Description: 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 m 2 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.

Description: Silvopastoral systems are sustainable production systems characterized by greater biodiversity and multifunctionality, compared with other livestock production methods. The complex functional dynamics, however, make silvopastoralism a difficult construct to design and study. The key design criterion for these complex land use practices is to optimize the use of spatial, temporal, and physical resources, by maximizing positive interactions (facilitation) and minimizing negative ones (competition) among the components, for which the principles of sustainable land use systems are relevant. In this paper we address the cardinal questions, how the general ecological principles common to complex natural systems apply to the design and management of silvopastoral systems and how sound management might be identified with the notion of sustained maximum yield. In particular, we explore (1) spatial and temporal heterogeneity for maximizing resource use efficiency, (2) competitive interactions in perennial systems, (3) structural and functional diversity for resource conservation, and (4) integration of the principles of disturbance ecology in silvopastoral system design.

Description: Annual screenings of forage grasses and legumes for shade tolerance were conducted from 1996 to 2001 in the outdoor Shade Tolerance Screening Laboratory at the Horticulture and Agroforestry Research Center, University of Missouri. Forty-three forages were grown under non-shade (100% of full sunlight), moderate shade (45%), and dense shade (20%) without competition for water and nutrients. Annual forage yield (g pot −1 ) was equal to or higher under moderate shade for all 43 forages and under dense shade for 31 forages than the non-shade control. Relative distance plasticity index (RDPI), a measure of a species’ adaptability to different environments, ranged from 0.104 to 0.567. Cool season grasses had the lowest RDPI (0.183), followed by warm season grasses (0.252), warm season legumes (0.274), and cool season legumes (0.314), indicating grasses tend to be more shade tolerant than legumes in terms of forage yield. Overall, most grass and legume forages have the potential to produce equivalent or higher yields in agroforestry practices featuring light to moderate shade than forages in open pastures when competition from tree roots is minimized.

Description: To alleviate the combined effects of water and heat stress prevailing in drylands, the choice and introduction of appropriate plant species to these conditions is essential for the success of planting in rehabilitation projects. The argan tree ( Argania spinosa ) is a vigorous plant, admirably adapted to dry climates, with indisputable physiological and ecological characteristics that make of this tree an ideal plant to fight against erosion and desertification process, which seriously threaten arid lands. However, the geographical origin of seeds/seedlings represents a determining factor. In this context, we investigated the morphological responses of growth in two provenances of argan, the provenance of Tindouf ‘PT’ from Algeria and that of Agadir ‘PA’ from Morocco; under water stress conditions. The experiment attempts to evaluate the level of drought tolerance of these two provenances for selecting the planting material that copes and adapts better to hot arid lands. Argan seedlings of both provenances (PA and PT) were submitted to a water stress gradient (75, 40, 20, and 10% of field capacity), then morphological parameters (shoot height, number of leaves, number of spines, root collar diameter, length of taproot) were measured after 3, 6, 9 and 12 months of growth. All variables of morphological growth varied significantly ( P  〈 0.001) between water stress levels, seed geographical provenances and seedling growth ages. The overall of results concerning morphological parameters indicated that the increase of water stress induced in both argan provenances: a decrease in shoot height associated with an increase in length of taproot that resulted in the reduction of leaf numbers and radial growth but the increase the number of spines. The argan plantlets of Agadir have completely failed to tolerate water stress of 10% FC. Under water stress (40, 20, 10% FC), argan seedlings of Tindouf revealed higher growth results than those of Agadir. PT seedlings offset the water deficit by root elongation to ensure growth of the various components of the aerial part. PT seedlings were more resilient to drought stress as compared to those of PA. The highest growth results were obtained with 40% FC in PT seedlings, and with 75% FC among PA seedlings. It is recommended to use the PT seeds in planting projects under drought conditions, while PA seeds are more suitable under conditions of non-water deficit.

Description: Allometric models predicting aboveground woody biomass for open grown valonian oak ( Q. ithaburensis subs. macrolepis L.) trees growing in a Mediterranean silvopastoral system were built based on Bayesian and classical statistical techniques. The simple power model M  =  aD b was used for predicting aboveground woody biomass ( M ), stem ( M S ) and branch ( M B ) biomass through tree diameter ( D ). An informative Bayesian approach (IB) based on prior information about a and b and increasing variance of predicted values in relation to D was applied on 25 destructively sampled trees for estimating M . Non-informative Bayesian (NB), log-linear regression (LR) and non-linear regression were also built for M , M S and M B . Quite similar M distribution was derived from LR and NB across the D range, totally different from IB predictions which provided biologically sound estimates. Tree height, stem length and crown length did not substantially improve predictions for M , M S and M B . Comparisons to oak trees growing in closed stands indicated that open-grown oaks sustain much less stem biomass but maintain larger branch biomass than forest-grown counterparts. Comparisons to published values for open-grown green ash trees supported the hypothesis that open grown broadleaved specimens may sustain similar M values, irrespectively of species, growth conditions and tree size. On the contrary, allocation pattern of organic matter to stem and branches seems to vary by species and/or site conditions. Finally, predictions for b  = 2.67 derived from a theoretical model was not supported by this dataset.

Description: Phosphorus (P) in soil exists both in organic and inorganic forms and their relative abundance could determine P supplying capacity of soil. Differential input of exogenous and plant-mediated phosphorus and carbon in soil under different land-uses could influence P availability and fertilizer P management. While the effect of land-use on soil organic carbon (SOC) is fairly well-documented, its effect on soil P fractions is relatively less known. We investigated the effect of different land-uses including rice–wheat, maize–wheat, cotton–wheat cropping systems and poplar-based agroforestry systems on soil P fractions and organic carbon accrual in soils. Total P concentration was the highest under agroforestry (569 mg P kg −1 ) and the lowest under maize–wheat (449 mg P kg −1 ) cropping systems. On the contrary, soils under rice–wheat had significantly higher available P concentration than the agroforestry systems, probably because of higher fertilizer P application in rice–wheat and prevailing wetland conditions during rice growth. In soils under sole cropping systems viz. rice–wheat, maize–wheat and cotton–wheat, inorganic P was the dominant fraction and accounted for 92.2–94.6% of total P. However, the soils under agroforestry had smaller proportion (73%) of total P existing as inorganic P. Among soil P fractions, water soluble inorganic P (0.13–0.26%) represented the smallest proportion inorganic P in soils under different land-uses. Agroforestry showed significantly ( p  〈 0.05) higher concentrations of SOC than the other land-uses. Soil organic C was significantly correlated with soil P fractions. It was concluded that poplar-based agroforestry systems besides leading to C accrual in soil result in build-up of organic P and the P supplying capacity of soil.

Description: Agroforestry systems have been considered a form of sustainable land use. Woody species in agroforestry systems can improve soil physicochemical properties by supplying leaf or stem litter. However, little is known about fungal community structure and diversity in agroforestry systems. In the present study, the culture-independent 18S rDNA-based polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method was used to investigate fungal community structure in rhizosphere and bulk soil in Populus euramevicana -barley and Taxodium distichum -barley agroforestry systems. DGGE profiling and cluster analysis revealed that the fungal community structure in the rhizosphere was more complex than that of bulk soil. Our results also indicated that the rhizosphere fungal community in barley was less affected by T. distichum than by P. euramevicana . In addition, an increase in the relative abundance of certain rhizosphere fungal populations was detected in this agroforestry system. Sequencing of prominent DGGE bands revealed an increase in the rhizosphere of a fungal species belonging to the genera Chaetomium , which includes potential biocontrol agents. A rare cellulolytic fungus, Acremonium alcalophilum , was found in the bulk soil from P. euramevicana and barley grown under P. euramevicana . Taken together, our findings may provide new insights into agroforestry practices.

Description: Several studies have emphasized the negative impact of the conventional soil management (CT) system on productivity and sustainability of chestnut orchards ( Castanea sativa Mill.) when compared to no-tillage with grass cover (NT). However, scarce information is available regarding the effects of these soil management systems on soil organic matter (SOM) dynamics and soil quality. SOM or soil organic carbon is a key component of soil quality and has different fractions with different lability, namely, organic C (POC), active C (AC) and hot-water extractable carbon (HWC). These are considered as indicators of changes in management-induced soil quality. Thus, a study was carried out to evaluate the effects of NT and CT systems applied in the chestnut orchards on: (i) total amount of soil organic C (TOC), including C from both organic and mineral layers; (ii) soil organic C concentration of mineral horizons (OC); (iii) labile soil organic fractions (POC, AC, HWC); (iv) and soil mineral-associated C. The study was developed in two 30-year old chestnut orchards located in Northeast Portugal, that were kept under different soil management systems (NT or CT) during the preceding 17 years. Soil samples were taken at 0–10 and 10–20 cm soil depth. No significant differences in OC concentration were observed between NT and CT, while TOC was significantly higher in NT than in CT (22.54 and 12.17 Mg/ha or 34.16 and 22.90 Mg/ha, considering the organic layer plus mineral layers at 0–10 and 0–20 cm depth (set of two depths). The NT practice led to significantly higher concentration of labile C fractions (POC, AC and HWC) than CT at 0–10 cm soil depth. These results indicate that measurement of labile soil organic C fractions, such as POC, AC and HWC, may provide a sensitive and consistent indication of changes in soil C and SOM dynamics in response to soil management practices. Overall, NT seems to ensure better soil quality than CT in chestnut orchards under Mediterranean climate conditions.

Description: Changes in land use management practices may have multiple effects on microclimate and soil properties that affect soil greenhouse gas (GHG) emissions. Soil surface GHG emissions need to be better quantified in order to assess the total environmental costs of current and possible alternative land uses in the Missouri River Floodplain (MRF). The objective of this study was to evaluate soil GHG emissions (CO 2 , CH 4 , N 2 O) in MRF soils under long-term agroforestry (AF), row-crop agriculture (AG) and riparian forest (FOR) systems in response to differences in soil water content, land use, and N fertilizer inputs. Intact soil cores were obtained from all three land use systems and incubated under constant temperature conditions for a period of 94 days using randomized complete block design with three replications. Cores were subjected to three different water regimes: flooded (FLD), optimal for CO 2 efflux (OPT), and fluctuating. Additional N fertilizer treatments for the AG and AF land uses were included during the incubation and designated as AG-N and AF-N, respectively. Soil CO 2 and N 2 O emissions were affected by the land use systems and soil moisture regimes. The AF land use resulted in significantly lower cumulative soil CO 2 and N 2 O emissions than FOR soils under the OPT water regime. Nitrogen application to AG and AF did not increase cumulative soil CO 2 emissions. FLD resulted in the highest soil N 2 O and CH 4 emissions, but did not cause any increases in soil cumulative CO 2 emissions compared to OPT water regime conditions. Cumulative soil CO 2 and N 2 O emissions were positively correlated with soil pH. Soil cumulative soil CH 4 emissions were only affected by water regimes and strongly correlated with soil redox potential.

Description: Shea ( Vitellaria paradoxa C. F. Gaertn.) is arguably socio-economically and environmentally the most important plant species in the semi-arid and arid zones of Africa where it is widely distributed. Apart from the economic gains in international export markets where shea butter is valued for use in luxury cosmetic, pharmaceutical and confectionary industries, locally the fat (butter) is the main cooking oil for over 86 million inhabitants. Research during the past decades has acknowledged the chemical and nutritional composition as well as the ethnobotanical uses of shea which has resulted in its butter being used in a wide array of products. This review summarizes the current knowledge of the morphological and genetic diversity; propagation, initial growth, and management; ecology and population structure; chemical and nutritional composition as well as the socioeconomic and livelihood empowerment potential of shea. Little is known about the fruiting behaviour and the responses of shea to the inevitable changes in climate. We suggest ecophysiological and dendrochronological studies as an option to predict how the domestication of this multipurpose tree species can be sustained even under the prospects of global climate change.