Marc J. J. Janssens

Plant diversity management in cocoa agroforestry systems in West and Central Africa—effects of markets and household needs

Abstract Cocoa production in humid forest landscapes has been one of the main cash providers of West and Central African economies. Along with the liberalization of the perennial tree sector, there are increased fluctuations of cocoa income. At the same time, the demand and interest for timber production and non-wood forest products have also been increasing. With the continuous disappearance of natural forests, the production of these commodities is being shifted into cocoa agroforests and plantations. In view of helping research and development institutions in promoting sustainable tree crop systems, this paper attempts, for the main cocoa producing countries of West Africa (Cameroon, Nigeria, Ghana and Côte d’Ivoire), to: (1) document the temporal evolution of the market demand for forests and non-wood forest products both at the local and international levels; (2) explore the set of tree species that can be produced in cocoa agroforests of WCA to satisfy this demand. Deforestation resulting partly from the expansion of perennial orchards and slash and burn agriculture is: (i) leading to a shortage of suitable forest land necessary to stabilize or increase national cocoa production and (ii) increasing the gap between the demand and availability/supply of non-wood forest products (NWFP) and timber by reducing the main source of these products—the forest. Demand of these products is increasing with the growth of urban and peri-urban centers. At the same time, perennial agroforestry systems such as cocoa agroforest are increasingly perceived as assets for Payment for Environmental Services (PES) such as carbon storage and biodiversity conservation, because of the potential of the resources that they can generate. These demands of products and payment for ecosystem services that can be provided by sustainable cocoa agroforestry systems depends upon the appropriate combination of cocoa, timber and non-timber forest trees on the same land. Such demands is still to be properly exploited in the region. Cocoa agroforests in West Africa are characterized by fewer species than those of Central Africa. The level of market access influences the types of species that are managed inside cocoa agroforests. Among the species potentially associable with cocoa, those demanded by the local, regional and international markets are not necessarily the ones that are more frequent in the cocoa fields. The gradual reduction of natural forest, from which timber and non-timber products are gathered, aroused the need to integrate the growing of such species in cocoa agroforestry systems.

Structure and composition of cocoa agroforests in the humid forest zone of Southern Cameroon

The distribution and composition of the tree component inside cocoa agroforests plays an important role in the economic and ecological services offered by these plantations. The presence of these plant components appears to be influenced by several factors controlling the introduction and management of associated plants inside cocoa agroforests. To date, few studies have tried to evaluate the horizontal and vertical distribution of plants inside cocoa plantations in Cameroon. This study determines the structure of cocoa plantations in Southern Cameroon. Field data were collected in 60 cocoa plantations belonging to 12 villages located along a contiguous gradient of market access, population density and resource use intensity in the humid forest zone of southern Cameroon. This study area comprises (i) the sub-region of Yaoundé, (ii) the sub-region of Mbalmayo, and (iii) the sub-region of Ebolowa. Market access, population density and resource use intensity all decreased from the first to the third sub-region. For cocoa and associated plants, we quantified (1) the density (2) the individual number, the species composition and the group uses of plants (edible, timber, medicinal, etc…) distribution across strata, and (3) the basal area in the 60 cocoa plantations located in the three main sub-regions. Results are presented for each sub-region and the whole study area. The paper develops cocoa agroforest typologies and discusses possible implications of cocoa agroforest structure diversity in the achievement of economic and ecological services.

Rapid assessment methods of resilience for natural and agricultural systems

The resilience, ecological function and quality of both agricultural and natural systems were evaluated in the mountainous region of the Atlantic Rain Forest of Rio de Janeiro through Rapid Assessment Methods. For this goal new indicators were proposed, such as eco-volume, eco-height, bio-volume, volume efficiency, and resilience index. The following agricultural and natural systems have been compared according: (i) vegetables (leaf, fruit and mixed); (ii) citrus; (iii) ecological system; (iv) cattle, (v) silvo-pastoral system, (vi) forest fragment and (vii) forest in regeneration stage (1, 2 and 3 years old). An alternative measure (index) of resilience was proposed by considering the actual bio-volume as a function of the potential eco-volume. The objectives and hypotheses were fulfilled; it is shown that there does exist a high positive correlation between resilience index, biomass, energy efficiency and biodiversity. Cattle and vegetable systems have lowest resilience, whilst ecological and silvo-pastoral systems have greatest resilience. This new approach offers a rapid, though valuable assessment tool for ecological studies, agricultural development and landscape planning, particularly in tropical countries.

Impact of Canavalia Cover Crop Management in Coffea arabica L. on Plant-Invertebrate Associations

Coffee ecosystems in the Soconusco, Chiapas, Mexico, with Coffea arabica are characterized by different cropping intensities, high diversity of soil and climate conditions. The main objective of this long-term study was the analysis of comprehensive relations between soil cover and weed-insect association. Biomass and weed cover community composition were analyzed together with weed-insect associations in coffee plantations that varied according to living soil cover management, weed control measures and coffee harvest traditions. Canavalia reduced significantly the presence of weeds. The treatment Canavalia + mulching under coffee plants produced with 3810 kg ha -1 the significantly highest av- erage coffee berry yield, peaking at 5457 kg ha -1 in 2003. Significant correlations exist between Canavalia + weed man- agement, year and coffee yield. The effects of different soil cover management regimes on the comparative biodiversity structures of weed - insects were evaluated between November 2002 and November 2003. Treatments with C. ensiformis supported smaller numbers of coffee berry borer (CBB) throughout the year. These data might be useful for new strategies in ecological coffee production.

Sweet potato [Ipomoea batatas (L.) Lam.] cultivated as tuber or leafy vegetable supplier as affected by elevated tropospheric ozone.

Sweet potato cultivars respond differently to elevated tropospheric ozone concentrations of ca. 130 mug m (-3), 8 h a day for 4 weeks, which affects their selection for cultivation. In the first cultivar presented here, an adequate leafy vegetable supplier, the ozone load resulted in a shift of biomass to maintain the canopy at the expense of tuber development. Starch content of leaves was reduced, indicating an impairment of quality, but carotenoid content remained stable. The second cultivar may be grown for tuber production. Although the ratio tuber/plant remained stable under ozone, tuber yield and its starch content were significantly reduced. The lower starch content indicated a worse quality for certain industrial processing, but it is desirable for chip production. Elevated tropospheric ozone concentrations also influenced free amino acids and macronutrient contents of tubers, but these modifications were of minor significance for tuber quality in the second cultivar.

Profiling Carbon Storage/Stocks of Cocoa Agroforests in the Forest Landscape of Southern Cameroon

Despite evidence that cocoa agroforests are composed of different types of associated plants leading to varieties of structures, few studies have been done to assess the implications of these variations on carbon stocks. The current studies profile the carbon storage of cocoa agroforests in Southern Cameroon by: (1) evaluating the carbon stocks of cocoa agroforests in different ecological zones (Yaounde, Mbalmayo, and Ebolowa), (2) evaluating the carbon stocks of cocoa agroforests under different management methods, (3) evaluating the contribution of some plant species to carbon sequestration inside cocoa agroforests, and (4) identifying the carbon stocks of some important species. Inside the cocoa agroforests of Southern Cameroon, associated plants store around 70% of the carbon. Cocoa agroforests with timber and NWFP (Non-Wood Forest Products) store more than twice what is found in systems rich with Musa and oil palm. In these systems, timber and NWFP store more than 2.5 times what is found in cocoa systems with high densities of cocoa, and such systems with timber and NWFP store more than 3.3 times the carbon of unshaded cocoa orchards.

Selection of maturity indices for compost derived from grape pomace

Compost quality is usually determined through chemical composition and sanitary parameters; however it is necessary to determine more precise maturity indices. The objective of this work was to identify sensitive properties to measure compost maturity using a novel approach based on quality indices. Nine mature compost piles were sampled and analyzed for extractable and total elements, NH4-N/NO3-N, electrical conductivity, C/N ratio, humic and fulvic fractions, hydrolytic enzyme activities, radish germination, respiration CO2 and microbiological parameters. The results indicated that humic acid: fulvic acid ratio, total bacteria count, and hydrolytic enzyme activities were sensitive parameters to define compost maturity and more specific tools to explain microbial activity and humification degree along the curing phase. The proposed model could be used to evaluate compost maturity with good reliability.

Fundamentals of agricultural sustainability or the quest for the Golden Fleece

Received 16.04.2013 Accepted 18.03.2014 Published 05.06.2014 In this paper, different aspects of development sustainability will be highlighted by stressing the fact that even the smartest drivers are necessarily characterized by the continuous uncertainty we all must live with. Different development drivers will be illustrated in the field of agriculture, nature and environment, all attempting to weigh the contradicting, even conflicting parameters of life and decay. Agricultural sustainability drivers will encompass human, cultural, social and political aspects together with components of metabolism, genetics, energy, environment and farm management. It will be concluded that each sustainability approach should be precisely documented using exact parameters and not unproven social or emotional attributes. Quantitative cost to benefit ratios will be proposed as sustainability indicators. In short, sustainability is an ideal state in the area of conflict between environmental change, evolution of life and thermodynamic laws. It cannot be defined as a stable state, but as a state of relative stability during a certain but limited period of time. Sustainability strongly depends on a reliable energy resource that, in thermodynamic terms, enables the preservation of order in an open (eco-) system at the expense of the order of the environment. Sustainability Resilience Adaptability Energy efficiency Input efficiency Journal of Natural Resources and Development 2014; 04: 34 45 34