Abstract:

The introduction of Robinia pseudoacacia (RP) has some effects on undergrowth herbaceous plants (UH), soil properties and their relationships, which may be related to the vegetation zone. However, few studies have tested effects of RP on UH and soil over a large-scale area of the Loess Plateau.

The study area consisted of three vegetation zones (the steppe, forest-steppe and forest zone). Two canopy plant types were selected: RP stands and adjacent native vegetation. We measured five leaf functional traits: leaf carbon content (LC), leaf nitrogen content (LN), leaf phosphorus content (LP), specific leaf area (SLA) and leaf tissue density (LTD). The functional diversity, species diversity and community-weighted mean (CWM) traits were calculated.

(i) CWM.LN, CWM.LP and CWM.SLA increased significantly, whereas CWM.LC and CWM.LTD decreased significantly in the three vegetation zones, compared with the native communities. (ii) Species diversity, functional diversity and community biomass decreased in the steppe zone, increased in the forest zone, and did not differ significantly in the forest-steppe zone. (iii) We found only soil organic carbon (P < 0.05) and soil total nitrogen (P < 0.05) in the forest zone decreased significantly compared with the native plots. (iv) The relationship between UH and soil properties was affected by RP and the vegetation zone. Overall, the effect of RP on UH and soil properties was associated with the vegetation zone. This result is of great significance to the planning of restoration and reconstruction of artificial forests in the Loess Plateau.

Key words: community-weighted mean traits, functional diversity, Robinia pseudoacacia, species diversity, Yanhe river basin