Above- and belowground dynamics of plant community succession following abandonment of farmland on the Loess Plateau, China

Aboveground and belowground changes during vegetation restoration and vegetation successions need to be characterized in relation to their individual responses to changes in soil resources. We examined above- and belowground vegetation characteristics, soil moisture, and nutrient status at the end of the growing season in 2006 in plots with vegetation succession ages of 2, 4, 6, and 8 years (two replicates each) that had been established on abandoned cropland, where potatoes had been grown for 3 years, using hoe and plow cultivation, immediately prior to vegetation clearance and subsequent natural plant colonization. A plant community comprising pioneer species [e.g., Artemisia capillaries, (subshrub)] was characterized by low levels of species richness (7.5 +/- 1.4 species m(-2)), plant density (35.7 +/- 4.2 stems m(-2)), fine root length density (940.1 +/- 90.1 m m(-2)), and root area density (2.3 +/- 0.3 m(2) m(-2)) that increased rapidly with time. Aboveground and belowground characteristics of both A. capillaries and the later successional species, Stipa bungeana (C3 perennial grass), increased in the first 6 years, but in the following 2 years A. capillaries declined while S. bungeana thrived. Thus, the fine root length density of A. capillaries, 812.4 m m(-2) after 2 years, changed by a factor of 1.7, 2.0, and 0.4 in the 4th, 6th, and 8th years, whereas that of S. bungeana changed from 278.4 m m(-2), after 4 years, and by 1.7 and 23.3 times in the 6th and 8th years, respectively. Secondary vegetation succession resulted in reduced soil moisture contents. Soil available P and N mainly influenced aboveground characteristics, while soil moisture mainly influenced belowground characteristics. However, soil moisture had no significant affect on S. bungeana belowground characteristics at the population level in this semiarid region