Abstract
Plant interactions greatly affect plant community structure. Dryland ecosystems are characterized by low amounts of unpredictable precipitation as well as by often having biological soil crusts (BSCs) on the soil surface. In dryland plant communities, plants interact mostly as they compete for water resources, and the direction and intensity of plant interaction varies as a function of the temporal fluctuation in water availability. Since BSCs influence water redistribution to some extent, a greenhouse experiment was conducted to test the hypothesis that the intensity and direction of plant interactions in a dryland plant community can be modified by BSCs. In the experiment, 14 combinations of four plant species (Artemisia ordosica, Artemisia sphaerocephala, Chloris virgata and Setaria viridis) were subjected to three levels of coverage of BSCs and three levels of water supply. The results show that: 1) BSCs affected plant interaction intensity for the four plant species: a 100% coverage of BSCs significantly reduced the intensity of competition between neighboring plants, while it was highest with a 50% coverage of BSCs in combination with the target species of A. sphaerocephala and C. virgata; 2) effects of the coverage of BSCs on plant interactions were modified by water regime when the target species were C. virgata and S. viridis; 3) plant interactions were species-specific. In conclusion, the percent coverage of BSCs affected plant interactions, and the effects were species-specific and could be modified by water regimes. Further studies should focus on effects of the coverage of BSCs on plant-soil hydrological processes.
Highlights
Plant interactions can greatly affect plant distribution, dynamics and diversity, affect plant community structure and function [1,2,3]
biological soil crusts (BSCs) coverage did not change the direction of plant interactions between the four plant species studied here; relative interaction index (RII) was significantly influenced by coverage of BSCs for A. sphaerocephala and C. virgata (Figure 1)
Our results showed that percent BSCs coverage had a strong effect on plant interactions (Table 1)
Summary
Plant interactions can greatly affect plant distribution, dynamics and diversity, affect plant community structure and function [1,2,3]. Competition (negative effects) has long been thought to be a mechanism to promote community stability in a variable environment [4,5]; on the other hand, facilitation (positive effects) has been considered to be a positive mechanism for community succession [6,7]. Dryland ecosystems are characterized by low amounts of unpredictable precipitation [14,15,16,17], such as occurs in the arid and semiarid areas of China Such arid and semiarid ecosystem often possess vegetation with sparse aboveground organs but dense below-ground organs, as well as often being associated with biological soil crusts (BSCs) on the soil surface [18,19]. P,0.05 is shown in boldface as significant. doi:10.1371/journal.pone.0087713.t001
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