Domestication of Irvingia gabonensis: 3. Phenotypic variation of fruits andkernels in a Nigerian village

Domestication of Irvingia gabonensis, a fruit tree grown in agroforestry systems in West and Central Africa, offers considerable scope for enhancing the nutritional and economic security of subsistence farmers in the region. Assessments of phenotypic variation in ten fruit, nut and kernel traits were made on twenty-four ripe fruits from 100 Irvingia gabonensis trees in Ugwuaji village in southeast Nigeria, a center of genetic diversity for this species. There were important differences between the young planted trees of this study and the older unplanted trees of a similar study in Cameroon. Significant and continuous tree-to-tree variation was found in fruit mass(69.0–419.8 g), flesh mass (59.5–388.8 g), nut mass (9.5–40.6 g), shell mass (4.9–30.9 g) and kernel mass (0.41–7.58 g); fruit length (49.2–89.3 mm) and width (46.2–100.5 mm) and flesh depth (12.9–31.4 mm), as well as considerable variation in flesh colour, skin colour, fruit taste and fibrosity. Some fruits were considerably bigger than those found in Cameroon. These quantitative results will help in the development of cultivars within participatory approaches to agroforestry tree domestication, and so promote poverty alleviation and sustainable agriculture. This revised version was published online in June 2006 with corrections to the Cover Date.     

Domestication of Irvingia gabonensis: 1. Phenotypic variation in fruits and kernels in two populations from Cameroon

Twenty four fruits from each of 52 Irvingia gabonensis trees from two villages (Nko'ovos II and Elig Nkouma) of the humid lowland forest zone of Cameroon (West Africa) were assessed to determine the extent of variation in ten fruit, nut (endocarp), and kernel (cotyledon) characteristics. Highly significant differences were found in fruit length (Range = 46.2 to 77.3 mm), fruit width (45.1 to 72.5 mm), flesh (mesocarp) depth (11.2 to 21.8 mm), fruit mass (44.5 to 195.4 g), kernel mass (0.54 to 6.9 g) and shell mass (5.4 to 18.6 g). In each of these traits there was continuous variation. Differences were also observed in fruit taste and fibrosity. The most frequent skin and flesh color was yellow (Methuen Color Code 4A8). Mean fruit length, fruit width, fruit mass, shell mass and kernel mass differed significantly between villages, but did not differ between different landuses (homegardens, cocoa farms, crop fields or fallows). These results represent the first quantitative assessment of tree-to-tree variation in fruit traits for this species and are discussed with regard to the domestication potential of I. gabonensis.This revised version was published online in November 2005 with corrections to the Cover Date.     

Domestication potential of Marula (<Emphasis Type="Italic">Sclerocarya birrea</Emphasis> subsp. <Emphasis Type="Italic">caffra</Emphasis>) in South Africa and Namibia: 3. Multiple trait selection

An understanding of the inter-relationships between the traits characterising tree-to-tree variation in fruits and kernels is fundamental to the development of selected cultivars based on multiple trait selection. Using data from previously characterised marula (Sclerocarya birrea) trees in Bushbuckridge, South Africa and North Central Region of Namibia, this study examines the relationships between the different traits (fruit pulp, flesh/juice mass, and nut shell and kernel mass) as a means to determine the opportunities to develop cultivars. Strong and highly significant relationships were found between fruit mass and pulp mass in trees from South Africa and Namibia, indicating that size is a good predictor of fruit pulp production. However, fruit size is not a good predictor of nut or kernel production, as there were weak relationships between fruit and nut and/or kernel mass, which varied between sites and landuses. Generally, the relationships between fruit mass and kernel mass were weaker than between fruit mass and nut mass. Relationships between kernel mass and shell mass were generally weak. The lack of strong relationships between fruit and kernel mass does, however, imply that there are opportunities to identify trees with either big fruits/small nuts for pulp production, or trees with large kernels in relatively small fruits for kernel oil production. However, within fruits from the same tree, nuts could contain 0–4 kernels, indicating that even in trees with an inherent propensity for large kernels, improved pollination may be required to maximise kernel mass through an increase in kernel number. Finally, the relationships between percentage kernel oil content and the measured morphological traits were also very weak. The conclusions of these results are that there is merit in identifying different combinations of traits for the selection of trees producing either pulp or kernels. Consequently, fruit and kernel ‘ideotypes’ are presented as guides to the selection of elite trees for cultivar development. These results have important implications for the domestication of the species as a producer of fruits or kernels for food/beverages or cosmetic oils.     

Domestication potential of Marula (Sclerocarya birrea subsp caffra)in South Africa and Namibia: 1. Phenotypic variation in fruit traits

Studies of tree-to-tree variation in fruit traits are a pre-requisite for cultivar development. Fruits were collected from each of 63 marula (Sclerocarya birrea) trees in Bushbuckridge, South Africa and from 55 trees from the North Central Region of Namibia. The South African trees were in farmers fields, communal land and natural woodland, at three sites: Acornhoek road, Allandale/Green Valley and Andover/Wits Rural Facility. The Namibian trees were all from farmers fields in three areas: North east, North west and West. The fruits were partitioned into skin and flesh/juice to examine the extent of the variation found in different components of marula fruits from different trees. Namibian fruits were significantly larger than those from South Africa (26.7 vs 20.1 g), due to their greater pulp mass (22.2 vs 16.2 g), especially the flesh/juice component. In South African fruits, those from farmers fields were significantly larger in all components (Fruit mass = 23.6 vs 19.3 and 18.0 g in natural woodland and communal land respectively). In Namibia, mean fruit mass did not differ significantly across sites (25.5 − 27.0 g). However, within each sample there was highly significant and continuous variation between trees in the pulp (S Africa = 7.5 − 31.3 g; Namibia = 8.3 − 36.0 g) and flesh/juice mass (S Africa = 2.2 − 7.6g; Namibia = 3.8 − 22. 6g), indicating the potential for selection of trees producing superior products. The fruits of the Namibian trees were compared with the fruits from one superior tree (‘Namibian Wonder) with a mean fruit mass of 69.9 g The percentage frequency distribution of fruit mass from trees in farmers fields in South Africa was skewed, while being bimodal in North east and North west populations from Namibia, suggesting that at these sites farmers are engaged in domestication through truncated selection of the best mother trees. It is concluded that there are trees in on-farm populations that have great potential to be propagated vegetatively as selected cultivars.     

Agroforestry potential of Dacryodes edulis in the oil palm-cassava belt of southeastern Nigeria

Between June 1993 and June 1994, 112 farmers in the oil palm (Elaeis guineensis)-cassava (Manihot esclentus) belt of southeastern Nigeria were interviewed to determine the status and agroforestry potential of Dacryodes edulis. Between 50% and 100% of respondents in different states within the belt owned D. edulis trees. On average, a farmer owned 9.3 trees, the largest number being 16, by farmers in Imo State. Twenty percent of farmers in the system rated D. edulis their best farm tree. It was present in all the farm niches: homegardens (51.4%), tree crop plots (20.7%) food crop plots (11.4%), secondary forest/fallow (14.2%) and virgin forest (2.5%). The tree is planted primarily for home consumption and sale to generate cash. At the current densities, on-farm D. edulis trees generally did not decrease yield of companion crops or trees. Except for ring weeding around the stem, D. edulis trees received little or no management attention. More than 50% of the trees produced 33 to 50 kg of fruit tree⁻¹ annually. This is valued at US $0.4 to 0.8 kg⁻¹. Farmers were willing to plant more D. edulis trees provided trees with traits such as less height for easy harvesting of fruits, larger fruit, more fruits, sweeter fruits and year round production of fruits were available. Possible agroforestry technologies into which D. edulis may fit include live fences, scattered trees in food crop fields, shade trees in tree crop plots and contour bund or hedgerow planting. Research is required to determine best tree accessions, canopy management strategies, optimum tree population and improved methods on post- harvest handling of fruits. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genetic variation among and within provenances of Adansonia digitata L. (Baobab) in seed germination and seedling growth from selected natural populations in Malawi

Baobab (Adansonia digitata L.) trees have a wide variety of subsistence and economic values across sub-Saharan Africa. Knowledge of the genetic variation within and between the species is essential for management and designing domestication, improvement and conservation strategies. Fifty-nine half-sib families were evaluated in the nursery to determine the genetic variation and control within and between the populations from four silvicultural zones. Seed germination and seven seedling growth parameters were assessed. Total phenotypic variance, family variance, within family variance, individual narrow sense heritability, and additive genetic coefficient of variation (AGCV) were derived from observed and expected mean squares. There were highly significant differences in seed germination, plant height, root collar diameter, number of leaves, shoot height and diameter, tuber diameter and weight. Provenance variation in germination ranged from 46.7?±?3.3 to 68.7?±?3.3% while tree-to-tree variation ranged from 6.3?±?8.6 to 95.5?±?8.6%. Coefficient of variation in seedling growth variables ranged from 18.6 to 43.6%. Individual narrow sense heritabilities (h²) ranged from 0.07 to 0.71. AGCV ranged from 3.21 to 14.67%. Morphological traits showed that mainland populations were genetically distant from the island one. High and moderate additive genetic control of traits and AGCV show the potential that Baobab can also respond well to tree improvement. High phenotypic variation found in the study offers an opportunity to effect selection of superior attributes at both provenance and individual tree-to-tree level.     

Domestication potential of Marula (Sclerocarya birrea subsp caffra) in South Africa and Namibia: 2. Phenotypic variation in nut and kernel traits

As part of a wider study characterizing tree-to-tree variation in fruit traits as a pre-requisite for cultivar development, fruits were collected from each of 63 marula (Sclerocarya birrea) trees in Bushbuckridge, South Africa and from 55 trees from the North Central Region of Namibia. The nuts were removed from the fruit flesh, and the kernels extracted, counted and weighed individually to determine the patterns of dry matter partitioning among the nut components (shell and kernel) of different trees. Mean nut, shell and kernel mass were not significantly different between the two countries. Between sites in South Africa there were highly significant differences in mean nut mass, shell mass, kernel mass and kernel number. In Namibia, there were highly significant differences between geographic areas in mean shell mass, kernel mass and kernel number, but not in nut mass. These differences had considerable impacts on shell:kernel ratios (8.0 - 15.4). In South Africa, mean kernel mass was significantly greater in fruits from farmers fields (0.42 g) than from communal land (0.30 g) or natural woodland (0.32 g). Within all sites, in both South Africa and Namibia, there was highly significant and continuous variation between individual trees in nut mass (South Africa = 2.3 - 7.1 g; Namibia = 2.7 - 6.4 g) and kernel mass (South Africa = 0.09 - 0.55 g; Namibia = 0.01 - 0.92 g). The small and valuable kernels constitute a small part of the nut (Namibia = 6.1- 11.1%; South Africa = 7.6 - 10.7%). There can be 4 kernels per nut, but even within the fruits of the same tree, kernel number can vary between 0-4, suggesting variation in pollination success, in addition to genetic variation. The nuts and kernels of the Namibian trees were compared with the fruits from one superior tree (Namibian Wonder: nuts = 10.9 g; kernels = 1.1 g). Oil content (%) and oil yield (g/fruit) also differed significantly between trees (44.7 - 72.3% and 8.0 - 53.0 g/fruit). The percentage frequency distribution of kernel mass was skewed from trees in farmers fields in South Africa and in some sites in Namibia, suggesting a level of anthropogenic selection. It is concluded that there is great potential for the development of cultivars for kernel traits, but there is also a need to determine how to increase the proportion of nuts with four kernels, perhaps through improved pollination success.     

Phenotypic variation of baobab (<Emphasis Type="Italic">Adansonia digitata</Emphasis> L.) fruit traits in Mali

We analyzed the phenotypic variation of baobab (Adansonia digitata L.) fruits from Mali to define the domestication potential of this species. 269 trees, selected from 10 provenances distributed along a rainfall gradient, were characterized. Five fruits were sampled from each tree. Total individual fruit weight was partitioned into shell, pulp, and seed weight. Ratios were calculated between pulp + seed and total weight, and between pulp and seed weight. For all the measured fruit traits, we detected significant differences between provenances, as well as between trees from the same provenance. Assuming that the measured traits are under genetic control, the latter facts indicate that there are considerable opportunities for tree selection on a local scale. However, candidate plus trees with specific properties, e.g., extremely high pulp or seed weight, were found only in some locations. Mean pulp yield per fruit might be considerably increased by selecting the 5% trees with the highest pulp weight (mean: 45 ± 1 g, best 5%: >100 g). The same might be true for seed production (mean: 71 ± 2 g, best 5%: >150 g). Also the ratio between pulp and seed weight can be an important fruit characteristic for selection: in fruits with a low ratio, relatively more pulp sticks to the seeds when separating the two fruit parts by grinding, and thus more pulp will be lost for further processing. We identified several trees with a high pulp weight combined with a high ratio between pulp and seed weight. It is concluded that there is considerable phenotypic variability in traits of baobab fruit in Mali, offering opportunities for cultivar selection.     

Domestication of Irvingia gabonensis: 2. The selection of multiple traits for potential cultivars from Cameroon and Nigeria.

Ten fruit and kernel traits were assessed in 24 fruits of each of 152Irvingia gabonensis trees in three distinct populations in west and central Africa [2 populations of non-planted trees in Cameroon: Nko'ovos II (21 trees) and Elig-Nkouma (31 trees) and 1 population of planted trees in Nigeria: Ugwuaji (100 trees)]. Strong relationships were found between fruit weight and other fruit traits (e.g. flesh weight[r ² = 0.99: P < 0.001],fruit length [r ² = 0.74–0.83:P < 0.001], fruit width[r ² = 0.77–0.88: P< 0.001]). In contrast, relationships between kernel weight and other kernel/nut traits (e.g. shell weight and nut weight) were found to be weak[r ² = 0.009–0.37, P =0.058–0.001], with the exception of nut weight at Nko'ovos II(r ² = 0.65, P < 0.001).Relations hips between fruit and kernel traits (fruit massv. kernel mass, fruit mass v. shell mass, flesh mass v. kernel mass, nut massv. fruit mass and flesh depth v.kernel mass) were found to be very weak. This indicates that domestication through the selection and vegetative propagation of multiple-trait superior phenotypes is unlikely to be able to combine good fruit characteristics and good kernel characteristics within cultivars. Consequently, domestication activities should independently focus on ideotypes representing: 'fresh fruit' traits, and 'kernel' traits, that combine high values of the different fruit and kernel characteristics respectively. Evidence from this study indicates that selection of the three trees closest to the fruit ideotype per village as the mother plants for vegetative propagation and cultivar development, should give village level gains of 1.3 – 2-fold in fruit mass, and up to 1.5-fold in taste. Similarly for the kernel ideotype, selection of the three trees with the best fit would give potential gains in kernel mass of 1.4 – 1.6-fold. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of collection date on capsule moisture content and germination of Populus ciliata Wall. ex Royle from central Himalaya

Seed maturity indices of Populus ciliata were investigated in collections from Sukhatal and Bhowali. Across both seed sources, mean capsule size varied from 68.0±1.5 mm² to 72.0±0.9 mm², while mean number of capsules/100 grams varied from 268±8 to 295±12. Mean weight of 100 capsules varied from 25.0±1.4 g to 27.0±1.4 g. Weight of 100 capsules among sources and individual trees differed significantly (P < 0.05), while number of capsules/100 grams and weight of 100 capsules was negatively correlated (r² = 0.69). As capsules matured moisture content decreased from 83.2±1.1% to 54.3±0.3% at Sukhatal and from 77.7±0.4% to 46.4±0.3% at Bhowali. The optimum germination was at 58–60% moisture content. Maturation was related to capsule colour changes as well as moisture content. These parameters were judged to be good indicators of when to collect P. ciliata seeds.     

Morphological variation in <Emphasis Type="Italic">Balanites aegyptiaca</Emphasis> fruits and seeds within and among parkland agroforests in eastern Niger

Balanites aegyptiaca (L.) Delile. is one of the priority indigenous fruit trees for rural communities in the West African Sahel. As part of a participatory tree domestication program in Niger, phenotypic variation in fruit and seed morphology was assessed in four natural populations in eastern Niger. Measured variables were weight of the fruit, seed coat and kernel; length and width of the fruit and seed (25 trees per population, 30 fruits per tree). Derived variables were the tree’s coefficient of variation (CVs) for each measured variable, and two sets of factor scores from principal components analysis of tree means and CVs. ANOVA indicated significant variation in all measured variables due to trees nested in populations. ANOVA and simple linear regression indicated significant geographic variation in some variables: the drier parts of the sample region tended to have heavier fruits and kernels, longer/narrower seeds, and lower within-tree variability in fruit and seed width. Length and width were strongly correlated between fruits and seeds, fruit weight was moderately correlated with seed dimensions, and CVs of fruit weight and width were moderately correlated with the CV of seed width. Some hypotheses for the geographic variation are presented, and some practical implications of the correlations for tree domestication programs are discussed.     

Insect (Salebria sp.) infestation and impact on Vitellaria paradoxa C.F. Gaertn. fruit production in agroforestry parklands

Vitellaria paradoxa, known as Shea tree or karité, is one of the dominant trees of agroforestry parklands in Sahelian region with an immense commercial value. In this study, we examined infestation of fruit-bearing shoots and fruits on two sites in western Burkina Faso across different reproductive phenophases, crown heights and aspects. The number of infested and healthy shoots and fruits were counted on 60 reproductively active trees randomly selected from on-year shea trees in each site, using a metal frame (0.5 × 0.5 m) to mark a fixed area of the canopy for sampling. The shoot and fruit borer was identified as Salebria sp. (Lepidoptera:Pyralidae), which was not reported earlier. The proportion of infested trees and shoots varied significantly between sites and among reproductive phenophases (P < 0.0001). The site close to the natural forest had the highest infestation rate than distantly located site. Among reproductive phenophases, the proportions of infested trees and shoots were the highest during flowering and fruit set, respectively. Fruit infestation also varied significantly between sites, crown heights and aspects (P < 0.001). The site close to the natural forest and the crown with north-east aspect were heavily infested while the bottom part of the crown had the lowest infestation. As a whole, 49–80% of trees, 24–31% of shoots and 4–15% of fruits were found infested, depending on the site. These infestation levels combined with precocious flower and fruit abscissions would pose serious economic losses that justify a call for immediate pest control initiatives.     

Fruit- and seed-germination characteristics of Strychnos cocculoides an indigenous fruit tree from natural populations in Zambia

Domestication and improvement of traditionally used wild indigenous fruit trees hold great promise in agroforestry development. Strychnos cocculoides is a wild indigenous fruit tree that was ranked third by farmers and is one of the priority species chosen for domestication in southern Africa. This study was conducted with the objective of determining the variability in fruit, seed and germination characteristics of four populations of Strychnos cocculoides collected from Zambia. Results showed significant differences (P < 0.05) between and within provenances in fruit, pericarp and pulp weights. Fruits from Kalulushi provenance were heaviest (296 g) whereas the lightest were Petauke provenance fruits (158 g). The pulp content of heavy and light fruits were 52.8% and 47.6% respectively. There was no significant difference (P > 0.05) in the number of seeds per fruit within and between the provenances. In contrast, the seed weight was significantly different (P < 0.05) within and between provenances. The heaviest seeds were found in the heaviest fruits — Kalulushi while the lightest were found in Serenje provenance. Fruit weight was positively correlated with pulp weight (P < 0.001, r = 0.70), pericarp weight (P < 0.001, r = 0.54) and seed weight (P < 0.001, r = 0.76). The provenances differed significantly (P < 0.05) in cumulative germination percentage, ranging from 56 (Kalulushi) to 83 (Kasama).This revised version was published online in November 2005 with corrections to the Cover Date.     

Fruit production ofAcacia tortilis andA. nilotica in semi-arid Ethiopia

Dry, dehiscent fruits ofAcacia tortilis provide important fodder for pastoral livestock in dry seasons on the central Borana Plateau, fruits ofA. nilotica may also be useful during drought. Information was needed on fruit yield to assess what these species could contribute to improved calf feeding systems based on local resources. Fruit production of 10 mature trees per species was measured at five sites for seven months during 1988–9 (n=50 per species). Fruit yields varied according to site, season and species x site (each atP<0.001), but there was no main effect of species (P=0.13). Yields were not correlated with trunk diameter at breast height (DBH) or canopy area within or across species (P>0.05 in all cases). Yields ranged from 0 to 40 kg DM per tree overall, with an average of 5.3 kg DM per tree (or 65 g DM/m² of canopy area). This average tree had a DBH of 26 cm and a canopy area of 81 m². Low and highly variable fruit yields appear to constrain enhanced use of these species here. These species warrant further attention in research and development, however, given their strategic value as forage resources in pastoral systems and their ability to persist in variable environments.     

The effect of cutting height and frequency on the forage,wood and seed production of sixSesbania sesban accessions

The forage, wood and seed production of sixSesbania sesban accessions was assessed under irrigated conditions for two cutting frequencies and heights. Control trees were left uncut to measure their seed production potential. The trial was conducted over an 18-month period. The fastest growing accession produced almost 10 t/ha total dry matter (DM) after six months of growth, 40% of it being leaves. Total DM yield was higher at the six-month cutting interval compared to the three months' interval with yields between 25–42 t/ha/year. Some accessions could not sustain their high level of production but showed drastic drops in yield after repeated cutting. In general leaf DM production increased with increased cutting height. When cut at 150 cm the DM leaf yield at the three-month cutting interval ranged form 9.7–18.2 t/ha. More plants survived at the three-month cutting frequency. Seed yields varied considerably between accessions (0.02–1.56 t/ha at the six months' interval). After 18 months of undisturbed growth the trees yielded 36.5–83.7 t/ha total DM comprising 21% leaves. Fresh wood biomass ranged between 56.4–138.0 t/ha and seed yields 2.7–6.6 t/ha.     

Phenotypic variation in fruit and seed morphology of Adansonia digitata L. (baobab) in five selected wild populations in Malawi

Adansonia digitata L. (Baobab) is widely distributed throughout Sub-Saharan Africa stretching from Senegal to Sudan, and from Ethiopia to Natal. Information of phenotypic and genetic variation is a prerequisite for the domestication and improvement of baobab fruits from the wild. A study was done to determine within and between provenance variability in fruit and seed characteristics of five populations selected from four silvicultural zones and assess whether morphometric traits could delineate populations from different zones into land races. Fruits were characterized from 55 trees representing a wide geographical range. Six fruit traits and three individual seed traits were assessed. Results showed highly significant differences (P????0.001) in fruit, pulp, and seed weight, fruit length and width, number of seed, individual seed weight, seed length and width within and between populations. Mean fruit weight ranged from 125.8?±?3.25 to 162.9?±?3.25?g, seed weight ranged from 38.6?±?2.5 to 66?±?2.01?g and pulp weight ranged from 28.7?±?1.33 to 41.4?±?1.33?g. Single seed weight showed pronounced evidence of divergence of populations into ecotypes. The rich diversity found between and within populations is important for domestication purposes and tree improvement through selection and breeding. All populations could be used for seed source but distribution should be consciously done recognizing existence of races.     

Quantitative descriptors of variation in the fruits and seeds of Irvingia gabonensis

Methods were developed to quantify variation in the fruit, nut and kernel traits using the fruits from four trees of Irvingia gabonensis, an indigenous fruit tree of west and central Africa. The measurement of 18 characteristics of 16–32 fruits per tree identified significant variation in fruit, nut and kernel size and weight, and flesh depth. Differences were also identified in shell weight and brittleness, fruit taste, fibrosity and flesh colour. Relationships between fruit size and weight with nut and kernel size and weight were found to be very weak, indicating that it is not possible to accurately predict the traits of the commercially-important kernel from fruit traits. Seven key qualitative traits are recommended for future assessments of the levels of genetic variation in fruits and kernels. These traits describe ideotypes for fresh fruit and kernel production.This revised version was published online in November 2005 with corrections to the Cover Date.     

Benefits and costs of intercropping reforestation in the Atlantic lowlands of Costa Rica.

Agroforestry options as a means of promoting reforestation were testedby establishing with 10 farmers simple comparisons between pure plantations andtimber trees with annual or perennial intercrops. Two year-old intercroppedtrees on-farm had 22–48% greater height and 24–38% greater diameterthan trees in pure plantations. The exception was Cordiaalliodora that did not respond significantly to intercropping withcassava (Manihot esculenta). Only intercrops with the mostvaluable crops on agricultural soils produced a return to labour above thedailywage rate. On non-agricultural soils, farmers only intercrop a small area oftheir plantations with subsistence crops to meet home consumption needs. In thecontext of Costa Rica intercropping appeared to have a limited potential tofinance the reforestation costs of farmers.     

Rehabilitation practices that shape cocoa agroforestry systems in Central Cameroon: key management strategies for long-term exploitation

In Africa’s main cocoa producing countries, rehabilitation of old cocoa orchards is increasingly debated but rarely adopted. In Central Cameroon, rehabilitation practices are regularly set up in old cocoa-based agroforestry systems (cAFS). To better understand the impact of such practices we built a chronosequence of 40 cAFS. We carried out specific surveys with farmers on each plot in order to check for rehabilitation effects on cocoa stands and associated woody species (AWS). We found that cocoa trees represented on average 88.2% of woody individuals and increased with age (from 84.7 to 91.5%). The cocoa stand basal area (BA) share significantly increased with age and reached up to 40.2% in the oldest systems. Cocoa, fruit and forest trees mean BA increased with aging. They were on average of 6.5, 5.7 and 10.7 m² ha^?1 respectively. Six different architectural types, different from the theoretical architectural evolution of cocoa trees over time, were identified. Among them, type 4 characterized by several orthotropic suckers of differing ages, was found typical of farmers’ cutting back practices. Type 4 cocoa trees density increased over time and its BA represented on average 60% of cocoa stand BA in the oldest systems. Concomitantly, farmer’s management of AWS led to continuous evolution of the systems both in terms of density and species composition. Our results show that (i) permanent densification and cutting back practices (type 4) allow the rejuvenation of cocoa stands while increasing cocoa stands BA share; (ii) the continuous management of AWS by farmers is undertaken to favour cocoa trees share over time by limiting inter-specific competition and promoting complementarity between cocoa trees and AWS. We argue that such practices explain a fair part of the long-term sustainability observed in cAFS from Central Cameroon and represent a model from which new rehabilitation schemes could be inspired.     

Predicting individual stem volumes of sugi (Cryptomeria japonica D. Don) plantations in mountainous areas using small-footprint airborne LiDAR

This study investigated which predictor variables with respect to crown properties, derived from small-footprint airborne light detection and ranging (LiDAR) data, together with LiDAR-derived tree height, could be useful in regression models to predict individual stem volumes. Comparisons were also made of the sum of predicted stem volumes for LiDAR-detected trees using the best regression model with field-measured total stem volumes for all trees within stands. The study area was a 48-year-old sugi (Cryptomeria japonica D. Don) plantation in mountainous forest. The topographies of the three stands with different stand characteristics analyzed in this study were steep slope (mean slope ± SD; 37.6° ± 5.8°), gentle slope (15.6° ± 3.7°), and gentle yet rough terrain (16.8° ± 7.8°). In the regression analysis, field-measured stem volumes were regressed against each of the six LiDAR-derived predictor variables with respect to crown properties, such as crown area, volume, and form, together with LiDAR-derived tree height. The model with sunny crown mantle volume (SCV) had the smallest standard error of the estimate obtained from the regression model in each stand. The standard errors (m³) were 0.144, 0.171, and 0.181, corresponding to 23.9%, 21.0%, and 20.6% of the average field-measured stem volume for detected trees in each of these stands, respectively. Furthermore, the sum of the individual stem volumes, predicted by regression models with SCV for the detected trees, occupied 83%–91% of field-measured total stem volumes within each stand, although 69%–86% of the total number of trees were correctly detected by a segmentation procedure using LiDAR data.