Data from: Acorn size is more important than nursery fertilization for outplanting performance of Quercus variabilis container seedlings
Description
Planting seedlings is the most common forestation method in oak restoration projects. Small acorns are usually discarded for seedling cultivation because they result in poor quality seedlings. However, this can potentially reduce genetic diversity of planted stocktype. A possible way to compensate for the potential lower quality of small acorn seedlings is to cultivate them at high fertilization rates. The objectives of this study were to assess the effect of acorn size on seedling out-planting performance, and to determine if nursery fertilization interacts with acorn size to determine seedling performance both at the end of nursery cultivation and after planting in a forestation site. Acorns from 20 individual trees were classified into large, medium, and small according to their fresh weight and cultivated under two contrasting nursery fertilization conditions (no fertilization and fertilized with 100 mg N per plant). Seedling emergence, morphology and tissue nutrient status was assessed at the end of the cultivation. Field survival and growth after transplanting in a forest site were also investigated for two years. Compared to medium and large acorns, small acorns represented 18% of the studied lot and showed lower moisture (3-5% less), nutrient content and emergence (55% less). When cultivated without fertilizer, small acorns resulted in smaller seedlings with lower nutrient concentration than medium and large acorn seedlings. Nursery fertilization increased slightly seedling growth and similarly for all acorn types but strongly increased nutrient concentration, especially in small acorn seedlings at the end of cultivation. Outplanting survival was not affected by nursery fertilization but small acorn seedlings showed 32% less survival than medium and large acorn plants. Conversely, fertilization increased outplanting growth similarly among acorn size classes and small acorn plants showed lower growth than medium and large acorn plants, with no differences among them. We conclude that with the fertilization rate used in this study acorn size is more determinant than fertilization for seedling quality and field performance. Fertilization increases seedling quality of plants grown from small acorn, but this increase did not translate into a significant increase in field performance.