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Within the field of ecosystem science, substantial progress has been made towards our knowledge of the factors which shape the global distribution of vegetation. However, factors which control the biogeography of belowground vegetation structure and function remain less understood than their aboveground counterpart. Vegetation types can differ substantially in terms of belowground processes such as root growth, root turnover, and resulting vertical root distributions. Fine roots provide an exchange surface, allowing transport of water and nutrients to the leaves. On the other hand they also represent a significant sink for photosynthetically fixed carbon to the soil in terms of maintenance and growth. Overall, root processes have a major influence on fluxes of water, carbon and nutrients within ecosystems. In this thesis, an electrical impedance method was used to determine the area of ‘active’ root in contact with the soil for the purpose of absorption. These measurements were compared to the leaf area of the trees, for the first time allowing the aboveground and the belowground resource exchange areas of plant to be contrasted. This approach was first developed to compare the exchange surface areas of leaves and roots within a Sitka spruce (Picea sitchensis) managed forest, making measurements in adjacent stands of differing tree density, but identical in age. Stem density was found to significantly influence the proportion of absorbing root area relative to leaves. Following the successful test of the method, it was used to compare the resource exchange areas of eight stands of forest and savanna vegetation in central Brazil. Across a broad gradient of vegetation structure, the results showed progressively more investment in fine root area relative to leaf area across the transition from dense forest to open savanna. However, a contrasting result showed that the forests had a higher absorbing root area to leaf area ratio than savannas. Furthermore, these measured ratios were strongly correlated with tree height across the eight structurally contrasting stands. It appears that absorbing root area index provides a physiologically meaningful way of characterising belowground water uptake ability, it is possible that excessive investment in fine root area, relative to leaf area, may reflect differences in the requirement for nutrient uptake in poor soils. Complementary to the analysis of root absorbing area, measurements of root activity and belowground carbon cycling were made by focussing on two of the eight tropical study sites. Here, the carbon costs of root growth and respiration were quantified to develop a belowground carbon budget for two structurally contrasting Brazilian savannas, using soil respiration measurements and a root presence/absence manipulation experiment. Annual estimates showed that at least 60% of the total CO2 efflux from the soil was contributed by autotrophic processes, with this value rising to 80% during the dry season. Seasonal fluctuations of soil respiration were strongly correlated with soil moisture for both the autotrophic (R2=0.79, pvalue< 0.05) and heterotrophic (R2=0.90, p-value<0.05) components, with maximum flux rates corresponding with 16.4 and 17.7% soil moisture content respectively. Furthermore, autotrophic respiration was found to varied with phonological patterns of fine root growth (R2=0.80, p-value<0.05). It follows that, the way in which phenological processes respond to a changing climate is of potential importance within seasonally dry regions. Diurnal fluctuations of heterotrophic CO2 efflux were correlated with soil temperature (R2=0.74, p-value<0.05), demonstrating a Q10 value of 1.6 across both sites. In contrast, total soil CO2 efflux was not correlated with temperature (p-value=0.31), suggesting that autotrophic respiration is predominantly limited by substrate supply.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xi, 56 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 41-44).

ABSTRACT This pilot study examines the knowledge about tree root systems amongst five tree planting professionals. The aim is to find out the professionals’ collective knowledge of the nature of root systems of various trees used in green areas. Furthermore; to explore how the professionals adapt landscaped green areas to the tree root properties in a sustainable manner. Questions: Which tree species have special root properties to consider and how do the professionals utilize this knowledge? And: How do the professionals in general adjust planting according to the root systems of trees in areas to create sustainable green environments? Interviews with the professionals were performed. Four of the five interviewees expressed that they had no root systems in mind when they chose trees to an area. However they considered properties such as wet soil, clay soil, sandy soil and the urban environment when they decided on the trees for an area. The interviewees discussed 22 different trees and their root systems and what kind of adaptations in landscaping they would make for the special root features to create sustainable tree plantings. As a result of the information a list was compiled and the collective knowledge of landscaping amongst the professionals was gathered into themes. These themes were then divided in to four headings: nutrition, root ball, design and soil conditions. In addition, all of the interviewees agreed that the most important thing for tree planting is to select the right tree species for the right soil. / SAMMANFATTNING Syftet med den här intervjustudien är att ta reda på en grupp yrkesverksammas samlade kunskap om rotsystemens olika egenskaper hos träd och sedan utforska hur de yrkesverksamma anpassar anlagda gröna miljöer till trädens rotegenskaper på ett hållbart sätt. Fem personer som arbetar med trädplantering intervjuades för att besvara studiens tre frågeställningar om rotsystemen hos träd. De två första frågeställningarna gällde: Vilka träd har särskilda rotegenskaper att ta hänsyn till och vilka anpassningar i anläggandet gör yrkesverksamma för de respektive trädens rotsystem? Utifrån intervjusvaren sammanställdes en lista där 22 träd med särskilda rotegenskaper presenteras tillsammans med vilken typ av anpassning de yrkesverksamma rekommenderar. Den tredje och sista frågeställningen var; Hur arbetar de yrkesverksamma generellt med rotsystem hos träd i anläggningar för att skapa hållbara gröna miljöer? Frågeställningen utmynnade i fyra huvudområden som beskriver hur de yrkesverksamma arbetar med näring, rotklump, design och mark för att skapa hållbara gröna miljöer. Slutligen svarade fyra av de fem informanterna att de inte hade rotsystemet i tanke när de valde träd till en plats. Trots det tog alla hänsyn till egenskaper som t.ex. blöt mark, lerjord, sandjord och urban miljö när de valde träd till en plats. Därutöver var alla var överrens om att artvalet är viktigt när träd ska planteras i en anläggning, dvs. rätt träd på rätt jord.

Thesis (M.S.)--University of Michigan, 1986.

Thesis (doctoral)--Münster in Westfalen, 1934.

Thesis (doctoral)--München, 1935.

Thesis (M.S.)--University of Michigan, 1986.

Thesis (doctoral)--München, 1935.

Thesis (doctoral)--Münster in Westfalen, 1934.