Exploring the causes and patterns of ring-formation in plants in an unknown diversity hotspot of the Namib Desert

探索纳米布沙漠未知多样性热点地区植物环形成的原因和模式

• 批准号: 508387707
• 负责人: Professorin Dr. Kerstin Wiegand
• 金额: --
• 依托单位: Abteilung Ökosystemmodellierung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/508387707?language=en
• 关键词: Exploring; causes; patterns; ring; formation

Ring formation in plants of the global drylands has attracted great interest in the research community, particularly regarding the mechanisms that generate these symmetric shapes. Here, plant rings include “tussock rings”, which result from slow vegetative growth processes of single tussock plants, and a new class of plant rings: “collective plant rings”, which were discovered in 2021 in the Namib Desert. Collective plant rings are composed of several individuals of annual grasses or annual forbs or a mixture of both, and they pop up spontaneously after rainfall events in the eastern Namib Desert. The function of these rings is currently unsolved and it is also unclear how their diameters, shapes, density, and spatial patterns change from rainy season to rainy season. Preliminary investigations suggest that the annual grasses and forbs form rings up to 1 m in diameter to collectively deplete the soil moisture within the rings. These rings could potentially be a consequence of vegetation self-organization whereby the individual plants on the ring periphery facilitate each other to increase their own biomass. However, in-depth research is necessary to better understand this new class of plant rings. Surprisingly, in 2021, altogether 10 different grass and forb species in the Namib desert were discovered to be ring-forming, making the Namib a genuine “diversity hotspot” of plant-ring formation. It is a major research gap that no information on the biogeographic diversity and range of plant rings exists for this ecosystem. Only the famous fairy circles have been widely studied in the Namib, but these vegetation gaps have much larger diameters than the plant rings, and are a different phenomenon. We will study the tremendous wealth of ring-forming plants in arid southwestern Africa. Our pioneering research will include a whole set of fieldwork methods. Using repeated drone monitoring during the rainy seasons, we will map both tussock rings and collective plant rings. From the drone data, we will derive digital terrain models and relate variables of topographical heterogeneity to the sizes, shapes, and spatial patterns of the rings. Potential aeolian feedback effects between soil and ring enlargement or ring shape will be investigated with in-situ measurements on infiltration rates, soil moisture, plant height and root length. Continuous soil-moisture measurements with data loggers will be used to test for biomass-water feedbacks and potential self-organization processes. Manipulative experiments on collective plant rings will investigate the cause of the rings, and all types of plant rings will be analyzed for microbial pathogens that may also contribute to their formation. Ultimately, our results will shed light on the basic processes of vegetation growth in water-stressed ecosystems that are increasingly prone to desertification under climate change.

全球旱地植物环的形成引起了研究界的极大兴趣，特别是关于产生这些对称形状的机制。这里的植物年轮包括“tussock rings”，这是由单个tussock植物缓慢的营养生长过程造成的，以及一类新的植物年轮：“集体植物年轮”，这是2021年在纳米布沙漠发现的。集体植物年轮是由几个一年生草本植物或一年生草本植物或两者的混合组成的，它们在降雨事件后自发地出现在纳米布沙漠东部。这些环的功能目前还不清楚，它们的直径、形状、密度和空间模式在雨季和雨季之间的变化也不清楚。初步调查表明，一年生草本植物和草本植物形成直径达1米的环，共同消耗环内的土壤水分。这些环可能是植被自组织的结果，即环上的单个植物相互促进以增加自己的生物量。然而，为了更好地了解这类新的植物环，有必要进行深入的研究。令人惊讶的是，在2021年，在纳米布沙漠中发现了总共10种不同的草和forb物种是环形的，使纳米布成为真正的植物环形形成的“多样性热点”。这一生态系统的生物地理多样性和植物年轮的分布范围是一个重大的研究空白。在纳米布，只有著名的仙女圈得到了广泛的研究，但这些植被间隙的直径比植物环大得多，是一种不同的现象。我们将研究非洲西南部干旱地区丰富的环状植物。我们的开创性研究将包括一整套实地考察方法。通过在雨季重复使用无人机监测，我们将绘制丛环和集体植物环。从无人机数据中，我们将推导出数字地形模型，并将地形异质性变量与年轮的大小、形状和空间格局联系起来。通过对入渗速率、土壤湿度、植物高度和根长的原位测量，研究土壤和环扩大或环形状之间潜在的风成反馈效应。用数据记录仪连续测量土壤水分将用于测试生物量-水分反馈和潜在的自组织过程。对集体植物年轮的操纵实验将调查年轮的原因，并对所有类型的植物年轮进行微生物病原体分析，这些微生物病原体也可能有助于它们的形成。最终，我们的研究结果将揭示在气候变化下日益容易发生荒漠化的缺水生态系统中植被生长的基本过程。