Allometric biomass equations for tree species used in agroforestry systems in Uganda

Estimates of above-ground biomass are required for better planning, sustainable management and monitoring of changes in carbon stocks in agroforestry systems. The objective of this study was to develop and compare biomass equations for Markhamia lutea, Casuarina equisetifolia, Maesopsis eminii and Grevillea robusta grown in a linear simultaneous agroforestry system in Uganda. These species were established in single rows in the middle of fields in 1995 from four-month old seedlings. A total of 57 trees were sampled for this study, 13 for M. lutea, 12 for C. equisetifolia, 16 for M. eminii and 16 for G. robusta. Biomass values of the various tree components (stem, branches and foliage) as well as the total above-ground biomass were fitted to linear and non-linear allometric models using total height, diameter-at-breast height (DBH), crown width as predictor variables. Although both DBH and height are typically used as independent variables for predicting above-ground biomass, the addition of height in biomass equations did not significantly improve model performance for M. eminii, M. lutea and G. robusta. However, addition of height significantly increased the proportion of variation explained in above-ground biomass for C. equisetifolia, while DBH did not significantly improve the prediction of biomass. The study confirmed the need for developing species-specific biomass equations.     

Allometric tree biomass models of various species grown in short-rotation agroforestry systems

Biomass equations for tree species and the early stages of growth used in short-rotation coppices and agroforestry systems are still lacking. Further, discussion about the structure and parameters of biomass equations are still ongoing. Yield estimations should be precise, while keeping efforts low. To determine the influence of tree species, farming system, and tree position (inner and outer row) on allometric relationships, we derived biomass equations for various tree species from organic and conventional silvoarable agroforestry systems with an alley-cropping configuration. The allometric equations were based on the power relationship between aboveground dry biomass and stem base diameter (SBD) as a single variable or in combination with tree height (H) and were calculated by log-linear mixed-effect regression. Equations span the third and fourth growth year of the first rotation and were validated on the fourth year. Neither farming system nor row position influenced allometric relationship, although biometric variables varied between trees from inner and outer rows. A general model across species explained 95% (\(R_{\text{cond}}^{2}\)) of the variation for tree dry weight or 97% (\(R_{\text{cond}}^{2}\)) with H as covariate. Yet, for the sake of precision, species-specific equations were necessary. The best fitting equation with only SBD as predictor had species-specific allometric factors and a general exponent across species. However, predicted yields were biased by 8–31%. Thus, functions incorporating H are recommended, as compensation for variances in height-diameter relationships due to the ontogenetic stage, site differences, or social status of the tree reduced the bias of biomass estimation (<10%).     

Productivity of Theobroma cacao agroforestry systems with timber or legume service shade trees

Timber production and cocoa yields were studied (initial 10?C11?years) in two experimental plantations: a Cocoa-Legume system (CL, Erythrina poeppigiana, Gliricidia sepium or Inga edulis), and a Cocoa-Timber system (CT, Cordia alliodora, Tabebuia rosea or Terminalia ivorensis, plus I. edulis for inter-site comparisons). These trials had two major goals: (1) to evaluate the use of mono-specific timber shade canopies as an alternative to traditional, mono-specific, legume service shade tree canopies; and (2) to determine the production potential of ten cocoa clonal bi-crosses under these shade tree species. Within each site, shade tree species did not influence dry cocoa bean yield nor pod counts (total number of pods produced, number of healthy pods harvested, pod losses due to monilia [Moniliophthora roreri], black pod [Phytophthora palmivora] or other causes??birds and squirrels in this study-, and total pod losses). Significant differences were found between cocoa bi-crosses for both cocoa bean yield and pod counts. Sites differed only in terms of total pod losses (43% in CL; 54% in CT) and their causal factors (mainly monilia in CL; both monilia, squirrels and birds in CT). At CT, all timber tree species grew rapidly, reaching 30?C34?cm?dbh, 17?C25?m total tree height and 97?C172?m³?ha^?1 total stem volume (age 10?years). Timber species should be promoted for the shade component of cacao plantations given their potential production and the fact that their presence did not negatively affect cocoa yields.     

Decomposition and nutrient release in leaves of Atlantic Rainforest tree species used in agroforestry systems

Aiming to support the use of native species from the Atlantic Rainforest in local agroforestry systems, we analysed chemical and biochemical components related to leaf decomposition of Inga subnuda, Senna macranthera, Erythrina verna, Luehea grandiflora, Zeyheria tuberculosa, Aegiphila sellowiana, and Persea americana. These tree species are native (except for P. americana) and commonly used in agroforestry systems in the Atlantic Rainforest. For the three first species (Fabaceae), we also analysed the remaining dry matter and released nutrients from leaves, using litter bags, and biological nitrogen fixation, using Bidens pilosa and Brachiaria plantaginea as references of non-N₂-fixing plants. Leaves from I. subnuda, L. grandiflora, and P. americana had a lower decomposition rate than the other species, exhibiting negative correlations with lignin/N and (lignin+polyphenol)/N ratios. The percentages of remaining dry matter after 1 year were 69 % (I. subnuda), 26 % (S. macranthera) and 16 % (E. verna). Higher nutrient release was found in decreasing order from residues of E. verna, S. macranthera, and I. subnuda. The percentages of nitrogen fixation were 22.6 % (E. verna), 20.6 % (I. subnuda) and 16.6 % (S. macranthera). Diversification of tree species in agroforestry systems allows for input of diversified organic material and can contribute to maintaining and improving soil functions resulting in improvements of soil quality.     

Improving multipurpose tree and shrub species for agroforestry systems

With the aid of an example of ICRAF's tree improvement research programme for the highlands of Eastern and Central Africa, a logical approach to selection and breeding of multipurpose trees and shrubs in agroforestry context is proposed. Criteria for selection of high priority species are proposed. Some species of high potential for agroforestry development in Sub Sahara Africa are proposed. The necessary sequential research steps are discussed.     

Supporting and regulating ecosystem services in cacao agroforestry systems

Cacao agroforestry systems (CAFS) can provide supporting services such as optimum light conditions for cacao growth, water and nutrient cycling and regulating services such as pest and disease control and climate regulation. This review considers recent literature on the manifestation of these services in CAFS around the world to provide an overview of scientific knowledge. Crown structures of associated trees can facilitate optimum light conditions for cacao growth, and provide water through vertical root segregation. Leaf litter fall and roots from associated species contribute to nutrient cycling. Both nitrogen-fixing and non-nitrogen-fixing species can provide nutrients to the cacao plant, though competition from certain species may limit phosphorus and potassium uptake. Pest and disease regulating services can arise through careful shade management to create a microclimate which reduces susceptibility of cacao to fungal diseases and sun-loving pests. All CAFS store carbon to varying degrees; those resembling original forest much more than simple two-species systems from which shade trees are removed after maturity of the cacao stand. CAFS also promotes biodiversity conservation depending on structure, management, and landscape arrangement, though not to the extent of natural forests. Research opportunities to increase provision of these services include optimal spatial arrangement for nutrient cycling and functional diversity as well as landscape connectivity for biodiversity conservation. Trade-offs between carbon storage, biodiversity, cacao yield and socio-economic resilience are presented, indicating that optimization of ecosystem services in CAFS requires consideration of interactions between all services, including socio-cultural and economic ones.     

Soil and litter fauna of cacao agroforestry systems in Bahia,Brazil

Agroforestry systems deposit great amounts of plant residues on soil and this leads to high levels of soil organic matter content and has increased soil biodiversity and improved its conservation. This study compares the distribution of meso and macrofaunal communities in soil and litter under cacao agroforestry systems and in a natural forest in the southern Bahia state of Brazil. Soil and litter samples were obtained in September 2003, February 2004, and August 2004 in five cacao agroforestry systems. The systems evaluated included: cacao renewed under Erythrina sp. (Erythrina poeppigiana) (CRE); cacao renewed under natural forest (Cabruca, CRF); an old cacao system under Erythrina sp. (OCE); an old cacao system under a natural forest system (Cabruca, OCF) and a cacao germplasm collection area (CGC). As a reference soil and litter under a natural forest (NF) was included. Organisms were collected over a 15-day period with a Berlese–Tullgren apparatus. The density and richness of total fauna varied distinctly according to sites, sampling time and material sampled (soil and litter). 16,409 of fauna were recovered from soil and litter samples and the density of total fauna was 2,094 individuals m⁻² in the litter and 641 individuals m⁻² in the soil. The richness was 11.8 in the litter and 7.5 in the soil. The cacao agroforestry systems adopted for growing cacao in the southern Bahia region of Brazil have beneficial effects on the soil and litter faunal communities, and such systems of cacao cultivation could be considered as a conservation system for soil fauna. The development of a litter layer resulted in higher abundance and diversity of soil fauna.     

Management of secondary tree species in agroforestry systems to improve production sustainability in Amazonian Ecuador

Three production systems (robusta coffee, cattle pastures and swidden agriculture), all associated with trees, have provided a strategy for regional development in the Ecuadorian Amazon. Feedback from more than 250 on-farm demonstrations, project evaluations and visitors have all contributed to strengthening the ability of the Ecuadorean Ministry of Agriculture's Forestry Directorate to provide colonists and indigenous groups with management guidelines for low-input sustainable agroforestry production. The existing market for 20 fastgrowing native tree species presents an opportunity for the diversification of farm income (currently dependent on robusta coffee) and for the development of a forest industrial base.The collective area of land owned and operated by these small holders constitutes a national resource and a Collective Forest Estate that can be individually managed. Commercial timber production in these extensive secondary forests can help alleviate conversion of primary forest without taking agricultural land out of production.     

Potential of some Neotropical Albizia species as shade trees whenreplanting cacao in Ghana

The Cocoa Research Institute of Ghana has embarked on studies to support the replanting of cacao (Theobroma cacao L) in areas, which previously carried the crop but are now degraded. A key component of the studies is to identify fast growing tree species capable of ameliorating degraded soils and ultimately providing suitable shade for cacao. A screening trial involving ten Albizia species in a randomized complete block design experiment was therefore initiated in 1996 to evaluate growth rate, leaf biomass production, carbon and nitrogen contents and decomposition rates. Over a four-year period, Albizia adenocephala, A. guachapele, A. niopoides, A. plurijuga,A. saman and A. tomentosa showed promising results, with 12.2 to 14.5 m height and between 12.4 and 22.4 cm stem diameter (DBH). Crown diameter ranged between 6.1 and 10.1 m, with light transmission through crowns averaging 50–65% of full sunlight throughout the year. Half-yearly leaf biomass production ranged between 3and 10 t ha^–1, yielding between 0.07 and 0.32 t N ha^–1 from each coppicing. Half-life for carbon and nitrogen release from leaves of the six species averaged 31.0 and 32.0 days respectively. This short-term release of C and N is an indication of the quality of the leaf prunings. These species can provide early ground cover, appropriate shade, N and organic matter requirements for re-establishing cacao on denuded and degraded lands. This revised version was published online in June 2006 with corrections to the Cover Date.     

Carbon dynamics in small tropical catchments under preserved forest and cacao agroforestry systems

Agroforestry Systems - Inland waters such as streams that receive carbon from terrestrial landscapes usually have a net heterotrophic metabolism and emit significant amounts of CO2 to the...     

Allometric estimation of above-ground biomass and leaf area in managed Grevillea robusta agroforestry systems

Non-destructive methods for determining the biomass and leaf area of individual trees throughout their growing cycle are an essential tool in agroforestry research, but must be capable of providing reliable estimates despite the influence that management strategies such as pruning may have on tree form. In the present study, allometric methods involving measurements of the diameter of all branches provided reliable estimates of canopy leaf area and biomass for grevillea trees (Grevillea robusta A. Cunn.; Proteaceae) grown as poles, but proved unsuitable for routine measurements because of their time-consuming nature. An alternative, less laborious method based on measurements of trunk cross-sectional area immediately below the first branch of the canopy provided satisfactory allometric estimates of leaf area and canopy biomass. Trunk biomass was determined from measurements of tree height and diameter at breast height using established methodology based on the assumption that trunk volume may be calculated using a quadratic paraboloid model; biomass was determined as the product of trunk volume and the specific gravity of the wood. The theoretical basis, development and validation of allometric methods for estimating tree growth are discussed and their wider applicability to other agroforestry systems is assessed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Root biomass and distribution of five agroforestry tree species

Knowledge of the quantitative assessment and structural development of root systems is essential to improve and optimize productivity of agroforestry systems. Studies on root biomass recovery by sieves of different mesh sizes (2.0, 1.0, 0.5 and 0.25 mm) and root distribution for four-year-old individuals of five agroforestry tree species viz.; Acacia auriculiformis A. Cunn. ex Benth, Azadirachta indica A. Juss, Bauhinia variegata L., Bombax ceiba L. and Wendlandia exserta Roxb. were conducted at the research farm of Rajendra Agricultural University, Pusa, Bihar, India. The results indicated that the 0.5 mm sieve was adequate for recovery of the majority of roots. All the tree species exhibited a large variation in root depth and horizontal root spread four years after planting. The maximum root depth was recorded in W. exserta (2.10 m) and minimum in B. variegata (1.00 m). Horizontal root spread was 2.05 m in B. ceiba and 8.05 m in A. auriculiformis. Root spread exceeded crown cover for all species. The primary roots were more horizontal than the secondary roots. The length and diameter of the main root were highest in A. indica (108.3 cm) and B. ceiba (23.2 cm), respectively. Highest length and diameter of lateral roots were recorded in B. variegata (201.6 cm) and A. indica (1.8 cm), respectively. Total root biomass among different species accounted for 18.2–37.9% of the total tree biomass. Results of this study infer that although all the species have potential to conserve moisture and improve fertility status of the soil, A. auriculiformis is the most effective for promoting soil fertility. The deep rooted W. exserta and A. auriculiformis will be preferred for cultivation under agroforestry systems and could reduce competition for nutrients and moisture with crops by pumping from deeper layers of soil.     

Environment and tree size controlling stem sap flux in a perhumid tropical forest of Central Sulawesi,Indonesia

• Introduction   

We studied stem sap flux density in seven common tree species in a perhumid tropical rainforest at pre-montane elevation in Sulawesi with the aims (1) to analyse the among-species variation in flow patterns, (2) to search for an assumed convergence in the response to controlling environmental factors, and (3) to investigate the effect of tree size on xylem flux.     

Multistoried agroforestry garden system in West Sumatra,Indonesia

The agroforestry garden system in Maninjau in West Sumatra is characterized by an intensive integration of forest species and commercial crops, forming a forest-like system. The intimate association of different species provides both subsistence and commercial products which supplement rice production. This complex agroforest is managed by the combination between cultural practices and respect of natural processes of vegetation production and reproduction. It represents a profitable production system and constitutes an efficient buffer between villages and protected forest. It is a good model of association between integration of forest resources and cultivation of cash crops in the form of a sustainable and flexible system.     

Growth characteristics of multipurpose tree species,crop productivity and soil properties in agroforestry systems under subtropical humid climate in India

Multipurpose tree species （MPTs） were studied in an agroforestry arboretum under subtropical humid climate in Northeast India. Out of 12 MPTs planted under agroforestry systems, Acacia auriculiformis in spacing of 2 m × 2 m （2500 stems·hm^-2） could have the potentiality to meet the timber/fuelwood requirement due to its high wood production of 635 m^3·hm^-2 with mean annual increment （MAI） of 2.54×10^-2 m^3.treel.a^-1 in a short rotation period of 10 years. Thus, A. auriculiformis is a short rotation forest tree species suitable to grow in subtropical humid climate. On the other hand, at 16 years of age, Eucalyptus hybrid and Michelia champaca in spacing of 3 m × 3 m （1111 stems.hm^2） produced appreciably high timber volume of 315 m^3.hm^-2 and 165 m^3.hm^-2 with MAI of 1.77×10^-2 m^3.tree^-1·a^-1 and 0.92×10.2 m^3.tree^-1.a^-1, respectively. At 16 years of age, Gmelina arborea produced a timber volume of 147 m^3.hm^-2 with MAI of 1.47×10^-2 m^3.tree^-1.a^-1 followed by Samania saman （140 m^3.hm^-2）, Albizziaprocera （113 m^3·hm^-2） and Tectona grandis （79 m3.hm^-2） with MAI of 1.40, 1.13 and 0.78 × 10^-2 m^3 .tree^-1a^-1, respectively in 4 m × 4 m spacing （625 stems.hm^-2）. Gliricidia maculata and Leucaena leucocephala could be used as live fences around the farm boundary to supply their N-rich leaves for mulch as well as manure to crops. In agroforestry arboretum, direct seeded upland rice （Oryza sativa - variety, AR-11）, groundnut （Arachis hypogaea - variety, JL-24） and sesamum （Sesamum indicum - variety, B-67） were grown during the initial period upto 8 years of tree establishment. Under other MPTs, there was a reduction in crop productivity as compared to open space. After 8 years of tree establishment, horti-silvi and silvi-pastoral systems were developed and pineapple （Ananas comosus - variety Queen）, turmeric （Curcuma longa -variety RCT -1） and cowpea （Vigna sinensis - variety Pusa Barsati） as forage crop were raised. The productivity of p     

Modelling agroforestry systems of cacao (Theobroma cacao) with laurel (Cordia alliodora) and cacao with poro (Erythrina poeppigiana) in Costa Rica

The hydrological balances for the agroforestry systems of Theobroma cacao with Cordia alliodora or Erythrina poeppigiana were calculated using measurements taken over four years (1983–1987) of the following parameters: climatic (precipitation, evaporation); edaphological (texture, soil moisture tension, hydraulic conductivity, variations in soil moisture content). Water fluxes (interception, simulation of transpiration and percolation) were estimated from one year of measurements (1986–1987). Weekly samples of percolated water were taken from March 1986 – March 1987 using lysimetric capsules at 100 cm soil depth. N, P, K, Ca and Mg concentrations were determined to calculate the annual leaching losses. Nutrient concentration values were extrapolated for the whole 4 years observation period, in order to calculate leaching losses for the whole study period. Precipitation samples were also taken to determine the corresponding annual nutrient inputs.     

Carbon, nitrogen, organic phosphorus, microbial biomass and N mineralization in soils under cacao agroforestry systems in Bahia, Brazil

Large amounts of plant litter deposited in cacao agroforestry systems play a key role in nutrient cycling. Organic matter, nitrogen and phosphorus cycling and microbial biomass were investigated in cacao agroforestry systems on Latosols and Cambisols in Bahia, Brazil. The objective of this study was to characterize the microbial C and N, mineralizable N and organic P in two soil orders under three types of cacao agroforestry systems and an adjacent natural forest in Bahia, Brazil and also to evaluate the relationship between P fractions, microbial biomass and mineralized N with other soil attributes. Overall, the average stocks of organic C, total N and total organic P across all systems for 0?C50?cm soil depth were 89,072, 8,838 and 790?kg?ha^?1, respectively. At this soil depth the average stock of labile organic P was 55.5?kg?ha^?1. For 0?C10?cm soil depth, there were large amounts of microbial biomass C (mean of 286?kg?ha^?1), microbial biomass N (mean of 168?kg?ha^?1) and mineralizable N (mean of 79?kg?ha^?1). Organic P (total and labile) was negatively related to organic C, reflecting that the dynamics of organic P in these cacao agroforestry systems are not directly associated with organic C dynamics in soils, in contrast to the dynamics of N. Furthermore, the amounts of soil microbial biomass, mineralizable N, and organic P could be relevant for cacao nutrition, considering the low amount of N and P exported in cacao seeds.