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This report describes a novel, comprehensive approach to identifying a fragment peak of monoclonal antibody-A (mAb-A), detected by sodium dodecyl sulfate-capillary gel electrophoresis (SDS-cGE). The fragment migrated close to the internal standard (10 kDa marker) of SDS-cGE and increased about 0.5% under a 25 °C condition for 6 months. Generally, identification of fragments observed in SDS-cGE is challenging to carry out due to the difficulty of collecting analytical amounts of fractionations from the capillary. In this study, in-gel digestion peptide mapping and reversed phase liquid chromatography-mass spectrometry (RPLC–MS) were employed to elucidate the structure of the fragment. In addition, a Gelfree 8100 fractionation system was newly introduced to collect the fragment and the fraction was applied to the structural analysis of a mAb for the first time. These three analytical methods showed comparable results, proving that the fragment was a fraction of heavy chain HC1-104. The fragment contained complementarity determining regions (CDRs), which are significant to antigen binding, and thus would affect the efficacy of mAb-A. In addition, SDS-cGE without the 10 kDa marker was demonstrated to clarify the increased amount of the fragment, and the experiment revealed that the fragment increases 0.2% per year in storage at 5 °C. The combination of the three analytical methodologies successfully identified the impurity peak detected by SDS-cGE, providing information critical to assuring the quality and stability of the biotherapeutics.

A well-organized molecularly imprinted polymer (MIP) provides the amazing selective molecular recognition ability, which have been close to natural enzymes and antibodies. One of the most efficient applications of MIPs is a selective separation and detection of pharmaceutical compounds in biological and/or environmental samples. MIP-based solid phase extraction now capacitates the selective concentration of the targeting compound from real samples. Also, many of the attractive methodological approaches and applications regarding the analysis of pharmaceutical samples using molecular imprinting technologies (MITs) have been reported in recent years. In this review, we summarize a part of the recent these works related to a new preparation concept of the adsorption adsorbents, sensitive sensor techniques, cell/bacteria separation, and drug delivery system. We believe that our concise summary will be of assistance to additional methodological MITs and highly selective separations/detections.

For highly sensitive determination of trace-level compounds in environmental, biological, and food samples, a selective separation and concentration are usually required with a removal of contaminants before quantitative detection by spectroscopic detection techniques, such as mass spectrometry. In the last few decades, molecularly imprinted adsorbents have widely contributed to the separation and concentration in liquid-phase separations. In this study, the latest preparation procedures, such as the use of surface modifications, inorganic substrates, and monolithic materials, in the molecular imprinting techniques are summarized. Recent achievements of practical quantitative determination in a variety of fields by new methodological protocols with molecular imprinting are also reported.

We report a thermo-responsive molecularly imprinted polymer (MIP) for methotrexate, an anticancer drug. The bulk MIPs were prepared with divinylbenzene as a crosslinker, a variety of functional monomers, and folic acid as a pseudo-template molecule. As a result of simple batch adsorption for methotrexate or folic acid using the MIPs, the selectivity depended on the functional monomers because the functional groups of methotrexate or folic acid were slightly different in each other. After optimization of the preparation conditions, only acidic functional monomers including methacrylic acid (MAA) and sodium p -styrenesulfonate (SS) contributed to the selective adsorption for methotrexate. Furthermore, only the MAA-based MIP provided the thermal responsibility for the binding/release of methotrexate by the suppression of hydrogen bonding at higher temperature, whereas a strong ionic interaction was contributed among broad temperature range in the SS-based MIP. Adsorption isotherms also well supported the differences of the molecular recognition based on the binding constants at low and higher temperatures. Finally, we successfully demonstrated the drug-releasing ability by simple temperature changing with the MAA-based MIP.

In traditional capillary electrophoresis (CE) with fluorescence detection, the difference of the migration time of analytes leads to the inequivalent photobleaching, therefore the quantitative determination of the analytes is usually difficult. Especially, when an internal standard (IS) is used, the fluorescent intensities of analytes are hardly comparable to that of the IS if the inequivalent photobleaching is not restricted. We propose a practical approach to reduce the effect of inequivalent photobleaching via an online fluorescence imaging system coupled with the IS method. The detection was operated by the acquisitions of the fluorescent intensities from the divided small section array in the detection window and the electropherograms were obtained from the integrated each acquisition. Compared with the traditional CE detection method, the proposed method demonstrates a real-time detection to collect the fluorescence signals of different analytes under the definite exposure time, rather than the same traversing length. Experimental demonstration for the proposed method was carried out by using DNA-dye conjugations. As a result, our method provided a lower relative error of the peak area ratio of 0.3–3.2 % and a more practical operation because the efforts to restrict the photobleaching are exempted. Revealed in this paper also includes the fact that the photobleaching process manipulated the determination of the peak width and separation resolution.

In the present study, nitromethylene neonicotinoid derivatives possessing substituents that contain a sulfur atom, oxygen atom or aromatic ring at position 5 on the imidazolidine ring were synthesized to evaluate their affinity for the nicotinic acetylcholine receptor (nAChR) and their insecticidal activity against adult female houseflies. Comparing the receptor affinity of the alkylated derivative with the receptor affinity of compounds possessing either ether or thioether groups revealed that conversion of the carbon atom to a sulfur atom did not influence the receptor affinity, whereas conversion to an oxygen atom was disadvantageous for the receptor affinity. The receptor affinity of compounds possessing a benzyl or phenyl group was lower than that of the unsubstituted compound. Analysis of the three-dimensional quantitative structure-activity relationship using comparative molecular field analysis demonstrated that steric hindrance of the receptor should exist around the C3 of an n-butyl group attached at position 5 on the imidazolidine ring. A docking study of the nAChR-ligand model suggested that the ligand-binding region expands as the length of the substituent increases by brushing against the amino acids that form the binding region. The insecticidal activity of the compounds was positively correlated with the receptor affinity by considering logP and the number of heteroatoms, including sulfur and oxygen atoms, in the substituents, suggesting that the insecticidal activity is influenced by the receptor affinity, hydrophobicity, and metabolic stability of the compounds.

Polystyrene (PS) films, upon deep UV exposure, readily formed nanostructures when soaking in a solvent. In this study, we provide compelling evidence confirming the critical roles of oxidation and solvent for the nanostructure formation. When the irradiation was carried out in argon, no structure could be generated on the films. Solvent is another critical parameter. Ordered concentric circular structures formed when the UV-irradiated PS films were soaked in an aromatic solvent such as toluene, benzene, and xylene. Addition of n-heptane to toluene reduced the size of the circles. The concentric circular structures disappeared when 0.1% methanol was added to the soaking solvent toluene. X-ray photoelectron spectroscopy (XPS) showed that the percentage of O-containing products decreased with increasing amount of added methanol, indicating that the polar solvent prevented the structure formation by removing the oxidation products from the films.

To achieve selective adsorption of gaseous compounds, we synthesized the molecularly imprinted polymers (MIPs). In this study, we utilized two different types of MIPs, the first one was examination of the effect by the porogen imprinting, and another was authentic molecular imprinting by template and a functional monomer. The results of BET evaluation of MIPs showed that the specific surface area were depended on octanol–water partition coefficient (log Pow) between cross-linker and porogenic solvents, also became larger as log Pow of porogen being closer to that of cross-linker. Furthermore, the adsorption performance per unit weight of MIPs was observed under single gas adsorption by using MIPs prepared with target compound as porogenic solvents. As results, each MIP which was prepared with chloroform or toluene showed selective adsorption for each vapor in point of the adsorbed amount. Thus, MIPs tended to have selective adsorption ability for the used porogen in preparation. Additionally, the Gas-MIPs prepared with a functional monomer and template molecule adsorbed target compound in selectively as increase the amount of functional monomer and template molecule. Consequently, the authentic molecular imprinting method could be worked for the effective adsorption of gaseous compounds as well as the general procedures in solution.

We have prepared several types of polymers derived from 2-methacryloyloxyethyl phosphorylcholine (MPC) to evaluate whether polymers of MPC work as cell membrane mimic or not. We firstly applied capturing test of target proteins of 4-carboxybenzenesulfonamide (Sul) or ibuprofen (Ibu) as a probe. As the results, the rather hydrophilic polymers based on MPC were able to suppress non-specific binding proteins as expected. Additionally, some of the MPC based polymeric surface was able to capture greater amount of carbonic anhydrase II than those of other polymers, when Sul was utilized as probe. In contrary, all the polymers having PC groups and Ibu probe were unable to capture Cyclooxygenase-1 (COX-1), its target protein. These results suggested that the position of PC groups realized hydrophilic polymer surface, while MPC based polymer was not able to supply the suitable environment for COX-1 to interact with Ibu.

We have developed hybrid photocatalysts by introducing molecular recognition sites to the surface of titanium dioxide (TiO2) nanoparticles. The synthesized hybrid photocatalysts indicated the selective recognition ability for target molecules based on specific molecular recognition sites constructed by the interval immobilization technique, and also the photostability of the recognition sites was confirmed by long time UV irradiation in an aqueous solution. Furthermore, the hybrid photocatalysts showed selective degradation performance to saxitoxins which are one of the famous neurotoxins. All basic and application results suggested that the newly developed methods for preparation of nano sized hybrid-TiO2 can be worked for selective adsorption and photodegradation of targeting compounds.

The diameter growth of trees may vary depending on the tree size, species and other tree-related factors. However, such variation is challenging to consider while estimating the growth response to weather conditions. This study investigated the effects of the weather conditions and variations in tree factors on diameter growth in a mature forest. In particular, we focused on diameter growth in June, the month of active diameter growth. We recorded the monthly diameter growth of 6 tree species for 7 years and constructed a generalized linear mixed model in which the mean growth was dependant on tree size, weather conditions, and the interaction between tree size and weather. The estimated growth responses to weather factors were different among species, but their interaction to tree size was unclear in all species. Sensitivity analysis of growth rate to weather conditions, such as temperature and precipitation, showed that the sensitivity to weather depended both on tree size and tree species.

We achieved preparation of co-continuous titania based monolithic materials using several organic polymer monoliths as pore templates. Firstly, the organic polymer monoliths that had well controlled structures were prepared, and filled the pores of polymer monolith with tetra-n-butyl titanate (titan monomer). The following hydrolysis of the titan monomer resulted in titanium dioxide. The polymer monolith was removed by calcination at elevated temperature. We carefully studied the utility of polymer monolithic template, filling method of the titan monomer, and calcination conditions to realize co-continuous titania monolith. In addition, by the change of domain size (size of a skeleton + size of through a pore) of template, we were able to control domain size of the resulting titania monoliths.

Sponge-like material was utilized as novel chromatographic media for high throughput analyses. The pore size of the sponge-like material was several dozen micrometer, and was named spongy monolith because it consists of continuous structured copolymers, which was made of poly(ethylene-co-vinyl acetate), such as monolithic materials including silica monoliths and organic polymer monoliths. The spongy monolith was packed into a stainless steel column (100 mm x 4.6 mm I.D.) and evaluated in liquid chromatography (LC) with an on-line column-switching LC concentration system. The results indicate that the packed column could be used with high flow rates and low back pressure (9.0 mL/min at 0.5 MPa). Furthermore, bisphenol A was quantitatively recovered by on-line column-switching LC concentration with the spongy monolithic column. Additionally, the adsorption capacity and physical strength of the media was enhanced via chemical modification of spongy monoliths using glycerol dimethacrylate. The results compared with original spongy monolith demonstrated that a higher adsorption capacity was achieved on a shorter column, and a stable low back pressure was obtained at high throughput elution even with a longer column.

In order to more accurately evaluate the functional activity of forest stands by canopy production and evapotranspiration, we improved the methods for field measurements and statistical modeling to estimate foliage configuration (spatial distribution of leaves) while simultaneously reconstructing the three-dimensional photosynthetically active photon flux density (PPFD) distribution (PPFD pattern) in a forest canopy. By using a sensor (photodiode) array, a PPFD pattern was observed in summer 2002 under the canopy in an even-aged, pure stand of Japanese mountain birch Betula ermanii Cham. (17-year-old) in Hokkaido, northern Japan. A Markov Chain Monte Carlo (MCMC) sampling technique is developed such that a set of foliage configurations generated by the model referred to as the Gibbs foliage canopy (GFC) approximates the field-measured PPFD pattern. The posterior distribution of the foliage configurations is generated by the parallel tempering MCMC of eight independent series of foliage configurations. The GFC model generated the posterior distribution of the LAI estimates (mean 4.56) that appeared to be appropriate in comparison to other LAI estimates of the B. ermanii stand based on the indirect and nondestructive methods by LAI-2000 (LAI = 3.43) and litterfall traps (LAI = 5.56) because they could be under- and overestimated, respectively. Our evaluations of the canopy production and evapotranspiration rates suggest that the relationship between LAI and canopy functions was not very simple because it depended on the nonlinear functional forms of the leaf responses of photosynthesis and transpiration to PPFD. The current study demonstrates an application of MCMC techniques that can generate a set of possible structures of unobserved/unobservable objects based on the high resolution data set obtained by some indirect (or remote-sensing) methods.

Colorless, transparent SnO–P 2 O 5 (SP) glasses with 60–70 mol% SnO compositions were prepared by melting at 880–1000 °C in Ar atmosphere using commercial SnO and P 2 O 5 powders as raw materials and vitreous carbon crucibles. SP glasses are characterized by glass transition temperature, onset of crystallization, thermal expansion coefficient and weight loss after immersion test. The viscosity of 67SnO–33P 2 O 5 glass was measured by a penetration method in the range of 10 7.9 –10 10.5 Pa s at 267–290 °C. The results of optical properties show that the transparent SP glasses have high refractive indexes over 1.75 and high transmission over 80% in the visible and IR region of 380 and 2700 nm.

The present study aimed to evaluate the short-term biomass accumulation of forest trees exposed to wet acidic depositions. A hierarchical Bayesian model of tree growth was developed based on the data of a short-term experiment in which 2-year-old Japanese red pine (Pinus densiflora Sieb. et Zucc.) seedlings were exposed to aqueous phase OH radicals generated by an iron-oxalate-H2O2 mist (a pseudo-polluted dew) over two growing periods. We conducted a statistical comparison of tree growth between the control and pollution treatment groups by using the growth model incorporated the random effects due to the unknown characteristics of each seedling. The variability among seedlings is expressed in this model by the posterior probabilistic distributions of unobserved dry weight of a stem cohort before exposure treatment. The analysis of the effects of pollution treatment on the stem growth revealed that this treatment decreases the biomass allocation in the current year stems. However, the effects on the relative growth rate of pre-existing stems were unclear. Based on these results, we can speculate that in a polluted environment, the short-term growth of the young stems in the seedlings inhibited by pollution treatment, thereby resulting in the slowdown of long-term biomass accumulation. This can explain the patterns observed in the declining Japanese red pine forests that are subjected to OH-generating dews in the polluted area of western Japan.

Cylindrospermopsin (CYN) was determined by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard. In the selected ion monitoring of LC/ESI-MS, m / z 414 for CYN and 237 for HEPES were monitored using the negative mode; the retention times of CYN and HEPES were 12.41 and 14.21 min, respectively. CYN was determined from peak area ratios of m / z 414/237. By the treatment of an anion exchange cartridge using a buffer at pH 10.5, CYN was isolated and condensed. No interfering peak was observed. Linearity of this method was observed at the range of 0.10–31.12 ng. Total coefficients of variation were 5.1 and 2.9% at 104 and 1038 μg CYN L −1 . The quantitative limit at a signal-to-noise (S/N) ratio of 10 was 0.16 ng. CYN concentration in natural waters is low. CYN in waters should be condensed for determination. This method including the treatment for isolation and condensation of CYN is useful for determination of CYN in environmental and/or drinking waters.

We prepared molecularly imprinted polymers for an amnesic shellfish poison, domoic acid. To prepare the polymer, we tested several commercial aromatic dicarboxylic compounds such as isomers of phthalic acid for templates of molecularly imprinted polymers. The highest selective recognition ability of the polymer for domoic acid in the tested compounds was found when o-phthalic acid was used as the template. The ability was due to the acidity of the carboxylic acids in the domoic acid and the similarity of the shape around the carboxylic acids of domoic acid and the templates. The effective chromatographic separation of domoic acid in the extract from blue mussels was achieved with a LC column packed with the fragment imprinted polymer using o-phthalic acid as the template. This polymer can be utilized for a clean up procedure of domoic acid in toxic shellfish.

To achieve the selective separation of brominated aromatic compounds, the polymer-based separation media were prepared by the fragment imprinting technique and were evaluated with high-performance liquid chromatography. In the results, the separation medium prepared with 2,6-bis-(trifluoromethyl)-benzoic acid as the template showed the selective retention abilities for 3,5- and/or 3′,5′-brominated or chlorinated bisphenol A homologues. The selective retention seems due to the shape recognition according to the alternative template molecule. Especially, the tetrabromo- or tetrachloro-bisphenol A homologues were selectively recognized by the imprinting effect.

A new simply and effective fractionation method for cylindrospermopsin (CYN) analyses was developed. The extract from cells of Cylindrospermopsis raciborskii was resuspended with 0.1 M carbonate buffer at pH 10.5, and pass through the double-cartridges column which was consisted of a styrene polymer cartridge and an anion exchange cartridge. CYN and deoxy-CYN were adsorbed with the anion exchange cartridge. After separation of the anion exchange cartridge, adsorbed compounds were eluted from the cartridge with 50% methanol containing 1% formic acid solution. CYN and deoxy-CYN were selectively condensed in the eluted solution. When CYN was analyzed by LC-photodiode array or LC/MS, only two peaks of CYN and deoxy-CYN were detected quantitatively. The results suggest that the fractionation method is a useful method for CYN analyses and must be utilized for CYN purification.

We studied an applicability of a silica monolithic membrane as separation medium for high-performance liquid chromatography (HPLC). We prepared porous monolithic silica membranes having a three-dimensional network structure to cut and shape into a membrane separation medium. We evaluated chromatographic properties of a variety of solutes using a column containing the membranes with HPLC to elucidate summable property of the membrane separation media. In addition, we made brief study on separation of HbA1c in whole blood with the “stacked” membranes having different surface characteristics in one column, which is a membrane column. We confirmed that the membrane column was able to separate HbA1c from other matrix in whole blood to some extent, and it also had an excellent ability for hydrophobic and ion exchange adsorption.

Uniformly sized polymeric separation media were prepared using o- or p-xylene as porogenic template to investigate chromatographic selectivity towards tetra-chlorinated dibenzo-p-dioxins (TCDDs). TCDDs having chlorine atoms at ortho positions of phenyl rings were selectively retained on stationary phase prepared with o-xylene as porogenic template, while TCDDs having chlorine atoms at para positions of phenyl ring were found to be retained selectively on the stationary phase imprinted by the porogenic template, p-xylene. Slightly longer cross-linking agent afforded chromatographically selective retention for larger TCDD isomers. It was also found that positional relationship between substituted chlorine atoms was also important for chromatographic recognition.

A pair of polymeric selectors potentially responding to stimulation was introduced onto monosized porous polymer particles to be evaluated as a packing material for HPLC. Possible complexes formed between polyacrylamide (PAAm) and poly(methacrylic acid) (PMAA) were utilized as stimulus responsive polymeric selectors. Uniformly sized base polymer particle was prepared by multi-step swelling and polymerization method, while the introduction of PAAm and PMAA was done by newly invented modification technique. In this technique, a solvent in which both acrylamide (AAm) and methacrylic acid (MAA) monomers are soluble, but PAAm and PMAA are insoluble, was utilized as a modification medium. The polymer particle doubly modified with PAAm and PMAA was utilized as packing material for HPLC and the stimulus responses were evaluated by changing temperature or pH to check change of the slope of a Van’t Hoff plot. By using water as a mobile phase, the expected inflection point of the Van’t Hoff plot was observed at upper critical solution temperature (UCST) of the polymer complexes and the temperature responsive ability was observed. Moreover, pH responsive ability was studied by using buffer of either pH 4 or 10 as mobile phase. Slope of the plot was changed in buffer of pH 4, but no change of slope was observed in the buffer of pH 10.

A polymer-based adsorption medium having molecular recognition ability for homologues of chlorinated bisphenol A produced in environment was prepared using a fragment imprinting technique. 2,6-Dimethyl phenol was utilized as a pseudo-template molecule and the adsorption media prepared was evaluated by high performance liquid chromatography (HPLC) and solid-phase extraction (SPE). As results, the adsorption medium showed preferable chromatographic retention and specific adsorption ability for the chlorinated bisphenol As having chlorine substituents at 3,5-positions through fragment imprinting effect.

Novel stimulus responsive, uniformly sized polymer-based adsorbent was prepared for a possible purification method of DNAs from humic matters in soil extracts. The prepared polymer adsorbent has a pair of anion exchangeable and cation exchangeable polymeric selectors, which are reversibly responded by the changes of column temperature as well as pH of mobile phase. At pH 5, DNAs and humic matters were completely adsorbed on the polymer adsorbent at room temperature, while up to 90% of the adsorbed DNAs were released and recovered at 70 degrees C with no release of adsorbed humic matters. Cleaning up of the polymer adsorbent could be performed by washing the adsorbed humic matters with alkaline mobile phase (pH 9) to recover those and realize repeatable use of the adsorbent.

In subalpine forests dominated by Abies species in Japan and northeastern United States, trees show traveling wave of regeneration with many striped zones of tree dieback, moving downwind at a constant rate. Previous theoretical studies have demonstrated that a very simple model can generate wave-like spatio-temporal patterns of tree regeneration in a lattice-structured habitat with each site occupied by a cohort of trees. A cohort taller than the average height of its windward neighbor experiences stand-level dieback in the next time step and the height becomes zero. Otherwise the cohort increases its height at a constant rate. Starting from a random initial pattern, this simple deterministic model can generate a saw-toothed pattern that moves downwind at a constant rate, but the distance between adjacent dieback zones has a large variance. In this paper, we study the effects of "noises" in tree dieback rules in two forms which help to generate more regular patterns: (1) additional random disturbances at a low rate, which change the size of "clusters" (defined as a group of cohorts between adjacent dieback zones) by splitting a large cluster into two or by merging a small one with a neighbor, and (2) the stochastic rule of tree dieback, represented by the probability of dieback in unit time being a sigmoidal function of the difference in the tree height between the site and the windward neighbors. These noises are effective both for one-dimensional and two-dimensional models, but spatial patterns are much more regular in the two-dimensional model than in the one-dimensional model. Copyright 1998 Academic Press

The beech Fagus crenata forest on Mt. Jippo in southwestern Japan has been reduced to small fragments by past human activity. The forest floor is covered by dense dwarf-bamboo, Sasa, which is an inhibitor of beech regeneration. One of the ecological features of Sasa is that it withers synchronously over a large area once every several decades. An individual based model (IBM) was developed to evaluate the sustainability of such a fragmented beech stand considering the dynamics of Sasa. The model has three submodels for beech individuals: growth, mortality and seed production. The parameters of these submodels are estimated from field measurements. By using this model together with Sasa dynamics, we can evaluate the adverse effect of Sasa on enhancing the risk of extinction of a single fragmented beech stand over 500 years. The results obtained by Monte Carlo simulations are: (1) Sasa has a strong impact on the sustainability of a isolated beech stand; (2) the effects of two parameters for Sasa life history, the longevity and the recovery time, can be statistically separated from each other; and (3) the probability of extinction of a beech stand depends much more strongly on the parameters of beech mortality than those of growth rate.

A recent study on a biennial plant demonstrated that pyrrolizidine alkaloids decrease with the age of leaves due to reallocation from old leaves to new leaves. Here we study the optimal age-specific pattern of defense chemical concentration in leaves that achieves the maximum growth rate of the plant. We consider a plant growing exponentially in a constant environment. Assumptions are the following: (1) The loss of leaves due to herbivory decreases with defense chemical concentration (2) The daily net photosynthesis of a leaf decreases with its age. (3) Using photosynthetic products, the plant produces new leaves that may contain defense chemicals. (4) Although there is a cost to producing new defense chemicals, such chemicals can be reallocated without cost. In the optimal schedule calculated using Pontryagin's maximum principle, the chemical defense level decreases with leaf age. The optimal level of chemical defense increases with the cost of leaf production and herbivory intensity but decreases with the cost of defense chemical production, effectiveness of the defense chemical, net productivity, and growth rate of the plant. If both generalist and specialist herbivores attack the same plant, the optimal defense level is dependent only on the generalists' abundance and sensitivity, but is independent of the specialists that are unaffected by the defense chemical.

Recent studies on forest dynamics in diverse forested ecosystems suggest that forest stands are disturbed more frequently if they are next to existing gaps, and that gaps once formed tend to expand their area in subsequent years. We examine total gap area and the size distribution of gaps at equilibrium in a lattice-structured forest model. Each site undergoes transition between two states (gaps and non-gaps), and the disturbance rate (transition from non-gap to gap) increases with the number of gap sites in the neighborhood. Dynamics based on a mean-field approximation (i.e. neglecting of spatial structure) failed to predict total gap area and the gap size distribution in the equilibrium forest. Pair approximation, which considers a closed dynamical system of average and local gap density (the conditional gap density among neighbors of a randomly chosen gap site), can predict the total gap area, the correlation between neighbors, and the gap size distribution fairly accurately. If the recruitment rate increases in proportion to non-gap area in the forest, the model may show bistability. We analyse data on forest spatial dynamics in the light of the model. We conclude that gap size distribution can often be described using two statistics (global and local gap densities) and that these in turn can be predicted by the dynamics of gap formation, gap expansion, regeneration, and gap closure.

A phenological segregation model of forest tree dynamics is studied, which has previously proposed to explain the observed gradient of species diversity along the length of an unfavorable season (e.g., winter or dry months). The assumptions are: the coexistyence of many species in a tropical rain forest is based on lottery competition. With gap formation occurring throughout the year, a season unfavorable for growth causes a peak regeneration opportunity in the beginning of the growing season. The synchronization of the regeneration opportunity jeopardizes the coexistence of many similar species. The model has the globally stable equilibrium, where the curve of regeneration opportunity is best matches by a weighted average of regeneration ability (or niche) curves calculated using the species composition. If the candidate species have the same niche width and different peak dates, the remaining community includes several distinct groups of species with a similar peak regeneration date. If the candidate species differ also in niche width, the equilibrium community includes broad niche species with the peak in the middle of the growing season and narrow niche species with the peak either in the beginning or in the end of the growing season.

Many mathematical or computer simulation models for forest gap dynamics assume an ensemble of independent patches. However, global or regional scaled fluctuation of weather would result in gap formation partially synchronized over distant patches. In addition, forest fire, land slide, and pest outbreak produce a spatially clumped disturbance. In this paper we study a simple mathematical model for forest gap dynamics in which gap formation in different patches tends to be synchronized. We trace the distribution of “age” of patches defined as the time since the latest disturbance by assuming that the age controls the biomass, productivity, species composition, etc., in the patch. Years of unfavorable climate come at random times, and in each of these years, a fraction of patches are disturbed. Then the states of distant patches that never interact with each other may become strongly correlated. If the biomass in a patch is a function of time since the latest disturbance, the degree of fluctuation in the total biomass in the forest may be much larger if gaps are formed more synchronously. Maximum likelihood estimate of the parameters from the age distribution of patches is given. We also analyzed the case in which disturbance events occur at a constant rate, and where each event resets all the patches within a circle centered at a randomly chosen location. This would produce a between-patch correlation that decreases with the distance.