Impact of Roots and Rhizomes on Wetland Archaeology: A Review

The general premise for successful archaeological in situ preservation in wetlands is that raising the water table will ‘seal the grave’ by preventing oxygen from reaching the deposit. The present review reveals that this may not be the entire picture, as a change in habitat may introduce new plant species that can damage site stratigraphy and artefacts. However, reviews on the types and degree of damage caused by vegetation to archaeological remains preserved in situ in wetlands have hitherto only been sporadically treated in the literature. Thus, this paper provides an overview of the adverse effects that various plants species have on the preservation status of wetland archaeology.Disturbance, due to growth of roots and rhizomes of the surrounding soil is denoted contextual disturbance, whereas deterioration of archaeological remains per se acts by several root-related factors that may be spatially and temporally concomitant. In waterlogged anoxic environments, deterioration is mainly related to (i) preferential growth of roots/rhizomes due to nutrient uptake and lesser soil resistance, (ii) root etching due to organic acid exudates, (iii) microbial growth due to root release of oxygen and labile organic compounds, and/or (iv) precipitation of hydroxides due to root release of oxygen. For example, roots of some wetland plants, such as marsh horsetail (Equisetum palustre), have been documented to penetrate archaeological artefacts down to c. 2 m in waterlogged anoxic soils. Here, we demonstrate that cultural heritage site management may unintentionally introduce deep-rooted or exudate aggressive plants by invoking change in hydrological conditions. Moreover, the implementation of biomass energy utilization and agricultural root depth optimization on a worldwide basis stresses the need for more research within root and rhizome impact on archaeological remains in wetlands. In conclusion, the worst-case scenario may be in situ deterioration instead of preservation, and one essential threat to archaeological wetland sites is the impact of wetland vegetation.     

Research and Monitoring on Conservation State and Preservation Conditions in Unsaturated Archaeological Deposits of a Medieval Farm Mound in Troms and a Late Stone Age Midden in Finnmark,Northern Norway

This paper presents archaeological observations and results of palaeoecological and geo-chemical analyses of archaeological deposits from two rural sites in northernmost Norway. These are combined with climate data and the first period of continuous monitoring of soil temperature, moisture, and redox potential in sections. This data constitutes the basic research material for evaluations of conservation state and preservation conditions. The data has been collected in collaboration with the partners of a cross-disciplinary project: ‘Archaeological Deposits in a Changing Climate. In situ Preservation of Farm Mounds in Northern Norway’ funded by the Norwegian Council for Research (http://www.niku.no/en/archaeology/environmental_monitoring/archaeological_deposits_in_a_changing_climate_in_situ_preservation_of_farm_mounds/). This is an important Norwegian research initiative on monitoring of rural archaeological deposits, and the results have consequences for heritage management of a large number of sites from all periods. Palaeoecological analyses and redox measurements have revealed ongoing decay that might not otherwise have been detected. Decay studies indicate that both site types may be at risk with the predicted climate change. Some mitigating acts are suggested.     

Boathouses as indicators of political organization

Remains of boathouses from the Iron Age and the Medieval Period have been studied for classifying and dating purposes. A classification based on the ratio length/breadth is compared with the height above sea level and tested by ¹⁴C‐dates, the measurements of preserved boats and ships, and archaeological finds. It is possible that we can define three groups of boathouses belonging to three different chronological periods. The distribution of large boathouses indicates a different naval organization during the Medieval Period than in the Late Roman/Migration Period. During the Medieval Period the coastal area was divided into many local districts, and each of them had to contribute to the king's fleet with a fully equipped ship. The Iron Age boathouses are found in groups, and it is suggested that the country was then divided into several chiefdoms, and the boathouses were concentrated around the chieftains’ administrative centres.     

Early agriculture in Scandinavia: Research problems related to pollen‐analytical studies

As a background for a discussion on errors and potentials of the palaeo‐botanical methods in the documentation of early prehistoric agriculture in Scandinavia, some methodological problems in pollen analysis are treated. Multidisciplinary research for understanding environmental changes is emphasized. Definition of long‐term changes in the cultural landscape is discussed. Different research strategies in Scandinavia are outlined. A survey of the introduction and expansion of agriculture in Scandinavia is presented. Finally, some palaeoecological interpretation problems related to the early agriculture landscape are listed.