Abstract
Salix psammophila has been used for tree planting in the Ordos Plateau in China. We estimated the standing crop of Salix psammophila according to the allometric relation based on various measurements of Salix psammophila growing on a wet lowland, sand-covered lowland, and sand dune. The investigated area in the wet lowland and sand-covered lowland was 2 × 2m2. The investigated area in the sand dune was sampled when necessary because individual trees are sparsely distributed. The dry trunk weight and the dry branch weight of each individual tree of Salix psammophila are proportional to those of (D5) 2H. The dry leaf weight is roughly proportional to the square of D5 and DHB, . Based on these results, we determined a formula for estimating the dry weight and coefficient according to (D5) 2 and (D5) 2 H. As a result of investigating the standing crop on the ground, the standing crop on the wet lowland is 867.3 (g · m-2), and the standing crop on the sand-covered lowland is 408.3 (g · m-2). To calculate the coefficient of the estimation formula, the sample count required to acquire a sufficiently reliable section was examined, and the value that provides a reliable section within the range of ± 10% was acquired.
Next, we dug up and investigated the rootstocks of the Salix psammophila to determine the underground status under different location conditions. For the wet lowland and the sand-covered lowland, the root amount was measured in an area of 1 × 1 m2. For the sand dune, the root amount was measured in an area of 2.5 × 4 m2 at intervals of 10 cm depth because the rootstocks are widely distributed. The rootstocks on wet lowland are horizontally distributed, meanwhile the rootstocks on sand-covered lowland are vertically distributed to deep depths. The rootstocks on sand dune are distributed collectively at two points: one point near the ground surface and another point 50 cm or deeper from the ground surface.
