Abstract:

Aims Deep soil desiccation so commonly occurs in black locust (Robinia pseudoacacia) forestlands of China’s Loess Plateau that it increasingly counteracts artificial vegetation construction. We analyzed and compared black locust forestlands under different rainfall regions in the Loess Plateau in terms of biomass and incidence and regional distribution of deep soil desiccation in order to provide scientific foundations for constructing black locust forestlands according to local conditions of the Loess Plateau.

Methods Based on datasets of weather, soil and crop parameters and simulation precision verification, we researched biomass and deep soil desiccation in the 1- to 45-year-old block of black locust forestlands of Luochuan and Changwu in the semi-humid region and Yan’an and Guyuan in the semi-arid region of the Loess Plateau from 1957 to 2001 using the WinEPIC model.

Important findings In Luochuan, Changwu, Yan’an and Guyuan, simulated annual net productivities of the 1- to 45-year-old black locust forestlands averaged 5.33 × 10³, 4.56 × 10³, 4.03 × 10³ and 3.35 × 10³ kg·hm^-2·a^-1, respectively. Productivity peaked when forestlands were 5- to 8-year-old and then tended to decrease in a pattern that followed the fluctuation of annual rainfall. In 1- to 7-year-old forestlands, annual water consumptions were higher than annual rainfalls, which resulted in soil drying at 0-10 m depth; soil desiccation rates in Luochuan, Changwu, Yan’an and Guyuan were 164.3, 165.7, 187.1 and 190.0 mm per year, respectively. In 8- to 45-year-old forestlands, the available water fluctuated at a low level within 0-250 mm as annual rainfalls varied. In 1- to 9-year-old forestlands, the 0-10 m soil humidity profiles sharply varied, with annual declines and thickening of dry soil layers. In 7- to 9-year-old forestlands dry soil layers exceeded 10 m thick, and in 8- to 45-year-old forestlands the dry soil layers had relatively stable water humidity. In forestlands of Luochuan and Changwu, the annual net productivities were high and relatively stable, and the growth periods of black locust could exceed 45 years. In forestlands of Yan’an and Guyuan, the annual net productivities were low and instable, and stable growth periods did not exceed 40 years.

Key words: biomass, Robinia pseudoacacia, soil desiccation, the Loess Plateau, WinEPIC model