The eco-geomorphological roles of rocky deep crevices for water supply on arid zone mountain slopes (case study: Mehriz–Yazd, Iran)

Effect of crevice density on biological soil crust development on rock cut slope in mountainous regions, Sichuan, China

“…The crevice density of each quadrat was expressed by the area index of the crevices (I R , %) of each quadrat, and estimated using Eq. (2) (Sehhati et al 2015):…”

“…Despite strong erosion occurring on newly formed RCSs, the crevices can trap soil grains in runoff derived from adjacent ecosystems, airborne particles, and the cells of cyanobacteria or microalgae, which is critical for BSC formation at the initial stage (Lu et al 2022a;Peer et al 2022;Reynolds et al 2001;Yuan et al 2006;Zhao et al 2020;Zhu 2011). In other words, the crevices on RCSs could provide a refuge for "seed" and "food" of BSCs, and push the attachment and development of BSCs (Sehhati et al 2015;Yuan et al 2006;Zhu 2011). Although BSCs are drought-tolerant fast pioneer colonizers, numerous studies showed that water plays an important role in the development of BSCs (Bu et al 2015b;Chen et al 2009;Langhans et al 2010;Lucieer et al 2014;Oishi 2019;Wu et al 2022;Zaady et al 2007;Zhang et al 2005b).…”

“…It is difficult to sustain soil grains on younger RCSs, which are highly vulnerable due to extremely dramatic runoff and wind erosion (Chen et al 2022;Cullen et al 1998;Huang 2005;Li et al 2018a;Yan et al 2022;Yuan et al 2006). However, compared with the relatively flat surfaces of RCSs, the crevices had more sunken spaces that could reduce external forces to provide a refuge for trapping weathering products, soils, and dust deposits carried by runoff and wind (Peer et al 2022;Reynolds et al 2001;Sehhati et al 2015;Yuan et al 2006;Zhu 2011).…”

“…Crevices (including grooves and cracks), as the main microtopographic features, have been found to exert an important ecological significance for plant growth in arid regions and on RCSs by providing space and nutrients for vascular plant roots (Liu et al 2019;Sehhati et al 2015;Yuan et al 2006;Zhu 2011). Topography (e.g., slope, aspect and latitude) of RCS and soil properties influenced the species composition of BSCs (Concostrina-Zubiri 2019).…”

Progresses of weathered bedrock ecohydrology in the Earth’s critical zone

“…距地表60 m深的基岩垂直裂隙中仍有牧豆树根系生长 [82] 。基岩裂缝中生长的根系可能比通过深 层土壤生长的根系遇到的机械阻力小得多，为植物根系生长提供相对开放的空间，同时因深层人 为和土壤动物扰动较小，根系寿命可能更长，深根吸水率更高；即便是植物的根系在下扎过程中 碰到岩石裂隙等障碍物时，也会逐渐降低生长速率，开始生长侧根 [83,84] 。量化研究发现，植物根 系可穿透到风化基岩中>4 m的深度，在干燥季节，从2.9 m厚的风化基岩吸取394 mm水，大约是 从0.35 m厚的土壤中可吸水的10倍 [81] ，基岩风化层作为储水器，提供了生长季节树木至少70％的 水 [76] 。然而，先前研究也指出，仅在土壤水分吸收部分枯竭而减少后，基岩风化层水分才可能 成为重要的植物有效水源 [4,45,81,86] ，且从基岩风化层中提取的水是植物可利用的最后一种来源 [87][88][89][90] ，该部分水分仍对植被分布、持续生长、年度蒸腾和植被生产力起到至关重要的作用 [4,[91][92][93][94] 。 此外，在岩石风化过程中，根的穿插生长可以增加基岩孔隙度和破碎度，将惰性岩石转化为可为 植物和微生物提供水分和营养物质的非土壤基质，其基岩风化层裂隙中的粘粒组成、矿物类型、 可溶性有机碳、可矿化性C、N与上伏土壤层相似，同时还含有大量的Ca、Mg、P、K等营养元 素，在相对贫瘠地区植物深根能插入基岩风化层中充分利用其养分和水分 [18,91,95,96] 。例如，对我 国喀斯特地区研究也发现，基岩化学特征能够解释55%的植被生产力差异性 [50] 。因此，基岩风化 层水分对植物可用水及部分元素补给意义重大，但其在生态水文循环过程中的调节功能、影响程 度和作用机理仍需进一步研究和量化。…”