Description of the corpus in this study.

Syntactic complexity, widely acknowledged as a key predictor of writing quality, has gained increasing attention in the realm of academic writing. A notable line of inquiry has centered on the factors that potentially influence syntactic complexity in academic writing. Instead of attending to one factor, the study focuses on multiple factors to examine how language background affects syntactic complexity across years and disciplines. Specifically, it compares the syntactic complexity in English academic writing between L1 English and L1 Chinese university students across four years and/or three disciplines. Fine-grained indices, which include five clausal indices and eight phrasal indices, are utilized to capture specific syntactic features for a full understanding and description of the syntactic preferences shown by L1 English and L1 Chinese students in academic discourse. The results revealed that L1 English students tended to produce more noun phrases in academic writing than L1 Chinese students with the increase of years. Additionally, both cohorts of students followed similar syntactic patterns in cross-disciplinary contexts, with highly frequent use of complex nominals in the Physical Sciences and clausal structures in the Social Sciences. In instances where language background, year, and discipline interact, texts produced by Chinese English learners exhibited reliance on the syntactic features of adverbial clauses, attributive adjectives, and pre-modifying nouns across all disciplines in the early years of their academic journey. Ultimately, some pedagogical implications for academic writing courses are put forward in an attempt to provide valuable insights for enhancing academic literacy among both L1 and L2 students.

句法复杂度（syntactic complexity）作为公认的写作质量关键预测指标，在学术写作领域受到了越来越多的关注。当前学界一条重要的研究脉络聚焦于学术写作中可能影响句法复杂度的各类因素。本研究并未局限于单一影响因素，而是选取多维度变量，探究语言背景如何在不同学年与学科维度下对句法复杂度产生影响。具体而言，本研究针对覆盖4个学年与3个学科的样本，对比母语英语（L1 English）与母语汉语（L1 Chinese）大学生的英语学术写作句法复杂度差异。本研究采用细粒度指标（fine-grained indices）开展分析，包含5项小句指标（clausal indices）与8项短语指标（phrasal indices），旨在捕捉具体句法特征，以全面理解并描述母语英语与母语汉语学生在学术语篇中展现出的句法偏好。研究结果表明，随着学年推进，母语英语学生在学术写作中产出的名词短语数量显著多于母语汉语学生。此外，两类学生群体在跨学科语境下展现出相似的句法模式：自然科学（Physical Sciences）领域高频使用复杂名词性结构，社会科学（Social Sciences）领域则高频使用小句结构。当语言背景、学年与学科三者产生交互作用时，中国英语学习者在求学早期的所有学科写作中，均倾向于使用状语从句（adverbial clauses）、定语形容词（attributive adjectives）与前置修饰名词（pre-modifying nouns）这类句法特征。最后，本研究针对学术写作课程提出若干教学启示，以期为提升母语与第二语言学习者的学术素养（academic literacy）提供有益参考。