Mean Annual Biomass Increment Research Articles

First-rotation growth and stand structure dynamics of tree species in organic and conventional short-rotation agroforestry systems

Short-rotation agroforestry systems can potentially maintain agricultural production and promote conservation of soil and biodiversity, especially if grown organically. Hereby, species-specific stand growth determines woody biomass yield and influences management decisions like planting density and harvest requirements. Studies of longer-term growth dynamics in Southern Germany are scarce and none analyzed differences between conventional and organic systems. In this study, four tree species (black alder, black locust, poplar clone Max 3, and willow clone Inger) were planted in an alley-cropping configuration in Southern Germany, grown under organic and conventional systems, and monitored from 2009 to 2012. Growth was assessed with stem base diameter, height, aboveground woody biomass, sprouting, and survival. The tree species did not show a uniform ranking in biometric variables and biomass over time. Four-year mean annual biomass increment (MAI) ranged from 7 to 10 t ha−1 a−1, with poplar and locust having the highest growth rates. Willow had the lowest MAI, as it had a low diameter growth paired with a low wood density, but it developed the highest number of shoots because of increased sprouting in the last year. Size inequality and skewness of the dominant stems increased for all species throughout the years suggesting asymmetric competition. Size inequality as well as mortality was greatest for black locust. Furthermore this was the only species, which developed a right skewed SBD distribution and the highest diameter size range. Size inequality was smallest for poplar and willow, with no or only minimal mortality. Alder was inbetween. For black locust and alder no difference in growth traits between organic and conventional systems appeared after four years. Organic poplar and willow stands performed better than conventional ones after the second year, leaving unclear whether this can be attributed to management or site effect.

Economic assessment of Eucalyptus globulus short rotation energy crops under contrasting silvicultural intensities on marginal agricultural land

Evolving bioenergy markets requires consideration of marginal lands for woody biomass production worldwide. Growing short rotation woody crops for bioenergy (SRWCs) on marginal land minimizes concerns about using croplands for agricultural production and reinforces sustainability of wood supply. Evaluation of the profitability of marginal land that may have SRWCs potential as sources of biomass for energy production has been rarely reported. This study attempts to account for investments uncertainties on SRWCs production considering Eucalyptus globulus managed under contrasting silvicultural intensities on marginal land by comparing four environments and four levels of initial planting density. Our study consider biomass yields over this gradient of productivity and biomass market prices and costs from local contractors. We estimated mean annual aboveground dry biomass increments (MAIs) and evaluated the economic feasibility of various cycles of harvest (2–6 years) using Monte Carlo simulation to examine how uncertainty over the input variables affects NPV of SRWCs. MAIs that ranged 3.91–18.07 Mg ha−1 yr−1 increased with stand density and harvesting age. Rotation length affected economic outcomes although the returns were poor due to high establishment and maintenance costs, low productivities and low biomass prices. Under an average scenario, current market price of biomass, absence of subsidies and current costs, SRWC are not profitable when productivities are lower than 351 m3 ha−1 of green biomass.

SRWC bioenergy productivity and economic feasibility on marginal lands

Evolving bioenergy markets necessitate consideration of marginal lands for woody biomass production worldwide particularly the southeastern U.S., a prominent wood pellet exporter to Europe. Growing short rotation woody crops (SRWCs) on marginal lands minimizes concerns about using croplands for bioenergy production and reinforces sustainability of wood supply to existing and growing global biomass markets. We estimated mean annual aboveground green biomass increments (MAIs) and assessed economic feasibility of various operationally established (0.5 ha–109 ha) SRWC stands on lands used to mitigate environmental liabilities of municipal wastewater, livestock wastewater and sludge, and subsurface contamination by petroleum and pesticides. MAIs (Mg ha−1 yr−1) had no consistent relationship with stand density or age. Non-irrigated Populus, Plantanus occidentalis L. and Pinus taeda L. stands produced 2.4–12.4 Mg ha−1 yr−1. Older, irrigated Taxodium distchum L., Fraxinus pennsylvanica L., and coppiced P. occidentalis stands had higher MAIs (10.6–21.3 Mg ha−1 yr−1) than irrigated Liquidambar styraciflua L. and non-coppiced, irrigated P. occidentalis (8–18 Mg ha−1 yr−1). Natural hardwood MAIs at 20–60 years were less than hardwood and P. taeda productivities at 5–20 years. Unlike weed control, irrigation and coppicing improved managed hardwood productivity. Rotation length affected economic outcomes although the returns were poor due to high establishment and maintenance costs, low productivities and low current stumpage values, which are expected to quickly change with development of robust global markets.

Dendrochronology-based stand growth estimation of Larix olgensis forest in relation with climate on the eastern slope of Changbai Mountain, NE China

The eastern slope of Changbai Mountain is characterized by pure larch forest (Larix olgensis) with little human disturbance. Response of tree growth to climate in this area remains unknown. Meanwhile, little is known about how climate variations affect the biomass increase which could be recognized as a three-dimensional tree growth index. The objective of this study is to investigate the climate effects on the radial and biomass growth of larch on eastern slope of Changbai Mountain. Tree-ring width chronologies and mean annual biomass increment were established using tree-ring data. We used correlation analysis and multiple regression analysis to explore the relationship between larch growth and climatic factors from 1957 to 2009. Results show that tree-ring growth and mean annual biomass increment were primarily and significantly affected by previous year climatic variables with slight difference among months. Temperatures were more consistently and strongly correlated to the chronologies and mean annual biomass increment than was precipitation. Temperature is the main factor limiting larch growth on Changbai Mountain and the ongoing climate warming may accelerate the growth of the species. The current stand biomass of the area was 240.72 Mg·ha−1 and the annual stand biomass increment in 2009 was 2.91 Mg·ha−1. In conclusion, the old-growth forest in the study area is still accumulating carbon efficiently.

Growth of mature boreal Norway spruce was not affected by elevated [CO2] and/or air temperature unless nutrient availability was improved

The growth responses of mature Norway spruce (Picea abies (L.) Karst.) trees exposed to elevated [CO(2)] (CE; 670-700 ppm) and long-term optimized nutrient availability or elevated air temperature (TE; ±3.9 °C) were studied in situ in northern Sweden in two 3 year field experiments using 12 whole-tree chambers in ca. 40-year-old forest. The first experiment (Exp. I) studied the interactions between CE and nutrient availability and the second (Exp. II) between CE and TE. It should be noted that only air temperature was elevated in Exp. II, while soil temperature was maintained close to ambient. In Exp. I, CE significantly increased the mean annual height increment, stem volume and biomass increment during the treatment period (25, 28, and 22%, respectively) when nutrients were supplied. There was, however, no significant positive CE effect found at the low natural nutrient availability. In Exp. II, which was conducted at the natural site fertility, neither CE nor TE significantly affected height or stem increment. It is concluded that the low nutrient availability (mainly nitrogen) in the boreal forests is likely to restrict their response to the continuous rise in [CO(2)] and/or TE.

Effect of wood ash on the biomass production and nutrient status of young silver birch (Betula pendula Roth) trees on cutaway peatlands in Estonia

The objective of the study was to quantify the effect of wood ash on the growth and nutrition of silver birch (Betula pendula Roth) on cutaway peatlands in Estonia. Two experimental areas were established: the Ulila experimental area (South Estonia) with treatments of 5 and 10tha−1 wood ash and control (unfertilised plot) in 2009 and the Puhatu experimental area (Northeast Estonia) with treatments of 10 and 15tha−1 wood ash and control in 2011. The best results were achieved with the wood ash dose of 10tha−1 on the Ulila area and with 15tha−1 on the Puhatu area, which means that the largest amounts of wood ash applied were the most favourable for the growth of young birches. Fertilisation with wood ash improved the balance of nutrients on the Ulila and Puhatu experimental area: the concentration of extractable P, K, Ca and Mg in the ash-treated peat had significantly increased. Already after the first growing season the annual height increment of trees on the ash-fertilised plots was greater (0.5–0.6m), than control (3–7cm) on both experimental areas, during the next two years more than 1m on the Ulila ash-treated experimental area. The mean root collar diameter of birches on the plot treated with 10tha−1 ash was 3.3cm on the Ulila experimental area and 1.9cm on the Puhatu experimental area. In the second year after fertilisation the mean tree biomass was 167.2g on the treated with 10tha−1 plot while on the control plot the mean tree biomass was only 1.4g on the Ulila area; in the fourth year the respective biomasses were 961.0g and 6.3g on the Ulila experimental area. On the Puhatu experimental area the mean tree biomass was 216.9g on the plot treated with 15tha−1 and 9.6g on the control plot in the second year. In the second year the mean annual biomass increment on the treated with 10tha−1 at Ulila was 136gyear−1, and almost the same results were obtained on the Puhatu experimental area with 15tha−1 wood ash treatment. On the Ulila experimental area the root mass ratio was higher on the control than on the ash-fertilised plots, but on the Puhatu experimental area the root mass ratio did not statistically differ between the treatments. On the plots treated with higher amount of wood ash a significant increase in the concentration of elements dominating in wood ash (P, K, Ca) was observed in assimilating organs.

Effectiveness of soil N availability indices in predicting site productivity in the oil sands region of Alberta

Background and aims Quantitative relationships between soil N availability indices and tree growth are lacking in the oil sands region of Alberta and this can hinder the development of guidelines for the reclamationof the disturbed landscape after oil sands extraction. The aim of this paper was to establish quantitative relationships between soilN availability indices and tree growth in the oil sands region of Alberta. Methods In situ N mineralization rates, in situ N availabilitymeasuredinthefieldusingPlant RootSimulators (PRS™probes),laboratoryaerobicandanaerobicsoilN mineralization rates, and soil C/N and N content were determined for both the forest floor and the 0–20 cm mineral soil in eight jack pine (Pinus banksiana Lamb.) stands in the oil sands region in northern Alberta. Tree growth rates were determined based on changes in tree ring width in the last 6 years and as mean annual aboveground biomass increment. Results Soil N availability indices across those forest stands varied and for each stand it was several times higher in the forest floor than in the mineral soil. The in situ and laboratory aerobic and anaerobic soil N mineralization rates, soil mineralized N, in situ N availability measured using PRS probes, soil C/N ratio and N content in both the forest floor and mineral soil,

Impacts of urban forests on offsetting carbon emissions from industrial energy use in Hangzhou, China

This study quantified carbon storage and sequestration by urban forests and carbon emissions from energy consumption by several industrial sources in Hangzhou, China. Carbon (C) storage and sequestration were quantified using urban forest inventory data and by applying volume-derived biomass equations and other models relating net primary productivity (NPP) and mean annual biomass increments. Industrial energy use C emissions were estimated by accounting for fossil fuel use and assigning C emission factors. Total C storage by Hangzhou's urban forests was estimated at 11.74 Tg C, and C storage per hectare was 30.25 t C. Carbon sequestration by urban forests was 1,328, 166.55 t C/year, and C sequestration per ha was 1.66 t C/ha/year. Carbon emissions from industrial energy use in Hangzhou were 7 Tg C/year. Urban forests, through sequestration, annually offset 18.57% of the amount of carbon emitted by industrial enterprises, and store an amount of C equivalent to 1.75 times the amount of annual C emitted by industrial energy uses within the city. Management practices for improving Hangzhou's urban forests function of offsetting C emissions from energy consumption are explored. These results can be used to evaluate the urban forests' role in reducing atmospheric carbon dioxide.

Tree Biomass of Planted Forests in the Tropical Dry Climatic Zone: Values in the Tropical Dry Climatic Zones of the Union of Myanmar and the Eastern Part of Sumba Island in the Republic of Indonesia

We measured the values for biomass and mean annual biomass increment (MAI) of planted forests in two parts of the Tropical Dry climatic zone (mean annual precipitation [MAP] < 1,000 mm) and in one site adjacent to one of the two parts and outside the Tropical Dry climatic zone to provide a comparison value for wet forests in the same region. MAI values of four planted forests averaged 2.60 (±1.61 SD) Mg ha -1 y -1 at a MAP of 637 mm in the central dry zone of Myanmar. The MAI of exotic fast-growing tree species (Eucalyptus camaldulensis Dehn.) did not differ significantly from those of three native non-fast-growing tree species in the central dry zone of Myanmar. MAI values appeared to be lower on land with a high gravel content in the soil or with a higher degree of erosion. In the eastern part of Sumba Island in Indonesia, MAI of planted Tectona grandis L. forest equaled 3.76 Mg ha -1 y -1 at a MAP of 500 mm and 4.49 Mg ha -1 y -1 at a MAP of 1,500 mm. A Leucaena leucocephala de Wit stand produced a higher MAI (9.62 Mg ha -1 y -1 ) at a MAP of 500 mm. The MAI values for fast-growing tree species that we measured or collected in the Tropical Dry climatic zone were less than 20% of those recorded in the Tropical Moist and Tropical Wet climatic zones and about one-third the value for forests of non-fast-growing tree species. Accordingly, fast-growing tree species may not be capable of achieving their fast growth rates under the Tropical Dry climate. This information will be useful in developing land-use programs based on plantation forestry in dry forest areas.

Regeneration of teak forests under joint forest management in Gujarat

In order to understand the impact of JFM in Gujarat, a study was conducted in three divisions viz., Baria, Rajpipala and Sabarkantha covering 24 villages. Vegetation parameters such as species richness, density of trees, basal areas, Shanon Weiner's diversity index, woody biomass and MAI were observed and compared with control plots in a non-JFM village. Stem density, species richness, species diversity, basal area, biomass and mean annual biomass increment were higher in JFM forests as compared to controls. This study also indicates that JFM forests are meeting substantial biomass needs of the community and contributes towards achieving sustainable forestry.

High rates of nitrogen fixation of Ulex species in the understory of maritime pine stands and the potential effect of phosphorus fertilization

Nitrogen (N2) fixation by Ulex species was studied in a range of mature maritime pine (Pinus pinaster Ait.) stands as well as in a phosphorus (P) fertilization trial in a young (6-year-old) open pine stand. The biomass was estimated by allometric relationships, and the percentage of N derived from atmosphere was calculated according to the natural 15N abundance method. Ulex stand biomass was lower in the mature pine stand than in the young open pine stand. In the latter pine stand, Ulex mean annual biomass increment ranged from 1 to 5 Mg·ha–1·year–1, increasing with P fertilization dose, as did the Ulex stand biomass, ranging from 5.4 to 31.1 Mg·ha–1 after six growing seasons in the most highly fertilized treatment. For the sites where the natural 15N abundance method was applicable, the calculated percentage of N in the Ulex europaeus L. tissues derived from atmosphere was very high (mean = 82%; range = 59%–100%). At the other sites, the N2 fixation was probably also very important but could not be calculated with confidence. Here, the mean fixation rate of the former sites was used to calculate the N2 fixation flux. The estimated annual N2 fixation flux ranged from 0.5 to 5.1 kg N·ha–1·year–1 in the mature pine stands. In the young open pine stand, the Ulex understory fixation ranged from 8.1 to 57.4 kg N·ha–1·year–1, increasing with P fertilization dose. Considering the low levels of N fluxes in theses ecosystems, these figures are very high.

A comparative study of aboveground biomass of three Mediterranean species in a post-fire succession

Abstract The aboveground biomass of three woody species ( Cistus albidus, Quercus coccifera and Pinus halepensis ) in two early successional stages (3- and 10-year old) of a post-fire Mediterranean ecosystem was investigated. Among these three species, which belong to the successional series of holm oak ( Quercus ilex ), C. albidus and Q. coccifera are two dominant shrub species in the garrigue ecosystem and P. halepensis is a pioneer tree species widely represented in the Mediterranean area. The results obtained showed that in monospecific stands, C. albidus and Q. coccifera had a high recovery potential. In the 3-year-old stands, the cover of P. halepensis was only 19.8% for a total biomass of 0.75 ± 0.21 t ha –1 , while the plant cover of C. albidus and Q. coccifera was, respectively, 26% and 85.5% and biomass was 4.72 ± 1.09 and 11.5 ± 0.16 t ha –1 . Only 10 years after fire, the plant cover of C. albidus and Q. coccifera was, respectively, 55% and 100% and total biomass 13.2 ± 1.7 and 35.8 ± 4.7 t ha –1 . The greatest increase in biomass was noted for P. halepensis (29.7 t ha –1 ). If mean annual biomass increments are considered, it appears that there was a significant decrease with the stand age for the two shrub species although the tree species showed an increase in productivity. These differing patterns in biomass and productivity of shrub and tree species with stand age provide information on biomass accumulation rates of pioneer species in a Mediterranean succession and their importance in the vegetation dynamics.

Above-ground biomass production and biomass equations for even-aged Gmelina arborea (ROXB) plantations in south-western Nigeria

Abstract Above-ground biomass production was estimated for Gmelina arborea (Roxb) plantations (ages 5–21 years) in Oluwa Forest Reserve, Nigeria. A total of 120 trees were harvested and weighed to provide data for the estimation of biomass as well as for developing biomass equations. The results showed that Gmelina has high biomass yield, ranging from 83.2 t ha −1 (5 years) to 394.9 t ha −1 (21 years). Mean annual biomass increment varied from 16.2 to 20.9 t ha −1 yr −1 . Average biomass allocations to different components of the tree were as follows: Stem about 84%; branch 13% and foliage 3%. The high biomass values were attributed to fast growth, high stand density (range: 837– 1275 stems ha −1 ) and good site conditions in the study area. Biomass values of the various tree components (stem, branch and foliage) as well as total above-ground biomass (TAGB) were regressed with diameter at breast height (dbh) on the one hand (equation form 1), and with dbh and total height (in the form of D2H) on the other (equation form 2), with the aim of choosing the most suitable equation form. All equations generated had very high adjusted R2 and very low standard error of estimate. Residuals for both equation forms were normally and randomly distributed. Only little improvement in the ability of the equations to explain the variations in biomass was achieved by including the variable of total height. Considering the ease and accuracy in obtaining dbh data and the enormous time, errors and difficulty in obtaining height data, the equation form involving only dbh data as independent variable was recommended for use in estimating biomass for Gmelina in Oluwa forest reserve.

Carbon distribution of a well‐ and poorly‐drained black spruce fire chronosequence

AbstractThe objective of this study was to quantify carbon (C) distribution for boreal black spruce (Picea mariana (Mill.) BSP) stands comprising a fire chronosequence in northern Manitoba, Canada. The experimental design included seven well‐drained (dry) and seven poorly‐drained (wet) stands that burned between 1998 and 1850. Vegetation C pools (above‐ground + below‐ground) steadily increased from 1.3 to 83.3 t C ha−1 for the dry chronosequence, and from 0.6 to 37.4 t C ha−1 for the wet chronosequence. The detritus C pools (woody debris + forest floor) varied from 10.3 to 96.0 t C ha−1 and from 12.6 to 77.4 t C ha−1 for the dry and wet chronosequence, respectively. Overstorey biomass, mean annual biomass increment (MAI), woody debris mass, and litterfall were significantly greater (α = 0.05) for the dry stands than for the wet stands, but the bryophyte, understorey, and forest floor C pools were significantly less for the dry than for the wet stands. The root mass ratio decreased with stand age until 37 years after fire, was fairly constant thereafter, and was not significantly affected by soil drainage. The C pools of the overstorey and bryophyte tended to increase with stand age. Foliage biomass, litterfall, and MAI (for the dry stands) peaked at 71 years after fire and declined in the oldest stands. The results from this study illustrate that the effects of disturbance and edaphic conditions must be accounted for in boreal forest C inventories and C models. The appropriateness of using chronosequences to examine effects of wildfire on ecosystem C distribution is discussed.

Estimating biomass and net primary production from forest inventory data: a case study of China’s Larix forests

Forest inventory data (FID) are important resources for understanding the dynamics of forest biomass, net primary production (NPP) and carbon cycling at landscape and regional scales, especially for complying with the Kyoto Protocol on greenhouse gas reduction and validating ecosystem dynamic models from regional and global scales. FID-based biomass and NPP estimation models for China’s Larix forests are discussed in this paper. The results indicated that the relationships between biomass ( B) and its volume ( V), NPP and mean annual biomass increment ( B/ A) or mean annual volume increment ( V/ A) can be expressed as hyperbola curves for both natural and planted Larix forests. The relationship between NPP and its biomass is not linear, which is not the same with the former studies. These FID-based models take into account the change in the ratio of forest biomass to volume with stand age and the effect of stand age on forest NPP. The result also indicates that natural and planted forests should be treated separately when biomass and NPP of forest are estimated based on FID.

Poplar breeding and testing strategies in the north-central U.S.: Demonstration of potential yield and consideration of future research needs

We present results from a Populus Regional Testing Program that has been conducted in Minnesota, Iowa, Wisconsin, and Michigan over the past six years. Our objectives have been to: 1) identify highly productive, disease resistant intra- and inter-specific clonal selections and 2) understand patterns of genotype × environment interactions within the region that would, logically, govern commercial deployment of new clones. Clones were developed by breeding and selection programs at the University of Illinois, Iowa State University, University of Minnesota, and the USDA Forest Service for experiments established in 1995. We report results of analyses of variance and principal component analyses of tree diameters and estimated above-ground biomass that demonstrate significant genotype main effects and significant genotype × environment interactions. Maximum mean annual above-ground biomass increments have surpassed 16 Mg ha−1 y−1, exceeding previously reported yields of poplars grown under similar conditions in the north-central U.S. We also discuss the breeding and selection of poplars in general with specific attention to regional research needs. Key words: Populus, biomass, multi-trait selection, genotype, genotype × environment interaction

Hybrid poplar spacing/productivity relations in short rotation intensive culture plantations

It is often argued that in short rotation intensive culture plantations, biomass productivity increases with narrower tree spacings. Biomass productivity and tree spacing relations were studied for up to 16 years in northern Wisconsin hybrid poplar plantations. Maximum mean annual biomass increment was 12.8 Mg ha −1 yr −1 for Populus clone NE-41 planted at a l m 2 spacing. Productivity differences related to spacing were found to be minor. Productivity was influenced mainly by clone, irrigation and disease. A hypothesis is proposed that time to canopy closure is linearly related to time to maximum mean annual biomass productivity. Wide spacing and wide-crown trees that permit wider tree spacing allow longer rotations, which can lower costs and increase flexibility in management.

Soil Productivity Index: Predictions of Site Quality for White Spruce Plantations

AbstractVery few site‐quality models have incorporated the biological effects of multiple soil properties on optimum root growth. One such model that was originally developed for agronomic crops and has been used for naturally forested stands is the soil productivity index (PI) model. Our objectives for this study were to determine if the PI model could be used to estimate site quality for white spruce (Picea glauca [Moench] Voss) plantations and to compare the use of PI vs. site index in equations describing changes in aboveground biomass with age. The PI model includes an estimate of optimum vertical root distributions that is used to weight the relative effects of mineral‐soil characteristics (bulk density, pH, available water capacity, and aeration) on aboveground biomass. Relative topographic (percent slope) and climatic (precipitation and evaporation potential) information are also used in the model. Results indicated that site index and PI were not significantly correlated. However, PI was more highly correlated with aboveground stand biomass and mean annual biomass increment than was site index. Site index was more highly correlated with biomass estimates in older plantations (35–43 yr), whereas PI was more highly correlated to biomass estimates in younger plantations (19–34 yr). To further assess the relationships between estimates of biomass and site quality, adjusted for age, a Schumacher‐type equation was used. Comparable results were observed between stand‐biomass equations using PI vs. site index.

Variation in overstory biomass among glacial landforms and ecological land units in northwestern Lower Michigan

Variation in overstory biomass and mean annual biomass increment (MABI) of upland forest stands was studied at two spatial scales: glacial landforms (1: 250 000–1: 000 000) and ecological land units (1: 10 000–1: 80 000). Ecological land units were defined based on combinations of ground-flora vegetation, soil, and physiography. Biomass estimates were based on allometric regression equations developed in the Lake States area. Analyses of covariance were used to study the patterns of total biomass and biomass increment among glacial landforms and among ecological land units; stand age was used as the covariate. Overstory biomass ranged from 105 t/ha (MABI = 1.5 t ha−1 year−1) on glacial outwash landforms to 208 t/ha (MABI = 3.2 t ha−1 year−1) on morainal landforms; 37% of the total variation in biomass was accounted for by landform. Analysis at the ecological land unit scale accounted for a higher proportion of variation, approximately 60% of the total. Overstory biomass among ecological land units ranged from 85 t/ha (MABI = 1.3 t ha−1 year−1) for oak-dominated forests occurring on xeric sandy outwash sediments to almost 250 t/ha (MABI = 3.6 t ha−1 year−1) for sugar maple–red oak forests occurring in mesic morainal positions. Variation in biomass appeared to be strongly related to differences in species composition and variation in soil moisture availability, as evidenced by differences in soil texture and the presence or absence of deep-lying textural bands. Since ground-flora composition often reflects variation in soil properties, we examined the relationship between ground-flora composition and biomass increment. Detrended correspondence analysis was used to ordinate stands along a floristic gradient. Regression of stand ordination scores against MABI was significant (r2 = 0.65), indicating a relatively strong association between ground-flora composition and productivity. One advantage of understanding spatial variation in site productivity is that ecological land units can be readily mapped, whereas traditional estimates of site potential, such as site index, are point specific.

An analytical review of production rates and stemwood biomass of tropical forest plantations

Data on stemwood biomass and mean annual biomass increment ( MABI) for seven tropical tree plantation species were synthesized from the literature to evaluate species adaptibility and potential yields in different environments. Stemwood biomass ranged from < 1 to 712 t ha −1, and MABI ranged from about 1 to 30 t ha −1 year −1 in plantations of Pinus caribaea, Tectona grandis, Pinus patula, Gmelina arborea, Cupressus lusitanica, Eucalyptus grandis, and Albizia falcataria. Stemwood biomass and MABI varied with species, plantation age, and climate. Linear models best described the relationship between stemwood biomass and age of plantation, and the slopes of these equations ( MABIs) varied among species and among life zones for a given species. Significant relations were found between stemwood biomass and MABI and water availability (the ratio of temperature to precipitation, T/ P). In general, stemwood biomass and MABI decreased at high (arid) and low (very humid) T/ P ratios. Each tree species had an optimal T/ P at which its maximum stemwood biomass and MABI occurred. Other site factors, such as soil fertility, modified plantation response to climate.