Morphological characteristics of rock fissure networks and the main factors affecting their soil nutrients and enzyme activities in Guizhou Province, China

Rock fissures constitute the main habitat type in the karst rocky desertification (KRD) area, but the effects of their network morphology on soil properties remain unknown. To address this, we investigated 46 rock vertical profile plots in Guizhou Province of China and classified their habitats using the morphological characteristics of their fissure networks. The response characteristics of soil nutrients and enzyme activities to the rock fissure morphologies in different rock habitats were discussed, and the main factors affecting soil nutrients and enzyme activities were comprehensively analyzed. Rock fissure networks were divided into three types: Type 1, a random type, with a low dip angle, long trace length, multiple turns, multiple connections, and high density; Type 2, a uniform type, with a moderate dip angle, moderate trace length, fewer turns, fewer connections, and moderate density; and Type 3, an aggregation type, with a high dip angle, short trace length, fewer turns, moderate connections, and low density. Soil nutrient levels and enzyme activities were the highest in Type 1, followed by Types 2 and 3. There were no significant differences between the total phosphorus and available phosphorus content in Types 1–3. The dip angle, fractal dimension, and average trace length were identified as the main factors affecting soil nutrients and enzyme activities, and Type 1 was the most conducive for soil nutrient and enzyme accumulation. The restoration of Type 2 and 3 areas should be emphasized in future research, as these results will help guide vegetation restoration in KRD areas.