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The literature covering the biology, invasion chronology, host plant responses, and control efforts of the armored scale Aulacaspis yasumatsui Takagi (Hempitera: Diaspididae) is reviewed. The small size of this cycad pest and complex surface morphology of the host cycad organs combine to make visual detection of every cryptic infestation difficult or impossible to achieve. The international movement of Cycas revoluta Thunb. nursery plants and the presence of C. revoluta nursery industries in so many countries have enabled this pest to wreak havoc on the international cycad horticulture trade over the last 25 years. The short pre-oviposition period and considerable female fecundity lead to rapid population expansion on the plants initially infested in newly invaded regions. A depletion of non-structural carbohydrates accompanies long-term infestations and precedes plant death. Enemy escape within the invasive range allows the scale population growth to remain unchecked until anthropogenic efforts establish non-native biological control.
Thomas Marler; Anders Lindström; Gillian Watson. Aulacaspis yasumatsui Delivers a Blow to International Cycad Horticulture. Horticulturae 2021, 7, 147 .
AMA StyleThomas Marler, Anders Lindström, Gillian Watson. Aulacaspis yasumatsui Delivers a Blow to International Cycad Horticulture. Horticulturae. 2021; 7 (6):147.
Chicago/Turabian StyleThomas Marler; Anders Lindström; Gillian Watson. 2021. "Aulacaspis yasumatsui Delivers a Blow to International Cycad Horticulture." Horticulturae 7, no. 6: 147.
A long-term reciprocal garden study was used to determine adaptive variation between Cycas micronesica K.D. Hill plants from north versus south Guam. Half-siblings from each location were planted as one-leaf seedlings in north and south gardens and monitored for 15 years. Stem height and diameter, and leaf number and maximum length were measured yearly. Survival and plant size traits were evaluated using a two-way factorial. In both locations, the local genotypes out-performed the foreign genotypes in terms of survival and growth. Survival of the foreign genotypes began to decline by year 4 and was less than 10% by year 15. Survival of the local genotypes was 70% for the north garden and 100% for the south garden. The north site was more hostile to plant performance because overall survival and plant growth were less than for the south site. The most likely environmental factor provoking local adaptation was highly contrasting soil characteristics between north and south Guam. The results indicates that long-term conservation success for C. micronesica and other cycad species must include the concept of local adaptation into decisions for transplantation and restoration projects.
Thomas Marler. Reciprocal Garden Study Reveals Acute Spatial-Edaphic Adaptation for Cycas micronesica. Diversity 2021, 13, 237 .
AMA StyleThomas Marler. Reciprocal Garden Study Reveals Acute Spatial-Edaphic Adaptation for Cycas micronesica. Diversity. 2021; 13 (6):237.
Chicago/Turabian StyleThomas Marler. 2021. "Reciprocal Garden Study Reveals Acute Spatial-Edaphic Adaptation for Cycas micronesica." Diversity 13, no. 6: 237.
The literature covering the biology, ecology, horticulture, and conservation of the critically endangered tree Serianthes nelsonii Merr. was reviewed. The roots, stems, and leaves of this charismatic legume tree revealed highly plastic traits and responded positively to horticultural manipulations to improve the quality of container-grown transplants. Pre-sowing seed treatments of seed coat scarification and 1 h of imbibition generated 85% to 90% germination at a temperature optimum of 26 °C. Adventitious root formation on air layers and successful unions on approach grafts were 100%. Seedling and sapling growth was maximum under 25% to 50% sunlight transmission, limited irrigation to ensure adequate root zone aeration, repetitive stem tip pruning to increase root:shoot quotient, and thigmic stress to retain an orthotropic orientation of stems. In situ regeneration on Guam was substantial but recruitment from seedling to sapling was nil. High quality leaf litter chemistry enabled rapid decomposition, and soils beneath the tree exhibited unique chemical traits that increased ecosystem health by creating spatial heterogeneity. The greatest unanswered questions focus on plant mortality. Research is needed to determine the reasons for the mortality of in situ seedlings, mortality within transplantation projects on Guam, and the mortality of 60% of the mature in situ tree population during the 26-year implementation of the national recovery plan. Horticultural researchers are ideally positioned to answer these urgent questions.
Thomas Marler; Cameron Musser; April Cascasan; Gil Cruz; Benjamin Deloso. Adaptive Management Lessons for Serianthes nelsonii Conservation. Horticulturae 2021, 7, 43 .
AMA StyleThomas Marler, Cameron Musser, April Cascasan, Gil Cruz, Benjamin Deloso. Adaptive Management Lessons for Serianthes nelsonii Conservation. Horticulturae. 2021; 7 (3):43.
Chicago/Turabian StyleThomas Marler; Cameron Musser; April Cascasan; Gil Cruz; Benjamin Deloso. 2021. "Adaptive Management Lessons for Serianthes nelsonii Conservation." Horticulturae 7, no. 3: 43.
Background and Aims Research required to clarify leaf nutrient relations of cycad species has been inadequate. Common garden studies are useful for determining the influence of genetics on leaf traits because of the homogeneous environment among experimental units. To date, there have been no common garden studies which included all ten genera of cycads. The full phylogenetic breadth has, therefore, not been included in this important area of study. Methods We examined macronutrient and micronutrient content of leaves from one representative species from each of the ten cycad genera at Nong Nooch Tropical Botanical Garden in Thailand. Nitrogen content was determined by dry combustion, and the remaining nutrients were quantified by spectrometry. Results The least variable elements were nitrogen and phosphorus, and the most variable elements were boron and sodium. Nutrient content based on leaflet area was more variable than based on leaflet mass, reflecting species differences in specific leaf area. There were no universal macronutrient or micronutrient signals indicating clear phylogenetic distinctions. Implications for Conservation: Active management of threatened cycad taxa requires research to develop the knowledge to enable evidence-based decisions. This common garden study inclusive of all 10 cycad genera creates a foundation to determine leaf nutrient sufficiency ranges to inform management decisions.
Thomas E. Marler; Anders J. Lindström. Leaf Nutrient Relations of Cycads in a Common Garden. Tropical Conservation Science 2021, 14, 1 .
AMA StyleThomas E. Marler, Anders J. Lindström. Leaf Nutrient Relations of Cycads in a Common Garden. Tropical Conservation Science. 2021; 14 ():1.
Chicago/Turabian StyleThomas E. Marler; Anders J. Lindström. 2021. "Leaf Nutrient Relations of Cycads in a Common Garden." Tropical Conservation Science 14, no. : 1.
Invasions of non-native species can threaten native biodiversity, and island ecosystems are ideal for studying these phenomena. In this article, first, we report on the invasive species that combine to threaten the island cycad Cycas micronesica by reviewing the history of previously reported invasions and providing an update of recent invasions. Then, we prioritize the threat status of each herbivore and the interactions among them. Plant damage was initiated in 2003─2005 by the non-native Aulacaspis yasumatsui Takagi armored scale, Erechthias sp. Meyrick leaf miner, and Luthrodes pandava Horsfield butterfly, which elicited unprecedented irruptions of the native Acalolepta marianarum Aurivillius stem borer and increased herbivory by feral pigs (Sus scrofa L.). The combined impact of these five consumers represents the greatest sustained threat to the cycad tree species. Mitigation of the damage caused by phytophagous non-native species is urgently needed to conserve this unique gymnosperm tree.
Benjamin E. Deloso; L. Irene Terry; Lee S. Yudin; Thomas E. Marler. Biotic Threats to Cycas micronesica Continue to Expand to Complicate Conservation Decisions. Insects 2020, 11, 888 .
AMA StyleBenjamin E. Deloso, L. Irene Terry, Lee S. Yudin, Thomas E. Marler. Biotic Threats to Cycas micronesica Continue to Expand to Complicate Conservation Decisions. Insects. 2020; 11 (12):888.
Chicago/Turabian StyleBenjamin E. Deloso; L. Irene Terry; Lee S. Yudin; Thomas E. Marler. 2020. "Biotic Threats to Cycas micronesica Continue to Expand to Complicate Conservation Decisions." Insects 11, no. 12: 888.
The United States is currently home to five native cycad species. We provide a discussion on these five cycad species to illuminate how evolutionary and geopolitical processes influence phytogeography and published checklists of threatened plants. The number of threatened species in need of protection within any given country is a product of speciation that is contingent with evolutionary processes. However, this number may change instantaneously along with shifting of geopolitical boundaries brought about by armed conflict between rival states and multilateral negotiations. There are five contemporary cycad species within the United States, and the various historical bilateral and multilateral agreements that have generated this list are reviewed. Three of these five cycad species are threatened and in need of urgent protection. A discussion on the history of United States cycads as a microcosm of worldwide conservation issues is presented, with a focus on how federal conservation endeavors of individual nations may influence the world’s biodiversity crisis.
Benjamin E. Deloso; Ulysses F. Ferreras; Thomas E. Marler. Does Phytogeography Change with Shifts in Geopolitics? The Curious Case of Cycads in the United States. Diversity 2020, 12, 445 .
AMA StyleBenjamin E. Deloso, Ulysses F. Ferreras, Thomas E. Marler. Does Phytogeography Change with Shifts in Geopolitics? The Curious Case of Cycads in the United States. Diversity. 2020; 12 (12):445.
Chicago/Turabian StyleBenjamin E. Deloso; Ulysses F. Ferreras; Thomas E. Marler. 2020. "Does Phytogeography Change with Shifts in Geopolitics? The Curious Case of Cycads in the United States." Diversity 12, no. 12: 445.
The literature containing which chemical elements are found in cycad leaves was reviewed to determine the range in values of concentrations reported for essential and beneficial elements. We found 46 of the 358 described cycad species had at least one element reported to date. The only genus that was missing from the data was Microcycas. Many of the species reports contained concentrations of one to several macronutrients and no other elements. The cycad leaves contained greater nitrogen and phosphorus concentrations than the reported means for plants throughout the world. Magnesium was identified as the macronutrient that has been least studied. Only 14 of the species were represented by data from in situ locations, with most of the data obtained from managed plants in botanic gardens. Leaf element concentrations were influenced by biotic factors such as plant size, leaf age, and leaflet position on the rachis. Leaf element concentrations were influenced by environmental factors such as incident light and soil nutrient concentrations within the root zone. These influential factors were missing from many of the reports, rendering the results ambiguous and comparisons among studies difficult. Future research should include the addition of more taxa, more in situ locations, the influence of season, and the influence of herbivory to more fully understand leaf nutrition for cycads.
Benjamin E. Deloso; Murukesan V. Krishnapillai; Ulysses F. Ferreras; Anders J. Lindström; Michael Calonje; Thomas E. Marler. Chemical Element Concentrations of Cycad Leaves: Do We Know Enough? Horticulturae 2020, 6, 85 .
AMA StyleBenjamin E. Deloso, Murukesan V. Krishnapillai, Ulysses F. Ferreras, Anders J. Lindström, Michael Calonje, Thomas E. Marler. Chemical Element Concentrations of Cycad Leaves: Do We Know Enough? Horticulturae. 2020; 6 (4):85.
Chicago/Turabian StyleBenjamin E. Deloso; Murukesan V. Krishnapillai; Ulysses F. Ferreras; Anders J. Lindström; Michael Calonje; Thomas E. Marler. 2020. "Chemical Element Concentrations of Cycad Leaves: Do We Know Enough?" Horticulturae 6, no. 4: 85.
Growth dynamics of pachycaulous stems of arborescent cycad plants are not well understood, and most observations have been made in cultivated garden plants. We studied Cycas micronesica plants in Guam, Tinian, and Yap to understand the influences of geography, plant size, sex, and herbivory on stem growth. We also determined the changes in demography of Guam's population after 15 years of damage by non-native insect herbivores. The height increment (HI) was similar for plants within the height range from 100 cm to more than 600 cm, so the relative growth rate declined with height. Female tree HI was 68% of male tree HI, and Yap tree HI was 87% of Guam tree HI. Chronic herbivory by non-native insect herbivores caused a mean 44% decline in HI. Plants in managed gardens grew more rapidly than plants in a wild habitat. The HI was used to estimate that Guam has experienced a complete loss of ≈70 y of demographic depth resulting from the selective mortality of small plants since 2005. When future conservation interventions successfully mitigate the ubiquitous biological threats, our HI may be useful for empirically quantifying recovery of plant health.
Thomas E. Marler; M. Patrick Griffith; Murukesan V. Krishnapillai. Height increment of Cycas micronesica informs conservation decisions. Plant Signaling & Behavior 2020, 15, 1830237 .
AMA StyleThomas E. Marler, M. Patrick Griffith, Murukesan V. Krishnapillai. Height increment of Cycas micronesica informs conservation decisions. Plant Signaling & Behavior. 2020; 15 (12):1830237.
Chicago/Turabian StyleThomas E. Marler; M. Patrick Griffith; Murukesan V. Krishnapillai. 2020. "Height increment of Cycas micronesica informs conservation decisions." Plant Signaling & Behavior 15, no. 12: 1830237.
Numerous leaf traits exhibit developmental plasticity in response to irradiance, an attribute that maximizes performance in the prevailing light. The use of leaflets to represent whole leaf traits of tree species with compound leaves is common in the acclimation literature. These methods ignore the potential for whole leaf plasticity to augment leaflet plasticity. We grew Serianthes nelsonii plants in incident light ranging from 6% to 100% of sunlight and quantified numerous leaflet and leaf traits to determine plasticity index (PI: (maximum-minimum)/maximum)) of each. Leaflet acclimation such as changes in length of palisade mesophyll occurred as expected. However, leaf-level morphometric traits such as rachillae insertion angle also exhibited acclimation potential. The leaf-level plastic behavior enabled acclimation approaches that simple-leaved species do not possess. We illuminate the need to look at the entire leaf when quantifying acclimation potential of tree leaves, and indicate that the historical use of leaflets to represent species with compound leaves under-estimated the acclimation potential when compared to species with simple leaves.
Benjamin E. Deloso; Thomas E. Marler. Bi-Pinnate Compound Serianthes nelsonii Leaf-Level Plasticity Magnifies Leaflet-Level Plasticity. Biology 2020, 9, 333 .
AMA StyleBenjamin E. Deloso, Thomas E. Marler. Bi-Pinnate Compound Serianthes nelsonii Leaf-Level Plasticity Magnifies Leaflet-Level Plasticity. Biology. 2020; 9 (10):333.
Chicago/Turabian StyleBenjamin E. Deloso; Thomas E. Marler. 2020. "Bi-Pinnate Compound Serianthes nelsonii Leaf-Level Plasticity Magnifies Leaflet-Level Plasticity." Biology 9, no. 10: 333.
The number of branches in male and female plants of Cycas micronesica K.D. Hill, Cycas edentata de Laub., Cycas wadei Merr., and Zamia encephalartoides D.W. Stev. were counted in Guam, Philippines, and Colombia, to confirm earlier reports that female plants develop fewer branches than males. Cycas plants produce determinate male strobili and indeterminate female strobili, but Zamia plants produce determinate strobili for both sexes. More than 80% of the female trees for each of the Cycas species were unbranched with a single stem, but more than 80% of the male trees exhibited two or more branches. The mean number of branches on male plants was more than double that of female plants. The number of branches of the Zamia male plants was almost triple that of female plants. Moreover, the Zamia plants produced 2.8-fold greater numbers of branches than the mean of the Cycas plants. Most of Guam’s unsexed C. micronesica trees in 2004 were unbranched, but after 15 years of damage from non-native insect herbivores, most of the remaining live trees in 2020 contained three or more branches. The results confirm that male Cycas and Zamia plants produce more branches than female plants and suggest cycad species with determinate female strobili produce more branches on female plants than species with indeterminate female strobili. Our results indicate that the years of plant mortality on Guam due to non-native insect herbivores have selectively killed more female C. micronesica trees. Horticulture and conservation decisions may be improved with this sexual dimorphism knowledge.
Thomas Marler; Michael Calonje. Stem Branching of Cycad Plants Informs Horticulture and Conservation Decisions. Horticulturae 2020, 6, 65 .
AMA StyleThomas Marler, Michael Calonje. Stem Branching of Cycad Plants Informs Horticulture and Conservation Decisions. Horticulturae. 2020; 6 (4):65.
Chicago/Turabian StyleThomas Marler; Michael Calonje. 2020. "Stem Branching of Cycad Plants Informs Horticulture and Conservation Decisions." Horticulturae 6, no. 4: 65.
An understanding of leaf nutrient relations is required for tree conservation and horticulture success. The study of cycad leaf nutrient dynamics has expanded in recent years, but direct comparisons among reports remains equivocal due to varying sampling protocols. We used Cycas micronesica K.D. Hill and Cycas nongnoochiae K.D. Hill trees to determine the influence on leaf nutrient concentrations of in situ versus ex situ locations and orientation of leaves within the tree canopy. Nitrogen, phosphorus, and potassium concentrations of leaves from ex situ plants exceeded those from in situ plants, and the differences were not explained by soil nutrient differences. Calcium concentrations of leaves varied among the site pairs, with differences primarily explained by soil calcium. Magnesium concentrations of leaves were not different among all location pairs even though soil magnesium concentrations varied among the sites more than any of the other elements. Differences in leaf macronutrient concentrations among four C. micronesica provenances were minimal when grown in a common garden. Lateral orientation of leaves did not influence any of the essential elements for either of the species. These findings indicate that the lateral orientation of cycad leaves does not influence leaf nutrient concentrations, leaf nutrient relations of cycad plants in managed ex situ settings do not align with leaf nutrient relations in habitat, and these differences are not explained by soil nutrition for most elements. We suggest that leaf nutrient concentrations should be determined in all niche habitats within the geographic range of a cycad species in order to fully understand the leaf physiology of each species.
Thomas E. Marler; Anders Lindstrom. Leaf nutrients of two Cycas L. species contrast among in situ and ex situ locations. Journal of Threatened Taxa 2020, 12, 16831 -16839.
AMA StyleThomas E. Marler, Anders Lindstrom. Leaf nutrients of two Cycas L. species contrast among in situ and ex situ locations. Journal of Threatened Taxa. 2020; 12 (13):16831-16839.
Chicago/Turabian StyleThomas E. Marler; Anders Lindstrom. 2020. "Leaf nutrients of two Cycas L. species contrast among in situ and ex situ locations." Journal of Threatened Taxa 12, no. 13: 16831-16839.
Plants that enter symbiotic relationships with nitrogen (N)-fixing microbes contribute some of their N to the community through leaf litter decomposition and mineralization processes. The speed of these processes varies greatly among tree species. Mesocosm methods were used to determine the speed of N and carbon (C) release from Cycas micronesica, Intsia bijuga, and Serianthes nelsonii leaf litter. Microcosm methods were used to determine soil respiration traits in soils containing the leaf litter. The speed of leaf litter N and C release during decomposition occurred in the order C. micronesica < I. bijuga < S. nelsonii. Soil carbon dioxide efflux was increased by adding leaf litter to incubation soils, and the increase was greatest for S. nelsonii and least for C. micronesica litter. Ammonium, nitrate, total N, organic C, and total C were increased by adding litter to incubation soils, and the differences among the species converged with incubation duration. The rate of increases in available N and decreases in organic C were greatest for S. nelsonii and least for C. micronesica litter. These findings indicate that S. nelsonii litter released N and C rapidly, C. micronesica litter released N and C slowly, and the leaf economic spectrum accurately predicted the differences.
Thomas E. Marler. Perennial Trees Associating with Nitrogen-Fixing Symbionts Differ in Leaf After-Life Nitrogen and Carbon Release. Nitrogen 2020, 1, 111 -124.
AMA StyleThomas E. Marler. Perennial Trees Associating with Nitrogen-Fixing Symbionts Differ in Leaf After-Life Nitrogen and Carbon Release. Nitrogen. 2020; 1 (2):111-124.
Chicago/Turabian StyleThomas E. Marler. 2020. "Perennial Trees Associating with Nitrogen-Fixing Symbionts Differ in Leaf After-Life Nitrogen and Carbon Release." Nitrogen 1, no. 2: 111-124.
Methods in sunfleck research commonly employ the use of experimental leaves which were constructed in homogeneous light. These experimental organs may behave unnaturally when they are challenged with fluctuating light. Photosynthetic responses to heterogeneous light and leaf macronutrient relations were determined for Cycas micronesica, Glycine max, and Zea mays leaves that were grown in homogeneous shade, heterogeneous shade, or full sun. The speed of priming where one light fleck increased the photosynthesis during a subsequent light fleck was greatest for the leaves grown in heterogeneous shade. The rate of induction and the ultimate steady-state photosynthesis were greater for the leaves that were grown in heterogeneous shade versus the leaves grown in homogeneous shade. The leaf mass per area, macronutrient concentration, and macronutrient stoichiometry were also influenced by the shade treatments. The amplitude and direction in which the three developmental light treatments influenced the response variables were not universal among the three model species. The results indicate that the historical practice of using experimental leaves which were constructed under homogeneous light to study leaf responses to fluctuating light may produce artifacts that generate dubious interpretations.
Thomas E. Marler. Artifleck: The Study of Artifactual Responses to Light Flecks with Inappropriate Leaves. Plants 2020, 9, 905 .
AMA StyleThomas E. Marler. Artifleck: The Study of Artifactual Responses to Light Flecks with Inappropriate Leaves. Plants. 2020; 9 (7):905.
Chicago/Turabian StyleThomas E. Marler. 2020. "Artifleck: The Study of Artifactual Responses to Light Flecks with Inappropriate Leaves." Plants 9, no. 7: 905.
Cycas micronesica is a foundation species in several Micronesian islands and its seeds have been a historical source of starch for the island residents. The species has become endangered by invasive specialist insect herbivores and conservationists struggle with the inability to estimate the age of observed seeds. To inform this agenda, we evaluated numerous Cycas micronesica seed traits to determine if any exhibited a relationship with age and a substantial change in absolute value. Of the 30 direct and derived seed traits that we evaluated, most of them were non-linear and exhibited minimal change after about 12 months in age. The only traits that emerged as unambiguous estimators of age were the quotients derived as gametophyte fresh weight/total seed fresh weight and sarcotesta dry weight/sclerotesta dry weight. These two simple metrics can be used to accurately estimate seed age for this arborescent cycad species.
Thomas Marler; Christopher Shaw. Fresh and Dry Weight Relations Are Predictors of Cycas micronesica Seed Age. Horticulturae 2020, 6, 29 .
AMA StyleThomas Marler, Christopher Shaw. Fresh and Dry Weight Relations Are Predictors of Cycas micronesica Seed Age. Horticulturae. 2020; 6 (2):29.
Chicago/Turabian StyleThomas Marler; Christopher Shaw. 2020. "Fresh and Dry Weight Relations Are Predictors of Cycas micronesica Seed Age." Horticulturae 6, no. 2: 29.
Island invasions may cause severe changes in biodiversity, but the factors that influence these changes are not well understood. We established 120 plots in Cycas micronesica habitats throughout Guam in 2005 following the invasion of the armored scale Aulacaspis yasumatsui, then observed plant mortality through 2020. We used transects in Yap as benchmarks, as the Yap C. micronesica population is not threatened. The initial Guam plots contained about 1600 seedlings, 1160 juveniles, and 1240 mature plants per ha. Seedling mortality was 100% by 2006, juvenile mortality was 100% by 2014, and the 2020 census revealed 96% mortality of the plant population. Localities in western Guam and isolated forest fragments exhibited the greatest mortality, with 100% extirpation from two fragmented western localities. The juvenile and mature trees in Yap were unchanged from 2010 to 2018, but the seedling count was heterogeneous among the years. Constrained recruitment from seedlings to juveniles explained these dynamics. Yap transects contained about 6120 seedlings, 3400 juveniles, and 1250 mature plants per ha. Biological control of the invasive insects remains the acute conservation action needed for the Guam population. Lessons learned may be useful in other regions where invasions of non-native pests threaten biodiversity.
Thomas E. Marler; Murukesan V. Krishnapillai. Longitude, Forest Fragmentation, and Plant Size Influence Cycas micronesica Mortality Following Island Insect Invasions. Diversity 2020, 12, 194 .
AMA StyleThomas E. Marler, Murukesan V. Krishnapillai. Longitude, Forest Fragmentation, and Plant Size Influence Cycas micronesica Mortality Following Island Insect Invasions. Diversity. 2020; 12 (5):194.
Chicago/Turabian StyleThomas E. Marler; Murukesan V. Krishnapillai. 2020. "Longitude, Forest Fragmentation, and Plant Size Influence Cycas micronesica Mortality Following Island Insect Invasions." Diversity 12, no. 5: 194.
The growth of synchronized leaf flushes or male cones on Cycas trees is an ephemeral event, and non-structural carbohydrates (NSCs) are likely deployed from stem and root storage tissues to support their construction. The relationships among various stem NSCs and these rapid growth events have not been studied to date. Monosaccharides, disaccharides, and starch were quantified in Cycas micronesica stem tissue prior to and immediately after the growth of leaf flushes or male cones to determine the influences on the concentration of these carbohydrates. The pre-existing leaves were removed from half of the plants to determine if the elimination of this carbon source would influence the NSC behaviors. Starch and sucrose dominated the NSC profiles, and these two NSCs declined following cone or new leaf growth. Removal of pre-existing leaves generated a greater decline in starch and sucrose for cone growth, and a greater decline in sucrose, but not starch following new leaf growth than in control trees with no leaf removal. The initial differences in starch and sucrose among cortex, vascular, and pith tissues disappeared as the concentrations declined in all three tissue categories to reach similar post-growth concentrations among the stem tissue categories. The fructose, glucose, and maltose behaviors were not consistent, and their concentrations were low such that their influence on the total NSC behaviors was minimal. These results provided indirect evidence that stem NSCs were mobilized to support ephemeral male cone and new leaf growth for this arborescent cycad. Growth of female strobili is slow and lengthy, so we did not include female trees in this study. The contributions of stem NSCs to female strobili growth remain to be studied with alternative methods.
Thomas E. Marler; Gil N. Cruz. Cycas micronesica Stem Carbohydrates Decline Following Leaf and Male Cone Growth Events. Plants 2020, 9, 517 .
AMA StyleThomas E. Marler, Gil N. Cruz. Cycas micronesica Stem Carbohydrates Decline Following Leaf and Male Cone Growth Events. Plants. 2020; 9 (4):517.
Chicago/Turabian StyleThomas E. Marler; Gil N. Cruz. 2020. "Cycas micronesica Stem Carbohydrates Decline Following Leaf and Male Cone Growth Events." Plants 9, no. 4: 517.
The influences of Cycas micronesica and Zamia integrifolia plants on soil chemistry were determined in Tinian and Florida in order to more fully understand how cycad plants affect the environments in which they grow. The introduction of C. micronesica plants into a karst habitat generated decreases in soil phosphorus after five years and increases in soil nitrogen after six years. The carbon:nitrogen:phosphorus stoichiometry beneath the cycad plants significantly diverged from those of the adjacent native forests with Pisonia grandis, Psychotria mariana, Aglaia mariannensis, Cynometra ramiflora, and Ficus sp. cover after five years. Mineralization traits were determined beneath nine-year-old C. micronesica plants and revealed the plants greatly increased net nitrification and decreased net ammonification when compared to the native forest soils with Bursera simaruba, Pinus elliottii, and Quercus virginiana cover. These flux changes increased the total available nitrogen and percent available nitrogen in the soils beneath the cycad plants. The substrates of two soil series exhibited increased carbon and nitrogen concentrations beneath Z. integrifolia plants when compared with soils away from the cycad plants. No other mineral or metal was influenced by proximity to the Z. integrifolia plants. These gymnosperms exhibit distinct interactions with their subtending soils, and some of these traits improve ecosystems by increasing recalcitrant carbon and nitrogen and increasing spatial heterogeneity of soil chemistry.
Thomas Marler; Michael Calonje. Two Cycad Species Affect the Carbon, Nitrogen, and Phosphorus Content of Soils. Horticulturae 2020, 6, 24 .
AMA StyleThomas Marler, Michael Calonje. Two Cycad Species Affect the Carbon, Nitrogen, and Phosphorus Content of Soils. Horticulturae. 2020; 6 (2):24.
Chicago/Turabian StyleThomas Marler; Michael Calonje. 2020. "Two Cycad Species Affect the Carbon, Nitrogen, and Phosphorus Content of Soils." Horticulturae 6, no. 2: 24.
Research Highlights: Established stands of Leucaena leucocephala (Lam.) de Wit, Spathodea campanulata P. Beauv., and Vitex parviflora Juss. modified soils in Guam’s limestone forests, reducing storage pools of carbon, nitrogen, and phosphorus. Background and Objectives: Invasive plants may engineer negative changes in ecosystem properties. This study was conducted to determine changes in soil chemistry following infestations of three problematic tree species on Guam. Materials and Methods: Minerals, metals, and mineralization dynamics were measured in invaded sites and paired sites with biodiverse native tree cover. Results: Most soil properties were significantly changed by long-term infestations of the invasive tree species. The soils within invaded sites exhibited total carbon, total nitrogen, and available phosphorus that were less than native sites. In contrast, the carbon/nitrogen ratio increased for every species-site combination. The other chemical properties were idiosyncratic among the sites and species. Conclusions: Mitigation and restoration activities that include the removal of these trees from project sites may require many years for the below-ground ecosystems to return to their native state. These three invasive trees decrease the ability of Guam soils to sequester recalcitrant forms of carbon, nitrogen, and phosphorus.
Thomas E. Marler. Three Invasive Tree Species Change Soil Chemistry in Guam Forests. Forests 2020, 11, 279 .
AMA StyleThomas E. Marler. Three Invasive Tree Species Change Soil Chemistry in Guam Forests. Forests. 2020; 11 (3):279.
Chicago/Turabian StyleThomas E. Marler. 2020. "Three Invasive Tree Species Change Soil Chemistry in Guam Forests." Forests 11, no. 3: 279.
The diel patterns of stem carbon dioxide efflux (Es) were determined for cycads, monocots, and woody eudicot and gymnosperm tree species. Stem Es at a height of 30–40 cm was measured every 2 h throughout 31-h campaigns. Our range of Es was 1.5–4.0 µmol·m−2·s−1 for cycads, 1.0–3.5 µmol·m−2·s−1 for arborescent monocots, and 1.5–4.5 µmol·m−2·s−1 for woody eudicot and gymnosperm trees species. Time of day did not influence Es of cycads or monocots. In contrast, the woody stems of eudicots and gymnosperms exhibited diurnal Es that was 36% to 40% greater than nocturnal Es. The established literature based on Es of woody tree species cannot be used to estimate habitat carbon cycles in habitats which contain cycad or monocot trees. Time of day must be included for accuracy of research on Es of woody tree species. Failures to account for the spatiotemporal differences of Es may explain some of the disparity in outcomes of published stem respiration studies.
Thomas E. Marler; Anders J. Lindström. Diel patterns of stem CO2 efflux vary among cycads, arborescent monocots, and woody eudicots and gymnosperms. Plant Signaling & Behavior 2020, 15, 1 .
AMA StyleThomas E. Marler, Anders J. Lindström. Diel patterns of stem CO2 efflux vary among cycads, arborescent monocots, and woody eudicots and gymnosperms. Plant Signaling & Behavior. 2020; 15 (3):1.
Chicago/Turabian StyleThomas E. Marler; Anders J. Lindström. 2020. "Diel patterns of stem CO2 efflux vary among cycads, arborescent monocots, and woody eudicots and gymnosperms." Plant Signaling & Behavior 15, no. 3: 1.
Stem respiration is influenced by the vertical location of tree stems, but the influence of vertical location on stem respiration in a representative cycad species has not been determined. We quantified the influence of vertical strata on stem carbon dioxide efflux (Es) for six arborescent Cycas L. species to characterize this component of stem respiration and ecosystem carbon cycling. The influence of strata on Es was remarkably consistent among the species, with a stable baseline flux characterizing the full mid-strata of the pachycaulous stems and an increase in Es at the lowest and highest strata. The mid-strata flux ranged from 1.8 μmol·m−2·s−1 for Cycas micronesica K.D. Hill to 3.5 μmol·m−2·s−1 for Cycas revoluta Thunb. For all species, Es increased about 30% at the lowest stratum and about 80% at the highest stratum. A significant quadratic model adequately described the Es patterns for all six species. The increase of Es at the lowest stratum was consistent with the influence of root-respired carbon dioxide entering the stem via sap flow, then contributing to Es via radial conductance to the stem surface. The substantial increase in Es at the highest stratum is likely a result of the growth and maintenance respiration of the massive cycad primary thickening meristem that constructs the unique pachycaulous cycad stem.
Thomas E. Marler; Murukesan V. Krishnapillai. Vertical Strata and Stem Carbon Dioxide Efflux in Cycas Trees. Plants 2020, 9, 230 .
AMA StyleThomas E. Marler, Murukesan V. Krishnapillai. Vertical Strata and Stem Carbon Dioxide Efflux in Cycas Trees. Plants. 2020; 9 (2):230.
Chicago/Turabian StyleThomas E. Marler; Murukesan V. Krishnapillai. 2020. "Vertical Strata and Stem Carbon Dioxide Efflux in Cycas Trees." Plants 9, no. 2: 230.