*Daniel Lawrence Morovitz*
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| Masters Thesis Abstract | |||||||||||||||
| Growth characteristics of Norway spruce (Picea abies [L.] Karst.) and biomass nutrient stocks in a near-to-nature mixed mountain forest compared to declining spruce stands on dolomitic sites in the Bavarian (Tyrolean) Limestone Alps. *Daniel Lawrence Morovitz* |
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| In this study the growth characteristics and nutrient stocks from four mature, healthy mixed mountain forest stands (MMF) were compared to four adjacent, young declining spruce monocultures that were planted after clear felling. The MMF and spruce stands are of the same soil type (rendzic and actric leptosols) and lie on steep, south- southwest facing slopes in the calcareous Bavarian Alps in the Forstamt Kreuth and Bayrischzell. Growth in the declining spruce stands has reached stagnation and has consistently grown less than 0.5 mm per year for the past several decades. In comparison, the MMF stands have shown consistent growth of approximately 1 mm per year for the past 100 years. The declining spruce stands are between 46 and 103 years old and are characterized by high levels of transparency, chlorosis, mortality, slow growth and a dense coverage of grass. In comparison, the MMF stands are much older (between 122 and 236 years old), have considerably lower levels of transparency and chlorosis is practically non existent. Additionally the humus layer on the formerly clear cut sites is virtually non existent and consists of mull humus forms while the MMF sites have thick Tangel humus layers which act as a water and nutrient storage facilitator which is of value on the thin nutrient poor soils of the calcareous Alps. The declining spruce stands had a successful establishment after the clear cuts, however, within thirty to forty years after planting the growth of the spruce fell into stagnation, and with the exception of a few trees, show no signs recovery. Needle nutrient analysis show deficient levels of nitrogen and phosphorous in both the MMF and the declining spruce stands which conforms to other studies conducted in the Alps. Additionally, two plots in the declining spruce stands showed significant deficiencies for the micronutrient manganese, which can cause an increase in transparency, chlorosis and a decrease in growth. The hydrological model BROOK90 was used to calculate the ratio of transpiration and potential transpiration (T/Tp) since 1938 and thus, reveals years in which drought stress had occurred (e.g. years with a low T/Tp) and was parameterized with soil information from the same study sites. BROOK90 calculated that in both the MMF stands and the declining spruce stands had high levels of drought stress in the years 1947, 1959, and 1956. This was confirmed by the analyzation of radial growth for all stands. In those three years decreases in growth for every stand in the study was apparent. The amount of drought stress received by the two forest types was not significantly different, thus indicating the soil water storage capacity between the MMF and the declining spruce stands are roughly the same. Therefore it can be deduced that the growth of spruce on formerly clear felled sites of this study is limited by chronic nutrient deficiencies and not as a result of drought stress. The nutritive deficiencies have likely arisen due to the degradation of the thick Tangel humus layers into thin Mull layers over time. After the clear cut, the spruces were able to be successfully established on a thick nutrient rich humus layers that had developed under the previous MMF and as a result, good growth was seen for three to four decades. It is the conclusion of this study that the affects of nutrient competition coupled with humus degradation over time resulted in extremely high transparency rates, high levels of chlorosis and stagnation of growth in the declining stands. | |||||||||||||||
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