Desirable root architecture for trees differs between sequential and simultaneous agroforestry systems. In sequential systems extensive tree root development may enhance nutrient capture and transfer to subsequent crops via organic pools. In simultaneous systems tree root development in the crop root zone leads to competition for resources. Fractal branching models provide relationships between proximal root diameter, close to the tree stem, and total root length or surface area. The main assumption is that a root branching proportionality factor is independent of root diameter. This was tested in a survey of 18 multipurpose trees growing on an acid soil in Lampung (Indonesia). The assumption appeared valid for all trees tested, for stems as well as roots. The proportionality factor showed a larger variability in roots than in stems and the effects of this variabilily should be further investigated. A simple index of tree root shallowness is proposed as indicator of tree root competitiveness, based on superficial roots and stem diameter. Pruning trees is a major way to benefit from tree products and at the same time reduce above-ground competition between trees and crops. It may have negative effects, however, on root distribution and enhance below-ground competition. In an experiment with five tree species, a lower height of stem pruning led to a larger number of superficial roots of smaller diameter, but had no effect on shoot:root ratios or the relative importance of the tap root.
Tag: architecture
Allometric equations based on a fractal branching model for estimating aboveground biomass of four native tree species in the Philippines
Fractal branching models can provide a non-destructive and generic tool for estimating tree shoot and root length and biomass, but field validation is rarely described in the literature. We compared estimates of above ground tree biomass for four indigenous tree used on farm in the Philippines based on the WanFBA model tree architecture with data from destructive sampling. Allometric equations for the four species varied in the constant (biomass at virtual stem diameter 1) and power of the scaling rule (b in Y = aDb), deviating from the value of 8/3 that is claimed to be universal. Allometric equations for aboveground biomass were 0.035 D2.87 for Shorea contorta, 0.133 D2.36 for Vitex parviflora, 0.063 D2.54 for Pterocarpus indicus and 0.065 D2.28 for Artocarpus heterophyllus, respectively. Allometric equations for branch biomass had a higher b factor than those for total biomass (except in Artocarpus); allometric equations for the leave twig fraction a lower b. The performance of the WanFBA model was significantly improved by introduction of a tapering factor”s” for decrease of branch diameter within a single link. All statistical tests performed on measured biomass versus biomass predicted from the WanFBA results confirm the viability of the WanFBA model as a non-destructive tool for predicting above-ground biomass equations for total biomass, branch biomass and the leaf twig fraction.
The politics of adaptiveness in agroecosystems and its role in transformations to sustainable food systems
Food systems are responsible for pushing human resource use past three thresholds of safe planetary operating space, yet the potential of agroecosystems to contribute to sustainability of food systems when managed for multiple benefits is underexplored. This gap has led to a call for food systems transformation. Previous reviews have acknowledged that governance of food systems transformations is not well understood. The aim of this review is to examine the challenges to transformative governance of agroecosystems, and the potential to apply existing paradigms of adaptiveness in agroecosystems for this transformation. Agricultural production landscapes have been found to be a key level of governance for realizing sustainability transformations of food systems and the landscape concept has been a key paradigm for managing multiple social and ecological objectives at a landscape scale. An examination of the landscape concept using five transformative governance characteristics and applying the earth system governance research lenses illustrated two key areas for further investigation and action for transformative governance. The first is landscape design for continuous social and ecological changes and evolving understandings of sustainability, and the second is the allocation of landscape costs, rights and benefits in present and future decision-making and among human and non-human entities. Managing the pluralistic diversities inherent to agroecosystems will be a key dynamic important to governance and policy for food systems transformations.