Search Results (58)

Snow serves as a crucial water source for vegetation growth on the Mongolian Plateau, and its temporal and spatial variations exert profound influences on terrestrial vegetation phenology. In recent years, global climate change has led to significant changes in snow and vegetation start of growing season (SOS). Therefore, it is necessary to study the mechanism of snow cover on vegetation growth and changes on the Mongolian Plateau. The study found that the spatial snow cover fraction (SCF) of the Mongolian Plateau ranged from 50% to 60%, and the snow melt date (SMD) ranged from day of the year (DOY) 88 to 220, mainly concentrated on the northwest Mongolian Plateau mountainous areas. Using different SOS methods to calculate the vegetation SOS distribution map. Vegetation SOS occurs earlier in the eastern part compared to the western part of the Mongolian Plateau. In this study, we assessed spatiotemporal distribution characteristics of snow on the Mongolian Plateau over the period from 2001 to 2023. The results showed that the SOS of the Mongolian Plateau was mainly concentrated on DOY 71-186. The Cox survival analysis model system established SCF and SMD on vegetation SOS. The SCF standard coefficient is 0.06, and the SMD standard coefficient is 0.02. The SOS_NDVI coefficient is −0.15, and the SOS_NDGI coefficient is −0.096. The results showed that the vegetation SOS process exhibited differential response characteristics to snow driving factors. These research results also highlight the important role of snow in vegetation phenology and emphasize the importance of incorporating the unique effects of vegetation SOS on the Mongolian Plateau. Full article

Monitoring vegetation phenology is crucial for understanding how plants respond to climate change and how the latter affects the role of vegetated ecosystems in biosphere cycles. It has been reported that the growing season has been extended, leading to an increase in global terrestrial productivity, but not much attention has been given to how different climatic variables affect specific tree species’ phenology. This study focuses on the main phenological events (SOS, Start Of Season; EOS, End Of Season; and LOS, Length Of Season) of two deciduous species (Fagus sylvatica L. and Castanea sativa Mill.) and the effects of temperature and precipitation on them. The analysis concerns a 23-year period (2000–2022) of various sites across southern Europe. The dates for each phenological event are estimated based on NDVI timeseries from MODIS satellite sensor. Both species show an elongation of their growing season, with SOS occurring 2.09 and 1.63 days/decade earlier and EOS 2.97 and 3.03 days/decade later for Fagus sylvatica and Castanea sativa, respectively, with this trend appearing more intense at lower altitudes. Temperature seems to be the major driver for these changes for both species, with higher temperatures before each phenological event leading to earlier SOS and delayed EOS. The effects of precipitation are less homogenous, showing different trends between sites and species. Full article

Spring phenology (start of growing season, SOS) in boreal forests plays a crucial role in the global carbon cycle. At present, more and more researchers are using solar-induced chlorophyll fluorescence (SIF) to evaluate the land surface phenology of boreal forests, but few studies have utilized the primary SIF directly detected by satellites (e.g., GOME-2 SIF) to estimate phenology, and most SIF datasets used are high-resolution products (e.g., GOSIF and CSIF) constructed by models with vegetation indices (VIs) and meteorological data. Thus, the difference and consistency between them in detecting the seasonal dynamics of boreal forests remain unclear. In this study, a comparison of spring phenology from GOME-2 SIF, GOSIF, EVI2 (MCD12Q2), and FLUX tower sites, PEP725 phenology observation sites, was conducted. Compared with GOSIF and EVI2, the primary GOME-2 SIF indicated a slightly earlier spring phenology onset date (about 5 days earlier on average) in boreal forests, at a regional scale; however, SOSs and SOS-climate relationships from GOME-2 SIF, GOSIF, and EVI2 showed significant correlations with the ground observations at a site scale. Regarding the absolute values of spring phenology onset date, GOME-2 SIF and FLUX-GPP had an average difference of 8 days, while GOSIF and EVI2 differed from FLUX-GPP by 16 days and 12 days, respectively. GOME-2 SIF and PEP725 had an average difference of 38 days, while GOSIF and EVI2 differed from PEP725 by 24 days and 23 days, respectively. This demonstrated the complementary roles of the three remote sensing datasets when studying spring phenology and its relationship with climate in boreal forests, enriching the available remote sensing data sources for phenological research. Full article

Under global climate change, fragmented urban vegetation is more susceptible to the external environment, and changes in vegetation phenology are one of the most apparent responses. In this study, phenological camera (phenocamera) photo data, Klosterman curve fitting, and a Gu model were employed to explore the phenological characteristics of an urban forest at different levels within different species. Differences between species and groups regarding the upturn date (UD), the stabilization date (SD), the downturn date (DD), the recession date (RD), and the length of the growing season (LOS) are displayed in detail. We found that the UD of Cinnamomum camphora groups began in late April (day of year 108th), the SD appeared in early May (121st), and the DD started in early October (283rd) and ended in late October (293rd), with an average LOS of 185 days. The phenological characteristics of the Cinnamomum camphora and Bischofia polycarpa groups differed significantly. The average LOS of Bischofia polycarpa was 47 days longer than that of Cinnamomum camphora. Between Cinnamomum camphora individuals and group levels, differences in the UD and the SD were not obvious, while differences in the DD, the RD, and the LOS were large (LOS > RD > DD). The LOS of Cinnamomum camphora was longer on the individual scale (209 days), while the average LOS on the group scale was 185 days. In conclusion, our results reflect the more refined quantitative results of urban vegetation phenology and will help to elucidate urban vegetation phenological changes, which has important theoretical and practical significance for future urban forest management practices. Full article

Exploring the relationship between leaf and xylem growth and nitrogen (N) deposition on tree growth helps us better understand how N deposition affects tree growth, but relevant studies are still limited. We tested if leaf and xylem growth and their relationship were affected by N deposition across multiple stages of leaf development. We studied two dominant tree species (Castanopsis chinensis and Schima superba) in a subtropical forest in South China, monitoring their leaf and xylem growth traits under canopy N addition of 0 (CK) and 50 kg N ha⁻¹ year⁻¹ (CAN) and compared these traits and their relationships across different treatments, periods, and species. We found that CAN significantly increased C. chinensis’s leaf carbon (C) content, while the same treatment reduced leaf C content in S. superba. Specific leaf area (SLA), specific leaf weight (SLW), leaf N content, and C:N ratio showed more variation between species and within species across developmental stages than in response to different N addition treatments. Nitrogen addition also significantly increased the xylem width in both species, but the weekly xylem increment before July was notably higher in S. superba than in C. chinensis. Moreover, the leaf C content during early leaf development (ELD) following N addition was significantly and negatively correlated with the start date of xylogenesis in C. chinensis but had no significant effect on the onset of xylogenesis in S. superba. Additionally, regardless of species, SLA in ELD was negatively correlated with xylem width at the end of the early growing season (EW) under CK. However, this relationship became insignificant under CAN, suggesting that N addition alleviated the trade-off between SLA in ELD and EW. These results demonstrated that the relationship between leaf and xylem growth is influenced by both the leaf developmental stage and N availability. Traditional analyses of the leaf–xylem relationship, based solely on mature leaf traits, might oversimplify the effects of N deposition on tree growth. Full article

Monitoring sugarcane phenology is essential since the globalized market requires reliable information on the quantity of raw materials for the industrial production of sugar and alcohol. In this context, the general objective of this study was to evaluate the phenological seasonality of the sugarcane varieties SP 79-1011 and VAP 90-212 observed from the NDVI time series over 19 years (2001–2020) from global databases. In addition, this research had the following specific objectives: (i) to estimate phenological parameters (Start of Season (SOS), End of Season (EOS), Length of Season (LOS), and Peak of Season (POS)) using TIMESAT software in version 3.3 applied to the NDVI time series over 19 years; (ii) to characterize the land use and land cover obtained from the MapBiomas project; (iii) to analyze rainfall variability; and (iv) to validate the sugarcane harvest date (SP 79-1011). This study was carried out in sugarcane growing areas in Juazeiro, Bahia, Brazil. The results showed that the NDVI time series did not follow the rainfall in the region. The sugarcane areas advanced over the savanna formation (Caatinga), reducing them to remnants along the irrigation channels. The comparison of the observed harvest dates of the SP 79-1011 variety to the values estimated with the TIMESAT software showed an excellent fit of 0.99. The mean absolute error in estimating the sugarcane harvest date was approximately ten days, with a performance index of 0.99 and a correlation coefficient of 0.99, significant at a 5% confidence level. The TIMESAT software was able to estimate the phenological parameters of sugarcane using MODIS sensor images processed on the Google Earth Engine platform during the evaluated period (2001 to 2020). Full article

The Montenegrin climate is characterised as very heterogeneous due to its complex topography. The viticultural heritage, dating back to before the Roman empire, is settled in a Mediterranean climate region, located south of the capital Podgorica, where climate conditions favour red wine production. However, an overall increase in warmer and drier periods affects traditional viticulture. The present study aims to discuss climate change impacts on Montenegrin viticulture. Bioclimatic indices, ensembled from five climate models, were analysed for both historical (1981–2010) and future (2041–2070) periods upon three socio-economic pathways: SSP1-2.6, SSP3-7.0 and SSP5-8.5. CHELSA (≈1 km) was the selected dataset for this analysis. Obtained results for all scenarios have shown the suppression of baseline conditions for viticulture. The average summer temperature might reach around 29.5 °C, and the growing season average temperature could become higher than 23.5 °C, advancing phenological events. The Winkler index is estimated to range from 2900 °C up to 3100 °C, which is too hot for viticulture. Montenegrin viticulture requires the application of adaptation measures focused on reducing temperature-increase impacts. The implementation of adaptation measures shall start in the coming years, to assure the lasting productivity and sustainability of viticulture. Full article

Recently, there has been a growing interest in relation to the female athlete, especially in widespread disciplines such as football. Concerns about vitamin D deficiency status have recently been considered due to its effects on the performance and health status of female footballers. However, its relationship to body composition and muscle damage in female football athletes remains unclear to date. The purpose of the present study was to analyse the association of the vitamin D status of Spanish elite female football players with anthropometric variables and markers of muscle damage. Ethical consent was obtained from a total of 21 players from a Spanish elite women’s football team (20–33 years). Anthropometric analysis was carried out according to the standardised protocol of the International Society for the Advancement of Kineanthropometry (ISAK). The clinical analyses, based on urine and blood samples, were carried out by the club’s medical staff at the start of the season in the early morning in a fasting state. The athletes were also asked about the regularity of their menstrual cycle and some dietary habits. Thirty-three percent of the female athletes had vitamin D levels below the reference values. Significantly higher FM values were observed in athletes with low vitamin D status (p < 0.05), as well as statistically significant negative correlations between vitamin D levels and FM (p < 0.05) in the group of female players with vitamin D levels below the baseline values. No significant associations were observed between markers of muscle damage and the other variables. Complementing an assessment of body composition with a biochemical analysis of vitamin D levels may be an interesting strategy in the process of monitoring the elite female football player throughout the season. Full article

Climate change inevitably affects vegetation growth in the Tibetan Plateau (TP). Understanding the dynamics of vegetation phenology and the responses of vegetation phenology to climate change are crucial for evaluating the impacts of climate change on terrestrial ecosystems. Despite many relevant studies conducted in the past, there still remain research gaps concerning the dominant factors that induce changes in the start date of the vegetation growing season (SOS). In this study, the spatial and temporal variations of the SOS were investigated by using a long-term series of the Normalized Difference Vegetation Index (NDVI) spanning from 2001 to 2020, and the response of the SOS to climate change and the predominant climatic factors (air temperature, LST or precipitation) affecting the SOS were explored. The main findings were as follows: the annual mean SOS concentrated on 100 DOY–170 DOY (day of a year), with a delay from east to west. Although the SOS across the entire region exhibited an advancing trend at a rate of 0.261 days/year, there were notable differences in the advancement trends of SOS among different vegetation types. In contrast to the current advancing SOS, the trend of future SOS changes shows a delayed trend. For the impacts of climate change on the SOS, winter T_max (maximum temperature) played the dominant role in the temporal shifting of spring phenology across the TP, and its effect on SOS was negative, meaning that an increase in winter T_max led to an earlier SOS. Considering the different conditions required for the growth of various types of vegetation, the leading factor was different for the four vegetation types. This study contributes to the understanding of the mechanism of SOS variation in the TP. Full article

It is necessary to understand the radial growth responses of trees in the Greater Khingan Range to climatic factors to predict changes in forest ecosystems under climate change scenarios. We sampled Mongolian pine (Pinus sylvestris var. mongolica) and Dahurian larch (Larix gmelinii (Rupr.) Kuzen) at four locations at elevations of 900–1100 m in the Greater Khingan Range to establish a tree-ring chronology. The Vaganov–Shashkin (VS) model was used to describe the relationship between tree radial growth and the dominant limiting climatic factors with a focus on physiological processes. The results showed that the VS model accurately reflected the effects of various climatic factors on the growth of Mongolian pine and Dahurian larch. The simulated and measured tree-ring widths index (RWI, the same as below) were consistent. The physiological parameters affecting tree growth differed for the two tree species in the study area. Mongolian pine required higher temperatures and less soil moisture for growth than Dahurian larch. The growth rings of the two tree species are more consistent across the elevation gradient. Higher-elevation trees had an “intensive strategy” with shorter growing periods and high growth rates, whereas low-elevation tree species had a “broad strategy” with lower maximum growth rates for longer periods. The start and cessation date of tree growth strongly affected the RWI of Mongolian pine and high-elevation Dahurian larch, but no significant effect on the RWI of low-elevation Dahurian larch. Differences in the limiting climatic factors were observed between Mongolian pine and Dahurian larch. Mongolian pine shows some similarity between high and low elevations, subject to the common limitations of temperature and soil moisture during the growing season for both, with a greater proportion of the lower elevations being limited by soil moisture. Dahurian larch was influenced by the growing season temperatures and May–August soil moisture at higher elevations and by the growing season soil moisture at lower elevations. This study provides a scientific basis for the management and conservation of forest ecosystems in the Greater Khingan Range. Full article

With global climate change, changes in vegetation phenology have become increasingly evident. Horqin Sandy Land is located near the eastern part of the West Liaohe River. It is the largest sandy land in China and its ecological environment is fragile. Investigating the changes in vegetation phenology in these sandy areas and determining the relationship between vegetation phenology and meteorological factors are of great importance for predicting the impacts of future climate change and understanding the response mechanisms of ecosystems. In this study, we used the time series of the Normalized Difference Vegetation Index (NDVI) from 2000 to 2021 and extracted the vegetation phenology in the Horqin Sandy Land using high-order curve fitting methods, including the start date of the growing season (SOS), the end date of the growing season (EOS), and the length of the growing season (LOS). We analyzed their temporal variation and used partial correlation analysis to determine their relationship with meteorological factors (temperature and precipitation). In addition, we compared the phenology and microclimate of forest and grassland within the study area. In the Horqin Sandy Land, the vegetation SOS was concentrated between the 115th and 150th day, the EOS was concentrated between the 260th and 305th day, and the LOS ranged from 125 to 190 days. Over the past 22 years, the SOS, EOS, and LOS of vegetation in the Horqin Sandy Land showed trends of delay, shift, and extension, with rates of change of 0.82 d/10a, 5.82 d/10a, and 5.00 d/10a, respectively. The start date of the growing season in the Horqin Sandy Land was mainly influenced by precipitation in April of the current year, while the end date was mainly influenced by precipitation in August of the current year. Overall, the SOS in the forested areas of the Horqin Sandy Land was slightly later than in the grasslands, but the EOS in the forested areas was significantly later than in the grasslands, resulting in a longer LOS in the forests. In addition, annual precipitation and the rate of precipitation increase were higher in the forested areas than in the grasslands, but soil temperature was higher in the grasslands than in the forests. Vegetation phenology in the Horqin Sandy Land has undergone significant changes, mainly manifested in the delayed end date of the growing season, the extended length of the growing season, and the differences between forest and grassland. This indicates that climate change has indeed affected phenological changes and provides a theoretical basis for subsequent ecological restoration and desertification prevention efforts in the region. Full article

Snow cover has significantly changed due to global warming in recent decades, causing large changes in the vegetation ecosystem. However, the impact of snow cover changes on the spring phenology of different vegetation types in Northeast China remains unclear. In this study, we investigated the response of the start of the growing season (SOS) to different snow cover indicators using partial correlation analysis and stepwise regression analysis in Northeast China from 1982 to 2015 based on multiple remote sensing datasets. Furthermore, we revealed the underlying mechanisms using a structural equation model. The results show that decreased snow cover days (SCD) and an advanced snow cover end date (SCED) led to an advanced SOS in forests. Conversely, an increased SCD and a delayed SCED led to an advanced SOS in grasslands. The trends of SCD and SCED did not exhibit significant changes in rainfed cropland. The maximum snow water equivalent (SWE_max) increased in most areas. However, the proportion of the correlation between SWE_max and SOS was small. The impact of snow cover changes on the SOS varied across different vegetation types. Snow cover indicators mainly exhibited positive correlations with the SOS of forests, including deciduous broadleaf forests and deciduous coniferous forests, with positive and negative correlations of 18.61% and 2.58%, respectively. However, snow cover indicators mainly exhibited negative correlations in the SOS of grasslands and rainfed croplands, exhibiting positive and negative correlations of 4.87% and 13.06%, respectively. Snow cover impacted the SOS through the “temperature effect” in deciduous broadleaf forests, deciduous coniferous forests, and rainfed croplands, while it affected SOS through the “moisture effect” in grasslands. These results provide an enhanced understanding of the differences in snow cover changes affecting SOS in different vegetation types under climate change in Northeast China. Full article

Strawberries are a very important economic crop; thus, a lot of research has been conducted on several production areas. However, phenological performance is still lacking information, especially when it comes to modeling. Therefore, this study aims to develop a phenological model for flower–fruit development under hydroponic conditions to support growers’ decision-making. Two day-neutral cultivars, ‘Albion’ and ‘San Andreas’, were established in a drip hydroponic system in Auburn, Alabama for the 2022–2023 production season. Phenological data were collected daily on 30 flowers per cultivar for three periods (Oct 25–Dec 16, Dec 27–Feb 21, and Feb 28–Apr 16). Weather data were obtained from a weather station placed in the greenhouse. Growing degree days (GDD) accumulation was calculated for each stage and cycle using a base temperature (Tb) of 3 °C. The Gaussian model was adjusted for each stage and cycle using a non-linear procedure to obtain Gaussian curves. Simulations were made for the model assuming temperature would increase or decrease by 1 °C. Six stages were identified, and their cycle ranged from 43–56 days to be accomplished. ‘Albion’ needed more days to reach maturity, with 51, 56, and 47 days, and ‘San Andreas’ took 43, 54, and 46 days for cycles 1, 2, and 3 respectively. In addition, for cycles 1 and 2, not all the buds reached maturity, as expected. Stage 5 (fruit formation) needed more days than the rest of the stages to be completed. Because of the different starting dates for each cycle, the starting GDD was different as well. A sensitivity analysis simulation of the model showed that if temperature decreases by 1 °C, the GDD accumulated to complete the stages would be less (same dates), and it would be more if the temperature increased by 1 °C. The opposite happened with the days, if the temperature increased by 1 °C, the duration of the stage decreased, and it would increase if the temperature decreased by 1 °C, affecting stages 4, 5, and 6. Overall, ‘San Andreas’ performed better than ‘Albion’ under hydroponic conditions during three productive cycles. Full article

Snow is one of the important water sources for vegetation growth in the Mongolian Plateau, and temporal and spatial changes to it have a profound impact on terrestrial vegetation phenology. In recent years, due to global climate change, the snow associated with the different vegetation types of the Mongolian Plateau has changed substantially, and the mechanism of the resulting change in the vegetation growth date needs to be studied. To address this issue, we used the modified Carnegie Ames Stanford Approach (CASA) model was to estimate the start of growing season net primary productivity (SOS_NPP) for different types of vegetation over the Mongolian Plateau from 2001 to 2019. An extensive study of the spatial changes in the SOS_NPP and the responses reflected by the winter snow cover fraction (SCF_Winter), spring snow melting date (SMD_Spring), and SOS_NPP to influencing factors is of great significance for ecosystem maintenance. We observed: (1) Different vegetation types exhibited similar changes; SCF_Winter underwent a significant decrease of −0.2%, and SMD_Spring followed a slow downward trend of −0.59 day of the year (DOY)/year for the whole study area. (2) In the Mongolia Plateau, SOS_NPP showed a trend of significant decrease of −0.53 DOY/year. (3) The local hydrothermal condition coupling relationship effect on different vegetation types. Spring temperature (TEM_Spring) has a direct effect on vegetation SOS_NPP, with a path coefficient of −0.09 in the Mongolian Plateau. SCF_Winter and SMD_Spring were shown through a path analysis to employ different effects on vegetation SOS_NPP. SMD_Spring has a direct effect on vegetation SOS_NPP, with a path coefficient of 0.53. (4) The SMD_Spring and PRE_Spring factors have a significant impact on vegetation SOS_NPP, and they account for 21.11% and 21.26% of the whole study area SOS_NPP, respectively. This study is expected to promote the examination of the snow phonological parameters of different related vegetation types and theoretical research on SOS_NPP. Full article

The use of very long spatial datasets from satellites has opened up numerous opportunities, including the monitoring of vegetation phenology over the course of time. Considering the importance of grassland systems and the influence of climate change on their phenology, the specific objectives of this study are: (a) to identify a methodology for a reliable estimation of grassland phenological dates from a satellite vegetation index (i.e., kernel normalized difference vegetation index, kNDVI) and (b) to quantify the changes that have occurred over the period 2001–2021 in a representative dataset of European grasslands and assess the extent of climate change impacts. In order to identify the best methodological approach for estimating the start (SOS), peak (POS) and end (EOS) of the growing season from the satellite, we compared dates extracted from the MODIS-kNDVI annual trajectories with different combinations of fitting models (FMs) and extraction methods (EM), with those extracted from the gross primary productivity (GPP) measured from eddy covariance flux towers in specific grasslands. SOS and POS were effectively identified with various FM×EM approaches, whereas satellite-EOS did not obtain sufficiently reliable estimates and was excluded from the trend analysis. The methodological indications (i.e., FM×EM selection) were then used to calculate the SOS and POS for 31 grassland sites in Europe from MODIS-kNDVI during the period 2001–2021. SOS tended towards an anticipation at the majority of sites (83.9%), with an average advance at significant sites of 0.76 days year⁻¹. For POS, the trend was also towards advancement, although the results are less homogeneous (67.7% of sites with advancement), and with a less marked advance at significant sites (0.56 days year⁻¹). From the analyses carried out, the SOS and POS of several sites were influenced by the winter and spring temperatures, which recorded rises during the period 2001–2021. Contrasting results were recorded for the SOS-POS duration, which did not show a clear trend towards lengthening or shortening. Considering latitude and altitude, the results highlighted that the greatest changes in terms of SOS and POS anticipation were recorded for sites at higher latitudes and lower altitudes. Full article