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PubMed2003

[Niche characteristics of dominant populations in natural forest in north Guangdong].

Two communities of the natural evergreen forest in Luoba Nature Reserve, North Guangdong, each represented by a 2500 m2 plot, were surveyed with Tree-layer-frequency method. Based on these data, the niche characteristics of 12 dominant populations, i.e., Castanopsis fargesii, Pinus massoniana, Schima superba, Liquidambar formosana, Diospyros morrisiana, Myrica rubra, Castanopsis lamontii, Adinandra milletii, Castanopsis eyrei, Elaeocarpus silvestris, Daphniphyllum calycinum, Neolitsea chuii, were described and analyzed, with stand layer as the resource state and tree abundance as the resource state descriptor of niche. The results indicate that most of the shade-tolerant tree species have higher niche breadth values, while the intolerant tree species have the lower ones, with zero value for Pinus massoniana and Liquidambar fomosana, which is in accordance with the declining status of the two species in the community. All the dominant populations, both shade-tolerant and intolerant, showed some adaptation to the community environment. 54.5% of the population-links had a niche similarity over 0.5, and 51.5% of them had a niche overlap over 0.2 in community 1. Niche characterization combined with conventional Tree-layer-frequency method could better determine the status and regenerating potential of tree species in the community. On the other hand, measuring tree abundance in different stand layers as the resource niche could demonstrate tree's requirement for the habitat. Variations in tree composition result in varied niche breadth, which lead to the variations of niche similarity and niche overlap values.

Algorithms↗
PubMed2003

[Nutrient characteristics in leaves of broadleaved seedlings in south China].

Nutrient concentrations and contents in leaves of broadleaved Elaeocarpus sylvestris, Castanopsis hystrix, Ormosia pinnata, Michelia macclurei, Camellia semiserata, Liquidambar formosana, Castanopsis fissa, Mytilaria laosensis and Cinnamomum camphora seedlings were studied. Leaf N, P and K concentrations in Ormosia pinnata, Castanopsis fissa and Cinnamomum camphora were higher than those of other tree species, and leaf N, P and K contents in Camellia semiserata, Castanopsis fissa and Cinnamomum camphora were higher than those of other tree species. Mean leaf nutrient concentration in upper crown and lower crown of 9 tree species was N 16.67 and 17.09 g.kg-1, P 1.29 and 0.84 g.kg-1, K 11.77 and 6.65 g.kg-1, respectively. Mean leaf nutrient content in upper crown and lower crown of 9 tree species was N 0.871 and 1.069 g.m-2, P 0.065 and 0.052 g.m-2, K 0.608 and 0.426 g.m-2, respectively. Leaf P and K concentrations and contents in the upper crown were generally higher than those of the lower crown. From the view of nutrient contents, mixing Camellia semiserata with other tree species, mixing Castanopsis hystrix or Mytilaria laosensis with Elaeocarpus sylvestris, Liquidambar formosana, Ormosia pinnata, Castanopsis fissa, and Cinnamomum camphora, and mixing Michelia macclurei with Castanopsis fissa and Cinnamomum camphora were suitable.

Nitrogen↗
PubMed2003

Leaf dynamics of a deciduous forest canopy: no response to elevated CO2.

Leaf area index (LAI) and its seasonal dynamics are key determinants of terrestrial productivity and, therefore, of the response of ecosystems to a rising atmospheric CO(2) concentration. Despite the central importance of LAI, there is very little evidence from which to assess how forest LAI will respond to increasing [CO(2)]. We assessed LAI and related leaf indices of a closed-canopy deciduous forest for 4 years in 25-m-diameter plots that were exposed to ambient or elevated CO(2) (542 ppm) in a free-air CO(2) enrichment (FACE) experiment. LAI of this Liquidambar styraciflua (sweetgum) stand was about 6 and was relatively constant year-to-year, including the 2 years prior to the onset of CO(2) treatment. LAI throughout the 1999-2002 growing seasons was assessed through a combination of data on photosynthetically active radiation (PAR) transmittance, mass of litter collected in traps, and leaf mass per unit area (LMA). There was no effect of [CO(2)] on any expression of leaf area, including peak LAI, average LAI, or leaf area duration. Canopy mass and LMA, however, were significantly increased by CO(2) enrichment. The hypothesized connection between light compensation point (LCP) and LAI was rejected because LCP was reduced by [CO(2)] enrichment only in leaves under full sun, but not in shaded leaves. Data on PAR interception also permitted calculation of absorbed PAR (APAR) and light use efficiency (LUE), which are key parameters connecting satellite assessments of terrestrial productivity with ecosystem models of future productivity. There was no effect of [CO(2)] on APAR, and the observed increase in net primary productivity in elevated [CO(2)] was ascribed to an increase in LUE, which ranged from 1.4 to 2.4 g MJ(-1). The current evidence seems convincing that LAI of non-expanding forest stands will not be different in a future CO(2)-enriched atmosphere and that increases in LUE and productivity in elevated [CO(2)] are driven primarily by functional responses rather than by structural changes. Ecosystem or regional models that incorporate feedbacks on resource use through LAI should not assume that LAI will increase with CO(2) enrichment of the atmosphere.

Adaptation, Physiological↗
PubMed2003

Regional assessment of ozone sensitive tree species using bioindicator plants.

Tropospheric ozone occurs at phytotoxic levels in the northeastern and mid-Atlantic regions of the United States. Quantifying possible regional-scale impacts of ambient ozone on forest tree species is difficult and is confounded by other factors, such as moisture and light, which influence the uptake of ozone by plants. Biomonitoring provides an approach to document direct foliar injury irrespective of direct measure of ozone uptake. We used bioindicator and field plot data from the USDA Forest Service to identify tree species likely to exhibit regional-scale ozone impacts. Approximately 24% of sampled sweetgum (Liquidambar styraciflua), 15% of sampled loblolly pine (Pinus taeda), and 12% of sampled black cherry (Prunus serotina) trees were in the highest risk category. Sweetgum and loblolly pine trees were at risk on the coastal plain of Maryland, Virginia and Delaware. Black cherry trees were at risk on the Allegheny Plateau (Pennsylvania), in the Allegheny Mountains (Pennsylvania, West Virginia, and Maryland) as well as coastal plain areas of Maryland and Virginia. Our findings indicate a need for more in-depth study of actual impacts on growth and reproduction of these three species.

Air Pollutants↗
PubMed2005

Radiation-use efficiency and gas exchange responses to water and nutrient availability in irrigated and fertilized stands of sweetgum and sycamore.

We investigated how water and nutrient availability affect radiation-use efficiency (epsilon) and assessed leaf gas exchange as a possible mechanism for shifts in epsilon. We measured aboveground net primary production (ANPP) and annual photosynthetically active radiation (PAR) capture to calculate epsilon as well as leaf-level physiological variables (light-saturated net photosynthesis, Asat; stomatal conductance, gs; leaf internal CO2 concentration, Ci; foliar nitrogen concentration, foliar [N]; and midday leaf water potential, Psileaf) during the second (2001) and third (2002) growing seasons in sweetgum (Liquidambar styraciflua L.) and sycamore (Platanus occidentalis L.) stands receiving a factorial combination of irrigation and fertilization at the Savannah River Site, South Carolina. Irrigation and fertilization increased PAR capture (maximum increase 60%) in 2001 and 2002 for both species and annual PAR capture was well correlated with ANPP (mean r2 = 0.77). A decreasing trend in epsilon was observed in non-irrigated stands for sweetgum in 2001 and for sycamore in both years, although this was only significant for sycamore in 2002. Irrigated stands maintained higher gas exchange rates than non-irrigated stands for sweetgum in 2001 and for sycamore in both years, although foliar [N] and Psileaf were generally unaffected. Because Ci decreased in proportion to gs in non-irrigated stands, it appeared that greater stomatal limitation of photosynthesis was associated with decreased Asat. On several measurement dates for sweetgum in 2001 and for sycamore in both years, epsilon was positively correlated with gas exchange variables (Asat, gs, Ci) (r ranged from 0.600 to 0.857). These results indicate that PAR capture is well correlated with ANPP and that gas exchange rates modified by irrigation can influence the conversion of captured light energy to biomass.

Fertilizers↗
PubMed2001

Genotypic effects of fertilization on seedling sweetgum biomass allocation, N uptake, and N use efficiency.

Screening and selecting tree genotypes that are responsive to N additions and that have high nutrient use efficiencies can provide better genetic material for short-rotation plantation establishment. A pot experiment was conducted to test the hypotheses that (1) sweetgum ( Liquidambar styraciflua L.) families have different patterns in biomass production and allocation, N uptake, and N use efficiency (NUE), because of their differences in growth strategies, and (2) sweetgum families that are more responsive to N additions will also have greater nutrient use efficiencies. Seedlings from two half-sib families (F10022 and F10023) that were known to have contrasting responses to fertility and other stress treatments were used for an experiment with two levels of N (0 vs. 100 kg N/ha equivalent) and two levels of P (0 vs. 50 kg P/ha equivalent) in a split-plot design. Sweetgum seedlings responded to N and P treatments rapidly, with increases in both size and biomass production, and those responses were greater with F10023 than with F10022. Growth response to N application was particularly strong. N and P application increased the proportional allocation of biomass to leaves. Under increased N supply, P application increased foliar N concentration and content, as well as total N uptake by the seedlings. However, NUE was decreased by N addition and was higher in F10023 than in F10022 when P was not limiting. A better understanding of genotype by fertility interactions is important in selecting genotypes for specific site conditions and for optimizing nutrient use in forestry production.

Biomass↗
PubMed2004

Phloem loading. A reevaluation of the relationship between plasmodesmatal frequencies and loading strategies.

The incidence of plasmodesmata in the minor vein phloem of leaves varies widely between species. On this basis, two pathways of phloem loading have been proposed: symplastic where frequencies are high, and apoplastic where they are low. However, putative symplastic-loading species fall into at least two categories. In one, the plants translocate raffinose-family oligosaccharides (RFOs). In the other, the primary sugar in the phloem sap is sucrose (Suc). While a thermodynamically feasible mechanism of symplastic loading has been postulated for species that transport RFOs, no such mechanism is known for Suc transporters. We used p-chloromercuribenzenesulfonic acid inhibition of apoplastic loading to distinguish between the two pathways in three species that have abundant minor vein plasmodesmata and are therefore putative symplastic loaders. Clethra barbinervis and Liquidambar styraciflua transport Suc, while Catalpa speciosa transports RFOs. The results indicate that, contrary to the hypothesis that all species with abundant minor vein plasmodesmata load symplastically, C. barbinervis and L. styraciflua load from the apoplast. C. speciosa, being an RFO transporter, loads from the symplast, as expected. Data from these three species, and from the literature, also indicate that plants with abundant plasmodesmata in the minor vein phloem have abundant plasmodesmata between mesophyll cells. Thus, plasmodesmatal frequencies in the minor veins may be a reflection of overall frequencies in the lamina and may have limited relevance to phloem loading. We suggest that symplastic loading is restricted to plants that translocate oligosaccharides larger than Suc, such as RFOs, and that other plants, no matter how many plasmodesmata they have in the minor vein phloem, load via the apoplast.

Bignoniaceae↗
PubMed2006

Performance of Lymantria xylina (Lepidoptera: Lymantriidae) on artificial and host plant diets.

Lymantria xylina Swinhoe (Lepidoptera: Lymantriidae) is a serious defoliator of hardwood and fruit trees in Taiwan. The larvae of L. xylina feed on >63 species of host plants, belonging to 29 families. Because a large number of larvae are needed for the production of nucleopolyhedrosis virus (NPV) or other related studies, the development of a suitable artificial diet is very important for the mass rearing of this moth in the laboratory. In this study, eight artificial diets, modified from different formulas, and one host plant, Liquidambar formosana Hance, were used to feed L. xylina caterpillars. Through various bioassays (first instar survival trial and long- and short-term feeding trials), the most suitable diet for the L. xylina was selected by performance comparisons with L. formosana. After the first instar survival trial, two of the diets were discarded, because no larva survived on these diets. The results of the long-term feeding trial indicated that the larvae grew successfully on only three kinds of artificial diet. Finally, results of the short-term feeding trial revealed that a diet (diet A), modified from the gypsy moth, Lymantria dispar (L.), formula diet, was the most appropriate for the L. xylina. Larvae fed on diet A had better survival rate, pupal weight, adult size, efficiency of conversion, and relative growth rate than larvae fed on other diets; they did not grow as well as those fed on L. formosana, however, except for pupal and adult weight, and approximate digestibility. In summary, diet A was found to be the best of the artificial diets for the L. xylina and is suitable for mass rearing of this moth in the laboratory.

Animal Feed↗
PubMed2006

Nitrogen uptake, distribution, turnover, and efficiency of use in a CO2-enriched sweetgum forest.

The Progressive Nitrogen Limitation (PNL) hypothesis suggests that ecosystems in a CO2-enriched atmosphere will sequester C and N in long-lived biomass and soil organic pools, thereby limiting available N and constraining the continued response of net primary productivity to elevated [CO2]. Here, we present a six-year record of N dynamics of a sweetgum (Liquidambar styraciflua) stand exposed to elevated [CO2] in the free-air CO2 enrichment (FACE) experiment at Oak Ridge, Tennessee, USA. We also evaluate the concept of PNL for this ecosystem from the perspective of N uptake, content, distribution, and turnover, and N-use efficiency. Leaf N content was 11% lower on a leaf mass basis (NM) and 7% lower on a leaf area basis (NA) in CO2-enriched trees. However, there was no effect of [CO2] on total canopy N content. Resorption of N during senescence was not altered by [CO2], so NM of litter, but not total N content, was reduced. The NM of fine roots was not affected, but the total amount of N required for fine-root production increased significantly, reflecting the large stimulation of fine-root production in this stand. Hence, total N requirement of the trees was higher in elevated [CO2], and the increased requirement was met through an increase in N uptake rather than increased retranslocation of stored reserves. Increased N uptake was correlated with increased net primary productivity (NPP). N-use efficiency, however, did not change with CO2 enrichment because increased N productivity was offset by lower mean residence time of N in the trees. None of the measured responses of plant N dynamics in this ecosystem indicated the occurrence of PNL, and the stimulation of NPP by elevated [CO2] was sustained for the first six years of the experiment. Although there are some indications of developing changes in the N economy, the N supply in the soil at this site may be sufficient to meet an increasing demand for available N, especially as the roots of CO2-enriched trees explore deeper in the soil profile.

Atmosphere↗
PubMed2002

[Chemical composition of fructus Liquidambaris--lulutong].

AIM: To study the chemical composition in the fruits of Liquidambar formana Hance. METHODS: Various column chromatographic techniques were used to separate and purify the constituents. Their physical and chemical properties and spectral data were measured for structural elucidation. RESULTS: Eleven compounds were isolated and identified as beta-sitosterol (1), 3-oxo-11 alpha, 12 alpha-epoxyleanan-28, 13 beta-olide (2), 3-oxo-12 alpha-hydroxy-oleanan-28, 13 beta-olide (3), 3 alpha-acetyloxy-25-hydroxyolean-12-en-28-oic acid (4), oleanolic acid (5), ursolic acid (6), daucosterol (7), betulonic acid (8), gallic acid (9), nonacosane (10) and n-triacontanoic acid (11). CONCLUSION: Among the isolated constituents, compound 4 is new compound, compound 3 is firstly isolated from the natural product and compound 5, 6, 7, 9, 10 and 11 are isolated from LuLuTong for the first time.

Fruit↗
PubMed2004

Insect herbivory in an intact forest understory under experimental CO2 enrichment.

Human-induced increases in atmospheric CO(2) concentration have the potential to alter the chemical composition of plant tissue, and thereby affect the amount of tissue consumed by herbivorous arthropods. At the Duke Forest free-air concentration enrichment (FACE) facility in North Carolina (FACTS-1 research facility), we measured the amount of leaf tissue damaged by insects and other herbivorous arthropods during two growing seasons in a deciduous forest understory continuously exposed to ambient (360 microl l(-1)) and elevated (approximately 560 microl l(-1)) CO(2) conditions. In 1999, there was a significant interaction between CO(2) and species such that winged elm ( Ulmus alata) showed lower herbivory in elevated CO(2) plots, whereas red maple (Acer rubra) and sweetgum (Liquidambar styraciflua) did not. In 2000, our results did not achieve statistical significance but the magnitude of the result was consistent with the 1999 results. In 1999 and 2000, we found a decline (10-46%) in community-level herbivory in elevated CO(2) plots driven primarily by reductions in herbivory on elm. The major contribution to total leaf damage was from missing tissue (66% of the damaged tissue), with galls, skeletonized, and discolored tissue making smaller contributions. It is unclear whether the decline in leaf damage is a result of altered insect populations, altered feeding, or a combination. We were not able to quantify insect populations, and our measurements did not resolve an effect of elevated CO(2) on leaf chemical composition (total nitrogen, carbon, C/N, sugars, phenolics, starch). Despite predictions from a large number of single-species studies that herbivory may increase under elevated CO(2), we have found a decrease in herbivory in a naturally established forest understory exposed to a full suite of insect herbivores and their predators.

Adaptation, Physiological↗
PubMed2005

Responses of floodplain forest species to spatially condensed gradients: a test of the flood-shade tolerance tradeoff hypothesis.

Previous work in southeastern US floodplains led to the hypothesis that a tradeoff between flood and shade tolerance underlies species-specific responses to flooding and light, which drive forest regeneration. In systems where community turnover can occur with small-scale environmental changes, testing this hypothesis requires recognizing that turnover of species along the two gradients can be large relative to the spatial distances involved. We test the tradeoff hypothesis in an old-growth bottomland hardwood forest by (1) comparing shade and moisture profiles of woody juveniles versus random points and (2) using individual-based sampling of woody juveniles to model probability of occurrence in response to distance-to-water table and canopy openness gradients. We found that juveniles of all species combined occupied a similar range of distance-to-water table compared to measurements taken at random points, but average canopy openness above seedlings was significantly higher than at random points. On average, shade-tolerant species, with the exception of Acer rubrum, were found in shaded areas that were also drier, whereas less shade-tolerant taxa, plus A. rubrum, were found in wetter, more open areas, suggesting a tradeoff between flood and shade tolerance. Predictive models of species occurrence, which incorporate the availability of canopy and microtopographic conditions, indicated that three taxa (Fraxinus pennsylvanica, Quercus spp., and Ulmus americana) had patterns consistent with a flood-shade tolerance tradeoff. In contrast, Asimina triloba, Celtis laevigata, and Liquidambar styraciflua had positive responses when the joint stresses of flooding and shade were diminished. A. rubrum appeared to be the most tolerant to both stresses. Our work not only lends support to the flood-shade tradeoff hypothesis but also indicates that a more general model is needed that includes a "flood-shade release" component. We also suggest that responses to small-scale gradients should not be overlooked, particularly in systems where the gradients are ecologically steep.

Disasters↗
PubMed2006

Aromatic resin characterisation by gas chromatography-mass spectrometry. Raw and archaeological materials.

An analytical procedure based on alkaline hydrolysis, solvent extraction and trimethyl-silylation followed by gas chromatography-mass spectrometry (GC-MS) analysis was used to study the chemical composition of benzoe and storax resins, water-insoluble exudates of trees of the Styrax and Liquidambar genus. They are chemically characterised by having aromatic acids, alcohols and esters as their main components and are thus known as aromatic and/or balsamic resins. This analytical procedure allowed us to characterise the main components of the two resins and, even though cinnamic acid is the main component of both the resins, the presence of other characteristic aromatic compounds and triterpenes permitted us to distinguish between the two materials. All the compounds identified in benzoe resin were detected in an archaeological organic residue from an Egyptian ceramic censer (fifth to seventh centuries a.d.), thus proving that this resin was used as one of the components of the mixture of organic materials burned as incense. These results provide the first chemical evidence of the presence of benzoe resin in an archaeological material from Mediterranean area.

Archaeology↗
PubMed1999

Coniferyl aldehyde 5-hydroxylation and methylation direct syringyl lignin biosynthesis in angiosperms.

A central question in lignin biosynthesis is how guaiacyl intermediates are hydroxylated and methylated to the syringyl monolignol in angiosperms. To address this question, we cloned cDNAs encoding a cytochrome P450 monooxygenase (LsM88) and a caffeate O-methyltransferase (COMT) from sweetgum (Liquidambar styraciflua) xylem. Mass spectrometry-based functional analysis of LsM88 in yeast identified it as coniferyl aldehyde 5-hydroxylase (CAld5H). COMT expressed in Escherichia coli methylated 5-hydroxyconiferyl aldehyde to sinapyl aldehyde. Together, CAld5H and COMT converted coniferyl aldehyde to sinapyl aldehyde, suggesting a CAld5H/COMT-mediated pathway from guaiacyl to syringyl monolignol biosynthesis via coniferyl aldehyde that contrasts with the generally accepted route to sinapate via ferulate. Although the CAld5H/COMT enzyme system can mediate the biosynthesis of syringyl monolignol intermediates through either route, k(cat)/K(m) of CAld5H for coniferyl aldehyde was approximately 140 times greater than that for ferulate. More significantly, when coniferyl aldehyde and ferulate were present together, coniferyl aldehyde was a noncompetitive inhibitor (K(i) = 0.59 microM) of ferulate 5-hydroxylation, thereby eliminating the entire reaction sequence from ferulate to sinapate. In contrast, ferulate had no effect on coniferyl aldehyde 5-hydroxylation. 5-Hydroxylation also could not be detected for feruloyl-CoA or coniferyl alcohol. Therefore, in the presence of coniferyl aldehyde, ferulate 5-hydroxylation does not occur, and the syringyl monolignol can be synthesized only from coniferyl aldehyde. Endogenous coniferyl, 5-hydroxyconiferyl, and sinapyl aldehydes were detected, consistent with in vivo operation of the CAld5H/COMT pathway from coniferyl to sinapyl aldehydes via 5-hydroxyconiferyl aldehyde for syringyl monolignol biosynthesis.

Cloning, Molecular↗
PubMed1992

Complete congruence between morphological and rbcL-based molecular phylogenies in birches and related species (Betulaceae).

Estimations of phylogenies from morphological and molecular data often show contrasting results. We compared morphological and molecular phylogenies in an ancient family of woody dicots, the Betulaceae (birch family). The phylogeny of the family was estimated from parsimony analysis of morphological characters in the genera Alnus, Betula, Carpinus, Corylus, Ostrya, and Ostryopsis and from parsimony and distance-matrix analyses of DNA sequences of the chloroplast gene encoding the large subunit of ribulose-1,5-biphosphate carboxylase (rbcL) in the genera Alnus, Betula, Carpinus, Corylus, and Ostrya and in two outgroups, Quercus and Liquidambar. The topologies obtained by the different methods were completely congruent, and bootstrapping strongly supported the division of the family Betulaceae into two major clades, Betuleae (Alnus and Betula) and Coryleae (other members). Only slightly more homoplasy was present in the rbcL sequence data set than in the morphological set. Relative-rate tests indicated that the Coryleae clade had a faster rate of rbcL evolution than did the Betuleae clade. Heterogeneity of rates of morphological evolution also paralleled those for rbcL.

Base Sequence↗
PubMedDate not supplied

Responses of loblolly pine, sweetgum and crab grass roots to localized increases in nitrogen in two watering regimes.

Root responses to differences in availability of nitrogen and soil water were studied in loblolly pine (Pinus taeda L.) seedlings grown in monoculture and in competition with sweetgum (Liquidambar styraciflua L.) or crab grass (Digitaria spp.). Rhizotron cells were maintained at high soil water availability (approximately -0.1 MPa) or subjected to three dry-down cycles to low soil water availability (approximately -1.0 MPa), over two growing seasons. Localized increases in nitrogen availability were created by adding nitrogen in solution to root ingress cores placed in each rhizotron cell. Presence of competitors reduced loblolly pine root growth regardless of the nitrogen or soil water treatment. On average, both total root length density and root surface area were reduced 60% when loblolly pine seedlings were grown with crab grass and 31% when grown with sweetgum. Low water availability reduced loblolly pine root length density and root surface area by 25 and 28%, respectively, compared with well-watered seedlings. Sweetgum root surface area was reduced 18% by the low water availability treatment, whereas crab grass root surface area was unaffected by this treatment. At all soil depths, loblolly pine root surface area and root length density were increased in localized areas of increased nitrogen availability. Sweetgum and crab grass root surface areas were also greater in areas of increased nitrogen availability. In the high soil water availability treatment, loblolly pine root surface area increased 128% in localized areas of increased nitrogen in all competition treatments. In the low soil water availability treatment, loblolly pine roots responded to increased nitrogen only in the absence of competitors. In general, loblolly pine and sweetgum roots responded to increases in resource availability similarly, whereas crab grass roots were relatively less affected.

Journal Article↗
PubMed1996

Long- and short-term flooding effects on survival and sink-source relationships of swamp-adapted tree species.

About 95% of swamp tupelo (Nyssa sylvatica var. biflora (Walt.) Sarg.) and sweetgum (Liquidambar styraciflua L.) seedlings survived continuous root flooding for more than two years, whereas none of the swamp chestnut oak (Quercus michauxii Nutt.) and cherrybark oak (Q. falcata var. pagodifolia Ell.) seedlings survived one year of flooding. Death of oak seedlings occurred in phases associated with periods of major vegetative growth, e.g., after bud burst in spring, after summer stem elongation, and during the winter deciduous stage, suggesting that stored reserves and sources were inadequate to maintain the seedlings when vegetative sinks were forming. Additional evidence that flooding induced a source deficiency in oak was that leaves of flooded oak were 65 to 75% smaller than leaves of nonflooded oak. Flooded swamp tupelo seedlings had a normal leaf size and patchy stomatal opening compared with nonflooded seedlings. Flooding caused increases in alcohol dehydrogenase (ADH) specific activity in taproot cambial tissues and increases in starch concentrations of swamp tupelo seedlings that were reversed when seedlings were removed from flooding. Flooding had little effect on soluble sugar concentrations in swamp tupelo or sweetgum. In the long-term flood-dry-flood treatment, in which all species had survivors, upper canopy leaf photosynthetic rates were higher in all species during the dry period than in nonflooded controls, whereas their starch and soluble sugars concentrations were similar to those of nonflooded controls. Based on seedling survival and the sink-source relationships, the order of flood tolerance was: swamp tupelo > sweetgum > swamp chestnut oak > cherrybark oak.

Journal Article↗
PubMed2001

Production efficiency of loblolly pine and sweetgum in response to four years of intensive management.

We tested the hypothesis that productivity of intensively managed loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) stands is dependent not only on leaf area, but also on foliar photosynthetic rate. Effects of irrigation (irrigation treatment), irrigation with a fertilizer solution (fertigation treatment), and fertigation + pest control (loblolly pine only; fertigation + pest control treatment) on leaf physiology and growth were compared with control plots during the third and fourth growing seasons. Complete weed control was maintained on all plots. Aboveground net primary productivity of loblolly pine and sweetgum increased from 16.3 to 40.5 Mg ha(-1) and from 4.2 to 23.9 Mg ha(-1), respectively, in response to the most intensive treatment. Relative to the control treatment, neither fertigation of sweetgum nor fertigation + pest control of loblolly pine had a significant or consistent influence on foliar N concentration, quantum yield, carboxylation efficiency, net photosynthesis, stomatal conductance, or production efficiency (increment in woody biomass per unit leaf area). Irrigation increased predawn leaf water potential and photosynthesis of loblolly pine, but it had no effect on production efficiency. Leaf area was the predominant determinant of maximum productivity in these rapidly growing plantations.

Forestry↗