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Anthropogenic activity has caused persistent and prominent losses of forest cover in dry tropical forests. Natural regeneration of forest trees in grazed areas often fails due to lack of seed sources and consumption by ungulates. To address this, the effective restoration of such sites often requires fencing and outplanting nursery-grown seedlings. In the degraded, dry forests of tropical Hawaii, USA, an additional challenge to restoration of native forest trees is the introduced kikuyu grass (Cenchrus clandestinus). This invasive, rapidly growing rhizomatous plant forms deep, dense mats. We studied the use of nursery cultural techniques to facilitate the establishment of koa (Acacia koa) seedlings outplanted amidst well-established kikuyu grass on a volcanic cinder cone on the dry, western side of Hawaii Island. Seedlings were grown four months in three container sizes (49, 164, 656 cm3) and with four rates (0, 4.8, 7.2, and 9.6 kg m−3) of 15–9–12 (NPK) controlled-release fertilizer incorporated into media prior to sowing. After 16 months in the field, seedling survival was > 80% for all treatments with two exceptions: the non-fertilized 49 cm3 (78%) and 164 cm3 (24%) containers. After 10 years, only these two treatments had significantly lower survival (35% and 10%, respectively) than the other treatments. One year following planting, none of the non-fertilized seedlings had transitioned to phyllodes from juvenile true leaves, regardless of container size. For the fertilized 656 cm3 container treatment, 78%–85% of seedlings had phyllodes, with mean values increasing by fertilizer rate. Phyllodes are known to confer greater drought resistance than true leaves in koa, which may help to explain the improved survival of fertilized trees on this relatively dry site. Overall, nursery fertilization was more influential on seedling height and diameter response than container size after outplanting. However, the largest container (656 cm3) with the addition of fertilizer, produced significantly larger trees than all other treatments during the early regeneration phase; early growth differences tended to fade at 10 years due to inter-tree canopy competition. Although koa is able to fix atmospheric nitrogen through rhizobium associations, our data confirm the importance of nursery fertilization in promoting regeneration establishment. Nursery cultural techniques may play an important role in forest restoration of dry tropical sites invaded by exotic vegetation.
Douglass F. Jacobs; Anthony S. Davis; R. Kasten Dumroese; Owen T. Burney. Nursery Cultural Techniques Facilitate Restoration of Acacia koa Competing with Invasive Grass in a Dry Tropical Forest. Forests 2020, 11, 1124 .
AMA StyleDouglass F. Jacobs, Anthony S. Davis, R. Kasten Dumroese, Owen T. Burney. Nursery Cultural Techniques Facilitate Restoration of Acacia koa Competing with Invasive Grass in a Dry Tropical Forest. Forests. 2020; 11 (11):1124.
Chicago/Turabian StyleDouglass F. Jacobs; Anthony S. Davis; R. Kasten Dumroese; Owen T. Burney. 2020. "Nursery Cultural Techniques Facilitate Restoration of Acacia koa Competing with Invasive Grass in a Dry Tropical Forest." Forests 11, no. 11: 1124.
Christina M St John; Anthony S Davis. Seed coat permeability and germination requirements of snowberry (Symphoricarpos albus (L.) S.F. Blake). Native Plants Journal 2020, 21, 334 -340.
AMA StyleChristina M St John, Anthony S Davis. Seed coat permeability and germination requirements of snowberry (Symphoricarpos albus (L.) S.F. Blake). Native Plants Journal. 2020; 21 (3):334-340.
Chicago/Turabian StyleChristina M St John; Anthony S Davis. 2020. "Seed coat permeability and germination requirements of snowberry (Symphoricarpos albus (L.) S.F. Blake)." Native Plants Journal 21, no. 3: 334-340.
Subirrigation (SI), where water is provided to container seedlings from below and rises through the growing media via capillary action, is regarded as an environmentally-responsible method of delivering water and fertilizer to nursery-grown plants, resulting in more uniform crops and improved production efficiency. While a concern around adopting this method is that a potential higher salt concentration in the upper layers of growing media under SI may inhibit root growth and result in decreased plant quality, few studies have focused on how root morphology is altered by SI. Therefore, a balanced two-factor factorial design with three rates of fertilization (50, 100, and 150 mg N seedling−1) and two irrigation methods (SI or overhead irrigation (OI)) was used to examine the growth response of Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr) seedlings for one nursery season. Associated changes between rhizosphere electrical conductivity (EC) and root morphology of different root size classes were analyzed. Results show that (1) height, root-collar diameter, and root volume were similar between seedlings grown under SI and OI. However, (2) compared to seedlings receiving OI, SI-seedlings had less root mass, length, and surface area but greater average root diameter (ARD). (3) Morphological differences were evident primarily in root diameter size classes I–III (D ≤ 1.0 mm). (4) Fertilizer rate influenced root length and surface area up to 130 days after sowing but affected ARD throughout the growing season such that seedlings treated with 50 mg N had smaller ARD than seedlings treated with 100 mg N. (5) As the growing season progressed, SI-media had significantly higher EC compared to OI-media and EC increased with increasing fertilizer rate under SI but not under OI. These results indicate that SI can produce larch seedlings of similar height and root collar diameter (RCD) compared to OI, but root systems are smaller overall with fewer small-diameter roots, which may be related to high EC levels in SI-media, which is exacerbated by the use of high rates of fertilizer. Therefore, the EC in the media should be monitored and adjusted by reducing fertilizer rates under SI.
Fangfang Wan; Amy L. Ross-Davis; Wenhui Shi; Christopher Weston; Xiehai Song; Xiaochao Chang; Anthony S. Davis; Yong Liu; Fei Teng. Subirrigation Effects on Larch Seedling Growth, Root Morphology, and Media Chemistry. Forests 2019, 10, 38 .
AMA StyleFangfang Wan, Amy L. Ross-Davis, Wenhui Shi, Christopher Weston, Xiehai Song, Xiaochao Chang, Anthony S. Davis, Yong Liu, Fei Teng. Subirrigation Effects on Larch Seedling Growth, Root Morphology, and Media Chemistry. Forests. 2019; 10 (1):38.
Chicago/Turabian StyleFangfang Wan; Amy L. Ross-Davis; Wenhui Shi; Christopher Weston; Xiehai Song; Xiaochao Chang; Anthony S. Davis; Yong Liu; Fei Teng. 2019. "Subirrigation Effects on Larch Seedling Growth, Root Morphology, and Media Chemistry." Forests 10, no. 1: 38.
Water conservation in nursery systems is an ever-increasing focus, yet there is relatively little guidance for growers producing seedlings intended for restoration regarding how practices such as subirrigation influence plant growth in the nursery and after outplanting. Our study investigated red-flowering currant (Ribes sanguineum Pursh) seedling development and early field performance using different fertilizer treatments under a subirrigation regime. Plants were fertilized with 1) incorporated organic fertilizer, 2) incorporated controlled-release fertilizer, 3) top-dressed controlled-release fertilizer, or 4) water-soluble fertilizer. We found that seedlings grown with organic fertilizer used significantly less water than all other treatments. Media electrical conductivity (EC) levels were significantly greater in the organic fertilizer treatment, and EC values in the top portion of the media were significantly greater than the middle or bottom portions for all fertilizer treatments. The remaining subirrigation water at the end of 22 weeks held 17% of applied nitrogen (N) from the water-soluble fertilizer treatment and less than 1% of applied N from the other fertilizer treatments. We observed no differences in plant morphology among fertilizer treatments. Seedlings were subsequently out-planted into low- and high-competition treatments, where myriad factors indicated reduced growth among high-competition compared with low-competition plots, highlighting that competition for soil water limited seedling performance. These results indicate that a variety of fertilizers can be used to grow red-flowering currant under subirrigation and that postplanting growth is enhanced with control of competing vegetation.
Layla J. Dunlap; Jeremiah R. Pinto; Anthony S. Davis. Effects of Fertilizer on Media Chemistry and Red-flowering Currant Seedling Growth Using a Subirrigation System. HortScience 2018, 53, 1862 -1871.
AMA StyleLayla J. Dunlap, Jeremiah R. Pinto, Anthony S. Davis. Effects of Fertilizer on Media Chemistry and Red-flowering Currant Seedling Growth Using a Subirrigation System. HortScience. 2018; 53 (12):1862-1871.
Chicago/Turabian StyleLayla J. Dunlap; Jeremiah R. Pinto; Anthony S. Davis. 2018. "Effects of Fertilizer on Media Chemistry and Red-flowering Currant Seedling Growth Using a Subirrigation System." HortScience 53, no. 12: 1862-1871.
Despite advances in restoration of degraded lands around the world, native plants are still underused. Selection of appropriate plant materials is a critical factor in determining plant establishment and persistence. To inform decision‐making, we examined cold hardiness dynamics, flowering phenology, and survival among five geographically distinct sulphur‐flower buckwheat (Polygonaceae: Eriogonum umbellatum Torr.) populations in a common garden. LT50 (a measure of freezing injury) was determined every 6 weeks across a complete year; one population was also evaluated at the source. Cold hardiness dynamics were similar across populations, with annual fluctuations in mean LT50 exceeding 40°C. Rate of deacclimation (i.e., loss of cold tolerance) in spring varied across populations and was not related to the elevation from which a population came. Plants were less cold‐hardy in October 2014 compared to October 2013, likely reflecting a response to colder local conditions in 2013. Although the range of LT50 was similar for a single comparison of common garden versus wild‐grown plants, wild‐grown plants acclimated and deacclimated earlier than common garden‐grown plants. Plants derived from a low‐elevation population showed delayed flowering phenology, while high‐elevation populations showed earliest flowering phenology, with one high‐elevation population having the lowest survival rate in the common garden. These results suggest that, despite considerable plasticity in seasonal cold hardiness dynamics, population variability in deacclimation and flowering phenology have implications for selection and movement of sulphur‐flower buckwheat for ecological restoration. This article is protected by copyright. All rights reserved.
Matthew R. Fisk; Kent G. Apostol; Amy L. Ross‐Davis; Dexter O. Cahoy; Anthony S. Davis. Informing native plant sourcing for ecological restoration: cold‐hardiness dynamics, flowering phenology, and survival ofEriogonum umbellatum. Restoration Ecology 2018, 27, 616 -625.
AMA StyleMatthew R. Fisk, Kent G. Apostol, Amy L. Ross‐Davis, Dexter O. Cahoy, Anthony S. Davis. Informing native plant sourcing for ecological restoration: cold‐hardiness dynamics, flowering phenology, and survival ofEriogonum umbellatum. Restoration Ecology. 2018; 27 (3):616-625.
Chicago/Turabian StyleMatthew R. Fisk; Kent G. Apostol; Amy L. Ross‐Davis; Dexter O. Cahoy; Anthony S. Davis. 2018. "Informing native plant sourcing for ecological restoration: cold‐hardiness dynamics, flowering phenology, and survival ofEriogonum umbellatum." Restoration Ecology 27, no. 3: 616-625.
Haiti has suffered great losses from deforestation, with little forest cover remaining today. Current reforestation efforts focus on seedling quantity rather than quality. This study examined limitations to the production of high-quality seedlings of the endemic Hispaniolan pine (Pinus occidentalis Swartz). Recognizing the importance of applying sustainable development principles to pine forest restoration, the effects of growing media and container types on seedling growth were evaluated with the goal of developing a propagation protocol to produce high-quality seedlings using economically feasible nursery practices. With regard to growing media, seedlings grew best in compost-based media amended with sand. Topsoil, widely used in nurseries throughout Haiti, produced the smallest seedlings overall. Despite a low water holding capacity and limited manganese, compost-based media provided adequate levels of essential mineral nutrients (particularly nitrogen), which allowed for sufficient seedling nutrition. Seedling shoot and root growth, as well as the ratio of shoot biomass to root biomass, were greater in polybags relative to D40s. Results indicate that economically feasible improvements to existing nursery practices in Haiti can improve the early growth rates of P. occidentalis seedlings.
Kyrstan L. Hubbel; Amy L. Ross-Davis; Jeremiah R. Pinto; Owen T. Burney; Anthony S. Davis. Toward Sustainable Cultivation of Pinus occidentalis Swartz in Haiti: Effects of Alternative Growing Media and Containers on Seedling Growth and Foliar Chemistry. Forests 2018, 9, 422 .
AMA StyleKyrstan L. Hubbel, Amy L. Ross-Davis, Jeremiah R. Pinto, Owen T. Burney, Anthony S. Davis. Toward Sustainable Cultivation of Pinus occidentalis Swartz in Haiti: Effects of Alternative Growing Media and Containers on Seedling Growth and Foliar Chemistry. Forests. 2018; 9 (7):422.
Chicago/Turabian StyleKyrstan L. Hubbel; Amy L. Ross-Davis; Jeremiah R. Pinto; Owen T. Burney; Anthony S. Davis. 2018. "Toward Sustainable Cultivation of Pinus occidentalis Swartz in Haiti: Effects of Alternative Growing Media and Containers on Seedling Growth and Foliar Chemistry." Forests 9, no. 7: 422.
Douglas fir (Pseudotsuga menziesii var. glauca (Mayr) Franco), and western larch (Larix occidentalis Nutt.) are species of ecological and commercial importance that occur throughout the Western United States. Effective reforestation of these species relies on successful seedling establishment, which is affected by planting stock quality, stocktype size, and site preparation techniques. This study examined the effects of container volume (80, 130, 200, and 250 cm3) and vegetative competition on seedling survival and physiological and morphological responses for two years, post-outplanting. Glyphosate application (GS) and grass planting (HC) were used to achieve low and high levels of competition. For all measured attributes, the container volume × vegetative competition was not significant. Mortality was strongly influenced by competition, with higher mortality observed for Douglas fir and western larch planted in HC plots one (28% and 98%) and two (61% and 99%) years following outplanting. When competition was controlled, seedlings of both species exhibited greater net photosynthesis (>9 μmol m−2 s−1), greater predawn water potential (>−0.35 MPa), and lower mortality (2–3%) following one year in the field, indicating establishment success. The 80 cm3 stocktype remained significantly smaller and exhibited lower growth rates for the duration of the study, while all other stocktypes were statistically similar. Our results demonstrate the importance of controlling vegetative competition regardless of stocktype, especially for western larch, and suggest that benefits to post-planting seedling physiology and growth in relation to container size plateau beyond 130 cm3 among the investigated stocktypes.
Jeremiah R. Pinto; Bridget A. McNassar; Olga A. Kildisheva; Anthony S. Davis. Stocktype and Vegetative Competition Influences on Pseudotsuga menziesii and Larix occidentalis Seedling Establishment. Forests 2018, 9, 228 .
AMA StyleJeremiah R. Pinto, Bridget A. McNassar, Olga A. Kildisheva, Anthony S. Davis. Stocktype and Vegetative Competition Influences on Pseudotsuga menziesii and Larix occidentalis Seedling Establishment. Forests. 2018; 9 (5):228.
Chicago/Turabian StyleJeremiah R. Pinto; Bridget A. McNassar; Olga A. Kildisheva; Anthony S. Davis. 2018. "Stocktype and Vegetative Competition Influences on Pseudotsuga menziesii and Larix occidentalis Seedling Establishment." Forests 9, no. 5: 228.
Diminishing milkweed (Asclepias sp.) populations are contributing to the conspicuous decline of the iconic monarch butterfly (Danaus plexippus). This research sought to improve milkweed propagation success, a core component of summer habitat restoration projects. Specifically, this research assessed the effects of container volume and fertilizer application rate on growth and first year field survival of two species of milkweed common to western North America, namely showy milkweed (A. speciosa) and narrowleaf milkweed (A. fascicularis). Generally, larger roots and shoots developed when plants were given the high rate of fertilizer (6.5 g·L−1) and when reared in the largest containers (2600 mL). For narrowleaf milkweed, nearly all plants developed a firm plug (i.e., one in which the root system remained intact when removed from the container) after 22 weeks. Most narrowleaf milkweed plants flowered 15 weeks after sowing when grown in the largest container with either the low (2.7 g·L−1) or high fertilizer rate or the midsized container (444 mL) with a high rate of fertilizer. For showy milkweed, a firm plug developed for nearly all individuals by the end of the growing season only when given the high fertilizer rate. None of the showy milkweed plants developed an inflorescence by 15 weeks. Results of this research improve our understanding of milkweed propagation and will aid in the efforts to restore the monarch butterfly’s summer breeding habitat by providing propagation protocols across a range of stocktypes.
Nikki Hanson; Amy L. Ross-Davis; Anthony S. Davis. Growth and Survival of Two Western Milkweed Species: Effects of Container Volume and Fertilizer Rate. HortTechnology 2017, 27, 482 -489.
AMA StyleNikki Hanson, Amy L. Ross-Davis, Anthony S. Davis. Growth and Survival of Two Western Milkweed Species: Effects of Container Volume and Fertilizer Rate. HortTechnology. 2017; 27 (4):482-489.
Chicago/Turabian StyleNikki Hanson; Amy L. Ross-Davis; Anthony S. Davis. 2017. "Growth and Survival of Two Western Milkweed Species: Effects of Container Volume and Fertilizer Rate." HortTechnology 27, no. 4: 482-489.