Local vegetation patterns of a Neolithic environment at the site of Tianluoshan, China, based on coprolite analysis
Introduction
Information on past environmental management or landscape modification by ancient humans in the Yangtze coastal lowlands has previously been revealed by paleoecological studies (e.g. Itzstein-Davey et al., 2007, Innes et al., 2009). Long-term landscape-scale anthropogenic influence is usually evident from the appearance and spread of domesticated plants and animals, expansion of agricultural and pastoral land use, forest clearance and the creation of open landscapes (Boivin et al., 2016). On the other hand, local vegetation patterns created either deliberately or accidentally by human activities usually leave much less evidence and are hard to recognize (Smith, 2015), especially when it comes to wild plants or early-cultivated crops still without distinct morphological changes.
Based on archaeological and ethnographic descriptions of indigenous North American communities, Smith (2011) proposed the term “human niche construction” to summarize six general categories of environmental manipulation by small-scale human societies, including (i) general establishment of mosaic landscapes with early-stage vegetation communities, (ii) broadcast sowing of small-seeded annuals, (iii) transplantation of perennial fruit-bearing species, (iv) in-place encouragement of fruit- and nut-bearing perennials, (v) transplantation and in-place encouragement of root crops, and (vi) landscape modification to enhance prey abundance. Through this model, it can be inferred that a settlement is usually surrounded by different types of patches created and maintained by human activities. Patches may refer to open and edge areas (fields, old fields and parklands) in North American history documents (Hammett, 1992), house gardens, terraces, anthropogenic forest islands and raised fields in the Amazonia area (Erickson, 2008), or “culture-steppe” in European Holocene forest (Whitehouse and Smith, 2004).
Based on studies at the Middle Neolithic sites Kuahuqiao and Tianluoshan in the Lower Yangtze Region, China, Pan (2011) and Pan et al., 2013, Pan et al., 2017 put forward the hypothesis that wetland and forest edge were two main habitats influenced by ancient people. Plant macro-remains in both sites showed a period with gradually reduced procurement of wetland plants and reinforcement of forest edge resources, reflecting diverse ecotones created by management practices (e.g. burning, cultivation, gathering) and a settlement-centered micro-landscape with different levels of human disturbances. Besides, Zong et al. (2007) and Shu et al. (2012) also argued that either local woods or alder-dominated wetland scrub was the target of fire clearance for rice cultivation at the Kuahuqiao site. On the other hand, from the model of on-site catchment analysis, Qin et al. (2010) described a relatively passive “gathering” activity of wild resources at the Tianluoshan site in a wide range of natural habitats including aquatic environments, bushes and high altitude mountains, as far as within 24–36 h walking distance. Considering these two perspectives above, it raises the questions of whether the modifications of local vegetation habitats by ancient communities occurred under such contexts, and to what extent.
In order to understand the micro-environmental settings, pollen spectra from coprolites have been used as indicators of vegetation in a local area (e.g. Carrión et al., 2005). Compared to sediment samples usually dominated by wind-pollinated pollen species from long distance transport, investigations of samples from soil surfaces, animal dung, and natural sediments in southeastern Spain demonstrated that dung pollen spectra provide the best analog of local and regional vegetation in terms of pollen concentration and taxon diversity, especially with higher abundances of zoophilous pollen types (Carrión, 2002). Based on the analysis of hyaena coprolites, Carrión et al. (2001) proposed that the dung pollen record is not substantially biased by dietary input, but may reflect the vegetation of the visiting areas of hyaenas or their prey. Although most previous studies of coprolites from wild animals mainly focused on the interpretations of natural environments, it can be assumed that the palynological analysis of coprolite samples in an archaeological context also provide a potential tool to reveal the surrounding vegetation patterns within human activity areas, which may largely complement the results obtained from natural pollen records and further reflect human impacts and different habitats associated with people's daily activities.
In the present study of the Tianluoshan coprolite samples, our tentative aims include: (i) to identify the origins of coprolites with lipid biomarkers and to discuss the implications for the interpretation of pollen and spore records; (ii) to examine the local vegetation patterns under possible human disturbances using pollen data; (iii) to test the relationships between non-pollen palynomorphs (NPPs) and the local environments of the Tianluoshan site.
Section snippets
The study site
The Tianluoshan site is located in Xiang'ao Village, Yuyao Municipality, Zhejiang Province in the Yao River Valley, surrounded by the Siming Mountains and 30–40 km away from the current coastline of the East China Sea (Zhejiang Provincial Institute of Cultural Relics and Archaeology, 2007; Fig. 1a). The natural upland vegetation is characterized by northern subtropical evergreen/deciduous broad-leaved forest. Major arboreal components consist of evergreen (Lithocarpus, Cyclobalanopsis, Quercus)
Materials and methods
During the excavation of the Tianluoshan site, coprolite remains have been found in the 8th and 7th layers of trenches 205, 206, 301, 304, 305, 306, 403, 404, 405 and 406 (Fig. 1c, d), within the main residential area of the early occupation period. A small proportion of each coprolite (ca. 1–4 cm3) was sampled at the storage room of the Tianluoshan site where they were kept for further analysis, using clean gravers and tweezers, wrapped in aluminum foil and sealed in plastic bags.
Non-pollen palynomorphs
Within 82 samples analyzed, 2 samples without NPPs were excluded from subsequent NPP statistics. Thirty-eight NPP types occuring in at least one sample and ≥ 1% abundance were included, of which seven types have been described in previous literature: Chaetomium-type (HdV-7A), Sordaria-type (HdV-55A), Cercophora-type (HdV-112), Sporormiella-type (HdV-113), Coniochaeta cf. ligniaria (HdV-172) (van Geel et al., 1983, van Geel et al., 2003), Tetraploa aristata (HdV-89) (van Geel, 1978) and Delitschia
Origins of coprolites
Mineral pseudomorphs of fecal bacteria have been described in coprolites from bone-digesting animals. Under Scanning Electron Microscope, Hollocher et al. (2010) and Pesquero et al. (2013) observed the coprolite matrix with branching fungal or bacterial hyphae and full of hollows, thin-walled mineral spheres, resembling bacteria in size and shape, indicating the crystallization of dietary calcium phosphate from the original scat. The predominance of short chain, mid-chain and cycloalkanes
Conclusions
Dung pollen spectra have been demonstrated to be the best analogue of local vegetation and among the non-pollen palynomorphs, fungal spores usually point to in-situ occurrences related to special habitats. Here, with 82 coprolites from the Tianluoshan site, we try to explore their potential in indicating micro-environments and human disturbances in an archaeological settlement background. In the biomarker analysis of 31 subsamples, the relatively high abundances of cholesterol, cholestanol,
Acknowledgements
We thank Annemarie Philip and Britte Heijink for preparing the microfossil samples, Jacqueline van Leeuwen and Dr. Junwu Shu for helping with pollen identifications, and Prof. Jianfeng Cui for SEM-EDS analysis. We also appreciate the two anonymous reviewers who gave valuable suggestions for revisions. This work was supported by the China Scholarship Council ([2017]3109).
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