Palaeoenvironment Studies
Current Directions
At first, much could be learned by developing palaeoenvironmental records within the hegemonies of Pre-Aksumite and Aksumite polities without an immediate archaeological context. This was fortunate because little archaeological excavation had occurred outside of the main urban or ceremonial centers of the two time-frames far to the west of our sampling areas. Dates were available for the rises and declines of those centers and these were useful for first pass efforts to evaluate possible influences of environment on at least these complexity extremes.
Nonetheless, we progressed to a point where we had the toolkit to reconstruct time sequences of palaeoenvironmental changes that could be directly connected to local-scale settlement histories. Unbeknownst to us at first, the Eastern Tigray Archaeological Project (ETAP) had simultaneously begun their geospatial quantification and some excavations of ancient settlements just north of our Adigrat sampling sequences. The ever evolving palaeoenvironmental group eventually joined the archaeologists to have an opportunity to reconstruct palaeoenvironments on far more local scales from soil sequences of immediate relevance to sites of emerging archaeological knowledge.
The palaeoenvironmental group has completed sampling and many analyses for triple sequences just next to the completed Mezber excavation and 3 kilometers down a stream that received effluent from Mezber and other settlements (Kila’at Valley). They hope to obtain more regional scale information about environmental variations near additional recent archaeological excavations. Like our earlier work, the Kila’at Valley sampling sequences are exposed soils of gullies (Figure 7A). Sampling time-ordered soils of landscapes that were immediately exposed to the activities surronding settlements was accomplished by either digging pits and sampling their walls (Figure 7B) or sampling the wall of one of the many well digging efforts that failed to yield water (Figure 7C).
In addition to using previously developed methods, we continue exploring ways to expand the environmental insights we can achieve. We have particularly been focusing on needs for information about three environmental factors: rainfall, vegetation, and fire history.
We continue to find analyzing δ2Hn-Cn values of land-plant derived n-alkanoic acids (especially n-C26) to provide the most accurate insights about relative rainfall amounts over time but are increasing the time resolution (shorter time intervals between measurements) of the values. Our vegetation identification records from earlier work could only be done to identify trees that had left macroscopic and durable charcoal fragments. We have been enhancing our present vegetation records by classification of fragile and microscopic charcoal particles to arboreal and non-arboreal fractions.
Fires are the main agent of land clearing worldwide, and have both natural and anthropogenic causes that can both be influenced by climate. Based on the ubiquity of visible and microscopic charcoal and its variety of distribution patterns throughout all soils we have examined thus far, fire clearly has a long and diverse history in Tigray. Between ETAP researchers’ interviews of local peoples (see Traditional Knowledge, Ethnoarchaeology, Palaeoethnobotany - page forthcoming), and our own interactions with people during fieldwork, we have found that humans set many different types of fire for agricultural purposes (Figure 8A and 8B). We are adding methods of quantifying arboreal and non-arboreal charcoal inputs that are detecting changes in fire activity and spatial variation in those changes over time (Figure 9). Together with information from our other analyses, these data can contribute insights about human contributions to fire and thus land cover impacts.
In addition to using previously developed methods, we continue exploring ways to expand the environmental insights we can achieve. We have particularly been focusing on needs for information about three environmental factors: rainfall, vegetation, and fire history.
We continue to find analyzing δ2Hn-Cn values of land-plant derived n-alkanoic acids (especially n-C26) to provide the most accurate insights about relative rainfall amounts over time but are increasing the time resolution (shorter time intervals between measurements) of the values. Our vegetation identification records from earlier work could only be done to identify trees that had left macroscopic and durable charcoal fragments. We have been enhancing our present vegetation records by classification of fragile and microscopic charcoal particles to arboreal and non-arboreal fractions.
Fires are the main agent of land clearing worldwide, and have both natural and anthropogenic causes that can both be influenced by climate. Based on the ubiquity of visible and microscopic charcoal and its variety of distribution patterns throughout all soils we have examined thus far, fire clearly has a long and diverse history in Tigray. Between ETAP researchers’ interviews of local peoples (see Traditional Knowledge, Ethnoarchaeology, Palaeoethnobotany), and our own interactions with people during fieldwork, we have found that humans set many different types of fire for agricultural purposes (Figure 8A and 8B). We are adding methods of quantifying arboreal and non-arboreal charcoal inputs that are detecting changes in fire activity and spatial variation in those changes over time (Figure 9). Together with information from our other analyses, these data can contribute insights about human contributions to fire and thus land cover impacts.
