Browsing by Subject "forest"

Climate change and the degradation of soils are global and increasingly prevalent issue. Pyrolyzed organic materials, biochars, are progressively studied as a promising tool to sequester carbon in soils, whilst also improving soil properties. It is important to understand how different biochars affect other integral features of the soil ecosystem, such as soil biota, before they are utilized. Biochars are currently mostly utilized in agricultural settings; in order to extend their use for carbon sequestration in forest soils, more research regarding different biochars in forest settings is necessary. This Master’s thesis was conducted as literature review and meta-analysis of existing forest field studies in which the effect of biochars on soil biota was measured. Two sources (the University of Helsinki digital library collection (Helka), and internet search engine Google Scholar were used. From the studies gathered, soil respiration and microbial biomass carbon (MBC) were used as variables to estimate the effect of biochars on soil biota. Due to the scarcity of existing research, experimental conditions included in this thesis are diverse, including plantations, three climatic regions (boreal, temperate and subtropic) and different biochar types. Subgroups were formed from received data according to different treatments and standard mean differences (SMD) were compared. Contrary to the hypothesis, within this meta-analysis, soils amended with biochars demonstrated either no change or decreased soil respiration and MBC. On average, soil respiration did not show any significant change to biochar amendment, whilst MBC decreased significantly in some subgroups: short-term studies (<= 12 months), small difference in pH between soil and biochar (< 4), low pyrolysis temperature of biochar (<= 450 ˚C) and small quantity of biochar applied (< 10 t/ha). The decreasing in MBC was not consistent and diminished with increasing quantity of biochar and in study periods over 12 months. Given that biochars do not seem to have clear effects on microbial forest soil biota or microbial respiration, the application of biochars to forest soils has its potentials. However, larger scale use should be considered with caution, and further research is necessary.

In the carbon cycle carbon is sequestrated from the atmosphere through photosynthesis in vegetation, returned into soils as litter and released into atmosphere in decomposition as carbon dioxide. In the boreal zone a large proportion of the organic carbon is bound into soil. The aim of this study was to find out how the amount of soil organic carbon (SOC) has changed in Finnish forests in last 20 years by comparing results of empirical measurements from two projects (1986-1995 and 2006). The purpose of the study was also to analyze how well the field measurements of SOC collected in two consecutive periods of time are suitable for characterization of changes in the SOC stock. The effect of soil structure, vegetation type and climatic factors on possible SOC changes were also studied. The average size of SOC stock (organic layer + mineral layer 0-40cm) in Finnish forests is 5.65 kg C m-2. About one third of SOC is in the organic layer (2.10 kg C m-2) and the rest of it is in the mineral soil (3.56 kg C m-2 ). Higher amount of SOC stock in the organic layer has been determined on plots with thicker organic layer, poor drainage and the presence of peat mosses. Higher amount of SOC in the mineral layer has been measured on plots which have a more southerly location, lower stoniness and high proportion of fine textures. Coefficients of determination in General Linear Models were between 23-61%. The average annual change of SOC (organic layer + mineral layer 0-40 cm) is +33.9 g C m-2a-1. Change in the organic layer has been +11.4 g C m-2a-1 and in the mineral soil +22.5 g C m-2a-1. The accumulation of organic carbon into the organic layer is positively correlated with the thickness of the organic layer, the southern location, pine dominance in tree layer and the age of the trees, while in the mineral soil higher carbon accumulation occurs in less stony soils and in more southern locations. Coefficients of determination in General Linear Models describing the change in SOC were low, between 11-14%. The largest positive or negative changes in SOC are in plots where the depth of the organic layer measured in two successive measurements was very different. Also, the differences in the measurements of SOC were large if the plots were drained, divided to two different sections or plots were excessively moist. Climate change and higher temperature will probably affect soil carbon sequestration positively, forecasted by using the results of the south-north gradient in which more carbon was accumulated into the soils of southern Finland. Soil monitoring research should be developed by using precise sampling methods and establishing permanent instructions for field work in order to avoid additional sources of error and to minimize variation.

Land-use change stands behind the current biodiversity crisis and all it entails in terms of ecosystem services. Guinea-Bissau, in West Africa, is originally characterized by a forest- savanna mosaic biome. However, while savannas have long been planted with rice, both rice paddies and forest remnants are now being converted into cashew monocultures – the only cash crop in the country – at unprecedented rates. The ecological impact of such rapid change is largely unknown. To help fill this gap, we examined how three diversity metrics – rarefied species richness, abundance and composition – varied across forest remnants, cashew orchards and rice paddies for amphibians and reptiles in northern Guinea-Bissau. To do so, visual encounter surveys were carried across 21 sampling sites, seven of each habitat type. A total of 703 amphibian and 266 reptile encounters was recorded from nine and 14 taxa, respectively. The results show class-specific responses to habitat type. Amphibians’ diversity in forest remnants and cashew orchards was similar across all metrics, but rice paddies had a higher abundance and unique composition compared to forest remnants. Reptiles’ abundance was highest in cashew orchards and this habitat had a distinct composition, when compared to forest remnants. Rice paddies sustained both lower reptile richness and abundance. Overall, our results are not in agreement with the expected detrimental impacts of cashew expansion, which might be due to the still high heterogeneity of habitat types within the landscape. Rice paddies proved particularly important for amphibians, and for open-habitat reptiles, boosting overall species diversity. In face of the eminent habitat conversion, maintaining heterogeneous landscapes, including the persistence of both forest remnants and rice paddies, will allow minimizing biodiversity loss in West Africa.

The European Commission and the Finnish government have released their respective roadmaps in sustainable forest policy. With the European Commission pushing for further cooperation and integration in a field with no dedicated framework, it becomes vital to have a consensus on the concept of “sustainable forestry” with Member States such as Finland. Finland, on the other hand, as the most forested Member State in terms of percentage of total land area, manifests opposite views regarding how the administration is supposed to effect policy. This thesis consists of an analysis of respective documents from the European Commission and the Finnish government: the New EU Forest Strategy for 2030 and the Government Report on Forest Policy 2050. Similar in scope and structure, they clearly reflect these different attitudes towards policymaking and the role of policymakers themselves in the coming decades. The focus of this analysis is, however, their respective use of metaphors. With the theoretical support of the Advocacy Coalition Framework of Hank Jenkins-Smith and Paul Sabatier and the Critical Metaphor Analysis of Jonathan Charteris-Black, these metaphor choices are then observed to explain which stakeholders—either forestry, administrative, or environmental—are favored in each document. In this thesis, metaphors are words whose basic meaning, which is usually the one easiest to imagine, is not the one used in their textual context. From associating that missing, metaphorical meaning to chosen key concepts, this analysis shows that the metaphors found are used in cohesion with each other. This reveals a re-conceptualization of those key terms according to the accompanying metaphors. For example, the European Commission presented forests in its Strategy as “towns”, while the Finnish government saw them as “(ore) mines”. The results of this thesis reveal the consistency of metaphor choices in discourse and their significance in depicting a potentially different set of narratives from those contained in conventional language, both overtly and covertly. With these results in mind, scholars can further pursue research in other fields thanks understanding of metaphor and its prevalence in communication, or even expand this line of research into the role of media, for example.