Plant morphological and functional characteristics combined with elevation and aspect influence phytogenic mound parameters in a dry-hot valley

Abstract

Isolated plants growing on steep slopes with erodible bedrock are usually associated with the formation of phytogenic mounds in semiarid and arid ecosystems. Identifying the plant characteristics that affect phytogenic mounds and predicting a plant community’s potential for erosion control are of great interest to workers seeking to improve the management of degraded ecosystems. We studied the phytogenic mounds of three dominant perennial grass species found between 1,400 and 1,700 m above sea level in Jiangjiagou Gully: <i>Heteropogon contortus, Eulaliopsis binata</i>, and <i>Eriophorum comosum</i>. Morphological and functional characteristics were measured for a total of 42 individuals from the three grass species on both sunny and shady slope aspects. Soil samples were collected from the mounds and from bare land 30 cm upslope from each mound to determine particle size distribution. Morphological and functional characteristics, as well as mound parameters, were summarized using principal component analysis (PCA). Pearson’s correlation analysis, linear regression analysis, and redundancy analysis were conducted to identify the relationships between plant characteristics and mound parameters. Then we used analysis of covariance to examine the combined effects of aspect and elevation and plant characteristics on mound parameters. We found that there are no differences in morphological characteristics, functional characteristics, or mound parameters between the three grass species, or soil particle size distribution between mounds and bare land. PCA shows that mound parameters are best correlated (positively) with interception length and total dry weight. Crown length in the direction of the slope and root width are also positively correlated with maximum height and maximum width but to a lesser extent. Plant morphological and functional characteristics can explain greater than 60% of the variance of all mound parameters except maximum length, with the greatest contributions from crown length and interception length. Aspect and elevation, combined with some plant characteristics, also affected mound parameters. Our study indicates that perennial grass species can accumulate sediment deposits during growth in a dry-hot valley. Our results provide useful information for evaluating the function of plants in erosion control and for identifying ways to improve the effectiveness of species in mound formation in dry-hot valley ecosystems.