Abstract
Abstract. In the quest to understand how biotic interactions respond to climate change, one area that remains poorly explored is how interactions involving organisms other than vascular plants will respond. However the interactions between plants and biological soil crusts (BSCs) are relevant in many ecosystems and they will likely respond uniquely to climate change. Simultaneous considerations of both plant–plant and plant–BSC interactions may substantially improve our understanding of this topic. The aim of this study is to assess whether water availability differentially affects the biotic effects of BSCs and pioneer shrubs on the early life-history stage of tree seedling growth. We conducted a greenhouse factorial experiment with soil surface cover (bare soil, soil covered by a creeping shrub and BSC covered soil) and water regime (control and drought) as factors. We monitored Nothofagus pumilio (a native tree species of ecological and economic relevance) seedling water status and growth as well as changes in soil water content and soil properties. The shrub cover had a positive effect on soil water conservation and on the water balance of seedlings under water stress. However, its effect was negative for seedling growth under both water conditions. The BSC also contributed to soil water conservation and apparently added nutrients to the soil. The net effect of the BSC on seedling growth was negative under full-watering conditions but positive under water stress conditions. This result highlights how the studied biotic interactions, and especially interactions involving BSCs, depend on changes in water availability.
Highlights
Interest in studying the impacts of biotic interactions and environmental change is growing since it is clear that biotic interactions play a central role in how plant communities may respond to global change (Tylianakis et al, 2008)
Soil volumetric water content (VWC) rapidly dropped below 5 % v/v after 10 d for bare soil, while persisting for about 20 d above 5 % v/v for crusted soils and was above 10 % v/v for the soils covered by E. rubrum (Fig. 2b, d, f)
In the initial soil samples, we found differences in most chemical and physical variables measured among soils covered by biological soil crusts (BSCs), bare soils, or soils covered by E. rubrum (Table 1)
Summary
Interest in studying the impacts of biotic interactions and environmental change is growing since it is clear that biotic interactions play a central role in how plant communities may respond to global change (Tylianakis et al, 2008). Plants influence their surrounding environment, changing microclimatic conditions by altering radiation, air and soil temperatures (Callaway and Walker, 1997). These environmental changes and their impact on other organisms in turn interact with changes in macroclimatic conditions. The future climate plants will experience will depend on global change scenarios and on neighboring organisms.
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