Root function and growth is critically important to the survival and performance of planted seedlings, especially in ecosystems with seasonal dry periods. In many restoration sites, limited access to soil moisture has the potential to reduce outplanting success. Root hydraulic conductance, Kr, measures the capacity of a plant’s root system to supply the shoot with water. Kr can be impacted by planting practices, environmental conditions, and subsequent seedling growth. Using techniques from plant hydraulic physiology, we conducted a greenhouse experiment to measure changes in root hydraulic conductance in Douglas-fir seedlings (Pseudotsuga menziesii) after transplanting. Douglas-fir is a key forest species in the western United States and planted Douglas-fir seedlings must survive summers with very little rainfall. We found that Kr increased linearly with seedling leaf area in well-watered conditions. However, in water-limited conditions, Kr did not increase as seedlings grew new needles, which in turn reduced photosynthesis and lowered total seedling biomass. These results indicate that water limitation changes root function even before the seedlings experience xylem cavitation and in ways that impact the water supply to the shoot. From these conclusions, we emphasize the importance of restoration practices that can mitigate water stress after planting, such as the timing of planting, site preparation methods that reduce competition for soil water, and nursery growing and handling protocols that promote high capacity for root growth. Careful attention to root quality, understanding root function, and taking actions to ensure root growth will be important for the success of restoration with planted seedlings.
Audio/Video, Conference Presentation, SER2019
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Society for Ecological Restoration