Pine Canopy Research Articles

Growth and development of silver fir (Abies alba Mill.) regeneration and restoration of the species in the Karkonosze Mountains

The main task of the study was to investigate the growth conditions of silver fir natural regeneration in the Karkonosze Mts. (Poland). The paper examines the quantity and quality of light reaching the forest floor in stands of different canopies. The aim of the study was also to define the optimal site conditions for silver fir planting under stand canopy. Data on the natural regeneration and stand structure of each investigated stand were collected on circular plots in a grid of 15 × 15 m in 1999 and 2000. Biometric measurements of fir plants planted under various stand canopies were done three times (May 1999, autumn 2000 and 2001). It was found that the fir was not a dominant tree in all size classes from seedlings to saplings. Seedlings (both phases) of spruce, beech, sycamore and rowan occurred in all studied stands. The optimal conditions for fir development were found under larch canopy. That was demonstrated by the highest increment of height, diameter and offshoots. The worst conditions for fir growth were under beech and spruce canopy, which was indicated by the lowest diameter and height. The highest PAR was recorded under pine canopy, whereas the lowest one under beech canopy. Beech stand induced a lower R:FR ratio than the other tree species both on sunny and cloudy days. The highest R:FR ratio was found under the canopy of larch and pine stands.

Temporal changes in species diversity and composition in abandoned fields in a trans-Himalayan landscape, Nepal

Secondary succession is an increasing phenomenon due to global changes in agriculture policies and practices. The empirical findings are biased towards the temperate zone. Abandonment of agriculture fields is less frequent in the subtropical and tropical zones where agriculture areas are, in general, expanding. But there are exceptions; a rapid rate of abandonment of agricultural fields have taken place in the arid trans-Himalayan region, due to today’s globalization of economy. We analysed agriculture fields that were abandoned between 1950 and 2003 in a large u-valley in central Nepal (3400 m a.s.l.). The potential forest vegetation is dominated by Pinus wallichina and shrubs of junipers and cotoneaster species. We tested the intermediate richness hypothesis in relation to vegetation cover, soil development and whether old-field succession is convergent or divergent with species data from 242 1 m2 plots in 5 age-classes. The main species compositional turnover expressed by Detrended Correspondence Analyses (DCA) correlated, as expected, with time after abandonment. Fields that were abandoned a long time ago are closer to forest at the periphery of the agricultural landscape. Moisture of the soil significantly increased with age of abandonment, but total vegetation cover and pH were negatively related to age. Beta diversity expressed in DCA SD-units showed an increasing trend with age of abandonment, supporting the divergence pattern in old-field succession. The reason why the succession is not converging may be due to browsing by domestic animals that prevent a closed canopy of pines and juniper to develop. There was a significant hump-shaped pattern in species richness along the temporal gradient, which agrees with the intermediate species-richness hypothesis. There was a rapid increase in species richness in plots close to the villages that were used for haymaking which increased the seed input significantly.

Simulation of snow processes beneath a boreal scots pine canopy

A physically-based multi-layer snow model Snow-Atmosphere-Soil-Transfer scheme (SAST) and a land surface model Biosphere-Atmosphere Transfer Scheme (BATS) were employed to investigate how boreal forests influence snow accumulation and ablation under the canopy. Mass balance and energetics of snow beneath a Scots pine canopy in Finland at different stages of the 2003-2004 and 2004-2005 snow seasons are analyzed. For the fairly dense Scots pine forest, drop-off of the canopy-intercepted snow contributes, in some cases, twice as much to the underlying snowpack as the direct throughfall of snow. During early winter snow melting, downward turbulent sensible and condensation heat fluxes play a dominant role together with downward net longwave radiation. In the final stage of snow ablation in middle spring, downward net allwave radiation dominates the snow melting. Although the downward sensible heat flux is comparable to the net solar radiation during this period, evaporative cooling of the melting snow surface makes the turbulent heat flux weaker than net radiation. Sensitivities of snow processes to leaf area index (LAI) indicate that a denser canopy speeds up early winter snowmelt, but also suppresses melting later in the snow season. Higher LAI increases the interception of snowfall, therefore reduces snow accumulation under the canopy during the snow season; this effect and the enhancement of downward longwave radiation by denser foliage outweighs the increased attenuation of solar radiation, resulting in earlier snow ablation under a denser canopy. The difference in sensitivities to LAI in two snow seasons implies that the impact of canopy density on the underlying snowpack is modulated by interannual variations of climate regimes.

A new monitoring PAM fluorometer (MONI-PAM) to study the short- and long-term acclimation of photosystem II in field conditions

We present and evaluate the performance of a new field monitoring PAM fluorometer (MONI-PAM) which is intended for short- and long-term monitoring of the acclimation of photosystem II (PSII). The instrument measures chlorophyll fluorescence, photosynthetic photon flux density (PPFD), and temperature in the field, and monitors exactly the same leaf area over prolonged periods of time, facilitating the estimation of both rapidly reversible and sustained non-photochemical quenching (NPQ). The MONI-PAM performance is evaluated in the lab and under natural conditions in a Scots pine canopy during spring recovery of photosynthesis. The instrument provides a new tool to study in detail the acclimation of PSII to the environment under natural field conditions.

Wildfire Behavior Study in a Mediterranean Pine Stand Using a Physically Based Model

The aim of this article is to study the propagation of a wildfire, propagating through two eco-systems characteristics of the Mediterranean region located in south of France: the garrigue and the aleppo pines forest. The behavior of a line fire is analysed using a physical model based on the resolution of conservation equations (mass, momentum, energy) governing the coupled system formed by the vegetation and the surrounding atmosphere. The effects of wind (ranged from 3 to 30 m/s) and slope of the terrain (ranged from 0 to 40°) have been studied for surface fires propagating through shrubs (quercus coccifera) composing the surface vegetation of a garrigue and the understorey vegetation of a young pines stand (pinus halepensis). Then the configuration has been generalized, in adding a solid fuel layer above the first one, representing the canopy of a young pines stand. The numerical results have highlighted the strong connection between the surface fire and the canopy. In all cases (on flat terrain) the active crown fire regime has never been reached, and the behaviour of fires, predicted with the model, was more representative of passive crown fires (torching).

Pine and eucalypt litterfall in a pine-invaded eucalypt woodland: The role of fire and canopy cover

The accumulation of considerable amounts of litter within Pinus populations can have adverse effects on litter fauna and native plant recruitment. In this two year study, we quantified Pinus radiata and Eucalyptus spp. litterfall in a eucalypt woodland invaded by pines. In the most heavily invaded areas pine basal area reached 11.3 m 2/ha and produced a mean annual litterfall rate of more than 1400 kg/(ha year) (dry weight) directly underneath the pine canopy, implying that in the latter stages of invasion wildling populations are capable of producing considerable amounts of pine litter. The significant positive relationship between P. radiata basal area and litterfall ( r = 0.861; p = 0.028) indicates that pine basal area is a good indicator of the area of land within an invaded area subject to direct litter impacts. Clumped adult pines results in heavy litter fall on a small area of land whereas uniformly spaced trees leads to uniformity of litterfall with lighter impacts. The majority of pine litter (>70%) fell directly below the pine canopy suggesting that most effects of litter will be restricted to these areas. Wildfire reduced litterfall from the trees that survived by 61% and 28% for pine and eucalypt, respectively, suggesting that any potential adverse consequences of pine litter will be reduced for several years following fire. In areas invaded by pines the addition of large amounts of highly flammable pine litter may increase the fire risk to the plantation resource.

Sulphur isotopes as tracers of the influence of a coal-fired power plant on a Scots pine forest in Catalonia (NE Spain)

Stable sulphur isotopes and major ionic composition were analysed in precipitation and throughfall samples from a Scots pine ( Pinus sylvestris, L.) forest near the Cercs coal-fired power plant (Catalonia, NE Spain). The purpose of the study was to determine the main sources of sulphur deposition on this pine forest. Sulphur isotope measurements from the SO 2 power plant stack emissions were used to identify the isotopic signature of this source. Net throughfall fluxes of sulphur (26.1 kg S ha 1 yr −1) and nitrogen (16.3 kg N ha −1 yr −1) were higher—5–25 times higher for S and 5–15 times for N—at this site than in other forests in Catalonia. Sulphur isotope analysis confirmed that the net throughfall fluxes of sulphur were mostly due to the dry deposition of the SO 2 power plant emissions onto the pine canopies. Two potential atmospheric end-members were distinguished: regional background rainwater (δ 34S=+7.2‰) and power plant emissions (δ 34S=−2.8‰). By applying a two-component sulphur isotope mixing model, we found that during periods of low power plant activity (⩽10 emission h day −1), 62% of the throughfall sulphate could be attributed to the power plant emissions. At higher activity periods (⩾14 emission h day −1), this contribution rose to 73%. Although power plant contribution to bulk deposition was lower in both cases (34% and 45%), the possible influence of sulphate coming with long-range transport events from the polluted areas in the Mediterranean basin (δ 34S≈0‰) was not discarded.

Vegetation structure, niche width, niche overlap and types of competition in temperate grazingland of Garhwal Himalaya, India

Temperate grazing lands in Garhwal Himalaya are rich in herbaceous vegetation and extensively used for grazing by locally owned livestock. Capillipedium parviflorum is a frequently occurring and dominant grass species under Pine canopy in associate with several herbs. Beside, grazing and extensive fire, interactions among associated species is a determining factor of community structure. In this article the dominant diversity pattern of vegetation in temperate grazing land along two different altitudes and having different slope aspects is described. Interaction between dominant and co-dominant species with their niche appearance and niche overlap measurement was also observed and presented here. South and west facing slopes had maximum species and diversity values while east north facing slopes had higher species dominant. Capillipedium parviflorum and other grasses had maximum niche values and were dominant and co dominant species. Three types of interspecific interaction were observed between species and grasses were observed as succeeding species in all sites of different topographic conditions. Dominant diversity pattern along with resource partitioning and interspecific competition is discussed and presented here.

Temporal dynamics and spatial variability in the enhancement of canopy leaf area under elevated atmospheric CO2

AbstractIncreased canopy leaf area (L) may lead to higher forest productivity and alter processes such as species dynamics and ecosystem mass and energy fluxes. Few CO2 enrichment studies have been conducted in closed canopy forests and none have shown a sustained enhancement of L. We reconstructed 8 years (1996–2003) of L at Duke's Free Air CO2 Enrichment experiment to determine the effects of elevated atmospheric CO2 concentration ([CO2]) on L before and after canopy closure in a pine forest with a hardwood component, focusing on interactions with temporal variation in water availability and spatial variation in nitrogen (N) supply. The dynamics of L were reconstructed using data on leaf litterfall mass and specific leaf area for hardwoods, and needle litterfall mass and specific leaf area combined with needle elongation rates, and fascicle and shoot counts for pines. The dynamics of pine L production and senescence were unaffected by elevated [CO2], although L senescence for hardwoods was slowed. Elevated [CO2] enhanced pine L and the total canopy L (combined pine and hardwood species; P<0.050); on average, enhancement following canopy closure was ∼16% and 14% respectively. However, variation in pine L and its response to elevated [CO2] was not random. Each year pine L under ambient and elevated [CO2] was spatially correlated to the variability in site nitrogen availability (e.g. r2=0.94 and 0.87 in 2001, when L was highest before declining due to droughts and storms), with the [CO2]‐induced enhancement increasing with N (P=0.061). Incorporating data on N beyond the range of native fertility, achieved through N fertilization, indicated that pine L had reached the site maximum under elevated [CO2] where native N was highest. Thus closed canopy pine forests may be able to increase leaf area under elevated [CO2] in moderate fertility sites, but are unable to respond to [CO2] in both infertile sites (insufficient resources) and sites having high levels of fertility (maximum utilization of resources). The total canopy L, representing the combined L of pine and hardwood species, was constant across the N gradient under both ambient and elevated [CO2], generating a constant enhancement of canopy L. Thus, in mixed species stands, L of canopy hardwoods which developed on lower fertility sites (∼3 g N inputs m−2 yr−1) may be sufficiently enhanced under elevated [CO2] to compensate for the lack of response in pine L, and generate an appreciable response of total canopy L (∼14%).

Influence of nurse birch and Scots pine seedlings on early aerial development of European beech seedlings in an open-field plantation of Central France

Beech woodland can be restored by direct planting of beech (Fagus sylvatica L.) seedlings in abandoned areas, but this method is generally avoided in forestry because of the growth difficulties of beech in full-light conditions. This study tested a method that consists of planting beech seedlings in full-light conditions with silver birch (Betula pendula Roth.) or Scots pine (Pinus sylvestris L.) as nurse trees. A total of 65 two-year-old beech seedlings surrounded by either 3, 4, 5 or 6 pine or birch seedlings or without competitors were planted in bare-soil open-field conditions in Central France. Tree growth and light availability were monitored at the end of each of the following 3 years, and soil moisture was also measured the last year. At the end of the experiment, aerial biomass measurements were made on the beeches. Results showed that relative beech growth in terms of diameter was significantly reduced by the local neighbouring trees and that this reduction was particularly noticeable in the pine treatments where there was extensive pine seedling development. In contrast, relative beech height did not exhibit any significant variations among the treatments. Light availability was decreased by the neighbouring trees, especially in the pine treatments. Light reduction was more pronounced in the last 2 years and in the middle or lower parts of the canopy of the subject beech. Soil water content was lower under the pine canopies than under the birch canopies, and was positively correlated to beech relative diameter growth. Specific leaf area, height-to-diameter ratio and crown length-to-crown width ratio weakly but significantly increased with competition from the neighbours. Beech biomass partitioning was only weakly affected by the treatments. This study showed that nurse trees tend to reduce beech growth but improve form although effects remained weak due to the insufficient length of the experiment. Further studies are also needed to quantify the effects of the neighbourhood on the growth of competitive herbaceous vegetation and on changes in the microclimatic conditions.

Effect of Pinus radiata plantations on water balance in Chile

AbstractThe effect of Pinus radiata (D. Don) plantations on water resources at different Chilean sites located between 33 and 40 south was determined. Incoming precipitation, canopy interception loss, evapotranspiration, net evapotranspiration (transpiration and evaporation from the soil), percolation and soil water content were measured in each site, where Pinus radiata plantations were 12 to 17 years old and between 700 and 830 trees ha−1 dense. The results were compared with those obtained from areas covered with perennial grasses and shrubs at the same sites. The pine canopies intercepted on average 36–40% of the annual rainfall at all sites where rainfall was less then 1200 mm, while only 15% of the mean rainfall was intercepted in the southernmost and rainy (2081 mm year−1) site. Annual net evapotranspiration increased from south to north from 32% of the incoming precipitation for the southernmost site to 55% for the one located at the lower latitude. In this northernmost site almost the entire incoming precipitation was evapotranspired. Annual percolation registered its minimum value in the northern site (5% of incoming precipitation) and its maxima in the southern one (53%). The values of net evapotranspiration and percolation were regulated by the pluviometric regime and the soil moisture retention capacity in each site. Compared with the shrub or grass covers, sites under Pinus radiata plantations registered higher water consumption by evapotranspiration and reduced percolation. Copyright © 2007 John Wiley & Sons, Ltd.

The perpetual forest: using undesirable species to bridge restoration

Summary Conversion of established forests of undesirable species composition or structure to a multi‐age, native forest community is a common restoration goal. However, for some ecosystems, the complexity of multiple disturbances and biotic factors requires unique approaches to advance community development. We use the longleaf pine (Pinus palustris Miller) ecosystem as a model of such a restoration paradigm with an approach that utilizes the undesirable species as a functional or structural bridge to foster ecological processes. In the conversion of adult slash pine (Pinus elliottii Engelm.) plantations to the biologically diverse longleaf pine forests that once dominated the south‐eastern US Coastal Plain, we examine techniques for restoring and maintaining critical structural and functional components. Through partial and variable retention of the undesirable slash pine canopy, establishment of longleaf pine seedlings is facilitated, while maintaining fuels essential for prescribed fire, a necessary management practice for longleaf pine. Furthermore, we project that with subsequent fires, fine fuels and species richness will be encouraged in the ground cover, and with future slash canopy harvest, established longleaf pine seedlings will be released. In this study, we present a statistical approach that examines the compositional movement of vegetation in restoration sites over time relative to the reference conditions that are also changing through time. Synthesis and applications. Restoration efforts that remove undesirable species initially may actually hinder rather than facilitate restoration. Restoration of fire‐maintained ecosystems in which the production of adequate fuels is an important consideration may require the retention of a portion of the existing canopy to provide fuels during the restoration process, even if the canopy is comprised of less preferred species. Individual species often provide similar structural features and influences on function within an ecosystem; thus, systems other than longleaf pine may also benefit from retention of the undesirable species through the restoration process. We conclude that a gradual approach to restoration may be advantageous when legacies of past management have altered complex ecological dynamics and promoted development along a successional pathway strongly differing from that of the reference conditions.

Comparison of Selected Ecotypes and Cultivars of Cocksfoot (Dactylis glomerata L.) Under Pinewoods in Spain

ABSTRACT Cocksfoot (Dactylis glomerata L.) entries, eight natural populations, and two commercial checks were sown under maritime pine (Pinus pinaster Ait.) and under red pine (P. sylvestris L.) canopies, as well as in an open field area in Galicia, NW Spain. Natural populations yielded less biomass and had a higher crude protein content under pine canopies than in an adjacent open field stand. In the first two years under P. pinaster, population Mg348 yielded, in general, significantly more dry matter than the commercial varieties and more than control plots, which were fertilized but not sown. In contrast, two years after sowing, control plots invaded by spontaneous grasses yielded significantly more than several cocksfoot entries under red pine and in the unshaded stand. Therefore, ecotypic selection in cocksfoot is an alternative to the use of commercial varieties in temporal pastures under P. pinaster. In the long term, however, cocksfoot does not persist significantly more than spontaneous grasses.

Canopy fuel characteristics and potential crown fire behavior in Aleppo pine (Pinus halepensis Mill.) forests

Canopy fuel characteristics that influence the initiation and spread of crown fires were measured in representative Aleppo pine (Pinus halepensis Mill.) stands in Greece. Vertical distribution profiles of canopy fuel load, canopy base height and canopy bulk density are presented. Aleppo pine canopy fuels are characterized by low canopy base height (3.0–6.5 m), while available canopy fuel load (0.96–1.80 kg/m2) and canopy bulk density (0.09–0.22 kg/m3) values are similar to other conifers worldwide. Crown fire behavior (probability of crown fire initiation, crown fire type, rate of spread, fireline intensity and flame length) in Aleppo pine stands with various understory fuel types was simulated with the most updated crown fire models. The probability of crown fire initiation was high even under moderate burning conditions, mainly due to the low canopy base height and the heavy surface fuel load. Passive crown fires resulted mostly in uneven aged stands, while even aged stands gave high intensity active crown fires. Assessment of canopy fuel characteristics and potential crown fire behavior can be useful in fuel management and fire suppression planning.

Water use strategies and ecosystem-atmosphere exchange of CO<sub>2</sub> in two highly seasonal environments

Abstract. We compare assimilation and respiration rates, and water use strategies in four divergent ecosystems located in cold-continental central Siberia and in semi-arid southern Africa. These seemingly unrelated systems have in common a harsh and highly seasonal environment with a very sharp transition between the dormant and the active season, with vegetation facing dry air and soil conditions for at least part of the year. Moreover, the northern high latitudes and the semi-arid tropics will likely experience changes in key environmental parameters (e.g., air temperature and precipitation) in the future; indeed, in some regions marked climate trends have already been observed over the last decade or so. The magnitude of instantaneous or daily assimilation and respiration rates, derived from one to two years of eddy covariance measurements in each of the four ecosystems, was not related to the growth environment. For instance, respiration rates were clearly highest in the two deciduous systems included in the analysis (a Mopane woodland in northern Botswana and a Downy birch forest in Siberia; >300 mmol m−2 d−1), while assimilation rates in the Mopane woodland were relatively similar to a Siberian Scots pine canopy for a large part of the active season (ca. 420 mmol m−2 d−1). Acknowledging the limited number of ecosystems compared here, these data nevertheless demonstrate that factors like vegetation type, canopy phenology or ecosystem age can override larger-scale climate differences in terms of their effects on carbon assimilation and respiration rates. By far the highest rates of assimilation were observed in Downy birch, an early successional species. These were achieved at a rather conservative water use, as indicated by relatively low levels of λ, the marginal water cost of plant carbon gain. Surprisingly, the Mopane woodland growing in the semi-arid environment had significantly higher values of λ. However, its water use strategy included a very plastic response to intermittently dry periods, and values of λ were much more conservative overall during a rainy season with low precipitation and high air saturation deficits. Our comparison demonstrates that forest ecosystems can respond very dynamically in terms of water use strategy, both on interannual and much shorter time scales. But it remains to be evaluated whether and in which ecosystems this plasticity is mainly due to a short-term stomatal response, or alternatively goes hand in hand with changes in canopy photosynthetic capacity.

Land Use History Effects In Mixed Pine - Hardwood Forests at Fort Benning1

Over decades, and especially on public lands subject to multiple uses, land use activities can affect forest composition or structure. We asked if current ground layer vegetation composition or stand structure (canopy openness, tree density, plus depth of the soil A layer) in 32 mixed pine-hardwood forest stands at Fort Benning, GA, reflects military use or fire frequency over the last 20 years. The 32 stands, half on sandy and half on clayey soil, were assigned to two military use categories (heavier, open to tracked vehicles, or lighter, with dismounted infantry training) and three fire frequency (# fires/20 yr) categories [low (0–2 fires), medium (3–4 fires), and high (5–6 fires)]. Ordination reflected abundance of grass and legume species, the proportion of pine in the canopy, canopy openness, and tree density and age; it revealed a relatively stronger influence of military land use and canopy composition, and weaker influence of fire frequency (over the past 20 years), on ground layer vegetation differences among the stands. Soil A-horizon depth, abundance of disturbance features, and tree density differed between lighter and heavier military use categories, but not among fire frequency categories. Our results suggest that mechanized military training has led to a loss of topsoil and convergence on abundant pines, grasses, and legumes, while a range of fire frequencies has led to an array of ground layer composition in stands with lighter military use. Under all land use scenarios examined, 70% pine canopy may be favorable for abundant grasses and legumes in ground layer vegetation.

THE DISRUPTION OF AN ANT–APHID MUTUALISM INCREASES THE EFFECTS OF BIRDS ON PINE HERBIVORES

Predators affect herbivores directly and indirectly, by consumptive and nonconsumptive effects, and the combined influence of multiple predators is shaped by interactions among predators. I documented the individual and combined effects of birds (chickadees, nuthatches, warblers) and ants (Formica podzolica) on arthropods residing in pine (Pinus ponderosa) canopies in a factorial field experiment. Birds and ants removed herbivores but simultaneously benefited them by removing predatory arthropods. Birds and ants had net negative and positive effects, respectively, on the abundance of herbivore prey, supporting the notion that vertebrate predators have stronger negative effects on herbivores than do arthropod predators. Aphids (ant-tended and untended species) constituted three-quarters of herbivore biomass. The effect of birds on ant-tended aphids was twice that on untended aphid species or tended aphid species without ants. This was not due to there being more ant-tended aphids for birds to prey on; tended and untended aphid species were in similar abundances in the absence of birds. Instead, the effects of birds were strengthened by attributes of the mutualism that rendered tended aphids susceptible to predation. These dynamics led to nonadditive effects of birds and ants: birds only reduced tended aphid species and total herbivore abundances on trees with ants, while ants only increased tended aphid species and total herbivore abundances in the absence of birds. Consequently, top predators in this system only influenced total herbivore abundance when they disrupted an ant-aphid mutualism.

Origin of atmospheric deposition and canopy buffering capacity in stands of radiata pine and pedunculate oak in the Basque Country

Total atmospheric deposition to four mature forest sites in the Basque Country was estimated using the canopy flux method and a generalised deposition model (average deposition velocities multiplied by average concentration of gases in the atmosphere). Potential acidity under aerobic conditions and acidity flux from atmospheric deposition entering the forest ecosystems were also estimated. The sites were close to a number of opencast limestone quarries and were located at different distances from a livestock farm, which was considered to be a source of emission of ammonia. Two forest stands, a Pinus radiata plantation and a semi-natural Quercus robur woodland (“Dur pine” and “Dur oak”, respectively), were selected in the vicinity of the livestock farm where approximately 300 head of cattle are grazed. Another radiata pine plantation and a pedunculate oak plantation at a distance of approximately 15 km from the farm were also selected for study: “Urk pine” and “Urk oak”, respectively. Bulk precipitation and throughfall were sampled and the concentration of different constituents analysed. Concentrations of gases in the atmosphere close to the field stations were provided by Basque Government's Environmental Protection Agency and best estimates of deposition velocities were based on data in the available literature. Calcium was the most abundant chemical species in bulk precipitation and throughfall at every site, whereas sulphate was the most abundant anion in these precipitation fractions. Precipitation was not acidic and the pH values at the “Dur” and the “Urk” site were 5.8 and 5.5, respectively. The results suggest that deposition of calcium carbonate from nearby quarries may be an important factor at both sites. A high proportion of the sodium collected in bulk precipitation at both sites was found to be of non-marine origin. Ammonium deposition in bulk precipitation and throughfall was higher at the “Dur” than at the “Urk” site. Statistical analyses showed that: (a) there exists a strong relationship among base cations (including sodium) at both sites indicating a possible common source for them; (b) co-deposition of SO x and NO y along with NH x occurs at both sites, but chloride was not co-deposited with ammonium, and (c) buffering of total deposition and ammonia uptake in forest canopies may be brought about by cation exchange. Total deposition of NH x and the acidity flux of total deposition were higher at the “Dur” than at the “Urk” site (approximately 30 kg ha −1 year −1 of N.NH x and from 270 to 290 mmolc m −2 year −1, respectively, at the former site and less than 10 kg ha −1 year −1 of N.NH x and from 65 to 85 mmolc m −2 year −1, respectively, at the latter site). At both sites the acidity flux entering the forest soil along with throughfall was higher under pine canopies than under oak (approximately 115% at the “Dur” site and almost 200% at the “Urk” site). Nevertheless, acidity entering the forest ecosystems along with the total deposition was very similar, regardless of the tree dominant species. The estimated nitrogen loads (NO y + NH x ) to the sites were approximately 35 kg ha −1 year −1 at the “Urk” site and 55 kg ha −1 year −1 at the “Dur” site. These values are higher than the critical threshold values, suggesting potential nitrogen saturation of these forest ecosystems.

Stand characteristics of sericea lespedeza on the Louisiana Coastal Plain

Sericea lespedeza has been an important forage legume in portions of the USA for decades but has recently been recognized as invasive in some ecosystems. Stand characteristics potentially affecting usefulness and invasiveness were assessed on forested and open sites of a Louisiana Coastal Plain landscape. Typical heavy weed competition, which was not overcome by increased seeding rate or extent of seedbed preparation, occurred in full sunlight. An open longleaf pine canopy suppressed competitive herbaceous species and enhanced establishment compared to that in full sunlight. Shade of either longleaf pines or dense overstory of tall weeds reduced productivity but not stands. Sericea lespedeza spread was limited to a few meters during 7 years, apparently due to lack of an effective dispersal mechanism. Long stand life under mature longleaf pines and in the open field along with ability to re-colonize from soil seed reserves contribute to both usefulness of sericea lespedeza for conservation, forage, and wildlife habitat in agricultural landscapes and potential undesired persistence, especially with land-use changes to less intensive management, on Louisiana Coastal Plain landscapes.

Change of evapotranspiration components due to the succession from Japanese red pine to evergreen oak

Extensive measurements of water balance components in a forest under the succession from Japanese red pine ( Pinus densiflora) to evergreen oak ( Quercus myrsinaefolia) were carried out. Significant decreases of transpiration from the red pines and forest interception loss were found based on the observational results in 1984/1985 and 2001/2002. The former was the pre-succession period and the latter was the middle succession period in the study forest. Although the forest had a main canopy of the red pines in 1984/1985, the multi-layered canopies were observed in 2001/2002, which were consisted of the upper canopy layer of the red pines and of the lower canopy layer of the evergreen oaks. On the other hand, no significant difference in the amount of total evapotranspiration between the two periods was observed, because the decrease of transpiration from the red pines was compensated by the increase of transpiration from the lower canopy layer, which was about three times larger than that of the red pines. Three factors were identified to produce the large amount of transpiration from the lower canopy layer: (i) increased net radiation over the lower canopy due to the increased gaps in the canopy of red pine, (ii) a relatively small difference of total sapwood area between the red pine and the lower canopies and (iii) larger sap flux densities of main species in the lower canopy which were around two times larger than that of the red pine canopy.