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，作为温室气体的制造者，它的历史对气候模型很重要。了解水稻农业的发展、多样化和传播不仅是我们理解亚洲人口增长、扩散和文明形成过程的核心，也是重建过去农业活动如何通过甲烷排放和森林砍伐影响全球气候的核心。考古植物学证据提供了一套强有力的工具，不仅可以记录过去水稻种植的地点和时间，还可以通过分析宏观遗骸组合和植物岩组合中相关杂草植物群的生态学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进行的研究（NE/G005540/1）中，对考古水稻杂草区系的研究和考古植物宏观遗骸与植物岩的结合进行了研究。我们建议将这种方法推广到更广泛的地理和文化领域，并通过一些额外的现代类似物来完善这种方法。我们建议将工作重点放在不太为人所知的亚洲地区，特别是东南亚大陆和中国南部地区，以及印度东部地区的进一步工作。这些地区是水稻种植传播假说的中心，包括将水稻传播与主要语系（如南亚语系和南岛语系）联系起来的模型，但缺乏对水稻种植本身的系统研究证据，也缺乏关于早期水稻是否代表冲冲性湿地种植系统的延伸的证据，就像新石器时代的长江（早期亚种粳稻）一样。典型的许多现代温带粳稻)或旱地雨养系统的发展（后者是许多现代热带粳稻的典型），随后在籼稻中平行发展了灌溉湿稻系统。因此，我们将结合包括杂草植物群在内的考古植物种子遗骸和植物岩来重建最早的水稻种植系统（新石器时代-青铜时代），沿着水稻从长江盆地向南扩散到东南亚的三个假设轨迹，即云南、广东和福建，以及一系列次区域。东南亚大陆（主要是泰国和越南）的环境和时期，以评估雨养和湿养灌溉系统的实践程度，以及是否可以重建不同的区域模式或单一的进化轨迹。在重建水稻耕作系统和杂草植物群组合的基础上，通过分析杂草植物群的地理和时间格局，评估水稻传播到东南亚的单一或多种途径的可能性。然后，我们将利用我们对中国南方和东南亚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和相关甲烷排放随时间变化的改进模型。研究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，但这些结果将在评估不同水稻农业传统的区域和全球影响、可持续性及其对古代人为甲烷排放的贡献方面产生更广泛的影响。

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.