Nursery stock quality as an indicator of bottomland hardwood forest restoration success in the Lower Mississippi River Alluvial Valley

Abstract

Seedling morphological quality standards are lacking for bottomland hardwood restoration plantings in the Lower Mississippi River Alluvial Valley, USA, which may contribute toward variable restoration success. We measured initial seedling morphology (shoot height, root collar diameter, number of first order lateral roots, fresh mass, and root volume), second year field heights and diameters, survival, browse, and top dieback of five species – cherrybark oak (Quercus pagoda Raf.), green ash (Fraxinus pennsylvanica Marsh.), Nuttall oak (Q. nuttallii Palmer), sweet pecan (Carya illinoensis (Wangenh.) K. Koch), and water oak (Q. nigra L.). Seedlings were obtained from three regional nurseries (Arkansas, Louisiana, and Mississippi), planted on three sites (Arkansas, Louisiana, and Mississippi), and treated with or without chemical weed control. Site×nursery interaction and weed control (without interactions) usually affected survival, whereas site×weed control interaction and nursery (without interactions) influenced second year heights and diameters. Weed control generally increased survival rates, as well as second year height and diameter. Effects of initial morphological characteristics on field survival and height and diameter growth were generally dependent on the other morphological parameters. Target morphological characteristics were identified as 99, 84, and 82 in height/diameter ratios (equal units) for cherrybark oak, green ash, and Nuttall oak, respectively; mean initial height of 40–43 cm in sweet pecan; and mean initial fresh mass/root volume of 2.7 g ml⁻¹ in water oak. Seedlings with means above these values may be more susceptible to dieback or mortality after outplanting, likely associated with excessive shoot relative to root biomass.

Keywords:

• Afforestation
• competition control
• field performance
• growth
• hardwood seedling quality

Acknowledgements

The USDA Forest Service Bottomland Hardwoods Laboratory in Stoneville, Mississippi provided significant funding, personnel, and site resources to help conduct this study. This research was further supported by the USDA Forest Service State and Private Forestry and the Hardwood Tree Improvement and Regeneration Center at Purdue University. We wish to thank State Forestry Agencies in Arkansas, Louisiana, and Mississippi for their interest in our research and seedling donations. We also appreciate important feedback from the National Resources Conservation Service. Mats Hannerz and two anonymous reviewers provided helpful comments that improved the article.