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Understanding the forest evolution is vital to answering the reforestation potential in karst areas. Here, we present the first‐ever pollen record in karst depression sediment, combined with comprehensive dating methods (137Cs, 210Pbex, and 14C) and historical documents, to reveal plant change history in southwest Guangxi, a severe rocky‐desertification region. We inferred three stages of "virgin forest–deforestation–sparse tree planting" over the past three centuries. Before the 1780s, the barren mountains used to be a lush mixed broadleaf forest probably. However, maize cultivation, along with explosive population growth and migration, accelerated mountain reclamation and deforestation, leading to severe rocky desertification since the 1780s, featured by the co‐occurrence of Zea pollen appearance and Dicranopteris spore surge from 0.92% to 12.18%. Since the 1930s, sparse tree planting began, as Cupressaceae/Taxodiaceae pollen abruptly increased by 32%. Our study is significant in understanding the rocky desertification causes and guiding ecological restoration in the region. Plain Language Summary: Rocky desertification refers to the transformation of a karst area once covered with vegetation into rock‐baer landscapes. In southwest China, rocky desertification is the greatest ecological degradation problem. Although hundreds of billions were invested to carry out ecological restoration, it is uncertain whether the region has reforestation potential. Therefore, we attempted to use pollen record in a closed‐environment sediment (karst depression) in southwest China to reveal the plant changes in the past three centuries. Combined with isotopic methods, we found that before the 1780s, tree pollens were high, implying the site used to be a lush forest. However, since the 1780s, maize pollen occurred, coinciding with the pollen percentage surge of another species indicative of ecological degradation. We inferred that maize cultivation, along with explosive population growth and migration, accelerated mountain reclamation and deforestation, leading to severe rocky desertification there. Since the 1930s, cypress and cedar pollens were abruptly increased, indicating that sparse tree planting began. These results are vital to supporting rocky desertification control and reforestation sustainability in the region. Key Points: The first‐ever pollen record of a karst depression in southwest China is presentedThree stages of "virgin forest–deforestation–sparse tree planting" over the past three centuries were inferredMaize cultivation since the 1780s triggered severe rocky desertification in the region [ABSTRACT FROM AUTHOR]

Exploring the effectiveness of the pilot project on comprehensive control of rock desertification since its launch by China's government is of great significance for regional sustainable development. Jointly affected by the karst surface-underground geological structure and human activities, the natural ecological environment is fragile in southwest Guangxi, with frequent droughts and floods, severe soil erosion and rock desertification. Consequently, the socio-economic development in this region is relatively lagging behind. With the support of national policies, southwest Guangxi has been comprehensively carrying out projects of controlling rocky desertification, promoting the control of rocky desertification and poverty alleviation in a coordinated manner. According to "Thirteenth Five-Year Plan for Comprehensive Control of Rocky Desertification in Karst Areas of Guangxi Zhuang Autonomous Region", southwest Guangxi is designated as an area for the control of cluster-peak depression, in which comprehensive control of rocky desertification has been carried out in terms of building ecological barriers, protecting biodiversity, and promoting the protection and the comprehensive utilization of water and soil resources. In order to further investigate the effectiveness of controlling rocky desertification in cluster-peak depression of southwest Guangxi, this study the physical exploration. Based on the correction of the data from the borehole, the parameter of geological radar, V, is taken to be 0.060 m•ns -1 which is applicable to the study area. The study results indicate that Biyun lake belongs to the oblique tectonic basin, where leakage points and underground river pipes are mainly developed close to the axis of the Babu compound oblique, along the lithological interface of three sections of greystone and the second section of the mudstone of Jialingjiang Group. The mudstone constitutes a water separating plate of the karst leakage zone. After lake water seeps along the zone, it flows northwest, and is discharged in the end at the outlet of the Babu underground river. In addition, the leakage of Biyun lake is mainly of the karst pipeline type. The karst leakage zone is located at the measuring point of 540 m, with a 40-meter- deep of karst pipeline; therefore, the leakage section is relatively narrow, and it is feasible to plug the leakage by grouting. The drilling test results confirm the reliability of the technical method used in karst areas, which is combined by hydrogeological investigation, tracer test and physical exploration, because this method can well determine the direction of the leakage channel and the location of the leakage zone, and thus providing guidance on the leakage control of lakes or reservoirs in karst areas. [ABSTRACT FROM AUTHOR]

The karst area in Southwest China is an important region for the implementation of sustainable development strategies in China, as well as an area with extremely fragile ecological environment and concentrated distribution of rocky desertification. As a "National Pilot Zone for Sustainable Development" and "National Pilot Demonstration Zone for the Innovative Sustainable Development Agenda", Gongcheng Yao autonomous county of Guangxi is an important demonstration area for the coordinated development of karst landscape resource conservation and special ecological agriculture. Therefore, exploring the spatiotemporal evolution and the driving mechanism of rocky desertification in this area can provide an important scientific basis for the comprehensive management of rocky desertification, and the protection and restoration of karst ecosystem in China's pilot zones for sustainable development. Based on remote sensing images of Landsat series satellite from 2000, 2005, 2010, 2015, and 2021, this study extracted information on rocky desertification by the interpretation of human-computer interaction, and quantitatively analyzed the spatiotemporal evolution law of rocky desertification in Gongcheng county. Meanwhile, by combining data of carbonate rock and land use, this study revealed the inherent driving mechanisms of geological conditions and land use changes about the evolution of rocky desertification in Gongcheng county. The study results show that the rocky desertification in Gongcheng county experienced three stages: accelerated deterioration from 2000 to 2005, rapid improvement from 2005 to 2015 and slow deterioration from 2015 to 2021. The total area of rocky desertification ranged from 88.96--229.55 km2. From 2000 to 2005, the rocky desertification in Gongcheng county shifted from no rocky desertification to mild and intermediate rock desertification, and reversely, it showed improvement from 2005 to 2021. The rocky desertification presented a spatial pattern of development from north to south in Gongcheng county. Xiling town, Lianhua town and Ping'an town were the main areas where rocky desertification occurred, accounting for 55.47%--61.31% of the total rocky desertification area of the county. In 2005 and 2010, when the rocky desertification was relatively severe, it was mainly at a moderate level in Xiling town, while it was mainly at a mild level in other years. In addition, the rocky desertification of Gongcheng county mainly occurred in the limestone area, accounted for 71.42%--75.85% of the total rocky desertification area of this county. But the rocky desertification area in orchards and shrub land accounted for 35.92%--39.21% and 31.77%--31.86% of the county's total area, respectively. The study results indicate that there exist strong karstification, severe soil erosion/leakage, and insufficient materials and slow rates of soil forming due to the wide distribution of pure limestone in Gongcheng county. Besides, the long-term cultivation of single economic fruit forests such as peaches and plums in orchards has led to a decline in fruit tree quality, and a large number of fruit trees have been cut down in recent years, resulting in an exacerbation of rocky desertification. Therefore, the local authority in Gongcheng county should consider constructing three-dimensional ecological planting model in the karst areas such as Xiling town, Lianhua town and Ping'an town during the comprehensive treatment of rocky desertification, so as to promote the coordinated and sustainable development of ecological industry, rocky desertification control and social economy. [ABSTRACT FROM AUTHOR]