The study of past global change is paramount to comprehending the present and future, as well as to better understand the mechanisms and influences of human–land interactions in a given region. The northeastern margin of the Qinghai–Tibetan Plateau has complex natural environments, sensitive to global change, and renowned for its long history of human occupancy. This makes it an ideal region for the study of anthropogenic impacts on the paleo-natural environment. This paper reconstructed the prehistoric temporal and spatial distribution of cultivated lands on the northeast margin of Qinghai–Tibetan Plateau, and analyzed the Dianziping pollen assemblage to disclose the anthropogenic impacts on the paleo-environment. The results demonstrated that around 4.3–4.0 cal ka BP, the rapid development of the Majiayao culture boosted the population to approximately 39,200 people, over 460 km2 of the land area was converted to cropland, concomitantly, evidence of tree pollen decreased significantly. This marked the earliest identification of anthropogenic impacts on vegetation through agricultural activity in this region. At 4.0–3.6 cal ka BP, the population appeared to have diminished in conjunction with the cultivated land area. Nevertheless, forested areas continued to decrease, primarily due to adverse climatic conditions, but, anthropogenic activities played an undeniable role. Dianziping profile demonstrated the existence of natural forest in the Hehuang Valley during Qijia cultural Period. There was also evidence for the occurrence of regional fire events, suggesting large-scale burning of land cover in the area. This further illustrates anthropogenic impacts. At 3.6–2.6 cal ka BP, populations reached approximately 61,300 people, coinciding with the peak of cropland expansion. Consequently, more of the natural vegetation were converted to crops, and the superimposed influences of farming and grazing aggravated the process of deforestation and vegetation succession. Likewise, deforestation during the historical period can be explained, mostly by human driven causes with limited influence from climatic factors. The extensive exploitation of forest and expansion of cropland consequently resulted in extensive land deterioration, leaving the region with forest islands scattered in less populated, mountainous regions.
The Qinghai-Tibetan Plateau (QTP) is essential for converging eastern, western, and northern prehistoric cultural spheres of Asia and Europe and for human adaptation to extreme environments. Reconstruction of the location and development of prehistoric exchange routes on the Qinghai-Tibetan Plateau underpins understanding human response to harsh environments and interaction and exchange between the three cultural spheres. This study simulates exchange routes for the Neolithic and Bronze Ages, using elevation, slope, vegetation, and rivers as cost data and site points as node data. A weighted network consisting of nodes and lines is constructed within the Qinghai-Tibetan Plateau using a weighted cumulative cyclic connectivity model among nodes-the simulation abstracts exchange routes as a path search problem on this weighted network. The final simulated route is the road with the lowest incremental cost. The results give a total length of Neolithic routes of about 16,900 km, with 15 main roads, and a total length of Bronze Age routes of approximately 16,300 km, with 18 main roads. Pathway development from the Neolithic to the Bronze Age shows an apparent successional relationship, with a spatial evolution from the marginal corridor to the marginal hinterland. The simulated routes overlap highly with archaeological evidence for transmission routes of corn and millet agriculture and wheat agriculture-domesticated animals-bronze metallurgy technology, indicating the reliability of the simulation results. Further analysis showed that the unique physical geography of the QTP constrained the formation and evolution of routes. River valleys were commonly chosen as routes to acclimatize people to the high, cold, and low oxygen levels of the Qinghai-Tibetan Plateau. Scattered small agricultural bases, established in areas of the QTP suitable for agricultural planting, are the basis for intersecting exchange routes. Road formation also reflects the clear differentiation in the agro-pastoral industry between high and low altitudes related to climate, ecological environment, and elevation. Interaction between agricultural and nomadic populations is the crucial motivation for forming and developing the exchange routes.
Human activities strongly influenced the present-day environment of the Tibetan Plateau, especially in the northeastern area. The questions over when and to what extent humans began to utilize the plateau environment have been long investigated, but there are still gaps in our understanding, such as the relationship between forest dynamics and anthropogenic activities. Here, we simulate the potential Holocene geographical distribution of the three dominant coniferous species in the Northeast Tibetan Plateau in response to climate/environment and analyze pollen records and multi-proxies for anthropogenic activities to explore human impact on natural forest dynamics. Simulation results show marked expansion of Picea and Pinus coniferous forests in the Early Holocene (11.5–8.3 ka BP), continuing into the Mid Holocene (8.3–4.0 ka BP). However, there was a slight contraction of forest in the Late Holocene (4.0–2.6 ka BP) in the western part of the region, and near disappearance in the eastern Qaidam Basin, although both Pinus and Picea slightly increased in Hehuang Valley. Pollen analysis confirms the patterns, with an increase in arboreal pollen mainly comprising Pinus and Picea from Early to Early Mid Holocene (11.5–5.3 ka BP), followed by a decrease. Proxies of anthropogenic activities, including carbon concentration, archeological sites, and, synanthropic plants, increased significantly after 5.3 ka BP, with archeological evidence for intensive exploitation of forest and turnover of natural vegetation. We argue that forest retreat at 5.3–4.0 ka BP was due to the expansion of cropland and increasing demand for wood. Significant coniferous forest retreat and degradation from 4.0 to 2.6 ka BP, with forest succession in Hehuang Valley, was driven by the booming population, extensive grazing, and forest exploitation; the drying cooling climate may have aggravated the pace of deforestation at higher elevations. This study presents new insights into the deforestation on the Northeast Tibetan Plateau in the Holocene.
The upper Yellow River valley in the northeastern Qinghai–Tibetan Plateau (QTP) is an important corridor for prehistoric migration to the hinterland plateau. However, most studies have focused on the Neolithic Age, with limited evidence for earlier periods. The Shalongka (SLK) site on the northeastern QTP spans the Epipaleolithic to Bronze Age and contains cultural deposits, so provides a good basis for unraveling the evolutionary history of the human-land relationship. In this study, we sampled the 420-cm-thick section T1406E at the SLK site and undertook lithologic stratigraphic description and analysis of grain size, redness, magnetic susceptibility, geochemical elements, pollen and charcoal. Dating control was provided by accelerated mass spectrometry 14C and optically stimulated luminescence methods. Results show that SLK site was affected by the local fluvial sedimentary environment. The absolute dating results of the SLK site have revealed that humans occupied the site during the Epipaleolithic (8.5–7.3 cal ka BP), Yangshao culture (5.9–5.1 ka) and Qijia Culture (4.1–3.9 cal ka BP). Pollen analysis showed that the humans lived in a landscape that was predominated by forest-steppe. Consolidating with multidisciplinary evidence, we learned that Epipaleolithic sites were occupied by microlithic hunter-gatherers and comprised by relatively fixed seasonal central campsites, and their mobility was significantly decreased from the early to late period. Subsequently, farmers of the Yangshao culture migrated from the low elevation (Chinese Loess Plateau) to the upper Yellow River valleys on the QTP and founded the earliest settlement villages (~5.9 ka) on the QTP. People of the Qijia culture adopted diversified survival strategies under the settled lifestyle. In all, we infered that SLK site may play an important role in the communication and integration between different people and cultures.
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