土壤pH是影响粮食产量的重要因素，土壤酸化是造成土壤退化的重要因素且成因较为复杂，景观格局是生态过程的重要影响因素，其对土壤酸化的影响机制尚不明确。本研究以广州市流溪河流域作为研究区域，以样点缓冲区作为研究单元，基于2010年的759个耕地表层土壤样点pH和1980s土壤pH分布，使用景观格局指数、地统计与相关性分析方法，分析流域耕地土壤酸化时空变化特征，定量探究景观格局对耕地土壤酸化的时空影响。研究结果表明：①2010年流域耕地以酸性土壤为主，土壤样点pH均值为5.79，86.03% 的样点和97.3% 的耕地土壤pH<6.5；不同耕地类型土壤pH均值：水浇地(6.03)>水田(5.68)>旱地(5.62)；各类土壤的pH均值：河积土田(5.92)>水稻土(5.84)>赤红壤(5.66)>紫色土(5.55)>黄壤(5.40)>红壤(5.39)。②1980—2010年土壤酸化显著，31.23% 的样点和24.76%的耕地土壤pH下降；水田和旱地土壤酸化显著，水浇地有pH上升的趋势；除河积土田外各类耕地土壤酸化显著，黄壤最显著，红壤次之。③流域自上游往下游，耕地土壤pH递增且分布变得更复杂，上游和中游东西两侧及下游东侧的pH较小，且在1980—2010年酸性土壤向外蔓延趋势显著；中游中部及下游西侧出现了pH升高的复杂组合。④除旱地、灌木林地、草地和未利用地之外的类型景观格局指数都与耕地土壤pH存有显著相关性，pH与水域和道路密度景观水平指数呈显著正相关，本研究选出各类景观的土壤酸化敏感性景观格局指数，发现自然林的破坏，水田、园地和水域的破碎化，不透水建设用地的零散分布有造成耕地土壤酸化风险，大片水域的流水更新与水田的集聚化可降低土壤酸化风险。本研究可为耕地土壤酸化防治与景观优化提供参考依据。

Soil acidity is a serious constraint to food production worldwide, soil degradation caused by soil acidification has become a global consensus. The impact factors of soil acidification were complex, landscape pattern is an important influential factor of ecological process, but the relationship between landscape pattern and soil acidification is not well understood. In order to discover the spatial and temporal patterns of farmland topsoil pH and watershed landscape, and to quantitatively examine the impacts of landscape pattern on farmland soil acidification. in this paper the Liuxihe watershed was selected as the study area and soil sample buffer as the research unit based on 759 farmland topsoil samples and land use pattern in 2010, distribution map of soil pH in 1980s, and the research methods included landscape pattern index analysis, spatial analysis and correlation analysis. The results showed that: 1) The watershed was dominated by acidic soil in 2010, soil mean pH was 5.79, 86.03% of the samples and 97.3% of the farmlands with pH<6.5; Soil pH were in an order of irrigated cropland (6.03)>irrigated paddy fields (5.68)>dry cropland (5.62), and in an order of alluvial soils (5.92)>paddy soils (5.84)>latosolic red earths (5.66)>purplish soils (5.55)>yellow earths (5.40)>red earths (5.39). 2)Soil acidification was significant during 1980—2010, soil pH decreased in 31.23% of the samples and 33.76 km2 (24.76%) of the farmlands; Soil acidification in paddy fields and dry cropland were significant (pH reduction rate>27%), and irrigated farmland soil pH showed an increasing trend. Soil pH decreased in 92.21% of yellow earths and 54.31% of red earths. Except alluvial soils with an increasing trend of pH, farmland soil acidification was significant in other soils, among of which yellow earths was most significant, followed by red earths. 3) Farmland soil pH was increased and the distribution became more complicated from the upper reaches to lower reaches. pH were lower in the upper reaches, two side of middle reaches and the east sides of the lower reaches, acidic soil was spread outwards during 1980—2010 and soil acidification was obvious. Soil pH increased in complex pattern in the middle of middle reaches and the west side of lower reaches. 4)Except dry cropland, significant correlation were found between landscape metrics of different land use types and soil pH in shrubbery land, grass land and bare land. Soil pH was positively correlated with the densities of water area and road. The destruction of natural forest, the fragmentation of paddy fields, garden plots and water, scattered distribution of impermeable construction land may increase the risk of soil acidification while large area of water renewal and agglomeration of paddy fields may reduce it. These conclusions are useful for the control and remediation of farmland acidification.

S153.4；P901

国家自然科学青年科学基金项目(41601558)，广东省科技计划项目(2017A040406021, 2018B030320003)，广州市科技计划项目(201709010010)，广东省科学院创新平台建设专项，广东省烟草专卖局科技项目(粤烟科项201705)和广东省农业与农村厅“广东省粮食生产功能区土壤酸化数据分析”项目资助。