Large termite mounds, regionally called Murundus, forming hillocks throughout the Brazilian territory, occur, with different names, across the entire tropical belt. Little is known about the genesis and age of these large biogenic structures in the semiarid zone, where termites have a limited range due to water deficit. We aimed to understand the process of mounds building on different types of soils at the ecotonal semiarid region of Minas Gerais state. In addition, we tested the hypothesis that these mounds have been produced by termites during the Holocene, and that the paleoenvironmental conditions during mound formation were different from today, helping to enhance the understanding of vegetation dynamics in the semiarid Caatinga Biome. For this, five mounds with and without living termites (M1, M2, M3, M4 and M5) and five adjacent soil profiles (P1, P2, P3, P4 and P5) were selected for morphological description, followed by physical, chemical, mineralogical and micromorphological analysis, as well as δ¹³C and ¹⁴C dating analysis. The occurrence of these large termite mounds in the semiarid landscape is unrelated to soils or parent material, and represent the products of cumulative termite activity in the edge of the semiarid domain. Mounds and adjacent soils formed after the mid Holocene (younger than 4000 years), based on ¹⁴C dating, and may be even older. The calculated rates of termite accretion (based on ¹⁴C dating) are consistent with previous reports of tropical soils, in the range of 0.027 to 0.066 cm soil/Ha/y. A comparative estimate based on mound volume and density was 0.188 cm soil/Ha/y, up to 3.5 times greater than the previous approach based on ¹⁴C dating. These figures suggest the production of a soil mantle in the range of 270–660 cm in 10,000 years, accounting for erosion. The mounds and adjacent soils have differences in micropedological features, notably related to bioturbation (excremental infillings), and contrasting textural variations with depth, with higher and more uniform clay and silt contents in mounds, and a kaolinitic/illitic mineralogical composition throughout. The chemical fertility of murundus depends on the type of underlying soil from which it was built, and does not increase in all cases. In the murundus studied, the microgranular structure typical of oxic materials is welded and massive, indicating that the natural compaction of soils dominated by kaolinite/illite under the semi-arid climate prevents the stability of loose aggregates formed by termite bioturbation, reorganizing the termitic microaggregate groundmass. This clearly shows the polycyclic (polyphasic) biogenic nature of mounds and adjacent soils, corroborated by carbon isotopes studies. Soils and mounds are younger than mid Holocene in the first 100 cm, and experienced alternations of dry and wet climate spells from the mid-Holocene onwards, resulting in apparent changes in vegetation at the ecotonal, southern limit of semi-arid Caatinga, over the last 5000 years. Since we did not reach the base of mounds, they should be even older; mounds represent fine proxies for Holocene paleoclimate reconstructions, if a more detailed pedostratigraphic study is carried out. A general model of termite mounds formation in relation to the interconnected pedological, geomorphological and vegetational evolution is presented, summarizing all present knowledge on these outstanding biogenic landforms.

大白蚁丘，在整个巴西热带地区以不同的名字出现，在整个巴西领土上形成丘陵，在当地被称为Murundus。对于半干旱地区这些大型生物发生结构的成因和年龄知之甚少，在半干旱地区，白蚁由于水分不足而作用范围有限。我们旨在了解米纳斯吉拉斯州经济半干旱地区在不同类型土壤上筑土的过程。此外，我们测试了以下假说：这些土墩是由全新世期间的白蚁产生的，并且土墩形成期间的古环境条件与今天不同，这有助于增进对半干旱Caatinga生物群落中植被动态的理解。为此，有五个有或没有活白蚁的土墩（M1，M2，M3，¹³ C和¹⁴ C约会分析。这些大型白蚁丘在半干旱景观中的发生与土壤或母体材料无关，代表了在半干旱区域边缘累积的白蚁活动的产物。根据¹⁴ C测年，在全新世中期（小于4000年）之后形成的土丘和邻近土壤，甚至可能更老。计算出的白蚁繁殖率（基于¹⁴ C测年）与以前的热带土壤报告一致，范围为0.027至0.066 cm土壤/公顷/年。根据土堆体积和密度进行的比较估算为0.188 cm土壤/公顷/年，比基于¹⁴的先前方法高3.5倍C约会。这些数字表明，在10,000年内产生了270-660 cm范围的土壤地幔，这是造成侵蚀的原因。土丘和附近的土壤在微生态学特征上存在差异，特别是与生物扰动（排泄物充填）有关，并且随着深度的变化而形成纹理差异，土丘中的粘土和淤泥含量越来越高，并且遍及整个高岭土/非法矿物成分。murundus的化学肥力取决于其下层土壤的类型，并不是在所有情况下都会增加。在研究的泥沙中，典型的有氧材料的微细颗粒结构是焊接的且块状的，这表明在半干旱气候下以高岭石/伊利石为主的土壤的自然压实会阻止白蚁生物扰动形成的松散聚集体的稳定性，重新组织白蚁微骨料基团。这清楚地表明，碳同位素研究证实了土丘和邻近土壤的多环（多相）生物成因。在最初的100厘米中，土壤和土墩比全新世中期年轻，从全新世中期开始经历了干旱和潮湿气候变化，导致半干旱Caatinga南部的经济区的植被发生了明显变化。持续了5000年 由于我们没有达到土墩的底脚，所以它们应该更大一些。如果进行更详细的地层学研究，则土墩代表全新世古气候重建的优良代表。提出了与相互联系的土壤学，地貌学和植被演化有关的白蚁丘形成的一般模型，