Of these stress factors, water availability is often the most limiting factor and results in plant moisture stress levels that adversely affect plant physiology and morphology ( Galmés et al., 2007 Claeys and Inzé, 2013) and increase the likelihood of seedling mortality ( Allen et al., 2010 Flathers et al., 2016 Mildrexler et al., 2016). This may ultimately translate to increased survival and growth performance on harsh outplanting sites.įorest restoration planting efforts on degraded landscapes, including post-fire and mine reclamation sites, are often hindered by abiotic and biotic stress factors that influence seedling performance ( Grossnickle, 2005 Anjum et al., 2011 Grossnickle, 2012). Overall, this study shows that nursery culture irrigation limitations, regardless of the seed sources tested, can improve seedling morphology and physiological functioning under simulated dry outplanting conditions. In the simulated outplanting experiment, seedlings subjected to less irrigation in the nursery had greater mean height, diameter, needle dry mass, and stem dry mass additionally, low irrigation levels in the nursery increased the amount of hydraulically active xylem and xylem flow velocity. Irrigation treatment levels from the nursery resulted in few morphological differences however, the low irrigation level increased physiological parameters such as net photosynthetic rate and water use efficiency. In the nursery study, the lack of interactions between seed source and irrigation main effects for most response variables indicate that low irrigation treatment level responses were consistent across a range of sources. This study was conducted as two separate experiments: (1) a nursery conditioning experiment examined seedling development of three New Mexico seed sources exposed to three irrigation levels (low, moderate, and high) (2) a simulated outplanting experiment examined a subset of the seedlings from experiment 1 in a controlled outplanting environment consisting of two soil moisture conditions (mesic, maintained via irrigation and dry, irrigated only once). ![]() To address this, a study was established to test alterations in seedling characteristics subjected to irrigation limitations during nursery culture and their subsequent outplanting performance. ![]() Seedling quality has an important influence on outplanting performance, but nursery practices that typically employ optimal growing environments may also be limiting seedling morphological and physiological performance on stressful outplanting sites. ![]() Successful establishment of Pinus ponderosa seedlings in the southwestern United States is often limited by stressful and harsh site conditions related to drought severity and severe disturbances such as wildfire and mining operations. Harrington Forestry Research Center, New Mexico State University, Mora, NM, United States 2Department of Forestry, New Mexico Highlands University, Las Vegas, NM, United States.1Rocky Mountain Research Station, United States Forest Service, Moscow, ID, United States.
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