Differences in morphological and physiological plasticity in two species of first-year conifer seedlings exposed to drought result in distinct survivorship patterns

2019 ◽  
Vol 39 (8) ◽  
pp. 1446-1460 ◽  
Author(s):  
Steven P Augustine ◽  
Keith Reinhardt
Keyword(s):  
Drought Tolerance ◽  
Pinus Ponderosa ◽  
Seedling Survival ◽  
Life Stage ◽  
Carbon Gain ◽  
Leaf Water Content ◽  
First Year ◽  
Carbon Budgets ◽  
Conifer Seedlings ◽  
Water Potentials

Abstract First-year tree seedlings represent a critical demographic life stage, functioning as a bottleneck to forest regeneration. Knowledge of how mortality is related to whole-seedling carbon and water relations is deficient and is required to understand how forest compositions will be altered in future climatic conditions. We performed a greenhouse drought experiment using first-year seedlings of two common pine species found in the Intermountain West, USA. Gas exchange, biomass gain, allometry and xylem water potentials were compared between well-watered and droughted seedlings from emergence until drought-induced mortality. In both species, morphological adjustments to confer drought tolerance, such as increased leaf mass per unit area, were not observed in seedlings exposed to drought, and droughted seedlings maintained photosynthesis and whole-seedling carbon gain well into the experiment. Yet, there were important differences between species in terms of carbon budgets, physiological responses and mortality patterns. In Pinus ponderosa P. & C. Lawson, physiological acclimation to drought was much greater, evident through stronger stomatal regulation and increased water-use efficiency. Photosynthesis and carbon budgets in P. ponderosa were greater than in Pinus contorta Dougl. ex. Loud., and survival was 100% until critical hydraulic thresholds in leaf water content and seedling water potentials were crossed. In P. contorta, physiological adjustments to drought were less, and mortality occurred much sooner and well before injurious hydraulic thresholds were approached. First-year conifer seedlings appear canalized for a suite of functional traits that prioritize short-term carbon gain over long-term drought tolerance, suggesting that conifer seedling survival is linked with carbon limitations, even during drought, with survival in species having narrower carbon survival margins being more hampered by carbon limitations.

scholarly journals 102 EFFECT OF BACKFILL AND PLANTING BED AMENDMENTS ON GROWTH AND DROUGHT TOLERANCE OF ACER RUBRUM

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 442g-443
Author(s):  
Timothy J. Smalley ◽  
Carleton B. Wood
Keyword(s):  
Drought Tolerance ◽  
Root Growth ◽  
Shoot Growth ◽  
Nitrogen Deficiency ◽  
Acer Rubrum ◽  
Pine Bark ◽  
Leaf Water Content ◽  
First Year ◽  
Native Soil ◽  
Expanded Shale

Commonly used planting techniques and soil amendments were compared to determine their effect on root growth, shoot growth, and drought tolerance of 2.5 cm caliper Acer rubrum. Study I: Trees were planted on 6 April 1992 into holes backfilled with 1) native soil, 2) 50% aged pine bark: 50% native soil, 3) 50% Mr. Natural™:50% native soil, or 4) 100% Mr. Natural™. Mr. Natural™ consists of granite sand, expanded shale, and composted poultry litter. After two years, no differences in growth or survival existed. Study II: On 8 April 1992, trees were planted in 1) unamended planting holes, 2) tilled planting beds, or 3) tilled and pine bark-amended planting beds. Five months after planting, the root growth in the tilled and tilled-amended beds did not differ, but both had more root growth than planting holes. Amendment-induced nitrogen deficiency reduced shoot growth of the tilled-amended treatment during the first year. After two years, the planting hole treatment exhibited the least shoot growth, while shoot growth of tilled and tilled-amended treatments did not differ. StudyIII: Selected trees in study II were drought stressed for 8 weeks beginning 4 August 1993. No differences in relative leaf water content among treatments were observed Results suggest that native soil should be used as backfill in planting holes; however, tilling a planting bed increases root and shoot growth compared to planting in a hole. Amending beds with pine bark did not increase growth or drought tolerance.

Mycorrhization, physiognomy, and first-year survivability of conifer seedlings following natural fire in Grand Teton National Park

1998 ◽  
Vol 28 (1) ◽  
pp. 115-122 ◽  
Author(s):  
Steven L Miller ◽  
Therese M McClean ◽  
Nancy L Stanton ◽  
Stephen E Williams
Keyword(s):  
National Park ◽  
Pinus Contorta ◽  
Carbon Allocation ◽  
Seedling Survival ◽  
Growing Season ◽  
First Year ◽  
Conifer Seedlings ◽  
Grand Teton National Park ◽  
Natural Fire ◽  
Root Shoot Ratio

Ectomycorrhiza formation, survivability, and physiognomic characteristics were assessed for conifer seedlings encountered 1 and 2 years postfire in the Huck burn site near Grand Teton National Park. Pinus contorta Dougl. ex Loud. germinated and was abundant throughout the first growing season. Abies lasiocarpa (Hook.) Nutt. germinated during May and June but was rarely encountered by September. First-year survivorship of P. contorta seedlings was about 50% for east-facing burn and edge and west-facing burn treatments. Mortality was higher in the west-facing edge treatment at about 64%. Pinus contorta seedlings collected in July and August had allocated approximately 75% more biomass to epicotyl production than to hypocotyl production, whereas by September seedlings had allocated 30-50% of their biomass to hypocotyls, regardless of site or treatment. Few or no ectomycorrhizae were formed until September. By September 100% of surviving seedlings were ectomycorrhizal. The number of ectomycorrhizae was positively correlated with the number of primary needles and the root/shoot ratio. These results highlight the importance of mycorrhizae to conifer seedling survival during the initial growing season and point to alteration of carbon allocation as a primary mechanism affecting seedling survival.

Variation in vegetation cover and seedling performance of tree species in a forest-savanna ecotone

2019 ◽  
Vol 35 (2) ◽  
pp. 74-82 ◽  
Author(s):  
Hamza Issifu ◽  
George K. D. Ametsitsi ◽  
Lana J. de Vries ◽  
Gloria Djaney Djagbletey ◽  
Stephen Adu-Bredu ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Cover ◽  
First Year ◽  
Transplant Experiment ◽  
Tree Seedling ◽  
Savanna Woodland ◽  
Specific Effects ◽  
Species Specific

AbstractDifferential tree seedling recruitment across forest-savanna ecotones is poorly understood, but hypothesized to be influenced by vegetation cover and associated factors. In a 3-y-long field transplant experiment in the forest-savanna ecotone of Ghana, we assessed performance and root allocation of 864 seedlings for two forest (Khaya ivorensis and Terminalia superba) and two savanna (Khaya senegalensis and Terminalia macroptera) species in savanna woodland, closed-woodland and forest. Herbaceous vegetation biomass was significantly higher in savanna woodland (1.0 ± 0.4 kg m−2 vs 0.2 ± 0.1 kg m−2 in forest) and hence expected fire intensities, while some soil properties were improved in forest. Regardless, seedling survival declined significantly in the first-year dry-season for all species with huge declines for the forest species (50% vs 6% for Khaya and 16% vs 2% for Terminalia) by year 2. After 3 y, only savanna species survived in savanna woodland. However, best performance for savanna Khaya was in forest, but in savanna woodland for savanna Terminalia which also had the highest biomass fraction (0.8 ± 0.1 g g−1 vs 0.6 ± 0.1 g g−1 and 0.4 ± 0.1 g g−1) and starch concentration (27% ± 10% vs 15% ± 7% and 10% ± 4%) in roots relative to savanna and forest Khaya respectively. Our results demonstrate that tree cover variation has species-specific effects on tree seedling recruitment which is related to root storage functions.

Fostering Communication

2022 ◽  
Vol 6 (GROUP) ◽  
pp. 1-23
Author(s):  
John Fowler ◽  
Mark Zachry ◽  
David W. McDonald
Keyword(s):  
Online Community ◽  
Foster Youth ◽  
Life Stage ◽  
Online Communication ◽  
Future Research ◽  
First Year ◽  
Former Foster Youth ◽  
Online Spaces ◽  
Effective Community ◽  
Descriptive Framework

The period of transition for foster youth into independent adulthood is an important life stage, and one that has yet to be explored in HCI circles. We studied an online community centered on the experiences of former foster youth through the first year of its existence to better understand how online spaces are being used by this population. Our mixed-method study included the coding of all posts from the first year of the online community and offers a mix of quantitative and qualitative findings. These findings include alignments and gaps in an established descriptive framework from the field of social work as it relates to the online communication of former foster youth. It also includes how the domains from the framework co-occur, and some potential implications of these co-occurrences. Future research on this subject is warranted, particularly related to why former foster youth seek online platforms to engage in conversations on these topics and how effective community members perceive the platform to be in safely and securely facilitating their needs.

Stand density, drought, and herbivory constrain ponderosa pine regeneration pulse

2020 ◽  
Vol 50 (9) ◽  
pp. 862-871 ◽  
Author(s):  
Thomas E. Kolb ◽  
Kelsey Flathers ◽  
John B. Bradford ◽  
Caitlin Andrews ◽  
Lance A. Asherin ◽  
...  
Keyword(s):  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Seedling Survival ◽  
Stand Density ◽  
Survival Duration ◽  
Northern Arizona ◽  
Growing Seasons ◽  
Pine Regeneration ◽  
Stand Thinning ◽  
Survival And Growth

Trees in dry forests often regenerate in episodic pulses when wet periods coincide with ample seed production. Factors leading to success or failure of regeneration pulses are poorly understood. We investigated the impacts of stand thinning on survival and growth of the 2013 cohort of ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) seedlings in northern Arizona, United States. We measured seedling survival and growth over the first five growing seasons after germination in six stand basal areas (BAs; 0, 7, 14, 23, 34, and 66 (unthinned) m2·ha−1) produced by long-term experimental thinnings. Five-year survival averaged 2.5% and varied among BAs. Mean survival duration was longer in intermediate BAs (11 to 16 months) than in clearings and high BAs (5 months). The BAs of 7, 14, and 23 m2·ha−1 had >2600 5-year-old seedlings·ha−1. In contrast, regeneration was lower in the clearing (666 seedlings·ha−1) and failed completely in the 34 m2·ha−1 and unthinned treatments. Seedling survival was highest during wet years and lowest during drought years. Many surviving seedlings had no net height growth between years 4 and 5 because of stem browsing. Results indicate that natural regeneration of ponderosa pine is influenced by stand BA, drought, herbivory, and interactions between extreme climatic events.

Reforestation with Abies cephalonica Loudon: a five-year study of seedling survival

2016 ◽  
Vol 27 (2) ◽  
pp. 136-145 ◽  
Author(s):  
Vassilis Detsis ◽  
Georgios Efthimiou ◽  
Olga Theodoropoulou ◽  
Stavroula Siorokou
Keyword(s):  
Management Practices ◽  
Seedling Survival ◽  
First Year ◽  
Seedling Height ◽  
Content Type ◽  
Abies Cephalonica ◽  
Site Characteristics ◽  
Statistical Relationships ◽  
Artificial Shading ◽  
Seedling Characteristics

Purpose – The purpose of this paper is to establish the effects on the survival of outplanted Abies cephalonica Loudon seedlings of seedling characteristics, site characteristics and management practices. Design/methodology/approach – The study was carried out by repeatedly monitoring survival of seedlings during a five-year period as well as establishing statistical relationships with a set of variables belonging to the aforementioned categories. It took place in plots reforested after a wildfire in the Parnitha Mt. National Park, near Athens, Greece. Findings – The odds of survival were found to be affected by bedrock type, dominant vegetation, initial seedling height and use of shading implements. Artificial shading was most important during the first year, site-related characteristics gained importance with increasing age and seedling height was of relatively constant importance. Shifts in temporal patterns of mortality and damage symptoms occurrence suggest that the mechanisms causing mortality changed with increasing age. Practical implications – The use of large seedlings in reforestation projects involving A. cephalonica should be preferred. Shading improves survival but due to the high costs this technique could be reserved for unfavorable plots, e.g. on limestone. Planting A. cephalonica in marginal sites should be avoided. Originality/value – The knowledge of the performance of A. cephalonica outplanted seedlings is very limited, while the need is increasing due to the spread of wildfires in this previously unaffected habitat.

scholarly journals Silicon Application Increases Drought Tolerance of Kentucky Bluegrass by Improving Plant Water Relations and Morphophysiological Functions

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Shah Saud ◽  
Xin Li ◽  
Yang Chen ◽  
Lu Zhang ◽  
Shah Fahad ◽  
...  
Keyword(s):  
Drought Stress ◽  
Drought Tolerance ◽  
Water Relations ◽  
Poa Pratensis ◽  
Kentucky Bluegrass ◽  
Leaf Water ◽  
Leaf Water Content ◽  
Plant Water Relations ◽  
Plant Water ◽  
Turf Quality

Drought stress encumbers the growth of turfgrass principally by disrupting the plant-water relations and physiological functions. The present study was carried out to appraise the role of silicon (Si) in improving the drought tolerance in Kentucky bluegrass (Poa pratensisL.). Drought stress and four levels (0, 200, 400, and 800 mg L−1) of Si (Na2SiO3·9H2O) were imposed after 2 months old plants cultured under glasshouse conditions. Drought stress was found to decrease the photosynthesis, transpiration rate, stomatal conductance, leaf water content, relative growth rate, water use efficiency, and turf quality, but to increase in the root/shoot and leaf carbon/nitrogen ratio. Such physiological interferences, disturbances in plant water relations, and visually noticeable growth reductions in Kentucky bluegrass were significantly alleviated by the addition of Si after drought stress. For example, Si application at 400 mg L−1significantly increased the net photosynthesis by 44%, leaf water contents by 33%, leaf green color by 42%, and turf quality by 44% after 20 days of drought stress. Si application proved beneficial in improving the performance of Kentucky bluegrass in the present study suggesting that manipulation of endogenous Si through genetic or biotechnological means may result in the development of drought resistance in grasses.

Interactive effects of tree and herb cover on survivorship, physiology, and microclimate of conifer seedlings at the alpine tree-line ecotone

2005 ◽  
Vol 35 (3) ◽  
pp. 567-574 ◽  
Author(s):  
Eliza L Maher ◽  
Matthew J Germino ◽  
Niles J Hasselquist
Keyword(s):  
Forest Succession ◽  
Interactive Effects ◽  
Tree Cover ◽  
First Year ◽  
Abies Lasiocarpa ◽  
Tree Line ◽  
Conifer Seedlings ◽  
Factors Affecting ◽  
Nighttime Temperatures ◽  
Snowy Range

Factors affecting the establishment of trees in subalpine meadows are important to population dynamics of trees in the alpine tree-line ecotone (ATE). Interactive effects of tree and herb cover on conifer seedlings were investigated in the ATE of the Snowy Range, Wyoming, USA. Microclimate, physiology, and survivorship of first-year conifer seedlings of Pinus albicaulis Engelm., Picea engelmannii Parry, and Abies lasiocarpa Hook. were measured in response to manipulations of surrounding herb and tree cover, as well as water availability. Tree and herb cover had nearly additive effects on survivorship and photosynthesis of conifer seedlings, except under alleviated water stress. In P. albicaulis, photosynthesis was greater near compared with away from trees and herbs, and photosynthetic efficiency (Fv/Fm) increased under herb cover. Tree cover led to greater nighttime temperatures, soil water contents, and, like herb cover, shade from solar radiation for seedlings. We did not detect any negative responses of conifer seedlings to surrounding vegetation. Furthermore, the effect of surrounding vegetation on conifer establishment appeared dependent on the type of surrounding vegetation, the species of conifer, and microsite stress level. These factors may lead to variation in the way conifer seedlings interact with surrounding vegetation and could explain changes in the relative abundances of tree species during forest succession in ATEs.

scholarly journals 198 EVALUATION OF DROUGHT TOLERANCE OF Fragaria chiloensis CLONES WITH POTENTIAL AS LOW-MAINTENANCE ORNAMENTAL GROUNDCOVERS

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 457e-457
Author(s):  
Ann Marie VanDerZanden ◽  
J. Scott Cameron
Keyword(s):  
Gas Exchange ◽  
Drought Tolerance ◽  
Control Group ◽  
Total Biomass ◽  
Stress Cycle ◽  
Chl A ◽  
Water Potentials ◽  
Fragaria Chiloensis ◽  
Fourth Derivative ◽  
Recovery Cycles

Fragaria chiloensis (Linnaeus) Is a viable. low maintenance alternative to groundcovers currently available in the ornamental landscape industry. There is considerable genetic variability within this specks for leaf morphology, growth and flowering habits as well as drought tolerance. Clones collected from 11 coastal sites in CA and OR were compared for drought tolerance after two Imposed water stress\recovery cycles. Predawn water potential, gas exchange, chlorophyll (chl) content, fourth derivative spectroscopy, carbon isotope discrimination, and total biomass production were evaluated and significant clonal differences were observed. Predawn water potentials after the first stress cycle ranged from -35.0 MPa to -6.5 MPa. Clones I05, DNT and G19 had highest predawn water potentials and gas exchange rates after both stress cycles. In the control group, I05 and DNT had higher levels of chl a, chl b, total chl and chl a\b. After the first stress cycle, clones DNT and I05 had the highest chl a\b ratio, however, after the second stress event there were no differences In any chl parameters. Varying adaptive abilities observed may suggest differential use in the landscape.

scholarly journals Drought Effects on Growth, Water Content, and Organic Osmoprotectants in Promising Almond Genotypes with Different Drought Tolerance

2021 ◽  
Author(s):  
Shabnam Gohari ◽  
Ali Imani ◽  
AliReza Talaei ◽  
Vahid Abdossi ◽  
Mohamad Reza Asghari
Keyword(s):  
Drought Stress ◽  
Drought Tolerance ◽  
Water Content ◽  
Light Stress ◽  
Stress Conditions ◽  
Growth And Yield ◽  
Leaf Water Content ◽  
Severe Stress ◽  
Drought Adaptation ◽  
Genotype A

Abstract Background Almonds ( Prunus amygdalus Batsch, syn. P. dulcis (Mill.) DA Webb) is a valuable nut crops species that is widely is cultivated in arid and semi-arid regions of Iran, due to drought tolerance and dehydration under drought stress. Almonds show physiological adaptations for survival in drought stress conditions, but the degree Drought adaptation varies between cultivars. However, to date, its morphological and physiological responses to drought, and the underlying mechanisms are not well understood. This study was aimed to investigate the morphological and physiological changes of almond genotypes under drought stress. almond genotypes were planted in pots and subjected to four levels of soil water treatments: above 80% (control), 60% (light stress), and 40% (severe stress) of field capacity. Results Within the total stress period (0–30 days), almond genotypes grew rapidly in the light stress, whereas severe stress had a negative impact on growth. So that, in this study, 10 selected almond genotypes using some morphological traits such as: plant height, trunk diameter at the top of the graft, new branch growth length, leaf yellowness and some physiological indicators under drought stress conditions such as Chlorophyll index was evaluated based on SPAD criterion, relative leaf water content, measurement of chlorophyll fluorescence and Organic Osmoprotectants to identify drought-resistant and sensitive genotypes under drought stress conditions. Among the selected genotypes studied, genotype A-7-100 was the most resistant and genotype A-124-1 was the most sensitive to drought stress. Conclusions Our results show that almond genotypes adapt to drought mainly by avoidance mechanisms, and its morphological and physiological characteristics are inhibited under severe stress, However, the degree of drought adaptation varies between different cultivars. These findings might help limited water resources to be fully used for increased the percentage of kernel and finally increased the growth and yield of plants under water stress.

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