The influence of the bamboo Yushania microphylla on regeneration of Abies densa in central Bhutan

1999 ◽  
Vol 29 (10) ◽  
pp. 1518-1527 ◽  
Author(s):  
G Gratzer ◽  
P B Rai ◽  
G Glatzel
Keyword(s):  
Forest Floor ◽  
Height Growth ◽  
Tree Regeneration ◽  
Average Height ◽  
Seedling Density ◽  
Tree Seedling ◽  
Term Survival ◽  
Light Levels ◽  
Gap Fraction ◽  
The Impact

To assess the impact of a dense understory of the bamboo Yushania microphylla Munro on tree regeneration in monospecific Abies densa Griff. stands of the central Bhutan Himalayas, the age-class distribution of fir regeneration, the microsite preferences, and height growth as well as the relationship between height of the bamboo, gap fraction, and tree seedling density were studied. Seedling densities were much lower on sites with bamboo. Recruitment was more or less continuous, and there was no indication of overall synchronized single-cohort regeneration in bamboo plots. On sites with bamboo understory, the light regime at the forest floor is strongly influenced by the height of the bamboo. A large portion of the variance of tree seedling density could be explained by the height of the bamboo. The mortality of fir seedlings is considerably reduced at elevated microsites. Fir establishment on the forest floor is restricted to sites where bamboo density is low and light levels are higher. On sites with dense, unbrowsed bamboo, light levels are too low for long-term survival of fir seedlings, resulting in a lack of suppressed regeneration with minimal height growth. Because of the absence of this fraction, the average height increment of fir seedlings is higher on sites with bamboo.

scholarly journals Plant-plant interactions change during succession on nurse logs in a northern temperate rainforest

2021 ◽  
Author(s):  
Carrie Woods ◽  
Katy Maleta ◽  
Kimmy Ortmann
Keyword(s):  
Community Structure ◽  
Forest Floor ◽  
Tree Regeneration ◽  
Forest Community ◽  
Tree Seedlings ◽  
Plant Interactions ◽  
Seedling Density ◽  
Tree Seedling ◽  
Nurse Logs ◽  
Plant Plant

Plant-plant interactions can vary depending on the severity of the environment. Positive interactions, such as facilitation, are important in early life stages while negative interactions, such as competition, predominate in later stages. Through succession, plant-plant interactions often change from facilitative to competitive. In northern temperate rainforests, gap dynamics result in tree falls that facilitate tree regeneration (nurse logs) as well as bryophyte succession. While the importance of nurse logs for tree seedlings is known, how the interactions of bryophyte communities and tree seedlings vary through succession of the log remains unclear. We examined the relationships of tree seedlings, bryophyte community composition, bryophyte depth, and percent canopy cover in 166 plots on nurse logs and the forest floor in the Hoh rainforest in Washington, USA. Tree seedling density was highest on young logs with early-colonizing bryophyte species (e.g., Rhizomnium glabrescens), and lowest on decayed logs with Hylocomium splendens, a long-lived moss that reaches depths >20 cm. As a result, bryophyte depth increased with nurse log decay and was negatively associated with tree seedling density. Tree seedling density was 4.6x higher on nurse logs than on the forest floor, which was likely due to competitive exclusion by H. splendens. Nurse logs had 17 species of bryophytes while the forest floor had six, indicating that nurse logs contribute to maintaining bryophyte diversity. Nurse logs are essential for forest dynamics as they enable both tree seedlings and smaller bryophyte species to avoid competition with the dominant forest floor bryophyte, H. splendens. Given that H. splendens has a global distribution and is often dominant in forested systems across the northern hemisphere, it is likely a widespread driver of plant community structure. Our findings indicate that plant-plant interactions shift with succession on nurse logs from facilitative to competitive and, thus, influence forest community structure and dynamics.

scholarly journals Abschätzung des Einflusses von Verbiss durch wildlebende Huftiere auf die Baumverjüngung

2019 ◽  
Vol 170 (3) ◽  
pp. 125-134
Author(s):  
Andrea D. Kupferschmid ◽  
Peter Brang ◽  
Harald Bugmann
Keyword(s):  
Relative Number ◽  
Height Growth ◽  
Tree Regeneration ◽  
Height Increment ◽  
Wild Ungulates ◽  
Ungulate Browsing ◽  
The Impact

Assessment of the impact of ungulate browsing on tree regeneration Browsing percentage is an objective and reproducible measure of the frequency of browsing by wild ungulates on tree regeneration. However, this relative number of browsed terminal shoots accounts for little of the effective long-term influence of browsing on tree regeneration. Apart from browsing percentage, the following four factors are important for estimating the influence of browsing: the density of tree regeneration, the within-tree browsing intensity, the height growth of the tree regeneration (and thus the time needed to grow out of the reach of browsers and the browsing-induced loss of height increment), and the mortality induced by browsing. At least the first three of these factors can be obtained easily and should thus be included in future browsing inventories.

Stability of Ponderosa Pine Provenance Performance: Results after 21 Years in Eastern South Dakota

1992 ◽  
Vol 9 (3) ◽  
pp. 102-107
Author(s):  
Peter R. Schaefer ◽  
Norman W. Baer
Keyword(s):  
Growth Rate ◽  
Great Plains ◽  
Ponderosa Pine ◽  
Height Growth ◽  
Term Survival ◽  
The North ◽  
Provenance Data ◽  
Performance Results ◽  
The Impact

Abstract Present seed source recommendations for ponderosa pine throughout most of the Great Plains are based on provenance data of trees up to 15 years old. There are indications in the literature that these recommendations may change as test plantations get older. Height and survival of 69 provenances of ponderosa pine were recorded 5, 10, 15, and 21 years following field establishment in 1968. The three provenances forming the north central Nebraska cluster maintained a significant height superiority over the remaining clusters at all measurement dates. Age/age correlations for total height growth declined over time; however, all were highly significant and the correlation between ages 10 and 21 was quite strong (r = 0.76). However, relative to the plantation mean, the growth rate of the rapid early growers was decreasing, while that of the slow early growers was increasing. Correlations between survival and growth rate were strong and highly significant at all ages, with the highest correlations for 5-or 10-year growth rate and 21-year survival (r = 0.74 and 0.75, respectively). If present growth trends continue, the historically strong age correlations for height growth will likely weaken. The impact on provenance recommendations should be minimal, because rapid early growth and long-term survival are the traits of interest. North. J. Appl. For. 9(3):102-107.

Tree seedling growth and survival over 6 years across different microsites in a temperate rain forest

2006 ◽  
Vol 36 (4) ◽  
pp. 910-918 ◽  
Author(s):  
P J Bellingham ◽  
S J Richardson
Keyword(s):  
Seedling Growth ◽  
Growth Rates ◽  
Mortality Rates ◽  
Tree Regeneration ◽  
High Light ◽  
Tree Seedling ◽  
Tree Fern ◽  
Foliar N ◽  
Light Levels ◽  
Tree Ferns

We investigated whether canopy tree seedlings have different growth and mortality rates on different microsites in montane rain forests of the western South Island, New Zealand. Seedling relative height growth rates of three species, Podocarpus hallii, Quintinia acutifolia, and Weinmannia racemosa, were very low (mean = 0.037 cm·cm–1·year–1). Seedling growth rates were higher on logs than on the ground at high light levels, but the probability of seedling death on logs was also greater at high light levels. Seedling foliar N and P concentrations were generally not different between logs and the ground. Growth rates and foliar N concentrations of Quintinia and Weinmannia were greater for seedlings on tree fern trunks than for seedlings on the ground. Mortality rates did not differ between seedlings on tree fern trunks and seedlings on the ground. Seedling densities of Quintinia and Weinmannia were greater on logs and tree ferns than on the ground. Podocarpus densities were not different between logs and the ground, and this species did not occur on tree ferns. Quintinia and Weinmannia benefit from establishment on elevated microsites but this is not clearly the case for Podocarpus. Tree regeneration niches for such slow-growing species can only be determined through long-term studies.

Tree regeneration in an Abiesfaxoniana forest after bamboo dieback, Wang Lang Natural Reserve, China

1995 ◽  
Vol 25 (12) ◽  
pp. 2034-2039 ◽  
Author(s):  
Alan H. Taylor ◽  
Zisheng Qin ◽  
Jie Liu
Keyword(s):  
Seedling Establishment ◽  
Forest Floor ◽  
Tree Regeneration ◽  
The Other ◽  
Regeneration Strategy ◽  
Tree Seedling ◽  
Natural Reserve ◽  
Closed Forest ◽  
Tree Seedling Establishment ◽  
Full Height

Bamboos in the understory of Abiesfaxoniana Render & Wilson forests in China impede tree regeneration when they are mature. However, bamboos die back every few decades and may synchronize tree seedling establishment on the forest floor. Tree seedling regeneration patterns were studied beneath 20 canopy gaps and adjacent closed forest in an old-growth A. faxoniana forest where understory bamboos died back in 1976. Most seedlings of A. faxoniana, Acercaudatum Wallich, and Betulautilis D. Don in gaps established 2 years after dieback of the bamboo Fargesiadenudata Yi. Acercaudatum seedlings in gaps were taller than those of B. utilis or A. faxoniana, and B. utilis seedlings were fourfold more abundant in gaps than the other species. All species (except A. caudatum) had greater seedling densities in gaps, but there were no density differences among species beneath closed forest. Bamboo cover and maximum culm height were greater under gaps than forest, and it takes bamboo seedlings about 18 years to grow to full height. Bamboo seems to reduce the success of an advanced regeneration strategy and promotes synchronized seedling establishment in gaps after it dies back.

scholarly journals Environmental Influences on Density and Height Growth of Natural Ponderosa Pine Regeneration following Wildfires

Fire ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 80
Author(s):  
Darcy H. Hammond ◽  
Eva K. Strand ◽  
Penelope Morgan ◽  
Andrew T. Hudak ◽  
Beth A. Newingham
Keyword(s):  
Ponderosa Pine ◽  
Seedling Establishment ◽  
Height Growth ◽  
Tree Regeneration ◽  
Forest Recovery ◽  
Productivity Index ◽  
Burn Severity ◽  
Seedling Density ◽  
Pine Regeneration ◽  
Precipitation Seasonality

Over the past century the size and severity of wildfires, as well as post-fire recovery processes (e.g., seedling establishment), have been altered from historical levels due to management policies and changing climate. Tree seedling establishment and growth drive future overstory tree dynamics after wildfire. Post-fire tree regeneration can be highly variable depending on burn severity, pre-fire forest condition, tree regeneration strategies, and climate; however, few studies have examined how different abiotic and biotic factors impact seedling density and growth and the interactions among those factors. We measured seedling density and height growth in the period 2015–2016 on three wildfires that burned in ponderosa pine (Pinus ponderosa) forests in the period 2000–2007 across broad environmental and burn severity gradients. Using a non-parametric multiplicative regression model, we found that downed woody fuel load, duff depth, and fall precipitation best explained variation in seedling density, while the distance to nearest seed tree, a soil productivity index, duff depth, and spring precipitation as snow best explained seedling height growth. Overall, results highlight the importance of burn severity and post-fire climate in tree regeneration, although the primary factors influencing seedling density and height growth vary. Drier conditions and changes to precipitation seasonality have the potential to influence tree establishment, survival, and growth in post-fire environments, which could lead to significant impacts for long-term forest recovery.

Effect of companion species on the growth of jack pine (Pinusbanksiana)

1994 ◽  
Vol 24 (9) ◽  
pp. 1846-1853 ◽  
Author(s):  
Marie-Hélène Longpré ◽  
Yves Bergeron ◽  
David Paré ◽  
Martin Béland
Keyword(s):  
Forest Floor ◽  
Site Index ◽  
Jack Pine ◽  
Height Growth ◽  
Growth And Yield ◽  
Average Height ◽  
Companion Species ◽  
Pine Trees ◽  
Paper Birch ◽  
Competition For Light

The growth and yield of jack pine (Pinusbanksiana Lamb.) was studied in even-aged stands of three types: pure jack pine, jack pine mixed with paper birch (Betulapapyrifera Marsh.), and jack pine mixed with trembling aspen (Populustremuloides Michx.) growing on moderately well-drained glaciolacustrine clay soils in the southern tip of the Clay Belt of northwestern Quebec. Site index, average DBH, and average height of jack pine, and the availability of nutrients in the forest floor were compared among stand types. No differences were found in the height growth of jack pine among stand types. However, diameters of jack pine in mixtures with paper birch were significantly greater than in either pure stands or in mixtures with aspen despite the fact that both mixed stand types showed higher forest floor pH and greater concentrations of exchangeable calcium and magnesium than the pure stands. These results, together with the pattern of height growth of the three species, suggest that the beneficial effect of paper birch on the diameter growth of jack pine is caused mainly by a reduction in the competition for light among individual jack pine trees. The silvicultural implications of the results are discussed.

scholarly journals Chemotherapy Delays Are Associated with Inferior Outcome in Acute Lymphoblastic Leukemia: A Retrospective Study from a Tertiary Cancer Center in South India

2021 ◽  
Vol 42 (01) ◽  
pp. 051-060
Author(s):  
Vineet Agrawal ◽  
Smita Kayal ◽  
Prasanth Ganesan ◽  
Biswajit Dubashi
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Lymphoblastic Leukemia ◽  
Univariate Analysis ◽  
Cancer Center ◽  
Survival Outcomes ◽  
Separate Analysis ◽  
Term Survival ◽  
Free Survival ◽  
Intensive Phase ◽  
The Impact

Abstract Background Treatment protocols for acute lymphoblastic leukemia (ALL) have evolved over time to give excellent cure rates in children and moderate outcomes in adults; however, little is known how delays in chemotherapy affect long-term survival. Objectives To find the association of delays during different treatment phases on the survival outcomes. Materials and Methods Data from 149 ALL cases treated between 2009 and 2015 were retrospectively analyzed. Treatment course in commonly used protocols was divided into three phases—induction, consolidation (postremission), maintenance, and also a combined intensive phase (induction plus consolidation) for the purpose of analysis, and delay in each phase was defined based on clinically acceptable breaks. Analysis was done to find the impact of treatment delay in each phase on the survival outcomes. Results The median age was 12 years (range, 1–57). Multi-center Protocol-841 (MCP-841) was used for 72%, German Multicenter Study Group for Adult ALL (GMALL) for 19%, and Berlin, Frankfurt, Muenster, 95 protocol (BFM-95) for 9% of patients. Delay in induction was seen in 52%, consolidation in 66%, and during maintenance in 42% of patients. The median follow-up was 41 months, and 3-year survival outcomes for the entire cohort were event-free survival (EFS)—60%, relapse-free survival (RFS)—72%, and overall survival (OS)—68%. On univariate analysis, delay in induction adversely affected EFS (hazard ratio [HR] = 1.78, p = 0.04), while delay in intensive phase had significantly worse EFS and RFS (HR = 2.41 [p = 0.03] and HR = 2.57 [p = 0.03], respectively). On separate analysis of MCP-841 cohort, delay in intensive phase affected both EFS (HR = 3.85, p = 0.02) and RFS (HR = 3.42, p = 0.04), whereas delay in consolidation significantly affected OS with (HR = 4.74, p = 0.04) independently. Conclusion Treatment delays mostly in intensive phase are associated with worse survival in ALL; attempts should be made to maintain protocol-defined treatment intensity while adequately managing toxicities.

scholarly journals Effects of Soil Abiotic and Biotic Factors on Tree Seedling Regeneration Following a Boreal Forest Wildfire

Ecosystems ◽  
2021 ◽  
Author(s):  
Theresa S. Ibáñez ◽  
David A. Wardle ◽  
Michael J. Gundale ◽  
Marie-Charlotte Nilsson
Keyword(s):  
Boreal Forest ◽  
Betula Pendula ◽  
Fire Severity ◽  
Tree Regeneration ◽  
Soil Biota ◽  
Fire Disturbance ◽  
Burn Severity ◽  
Soil Conditions ◽  
Tree Seedling ◽  
Seedling Regeneration

AbstractWildfire disturbance is important for tree regeneration in boreal ecosystems. A considerable amount of literature has been published on how wildfires affect boreal forest regeneration. However, we lack understanding about how soil-mediated effects of fire disturbance on seedlings occur via soil abiotic properties versus soil biota. We collected soil from stands with three different severities of burning (high, low and unburned) and conducted two greenhouse experiments to explore how seedlings of tree species (Betula pendula, Pinus sylvestris and Picea abies) performed in live soils and in sterilized soil inoculated by live soil from each of the three burning severities. Seedlings grown in live soil grew best in unburned soil. When sterilized soils were reinoculated with live soil, seedlings of P. abies and P. sylvestris grew better in soil from low burn severity stands than soil from either high severity or unburned stands, demonstrating that fire disturbance may favor post-fire regeneration of conifers in part due to the presence of soil biota that persists when fire severity is low or recovers quickly post-fire. Betula pendula did not respond to soil biota and was instead driven by changes in abiotic soil properties following fire. Our study provides strong evidence that high fire severity creates soil conditions that are adverse for seedling regeneration, but that low burn severity promotes soil biota that stimulates growth and potential regeneration of conifers. It also shows that species-specific responses to abiotic and biotic soil characteristics are altered by variation in fire severity. This has important implications for tree regeneration because it points to the role of plant–soil–microbial feedbacks in promoting successful establishment, and potentially successional trajectories and species dominance in boreal forests in the future as fire regimes become increasingly severe through climate change.

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