Akira Osawa

Allometric Theory Explains Self‐Thinning Relationships of Mountain Beech and Red Pine

Allometric theory on mechanisms of the self—thinning rule was tested for Nothofagus solandri populations from the Craigieburn Range, New Zealand and for Pinus densiflora stands from northern Japan. The self—thinning rule describes a consistent relationship of mean plant mass to the approximately —3/2 power of plant density in evenaged monocultures. Although his rule has been described for various species, mechanisms that produce certain relationships have not been well understood. We tested an allometric theory of Long and Smith of the self—thinning rule that assumes constant foliage mass density and allometry for mean dimensions of populations that represent dense conditions for given mean plant sizes. Only stands at maximum crowding were selected for analysis. The self—thinning boundary of N. solandri showed an exponent —1.13 with a 95% ci of —1.25 to —1.02 for mean stem mass. This was significantly shallower than the conventional value of the exponent —3/2, but was identical to the predicted exponent from the allometric theory. The thinning coefficient was also explained numerically by this hypothesis. In contrast, analysis of published data for P. densiflora indicated that the thinning exponent did not differ from the proposed —3/2. Empirical thinning lines varied substantially depending on species and plant parts considered; however, the allometric theory consistently provided predictions that agreed with the observed thinning relationships. Implications for the geometry of self—thinning populations and generality of the allometric theory are discussed.

The Self‐Thinning Rule: Another Interpretation of Weller's Results

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Root system development of Larix gmelinii trees affected by micro-scale conditions of permafrost soils in central Siberia

Spatial distributions of root systems of Larix gmelinii (Rupr.) Rupr. trees were examined in two stands in central Siberia: an even-aged stand (ca. 100 yrs-old) and a mature, uneven-aged (240–280 yrs-old) stand. Five larch trees of different sizes were sampled by excavating coarse roots (diameter > 5 mm) in each stand. Dimensions and ages of all first-order lateral roots were measured. Micro-scale conditions of soil temperature and soil water suction (each 10 cm deep) were also examined in relation to earth hummock topography (mound vs. trough) and/or ground floor vegetation types (moss vs. lichens). All larch trees developed superficial root systems, consisting of the aborted short tap root (10–40 cm in soil depth) and some well-spread lateral roots (n = 4 – 13). The root network of each tree was asymmetric, and its rooting area reached about four times the crown projection area. Lateral roots generally expanded into the upper soil layers of the mounds where summer soil temperature was 1–6 °C higher than inside nearby troughs. Chronological analysis indicated that lateral root expansion started successively from lower to upper parts of each aborted tap root, and some lateral roots occurred simultaneously at several decades after tree establishment. The process of root system development was likely to be primarily linked with post-fire dynamics of rhizosphere environment of the permafrost soils.

Individual-based measurement and analysis of root system development: Case studies for Larix gmelinii trees growing on the permafrost region in Siberia

We present results of individual-based root system measurement and analysis applied for Larix gmelinii trees growing on the continuous permafrost region of central Siberia. The data of root excavation taken from the three stands were used for the analyses; young (26 years old), mature (105 years old), and uneven-aged over-mature stand (220 years old). In this article, we highlight two topics: (1) factors affecting spatio-temporal pattern of root system development, and (2) interactions between aboveground (i.e., crown) and belowground (i.e., root) competition. For the first topic, the detailed observation of lateral roots was applied to one sample tree of the overmature stand. The tree constructed a superficial (<30 cm in depth) and rather asymmetric root system, and each lateral root expanded mainly into elevated mounds rather than depressed troughs. This indicated that spatial development of an individual root system was largely affected by microtopography (i.e., earth hummocks). For these lateral roots, elongation growth curves were reconstructed using annual-ring data, and annual growth rates and patterns were compared among them. The comparison suggested that temporal root system development is associated with differences in carbon allocation among the lateral roots. For the second topic, we examined relationships between individual crown projection area (CA) and horizontal rooting area (RA) for the sample trees of each stand. RA was almost equal to CA in the young stand, while RA was much larger (three or four times) than CA in the mature and overmature stands. Two measures of stand-level space occupation, crown area index (aboveground: CAI; sum of CAs per unit land area) and rooting area index (belowground: RAI; sum of RAs), were estimated in each stand. The estimates of RAI (1.3–1.8 m2 m−2) exceeded unity in all stands. In contrast, CAI exceeded unity (1.3 m2 m−2) only in the young stand, and was much smaller (<0.3 m2 m−2) in the two older stands. These between-stand differences in RAI–CAI relationships suggest that intertree competition for both aboveground and belowground spaces occurred in the young stand, but only belowground competition still occurred in the two older stands. Based on this finding, we hypothesized that competition below the ground may become predominant as a stand ages in L. gmelinii forests. Methodological limitations of our analysis are also discussed, especially for the analysis using the two indices of space occupation (CAI, RAI).

A profile theory of tree growth

Abstract We present a profile theory of tree growth that describes the relationship between stem growth of an entire tree and stem mass density at crown base. Several other variables, e.g. height growth, total foliage mass, and length of clear bole, are included in the equation. The theory also predicts leaf efficiency from those variables. This is an improved version of another idea that proposed that the stem mass density at crown base is equivalent to the stem growth of an entire tree. The previous argument was based on a new interpretation of the profile diagram for production structure of plant populations and individuals. The profile theory is built on three assumptions: (1) vertical distribution pattern of foliage mass does not change, except that it moves upward over time; (2) stem-wood increment at a certain location along a stem is proportional to the foliage mass above that point (the proportionality constant being μ); and (3) annual height growth is constant. The present theory and the previous one were tested comparatively using the production data from individual trees of six species: Cryptomeria japonica, Chamaecyparis obtusa, Quercus mongolica, Betula platyphylla, Abies sachalinensis and Larix kaempferi. Judging from the linear regression analysis of calculated versus observed value relationships, including examination of such statistics as the mean square error (MSE) and the coefficient of determination (R2), the profile theory yielded improved predictions of the stem growth and leaf efficiency in all cases but one; stem growth of B. platyphylla was the exception. The original theory failed to produce reasonable predictions especially in A. sachalinensis and L. kaempferi. The theory was then generalized by relaxing the second and the third assumptions. It was assumed that the proportionality constant, μ, and the height growth had shifted to new values during the most recent years. This was to account for the sudden reduction in radial increment that was noted in some samples of B. platyphylla and A. sachalinensis. The fit of the model to the data from these two species was greatly improved by the more generalized theory. Overall, predictions from the profile theory (including its generalized form) were not different from the observed values at the 5% significance level. The calculated values of stem growth and leaf efficiency agreed with the observation reasonably well.

Spatial leaf distribution and self-thinning exponent of Pinus banksiana and Populus tremuloides

A hypothesis that the pattern of spatial leaf distribution in forest canopies is numerically related to the exponent of the self-thinning relationship in even-aged monocultures was tested by evaluating the crown fractal dimension of Pinus banksiana (jack pine) and Populus tremuloides (quaking aspen) in Wood Buffalo National Park, Canada. Pure species stands that were considered the most dense for a given mean tree size were measured to establish the empirical self-thinning relationships. The value of the self-thinning exponent was estimated as –1.42 with 95% Confidence Interval (CI) (−1.47, −1.36) for Pinus banksiana, and –1.29 with 95% CI (−1.45, −1.14) for Populus tremuloides. For each species the box dimension of spatial leaf distribution was estimated from unit cylinders described by sequentially lowering in forest canopies, horizontal “flaps” of one of various diameters attached to the top of a height-measuring pole. The box dimension appeared as 1.95 (1.84, 2.06) for Pinus banksiana, and 2.24 (2.05, 2.43) for Populus tremuloides. By assuming that the box dimension is equivalent to the fractal dimension at the inter-population level, the self-thinning exponent was predicted to be –1.53 (−1.62, −1.45) for Pinus banksiana, and –1.33 (−1.45, −1.23) for Populus tremuloides. The empirical exponent was equivalent to that predicted from the box fractal dimension, as judged by the 95% CI of the dimensions. We conclude that spatial patterns of leaf distribution in forest canopies, as being characterized by the box fractal dimension, are closely related to the value of the self-thinning exponent in the dense monocultures of the species we examined.

A light-weight CCD camera technique for estimating three-dimensional distribution of foliage density in tree crowns

A method was developed for non-destructively estimating spatial density of foliage mass and area in crowns of small individual trees. A light-weight CCD camera with a capability for wireless image ...

Testing a method for reconstructing structural development of even-aged Abies sachalinensis stands

Accuracy of a stand reconstruction technique was examined by comparing the estimated values of the aboveground biomass, total stem volume, stem volume growth, and stand density of Abies sachalinensis stands to those observed between 1980 and 1998 in Hokkaido, northern Japan. Census data from two stands established in 1973, one fertilized and the other unfertilized, were used for the examination. The stand statistics in the past were estimated from the DBH and height of individual trees measured in 1998, data on the aboveground biomass and stem volume with bark for nine living trees of various sizes harvested in each plot in 1998 or in 1999, and data from the stem analysis of the same harvested trees. We showed that the reconstructed patterns of the frequency distribution in aboveground biomass and in stem volume were generally the same as those observed in both plots and in any year in the past (except for 1982 and/or 1980), and that the reproduced patterns of stand development over time were similar to those observed directly in the past. Accuracy in predicting stand statistics was generally in the order of ±10% relative error. We consider that the present method of stand reconstruction could be used to estimate aboveground biomass, total stem volume, and stem volume growth of a stand in the past. Interpretation of results for the early years (1982 and 1980) and for the stand density requires caution.

Comparative reproductive phenology of subtropical mangrove communities at Manko Wetland, Okinawa Island, Japan

ABSTRACT We aimed to investigate and compare the reproductive phenology of Bruguiera gymnorrhiza, Kandelia obovata, and Rhizophora stylosa in subtropical area, over 5 years. The three mangrove species of the Rhizophorace family yielded reproductive organs throughout the entire annual cycle, with the exception of K. obovata. In case of B. gymnorrhiza, flowers were observed throughout the year, with a massive production in September, whereas propagule production was highest in July. Reproductive organs of K. obovata followed a very specific monthly periodicity. The highest production of flowers, fruits were observed in July, and massive production of propagule was observed in September for R. stylosa. The highest number of flowers was recorded in R. stylosa followed by K. obovata and B. gymnorrhiza. However, propagule setting was lowest in R. stylosa as compared to other two species. The largest propagule was also observed in R. stylosa. This was significantly different from that of other two species. Multiple regression analysis showed that reproductive organs of the three species were pronouncedly influenced by monthly mean air temperature and day length. Mean production of reproductive organs in B. gymnorrhiza, K. obovata, and R. stylosa contributed 37.5%, 18.7%, and 21.5% to the total litterfall, respectively.