Forest ecosystem

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Changes in ecosystem functions following disturbances are of central concern in ecology and a challenge for ecologists is to understand the factors that affect the resilience of community structures and ecosystem functions. In many forest ecosystems, one such important natural disturbance is fire. The aim of this study was to understand the variation of resilience in six functional groups of invertebrates in response to different fire frequencies in southern Switzerland. We measured resilience by analysing arthropod species composition, abundance and diversity in plots where the elapsed time after single or repeated fires, as determined by dendrochronology, varied. We compared data from these plots with data from plots that had not burned recently and defined high resilience as the rapid recovery of the species composition to that prior to fire. Pooling all functional groups showed that they were more resilient to single fires than to repeated events, recovering 6–14 years after a single fire, but only 17–24 years after the last of several fires. Flying zoophagous and phytophagous arthropods were the most resilient groups. Pollinophagous and epigaeic zoophagous species showed intermediate resilience, while ground-litter saprophagous and saproxylophagous arthropods clearly displayed the lowest resilience to fire. Their species composition 17–24 years post-burn still differed markedly from that of the unburned control plots. Depending on the fire history of a forest plot, we found significant differences in the dominance hierarchy among invertebrate species. Any attempt to imitate natural disturbances, such as fire, through forest management must take into account the recovery times of biodiversity, including functional group composition, to ensure the conservation of multiple taxa and ecosystem functions in a sustainable manner.

Global climate change may impact the cycling of C, N, and S in forest ecosystems because increased soil temperatures could alter rates of microbially mediated processes. We studied the effects of temperature on microbial respiration and net N and S mineralization in surface soils from four northern hardwood forests in the Great Lakes region. Soil samples were incubated in the laboratory at five temperatures (5, 10, 15, 20, and 25°C) for 32 wk. Headspace gas was analyzed for CO 2-C at 2-wk intervals, and soils were extracted to determine inorganic N and S. Cumulative respired C and mineralized N and S increased with temperature at all sites and were strongly related (r 2 = 0.67 to 0.90, significant at P = 0.001) to an interaction between temperature and soil organic C. Production of respired C and mineralized N was closely fit by first-order kinetic models (r 2 > 0.94, P = 0.001), whereas mineralized S was best described by zero-order kinetics. Contrary to common assumptions, rate constants estimated from the first-order models were not consistently related to temperature, but apparent pool sizes of C and N were highly temperature dependent. Temperature effects on microbial respiration could not be accurately predicted using temperature-adjusted rate constants combined with a constant pool size of labile C. Results suggest that rates of microbial respiration and the mineralization of N and S may be related to a temperature-dependent constraint on microbial access to substrate pools. Simulation models should rely on a thorough understanding of the biological basis underlying microbially mediated C, N, and S transformations in soil.

Ecosystem management of protection forests aims at maintaining forests near a state during which effective protection is secured. As the evolution of a dynamic forest ecosystem cannot be stopped, silvicultural measures are required which aim at maintaining both the ecosystem integrity and the protective function of mountain forests. Ecosystem integrity is defined as the system's capacity to maintain structure and ecosystem functions using processes and elements characteristic for its ecoregion. Here, ecosystem functions also reflect the capability of the ecosystem to provide functions of value to humans. Ecosystem integrity of a protection forest implies that the stability (mainly the property resilience is addressed) of the forest is high, because that is required to provide a high level of protection in the long term. The main conditions promoting natural evolutionary processes and ecological stability in protection forests are: (1) a diverse composition of species; (2) sufficient natural regeneration; (3) an optimal forest structure. The first example in this chapter explains how these conditions might be achieved by silvicultural interventions in a forest that mainly protects against rockfall in the Austrian Alps. The second example deals with socioeconomic aspects of ecosystem integrity of a forest that also protects against rockfall, but then in the French Alps. Both examples show that forest authorities are aware of techniques to improve the stand stability of protection forests, but the problem is that current forest management is often a kind of trial and error, because the exact consequences of interventions for forest ecosystem dynamics are not known. Therefore, it is proposed that forest ecosystem research should shift focus from protection forest dynamics to the geo-ecosystem functioning of protection forests, including the effects of natural and human disturbances. For this, the concept of panarchy may be a promising way forward.

The current work presents the testing of a modeling strategy that has been recently developed to simulate the gross and net carbon fluxes of Mediterranean forest ecosystems. The strategy is based on the use of a NDVI-driven parametric model, C-Fix, and of a biogeochemical model, BIOME-BGC, whose outputs are combined to simulate the behavior of forest ecosystems at different development stages. The performances of the modeling strategy are evaluated in three Italian study sites (San Rossore, Lecceto and Pianosa), where carbon fluxes are being measured through the eddy correlation technique. These sites are characterized by variable Mediterranean climates and are covered by different types of forest vegetation (pine wood, Holm oak forest and Macchia, respectively). The results of the tests indicate that the modeling strategy is generally capable of reproducing monthly GPP and NEE patterns in all three study sites. The highest accuracy is obtained in the most mature, homogenous pine wood of San Rossore, while the worst results are found in the Lecceto forest, where there are the most heterogeneous terrain, soil and vegetation conditions. The main error sources are identified in the inaccurate definition of the model inputs, particularly those regulating the site water budgets, which exert a strong control on forest productivity during the Mediterranean summer dry season. In general, the incorporation of NDVI-derived fAPAR estimates corrects for most of these errors and renders the forest flux simulations more stable and accurate.

Latitudinal shifts in tree species distributions are a potential impact of climate change on forest ecosystems. It has been hypothesized that some tree species may become extirpated as climate change effects may exceed their migration ability. The goal of this study was to compare tree species compositions in northern urban areas to tree compositions in forestland areas in the eastern U.S. as an indicator of the potential for urban trees to facilitate future forest tree species migration. Results indicated that a number of tree species native to eastern U.S. forests of southern latitudes are currently present in northern urban forests. The biomass density (Mg/ha) of urban tree species is typically less than half of forestland densities with the majority of urban tree species found in nearby (<100 km) forestland. Urban tree propagation is often facilitated by humans, whereas the necessary pollinators and agents of tree seed dispersal in forestlands may be lacking regardless of climate change. It is suggested that urban areas may serve divergent, dual roles as both a native tree seed source and refuge for a limited number of forestland tree species, but also a facilitator of non-native tree invasion.

In unpolluted regions, where inorganic nitrogen (N) inputs from the atmosphere are minimal, such as remote locations in southern South America, litterfall dynamics and N use efficiency of tree species should be coupled to the internal N cycle of forest ecosystems. This hypothesis was examined in two evergreen temperate forests in southern Chile (42 Њ 30 Ј S), a mixed broad-leaved forest (MBF) and a conifer forest (CF). Although these forests grow under the same climate and on the same parental material, they differ greatly in floristic structure and canopy dynamics (slower in the CF). In both forests, biomass, N flux, and C/N ratios of fine litterfall were measured monthly from May 1995 to March 1999. There was a continuous litter flux over the annual cycle in both forests, with a peak during autumn in the CF. In the MBF, litterfall decreased during spring. In both forests, the C/N ratios of litterfall varied over the annual cycle with a maximum in autumn. Annual litterfall biomass flux (Mean ± SD = 3.3 ± 0.5 vs 2.0 ± 0.5 Mg ha -1 ) and N return (34.8 ± 16 vs 9.1 ± 2.8 kg N ha -1 ) were higher in the MBF than in the CF. At the ecosystem level, litterfall C/N was lower in the MBF (mean C/N ratio = 60.1 ± 15, n = 3 years) suggesting decreased N use efficiency compared with CF (mean C/N ratio = 103 ± 19.6, n = 3 years). At the species level, subordinated (subcanopy) tree species in the MBF had significantly lower C/N ratios (<50) of litterfall than the dominant trees in the CF and MBF (>85). The litterfall C/N ratio and percentage N retranslocated were significantly correlated and were lower in the MBF. The higher net N mineralization in soils of the MBF is related to a lower N use efficiency at the ecosystem and species level.

The viability of the many civilisations of Europe has depended, to a very large extent, on an adequate supply of wood. In the Ancient World, this supply was secured through the exploitation of forest reserves, the conquest of new territories and, when these opportunities no longer presented themselves, through the conservation of diminishing resources. Ultimately, civilisations collapsed because of the shortage of wood. Although some silvicultural techniques were known in the pre-Christian era, the scienti®c management of forests was not widely practised until the late 18th century. It is argued that the controlled exploitation of`nature', on sustained yield principles, only became possible when men came to view the forest, not as a nuisance, an Arcadia or a pagan horror, but as a centre of wood production, a biological factory.

By allowing the estimation of forest structural and biophysical characteristics at different temporal and spatial scales, remote sensing may contribute to our understanding and monitoring of planted forests. Here, we studied 9-year time-series of the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on a network of 16 stands in fast-growing Eucalyptus plantations in São Paulo State, Brazil. We aimed to examine the relationships between NDVI time-series spanning entire rotations and stand structural characteristics (volume, dominant height, mean annual increment) in these simple forest ecosystems. Our second objective was to examine spatial and temporal variations of light use efficiency for wood production, by comparing time-series of Absorbed Photosynthetically Active Radiation (APAR) with inventory data.

Process-based models are increasingly being used to model growth dynamics of forest ecosystems. Ideally, estimates of the parameters for these types of models should be obtained through physiological experiments. However, in many situations there is little or no experimental data available to parameterize such models. This paper presents some results of an ongoing study on alternative methods to estimate physiological parameters that are not readily available. The specific focus of this paper is the use of a Bayesian approach based on rejection sampling for estimating physiological parameters using observed state variables of process-based models for forest growth. The method is computationally intensive and can be used to estimate model parameters and their multi-dimensional distributions. The method is used to estimate some of the physiological parameters of a process-based growth model for Norway spruce [Picea abies (L.) Karst.] in Denmark. The estimated one-, two-, and three-dimensional distributions of the parameters of the process-based growth model are given. : S 0 3 0 4 -3 8 0 0 ( 9 9 ) 0 0 0 6 7 -8

There is currently great interest in improving the applicability of forest gap models to changing environmental conditions, in order to facilitate the assessment of possible impacts of climatic change on forest ecosystems. Moreover, for the development of mitigation strategies, it is necessary to include forest management options in the models. Both the simulation of transient effects of climatic change and of forest management regimes require a realistic representation of stand structure in gap models, since tree species respond to variations in stand density in characteristic ways, depending on their ecological strategies.

This article reports responses of two different forest ecosystems to 9 years (1988-96) of chronic nitrogen (N) additions at the Harvard Forest, Petersham, Massachusetts. Ammonium nitrate (NH 4 NO 3 ) was applied to a pine plantation and a native deciduous broad-leaved (hardwood) forest in six equal monthly doses (May-September) at four rates: control (no fertilizer addition), low N (5 g N m -2 y -1 ), high N (15 g N m -2 y -1 ), and low N ϩ sulfur (5 g N m -2 y -1 plus 7.4 g S m -2 y -1 ). Measurements were made of net N mineralization, net nitrification, N retention, wood production, foliar N content and litter production, soil C and N content, and concentrations of dissolved organic carbon (DOC) and nitrogen (DON) in soil water. In the pine stand, nitrate losses were measured after the first year of additions (1989) in the high N plot and increased again in 1995 and 1996. The hardwood stand showed no significant increases in nitrate leaching until 1995 (high N only), with further increases in 1996. Overall N retention efficiency (percentage of added N retained) over the 9-year period was 97-100% in the control and low N plots of both stands, 96% in the hardwood high N plot, and 85% in the pine high N plot. Storage in aboveground biomass, fine roots, and soil extractable pools accounted for only 16-32% of the added N retained in the amended plots, suggesting that the one major unmeasured pool, soil organic matter, contains the remaining 68-84%. Short-term redistribution of 15 N tracer at natural abundance levels showed similar division between plant and soil pools. Direct measurements of changes in total soil C and N pools were inconclusive due to high variation in both stands. Woody biomass production increased in the hardwood high N plot but was significantly reduced in the pine high N plot, relative to controls. A drought-induced increase in foliar litterfall in the pine stand in 1995 is one possible factor leading to a measured increase in N mineralization, nitrification, and nitrate loss in the pine high N plot in 1996.

Dissolved organic matter (DOM) is a major vehicle for the translocation and loss of N and P from forest ecosystems. The chemical properties of DOM and its interactions with soil surfaces are crucial in determining the mobility of these organic nutrients. We fractionated DOM from throughfall; all soil horizons (Ultisols and Inceptisols), and stream water from an Appalachian mountain forest ecosystem into hydrophobic or hydrophilic acids, neutrals, and bases. \Ve analyzed each fraction for dissolved organic C (DOC), N (DON), and P (DOP). Most of the DOC was in the acid fractions, with the humic fractions (hydrophobic acids and phenols) comprising 35 to 57% of the DOC in all samples except summer throughfall. Concentrations of all fractions declined with depth in the soil. As a percent of total DOC, the humics declined with depth, whereas the hydrophilic neutrals increased. Bases, which we expected to contain cationic amino groups, were < 2.5% of the DOC. Instead, most DON was in the humic. hydrophilic acid, and hydrophilic neutral fractions. Most DOP occurred in the hydrophilic acid, humic, and hydrophilic neutral fractions. The functional groups in which N and P occur had little influence on the behavior of most of the DOM as a whole since: (i) cationic DOM was such a minor component, and (ii) P was simply too rare to influence the anionic behavior of many molecules. Nevertheless, for those molecules in which P did occur, P may have influenced their behavior since a large percentage of the DOP was in the hydrophilic acid (i.e., anionic) fraction. The carboxylic and phenolic functional groups, or in some cases the neutrality, of the DOM molecules appeared to be much more important than N-containing groups in influencing the behavior of the N carried passively by the DOM.

Leaf area index (LAI) is one of the most frequently used parameters for the analysis of canopy structure and it has also been shown to be an important structural characteristic of the forest ecosystem and forest productivity. The objectives of this study were: (1) to calibrate optical estimates of PAI (plant area index) from the LAI-2000 using leaf area index derived from allometric models for six different tropical tree species and (2) to explore the corresponding relationship of calibrated LAI-2000 with stand productivity indices and environmental factors along a strong environmental gradient in the southern region of Costa Rica. From sixteen 6-year-old pure stand plantations (trees spaced 3 m  3 m) of four fast growing native species (Terminalia amazonia, Vochysia ferruginea, Vochysia guatemalensis and Hieronyma alchorneoides) and two introduced species (Pinus caribaea var hondurensis and Gmelina arborea), the plant area index (PAI) was estimated indirectly using the LAI-2000 plant canopy analyzer (LI-COR, Lincoln, NE), under cloudy sky conditions at a fixed height of 1.3 m above the ground with a 458 view cap. In addition, leaf area index (LAI) was estimated allometrically by felling four selected trees and measuring the area and biomass of leaves. The specific leaf area (SLA) showed typical values for each tree species that ranged between 81 cm 2 g À1 (V. ferruginea) and 106 cm 2 g À1 (G. arborea). Based on the characteristic SLA, for all tree species, the leaf area per tree could be estimated by allometric equations using the dbh (diameter at 1.3 m) as the independent variable. The calibration of the LAI-2000 PAI data versus the allometric estimate of leaf area showed strong and unbiased relationship for the species: T. amazonia, V. guatemalensis, H. alchorneoides and P. caribaea. In the case of G. arborea and V. ferruginea the LAI-2000 PAI values underestimated and overestimated the allometric measurements of LAI. For all tree species, calibrated LAI-2000 values were used as an independent variable in highly significant regression equations to estimate dominant tree height in each stand (in m) and stand yield in m 3 ha À1 year À1 , implying that calibrated LAI-2000 can be used to evaluate site quality and stand productivity. The generalized relationships for all species, between average calibrated LAI-2000 with stands yield or dominant tree height among four Eco-regions, indicated that as soil nutrient and water supply become optimal for tree growth, maximum LAI, dominant stand height and yield values are obtained.

Phenology shows sensitive responses to seasonal changes in atmospheric conditions. Forest understory phenology, in particular, is a crucial component of the forest ecosystem that interacts with meteorological factors, and ecosystem functions such as carbon exchange and nutrient cycling. Quantifying understory phenology is challenging due to the multiplicity of species and heterogeneous spatial distribution. The use of digital photography for assessing forest understory phenology was systematically tested in this study within a temperate forest during spring 2007. Five phenology metrics (phenometrics) were extracted from digital photos using three band algebra and two greenness percentage (image binarization) methods. Phenometrics were compared with a comprehensive suite of concurrent meteorological variables. Results show that greenness percentage cover approaches were relatively robust in capturing forest understory green-up. Derived spring phenology of understory plants responded to accumulated air temperature as anticipated, and with dayto-day changes strongly affected by estimated moisture availability. This study suggests that visible-light photo-graphic assessment is useful for efficient forest understory phenology monitoring and allows more comprehensive data collection in support of ecosystem/land surface models.

The harmonisation of a sub-set of forest health attributes suitable for aggregating, through scales ranging from individual trees to the operational forest management unit and up to the national level, has been achieved in countries such as the USA and Canada. In Australia, however, data collected on forest health is currently obtained on an ad hoc basis with only a small proportion of the national forest estate actually having been assessed. National guidelines are required for the objective assessment of a set of indices relating to forest health before Australia is in a position to report adequately on forest ecosystem health and vitality as recommended by the (Australian) Montreal Process Implementation Group. Obtaining these indices must be an affordable process that fulfills forest health reporting requirements for a range of national, state and regional reporting commitments such as the State of the Forests Reports and for the Regional Forest Agreements review process. In addition, it is envisaged that the indices will contribute to the verification process for the forest health and vitality criterion described in the Australian Forestry Standard for certification of sustainable forest management practices.

Understanding and predicting ecosystem functioning (e.g., carbon and water fluxes) and the role of soils in carbon storage requires an accurate assessment of plant rooting distributions. Here, in a comprehensive literature synthesis, we analyze rooting patterns for terrestrial biomes and compare distributions for various plant functional groups. We compiled a database of 250 root studies, subdividing suitable results into 11 biorues, and fitted the depth coefficient 1~ to the data for each biome (Gale and Grigal 1987). ~ is a simple numerical index of rooting distribution based on the asymptotic equation Y = 1-~ a, where d = depth and Y = the proportion of roots from the surface to depth d. High values of [3 correspond to a greater proportion of roots with depth. Tundra, boreal forest, and temperate grasslands showed the shallowest rooting profiles ([3 = 0.913, 0.943, and 0.943, respectively), with 80-90% of roots in the top 30 cm of soil; deserts and temperate coniferous forests showed the deepest profiles ([3 = 0.975 and 0.976, respectively) and had only 50% of their roots in the upper 30 cm. Standing root biomass varied by over an order of magnitude across biomes, from approximately 0.2 to 5 kg m -2. Tropical evergreen forests had the highest root biomass (5 kg m-2), but other forest biomes and sclerophyllous shrublands were of similar magnitude. Root biomass for croplands, deserts, tundra and grasslands was below 1.5 kg m -2. Root/shoot (R/S) ratios were highest for tundra, grasslands, and cold deserts (ranging from 4 to 7); forest ecosystems and croplands had the lowest R/S ratios (approximately 0.1 to 0.5). Comparing data across biomes for plant functional groups, grasses had 44% of their roots in the top 10 cm of soil ([3 = 0.952), while shrubs had only 21% in the same depth increment ([3 = 0.978). The rooting distribution of all temperate and tropical trees was ~ = 0.970 with 26% of roots in the top 10 cm and 60% in the top 30 cm. Overall, the globally averaged root distribution for all ecosystems was ~ = 0.966 (r 2 = 0.89) with approximately 30%, 50%, and 75% of roots in the top 10 cm, 20 cm, and 40 cm, respectively. We discuss the merits and possible shortcomings of our analysis in the context of root biomass and root functioning.

Dead wood is a substantial carbon stock in terrestrial forest ecosystems and hence a critical component of global carbon cycles. Given the limited amounts of dead wood biomass and carbon stock information for Caribbean forests, our objectives were to: (1) describe the relative contribution of down woody materials (DWM) to carbon stocks on the island of St. John; (2) compare these contributions among differing stand characteristics in subtropical moist and dry forests; and (3) compare down woody material carbon stocks on St. John to those observed in other tropical and temperate forests. Our results indicate that dead wood and litter comprise an average of 20 percent of total carbon stocks on St. John in both moist and dry forest life zones. Island-wide, dead wood biomass on the ground ranged from 4.55 to 28.11 Mg/ha. Coarse woody material biomass and carbon content were higher in moist forests than in dry forests. No other down woody material components differed between life zones or among vegetation categories (P > 0.05). Live tree density was positively correlated with fine woody material and litter in the moist forest life zone (R = 0.57 and 0.84, respectively) and snag basal area was positively correlated with total down woody material amounts (R = 0.50) in dry forest. Our study indicates that DWM are important contributors to the total biomass and, therefore, carbon budgets in subtropical systems, and that contributions of DWM on St. John appear to be comparable to values given for similar dry forest systems.

The complex interactions among endangered ecosystems, landowners’ interests, and different models of land tenure and use, constitute an important series of challenges for those seeking to maintain and restore biodiversity and augment the flow of ecosystem services. Over the past 10 years, we have developed a data-based approach to address these challenges and to achieve medium and large-scale ecological restoration

Conservation organizations have most often focused on land-use change, climate change, and invasive species as prime threats to biodiversity conservation. Although air pollution is an acknowledged widespread problem, it is rarely considered in conservation planning or management. In this synthesis, the state of scientific knowledge on the effects of air pollution on plants and animals in the Northeastern and Mid-Atlantic regions of the United States is summarized. Four air pollutants (sulfur, nitrogen, ozone, and mercury) and eight ecosystem types ranging from estuaries to alpine tundra are considered. Effects of air pollution were identified, with varying levels of certainty, in all the ecosystem types examined. None of these ecosystem types is free of the impacts of air pollution, and most are affected by multiple pollutants. In aquatic ecosystems, effects of acidity, nitrogen, and mercury on organisms and biogeochemical processes are well documented. Air pollution causes or contributes to acidification of lakes, eutrophication of estuaries and coastal waters, and mercury bioaccumulation in aquatic food webs. In terrestrial ecosystems, the effects of air pollution on biogeochemical cycling are also very well documented, but the effects on most organisms and the interaction of air pollution with other stressors are less well understood. Nevertheless, there is strong evidence for effects of nitrogen deposition on plants in grasslands, alpine areas, and bogs, and for nitrogen effects on forest mycorrhizae. Soil acidification is widespread in forest ecosystems across the eastern United States and is likely to affect the composition and function of forests in acid-sensitive areas over the long term. Ozone is known to cause reductions in photosynthesis in many terrestrial plant species. For the most part, the effects of these pollutants are chronic, not acute, at the exposure levels common in the eastern United States. Mortality is often observed only at experimentally elevated exposure levels or in combination with other stresses such as drought, freezing, or pathogens. The notable exceptions are the acid/aluminum effects on aquatic organisms, which can be lethal at levels of acidity observed in many surface waters in the region. Although the effects are often subtle, they are important to biological conservation. Changes in species composition caused by terrestrial or aquatic acidification or eutrophication can propagate throughout the food webs to affect many organisms beyond those that are directly sensitive to the pollution. Likewise, sublethal Annals of the New York Academy of Sciences doses of toxic pollutants may reduce the reproductive success of the affected organisms or make them more susceptible to potentially lethal pathogens. Many serious gaps in knowledge that warrant further research were identified. Among those gaps are the effects of acidification, ozone, and mercury on alpine systems, effects of nitrogen on species composition of forests, effects of mercury in terrestrial food webs, interactive effects of multiple pollutants, and interactions among air pollution and other environmental changes such as climate change and invasive species. These gaps in knowledge, coupled with the strong likelihood of impacts on ecosystems that have not been studied in the region, suggests that current knowledge underestimates the actual impact of air pollutants on biodiversity. Nonetheless, because known or likely impacts of air pollution on the biodiversity and function of natural ecosystems are widespread in the Northeast and Mid-Atlantic regions, the effects of air pollution should be considered in any long-term conservation strategy. It is recommended that ecologically relevant standards, such as "critical loads," be adopted for air pollutants and the importance of long-term monitoring of air pollution and its effects is emphasized.

The biotic cycling of potassium (K) in forest systems has been relatively understudied in comparison with nitrogen (N) and phosphorus (P) despite its critical roles in maintaining the nutrition of primary production in forests. We investigated the ecological significance of K in forests from a literature review and data synthesis. We focused on (1) describing patterns of the effects of K availability on aboveground growth and change in foliar tissue of tree species from a variety of forests; and (2) documenting previously unreported relationships between hydrologic losses of K and N in forested watersheds from the Americas. In a review of studies examining tree growth under K manipulations/fertilizations, a high percentage (69% of studies) showed a positive response to increases in K availability in forest soils. In addition, 76% of the tree studies reviewed showed a positive and significant increase in K concentrations in plant tissue after soil K manipulation/fertilization. A meta-analysis on a subset of the reviewed studies was found to provide further evidence that potassium effects tree growth and increased tissue [K] with an effect size of 0.709 for growth and an overall effect size of 0.56. In our review of watershed studies, we observed that concentrations of K typically decreased during growing seasons in streams draining forested areas in the Temperate Zones and were responsive to vegetation disturbance in both temperate and tropical regions. We found a strong relationship (r 2 ¼ 0.42-0.99) between concentrations of K and N (another critical plant nutrient) in stream water, suggesting that similar mechanisms of biotic retention may control the flow of these nutrients. Furthermore, K dynamics appear to be unique among the base cations, e.g. calcium, magnesium, and sodium, because the others do not show similar seasonal patterns to K. We suggest that K may be important to the productivity and sustenance of many forests, and its dynamics and ecological significance warrant further study. We suggest that knowledge about the dynamics of this understudied element is imperative for our understanding patterns and processes in forest ecosystems.

Surface coal mining in Appalachia has caused extensive replacement of forest with non-forested land cover, much of which is unmanaged and unproductive. Although forested ecosystems are valued by society for both marketable products and ecosystem services, forests have not been restored on most Appalachian mined lands because traditional reclamation practices, encouraged by regulatory policies, created conditions poorly suited for reforestation. Reclamation scientists have studied productive forests growing on older mine sites, established forest vegetation experimentally on recent mines, and identified mine reclamation practices that encourage forest vegetation re-establishment. Based on these findings, they developed a Forestry Reclamation Approach (FRA) that can be employed by coal mining firms to restore forest vegetation. Scientists and mine regulators, working collaboratively, have communicated the FRA to the coal industry and to regulatory enforcement personnel. Today, the FRA is used routinely by many coal mining firms, and thousands of mined hectares have been reclaimed to restore productive mine soils and planted with native forest trees. Reclamation of coal mines using the FRA is expected to restore these lands&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; capabilities to provide forest-based ecosystem services, such as wood production, atmospheric carbon sequestration, wildlife habitat, watershed protection, and water quality protection to a greater extent than conventional reclamation practices.

Several leaf litter decay studies have indicated that decomposition occurs more rapidly when litter is placed beneath the plant species from which it had been derived than beneath a different plant species (i.e. home-field advantage, HFA), although support for this notion has not been universal. We provide the first quantification of HFA in relation to leaf litter decomposition using published litter mass loss data from forest ecosystems in North America, South America, and Europe. Our findings indicate that HFA is widespread in forest ecosystems; on average litter mass loss was 8% faster at home than away. We hypothesize that HFA results from specialization of the soil biotic community in decomposing litter derived from the plant above it. Climate and initial litter quality data can be used to explain about 70% of the variability in litter decomposition at a global scale, leaving about 30% unexplained. We suggest that HFA be recognized as a factor that explains some of this remaining variability.

Stable Cs was measured in soil and vegetation samples taken from a coniferous forest in Bavaria, Germany. This site has been under continuous investigation since 1987, mainly with respect to radiocaesium. Soil pro"les for stable Cs, expressed in mg kg\ dry weight, and radioactive Cs and Cs, expressed in Bq kg\ dry weight, were established for 1993, 1995, and 1996, and compared. The pro"le for Chernobyl Cs shows a clear maximum in the Of and Oh horizon. The pro"les for weapons fallout Cs and stable Cs are similar for the organic layers including the Ah horizon. Both pro"les exhibit a gradual increase from the L to the Ah horizon, in contrast to the pro"le for Chernobyl Cs. For four edible fungal species (Clitocybe nebularis (Batsch: Fr.) Kummer, Xerocomus badius (Fr.) KuK hner ex Gilbert, Hydnum repandum L. ex Fr., and Russula cyanoxantha (Schae!er ex Fries)) and one plant species (leaves of bilberry [<accinium myrtillus L.], berries edible), transfer factors for stable Cs were calculated on the basis of its concentration in those soil layers, from which the corresponding species takes up radiocaesium. Using this de"nition, transfer factors for radioactive Cs agree within a factor of 2 or better with the corresponding transfer factors for stable Cs. Since the stable Cs is expected to have attained a dynamic equilibrium within the forest ecosystem, the similar bioavailability for stable Cs and radiocaesium indicates that the current distribution of stable Cs within the organic soil layers and understory vegetation represents the equilibrium distribution which is expected for decay-corrected radioactive Cs and Cs several decades after deposition. It is concluded that the transfer factors for radiocaesium will not

A major gap currently exists in our understanding of how landscape-level operational silviculture affects ponderosa pine (Pinus ponderosa) forest ecosystem health in northern Arizona. More than 70% of our forested landscape is in relatively young, evenaged stands resulting from a history of grazing, fire exclusion, atypical climatic events, and large ('yellow') pine removal. This multi-year, multiple-investigator project specifically examined stands that have been thinned to improve forest ecosystem health, or similarly thinned and then treated with prescribed underburning. These two treatments were not different from one another with respect to any aboveground structural characteristic. However, every measure of living overstory density (trees and saplings) was lower in thinned treatments than in untreated stands, and mean tree size (stem and crown) was consistently greater in thinned treatments. Areas burned by stand-replacing wildfire in 1996, now without an overstory, had zero seedlings and saplings as well as greater densities of standing dead trees than treated and untreated stands. The STIFH project as a whole is examining a range of species-specific and ecosystem responses to this spectrum of stand conditions, including fungi, insect, and understory plant composition.

The stability of the slash-and-burn system is more a function of the total nutrient stock of the entire ecosystem than the net gain of the soil after slash-and-burn. During the first cycle of land exploitation, slash-and-burn releases a large portion of nutrients stored in the above-ground biomass into the soil. Therefore, the gain of nutrient stock in the soil is at the expense of the plant biomass. Published data on slash-and-burn systems are mostly concerned with the changes in soil nutrient status during cropping. Studies dealing with the dynamics of total nutrient stock in the primary forest ecosystem and the subsequent cropping and fallow cycles are scarce.

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.

Estimating populations of both pest and natural enemy species is important in the planning and implementation of biological control. For example, synthetic pheromone lures are used to sample bark beetles, and sometimes their predators, in forest ecosystems. However, insect attraction to natural pheromone sources may differ from attraction to synthetic pheromone lures. Moreover, these differences may vary systematically between the target pest and some important natural enemies. Thus, the accuracy of both absolute and relative abundances of bark beetles and predators could vary with lure selection. We evaluated a series of synthetic lures to determine which lure gave the closest approximation to actual numbers of Ips pini (Say) and predators arriving at hosts infested with I. pini in Wisconsin. We deployed synthetic lures containing various ratios of the (ϩ) and (Ϫ) enantiomers of the principal I. pini pheromone component, ipsdienol, with or without an additional component, lanierone. I. pini showed strong preferences for speciÞc enantiomeric ratios of ipsdienol, and these responses were synergized by lanierone. Predators showed equally strong attraction to ipsdienol, but preferred different ratios of the stereoisomers. The addition of lanierone had no effect on predators. The most abundant predator, Thanasimus dubius (F.), showed greater preference for host material infested with I. pini than any synthetic lure. These disparities in responses, combined with strong disparities in seasonal ßight patterns, provided estimates of pest to predator ratios that varied by as little as 12% to as much as 12 times, from pest:predator ratios arriving at host material infested with I. pini. These results suggest that variation between herbivores and their natural enemies in their phenology, preferred pheromone blends, and infested host material should be considered when developing estimates of relative pest and predator densities for subsequent management options.

Climate change and Philippine forests are directly linked to each other. Changes in climate are affecting the forests and its ability to deliver its environmental services. In the same manner, degradation of the forest resources results to emission of carbon dioxide (CO 2 ) in the atmosphere which contributes to climate change. To enhance the mitigation role of the forests and at the same time increase their resilience to climate change, policies and programs must be put in place. Such policies and programs must however be science-based. This paper reviewed one decade of research on climate change and forest ecosystems in the Philippines. Limited research suggests that dry forest types are the most vulnerable to climate change. Potential adaptation strategies do exist but have not yet been adequately studied. Most of the past research has focused on the mitigation potential of terrestrial ecosystems. Significant amount of carbon is conserved in natural forests (up to 250 MgC/ha). These stored carbon can be emitted to the atmosphere as CO 2 gas through deforestation. Planted trees have a high rate of carbon sequestration (mean of 4.3 MgC/ ha/yr) and could help mitigate greenhouse gas concentration. Lessons that are relevant to forest management in the country are extracted. Future research needs are suggested.

Ungulates can profoundly alter the structure and composition of forest communities via both direct and indirect mechanisms. Individual plant species often respond in a unique way to the direct effect of herbivory as a function of their sensitivity to browse damage, ungulate food preferences, and the density of ungulates present. Sustained browsing pressure can limit the regeneration of favored and susceptible woody plants and eliminate populations of favored or susceptible herbaceous plants. These losses, in turn, give rise to indirect effects via trophic cascades or physical habitat modification. These indirect effects affect many other plant and animal populations. In the mixed conifer-hardwood forests around the Great Lakes in North America, widespread habitat modification and the extirpation of native predators and other ungulates have acted to boost populations of white-tailed deer (Odocoileus virginianus) to historically high densities. Such densities have curtailed regeneration of several important conifers (e.g. Tsuga canadensis and Thuja occidentalis) as evidenced by demographic analysis. Deer also appear to limit regeneration of Quercus and Betula in many areas. Impacts on understory herbs are harder to assess, but baseline data from 50 years ago indicate that these communities are changing in a pattern that implicates deer: grasses, sedges, and some ferns are increasing while overall herb diversity is declining. Thus, deer are playing a keystone role in these communities. We are currently assessing an additional set of questions, including: How best can we measure and represent ungulate impacts? At which densities do deer threaten forest diversity? How do impacts depend on initial plant and ungulate densities? Which species emerge as 'winners' or 'losers' in heavily-browsed landscapes? What characteristics or traits make a species susceptible to ungulate herbivory? How do ungulates affect patterns of diversity and relative abundance in ecological communities? What are the pathways by which ungulates exert indirect effects on species? and How significant are indirect effects? #

Amami Island has many terrestrial wildlife species and subspecies that are endemic to the Nansei Archipelago. Many of them live in the forest ecosystems, while young secondary forests have replaced the majority of the original forests due to the past clear-cutting forestry. Of those species, the great scaly thrush Zoothera dauma major, Owston white-backed woodpecker Drendrocopos leucotos owstoni, long-haired rat Diplothrix legata and Amami pygmy woodpecker Dendrocopos kizuki amamii, appear to be so dependent on the mature forests (uncut for at least 50 years after selective felling) that their numbers must have decreased at least for the last few decades. On the other hand, the populations of Amami rabbit Pentalagus furnessi, purple jay Garrulus lidthi, Amami woodcock Scolopax mira, Ryukyu robin Erithacus komadori and spinous rat Tokudaia osimensis have decreased in the central part of the island, where mongoose numbers have skyrocketed in recent years. In the mean time, forestry practices that turned out to be economically unprofitable have resulted in a precipitous decline in production in the early 1990s. Mongoose control has also encountered critical financial problems due to the ignorance of the local community. These situations are rooted in a local economy that has been deeply dependent on government subsidies, which facilitated various development activities.

A range of reviews and technical reports have been presented in this volume that cover many components of the jarrah forest ecosystem and its restoration after bauxite mining in Western Australia. This synthesis reviews these papers and attempts to decide if the jarrah forest ecosystem has been restored. All ecosystem functions, including nutrient cycling and nutrient accumulation, appear to be successful or developing on an appropriate trajectory. Structural attributes of the restored vegetation are controlled by the floristic composition and growth of the vegetation and are developing favorably with time. Biodiversity measures show some deficiencies, which should be solved by time (e.g., lack of old rotting wood and tree hollows for fauna) or are the subject of ongoing research and development (e.g., imbalance of seeder/resprouter plant species). Various ways of measuring the success of Alcoa’s restoration are discussed and a numerical scorecard is presented. The overall scores were calculated as between 90 and 92% depending on the input parameters used. Such scores seem to agree with the overall subjective impression that Alcoa’s mine restoration is largely successful at restoring the jarrah forest ecosystem. A single measure of ecosystem restoration success, which acts as a surrogate for all others, does not exist, but the use of two such measures, soil organic carbon levels and floristic similarity, would adequately integrate all ecosystem components and could be used to determine the level of ecosystem restoration in this region.