Single-stemmed Trees Research Articles

WITHDRAWN: Multiple resprouting strategies coexist after fire in southeastern Brazil cerrado trees

Many trees of the Brazilian savannah have underground organs from which they resprout after a fire, although the relationship between the presence of these organs and the presence of underground resprouts (basal resprouts and root suckers) is unclear. Other relationships may also exist between the height of underground resprouts and the presence of live aerial biomass, multi-stemness and fire impact, tree age and the presence of underground resprouts, and epicormic bud distribution and fire impact. To test all these relationships, data from 367 mature cerrado trees subject to a single prescribed burn in southeastern Brazil were analysed. There was no clear relationship between the presence of underground organs and the presence of underground resprouts, although fire impact strongly influenced the presence of basal resprouts, with 90% of topkilled trees presenting basal resprouts, and this strong influence may have concealed a potential relationship between the presence of underground organs and resprouts. Underground resprouts were 45% taller when trees lacked live aerial biomass because more ground-level sunlight was available for these resprouts to grow. Single-stemmed trees had on average more basal resprouts than multi-stemmed trees, which concerned the translocation of carbohydrate reserves in multi-stemmed trees to maintain the fitness of multiple stems, while single-stemmed trees could store more reserves in their underground organs. However, multi-stemmed trees were more likely than single-stemmed trees to remain unburnt, an effect of less sunlight reaching the ground, suppressing grass cover. Trees >13 years resprouted basally less often since, as the trees were not burnt frequently, they developed deeper roots instead of investing in underground buds. Epicormic bud density was highest in medium fire impacts because a high fire impact led to topkill, while a low fire impact was insufficient to break epicormic bud dormancy. Moreover, the position of the lowest and highest epicormic buds was determined by epicormic bud density, suggesting that, at medium fire impacts, there was greater mobilisation of reserves along the tree stem to activate more epicormic buds.

Multi-stemming enhances tree survival and growth in Borneo’s logged forests

Multi-stemmed architecture is a common but overlooked tree growth form in tropical rainforests. Although multi-stemming is thought to be a key trait for tree persistence after disturbance, the role of multi-stemmed trees in post-disturbance demographic processes has been largely unexplored in logged rainforests. Here, we used decade-long measurements on nearly 14,000 tree stems to study post-logging growth and survival along a logging disturbance gradient in Malaysian Borneo. We found that multi-stemming enhanced tree persistence after logging. Along the entire disturbance gradient, multi-stemmed trees suffered significantly lower mortality than single-stemmed trees, and survival strongly increased with the number of stems. Small to medium-sized trees with multiple stems showed greater growth than similar-sized single-stemmed trees, with the difference increasing as the disturbance increased. Our findings demonstrate the significance of multi-stemmed architecture after logging in Borneo’s rainforests and highlight the need to consider the multi-stemmed growth form in forest inventories and models of post-disturbance forest dynamics.

A Trial of Fire and Ice: Assessment of Control Techniques forPyrus calleryanaInvasion of Grasslands in Southwestern Ohio, USA

<h3>ABSTRACT</h3> <i>Pyrus calleryana</i> (Callery pear) is an invasive plant that threatens ecosystems in the eastern United States. We investigated the efficacy of various control techniques on <i>P</i>. <i>calleryana</i> invasion in grasslands. Treatments were applied to (a) <i>P. calleryana</i> stems that had experienced mowing annually for several years and were sprouting (<i>n</i> = 100 stems; “trees-sprouting”) and (b) stems that had established ca. 10 years earlier, had never been cut, and were single-stemmed trees (<i>n</i> = 40 stems; “trees-intact”). In both experiments, existing stems were cut and randomly assigned one of the following treatments: cut only (control), burning, freezing, or herbicide, and in the trees-sprouting experiment there was also a negative control of monitoring existing sprouts. All trees in which the cut stumps were treated with herbicide were effectively killed, whereas stems in all other treatments, in both experiments, generated a vigorous sprout response. In the trees-sprouting experiment, there was a strong overall effect of treatments (RMANOVA; <i>p</i> &lt; 0.001) and prescribed fire created a statistically significant increase in sprout number in relationship to the negative control (<i>post-hoc</i> test; <i>p</i> = 0.036). In the trees-intact experiment, there was vigorous sprouting in response to all treatments other than herbicide. Stump freezing resulted in a delay in sprout response; however, all frozen stems eventually sprouted. The ability of this species to sprout vigorously, even after experiencing frequent and intense ecological disturbance, creates the potential for a fundamental alteration of old-field succession in habitats where this species is present.

Multi-Stemmed Habit in Trees Contributes Climate Resilience in Tropical Dry Forest

Understanding how environmental adaptations mediate plant and ecosystem responses becomes increasingly important under accelerating global environmental change. Multi-stemmed trees, for example, differ in form and function from single-stemmed trees and may possess physiological advantages that allow for persistence during stressful climatic events such as extended drought. Following the worst drought in Hawaii in a century, we examined patterns of stem abundance and turnover in a Hawaiian lowland dry forest (LDF) and a montane wet forest (MWF) to investigate how multi-stemmed trees might influence site persistence, and how stem abundance and turnover relate to key functional traits. We found stem abundance and multi-stemmed trees to be an important component for climate resilience within the LDF. The LDF had higher relative abundance of multi-stemmed trees, stem abundance, and mean stem abundance compared to a reference MWF. Within the LDF, multi-stemmed trees had higher relative stem abundance (i.e., percent composition of stems to the total number of stems in the LDF) and higher estimated aboveground carbon than single-stemmed trees. Stem abundance varied among species and tree size classes. Stem turnover (i.e., change in stem abundance between five-year censuses) varied among species and tree size classes and species mean stem turnover was correlated with mean species stem abundance per tree. At the plot level, stem abundance per tree is also a predictor of survival, though mortality did not differ between multiple- and single-stemmed trees. Lastly, species with higher mean stem abundance per tree tended to have traits associated with a higher light-saturated photosynthetic rate, suggesting greater productivity in periods with higher water supply. Identifying the traits that allow species and forest communities to persist in dry environments or respond to disturbance is useful for forecasting ecological climate resilience or potential for restoration in tropical dry forests.

A review of kowhai (Sophora spp.) and its potential for commercial forestry

Background: Demand for imported sawn timbers in New Zealand has increased over the last decade, reflecting the lack of New Zealand-grown, naturally durable timber in the domestic market. Therefore, a market opportunity exists for sustainably grown, naturally durable timbers in New Zealand for specialty applications. Kowhai (Sophora spp.) are New Zealand native tree species, known for their bright, yellow flowers and reported to produce coloured, naturally durable heartwood.Methods: Information on kowhai was collated from literature, focusing on their potential for commercial forestry. The taxonomic relationships, species descriptions, establishment, and growth rates of kowhai were examined, along with timber properties and historical uses, as well as medicinal applications. The review identified potential market opportunities for kowhai and key areas for further research.Results: Kowhai refers to eight different Sophora species that are endemic to New Zealand. Kowhai is easily established and the different species hybridise readily. While growth and form of kowhai varies with species, site, and management, examples of straight single-stemmed trees and annual diameter increments exceeding 20 mm have been found. Kowhai timber properties might be comparable to those of teak (Tectona grandis L.f.). Kowhai contains alkaloids, a class of compounds used in pharmaceutical applications. The species have been used for timber and traditional medicine by Maori in the past, while European settlers used kowhai for their durable and flexible timber.Conclusions: Kowhai could be established as a sustainable, domestic source of high-quality timber and substitute imported specialty timbers in New Zealand on account of their natural durability, strength, stiffness, colour, and density properties. The residues could support a secondary industry, as a source of alkaloids for pharmaceutical applications or natural dyes. Key areas that require further study include growth rates and silviculture, mechanical timber properties, machining/processing characteristics, natural durability and cytisine levels in kowhai, as well as the cultural, economic, and ecological framework required for a commercial kowhai forestry industry. Lack of literature on, and expertise in the use of native timbers in general are barriers to promoting native species for commercial forestry in New Zealand.

ПЛАТАН КЛЕНОЛИСТИЙ (PLATANUS ACERIFOLIA WILLD.) В УМОВАХ МІСТ СТЕПОВОЇ ЗОНИ УКРАЇНИ

For steppe cities, it is important to replenish the range with durable decorative species that grow quickly and form a three-dimensional crown. Such plants due to the shading of large areas create more comfortable living conditions for people in steppe cities. These species include London planetree (Platanus acerifolia Willd.), which sporadically began to be planted in some cities in the postwar period. The viability of P. acerifolia in the steppe is different. Since the biological peculiarities of this introduced species have been studied in various socio-economic problems in cities, we conducted a comparative analysis of the vital state and biometric parameters of P. acerifolia in the plantations of two cities of the steppe zone of Ukraine. We found out that P. acerifolia is widely used in landscaping of Kherson, while in Kryvyi Rih it is rare. In Kherson, the species is distributed near administrative buildings, schools, hospitals; it grows in parks, squares and yards of high-rise buildings, and in Kryvyi Rih only in one subdistrict and in the arboretum of the Kryvyi Rih Botanical Garden. The trees in Kherson are aged 38–60. The vital state is estimated as high and close to high – 77.8–96.3%. Older trees are 18.4–21.5 m of height and a maximum trunk diameter is 80.1–99.4 cm. Plants of all plantations in Kherson have dry branches, with a rate of 6.3–28.7%. In Kryvyi Rih, 28–42-year-old trees grow. In different plantations of P. acerifolia, the number of dry branches varies in the range of 0.3–44.5%, and the vital state – from 55.5 to 100% depending on the place of growth. The height of P. acerifolia trees is 6.2–20.3 m, and the trunk diameter is 12.2–68.7 cm. The study has proved that the differences in vital state and morphometric parameters of trees in the plantations of these cities depend on the age of trees, their planting density, lighting and other growing conditions. Trees in Kryvyi Rih are more significantly damaged by cold winds than in Kherson. &#x0D; The life form of P. acerifolia in the plantations of Kherson and Kryvyi Rih is almost everywhere a single-stemmed tree. This species is beginning to naturalize in the conditions of Kherson. Several plants of self-seeding origin were found during the research studies. Restoration of plants with young sprouts produced by stumps after cutting the plant trunks in Kherson was also noticed. The leaf apparatus of plants during the growing season is practically not damaged by diseases and pests and no slimy stains are formed on the leaves. &#x0D; We determined that P. acerifolia is a promising species for wider use in landscaping of the cities of the Black Sea coast and settlements of the Right-Bank Steppe, but in the latter case requires successful selection of exhibition sites for successful growth. These, first of all, should be cozy places protected from the effects of cold winds in winter and dry winds in spring and summer.

How do social status and tree architecture influence radial growth, wood density and drought response in spontaneously established oak forests?

During the past decades, a multitude of oak stands have spontaneously established across the pine-dominated landscapes of the French Landes de Gascogne. Yet their future performance under modern climate change is unknown. We show that coppiced, dominant trees are most prepared to cope with drought episodes, displaying higher basal area increment and lower sensitivity to extreme events. Forest stands dominated by pedunculate oak (Quercus robur L.) have spontaneously established across the pine-dominated landscapes of the French Landes de Gascogne. These oak stands are typically unmanaged and unsystematically coppiced, resulting in mixtures of single- and multi-stemmed (coppiced) trees. To determine the ability of spontaneous oak forest stands to face climate change–related hazards, by analysing differences in growth (tree-ring width and basal area increment—BAI), wood density and climate sensitivity depending on their tree architecture (single- vs multi-stemmed trees) and their social status in the forest. We exhaustively cored 15 oak stands (n = 657 trees). We compared stand characteristics and climate sensitivity between tree architectures considering two sampling designs, either all sampled trees (the exhaustive sampling) or those with a dominant status (dominant sampling). At the tree level, we used linear mixed effects models to compare wood density and growth between tree architectures and the trees’ social status within the canopy layer (dominant- vs non-dominant trees). Multi-stemmed trees exhibited higher wood density than single-stemmed trees for diameters > 30 cm. Dominant multi-stemmed trees showed lower sensitivity to extreme events (pointer years), higher BAI but lower annual growth rates than dominant single-stemmed trees. Dominant multi-stemmed trees are potentially the most prepared ones to cope with increasing soil water deficit following drought episodes, at least during the first 60 years of the life of the tree. The vulnerability to face harsher climate conditions for Q. robur stands can be misled when using a dominant sampling design.

Drones as a Tool for Monoculture Plantation Assessment in the Steepland Tropics

Smallholder tree plantations are expanding in the steepland tropics due to demand for timber and interest in ecosystem services, such as carbon storage. Financial mechanisms are developing to compensate vegetation carbon stores. However, measuring biomass—necessary for accessing carbon funds—at small scales is costly and time-intensive. Therefore, we test whether low-cost drones can accurately estimate height and biomass in monoculture plantations in the tropics. We used Ecosynth, a drone-based structure from motion technique, to build 3D vegetation models from drone photographs. These data were filtered to create a digital terrain model (DTM) and digital surface model (DSM). Two different canopy height models (CHMs) from the Ecosynth DSM were obtained by subtracting terrain elevations from the Ecosynth DTM and a LIDAR DTM. We compared height and biomass derived from these CHMs to field data. Both CHMs accurately predicted the height of all species combined; however, the CHM from the LiDAR DTM predicted heights and biomass on a per-species basis more accurately. Height and biomass estimates were strong for evergreen single-stemmed trees, and unreliable for small leaf-off species during the dry season. This study demonstrates that drones can estimate plantation biomass for select species when used with an accurate DTM.

Adaptive strategy of tree communities on an environmental harshness hinterland inselberg in Minas Gerais, Brazil

Trees and other plants growing in stressful environments can display adaptive strategies such as sprouting, which is considered to be a functional trait for the persistence niche. For example, inselbergs are rocky outcrops that impose limitations on many plant forms through selective pressure to adapt to these environments. The present research tested the hypotheses that environmental harshness enhances sprouting, and that multi-stemmed trees have different persistence dynamics compared with single-stemmed trees. We sampled vegetation in 2006 and 2011 across a soil depth gradient in three areas: riparian forest, inselbergs and a corridor between the first two areas. Trees with a diameter at the breast height (dbh) ≥5 cm were sampled, and sprouts were counted. Results showed that the inselberg had more sprouted individuals and a larger amount of sprouts than the other areas. Thus, sprouting as a survival strategy was efficient in dealing with the environmental harshness and may be considered an adaptive strategy of trees to enable them to persist in such environments. The dynamic of multi-stemmed trees differed from single-stemmed ones, and the inselberg was distinct from the other areas. Over the 5 years of the present study, sprouting proved to be a strategy of persistence in this habitat, a finding that is in accordance with our hypothesis. Factors contributing to the environmental harshness, such as soil depth, may be the cause of sprouting in trees.

Above-Ground Biomass, Nutrients and Carbon in &amp;lt;i&amp;gt;Aegiceras corniculatum&amp;lt;/i&amp;gt; of the Sundarbans

Aegiceras corniculatum grows as single-stemmed evergreen shrub or small tree in the Sundarbans mangrove forest of Bangladesh. The objectives of this study were to derive the allometric models for estimating above-ground biomass, nutrients (N, P and K) and carbon stock in A. corniclatum. A total of 8 linear models (y = aX + b, , y = aLogX + b, Logy = aX + b, Logy = aLogX + b, y = alnX + b, Lny = aX + b and Lny = alnX + b) with 64 regression equations were tested to derive the allometric model for biomass of each plant part; and nutrients and carbon stock in total aboveground biomass. The best fit allometric models were selected by considering the values of R2, CV, Rmse, MSerror, Sa, Sb, F value, AICc and Furnival Index. The selected allometric models were Logbiomass = 0.76LogDBH2 - 1.39; Biomass = 0.07DBH2 - 0.49; Logbiomass = 1.04LogDBH2 - 1.80; Logbiomass = 1.04LogDBH2 - 0.99; = 0.48DBH - 0.13 for leaves, branches, bark, stem without bark and total above-ground biomass respectively. The selected allometric models for Nitrogen, Phosphorous, Potassium and Carbon stock in total above-ground biomass were = 0.67DBH + 0.11; = 0.94DBH + 0.08; = 1.06DBH - 0.18; = 0.33DBH - 0.09 respectively.

Genetic and morphological analysis of multi-stemmed plants of tuart (Eucalyptus gomphocephala)

The tuart–banksia woodlands of the Swan Coastal Plain in Western Australia are characteristic vegetation communities of this coastal region, and Eucalyptus gomphocephala DC. (Myrtaceae; tuart) is an iconic tree of these communities. The species primarily occurs as a tall single-stemmed tree, but at the northern end of the distribution, it also occurs in a multi-stemmed form. Growth habit is frequently used as a taxonomic character in eucalypts, with many complexes having tree and mallee forms, although the genetic characterisation of growth habit in eucalypts has been limited. We investigated the genetic and morphological differentiation among populations of tree and multi-stemmed forms of tuart at the northern end of its distribution. Although the populations showed moderate levels of genetic diversity on the basis of microsatellite markers, as might be expected from populations on the periphery of the distribution, there was no evidence of genetic differentiation associated with the tree and multi-stemmed forms. Morphometric analysis showed some differences in the size of buds and fruits among the populations. Our analysis is consistent with environmentally induced variation in tuart in near-coastal populations where plants grow on poor soils and form may be affected by wind and salt exposure. This result adds to other evidence from pines and Nothofagus of environmental rather than genetic influences on growth form, particularly in stressful environments.

Variability in allometric relationships for temperate woodland Eucalyptus trees

Essential to effective vegetation management and habitat conservation is an understanding of tree and stand structure. However, such data for Australian Eucalyptus woodlands come mostly from forestry research and tend to be restricted to production forest types, and merchantable stems and species. We aimed to improve understanding of allometric relationships and stand dynamics for temperate Eucalyptus from critically endangered temperate woodlands. We explored relationships among tree height, diameter at breast height (DBH), crown width, crown senescence, and vegetation density. We measured 3748 naturally-occurring trees on 105 one-hectare sites in remnant vegetation in an agricultural landscape in semi-arid eastern Australia. Four species accounted for 94% of trees measured: Eucalyptus camaldulensis Dehnh. (river red gum), E. melliodora A.Cunn. ex Schauer (yellow box), E. microcarpa Maiden (grey box) and E. populnea F.Muell. subsp. bimbil L.A.S.Johnson & K.D.Hill (poplar box). Six Eucalyptus species were present in relatively low numbers. At about 15cm DBH, growth changed from being directed primarily at height gain to increasing relative crown width. Trees with DBH⩾15cm showed large and increasing variation in shape with increasing DBH, and tree dimensions varied among species. For a given DBH, yellow box were taller with relatively narrow crowns than poplar box, and river red gum and grey box intermediate to these two species. Human manipulation of the agricultural landscapes has impacted on these allometric relationships. Past attempts by people to kill trees has resulted in frequent coppicing, with up to 13 trunks. Up to 50% of trees of each species (mean 29%) had multiple stems and multi-stemmed trees had relatively broader crowns than single-stemmed trees. Similarly, decreasing vegetation density by tree removal generally resulted in shorter trees with wider canopies for any DBH. Progression through crown development and senescence was similar among species except that it occurred at different trunk sizes for different species. The variability of allometric relationships within temperate Eucalyptus species, combined with their variable growth rates, makes it difficult to accurately predict outcomes of current land management decisions in terms of vegetation structure and biological habitat attributes.

Treeline advances along the Urals mountain range - driven by improved winter conditions?

High-altitude treelines are temperature-limited vegetation boundaries, but little quantitative evidence exists about the impact of climate change on treelines in untouched areas of Russia. Here, we estimated how forest-tundra ecotones have changed during the last century along the Ural mountains. In the South, North, Sub-Polar, and Polar Urals, we compared 450 historical and recent photographs and determined the ages of 11,100 trees along 16 altitudinal gradients. In these four regions, boundaries of open and closed forests (crown covers above 20% and 40%) expanded upwards by 4 to 8 m in altitude per decade. Results strongly suggest that snow was an important driver for these forest advances: (i) Winter precipitation has increased substantially throughout the Urals (~7 mm decade(-1) ), which corresponds to almost a doubling in the Polar Urals, while summer temperatures have only changed slightly (~0.05°C decade(-1) ). (ii) There was a positive correlation between canopy cover, snow height and soil temperatures, suggesting that an increasing canopy cover promotes snow accumulation and, hence, a more favorable microclimate. (iii) Tree age analysis showed that forest expansion mainly began around the year 1900 on concave wind-sheltered slopes with thick snow covers, while it started in the 1950s and 1970s on slopes with shallower snow covers. (iv) During the 20th century, dominant growth forms of trees have changed from multistemmed trees, resulting from harsh winter conditions, to single-stemmed trees. While 87%, 31%, and 93% of stems appearing before 1950 were from multistemmed trees in the South, North and Polar Urals, more than 95% of the younger trees had a single stem. Currently, there is a high density of seedlings and saplings in the forest-tundra ecotone, indicating that forest expansion is ongoing and that alpine tundra vegetation will disappear from most mountains of the South and North Urals where treeline is already close to the highest peaks.

Allometric relationships in coppice biomass production for two North American willows (Salix spp.) across three different sites

Biomass yield and component coppice growth traits were assessed for two native North American willow species, Salix discolor (DIS) and Salix eriocephala (ERI), established together in clonally replicated common garden field tests on three sites of differing quality but similar climates. These willows are widely distributed across eastern and central Canada and were selected for use in biomass production plantations. There was no species effect on the average stem length–diameter relationship, but there was a strong site effect. Increased number of stems within a plant decreases average stem diameter but not average stem length. Yield is positively related to site quality and number of stems per plant but also to the interaction between species and number of stems per plant. Allometric relationships between stem basal diameter, stem length, number of stems per plant, and biomass yield (tha−1) clearly reflected site quality differences and could be used in the same way that stem height at a specific age has been used for single stemmed trees to define site quality (site index) in forest timber production. Plant stem length and basal stem diameter measurements on up to 20 stems per plant indicated that measurements based on the average of the three longest stems per plant had the strongest relationship to biomass yield (R2=0.813) and that the average stem diameter of the three largest stems had the strongest relationship to biomass yield (R2=0.781).

PAPAYA INDUSTRY IN KENYA: PRODUCTION, CONSUMPTION AND OUTLOOK

Papaya is an important fruit crop of Kenya for both local and export markets. The plant is medium sized with a potential to produce fruits throughout the year. The ripe fruits, which are very rich in vitamins A and C, are popularly used for dessert or processed into jam or wine. Due to its habit as a single stemmed tree it can be economically produced in any size of land from kitchen gardens to large plantations. This paper is based on country wide surveys and validated statistics of papaya production from Horticultural Crops Development Authority (HCDA), Kenya. The major commercial papaya farms in this country are located in the eastern and coastal areas at altitudes ranging from 0 to 1500 m above sea level. In 2006, the total volume of fruits produced in this country was about 2.5 million metric tons (MT), of which papaya contributed 229,950 MT as the 4th most important fruit crop. In the same year, 100% of all the papaya fruits produced were consumed locally. However, recent statistics of 2008 and 2009 reveal that small quantities of papaya were exported to UK and France. A country-wide survey reported the major constraints to papaya production in Kenya as lack of improved cultivars, unreliable methods of picking the required sex of seedlings at planting time, insufficient water, devastating pests and diseases among others. It is possible that although the papaya industry in Kenya was devastated in the last few decades by major diseases like Papaya ringspot virus (PRSV), there is a reawakening that cannot be ignored. Some immediate and long term remedies need to be sought to revamp this crop to its rightful position in contributing meaningfully to the economic growth of Kenya.

Hollow occurrence and abundance varies with tree characteristics and among species in temperate woodlandEucalyptus

Tree hollows are a critical but diminishing resource for a wide range of fauna around the world. Conservation of these fauna depends on sustainable management of tree species that produce the hollows on which they depend. This study addressed the need for empirical data about intraspecific and interspecific variation in hollow occurrence and abundance in woodland trees in Australia. We measured and performed hollow surveys on 1817 trees of seven species of woodland Eucalyptus in central-western New South Wales, Australia. Trees were surveyed at 51 one-hectare sites and about 30% of trees surveyed had multiple stems. Generalized linear mixed models that accounted for nestedness of stems within trees and trees within sites detected a significant amount of variation in hollow occurrence and abundance. Models for individual tree stems of live trees showed hollow probability and abundance increased with diameter at breast height (DBH) and with increasing senescence (form). Stems of Eucalyptus microcarpa Maiden had a higher probability of having hollows than similar DBH stems of Eucalyptus camaldulensis Dehnh., Eucalyptus melliodora A.Cunn. ex Schauer or Eucalyptus populnea ssp. bimbil L.A.S.Johnson & K.D.Hill. Dead stems in live trees were more likely to have hollows than live stems of similar DBH. Each stem in a multi-stemmed tree had a lower probability of hollow occurrence and lower abundance of hollows than single-stemmed trees of similar DBH. For stems of dead trees, hollow occurrence and abundance increased with DBH and differed depending on stage of senescence. A comparison of our data with other studies indicates regional variation of hollow abundances within tree species.

A monograph of the genus Orania (Arecaceae: Oranieae)

Orania Zipp. (Oranieae: Arecoideae: Arecaceae) is a genus of solitary, single stemmed tree palms consisting of 28 species, of which 11 species are new and described for the first time in this paper. The genus has an interesting disjunct distribution, with 25 species found in Malesia and three species confined to Madagascar. The 11 new species, O. bakeri A. P. Keim & J. Dransf., O. dafonsoroensis A. P. Keim & J. Dransf., O. deflexa A. P. Keim & J. Dransf., O. ferruginea A. P. Keim & J. Dransf., O. grandiflora A. P. Keim & J. Dransf., O. littoralis A. P. Keim & J. Dransf., O. longistaminodia A. P. Keim & J. Dransf., O. subdisticha A. P. Keim & J. Dransf., O. tabubilensis A. P. Keim & J. Dransf., O. timikae A. P. Keim & J. Dransf. and O. zonae A. P. Keim & J. Dransf. are found in New Guinea. A determination key is produced and detailed descriptions provided for all taxa.

Reconstructing the development of two Ozark chinquapin (Castanea ozarkensis) stands in the pre-blight forests of northwest Arkansas1

Abstract A survey of Ozark chinquapin in northwest Arkansas showed the tree to be widespread but uncommon, locally concentrated on sandstone benches and upper slopes in karst terrain. The remains of pre-blight chinquapin trees were mapped and measured on two 200 ha sites in Benton and Washington counties. Tree density was estimated at about 1 tree per ha, consistent with published upland witness tree surveys. 108 relatively intact logs were documented, representing about half of the total large chinquapins estimated to have grown on the two sites. Most of these grew as single-stemmed trees up to 20 m in height and 40 cm in diameter. The predominance of single-stemmed trees may indicate the relative absence of fire in pre-blight forests. The lack of subsequent sprouts from the base of large trees and the abundance of living sprout clones not associated with old trees indicates most sprouts are old seedlings. Tree rings were used to reconstruct stand history on six 20 × 60 m plots. Release of adjacent trees...

Interactive Data Visualisation for Animating Urban Tree Growth

Given a set of global (natural) tree parameters measured for many specimens of different ages for a range of species, we have developed a tool that visualizes these parameters over time. The parameters include measures of tree dimensions such as heights, diameters, and crown shape, and measures of costs and benefits for growing the tree. We visualize the tree dimensions by animating tree growth over time, while the accumulated costs and benefits are visualized using animated bar charts.As our vizualisation system is targeted towards application for city planning purposes, the tree growth animation should produce trees of an appearance close to nature while being on conformation with the measured parameters. We have developed a system for single-stemmed trees that creates branching structures for different species, where the local bifurcation and elongation parameters are derived from the globally measured parameters. In addition to the measured data, we use biological knowledge to model general tree growth and to adjust to specific species. We have implemented several computationally fast methods to improve the natural growth and appearance of the trees, where the main task was to keep the tree growth modelling and the tree rendering interactive. Thus, the user can interact with the 3D visualization system during the tree growth modelling and rendering process. We have applied our visualization techniques to the growth and the temporal costs/benefits changes of nine single-stemmed tree species.

Empirical estimate of the reliability of the use of the Point-Centred Quarter Method (PCQM): Solutions to ambiguous field situations and description of the PCQM+ protocol

This paper reports problems associated to the use of the Point-Centred Quarter Method (PCQM), as well as their possible solutions. Problematic settings in the application of the PCQM are amongst others due to the presence of multiple-stemmed trees (MST), to ambiguous settings for measuring the sampling point to nearest tree distance or the tree diameter, both of which may result in erroneous estimation of silvimetric variables and parameters. The analysis is based on a database of effective individual tree records including distances, diameters, and heights measured in the field in a Sri Lankan mangrove forest between 1997 and 2002, and randomly compiles a series of records that were used as PCQM sampling points. Various structural forest parameters were calculated, with particular emphasis on density and basal area. After proving that multiple- and single-stemmed trees have different silvimetric characteristics, we adopted an empirical approach to demonstrate the classical PCQM protocol applied to MST generates significantly different densities (overestimation) and basal areas (underestimation) depending on which stems are considered for measurement, and we suggest an adapted PCQM+ protocol (measurement of central stem instead of nearest stem). We test both protocols in two mangrove assemblages (one composed of Excoecaria agallocha only, and an Excoecaria agallocha/ Rhizophora apiculata mixed forest) with MST proportions varying between 0% and 100%, at 5% intervals. The results indicated that the classical PCQM protocol generates density and basal area results that are strongly correlated with the MST proportion in the assemblage ( p < 0.001), whereas the PCQM+ protocol shows a robustness with no such correlations for density. For basal area the results of the PCQM+ protocol showed a weak correlation with the MST proportion, and regression-ANCOVA results indicated that they were significantly different from those of the highly sensitive PCQM protocol ( p < 0.001). Finally, we conclude by writing out the entire PCQM+ protocol, elaborating on the solutions to other common problems related to ambiguous settings for the consideration of stems or the measurement of their diameter (aerial roots, split trunks, dwarf growth, horizontally developing stems, boundary of an individual in MST, selectively cut trees or tree parts, very sparse assemblages, use of PCQM for remote sensing ground-truth), and by nevertheless highlighting the potential of the PCQM/PCQM+ approach. Although we used a mangrove forest data set, the PCQ-Method and our suggestions are widely applicable to other forest types. In addition, this paper is accompanied by the first interface that automatically processes standard PCQM-related data (regardless of forest type) to generate common silvimetric or forestry parameters elaborated in this paper, and it is freely available in Appendix C and from http://www.vub.ac.be/APNA/staff/FDG/pub/pub.html.