Stemflow volume per unit rainfall as a good variable to determine the relationship between stemflow amount and morphological metrics of shrubs

- Stemflow of two xerophytic shrubs were monitored during 3 growing seasons.
- Stemflow volume per unit rainfall amount (SfVPR) was used.
- Relationship between SfVPR and morphological metrics of two shrubs were quantified.

In this study, we determined the relationship between stemflow amount and morphological metrics of plants. Previous studies on this issue generally neglected the influence of differential rainfall amounts on stemflow, which somehow bias the relationship between stemflow amount and morphological metrics. Here, field observation of stemflow in two xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) of varying sizes were conducted during three growing seasons in 2011-2013 to evaluate this relationship by using a simple variable, i.e., stemflow volume per unit rainfall (SfVPR, mL mm−1). This stemflow index directly defines the influence of rainfall depth on the morphological metrics of plants, and it has the following advantages over the conventional stemflow coefficient that has been used to determine the influence of tree/shrub morphological metrics on the stemflow amount: (1) it avoids the bias caused by the influences of differential rainfall amount on stemflow yield and (2) it is suitable for use in hydrological models. Our results showed that SfVPR can well be used to determine the relationship between stemflow amount and shrub morphological metrics. Moreover, by using multiple regression model, we found that projected canopy area (or canopy volume, or basal area), plant area index, and stem diameter are the most influential factors for the stemflow amount of C. korshinskii, whereas no significant explanatory variables were found for that of A. ordosica.