Post Burn Restoration Response of Encelia virginensis within a Small Wash System in the Mojave Desert

Abstract

Spatial variation in response to restoration treatments within landscapes can be a significant but poorly understood driver of successful ecological restoration. We conducted a field experiment to assess effectiveness of out-planting restoration techniques for the native shrub Encelia virginensis across a soil hydrological gradient. We planted seedlings at five wash locations separated by varying distances based on elevation and percent slope. At each of these plots we planted seedlings, half on the side wall slopes of the wash system and half adjacent to the central wash. Seedlings received either cages, hydrogel, cages and hydrogel, or no treatments. We assessed survival and growth over 30 months. Survival declined rapidly by summer of the first year, declining to an overall rate of 24% after 30 months. Probability of survival analysis indicated a non-significant difference in survival between cage and cage plus hydrogel treatments with both varying significantly from controls. However, two months after the last hydrogel addition a significantly higher number of plants survived in the cage plus hydrogel treatment (63%) versus. all other treatments (≤ 43%) (F_12,100 = 2.39, p = 0.009), suggesting that if we continued hydrogel additions into the second year a significant difference in survival between the cage and cage plus hydrogel treatments might have occurred. Cost analysis based on comparing the control with the other treatments justified the expense of providing cages, as 79% of all surviving plants had cages.