Photoperiod controls vegetation phenology across Africa

Abstract Vegetation phenology is driven by environmental factors such as photoperiod, precipitation, temperature, insolation, and nutrient availability. However, across Africa, there’s ambiguity about these drivers, which can lead to uncertainty in the predictions of global warming impacts on terrestrial ecosystems and their representation in dynamic vegetation models. Using satellite data, we undertook a systematic analysis of the relationship between phenological parameters and these drivers. The analysis across different regions consistently revealed photoperiod as the dominant factor controlling the onset and end of vegetation growing season. Moreover, the results suggest that not one, but a combination of drivers control phenological events. Consequently, to enhance our predictions of climate change impacts, the role of photoperiod should be incorporated into vegetation-climate and ecosystem modelling. Furthermore, it is necessary to define clearly the responses of vegetation to interactions between a consistent photoperiod cue and inter-annual variation in other drivers, especially under a changing climate.

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Tracking vegetation phenology across diverse North American biomes using PhenoCam imagery

Scientific Data ◽

10.1038/sdata.2018.28 ◽

2018 ◽

Vol 5 (1) ◽

Cited By ~ 110

Author(s):

Andrew D. Richardson ◽

Koen Hufkens ◽

Tom Milliman ◽

Donald M. Aubrecht ◽

Min Chen ◽

...

Keyword(s):

Climate Change ◽

Vegetation Type ◽

Digital Camera ◽

Region Of Interest ◽

Remote Sensing Data ◽

Climate Change Impacts ◽

Terrestrial Ecosystems ◽

Vegetation Phenology ◽

Phenological Model ◽

Vegetation Activity

Abstract Vegetation phenology controls the seasonality of many ecosystem processes, as well as numerous biosphere-atmosphere feedbacks. Phenology is also highly sensitive to climate change and variability. Here we present a series of datasets, together consisting of almost 750 years of observations, characterizing vegetation phenology in diverse ecosystems across North America. Our data are derived from conventional, visible-wavelength, automated digital camera imagery collected through the PhenoCam network. For each archived image, we extracted RGB (red, green, blue) colour channel information, with means and other statistics calculated across a region-of-interest (ROI) delineating a specific vegetation type. From the high-frequency (typically, 30 min) imagery, we derived time series characterizing vegetation colour, including “canopy greenness”, processed to 1- and 3-day intervals. For ecosystems with one or more annual cycles of vegetation activity, we provide estimates, with uncertainties, for the start of the “greenness rising” and end of the “greenness falling” stages. The database can be used for phenological model validation and development, evaluation of satellite remote sensing data products, benchmarking earth system models, and studies of climate change impacts on terrestrial ecosystems.

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The Influence of Motivation, Competency, and Work Environment to The Work Achievement The Officer of The Hasanuddin University

International Journal of Management Progress ◽

10.35326/ijmp.v1i1.410 ◽

2019 ◽

Vol 1 (1) ◽

pp. 33-42

Author(s):

Kustiany Kustiany

Keyword(s):

Human Resources ◽

Job Performance ◽

Work Environment ◽

Statistical Methods ◽

Dominant Factor ◽

Independent Variables ◽

Head Office ◽

The Relationship ◽

Correlation Level

The role of quality human resources is very important to direct and formulate policies needed by organizations/agencies. The purpose of this study was to determine the Effect of Motivation, Competence and Work Environment on Employee Job Performance at the Head Office of Hasanuddin University. The method in collecting data in this study is a questionnaire, observation (observation), interviews and documentation. The method of data analysis uses inferential statistical methods namely by using multiple linear regression statistical methods to measure the Effect of Motivation, Competence and Work Environment on Employee Job Performance at the Head Office of Hasanuddin University. Based on the F test the independent variables (motivation, competence and work environment) together have a positive and significant effect on the dependent variable (job performance). Through testing the correlation coefficient (R) obtained that the correlation level of the relationship between Motivation, Competence and Work Environment Against Employee Job Performance is a high relationship that is 67.2%, while the remaining 32.8% is influenced by other factors. And motivation is the most dominant factor affecting the Job Performance of Hasanuddin University Headquarters.

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Does seasonal variation in forage quality influence the potential for resource competition between muskoxen and Peary caribou on Banks Island?

Rangifer ◽

10.7557/2.22.2.1533 ◽

2002 ◽

Vol 22 (2) ◽

pp. 143 ◽

Cited By ~ 2

Author(s):

Nicholas C. Larter ◽

John A. Nagy ◽

David S. Hik

Keyword(s):

Seasonal Variation ◽

Annual Variation ◽

Resource Competition ◽

Energy Content ◽

Forage Quality ◽

Growing Season ◽

Dry Matter Digestibility ◽

Banks Island ◽

The Relationship

Inter- and intra-annual variation in forage quality may influence population dynamics of Peary caribou and muskoxen on Banks Island. From 1993 to 1998 we collected 300 composite samples of sedge (Carex aquatilis and Carex spp.), willow (Salix arctica), legume (Oxytropis spp. and Astragalus spp.), and avens (Dryas integrifolia). Samples were collected in mid-June (start of the growing season), mid-July (peak of the growing season), mid-late August (senescence), and early (November), mid- (February), and late- (April/May) winter. We analysed forages for percent digestibility (in vitro acid-pepsin dry matter digestibility), crude protein (CP), fibre, lignin, and energy content. There was significant inter-annual variation in levels of lignin, fibre, and energy, and significant intra-annual (seasonal) variation for all quality measures and forages, which reflected the strong difference in quality between summer and winter. We discuss the relationship between forage quality and seasonal diet composition of Peary caribou and muskoxen, and the potential implications for the reduced Peary caribou and high muskoxen populations.

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The Links between Canopy Solar-Induced Chlorophyll Fluorescence and Gross Primary Production Responses to Meteorological Factors in the Growing Season in Deciduous Broadleaf Forest

Remote Sensing ◽

10.3390/rs13122363 ◽

2021 ◽

Vol 13 (12) ◽

pp. 2363

Author(s):

Xiangfen Cheng ◽

Yu Zhou ◽

Meijun Hu ◽

Feng Wang ◽

Hui Huang ◽

...

Keyword(s):

Remote Sensing ◽

Chlorophyll Fluorescence ◽

Primary Production ◽

Forest Canopy ◽

Meteorological Factors ◽

Gross Primary Production ◽

Terrestrial Ecosystems ◽

Growing Season ◽

Near Surface ◽

The Relationship

Solar-induced chlorophyll fluorescence (SIF) is a hopeful indicator, which along with remote sensing, is used to measure the photosynthetic efficiency and gross primary production (GPP) of vegetation in regional terrestrial ecosystems. Studies have found a significant linear correlation between SIF and GPP in a variety of ecosystems. However, this relationship has mainly been established using SIF and GPP data derived from satellite remote sensing and continuous ground-based observations, respectively, which are difficult to accurately match. To overcome this, some studies have begun to use tower-based automatic observation instruments to study the changes of near-surface SIF and GPP. This study conducts continuous simultaneous observation of SIF, carbon flux, and meteorological factors on the forest canopy of a cork oak plantation during the growing season to explore how meteorological factors impact on canopy SIF and its relationship with GPP. This research found that the canopy SIF has obvious diurnal and day-to-day variations during the growing season but overall is relatively stable. Furthermore, SIF is greatly affected by incident radiation in different weather conditions and can change daily. Meteorological factors have a major role in the relationship between SIF and GPP; overall, the relationship shows a significant linear regression on the 30 min scale, but weakens when aggregating to the diurnal scale. Photosynthetically active radiation (PAR) drives SIF on a daily basis and changes the relationship between SIF and GPP on a seasonal timescale. As PAR increases, the daily slopes of the linear regressions between SIF and GPP decrease. On the 30 min timescale, both SIF and GPP increase with PAR until it reaches 1250 μmol·m−2·s−1; subsequently, SIF continues to increase while GPP decreases and they show opposite trends. Soil moisture and vapor pressure deficit influence SIF and GPP, respectively. Our findings demonstrate that meteorological factors affect the relationship between SIF and GPP, thereby enhancing the understanding of the mechanistic link between chlorophyll fluorescence and photosynthesis.

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Influence of spring phenology on seasonal net primary productivity in the alpine grassland on the Tibetan Plateau

10.5194/egusphere-egu2020-12393 ◽

2020 ◽

Author(s):

Zhoutao Zheng ◽

Wenquan Zhu ◽

Yangjian Zhang ◽

Ke Huang ◽

Nan Cong

Keyword(s):

Primary Productivity ◽

Net Primary Productivity ◽

Growing Season ◽

Ecosystem Model ◽

Alpine Grassland ◽

The Tibetan Plateau ◽

Field Observations ◽

Vegetation Phenology ◽

Spring Phenology ◽

The Relationship

Vegetation phenology is recognized to exert crucial influences on carbon sequestration and the role of vegetation phenology in mediating carbon cycle varies with ecosystem type. However, the relationship between vegetation phenology and productivity has not been fully understood in the alpine ecosystem due to a lack of field observations, poor model performances and their complex mechanisms. In this study, we examined the spatio-temporal variation in beginning of growing season (BGS) and net primary productivity (NPP) for the alpine grassland on the Tibetan Plateau (TP) and the regulation effects of spring phenology on seasonal NPP by integrating field observations, remote sensing monitoring and ecosystem model simulation. The ecosystem model performances were improved by optimizing ecosystem parameters from field observations. The results indicated a significant advance in BGS with a rate of 0.31 days/yr (P < 0.1) in the alpine grassland during 2001-2015 while the annual NPP increased significantly at a rate of 1.25 gC/m2/yr (P < 0.01). With regard to the relationship between BGS and NPP, large spatial heterogeneities were identified. Overall, a negative but non-significant correlation (R = -0.34, P > 0.1) was observed between BGS and annual NPP for the entire grassland ecosystem on the TP. But responses of NPP to BGS varied with seasons. Specifically, BGS showed significant negative correlation with spring NPP (R = -0.73, P < 0.01), and advanced spring led to increased spring NPP. The positive effects of advanced BGS on NPP tended to weaken in summer. Moreover, BGS was significantly and positively correlated with autumn NPP in some relatively arid zones of the southwestern TP, suggesting the suppressing effects of earlier spring on carbon assimilation during the later growing season in water limited areas. This study improved our understanding on the impacts of biotic factors on carbon cycles of the alpine ecosystem and implies that the effects of phenology can&#8217;t be concluded simply for an annual sum, and their relationships for each separate season are also critical.

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The wounded school. Framing race pedagogies through INDIRE digital collections

Rivista di Storia dell’Educazione ◽

10.36253/rse-9398 ◽

2020 ◽

Vol 7 (1) ◽

pp. 115-127

Author(s):

Pamela Giorgi ◽

Elena Mazzini ◽

Patrizia Garista

Keyword(s):

Cultural Heritage ◽

Educational Experience ◽

Digital Collections ◽

Systematic Analysis ◽

Historical Archive ◽

The Future ◽

Historical Heritage ◽

The Relationship

Contemporary challenges in school and society, against any form of racism, refer to the urgency and the pedagogical potential of “memories” as a cultural heritage and as an “educational experience” to be exposed as educators and to which the school itself should be exposed. Moving up from the Indire Archive studies on racial laws, the present proposal intends to investigate the relationship between school and fascism from a perspective that aims to grasp the elements of resistance and metamorphosis, by tracing the possible didactic implications of a digitized historical heritage. Nevertheless, the scarring of racial laws becomes an opportunity for reflection and transformation, where the archive offers itself as a chance to build narratives-bridge with the future. The sources, which the contribution proposes as a documentary apparatus, come from the Indire historical archive, from which the project documented by an exhibition with materials dating back to the National Educational Exhibition of 1925 was developed. The systematic analysis of school materials is presented here following the results of cataloging, returning markedly ideological elaborations in languages, as then reflected in the contents, of a pedagogy gradually eroded in its role of development in favor of indoctrination.

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On The Role Of Management Commitment In Export Performance: A Meta-Analysis

Journal of Applied Business Research (JABR) ◽

10.19030/jabr.v30i4.8661 ◽

2014 ◽

Vol 30 (4) ◽

pp. 1151

Author(s):

Hind El Makrini ◽

Anissa Chaibi

Keyword(s):

Positive Relationship ◽

Export Performance ◽

Meta Analysis ◽

Future Research ◽

Systematic Analysis ◽

Analysis Techniques ◽

Management Commitment ◽

Meta Analyses ◽

The Relationship

Research on exporting frequently points the role of management commitment in the export performance of the firm. This article reviews the conceptual, methodological, and empirical insights gained from a systematic analysis of 65 studies conducted on this subject. Undoubtedly, this stream of research has enhanced understanding of the importance of management commitment in affecting exporting activities. However, conceptually, there is still a lack of integral theoretical framework. Methodologically, limitations are identified concerning sampling designs, fieldwork procedures, and analytical methods. Empirically, hypothesized associations between export commitment and export performance lead to conflicting findings. After a presentation of meta-analysis techniques used and articles compiled, our paper provides an original investigation of this issue by implementing three meta-analyses to examine the relationship between commitment to export and export performance. The meta-analysis, more relevant than simple literature surveys, generally leads to the conclusion that there is a significant positive relationship between export commitment and export performance. Moreover, our findings suggest directions for future research in the field.

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The Role of Vitamin D in Respiratory Allergies Prevention. Why the Effect Is so Difficult to Disentangle?

Nutrients ◽

10.3390/nu12061801 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1801 ◽

Cited By ~ 2

Author(s):

Hanna Sikorska-Szaflik ◽

Barbara Sozańska

Keyword(s):

Vitamin D ◽

Allergic Rhinitis ◽

Allergic Diseases ◽

Childhood Diseases ◽

Systematic Analysis ◽

Hydroxyvitamin D ◽

Respiratory Allergies ◽

25 Hydroxyvitamin D ◽

The Relationship

Asthma and allergic rhinitis are the most common chronic childhood diseases with an increasing prevalence worldwide. There is an urgent need to look for methods of preventing allergic diseases from an early age. The relationship between vitamin D status and allergic diseases has been discussed in several studies recently. 25-hydroxyvitamin D (25(OH)D) is suggested to affect the development and/or severity of asthma and allergic rhinitis. Observational studies have seemed to confirm that vitamin D deficiency may contribute to an increase in allergy and asthma. Following interventional studies, however, have yielded ambiguous results. In this review, we describe recent findings regarding 25(OH)D impact on allergic diseases and provide a systematic analysis of the causes of great variability of the achieved results in different studies.

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Mapping Statistical Characteristics of Frosts in Iran

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsarchives-xl-2-w3-175-2014 ◽

2014 ◽

Vol XL-2/W3 ◽

pp. 175-180 ◽

Cited By ~ 4

Author(s):

P. Mahmoudi

Keyword(s):

Dominant Role ◽

Growing Season ◽

Spatial Arrangement ◽

Statistical Characteristics ◽

Frequency Of Occurrence ◽

Climate Factors ◽

Kriging Interpolation Method ◽

Frost Period ◽

The Relationship

To model and map the statistical characteristics of frost in Iran, the data related to the minimum daily temperature for a 15-year period (1990–2005) was obtained from Iran Meteorological Organization. Then using multivariate regression models, the relationship among five statistical characteristics, i.e. the mean Julian day of the first frost, mean Julian day of the last frost, mean number of frost days per year, mean length of the frost period and mean length of growing season were modeled by three geo – climate factors: elevation, longitude and latitude. The precision of each model was explored using four hypotheses: linearity of the relationship between independent variables and the dependent variable, normality of errors, constancy of error variance and lake of correlation of errors were tested, and their precisions were confirmed. At the second stage, contour lines resulting from STRM were converted to the point features class. Altogether, 661 474 points were gathered from all over Iran. Then, the studied five frost characteristics were generalized to 661 474 points; then, the regionalization maps of statistical characteristics of frost were obtained for Iran using Kriging interpolation method. The results showed that the temperature of highland areas above 4200 m above sea level always was at least zero and below zero during the year, and also the coastal strip of southern Iran had no frost. Elevation was the most effective factor in the spatial arrangement for the frequency of occurrence of Julian day of the first frost. The most effective factors in spatial arrangement for the frequency of occurrence of Julian day of the last frost, length of frost period and length of growing season were elevation and latitude. Finally, spatial arrangement for the frequency of occurrence of the frost days was also a function of three factors of elevation, longitude and latitude. The dominant role of elevation in spatial arrangement for the occurrence of the first frost day in Iran showed that the occurrence of the first frost day in Iran could be of the type of radiation frosts and the dominant role of elevation and latitude demonstrated that late-winter frosts can be mostly of the type of advection frosts. Therefore, arrangement of statistical features of frost in Iran is both a function of geo – climate factors and the synoptic systems which have entered the country.

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