Storage versus substrate limitation to bole respiratory potential in two coniferous tree species of contrasting sapwood width

Two coniferous tree species of contrasting sapwood width (Pinus ponderosa L., ponderosa pine and Pseudotsuga menziesii Mirb., Douglas-fir) were compared to determine whether bole respiratory potential was correlated with available storage space in ray parenchyma cells and/or respiratory substrate concentration of tissues (total nitrogen content, N; and total non-structural carbohydrate content, TNC). An increment core-based, laboratory method under controlled temperature was used to measure tissue-level respiration (termed respiratory potential) from multiple positions in mature boles (>100-years-old). The most significant tissue-level differences that occurred were that N and TNC were two to six times higher for inner bark than sapwood, TNC was about two times higher in ponderosa pine than Douglas-fir and there was significant seasonal variation in TNC. Ray cell abundance was not correlated with sapwood respiratory potential, whereas N and TNC often were, implying that respiratory potential tended to be more limited by substrate than storage space. When scaled from cores to whole boles (excluding branches), potential net CO2 efflux correlated positively with live bole volume (inner bark plus sapwood), live bole ray volume, N mass, and TNC mass (adjusted R2 > or =0.4). This relationship did not differ between species for N mass, but did for live bole volume, live bole ray volume, and TNC mass. Therefore, N mass appeared to be a good predictor of bole respiratory potential. The differences in net CO2 efflux between the species were largely explained by the species' relative amounts of whole-bole storage space or substrate mass. For example, ponderosa pine's inner bark was thinner than Douglas-fir's, which had the greater concentration of ray cells and TNC compared with the sapwood. This resulted in ponderosa pine boles having 30-60% less ray volume and 10-30% less TNC mass, and caused ponderosa pine net CO2 efflux/ray volume and net CO2 efflux/TNC mass to be 20-50% higher than Douglas-fir. In addition, because inner bark respiratory potential was 2-25 times higher than that of sapwood, ponderosa pine's thinner inner bark and deeper sapwood (relative to Douglas-fir) caused its bole net CO2 efflux/live bole volume to be 20-25% lower than that of similarly-sized Douglas-fir trees.     

Woody-tissue respiration for Simarouba amara and Minquartia guianensis,two tropical wet forest trees with different growth habits

We measured CO₂ efflux from stems of two tropical wet forest trees, both found in the canopy, but with very different growth habits. The species were Simarouba amara, a fast-growing species associated with gaps in old-growth forest and abundant in secondary forest, and Minquartia guianensis, a slow-growing species tolerant of low-light conditions in old-growth forest. Per unit of bole surface, CO₂ efflux averaged 1.24 mol m^–2 s^–1 for Simarouba and 0.83 mol m^–2s^–1 for Minquartia. CO₂ efflux was highly correlated with annual wood production (r ²=0.65), but only weakly correlated with stem diameter (r ²=0.22). We also partitioned the CO₂ efflux into the functional components of construction and maintenance respiration. Construction respiration was estimated from annual stem dry matter production and maintenance respiration by subtracting construction respiration from the instantaneous CO₂ flux. Estimated maintenance respiration was linearly related to sapwood volume (39.6 mol m^–3s^–1 at 24.6° C, r ²=0.58), with no difference in the rate for the two species. Maintenance respiration per unit of sapwood volume for these tropical wet forest trees was roughly twice that of temperate conifers. A model combining construction and maintenance respiration estimated CO₂ very well for these species (r ²=0.85). For our sample, maintenance respiration was 54% of the total CO₂ efflux for Simarouba and 82% for Minquartia. For our sample, sapwood volume averaged 23% of stem volume when weighted by tree size, or 40% with no size weighting. Using these fractions, and a published estimate of aboveground dry-matter production, we estimate the annual cost of woody tissue respiration for primary forest at La Selva to be 220 or 350 g C m^–2 year^–1, depending on the assumed sapwood volume. These costs are estimated to be less than 13% of the gross production for the forest.     

Stem respiration of ponderosa pines grown in contrasting climates: implications for global climate change

We examined the effects of climate and allocation patterns on stem respiration in ponderosa pine (Pinus ponderosa) growing on identical substrate in the cool, moist Sierra Nevada mountains and the warm, dry, Great Basin Desert. These environments are representative of current climatic conditions and those predicted to accompany a doubling of atmospheric CO₂, respectively, throughout the range of many western north American conifers. A previous study found that trees growing in the desert allocate proportionally more biomass to sapwood and less to leaf area than montane trees. We tested the hypothesis that respiration rates of sapwood are lower in desert trees than in montane trees due to reduced stem maintenance respiration (physiological acclimation) or reduced construction cost of stem tissue (structural acclimation). Maintenance respiration per unit sapwood volume at 15°C did not differ between populations (desert: 6.39 ± 1.14 SE μmol m⁻³ s⁻¹, montane: 6.54 ± 1.13 SE μmol m⁻³ s⁻¹, P = 0.71) and declined with increasing stem diameter (P = 0.001). The temperature coefficient of respiration (Q ₁₀) varied seasonally within both environments (P = 0.05). Construction cost of stem sapwood was the same in both environments (desert: 1.46 ± 0.009 SE g glucose g⁻¹ sapwood, montane: 1.48 ± 0.009 SE glucose g⁻¹ sapwood, P = 0.14). Annual construction respiration calculated from construction cost, percent carbon and relative growth rate was greater in montane populations due to higher growth rates. These data provide no evidence of respiratory acclimation by desert trees. Estimated yearly stem maintenance respiration was greater in large desert trees than in large montane trees because of higher temperatures in the desert and because of increased allocation of biomass to sapwood. By analogy, these data suggest that under predicted increases in temperature and aridity, potential increases in aboveground carbon gain due to enhanced photosynthetic rates may be partially offset by increases in maintenance respiration in large trees growing in CO₂-enriched atmospheres. Received: 4 November 1996 / Accepted: 23 January 1997     

Coordination of leaf and stem water transport properties in tropical forest trees

Stomatal regulation of transpiration constrains leaf water potential (Ψ_L) within species-specific ranges that presumably avoid excessive tension and embolism in the stem xylem upstream. However, the hydraulic resistance of leaves can be highly variable over short time scales, uncoupling tension in the xylem of leaves from that in the stems to which they are attached. We evaluated a suite of leaf and stem functional traits governing water relations in individuals of 11 lowland tropical forest tree species to determine the manner in which the traits were coordinated with stem xylem vulnerability to embolism. Stomatal regulation of Ψ_L was associated with minimum values of water potential in branches (Ψ_br) whose functional significance was similar across species. Minimum values of Ψ_br coincided with the bulk sapwood tissue osmotic potential at zero turgor derived from pressure–volume curves and with the transition from a linear to exponential increase in xylem embolism with increasing sapwood water deficits. Branch xylem pressure corresponding to 50% loss of hydraulic conductivity (P ₅₀) declined linearly with daily minimum Ψ_br in a manner that caused the difference between Ψ_br and P ₅₀ to increase from 0.4 MPa in the species with the least negative Ψ_br to 1.2 MPa in the species with the most negative Ψ_br. Both branch P ₅₀ and minimum Ψ_br increased linearly with sapwood capacitance (C) such that the difference between Ψ_br and P ₅₀, an estimate of the safety margin for avoiding runaway embolism, decreased with increasing sapwood C. The results implied a trade-off between maximizing water transport and minimizing the risk of xylem embolism, suggesting a prominent role for the buffering effect of C in preserving the integrity of xylem water transport. At the whole-tree level, discharge and recharge of internal C appeared to generate variations in apparent leaf-specific conductance to which stomata respond dynamically.     

Two new soldierfishes (Beryciformes: Holocentridae:Myripristis) from Japan

Two species of the holocentrid fish genusMyripristis are described as new from Japan, both with a single pair of tooth patches outside the gape at tip of lower jaw, the third anal spine longer than the fourth, and 28–29 lateral-line scales:M. kochiensis from Kashiwa-jima, Kochi Prefecture, previously misidentified asM. murdjan, is distinct in having small scales in axil of pectoral fins, 32–36 gill rakers, interorbital space 4.45–5.1 in head, and lower jaw not strongly projecting when mouth closed;M. greenfieldi, from the Ryukyu Islands and Ogasawara Islands to Kochi Prefecture, previously misidentified asM. woodsi andM. randalli, is distinct in lacking scales in the pectoral axil, having 35–52 cteni on largest body scales, 43–47 gill rakers, and longest dorsal spine 2.0–2.25 in head.     

Convergence of tree water use within an arid-zone woodland

We examined spatial and temporal patterns of tree water use and aspects of hydraulic architecture in four common tree species of central Australia—Corymbia opaca, Eucalyptus victrix, E. camaldulensis and Acacia aneura—to better understand processes that constrain water use in these environments. These four widely distributed species occupy contrasting niches within arid environments including woodlands, floodplains and riparian environments. Measurements of tree water use and leaf water potential were made at two sites with contrasting water table depths during a period of high soil water availability following summer rainfall and during a period of low soil water availability following 7 months of very little rainfall during 2007. There were significant differences in specific leaf area (SLA), sapwood area to leaf area ratios and sapwood density between species. Sapwood to leaf area ratio increased in all species from April to November indicating a decline in leaf area per unit sapwood area. Despite very little rainfall in the intervening period three species, C. opaca, E. victrix and E. camaldulensis maintained high leaf water potentials and tree water use during both periods. In contrast, leaf water potential and water use in the A. aneura were significantly reduced in November compared to April. Despite contrasting morphology and water use strategies, we observed considerable convergence in water use among the four species. Wood density in particular was strongly related to SLA, sapwood area to leaf area ratios and soil to leaf conductance, with all four species converging on a common relationship. Identifying convergence in hydraulic traits can potentially provide powerful tools for scaling physiological processes in natural ecosystems.     

Interrelations between respiration and dormancy in buds of three hardwood species with different chilling requirements for dormancy release

 Respiration in vegetative buds of mature Betula pendula, Alnus glutinosa and Prunus padus trees was measured monthly at 15°C from mid-October 1996 to natural outdoor budburst in April 1997. In B. pendula the effect of bud water content on respiration was also estimated (December–April) by artificial imbibition of buds for 24 h prior to measurement of respiration. For estimation of corresponding bud dormancy status, batches of twigs were forced at identical monthly intervals at 15°C in long days (24 h), and budburst recorded. In all species dormancy was deepest when the leaves were shed in October, and dormancy was first alleviated in P. padus followed by B. pendula and A. glutinosa. However, bud respiration capacity was not related to dormancy release as it decreased in all species from October to November and displayed no notable increase until February in P. padus, March in B. pendula and April in A. glutinosa, after completion of dormancy release. Rather, increase in respiration coincided with growth resumption prior to budburst. Artificial imbibition of B. pendula buds increased the water content by approximately 10% (FW) and induced a doubling of the respiration rate (December–February). Moreover, the seasonal variation in bud water content (October–April) explained 94% of the variation in respiration in B. pendula and P. padus, and 84% in A. glutinosa. These observations suggest an important role of water content for respiration. During a cold period from mid-December to mid-January with mean temperature of –9.7°C dormancy release was arrested in P. padus, and to some degree in A. glutinosa, whereas dormancy release progressed normally in B. pendula. This indicates species differences in lower critical temperatures for dormancy release. Received: 30 June 1997 / Acceped: 1 October 1997     

A comparison of sap flux and water relations of leaves of various isolated trees with special reference to foundation movement in clay soil

Diurnal variation in sap flux (S) through stems of six trees, two each of Ulmus procera SALISB., Melaleuca styphelioides SM. and Prunus cerasifera EHRH. ‘Nigra’ (referred to hereafter by their generic names), were estimated from measurements of heat pulse velocities. Leaf water potential (ψ), stomatal conductance (g _s ) and transpiration from leaves (T) of all replicate trees were measured at 1300–1500h, once during the summer. On two separate occasions measurements were made of S, ψ, (g _s ) and T for one each of Ulmus and Melaleuca trees to study diurnal variations in these parameters. A 12×12 m² area around each tree was kept covered to simulate the condition of trees growing on pavements adjacent to residential properties. Sap flux for these tree species was in the order Melaleuca>Ulmus>Prunus. It is suggested that the smaller canopy and sapwood area in Prunus compared to the other two species is responsible for lower water potential and lower transpiration rate than the other species. Detailed analysis of the diurnal variation in sap flux and water relation of leaves of Melaleuca and Ulmus indicated sap flux of Melaleuca to be greater than that of Ulmus at the same transpiration rate per unit leaf area although the sapwood area of the two species was marginally different. This may have been due either to the difference in canopy conductance or in leaf area between the two species. With the assumption that sap flux closely resembles the rate of soil water extraction for both species, results indicate that Melaleuca is likely to extract soil water at a higher rate than Ulmus and hence is capable of causing greater shrinkage and soil movement than Ulmus.     

Acetylene reduction and indoleacetic acid production by Azospirillum isolates from Cactaceous plants

Azospirillum isolates were obtained from rhizosphere soil and roots of three cactaceae species growing under arid conditions. All Azospirillum isolates from rhizosphere and roots ofStenocereus pruinosus andStenocereus stellatus were identified asA. brasilense; isolates of surface-sterilized roots fromOpuntia ficus-indica were bothA. brasilense andA. lipoferum. Azospirilla per g of fresh root in the three species ranged from 70×10³ to 11×10³. The most active strains in terms of C₂H₂ reduction (25–49.6 nmol/h·ml) and indoleacetic acid (IAA) production (36.5–77 μg/ml) were those identified asA. brasilense and isolated from Stenocereus roots.A. lipoferum isolated from Opuntia roots produced low amounts of IAA (6.5–17.5 μg/ml) and low C₂H₂-reduction activity (17.8–21.2 nmol/h·ml).     

Application of a rapid thin section method for observations on decomposing litter in mor humus form in a subalpine coniferous forest

Morphological changes in the decomposing litter ofAbies spp. andBetula spp. in a mor humus form were studied by a rapid thin section method. According to the morphological characteristics, the epidermis, mesophyll and vascular bundleof Abies needle litter were classified into four types: (i) newly fallen; (ii) slightly decomposed; (iii) moderately decomposed; and (iv) greatly decomposed. The distribution of these tissue types along the profile of the forest floor was then investigated. The morphological changes in other litter types, such as branches, scales andBetula leaves during decomposition were observed directly with microscope and electron microscope. Five vertical thin sections and 80 horizontal thin sections were used for these observations and investigations. the decomposition ofAbies litter was slower than that ofBetula litter. The relative decomposition rate of the tissues was in the order of: mesophyll>vascular bundle >epidermis inAbies needles; mesophyll≥epidermis>vascular bundles inBetula leaves; and inner bark >xylem>outer bark in bothAbies andBetula branches. The last remains of the litter were usually stomata, segments of seminiferous scale and outer bark ofAbies. The decomposition of plant litter occurred mainly within the L and F layers of the soil (0–5 cm in depth).Abies needles andBetula leaves completely disappeared at depths of 0–6 cm and 0–4 cm, respectively. Branches disappeared within the top of 5 cm and 6–8 cm forBetula and forAbies, respectively. The scales ofAbies were most slowly decomposed in the soil layers.     

Thermal sensitivity of cellular energy budgets in some Antarctic fish hepatocytes

Oxygen demand elicited by the main cellular energy consumers was examined in isolated hepatocytes of sub-Antarctic (Lepidonotothen larseni) and high-Antarctic notothenioids (Trematomus eulepidotus, Trematomus pennellii, Trematomus lepidorhinus, Trematomus bernacchii, Artedidraco orianae) and in a zoarcid (Pachycara brachycephalum) fish with respect to the role of cellular metabolism in co-defining thermal tolerance. The relative proportions of energy allocated to protein and RNA/DNA synthesis, ion regulation and ATP synthesis were quantified between 0°C and 15°C by analysis of inhibitor sensitive cellular respiration. In all the investigated species, protein synthesis constituted 25–37%, RNA synthesis 24–35%, Na⁺/K⁺-ATPase 40–45% and mitochondrial ATP synthesis 57–65% of total respiration. The sub-Antarctic nototheniid L. larseni displayed lower cellular protein synthesis rates but somewhat higher active ion regulation activities than its high-Antarctic confamilials, as is typical for more eurythermal species. Assumed thermal optima were mirrored in minimized overall cellular energy demand. In the sub-Antarctic L. larseni and P. brachycephalum, minima of oxygen consumption were located between 3°C and 6°C, indicating elevated energy turnover below and above these temperatures. In contrast, the high-Antarctic species displayed progressively rising respiration rates during warming with a cellular energetic minimum at 0°C. The sub-Antarctic nototheniid and the zoarcid showed signs of cold-eurythermy and appear to live close to their lower limit of thermal tolerance, while high-Antarctic notothenioids show high degrees of energetic efficiency at 0°C. All cellular preparations maintained energy budgets over a wide thermal range, supporting the recent concept that thermal limits are set by oxygen and associated energy limitations at the whole organism level.     

Biomass and aboveground net primary production in a subtropical mangrove stand of Kandelia obovata (S., L.) Yong at Manko Wetland, Okinawa, Japan

Biomass and aboveground net primary production (ANPP) in a monospecific pioneer stand of a mangrove Kandelia obovata (S., L.) Yong were quantified. The estimated biomasses in leaves, branches, stems, roots, aboveground and total were 5.61 (3.68%), 28.8 (18.9%), 46.1 (30.2%), 71.8 (47.2%), 80.5 (52.8%) and 152 Mg ha⁻¹ (100%), respectively. Stem phytomass increment per tree was estimated using allometric relationships and stem analysis. Stem volume without bark of harvested trees showed a strong allometric relationship with D _0.1² H (D _0.1, diameter at a height of one-tenth of tree height H) (R ² = 0.924). Annual stem volume increment per tree showed a strong allometric relationship with D _0.1² H (R ² = 0.860). Litterfall rate ranges from 3.87 to 56.1 kg ha⁻¹ day⁻¹ for leaves and 0.177 to 46.2 kg ha⁻¹ day⁻¹ for branches. Seasonal changes of litterfall rate were observed, which showed a peak during wet season (August–September). Total annual litterfall was estimated as 10.6 Mg ha⁻¹ year⁻¹, in which 68.2% was contributed by the leaves. The ANPP in the K. obovata stand was 29.9–32.1 Mg ha⁻¹ year⁻¹, which is ca. 2.8–3.0 times of annual litterfall. The growth efficiency (aboveground biomass increment/LAI) was 5.35–5.98 Mg ha⁻¹ year⁻¹. The low leaf longevity (9.3 months) and high growth efficiency of K. obovata makes it a highly productive mangrove species.     

Sap flux of five co-occurring tree species in a temperate broad-leaved forest during seasonal soil drought

In an old-growth forest in Central Germany, sap flux was studied in five broad-leaved tree species that were assumed to differ in drought sensitivity. Under moist soil conditions, average daily sap flux density (J _s) in the outermost xylem varied by a factor of 2.3 among the species (67–152 g cm⁻² per day, n=5 trees per species), and declined in the sequence Fagus sylvatica > Acer pseudoplatanus > Tilia cordata > Carpinus betulus > Fraxinus excelsior. Decreasing soil moisture content (Θ) resulted in linearly reduced J _s in four of the species. During a dry period, J _s was reduced by 44% in T. cordata, 39% in F. sylvatica, 37% in A. pseudoplatanus and 31% in C. betulus compared to sap flux at equal vapour pressure deficit (D) in the wet period. F. excelsior, the only ring-porous species studied, lacked a significant response in J _s to D and Θ. The relative reduction in water use during the dry period was not related to the assumed drought sensitivity of the species as inferred from their abundance in natural woodlands. J _s was positively correlated with tree diameter at breast height (DBH) in three species but decreased with DBH in two species. Dyeing experiments revealed that DBH accounted for 94% of the variation in sapwood area found in a bulk sample of all diffuse-porous trees. This suggests that DBH is a reliable estimator of sapwood area of temperate diffuse-porous species irrespective of species identity. In contrast, sap flux density was found to be greatly dependent on tree species. The estimated whole-plant water use for diffuse-porous trees of a given diameter (49 cm) ranged between 74 and 168 kg per day per species under moist soil conditions. Thus, in temperate mixed forests, species-specific differences in water use can result in a considerable spatial heterogeneity of canopy transpiration.     

Decomposition and carbon cycling of dead trees in tropical forests of the central Amazon

Decomposition rate constants were measured for boles of 155 large dead trees (>10 cm diameter) in central Amazon forests. Mortality data from 21 ha of permanent inventory plots, monitored for 10–15 years, were used to select dead trees for sampling. Measured rate constants varied by over 1.5 orders of magnitude (0.015–0.67 year^–1), averaging 0.19 year^–1 with predicted error of 0.026 year. Wood density and bole diameter were significantly and inversely correlated with rate constants. A tree of average biomass was predicted to decompose at 0.17 year^–1. Based on mortality data, an average of 7.0 trees ha^–1 year^–1 died producing 3.6 Mg ha^–1 year^–1 of coarse litter (>10 cm diameter). Mean coarse litter standing-stocks were predicted to be 21 Mg ha^–1, with a mean residence time of 5.9 years, and a maximum mean carbon flux to the atmosphere of 1.8 Mg C ha^–1 year^–1. Total litter is estimated to be partitioned into 16% fine wood, 30% coarse wood, and 54% non-woody litter (e.g., leaves, fruits, flowers). Decomposition rate constants for coarse litter were compiled from 20 globally distributed studies. Rates were highly correlated with mean annual temperature, giving a respiration quotient (Q ₁₀) of 2.4 (10°C^–1). Received: 14 June 1999 / Accepted: 31 August 1999     

Temporal and spatial partitioning of water resources among eight woody species in a Hawaiian dry forest

Lowland dry forests are unique in Hawaii for their high diversity of tree species compared with wet forests. We characterized spatial and temporal partitioning of soil water resources among seven indigenous and one invasive dry forest species to determine whether the degree of partitioning was consistent with the relatively high species richness in these forests. Patterns of water utilization were inferred from stable hydrogen isotope ratios (δD) of soil and xylem water, zones of soil water depletion, plant water status, leaf phenology, and spatial patterns of species distribution. Soil water δD values ranged from –20‰ near the surface to –48‰ at 130 cm depth. Metrosideros polymorpha, an evergreen species, and Reynoldsia sandwicensis, a drought-deciduous species, had xylem sap δD values of about –52‰, and appeared to obtain their water largely from deeper soil layers. The remaining six species had xylem δD values ranging from –33 to –42‰, and apparently obtained water from shallower soil layers. Xylem water δD values were negatively correlated with minimum annual leaf water potential and positively correlated with leaf solute content, an integrated measure of leaf water deficit. Seasonal patterns of leaf production ranged from dry season deciduous at one extreme to evergreen with near constant leaf expansion rates at the other. Species tapping water more actively from deeper soil layers tended to exhibit larger seasonality of leaf production than species relying on shallower soil water sources. Individuals of Myoporum sandwicense were more spatially isolated than would be expected by chance. Even though this species apparently extracted water primarily from shallow soil layers, as indicated by its xylem δD values, its nearly constant growth rates across all seasons may have been the result of a larger volume of soil water available per individual. The two dominant species, Diospyros sandwicensis and Nestegis sandwicensis, exhibited low leaf water potentials during the dry season and apparently drew water mostly from the upper portion of the soil profile, which may have allowed them to exploit light precipitation events more effectively than the more deeply rooted species. Character displacement in spatial and temporal patterns of soil water uptake was consistent with the relatively high diversity of woody species in Hawaiian dry forests. Received: 20 May 1999 / Accepted: 2 March 2000     

A comparative study of positional behavior in three species of tamarin monkeys

Tamarins of the genusSaguinus are small-bodied New World monkeys that exhibit clawlike or modified nails. Patterns of positional behavior and habitat utilization are presented for three species,Saguinus fuscicollis, S. geoffroy, andS. mystax. These data were collected on free-ranging tamarin populations in Panama and Peru. Despite considerable differences in body weight, all three species exhibited very similar patterns of positional behavior, with quadrupedal bounding and running accounting for 43 – 52% of travel time. Leaping was the second most common locomotor activity and accounted for 31 – 41% of travel. Although each species leaped principally on small supports in the perimeter of the tree crown, approximately 20% of all leaps inS. fuscicollis involved moderate to large sized vertical trunks located in the undercanopy. Leaping between trunks was rare in the two larger tamarin species. Measurements taken on live wild-trapped adults reveal that compared toSaguinus geoffroyi andS. mystax, S. fuscicollis is characterized by a long legspan and an especially long armspan. It is proposed that inS. fuscicollis, elongated forelimbs play an important role in maneuvering and rotating the body during the in-air phase of trunk-to-trunk leaping, and increase the breaking distance needed to decelerate the body upon impact. Additional relationships between body size, substrate preference, and positional behavior in callitrichines are discussed.     

On biology of limoniid flies of the genus Teucholabis Osten-Sacken (Diptera, Limoniidae) with a description of immature stages of Teucholabis esakii (Alexander) and T. yezoensis Alexander

The larvae and pupae of two xylobiont species of limoniid flies, Teucholabis esakii (Al.) and T. yezoensis Al., are described for the first time. The larvae live under bark among bast fibers of Maackia amurensis and Phellodendron amurense, rarely under bark of various species of oak, aspen, birch, and maple. A key to larvae and pupae of the two species is provided. Original Russian Text ? M.G. Krivosheina, 2009, published in Entomologicheskoe Obozrenie, 2009, Vol. 88, No. 1, pp. 185–193.     

Respiration of turions and winter apices in aquatic carnivorous plants

Basic respiration characteristics were measured in turions of six aquatic plant species differing greatly in their ecological and overwintering characteristics both before and after overwintering, i.e., in dormant and non-dormant state: non-carnivorous Hydrocharis morsus-ranae and Caldesia parnassifolia and carnivorous Aldrovanda vesiculosa, Utricularia australis, U. ochroleuca, and U. bremii, and in non-dormant winter apices of three Australian (sub)tropical populations of Aldrovanda and of two temperate North American Utricularia species, U. purpurea and U. radiata. Respiration rate of autumnal (dormant) turions at 20°C ranged from 0.36 to 1.3 μmol O₂ kg⁻¹ (FM) s⁻¹ and, except for U. bremii, increased by 11–114% after overwintering. However, this increase was statistically significant only in two species. Respiration Q₁₀ in dormant turions ranged within 1.8–2.6 and within 2.3–3.4 in spring (non-dormant) turions. Turions of aquatic plants behave as typical storage, overwintering organs with low respiration rates. No relationship was found between respiration rate of turions and overwintering strategy. In spite of their low respiration rates, turions can usually survive only from one season to another, due to their limited reserves of respiratory substrates for long periods. Contrary to true turions, respiration rates in non-dormant winter apices both in Australian Aldrovanda populations and temperate U. radiata and U. purpurea, in sprouting turions, and growing shoot apices of Aldrovanda were high and ranged from 2.1 to 3.1 μmol kg⁻¹ (FM) s⁻¹, which is comparable to that in aquatic plant leaves or shoots.     

Gas diffusion through wood: implications for oxygen supply

Living tissue in tree stems has to be supplied with oxygen, which can be transported upwards with the transpiration stream; but in times of zero sapflow, the only source is the oxygen stored or diffusing radially through bark and xylem. We measured radial and axial diffusion of oxygen against nitrogen gas in wood of coniferous (Picea abies (L.) Karst. and Taxus baccata L.), ring-porous (Quercus robur L. and Fraxinus excelsior L.) and diffuse-porous (Fagus sylvatica L. and Carpinus betulus L.) trees at different water and gas contents in the laboratory. The diffusion coefficient (D) in radial direction was mostly between 10⁻¹¹ and 10⁻⁷ m² s⁻¹ and was strongly related to the gas content. At 40% gas volume, D increased 5–13-fold in Picea, Taxus and Quercus, 36-fold in Fraxinus, and about 1000-fold in Carpinus and Fagus relative to D at 15% gas volume. In the axial direction, diffusion was 1 or 2 orders of magnitude faster. Between-species differences in diffusion velocities can largely be explained by wood structure. In general, D was lowest in conifers, highest in diffuse-porous and intermediate in ring-porous hardwoods, where the large vessels were mostly blocked by tyloses. Model calculations showed that at very high water content, radial diffusion can be too low to ensure the supply of respiring sapwood with sufficient oxygen and an important function of gas in living stems appears to be the supply of oxygen through storage and diffusion.     

Attack preference of Ips pini on Pinus ponderosa in northern Arizona: tree size and bole position

1 The present study investigated the influence of tree size and bole position on selection of ponderosa pines (Pinus ponderosa Dougl. ex Laws.) by Ips pini Say (Coleoptera: Curculionidae: Scolytinae) in a northern Arizona forest. Ips pini were attracted to lower and upper bole positions with pheromone lures, and the number of attacks counted. In addition, tree phloem and bark thickness, resin flow in response to wounding and characteristics of tree water and carbon relations were all measured. 2 Bark thickness was the most strongly related tree characteristic to number of I. pini attacks. Thin bark and a high number of attacks occurred at the lower bole position of 10‐cm diameter trees and upper bole positions of 23‐, 35‐, and 50‐cm diameter trees. 3 Phloem thickness increased directly with tree size, was greater at the upper bole compared with the lower bole, but was not associated with number of attacks. 4 Resin flow did not differ strongly over tree sizes or bole positions, and was not related to number of I. pini attacks. Attacks were not related to characteristics of tree carbon and water relations measured during I. pini flights.