As a result of canopy interception and transpiration, trees are often assumed to have negative effects on the local hydrological budget resulting in reduced soil and groundwater resources. However, it has also been shown that trees can have positive effects through reducing surface run-off and improving soil infiltrability and groundwater recharge, especially in many tropical ecosystems characterized by high rain intensity and degradation-prone soils. In this study, we used isotopic measurements of soil water to better understand the main processes by which trees influence local soil water dynamics within a tropical pasture with scattered tree cover in the Copan River catchment, Honduras. We also determined the stable isotope signature of xylem water in grasses and trees to assess potential competition for water sources during the wet and dry seasons. During the wet season, when soil water availability was not limiting, both grasses and trees primarily utilized soil water near the soil surface (i.e., 0–10 cm). In contrast, during the dry season, we observed niche partitioning for water resources where grasses primarily utilized soil moisture at deeper soil depth (i.e., 90–100 cm) while trees relied heavily on groundwater. Moreover, isotopic data of soil water suggest that trees reduce evaporative water losses from the soil surface, as indicated by the lack of correlation between soil water content and lc-excess (line condition excess) values of surface soil water under trees, and enhance preferential flow as suggested by less negative lc-excess values under trees compared to open areas during the dry season. Taken together, our findings provide further support that trees can have positive effects on the local water balance with implication for landscape management, promoting the inclusion of scattered trees to provide water ecosystem services in silvopastoral systems, adding to other ecosystem services like biodiversity or carbon sequestration.

Huit ans de travaux de recherche sur les services ecosystemiques dans une grande ferme cafeiere du Costa Rica (observatoire collaboratif Coffee-Flux, en systeme agroforestier a base de cafeiers sous de grands arbres d'Erythrina poeppigiana, surface projetee de couronne de l'ordre de 16 %) ont suggere plusieurs applications pour les agriculteurs et les decideurs. Il est apparu que de nombreux services ecosystemiques dependaient des proprietes du sol (ici des Andisols), en particulier de l'erosion, de l'infiltration, de la capacite de stockage de l'eau et des elements nutritifs. Nous confirmons qu'il est essentiel de lier les services hydrologiques et de conservation au type de sol en presence. Une densite adequate d'arbres d'ombrage (plutot faible ici) permet de reduire la severite des maladies foliaires avec, en perspective, une reduction de l'usage de pesticides-fongicides. Un simple inventaire de la surface basale au collet des cafeiers permet d'estimer la biomasse souterraine et la moyenne d'âge d'une plantation de cafeiers, ce qui permet d'evaluer sa valeur marchande ou de planifier son remplacement. Le protocole de calcul actuel pour la neutralite carbone des systemes agroforestiers ne prend en compte que les arbres d'ombrage, pas la culture intercalaire. Dans la realite, si on inclut les cafeiers, on se rapproche tres probablement de la neutralite. Des evaluations plus completes, incluant les arbres, les cafeiers, la litiere, le sol et les racines dans le bilan en carbone du systeme agroforestier sont proposees. Les arbres d'ombrage offrent de nombreux servies ecosystemiques s'ils sont geres de maniere adequate dans le contexte local. Par rapport aux parcelles en plein soleil, nous montrons qu'ils reduisent l'erosion laminaire d'un facteur 2, augmentent la fixation de l'azote (N2) atmospherique et le pourcentage d'azote recycle dans le systeme, reduisant ainsi les besoins en engrais. Ils reduisent aussi la severite des maladies foliaires, augmentent la sequestration de carbone, ameliorent le microclimat et attenuent substantiellement les effets des changements climatiques. Dans notre etude de cas, aucun effet negatif sur le rendement n'a ete enregistre.

A growing world population and rapid expansion of cities increase the pressure on basic resources such as water, food and energy. To safeguard the provision of these resources, restoration and sustainable management of landscapes is pivotal, including sustainable forest and water management. Sustainable forest management includes forest conservation, restoration, forestry and agroforestry practices. Interlinkages between forests and water are fundamental to moderate water budgets, stabilize runoff, reduce erosion and improve biodiversity and water quality. Sweden has gained substantial experience in sustainable forest management in the past century. Through significant restoration efforts, a largely depleted Swedish forest has transformed into a well-managed production forest within a century, leading to sustainable economic growth through the provision of forest products. More recently, ecosystem services are also included in management decisions. Such a transformation depends on broad stakeholder dialog, combined with an enabling institutional and policy environment. Based on seminars and workshops with a wide range of key stakeholders managing Sweden's forests and waters, this article draws lessons from the history of forest management in Sweden. These lessons are particularly relevant for countries in the Global South that currently experience similar challenges in forest and landscape management. The authors argue that an integrated landscape approach involving a broad array of sectors and stakeholders is needed to achieve sustainable forest and water management. Sustainable landscape management—integrating water, agriculture and forests—is imperative to achieving resilient socio-economic systems and landscapes.

Chapter published in Forest and Water on a Changing Planet: Vulnerability, Adaptation and Governance Opportunities. A Global Assessment Report

Despite the widely held assumption that trees negatively affect the local water budget in densely planted tree plantations, we still lack a clear understanding of the underlying processes by which canopy cover influences local soil water dynamics in more open, humid tropical ecosystems. In this study, we propose a new conceptual model that uses a combination of stable isotope and soil moisture measurements throughout the soil profile to assess potential mechanisms by which evaporation (of surface soil water and of canopy-intercepted rainfall) affects the relationship between surface soil water isotopic enrichment (lc-excess) and soil water content. Our conceptual model was derived from soil water data collected under deciduous and evergreen plants in a shade grown coffee agroforestry system in Costa Rica. Reduced soil moisture under shade trees during the drier season, coinciding when these trees were defoliated, was largely the result of increase soil water evaporation as indicated by the positive relationship between soil water content and lc-excess of surface soil water. In contrast, the evergreen coffee shrubs had a higher leaf area index during the drier season, leading to enhanced rainfall interception and a negative relationship between lc-excess and soil water content. During the wet season, there was no clear relationship between soil water content and between lc-excess of surface soil water. Greater surface soil water under coffee during the dry season may, in part, explain greater preferential flow under coffee compared with under trees in conditions of low rainfall intensities. However, with increasing rainfall intensities during the wet season, there was no obvious difference in preferential flow between the two canopy covers. Results from this study indicate that our new conceptual model can be used to help disentangling the relative influence of canopy cover on local soil water isotopic composition and dynamics, yet also stresses the need for additional measurements to better resolve the underlying processes by which canopy structure influences local water dynamics.

Maintaining appropriate levels of soil infiltrability is important for avoiding undesirable levels of surface runoff and erosion and for maintaining adequate rates of soil and groundwater recharge.This study was conducted with the aim of investigating the effects of Faidherbia albida (apple-ring acacia) and Vitellaria paradoxa (shea butter tree) trees and additions of inorganic fertilizer, leaves and compost on soil infiltrability in two agroforestry parkland systems in the western part of Burkina Faso.Infiltrability was measured before tilling both under and outside canopies of these trees, using tension disc and double-ring infiltrometers.The results show that infiltrability was 33% higher on average under than outside canopies in both agroforestry parkland systems.The compost, leaves and inorganic fertilizer did not improve infiltrability significantly during the study period.More than 75% of the infiltrability estimates obtained using ring infiltrometers outside the canopies were lower than 40 mm/h.In contrast, less than 10% of those obtained from under canopies were lower than this.This could have highly significant effects on run-off, erosion and recharge since rain intensity measurements collected over three years at 30 min intervals showed that up to 35% of the annual precipitation fell with intensities ≥ 40 mm/h.The study demonstrates the potential of improving infiltrability and reducing surface runoff by managing trees appropriately in agroforestry systems in semi-arid tropics.

Coffee-flux is a platform where collaborative research on coffee agroforestry is promoted: data are being shared between collaborators and positive interactions are enhanced. The philosophy is to concentrate several investigations on one specific site and for several years, to share a useful common experimental database, to develop modelling and to publish results in highly-ranked scientific journals. Applied research is also highly encouraged (e.g. C-Neutral certification, NAMA, Agronomy, etc.). Coffee-Flux benefits from infrastructure, easy access from CATIE and very good security, ready to welcome complementary scientific investigations and collaborations. The project is wide open to complementary projects, scientists and of course to students. The core data base is for sharing. The aim of Coffee-Flux is to assess carbon, nutrients, water and sediment Ecosystem Services (ES) at the scale of a coffee agroforestry watershed. Observation, experimentation, modelling and remote-sensing are combined, collecting data and calibrating models locally, then upscaling to larger regions. The project has been running continuously since 2009, in order to encompass seasonal and inter-annual fluctuations of coffee productivity and ecosystem services.

The recent interest in multi-functional agricultural landscapes has not been matched with formal assessment of the roles that trees play across the spectrum of ecosystem services (ESs) provided in Sub-Saharan Africa (SSA). A structured literature review (1995–2014) assessed 350 journal articles about provision of one or more ESs by trees on farms and in agricultural landscapes in SSA. This revealed information on 15 ESs from studies in 23 countries covering arid (1% of studies), semi-arid (49%), sub-humid (26%) and humid (24%) agro-ecological zones. The majority of the studies reported provisioning (39%) and supporting (35%) followed by regulating (26%) ESs while studies on cultural services were scarce. Beneficial impacts of trees were dominating (58%), in particular in semi-arid zones where they were associated with enhancing water and nutrient cycling. A decline in some ESs was reported in 15% of the studies, while 28% found no effect of trees. Although the effects of trees were mainly positive, a decline in crop production was noted as a key trade-off against the provisions of ESs, such as modification of microclimate. This highlights the need to manage trade-offs among impacts of trees on ES provision to reduce competition and increase complementarity between trees and crops.

To determine the resilience of soil organic C and N pools during land degradation processes in a semi-arid landscape of West Africa, we compared the magnitude of soil organic C and N differences in bulk soil and aggregate fractions between contrasting types of land cover (degraded land and native land cover) and soil (Luvisols and Cambisols). We analyzed the following soil key indicators: CEC, soil respiration, C and N contents, and delta C-13 and delta N-15 signatures of soil organic C.The average CO2 respired from native land cover was at least 82% higher than its value from degraded land cover and was significantly higher in Luvisols than in Cambisols. Likewise, the soil organic C and N contents in bulk soil were significantly affected by land cover and soil contrasts. The average C loss in bulk soil from degraded land cover was equivalent to 49% in Cambisols and 54% in Luvisols. In both soil types, all aggregate fractions were sensitive to land degradation processes and the C loss decreased from macroaggregates to the clay + silt fraction. Compared to the native land cover, organic C loss from the macroaggregates in degraded land cover was 92% and 84%, respectively, in Cambisols and Luvisols. The soil type affected significantly the C content only in the clay + silt fraction. The C/N ratio of finer fractions (microaggregates and clay + silt) was significantly higher in degraded land cover than in native land cover, indicating greater losses of N than C during land degradation processes. The differences of delta C-13 signatures throughout C pools between the two types of land cover suggest a relative dominance of C-3 derived C in macroaggregates and C-4 derived C in the clay + silt fraction in the degraded lands. The reduction of soil respiration and the rapid N loss in degraded land cover slowed down the humification processes of C-3 plant derived materials which were effectively dominant in macroaggregates. (C) 2014 Elsevier B.V. All rights reserved.

Dryland livestock production systems are changing in many parts of the world, as a result of growing human populations and associated pressure on water and land. Based on a combination of social and natural science methods, we studied a 30-year transformation process from pastoralism to a livestock-based agro-pastoral system in northwestern Kenya, with the overall aim to increase the understanding of the ongoing transition towards intensified agro-pastoralist production systems in dryland East Africa.Key to this transformation was the use of enclosures for land rehabilitation, fodder production, and land and livestock management. Enclosures have more soil carbon and a higher vegetation cover than adjacent areas with open grazing. The level of adoption of enclosures as a management tool has been very high, and their use has enabled agricultural diversification, e.g. increased crop agriculture, poultry production and the inclusion of improved livestock. Following the use of enclosures, livelihoods have become less dependent on livestock migration, are increasingly directed towards agribusinesses and present new opportunities and constraints for women. These livelihood changes are closely associated with, and depend on, an ongoing privatization of land under different tenure regimes.The results indicate that the observed transformation provides opportunities for a pathway towards a sustainable livestock-based agro-pastoral system that could be valid in many dryland areas in East Africa. However, we also show that emergent risks of conflicts and inequalities in relation to land, triggered by the weakening of collective property rights, pose a threat to the sustainability of this pathway.

Fire has long been a principal tool for manipulating ecosystems, notably for pastoralist cultures, but in modern times, fire use has often been a source of conflicts with state bureaucracies. Despite this, traditional fire management practices have rarely been examined from a perspective of fire behavior and fire effects, which hampers dialogue on management options. In order to analyze the rationale for fire use, its practical handling, and ecological effects in high-elevation ericaceous heathlands in Ethiopia, we used three different information sources: interviews with pastoralists, field observations of fires, and analysis of vegetation age structure at the landscape level. The interviews revealed three primary reasons for burning: increasing the grazing value, controlling a toxic caterpillar, and reducing predator attacks. Informants were well aware of critical factors governing fire behavior, such as slope, wind, vertical and horizontal fuel structure, and fuel moisture. Recent burns (1-4 years since fire) were used as firebreaks to control the size of individual burns, which resulted in a mosaic of vegetation of different ages. The age structure indicated an average fire return interval of ~10 years. At these elevations (> 3500 m), the dry period is unreliable, with occasional rains. Of all observed fires, 83% were ignited during very high Fire Weather Index levels, reached during only 11% of all days of the year. Burning is illegal, but if this ban was respected, our data suggest that the Erica shrubs would grow out of reach of cattle within a few years only, creating a dense and continuous canopy. This would also create a risk of large high-intensity wildfires since the landscape is virtually devoid of natural fuel breaks. Under the present management regime, this heathland ecosystem should be quite resilient to degradation by fire due to a relatively slow fuel buildup (limiting fire intervals) and an effective regrowth of Erica shoots. Nevertheless, if burning is done during severe drought, there may be a risk of smoldering fires killing the lignotubers. Given the intimate knowledge of fire behavior and fire effects among these pastoralists, it should be possible to develop a fire management plan that can sustain the present land use and ecosystem, and be sanctioned by both authorities and the local community.

On-farm experiments were conducted on two soil types (Lixisol and Luvisol) in the western cotton area of Burkina Faso with the objective to develop sustainable water and soil fertility management techniques that improve cotton–maize productivity. The hypothesis that reducing ploughing frequency with addition of organic and mineral fertilizers may improve cotton (Gossypium hirsutum) and maize (Zea mays L.) productions was tested. The treatments were combination of two tillage regimes (annual oxen ploughing, AP and ploughing/manual scarifying, RT) with compost (Co) and without compost (nCo) application. The treatment annual ploughing with compost addition (AP + Co) had the highest soil water content (WC) on both the Lixisol and the Luvisol. The cotton yield increase was 46 and 36% on reduced tillage plot with compost additions (RT + Co) compared to the control in the Lixisol and the Luvisol, respectively. In the Lixisol the highest maize grain yield was recorded in the annual ploughing plot with the additional amount of nitrogen equivalent to the compost nitrogen content. Reduced tillage together with compost additions had the highest maize yield in the Luvisol. These results confirmed the hypothesis that reduced tillage with organic and mineral fertilization improved cotton and maize productions.

Tree planting in the tropics is conducted for a number of reasons including carbon sequestration, but often competes with increasingly scarce water resources. The basics of forest and water relations are frequently said to be well understood but there is a pressing need to better understand and predict the hydrological effects of land-use and climate change in the complex and dynamic landscapes of the tropics. This will remain elusive without the empirical data required to feed hydrological process models. It is argued that the current state of knowledge is confused by too broad a use of the terms 'forest' and '(af)forestation', as well as by a bias towards using data generated mostly outside the tropics and for nondegraded soil conditions. Definitions of forest, afforestation and reforestation as used in the climate change community and their application by land and water managers need to be reconciled.

Miombo is a significant biome covering about 10% of the African landmass. Climate semi-aridity is the main edaphic determinant. Range of annual rainfall and dry season length is high, but the unimodal rain- fall distribution is common for all miombo. Water is increasingly an issue of trade-off between different land uses and increasing demand on biomass production. This review gives a basic description of major components in the relations between tree cover and water in semi-arid landscapes. From this, in lack of relevant research within miombo landscapes, a scientifically based discussion is given on how future uses and management of these complex woodlands could serve in better management of scarce water re- sources and in what ways more research in these aspects could enlighten this discussion. It is concluded that, like for other semi-arid landscapes, there is need for understanding and developing more complex stand management to optimize biomass production and water use efficiency. At the same time climate change adaptation will add to this need of deepened biophysical process understanding.

Green leaves of Albizia gummifera G.F. Gmel, Milletia ferruginea (Hochst.) Baker, Cordia africana Lam., and Croton macrostachyus Del. were collected from trees growing in fields in southern Ethiopia, and used in laboratory and field experiments. The aim was to investigate differences in C mineralization parameters related to differences in the leaf qualities of the respective species, and to examine effects of amending soil (Mollic Andosols) with leaves plus N, P, or N + P on decomposition and microbial activity. Rates of carbon mineralization were determined by measuring CO2 evolution using an automated respirometer (Respicond V) in the laboratory and an infrared gas analyser in the field studies. When no nutrients were added about 11–44% and 10–42%, on average, of the initial C applied as leaves was mineralized within a month in the laboratory and field respiration experiments, respectively. In both experiments, the rates of C mineralization were highest for C. macrostachyus leaves, followed by M. ferruginea then A. gummifera and lowest for C. africana leaves. Hence the results of our short-term laboratory study agreed well with those of the field experiment. Microbial activity (e.g. specific growth rate) was generally stimulated by supplemental nutrients. However, in most cases cumulative C mineralization was either slightly depressed or not significantly affected by supplemental N or N + P. Similarly, P addition caused either a reduction in C mineralization or had little effect. Hence the quality of the leaves was more influential than the nutrient additions. The absence of a pronounced respiratory response to the added N and/or P might be due to increased microbial C-use efficiency, to adequate amounts of these nutrients being available from the leaves and/or soil, or both. Further in-depth studies using soils of differing soil fertility are needed to test these hypotheses.