A model for the relationship between form-factors for stem volume and those for stem surface area in coniferous species

A model that describes the relationship between the form-factors for stem volume and those for stem surface area in coniferous species is proposed. The model is derived assuming that the stem form of a tree can be expressed by Kunze's equation. The model indicated that the form-factor for stem surface area was directly proportional to the square root of the form-factor for stem surface volume, independent of the stem position. The proposed model expressed the relationship of the form-factors for Japanese cedar (Cryptomeria japonica D. Don) and Japanese cypress (Chamaecyparis obtusa Endl.) trees well. Therefore, the form-factors for stem surface area could be estimated from those for stem volume. No significant difference in the coefficient was found between Japanese cedar and Japanese cypress trees, indicating that the proportional coefficient would be common between the two species. Many studies have shown that the form-factors for stem volume at 0.7 and 0.5 in relative height were, respectively, almost steady at 0.7 and 1.0, independent of species, district, density control, and growth stage. Substituting these universal values into the proposed model, the form-factors for stem surface area at 0.7 and 0.5 in relative height were estimated to be 0.730 and 0.873, respectively. The estimated values of the form-factors for stem surface area would be universal for coniferous species. The proposed model also showed that the breast height form-factor for stem surface area decreased sharply with the increase in total tree height, when the height was less than 10 m. However, after the tree attained the total height of 10 m, the breast height form-factor gradually decreased with the total tree height approaching its asymptotic value of 0.605. In conclusion, the model proposed here can be used to describe the relationship between form-factors for stem volume and those for stem surface area successfully.     

Relationships of culm surface area to other culm dimensions for bamboo, Phyllostachys pubescens

We determine the relationships of culm surface area to other culm dimensions for one of the largest bamboo species, Phyllostachys pubescens Mazel ex Houzeau de Lehaie. A total number of 150 sample culms were collected from a stand of P. pubescens in Mt. Toshima, Kumamoto Prefecture, western Japan. The culm surface area for each sample was calculated, and then the relationships of the culm surface area to basal area and product of diameter at breast height (dbh) and culm height were analyzed. The relationship between culm surface area and basal area could be described successfully by the power equation, whereas there was a linear relationship of culm surface area to product of dbh and height. Although the regression equations determined here would be useful in estimating culm surface area of P. pubescens, it is necessary to select an appropriate equation depending on the purpose and available time and labor.     

Aboveground biomass equations for individual trees of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>, <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> and <Emphasis Type="Italic">Larix kaempferi</Emphasis> in Japan

Generic equations are proposed for stem, branch and foliage biomass of individual trees in even-aged pure stands of Cryptomeria japonica, Chamaecyparis obtusa and Larix kaempferi. Biomass data was collected from a total of 1,016 individual trees from 247 stands throughout Japan, and five regression models were assessed by root mean square error, mean bias, fit index (FI), and AIC. The results show that a power equation using diameter at breast height (dbh) and height is the most suitable for all species and components. This equation is more accurate than the familiar power equation that uses ‘dbh² height’, and it expresses the greater volume of branch and foliage mass of trees with a lower height/diameter ratio. A power equation using dbh is more reasonable for models with dbh as the only independent variable and more accurate than a power equation using ‘dbh² height’ for estimating branch and foliage mass. Estimating error for branch and foliage mass is larger than that for stem mass, but the entire aboveground biomass can be estimated with an error of less than 19%, except in the case of small trees with dbh less than 10 cm.     

Culm form analysis for bamboo, Phyllostachys pubescens

We investigated the culm form for one of the largest bamboo species, Phyllostachys pubescens Mazel ex Houz. in relation to the mechanical constraint principles, i.e., elastic, stress and geometric similarity. The fine-resolution analysis of the culm taper indicated that the culm for P. pubescens consisted of three or four segments with various forms, except for the butt swell. This implied that the taper of the whole culm for P. pubescens could be expressed by neither of these principles. The regression slope between culm height and diameter at breast height on the double logarithmic coordinates was 0.629, which was significantly different from the values predicted from these principles. In conclusion, none of these mechanical constraint principles can express the culm taper and height-diameter relationship, and there may be a need for a more complicated model to express the culm form for P. pubescens.     

Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> L.) regeneration and growth of understory trees under single-tree selection silviculture in Finland

This study presents empirical data on regeneration and growth of understory trees and constructs simple models for predicting these characteristics at various stand structure and post-thinning standing volume levels. The field experiment was established on a grass/herb mineral soil site in central Finland. Regeneration and understory tree growth data were collected from 24 Norway spruce (Picea abies L.)-dominated mixed substands. Seedlings with heights from 5 to 130 cm were measured in 1996 and 2007. In addition, the annual height growth of Norway spruce seedlings was measured in 2007. The spatial pattern of the substands varied from clustered to regular with a decreasing standing volume. Stand complexity was uniform across the range of standing volume. In the 2007 survey, the amount of Norway spruce regeneration increased from approximately 400 to 5,000 seedlings ha⁻¹ when the post-thinning standing volume level was reduced from 230 to 90 m³ ha⁻¹, respectively. Nearly no seedlings were found when the standing volume was over 300 m³ ha⁻¹. The annual diameter increment in Norway spruce understory (dbh < 5 cm) trees decreased, on the average, from 2.3 to 0.3 mm with an increase in the standing volume level from 90 to 340 m³ ha⁻¹, respectively; their height growth showed also a decreasing trend when the standing volume increased. The results indicated that a post-thinning standing volume lower than 150 m³ ha⁻¹ with a regular overstory spatial structure provides a suitable environment for regeneration and growth of Norway spruce understory trees in the studied forest type.     

Hybrid poplar (<Emphasis Type="Italic">Populus</Emphasis> ssp.) selections for arid and semi-arid intermountain regions of the western United States

The rapid growth rates of hybrid poplar (Populus spp.) enable rotations of 3–6 years for biofuels or 10–15 years to obtain merchantable timber, but many clones are susceptible to nutrient deficiencies when grown in alkaline soils. A 1995 Oregon study demonstrated that clone OP-367 (P. deltoides × P. nigra) was the only clone tested that performed well on alkaline soils. Tests in Colorado and New Mexico confirmed the adaptation of this clone. A multi-clonal trial was established in 2003 at Farmington, New Mexico and Ontario, Oregon in order to screen a larger number of clones for adaptability to alkaline soils. Trees were planted at 1.5 × 1.5 m spacing and irrigated by surface drip irrigation. Diameter at breast height (DBH) and tree height were recorded annually (2003–2006); wood volumes (WVol) and total aboveground biomass (TAB) were calculated from these measurements. Of the 25 clones tested, 19 were common to both sites. Mean height was greater at the Ontario site through the first 3 years (2003–2005). By the end of four seasons, the tallest Farmington entry was OP-367 at 9.4 m with 177 Mg ha⁻¹ TAB while the tallest Ontario entry was Malheur-3 at 8.9 m with 195 Mg ha⁻¹ TAB and several other clones had statistically similar production. Given the growth and productivity range at these two sites, it is difficult to make generalizations across wide areas, but it appears feasible to identify clones suited to alkaline soils in arid and semi-arid regions.     

Evaluation of sap flow density of <Emphasis Type="Italic">Acacia melanoxylon</Emphasis> R. Br. (blackwood) trees in overstocked stands in north-western Iberian Peninsula

Sap flow density and meteorological variables were monitored in a very dense Acacia melanoxylon stand (about 9,000 trees/ha) in north-western Iberian Peninsula during the growing season of 2006 (from 8 June to 24 August). Evidences of an increment of stomatal control on transpiration were observed during the study period, probably as a consequence of higher evaporative demand of the atmosphere. However, high sap flow density values observed for the whole study period (from 1.14 to 52.73 dm³ dm⁻² day⁻¹) were similar than those found for other fast-growing species. Mean transpiration for the whole study period was 2.21 mm day⁻¹, with a maximum value of 3.17 mm day⁻¹ and a minimum of 1.23 mm day⁻¹. Mean sap flow density values were correlated with crown length and crown ratio, relationships being fairly weak with other dendrometric parameters such as tree diameter or height. Mean transpiration values were correlated with main dendrometric parameters (diameter at breast height, total height, crown length, sapwood area and leaf biomass). It was found that the degree of competition per tree could be used as a good index for sap flow density. Taking into account the high tree density of the stand and the sap flow density values, water consumptions of A. melanoxylon can be very high, playing a relevant role in the hydrological balances of the watersheds where it grows.     

屏边空竹四季出笋及幼竹生长发育规律研究

[目的]揭示屏边空竹的发笋、退笋和幼竹生长规律。[方法]定点观测了30丛屏边空竹周年的出笋、退笋、秆高及地径生长数据,运用SPSS软件分析评价了不同季节出笋及幼竹生长规律。[结果](1)屏边空竹笋期历时9个月左右(从9月至次年5月),根据出笋量的差异可分为初期、盛期和末期,春季最多而夏季最少;其中5丛(16. 67%)每季出笋,具有四季发笋的习性。(2)退笋率随着笋期逐渐增加,在出笋末期达到最高,为87. 76%。(3)笋-幼竹高生长约130 d完成,平均秆高达6. 36 m;呈现"慢-快-慢"的生长规律,生长曲线可用三次曲线方程描述:H=0. 806-0. 029t+0. 001t2-5. 894×10-6t3,R2=0. 980。(4)地径的生长历时16 d左右,平均地径为18. 50 mm,也呈现"慢-快-慢"的生长规律。[结论]屏边空竹发笋期长约9个月,具有四季发笋的习性,但各季节出笋量差异显著;秆高和地径呈现"慢-快-慢"的生长规律。     

Estimation of stand volumes using the <Emphasis Type="Italic">k</Emphasis>-nearest neighbors method in Kyushu,Japan

The k-nearest neighbors (kNN) method is widely employed in national forest inventory applications using remote sensing data. The objective of this study was to evaluate the kNN method for stand volume estimation by combining LANDSAT/ETM+ data with 622 field sample plots from the Japanese National Forest Inventory (NFI) in Kyushu, Japan. The root mean square error (RMSE) and relative RMSE of the volume estimates rapidly decreased as the number of nearest neighbors (k) increased up to five, and then it slightly declined. They were consistently smaller for the Euclidean distance than for the Mahalanobis distance. The estimation errors (RMSE and relative RMSE) were 169.2 m³/ha and 66.2%, respectively (k = 10). The relative RMSE was similar to the previous studies. The estimated values were more accurate towards the mean value of the total volume, with an overestimation of the low volumes and an underestimation of the high volumes. We found a significant linear relationship between the observed stand volumes and estimated errors, which suggests that systematic errors may be reduced using this linearity. This research concluded that the kNN method is suitable for estimating stand volumes in Kyushu.     

A comparison of different methods for forest resource estimation using information from airborne laser scanning and CIR orthophotos

This article compares three methods for forest resource estimation based on remote sensing features extracted from Airborne laser scanning and CIR orthophotos. The estimation was made exemplarily for the total stem volume of trees for a given area, measured in cubic metres per hectare [m3 ha⁻¹] (as one of the most important quantitative parameters to characterise a forest stand). The following methods were compared: Regression Analysis (RA), k-NN (nearest neighbour) method and a method that utilises regional yield tables, referred to as the yield table method (YT-method). The estimation of stem volume was examined in a mixed forest in Southern Germany using 300 circular inventory plots, each with a size of 452 m2. Remote sensing features relating to vegetation height and structures were extracted and used as input variables in the different approaches. The accuracy of the estimation was analysed using scatter plots and quantified using absolute and relative root mean square errors (RMSE). The comparison was made for all plots, as well as for averaged plot values located within forest stands that have the same age class. On “plot level” the RMSE yielded 79.79 m3 ha⁻¹ (RA), 81.93 m3 ha⁻¹ (k-NN) and 81.78 m3 ha⁻¹ (YT-method) and for the averaged values 35.75 m3 ha⁻¹ (RA), 35.06 m3 ha⁻¹ (k-NN) and 42.98 m3 ha⁻¹ (YT-method). Advantages and disadvantages, as well as requirements, of the methods are discussed.     

Weeds in <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> subsp. <Emphasis Type="Italic">maidenii</Emphasis> (F. Muell) establishment: effects of competition on sapling growth and survivorship

The effect of herbaceous vegetation on growth and survival was assessed in planted eucalyptus saplings grown under four levels of weed cover. Seedlings of Eucalyptus globulus subsp. maidenii were planted with 0 (W0), 25 (W25), 50 (W50) and 100% (W100) weed cover. Weed species composition and aboveground biomass was determined. Soil water content was evaluated by the gravimetric method. Seedling leaf area, diameter and height were evaluated at planting and during the 3 months following establishment. Tree height, diameter and stem volume was estimated at 12, 24 and 36 months. First year tree survival was recorded. The ratio of cumulative stem growth under W100: cumulative stem growth under W0 was used to measure competitive performance. Regression analysis was used to determine competition thresholds. Weeds seriously threaten the growth of E. globulus subsp. maidenii. Early negative effects of competition on growth were evident as from the second month after establishment, and both seedlings and 1-year-old saplings were more affected than 2- and 3-year-old ones. A “minimum-response threshold” was determined near 500 kg/ha (corresponding to W25 cover). No clear effect was found between sapling survival and weed biomass.     

Analysis of sawn lumber production from logging residues of branchwood of <Emphasis Type="Italic">Aningeria robusta</Emphasis> and <Emphasis Type="Italic">Terminalia ivorensis</Emphasis>

One way of meeting the supply demands of the wood industry is through the reduction of waste in timber processing. It has been estimated in Ghana that for every tree felled, nearly 50% of the tree volume is left in the forest in the form of branches, crownwood, and stumps. In this study, the potential of utilizing branchwood as raw material from logging residues to help meet the timber demands of the downstream processing sector was analyzed experimentally. The sawing characteristics of the branchwood of Aningeria robusta and Terminalia ivorensis with diameters in the range 10–25 cm using live sawing and cant sawing methods were determined using a randomized complete block design, 2 × 4 factorial with three replications. Experimental results indicate that, the relative lumber value yields for first and second grade boards of A. robusta and T. ivorensis branches were 25 and 20%, respectively, while the green lumber volume yields were 40 and 32%, respectively. A high proportion of sapwood and the occurrence of washboarding in T. ivorensis contributed to that species’ relatively low lumber value and volume yield. The experimental results further indicate that the sawing technique used had no significant influence on lumber yields. However, at 5% level of significance, significant differences in lumber yield existed between some of the diameter classes.     

Effect of pruning frequency and pruning height on the biomass production of <Emphasis Type="Italic">Tithonia diversifolia</Emphasis> (Hemsl) A. Gray

Addition of tree or shrub prunings through alley cropping or biomass transfer systems have contributed to sustainable land-use systems in the tropics. Long term productivity of biomass transfer systems require shrub or tree species that coppice after cutting to provide sufficient plant nutrients. The effect of pruning frequency and cutting height on the biomass production of Tithonia diversifolia was studied to provide information for managing hedges. Results showed that height of cutting, pruning frequency, and their interactions significantly affected dry matter production of T. diversifolia. The results also showed that a significantly higher biomass production could be produced when Tithonia was pruned at long time intervals. Pruning height was also of importance in the harvesting of Tithonia biomass and it was evident that dry matter production was highest when Tithonia was pruned bimonthly at 50 cm height. With bi-monthly pruning frequency, dry matter production could be as high as 7.2 t ha⁻¹ yr⁻¹ which might be a sufficient biomass to improve soil productivity in biomass transfer systems.     

Partitioning of simulated rainfall in a kaolinitic soil under improved fallow–maize rotation in Zimbabwe

Research on improved fallows has concentrated on soil fertility benefits neglecting possible benefits to soil and water conservation. The effects of improved fallows on rainfall partitioning and associated soil loss were investigated using simulated rainfall on a kaolinitic soil in Zimbabwe. Simulated rainfall at an intensity of 35 mm h⁻¹ was applied onto plots that were under planted fallows of Acacia angustissima and Sesbania sesban, natural fallow and maize (Zea mays L.) for two years. At the end of 2-years in October 2000, steady state infiltration rates could not be determined in A. angustissima and natural fallow plots, but they were 24 mm h⁻¹ in S. sesban and 5 mm h⁻¹ in continuous maize. The estimated runoff losses after 30 min of rainfall were 44% from continuous maize compared with 22% from S. sesban and none from A. angustissima and natural fallow plots. Infiltration rate decay coefficients were 36 mm and 10 mm for S. sesban and continuous maize, respectively. In October 2001 after one post-fallow crop, it was still not possible to determine the steady state infiltration rates in A. angustissima and natural fallows, but they were 8 and 5 mm h⁻¹ for, S. sesban and continuous maize systems, respectively. The runoff loss, averaged across tilled and no-tilled plots, increased to 30% in the case of S. sesban fallowed plots and 57% for continuous maize; there was still no runoff loss from the other treatments. There were significant differences (P<0.05) in infiltration rate decay coefficients among treatments. The infiltration rate decay coefficient was 25 mm for S. sesban and it remained unchanged at 10 mm for continuous maize. It is concluded that planted tree fallows increase steady state infiltration rates and reduce runoff rates, but these effects markedly decrease after the first year of maize cropping in non-coppicing tree fallows. This revised version was published online in June 2006 with corrections to the Cover Date.     

Allometric model of the Reineke equation for Japanese cypress (<Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis>) and red pine (<Emphasis Type="Italic">Pinus densiflora</Emphasis>) stands

An allometric model that explains the mechanism of the difference in the slope of the Reineke equation (A) among species was proposed based on the allometric relationships of mean tree height (H) to quadratic mean diameter D (H ∝ D ^θ ) and stand density N (H ∝ N ^δ ), i.e., A = θ/δ. The proposed model was fitted to Japanese cypress (Chamaecyparis obtusa Endl.) and red pine (Pinus densiflora) stands. The allometric exponents θ and δ were, respectively, 0.8995 and −0.5000 for cypress and 0.8612 and −0.6619 for pine. The difference between cypress and pine was significant for δ but not for θ. Inserting the exponents into the model resulted in predicted slopes of −1.7991 for cypress and −1.3011 for pine. The difference in the slope of the Reineke equation between the two species was produced by characteristics related to the tree crown, rather than characteristics related to stem slenderness. The proposed model enables us to estimate the slope of the Reineke equation from commonly measured stand attributes, such as mean tree height and quadratic mean diameter. Therefore, the proposed model is expected to be practical and convenient for estimating the slope of the Reineke equation and for explaining the mechanism of its variation among species. The model should be also accepted as a generalized model of the stand density versus quadratic mean diameter relationship, whereas the original Reineke equation should be seen as a specific case of this model.     

Growth and yield of maize and timber trees in smallholder agroforestry systems in Claveria,northern Mindanao,Philippines

On-farm experiments were conducted in the Philippines to study over a 4-year period the growth of two timber trees, gmelina (Gmelina arborea R. Br.) and bagras (Eucalyptus deglupta Blume), and their impact on the grain yield of intercropped maize. The experiment consisted of maize monocropping plots (control) and maize intercropped between trees planted in block (2 × 2.5 m), and hedgerow arrangement (1 × 10 m). Three maize crops were planted in the block plots before canopy closure, and seven maize crops were planted in the hedgerow and monocropping plots. Maize grain yield in the hedgerow and in the block arrangement with gmelina were respectively 37% (16.58 tons ha⁻¹) and 68% (8.3 tons ha⁻¹) lower than in monocropping (26.21 tons ha⁻¹). In the plots with bagras, maize grain yield in hedgerow and in block arrangement were respectively 19% (24.8 tons ha⁻¹) and 66% (10.4 tons ha⁻¹) lower than in monocropping (30.6 tons ha⁻¹). For both tree species, the diameter at breast height (dbh) was greater in hedgerow than in block arrangement, with the difference being more pronounced with age. It was estimated that gmelina planted in hedgerows would produce 6–8 m³ ha⁻¹ of merchantable volume more than if planted in block. The study verifies the hypothesis that intercropping between widely-spaced trees rows (planted at 10 m or more) is more profitable and feasible to smallholders than either maize monocropping or woodlots, and concludes with recommendations on how to further improve the productivity of tree-intercropping systems.     

Gas exchange responses of <Emphasis Type="Italic">Eucalyptus</Emphasis>, <Emphasis Type="Italic">C. africana</Emphasis> and <Emphasis Type="Italic">G. robusta</Emphasis> to varying soil moisture content in semi-arid (Thika) Kenya

A dramatic decline in forest cover in eastern Africa along with a growing population means that timber and poles for building and fuelwood are in short supply. To overcome this shortage, the region is increasingly turning to eucalyptus. But eucalyptus raises environmental concerns of its own. Fears that it will deplete water supply, affect wildlife and reduce associated crop yields have caused many countries in the region to discourage farmers from planting this exotic. This paper is part of a series of investigations on the growth and water use efficiency of faster growing eucalyptus hybrids, which was introduced from South Africa to Kenya. The hypothesis is that the new hybrids are more efficient in using water and more suitable for the semi-arid tropics than existing eucalyptus and two popular agroforestry species. Gas exchange characteristics of juvenile Eucalyptus grandis (W. Hill ex Maiden), two eucalyptus hybrids (E. grandis × Eucalyptus camaldulensis Dehnh.), Grevillea robusta (A. Cunn) and Cordia africana (Lam) was studied under field and pot conditions using an infrared gas analyzer was used to measure photosynthetic active radiation (PAR), net photosynthetic rate (A), stomatal conductance (g _s) and transpiration rate (E) at CO₂ concentrations of 360 μmol mol⁻¹ and ambient humidity and temperature. A, E and g _s varied between species, being highest in eucalyptus hybrid GC 15 (24.6 μmol m⁻² s⁻¹) compared to eucalyptus hybrid GC 584 (21.0 μmol m⁻² s⁻¹), E. grandis (19.2 μmol m⁻² s⁻¹), C. africana (17.7 μmol m⁻² s⁻¹) and G. robusta (11.1 μmol m⁻² s⁻¹). C. africana exhibited high E values (7.0 mmol m⁻² s⁻¹) at optimal soil moisture contents than G. robusta (3.9 mmol m⁻² s⁻¹) and eucalyptus (5.3 mmol m⁻² s⁻¹) in field experiment and G. robusta (3.2 mmol m⁻² s⁻¹) and eucalyptus (4.2 mmol m⁻² s⁻¹) in pot-grown trees. At very low soil moisture content, extremely small g _s values were recorded in GC 15 and E. grandis (8 mmol m⁻² s⁻¹) and G. robusta (14 mmol m⁻² s⁻¹) compared to GC 584 (46.9 mmol m⁻² s⁻¹) and C. africana (90.0 mmol m⁻² s⁻¹) indicating strong stomatal control by the species. Instantaneous water use efficiency ranged between 3 and 5 μmol mmol⁻¹ and generally decreased with decline in soil moisture in pot-grown trees but increased with declining soil moisture in field-grown trees.     

Sampling procedure for density estimation of bamboo galls induced by <Emphasis Type="Italic">Aiolomorphus rhopaloides</Emphasis> (Hymenoptera: Eurytomidae) in a bamboo stand

 To establish a sampling procedure for estimating the density of bamboo galls induced by Aiolomorphus rhopaloides Walker (Hymenoptera: Eurytomidae) in a stand of bamboo Phyllostachys heterocycla (Carr. Mitf.) (Monocotyledoneae: Gramineae), 5–12 bamboo culms were cut at random in late March of each year during 1998–2001 just before gall-maker emergence. The number of galls on the branches of each bamboo culm was counted. The spatial patterns of the galls on the culms in the stand and on the branches within each culm were measured by Iwao's patchiness regression. Galls were distributed contagiously both on culms and on branches. Current bamboo culms that emerged the previous summer did not require sampling because no galls were observed on them. Except for this, there was no difference in gall density on young and old culms, suggesting that it is not necessary to distinguish them. There were few (<4%) galls above 6 m height during the 4 years. There was no significant difference in gall density up to 4 m and above 4 m, suggesting that branches up to 4 m can be sampled with confidence. Kuno's two-stage sampling method at different precision levels showed that the number of culms to be sampled varied with gall density. For example, at mean density m = 1.0 per branch when the number of sampled branches per culm is 10, a total of 24 culms is required to estimate gall number at a precision level of D = 0.2, where D is the ratio of standard error to mean. Received: July 10, 2002 / Accepted: November 25, 2002 Acknowledgments I thank Dr. K. Kamijo for insect identification. Thanks are also due to the members of the Laboratory of Forest Protection for their kind help with the fieldwork. This study was supported in part by a Grant-in-Aid for Scientific Research (No. 11460068) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.     

Responses of fine root mass,length, production and turnover to soil nitrogen fertilization in <Emphasis Type="Italic">Larix gmelinii</Emphasis> and <Emphasis Type="Italic">Fraxinus mandshurica</Emphasis> forests in Northeastern China

The responses of fine root mass, length, production and turnover to the increase in soil N availability are not well understood in forest ecosystems. In this study, sequential soil core and ingrowth core methods were employed to examine the responses of fine root (≤1 mm) standing biomass, root length density (RLD), specific root length (SRL), biomass production and turnover rate to soil N fertilization (10 g N m⁻² year⁻¹) in Larix gmelinii (larch) and Fraxinus mandshurica (ash) plantations. N fertilization significantly reduced fine root standing biomass from 130.7 to 103.4 g m⁻² in ash, but had no significant influence in larch (81.5 g m⁻² in the control and 81.9 g m⁻² in the fertilized plots). Similarly, N fertilization reduced mean RLD from 6,857 to 5,822 m m⁻² in ash, but did not influence RLD in larch (1,875 m m⁻² in the control and 1,858 m m⁻² in the fertilized plots). In both species, N fertilization did not alter SRL. Additionally, N fertilization did not significantly alter root production and turnover rate estimated from sequential soil cores, but did reduce root production and turnover rate estimated from the ingrowth core method. These results suggested that N fertilization had a substantial influence on fine root standing biomass, RLD, biomass production and turnover rate, but the direction and magnitude of the influence depended on species and methods.     

Tree and stand growth for clonal <Emphasis Type="Italic">E. urophylla</Emphasis> × <Emphasis Type="Italic">grandis</Emphasis> across a range of initial stockings in southern China

A large initial stocking × fertilizer factorial field trial established in 1993 with a Eucalyptus urophylla × grandis hybrid clone in southern Guangxi province, China, included 6 initial stocking treatments ranging from 667 to 2,222 trees ha⁻¹ and 6 fertilizer treatments. Growth data was collected at various intervals up to age 192 months and also data on outer-wood pilodyn penetration (as an indicator of wood density) and acoustic velocity through the outer-wood (as an indicator of modulus of elasticity) at the last assessment. This report examines the results for the main effect of initial stocking treatments and stocking × fertilizer interactions across ages. There were significant differences between initial stockings for both average individual tree volume and standing volume ha⁻¹ at all ages up to 144 months, but just average individual tree volume at 192 months. At ages up to 75 months total standing volume decreased as initial stocking decreased—maximum volume being obtained at 2,222 trees ha⁻¹. From 88 to 110 months the highest standing volume was obtained at 1,667 trees ha⁻¹ and then at ages 144 and 192 months, 833 trees ha⁻¹ provided the highest standing volume. Average individual tree volume at all ages generally increased as initial stocking decreased—the largest trees were obtained at 667 trees ha⁻¹. As age increased the proportional differences between tree volumes at higher and lower stockings increased—at age 27 months average individual tree volume at 667 trees ha⁻¹ was 72% greater than that at 2,222 trees ha⁻¹ and differences increased steadily with age up to 190% at 192 months. There were no significant differences between initial stockings for the properties of the outer-wood assessed by pilodyn penetration and acoustic velocity. Also, no significant interactions were found between initial stocking and fertilizer treatments for any traits at any ages implying that effects of initial stocking and fertilizer are additive for the traits assessed.