The impact of evolving of rice systems from China to Southeast Asia

作为世界上产量最高的作物，水稻的历史和潜力引起了作物科学家和考古学家的极大兴趣，作为温室气体排放者，水稻的历史对气候模型具有重要意义。了解水稻农业的发展、多样化和传播不仅对于我们理解亚洲人口增长、扩散和城市化的过程至关重要，而且对于重建过去的农业活动如何通过甲烷排放和砍伐森林来影响全球气候也是至关重要的。考古植物学证据提供了一套强大的工具，不仅可以记录过去水稻种植的地点和时间，而且还可以通过分析大型遗迹组合和植硅体组合中相关杂草植物群的生态来记录水稻是如何种植的。我们最近在印度、斯里兰卡和中国的部分地区(NE/G005540/1)进行了考古水稻杂草植物群的研究以及考古植物宏观遗骸和植硅体的组合研究。我们建议在更广泛的地理和文化领域推广这种方法，并通过一些额外的现代类似物来完善这种方法。我们建议把工作重点放在亚洲鲜为人知的地区，特别是东南亚大陆和中国的南部地区，以及印度东部地区的进一步工作。这些区域是水稻种植扩散假说的核心，包括将水稻的传播与主要语系如南洋和南岛语系联系起来的模型，但缺乏系统地研究水稻种植本身的证据，或关于早期水稻是否代表新石器时代长江(早期亚种水稻，许多现代温带水稻的典型)或旱地旱作系统(后者是许多现代热带水稻的典型特征)的冲积湿地耕作系统的延伸，以及后来在籼稻中灌溉的湿稻系统的次生平行进化的证据。因此，我们将结合考古植物种子遗骸，包括杂草植物群和植硅体来重建最早的水稻种植系统(新石器时代-青铜时代)，沿着三条假设的水稻从长江盆地向南扩散到东南亚的轨迹，即云南、广东和福建，以及跨越东南亚大陆(主要是泰国和越南)的一系列次区域、环境和时期，来评估雨灌和湿灌溉制度的实施程度。以及是否可以重建不同的区域模式或单一的进化轨迹。在我们重建的水稻耕作系统和杂草区系组合的基础上，通过分析杂草区系的地理和年代学模式，评估水稻传播到东南亚的单一或多条途径的可能性。然后，我们将利用我们对中国南部和东南亚不同时期和不同时期水稻种植方式的更好理解，以过去水稻种植的经验证据为基础，建立过去湿地水稻面积的改进模型，并将甲烷排放与一段时间的联系起来。这些结果将与对全新世亚洲和水稻农业感兴趣的史前学家和第四纪科学家直接相关，但这种结果将在评估不同水稻农业传统及其对古代人为甲烷排放的贡献方面产生更广泛的影响和全球影响。

As the world's most productive crop, the history and potential of rice is of great interest to crop scientists and archaeologists, and as a greenhouse gas producer its history is important to climatic modelling. Understanding the development, diversification and spread of rice agriculture is central not only to our understanding of the processes of human population growth, dispersal and formation of civi-lizations in Asia, it is also central to reconstructing how past agricultural activities might have im-pacted global climate through methane emissions and deforestation. Archaeobotanical evidence offers a powerful set of tools for not only documenting where and when rice was cultivated in the past, but how it was cultivated through the analysis of ecology of associated weed flora in macro-remains assemblages and phytolith assemblages. We have pio-neered the study archaeological rice weed flora and the combination of archaeological plant macro-remains and phytoliths in our recent NERC-supported research in parts of India, Sri Lanka and China (NE/G005540/1). We propose to roll out this method over a wider geographical and cultural area, as well refining the approach through some additional modern analogues. we propose to focus our work on the less known parts of Asia, especially mainland Southeast Asia and the southern parts of China, as well as further work in the eastern parts of India. These regions are central to hypotheses on the dispersal of rice cultivation, including models linking the spread of rice to major language families such as Austroasiatic and Austronesian, and yet a lack systematically-studied evidence for rice cultivation itself, or evidence as to whether early rice represented an extension of the alluvial wetland cultivation systems like those of the Neolithic Yangtze (early subspecies japonica, typical of many modern temperate japonica) or the develop-ment of upland rainfed systems (the latter typical of many modern tropical japonica rices), with a secondary later parallel evolution of irrigated wet rice systems amongst indica rices. Therefore we will use a combination of archaeobotanical seed remains, including weed flora, and phytoliths to reconstruct the earliest rice cultivation systems (Neolithic-Bronze Age) along the three hypothesized trajectories of rice diffusion southwards from the Yangtze basin towards south-east Asia, namely in Yunnan, Guangdong, and Fujian, as well as across a range of subregions, environments and periods in mainland Southeast Asia (mainly in Thailand and Vietnam) to assess the extent to which rainfed and wet irrigated systems were practiced, and whether different regional patterns or a single evolutionary trajectory can be reconstructed.On the basis of our reconstructed rice arable systems and weed flora assemblages to as-sess the likelihood of single or multiple pathways for the spread of rice into Southeast Asia, by analysing the geographical and chronological patterns of weed flora. We will then use our improved understanding of how rice was cultivated in different times and periods of southern China and Southeastern Asia to produce improved models of past wetland rice area and linked methane emissions over time, grounded in the empirical evidence for past rice cultivation. Results will be of direct relevance to prehistorians and quaternary scientists interested in Holocene Asia and rice agriculture, but such results will have a wider impact in terms of assessing the regional and global impact, and sustainability, of different traditions of rice agriculture, and its contribution to ancient anthropogenic methane emissions.