Is water availability really the main environmental factor controlling the phenology of woody vegetation in the central Sahel?

Seghieri, Josiane; Carreau, Julie; Boulain, N.; Rosnay, Patricia de; Arjounin, Marc; Timouk, Franck

doi:10.1007/s11258-012-0048-y

Cited by 37 publications

(33 citation statements)

References 41 publications

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“…Máguas et al 2011), one would expect them to respond to climatic variables by adjusting their phenological phases (i.e. the timing of phenological events), as had been previously demonstrated (Seghieri et al 2012;Schröder et al 2014). The abovementioned findings corroborate our observations that A. longifolia displayed different phenological timings in a mesic and in a xeric climate (Fig.…”

Section: Discussionsupporting

confidence: 91%

Do climatic and habitat conditions affect the reproductive success of an invasive tree species? An assessment of the phenology of Acacia longifolia in Portugal

et al. 2014

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Plant phenological events are some of the most sensitive indicators of how plant species respond to favourable or stressful conditions. The evaluation of the flowering phenology of invasive plant species is particularly relevant, mainly due to its crucial importance in determining plant reproductive success and the outcome of invasion. We studied the phenology of Acacia longifolia, an aggressive, invasive plant species in the Mediterranean basin. We measured its vegetative growth and reproductive traits, specifically flowering phenophases and fruit production, under different climatic conditions (mesic and xeric Mediterranean climates), and in two different habitats (pine forest and open area). All the measured phenological phases began earlier at the xeric site than at the mesic site; this was particularly evident when comparing reproductive phenophases. Flowering dates were significantly associated with air temperature, with early peak flowering dates linked to increases in air temperature. The number of fruiting flowers per inflorescence in A. longifolia trees was higher at the mesic site, mainly in the pine forest plot, and the number of aborted fruits was notably lower than in the xeric plots. The presence of a pine forest at the mesic site strongly influenced the flowering phenology of A. longifolia and resulted in the highest reproductive success and the lowest branch growth rate. Our results demonstrate that a combination of climate and forest structure can cause pronounced differences in phenology and reproductive success of A. longifolia. These data can help to understand the variations in invasive rates of A. longifolia across the Mediterranean basin.

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Section: Discussionsupporting

confidence: 91%

Do climatic and habitat conditions affect the reproductive success of an invasive tree species? An assessment of the phenology of Acacia longifolia in Portugal

et al. 2014

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“…Firstly, the image acquisition date in early June (i.e., early wet season) provided good contrast between tree cover and background components due to low growth activity of grasses, crops, and shrubs [95]. Specifically, the foliage of Sudan-Sahelian tree species is known to develop before the re-growth of the herbaceous vegetation [96,97]. Secondly, the size of the 15 m panchromatic pixels seemed to be better suited to capture the reflectance contributions from trees, which may be mixed (e.g., trees and grass) in the larger 30 m Landsat multispectral pixels when the tree canopy is open [28].…”

Section: Relationships Between Predictor Variables and Tree Cover Attmentioning

confidence: 99%

Mapping Tree Canopy Cover and Aboveground Biomass in Sudano-Sahelian Woodlands Using Landsat 8 and Random Forest

et al. 2015

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Accurate and timely maps of tree cover attributes are important tools for environmental research and natural resource management. We evaluate the utility of Landsat 8 for mapping tree canopy cover (TCC) and aboveground biomass (AGB) in a woodland landscape in Burkina Faso. Field data and WorldView-2 imagery were used to assemble the reference dataset. Spectral, texture, and phenology predictor variables were extracted from Landsat 8 imagery and used as input to Random Forest (RF) models. RF models based on multi-temporal and single date imagery were compared to determine the influence of phenology predictor variables. The effect of reducing the number of predictor variables on the RF predictions was also investigated. The model error was assessed using 10-fold cross ). This mapping approach is based on freely available Landsat 8 data and relatively simple analytical methods, and is therefore applicable in woodland areas where sufficient reference data are available.

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“…In addition, this first‐order seasonal correspondence could not explain what specific environmental factors trigger canopy leaf flushing and senescence and what factors control interannual variability in these phenological properties. For example, early leaf flushing in the African Miombo Woodlands has been widely observed before the arrival of seasonal rainfall [ Chidumayo , ; Fuller and Prince , ; Seghieri et al ., , ], with delayed senescence in many woody species after the end of the rainy season [ Bie et al ., ; Seghieri et al ., ]. These unresolved phenological behaviors call for a more detailed study on the relationships between the rainy season and regional land surface phenology, including canopy growth onset and senescence.…”

Section: Introductionmentioning

confidence: 99%

Terrestrial hydrological controls on land surface phenology of African savannas and woodlands

Guan

Wood

Medvigy

et al. 2014

J. Geophys. Res. Biogeosci.

134

122

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This paper presents a continental-scale phenological analysis of African savannas and woodlands.We apply an array of synergistic vegetation and hydrological data records from satellite remote sensing and model simulations to explore the influence of rainy season timing and duration on regional land surface phenology and ecosystem structure. We find that (i) the rainy season onset precedes and is an effective predictor of the growing season onset in African grasslands. (ii) African woodlands generally have early green-up before rainy season onset and have a variable delayed senescence period after the rainy season, with this delay correlated nonlinearly with tree fraction. These woodland responses suggest their complex water use mechanisms (either from potential groundwater use by relatively deep roots or stem-water reserve) to maintain dry season activity. (iii) We empirically find that the rainy season length has strong nonlinear impacts on tree fractional cover in the annual rainfall range from 600 to 1800 mm/yr, which may lend some support to the previous modeling study that given the same amount of total rainfall to the tree fraction may first increase with the lengthening of rainy season until reaching an "optimal rainy season length," after which tree fraction decreases with the further lengthening of rainy season. This nonlinear response is resulted from compound mechanisms of hydrological cycle, fire, and other factors. We conclude that African savannas and deciduous woodlands have distinctive responses in their phenology and ecosystem functioning to rainy season. Further research is needed to address interaction between groundwater and tropical woodland as well as to explicitly consider the ecological significance of rainy season length under climate change.

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Is water availability really the main environmental factor controlling the phenology of woody vegetation in the central Sahel?

Cited by 37 publications

References 41 publications

Do climatic and habitat conditions affect the reproductive success of an invasive tree species? An assessment of the phenology of Acacia longifolia in Portugal

Do climatic and habitat conditions affect the reproductive success of an invasive tree species? An assessment of the phenology of Acacia longifolia in Portugal

Mapping Tree Canopy Cover and Aboveground Biomass in Sudano-Sahelian Woodlands Using Landsat 8 and Random Forest

Terrestrial hydrological controls on land surface phenology of African savannas and woodlands

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