Relative Accumulation Rate Research Articles

Cycling and composition of organic matter in terrestrial and marine ecosystems

Decomposing natural organic matter found in terrestrial and marine environments consists of a heterogenous mixture of particles and molecules with variable physical and chemical properties. The amount of organic matter present in these systems is controlled by the relative rates of accumulation and loss. Accumulation is controlled principally by net primary productivity whilst losses are mainly a function of the biological stability of the biomolecules present. Processes of lateral transfer can also be significant to both rates of accumulation and loss in localized zones. In this paper, the processes and properties responsible for defining the biological stability of organic matter in terrestrial and marine ecosystems are examined. A conceptual model illustrating the implications that mechanisms of biological stabilisation can have on the molecular composition of natural organic matter in these ecosystems is presented. Molecular composition has typically been determined using a variety of selective degradative methodologies either individually or in combination. These methodologies often only identify 20–80% of the organic matter present with the extent of identification decreasing as the degree of biological processing increases. Solid-state 13C nuclear magnetic resonance (NMR) can be used for routine assessment of the chemistry of organic materials; however, no direct measure of the molecular composition can be obtained. Previous work that examined the ability of using solid-state 13C NMR data in a simple mixing model to predict molecular composition is extended in this study. The extended mixing model is then used to characterise changes in the molecular composition of decomposing organic material in soil and marine systems. The extended mixing model accounted for the distribution of 13C NMR signal intensity of all samples examined and allowed the biomolecular and elemental composition to be estimated. Decomposition induced changes in molecular composition were very different in the terrestrial and marine systems examined, but the direction of change suggested a convergence towards the formation of similar decomposition products.

서태평양 적도 지역의 플라이스토세 후기 고해양 변화

To delineate Late Pleistocene paleoceanographic change of the West Pacific, we analyzed the oxygen and carbon isotopic ratios of two planktonic foraminifera species ( G. sacculifer and N. dutertrei) from a piston core (KODOS-313) taken from the West equatorial Pacific, and they are compared with the published results of the East Pacific (ODP site 847 and RC 11-210), in terms of relative amounts and mass accumulation rates of CaCO3 and eolian component, back to marine isotopic stage (MIS) 6. Differences in oxygen and carbon isotope values between two foraminifera species (0.75‰ in δ 18 O, 0.05‰ in δ 13 C) are less than those of the East Pacific (1.30‰ in δ 18 O, 0.14‰ in δ 13 C), which indicates smaller vertical contrasts in both temperature and nutrient between mixin g-zone and thermocline in the West Pacific. Strong deviation in δ 18 O of G. sacculifer from SPECMAP suggests the carbonate fraction of KODOS-313 was subjected to partial dissolution by bottom water under lysocline. Lower accumulation rates of CaCO3 and eolian component during glacial times are likely due to low sedimentation rate (ave. 0.75 cm/1000 yr) combined with carbonate dissolution in KODOS-313 site. However, the high CaCO3 contents during the glacial periods clearly follow the general pattern of equatorial Pacific ocean.

Electrofishing Effort and Fish Species Richness and Relative Abundance in Ozark Highland Streams of Arkansas

Abstract We sampled 15 stream sites in the Ozark Highlands ecoregion of Arkansas and examined the effect of increased backpack electrofishing effort on the richness and relative abundance estimates of fish species. Each site was 75 mean stream widths (MSWs) long and was divided into 15 consecutive segments that were each 5 MSWs long. For each site the percent of empirical and theoretical species richness and the percent of relative abundance similarity to the entire fish assemblage were calculated by adding consecutive segments using an approach that resulted in 15 accumulation curves per assemblage character for each stream site. On average, a distance of 53.8 MSWs (SD = 7.4) was needed to sample 95% of empirical species richness at a stream site, which was equal to an area of 2,722.0 m2 (SD = 1,967.0). For sampling 95% of theoretical species richness, an average of 101.8 MSWs (SD = 34.5), or 5,055.7 m2 (SD = 3,667.4), was needed. Obtaining 95% relative abundance similarity required an average sampling effort equivalent to 24.0 MSWs (SD = 8.9), or 1,269.7 m2 (SD = 932.1). Mean stream width explained more variance in the reach lengths and areas needed for estimates of species richness and relative abundance than did riffle-pool sequence length or watershed size. Our results should offer insight into species richness and relative abundance accumulation rates when using a one-pass backpack electrofishing sample in Ozark Highland streams of Arkansas.

U–Pb SHRIMP ages of volcanic zircons from the Merrions and Turondale Formations, New South Wales, and the Early Devonian time‐scale: A biostratigraphic and sedimentological assessment

U–Pb ages for volcanic zircons from the Lower Devonian Turondale and Merrions Formations initially dated by Jagodzinski and Black (1999) have been recalculated by Compston (2000, 2001). The Turondale, Waterbeach and Merrions Formations are, in ascending stratigraphic order, three of the Lower Devonian deep‐water formations of the Hill End Trough. The recent discovery of a Lochkovian conodont fauna of the delta zone in derived limestone blocks from the uppermost beds of the Turondale Formation has established a maximum age for that horizon. The principal lithological assemblages of the formations are volcanic (megaturbidite and lavas), epiclastic turbidites and essentially hemipelagic lithologies. The mean zircon ages suggest a long duration for the Merrions Formation, 615 m thick and 91% volcanic, and a very much shorter interval for the upper two‐thirds of the Turondale Formation, 360 m thick and 34% volcanic, plus the intervening non‐volcanic Waterbeach Formation, 512 m thick. A sedimentological model based on scaled depositional rates for the facies has been used to estimate the relative accumulation rates and durations of the succession from the base of the Turondale Formation to the top of the Merrions Formation. The model indicates that the Merrions Formation accumulated in a much shorter time than the interval from the top of the lower Turondale Formation to the base of the Merrions Formation. The analytical uncertainties of the Jagodzinski and Black (1999) zircon ages are large enough to be compatible with the sedimentological model, but the smaller analytical uncertainties calculated by Compston (2000, 2001) fall far from the scaled sedimentological model. Grouping together of the lower Merrions Formation and lower Turondale Formation zircon dates in Compston (2000) for a single mid‐Lochkovian age is in conflict with the biostratigraphic and sedimentological evidence available and the derived time‐scale for the Early Devonian is highly questionable. Given the incompatibility of the recalculated zircon ages with the depositional history and the uncertainty of biostratigraphic dating of the formations, neither of the quite different sets of ages quoted in Compston (2000, 2001) are useful for the definition of a numerical time‐scale.

Effect of nitrogen deficiency on biomass production, photosynthesis, carbon partitioning, and nitrogen nutrition status of Melaleuca and Eucalyptus species

Genetic variation in response to N-deficiency between tropical woody plants was assessed by growing two species each of the genus Melaleuca (M. leucadendra and M. cajuputi) and Eucalyptus (E. camaldulensis and E. tereticornis) hydroponically at two levels of N. Biomass, N content and carbohydrate contents of various plant parts, leaf photosynthetic rate, and photo assimilate distribution were determined in all the plants at both control N (2.14 mM) and low N (0.36 mM) levels. Although the Eucalyptus genotype grew faster than Melaleuca under control conditions, the reduction of stem elongation and growth by N-deficiency was more severe in Eucalyptus species than in Melaleuca. In the same way as the effect on growth, N-deficiency reduced the photosynthetic rate and leaf area in all the species. The better performance at a low N level of Melaleuca compared with Eucalyptus species could be attributed to the lower reduction of either the photosynthetic rate (M. cajuputi) or the leaf area expansion (M. leucadendra). M. cajuputi had a higher leaf N concentration that was less affected by stress in this species than in the others. N-deficiency induced a better N use efficiency in the leaves of Melaleuca by enhancing significantly the photosynthetic rate per unit leaf N. In response to N-deficiency, all the plants except for M. cajuputi accumulated a remarkably higher concentration of sugars and starch in different organs like roots, stem, and leaves, but the partitioning of photoassimilates was directed preferentially to the growth of the roots in Eucalyptus compared to Melaleuca species. Although the relative rate of biomass accumulation was positively correlated with the N concentration of the plant in both genera studied, the associations were stronger and regression coefficients were higher in Eucalyptus than in Melaleuca, with the crossing points of their regression lines occuring between the values in the low N and control treatments. The total N content in the plant exhibited a stronger correlation with N absorption per unit root weight than with the root weight. These results suggest that Melaleuca species are more resistant than Eucalyptus to N-deficiency owing to the maintenance of (1) a higher ability of N uptake by roots, (2) higher source activity represented by either the photosynthetic rate or the leaf area, and (3) more efficient N utilization of the source activity at a low N level in the growth medium.

Low Winter Soil Temperature Affects Summertime Nutrient Uptake Capacity and Growth Rate of Mountain Birch Seedlings in the Subarctic, Swedisn Lapland

Effects of different winter soil temperature on summertime growth rate of individual seedlings of mountain birch (Betula pubescens ssp. czerepanovii) were evaluated in an outdoor pot experiment in subarctic Sweden. The hypothesis tested was that low winter soil temperature could decrease growing-season nutrient uptake capacity and growth rate by injury of the root system; further, the root damage should stimulate growth of replacement roots, which should be reflected by increased summertime biomass allocation to roots. Mountain birch seedlings were exposed to two soil temperatures during wintertime by manipulation of snow depth that accumulated on top of the pots. Minimum soil temperature (hourly recordings) during winter was –1.7°C in the “protected” treatment (deep snow cover) and – 10.5°C in the “exposed” treatment (thin snow cover). The treatments simulated the soil temperature conditions of a local mountain birch forest and heath site, respectively. During June and July, the relative growth rate (RG) and nitrogen accumulation rate (RN) in the exposed treatment were lower compared to the protected treatment. In addition, the seedlings of the exposed treatment allocated a greater proportion of biomass to roots compared to the protected treatment. Thus, leaf growth was reduced in the exposed compared to the protected treatment. We concluded that lower winter temperature in soils can result in stronger root injury that stimulates the growth of replacement roots and reduces nutrient uptake capacity and growth rate during summer. In concert with other possible factors causing root disruption during winter, e.g., frequent freeze-thaw cycles, the mechanism identified here might be important for survival of tree seedlings in subarctic and alpine areas, especially near treelines. The implications are discussed specifically for mountain birch seedling growth and survival in treeless subarctic heath sites and above treelines in northern Europe.

Low Winter Soil Temperature Affects Summertime Nutrient Uptake Capacity and Growth Rate of Mountain Birch Seedlings in the Subarctic, Swedish Lapland

Effects of different winter soil temperature on summertime growth rate of individual seedlings of mountain birch (Betula pubescens ssp. czerepanovii) were evaluated in an outdoor pot experiment in subarctic Sweden. The hypothesis tested was that low winter soil temperature could decrease growing-season nutrient uptake capacity and growth rate by injury of the root system; further, the root damage should stimulate growth of replacement roots, which should be reflected by increased summertime biomass allocation to roots. Mountain birch seedlings were exposed to two soil temperatures during wintertime by manipulation of snow depth that accumulated on top of the pots. Minimum soil temperature (hourly recordings) during winter was –1.7°C in the “protected” treatment (deep snow cover) and – 10.5°C in the “exposed” treatment (thin snow cover). The treatments simulated the soil temperature conditions of a local mountain birch forest and heath site, respectively. During June and July, the relative growth rate (RG) and nitrogen accumulation rate (RN) in the exposed treatment were lower compared to the protected treatment. In addition, the seedlings of the exposed treatment allocated a greater proportion of biomass to roots compared to the protected treatment. Thus, leaf growth was reduced in the exposed compared to the protected treatment. We concluded that lower winter temperature in soils can result in stronger root injury that stimulates the growth of replacement roots and reduces nutrient uptake capacity and growth rate during summer. In concert with other possible factors causing root disruption during winter, e.g., frequent freeze-thaw cycles, the mechanism identified here might be important for survival of tree seedlings in subarctic and alpine areas, especially near treelines. The implications are discussed specifically for mountain birch seedling growth and survival in treeless subarctic heath sites and above treelines in northern Europe.

A linear model for quantitating the accumulation of zeins and their fractions (α+δ, β&γ) in developing endosperm of wild-type and mutant maizes

A model based upon the occurrence of a linear relationship between the amounts of zeins and total proteins present in developing maize endosperm was applied to some data of the literature. Those were concerned with grains of W64A, Illinois high and low protein (IHP and ILP) cultured in vivo and in vitro together with in vivo grown grains of opaque-2 ( o2) and Mucronate ( Mc) mutants, and Mco2 double mutant. The relative rate of zein accumulation, corresponding to the slope of a straight line, was found to be insensitive to environmental factors. It was assessed to 0.217, 0.431, 0.490, 0.598 and 0.799 for Mco2, ILP, o2, W64A and IHP maizes, respectively. The same type of relationship was tested between the amounts of zein fractions (α+δ, β and γ) and total zeins present in developing endosperm of three genotypes. The relative accumulation rate for a given fraction was very close to its proportion determined from mature endosperm irrespective of the genotype. According to the sign of y-intercept γ-zeins were found to be synthesized prior to (α+δ)-zeins, in agreement with the analysis of protein bodies using immuno-localisation; β-zein was synthesized after (α+δ)-zeins, contrary to the findings of immuno-localisation experiments, suggesting two different accumulation rates for this fraction.

Heat-shock responses in two leguminous plants: a comparative study

Relative growth rates, basal and acclimated thermotolerance, membrane damage, fluorescence emission, and relative levels of free and conjugated ubiquitin and HSP70 were compared after 2 h of treatment at different temperatures between Prosopis chilensis and Glycine max (soybean), cv. McCall, to evaluate if the thermotolerance of these two plants was related to levels of accumulation of heat shock proteins. Seedlings of P. chilensis germinated at 25 degrees C and at 35 degrees C and grown at temperatures above germination temperature showed higher relative growth than soybean seedlings treated under the same conditions. The lethal temperature of both species was 50 degrees C after germination at 25 degrees C. However, they were able to grow at 50 degrees C after germination at 35 degrees C. Membrane damage determinations in leaves showed that P. chilensis has an LT(50) 6 degrees C higher than that of soybean. There were no differences in the quantum yield of photosynthesis (F(v)/F(m)), between both plants when the temperatures were raised. P. chilensis showed higher relative levels of free ubiquitin, conjugated ubiquitin and HSP70 than soybean seedlings when the temperatures were raised. Time-course studies of accumulation of these proteins performed at 40 degrees C showed that the relative accumulation rates of ubiquitin, conjugated ubiquitin and HSP70 were higher in P. chilensis than in soybean. In both plants, free ubiquitin decreased during the first 5 min and increased after 30 min of heat shock, conjugated ubiquitin increased after 30 min and HSP70 began to increase dramatically after 20 min of heat shock. From these data it is concluded that P. chilensis is more tolerant to acute heat stress than soybean.

ONTOGENY OF ANNUAL GRASS GRAIN PROTEIN FRACTIONS AND AMINO ACIDS AFFECTED BY NITROGEN SUPPLY

Mechanisms involved in uptake, assimilation, and distribution of nitrogen (N) in plants may reflect the effectiveness of various physiological functions developed under the conditions a species was evolved. The purpose of these studies was to determine the influences of N nutrition on the partitioning of different N forms within the Avena sativa grain during its maturation. Plants were grown in a glasshouse using nutrient solution sand culture with four N treatments: two high-N (5.33 mM), a mid-N (2.67 mM) and a low-N (5.33mM before anthesis and no N after anthesis).One high-N series was labeled with 15N at anthesis to distinguish the N in the grain taken up after anthesis (exogenous N) from that absorbed prior to anthesis and translocated to the grain (endogenous N). Exogenous N accumulated in a sigmoidal pattern for the measured grain protein fractions and total grain- N, reaching 35–40% of the N for these three fractions/classes of N. The grain prolamin-glutelin protein fraction responds more to differences in N provided after anthesis than does the albumin-globulin protein fraction. A measure of constituent deposition in the grain, relative accumulation rate, is represented as RAR = 1/x · dx/dt, where x is the concentration of a fraction and t is time. Albumin-globulin RAR had two increases, while prolamin-globulin RAR had a single longer increase during grain maturation. At individual samplings the distribution of exogenous N between the two protein fractions coincided with their RAR's. For oat grain uptake, exogenous N was the most important source of N in the fastest accumulating protein fraction. When comparing grain of high-N with mid-N, individual amino acid concentrations ranged from an increase of 16.3% to a decrease of 17%. The average glucose requirement for the synthesis of amino acids which increased at high-N was less than that of the amino acids which decreased. The bisynthethic efficiency and production values (reciprocal of construction cost referenced to glucose required by the metabolic product synthesis) were significantly related to the significantly skewed distribution of amino acids in the grain protein. The most bioenergetically efficient amino acids were the most utilized in the grain proteins; energy expenditure regulation is a possible reason.

Growth and physiological characterisation of regenerated potato (Solanum tuberosum) plants affected by NaCI stress

A comparative growth analysis was made between salt‐tolerant plants obtained by recurrent selection methods in vitro and Solanum tuberosum L. ‘Kennebec’ original mother plants (wild type). They were grown at three different salt concentrations (0.5, 25, and 100 mMNaCl) by hy‐droponic culture. Fourteen days after the saline treatment was applied, no differences in growth were observed between clones. However, 14 days later (Day 28), the comparative analysis between clones revealed intra‐especific differences. The salt‐tolerant line (clone 150) exhibited greater tolerance to the highest salt doses. Plants of this clone had greater biomass than wild type (clone T) at all salt concentrations tested. The relative growth rate (RGR) and components, as well as the relative accumulation rate of water (RARwater) and K+ and Na+ content, should explain, at least in part, the salt‐tolerance of clone 150.

Effect of Nitrogen Availability on Oat Grain Growth and Nutrient Deposition

Quantitative analysis of seed growth and nutrient deposition can provide a bridge between grain and whole plant efficiency measures when the seed is treated as part of a whole plant adaptation. Grain relative growth rate (RGR)=1/ w d w /d t , where w is the grain weight and t is time; and grain nutrient relative accumulation rate (RAR)= 1/[ x ] d[ x ]/d t , where [ x ] is a nutrient concentration, were analysed to show oat grain ontogeny. These equations provide rates and duration of nutrient deposition (allocation in relation to growth). Four nitrogen (N) treatments provided a range of grain nutrient allocation to growth. Oat plants ( Avena sativa L. cv. Montezuma) grew in a nutrient solution-irrigated sand culture. Seed number (sink size) was related to grain N-RAR. The P- and Mg-RAR differed from the N-RAR by having proportionally higher initial and final rates, together with lower middle period rates. N harvest index (grain N content/total plant N content) and N utilization efficiency (grain weight/total plant N content) were linearly related to the grain NRAR and also linearly inversely related to the grain RGR. Using grain RGR and RAR with NHI and NUE, it appears possible to optimize mineral utilization for grain nutrient quality maximization relative to yield.

Trace Metals and Radionuclides Reveal Sediment Sources and Accumulation Rates in Jordan Cove, Connecticut

Many small estuaries are influenced by flow restrictions resulting from transportation rights-of-way and other causes. The biogeochemical functioning and history of such systems can be evaluated through study of their sediments. Ten long and six short cores were collected from the length of Jordan Cove, Connecticut, a Long Island Sound subestuary, and analyzed for stratigraphy, radionuclides (14C, 210Pb, 226Ra, 137Cs, and 60Co), and metals (Ag, Cd, Cu, Pb, Zn, Fe, and Al). For at least 3,800 yr, rising sea level has gradually inundated Jordan Cove, filling it with mud similar to that currently being deposited there. Long-term sediment accumulation in the cove averaged close to 0.1 cm yr−1 over the last three millennia. Recent sediment accumulation rates decrease inland from 0.84 cm yr−1 to 0.40 cm yr−1, and are slightly faster than relative sea-level rise at this site (0.3 cm yr−1). Similarity of depth distributions of trace metals was used to confirm relative sediment accumulation rates. 60Co and Ag are derived from sources outside the cove and its watershed, presumably the Millstone nuclear power plant and regional contaminated sediments, respectively. The combined data suggest that Long Island Sound is an important source of sediment to the cove; a minor part of total sediment is supplied from the local watershed. Trace metal levels are strongly correlated with Fe but not with either organic matter or Al. Sediment quality has declined in the cove over the past 60 yr, but only slightly. Cu, Pb, and Zn data correlate strongly with Fe but not with either organic matter or aluminum. Ratios of Ag to Fe and to trace metals suggest that Ag in the cove is derived almost entirely from Long Island Sound. This result supports the notion that Fenormalized Ag can serve as a better tracer of some kinds of contamination than more common and abundant metals, like Cu, Pb, and Zn. *** DIRECT SUPPORT *** A01BY085 00008

Benthic foraminiferal paleoceanography of the South China Sea over the last 40,000 years

Benthic foraminifera in gravity and piston cores from two sites of the northern and southern slopes of the South China Sea (SCS) were analyzed to evaluate changes in surface productivity and deep-water mass characteristics over the last 40,000 years. Our observations suggest that changes in organic carbon flux, that is food supply, and chemical and/or physical properties of the ambient water mass may be the two primary and intercorrelated factors controlling the distribution patterns of benthic foraminifera. When organic carbon flux increased above 3.5 g C m −2 yr −1 in the southern SCS during the last glacial maximum and in the northern SCS during the first part of the Holocene around 10 ka B.P., a group of detritus feeders including Bulimina aculeata and Uvigerina peregrina dominated the benthic foraminiferal assemblage as shown by relative abundance (%) and accumulation rates. This may reflect episodes of increased surface productivity, possibly induced by increased input of nutrients from nearby river runoff. Suspension feeders such as Cibicidoides wuellerstorfi and a group of `opportunistic' species including Oridorsalis umbonatus, Melonis barleeanum and Chilostomella ovoidea gradually became more abundant than detritus feeders as soon as the organic carbon flux decreased to 2.5–3.5 g C m −2 yr −1. Similar glacial to interglacial changes in relative abundance and accumulation rates were observed in both cores for a number of species, including Eggerella bradyi, Globocassidulina subglobosa, Astrononion novozealandicum, Sphaeroidina bulloides and Cibicidoides robertsonianus. These changes were not correlated to the distribution patterns of organic carbon in both cores and may have been related to yet unspecified changes in chemical and/or physical properties of the ambient water mass, independent of changes in organic carbon flux.

Terrigenous sedimentation and coral reef growth: a conceptual framework

The role of terrigenous (and non-framework carbonate) sedimentation has not been prominent in models of coral reef growth and evolution. We derive and discuss a semi-quantitative model which relates coral reef growth to sedimentation. The model is independent of coral biology and is based upon the relative net rates of framework and non-framework sediment accumulation and/or removal. The model might enable some forecasting of long-term responses to changes in sedimentation regime and other environmental factors. The occurrence of turbid-zone reefs is successfully explained in regions of very high turbidity but with little or no net sediment accumulation. Potential future use of the model may include aiding prediction of the effects of other geological and oceanographic factors on the growth or demise of coralline communities.

The simulation of soil organic matter and nitrogen accumulation in Scots pine plantations on bare parent material using the combined forest model EFIMOD

The individual-based combined forest model EFIMOD including the soil-sub model SOMM has been used for the simulation of Scots pine stand growth and soil organic matter (SOM) accumulation on a humus-free bare mineral surface. The growth of Scots pine plantation, with an initial density of 10 000 trees ha 1 and average tree biomass of 0.01 kg was simulated for 50 yr under Central European climatic conditions (i) with varying atmospheric nitrogen inputs and (ii) different rates of initial application of raw undecomposed organic material or compost, on humusfree parent material. The accumulation of typical raw humus was simulated in all cases. The accumulation was most intensive in the simulation of high atmospheric nitrogen input. The humus pool in the mineral topsoil was small but achieved its maximum value with compost application. SOM nitrogen accumulation was scant in all cases, except the compost applications with low atmospheric nitrogen input. No statistically significant differences of SOM and stand parameters were found between variants without organic matter and those with low input of organic manure. However, the maximum relative rate of SOM and nitrogen accumulation was found in the scenario without organic manure, under slowly growing unstable Scots pine plantation.

Leaf Mass Partitioning as a Determinant of Dry Matter Accumulation in Zantedeschia

Dry matter accumulation and partitioning in plants of Zantedeschia Spreng. `Best Gold' aff. Z. pentlandii (Wats.) Wittm. (syn. Richardia pentlandii Wats.) were quantified under a range of temperature and photosynthetic photon flux (PPF) regimes using plant growth analysis. The relative rate of dry matter accumulation [relative growth rate (RGRM), g·g-1·d-1] was highly correlated with the partitioning of the daily increment of dry matter into leaf tissue [leaf matter partitioning (LMP), g·d-1 per g·d-1]. In contrast, a poor correlation existed between RGRM and net assimilation rate (NAR, g·m-2·d-1). Maximum values of RGRM increased linearly with increasing temperature (from 13 to 28 °C), with a base temperature of 2.1 ± 2.7 °C. The optimum temperature for growth was PPF dependent with maximum total plant dry mass occurring under high PPF (694 μmol·m-2·s-1) at 25 °C. However, as the plant responded to PPF by altering LMP, final total plant dry mass was actually greater under the low PPF regime (348 μmol·m-2·s-1) at temperatures <22 °C. The optimum temperature for dry matter accumulation was close to the average daily air temperature during the growing season for the natural habitat of the parent species. Similarly, the greater dry matter accumulation under the combination of either low PPF and cooler temperatures or high PPF and warmer temperatures was paralleled by the diversity of PPF habitats in the natural open grassland and forest margin the parent species occupies. It is therefore suggested that Zantedeschia `Best Gold' is well adapted to optimize growth under these environmental conditions.

New species of the genus <i>Parkiella</i> (Foraminifera) from the Late Cretaceous Central Pacific Ocean: biostratigraphy, biogeography, and the Cretaceous–Palaeogene boundary

Abstract. Two new species, Parkiella angulocamerata sp. nov. and P. globocamerata sp. nov., are described from the Late Cretaceous (late Maastrichtian) Central Pacific Ocean, DSDP Sites 465 and 171. Examination under the SEM revealed apertural features that were not documented in the original description of Parkiella. An ‘L’-shaped aperture was originally considered as a diagnostic character of Parkiella; we suggest that this is a preservational artefact and question its diagnostic value. The existence of internal toothplates determine both Parkiella described here as members of the family Turrilinidae Cushman 1927. Both species were found to be endemic to the tropical Pacific Ocean. They occurred in sequence throughout the Maastrichtian section at Site 465 with a minimum (one sample) stratigraphic overlap. Parkiella globocamerata is one of the few deep-sea benthic foraminiferal species that indeed became extinct at the Cretaceous/Palaeogene (K/Pg) boundary. However, we document a decrease in both relative abundance and accumulation rate of the species already prior to the K/Pg transition. We propose that the interval between the LO (Last Occurrence) of P. angulocamerata and the LO of P. globocamerata is indicative of uppermost Cretaceous (Micula prinsii Zone) strata in the tropical Pacific.

Growth of foxtail pine seedlings at treeline in the southeastern Sierra Nevada, California, U.S.A.

I examined elevational trends in growth and nutrient use of foxtail pine (Pinus balfouriana) seedlings in the south-eastern Sierra Nevada, U.S.A., in areas where seedlings have established above the current treeline. I measured growth, foliar nitrogen concentration, and nitrogen relative accumulation rates of seedlings at three elevations: (i) forest interior sites (3435 m), (ii) treeline (3460 m), and (iii) above treeline (3485 m). As elevation increased, the basal area of adult trees and density of seedlings declined, nutrient inputs from aboveground litter declined, and litter C:N ratio declined. Annual height growth of seedlings increased significantly with elevation in 7 of 8 years measured (1985-1992). There was no significant change in annual lateral twig growth with elevation. There was a positive trend in relative growth rates and nitrogen relative accumulation rates with elevation. Variance among years in height and twig growth was higher at and above treeline than in forested sites. Significant correlations between annual growth and climate were few and inconsistent among variables and elevations. The concentration of nitrogen in needles declined with needle age, but neither nitrogen concentration nor nitrogen relative accumulation rate in seedlings differed significantly among elevations. Based on patterns of seedling growth, I conclude that, relative to forest interior sites, conditions above the treeline were favorable for seedling growth during the last 12 years.

Impact of balsam fir flowering on pollen and foliage biochemistry in relation to spruce budworm growth, development and food utilization

AbstractThe impact of balsam fir (Abies balsamea (L.) Miller) flowering on nutritional and allelochemical quality of pollen, current‐year and one‐year‐old foliage is studied in relation to spruce budworm (Choristoneura fumiferana Clem.) (Lepidoptera: Tortricidae) growth, development and utilization of food and nitrogen. In the laboratory, using fresh food from the field, we simulated conditions of low larval population density, in which there is no current‐year foliage depletion during the spruce budworm feeding period. Similarly, we simulated conditions of high larval population density when current‐year foliage depletion occurs.Because of the high nutritive value of pollen (high amounts of amino acids and minerals, especially nitrogen; low monoterpene content), insects from flowering trees reached the fifth instar five days earlier than those from non‐flowering trees, and had heavier dry‐ and nitrogen‐weights at the beginning of the fifth instar. At budbreak, switching from pollen to current‐year foliage negatively affected conversion efficiencies and digestibilities of food and nitrogen (AD; ADN; ECDN; ECI; ECIN). The switch from pollen to new foliage had a detrimental impact on fifth‐instar survival and on newly‐moulted sixth‐instar dry‐ and nitrogen‐weights. Moreover, during the fifth instar, balsam fir flowering reduced the nutritive value of current‐year foliage, which in turn, might have contributed to the reduced larval growth. Nevertheless, during the sixth instar, balsam fir flowering affected the biochemistry of current‐year foliage in ways that enabled larvae to compensate for their low fifth‐instar biological performance; larvae also managed to reach pupal dry weight similar to larvae reared on non‐flowering trees. Current‐year foliage from flowering trees contained less nitrogen, total soluble sugars and total monoterpenes. Those foliar characteristics enabled larvae to increase food and nitrogen consumption rates (RCR; RNCR), because of lower repellency and/or post‐ingestional feedback from monoterpenes.As for current‐year foliage, balsam fir flowering reduced nitrogen, total soluble sugar and total monoterpene contents in one‐year‐old foliage during the sixth‐instar feeding period. These characteristics enabled sixth‐instar larvae, fed on old foliage from flowering trees, to have high relative food and nitrogen consumption rates (RCR; RNCR). Larvae were also able to reach higher relative growth rates (RGR) and relative nitrogen accumulation rates (RNAR) compared to larvae reared on one‐year‐old foliage from non‐flowering trees. Finally, larvae on flowering trees had pupal dry weight similar to those from non‐flowering trees, but reached the adult stage nine days earlier.Regardless the foliage type consumed by spruce budworm larvae during the sixth instar, pollen consumption during early larval stages reduced total development time, and thus exposure time to natural enemies. This phenomenon might increase larval survival. Balsam fir flowering changed the biochemistry of one‐year‐old and current‐year foliages, but did not affect pupal dry weights of larvae reared on flowering trees compared to those reared on non‐flowering trees. Thus, at low population density, spruce budworm populations in balsam fir flowering stands might be favoured over those in balsam fir non‐flowering stands. In addition, when larvae consumed one‐year‐old foliage during the entire sixth instar, those on flowering trees are probably favoured over those on non‐flowering trees. However, because flowering trees produce less new foliage than non‐flowering trees, current‐year foliage depletion may occur earlier on flowering trees than on non‐flowering trees. Thus, at similar larval population density, larvae on flowering trees might have to feed on one‐year‐old foliage earlier than those on non‐flowering trees. In that case, spruce budworm populations on non‐flowering stands would be favoured over those on flowering stands.