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Salako, et al.

1. Introduction To achieve this, a careful selection of relevant
vegetation phenotypic data from the tree species is
Vitellaria paradoxa C.F. Gaertn (shea nut tree) is needed to infer chlorophyll content (greenness) and,
primarily found in the Guinea savanna ecosystem of invariably, plant health, biomass, and yield – key
West Africa and the Nigeria states of Kwara, Niger, factors in selecting viable seeds from tree populations.
and Oyo North. It holds immense socioeconomic, The combination of geospatial technology and species
1
industrial, health, and ecological values. Thousands distribution modeling (SDM) is one of the feasible
2
of rural citizens, especially women, depend on this tree approaches for this task, as traditional field surveys
species for food, condiments, income, and household are often unfeasible at larger spatial scales due to
needs, such as cream, soap, and fuelwood. However, resource limitations. SDM works by correlating species
3,4
the excessive cutting and burning of these trees for field observations, primarily species occurrence data,
domestic fuelwood and charcoal production over with environmental predictor variables that reflect the
the past 30 years poses a dangerous trend not only to ecological requirements of the species to predict habitat
the survival of the species but also to the economic suitability. 12
and ecological services it provides. Over 5 million Remote sensing platforms, such as spaceborne/
metric tons of charcoal have been produced from this satellite (optical and radar) and unmanned aerial vehicle
tree species in West Africa, primarily in Ghana and mounted with different sensors, have become valuable
Nigeria. Notably, V. paradoxa is currently classified instruments to rapidly and non-destructively assess plant
5,6
as a vulnerable species on the International Union for and vegetation status. A number of useful vegetation
Conservation of Nature’s Red List. 7 phenotype parameters or vegetation indices can be
Although this tree species primarily grows in the wild, derived from these remote sensing platforms to infer
its propagation and cultivation remain major challenges plant productivity (e.g., chlorophyll contents or index),
in the tropics. Seed germination and maturation take a plant health status (e.g., green index), plant biomass
long time, and the absence of reliable and viable seeds and yield (e.g., normalized difference vegetation index
for vegetative propagation further complicates the [NDVI], plant water stress (normalized difference
process. 4 water index [NDWI]). These indices have been well
Given the socioeconomic benefits of this tree described in the literature. 13-17 Vegetation phenological
species, especially to rural females, as previously parameters or vegetation indices in remote sensing are
mentioned, and its ecological importance in carbon usually estimated using arithmetic combinations of
sequestration (with an average of 36 V. paradoxa spectral reflectance values, mainly from the red and
trees capable of sequestering approximately 2.49 near-infrared regions of the electromagnetic spectrum.
Mg/ha), the present rate of exploitation for charcoal Similarly, a strong understanding of tree population
8
production is unsustainable. Therefore, it is imperative seed zones can provide valuable guidance for tree
to implement conservation measures and to identify restoration and conservation activities. A seed zone
and select viable, healthy seeds for propagation and or seed transfer zone is defined as a geographically
restoration. V. paradoxa is a deciduous tree species that delineated area having similar climatic characteristics
sheds its leaves during the dry season, underscoring from which seeds could be transferred with a minor risk
9
the importance of monitoring its vegetation phenology of maladaptation. 18,19 The delineation of seed zones has
– particularly its growth patterns, leaf development, and mostly relied on climatic variables, such as precipitation
greenness – to effectively secure viable seeds for its and temperature. 18,19 Generalized provisional seed zones
propagation and restoration. can be constructed using geographic information system
A preliminary investigation showed that, despite (GIS)-based models of spatial layers combination,
existing research efforts to improve seed propagation for example, the most influential geospatial climate/
through vegetative techniques, no vegetation index environmental variables, 18,20,21 or through multivariate
2,4
assessment has been conducted on V. paradoxa to clustering of environmental variables. 22,23 In temperate
identify reliable seed sources for vegetative propagation. regions, the temperature of the coldest month has been
Therefore, measuring the species’ leaf spectral identified as one of the most important climatic variables
reflectance to assess its health status or to quantify affecting plant adaptation and distribution. This has
the extent of its viability, particularly distinguishing informed the use of winter minimum temperatures
between diseased and healthy tissues, could be a in constructing seed zone maps (SZM) in the United
promising tool for tackling this challenge. 10,11 States and the plant hardiness zone map by the United
20

Volume 22 Issue 4 (2025) 90 doi: 10.36922/AJWEP025210160