Vertical distribution of fine root area in relation to stand age and environmental factors in black locust (Robinia pseudoacacia L.) forests of the Chinese Loess Plateau

To examine the tempo-spatial characteristics of fine root area distribution and its relationship with stand age and environmental factors in black locust on the Chinese Loess Plateau, black locust stands were selected at four sites along a precipitation gradient, four stands of different ages and a transect along a hillslope were also selected at one of the sites. With increasing stand age, fine root area at tree level increased exponentially, and the rooting pattern tended to be deeper for trees up to 15-years-old and then shallower thereafter. The temporal changes of fine root distribution could be quantified using stand age and soil nutrients. At the hillslope scale, fine root area index (FRAI) was lower while the rooting pattern was deeper in the middle slope than upper and lower slope, and the fine root distribution could be quantified using elevation and soil properties. At the regional scale, FRAI decreased substantially while exhibited similar rooting patterns with decreasing soil water and nutrients availability along the precipitation gradient. Humidity index represented the regional environmental variation and could be used to quantify FRAI. These findings will be helpful for improving quantification of fine roots and enhancing the accuracy of eco-hydrological models.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author