Carbon stock assessment for a forest-to-coffee conversion landscape in Sumber-Jaya (Lampung, Indonesia): from allometric equations to land use change analysis

The change in stored carbon (C) stocks was assessed for a 700 km~2 area where forestcover decreased from 60% to 10% in the last 30 years. At the same time, the area under coffee increased from 7% to 70% with a gradual evolution from open "sun coffee" systems to multi-strata "shade coffee" systems that provide a partial compensation for C loss. The use of a generic tropi-cal forest rather than tree-specific allometric equation can lead to substantial (up to 100%) overes-timates of aboveground biomass depending on wood density and tree shape. The shoot: root ratio (biomass) of coffee shifted with age, from the 4∶1 value often assumed for tropical trees to 2∶1.Annual aboveground C stock accumulation rates during the establishment stage after slash-and-burn land clearing were 1, close to 2 or 3.5 Mg C ha~(-1)a~(-1) for sun coffee, shade coffee and fallowregrowth, respectively. Forest remnants, shade coffee and sun coffee had soil C stocks in the up-per 30 cm of the soil that were 79%, 60% or 45%, respectively, of the values expected for primary forest in Sumatra. Total C stock (time averaged, above-0.3 m in the soil) for forest, shade and sun coffee was 262, 82 and 52 Mg C ha~(-1), respectively. In the 1970-1984 period, while forest cover was reduced from 59.5% to 19.7%, the landscape lost on average 6.8 Mg C ha~(-1) a~(-1). In the1984-2000 period forest cover was further reduced to 12.6%, but the landscape lost only 0.39 MgC ha~(-1) a~(-1), as forest loss was partially compensated by an increase in shade coffee systems. Conversion of all current sun coffee to shade coffee systems while protecting the remaining forest,could increase average landscape level C stocks by 10 Mg ha~(-1) over a time frame of say 20 years,or 0.5 Mg C ha~(-1) a~(-1).     

Managing water in agricultural landscapes with short‐rotation biomass plantations

Bioenergy production using woody biomass is a major climate change mitigation strategy but is often considered in terms of competitive effects on water. This paper describes the use of a short‐rotation biomass system (Phase Farming with Trees PFT or ‘Kamikaze Forestry’) to manage water in dryland farming systems where this has accumulated below the root zone and has on and off‐site environmental impacts. This excess water can be utilized for growth by deep‐rooted, high‐density biomass plantations inserted as short rotations into agricultural land. The objective is to promote rapid growth and mining of deep stored water through strategies such as high planting densities, the use of fast‐growing species or fertilization each of which increases leaf area. Once the water is used, the trees are harvested and excess water is allowed to build up again in the subsequent cropping phase. Biomass production and water depletion were measured in a five‐year rotation of trees inserted into a dryland (367 mm yr^?1 mean annual rainfall) cereal farming system in south‐western Australia. Both were markedly affected by tree age, planting density, and landscape position on a very minor slope. The greatest biomass production was achieved with high‐density (4000 stems ha^?1) plantings of Eucalyptus occidentalis and Eucalyptus globulus in lower landscape positions. High‐density plots of these species in mid and upper landscape positions succumbed to drought after 3–4 years, but depleted available soil water to depths of >8 m, equivalent to 771 mm of stored available water. These results suggest that biomass yield can be readily manipulated through planting density and site selection. Moreover, biomass production can produce positive water management co‐benefits.     

Carbon stock assessment for a forest-to-coffee conversion landscape in Sumber-Jaya (Lampung, Indonesia): from allometric equations to land use change analysis

The change in stored carbon (C) stocks was assessed for a 700 km2 areawhere forest cover decreased from 60% to 10% in the last 30 years. At the same time, the area under coffee increased from 7% to 70% with a gradual evolution from open "sun coffee" systems to multi-strata "shade coffee" systems that providea partial compensation for C loss. The use of a generic tropical forest rather than tree-specific allometric equation can lead to substantial (up to 100%) overestimates of aboveground biomass depending on wood density and tree shape. The shoot:root ratio (biomass) of coffee shifted with age, from the 4:1 value often assumed for tropical trees to 2:1. Annual aboveground C stock accumulation rates during the establishment stage after slash-and- burn land clearing were 1, closeto 2 or 3.5 Mg C ha-1a-1 for sun coffee, shade coffee and fallow regrowth, respectively. Forest remnants, shade coffee and sun coffee had soil C stocks in the upper 30 cm of the soil that were 79%, 60% or 45%, respectively, of the values expected for primary forest in Sumatra. Total C stock (time averaged, above - 0.3m in the soil) for forest, shade and sun coffee was 262, 82 and 52 Mg C ha-1, respectively. In the 1970-1984 period, while forest cover was reduced from 59.5%to 19.7%, the landscape lost on average 6.8 Mg C ha-1 a-1. In the 1984-2000 period forest cover was further reduced to 12.6%, but the landscape lost only 0.39Mg C ha-1 a-1, as forest loss was partially compensated by an increase in shadecoffee systems. Conversion of all current sun coffee to shade coffee systems while protecting the remaining forest, could increase average landscape level C stocks by 10 Mg ha-1 over a time frame of say 20 years, or 0.5 Mg C ha-1 a-1.