Combined effects of cotyledon excision and nursery fertilization on root growth, nutrient status and outplanting performance of Quercus variabilis container seedlings

Artificial excision of the distal part of acorns in order to promote germination is well researched in oak seedling cultivation studies. However, studies of combined effects of cotyledon excision and nursery fertilization on container seedlings are lacking, especially for seedling root growth and outplanting performance. This study aimed to explore the main effects of cotyledon excision on Quercus variabilis seedling emergence characteristics and demonstrated the combined effects of cotyledon excision and nursery fertilization on seedling quality to improve Quercus variabilis seedling outplanting performance. Four cotyledon excision treatments and two classes of nursery fertilization were implemented. Seedling emergence was noted every week after sowing. Seedling dry mass, morphology, and nutrient status were assessed at the end of the nursery season. After the first outplanting season, the aforementioned measurements along with seedling survival were determined once again. The results showed that cotyledon excision generally induced greater and more rapid seedling emergence, but did not affect shoot emergence synchronicity. The highest total emergence and emergence rate occurred with Intermediate excision (1/2 of the distal end of acorn was excised). Effects of nutrient loss due to cotyledon excision on seedling quality and outplanting performance were somewhat compensated by nursery fertilization. Nursery fertilization promoted dry mass increment (the net increment from T0 to T2 for dry mass) for excised seedlings after outplanting, resulting in better performance for Slight (1/3 of the distal end of acorn was excised) and Intermediate excision treatments in the field. Thus we conclude Intermediate excision combined with reasonable nursery fertilization can be recommended for production of nursery grown seedlings for afforestation.为促进发芽而对橡子远端进行人工切除的方法，在栎类幼苗培育研究中已有较为充分的研究。然而，目前尚缺乏关于子叶切除与苗圃施肥对容器苗的复合效应的研究，尤其是针对幼苗根系生长与造林成活表现的相关研究。本研究旨在探究子叶切除对栓皮栎（Quercus variabilis）幼苗出苗特性的主要效应，并阐明子叶切除与苗圃施肥对幼苗质量的复合效应，以提升栓皮栎幼苗的造林成活表现。本研究设置了4种子叶切除处理与2类苗圃施肥方案。播种后每周记录幼苗出苗情况。苗圃培育期结束时，测定幼苗的干物质质量、形态特征与养分状况。首个造林季结束后，再次测定上述指标并记录幼苗存活率。结果表明，子叶切除总体上可提升出苗量并加快出苗速度，但对幼苗地上部分出苗同步性无显著影响。中度切除（切除橡子远端1/2）处理的总出苗量与出苗率最高。子叶切除导致的养分流失对幼苗质量与造林表现的负面影响，可通过苗圃施肥得到一定程度的补偿。苗圃施肥可促进切除子叶的幼苗在造林后的干物质积累量提升（即T0至T2时期干物质的净增量），使得轻度切除（切除橡子远端1/3）与中度切除处理的幼苗在田间表现更优。综上，建议将中度切除与合理的苗圃施肥相结合，用于培育造林用容器苗。