Browsing by Subject "Agroforestry"

Agroforestry, a widespread land-use in tropics and especially in tropical drylands, is gaining increasing attention due its carbon sequestration and storage potential. Majority of African countries acknowledge agroforestry as a national climate change mitigation and adaptation strategy. Despite the large extent of African drylands and the commonness and importance of agroforestry systems to dryland livelihoods, these systems are scarcely studied and research on dryland African agroforestry carbon stocks are few. The aim of the study was to compare carbon stocks of three land-uses: Vitellaria paradoxa dominated parkland (PL), improved agroforestry system (IA) and, as a control, abandoned land (AL), to study carbon allocation between and within the land-uses and to examine the variability of biomass estimates of different allometric equations used in carbon inventory in West African Sahel. Study was conducted in two villages in Yorosso, Southern Mali. Carbon stocks accounted were woody above- and belowground biomass, litter and top-soil organic carbon. Allometric equations and root-to-shoot ratios were used for woody biomass measurement. Comparison of biomass estimations of different allometric equations and root-to-shoot-ratios was conducted by using multiple equations for the dataset. Total system carbon stocks were 24.7 MgC haˉ¹, 29.9 MgC haˉ¹ and 42.2 MgC haˉ¹, for PL, AL and IA, respectively, with statistically significant difference between PL and IA. Top-soil organic carbon (SOC) was important carbon pool, accounting 34.8 % of total system carbon in PL and IA, and 49.6 % in AL. There were no statistically significant differences on the SOC/biomass C ratios between the land-uses. PL had lower SOC stocks than IA or AL, difference being statistically significant. The reason for lower SOC stock of PL could not be explained in this study. IA had larger woody biomass carbon stocks (27.0 MgC haˉ¹) than PL (15.5 MgC haˉ¹ ) and AL (14.4 MgC haˉ¹), but the difference was not statistically significant due to the similar density of large mature trees in all of the land-uses and partly due to the large woody biomass variation within the land-uses. In all of the land-uses, most of biomass carbon was stored in large mature trees and in two species: V. paradoxa and Parkia biglobosa. Large woody individuals had major impact on the land-use level carbon stocks. For carbon conservation, these individuals should be preserved and spared even during land-use change. Despite relatively large density, young trees and shrubs stored diminutive amount of carbon compared to mature trees. As the currently young planted trees in IA will grow and mature in the future, the woody biomass carbon stocks of the system will increase significantly. Lack of regeneration observed in PL threatens the sustainability of the system and its carbon stocks. Future carbon storage potential of AL depends on the regeneration potential of large tree species. Comparison of different allometric equations for tree biomass estimation revealed substantial variation. The choice of allometric equation used affects the obtained results, hampering the comparison of studies using different equations. Commonly used root-to-shoot ratios vary on their estimations, and most probably by underestimating root biomass. There is a clear need for specialised and standard carbon inventory methods for drylands and agroforestry systems.

Agroforestry is a collective name for agricultural land-use practices where combinations of woody perennials such as trees and shrubs are intentionally managed with crops and/or livestock in same land units for various environmental and economic benefits. As a sustainable farming practice, agroforestry is used to increase food production without adding harmful impacts of agriculture on natural environment. Agroforestry is a common farming practice in Taita Hills, Kenya, where it is motivated by Kenyan policies supporting tree planting in the fields. This study aims to find out how canopy height and canopy cover have changed during the last ten years in the croplands of Taita Hills to get more knowledge on the state and trends of agroforestry in the study area. Changes in canopy height and canopy cover in croplands are approached by multitemporal airborne laser scanning (ALS) data. ALS is an active remote sensing method used to acquire three-dimensional point cloud data of a target landscape. Canopy height models (CHM), 99th percentile canopy height and canopy cover data were derived from two ALS data sets from 2014/2015 and 2022 and used for the change detection of canopy height and canopy cover during the study period. Field data from 2013 and 2022 containing tree measurements from 28 field plots were used in the validation of ALS-based analyses. The results indicate that there has been a slight increase in canopy height and canopy cover during the study period. It is acknowledged that the study period is quite short to detect changes in tree growth. Hence, only slight positive changes in canopy height and canopy cover were expected. Based on CHM changes, almost 20% of the area outside forests had ≥ 2 m increase in the canopy height. Furthermore, 7% of the area outside forests had ≤ -5 m decrease in the canopy height, which corresponds to tree loss. Results for CHM based canopy height were supported by 99th percentile canopy height changes. The area outside forest with ≥ 10% canopy cover increased from 67.4% to 68.0%. Even though canopy height and canopy cover had a slight increase in the croplands, forest cover was detected to be increasing during the study period. ALS and field measurements matched well with each other. In the tree height measurements, there were more variance with taller trees, probably caused by difficulties in measuring taller trees in the field. Moreover, ALS data was found to underestimate tree height changes. The average absolute deviation for tree height changes was 1.3 m shorter for ALS-measured tree heights than field measurements. Number of trees in field plots has mainly decreased during 20132022. ALS-based mean canopy height and canopy cover changes in the plots explain the actual changes well if large number of trees have been cut down during the study period. The thesis provides valuable information on the state and trends of agroforestry in Taita Hills. However, more exact land cover classification could have enhanced the accuracy of the results even more. All in all, the results were mainly positive, indicating that there has been an increasing trend in canopy height and canopy cover in the croplands in Taita Hills.

Agriculture is emitting ~6.2 Gt CO2-Eq. annually, which accounts for ~12 % of the total annual net anthropogenic greenhouse gas (GHG) emissions globally. Agriculture emits N2O and CH4, and it is responsible globally for ~79% of N2O emissions and ~40% CH4 emissions. These emissions are vital since N2O and CH4 are 273- and 27-times greater GHG than CO2, respectively. There are many different food production systems developed to reduce these emissions. One of the most promising systems is agroforestry. Agroforestry is a complex system where trees and/or shrubs are interacting with crops and/or animals. Agroforestry is an old practice which can provide plenty of advantages, e.g., increased yields, increased biodiversity, and increased carbon sequestration. Therefore, the interest towards it has been increasing in the last decades. In this master’s thesis the different maize production systems in Zambia were studied. The comparison was conducted between low-input maize monoculture where only external input was maize seed for sowing; high-input maize monoculture where mineral fertilizers and seeds for sowing were used; and maize-Faidherbia albida agroforestry system where only external input was maize seed for sowing. The goal of this master’s thesis was to find out, which production system is having the lowest climate change potential in the Central Province of Zambia. To conduct this study, Life Cycle Assessment (LCA) -method was used. Two cases were used in LCA, i.e., Case 1 with functional unit (FU) of 1000 kg d.m. maize grain, and Case 2 with FU of 3 ha maize field. Also, four sensitivity analyses were conducted. The result from this study indicates that agroforestry system had the lowest climate change potential in both cases, and in most of the sensitivity analyses. Only exception was found in the sensitivity analysis where above-ground biomass of F. albida was substituting hydropower. In this sensitivity analysis the monoculture without external inputs had the lowest climate change potential. Since the food production in Zambia must increase in the future to reduce the hunger, the high-input system or agroforestry system are more favourable options as they produce higher crop yields. When taking the climate change potential into account, according to the results of this thesis, the agroforestry system provides more benefits. The results of this thesis can provide new knowledge which could be used in the future decision-making processes. Yet, in the future studies, more complex agroforestry systems with more sustainability pillars should be considered to provide improved information for decision-making.