Agroforestry systems hold potential for wood and tree biomass production without the need of felling trees. Branch wood harvesting provides access to considerable amounts of lignocellulosic biomass while leaving the tree standing. Aiming at alternatives for wood provision, we assessed the actual woody structure of a silvopastoral system in the African Savannah ecoregion, utilising terrestrial LiDAR technology and quantitative structure models to simulate branch removals and estimate harvesting yields. In addition, the stand structure and harvested wood were examined for the provision of four types of assortments meeting local needs, and operational metrics for each treatment were derived. The stand had large variability in woody structures. Branch harvesting interventions removed up to 18.2% of total stand volume, yielded 5.9 m3 ha−1 of branch wood, and delivered 2.54 m3 ha−1 of pole wood quality, retaining on average more than 75% of the original tree structures. Among the most intense simulations, a mean of 54.7 litres (L) of branch wood was provided per tree, or approximately 34.2 kg of fresh biomass. The choice of an ideal harvesting treatment is subject to practitioners’ interests, while the discussion on aspects of the operation, and stand and tree conditions after treatment, together with outputs, assist decision making. The partitioning of tree structures and branch removal simulations are tools to support the design of tending operations aiming for wood and tree biomass harvesting in agroforestry systems while retaining different functional roles of trees in situ.
Light is a limiting resource for crops within integrated land use systems especially those including woody perennials. The amount of available light at ground level can be modified by artificially pruning the overstory. Aiming to increase the understanding of light management strategies, we simulated the pruning of wild cherry trees and compared the shading effects of the resulting tree structures over a complete growing season, with fine spatiotemporal resolution. Original 3D-tree structures were retrieved employing terrestrial laser scanning and quantitative structure models, and subjected to two pruning treatments at low and high intensities. By using the ‘shadow model’, the analogous tree structures created diverse shaded scenarios varying in size and intensity of insolation reduction. Conventional pruning treatments reduced the crown structure to the uppermost portion of the tree bole, reducing the shading effects, and thus, shrinking the shaded area on the ground by up to 38%, together with the shading intensity. As an alternative, the selective removal of branches reduced the shading effects, while keeping a more similar spatial distribution compared to the unpruned tree. Hence, the virtual pruning of tree structures can support designing and selecting adequate tending operations for the management of light distribution in agroforestry systems. The evidence assembled in this study is highly relevant for agroecosystems and can be strategically used for maintaining, planning and designing integrated tree-crop agricultural systems.
Reduced solar radiation brought about by trees on agricultural land can both positively and negatively affect crop growth. For a better understanding of this issue, we aim for an improved simulation of the shade cast by trees in agroforestry systems and a precise estimation of insolation reduction. We present a leaf creation algorithm to generate realistic leaves to be placed upon quantitative structure models (QSMs) of real trees. Further, we couple it with an enhanced approach of a 3D model capable of quantifying shading effects of a tree, at a high temporal and spatial resolution. Hence, 3D data derived from wild cherry trees (Prunus avium L.) generated by terrestrial laser scanner technology formed a basis for the tree reconstruction, and served as leaf-off mode. Two leaf-on modes were simulated: realistic leaves, fed with leaf data from wild cherry trees; and ellipsoidal leaves, having ellipsoids as leaf-replacement. For comparison, we assessed the shading effects using hemispherical photography as an alternative method. Results showed that insolation reduction was higher using realistic leaves, and that the shaded area was greater in size than with the ellipsoidal leaves or leaf-off conditions. All shading effects were similarly distributed on the ground, with the exception of those derived through hemispherical photography, which were greater in size, but with less insolation reduction than realistic leaves. The main achievements of this study are: the enhancement of the leaf-on mode for QSMs with realistic leaves, the updates of the shadow model, and the comparison of shading effects. We provide evidence that the inclusion of realistic leaves with precise 3D data might be fundamental to accurately model the shading effects of trees.
Landscape elements play an important role in preventing wind erosion and protecting arable land outside of tillage and crop management practices. The wind reducing effect of any landscape element may influence leeward distances up to the 40-fold of its height. In addition, when the sun is shining, areas close to the landscape elements are shaded. Wind velocity and solar radiation are the primary affected parameter, which again have impact on temperature, dew formation, evaporation and soil moisture in the zones influenced by landscape elements (Veste et al., 2020). Therefore, not only the wind erosion susceptibility of a soil but also plant growth factors can vary considerably within short distances. The combination of large fields and dry climatic conditions are favoring factors for wind erosion in the Federal State of Brandenburg. On the other hand, Brandenburg has a very diverse landscape structure, including forests, alley trees, hedges, small groves and many other habitats. Within the framework of the Cross Compliance regulations ((EC) No 73/2009) for direct support schemes for farmers a method has been developed, to include the influence of landscape structure in the assessment of wind erosion susceptibility of soils (DIN 19706; Funk et al., 2004). This method has been continuously developed and now uses the Digital Surface Model (DSM) from the laser scanning survey of Brandenburg to determine the location and height of any landscape element with a horizontal resolution of 1 x 1 m and a vertical resolution in the centimeter range. The height of each landscape element can be used to calculate the shading effects of the wind or the sun in a GIS. These calculations were compared with detailed measurements of meteorological parameter in and around shelter belts in an orchard.
Landscape elements play an important role in preventing wind erosion and protecting arable land outside of tillage and crop management practices. The wind reducing effect of any landscape element may influence leeward distances up to the 40-fold of its height. In addition, when the sun is shining, areas close to the landscape elements are shaded. Wind velocity and solar radiation are the primary affected parameter, which again have impact on temperature, dew formation, evaporation and soil moisture in the zones influenced by landscape elements (Veste et al. 2020). Therefore, not only the wind erosion susceptibility of a soil but also plant growth factors can vary considerably within short distances. The combination of large fields and dry climatic conditions are favoring factors for wind erosion in the Federal State of Brandenburg. On the other hand, Brandenburg has a very diverse landscape structure, including forests, alley trees, hedges, small groves and many other habitats. Within the framework of the Cross Compliance regulations ((EC) No 73/2009) for direct support schemes for farmers a method has been developed, to include the influence of landscape structure in the assessment of wind erosion susceptibility of soils (DIN 19706; Funk et al. 2004). This method has been continuously developed and now uses the Digital Surface Model (DSM) from the laser scanning survey of Brandenburg to determine the location and height of any landscape element with a horizontal resolution of 1 x 1 m and a vertical resolution in the centimeter range. The height of each landscape element can be used to calculate the shading effects of the wind or the sun in a GIS. These calculations were compared with detailed measurements of the meteorological parameters in and around shelterbelts in an orchard.
In the context of ongoing climate change and increasing population, there is an urgent need to optimize the water consumption of surface and groundwater in agricultural production. In recent years, intensive irrigated viticulture and horticulture have faced increasing demand pressure in many water-limited areas including the Western Cape Province in South Africa. Shelterbelts of trees are often used to reduce wind speed and water demands as an eco-engineering measure directly influencing soil evaporation and crop transpiration. Objectives are (i) to evaluate the extent of impacts of wind speed from shelterbelts at canopy level in citrus orchards and vineyards (ii) to assess the wind effects at leaf level including leaf temperature and related ecophysiological performance in irrigated vineyards.
Agroforestry is often discussed as a strategy that can be used both for the adaptation to and the mitigation of climate change effects. The climate of southern Africa is predicted to be severely affected by such changes. With agriculture noted as the continent's largest economic sector, issues such as food security and land degradation are in the forefront. In the light of such concerns we review the current literature to investigate if agroforestry systems (AFS) are a suitable response to the challenges besetting traditional agricultural caused by a changing climate. The benefits bestowed by AFS are multiple, offering ecosystem services, influence over crop production and positive impacts on rural livelihoods through provisioning and income generation. Nevertheless, knowledge gaps remain. We identify outstanding questions requiring further investigation such as the interplay between trees and crops and their combination, with a discussion of potential benefits. Furthermore, we identify deficiencies in the institutional and policy frameworks that underlie the adoption and stimulus of AFS in the southern African region. We uphold the concept that AFS remains an appropriate and sustainable response for an increased resilience against a changing climate in southern Africa for the benefit of livelihoods and multiple environmental values.
This review provides perspectives and insights of forest researchers from four continents representing a range of geo-regions, with examples from diverse and dynamic use of forest products that are undervalued and often misrepresented. A comprehensive discussion of the subject provides special attention to property, tenancy, public goods and access rights to non-wood forest products (NWFP), seen as forest ecosystem services in a framework for forest management decisions. The overall purpose is to provide a logical argument for transitioning to sustainable management of forests for timber and NWFP. Multifunctional ecosystem-based approaches are transforming our understanding of forests. The prevailing economic relevance of NWFP for trade and sustenance requires their operative integration into forest management. Integration of NWFP will shift a traditional timber-oriented management paradigm towards an inclusive ecosystem forest management approach. We show that the impact of NWFP resources on livelihoods provides multiple benefits to all sectors of global society. Policy and property rights affect the availability and sustainability of the resource, while regulations, restrictions and prohibitions target the sustainable harvest of NWFP under growing demand. Official reporting of production volumes of NWFP is sparse, erratic or inaccurate due to a complex system that is opaque and with inadequately understood value chains, yet research is underway to better understand all NWFP sectors. A shift from command-and-control forest management to broader governance schemes is observed, yet despite a growing awareness of their importance, NWFP and their potential for a bio-based economy require more research. A conceptual framework for transitioning to sustainable co-production management of timber and NWFP is presented. Such a transition is needed to ensure long-term forest security, health and resilience.
Southern Africa is faced with impacting issues such as climate change, degraded landscapes, food insecurity and other severe economic, social and environmental challenges. Yet, the southern African region presents the opportunity to address these pressing issues by exploiting technological advancements for accurate aboveground biomass estimation of trees. Simultaneously, the employment of innovative and sustainable land use systems such as agroforestry systems (combining agricultural crops and trees) is expected to be part of the solution by building resilience against a changing climate. Through inclusion of trees within farmed landscapes increased carbon sequestration, water retention, soil erosion control and enhancement of rural livelihoods can be achieved. Therefore, in order to promote trees and agroforestry systems, the application of terrestrial laser scanning technology is of high interest and importance. A non-destructive methodology to estimate the aboveground carbon sequestration potential of tree species growing in southern African landscapes is applied under the framework of the ASAP project (“Agroforestry in southern Africa – new pathways of innovative land use systems under a changing climate, grant number 01LL1803 funded by the German Federal Ministry of Education and Research”). We use 3D data derived from single trees scanned in multiple positions for the assessment of tree volume. In this context, the tree volume data estimated through quantitative structure models (QSMs) is used as basis for calculating the aboveground tree biomass. For this purpose, we combine the tree volume with species specific wood density. The use of QSMs enables a truthful description and examination of the topological (branching structure), geometric and volumetric properties of the woody structure of a tree. The eventual absence of 3D data specific to agroforestry trees is overcome by selecting trees growing in more open landscape conditions (open forests, individual trees, trees outside forests) and that are already utilized in agroforestry systems. Standard tree parameters such as crown base height, crown volume and tree height, help to quantify the tree impact on the neighbouring crops. Equally important are TLS detectable tree attributes that relate to wood quality and efficient wood utilization (e.g. stem volume, sweep, taper, branchiness). Furthermore, we place a special focus on the biomass distribution between differing tree components (e.g. between stem and branch fractions) and distinct tree species occurring in agroforestry systems.
Der Bevölkerung im südlichen Afrika stehen enorme Herausforderungen hinsichtlich des sich ändernden Klimas bevor. So stellen die durch den Klimawandel hervorgerufenen Risiken eine massive Bedrohung der ökonomischen, und sozialen Entwicklung der Länder im südlichen Afrika dar und belastet zusätzlich die Ökkosysteme, die durch das ransante Bevölkerungswachstum ohnehin stark unter Druck geraten sind. Agroforstsysteme bieten vielversprechende Möglichkeiten, die landwirtschaftlichen Produktionssysteme resistenter und resilienter hinsichtlich des Klimawandels zu gestalten. Hier setzt das BMBF- Projekt ASAP, „Agroforstwirtschaft im südlichen Afrika- neue Lösungsansätze innovativer Landnutzungssysteme unter einem sich ändernden Klima“, an. Ziel ist es zu untersuchen wie die Bioökonomie in ländlichen Gebieten des südlichen Afrikas durch optimierte agroforstliche Landnutzungssysteme gestärkt werden kann. Neben den Anpassungspotenzialen an den Klimawandel sollen dabei auch die Potenziale solcher Systeme zur Verminderung der Folgen des Klimawandels untersucht und bewertet werden. Dazu werden im Rahmen von ASAP einerseits die Wirkungen von Bäumen in Agroforstsystemen auf Bodenprozesse, das Mikroklima und den Wasserhaushalt untersucht, andererseits soll die Produktivität des Gesamtsystems und die Biodiversität in solchen Systemen erfasst werden. Darüber hinaus werden auch sozio-ökonomische Aspekte beleuchtet, um herauszufinden, wie solche Systeme von der Bevölkerung und den Landbewirtschaftern wahrgenommen werden, und wie sie die Lebensgrundlage der ländlichen Bevölkerung verbessern können. The population in southern Africa faces enormous challenges with regard to the changing climate. The risks posed by climate change pose a massive threat to the economic and social development of the countries in southern Africa and also place a strain on the ecosystems, which are already under great pressure due to the rapid population growth. Agroforestry systems offer promising opportunities to make agricultural production systems more resistant and resilient to climate change. This is where the BMBF project ASAP, "Agroforestry in Southern Africa - New Approaches to Innovative Land Use Systems under a Changing Climate", comes in. The aim is to investigate how the bioeconomy in rural areas of southern Africa can be strengthened by optimized agroforestry land use systems. In addition to the potential for adaptation to climate change, the potential of such systems to mitigate the consequences of climate change will also be investigated and evaluated. ASAP is investigating the effects of trees in agroforestry systems on soil processes, the microclimate and the water balance on the one hand, and the productivity of the overall system and biodiversity in such systems on the other. In addition, socio-economic aspects will be examined in order to find out how such systems are perceived by the population and farmers and how they can improve the livelihood of the rural population.
Climate change is already a measurable reality generating significant social, economic and environmental challenges, impacting sustainable development around the globe. The African continent is most vulnerable to the forecasted change in global climate, southern Africa in particular will face severe challenges within the upcoming decades. Innovative, flexible and improved land use systems are expected to be part of the adaptive solution, mitigating the effects of a changing climate and positively influencing agriculture and food security under altered conditions. The BMBF funded research project ‘Agroforestry in Southern Africa - new Pathways of innovative land use systems under a changing climate’ (acronym ASAP; grant number: 0LL1803) incorporating partners from South Africa, Namibia, Mozambique, Malawi and Zambia alongside researchers from Germany, targets the employment of agroforestry systems (AFS), as an appropriate response to climate change. ASAP aims at investigating ecosystem services as well as socio-economic and environmental benefits of AFS in the southern Africa region. The chosen transdisciplinary approach to investigate the biophysical environment and ecosystem services in conjunction with socio-economic aspects of AFS will help develop a better understanding of a range of possible solutions using AFS for varied agro-climatic zones and landscape scales. The exploration of human-environment interactions within AFS is a major focus with the intention of facilitating a sustainable improvement to rural livelihood utilising AFS. Project outputs will be disseminated to practitioners and researchers through local facilitators in the framework of workshops, lectures and practical guidance in order to establish a paradigm shift.
New and innovative land use solutions are needed to adapt to a rapidly changing climate and to mitigate the predicted impacts on rural livelihoods. Projected changes to current climate patterns are suggested to severely impact southern Africa in the near future. This may be realised as an increase in drought and flooding events and shifts in rainfall patterns causing a loss of productive cropland, thus, negatively affecting economic, ecological and social aspects of sustainable development. Agroforestry systems (AFS) present the potential to improve the bio-economy in rural areas, to provide an adaptation strategy for human needs, and to preserve natural resources and biodiversity against climate change influences. Targeting the application of AFS as a suitable response to the impacts of climate change, the research project ‘Agroforestry in southern Africa - new pathways of innovative land use systems under a changing climate (ASAP)’ with a project period of 2018 to 2021 incorporates research partners from Namibia, Mozambique, Malawi, Zambia, South Africa and Germany. In a transdisciplinary approach the ASAP project aims to both develop and cement knowledge concerning AFS in southern Africa, utilising simple easily replicable methodology across the entire study region. The project will utilise traditional knowledge and combine it with innovative technical solutions, learning from existing systems and technology. ASAP targets an understanding of the social demands and impacts that AFS can bring to the study region. This is undertaken by attaining an understanding of the needs of stakeholders, land managers and subsistence farmers, as well acknowledging the potential pressures such actors will face due to a changing climate. Results of the project will aid regional policy makers in evaluating future support for such innovative land-use systems in a science-policy exchange. The project consortium will perform an examination of the effects of the utilisation of trees within a farmed landscape in terms of soil processes, hydrological fluxes and flows, shading and nutrient export as well as assessment of woody biomass production, to allow researchers and land managers to target future research where it is needed. Project output will be designed to promote AFS as a viable approach to land use, agriculture and food production and as a modified alternative to conventional or traditional agricultural practices. The project stands as an interdisciplinary platform for transnational research, capacity building, information exchange, contributing knowledge and solutions for sustainable AFS management, while meeting stakeholder’s needs at a grassroots level and promoting the implementation of AFS as an innovative, flexible and sustainable land use system under a changing climate. The ASAP project is funded by the BMBF (German Federal Ministry of Education and Research) under grant number 01LL1803, as part of the SPACES II funding program.