Abstract:

Aims We selected three representative grasses in Horqin Sandy Land and measured their root dynamic by minirhizotrons, a nondestructive, in situ method for directly viewing and studying root dynamics.

Methods The experiment was conducted on three quarters (2 m×2 m) of Naiman Desertification Research Station, Chinese Academy of Sciences during the 2005 growing season. The sandy soil was transported from a sandy dune and sifted through a 0.5 mm sieve. On May 15, seeds ofSetaria viridis, Artemisia scoparia and Agriophyllum squarrosum were cultivated in each quarter, respectively. Three minirhizotrons (50 cm long and 7 cm outer diameter) per treatment were installed at right angles. A black cover blocked light from entering the section of the transparent tube left above ground. For each treatment, three tubes were installed in the center parallel to the plant row, 10 cm from the row. Each quarter was supplied with enough water until June 5, and thereafter precipitation was the only water source. According to plant needs, seedlings of three grasses were kept 15 cm apart in rows and 20 cm apart between rows. The number of roots on the minirhizotron wall was obtained using a mirror, and root length was estimated counting the number of intersections of roots with a 1 cm-mesh grid, using the modified Newman-Line-Intersect method.

Important findings The curves of total root number of S. viridis and Artemisia scoparia after seed germination fitted a cubic regression model, while that of Agriophyllum squarrosum showed exponential increase. The production of S. viridis and Artemisia scoparia peaked by the end of July or the beginning of August and then decreased, while Agriophyllum squarrosum showed an opposite trend. Roots of S. viridis were concentrated within the top 30 cm of the soil profile where the maximum root length intensity achieved 2.23 cm·cm^-2. Vertical root distribution of S. scoparia had an almost symmetrical pattern. At the prophase of growth period, it preferentially developed superficial roots, while at the end of the growth period, roots occurred dominantly in deep soil. In contrast, Agriophyllum squarrosum showed an opposite growth process. S. viridis had the highest root length intensity during the prophase and early in the growth period, but root length intensity of Agriophyllum squarrosum was higher than S. viridis at the end of the growth period.

Key words: minirhizotrons, annual grasses, root growth dynamic, Horqin Sandy Land