Epsilon Archive for Student Projects

Abstract

Agroforestry is an old agricultural practice which has got renewed interest during the last decades as an alternative to industrialized agriculture. Agroforestry is a practice with potential to promote several ecosystem services, e.g. carbon seques-tration and soil improvement. This study looks into how carbon sequestration and soil fertility can be measured in one of the most diverse agroforestry systems; forest gardens. Five forest gardens located in southern Sweden were included in the study; Tystinge (T), Rikkenstorp (R), Hånsta Östergärde (H.Ö.), Holma skogsträdgård (H.o.) and Klockaregården (K), representing different soils, climates and manage-ments. Standing biomass was estimated for herbs, trees and shrubs. Herbal vegeta-tion was harvested and brought back to the lab, while trees and shrubs were meas-ured in the field and biomass was calculated by using allometric equations. Soil samples were collected to estimate root biomass, respiration, carbon content and C/N ratio. A soil profile description was performed, and a method to estimate my-chorrizal colonization was also tried out. It was shown that the biomass production and carbon in standing biomass varies depending on site and management. Previ-ous land use will determine whether the establishment of a forest garden will im-prove or impair biomass production. Herbal biomass was twice as high at T com-pared to H.Ö. Biomass of trees and shrubs varied as well, with the highest woody biomass being more than twice as high as the lowest, found at H.o. and K respec-tively. After the forest gardens had been established root biomass decreased with 60% at R, while it increased with 50% at H.Ö. At all sites soil respiration was lower in the forest garden than at reference spots outside the garden. The forest gardens seemed to favor earthworm activity, while no changes in carbon content or C/N ratio were seen. C/N ratios were strongly connected to the respective sites. For prop-er estimations of above- and belowground biomass of trees and shrubs more spe-cific allometric equations needs to be developed, suiting the species of relevance and the climatic conditions. A similar method would also provide the best estima-tion of herbal biomass. Carbon content in soils changes slowly and to see whether the forest gardens have had a long-term impact on carbon content new measure-ments needs to be made in the future. Respiration should be measured several times a year for reliable modeling of carbon sequestration to be possible. Data on degradation rates of different plant components are also needed for proper models on carbon flows to be developed. Better understanding of the components of forest gardens, and their interactions, would help in finding the potentials of forest gar-dens in Sweden.