal to or more than 80% of flowers open in an index tree; after BBCH65) in Shinhidaka (day of year (DOY) 126 and 130) are later than the long national holiday of Golden Week (DOY 119 to 125). The respective dates in Takayama (DOY 106 and 111, respectively) are later than the local a festival period (DOY 104 and 105). Under a scenario of 1.0 to 2.0 °C warming, the full blooming dates in Shinhidaka will coincide with Golden Week, whereas under 1.0 to 1.5 °C warming, the full blooming dates in Takayama will coincide with the spring festival period. Thus, moderate warming may increase the value of cherry blossoms to the tourism industry. Under more than 3.5 °C warming in Shinhidaka and 2.5 °C warming in Takayama, however, cherry blossoms will have already dropped by Golden Week and the spring festival period, respectively, suggesting that greater warming may decrease the value of this tourism resource.
•MAT is related to the spatial variability of carbon fluxes in monsoon Asian forests.•GPP exerts stronger control on the spatial variability of carbon fluxes than climate.•NEP is positively related ...to component fluxes in high–mid latitudes.•NEP is negatively related to component fluxes in low latitudes.•Nitrogen deposition and age are potential factors in the unique variability of NEP.
Forest ecosystems sequester large amounts of atmospheric CO2, and the contribution from forests in Asia is not negligible. Previous syntheses of carbon fluxes in Asian ecosystems mainly employed estimates of eddy covariance measurements, net ecosystem production (NEP), gross primary production (GPP), and ecosystem respiration (RE); however, to understand the variability within carbon cycles, fluxes such as autotropic respiration (AR), net primary production (NPP), litterfall, heterotrophic respiration (HR), and soil respiration (SR) need to be analyzed comprehensively in conjunction with NEP, GPP, and RE. Here we investigated the spatial variability of component fluxes of carbon balance (GPP, AR, NPP, litterfall, HR, SR, and RE) in relation to climate factors, between carbon fluxes, and to NEP using observations compiled from the literature for 22 forest sites in monsoon Asia. We found that mean annual temperature (MAT) largely relates to the spatial variability of component fluxes in monsoon Asian forests, with stronger positive effect in the mid–high latitude forests than in the low latitude forests, but even stronger relationships were identified between component fluxes regardless of regions. This finding suggests that the spatial variability of carbon fluxes in monsoon Asia is certainly influenced by climatic factors such as MAT, but that the overall spatial variability of AR, NPP, litterfall, HR, SR, and RE is rather controlled by that of productivity (i.e., GPP). Furthermore, component fluxes of the mid–high and low latitude forests showed positive and negative relationships, respectively, with NEP. Further investigation identified a common spatial variability in NEP and annual aboveground biomass changes with respect to GPP. The relationship between GPP and NEP in the mid–high latitudes implies that productivity and net carbon sequestration increase simultaneously in boreal and temperate forests. Meanwhile, the relationship between GPP and NEP in the low latitudes indicates that net carbon sequestration decreases with productivity, potentially due to the regional contrast in nitrogen depositions and stand age within sub-tropical and tropical forests; however, it requires further data syntheses or modelling investigations for confirmation of its general validity. These unique features of monsoon Asian forest carbon fluxes provide useful information for improving ecosystem model simulations, which still differ in their predictability of carbon flux variability.
How global warming will affect soil respiration (R S) and its source components is poorly understood despite its importance for accurate prediction of global carbon (C) cycles. We examined the ...responses of R S, heterotrophic respiration (R H), autotrophic respiration (R A), nitrogen (N) availability, and fine-root biomass to increased temperature in an open-field soil warming experiment. The experiment was conducted in a cool-temperate deciduous forest ecosystem in northern Japan. As this forest is subjected to strong temporal variation in temperature, on scales ranging from daily to seasonal, we also investigated the temporal variation in the effects of soil warming on R S, R H, and R A. Soil temperature was continuously elevated by about 4.0°C from 2007 to 2014 using heating wires buried in the soil, and we measured soil respiratory processes in all four seasons from 2012 to 2014. Soil warming increased annual R S by 32–45%, but the magnitude of the increase was different between the components: R H and R A were also stimulated, and increased by 39–41 and 17–18%, respectively. Soil N availability during the growing season and fine-root biomass were not remarkably affected by the warming treatment. We found that the warming effects varied seasonally. R H increased significantly throughout the year, but the warming effect showed remarkable seasonal differences, with the maximum stimulation in the spring. This suggests that warmer spring temperature will produce a greater increase in CO₂ release than warmer summer temperatures. In addition, we found that soil warming reduced the temperature sensitivity (Q ₁₀) of R S. Although the Q ₁₀ of both R H and R A tended to be reduced, the decrease in the Q ₁₀ of R S was caused mainly by a decrease in the response of R A to warming. These long-term results indicate that a balance between the rapid and large response of soil microbes and the acclimation of plant roots both play important roles in determining the response of R S to soil warming, and must be carefully considered to predict the responses of soil C dynamics under future temperature conditions.
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