A sustainable agricultural landscape for Australia: A review of interlacing carbon sequestration, biodiversity and salinity management in agroforestry systems

Transformation of the south-western Australian landscape from deep-rooted woody vegetation systems to shallow-rooted annual cropping systems has resulted in the severe loss of biodiversity and this loss has been exacerbated by rising ground waters that have mobilised stored salts causing extensive dry land salinity. Since the original plant communities were mostly perennial and deep rooted, the model for sustainable agriculture and landscape water management invariably includes deep rooted trees. Commercial forestry is however only economical in higher rainfall (>700 mm yr−1) areas whereas much of the area where biodiversity is threatened has lower rainfall (300–700 mm yr−1). Agroforestry may provide the opportunity to develop new agricultural landscapes that interlace ecosystem services such as carbon mitigation via carbon sequestration and biofuels, biodiversity restoration, watershed management while maintaining food production. Active markets are developing for some of these ecosystem services, however a lack of predictive metrics and the regulatory environment are impeding the adoption of several ecosystem services. Nonetheless, a clear opportunity exists for four major issues – the maintenance of food and fibre production, salinisation, biodiversity decline and climate change mitigation – to be managed at a meaningful scale and a new, sustainable agricultural landscape to be developed.

Growth parameters and nutrient content in four multipurpose tree species with potential characteristics for agroforestry systems in a Cerrado region in Botucatu, São Paulo State, Brazil

In order to evaluate growth characteristics, adaptability, biomass production, nutrient recycling, nutrient distribution and the ability to regenerate degraded land, a trial using four multipurpose tree species (Leucaena leucocephala, Leucaena diversifolia, Acacia melanoxylon and Mimosa scabrella) was undertaken over two years in a distrophic red yellow latosol (oxisol) following a randomized block experimental design with four replications. At the age of two years, A. melanoxylon and L. diversifolia were the tallest species (5.25 and 4.97 m, respectively) and A. melanoxylon and M. scabrella had the largest diameters at 20 cm from tree base. Mimosa scabrella and A. melanoxylon had the highest dry matter production and quantity of nutrients in the above ground biomass. In all species, the highest nutrient contents were found in the leaves, followed by branches and stems. From all species, the highest Nutrient Utilization Efficiency Indexes were obtained for sulphur, phosphorous, and magnesium; L. diversifolia was the most efficient for nitrogen, potassium, calcium, sulphur, and manganese, while A. melanoxylon was the most efficient for phosphorus, magnesium, boron, iron, and zinc. Litter production levels over a three month period were as follows: M. scabrella > A. melanoxylon > L. diversifolia > L. leucocephala. Litter nutrient content was higher in M. scabrella than in the other species.

Agroforestry in the Amazon Basin: practice, theory and limits of a promising land use

Includes bibliography

AGROFORESTRY ADDRESSING SOCIAL AND ENVIRONMENTAL ISSUES IN PARAGUAY

Paraguay is characterized in part by an economy reliant on a massive soy industry and as facing social and economic challenges resulting from highly inequitable distribution of wealth and land ownership, particularly for smallholder farmers in the rural areas of the country. Yerba mate (Ilex paraguariensis), a native tree of which the leaves are used in tea, has become an increasingly common crop grown among common among smallholder farmers (owners of 10 hectares or less) as a viable alternative to soy production on a small scale. In the rural agricultural community of Libertad del Sur, located in the heart of the severely deforested Bosque Atlántico del Alto-Paraná, a series of development initiatives including tree nurseries and agroforestry projects with yerba mate were implemented with involvement of several governmental and nongovernmental organizations. Research was conducted to identify effectiveness of an agroforestry strategy to promote reforestation activities and sustainable agriculture to achieve economic and subsistence goals of the rural population. Despite a severe drought impacting initial research goals, important lessons are considered regarding promotion of development work within the community as well as community perceptions towards development agencies. Pursuit of compromise between community member and agency goals using sustainable agricultural practices is identified as an effective means to promote mutually beneficial development strategies.

UNDERSTANDING FARMERS’ PERCEPTIONS AND THE EFFECTS OF SHEA TREE Vitellaria paradoxa DISTRIBUTION IN AGROFORESTRY PARKLANDS OF THE UPPER WEST REGION, GHANA

Agroforestry parklands represent a vast majority of the agricultural landscape under subsistent-oriented farming in semi-arid West Africa. Parklands are characterized by the growth of well- maintained trees (e.g., shea) on cultivated fields as a result of both environmental and human influences. Shea (Vitellaria paradoxa) provides a cultural and economic benefit to the local people of Ghana, especially women. Periods between traditional fallow rotation systems have reduced recently due to agricultural development and a demand for higher production. As a result, shea trees, which regenerate during fallow periods, has decreased over the landscape. The aim of this study was to determine beneficial spatial distributions of V. paradoxa to maintain high yields of staple crops, and how management of V. paradoxa will differ between male and female farmers as a result of farmer based needs and use of shea. Vegetation growth and grain yield of maize (Zea mays) associated with individual trees, clumped trees, and open fields were measured. Soil moisture and light availability were also measured to determine how V. paradoxa affected resource availability of maize in either clumped or scattered distributions of V. paradoxa. As expected, light availability increased as measurement locations moved farther away from all trees. However, soil moisture was actually greater under trees in clumps than under individual trees. Maize stalk height and cob length showed no difference between clumped and single trees at each measurement location. Grain yield per plot and per cob increased as measurement locations moved farther from single trees, but was actually greater near clumped trees that in the open field subplots. Cob length and maize stalk height increased with greater light availability, but grain yield per cob or per plot showed no relationship with light, but were not affected by soil moisture. Conversely, grain yield increased with increasing soil moisture, but had no relationship with light availability. Initial farming capital is the largest constraint to female farmers; therefore the collection of shea can help provide women with added income that could meet their specific farming needs. Our data indicate that overall effects of maintaining clumped distributions of V. paradoxa provided beneficial microclimates for staple crops when compared to single trees. It is recommended that male and female farmers allow shea to grow in clumped spatial distributions rather than maintaining scattered, individual trees.

Knowledge and valuation of Andean agroforestry species: the role of sex, age, and migration among members of a rural community in Bolivia

Background Agroforestry is a sustainable land use method with a long tradition in the Bolivian Andes. A better understanding of people’s knowledge and valuation of woody species can help to adjust actor-oriented agroforestry systems. In this case study, carried out in a peasant community of the Bolivian Andes, we aimed at calculating the cultural importance of selected agroforestry species, and at analysing the intracultural variation in the cultural importance and knowledge of plants according to peasants’ sex, age, and migration. Methods Data collection was based on semi-structured interviews and freelisting exercises. Two ethnobotanical indices (Composite Salience, Cultural Importance) were used for calculating the cultural importance of plants. Intracultural variation in the cultural importance and knowledge of plants was detected by using linear and generalised linear (mixed) models. Results and discussion The culturally most important woody species were mainly trees and exotic species (e.g. Schinus molle, Prosopis laevigata, Eucalyptus globulus). We found that knowledge and valuation of plants increased with age but that they were lower for migrants; sex, by contrast, played a minor role. The age effects possibly result from decreasing ecological apparency of valuable native species, and their substitution by exotic marketable trees, loss of traditional plant uses or the use of other materials (e.g. plastic) instead of wood. Decreasing dedication to traditional farming may have led to successive abandonment of traditional tool uses, and the overall transformation of woody plant use is possibly related to diminishing medicinal knowledge. Conclusions Age and migration affect how people value woody species and what they know about their uses. For this reason, we recommend paying particular attention to the potential of native species, which could open promising perspectives especially for the young migrating peasant generation and draw their interest in agroforestry. These native species should be ecologically sound and selected on their potential to provide subsistence and promising commercial uses. In addition to offering socio-economic and environmental services, agroforestry initiatives using native trees and shrubs can play a crucial role in recovering elements of the lost ancient landscape that still forms part of local people’s collective identity.

Avian species identity and predation success in tropical cacao agroforestry of the Napu Valley in Central Sulawesi, Indonesia

Avian ecosystem services such as the suppression of pests are considered being of high ecological and economic importance in a range of ecosystems, especially in tropical agroforestry. But how bird predation success is related to the diversity and composition of the bird community, as well as local and landscape factors, is poorly understood. The author quantified arthropod predation in relation to the identity and diversity of insectivorous birds, using experimental exposure of artificial, caterpillar-like prey on smallholder cacao agroforestry systems, differing in local shade management and distance to primary forest. The bird community was assessed using both mist netting (targeting on active understory insectivores) and point count (higher completeness of species inventories) sampling. The study was conducted in a land use dominated area in Central Sulawesi, Indonesia, adjacent to the Lore Lindu National Park. We selected 15 smallholder cacao plantations as sites for bird and bat exclosure experiments in March 2010. Until July 2011, we recorded several data in this study area, including the bird community data, cacao tree data and bird predation experiments that are presented here. We found that avian predation success can be driven by single and abundant insectivorous species, rather than by overall bird species richness. Forest proximity was important for enhancing the density of this key species, but did also promote bird species richness. The availability of local shade trees had no effects on the local bird community or avian predation success. Our findings are both of economical as well as ecological interest because the conservation of nearby forest remnants will likely benefit human needs and biodiversity conservation alike.

Bird observation and sampling in tropical agroforestry landscapes of the Napu Valley in Central Sulawesi, Indonesia

We investigated the local bird community in Central Sulawesi (Indonesia), with focus on insectivorous species in the agroforestry landscapes adjacent to the Lore Lindu National Park. All study sites were situated at the northern tip of Napu Valley in Central Sulawesi, Indonesia. After an initial mapping of the study area, we selected 15 smallholder cacao plantations as sites for our study in March 2010. These sides were mainly used for bird and bat exclosure experiments. All sited were situated along a local gradient (shade availability on each plantation) and a landscape gradient (distance to primary forest), which were independent from each other. In September 2010 and from February until June 2011, we assessed the bird community on our 15 study sites using monthly point count and mist netting sampling. Point count (20 minutes between 07 am and 10 am and in between the net checking hours) and mist netting surveys (12 hours, between 05:30 am and 17:30 pm) were conducted simultaneously but only once per month on each study site, to avoid habituation of the local bird community to our surveys. Further, point counts were conducted at least 100 m apart from the mist netting sites, to avoid potential disturbance between the two methods. We discarded all observations beyond 50 m (including those individuals that flew over the canopy) from the statistical analysis, as well as recaptures of individuals within identical mist netting rounds.

Flujos de gases de efecto invernadero en suelos forestales y agroforestales del centro de la Península Ibérica=Greenhouse gas flows in forest and agroforestry soils in the center of the Iberian Peninsula

Debido a la complejidad de los procesos que controlan el intercambio de gases de carbono (C) y nitrógeno (N) entre el suelo y la atmósfera, en los sistemas forestales y agroforestales, son comprensibles las incógnitas existentes respecto a la estimación de los flujos de los gases de efecto invernadero (GEI) y la capacidad como reservorios de carbono de los suelos, bajo diferentes formas de uso y regímenes de alteración a escala regional y global. Esta escasez de información justifica la necesidad de caracterizar la dinámica de intercambio de GEI en los ecosistemas Mediterráneos, en especial en el contexto actual de cambio climático, y el incremento asociado de temperatura y periodos de sequía, alteración de los patrones de precipitación, y el riesgo de incendios forestales; cuyas consecuencias afectarán tanto a los compartimentos de C y de N del suelo como a la capacidad de secuestro de C de estos ecosistemas. Dentro de este contexto se enmarca la presente tesis doctoral cuyo objetivo ha sido cuantificar y caracterizar los flujos de dióxido de carbono (CO2), de oxido nitroso (N2O) y de metano (CH4), junto con los stocks de C y N, en suelos forestales de Quercus ilex, Quercus pyrenaica y Pinus sylvestris afectados por incendios forestales; así como el estudiar el efecto de la gestión y la cubierta arbórea en la respiración del suelo y los stocks de C y N en una dehesa situada en el centro de la Península Ibérica. De manera que los flujos de CO2, N2O y CH4; y los parámetros físico-químicos y biológicos del suelo fueron estudiados en los diferentes tratamientos y ecosistemas a lo largo del trabajo que se presenta. Los resultados obtenidos muestran la existencia de variaciones temporales y espaciales de la respiración del suelo dentro de una escala geográfica pequeña, controladas principalmente por la temperatura y la humedad del suelo; y por los contenidos de C y N del suelo en un bosque de Pinus sylvestris en la vertiente norte de la Sierra de Guadarrama , en España. El análisis de los efectos de los incendios forestales a largo plazo (6-8 años) revela que las pérdidas anuales de C a través de la respiración del suelo en las zonas quemadas de Quercus ilex, Quercus pyrenaica y Pinus sylvestris fueron 450 gCm-2yr-1, 790 gCm-2yr-1 y 1220 gCm-2yr-1, respectivamente; lo que representa una reducción del 43%, 22% y 11% en comparación con las zonas no quemadas de dichas especies, debido a la destrucción de la masa arbórea. El efecto del fuego también alteró los flujos N2O y CH4 del suelo, de una forma diferente en los distintos ecosistemas y estacionalidades estudiadas. De tal modo, que los suelos quemados mostraron una mayor oxidación del CH4 en las masas de Q. ilex, y una menor oxidación en las de P. sylvestris; además de una disminución de los flujos de N2O en Q. pyrenaica. Los incendios también afectaron los parámetros microclimáticos de los suelos forestales, observándose un incremento de la temperatura del suelo y una disminución de la humedad en los emplazamientos quemados que en los no quemados. Los cationes intercambiables, el pH, el cociente C/N, el contenido en raicillas y la biomasa microbiana también disminuyeron en las zonas quemadas. Aunque el C orgánico del suelo no se alteró de manera significativa, si lo hizo la calidad de la materia orgánica, disminuyendo el carbono lábil y aumentando las formas recalcitrantes lo que se tradujo en menor sensibilidad de la respiración del suelo a la temperatura (valores de Q10) en las zonas quemadas. Los resultados del estudio realizado en la Dehesa muestran que las actividades silvopastorales estudiadas afectaron levemente y de forma no constante a la respiración del suelo y las condiciones microclimáticas del suelo. Se observó una reducción 12% de la respiración del suelo por efecto del pastoreo no intensivo. Sin embargo, se observaron incrementos de 3Mg/ha en los stocks de C y de 0.3 Mg/ha en los stocks de N en los suelos pastoreados en comparación con los no pastoreados. Aunque, no se observó un claro efecto de la labranza sobre la respiración del suelo en nuestro experimento, sin embargo si se observó una disminución de 3.5 Mg/ha en las reservas de C y de 0.3 Mg/ ha en las de N en los suelos labrados comparados con los no labrados. La copa del arbolado influyó de forma positiva tanto en la respiración del suelo, como en los stocks de C y N de los suelos. La humedad del suelo jugó un papel relevante en la sensibilidad de la respiración a la temperatura del suelo. Nuestros resultados ponen de manifiesto la sensibilidad de la respiración del suelo a cambios en la humedad y los parámetros edáficos, y sugieren que la aplicación de modelos estándar para estimar la respiración del suelo en áreas geográficas pequeñas puede no ser adecuada a menos que otros factores sean considerados en combinación con la temperatura del suelo. Además, las diferentes respuestas de los flujos de gases de efecto invernadero a los cambios, años después de la ocurrencia de incendios forestales, destaca la necesidad de incluir estos cambios en las futuras investigaciones de la dinámica del carbono en los ecosistemas mediterráneos. Por otra parte, las respuestas divergentes en los valores de respiración del suelo y en los contenidos de C y N del suelo observados en la dehesa, además de la contribución de la copa de los árboles en los nutrientes del suelo ilustran la importancia de mantener la gestión tradicional aplicada en beneficio de la capacidad de almacenar C en la dehesa estudiada. La información obtenida en este trabajo pretende contribuir a la mejora del conocimiento de la dinámica y el balance de C en los sistemas mediterráneos, además de ayudar a predecir el impacto del cambio climático en el intercambio de C entre los ecosistemas forestales y agroforestales y la atmósfera. ABSTRACT Due to the complexity of the processes that control the exchange of carbon (C) and nitrogen (N) gasses between soils and the atmosphere in forest and agroforestry ecosystems, understandable uncertainties exist as regards the estimation of greenhouse gas (GHG) fluxes and the soil sink capacity at regional and global scale under different forms of land use and disturbance regimes. These uncertainties justify the need to characterize the exchange dynamics of GHG between the atmosphere and soils in Mediterranean terrestrial ecosystems, particularly in the current context of climate change and the associated increase in temperature, drought periods, heavy rainfall events, and increased risk of wildfires, which affect not only the C and N pools but also the soil C sink capacity of these ecosystems. Within this context, the aims of the present thesis were, firstly, to quantify and characterize the fluxes of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) as well as the C and N stocks in Quercus ilex, Quercus pyrenaica and Pinus sylvestris stands affected by wildfires, and secondly, to study the effects of Quercus ilex canopy and management on both soil respiration and C and N pools in dehesa systems in the center of Iberian Peninsula. Soil CO2, N2O and CH4 fluxes, and soil physical-chemical and biological parameters were studied under the different treatments and ecosystems considered in this study. The results showed seasonal and spatial variations in soil respiration within small geographic areas, mainly controlled by soil temperature and moisture in addition to soil carbon and nitrogen stocks in mixed pine–oak forest ecosystems on the north facing slopes of the Sierra de Guadarrama in Spain. The analysis of long term effects of wildfires (6–8 years) revealed that annual carbon losses through soil respiration from burned sites in Quercus ilex, Quercus pyrenaica and Pinus sylvestris stands were 450 gCm-2yr-1, 790 gCm-2yr-1 and 1220 gCm-2yr-1, respectively; with burned sites emitting 43%, 22% and 11% less in burned as opposed to non-burned sites due the loss of trees. Fire may alter both N2O and CH4 fluxes although the magnitude of such variation depends on the site, soil characteristics and seasonal climatic conditions. The burned sites showed higher CH4 oxidation in Q.ilex stands, and lower oxidation rates in P. sylvestris stands. A reduction in N2O fluxes in Q. pyrenaica stands was detected at burned sites along with changes in soil microclimate; higher soil temperature and lower soil moisture content. Exchangeable cations, the C/N ratio, pH, fine root and microbial biomass were also found to decrease at burned sites. Although the soil organic carbon was not significantly altered, the quality of the organic matter changed, displaying a decrease in labile carbon and a relative increase in refractory forms, leading to lower sensitivity of soil respiration to temperature (Q10 values) at burned sites. The results from the dehesa study show that light grazing and superficial tilling practices used in the studied dehesa system in Spain had a slight but non-consistent impact on soil respiration and soil microclimate over the study period. The reduction in soil respiration in the dehesa system due to the effects of grazing was around 12 %. However, increments of 3Mg/ha in C stocks and 0.3 Mg/ha in N stocks in grazed soils were observed. Although no clear effect of tilling on soil respiration was found, a decrease of 3.5 Mg/ha in C stocks and 0.3 Mg/ha in N stocks was detected for tilled soils. The presence of a tree canopy induced increases in soil respiration, soil C and N stocks, while soil moisture was found to play an important role in soil respiration temperature response. Our results suggest that the use of standard models to estimate soil respiration in small geographical areas may not be adequate unless other factors are considered in addition to soil temperature. Furthermore, the different responses of GHG flux to climatic shifts, many years after the occurrence of wildfire, highlight the need to include these shifts in C dynamics in future research undertaken in Mediterranean ecosystems. Furthermore, divergent responses in soil respiration and soil C and N stocks to grazing or tilling practices in Dehesa systems, and the influence of tree canopy on soil respiration and soil nutrient content, illustrate the importance of maintaining beneficial management practices. Moreover, the carbon sequestration capacity of the Dehesa system studied may be enhanced through improvements in the management applied. It is hoped that the information obtained through this research will contribute towards improving our understanding of the dynamics and balance of C in Mediterranean systems, and help predict the impact of climate change on the exchange of C between forest and agroforestry ecosystems and the atmosphere.

Tree and grazing influence on herbaceous pasture diversity in the Dehesa agroforestry system

Mediterranean Dehesas are one of the European natural habitat types of Community interest (43/92/EEC Directive), associated to high diversity levels and producer of important goods and services. In this work, tree contribution and grazing influence over pasture alpha diversity in a Dehesa in Central Spain was studied. We analyzed Richness and Shannon-Wiener (SW) indexes on herbaceous layer under 16 holms oak trees (64 sampling units distributed in two directions and in two distances to the trunk) distributed in four different grazing management zones (depending on species and stocking rate). Floristic composition by species or morphospecies and species abundance were analyzed for each sample unit. Linear mixed models (LMM) and generalized linear mixed models (GLMMs) were used to study relationships between alpha diversity measures and independent factors. Edge crown influence showed the highest values of Richness and SW index. No significant differences were found between orientations under tree crown influence. Grazing management had a significant effect over Richness and SW measures, specially the grazing species (cattle or sheep). We preliminary quantify and analyze the interaction of tree stratum and grazing management over herbaceous diversity in a year of extreme climatic conditions.

Modeling and Mapping Agroforestry Aboveground Biomass in the Brazilian Amazon Using Airborne Lidar Data.

Agroforestry has large potential for carbon (C) sequestration while providing many economical, social, and ecological benefits via its diversified products. Airborne lidar is considered as the most accurate technology for mapping aboveground biomass (AGB) over landscape levels. However, little research in the past has been done to study AGB of agroforestry systems using airborne lidar data. Focusing on an agroforestry system in the Brazilian Amazon, this study first predicted plot-level AGB using fixed-effects regression models that assumed the regression coefficients to be constants. The model prediction errors were then analyzed from the perspectives of tree DBH (diameter at breast height)?height relationships and plot-level wood density, which suggested the need for stratifying agroforestry fields to improve plot-level AGB modeling. We separated teak plantations from other agroforestry types and predicted AGB using mixed-effects models that can incorporate the variation of AGB-height relationship across agroforestry types. We found that, at the plot scale, mixed-effects models led to better model prediction performance (based on leave-one-out cross-validation) than the fixed-effects models, with the coefficient of determination (R2) increasing from 0.38 to 0.64. At the landscape level, the difference between AGB densities from the two types of models was ~10% on average and up to ~30% at the pixel level. This study suggested the importance of stratification based on tree AGB allometry and the utility of mixed-effects models in modeling and mapping AGB of agroforestry systems.