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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.

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.

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...

Huit ans de travaux de recherche sur les services écosystémiques dans une grande ferme caféière du Costa Rica (observatoire collaboratif Coffee-Flux, en système agroforestier à base de caféiers sous de grands arbres d'Erythrina poeppigiana, surface projetée de couronne de l'ordre de 16 %) ont suggéré plusieurs applications pour les agriculteurs et les décideurs. Il est apparu que de nombreux services écosystémiques dépendaient des propriétés du sol (ici des Andisols), en particulier de l'érosion, de l'infiltration, de la capacité de stockage de l'eau et des éléments nutritifs. Nous confirmons qu'il est essentiel de lier les services hydrologiques et de conservation au type de sol en présence. Une densité adéquate d'arbres d'ombrage (plutôt faible ici) permet de réduire la sévérité des maladies foliaires avec, en perspective, une réduction de l'usage de pesticides-fongicides. Un simple inventaire de la surface basale au collet des caféiers permet d'estimer la biomasse souterraine et la moyenne d'âge d'une plantation de caféiers, ce qui permet d'évaluer sa valeur marchande ou de planifier son remplacement. Le protocole de calcul actuel pour la neutralité carbone des systèmes agroforestiers ne prend en compte que les arbres d'ombrage, pas la culture intercalaire. Dans la réalité, si on inclut les caféiers, on se rapproche très probablement de la neutralité. Des évaluations plus complètes, incluant les arbres, les caféiers, la litière, le sol et les racines dans le bilan en carbone du système agroforestier sont proposées. Les arbres d'ombrage offrent de nombreux servies écosystémiques s'ils sont gérés de manière adéquate dans le contexte local. Par rapport aux parcelles en plein soleil, nous montrons qu'ils réduisent l'érosion laminaire d'un facteur 2, augmentent la fixation de l'azote (N2) atmosphérique et le pourcentage d'azote recyclé dans le système, réduisant ainsi les besoins en engrais. Ils réduisent aussi la sévérité des maladies foliaires, augmentent la séquestration de carbone, améliorent le microclimat et atténuent substantiellement les effets des changements climatiques. Dans notre étude de cas, aucun effet négatif sur le rendement n'a été enregistré., Eight years of studying coffee ecophysiology and monitoring ecosystem services (ES) in a large coffee farm in Costa Rica revealed several practical recommendations for farmers and policy makers. The cropping system studied within our collaborative observatory (Coffee-Flux) corresponds to a coffee-based agroforestry system (AFS) under the shade of large trees of Erythrina poeppigiana (16 % of canopy cover). A lot of ES and disservices depend on local soil properties (here Andisols), especially erosion/infiltration, water/carbon and nutrient storage capacity. Therefore, for ES assessment, the type of soil is crucial. An adequate density of shade trees (rather low here) reduced the severity of leaf diseases with the prospect of reducing pesticide-fungicide use. A simple inventory of the basal area at collar of the coffee plants allowed estimating the belowground biomass and the average age of the plantation, to judge of its market value and to decide when to replace it. Coffee farms are probably much closer to C neutrality than predicted by the current C-Neutral protocol, which only considers shade trees. More comprehensive assessments, including trees, coffee, litter, soil, and roots in the C balance of the AFS are proposed. Shade trees offer many ES if they are adequately managed in the local context. As compared to full sun conditions, shade trees may (i) reduce laminar erosion by a factor of 2, (ii) increase N2 fixation and the % of N recycled into the system, thus reducing fertilizer requirements, (iii) reduce the severity of leaf diseases, (iv) increase C sequestration, (v) improve the microclimate, and (vi) substantially reduce the effects of climate change. In our case study, no negative effect on coffee yield was found.

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 δ 13 C and δ 15 N signatures of soil organic C. The average CO 2 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 δ 13 C 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.

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.

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. © 2009 Blackwell Publishing Ltd.

Cropping systems have a strong influence on soil structural characteristics, including aggregate stability. An experiment combining compost (Co) and mineral fertilizer inputs with different tillage frequencies was conducted in a cotton-maize rotation system on two soil types (Lixisol and Luvisol) in Burkina Faso. The objective was to investigate an alternative soil fertility management regime that protects soil structure for cotton and maize production. We tested the hypothesis that organic fertilizer applications and reduced ploughing frequency can improve aggregate stability. The effects of reduced tillage (RT; ox-ploughing/hand hoe scarifying the next year) and annual ox-ploughing (AP) combined with Co and no compost (nCo) applications on the stability of soil aggregates subjected to wet sieving, were assessed. In the second year of the experiment (maize), the macroaggregate stability in the RT plots was 87% higher than in the AP plots on the Lixisol, 26% higher on the Luvisol. In the third year (cotton) the difference in treatment effects was less. The treatments influenced macroaggregate stability in the year of scarification, and the microaggregate stability in the year they were ploughed. We concluded that a soil management regime, with ploughing only every second year and with compost as well as mineral fertilizer inputs, is appropriate to replace the common practice of annual ploughing with application of mineral fertilizers in this cotton-maize cropping system.

We investigated under field and laboratory conditions the decomposition and nutrient release from mixed leaf litters of Faidherbia albida (Del) A. Chev. and Vitellaria paradoxa C.F. Gaertn. f. in the south-Sudanese zone of West Africa. Litterbags containing F. albida and V. paradoxa litters in varying proportions were placed on the soil surface and buried in plots receiving the following treatments: no fertilizer (control); nitrogen; phosphorus as Triple Superphosphate (TSP); and phosphorus as rock phosphate from Burkina Faso (BP). At each litterbags collection date, the undecomposed litter from each species was separated, and its remaining mass, nitrogen, phosphorus and potassium contents were determined. F. albida decomposed faster (k-values ranged from 0.060 to 0.171 week−1) than V. paradoxa (k-values ranged from 0.020 to 0.056 week−1) and released more nutrient than V. paradoxa. Mixing litters accelerated the decomposition rate of both F. albida and V. paradoxa litter. Decomposition was faster in the nitrogen and TSP plots than in the control and BP plots, and buried litter decomposed more rapidly than surface litter Also under laboratory conditions, F. albida litter decomposed more rapidly than V. paradoxa litter as the microbial specific growth rate were 0.135 h−1 and 0.069 h−1, respectively. Results indicated that mixing litters of contrasting qualities may be a promising option to regulating decomposition/mineralization rates from organic material.

We studied nutrient limitation and availability for soil microbial respiration after additions of glucose (C), in combination with nitrogen (N) and phosphorus (P) in soil samples taken from parklands of Vitellaria paradoxa and Faidherbia albida. We hypothesized that in these P-fixing soils: (i) after C addition, respiration will be limited by P, but P-limitation will be lower under tree canopies; and (ii) the maximum respiration rates after adding C will be higher with than without applications of inorganic fertilizer (NPK) in the field. The study site was located in the south-Sudanese zone of Burkina Faso. Microbial respiration was measured as CO2 evolution from soil samples incubated under laboratory conditions. Two microbial growth peaks were observed after addition of C plus P to the soil samples. When P was added together with C, the initial increase in the microbial respiration rate was higher than when N and C were added, and the maximum respiration rate was also reached earlier. We conclude that P limited the initial rate of respiration. Under the tree canopy the P and N availability, was higher under both F. albida and V. paradoxa trees, than in areas beyond their canopies. NPK fertilization in the field resulted in higher soil reserves of N and P, but these nutrients had low availability in the short term. Results indicated that more P is available in forms that are immediately accessible to microorganisms under tree canopies, than outside the cover of their canopies.

Soil water infiltration influences groundwater recharge and potential top soil loss by erosion, as well as the partitioning of runoff into slow flow and quick flow. The aim of the work presented here was to critically review studies of the effects of afforestation on infiltrability in the tropics, using a systematic review approach to select peer-reviewed articles published in English and French. We then applied meta-analysis to test the hypothesis that afforestation or the use of trees in agriculture increases infiltration capacity. After assessing titles and abstracts, on the basis of specified selection and quality criteria, four references remained, comprising 14 comparative experiments. The overall result of the meta-analysis was that infiltration capacity increased on average approximately three-fold after afforestation or planting trees in agricultural fields (95% confidence interval: 2.4-4.7). For the meta-analysis, the most common problems resulting in exclusion of otherwise relevant experiments were issues with the experimental design, and the absence of statistics (variances and replicates). Even considering the studies that were excluded in the meta analysis (a total of six), the low number of studies examining the effects of afforestation is a severe problem with respect to modelling and examining the underlying processes associated with the full range of different edaphic situations, different species and different methods of establishment.

One of the key issues to increase soil productivity in the Sahel is to ensure water infiltration and storage in the soil. We hypothesised that reducing tillage from annual to biennial ploughing and the use of organic matter, like compost, would better sustain soil hydraulic properties. The study had the objective to propose sustainable soil fertility management techniques in the cotton–maize cropping systems. The effects of reduced tillage (RT) and annual ploughing (AP) combined with compost application (Co) on soil infiltration parameters were assessed on two soil types. Topsoil mean saturated hydraulic conductivities ( K s ) were between 9 and 48 mm h −1 in the Luvisol, while in the Lixisol they were between 18 and 275 mm h −1 . In the two soil types compost additions with reduced tillage or with annual ploughing had the largest effect on K s . Soil hydraulic behaviour was in reasonable agreement with soil pore size distribution (mean values varied from 19.5 to 237 μm) modified by tillage frequency and organo-mineral fertilization. Already the first 3 years of this study showed that use of organic matter, improved soil infiltration characteristics when annual ploughing was used. Also biennial ploughing showed promising results and may be a useful strategy for smallholders to manage these soils.

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.

COFFEE-FLUX (Costa Rica): observatory for monitoring and modeling carbon, nutrients, water and sediment ecosystem services in coffee agroforestry systems; mitigation and adaptation to climate changes through ecosystem manipulation. Journée de l'Infrasctructure nationale AnaEE France

The effect of combined inputs of green manure (GM) and urea on maize (Zea mays L.) productivity and soil characteristics was studied in an on-farm trial at Wondo Genet, southern Ethiopia. The GM species used were the legumes Albizia gummifera G.F. Gmel and Milletia ferruginea (Hochst.) Baker and the non-legumes Cordia africana Lam and Croton macrostachyus Del. The GM and urea were applied separately or combined in different proportions to give equal rates of 100 kg N ha−1, while varying amounts of P and K were supplied by the GM. The experiment was carried out for two consecutive cropping seasons, but treatments were applied only during the first season. Yield increased by 10–84% in the combined treatments compared to the control, with the increase being significant in those treatments containing GM from Cordia and Croton, which had higher P and K but lower N and total polyphenol contents than those from Albizia and Milletia. Increasing the proportion of GM from the non-legumes tended to increase yield, but the opposite was true when the proportion of GM from the legumes was increased. This suggests that N interacted negatively with polyphenols, and/or the P and K supply from GM was more important than that of N. However, treatment effects on soil properties were not pronounced. It was concluded that a ȁ8modestȁ9 input of ≤3.0 Mg ha−1 GM from Cordia/Croton might effect a reasonable yield but that the additional use of inorganic fertilisers is necessary for the GM to have a substantially increased effect. In addition, when organic materials having both high N and high total polyphenol contents (e.g. Albizia and Milletia) are used, they should constitute the smaller proportion of the GM/fertiliser mixture.

Extracting timber with heavy machinery on humid tropical soils degrades the soil structure and decreases plant growth. We investigated how disturbance by crawler tractors affected soil chemical and biological properties in a second-generation plantation in Sabah, Malaysia. Total N, total P, and anion resin-extractable P contents were analyzed. N- and P-limited microbial respiration kinetics were bioassayed (by measuring them before and after the addition of glucose + P and glucose + N, respectively), to assess changes in the soil's biological properties. Three months after planting, the soil's organic content were 25% lower on tracks compared to control plots that had not been affected by crawler tractors, while microbial indices of N and P availability were about 50% lower. Two years after planting acid-digestible P, N, and anion resin-extractable P contents were still lower along the tracks, as was one of two indices of microbial P and N availability, respectively. Therefore, the results indicate that soil conservation needs to be improved during the establishment phase to maintain the fertility of forest plantations such as the one studied. If crawler tractors are used, skid-tracks should be designated and their coverage minimized.

In most parts of tropical Africa, conversion of forests into agricultural lands is often accompanied by drastic changes in soil properties. However, little study has been done to examine changes in biological properties of soils from different land-uses in response to addition of C and nutrients. We conducted this study with the aim of investigating nutrient limitations for microbial activity in soils from agricultural (farm) and forest land-uses at Wondo Genet (Ethiopia) after amendment with C and limiting nutrients. We measured CO 2 respiration rates from the soils incubated in the laboratory before and after addition of glucose-C together with N and/or P in excess and/or limiting amounts. Based on the respiration kinetics, we determined the basal respiration (BR), substrate-induced respiration (SIR), specific-microbial growth rate ( μ ), respiration maxima ( R max ), % of glucose-C respired, and microbially available N and P in the soils. We found that N was more limiting than P for the micro-biota in the soils considered, suggesting the presence of ample amounts of indigenous P that could be extracted by the micro-biota, if provided with C. Addition of P resulted in a respiration pattern with two peaks, presumably reflecting different N pools being available over time. The SIR, Respiration maxima, μ and microbially available P were higher in soils from the farm, while %C respired was higher in the forest, suggesting increased C costs for micro-biota to be able to utilize nutrients that are strongly bound to organic-matter or clay minerals. Depending on land-use, about 49–69% of added glucose-C was respired during two and a half weeks time, but differences between N or P additions were not significant. The correlation between soil physical and chemical properties and respiration parameters, however, depended on whether N or P was limiting. We concluded that examining the soil respiration kinetics could provide vital information on nutritional status of micro-organisms under different land-uses and on potential availability of nutrients to plants.

Timber extraction with crawler tractors in humid tropical forests causes degradation of soil physical properties and decreases plant growth. We tested rehabilitation of tracks in a second rotation Acacia mangium plantation in Sabah, Malaysia, by tilling with additions of NPK-fertilizer, ash and organic material to a depth of 15–20 cm. Two years after planting total basal area of A. mangium seedlings was 62% higher outside tracks compared to unimproved tracks, while on NPK-fertilized tracks performance was 700% higher compared to unimproved tracks. Corresponding figures for average height were 40 and 80%. After 8 days with little rain track topsoil experienced water shortage with all studied soil improvements. For ‘non-tracked’ areas wilting-point (−1500 kPa) was not reached during 17 days of dry weather, and more meso-pores were present. Consequently, depending on rainfall after planting the effect of soil rehabilitation on tree performance may be less positive than shown here, because dry periods of 2 weeks length are common in the humid tropics. Bulk density on plots outside tracks in this second-generation plantation was 60% higher than have been reported in similar first-generation plantations. It is discussed that this might be a warning that repeated logging and fire may have a detrimental effect on soil physical properties.

To explore the potential of trees and shrubs on farmlands on traditional systems in southern Ethiopia, mineralization of macronutrients and loss of organics from leaves of Cordia africana and Albizia gummifera were studied under shaded-coffee and agricultural land-uses during the dry season. Leaves in litterbags were incorporated at 15 cm depth in soil under both land uses and residues were recovered after 2, 4, 8, 12 and 16 weeks. Contents of macronutrients and organics in initial and recovered residues were measured. Single- or double-exponential decay or quadratic functions were fitted to describe patterns of decay or release of various leaf constituents. The two species differed significantly (P 0.70). Higher rate of release of CT seems to have facilitated decomposition in Albizia despite higher initial PL and CT in the leaves of this species. There was no significant land-use effect on any of the variables considered. It was concluded that under drier conditions, tree cover might not affect decomposition, and that organic residues with high content of polyphenols, particularly condensed tannins could decompose faster than those with lower content. This suggests that indigenous tree species with high concentrations of tannins, supposedly considered to be of ‘poor quality’, might still be quite useful as an organic input for improving soil fertility and productivity in the tropics.

In 1998 a wild fire struck a paired catchment research area under long-term monitoring of hydrological and nutrient budgets. Streamwater quality as concentrations of dissolved and suspended particulate matter was monitored during 1·5–2·5 years after the fire in streams from seven different catchments. As the catchments, due to earlier experimental treatments, had different vegetations, varying effects related to different fire intensities were observed. The highest, mean stormflow, suspended sediment concentrations resulted from intensive fire in secondary vegetation that had experienced severe soil disturbance in previous treatments (crawler tractor timber extraction 10 years earlier). Stormflow concentrations were typically still about 400 mg l−1 in 1999 (10–21 months after the fire), which was about the maximum recorded concentration in streams during initial soil disturbance in 1988. Forest fire in natural forest resulted in less than half as high stormflow concentrations. For dissolved elements in streamwater there was a positive relation between fuel load (and fire intensity) and concentration and longevity of effects. Stream baseflow dissolved nutrient concentrations were high in the months following the fire. Mean baseflow K concentrations were 8–15 mg l−1 in streams draining catchments with intensive fire in secondary vegetation with large amounts of fuel. After controlled fire for forest plantation establishment in 1988 corresponding concentrations were 3–5 mg l−1, and after forest fire in natural forest in this study about 2 mg l−1. This study shows differences in response from controlled fire for land management, forest fire in natural forests and wild fires in manmade vegetations. These differences relate to resistance and resilience to fire for the involved ecosystems. There is reason to believe that wild fires and repeated wild fires during or after droughts, in successions caused by human influence, may lead to larger losses of ecosystem nutrient capital from sites compared with forest fires in natural forests. As fire in the humid tropics becomes more common, in an increasingly spatially fragmented landscape, it will be important to be aware of these differences. Copyright © 2004 John Wiley & Sons, Ltd.

Changes in soil caused by drought and wildfire in a Dipterocarp rainforest in Sabah, Malaysia were assessed by phosphorus fractionation, extractable nitrogen and nutrient limited respiration kinetics (after addition of glucose+N or P). Fire increased the concentration of total phosphorus (P) in the litter layer (per ha and per dry soil) by raising the 0.2 M NaOH extractable-P. In the soil organic layer, membrane exchangeable P was reduced by fire while 1.0 M HCl extractable-P, and 0.5 M NaHCO 3 extractable-P increased. Microbially available P increased after the fire and was most closely related to NaOH extractable-P that has been considered available to plants only over long time-scales. Total nitrogen (N) increased in the litter layer (per ha and per dry soil) due to post-fire litter fall, while the NO 3 − increased up to 10-fold down to the 10 cm mineral soil. In contrast, the microbially available N decreased by 50%. Basal respiration and substrate-induced respiration increased in the litter layer and decreased in the organic horizon (per dry soil and per organic matter). P limited microbial growth resulted in a slow and non-exponential increase in respiration, presumably reflecting the P-fixing nature of the soils, while N limitation resulted in a fast exponential increase. However, higher respiration rates were eventually achieved under P limitation than under N limitation.

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. 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.

The measurements of water content most often used by soil microbiologists are gravimetric water content (Wg), volumetric water content (Wv), percentage of water holding capacity (%WHC), percentage of water filled porosity (%WFP), and water potential (Wp). This study investigated the relationship of these water measurements to soil respiration, before and after substrate addition (glucose, nitrogen and phosphorus), focusing on the water contents at which the exponential respiration rates after amendments (μ) were at their maximum. Three tropical Haplic Acrisols and one boreal mor layer were used. One Acrisol had high loss of ignition (LOI 17.4% w/w) and high clay content. The second Acrisol had high clay content and low LOI (3.9%), and the third had low clay content and low LOI (5.7%). The mor layer had a LOI of 95.6%. The maximum μ was found at −15 kPa, (50% WHC), irrespectively of the soil type. The decrease in μ above −15 kPa was not as pronounced for the Swedish mor layer as for the Acrisols. At water potentials above −2 kPa the respiration rate was no longer exponential for the Acrisols, making it impossible to define μ. For Wg, WFP, and Wv the maximum differed greatly between the soils. The maximum for basal respiration was found to be at higher water content than the maximum for μ. However, the water contents used were not high enough to specify optimum water content for basal respiration except for the humus rich Acrisol which was at 66% of the WHC or about −5 kPa. It is suggested that respiration measurements of the Acrisols, after substrate addition, should not be made using water contents exceeding −15 kPa or 50% WHC. Because of the dependency of method, WHC must be defined and complemented by water potential. The use of WFP, Wv, and Wg is not recommended for adjusting the water contents of these soils.

We tested the hypothesis that trees have measurable effects on infiltrability, macroporosity, and preferential flows in agrosilvopastoral systems. Managing agricultural systems for water conservation is a critical component of sustainable systems. We investigated the relationship between infiltrability and the distance to the nearest tree, and whether differences in macroporosity can account for differences in infiltrability. In both systems, preferential soil water flows were dominant compared to matrix flow. Trees in the pasture landscape improved infiltrability and preferential flow but had no significant effect in the coffee agroforestry system. After comparing rainfall intensity and frequency data to the measured infiltrability values, we conclude that trees in the pasture system reduce surface runoff at the highest observed rainfall intensities (>50 mm h −1 ). The volcanic soils of the coffee plantation are less degraded and their high natural permeability has been maintained. Since the coffee plants at this site are established (40 years) perennial vegetation with substantial residues and extensive root systems like trees, they improve soil physical properties similarly to trees. Trees increase hydrologic services in pasture lands, a rapidly expanding land use type across Latin America, and therefore may be a viable land management option for mitigating some of the negative environmental impacts associated with land clearing and animal husbandry. However, in land management practices where understorey perennial vegetation makes up a large proportion of the cover, such as for coffee agroforestry systems, the effect of trees on infiltration-related ecosystem services could be less pronounced

Most estimates of P export from natural or disturbed humid tropical ecosystems by streams have been based only on export of dissolved P, even though P often is limiting and can be expected to be strongly associated to particles. Therefore loss of ignition (LOI) and particulate P (Ppart) analyses were made on organic and inorganic detritus resulting from surface erosion and on stream-suspended sediments in an undisturbed rain forest (control), as well as during and after conversion of rain forest into forest plantation. Control forest surface erosion and stream sediments consisted mainly of organics, and dissolved P (Pdiss) dominated over Ppart in stream water. The same relation was found after conversion, with a maximum mean Pdiss/Ppart ratio of up to 10 after burning, compared with 2–2.5 for control forests. This larger difference was assumed to depend on PO4 dissolved from ashes to larger concentrations than could be adsorbed during the short time (

Streamwatcr chemistry was monitored for five years in six streams in a paired catchment experiment in Mendolong, Sabah, Malaysia, including controls in rain forest and secondary vegetation after the [Borneo fire] of 1982–3 and comparing the effects of different ways of establishing forest plantations with Acacia mangium. Three catchments were covered with selectively logged lowland hill dipterocarp forest (W4-W6) and three (W1-W3) with secondary vegetation after forest fires. The control catchments, W3 and W6 reported in this paper, had no treatments applied. Reference monitoring at all streams was for 25 months and the total period of study reported here is 64 months. The soils in the catchments were mainly Orthic Acrisol in W3 and Gleyic Podsol in W6 and a mix of both soil types in the other catchments. Element baseflow concentrations were generally low and not significantly different from stormflow concentrations for all streams during the reference period. Concentrations were also generally consistently low for the two control streams during the whole period of measurement. Chemical inputs as wet deposition were low as a result of a high input from local convection. The rain forest on the Podsol had a tight nutrient circulation indicated by small net losses of macronutrients. The Podsol was found to have poorer conditions for soil mineralization and more surficial runoff, resulting in higher loads of S, C and N in the organic phases, with higher organic C/N ratio, in the discharge. Nitrogen was found to accumulate in both catchments. An almost double accumulation of N in W3 was attributed to a larger biomass accumulation continuing after the forest fire 3–8 years earlier. On the other hand, the Acrisol in W3 had much larger net losses of S, Si, K, Ca, Mg and Na. Most of differences could be attributed to differences in weathering between the soils and local mineralogical differences.

Streamwater chemistry was monitored for five years in six streams in a paired catchment experiment in Mendolong, Sabah, Malaysia, comparing the effects of different ways to establish forest plantations with Acacia mangium. At the start of the monitoring in 1985 three catchments were covered with selectively logged rain forest (W4-W6) and three with secondary vegetation after forest fire (W1-W3). The treatments were: (1) clearing of secondary vegetation, burning and planting (W1 and W2); (2) clear-felling, crawler tractor extraction, burning and planting (W5); and (3) clear-felling, manual extraction, no burning and planting (W4). W3 and W6, with no treatment, were monitored as control catchments. Reference monitoring at all streams was for two years and was followed by treatments which lasted for nine months before the full establishment of a new vegetation cover. This paper covers monitoring for a further 2.5 years. The soil types of the catchments were Orthic Acrisol in W3, Gleyic Podsol in W6 and a mix of both soil types in the other catchments. The effect of treatments on streamwater chemistry was clear at both base- and stormflows. Concentrations of major plant nutrients (N, P and K.) became positively correlated to streamflow during treatments. The response of leaching from slash at clear-felling was fast and larger from the clear-felling residues (W4 and W5) than the cleared secondary vegetation (W1 and W2). The intense response to burning was more marked. The stormflow period mean nutrient concentrations were approximately 10-fold for N and K and 10-100 fold for P after burning compared with baseflow mean concentrations over the same period. Significant differences in baseflow concentrations in treated streams generally lasted one year for most elements, but elevated concentrations were still detectable after three years. The first large pulse of leaching was related to mineralization after tree-felling and particularly burning. The longer lasting elevated concentrations in baseflow were associated with the loss of weathering products. The amounts of nutrients lost, calculated by regression analysis as the effect of treatment compared with control, were found to be higher with the degree of vegetation killed and with increased soil disturbance. Consequently, normal forestry practices, with crawler tractor extraction and burning before planting, created the largest leaching losses. The total calculated effect of losses in total N, P and K were (i) W1 + W2 0.5, 1.8, 83.9; (ii) W4 0.8, 0.8, 105.6; and (iii) W5 1.3, 1.3, 189.4 kg ha−1 for the period of 33 months during and after treatment. With normal forestry practice using crawler tractors and with burning before planting (W5), the treatment-induced loss of K was equivalent to 86% of the content of easily decomposed parts of the biomass (leaves, twigs, fine roots and ground vegetation) of the old forest, or larger than K removed by harvest. Exhaustion effects of lowered leaching after repeated burning (forest fire and pre-planting fire) was observed for several elements, indicating possible nutrient deficiencies.

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.

The rate of infiltration, or infiltrability, is known to change due to soil disturbance. The infiltrability is normally higher in the initial stages of infiltration before wetting of the soil, when pressure gradients predominate over the gravitational forces. This is described by the term ‘sorptivity’ which is the cumulative infiltration as a function of the square root of time, which often is constant during early stages of infiltration. As gravitation starts to dominate, infiltrability decreases to a constant-rate, steady-state infiltrability. Drastic changes in infiltrability may lead to overland flow causing erosion and nutrient leaching. Dry bulk density, steady-state infiltrability and sorptivity were measured in reference forest and after manual and crawler-tractor timber extraction in different watersheds on Orthic Acrisol (40% clay, 40% sand) and Gleyic Podsol (10% clay, 80% sand). Six-year-old tractor tracks after selective logging were also investigated. New tractor tracks covered 24% of the mechanically extracted area, while skid rails covered 4% of the manually extracted area. In the top 10 cm, mean dry bulk density increased after all treatments, but was significant only in the top 5 cm on clay soil after tractor extraction, where it increased from 0.82 to 1.28 g cm−3. Means of steady-state infiltrability and sorptivity were lower on treated areas than in the forest. Differences of mean steady-state infiltrability were significant for all tractor treatments compared with reference forest on both soil types and also with manual extraction on clay soil. On clay soil (and sand) mean stead state infiltrabilities were 154 (48.7), 36.7 (11.6), 0.28 (1.26) and 0.63 (−) mm h−1 in forest, on manual and on new and old tractor tracks respectively.

Physical properties of mineral top soil were investigated on and outside 6 and 13 year old tractor tracks (and outside tractor tracks) on Haplic Acrisol (Ultisol) under selectively logged forest, secondary forest after forest fire and plantation forest. The analysis of possible rehabilitation to pre disturbance soil properties also included earlier published data for new tractor tracks and control forest in the same experimental area. Dry bulk density (DBD), loss on ignition (LOI) and steady state infiltrability (SSI), as well as visual descriptions of vegetation, top soil and erosion, were recorded for 3 positions in slopes as well as for 3 degrees of tractor disturbance to try to resolve the process of top soil rehabilitation.