Latitudinal shift in the timing of flowering of tree species across tropical Africa: insights from field observations and herbarium collections

2020 ◽  
Vol 36 (4) ◽  
pp. 159-173
Author(s):  
Dakis-Yaoba Ouédraogo ◽  
Olivier J. Hardy ◽  
Jean-Louis Doucet ◽  
Steven B. Janssens ◽  
Jan J. Wieringa ◽  
...  
Keyword(s):  
Tree Species ◽  
Central Africa ◽  
Flowering Phenology ◽  
Graphical Analysis ◽  
Dry Season ◽  
Circular Statistics ◽  
Significant Shift ◽  
The North ◽  
Herbarium Data ◽  
Herbarium Collections

AbstractTemporal and spatial patterns in flowering phenology were assessed for eight tropical African tree species. Specifically, the frequency and seasonality of flowering at seven sites in central Africa were determined using field data, graphical analysis and circular statistics. Additionally, spatial variation in the timing of flowering across species range was investigated using herbarium data, analysing the relative influence of latitude, longitude and timing of the dry season with a Bayesian circular generalized linear model. Annual flowering was found for 20 out of the 25 populations studied. For 21 populations located at the north of the climatic hinge flowering was occurring during the dry season. The analysis of herbarium collections revealed a significant shift in the timing of flowering with latitude for E. suaveolens, and with the timing of the dry season for M. excelsa (and to a lesser extent L. alata), with the coexistence of two flowering peaks near the equator where the distribution of monthly rainfall is bimodal. For the other species, none of latitude, longitude or timing of the dry season had an effect on the timing of flowering. Our study highlights the need to identify the drivers of the flowering phenology of economically important African tree species.

scholarly journals Phylogenomic approaches reveal how a climatic inversion and glacial refugia shape patterns of diversity in an African rain forest tree species

2019 ◽  
Author(s):  
Andrew J. Helmstetter ◽  
Biowa E. N. Amoussou ◽  
Kevin Bethune ◽  
Narcisse G. Kandem ◽  
Romain Glèlè Kakaï ◽  
...  
Keyword(s):  
Tree Species ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
Evolutionary Dynamics ◽  
Central Africa ◽  
Glacial Refugia ◽  
Forest Tree ◽  
Ancestral Population ◽  
Forest Tree Species ◽  
The North

AbstractThe world’s second largest expanse of tropical rain forest is in Central Africa and it harbours enormous species diversity. Population genetic studies have consistently revealed significant structure across central African rain forest plants, in particular a North-South genetic discontinuity close to the equator at the level of a climatic inversion. Here, we take a phylogeographic approach using 351 nuclear markers in 112 individuals across the distribution of the African rain forest tree species Annickia affinis (Annonaceae). We show for the first time that the North-South divide is the result of a single major colonisation event across the climatic inversion from an ancestral population located in Gabon. We suggest that differences in ecological niche of populations distributed either side of this inversion may have contributed to this phylogenetic discontinuity. We find evidence for inland dispersal, predominantly in northern areas, and variable demographic histories among genetic clusters, indicating that populations responded differently to past climate change. We show how newly-developed genomic tools can provide invaluable insights into our understanding of tropical rain forest evolutionary dynamics.

Tree-Ring Formation, Radial Increment Periodicity, and Phenology of Tree Species from a Seasonal Semi-Deciduous Forest in Southeast Brazil

IAWA Journal ◽  
2008 ◽  
Vol 29 (2) ◽  
pp. 189-207 ◽  
Author(s):  
Claudio S. Lisi ◽  
Mário Tomazello Fo ◽  
Paulo C. Botosso ◽  
Fidel A. Roig ◽  
Vivian R.B. Maria ◽  
...  
Keyword(s):  
Tree Rings ◽  
Tree Species ◽  
Deciduous Forest ◽  
Growth Ring ◽  
Climatic Conditions ◽  
Dry Season ◽  
Tree Age ◽  
Radial Increment ◽  
Future Studies ◽  
Southeast Brazil

Many tropical tree species produce growth rings in response to seasonal environmental factors that influence the activity of the vascular cambium. We applied the following methods to analyze the annual nature of treering formation of 24 tree species from a seasonal semi-deciduous forest of southeast Brazil: describing wood anatomy and phenology, counting tree rings after cambium markings, and using permanent dendrometer bands. After 7 years of systematic observations and measurements, we found the following: the trees lost their leaves during the dry season and grew new leaves at the end of the same season; trunk increment dynamics corresponded to seasonal changes in precipitation, with higher increment (active period) during the rainy season (October–April) and lower increment (dormant period) during the dry season (May–September); the number of tree rings formed after injuries to the cambium coincided with the number of years since the extraction of the wood samples. As a result of these observations, it was concluded that most study trees formed one growth ring per year. This suggests that tree species from the seasonal semi-deciduous forests of Brazil have an annual cycle of wood formation. Therefore, these trees have potential for use in future studies of tree age and radial growth rates, as well as to infer ecological and regional climatic conditions. These future studies can provide important information for the management and conservation of these endangered forests.

Flowering phenology and flower predation of Cullenia exarillata (Bombacaceae) by arboreal vertebrates in Western Ghats, India

1997 ◽  
Vol 13 (3) ◽  
pp. 459-468 ◽  
Author(s):  
T. Ganesh ◽  
Priya Davidar
Keyword(s):  
Western Ghats ◽  
Keystone Species ◽  
Flowering Phenology ◽  
Dry Season ◽  
Community Level ◽  
Canopy Tree ◽  
Southern Western Ghats ◽  
Annual Period

ABSTRACTThe flowering phenology and flower predation of Cullenia exarillata, a canopy tree at Kakachi in the southern Western Ghats, India, was studied from 1991 to 1993 in relation to general phenological patterns at the community level. Flowering was monitored from 30 marked trees and flower predation estimated from fallen flowers in 40, 1 m2 nets placed under the trees. Flowering occurs in the dry season and coincides with the period of fruit scarcity in the forest. Flowering is synchronous in the population and each tree produces a mean of c. 8730 flowers per tree over a period of c. 47 d. Flowers produced little nectar but the edible fleshy sepals compensated for this. Six species of arboreal mammals and seven species of birds ate the flowers. These consumed 57% of the flower crop of which 37% were completely destroyed. Flower predators could be important in flower fertilization. The overabundance of the flower crop and the timing of flowering, may have evolved as a strategy to satiate predators and enable the flowers to be pollinated during the annual period of fruit scarcity in the forest. This in turn makes Cullenia exarillata a possible keystone species in this forest.

Rising ecosystem water demand exacerbates the lengthening of tropical dry seasons

2021 ◽  
Author(s):  
Hao Xu ◽  
Xu Lian ◽  
Ingrid Slette ◽  
Hui Yang ◽  
Yuan Zhang ◽  
...  
Keyword(s):  
Water Demand ◽  
Potential Evapotranspiration ◽  
Central Africa ◽  
Dry Season ◽  
Land Area ◽  
Key Factor ◽  
Dry Seasons ◽  
The Tropics ◽  
Factor Governing

Abstract The timing and length of the dry season is a key factor governing ecosystem productivity and the carbon cycle of the tropics. Mounting evidence has suggested a lengthening of the dry season with ongoing climate change. However, this conclusion is largely based on changes in precipitation (P) compared to its long-term average (P ̅) and lacks consideration of the simultaneous changes in ecosystem water demand (measured by potential evapotranspiration, Ep, or actual evapotranspiration, E). Using several long-term (1979-2018) observational datasets, we compared changes in tropical dry season length (DSL) and timing (dry season arrival, DSA, and dry season end, DSE) among three common metrics used to define the dry season: P < P ̅, P < Ep, and P < E. We found that all three definitions show that dry seasons have lengthened in much of the tropics since 1979. Among the three definitions, P < E estimates the largest fraction (49.0%) of tropical land area likely experiencing longer dry seasons, followed by P < Ep (41.4%) and P < P ̅ (34.4%). The largest differences in multi-year mean DSL (> 120 days) among the three definitions occurred in the most arid and the most humid regions of the tropics. All definitions and datasets consistently showed longer dry seasons in southern Amazon (due to delayed DSE) and central Africa (due to both earlier DSA and delayed DSE). However, definitions that account for changing water demand estimated longer DSL extension over those two regions. These results indicate that warming-enhanced evapotranspiration exacerbates dry season lengthening and ecosystem water deficit. Thus, it is necessity to account for the evolving water demand of tropical ecosystems when characterizing changes in seasonal dry periods and ecosystem water deficits in an increasingly warmer and drier climate.

scholarly journals The Orbiting Carbon Observatory-2: first 18 months of science data products

2017 ◽  
Vol 10 (2) ◽  
pp. 549-563 ◽  
Author(s):  
Annmarie Eldering ◽  
Chris W. O'Dell ◽  
Paul O. Wennberg ◽  
David Crisp ◽  
Michael R. Gunson ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Atmospheric Carbon Dioxide ◽  
Eastern China ◽  
Regional Scale ◽  
Central Africa ◽  
Retrieval Algorithm ◽  
Science Data ◽  
The North ◽  
Data Products ◽  
Atmospheric Carbon

Abstract. The Orbiting Carbon Observatory-2 (OCO-2) is the first National Aeronautics and Space Administration (NASA) satellite designed to measure atmospheric carbon dioxide (CO2) with the accuracy, resolution, and coverage needed to quantify CO2 fluxes (sources and sinks) on regional scales. OCO-2 was successfully launched on 2 July 2014 and has gathered more than 2 years of observations. The v7/v7r operational data products from September 2014 to January 2016 are discussed here. On monthly timescales, 7 to 12 % of these measurements are sufficiently cloud and aerosol free to yield estimates of the column-averaged atmospheric CO2 dry air mole fraction, XCO2, that pass all quality tests. During the first year of operations, the observing strategy, instrument calibration, and retrieval algorithm were optimized to improve both the data yield and the accuracy of the products. With these changes, global maps of XCO2 derived from the OCO-2 data are revealing some of the most robust features of the atmospheric carbon cycle. This includes XCO2 enhancements co-located with intense fossil fuel emissions in eastern US and eastern China, which are most obvious between October and December, when the north–south XCO2 gradient is small. Enhanced XCO2 coincident with biomass burning in the Amazon, central Africa, and Indonesia is also evident in this season. In May and June, when the north–south XCO2 gradient is largest, these sources are less apparent in global maps. During this part of the year, OCO-2 maps show a more than 10 ppm reduction in XCO2 across the Northern Hemisphere, as photosynthesis by the land biosphere rapidly absorbs CO2. As the carbon cycle science community continues to analyze these OCO-2 data, information on regional-scale sources (emitters) and sinks (absorbers) which impart XCO2 changes on the order of 1 ppm, as well as far more subtle features, will emerge from this high-resolution global dataset.

scholarly journals Leaf traits and gas exchange in saplings of native tree species in the Central Amazon

2010 ◽  
Vol 67 (6) ◽  
pp. 624-632 ◽  
Author(s):  
Keila Rego Mendes ◽  
Ricardo Antonio Marenco
Keyword(s):  
Gas Exchange ◽  
Nitrogen Content ◽  
Leaf Area ◽  
Tree Species ◽  
Leaf Traits ◽  
Leaf Nitrogen ◽  
Dry Season ◽  
Leaf Thickness ◽  
Rainfall Regime ◽  
Leaf Nitrogen Content

Global climate models predict changes on the length of the dry season in the Amazon which may affect tree physiology. The aims of this work were to determine the effect of the rainfall regime and fraction of sky visible (FSV) at the forest understory on leaf traits and gas exchange of ten rainforest tree species in the Central Amazon, Brazil. We also examined the relationship between specific leaf area (SLA), leaf thickness (LT), and leaf nitrogen content on photosynthetic parameters. Data were collected in January (rainy season) and August (dry season) of 2008. A diurnal pattern was observed for light saturated photosynthesis (Amax) and stomatal conductance (g s), and irrespective of species, Amax was lower in the dry season. However, no effect of the rainfall regime was observed on g s nor on the photosynthetic capacity (Apot, measured at saturating [CO2]). Apot and leaf thickness increased with FSV, the converse was true for the FSV-SLA relationship. Also, a positive relationship was observed between Apot per unit leaf area and leaf nitrogen content, and between Apot per unit mass and SLA. Although the rainfall regime only slightly affects soil moisture, photosynthetic traits seem to be responsive to rainfall-related environmental factors, which eventually lead to an effect on Amax. Finally, we report that little variation in FSV seems to affect leaf physiology (Apot) and leaf anatomy (leaf thickness).

scholarly journals Implementasi Konsep Konservasi Air di Gedung Apartemen X

2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Vine Valenia David ◽  
Kancitra Pharmawati ◽  
Djoni Kusmulyana Usman
Keyword(s):  
Water Conservation ◽  
Rainy Season ◽  
Rainwater Harvesting ◽  
Wastewater Reuse ◽  
Dry Season ◽  
Clean Water ◽  
Groundwater Availability ◽  
The North ◽  
Water Recycle ◽  
Runoff Rate

<p>Clean water crisis that occurred in Bandung is caused by land conversion in North Bandung area which is a recharge area into commercial buildings. This increases runoff rate from 40% to 70% that can lead can lead to flooding and reduced groundwater availability. Therefore, it is necessary to save water by implementing water conservation. Considering those problems, this study aims to apply the concept of water conservation in X Apartment building that is located in the North Bandung Region by referring to Mayor Regulation of Bandung in 2016. Water conservation efforts that will be applied are wastewater reuse into water recycle, rainwater harvesting, infiltration well construction and placing water meters. The application of water conservation concept considers two conditions, namely in rainy season and dry season. Total need for clean water can be saved by 45,8% in dry season, while in rainy season clean water can be saved by 31,74%.</p>

scholarly journals Pengaruh Angin Dan Kelembapan Atmosfer Lapisan Atas Terhadap Lapisan Permukaan Di Manado

Jurnal MIPA ◽  
2014 ◽  
Vol 3 (1) ◽  
pp. 58 ◽  
Author(s):  
Farid Mufti ◽  
As'ari .
Keyword(s):  
Surface Layer ◽  
Wind Speed ◽  
Correlation Coefficient ◽  
Rainy Season ◽  
Primary Objective ◽  
Dry Season ◽  
Correlation Technique ◽  
Wind Condition ◽  
The North ◽  
Positive Correlation Coefficient

Penelitian ini mengkaji lebih dalam kondisi angin dan kelembapan udara pada saat musim hujan dan musim kemarau di Manado dengan menggunakan data di lapisan permukaan dan data udara atas dari Stasiun Meteorologi Sam Ratulangi Manado. Tujuan utama dari penelitian ini adalah mendapatkan hubungan antara kondisi angin dan kelembapan lapisan atas terhadap lapisan permukaan, sehingga dapat memprakirakan kondisi angin dan kelembapan lapisan permukaan dengan berdasarkan keadaan lapisan atas. Metode yang digunakan adalah mengkomponenkan angin dalam arah utara-selatan dan timur-barat, selanjutnya mencari keterkaitan dengan menggunakan teknik korelasi. Hasil penelitian ini menunjukkan pada saat musim hujan angin pada lapisan 1500 m dan angin di lapisan permukaan memiliki arah yang sama dan saling menguatkan untuk komponen timur-barat (zonal) dengan koefisien korelasi r=0,56, sedangkan pada saat musim kemarau angin pada lapisan 1500 m dan angin di lapisan permukaan memiliki arah yang sama dan saling menguatkan untuk komponen utara-selatan (meridional) dengan koefisien korelasi r=0,45. Keterkaitan yang cukup kuat antara angin dengan kelembapan terjadi pada komponen V (meridional) yaitu, pada saat musim hujan, semakin besar kecepatan angin komponen negatif (utara) semakin besar pula kelembapan udara di lapisan permukaan, dengan koefisien korelasi benilai positif r=0.40. Pada saat musim kemarau, semakin besar kecepatan angin komponen positif (selatan) semakin kecil kelembapan udara di lapisan permukaan, dengan koefisien korelasi bernilai negatif r=— 0,48.This study examined the wind and humidity condition in the rainy season and dry season in Manado by using the data in surface layer and upper air data from the Sam Ratulangi Meteorological Station. The primary objective of this study was to find the relationship between wind condition and upper layer humidity to surface layer, using correlation technique, in order to predict wind condition and humidity of the surface layer based on the condition of the upper layer. The results showed that, during the rainy season, the wind at layer 1500 m and surface layer had the same direction and mutually reinforced for the east-west component (zonal) with correlation coefficient r=0.56, whereas during the dry season, wind at layer 1500 m and at surface layer had the same direction and mutually reinforced for the north-south component (meridional) with correlation coefficient r=0.45. A relationship between wind and humidity was found at V component (meridional), which was, at rainy season, the higher the wind speed of negative component (north) the higher the humidity at surface layer with positive correlation coefficient r=0.40. At dry season, the higher the wind speed of positive component (south), the lower the humidity at the surface layer, with negative correlation coefficient r=—0.48.

Migratory Labour from North-Wester Nigeria

Africa ◽  
1957 ◽  
Vol 27 (3) ◽  
pp. 251-261 ◽  
Author(s):  
R. Mansell Prothero
Keyword(s):  
Large Scale ◽  
Source Area ◽  
Dry Season ◽  
Labour Migration ◽  
Agricultural Activity ◽  
Wet Season ◽  
The North ◽  
The People ◽  
Limited Scale ◽  
Opening Paragraph

Opening ParagraphReaders of Africa will be well aware of population migration as a characteristic feature of a continent where movement between one part and another is largely unrestricted as compared with the more settled parts of the world. There is much evidence of large-scale tribal migrations in the past, of the age-old seasonal wanderings of herders, and of recent labour migration to centres of mineral and industrial production, the last particularly in Central and South Africa. Information is more limited concerning the features of labour migration in West Africa at the present day. In general it is thought that migrants leave their home areas, after the harvest at the commencement of the dry season, to seek work elsewhere for a period of from three to six months and then return to take up farming with the commencement of the next rains. The major source area for these migrants is to the north of the tenth parallel where the wet season is concentrated into a period of about four months, thus severely restricting agricultural activity. Cultivation during the dry season is possible only on a very limited scale. There is thus a considerable period of the year when the primary economic activity of the people is not possible. It is logical that they should seek work elsewhere.

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