Comparison of Multi-Methods for Identifying Maize Phenology Using PhenoCams

Accurately identifying the phenology of summer maize is crucial for both cultivar breeding and fertilizer controlling in precision agriculture. In this study, daily RGB images covering the entire growth of summer maize were collected using phenocams at sites in Shangqiu (2018, 2019 and 2020) and Nanpi (2020) in China. Four phenological dates, including six leaves, booting, heading and maturity of summer maize, were pre-defined and extracted from the phenocam-based images. The spectral indices, textural indices and integrated spectral and textural indices were calculated using the improved adaptive feature-weighting method. The double logistic function, harmonic analysis of time series, Savitzky–Golay and spline interpolation were applied to filter these indices and pre-defined phenology was identified and compared with the ground observations. The results show that the DLF achieved the highest accuracy, with the coefficient of determination (R2) and the root-mean-square error (RMSE) being 0.86 and 9.32 days, respectively. The new index performed better than the single usage of spectral and textural indices, of which the R2 and RMSE were 0.92 and 9.38 days, respectively. The phenological extraction using the new index and double logistic function based on the PhenoCam data was effective and convenient, obtaining high accuracy. Therefore, it is recommended the adoption of the new index by integrating the spectral and textural indices for extracting maize phenology using PhenoCam data.

Coefficients of originality of Hippophae rhamnoides L. by phenological dates.

Sea buckthorn is often perceived and used precisely as a fruit crop, but it also has decorative qualities. When choosing varieties for gardening, it is important to know the phenological dates of the onset of decorative phases, but literary sources often indicate only one phenophase - the period of fruit ripening. The purpose of this work is to analyze 18 varieties of sea buckthorn of the average ripening period according to the degree of originality of the onset of a number of phenophases. Female sea buckthorn plants are in the collection of the Main Botanical Garden. N.V. Tsitsina (Moscow, Russia). Annually from 2014 to 2019, 16 phenodates were noted (swelling and blooming of buds, appearance and blooming of leaves, complete leafing, yellowing of leaves, leaf fall, beginning of budding, mass budding, beginning of flowering, mass and end of flowering, fruit setting, single ripening, mass ripening , fruit fall). Originality coefficients were calculated by a statistical method for assessing the modality weight. It was found that among the varieties of the average ripening period, the Chuiskaya and Gus-Khrustalnaya varieties have a high degree of originality of the complex of phenological dates, and the overwhelming majority of varieties are the most typical in the sample. Keywords: HIPPOPHAE RHAMNOIDES L., ORNAMENTAL PLANTS, ORIGINALITY, VARIETY, SEA BUCKTHORN, PHENODATES, PHENOLOGY

Study of the phenological dates of the Yesso scallop (Mizuhopecten yessoensis Jay, 1857) spawning and settling onsets in Minonosok Inlet (Posiet Bay, Peter the Great Bay, East Sea/Sea of Japan)

Проанализированы многолетние изменения фенодат начала нереста и оседания приморского гребешка (Mizuhopecten (=Patinopecten) yessoensis Jay, 1857) в бухте Миноносок (зал. Посьета, зал. Петра Великого, Японское море) в 1970–2011 гг. Выявлен сдвиг среднемноголетних сроков нереста и оседания на более ранние даты. Рассчитана энтропия процессов. The long-term changes of the phenological dates of the Yesso scallop (Mizuhopecten (=Patinopecten) yessoensis Jay, 1857) spawning and settling onsets in Minonosok Inlet (Posiet Bay, Peter the Great Bay, East Sea/Sea of Japan) were analyzed in 1970–2011. It was found that the long-term average spawning and settling periods were moved to earlier dates. The entropy of processes was calculated.

Climatic Causes of Plant Flowering Time Displacement in the Central Forest Reserve

Meteorological series and phenological data in the framework of our environmental monitoring in the South taiga Central Forest Reserve were analyzed. During 1984– 2017, the average annual air temperature was 4.63±0.41°C, and the average annual rainfall was 2.14±0.12 mm/day. For eight of the 43 (19%) climatic parameters, reliable linear trends of variability were found: an increase of air temperature in July, August, September, and December; an increase of soil temperature in December; an increase of precipitation in November and December; and a decrease of precipitation in September. Three causes of their directed long-term changes were revealed, namely: a shift of the winter timing, violation of the annual dynamics of climatic parameters and a change in the precipitation type during a longer autumn – snow to be replaced by rain. Of the 11 species of vascular plants, the statistical significance of the long-term displacement of phenological dates was proven for Anemone nemorosa: the longer the autumn and softer the beginning of the winter, the earlier the onset of its flowering. Two classification types of vascular plants in identifying interspecific synchrony in the phenological events variation were considered. Variability components of phenological phenomena occurrence was estimated: the share of long-term trends of the shift in phenological dates timing due to changes in reserve climatic system is from 20 to 68% of the total sign dispersion; interannual climatic fluctuations explain 5–34% of its variability; and the proportion of variability under unaccounted factors influence is high (21–64%). Species with a high proportion of their long-term variability components (Anemone nemorosa: more than 60%) are recommended to use as indicators of climate change under the conditions of the study area.

Monitoring Mediterranean grass phenology from digital terrestrial camera and Sentinel-2 vegetation indices in an oak-grass savanna ecosystem

<p>Annual grasslands are an essential component of Mediterranean oak savannas, the most extensive agroforestry system in Europe, as the primary source of fodder for livestock and wildlife. Monitoring its phenology is key to adequately assess the impacts of global warming on different time scales and identify pre-critical states in the framework of early warning decision making systems. The natural variability of the climatic-hydrological regime in these areas and the usually complex spatial patterns of the vegetation, with sparse distribution and multiple layers, encourage the exploitation of available data from remote sensing sources. This work presents an assessment of vegetation indexes (VI) from Sentinel-2 validated against field data from terrestrial photography in an oak-grass system in southern Spain as a multi-approach method to monitor phenology in grass pastures. The analysis also has provided an insight into the links of the phenology dynamics with hydrological variables under these conditions.</p><p>From December 2017 to May 2019 a quantitative value of grassland greenness was computed using the Green Chromatic Coordinate (GCC) index. The phenological parameters of the start of the season (SOS), the peak of the season (POS) and end of the season (EOS) were extracted using the 50% amplitude method and confirmed using field photography. These values were compared with those provided by eight VI's derived from Sentinel-2 (NDVI, GNDVI, SAVI, EVI, EVI2, MTCI, IRECI and S2REP) and the difference in days between the key phenological dates were estimated. The results showed that for annual grasslands NDVI was the index providing estimations closest to those of ground GCC, with differences below 10 days for all phenological dates and the best correlation with GCC values (r = 0.83, p <0.001). None of the VIs using bands in the red-edge region have improved the NDVI results. Two of them, MTCI and S2REP, followed a different trend that the rest of explored indices, presenting a high temporal variability. The high diversity of species, typical of Mediterranean grasslands, might explain the high variability observed in these values. However, the third index using red-edge bands, IRECI, presented a high correlation with GCC. In this case, the index was designed to focus on the chlorophyll content of the canopy instead of the leaf scale addressed by S2REP. The influence of the vegetation ground coverage and foliage density is then higher and more similar to the broad-band indices. GNDVI also provided good general results. Soil moisture (SM) time-series were also used to estimate phenology and have presented a good agreement with GCC in SOS and EOS estimations, with SM reaching threshold values a few days before greenness ones, as measured by GCC. However, SM was not a good indicator of the POS, presenting significant biases with respect to GCC estimations.</p>

Exploring the relationship between phenology and hydrology using Sentinel-2 and terrestrial photography in Mediterranean grasslands

<p>Mediterranean grasslands are an essential component of rural economy as the primary source of fodder for livestock in extensive areas. These annual grasslands present an escape mechanism to cope with the long summer dry season and the recurrent water scarcity events of the Mediterranean climate, completing their life cycle before serious soil and plant water deficits develop. It results in a close link between grass phenology and soil water dynamics. In this work we have explored this relationship using satellite and ground remote sensing (Sentinel-2 (S2) and a terrestrial digital camera) and ground measurements of hydrological variables.</p><p>The terrestrial photography was used as a field validator, grass greenness was assessed using the Green Chromatic Coordinate Index (GCC) and key phenological dates were extracted from the variation of this index during a calibration period (December 2017 to May 2019). The evolution of GCC index was highly correlated with soil moisture (SM) dynamic, which is consistent with the water-limited condition of the ecosystem. Some other variables, including vapor pressure deficit, solar radiation, and minimum, medium and maximum air temperatures were inversely correlated with greenness. Rainfall, although positively correlated, presented the lowest coefficient of all analyzed variables. The capability of SM and S2-NDVI to predict the phenology of the grass canopy was assessed by fitting a double-logistic function to the variables time-series and extracting the phenological parameters start of season (SOS), peak of season (POS) and end of season (EOS) using the 50% amplitude method. The comparison with the terrestrial camera resulted in differences less than 10 days for all phenological dates parameters studied (representing less than 5% error within a grass cycle). The behavior of S2-NDVI and SM relationship during four growing seasons was analyzed. It pointed out the synchronized seasonality shown in this system by the vegetation greenness, measured here by the NDVI, and the soil moisture. The higher agreement was found at the beginning and the end of the dry season, with stage changes estimated first by SM, followed by NDVI with a delay between 3 to 10 days. These results highlight the close relationship between these phenological parameters and the soil moisture dynamic under the study conditions, and the capability of satellite data to track these parameters.</p>

Analysis of the Modulation of Dormancy Release in Almond (Prunus dulcis) in Relation to the Flowering and Ripening Dates and Production under Controlled Temperature Conditions

In this study, the control of eco- and endo-dormancy release led to the modulation of the flowering time in almond (Prunus dulcis (Mill.) D.A. Webb). The study was performed in almond cultivars with contrasting flowering times: the extra-early flowering cultivar Desmayo Largueta and the ultra-late cultivar Tardona. Temperature control in the “Autumn”, “Winter” and “Spring” chambers successfully delayed the flowering time in Desmayo Largueta. Advance flowering in the cultivar Tardona was limited, however, even with the application of sufficient chill in the Winter chamber. The ecodormancy period and the heat accumulation for flowering were not stable among cultivars, even though the heat accumulation was generally high, in accordance with that accumulated in field conditions. The heat requirements of the early cultivar Desmayo Largueta were lower than those of the ultra-late cultivar Tardona. We observed a decreasing pattern in ecodormancy along treatments that was probably related to the temperature in the Spring chamber. Finally, flowering and fruit set were highly variable, and these parameters were more dependent on the cultivar assayed than on the treatment applied. Although the ripening time under our experimental conditions was earlier than the phenological dates observed in the field, the flowering time delayed the ripening time in the case of the extra-early cultivar Desmayo Largueta. The fruit weight increased in the last treatments, whereas the kernel/fruit ratio decreased, as the kernel weight did not vary significantly along treatments. The results obtained show that flowering time can be modulated by temperature control and that other uncontrolled factors, such as photoperiod, can be involved in the control of endodormancy release and flowering time, especially in late flowering cultivars.

Characterizing ecosystem phenological diversity and its macroecology with snow cover phenology

One critical challenge of exploring flora phenology is on characterizing ecosystem phenological diversity (EPD), and thus how EPD’s performance is influenced by climate changes has also been an open macro-ecological question. To fill these two gaps, we proposed an innovative method for reflecting EPD, by taking the advantage of the often-classified inverse factor of spatial resolution discrepancy between the used remote sensing datasets of vegetation phenological dates (green-up and brown-up) and snow cover phenological dates (SPDs) (onset and end) around the Arctic, and further, we examined the cross response/feedbacks of the two kinds of EPDs to the two categories of SPDs. We found that the circumpolar green-up and brown-up EPDs both were shrinking, driven more by the delaying of the onset SPDs than the advancing of the end SPDs; North America and North Eurasia performed with inconsistent EPD response/feedbacks to the related SPD anomalies; and further, the EPD-SPD response/feedbacks in some locations exhibited the time-lag effect, e.g., the green-up EPDs made the strongest response to the onset SPDs of two years earlier. Overall, the validated method and the new findings are of implications for improving the phenology modules in Earth system models, and the contributions of the present study have enlightening significance for kicking off the new EPD branch in macrosystem phenological ecology.