Sophie Graefe

Peach palm (Bactris gasipaes) in tropical Latin America: implications for biodiversity conservation, natural resource management and human nutrition

Peach palm (Bactris gasipaes) is a multi-purpose palm tree native to tropical Latin America, which is predominantly cultivated by smallholders in agroforestry systems. The fruits are rich in starch and contribute importantly to food security and the cash income of farmers who cultivate them. Complex value chains have emerged that link producers to consumers, but irregular product quality and market chain inequalities undermine the economic well-being of producers and retailers. Peach palm is genetically diverse, but screening for traits of commercial and nutritional interest is required to enhance the use of its genetic resources. Alliances between public organizations and private enterprises are needed to realize the potential for processing novel products from peach palm, especially in the pharmaceutical and cosmetic sectors. The diverse challenges that emerge at different stages of production, processing and marketing require participatory research that directly involves stakeholders from the beginning.

The Carbon Balance of Tropical Mountain Forests Along an Altitudinal Transect

Not much is known about the role of tropical mountain forests in the global carbon cycle. This chapter summarises a decade of research on C pools and C fluxes in Andean mountain forests of the San Francisco region along an elevation transect from 1,000 m to 3,000 m a.s.l. based on measurements in 5 (3) intensively studied stands at five elevations and supplementary data collected in additional 54 forest plots at three elevations covering different topographic positions at these altitudes. With ecosystem C pools in the range of 320–370 Mg C ha−1, these forests store equally large, or even larger, amounts of C than neotropical lowland forests, despite the decrease in aboveground biomass with elevation. Gross and net primary production (NPP) and net ecosystem production all decrease largely with elevation while fine root production seems to increase. Our results show that tropical mountain forests are playing an important, yet underestimated, role as C stores.

Biomass and productivity of fine and coarse roots in five tropical mountain forests stands along an altitudinal transect in southern Ecuador

Background: Data on below-ground production of tropical montane forests along elevation gradients are scarce. Aims: To determine fine, coarse and large root biomass and productivity along a 2000 m elevation transect. Methods: In five south Ecuadorian mountain forests along a transect from 1000 to 3000 m above sea level, fine (< 2 mm diameter), coarse (2–50 mm) and large root biomass (> 50 mm) were analysed by soil coring and excavation of soil pits. Fine root production was estimated synchronously by three different approaches (sequential soil coring, the ingrowth core method, and the mini-rhizotron technique). Coarse and large root production was estimated by recording diameter increment using dendrometer tapes. Results: Fine root biomass increased four-fold between 1000 and 3000 m; coarse and large root biomass doubled. The three approaches for estimating fine root production yielded highly divergent results, with the mini-rhizotron approach giving the most reliable data, and indicating a significant increase in fine root production with elevation. Conclusions: Our results indicate a marked carbon allocation shift from above- to below-ground towards higher elevations, which is probably a consequence of increasing nutrient limitation of tree growth with increasing elevation.

Climate-smart livestock systems: an assessment of carbon stocks and GHG emissions in Nicaragua

Livestock systems in the tropics can contribute to mitigate climate change by reducing greenhouse gas (GHG) emissions and increasing carbon accumulation. We quantified C stocks and GHG emissions of 30 dual-purpose cattle farms in Nicaragua using farm inventories and lifecycle analysis. Trees in silvo-pastoral systems were the main C stock above-ground (16–24 Mg ha-1), compared with adjacent secondary forests (43 Mg C ha-1). We estimated that methane from enteric fermentation contributed 1.6 kg CO2-eq., and nitrous oxide from excreta 0.4 kg CO2-eq. per kg of milk produced. Seven farms that we classified as climate-smart agriculture (CSA) out of 16 farms had highest milk yields (6.2 kg cow-1day-1) and lowest emissions (1.7 kg CO2-eq. per kg milk produced). Livestock on these farms had higher-quality diets, especially during the dry season, and manure was managed better. Increasing the numbers of CSA farms and improving CSA technology will require better enabling policy and incentives such as payments for ecosystem services.

Characterization of cocoa production, income diversification and shade tree management along a climate gradient in Ghana

Reduced climatic suitability due to climate change in cocoa growing regions of Ghana is expected in the coming decades. This threatens farmers’ livelihood and the cocoa sector. Climate change adaptation requires an improved understanding of existing cocoa production systems and farmers’ coping strategies. This study characterized current cocoa production, income diversification and shade tree management along a climate gradient within the cocoa belt of Ghana. The objectives were to 1) compare existing production and income diversification between dry, mid and wet climatic regions, and 2) identify shade trees in cocoa agroforestry systems and their distribution along the climatic gradient. Our results showed that current mean cocoa yield level of 288kg ha-1yr-1 in the dry region was significantly lower than in the mid and wet regions with mean yields of 712 and 849 kg ha-1 yr-1, respectively. In the dry region, farmers diversified their income sources with non-cocoa crops and off-farm activities while farmers at the mid and wet regions mainly depended on cocoa (over 80% of annual income). Two shade systems classified as medium and low shade cocoa agroforestry systems were identified across the studied regions. The medium shade system was more abundant in the dry region and associated to adaptation to marginal climatic conditions. The low shade system showed significantly higher yield in the wet region but no difference was observed between the mid and dry regions. This study highlights the need for optimum shade level recommendation to be climatic region specific.

Cocoa agroforestry is less resilient to suboptimal and extreme climate than cocoa in full sun: Reply to Norgrove (2017)

Resilience of cocoa agroforestry vs. full sun under extreme climatic conditions. In the specific case of our study, the two shade tree species associated with cocoa resulted in strong competition for water and became a disadvantage to the cocoa plants contrary to expected positive effects.

Tree Water Use Patterns as Influenced by Phenology in a Dry Forest of Southern Ecuador

Tropical dry forests are composed of tree species with different drought coping strategies and encompass heterogeneous site conditions. Actual water use will be controlled by soil moisture availability. In a premontane dry forest of southern Ecuador, tree water use patterns of four tree species of different phenologies were studied along an elevational gradient, in which soil moisture availability increases with altitude. Main interest was the influence of variation in soil moisture, vapor pressure deficit, species (representing phenology), elevation, and tree diameter on water use. Special emphasis was put on the stem succulent, deciduous Ceiba trichistandra, as high water use rates and drought coping involving stem succulence was to be expected. Tree water use rates increased linearly with diameter across species at high soil water content. However, when soil moisture declined, sap flux densities of the species responded differently. The stem succulent, deciduous Ceiba and other deciduous tree species reduced sap flux sensitively, whereas sap flux densities of the evergreen (broad leaved) Capparis scabrida were increasing. This was also reflected in diurnal hysteresis loops of sap flux vs. vapor pressure deficit (VPD) of the air. Under dry soil conditions, Ceiba and other deciduous tree species had much smaller areas in the hysteresis loop, whereas the area of Capparis was largely enhanced compared to wet conditions. The evergreen Capparis potentially had access to deeper soil water resources as water use patterns suggest that top soil drought was tolerated. The deciduous species followed a drought avoidance strategy by being leafless in the dry season. The stem succulent deciduous Ceiba flushed leaves at the end of the dry season before the rainy season began and also re-flushed early in the dry season after a rain event; however, water use rates at this occasion remained low. Ceiba was also ready for fast and strong response in water use when conditions were most favorable during the wet season. The study thus indicates a strong influence of species’ drought coping strategy on water use patterns in tropical dry forests.