Reconciling root plasticity and architectural ground rules in tree root growth models with voxel automata

Contacts: [email protected] models of tree root growth and function have to reconcile the architectural rules for coarse root topology with the dynamics of fine root growth (and decay) in order to predict the strategic plus opportunistic behaviour of a tree root system in a heterogeneous soil. We present an algorithm for a 3D model based on both local (soil voxel level) and global (tree level) controls of root growth, with development of structural roots as a consequence of fine root function, rather than as driver. The suggested allocation rules of carbon to fine root growth in each rooted voxel depend on the success in water uptake in this voxel during the previous day, relative to overall supply and demand at plant level. The allocated C in each voxel is then split into proliferation (within voxel growth) and extension into neighbouring voxels (colonisation), with scale-dependent thresholds and transfer coefficients. The fine root colonisation process defines a dynamic and spatially explicit demand for transport functions. C allocation to development of a coarse root infrastructure linking all rooted voxels depends on the apparent need for adjustment of root diameter to meet the topologically defined sap flow through this voxel during the previous day. The allometric properties of the coarse root system are maintained to be in line with fractal branching theory. The model can predict the dynamics of the shape and structure (fine root density, coarse root topology and biomass) of the root system either independently of soil conditions (purely genetically-driven) or including both the genetic and environmental effects of roots interacting with soil water supply and its external replenishment, linking in with existing water balance models. Sensitivity of the initial model to voxel dimensions was addressed through explicit scaling rules resulting in scale-independent parameters. The model was parameterised for two tree species: hybrid walnut (Juglans nigra x regia) and wild cherry (Prunus avium L.) using results of a pot experiment. The model satisfactorily predicted the root growth behaviour of the two species. The model is sparse in parameters and yet applicable to heterogeneous soils, and could easily be upgraded to include additional local influences on root growth (and decay) such as local success in nutrient uptake or dynamic soil physical propertie

Potential mitigation contribution from coffee agroforestry in three regions of Viet Nam

Coffee agroforestry is one of the main agroforestry systems in Viet Nam in terms of total land area in the country, potential economic contribution, and ecosystem services provided by the shading tree species in the system. This report presents the results of a study that aimed to estimate potential mitigation contribution from carbon storage from coffee agroforestry systems in the three regions of the country. The estimated C storage of arabica coffee systems in the Northwest region of Viet Nam ranges from 2.6 to 17.0 ton ha-1. Potential storage at province level reaches 246,224 ton in Son La province, as it has a higher total area of coffee plantations than Dien Bien province. In the Southeast and Central Highlands region, the estimated C storage of robusta and arabica coffee agroforestry systems ranges from 5.8 to 10.4 ton ha-1, in general due to variation in shading tree species and density. The potential C storage at province level can reach up to 2.1 million ton as in the case of Dak Lak province. From local interviews with provincial authorities and smallholder farmers in the three regions, stakeholders could see the economic and environmental benefits that can be derived from the coffee agroforestry systems. However, the lack of knowledge in planting design and plot management options constrain farmers from transforming their coffee monoculture into agroforestry systems, or expanding the system into available areas for coffee cultivation. We recommend that the provincial authorities keep supporting and encouraging research on coffee agroforestry and provide reliable technical guidance for farmers to develop coffee agroforestry systems with appropriate design

Agroforestry with contour planting of grass contributes to terrace formation and conservation of soil and nutrients on sloping land

In hilly areas, agroforestry can be a more sustainable way of producing food and other products and services than agriculture based on sole-cropping. However, research is needed to evaluate and quantify formation of natural terraces in agroforestry and their contribution to soil conservation. This study quantified natural terrace formation and examined its role in reducing soil and nutrient losses during early stages of agroforestry with fruit trees, contour grass strips and maize or coffee in agroforestry systems on sloping land in northwest Vietnam. Two agroforestry systems, comprising longan (Dimocarpus longan L.)-mango (Mangifera indica L.)-maize (Zea mays L.)-guinea grass (Panicum maximum Jacq.) (fruit-maize-AF) and son tra (Docynia indica (Wall.) Decne.)-coffee (Coffea arabica L.)-guinea grass (fruit-coffee-AF) were compared with sole-cropped maize (sole-maize) and sole-cropped coffee (sole-coffee), respectively. Terrace formation was evaluated over five years using erosion pins placed above grass strips and the volume of terrace formed was estimated. Soil and nutrient losses were quantified using soil traps. The results showed that terraces formed as the systems developed, through gradual deposition of soil sediment above the living grass strips and trees. Accumulated soil sedimentation above the grass strips during the five-year study period raised the soil surface by 4.0 cm in fruit-maize-AF and 4.2 cm in fruit-coffee-AF, and the volume of terraces generated by the grass strips was 0.26 and 0.43 m3/m respectively. The fruit-maize-AF and fruit-coffee-AF systems significantly reduced losses of soil, soil organic carbon (SOC) and associated nutrients (N, P, K) compared with sole-maize and sole-coffee already in the first two years, while the reductions were greater from year 3 onwards. On average across experiments and years, the agroforestry systems reduced soil, SOC, N, P and K losses by 27–76%, 21–78%, 20–82%, 24–82% and 22–84%, respectively. These findings show that agroforestry with fruit trees, grass strips and crops could be a useful management practice and viable option for sustainable agricultural systems on sloping land, by reducing soil (and carbon and nutrient) losses through terrace formation

Potential mitigation contribution from agroforestry to Viet Nam’s NDC

Viet Nam is among the 196 Parties in the Paris Agreement that has committed to low-emission development pathways. The country has formulated national climate change mitigation strategies that relate to forestry and agricultural sector, with a potential revision in 2019 that can include agroforestry (AF), provided that the potential mitigation contribution from this sector can be monitored and reported. This paper presents two approaches to measurement and reporting of AF, based on potential expansion domain (PED) of main AF systems in different regions across the country and the spatial distribution of trees outside forests (TOF), to estimate the potential mitigation contribution from AF, represented by total aboveground carbon (C) sequestration at national scale. Based on the PED approach, the total PED area of different AFs such as coffee, rubber or acacia-based, not including natural forest lands, is ≈10.1 million ha, or about 1/3 of the total land area in the country. Assuming the baseline land uses in the PED can be classified as “cultivated and managed lands,” which according to the Intergovernmental Panel on Climate Change (IPCC) has an average C stock 5 ton ha-1, expansion of the main AF systems across the country results in 262 ± 77 million tons of sequestered C per year, for ten years after plantation. The related total establishment cost for the expansion is USD 24.3 ± 11.3 billion. Using the TOF approach to estimate total tree coverage outside natural forest lands in 2010, total C storage of AF in Viet Nam is ≈355 million ton C, with an average of ≈21.8 ton C ha-1 from ≈20 million ha or about 2/3 of the total land area in the country. Comparing the PED and TOF approach under similar land coverage area of ≈10.1 million ha, the latter estimates a total C storage of ≈ 220 million ton C. By assuming it as total baseline C storage for the PED approach, the potential C gain from AF expansion is ≈92 million ton C, compared to ≈262 million ton C under the assumption of 5 ton ha-1 as average C stock for baseline land uses. This potential mitigation contribution from AF can be reported to relevant authorities, such as the Ministry of Agriculture and Rural Development (MARD) and its sub-institutions, that have a mandate to revise the potential mitigation contribution from the Agriculture and Land Use, Land Use Change, and Forestry sector to the country’s Nationally Determined Contribution (NDC). The challenges in integrating the potential contribution from AF to the agriculture sector or land use sector that focuses on forestry, or as a segregated land use category, should be further discussed with the relevant authorities

Making trees count: Measurement and reporting of agroforestry in UNFCCC national communications of non-Annex I countries

Agroforestry—the integration of trees with crops and livestock—generates many benefits directly relevant to the UNFCCC\u27s Koronivia Joint Work on Agriculture, including: (i) building resilience, (ii) increasing soil carbon and improving soil health, (iii) providing fodder and shade for sustainable livestock production and (iv) diversifying human diets and economic opportunities. Despite its significance to the climate agenda, agroforestry may not be included in measurement, reporting and verification (MRV) systems under the UNFCCC. Here we report on a first appraisal of how agroforestry is treated in national MRV systems under the UNFCCC. We examined national communications (NCs) and Nationally Determined Contributions (NDCs) of 147 countries, REDD + strategies and plans of 73 countries, and 283 Nationally Appropriate Mitigation Actions (NAMAs), as well as conducted interviews with representatives of 12 countries in Africa, Asia and Latin America. We found that there is a significant gap between national ambition and national ability to measure and report on agroforestry. Forty percent of the countries assessed explicitly propose agroforestry as a solution in their NDCs, with agroforestry being embraced most widely in Africa (71%) and less broadly in the Americas (34%), Asia (21%) and Oceania (7%). Seven countries proposed 10 agroforestry-based NAMAs. Of 73 developing countries that have REDD + strategies, about 50% identified agroforestry as a way to combat forest decline. Despite these intentions, however, agroforestry is not visible in many MRV systems. For example, although 66% of the countries reported non-forest trees in the national inventory, only 11% gave a quantitative estimate of number of trees or areal extent. Interviews revealed institutional, technical and financial challenges preventing comprehensive, transparent inclusion of agroforestry in MRV systems. The absence has serious implications. If such trees are not counted in inventories or climate change programs, then a major carbon sink is not being accounted for. Only if agroforestry resources are measured, reported and verified will they gain access to finance and other support. We discuss four recommendations to better match ability to ambition

Open- and crowd-sourced MRV for agroforestry?: Preliminary results and lessons learned from a pilot study using Collect Earth to identify agroforestry on multiple land uses in Viet Nam and Colombia

Key messages ◼ Forty percent of developing countries plan to use agroforestry to meet climate and development goals, yet available systems for measurement, reporting and verification (MRV) are not capable of counting trees in agroforestry systems. ◼ Before agroforestry can become an important response to climate change, countries need access to affordable, accessible tools to improve their ability to monitor agroforestry. ◼ We evaluated the effectiveness of Collect Earth, an open-source platform that allows assessment of land use using freely available high-resolution imagery, for identifying primary types of agroforestry systems in Colombia and Viet Nam. ◼ Preliminary results are mixed but showed promise. Collect Earth is highly effective in identifying some easily distinguished types of agroforestry systems (such as agrisilviculture, boundary planting, and home gardens) but falls short with others (including some types of shadow and silvopastoral systems). ◼ Refinements to our approach—including the integration of local expertise into the photo- interpretation process— could help Collect Earth become a valuable tool to ensure that agroforestry trees count toward climate goals

Open- and crowd-sourced MRV for agroforestry?: Preliminary results and lessons learned from a pilot study using Collect Earth to identify agroforestry on multiple land uses in Viet Nam and Colombia

Key messages ◼ Forty percent of developing countries plan to use agroforestry to meet climate and development goals, yet available systems for measurement, reporting and verification (MRV) are not capable of counting trees in agroforestry systems. ◼ Before agroforestry can become an important response to climate change, countries need access to affordable, accessible tools to improve their ability to monitor agroforestry. ◼ We evaluated the effectiveness of Collect Earth, an open-source platform that allows assessment of land use using freely available high-resolution imagery, for identifying primary types of agroforestry systems in Colombia and Viet Nam. ◼ Preliminary results are mixed but showed promise. Collect Earth is highly effective in identifying some easily distinguished types of agroforestry systems (such as agrisilviculture, boundary planting, and home gardens) but falls short with others (including some types of shadow and silvopastoral systems). ◼ Refinements to our approach—including the integration of local expertise into the photo- interpretation process— could help Collect Earth become a valuable tool to ensure that agroforestry trees count toward climate goals

Women’s involvement in coffee agroforestry value-chains: Financial training, Village Savings and Loans Associations, and Decision power in Northwest Vietnam

Globally, in the coffee sector and smallholder agriculture in developing countries, there is a distinct gender gap in key factors that enable women’s active participation in and contribution to the coffee value chain and in farm and domestic decisions, such as decisions over credit, agricultural inputs, and training opportunities and division of labor and time. This study assesses Village Savings and Loans Associations (VSLA) impacts and related training on gender equality and women’s access to coffee markets in an ongoing coffee- project in northwest Vietnam. All 169 women in this survey received gender equality and finance training, with one group being members of a VSLA and taking out small loans. With Women’s Empowerment in Agriculture Index (WEAI), women rated their perception of their decision-making power over a range of 18 tasks related to household and agricultural responsibilities and use of income and social activities over 18 months. There were significant improvements in decision-making power in categories with previously low participation and increased sharing of domestic responsibilities. The categories with the biggest gains were decision-making over large purchases and use of income, especially for VSLA-members who sought out market information before engaging with potential coffee buyers and enhanced their negotiating abilities to arrange more favorable outcomes successfully. These results indicate that active gender and finance training translated to real changes in gender dynamics, and membership of a VSLA also helped women improve their financial literacy and improve their negotiating abilities. Husbands to women in the study also began to reconsider gender roles and shift towards equal sharing of responsibility and decision- making with their wives. Based on this study, we recommend (1) implementing gender and finance training and enabling access to loans for women as a means for their inclusion in agriculture value chains, and (2) engaging the whole household in gender training in order for all family members to be receptive to adjustments in the gender division of responsibility, labor and decision-making. The results indicate the conditions under which women can benefit from activities involving agroforestry systems that also enhance carbon sequestration for climate change mitigation compared to coffee monoculture

Hi-sAFe: a 3D agroforestry model for integrating dynamic tree–crop interactions

Agroforestry, the intentional integration of trees with crops and/or livestock, can lead to multiple economic and ecological benefits compared to trees and crops/livestock grown separately. Field experimentation has been the primary approach to understanding the tree–crop interactions inherent in agroforestry. However, the number of field experiments has been limited by slow tree maturation and difficulty in obtaining consistent funding. Models have the potential to overcome these hurdles and rapidly advance understanding of agroforestry systems. Hi-sAFe is a mechanistic, biophysical model designed to explore the interactions within agroforestry systems that mix trees with crops. The model couples the pre-existing STICS crop model to a new tree model that includes several plasticity mechanisms responsive to tree–tree and tree–crop competition for light, water, and nitrogen. Monoculture crop and tree systems can also be simulated, enabling calculation of the land equivalent ratio. The model’s 3D and spatially explicit form is key for accurately representing many competition and facilitation processes. Hi-sAFe is a novel tool for exploring agroforestry designs (e.g., tree spacing, crop type, tree row orientation), management strategies (e.g., thinning, branch pruning, root pruning, fertilization, irrigation), and responses to environmental variation (e.g., latitude, climate change, soil depth, soil structure and fertility, fluctuating water table). By improving our understanding of the complex interactions within agroforestry systems, Hi-sAFe can ultimately facilitate adoption of agroforestry as a sustainable land-use practice