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1
Jones, Trevor A., Grant M. Domke, and Sean C. Thomas. "Canopy tree growth responses following selection harvest in seven species varying in shade tolerance." Canadian Journal of Forest Research 39, no. 2 (2009): 430–40. http://dx.doi.org/10.1139/x08-186.
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We used tree ring measurements to investigate the temporal response of basal area increment (BAI) of canopy trees following selection harvests by sampling across a chronosequence of stands with known harvest dates in tolerant hardwood (Great Lakes – St. Lawrence) stands in central Ontario. Seven tree species of various shade tolerances ranged widely in their responses to reduced competition. The more shade-tolerant species responded more positively: shade-tolerant species showed an average increase in BAI of 35% 4–15 years postharvest compared with 16% for mid-tolerant species and –7.5% for intolerant species. All species showed a time-lag in postharvest growth responses, with maximum growth responses occurring between 3 and 15 years postharvest. Tree size was the most important factor determining the magnitude of BAI response, with smaller trees consistently responding more than larger trees. We suggest that higher growth responses to selection harvests among shade-tolerant species may contribute to declines in mid-tolerant species abundance in selection-managed stands. More broadly, interspecific variability in canopy tree responses to forest disturbance appears to follow patterns distinct from seedling and sapling responses, with important implications to forest community dynamics in both managed and unmanaged forests.
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Wyckoff, Peter H., and James S. Clark. "Tree growth prediction using size and exposed crown area." Canadian Journal of Forest Research 35, no. 1 (2005): 13–20. http://dx.doi.org/10.1139/x04-142.
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We address the relationships between tree growth rate and growing environment for 21 co-occurring species. Tree growth rates are obtained from mapped plots at the Coweeta Long-Term Ecological Research site in the southern Appalachian Mountains. We employ high-resolution aerial photography to assess the light environment for trees growing in these plots, using exposed crown area (ECA) as a surrogate for light interception. The relationship between growth and ECA is compared with two other growth predictors: tree size and shade-tolerance classification. We find that ECA is an excellent predictor of tree growth (average R2 = 0.69 for nine species). When ECA is combined with tree size, growth rate prediction is improved (average R2 = 0.76). Tree size alone is also a strong predictor of tree growth (average R2 = 0.68). Shade-tolerance classification, by contrast, is a poor predictor of tree growth.
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Pantic, Damjan, Milan Medarevic, Matthias Dees, et al. "Analysis of the growth characteristics of a 450-year-old silver fir tree." Archives of Biological Sciences 67, no. 1 (2015): 155–60. http://dx.doi.org/10.2298/abs140919018p.
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The growth characteristics of silver fir are of high importance for selection forest management, and for the current aims laid out in Serbia?s forest management focused on increasing the share of silver firs in Serbia?s growing stock. With the objective of increasing the understanding of the growth characteristics of silver fir, the growth of two silver fir trees felled during forest site production research on Mt. Goc, located in Central Serbia, have been analyzed. Both trees showed significant differences in their growth dynamics over long periods as results of micro-site and micro-stand effects (primarily ambient light regime). The common growth characteristic of the two trees, a 450-year-old tree as the main study object (labeled Tree A) and a 270-year-old Tree B is a long stagnation stage. For Tree A the latent phase, with small interruptions, lasted 410 years; one phase lasted 330 years in continuity, which is the longest period of silver fir stagnation recorded in Europe. Tree B showed a long-lasting stagnation stage that lasted 170 years. The long stagnation stage of Tree A, characterized by an average diameter increment of 1.4 mm/year (average growth ring width of 0.7 mm) and an average height increment of 0.08 m/year, shows the extraordinary silver fir capacity for physiological survival in complete shade. This study adds to the existing knowledge of the shade tolerance of the silver fir. Therefore, the silver fir belongs to the group of extremely shade-tolerant tree species. This characteristic makes silver fir an irreplaceable tree species in the selection forest structure. It offers a wide range of silvicultural flexibility in the management of these forests, and is applicable to silver fir selection Serbia?s forests.
4
Baker, Patrick J., and Sarayudh Bunyavejchewin. "Suppression, release and canopy recruitment in five tree species from a seasonal tropical forest in western Thailand." Journal of Tropical Ecology 22, no. 5 (2006): 521–29. http://dx.doi.org/10.1017/s0266467406003312.
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We used tree-rings to reconstruct long-term patterns of suppression, release and growth among five sympatric canopy tree species representing the full range of shade tolerance in a seasonal tropical forest in western Thailand. We expected that the frequency and duration of suppression and release events would be positively correlated with shade tolerance. All five species showed evidence of major and moderate growth releases. As expected, Melia azederach, an extreme heliophile, had the fewest releases. However, among the other species the number of major releases was consistent across the range of shade tolerance. The most significant difference among the species was the number of moderate releases recorded. There was a general positive correlation between the number of moderate releases and shade tolerance; however, Chukrasia tabularis, a relatively shade-intolerant species, had an anomalously high number of moderate releases. The study species also showed considerable variation in canopy accession strategies. The least common canopy accession strategy was establishment in the understorey and growth into the canopy in the absence of any gaps. However, with the exception of Melia, all four study species had one or more individuals that successfully reached the canopy using each of the four canopy accession strategies. These results highlight the importance of periodic or episodic bouts of gap formation on canopy tree recruitment and the utility of tree-rings for reconstructing long-term growth patterns in tropical trees.
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Kobayashi, Kent D., Mary A. Young, David L. Hensley, H. C. Bittenbender, and Julie Ann T. Yogi. "Farmer's Bookshelf: Hypermedia Information System to Recommend Trees for Landscaping." HortScience 31, no. 4 (1996): 652c—652. http://dx.doi.org/10.21273/hortsci.31.4.652c.
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A hypermedia information system was developed to recommend trees for landscaping and to obtain information on these individual trees. Using the software HyperCard on the Macintosh computer, we developed a system that uses the idea of index cards with information being stored on separate screens called “cards.” Using a mouse, the user navigates from one card to another by click on a “button” on the card. The user may select from several criteria including tree type, tree height, soil type, drought tolerance, wind tolerance, shade tolerance, salt tolerance, and growth rate. The program then finds which trees meet the desired criteria and provides information on these trees. This easy-to-use system requires no typing except to enter a word to search for. The user can quickly browse for the desired information and save it as a text file or print it. The Farmer's Bookshelf provides a tool for extension agents, growers, and homeowners to easily obtain vitally needed information. The program has further application for landscape companies, Master Gardener programs, and in horticultural courses.
6
Lusk, C. H., K. M. Sendall, and P. J. Clarke. "Seedling growth rates and light requirements of subtropical rainforest trees associated with basaltic and rhyolitic soils." Australian Journal of Botany 62, no. 1 (2014): 48. http://dx.doi.org/10.1071/bt13262.
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A trade-off between shade tolerance and growth in open conditions is widely believed to underlie the dynamics of humid forests. Little is known about how the growth versus shade tolerance trade-off interacts with other major trade-offs associated with differential adaptation to major environmental factors besides light. We asked whether the growth versus shade tolerance trade-off differed between subtropical rainforest tree assemblages native to basaltic (fertile) and rhyolitic (infertile) soils in northern New South Wales, because of the allocational costs of adaptation to low nutrient availability. Seedling relative growth rates of six basalt specialists and five rhyolite specialists were measured in a glasshouse and the minimum light requirements of each species were quantified in the field by determining the 10th percentile of juvenile tree distributions in relation to understorey light availability. A similar range of light requirements was observed in the two assemblages, and although the two fastest growing species were basalt specialists, seedling growth rates did not differ significantly between the two substrates. The overall relationship between light requirements and growth rate was weak, and there was no compelling evidence that the slope or elevation of this relationship differed between the two assemblages. Growth rates were significantly correlated, overall, with specific leaf area, and marginally with leaf area ratio. The apparent similarity of the growth versus shade tolerance trade-off in the two suites of species could reflect effects of leaf nutrient content on respiration rates; basalt specialists tended to have a smaller root mass fraction, but this may have been offset by the effects of leaf nitrogen status on respiration rates, with higher respiration rates expected on fertile basaltic soils. However, the results might also partly reflect impairment of the field performance of two basalt specialists that were heavily attacked by natural enemies.
7
Arévalo-Gardini, Enrique, Abel Farfán, Fiorella Barraza, et al. "Growth, Physiological, Nutrient-Uptake-Efficiency and Shade-Tolerance Responses of Cacao Genotypes under Different Shades." Agronomy 11, no. 8 (2021): 1536. http://dx.doi.org/10.3390/agronomy11081536.
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Cacao is an understory plant cultivated in full-sun monocultures, multistrata agroforestry systems, where cacao trees are planted together with fruit, timber, firewood, and leguminous trees, or within thinned native forests. In agroforestry systems of cultivation, cacao is subjected to excess shade due to high density, excess growth, and the unmanaged pruning of shade trees. Cacao is tolerant to shade, and the maximum photosynthetic rate occurs at an irradiance of around 400 μmol m−2 s−1. However, excess shade further reduces the irradiance, which is detrimental to photosynthesis and growth functions. Intra-specific variation is known to exist in cacao for the required saturation irradiance. A greenhouse study was implemented with 58 cacao genotypes selected from four geographically diverse groups: (i) wild cacao from river basins of the Peruvian Amazon (PWC); (ii) Peruvian farmers’ collection (PFC); (iii) Brazilian cacao collection (BCC); and (iv) national and international cacao collections (NIC). All of the cacao genotypes were subjected to 50% and 80% shade where photosynthetic photon flux density (PPFD) was 1000 and 400 μmol m−2 s−1, respectively. Intra-specific variations were observed for growth, physiological and nutritional traits, and tolerance to shade. Cacao genotypes tolerant to shade were: UNG-77 and UGU-130 from PWC; ICT-2173, ICT-2142, ICT-2172, ICT-1506, ICT-1087, and ICT-2171 from PFC; PH-21, CA-14, PH-990, and PH-144 from BCC; and ICS-1, ICS-39, UF-613, and POUND-12 from NIC. Genotypes that tolerate excess shade may be useful plant types for maintaining productivity and sustainability in agroforestry systems of cacao management.
8
Sherich, Kelsey, Amy Pocewicz, and Penelope Morgan. "Canopy characteristics and growth rates of ponderosa pine and Douglas-fir at long-established forest edges." Canadian Journal of Forest Research 37, no. 11 (2007): 2096–105. http://dx.doi.org/10.1139/x07-105.
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Trees respond to edge-to-interior microclimate differences in fragmented forests. To better understand tree physiological responses to fragmentation, we measured ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws) and Douglas-fir ( Pseudotsuga menziesii (Mirbel) Franco) leaf area, crown ratios, sapwood area, basal area (BA) growth rates, and BA growth efficiency at 23 long-established (>50 year) forest edges in northern Idaho. Trees located at forest edges had more leaf area, deeper crowns, higher BA growth rates, and more sapwood area at breast height than interior trees. Ponderosa pine had significantly higher BA growth efficiency at forest edges than interiors, but Douglas-fir BA growth efficiency did not differ, which may relate to differences in photosynthetic capacity and drought and shade tolerance. Edge orientation affected BA growth efficiency, with higher values at northeast-facing edges for both species. Edge effects were significant even after accounting for variation in stand density, which did not differ between the forest edge and interior. Although edge trees had significantly greater canopy depth on their edge-facing than forest-facing side, sapwood area was evenly distributed. We found no evidence that growing conditions at the forest edge were currently subjecting trees to stress, but higher leaf area and deeper crowns could result in lower tolerance to future drought conditions.
9
DeMeo, Robin A., and Thomas E. Marler. "Growth, Morphology, and Physiology of Intsia bijuga Trees Under Varied Light Conditions." HortScience 33, no. 3 (1998): 480c—480. http://dx.doi.org/10.21273/hortsci.33.3.480c.
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Six studies were conducted with Intsia bijuga seedlings to determine the methods and extent of shade tolerance for this species. Growth differences were minimal among plants receiving varied light exposure, although treatments ranged from 19% to 100% sunlight exposure. Light saturated photosynthesis of leaves on plants receiving 24% sunlight was achieved at a photosynthetic photon flux (PPF) of about one-fourth of that for the leaves on plants receiving 100% sunlight exposure. However, photosynthesis under conditions of extremely low PPF was higher for shade-grown plants than for full-sun plants. Shaded plants exhibited lower dark respiration, light compensation point, and light-saturated photosynthesis than full sun plants. Leaflet thickness, palisade layer number, and stomatal density of leaves of shaded plants were reduced compared with full sun plants. At seedling emergence and for several months thereafter, the plants responded to shade primarily with obligate sun plant characteristics. After the plants were established, however, responses to the varied light conditions indicated facultative structural and physiological characteristics.
10
Hawkins, Ashley E., and Terry W. Henkel. "Native forest pathogens facilitate persistence of Douglas-fir in old-growth forests of northwestern California." Canadian Journal of Forest Research 41, no. 6 (2011): 1256–66. http://dx.doi.org/10.1139/x11-053.
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Forest pathogens and insects can accelerate tree mortality, increase stand structural heterogeneity, and alter tree community composition. In northern California, the canopy trees Abies concolor var. lowiana (Gord. & Glend.) Lemmon (white fir) and Pseudotsuga menziesii var. menziesii (Mirbel) Franco (Douglas-fir) co-occur but vary in shade tolerance and regenerative abilities following disturbance. Field observations suggested that mortality and turnover of white fir exceeded that of Douglas-fir and that native pathogens may be important drivers in the absence of fire. Pathogens and bark beetles were sampled in old-growth white fir – Douglas-fir stands in northwestern California to assess their contribution to tree mortality, gap formation, and regeneration. We determined abundances and size class distributions of canopy trees, presence of pathogens and bark beetles, and causes of tree mortality. We sampled canopy gaps and closed-canopy forests for overstory species composition, cause of mortality of gap-maker trees, and regeneration of white fir and Douglas-fir. Root-rot fungi accounted for significantly higher mortality and gap formation in white fir than in Douglas-fir. Relative seedling–sapling density of Douglas-fir was higher in pathogen-induced canopy gaps than in closed-canopy forest. In the absence of fire, native forest pathogens enable regeneration and persistence of Douglas-fir by enhancing mortality of white fir, resulting in canopy gap formation.
11
Bazzaz, F. A., J. S. Coleman, and S. R. Morse. "Growth responses of seven major co-occurring tree species of the northeastern United States to elevated CO2." Canadian Journal of Forest Research 20, no. 9 (1990): 1479–84. http://dx.doi.org/10.1139/x90-195.
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We examined how elevated CO2 affected the growth of seven co-occurring tree species: American beech (Fagusgrandifolia Ehrh.), paper birch (Betulapapyrifera Marsh.), black cherry (Prunusserotina Ehrh.), white pine (Pinusstrobus L.), red maple (Acerrubrum L.), sugar maple (Acersaccharum Marsh.), and eastern hemlock (Tsugacanadensis (L.) Carr). We also tested whether the degree of shade tolerance of species and the age of seedlings affected plant responses to enhanced CO2 levels. Seedlings that were at least 1 year old, for all species except beech, were removed while dormant from Harvard Forest, Petersham, Massachusetts. Seeds of red maple and paper birch were obtained from parent trees at Harvard Forest, and seeds of American beech were obtained from a population of beeches in Nova Scotia. Seedlings and transplants were grown in one of four plant growth chambers for 60 d (beech, paper birch, red maple, black cherry) or 100 d (white pine, hemlock, sugar maple) under CO2 levels of 400 or 700 μL•L−1. Plants were then harvested for biomass and growth determinations. The results showed that the biomass of beech, paper birch, black cherry, sugar maple, and hemlock significantly increased in elevated CO2, but the biomass of red maple and white pine only marginally increased in these conditions. Furthermore, there were large differences in the magnitude of growth enhancement by increased levels of CO2 between species, so it seems reasonable to predict that one consequence of rising levels of CO2 may be to increase the competitive ability of some species relative to others. Additionally, the three species exhibiting the largest increase in growth with increased CO2 concentrations were the shade-tolerant species (i.e., beech, sugar maple, and hemlock). Thus, elevated CO2 levels may enhance the growth of relatively shade-tolerant forest trees to a greater extent than growth of shade-intolerant trees, at least under the light and nutrient conditions of this experiment. We found no evidence to suggest that the age of tree seedlings greatly affected their response to elevated CO2 concentrations.
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Lehnebach, Romain, Julie Bossu, Stéphanie Va, et al. "Wood Density Variations of Legume Trees in French Guiana along the Shade Tolerance Continuum: Heartwood Effects on Radial Patterns and Gradients." Forests 10, no. 2 (2019): 80. http://dx.doi.org/10.3390/f10020080.
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Increasing or decreasing wood density (WD) from pith to bark is commonly observed in tropical tree species. The different types of WD radial variations, long been considered to depict the diversity of growth and mechanical strategies among forest guilds (heliophilic vs. shade-tolerant), were never analyzed in the light of heartwood (HW) formation. Yet, the additional mass of chemical extractives associated to HW formation increases WD and might affect both WD radial gradient (i.e., the slope of the relation between WD and radial distance) and pattern (i.e., linear or nonlinear variation). We studied 16 legumes species from French Guiana representing a wide diversity of growth strategies and positions on the shade-tolerance continuum. Using WD measurements and available HW extractives content values, we computed WD corrected by the extractive content and analyzed the effect of HW on WD radial gradients and patterns. We also related WD variations to demographic variables, such as sapling growth and mortality rates. Regardless of the position along the shade-tolerance continuum, correcting WD gradients reveals only increasing gradients. We determined three types of corrected WD patterns: (1) the upward curvilinear pattern is a specific feature of heliophilic species, whereas (2) the linear and (3) the downward curvilinear patterns are observed in both mid- and late-successional species. In addition, we found that saplings growth and mortality rates are better correlated with the corrected WD at stem center than with the uncorrected value: taking into account the effect of HW extractives on WD radial variations provides unbiased interpretation of biomass accumulation and tree mechanical strategies. Rather than a specific feature of heliophilic species, the increasing WD gradient is a shared strategy regardless of the shade tolerance habit. Finally, our study stresses to consider the occurrence of HW when using WD.
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Thompson, WA, GC Stocker, and PE Kriedemann. "Growth and Photosynthetic Response to Light and Nutrients of Flindersia brayleyana F. Muell., A Rainforest Tree With Broad Tolerance to Sun and Shade." Functional Plant Biology 15, no. 2 (1988): 299. http://dx.doi.org/10.1071/pp9880299.
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Seed from four species of rainforest trees with widely contrasting sunlight requirements for growth and development were sown within disturbance gaps amidst mature forest on the Herberton Range in North Queensland. Observations on seedling persistence plus comparative growth of young trees of Acacia aulacocarpa, Toona australis, Flindersia brayleyana and Darlingia darlingiana (species ranked according to adaptation from full sun to deep shade) confirmed a broad tolerance of Flindersia to sunlight under all conditions, from wide to narrow gaps (minimum 0.6% full sun equivalent). Photosynthetic attributes which underlie such broad tolerance were subsequently inferred from single leaf gas exchange, plus foliar analyses of nitrogen, phosphorus and chlorophyll on tree seedlings held for 180 days under two nutrient × three irradiance levels adjusted to represent natural irradiance incident upon the forest floor (low), mid-canopy (medium) and emergent crowns (high irradiance treatment). Medium irradiance plus high nutrients proved optimal for leaf expansion, chlorophyll content and photosynthesis in air. Growth under low irradiance was characterised by thinner leaf palisade tissue, lower rates of dark respiration, increased leaf chlorophyll per unit nitrogen and lower light compensation point for photosynthesis. Such leaves retained a relatively high photosynthetic capacity despite these other shade-leaf attributes. High irradiance plus low nutrients proved supraoptimal for leaf expansion and expression of photosynthetic activity. Chronic photoinhibition appeared to prevail because apparent quantum yield was reduced, while photosynthetic processes on a nitrogen basis were substantially impaired. Nitrogen use efficiency, as inferred from leaf chlorophyll content, light saturated CO2 assimilation rate, electron transport rate and carboxylation rate on a nitrogen basis declined with increasing growth irradiance. Some ecological implications for the establishment and growth of these rainforest tree species in disturbance gaps are discussed.
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Khurana, E., and J. S. Singh. "Impact of life-history traits on response of seedlings of five tree species of tropical dry forest to shade." Journal of Tropical Ecology 22, no. 6 (2006): 653–61. http://dx.doi.org/10.1017/s0266467406003518.
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Seedling growth under three shade levels was studied at Varanasi, India, for five tree species of tropical dry forest, which differed in life-history traits. Three of these were small-seeded pioneer (Albizia procera, Acacia nilotica and Phyllanthus emblica) and the other two were large-seeded non-pioneer (Terminalia arjuna and Terminalia chebula) species. Seedlings of all the species were subjected to three light levels (80–100%, 20–30% and 3–7% of full sunlight) comparable to sunlit gaps and shaded microsites in the dry forest. After 4 mo of shade treatment, height, basal area, biomass and other growth traits, viz. RGR (relative growth rate), NAR (net assimilation rate), and SLA (specific leaf area) were determined. Etiolation and plasticity indices were calculated. Reduction in seedling height, biomass and relative growth rates and enhancement in SLA due to shade was greater for small-seeded pioneer species. Seedlings from large-seeded non-pioneer species exhibited a stronger etiolation response to shade than seedlings from small-seeded species. Phenotypic plasticity indices for basal area, plant biomass and relative growth rate were greater for the three small-seeded early successional species (A. procera, A. nilotica and P. emblica), indicating their specialization in a more favourable light environment such as large gaps and forest peripheries. The non-pioneer and pioneer species differed only in the degree of shade tolerance, and we suggest that dry forest species cannot be strictly categorized into two distinct groups (shade tolerant vs. intolerant), rather shade preference and gap preference would be the more expressive terms. Marked environmental heterogeneity in terms of irradiance and the phenology of dry tropical trees permits coexistence of species of varying ecological traits, contributing to the maintenance of diversity in the dry forest.
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Avalos, Gerardo. "Shade tolerance within the context of the successional process in tropical rain forests." Revista de Biología Tropical 67, no. 2SUPL (2019): S53—S77. http://dx.doi.org/10.15517/rbt.v67i2supl.37206.
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Shade tolerance (the capacity to survive and grow over long periods under shade) is a key component of plant fitness and the foundation of current theories of forest succession in tropical rain forests. It serves as a paradigm to understand the optimal allocation of limited resources under dynamic light regimes. I analyze how tropical rain forest succession influences the expression of ecophysiological mechanisms leading to shade tolerance, and identify future areas that will increase our understanding of the ecological and evolutionary consequences of this phenomenon. Shade tolerance is a multivariate, continuous functional trait reflecting the growth-mortality trade-off of investing resources under limited light vs. exploiting high light conditions. I propose the life cycle successional trajectory model of Gómez-Pompa & Vázquez-Yanes as an integrative tool to understand tropical rain forest succession. This model shows how species distribute along the successional environmental gradient based on their degree of shade tolerance and represents a more integrative paradigm to understand the interface between different aspects of species diversity (ontogenetic variation and functional diversity) throughout succession. It proposes that different trait combinations determining shade tolerance are expressed at different stages of the life cycle, which affects how and when plants enter the successional trajectory. Models explaining the expression of shade tolerance (resource availability, carbon gain, CSR, resource competition) are based on whole-plant economics and are not mutually exclusive. The analysis of shade tolerance is biased towards tree seedlings in the understory of mature forests. Other life stages (juvenile and adult trees), life forms, and microhabitats throughout the forest profile are almost always excluded from these analyses. More integrative explanations based on the distribution of functional traits among species, ontogenetic stages, and the nature of the environmental gradient are being developed based on long-term data and chronosequence comparisons. In summary, shade-tolerance is a complex phenomenon, is determined by multiple characters that change ontogenetically over space and time and entails considerable plasticity. Current methods do not account for this plasticity. Understanding the nature of shade tolerance and its functional basis is critical to comprehending plant performance and improving the management, restoration and conservation of tropical rain forests given the combined threats of global warming and habitat loss
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Frelich, Lee E., and Peter B. Reich. "Perspectives on development of definitions and values related to old-growth forests." Environmental Reviews 11, S1 (2003): S9—S22. http://dx.doi.org/10.1139/a03-011.
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Old-growth forests are those that meet some threshold(s) determined by a scientific and political process. The main issue is what criteria to use to determine these thresholds; they must be practical enough to allow managers to delimit and manage old-growth stands in the field. People value forests with old and (or) big trees and primary forests that have a continuous heritage of natural disturbance and regeneration, even though the latter may include all stages of stand development and succession. We advocate uniting these two and using "primary forest", also called "natural heritage forest", as the criterion for delimiting old growth in regions where primary forest still exists. This criterion recognizes that the stage of development with big, old trees is part of a cycle of development, and it is necessary to have all the parts to continue to produce new examples of the older stages. The best available second-growth stands can be used in regions where primary forests are not available. Alternatively, threshold criteria for delimiting old growth can be based on tree size and age, but arbitrary criteria based on human size and age scales should be avoided in favour of criteria that specify stands dominated by trees relatively large and old for the species and site. Such criteria allow for old growth to occur across a variety of levels of site productivity, with trees of widely varying stature and with varying life-history characteristics, such as longevity, shade tolerance, and successional status. In any case, managers and scientists should work together to make sure that definitions work in the field but also include the ecological processes necessary to maintain the unique biological resources of old growth. The biological resources present in old growth may help to restore the second-growth landscape and allow reconstitution of forests in new places after global warming. Old-growth forests provide a baseline for comparison of effects of logging and natural disturbance, with respect to resilience to climatic change and disturbance, maintenance of species richness, and natural genetic structure of tree populations, which respond to different selective regimes in old growth and harvested forests. The species in old-growth remnants, their interactions and the resilience of the system after disturbance are as important or perhaps more so than the age and size of the trees at a given point in time. Key words: dwarf forest, Minnesota, old-growth processes, tree height.
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Thomas, Sean C. "Biochar effects on germination and radicle extension in temperate tree seedlings under field conditions." Canadian Journal of Forest Research 51, no. 1 (2021): 10–17. http://dx.doi.org/10.1139/cjfr-2019-0386.
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Pyrolyzed organic matter, or biochar, generally increases the growth of established plants; in some cases, biochar also promotes seed germination in agricultural species, but comparable effects on tree species have received little attention. Potential biochar effects on seed germination and early seedling development were examined in a field experiment involving 14 species of temperate forest trees. Replicated sets of seeds with and without biochar (at 5 t·ha–1) were placed in mesh bags beneath leaf litter near the time of autumnal leaf fall and retrieved the following spring. Pooled analyses show a positive but small average effect of biochar on germination. Effects on seedling radicle extension growth were more pronounced, with more than a doubling in growth observed overall and large increases observed in some species, including both conifers (e.g., Picea mariana (Mill.) Britton, Sterns & Poggenb. and Pinus resinosa Sol. ex Aiton) and angiosperms (Betula papyrifera Marsh., Prunus virginiana L., and Ulmus americana L.). Species varied in responses, but differences were not related to fire or shade tolerance. The results indicate that biochar can substantially enhance early seedling development in temperate trees; likely mechanisms involve “priming” effects resulting from increased pH and potassium availability or sorption of germination-inhibiting phenolics in the litter layer.
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ORTIZ, Daniel, Flavio MORENO, and Maria Claudia DÍEZ. "Photosynthesis, growth, and survival in seedlings of four tropical fruit-tree species under intense radiation." Acta Amazonica 51, no. 1 (2021): 1–9. http://dx.doi.org/10.1590/1809-4392202000752.
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ABSTRACT In the Amazon region, agroforestry systems (AFSs) are recommended as a sustainable production alternative for local communities. A common component in Amazonian AFSs are tropical fruit trees, which can form the canopy or grow in the understory. In this study, we evaluated the effect of high radiation on photosynthesis, growth and seedling survival of four Amazonian fruit-tree species: Theobroma cacao, Eugenia stipitata, Inga edulis and Psidium guajava. Growth, chlorophyll fluorescence, gas exchange, and leaf pigments were measured in seedlings of each species grown for 12 months inside shade houses with low (8%), medium (30%) and high relative illumination (100%). Eugenia stipitata and T. cacao had the lowest acclimation capacity to high solar radiation, followed by I. edulis. Therefore, these species must be grown under intermediate light levels in early growth stages, to protect them from direct sunlight. In contrast, P. guajava seedlings demonstrated high tolerance to elevated radiation, therefore, this species can be planted under full sunlight.
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Lee, Thomas D., Audrey L. Perkins, Andrew S. Campbell, et al. "Incipient Invasion of Urban and Forest Habitats in New Hampshire, USA, by the Nonnative Tree, Kalopanax septemlobus." Invasive Plant Science and Management 8, no. 2 (2015): 111–21. http://dx.doi.org/10.1614/ipsm-d-14-00047.1.
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We analyzed the recent (< 25 yr) spread in New Hampshire, USA, of the exotic tree Kalopanax septemlobus, native to Asia. The invasion was likely initiated by a single tree planted ca. 1972. Our objective was to assess the viability of the invasion, especially in light of the small propagule size. We tallied, mapped, aged, and measured the height and growth of K. septemlobus individuals at two sites, the University of New Hampshire campus (UC) and Thompson Farm (TF), both in Durham. We found over 3,800 plants at UC and 270 at TF in < 120 ha (296 ac) total area. Plant age ranged from 0 to 22 yr, and UC plants were as far as 775 m (2,543 ft) from the purported parent tree. Annual height growth was comparable to midtolerant native trees. Plants occurred in both open and forested habitats, and the mean level of photosynthetically active radiation incident on understory plants was 4 to 6% of full sun. The large population size, shade tolerance, rapid height growth, and ability to sprout from damaged stems suggest potential for K. septemlobus to invade and persist in forests, the most common natural ecosystem in the northeastern United States. We further suggest that small propagule size, likely a single tree, has not prevented K. septemlobus from initiating a spatially extensive and vigorous population. Kalopanax septemlobus has been planted as an ornamental in the northeastern United States, and prevention of region-wide invasion might depend on removal of these trees, even when they occur as single individuals.
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Woods, Kerry D. "Living long by staying small: stem layering as an adaptive life-history trait in shade-tolerant tree seedlings." Canadian Journal of Forest Research 38, no. 3 (2008): 480–87. http://dx.doi.org/10.1139/x07-136.
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Suppressed seedling banks are important in replacement dynamics in late-successional forests. However, demographic properties of seedling populations are poorly known, and there has been little attention to traits that might affect fitness in suppressed seedlings. Acer saccharum Marsh., a shade-tolerant dominant in eastern North American forests, frequently develops adventitious roots along prostrate portions of stems (“layering”). Measurements of Acer seedlings in old-growth forests in Michigan indicate that layered seedlings proportionally reduce structural allocations to older layered stem tissues, retain leaf area / height ratios of younger unlayered seedlings, and tend to survive longer. In tree seedlings, allometric consequences of normal stem growth lead to declining ratios of photosynthetic to nonphotosynthetic biomass, which potentially reduces shade tolerance and limiting age. The layering habit may defer this penalty by changing the allometry of growth. Resulting increases in life expectancy should increase chance of access to increased light and of reaching the canopy. Thus, because flowering is generally restricted to canopy trees, the tendency to layer may increase fitness. Properties of individuals in suppressed seedling banks may be selectively and ecologically important, shaping life histories and population dynamics.
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Syvertsen, James P., Juan C. Melgar, and Francisco García-Sánchez. "Salinity Tolerance and Leaf Water Use Efficiency in Citrus." Journal of the American Society for Horticultural Science 135, no. 1 (2010): 33–39. http://dx.doi.org/10.21273/jashs.135.1.33.
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In three separate experiments, the growth and water use of salinized citrus rootstock seedlings and grafted trees were modified using different growth substrates, elevated CO2, or 50% shade screen under field conditions. By reanalyzing previously published data, we tested the hypothesis that salinity tolerance in citrus can be characterized as the ability to maintain low levels of leaf Cl− accumulation through high plant growth and high water use efficiency (WUE) under saline conditions. Well-irrigated salinized seedlings of the relatively salt-sensitive Carrizo citrange [Carr (Citrus sinensis × Poncirus trifoliata)] were grown in sand, clay, or a peat-based soilless media. Salinity stress reduced plant growth and water use. Leaf Cl− concentration was negatively related to plant growth, but leaf Cl− increased with transpiration rate in low-saline treatments. In a second experiment using salinized seedlings of the relatively salt-tolerant Cleopatra mandarin [Cleo (Citrus reticulata)] grown along with Carr seedlings with or without elevated CO2, leaf Cl− was negatively related to growth and to shoot/root dry weight ratio, but was positively related to water use such that leaf Cl− was negatively related to leaf WUE. In a third experiment using salinized 2-year-old ‘Valencia’ orange (C. sinensis) trees grafted on Cleo or Carr rootstocks and grown with or without shadecloth, leaf Cl− was positively related to leaf transpiration as both were higher in the spring than in the fall, regardless of rootstock or shade treatment. Overall, leaf Cl− was positively related to water use and was negatively related to leaf WUE. High growth, low water use, and consequently, high WUE of salinized citrus were related to low leaf Cl−. Such relationships can be used as indicators of salinity tolerance.
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Thompson, WA, PE Kriedemann, and IE Craig. "Photosynthetic Response to Light and Nutrients in Sun-Tolerant and Shade-Tolerant Rainforest Trees. I. Growth, Leaf Anatomy and Nutrient Content." Functional Plant Biology 19, no. 1 (1992): 1. http://dx.doi.org/10.1071/pp9920001.
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Seedling trees of Argyrodendron sp., A. trifoliolaturn, Flindersia brayleyana and Toona australis were grown for c. 180 days under one of three light regimes with either of two nutrient levels (6 treatments in all). Light regimes spanned the range of environmental conditions which these species would normally experience in northern Queensland rainforest: deep shade (1.3 mol quanta m-2 day-1, equivalent to forest floor), moderate light (5.6 mol quanta m-2 day-1, comparable to midcanopy), and strong light (23 mol quanta m-2 day-1, matching daily irradiance of exposed crowns). Long-term shade tolerance in Argyrodendron sp. and A. trifoliolaturn was associated with limited responses in growth and leaf anatomy to low light and nutrients. Starch accumulation in leaves under all treatments, and especially low nutrients, implied that supply of photoassimilate exceeded demand. Such a conservative carbon economy, plus the accumulation of stem P reserves, even in a weak light environment, is consistent with a protracted existence as part of a forest floor community. By contrast, shade-intolerant Toona is an early successional species and lacks such adaptive features. Instead, light and nutrients had a strong interactive effect on growth. Flindersia, with a broad tolerance to sun and shade, was intermediate in growth response and leaf adjustment, which is consistent with its success across a wide size range of forest gaps.
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Rodríguez-Calcerrada, Jesús, Roberto L. Salomón, Guillermo G. Gordaliza, et al. "Respiratory costs of producing and maintaining stem biomass in eight co-occurring tree species." Tree Physiology 39, no. 11 (2019): 1838–54. http://dx.doi.org/10.1093/treephys/tpz069.
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AbstractGiven the importance of carbon allocation for plant performance and fitness, it is expected that competition and abiotic stress influence respiratory costs associated with stem wood biomass production and maintenance. In this study, stem respiration (R) was measured together with stem diameter increment in adult trees of eight co-occurring species in a sub-Mediterranean forest stand for 2 years. We estimated growth R (Rg), maintenance R (Rm) and the growth respiration coefficient (GRC) using two gas exchange methods: (i) estimating Rg as the product of growth and GRC (then Rm as R minus Rg) and (ii) estimating Rm from temperature-dependent kinetics of basal Rm at the dormant season (then Rg as R minus Rm). In both cases, stem basal-area growth rates governed intra-annual variation in R, Rg and Rm. Maximum annual Rm occurred slightly before or after maximum Rg. The mean contribution of Rm to R during the growing season ranged from 56% to 88% across species using method 1 and from 23% to 66% using method 2. An analysis accounting for the phylogenetic distance among species indicated that more shade-tolerant, faster growing species exhibited higher Rm and Rg than less shade-tolerant, slower growing ones, suggesting a balance between carbon supply and demand mediated by growth. However, GRC was not related to species growth rate, wood density, or drought and shade tolerance across the surveyed species nor across 27 tree species for which GRC was compiled. The GRC estimates based on wood chemical analysis were lower (0.19) than those based on gas exchange methods (0.35). These results give partial support to the hypothesis that wood production and maintenance costs are related to species ecology and highlight the divergence of respiratory parameters widely used in plant models according to the methodological approach applied to derive them.
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Canham, Charles D., Adrien C. Finzi, Stephen W. Pacala, and Diane H. Burbank. "Causes and consequences of resource heterogeneity in forests: interspecific variation in light transmission by canopy trees." Canadian Journal of Forest Research 24, no. 2 (1994): 337–49. http://dx.doi.org/10.1139/x94-046.
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We have analyzed the light transmission characteristics of the nine deciduous and coniferous species that dominate the transition oak–northern hardwood forests of southern New England. Maximum likelihood techniques were used to estimate species-specific light extinction coefficients, using fish-eye photography combined with data on the locations and geometry of trees in the neighborhood around each photo point. Quantum sensors were also used to quantify interspecific variation in the importance of sunflecks and beam enrichment. Variation in light extinction was closely correlated with shade tolerance and successional status of the species. The most shade-tolerant species (Fagusgrandifolia Ehrh. and Tsugacanadensis (L.) Carr.) cast the deepest shade (<2% of full sun), while earlier successional species such as Quercusrubra L. and Fraxinusamericana L. allowed greater light penetration (>5% full sun). These differences were more closely related to differences in crown depth than to differences in light extinction per unit depth of crown. Sunflecks contributed relatively little radiation beneath late successional species (<10% of total understory photosynthetically active radiation), but represented a major fraction (40–50%) of radiation beneath less shade-tolerant species. Using growth and mortality functions for the same species developed in a related study, our results indicate that saplings of all of the species have high survivorship in the shade cast by conspecific adults. However, only the three most shade-tolerant species have low rates of sapling mortality under the low light levels characteristic of stands dominated by late successional species. Our results are consistent with previously reported models, which propose that secondary succession is driven by interspecific differences in resource uptake and tolerance.
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Nischwitz, C., and G. Newcombe. "First Report of Powdery Mildew (Sawadaea bicornis) on Norway Maple (Acer platanoides) in North America." Plant Disease 87, no. 4 (2003): 451. http://dx.doi.org/10.1094/pdis.2003.87.4.451a.
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Norway maple (Acer platanoides L.) was introduced into the continental United States around 1756 as a street tree (2). It is a widely planted shade tree in the northern United States and Canada due to its fast growth rate when young and its tolerance of pavement and dry soils. Powdery mildew is common on Norway maple in Europe with records from at least 22 countries according to the databases of the U.S. National Fungus Collections. However, there are no North American records. In September 2002, powdery mildew was observed on young Norway maple trees along the Idaho-Washington border in Moscow and Pullman, respectively. Mildew was not observed on older Norway maple trees. The mildew occurred mainly on the upper leaf surface as patches of dense, white mycelium with scattered or gregarious cleistothecia. Mean diameter of the cleistothecia was 146 (± 13.4) μm. Short stalked and subsessile asci averaged 69 (± 4.1) μm × 48 (± 5.4) μm. Ascospores averaged 27 (± 3.2) μm × 12 (±0.9) μm. Appendages were deeply cleft, simple, or one to three times dichotomously branched. This mildew fits the description of the European species Sawadaea bicornis (Wallr:Fr.) Homma (1). Also, conforming to S. bicornis were chains of macroconidia (21 (± 2.7) × 14 (± 1.5) μm) and microconida. Fibrosin bodies were seen in both. Infection of only some young trees and its absence in previous years lead us to believe that the introduction is recent in the Pacific Northwest. The susceptibility of native maples to the Norway maple mildew remains to be determined. Specimens have been deposited in the U.S. National Fungus Collections (BPI 842088). References: (1) U. Braun. A monograph of the Erysiphales (powdery mildews) J. Cramer, Berlin-Stuttgart, 1987. (2) D. J. Nowak and R. A. Rowntree. J. Arboric. 16:291, 1990.
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Silveira, Gleydson Vinicius, Alan Cauê Holanda, Allyson Rocha Alves, Françóyse Dávilla Silva, and João Lucas Oliveira. "DEVELOPMENT OF Tabebuia aurea AND Anadenanthera macrocarpa UNDER DIFFERENT LEVELS OF SHADING." REVISTA ENGENHARIA NA AGRICULTURA - REVENG 28 (November 26, 2020): 357–63. http://dx.doi.org/10.13083/reveng.v29i1.8857.
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The efficiency in the initial growth of trees can be related to the ability of the seedlings in adapting to different light intensites in the enviroment. The objective of this work was to evaluate the influence of different levels of shading in the initial growth of Tabebuia aurea and Angico (Anadenanthera macrocarpa) in the nursery phase. The experiment was conducted at the Federal Rural University of Semiárido located in Mossoró-RN. The seeds of A. macrocarpa and T. aurea were collected from parent trees and donated by the Caatinga/ UFERSA / Petrobras Project, where, afterwards, they were processed. The composting used in the experiment was coconut fiber, after the substrate was placed in 55-cm³ tubes and organized in plastic supports. The seedlings were submitted to three levels of shade, full sun (absence of shade), shade of 50% and 80%. For the different levels of shading, mean values of the height/diameter ratio of the neck were obtained of 3.74 (A. macrocarpa) and 1.57 (T. aurea) for cultivation in full sun, 0% of shading, indicating that the growth of this cropt may have better results under these conditions. The highest values of the Dickson Quality Index (DQI) were observed in seedlings grown under a lower shade level of 0.03454 and 0.11719. The species T. aurea shows little tolerance when subjected to high levels of shading, showing that the luminosity interfere in the initial growth of the species. A. macrocarpa, also acquired a better development in full sun, showing less progress at higher levels of shading.
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Kunstler, Georges, David A. Coomes, and Charles D. Canham. "Size-dependence of growth and mortality influence the shade tolerance of trees in a lowland temperate rain forest." Journal of Ecology 97, no. 4 (2009): 685–95. http://dx.doi.org/10.1111/j.1365-2745.2009.01482.x.
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St-Gelais, Vincent, Martin Béland, and Nelson Thiffault. "Exploring the potential of two-aged white spruce plantations for the production of sawlog volume with simulations using SORTIE-ND." Reforesta, no. 10 (December 30, 2020): 11–24. http://dx.doi.org/10.21750/refor.10.02.85.
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The main objective for even-aged plantation (EAP) management of producing sawlog material has driven practices towards low initial planting densities and lower post thinning densities. For semi-shade tolerant species, the resulting stand density potentially leaves enough growing space for the introduction of a second cohort of trees in the understory, making it a two-aged plantation (TAP). TAP could have many silvicultural benefits, especially in sensitive areas where intensive treatments associated with EAP are incompatible with local management objectives. White spruce (Picea glauca) is a good candidate species for modeling TAP because it is the most widely planted tree species in Canada and has proven tolerance to understory planting. SORTIE-ND, a single-tree spatially explicit growth model was used to explore the yield of variable density and rotation length scenarios when each white spruce cohort is introduced mid rotation, compared to traditional even-aged management. All TAP scenarios tested produced more sawlog volume and more merchantable volume than equivalent densities of EAPs. The lowest density tested, 400 stems ha-1 planted every 35 years, had the highest sawlog yields (3.23 m3 ha-1 yr-1). Considering smaller size products changes the optimum TAP scenario but maintains the advantage over EAPs.
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Sendall, Kerrie M., Christopher H. Lusk, and Peter B. Reich. "Trade‐offs in juvenile growth potential vs. shade tolerance among subtropical rain forest trees on soils of contrasting fertility." Functional Ecology 30, no. 6 (2015): 845–55. http://dx.doi.org/10.1111/1365-2435.12573.
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SHEIL, DOUGLAS, STEPHEN JENNINGS, and PETER SAVILL. "Long-term permanent plot observations of vegetation dynamics in Budongo, a Ugandan rain forest." Journal of Tropical Ecology 16, no. 6 (2000): 865–82. http://dx.doi.org/10.1017/s0266467400001723.
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Species composition and turnover that have occurred in a series of permanent sample plots established during the 1930s and 1940s in Budongo, a semi-deciduous Ugandan forest, are reported. The plots were established as part of a sequence first used to describe forest succession, five of which have been maintained and which were last measured in 1992-1993. One plot (plot 7) provides 53 y of data from old-growth pristine forest. Plot 15 was established in wooded grassland at the forest edge and is now closed high forest. Evaluation of the remaining three plots is complicated by silvicultural interventions carried out in the 1950s. Forty species have been added since the first evaluations and a total of 188 tree species (over 80% of Budongo's forest tree flora, and including two exotics) has now been recorded from within the plots. The pattern of shade-tolerance in the original plot series conforms to patterns expected for succession with an increasing proportion of shade-tolerant species with development, and large stems appearing to ‘lag behind’ smaller stems in this respect. The time series data are less consistent, and while plot 7 increased in the proportion of shade-tolerant stems through time, the proportion of shade-tolerant species actually declines. Stem-turnover (the mean of mortality and recruitment) slowed with implied successional stage. Most species have a higher recruitment than mortality rate and stem numbers have thus increased in all plots. This is most pronounced in the putatively ‘early successional’ plot. Stem size structure has changed within the plots, with an increased proportion of smaller stems. Species show different rates of turnover and these vary from plot to plot and period to period. In plot 7, the overall mortality rate decreased with initial stem size. Estimates imply that some tree species may easily live longer than 500 y after reaching 10 cm DBH, and that 1000 y is possible. The importance of large trees in determining forest dynamics is illustrated by the finding that death of only seven stems in plot 7 contributed over 60% of net basal area losses recorded over the 53-y observation period. Many of the observed patterns were not predicted and could only have been found by long-term studies.
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Dyer, Jacob H., Stith T. Gower, Jodi A. Forrester, Craig G. Lorimer, David J. Mladenoff, and Julia I. Burton. "Effects of selective tree harvests on aboveground biomass and net primary productivity of a second-growth northern hardwood forest." Canadian Journal of Forest Research 40, no. 12 (2010): 2360–69. http://dx.doi.org/10.1139/x10-184.
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Restoring structural features of old-growth forests, such as increased canopy gap sizes and coarse woody debris, is a common management goal for second-growth, even-aged stands. We experimentally manipulated forest structure by creating variable-size canopy gaps in a second-growth northern hardwood forest in north-central Wisconsin following two growing seasons of pre-treatment monitoring. The objectives of this study were to quantify the influence of canopy gaps of different sizes (50–380 m2) on aboveground biomass and productivity of each vegetation stratum two growing seasons following treatment. Two years after treatment, ground layer biomass in canopy openings increased significantly relative to surrounding undisturbed transition zones. The response of ground layer biomass was greatest in the large versus the medium and small gaps. Sapling aboveground net primary productivity was significantly greater in undisturbed transition zones than within gaps across gap sizes following the second post-treatment growing season. Annual stem diameter increment was greatest for trees along gap borders and was correlated with crown class, percentage of crown perimeter exposed, gap area, and shade tolerance. Total aboveground net primary productivity was significantly lower in the gap addition plots the first year but by the second post-treatment growing season no longer differed from that in the control plots.
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Ibáñez, Inés, and Sarah McCarthy-Neumann. "Effects of mycorrhizal fungi on tree seedling growth: quantifying the parasitism–mutualism transition along a light gradient." Canadian Journal of Forest Research 46, no. 1 (2016): 48–57. http://dx.doi.org/10.1139/cjfr-2015-0327.
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Mycorrhizal fungi colonize tree seedlings shortly after germination, and the nature of this relationship (mutualistic to parasitic) has been reported to vary as a function of resources; however, this transition has rarely been quantified. Using a light gradient, we grew seedlings of eight tree species in soils that were cultivated by several co-existing species of trees. We used data on root mycorrhizal fungi to quantify colonization along the gradient of light. We then analyzed plant growth as a function of both the light gradient and the extent of mycorrhizal colonization. Mycorrhizal fungi colonization varied among species but was not correlated with the species’ seed sizes or shade tolerances. Within a species, colonization varied among soil sources, but those differences followed neither the conspecific–heterospecific dichotomy, nor the soil host’s arbuscular–ectomycorrhizal associations commonly reported. At high light levels, seedlings growth increased with increasing levels of colonization for seven species, and at low light levels, the effect of colonization was negative for five species. We also quantified the light threshold at which the plant – mycorrhizal fungi relationship shifted from neutral to positive (four species), from negative to neutral (one species), and from neutral to negative (one species), documenting differences among species that could exacerbate competitive interactions during recruitment.
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Kenefic, Laura S., John M. Kabrick, Benjamin O. Knapp, et al. "Mixedwood silviculture in North America: the science and art of managing for complex, multi-species temperate forests." Canadian Journal of Forest Research 51, no. 7 (2021): 921–34. http://dx.doi.org/10.1139/cjfr-2020-0410.
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Temperate mixedwoods (hardwood–softwood mixtures) in central and eastern United States and Canada can be classified into two overarching categories: those with shade-tolerant softwoods maintained by light to moderate disturbances and those with shade-intolerant to mid-tolerant softwoods maintained by moderate to severe disturbances. The former includes red spruce (Picea rubens Sarg.), balsam fir (Abies balsamea (L.) Mill.), or eastern hemlock (Tsuga canadensis (L.) Carr.) in mixture with northern hardwood species; the latter includes pine (Pinus) – oak (Quercus) mixtures. Such forests have desirable socio-economic values, wildlife habitat potential, and (or) adaptive capacity, but management is challenging because one or more softwood species in each can be limited by depleted seed sources, narrow regeneration requirements, or poor competitive ability. Appropriate silvicultural systems vary among mixedwood compositions depending on shade tolerance and severity of disturbance associated with the limiting softwoods, site quality, and level of herbivory. Sustainability of mixedwood composition requires that stand structure and composition be managed at each entry to maintain vigorous trees of species with different growth rates and longevities and to encourage development of advance reproduction or seed-producing trees of desired species. Regardless of silvicultural system, maintaining seed sources of limiting softwoods, providing suitable germination substrates, and controlling competition are critical. Here, we describe commonalities among temperate mixedwoods in central and eastern North America and present a framework for managing them.
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Uemura, Shigeru. "Patterns of leaf phenology in forest understory." Canadian Journal of Botany 72, no. 4 (1994): 409–14. http://dx.doi.org/10.1139/b94-055.
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Foliar phenologies of forest understory plants were categorized, and the distribution pattern of leaf habit was examined among different forest environments. Various patterns of foliar phenology were found, especially in herbaceous plants. In addition to the seasonal light regime controlled by the phenology of canopy trees, differences in the length of period with snow cover led to the divergence. Perennial-leaved plants predominate in intensely shaded habitats while annual-leaved plants are more abundant in less shaded habitats. The shade tolerance of perenniel-leaved plants can be considered a preadaptation to snow tolerance. In contrast with the perennial-leaved plants, biennial-leaved plants with leaves overwintering 1 year appear to be favored in euphotic habitats with high insulation both in spring and in autumn. These species are effective competitors in spring because of rapid emergence of current leaves, probably through retranslocation of resources accumulated in the previous year. Another adaptive trait is found in heteroptic plants simultaneously having summer-green leaves and overwintering leaves; these types of leaves seem to function in predictable and quite different environments in a year. Key words: foliar phenology, growth form, light resource, overwintering leaf, snow cover.
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Newbery, D. M., D. N. Kennedy, G. H. Petol, L. Madani, and C. E. Ridsdale. "Primary forest dynamics in lowland dipterocarp forest at Danum Valley, Sabah, Malaysia, and the role of the understorey." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 354, no. 1391 (1999): 1763–82. http://dx.doi.org/10.1098/rstb.1999.0519.
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Changes in species composition in two 4–ha plots of lowland dipterocarp rainforest at Danum, Sabah, were measured over ten years (1986 to 1996) for trees greater than or equal to 10 cm girth at breast height (gbh). Each included a lower–slope to ridge gradient. The period lay between two drought events of moderate intensity but the forest showed no large lasting responses, suggesting that its species were well adapted to this regime. Mortality and recruitment rates were not unusual in global or regional comparisons. The forest continued to aggrade from its relatively (for Sabah) low basal area in 1986 and, together with the very open upper canopy structure and an abundance of lianas, this suggests a forest in a late stage of recovery from a major disturbance, yet one continually affected by smaller recent setbacks. Mortality and recruitment rates were not related to population size in 1986, but across subplots recruitment was positively correlated with the density and basal area of small trees (10 to <50 cm gbh) forming the dense understorey. Neither rate was related to topography. While species with larger mean gbh had greater relative growth rates (rgr) than smaller ones, subplot mean recruitment rates were correlated with rgr among small trees. Separating understorey species (typically the Euphorbiaceae) from the overstorey (Dipterocarpaceae) showed marked differences in change in mortality with increasing gbh: in the former it increased, in the latter it decreased. Forest processes are centred on this understorey quasi–stratum. The two replicate plots showed a high correspondence in the mortality, recruitment, population changes and growth rates of small trees for the 49 most abundant species in common to both. Overstorey species had higher rgrs than understorey ones, but both showed considerable ranges in mortality and recruitment rates. The supposed trade–off in traits, viz slower rgr, shade tolerance and lower population turnover in the understorey group versus faster potential growth rate, high light responsiveness and high turnover in the overstorey group, was only partly met, as some understorey species were also very dynamic. The forest at Danum, under such a disturbance–recovery regime, can be viewed as having a dynamic equilibrium in functional and structural terms. A second trade–off in shade–tolerance versus drought–tolerance is suggested for among the understorey species. A two–storey (or vertical component) model is proposed where the understorey–overstorey species’ ratio of small stems (currently 2:1) is maintained by a major feedback process. The understorey appears to be an important part of this forest, giving resilience against drought and protecting the overstorey saplings in the long term. This view could be valuable for understanding forest responses to climate change where drought frequency in Borneo is predicted to intensify in the coming decades.
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Gedalof, Ze’ev, and Jennifer Franks. "Stand Structure and Composition Affect the Drought Sensitivity of Oregon White Oak (Quercus garryana Douglas ex Hook.) and Douglas-Fir (Pseudotsuga menziesii (Mirb.) Franco)." Forests 10, no. 5 (2019): 381. http://dx.doi.org/10.3390/f10050381.
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Due to a suite of environmental changes, Oregon white oak (Quercus garryana Douglas ex Hook; called Gary oak in Canada) associated ecosystems at many North American sites are being encroached upon by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) and other conifer species. Alteration of stand structure and composition is causing substantial changes in the dynamics of these ecosystems, creating an environment in which Oregon white oak is not thriving. In this study we used dendrochronology to investigate the competitive dynamics between Oregon white oak and Douglas-fir in a mixed forest stand on Southern Vancouver Island. Significant species-specific differences in radial growth sensitivity to drought were found between Oregon white oak and Douglas-fir. Oregon white oak trees growing at high densities, or competing with Douglas-fir for moisture were found to be more sensitive to drought and more sensitive to growing conditions during the prior year. The response of Douglas-fir to drought was less variable, possibly due to the relatively low conifer densities at our study site, as well as the species’ ability to root graft, its higher shade tolerance than Oregon white oak, and its rapid growth rates that allow it to achieve a more dominant canopy position. The non-stationary response to climate exhibited by Oregon white oak provides insights into the mechanisms by which Oregon white oak savannas are being converted to coniferous woodland, but also suggest that tree-ring reconstructions of climate need to explicitly address changes in stand dynamics that could influence the growth–climate relationship
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Robakowski, Piotr, Tomasz P. Wyka, Wojciech Kowalkowski, et al. "Practical Implications of Different Phenotypic and Molecular Responses of Evergreen Conifer and Broadleaf Deciduous Forest Tree Species to Regulated Water Deficit in a Container Nursery." Forests 11, no. 9 (2020): 1011. http://dx.doi.org/10.3390/f11091011.
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Recent climatic changes have resulted in an increased frequency and prolonged periods of drought and strained water resources affecting plant production. We explored the possibility of reducing irrigation in a container nursery and studied the growth responses of seedlings of four economically important forest trees: broadleaf deciduous angiosperms Fagus sylvatica L., Quercus petraea (Matt.) Liebl., and evergreen conifers Abies alba Mill. and Pinus sylvestris L. We also studied markers of water stress including modifications of biomass allocation, leaf anatomy, proline accumulation, and expression of selected genes. Growth of the broadleaved deciduous species was more sensitive to the reduced water supply than that of conifers. Remarkably, growth of the shade tolerant Abies was not affected. Adjustment of biomass allocations was strongest in P. sylvestris, with a remarkable increase in allocation to roots. In response to water deficit both deciduous species accumulated proline in leaves and produced leaves with shorter palisade cells, reduced vascular tissues, and smaller conduit diameters. These responses did not occur in conifers. Relative transcript abundance of a gene encoding the Zn-finger protein in Q. petraea and a gene encoding the pore calcium channel protein 1 in A. alba increased as water deficit increased. Our study shows major differences between functional groups in response to irrigation, with seedlings of evergreen conifers having higher tolerance than the deciduous species. This suggests that major water savings could be achieved by adjusting irrigation regime to functional group or species requirements.
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CARR, M. K. V. "THE WATER RELATIONS OF RUBBER (HEVEA BRASILIENSIS): A REVIEW." Experimental Agriculture 48, no. 2 (2011): 176–93. http://dx.doi.org/10.1017/s0014479711000901.
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SUMMARYThe results of research done on water relations of rubber are collated and summarised in an attempt to link fundamental studies on crop physiology to crop management practices. Background information is given on the centres of origin (Amazon Basin) and production of rubber (humid tropics; south-east Asia), but the crop is now being grown in drier regions. The effects of water stress on the development processes of the crop are summarised, followed by reviews of its water relations, water requirements and water productivity. The majority of the recent research published in the international literature has been conducted in south-east Asia. The rubber tree has a single straight trunk, the growth of which is restricted by ‘tapping’ for latex. Increase in stem height is discontinuous, a period of elongation being followed by a ‘rest’ period during which emergence of leaves takes place. Leaves are produced in tiers separated by lengths of bare stem. Trees older than three to four years shed senescent leaves (a process known as ‘wintering’). ‘Wintering’ is induced by dry, or less wet, weather; trees may remain (nearly) leafless for up to four weeks. The more pronounced the dry season the shorter the period of defoliation. Re-foliation begins before the rains start. The supply of latex is dependent on the pressure potential in the latex vessels, whereas the rate of flow is negatively correlated with the saturation deficit of the air. Radial growth of the stem declines in tapped trees relative to untapped trees within two weeks of the start of tapping. Roots can extend in depth to more than 4 m and laterally more than 9 m from the trunk. The majority of roots are found within 0.3 m of the soil surface. Root elongation is depressed during leaf growth, while root branching is enhanced. Stomata are only found on the lower surface of the leaf, at densities from 280 to 700 mm−2. The xylem vessels of rubber trees under drought stress are vulnerable to cavitation, particularly in the leaf petiole. By closing, the stomata play an essential role in limiting cavitation. Clones differ in their susceptibility to cavitation, which occurs at xylem water potentials in the range of −1.8 to −2.0 MPa. Clone RRII 105 is capable of maintaining higher leaf water potentials than other clones because of stomatal closure, supporting its reputation for drought tolerance. Clones differ in their photosynthetic rates. Light inhibition of photosynthesis can occur, particularly in young plants, when shade can be beneficial. Girth measurements have been used to identify drought-tolerant clones. Very little research on the water requirements of rubber has been reported, and it is difficult to judge the validity of the assumptions made in some of the methodologies described. The actual evapotranspiration rates reported are generally lower than might be expected for a tree crop growing in the tropics (<3 mm d−1). Virtually no research on the yield responses to water has been reported and, with the crop now being grown in drier regions, this is surprising. In these areas, irrigation can reduce the immaturity period from more than 10 years to six years. The important role that rubber plays in the livelihoods of smallholders, and in the integrated farming systems practised in south-east Asia, is summarized.
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Drever, C. Ronnie, and Kenneth P. Lertzman. "Light-growth responses of coastal Douglas-fir and western redcedar saplings under different regimes of soil moisture and nutrients." Canadian Journal of Forest Research 31, no. 12 (2001): 2124–33. http://dx.doi.org/10.1139/x01-149.
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We characterized the radial and height growth response to light for coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) and western redcedar (Thuja plicata Donn ex D. Don) saplings growing in sites of different regimes of soil moisture and nutrients on the east coast of Vancouver Island, British Columbia. We determined that at low light levels, site quality has little effect on the growth response of Douglas-fir saplings. At light levels above approximately 40 and 60% full sun, Douglas-fir saplings show statistically significant differences in height and radial growth, respectively, that reflect the differences in soil moisture and nutrient regimes of the sites we examined. Western redcedar approaches its maximum radial and height growth rates at about 30% full sun. Our data suggest that partial-cutting treatments need to create light environments greater than about 40% full sun to achieve growth that represents a high proportion of the site growing potential for Douglas-fir at full sun, while the high shade tolerance of western redcedar allows silvicultural treatments that retain a high amount of forest structure without compromising growth rates of young trees.
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Niinemets, Ülo. "Growth of Young Trees of Acer platanoides and Quercus robur Along a Gap- Understory Continuum: Interrelationships between Allometry, Biomass Partitioning, Nitrogen, and Shade Tolerance." International Journal of Plant Sciences 159, no. 2 (1998): 318–30. http://dx.doi.org/10.1086/297553.
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Fajvan, Mary Ann, and Robert S. Seymour. "Canopy stratification, age structure, and development of multicohort stands of eastern white pine, eastern hemlock, and red spruce." Canadian Journal of Forest Research 23, no. 9 (1993): 1799–809. http://dx.doi.org/10.1139/x93-228.
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The causes of canopy stratification were investigated in five mixed stands of red spruce (Picearubens Sarg.), hemlock (Tsugacanadensis (L.) Carr.), and white pine (Pinusstrobus L.) in eastern Maine. All species were present in all crown classes; however, there was a clear pattern of pine dominance and eventual emergence. Red spruce was prevalent in the middle stratum, and hemlock most common in the lower strata. Canopy stratification was caused by interspecific differences in shade tolerance and height growth, and by multicohort structures. The multicohort structures developed as a result of episodic partial disturbances such as spruce budworm (Choristoneurafumiferana Clemens) outbreaks and partial harvesting that both initiated regeneration and released previously suppressed trees of older, surviving cohorts. Spatial and temporal variability in disturbances created extremely variable patterns of competition among cohorts, resulting in a more complex developmental pattern than would be found in a single-cohort model involving stand-replacing disturbances.
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Cain, Michael D., and Michael G. Shelton. "Thirty-eight years of autogenic, woody understory dynamics in a mature, temperate pine–oak forest." Canadian Journal of Forest Research 25, no. 12 (1995): 1997–2009. http://dx.doi.org/10.1139/x95-216.
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In 1935, 32 ha of a pine–hardwood forest were set aside from future timber management in southern Arkansas, U.S.A. Old-growth timber had been cut to a 36-cm stump diameter before 1915. Between 1952 and 1993, four inventories were made of the overstory and midstory components (number of live trees ≥9 cm in diameter breast height (DBH) taken at 1.37 m, by 2.54-cm DBH classes). Between 1954 and 1992, four corresponding inventories were made of the woody understory vegetation (>15 cm tall but <9 cm DBH) by counting rootstocks within 52 systematically spaced 8-m2 circular quadrats. Understory species importance values (relative density + relative height + relative frequency) were used to compute diversity and similarity indices. During 38 years of assessment, no catastrophic disturbances occurred within the 32-ha forest. Although loblolly pine (Pinustaeda L.) and shortleaf pine (Pinusechinata Mill.) dominated the overstory (64% of basal area in 1954 and 63% in 1993), pines were absent from the understory in all but seedling size classes for the last 38 years. Woody understory diversity indices were essentially stable for 38 years, but the similarity of understory species tended to decline as the time between inventories increased. Relative importance values for woody understory species tended to increase for the more shade-tolerant genera and decrease for less tolerant genera. Survival and height growth of woody understory species were also found to be positively correlated with shade tolerance.
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Ntawuhiganayo, Elisée Bahati, Félicien K. Uwizeye, Etienne Zibera, et al. "Traits controlling shade tolerance in tropical montane trees." Tree Physiology 40, no. 2 (2019): 183–97. http://dx.doi.org/10.1093/treephys/tpz119.
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Abstract Tropical canopies are complex, with multiple canopy layers and pronounced gap dynamics contributing to their high species diversity and productivity. An important reason for this complexity is the large variation in shade tolerance among different tree species. At present, we lack a clear understanding of which plant traits control this variation, e.g., regarding the relative contributions of whole-plant versus leaf traits or structural versus physiological traits. We investigated a broad range of traits in six tropical montane rainforest tree species with different degrees of shade tolerance, grown under three different radiation regimes (under the open sky or beneath sparse or dense canopies). The two distinct shade-tolerant species had higher fractional biomass in leaves and branches while shade-intolerant species invested more into stems, and these differences were greater under low radiation. Leaf respiration and photosynthetic light compensation point did not vary with species shade tolerance, regardless of radiation regime. Leaf temperatures in open plots were markedly higher in shade-tolerant species due to their low transpiration rates and large leaf sizes. Our results suggest that interspecific variation in shade tolerance of tropical montane trees is controlled by species differences in whole-plant biomass allocation strategy rather than by difference in physiological leaf traits determining leaf carbon balance at low radiation.
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Liu, Guofan, and Kent D. Kobayashi. "249 Shading Effects on Vegetative Growth and Fruiting of Coffee." HortScience 34, no. 3 (1999): 485B—485. http://dx.doi.org/10.21273/hortsci.34.3.485b.
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A shade experiment for pruned coffee trees was conducted on Maui, Hawaii, in 1996. Nine-year-old `Guadalupe' trees were stumped at 70 cm above the ground, and three main verticals were allowed to remain on the main trunk. Each stumped tree was randomly selected and covered with shade cloth. The shade cloths were 30%, 50%, and 70% shade, and each shade structure had a length × width × height of 1.5 × 1.5 × 2.5 m. Data were collected in 1997. In general, the basal diameters of the verticals were similar in all treatments, as were the lengths of the verticals. The total number of laterals in the full-light treatment was slightly more than that of the other treatments. The numbers of flowering laterals were similar in all treatments. The numbers of fruit per tree in the full light, 30%, 50%, and 70% shade treatments were 1876, 3434, 2399, and 403, respectively. Fruit per flowering node was the best index relating to yield. Fruit per node was highest under 30% shade, followed by full light and 70% shade. At the beginning, fruit ripened faster in the full light treatment than in the other treatments, but at the end of September, fruit in 70% shade ripened slower than the other treatments. Therefore, after stumping, coffee trees grew best under 30% shade. For coffee, pruning under the field condition, stumping every other row of trees may be a satisfactory way to obtain the best yield in the future.
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Silva Neto, Francisco José da, Leila Bonfanti, Rodrigo Gazaffi, and Anastácia Fontanetti. "EFFECTS OF SHADE TREE SPATIAL DISTRIBUTION AND SPECIES ON PHOTOSYNTHETIC RATE OF COFFEE TREES." Coffee Science 14, no. 3 (2019): 326. http://dx.doi.org/10.25186/cs.v14i3.1584.
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The use of shade trees in coffee fields have been motivated by climatic changes. However, microclimatic conditions in shaded coffee fields differ due to shade tree spatial distribution and species, altering physiological responses of coffee trees. This study aimed to evaluate the effects of shade tree spatial distribution and species on coffee trees photosynthetic rate in two growth seasons, of high (HSD) and low (LSD) sink demand. The experimental design consisted of randomized blocks with three replicates in split-split-plots. Plots were the shade tree species: <em>Anadenanthera falcata</em>, <em>Cassia grandis</em> and <em>Peltophorum dubium</em>. Split plot was formed by five distances between coffee trees and shade tree trunks: coffee trees on planting row of shade trees, distancing one (D1L) and five (D5L) meters from shade trees trunk; coffee trees on inter-rows of shade trees, parallel to D1L and D5L (D1E and D5E); coffee trees distancing 77 meters from shade tree trunks, in a full-sun field (PS). The split-split-plots correspond to coffee tree canopy exposure to the sun: branches facing North or South. Shade trees canopy density and occupation was evaluated with a convex densiometer. Photosynthetic rate (Pn)and photosynthetic active radiation (PAR) were measured with an Infrared Gas Analyzer (IRGA) on two time-frames, between 7.00 and 9.00 solar hours and between 11.00 and 13.00. Shade tree canopy density and occupation was not homogenous during the change of seasons and shift due to spatial distribution, which also changes PAR levels. Shade trees reduce PAR to more suitable values for coffee tree exploitation, especially on D1L and D5L. During HSD, shading did not affect P<sub>n</sub>, which was greater in branches facing North. Yet, in LSD, between 11.00 and 13.00, coffee trees shaded with <em>A. falcata</em> showed greater P<sub>n</sub> than at PS. Coffee trees shaded with <em>C. grandis</em> at D5L and D1E had greater values of P<sub>n</sub> than PS.
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Feng, Jiayi, Kangning Zhao, Dong He, et al. "Comparing shade tolerance measures of woody forest species." PeerJ 6 (October 9, 2018): e5736. http://dx.doi.org/10.7717/peerj.5736.
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Shade tolerance, the minimum light requirement for plant survival, is a key trait for understanding community assembly and forest dynamics. However, it is poorly defined for tree species to date. Current methods of measuring shade tolerance vary considerably in their performance. For instance, some measures of shade tolerance are unreliable except under some specific conditions. Therefore, it is necessary to compare the performance of these methods to provide guidance of choosing appropriate shade tolerance measures in future studies. We collected a large dataset of light traits and other life history traits for 137 understory wood species in a subtropical forest and tested the performance of five commonly used shade-tolerance indices. Results showed that all the shade-tolerance measures, except the low-light abundance index, performed poorly in distinguishing and ranking shade tolerance of the tested species. The shade tolerance quantified by the low-light abundance was consistent with empirical classification of shade-tolerance/intolerance groups and successional seral stages of species. Comparison of the shade tolerance between trees of different diameter at breast height (DBH) or height classes further confirmed the reliability of low-light abundance. We conclude that low-light abundance is the most objective and practical of the five most commonly-used methods for measuring and ranking shade tolerance of understory wood species in our study forest, and likely in other forests as well. The simplicity of the method should greatly facilitate the assessment of light niche differentiation between species and thus contribute to understanding coexistence of tree species in forests.
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Rahman, MA, ZR Moni, MA Rahman, and S. Nasreen. "Investigation of Shade Tree Species Used in Tea Garden in Bangladesh." SAARC Journal of Agriculture 18, no. 1 (2020): 219–37. http://dx.doi.org/10.3329/sja.v18i1.48395.
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The shade trees are an integral component of tea cultivation in Bangladesh. The shade trees are essential for modulating the environment of the tea ecosystem, enriching the soil fertility, reducing temperature and the evaporative capacity, conserve soil moisture and helps in the control of certain pests and diseases which are positively thermotropic in nature. The shade trees provide partial shade to the tea plants, which is important for improving the quality of the tea leaf. The right type of shade trees and their proper management is a prerequisite for successful tea crop growing. For this persists, a floristic exploration of shade trees was carried out at fifteen tea gardens in Chattogram and Moulvibazar District of Bangladesh from November 2017 to December 2018. During the investigation, a total of 44 species of Angiosperm representing 31 genera of 9 families was enlisted. For every species, scientific name, vernacular name, status, and necessary photographs are mentioned. In the assessment, the Fabaceae family shows the highest number of shade trees comprising 19 genera and 31 species. The most common permanent shade tree species among the tea gardens are Albizia odoratissima, A. chinensis, A. lebbeck, A. lucidior, A. procera, and Derris robusta. Indigofera teysmannii is frequently using as a temporary shade species in all investigated tea gardens. Cajanus cajan, Tephrosia candida, Tephrosia candida, Gliricidia sepium, Erythrina lithosperma and Desmodium gyroides species are also used as temporary shade trees in many tea gardens. Further investigations, however,are required to find out the right type of shade tree species on the growth and yield of tea plants in tea cultivation areas of Bangladesh.
 SAARC J. Agri., 18(1): 219-237 (2020)
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Lieberman, Diana, Milton Lieberman, Gary Hartshorn, and Rodolfo Peralta. "Growth rates and age-size relationships of tropical wet forest trees in Costa Rica." Journal of Tropical Ecology 1, no. 2 (1985): 97–109. http://dx.doi.org/10.1017/s026646740000016x.
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ABSTRACTDiameter growth rates and age-size relationships are reported for 45 abundant tree species and one liana in tropical wet forest at La Selva, Costa Rica. Thirteen-year increments in each species were analysed using growth simulation, a stochastic technique which projects growth trajectories.Median growth rates ranged from 0.35 mm yr-1 (Anaxagorea crassipetala) to 13.41 mm yr-1) (Stryphnodendron excelsum). Maximum ranges ranged from 0.95 mm yr-1 (Quararibea brac-teolosa) to 14.62 mm yr-1 (Hernandia didymanthera). Minimum rates ranged from zero growth (Capparis pittieri, Colubrina spinosa, Doliocarpus spp.) to 7.45 mm yr-1 (Stryphno dendron excelsum).Projected lifespan (from 100 mm dbh to the maximum dbh for the species) varied from 52 years (Anaxagorea crassipetala, Guatteria inuncta) to 442 years (Carapa guianensis). The mean longevity among the 45 tree species studied is 190 years.Four main patterns of growth behaviour are recognized, based upon longevity and growth rates: (1) understorey species have slow maximum growth rates and short lifespans; (2) shade-tolerant subcanopy trees live around twice as long as understorey trees and grow at approxi-mately the same maximum rates; (3) canopy and subcanopy trees that are shade-tolerant but respond opportunistically to increased light levels have long lifespans and fast maximum growth rates; (4) shade-intolerant canopy and subcanopy species are short-lived and have fast maximum growth rates. Understorey species intergrade with shade-tolerant subcanopy species in terms of growth behaviour; shade-tolerant subcanopy species with opportunistic, shade-tolerant species; and opportunistic, shade-tolerant with shade-intolerant species.Intraspecific variation in growth rates is lower in short-lived trees (understorey species with uniformly slow growth and shade-intolerant species with uniformly rapid growth) than in the two long-lived groups. These patterns are discussed in the context of tree ecophysiology and forest light environments.
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Lin, Jie, Paul A. Harcombe, and Mark R. Fulton. "Characterizing shade tolerance by the relationship between mortality and growth in tree saplings in a southeastern Texas forest." Canadian Journal of Forest Research 31, no. 2 (2001): 345–49. http://dx.doi.org/10.1139/x00-157.
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We investigated the relationship between shade tolerance and sapling mortality using data collected over 15 years in a mesic forest in southeastern Texas. Seven species representing a range of shade-tolerance classes were included in the study. We used survival analysis to estimate species-specific sapling mortality risk (hazard) as a function of recent growth. We found that shade-intolerant species had higher mortality risk at zero growth than shade-tolerant species. The results strongly support the point that shade tolerance can be characterized by the relationship between sapling mortality and growth.
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Williams, J. David, Charles H. Gilliam, Gary J. Keever, and John Owens. "The Auburn University Shade Tree Evaluation: Its Roots and Fruit." HortScience 35, no. 4 (2000): 566D—566c. http://dx.doi.org/10.21273/hortsci.35.4.566d.
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Auburn Univ.'s shade tree evaluation is an ongoing study comparing a moderately diverse range of species, varieties and cultivars of larger-growing trees. Initiated in 1980, there were 250 tree selections planted in three replications located at the Piedmont Substation near Camp Hill, Ala. Among the published “fruits” of the evaluation have been critical comparisons of 10 Acer rubrum selections with respect to growth and fall color characteristics; growth rate and aesthetic characteristics of fourteen Quercus selections; growth and fireblight susceptibility of 10 Pyrus calleryana selections; and the best performing trees overall in the first 12 years of the study. The shade tree evaluation has served as an important precedent for initiation of six additional landscape tree tests in Alabama. Besides its benefits as a research project, the shade tree evaluation has provided a living laboratory for a wide range of educational audiences including landscape and nursery professionals, county extension agents, urban foresters, Master Gardeners, garden club members, and horticulture students. Knowledge gained from the shade tree evaluation has also been shared through presentations at many meetings and conferences.