The tradeoff strategy between growth and survival in Quercus variabilis seedlings: determining the most limiting resource in the field drive shoot dieback

Abstract

Shoot dieback is an important survival strategy in juvenile Quercus spp. However, it is unknown how nursery practices can influence the regulatory mechanisms of shoot dieback after planting. Furthermore, there is scarce information about the interactive effects between container depth and nursery fertilization on field seedling performance, and in combination with field weed control. Here, Quercus variabilis seedlings were cultivated the first year in with two container depths (25 cm, D40; 36 cm, D60) and with two nitrogen-loading levels (25, N25; 100 mg seedling−1, N100) in the nursery, and the following year, they were out-planted with/without weed elimination. We evaluated first year seedlings’ functional traits after nursery culture (plant and root morphology and nutritional status) and second year field performance (survival, shoot dieback, growth and nutrient increments), and their relationship. Independently of nursery culture, weed management was an irreplaceable practice to optimize seedling field performance. Seedlings grown in deep containers (D60) showed enhanced field growth and nutrient acquisition and reduced shoot dieback. Fertilization increased N and K loading (content and concentration) in the nursery, but showed no effect in the field. Low quality seedlings (low fertilization and normal container) maintained high survival rates at the expense of increasing shoot dieback rate. Thus, field survival did not differ among seedlings with differing nursery practices. Together, deep container and high N fertilization, increased plant nutritional reserves (content) and improved root system development, consequently, mitigating field shoot dieback. Under our experimental conditions, improved seedling quality by the use of deep container (D60) was sufficient to optimize field seedling performance without weed competition. However, both, deep container and nitrogen loading (D60-N100) were the best nursery practices to optimize seedling success without weed control in the field. Our study highlights that shoot dieback is a paramount trade-off strategy between growth and survival, which should be considered as an important indicator for further evaluating seedling field performance.