Tree Saplings Research Articles

Simulating boreal forest dynamics from perspectives of ecophysiology, resource availability, and climate change

AbstractBoreal forests are under strong influences from climate change, and alterations in forest dynamics will have significant impacts on global climate‐biosphere feedback as well as local to regional conservation and resource management. To understand the mechanisms of forest dynamics and to assess the fate of boreal forests, simulation studies should be based on plant ecophysiological responses onto environmental conditions. In central Canadian boreal forests, local geomorphology created by past glacial activities often generates a mosaic of very distinctive forest types. On sandy hilltop of a glacial till, due to limitations in moisture availability and short fire return intervals, drought‐tolerant and fire‐adapted jack pine usually becomes the dominant species. On mesic and nutrient‐rich slopes, fast‐growing and resource‐demanding trembling aspen forms mixed forests with coniferous species. In bottomland, black spruce, slowly growing but tolerant species, is often the only species that can survive to the adult stage. These three very distinctive forest types often occur within a scale of 10 m. Simulation models of boreal forests should be able to reproduce this heterogeneity in forest structure and composition as an emergent property of plant ecophysiological responses to varying environmental properties. In this study, a process‐based forest dynamics model, ecosystem demography model version 1.0, is used to mechanically reproduce the landscape heterogeneity due to edaphic variations. First, boreal tree species of northern Manitoba, Canada, are parameterized according to field observations, and, to explicitly capture interactions among tree saplings, allometric equations based on diameter at height of 0.15 m, instead of the conventional breast height of 1.37 m, is parameterized. Then, soil moisture regime and nutrient concentrations are statistically incorporated from a dataset. The resultant simulation successfully reproduces the distinctive forest dynamics influenced by the edaphic heterogeneity. The sequences of succession and the trajectories of forest development are generally consistent with the field observations. The differences in resource availability are the essential control on equilibrium values of total forest leaf area index. Next, to show the effect of anthropogenic atmospheric changes, changes in temperature and CO2 concentrations are studied by a set of factorial experiments. The magnitude of CO2 fertilization is largely affected by soil fertility. The temperature rise will increase the length of growing season, but can have a negative impact on forest growth by increasing aridity and autotrophic respiration. Overall, the boreal forest responses to climate change are complex due to the inherent edaphic variations and ecophysiological responses.

Introduced deer reduce native plant cover and facilitate invasion of non-native tree species: evidence for invasional meltdown

Invasive species are a major threat to native communities and ecosystems worldwide. One factor frequently invoked to explain the invasiveness of exotic species is their release in the new habitat from control by natural enemies (enemy-release hypothesis). More recently, interactions between exotic species have been proposed as a potential mechanism to facilitate invasions (invasional melt- down hypothesis). We studied the effects of intro- duced deer on native plant communities and exotic plant species on an island in Patagonia, Argentina using five 400 m 2 exclosures paired with control areas in an Austrocedrus chilensis native forest stand. We hypothesized that introduced deer modify native understory composition and abundance and facilitate invasion of introduced tree species that have been widely planted in the region. After 4 years of deer exclusion, native Austrocedrus and exotic Pseudots- uga menziesii tree sapling abundances are not differ- ent inside and outside exclosures. However, deer browsing has strongly inhibited growth of native tree saplings (relative height growth is 77% lower with deer present), while exotic tree sapling growth is less affected (relative height growth is 3.3% lower). Deer significantly change abundance and composition of native understory plants. Cover of native plants in exclosures increased while cover in controls remained constant. Understory composition in exclosures after only 4 years differs greatly from that in controls, mainly owing to the abundance of highly-browsed native species. This study shows that introduced deer can aid the invasion of non-native tree species through negatively affecting native plant species.

Individual growing conditions that affect diameter increment of tree saplings after selection harvesting in a mixed forest in northern Japan

We analyzed temporal patterns in diameter growth of saplings following selection harvesting in an uneven-aged mixed stand dominated by Abies sachalinensis, Acer mono, Quercus crispula, and Betula ermanii in Hokkaido, northern Japan. We examined interspecific differences in growth responses to local growing conditions including harvesting intensity, crowding, stem size, and past duration of the small growth period. Consistent with expectations based on shade tolerance of the species, the age at which the individual reached a diameter at breast height (DBH) of 12.5 cm was highest for A. sachalinensis and lowest for B. ermanii. The interspecific growth differences between saplings that had or had not experienced local harvesting increased gradually for A. sachalinensis and B. ermanii, but peaked at around 4–6 years after harvesting for Q. crispula. Generalized linear mixed model analysis clearly suggested that individual growth conditions required to enhance diameter growth of saplings differed considerably among species. For Q. crispula and B. ermanii, local harvesting intensity was most strongly and positively associated with diameter growth rate, whereas for A. sachalinensis and A. mono, stem size had the strongest negative effect. Abies sachalinensis saplings responded more to surrounding harvesting when they were relatively small, whereas A. mono showed a weak opposite response. The duration of the small growth period before harvesting had negative effect for A. sachalinensis, but not for the other species. Our study indicated that the influence of selection harvesting on growth of shade-tolerant species depends upon pre- and post-harvest growing conditions.

Reduction of herbivore density as a tool for reduction of herbivore browsing on palatable tree species

Browsing of overabundant free-living herbivores often limits the natural as well as artificial regeneration of forest in Central-European Mountains. The aim of the study was to assess the efficiency of the extensive reductions of herbivore populations for protection of forest regeneration in preferred areas. We analysed the relationship between the intensity of shoot browsing and relative density of herbivores in viewpoint of natural regeneration of secondary mountain spruce stands with low proportion of broadleaved trees in Kralický Sněžnik Reserve (Czech Republic). The distribution of seasonally migrating herbivores was established by counting faecal pellet groups (standing crop method) in growing season. The intensity of browsing of spruce, beech and rowan was assessed using the proportion of browsed shoots on individual tree sapling. Density of red deer was re-counted from the number of pellet groups and it was 15–56 individual/km2. The intensity of spruce browsing was low in the whole area in all seasons. In general, the intensity of rowan and beech shoot browsing was high in the whole area. There were no correlations between deer density and browsing intensity of rowan (browsing was severe in all plots). We conclude that the natural regeneration of attractive trees and shrubs is nearly impossible in habitats where proportion of these food items is too small, even when the density of herbivores is low. Reduction of herbivores density is useful for protecting spruce and other tree species with low preference by herbivores. Forest managers should take into account the high palatability of deciduous tree species and distribution of herbivores on localities. Preference of localities is often based on grasses in the food supply. Regeneration of highly palatable tree species requires both low density of herbivores and sufficient protection of saplings.

Do ungulates preferentially feed in forest gaps in European temperate forest?

Ungulate populations across Europe have been strongly increasing over the past decades. Simultaneously with this increase, concerns about the impact of ungulates on forest systems, and forestry specifically, are increasing. In this study we discuss how the common forestry practice of creating clear cuts in relatively homogenous, managed forests may increase the potential impact of ungulates. Growth of trees in full light conditions is generally higher, but due to higher photosynthetic activity they tend to have higher C:N ratio in their leaves thus decreasing food quality. Next to that, biomass of herbaceous vegetation is enhanced in clear cuts. These changes likely affect foraging decisions of ungulates and it has been suggested that ungulates forage in forest gaps rather than in closed forest. We tested this hypothesis by using an experimental approach. The experiment was conducted in the Białowieża Primeval Forest in Poland, where a full assemblage of native large herbivores occurs. Six plots (6 m × 6 m) inside small clear cuts were compared to six control plots in adjacent closed forest. To exclude the effect of differences in number and species composition of available tree saplings, equal numbers of trees saplings of five species were planted at each plot. Ungulate visitation frequency and visitation time were measured by means of three methods: track plots, camera- and video trapping, and pellet counts. Visitation frequency of all ungulates combined (European bison, red deer, roe deer, moose and wild boar) was almost twice as high inside forest gaps compared to closed forest. Also cumulative visitation time by all ungulates tended to be higher inside forest gaps. Red deer showed the strongest preference for gaps, and duration of single visits was almost seven times longer for forest gaps than in closed forest. The observed preferential foraging of ungulates in forest gaps leads to an uneven distribution of their browsing behaviour. Hence, the creation of forest gaps by clear cutting followed by reforestation provides attractive foraging patches for ungulates potentially leading to high damage. In this way, forestry practices may enhance damage of ungulates to plantations especially when due to management the surrounding forest has a low carrying capacity for ungulates. We suggest that there is much to gain if management approaches would focus at influencing foraging behaviour of ungulates and reduce their concentration in forest gaps, rather than purely focusing on population control.

The Effects of Cyclone Hudah on the Forest of Masoala Peninsula, Madagascar

Cyclones regularly impact the east coast of Madagascar but almost nothing is known about their effects on Malagasy ecosystems. On 2 April 2000 the powerful winds of Cyclone Hudah struck the humid forests in the northern part of Masoala Peninsula. An analysis of satellite images revealed that 3 % of the forest here was severely damaged or 22 % when just the forest of the northeast was considered. In 2001 the vegetation in this area was studied using fifteen 0.1 ha plots located in differently impacted sites. The cyclone had caused tree death (up to 53 % of the trunks within a plot); a reduction in trunk basal area (to 64 %); uprooting (to 46 %); snapping of trunks (to 51 %); reduction of crown volume (to mean of 83 %); an increase in herbs, liana and woody pioneer species and decrease in saplings of primary forest species; an increase in vegetation in the “shrub” layer and decrease in vegetation in the “canopy” layer. Among a sample of 340 trees killed by the cyclone, 39 % were uprooted, 37 % snapped, and 24 % were still standing. Mortality was relatively low for trees with either small or large trunk diameter compared to trees with intermediate size. In 2003 the plots were re - examined. Six had been impacted by human activities (fire or timber exploitation). A comparison between the vegetation in 2001 and 2003 in 6 plots that had been moderately or seriously impacted by Cyclone Hudah but not impacted by human activity revealed a further decrease in trunk density, an increase in the frequency of herbs and woody pioneers, a decrease in the frequency of liana and saplings of primary forest trees in the “shrub layer”, and an increase of vegetation in the “shrub layer” but decrease of vegetation in the “canopy layer”. The lack of recovery of this vegetation towards its pre - cyclone state may be explained by the impact of Cyclone Ihary, in 2002. Recovery may yet occur provided the vegetation is not impacted by human activities, particularly burning, that can derail this process. It is recommended that following cyclones conservation managers prioritize fire control.

Reclamation of tannery polluted soil through phytoremediation.

The huge volume of sludge emanating from the tannery effluent treatment plants poses a serious environmental problem. Phytoremediation is an emerging technology in which the plants are employed to reclamate the contaminated soil strewn with heavy metals (metalloids) and toxic compounds. This work focuses the impact of application of tannery sludge on biochemical properties of 6 months old tree saplings of Azadirachta indica A. Juss. (Neem), Melia azedarach Linn. (Wild Neem) and Leucaena leucocephala (Lam) de Wit (Subabool) raised over the tannery sludge in an attempt to use these plants for phytoremediation. The plants raised over the garden soil served as the control. The porosity and water holding capacity of the tannery sludge were higher. The plant growth supporting elements such as Ca, total N2, NO3 and Mg were higher in the sludge. The plants raised over the sludge were found to be dark green with increased morphometric parameters. Electrophoretic profile revealed amplification of a few polypeptides (100, 105, 49 and 55 KDa). The levels of biomolecules and the CO2 absorption increased in 6 months old plants. There was a significant uptake and transport of chromium in all the three tree species suggesting that these plants could be employed in phytoremediation of soils contaminated with heavy metals.

Strong impacts of belowground tree inputs on soil nematode trophic composition

Trees have a key role in determining the composition of soil biota via both above and belowground resource-based mechanisms, and by altering abiotic conditions. We conducted an outdoor mesocosm experiment to investigate the relative impact of above and belowground tree inputs on soil nematode trophic composition, and examine whether tree-driven impacts differed between contrasting species (birch and pine). For both species, we created a factorial design of litter addition and root presence treatments. The litter addition treatment was equivalent to natural levels of litterfall; tree saplings were planted in mesocosms for the root presence treatment and an unplanted control treatment was established that had no litter or root inputs. Litter addition had a limited impact on soil nematode community composition: it primarily decreased omnivore and predatory nematode abundance in birch but had few other effects on the nematode community. By contrast, root presence markedly altered nematode community composition through changes in a range of trophic groups. For both birch and pine, there were significant increases in total, fungivore and predatory nematode abundance in root presence treatments, and furthermore, total and fungivore abundances were positively related to root biomass. Root presence of these contrasting tree species also had a distinctive impact on some specific nematode trophic groups; pine roots promoted bacterivore abundance while birch roots promoted root-hair feeding nematode abundance. These findings suggest strong bottom-up effects of belowground tree inputs, and indicate that particular components of the nematode community may be affected differently by resource quantity and quality. Consequently, we suggest that, in the short-term, belowground rather than aboveground tree inputs have a strong impact on soil food web structure and complexity.

Sapling herbivory, invertebrate herbivores and predators across a natural tree diversity gradient in Germany’s largest connected deciduous forest

Tree species-rich forests are hypothesised to be less susceptible to insect herbivores, but so far herbivory–diversity relationships have rarely been tested for tree saplings, and no such study has been published for deciduous forests in Central Europe. We expected that diverse tree communities reduce the probability of detection of host plants and increase abundance of predators, thereby reducing herbivory. We examined levels of herbivory suffered by beech (Fagus sylvatica L.) and maple saplings (Acer pseudoplatanus L. and Acer platanoides L.) across a tree species diversity gradient within Germany’s largest remaining deciduous forest area, and investigated whether simple beech or mixed stands were less prone to damage caused by herbivorous insects. Leaf area loss and the frequency of galls and mines were recorded for 1,040 saplings (>13,000 leaves) in June and August 2006. In addition, relative abundance of predators was assessed to test for potential top-down control. Leaf area loss was generally higher in the two species of maple compared to beech saplings, while only beech showed a decline in damage caused by leaf-chewing herbivores across the tree diversity gradient. No significant patterns were found for galls and mines. Relative abundance of predators on beech showed a seasonal response and increased on species-rich plots in June, suggesting higher biological control. We conclude that, in temperate deciduous forests, herbivory–tree diversity relationships are significant, but are tree species-dependent with bottom-up and top-down control as possible mechanisms. In contrast to maple, beech profits from growing in a neighbourhood of higher tree richness, which implies that species identity effects may be of greater importance than tree diversity effects per se. Hence, herbivory on beech appeared to be mediated bottom-up by resource concentration in the sampled forest stands, as well as regulated top-down through biocontrol by natural enemies.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-009-1304-2) contains supplementary material, which is available to authorised users.

An assessment of the benefits and limitations of the shamba agroforestry system in Kenya and of management and policy requirements for its successful and sustainable reintroduction

The shamba system involves farmers tending tree saplings on state-owned forest land in return for being permitted to intercrop perennial food crops until canopy closure. At one time the system was used throughout all state-owned forest lands in Kenya, accounting for a large proportion of some 160,000 ha. The system should theoretically be mutually beneficial to both local people and the government. However the system has had a chequered past in Kenya due to widespread malpractice and associated environmental degradation. It was last banned in 2003 but in early 2008 field trials were initiated for its reintroduction. This study aimed to: assess the benefits and limitations of the shamba system in Kenya; assess the main influences on the extent to which the limitations and benefits are realised and; consider the management and policy requirements for the system’s successful and sustainable operation. Information was obtained from 133 questionnaires using mainly open ended questions and six participatory workshops carried out in forest-adjacent communities on the western slopes of Mount Kenya in Nyeri district. In addition interviews were conducted with key informants from communities and organisations. There was strong desire amongst local people for the system’s reintroduction given that it had provided significant food, income and employment. Local perceptions of the failings of the system included firstly mismanagement by government or forest authorities and secondly abuse of the system by shamba farmers and outsiders. Improvements local people considered necessary for the shamba system to work included more accountability and transparency in administration and better rules with respect to plot allocation and stewardship. Ninety-seven percent of respondents said they would like to be more involved in management of the forest and 80% that they were willing to pay for the use of a plot. The study concludes that the structural framework laid down by the 2005 Forests Act, which includes provision for the reimplementation of the shamba system under the new plantation establishment and livelihood improvement scheme (PELIS) [It should be noted that whilst the shamba system was re-branded in 2008 under the acronym PELIS, for the sake of simplicity the authors continue to refer to the ‘shamba system’ and ‘shamba farmers’ throughout this paper.], is weakened because insufficient power is likely to be devolved to local people, casting them merely as ‘forest users’ and the shamba system as a ‘forest user right’. In so doing the system’s potential to both facilitate and embody the participation of local people in forest management is limited and the long-term sustainability of the new system is questionable. Suggested instruments to address this include some degree of sharing of profits from forest timber, performance related guarantees for farmers to gain a new plot and use of joint committees consisting of local people and the forest authorities for long term management of forests.

Composition and Structure of Bottomland Forest Vegetation at the Tiak Research Natural Area, McCurtain County, Oklahoma

Although southeastern Oklahoma has substantial areas of bottomland forest, few studies exist of this vegetation type. We analyzed forest community structure at the Tiak Research Natural Area of the Ouachita National Forest on the Upper Gulf Coastal Plain. Vegetation data were collected from 24 12m x 8m macroplots. Percent cover data were recorded for ferns, fern-allies, and herbaceous angiosperms. Tree sapling and shrub species were recorded in diameter classes, and numbers of stems in estimated height classes were recorded for midlevel and canopy trees. One hundred fifty-two taxa of woody and herbaceous plants were encountered. Toxicodendron radicans and Arundinaria gigantea were the common understory species. Acer rubrum, A. saccharum, Carpinus caroliniana, Carya alba, C. texana, Cornus florida, Fraxinus americana, Liquidambar styraciflua, and Nyssa sylvatica were common as mid-level species. Quercus lyrata and Q. phellos were the most common canopy layer trees.

Changes in growth and competitions of cool-temperate deciduous broad-leaved tree saplings grown under elevated [CO_2

Changes in growth and competitions of cool-temperate deciduous broad-leaved tree saplings grown under elevated [CO_2

Does the strength of facilitation by nurse shrubs depend on grazing resistance of tree saplings?

Facilitation of tree regeneration by nurse shrubs that offer protection against large herbivores is an important driver of wood-pasture dynamics. Here we asked whether the response to facilitation by nurse shrubs depends on the grazing resistance of the protégé saplings. We experimentally tested the protective effects of the thorny Rosa rubiginosa on browsing frequency, survival, and biomass change of saplings of two species-groups, presumably differing in grazing resistance: the coniferous Abies alba and Picea abies and the deciduous Acer pseudoplatanus and Fagus sylvatica saplings. The saplings were planted under and outside (1.5 m) planted nurse shrubs, under zero, low and high grazing intensity. In total, 1920 young saplings were transplanted to 60 blocks and followed for 1 year. Although the number of saplings browsed did not differ between species-groups, the coniferous saplings showed lower resistance to cattle browsing (i.e. lower survival and growth rates) than the deciduous saplings. The less resistant coniferous saplings benefited significantly more from nurse shrubs than the more resistant deciduous species in terms of growth of the surviving saplings, but not in terms of overall survival. This was likely due to herbivory on the nurse shrubs causing incidental browsing on protégé saplings and differences in biomass off-take. At high grazing intensity facilitative effects of the nurse shrubs decreased, especially for the coniferous species. These results have important management implications for the endangered wood-pastures in Western Europe. For a sustainable management and conservation that allows tree recruitment, grazing intensity should remain low to best promote facilitation processes for all tree species, but in particular for the less resistant conifer saplings. Die Förderung der Baumregeneration durch Ammengebüsche, die einen Schutz gegen große Herbivoren bieten, ist eine wichtige treibende Kraft für die Dynamik von Waldweiden. An dieser Stelle fragten wir uns, ob die Reaktion auf die Förderung durch Ammengebüsch von der Beweidungsresistenz der geschützten Schösslinge abhängt. Wir untersuchten den schützenden Effekt der dornigen Rosa rubiginosa auf die Beweidungsfrequenz, die Überlebensrate und die Veränderungen in der Biomasse für Schösslinge aus zwei Artengruppen experimentell, von denen wir annehmen, dass sie sich in der Beweidungsresistenz unterscheiden: die Nadelbäume Abies alba und Picea abies und die Laubbäume Acer pseudoplatanus und Fagus sylvatica . Die Schösslinge wurden unter die und außerhalb (1,5 m) der gepflanzten Ammengebüsche bei fehlender Beweidung, geringer und hoher Beweidungsintensität gepflanzt. Insgesamt wurden 1920 junge Schösslinge in 60 Blöcken verpflanzt und über ein Jahr beobachtet. Obwohl sich die Anzahl der beweideten Schösslinge nicht zwischen den Artengruppen unterschied, zeigten die Nadelbaumschösslinge eine geringere Resistenz gegenüber der Rinderbeweidung (d. h. geringere Überlebens- und Wachstumsraten) als die Laubbaumschösslinge. Die weniger resistenten Nadelbaumschösslinge profitierten signifikant mehr von den Ammengebüschen als die resistenteren Laubbaumschösslinge in Bezug auf das Wachstum der überlebenden Schösslinge, aber nicht in Bezug auf die Überlebensrate. Dies war wahrscheinlich auf die Beweidung der Ammengebüsche zurückzuführen, bei der zufällig die geschützten Schösslinge mit beweidet wurden, und auf die unterschiedliche Wegnahme von Biomasse. Bei hohen Beweidungsintensitäten nahmen die fördernden Effekte der Ammengebüsche insbesondere für die Nadelbäume ab. Diese Ergebnisse haben wichtige Schlussfolgerungen für die gefährdeten Waldweiden in Westeuropa. Für ein nachhaltiges Management und einen Schutz, der ein Nachwachsen der Bäume ermöglicht, sollte die Beweidungsintensität niedrig bleiben, um den besten Förderungsprozess zu für alle Baumarten zu erlauben, insbesondere für die weniger resistenten Nadelbaumschösslinge.

Soil and light effects on the sapling performance of the shade-tolerant speciesBrosimum alicastrum(Moraceae) in a Mexican tropical rain forest

Abstract:Many studies conclude that light is the most important resource that determines plant performance of tree saplings in tropical rain forests, and implicitly suggest that soil resources are less important. To provide a quantitative test for soil versus light effects on sapling performance, we studied how saplings of the shade-tolerant tree speciesBrosimum alicastrumresponded to contrasting levels of light availability and soil fertility in a Mexican tropical rain forest. Therefore saplings were selected from ten low-light exposure (crown position index <1.5) and ten high-light exposure (crown position index ≥2.5) sites either on productive alluvial soils, or on poor sandy soils on adjacent hills. Annual growth responses were scored for 58 saplings. The soil–light interaction had a strong positive effect on branching rate and leaf area production, rather than light or soil alone. Height growth only increased at higher light availability. Herbivore damage was higher on the more productive soil and, to a lesser extent, at higher light availability. Our results suggest that saplings (1) responded differently to soil and light availability, (2) expanded in overall size when both soil and light limitations are released, but only increased in height with increasing light intensity (3) and faced a trade-off between expansion and defence along both soil and light gradients. This study emphasizes the role of soil resources, in interaction with light availability, on the plastic responses in saplings living in a tropical forest understorey.

Mechanical characterization of juvenile European aspen (Populus tremula) and hybrid aspen (Populus tremula × Populus tremuloides) using full-field strain measurements

Functional analysis of genes and proteins involved in wood formation and fiber properties often involves phenotyping saplings of transgenic trees. The objective of the present study was to develop a tensile test method for small green samples from saplings, and to compare mechanical properties of juvenile European aspen (Populus tremula) and hybrid aspen (Populus tremula × tremuloides). Small microtomed sections were manufactured and successfully tested in tension parallel to fiber orientation. Strain was determined by digital speckle photography. Results showed significantly lower values for juvenile hybrid aspen in both Young’s modulus and tensile strength parallel to the grain. Average Young’s moduli spanned the ranges of 5.9–6.6 and 4.8–6.0 GPa for European aspen and hybrid aspen, respectively. Tensile strength was in the range of 45–49 MPa for European aspen and 32–45 MPa for hybrid aspen. The average density (oven-dry) was 284 kg/m3 for European aspen and 221 kg/m3 for hybrid aspen. Differences in mechanical properties correlated with differences in density.

The impact of single natural vegetation elements on flow characteristics

AbstractIn this experimental study, measurements were conducted to explore the impacts of different forms of individual natural vegetative elements within the flow domain on velocity and turbulence characteristics. All the experiments were performed in a flume measuring 26 m in length, 0·98 m in width and 0·85 m in depth, and real tree saplings were utilized to represent the vegetation element. In order to analyse this commonly observed nature phenomenon in floodplains, trees with wide trunks were classified into three groups on the basis of their volume versus height relation. Throughout the velocity measurements three acoustic Doppler velocimeters were employed. Time‐averaged velocity, streamwise and vertical turbulence intensities and turbulent kinetic energy parameters were examined. Additionally, a formulation that gives the velocity profile at a certain distance downstream of vegetation was introduced and the validity of the proposed formulation was checked with experimental data. It is seen that despite their porous structures, the presence of vegetation considerably disturbs the flow field and dissipates a remarkable amount of energy by turbulence. Copyright © 2008 John Wiley & Sons, Ltd.

Comparisons of recruitment, survival, and growth in invasive and native saplings on a volcano

We monitored the recruitment, survival, and growth of tree saplings on invasive (Larix kaempferi) versus native species (Betula and Populus) using 16 20 m × 20 m plots established along elevation gradient on the volcano Mount Koma, Japan, for 7 years because the sapling behaviors should determine forest structures. The crowding of overstory consists mostly of Larix decreased with increasing elevation. Larix recruits were conspicuous, particularly at middle elevation where overstory crowding was intermediate, while Betula recruits were least. Larix overstory crowding inhibited the recruitment of all the taxa, although intermediate crowding promoted the recruitment of Larix. The restriction of sapling emergence was conspicuous at lower elevation where the overstory crowding was highest, probably because of shading, and/or competition with overstory trees. Sapling recruitment for all taxa was restricted at higher elevation, due to high stresses derived from direct solar radiation and strong wind without overstory. The survival of saplings was 96% for Larix and Betula, while it was ca. 50% for Populus. Larix overstory decreased the survival and growth of all the taxa, except Larix survival and Betula growth. The results implied that Larix could establish by high survival once the recruits succeeded everywhere and native sapling regeneration was restricted by Larix overstory. Strong recruitment, survival, and growth of Larix, together with resistance to overstory crowding, enables it to dominate and persist in such disturbed areas regardless of the canopy closure.

Conifer Seedling Survival Under Closed-Canopy And Manzanita Patches In the Sierra Nevada

After a century of fire suppression, prescribed fire and mechanical thinning are widely used to restore mixed-conifer forests in California's Sierra Nevada, yet after these treatments, trees sometimes fail to regenerate on many sites, for several possible reasons. Notably, competition between shrubs and tree seedlings for scarce water during prolonged summer dry seasons is suspected to influence seedling survival, yet this hypothesis has been tested in few manipulated field experiments. We investigated the effects of vegetation patch types, root competition, putative mycorrhizal connections, soil moisture, and microclimate on the establishment of sugar pine (Pinus lambertiana) and white fir (Abies concolor) seedlings in an old-growth, mixed-conifer forest in the southern Sierra Nevada. Seedling survival rates were significantly higher under closed tree canopies than in patches dominated by manzanita (Arctostaphylos patula) shrubs. Treatments that allowed seedlings to connect with existing ectomycorrhizal networks did not enhance their survival. Isotope signatures suggest that mature conifer trees rely on water from deep soil layers (>50 cm), while shrubs and tree saplings (1–3 m in height) rely on water from shallower layers (0–50 cm) at the beginning of the season, but as soils become drier the shrub's and the sapling's primary zone of uptake shifts downward in the soil profile. These findings imply that shrubs may inhibit the survival of establishing tree seedlings until the seedlings have a deep enough root system to extract soil moisture from soil below 50 cm. Our study suggests that tree seedling survival may depend on a seedling's ability to compete with shrubs for scarce soil moisture in the near-surface soil layers.

Effects of sika deer ( Cervus nippon yakushimae) population growth on saplings in an evergreen broad-leaved forest

An increase in size of sika deer populations has caused severe damage to forest vegetation in many regions of Japan. In a Natural World Heritage area on the western part of Yakushima Island, existing high densities of deer are thought to be increasing, but the impact of deer on forest vegetation has not been estimated. Roadside censuses of deer between 1988 and 2006 showed that encounter rates are continuing to increase. Long-term monitoring of individual tree saplings in a 0.13 ha area of the forest between 1992 and 2005 showed that many saplings still remain despite increases in sika deer density. However, differences in growth and mortality rates of preferred, neutral (neither preferred nor avoided) and avoided sika deer food species varied over time. As a group, preferred species continuously had a low growth rate, while their mortality rate increased through time. The growth rates of the neutral and avoided groups decreased especially in the second half of our study period at the same time that their mortality rates increased. These data suggest that in spite of food species preference, direct feeding pressures as well as indirect physical effects by increasing sika deer density are affecting growth and mortality of tree saplings. Clearly, it is difficult to predict how plant communities will respond to possible continued sika deer population growth, and it is therefore important to continue monitoring these forest communities in the interest of preserving the unique ecosystems on Yakushima Island.

Fuel switching from wood to LPG can benefit the environment

The Himalaya in India is one of the world's biodiversity hotspots. Various scientific studies have reported and proven that many factors are responsible for the tremendous decline of the Himalayan forests. Extraction of wood biomass from the forests for fuel is one of the factors, as rural households rely entirely on this for their domestic energy. Efforts continue for both conservation and development of the Himalayan forests and landscape. It has been reported that people are still looking for more viable solutions that could help them to improve their lifestyle as well as facilitate ecosystem conservation and preservation of existing biodiversity. In this direction, we have documented the potential of the introduction of liquefied petroleum gas (LPG), which is one of the solutions that have been offered to the local people as a substitute for woodfuel to help meet their domestic energy demand. The results of the current study found dramatic change in per capita woodfuel consumption in the last two decades in the villages where people are using LPG. The outcome showed that woodfuel consumption had been about 475 kg per capita per year in the region, but after introduction of LPG, this was reduced to 285 kg per capita per year in 1990–1995, and was further reduced to 46 kg per capita per year in 2000–2005. Besides improving the living conditions of the local people, this transformation has had great environmental consequences. Empirical evidence shows that this new paradigm shift is having positive external effects on the surrounding forests. Consequently, we have observed a high density of tree saplings and seedlings in adjacent forests, which serves as an assessment indicator of forest health. With the help of the current study, we propose that when thinking about a top-down approach to conservation, better solutions, which are often ignored, should be offered to local people.