# The Role of Cryptogams in Soil Property Regulation and Vascular Plant Regeneration: A Review
## 2 Effects of Cryptogam on Soil Properties
### Effects of Cryptogam on Content and Vertical Distribution of Soil Water
found that when the soil water content was the same, the moss crust caused a significant decrease in the soil water diffusion rate and adsorption ability, which led to the accumulation of water on the soil surface (0-10 cm). On the other hand, soil water content decreased in deep soil (10-20 cm) due to reduced water acquisition [13]. Through the artificial cultivation of biological crust in semi-arid areas, [PERSON] et al. found that the artificial moss crust increased the soil moisture content of the surface layer (0-20 cm) but seriously decreased the soil moisture content below 30 cm, leading to a decrease in the total soil moisture content on the whole. Overall, the longer the development time of the moss crust, the more obvious the reduction effect is [11]. However, other studies have reached the opposite result. Through an artificial rainfall simulation experiment, [PERSON] found that lichen and moss crusts are conducive to precipitation infiltration into deeper soil [10]. The effect of cryptogams on soil water content seems to be regulated by precipitation or soil water content. In [PERSON]'s simulated rainfall research, the increase in artificial rainfall led to a significant increase in the infiltration of deep soil water [40]. In [PERSON]'s study, the average annual precipitation in the local area was only 95 mm. In the outdoor experiment, the presence of moss crust resulted in a decrease in soil water content. In petri dish experiments, the soil was saturated with water and then exposed to an environment identical to that of the outdoor experiment. In such scenarios, the moss causes the soil to retain more water [46]. [PERSON] et al. 's study also found that biological crust significantly reduced soil water content; however, on the gully floor with sufficient water, this reduction was significantly mitigated [50]. The above studies seem to imply that cryptogams are beneficial to the maintenance of soil water content in humid environments but will exacerbate soil and water loss in drought conditions. In the absence of artificial irrigation and other water sources, the boundary between humidity and drought seemed to be between 500-600 mm in terms of annual precipitation (Table 1). We speculate that the reason for this phenomenon was that a single precipitation was thin in the region with low precipitation. This may only be enough water to infiltrate the cortex and the surface soil, and it is often lost due to evaporation. In areas with high precipitation, rainfall successfully enters the soil layer in large quantities, and this part of the water is protected by better soil texture and more organic composition created by moss [8]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Geomorphic Feature** & **Cryptogam Species** & \begin{tabular}{c} **Effects of Cryptogam on** \\ **Soil Water Content** \\ \end{tabular} & \begin{tabular}{c} **Annual** \\ **Precipitation (mm)** \\ \end{tabular} & **References** \\ \hline \begin{tabular}{c} Desert \\ Desert \\ \end{tabular} & \
\begin{tabular}{c} Natural moss-dominated crusts \\ Natural moss-dominated crusts \\ \end{tabular} & Decreasing & 95 & [46] \\
\begin{tabular}{c} Lichens: _Pson decipients_, _Diploschistes_ \\ _diacapsis_, _Collema tenax_, _Fulgensia_ \\ _bracetaa_, _Squamarina cartilageinea_, \\ _Toninia sedifolia_ and _Caloplaca tonniti_. \\ Moss: _Tortula revolvens_, _Aloina bifrus_, _Aloina aloidas_ and _Barbula trifaria_ \\ \end{tabular} & Increasing & 273 [10] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Effect of cryptogam on soil water content in zone with different annual precipitation.