Soil carbon sequestration in a changing global environment

Throughout its long history the Earth has undergone warm periods with high atmospheric concentrations of greenhouse gases (GHG), and has responded with different buffering mechanisms whereby atmospheric C has been transferred to other geochemical compartments. Strategies for the mitigation and adaptation to the current climatic forcing may thus be generated by the acceleration of such natural mechanisms, especially those involved in short cycles, mainly in the biosphere and the pedosphere. Although these contain smaller C stocks than other compartments (< 0.01% of the total C), they circulate large amounts of C from the atmosphere through photosynthesis and mineral weathering (e.g., 120 Pg C are circulated through terrestrial ecosystems and total C in the atmospheric compartment is 805 Pg C). Increased C sequestration can thus be achieved in terrestrial ecosystems, by: (1) favouring growth of biomass; (2) promoting and facilitating carbonation processes; (3) reducing erosion and favouring pedogenesis; (4) developing organic matter-rich horizons; (5) recovering degraded or contaminated soils, and/or (6) managing waste by use of systems that minimize emissions of GHG. Within the latter option, the following actions are considered here in more detail: 1) production of Technosols, and 2) production of biochar. All of the above options should form part of a strategy for the mitigation and adaptation to global climate change. In this review, we analyze those focused on promoting soil conservation, soil restoration and soil formation.     

Development of an agroforestry carbon sequestration project in Khammam district,India

This paper addresses methodological issues in estimating carbon (C) sequestration potential, baseline determination, additionality and leakage in Khammam district, Andhra Pradesh, southern part of India. Technical potential for afforestation on cultivable wastelands, fallow, and marginal croplands was considered for Eucalyptus clonal plantations. Field studies for aboveground and belowground biomass, woody litter, and soil organic carbon for baseline and project scenarios were conducted to estimate the carbon sequestration potential. The baseline carbon stock was estimated to be 45.3 t C/ha, predominately in soils. The additional carbon sequestration potential under the project scenario for 30 years is estimated to be 12.8 t C/ha/year inclusive of harvest regimes and carbon emissions due to biomass burning and fertilizer application. Considering carbon storage in harvested wood, an additional 45% carbon benefit can be accounted. The project scenario has a higher benefit/cost ratio compared to the baseline scenario. The initial investment cost requirement, however, is high and lack of access to investment is a significant barrier for adoption of agroforestry in the district.

Socioeconomic potential of carbon sequestration through agroforestry in the West African Sahel

The recognition of agroforestry as a greenhouse-gas mitigation strategy under the Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) offers an opportunity to agroforestry practitioners to benefit from the global Carbon (C) credit market. Our knowledge on this important topic from the semiarid regions such as the West African Sahel (WAS) is, however, very limited. In order to fill this gap, this study was undertaken in the Ségou region of Mali (annual temperature, 29°C; annual rainfall, 300–700 mm in 60 to 90 days), focusing on two improved agroforestry systems (live fence and fodder bank) along with traditional parkland agroforestry systems of the region. A cost–benefit analysis was conducted to assess the economic profitability and risks associated with the systems considering them as 25-year projects and their potential for participation in C credit market. The traditional systems had high C stock in their biomass and soil, but little potential for sequestering additional C; on the other hand, the improved systems had low C stock, but high sequestration potential. For the standard size live fence (291 m) and fodder bank (0.25 ha) projects, the estimated net present values (NPV) were $ 96.0 and $158.8 without C credit sale, and $109.9 and $179.3 with C sale, respectively. From the C sale perspective, live fence seemed less risky and more profitable than fodder bank. Carbon credit sale is likely to contribute to economic development of the subsistence farmers in the WAS.

Transaction costs for carbon sequestration projects in the tropical forest sector

There is general consensus that carbon (C) sequestration projects in forests are a relatively low cost option for mitigating climate change, but most studies on the subject have assumed that transaction costs are negligible. The objectives of the study were to examine transaction costs for forest C sequestration projects and to determine the significance of the costs based on economic analyses. Here we examine four case studies of active C sequestration projects being implemented in tropical countries and developed for the C market. The results from the case studies were then used with a dynamic forest and land use economic model to investigate how transaction costs affect the efficiency and cost of forest C projects globally. In the case studies transaction costs ranged from 0.38 to 27 million US dollars ($0.09 to $7.71/t CO₂) or 0.3 to 270 % of anticipated income depending principally on the price of C and project size. The three largest cost categories were insurance (under the voluntary market; 41–89 % of total costs), monitoring (3–42 %) and regulatory approval (8–50 %). The global analysis indicated that most existing estimates of marginal costs of C sequestration are underestimated by up to 30 % because transaction costs were not included.     

Soil carbon sequestration and associated economic costs for farming systems of the Indo-Gangetic Plain: A meta-analysis

Soil organic carbon sequestration rates over 20 years based on the Intergovernmental Panel for Climate Change (IPCC) methodology were combined with local economic data to determine the potential for soil C sequestration in wheat-based production systems on the Indo-Gangetic Plain (IGP). The C sequestration potential of rice-wheat systems of India on conversion to no-tillage is estimated to be 44.1 Mt C over 20 years. Implementing no-tillage practices in maize-wheat and cotton-wheat production systems would yield an additional 6.6 Mt C. This offset is equivalent to 9.6% of India's annual greenhouse gas emissions (519 Mt C) from all sectors (excluding land use change and forestry), or less than one percent per annum. The economic analysis was summarized as carbon supply curves expressing the total additional C accumulated over 20 year for a price per tonne of carbon sequestered ranging from zero to USD 200. At a carbon price of USD 25 Mg C⁻¹, 3 Mt C (7% of the soil C sequestration potential) could be sequestered over 20 years through the implementation of no-till cropping practices in rice-wheat systems of the Indian States of the IGP, increasing to 7.3 Mt C (17% of the soil C sequestration potential) at USD 50 Mg C⁻¹. Maximum levels of sequestration could be attained with carbon prices approaching USD 200 Mg C⁻¹ for the States of Bihar and Punjab. At this carbon price, a total of 34.7 Mt C (79% of the estimated C sequestration potential) could be sequestered over 20 years across the rice-wheat region of India, with Uttar Pradesh contributing 13.9 Mt C.     

Microalgae: a promising tool for carbon sequestration

Increasing trends in global warming already evident, the likelihood of further rise continuing, and their impacts give urgency to addressing carbon sequestration technologies more coherently and effectively. Carbon dioxide (CO₂) is responsible for over half the warming potential of all greenhouse gases (GHG), due to the dependence of world economies on fossil fuels. The processes involving CO₂ capture and storage (CCS) are gaining attention as an alternative for reducing CO₂ concentration in the ambient air. However, these technologies are considered as short-term solutions, as there are still concerns about the environmental sustainability of these processes. A promising technology could be the biological capture of CO₂ using microalgae due to its unmatched advantages over higher plants and ocean fertilization. Microalgae are phototrophic microorganisms with simple nutritional requirements, and comprising the major primary producers on this planet. Specific pathways include autotrophic production via both open pond or closed photobioreactor (PBR) systems. Photosynthetic efficiency of microalgae ranged from 10?C20 % in comparison with 1?C2 % of most terrestrial plants. Some algal species, during their exponential growth, can double their biomass in periods as short as 3.5 hours. Moreover, advantage of being tolerant of high concentration of CO₂ (flue gas), low light intensity requirements, environmentally sustainable, and co-producing added value products put these as the favoured organisms. Advantages of microalgae in comparison with other sequestration methodologies are discussed, which includes the cultivation systems, the key process parameters, wastewater treatment, harvesting and the novel bio-products produced by microalgal biomass.     

Mediterranean shrublands carbon sequestration: environmental and economic benefits

To date, only a few attempts have been done to estimate the contribution of Mediterranean ecosystems to the global carbon cycle. Within this context, shrub species, composition and structure of the Mediterranean shrublands developing along the Latium coast (Italy) were analyzed in order to evaluate their contribution to carbon (C) sequestration, also taking into consideration the economic benefits at a national level. The considered shrublands had a shrub density of 1,200?±?500 shrubs ha^?1. Shrubs were classified into small (S), medium (M) and large (L), according to their volume (V) and leaf area index (LAI). The total yearly carbon dioxide (CO₂) sequestration per species (SC_y) was calculated multiplying the total photosynthetic leaf surface area (spt) of each species by the mean yearly photosynthetic rate and the total yearly photosynthetic activity time (in hours). Q. ilex and A. unedo had the highest SC_y (46.2?±?15.8 kg CO₂ year^?1, mean value), followed by P. latifolia (17.5?±?6.2 kg CO₂ year^?1), E. arborea, E. multiflora, C. incanus, P. lentiscus, R. officinalis, and S. aspera (6.8?±?4.2 kg CO₂ year^?1, mean value). The total yearly CO₂ sequestration per shrub (SC_shy) was 149?±?5 kg CO₂ year^?1 in L, decreasing 30 % in M and 80 % in S shrubs. Taking into account the frequency of S, M and L and their SC_shy, the total CO₂ sequestration of the Mediterranean maquis was quantified in 80 Mg CO₂ ha^?1?year^?1, corresponding to 22 Mg C ha^?1?year^?1. From a monetary viewpoint, this quantity could be valued to more than 500 US$ ha^?1?year^?1. Extending this benefit to the Mediterranean shrublands throughout the whole country, we obtained a nationwide estimated annual benefit in the order of $500 million.     

Biodiversity,carbon stocks and sequestration potential in aboveground biomass in smallholder farming systems of western Kenya

While Carbon (C) sequestration on farmlands may contribute to mitigate CO₂ concentrations in the atmosphere, greater agro-biodiversity may ensure longer term stability of C storage in fluctuating environments. This study was conducted in the highlands of western Kenya, a region with high potential for agroforestry, with the objectives of assessing current biodiversity and aboveground C stocks in perennial vegetation growing on farmland, and estimating C sequestration potential in aboveground C pools. Allometric models were developed to estimate aboveground biomass of trees and hedgerows, and an inventory of perennial vegetation was conducted in 35 farms in Vihiga and Siaya districts. Values of the Shannon index (H), used to evaluate biodiversity, ranged from 0.01 in woodlots through 0.4–0.6 in food crop plots, to 1.3–1.6 in homegardens. Eucalyptus saligna was the most frequent tree species found as individual trees (20%), in windrows (47%), and in woodlots (99%) in Vihiga and the most frequent in woodlots (96%) in Siaya. Trees represented the most important C pool in aboveground biomass of perennial plants growing on-farm, contributing to 81 and 55% of total aboveground farm C in Vihiga and Siaya, respectively, followed by hedgerows (13 and 39%, respectively) and permanent crop stands (5 and 6%, respectively). Most of the tree C was located in woodlots in Vihiga (61%) and in individual trees growing in or around food crop plots in Siaya (57%). The homegardens represented the second C pool in importance, with 25 and 33% of C stocks in Vihiga and Siaya, respectively. Considering the mean total aboveground C stocks observed, and taking the average farm sizes of Vihiga (0.6 ha) and Siaya (1.4 ha), an average farm would store 6.5 ± 0.1 Mg C farm^?1 in Vihiga and 12.4 ± 0.1 Mg C farm^?1 in Siaya. At both sites, the C sequestration potential in perennial aboveground biomass was estimated at ca. 16 Mg C ha^?1. With the current market price for carbon, the implementation of Clean Development Mechanism Afforestation/Reforestation (CDM A/R) projects seems unfeasible, due to the large number of small farms (between 140 and 300) necessary to achieve a critical land area able to compensate the concomitant minimum transaction costs. Higher financial compensation for C sequestration projects that encourage biodiversity would allow clearer win–win scenarios for smallholder farmers. Thus, a better valuation of ecosystem services should encourage C sequestration together with on-farm biodiversity when promoting CDM A/R projects.     

Long-term impact of a gliricidia-maize intercropping system on carbon sequestration in southern Malawi

Tree/crop systems under agroforestry practice are capable of sequestering carbon (C) in the standing biomass and soil. Although studies have been conducted to understand soil organic C increases in some agroforestry technologies, little is known about C sequestered in simultaneous tree/crop intercropping systems. The main objective of this study was to determine the effect of agroforestry practice on C sequestration and CO₂-C efflux in a gliricidia-maize intercropping system. The experiment was conducted at an experimental site located at the Makoka Agricultural Research Station, in Malawi. The studies involved two field plots, 7-year (MZ21) and 10-year (MZ12), two production systems (sole-maize and gliricidia-maize simultaneous intercropping systems). A 7-year-old grass fallow (Grass-F) was also included. Gliricidia prunings were incorporated at each time of tree pruning in the gliricidia-maize. The amount of organic C recycled varied from 0.8 to 4.8 Mg C ha⁻¹ in gliricidia-maize and from 0.4 to 1.0 Mg C ha⁻¹ in sole-maize. In sole-maize, net decreases of soil carbon of 6 Mg C ha⁻¹ at MZ12 and 7 Mg C ha⁻¹ at MZ21 in the topsoil (0–20 cm) relative to the initial soil C were observed. After 10 years of continuous application of tree prunings C was sequestered in the topsoil (0–20 cm) in gliricidia-maize was 1.6 times more than in sole-maize. A total of 123–149 Mg C ha⁻¹ were sequestered in the soil (0–200 cm depth), through root turnover and pruning application in the gliricidia-maize system. Carbon dioxide evolution varied from 10 to 28 kg ha⁻¹ day⁻¹ in sole-maize and 23 to 83 kg ha⁻¹ day⁻¹ in gliricidia-maize. We concluded that gliricidia-maize intercropping system could sequester more C in the soil than sole-maize.     

Potential for carbon sequestration in Canadian forests and agroecosystems

The potential for carbon (C) sequestration was examined in selectedCanadian forest settings and prairie agroecosystems under severalmanagement scenarios. A simple C budget model was developed toquantitatively examine C sequestration potential in living biomass of forestecosystems, in associated forest-product C pools, and in displaced fossil-fuelC. A review of previous studies was conducted to examine C sequestrationpotential in prairie agroecosystems. In the forest settings examined, ourwork suggests that substantial C sequestration opportunities can be realizedin the short term through the establishment of protected forest-C reserves.Where stands can be effectively protected from natural disturbance, peaklevels of biomass C storage can exceed that under alternative managementstrategies for 200 years or more. In settings where it is not feasible tomaintain protected forest-C reserves, C sequestration opportunities can berealized through maximum sustained yield management with harvestedbiomass put towards the displacement of fossil fuels. Because there is afinite capacity for C storage in protected forest-C reserves, harvesting forestbiomass and using it to displace the use of fossil fuels, either directlythrough the production of biofuels or indirectly through the production oflong-lived forest products that displace the use of energy-intensive materialssuch as steel or concrete, can provide the greatest opportunity to mitigategreenhouse gas emissions in the long term. In Canadian prairieagroecosystems, modest C sequestration can be realized while enhancingsoil fertility and improving the efficiency of crop production. This can bedone in situations where soil organic C can be enhanced without relianceupon ongoing inputs of nitrogen fertilizer, or where the use of fossil fuelsin agriculture can be reduced. More substantial C offsets can be generatedthrough the production of dedicated energy crops to displace the use offossil fuels. Where afforestation or reconstruction of native prairieecosystems on previously cultivated land is possible, this represents thegreatest opportunity to sequester C on a per unit-area basis. However,these last two strategies involve the removal of land from crop production,and so they are not applicable on as wide a scale as some other Csequestration options which only involve modifications to currentagricultural practices.     

Temporal organization among pollination systems in a tropical seasonal forest

The Placerias/Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic vertebrate locality known. We report a new short-faced archosauriform, Syntomiprosopus sucherorum gen. et sp. nov., represented by four incomplete mandibles, that expands that diversity with a morphology unique among Late Triassic archosauriforms. The most distinctive feature of Syntomiprosopus gen. nov. is its anteroposteriorly short, robust mandible with 3–4 anterior, a larger caniniform, and 1–3 “postcanine” alveoli. The size and shape of the alveoli and the preserved tips of replacement teeth preclude assignment to any taxon known only from teeth. Additional autapomorphies of S. sucherorum gen. et sp. nov. include a large fossa associated with the mandibular fenestra, an interdigitating suture of the surangular with the dentary, fine texture ornamenting the medial surface of the splenial, and a surangular ridge that completes a 90° arc. The external surfaces of the mandibles bear shallow, densely packed, irregular, fine pits and narrow, arcuate grooves. This combination of character states allows an archosauriform assignment; however, an associated and similarly sized braincase indicates that Syntomiprosopus n. gen. may represent previously unsampled disparity in early-diverging crocodylomorphs. The Placerias Quarry is Adamanian (Norian, maximum depositional age ~219 Ma), and this specimen appears to be an early example of shortening of the skull, which occurs later in diverse archosaur lineages, including the Late Cretaceous crocodyliform Simosuchus. This is another case where Triassic archosauriforms occupied morphospace converged upon by other archosaurs later in the Mesozoic and further demonstrates that even well-sampled localities can yield new taxa.

     

中国的碳排放交易,可行度几何?

<正>为什么要碳排放交易?2014年11月12日上午,世界上最大的两个经济体领导人于APEC峰会期间站在一起,宣布了关于气候变化的联合声明。在这份获得全球掌声的联合声明中,中美两国都第一次设定了各自的后2020时代应对气候变化的目标。习近平主席和奥巴马总统都分别宣布了各自雄心勃勃的目标:中国承诺在2030年前后其二氧化碳排放达到峰值,届时非化石能源在一次能源消费中的占比也将提高至20%左右;美国承诺于2025年实现在2005年基     

Optimizing carbon sequestration in commercial forests by integrating carbon management objectives in wood supply modeling

This paper provides a methodology for generating forest management plans, which explicitly maximize carbon (C) sequestration at the forest-landscape level. This paper takes advantage of concepts first presented in a paper by Meng et al. (2003; Mitigation Adaptation Strategies Global Change 8:371–403) by integrating C-sequestration objective functions in existing wood supply models. Carbon-stock calculations performed in Woodstock^TM (RemSoft Inc.) are based on C yields generated from volume table data obtained from local Forest Development Survey plots and a series of wood volume-to-C content conversion factors specified in von Mirbach (2000). The approach is used to investigate the impact of three demonstration forest-management scenarios on the C budget in a 110,000 ha forest in south-central New Brunswick, Canada. Explicit demonstration scenarios addressed include (1) maximizing timber extraction either by clearcut or selection harvesting for greatest revenue generation, (2) maximizing total C storage in the forest landscape and in wood products generated from harvesting, and (3) maximizing C storage together with revenue generation. The level of clearcut harvesting was greatest for scenario 1 (≥15 × 10⁴ m³ of wood and ≥943 ha of land per harvesting period), and least for scenario 2 (=0 m³ per harvesting period) where selection harvesting dominated. Because softwood saw logs were worth more than pulpwood ($60 m⁻³ vs. $40 m⁻³) and were strategic to the long-term storage of C, the production of softwood saw logs exceeded the production of pulpwood in all scenarios. Selection harvesting was generally the preferred harvesting method across scenarios. Only in scenario 1 did levels of clearcut harvesting occasionally exceed those of selection harvesting, mainly in the removal of old, dilapidated stands early in the simulation (i.e., during periods 1 through 3). Scenario 2 provided the greatest total C-storage increase over 80 years (i.e., 14 × 10⁶ Mg C, or roughly 264 Mg ha⁻¹) at a cost of $111 per Mg C due to lost revenues. Scenarios 3 and 1 produced reduced storage rates of roughly 9 × 10⁶ Mg C and 3 × 10⁶ Mg C, respectively; about 64% and 22% of the total, 80-year C storage calculated in scenario 2. The bulk of the C in scenario 2 was stored in the forest, amounting to about 76% of the total C sequestered.     

Analysis of leakage in carbon sequestration projects in forestry: a case study of upper magat watershed,Philippines

The role of forestry projects in carbon conservation and sequestration is receiving much attention because of their role in the mitigation of climate change. The main objective of the study is to analyze the potential of the Upper Magat Watershed for a carbon sequestration project. The three main development components of the project are forest conservation: tree plantations, and agroforestry farm development. At Year 30, the watershed can attain a net carbon benefit of 19.5 M tC at a cost of US$ 34.5 M. The potential leakage of the project is estimated using historical experience in technology adoption in watershed areas in the Philippines and a high adoption rate. Two leakage scenarios were used: baseline and project leakage scenarios. Most of the leakage occurs in the first 10 years of the project as displacement of livelihood occurs during this time. The carbon lost via leakage is estimated to be 3.7 M tC in the historical adoption scenario, and 8.1 M tC under the enhanced adoption scenario.     

Dynamics and the economics of carbon sequestration: common oversights and their implications

Accurate assessment of the cost of carbon sequestration is important for the development of mitigation policies globally. Given that sequestration in soils or vegetation is a lengthy process, such assessment requires financial discounting and making realistic assumptions about changes over time in the rate of sequestration, the price of carbon, and the opportunity cost incurred by adopting sequestration practices. Our objective is to demonstrate how these assumptions affect estimates of the cost of sequestration-based mitigation strategies. Using an Australian case study of soil carbon sequestration, our estimates of the carbon price required for financial viability are highly sensitive to dynamic assumptions, varying by a factor of four with different assumptions. Yet the influence of these time-related assumptions is poorly acknowledged in the literature, with many studies either failing to disclose their assumptions, or employing questionable assumptions and methods. Recommended global strategies are for researchers to report their assumptions related to dynamics much more transparently and to improve their research methods and the realism of their assumptions when analysing the economics of carbon sequestration. We recommend that policymakers become better aware of the issues created by dynamics, so that they are able to validly interpret assessments of the cost of sequestration and to ensure that they design policies in a way that facilitates fair comparison of the costs of mitigation strategies that operate over different timescales.     

The impact of climate change under different thinning regimes on carbon sequestration in a German forest district

The objective of this paper is to assess how much carbon (C) is currently stored in a forest district in Thuringia, Germany, and how the carbon stocks will develop up to the year 2099 with a changing climate and under various management regimes (including no management), with different assumptions about carbon dioxide (CO₂) fertilization effects. We applied the process-based model 4C and a wood product model to a forest district in Germany and evaluated both models for the period from 2002 to 2010, based on forest inventory data for the stands in the district. Then, we simulated the growth of the stands in the forest district under three different realizations of a climate change scenario, combined with different management regimes. Our simulations show that in 2099, between 630 and 1149 t C ha^?1 will be stored in this district. The simulations also showed that climate change affects carbon sequestration. The no management strategy sequestered the highest amount of carbon (8.7 t C ha^?1 year^?1), which was greater than the management regimes. In the model, the possible fertilization effect of CO₂ is an important factor. However, forest management remains the determining factor in this forest district.     

The potential of cropland soil carbon sequestration in the Loess Plateau, China

It is generally accepted that cropland soils could be managed to store significant carbon (C), however little information is available regarding the cropland soil C sequestration potential of the Loess Plateau in northern China. This study aimed to estimate the cropland soil C sequestration potential in this area using the United Nations Intergovernmental Panel on Climate Change (IPCC) method with region-specific C stock change factors. The results show that the C sequestration potential can reach 6.054 Tg C yr^?1 (1Tg?=?10¹² g) in cropland soils of the Loess Plateau using techniques that are currently available (no-tillage and high residue incorporation). Although the results show a high degree of uncertainty in this estimate with 95 % confidence interval ranges from 2.623 to 11.94 Tg C yr^?1, our study suggests that cropland soil C sequestration could play a meaningful role in helping to mitigate greenhouse gas increases in the Chinese Loess Plateau.     

Reviewing the carbon footprint analysis of hotels: Life Cycle Energy Analysis (LCEA) as a holistic method for carbon impact appraisal of tourist accommodation

This study discusses the potential for Life Cycle Assessment (LCA) to be utilized for the environmental assessment of tourism accommodation facilities, and their contribution to global carbon footprint. To demonstrate the viability of employing LCA in the hotel sector, its simplified derivative, Life Cycle Energy Analysis (LCEA), is applied to two tourism accommodation facilities in Poole, Dorset (UK) to quantify their CO₂ emissions. The results indicate that the reviewed hotels are less energy and carbon-intense than the tourism accommodation establishments reported in the literature. This may indirectly imply the continuous progress of hotel’s energy efficiency over time. The implications of the current energy use practices in the reviewed hotels are discussed and suggestions are made on how to further improve the energy performance and therefore cut the carbon footprint. Recommendations for hotel management and policy-making are developed to reduce the energy and carbon intensity of the hotel industry. A method for energy and carbon footprint analysis of outsourced laundries and breakfast services is also proposed.     

Protective shade, tree diversity and soil properties in coffee agroforestry systems in the Atlantic Rainforest biome

Sustainable production and biodiversity conservation can be mutually supportive in providing multiple ecosystem services to farmers and society. This study aimed to determine the contribution of agroforestry systems, as tested by family farmers in the Brazilian Rainforest region since 1993, to tree biodiversity and evaluated farmers’ criteria for tree species selection. In addition, long-term effects on microclimatic temperature conditions for coffee production and chemical and biological soil characteristics at the field scale were compared to full-sun coffee systems. A floristic inventory of 8 agroforests and 4 reference forest sites identified 231 tree species in total. Seventy-eight percent of the tree species found in agroforests were native. The variation in species composition among agroforests contributed to a greater γ-diversity than α-diversity. Monthly average maximum temperatures were approximately 6 °C higher in full-sun coffee than in agroforests and forests. Total soil organic C, N mineralization and soil microbial activity were higher in forests than in coffee systems, whereas the chemical and biological soil quality in agroforests did not differ significantly from full-sun coffee after 13 years. Given its contribution to the conservation of biodiversity and its capacity to adapt coffee production to future climate change, coffee agroforestry offers a promising strategy for the area.     

The influence of shade trees on coffee quality in small holder coffee agroforestry systems in Southern Colombia

Production of coffee, especially by small holders, is often associated with various forms of shade management. To analyse the effects of shade on physical coffee quality and on sensorial cup quality of Coffea arabica L. cv. Caturra KMC, a study was carried out with 94 plots on 16 farms in two municipalities, Timaná and Oporapa, located at elevations from 1272 to 1730 masl. in Huila, Colombia. The study was designed with emphasis on shade cover variation within each of the two study areas, while minimizing the variability of environment, agronomic management other than shade, and post-harvest processing. 46 samples of shade coffee and 46 samples of sun coffee were evaluated for physical and sensorial attributes using three professional coffee cuppers (assessors). A principal component analysis including all quality and environmental variables showed that sensory attributes were influenced negatively by shade, and that physical attributes were influenced positively by altitude. A mixed linear model, with coffee cupper and farm as random variables, revealed different shade effects on coffee quality in the two areas. In Oporapa, situated at high altitudes, shade had a negative effect on fragrance, acidity, body, sweetness and preference of the beverage, while no effect was found on the physical quality. In Timaná, situated at lower altitudes, shade did not have a significant effect on sensorial attributes, but significantly reduced the number of small beans. At high altitudes with low temperatures and no nutrient or water deficits, shade trees may thus have a partly adverse effect on C. arabica cv. Caturra resulting in reduced sensory quality. The occurrence of berry borer (Hypothenemus hampei) was lower at high altitudes and higher under shade. Future studies on shade and coffee quality should focus on the interaction between physical and chemical characteristics of beans.