Oxygen consumption of pelagic juveniles and demersal adults of the deep-sea fish Sebastolobus altivelis,measured at depth

Oxygen consumption rates of the deep-sea fish Sebastolobus altivelis were measured in situ on pelagic juveniles at mesopelagic depths (608 m) and on demersal adults at bathyal depths (1 300 m) in the Santa Catalina Basin in March 1982. Two pelagic juveniles were individually collected, and respiration was measured continuously for approximately 2 d with a slurp gun respirometer manipulated from the submersible “Alvin”. Oxygen consumption rates of these juveniles were highly variable and were 1.5 to 1.8 times higher during the night than during the day. Gut contents of the juveniles were mainly euphausiids (Euphausia pacifica and Nematoscelis difficilis). Four demersal adults were collected by “Alvin” and individually placed in fish-trap respirometers on the bottom where respiration was measured continuously for approximately 1 d. Weight-specific O₂ consumption rates for adults decreased with increasing body weight and were consistent in magnitude throughout the incubation period. Population O₂ consumption for demersal S. altivelis (calculated from abundance, size-frequency distribution, and O₂ consumption regression equation) was 11.01 μl O₂ m^-2 h^-1, which is two orders of magnitude less than the O₂ consumption rate for the population of the most abundant epibenthic megafaunal species in the Santa Catalina Basin, the ophiuroid Ophiophthalmus normani. O. normani is a principal prey for adults of S. altivelis based on gutcontent analysis. Given the population O₂ consumption rate as an estimate of food energy demand, the demersal population of S. altivelis would assimilate only 0.007% of the standing crop of O. normani per day.     

Oxygen consumption of midwater fishes and crustaceans from the eastern Gulf of Mexico

Oxygen consumption was measured as a function of temperature, oxygen partial-pressure (P_O2)and species depth of occurrence for twenty-three species of midwater fishes and crustaceans collected from the eastern Gulf of Mexico from June 1981 to July 1985. Q₁₀s (7° to 20°C) of 3.90 and 3.24 were recorded for myctophid and non-myctophid fish groups, respectively, while values of 2.22, 2.19, 2.19 and 2.54 were calculated for sergestid, penaeid, carid and euphausiid crustacean groups, respectively. Q₁₀s were consistent for species within each group. All of the species tested regulated their oxygen consumption to P_O2levels normally encountered within the eastern Gulf. Values of critical partial pressure (P_c) ranged from 20 to 40mm Hg and increased slightly with increasing temperature and respiration rate. Declining respiration with increasing minimum depth of occurrence was primarily a function of temperature alone. Changes in size, dry weight and water content contributed only a small fraction to the observed decrease. This finding contrasts with studies from the eastern Pacific Ocean, where temperature is a minor contributor to changes in respiration rate with depth.     

Parameter estimation for distributed delay based population models from laboratory data: egg hatching of Oulema duftschmidi Redthenbacher (Coleoptera,Chrysomelidae) as an example

The cohort development of poikilotherms under favorable temperature conditions may be described by the time-invariant distributed delay models that require three parameters, i.e. the thermal threshold T₀, the thermal constant W and the variability parameter H representing distributed maturation times, also known as time distributed or stochastic development. Here, a parsimonious method is developed that uses stage-frequency matrices obtained under controlled conditions. The analysis of these matrices permits the estimation of the three parameters, while the incorporation of both developmental threshold and thermal constant into the time-invariant distributed delay model permits the representation of stochastic cohort development under constant temperatures. The evaluated parameters can also be used in time-varying distributed delay models that are particularly useful for a wide range of fluctuating temperature conditions.We consider stage-frequency matrices obtained from cohorts of eggs and larvae of Oulema duftschmidi Redthenbacher at different constant temperatures. A visual inspection of the matrices clearly shows the temperature dependent as well as the time distributed passage from the egg to the larval stage. Under the current range of temperatures, a linear model for developmental rate satisfactorily describes egg development, and estimates the thermal threshold (T₀=11.2 °C), the thermal constant (W=81.3 day-degrees) and the delay order parameter (H=70). The resulting model can be used to represent the development of cohorts of O. duftschmidi eggs in a favorable temperature range.     

Modeling and coupling of soil respiration and soil water content in fenced Leymus chinensis steppe,Inner Mongolia

Soil respiration was measured with the enclosed chamber method during 2 years in fenced Leymus chinensis steppe, Inner Mongolia, China. Soil water content at 0–10 cm depth was a major limited factor of soil respiration in semi-arid grassland, accounting for 76.4% of the variation. The temperature-dependent exponential function could only explain 38.7% of the variation in soil respiration. With 246 data over the entire experimental period, multiple linear stepwise regressions of soil respiration rate were analyzed with the influencing factors, including soil water content at 0–10 cm depth, air temperature, air pressure, air humidity, total radiation and their interactions. With soil water content at 0–10 cm depth (W) and air temperature (T_h) as combined factors, the twice linear regression (F = 1.68WT_h − 109.09) was simple and its coefficients were significant, accounting for 83.1% of the variation in soil respiration. Due to the lack of long-term and continuous soil water content, a water sub-model based on precipitation and evapotranspiration was introduced, which could provide better fits with the measured values (R² = 0.813). The magnitudes of soil respiration calculated from the twice linear regression equation and water sub-model were 439.58 and 463.06 g CO₂ m⁻² in 2001 (19 June–23 September) and in 2002 (1 June–24 September), respectively. The mean hourly soil respiration rates were in the range of the previous studies in the adjacent region and the world's major temperate grasslands.     

Influence des conditions hivernales sur les productions phyto- et zooplanctoniques en Méditerranée Nord-Occidentale. IV. Distribution verticale des taux d'adénosine triphosphate et de production primaire

This paper describes a method which utilizes ¹⁴C-labelled glucose for measuring the assimilation and mineralization of dissolved organic compounds in the sea. Incubation is carried out in 500 ml conic flasks, in darkness, at a temperature similar to that of the in-situ sampling levels. Direct trapping of CO₂ respired is performed in a scintillation vial, with an efficiency of 92% over a period of 4 h. The hyamin, utilized to trap the CO₂, excites the scintillating liquid in the presence of CO₂; the respiration data must then be corrected by a factor of 0.62. When HA Millipore filters are used for filtration, they quench assimilation values and the results must be corrected by a factor of 1.06. The reproducibility of the described method is good. Some parameters have been calculated: total heterotrophic activity, assimilation rate, respiration rate, bacterian yield, and the turn-over time of substrate in the water.     

Untersuchungen über die temperaturabhängigkeit des sauerstoffverbrauchs von Crepidula fornicata (Mollusca: Prosobranchia)

The oxygen consumption of the sessile gastropod Crepidula fornicata was measured during autumn 1962 as a function of soft body wet weight (0.04 to 5.2 g) and temperature (2° to 30° C). From the data obtained, the parameters of the allometric formula were derived for describing the relationship between respiration and body size. The parameters were then used for calculating the oxygen consumption of 3 different weight groups (0.1 g, 1.0 g, 10.0 g) at different temperatures. The resulting plot reveals different curves, demonstrating that the influence of temperature on the metabolism of C. fornicata is a function of body size. The ourves relating oxygen consumption to temperature may well be described by a modified Arrhenius-function proposed some years ago (Krüger, 1962). Biological temperature curves may be described by growth functions. Therefore, it is possible to apply the simple Walfordplot for identifying the “normal curves” of Krogh (1914).     

Metabolic adaptation of Cancer irroratus developmental stages to cyclic temperatures

Metabolic-temperature responses of the developmental stages of the sublittoral crab Cancer irroratus cultured at 10° to 20°C daily cyclic and 15°C constant temperatures were determined. Generally, the metabolic rate increased with temperature in the lower range with Q₁₀'s (temperature coefficients) above 2, compensated in the midrange with Q₁₀'s between 1 and 2, and declined at the higher temperatures with Q₁₀ values less than 1. For the larvae cultured at a constant temperature of 15°C, the compensatory response range narrowed with development from first zoeae to the later zoeal stages. In contrast, the compensatory response of the first zoeae, megalops, and crab stages within the range 10° to 25°C was interrupted by a zone of thermal sensitivity between 15° and 20°C for those individuals cultured in the 10° to 20°C cyclic regime. The compensatory response range is narrower for the third stage zoeae and broader for the second, fourth, and fifth stage zoeae. Metabolic rate-temperature (M-T) patterns of C. irroratus developmental stages cultured under the cyclic regime varied from those held at constant temperature by increased respiration and metabolic rate compensation between 20° and 25°C, and by an extension of the metabolically active range towards higher temperatures.     

Respiratory metabolism of crabs from marine and estuarine habitats: an interspecific comparison

The gill-surface area and R-T (metabolic rate-temperature) response during aquatic and aerial respiration of three different species of crabs, the subtidal Scylla serrata, the intertidal Sesarma quadratum, and the supratidal Ocypoda platytarsis, were compared. Scylla serrata has the highest, Sesarma quadratum the second highest, and O.platytarsis the lowest gill-surface area. Oxygen-consumption values in water under different ambient partial pressures of oxygen indicate that all three species display equally efficient aquatic respiration despite variation in gill area and number. There is no coherent R-T response either inter- or intra-specifically. However, the ability to extract oxygen from the surrounding medium (respiratory efficiency) conditions the R-T response in the different species. The R-T trends in aquatic respiration of Scylla serrata and aerial respiration of O.platytarsis reveal a normal response to temperature. The proportion of aquaticoxygen uptake to total respiration in all sizes in both Scylla serrata and Sesarma quadratum remains more or less constant (between 88 and 92%), whereas in the supratidal O.platytarsis, this proportion decreases with increasing weight (from 88 to 64 %), indicating a progressive loss of gill respiration to total respiration. All three species are metabolically equally efficient; what one lacks in respiratory surface it compensates by respiratory efficiency.     

The ecological energies of growth,respiration and assimilation in the intertidal American oyster Crassostrea virginica

Seasonal variations in the growth, respiration and assimilation of the intertidal oyster Crassostrea virginica (Gmelin) of different sizes were determined. The instantaneous growth rates for intertidal oysters decreased with increasing size and with lower temperatures. Q₁₀ values computed from instantaneous growth rates were approximately 2 during the warm growing season, but were higher in the colder months. Oxygen consumption increased with temperature and body size. A model was developed to predict oxygen consumption at any environmental temperature from 10° to 30°C for oysters ranging in weight from 0.1 to 100.0 g. Q₁₀ values computed from oxygen-consumption rates decreased with increasing temperature and increasing body size. Intertidal oysters utilize a large proportion of their assimilated energy in growth.Supported by a Belle W. Baruch Fellowship in Marine Ecology.     

The influence of fresh weight and water temperature on metabolic rates and the energy budget of Meretrix meretrix Linnaeus

Meretrix meretrix L. was held in the laboratory under simulated natural conditions to measure specific physiological parameters of its energy budget. O₂ consumption rate, NH₃ excretion rate (NR), ingestion rate, faeces excretion rate and scope for growth (SFG) were negatively related in an exponential manner to the fresh weight of the clams at all water temperatures, while almost all metabolic rates of the clams were positively related in an exponential or e-exponential manner with water temperature. However, the co-relationship between metabolic rates and water temperature was not as close as that between metabolic rates and fresh weight of the clam. The combined effect of fresh weight and water temperature was observed on all metabolic rates except for NR and SFG. At all culture temperatures and for all fresh weights of clams used, respiration took the largest percentage of ingested energy (41.5–51.2%), faeces excretion was second (31.0–42.3%), growth third (12.1–15.5%) and urine production last (2.1–5.6%).     

Laboratory evaluation of kinetic parameters for lake sediment denitrification models

Laboratory experiments using the acetylene blockage technique showed that denitrification rates in sediments from Lake Okeechobee, Florida, are described by Michaelis-Menten nitrate dependence and Arrhenius temperature dependence (E_act = 15.5 kcal, but do not appear to be affected by seasonal differences in the supply of carbon substrates in this eutrophic lake. Peak nitrate concentrations in the sediments are in the range of the half-saturation constant, and thus, for a given temperature, k_d varies by a factor of approximately two over the typical range of nitrate concentrations. Most diagenetic sediment denitrification models employ a single-valued rate constant k_d, to describe nitrate dependence. However, the use of a constant k_d for eutrophic lake sediments may result in a significantly erroneous estimate of annual denitrification loss.     

Sensitivity of benthic community respiration and primary production to changes in temperature and light

In-situ measurements of benthic community respiration and primary production on an intertidal sandflat in Nova Scotia, Canada were used to test the hypothesis that community responses to light and temperature were similar within and between seasons. Multiple regression indicated that mean incubation temperature explained 57% of the variance in total sediment oxygen demand (TOD). The logarithmic relationship between TOD and temperature (Q₁₀=6.5) was not significantly different between fall and spring, suggesting no acclimation within season. Chemical oxygen demand measured in formalin-poisoned cores averaged 30% of TOD. Microalgal gross primary production (GROSS) was measured as oxygen production in light cores. Mean incubation temperature and sediment chlorophylla explained 56% of the variance. The linear relationship between GROSS and temperature had Q₁₀=2.0. When production was normalized to chlorophylla [GROSS(SP)], seasonal production-temperature curves were significantly different. The spring curve had Q₁₀=3.3; in the fall, production and temperature were not related. GROSS(SP)-light curves derived from Plexiglas shade experiments in the field were linear and not significantly different between fall and spring. Temperature alone was a better predictor of GROSS(SP) than light, even when P/I curves were adjusted for temperature. One can therefore model community respiration and photosynthesis at this site using daily averages in temperature, which are then summed over longer time scales to estimate monthly or seasonal rates.     

Animal community structure and energy budget calculations of a Daphnia magna (straus) population in relation to the rock pool environment

The fauna and environmental conditions in a freshwater rock pool ecosystem were followed by a weekly quantitative sampling program from April to August, 1974. The rock pool, situated on a small island in the northern Baltic Sea, was heavily eutrophicated by droppings from the surrounding colony of sea birds. The intermittent flushing of the pool with rainwater and the input of bird droppings, as well as the biological activity, contributed to the large seasonal variations in nutrients and organic matter that were observed. A dense algal bloom of flagellates occurred in April but vanished when the animal population started to increase in the middle of May. During the rest of the summer, most of the photosynthetic pigments were found in the bottom sediment, mostly as degraded phaeo-pigments due to intensive grazing by the animals in the pool. Very few animal taxa were found and the phyllopod Daphnia magna (Straus) dominated throughout the whole sampling period. D. magna contributed to more than 50% of the total biomass, except in late July when chironomid larvae were most abundant. The total biomass in the pool increased from about 15 mg (dry weight) l^?1 in May to a maximum of about 60 mg l^?1 at the end of June. There were few carnivores in the system, except during the spring when the water bug Deronectes griseostriatus (de Geer) was common.Analyses of size, age and sex structure and calculations of birth and death rates of the D. magna population showed large seasonal variations, correlated with the volume fluctuations and flushings of the pool which stimulated both the algal production and the growth and reproduction of Daphnia. Data from the extensive literature that exists on D. magna and other species of the same genus were used, together with field and experimental data from the rock pool population, in a numerical model describing the energy budget of this species. The model describes variations in weight-specific growth, reproduction, moulting, feeding and respiration rates in relation to temperatures and food concentrations. Energy budget relationships that maximise the chances for survival and utilisation of the available energy for a population exposed to varying food concentrations are predicted by the model. The energy budget model was also used to estimate the secondary production of the rock pool population of D. magna. The total production between April and August was 203 mg (dry weight) l^?1 and the average production per biomass ratio was 0.094 day^?1. The average net production efficiency was 42%, very close to other values reported for D. magna from other biotopes. The relative importance of different factors controlling the production was also analysed with the model. Production per biomass ratio was calculated, assuming a constant temperature and/or food concentration for the whole sampling period. The varying food concentrations in the rock pool had the most pronounced influence, greater than that of temperature and size structure variations in the population.     

Modeling effects of toxin exposure in fish on long-term population size, with an application to selenium toxicity in bluegill (Lepomis macrochirus)

A primary goal in ecotoxicology is the prediction of population-level effects of contaminant exposure based on individual-level response. Assessment of toxicity at the population level has predominately focused on the population growth rate (PGR), but the PGR may not be a relevant toxicological endpoint for populations at equilibrium. Equilibrium population size may be a more meaningful endpoint than the PGR because a population with smaller equilibrium size is more susceptible to the negative effects of environmental variability. We address the individual-to-population extrapolation problem with modeling utilizing classical mathematical theory. We developed and analyzed a general model applicable to many freshwater fish species, that includes density-dependent juvenile survival and additional juvenile mortality due to toxicity exposure, and we quantified effect on equilibrium population size as a means of assessing toxicity. Individual-level effects are typically greater than population-level effects until the individual effect is large, due to compensatory density-dependent relationships. These effects are sensitive to the recruitment potential of a population, in particular the low-density first-year survival rate S_b. Assuming high S_b could result in underestimating effects of population-level toxicity. The equilibrium size depends directly on S_b, the reproductive potential, the toxin concentration at which mean mortality is 50% (LC₅₀), and the rate at which individual mortality increases with increasing toxin concentration. More experimental data are needed to decrease the uncertainty in estimating these parameters. We then used existing data for selenium toxicity in bluegill sunfish to parameterize a simulation version of the model as an example to assess the effects of environmental stochasticity on toxicity response. Effects of environmental variability resulted in simulated extinctions at much lower toxin concentrations than predicted deterministically.     

Carbon-dioxide production and metabolic parameters in the ophiurid Ophiothrix fragilis

As part of the evaluation of fluxes between the water column and a rich benthic community of the Dover Strait (Eastern English Channel), laboratory measurements of oxygen consumption were carried out on a common ophiurid, Ophiothrix fragilis (Abildgaard), from February 1993 to February 1995. The mean O₂-consumption rate was evaluated at 0.31 mg O₂ g⁻¹ h⁻¹ (ash-free dry weight). Simultaneous measurements of O₂ consumption and CO₂ production using the pH-alkalinity method revealed an average respiratory quotient of 0.69 proved suitable for converting oxygen demand to carbon flux. A seasonal trend in respiration data was demonstrated by sinusoidal curves fitted to O₂-uptake and CO₂-release data as a function of time. The influence on respiration rate of two seasonal parameters (temperature and food availability) is discussed; linear regression indicated a highly significant relationship between O₂ consumption (or CO₂ production) and temperature; both O₂-consumption and CO₂-production rates decreased with starvation. The average O:N ratio was estimated at 8.46, close to the theoretical value when proteins constitute the catabolic substrate. The annual carbon respired by the O. fragilis community examined and the estimated annual primary production by phytoplankton indicate that the respiration of the O. fragilis community could supply 35% of phytoplankton carbon requirements. Received: 1 August 1996 / Accepted: 4 September 1996     

Die Bedeutung in Meerwasser gelöster Glucose für die Ernährung von Anemonia sulcata (Coelenterata: Anthozoa)

Anemonia sulcata Pennant absorbs and accumulates tritiated D-glucose dissolved in sea water in natural concentrations (80 μg/l). The rate of decrease of glucose concentration in the sea water can best be described by an exponential function, when the concentration of added glucose exceeds 20 to 25 μg/l. The glucose, absorbed through the ectoderm, is immediately metabolized. This is determinable experimentally by tritiated water which is emitted into the sea water. The rate of uptake estimated experimentally was in the range 3 to 4 μg glucose/g wet weight/h, whilst the rate calculated by V _max (maximum absorption rate) was 20 μg/g wet weight/h. The concentration of free glucose in the tentacle tissue is greater by a factor of 10⁵ than that of the medium in which absorption takes place. Absorption is temperature-dependent; the Q₁₀ between 15° and 25°C exceeds 2; translocation is, therefore, energy-dependent. Absorption was diminished by inhibitors, especially by phlorizin. The actinians increase their energy reserves by absorption of glucose (and other dissolved organic substances). The energetic net profit by taking up glucose comprises up to 50% of the energy amount which is equivalent to the oxygen consumption.     

Etude de la respiration chez des copépodes de niveaux bathymétriques variés dans la région sud marocaine et canarienne

The results of 281 respiration analyses of pelagic copepods sampled in the South Moroccan and Canarian area are described. The copepods used in experimentation were collected from various bathymetric levels: hyponeustonic species (Anomalocera patersoni, Pontellopsis villosa, P. regalis, Labidocera wollastoni, Pontella lo biancoi), epipelagic species (Centropages typicus, Temora stylifera, Calanus helgolandicus, Acartia clausi), meso and bathypelagic species (Pleuromma xiphias, P. abdominalis, Euchaeta acuta, Undeuchaeta plumosa and some other rare species). Analysis of the metabolismtemperature curve makes it possible to describe different modes of adaptation in relation to geographical distribution, altitudinal repartition, and dietary characteristics. When all species are studied together, a strong correlation exists between the log of respiration and the log of weight. The regression coefficient varies with temperature; it is strongest at a temperature near that of the natural thermic conditions.     

Brooded coral larvae differ in their response to high temperature and elevated pCO2 depending on the day of release

To evaluate the effects of temperature and pCO₂ on coral larvae, brooded larvae of Pocillopora damicornis from Nanwan Bay, Taiwan (21°56.179′N, 120°44.85′E), were exposed to ambient (419–470 μatm) and high (604–742 μatm) pCO₂ at ~25 and ~29 °C in two experiments conducted in March 2010 and March 2012. Larvae were sampled from four consecutive lunar days (LD) synchronized with spawning following the new moon, incubated in treatments for 24 h, and measured for respiration, maximum photochemical efficiency of PSII (F _v/F _m), and mortality. The most striking outcome was a strong effect of time (i.e., LD) on larvae performance: respiration was affected by an LD × temperature interaction in 2010 and 2012, as well as an LD × pCO₂ × temperature interaction in 2012; F _v/F _m was affected by LD in 2010 (but not 2012); and mortality was affected by an LD × pCO₂ interaction in 2010, and an LD × temperature interaction in 2012. There were no main effects of pCO₂ in 2010, but in 2012, high pCO₂ depressed metabolic rate and reduced mortality. Therefore, differences in larval performance depended on day of release and resulted in varying susceptibility to future predicted environmental conditions. These results underscore the importance of considering larval brood variation across days when designing experiments. Subtle differences in experimental outcomes between years suggest that transgenerational plasticity in combination with unique histories of exposure to physical conditions can modulate the response of brooded coral larvae to climate change and ocean acidification.     

Community metabolism of intertidal flats in the Ems-Dollard estuary

To obtain an insight into the flux of carbon through intertidal sediments of the Ems-Dollard estuary, the annual cycles of gross benthic primary production and community respiration were measured at six stations, together with a set of environmental parameters. In a stepwise multiple regression analysis it was shown that temperature alone and temperature plus viable bacteria explained 50 and 70% respectively of the observed variation in community respiration. Other variables, including the rate of primary production and amount of organic carbon in the sediment were less important. The rate of primary production could not be fitted adequately into a multiple regression equation. The annual values of community respiration (177–794 gO₂·m^-2·yr^-1) and primary production (82–628 gO₂·m^-2·yr^-1) were within the range of published values. except for one station in the vicinity of a wastewater outfall, which had an extreme production (average 984 gO₂·m^-2·yr^-1). At four stations, annual community respiration exceeded primary production by 40%. It is concluded that the main carbon flux within the sediment, from CO₂ to benthic primary producers, to benthic consumers and from there to CO₂ again,was completed within a month or so, leaving untouched the large bulk of organic matter within the sediment. Possible effects of wastewater discharges on community metabolism are discussed.Publication No. 43 of the project Biological Research in the Ems-Dollard Estuary     

Water budget and the consequent duration of canopy carbon gain in a teak plantation in a dry tropical region: Analysis using a soil–plant–air continuum multilayer model

A soil–plant–air continuum multilayer model was used to numerically simulate canopy net assimilation (A_n), evapotranspiration (ET), and soil moisture in a deciduous teak plantation in a dry tropical climate of northern Thailand to examine the influence of soil drought on A_n. The timings of leaf flush and the end of the canopy duration period (CDP) were also investigated from the perspective of the temporal positive carbon gain. Two numerical experiments with different seasonal patterns of leaf area index (LAI) were carried out using above-canopy hydrometeorological data as input data. The first experiment involved seasonally varying LAI estimated based on time-series of radiative transmittance through the canopy, and the second experiment applied an annually constant LAI. The first simulation captured the measured seasonal changes in soil surface moisture; the simulated transpiration agreed with seasonal changes in heat pulse velocity, corresponding to the water use of individual trees, and the simulated A_n became slightly negative. However, in the second simulation, A_n became negative in the dry season because the decline in stomatal conductance due to severe soil drought limited the assimilation, and the simultaneous increase in leaf temperature increased dark respiration. Thus, these experiments revealed that the leaflessness in the dry season is reasonable for carbon gain and emphasized the unfavorable soil water status for carbon gain in the dry season. Examining the duration of positive A_n (DPA) in the second simulation showed that the start of the longest DPA (LDPA) in a year approached the timing of leaf flush in the teak plantation after the spring equinox. On the other hand, the end appeared earlier than that of all CDPs. This result is consistent with the sap flow stopping earlier than the complete leaf fall, implying that the carbon assimilation period ends before the completion of defoliation. The model sensitivity analysis in the second simulation suggests that a smaller LAI and slower maximum rate of carboxylation likely extend the LDPA because soil water from the surface to rooting depth is maintained longer at levels adequate for carbon gain by decreased canopy transpiration. The experiments also suggest that lower soil hydraulic conductivity and deeper rooting depth can postpone the end of the LDPA by increasing soil water retention and the soil water capacity, respectively.