State Of Forest Ecosystems Research Articles

Anatomical Structure of Ectomycorrhiza in Abies sibirica Ledeb. and Picea obovata Ledeb. under Conditions of Forest Ecosystems Polluted with Emissions from Copper-Smelting Works

Changes in the anatomical characters of ectomycorrhiza in Siberian fir and Siberian spruce were studied in natural forests polluted with heavy metals (Cu, Zn, Cd, Pb, As, and Fe) and sulfur dioxide. As technogenic load increased, the total radius of mycorhiza terminals and plant roots included in them increased in the organic horizon and decreased in the mineral part of the soil. The absolute thickness of fungal mycorhiza caps and their relative contribution to the total volume of consuming organs increased under pollution. The observed responses were regarded as adaptive, aimed at compensating the adverse effects caused by technogenic pollution.

Old-growth forest: An ancient and stable sylvan equilibrium, or a relatively transitory ecosystem condition that offers people a visual and emotional feast? Answer—it depends

As a species, humans depend heavily on their visual sense, make decisions as much from their hearts as from their heads (emotion-and value-based decisions versus analytical, logic- and knowledge-based decisions), and dislike environmental and other change. Societies in early stages of development have generally revered old people for their wisdom and experience, whereas many societies at more advanced stages of development have adopted a culture of youth. Attitudes toward forests have shown a similar trend. Respect for large and old trees was a feature of some early societies, whereas societies in and after the industrial revolution became more interested in younger, faster growing trees for technical and utilitarian reasons. However, as human population growth caused the area of unmanaged forest, old forest, and forests of large trees to decline, reverence has revived for large, old trees and for old forests. This trend has not been matched by a renewed respect for scientific knowledge about forests and for wisdom about forests based on long experience. Reflecting the pervasive effects of the culture of youth, issues in forestry, including the issue of old forests, are being judged largely on an aesthetic basis, on human emotional response to snapshot visual aspects, and on a dislike for change—the Peter Pan syndrome. "Old-growth" forest, whatever it is, has been deified as a symbol of the mythical "balance of nature," a concept discredited by ecologists as a Victorian anachronism. There are important spiritual, aesthetic, wildlife, and environmental values associated with old forests, and the area of such forests is declining. There are many valid reasons (social, scientific, and environmental) for sustaining significant and representative areas of such forests. However, conservation of such forests and ensuring a future supply of the values they provide will not be achieved unless the reverential respect for such forests is matched by another meaning of respect: understanding such forests and basing our relationship with them on that understanding. This paper challenges forest managers and forest scientists to gain a significant understanding of "old growth" to provide a logical, knowledge-based, and experience-based foundation for the identification, inventory, conservation, and management of this forest ecosystem condition, and to assert this understanding as a counterbalance to the necessary, but insufficient, value-based attitude toward old forests that arises largely from visual snapshots and the emotions they arouse. Key words: old growth, biodiversity, sustainability, stability, succession, stand dynamics, respect for nature

Is Nitrogen Deposition Altering the Nitrogen Status of Northeastern Forests?

Concern is resurfacing in the United States over the long-term effects of excess nitrogen (N) deposition and mobility in the environment. We present here a new synthesis of existing data sets for the northeastern United States, intended to answer a single question: Is N deposition altering the N status of forest ecosystems in this region? Surface water data suggest a significant increase in nitrate losses with N deposition. Soil data show an increase in nitrification with decreasing ratio of soil carbon to nitrogen (C:N) but weaker relationships between N deposition and soil C:N ratio or nitrification. Relationships between foliar chemistry and N deposition are no stronger than with gradients of climate and elevation. The differences in patterns for these three groups of indicators are explained by the degree of spatial and temporal integration represented by each sample type. The surface water data integrate more effectively over space than the foliar or soil data and therefore allow a more comprehensive view of N saturation. We conclude from these data that N deposition is altering N status in northeastern forests.

Inorganic Nitrogen Losses from a Forested Ecosystem in Responseto Physical, Chemical, Biotic,and Climatic Perturbations

Nitrate leaching to streams is a sensitive indicator of the biogeochemical status of forest ecosystems. Two primary theories predicting long-term (decadal) changes in nitrate loss rates (N saturation theory and the nutrient retention hypothesis) both predict increasing dissolved inorganic nitrogen (DIN) losses for watershed 6 (W6), the biogeochemical reference watershed at the Hubbard Brook Experimental Forest (HBEF). Measured values, however, have declined substantially since measurements began in the mid-1960s. Are these theories wrong, or are there other important controls on DIN losses at the annual to decadal time scale that have obscured the tendency toward higher losses over time? We tested the individual and combined effects of several forms of disturbance on DIN loss rates from northern hardwood forests by comparing predictions from a relatively simple model of forest carbon, nitrogen, and water dynamics (PnET-CN) with the long-term record of annual DIN loss from W6 at HBEF. Perturbations tested include interannual climate variation, changes in atmospheric chemistry (CO2, O3, N deposition), and physical and biotic disturbances (two harvests, a hurricane salvage, and a defoliation event). No single disturbance caused changes in DIN losses to mimic measured values. Only when run with all of the disturbances combined did the model-predicted pattern of interannual change in DIN loss approach the measured record. Single-disturbance simulations allow an estimation of the role of each in the total pattern of DIN loss. We conclude that DIN losses from W6 were elevated in the 1960s by a combination of recovery from extreme drought and a significant defoliation event. N deposition alone, in the absence of other disturbances, would have increased DIN losses by 0.35 g N m−2y−1. These findings indicate that predictions of DIN losses must take into account the full spectrum of disturbance events and changes in environmental conditions impacting the systems examined.

Litterfall and Leaf Area Index in the CONECOFOR Permanent Monitoring Plots

Forest canopies are more sensitive and react more promptly to abiotic and biotic disturbances than other stand structural components. Monitoring crown and canopy characteristics is therefore a crucial issue for intensive and continuous monitoring programs of forest ecosystem status. These observations formed the basis for the measurement of annual litter production and leaf area index (LAI) in the Italian permanent monitoring plots (CONECOFOR program) established within the EC-UN/ECE program "Intensive Monitoring (Level II) of Forest Ecosystems". Preliminary results after three years of observation are presented. The low value of within plot mean relative standard deviation (20.8 ± 1.9%) of litter production, which in any case never exceeded 30%, accounted for the good sampling error and accuracy of the chosen method, which seems to be accurate enough to detect changes in litter production through the years. The higher inconsistency of the amount of woody and fruits fractions over the years demonstrated the greater reliability of leaf fraction or, on the other hand, of LAI compared to total litter. Mean values of annual leaf-litter and total litter production and LAI were rather high in comparison with data reported in literature for similar stands, and reflected both a medium-high productivity and a juvenile phase in the development of the selected stands on average. Focusing on changes in litter production through the years, statistical analysis on a sub-sample of plots showed the existence of significant differences both in leaf litter and total litter production. These findings seem to attribute to the "year" factor a driving role in determining changes in litter production and LAI. Temporal intermittence in data collection, together with the shortness of the monitoring period, make it difficult to speculate or arrive at definitive conclusions on changes in litter production due to time-dependent factors. The importance of having a complete database to increase index representativeness and reliability and, on the other hand, of performing an integrated results analysis which takes into account the outcomes of other research actions, is recognized as an indispensable requirement for achieving the goals of the monitoring program.

Intensive monitoring of forest ecosystems in Europe: 1. Objectives, set-up and evaluation strategy

In order to contribute to a better understanding of the impact of air pollution and other environmental factors on forest ecosystems, a Pan-European Programme for Intensive and Continuous Monitoring of Forest Ecosystems has been implemented in 1994. Results of the Programme must contribute to a European wide overview of impacts of air pollution and the further development of its control strategies, being described in air pollution protocols. Objectives of the Intensive Monitoring Programme related to air pollution are the assessment of: (i) responses of forest ecosystems to changes in air pollution; (ii) differences between present loads and critical loads (long-term sustainable inputs) of atmospheric deposition; and (iii) impacts of future scenarios of atmospheric deposition on the ecosystem condition. Furthermore, the Intensive Monitoring Programme contributes to the assessment of ‘criteria and indicators for sustainable forest management’, such as the maintenance of forests as a net carbon sink to reduce the build up of atmospheric greenhouse gasses and the maintenance of species diversity of ground vegetation. The Intensive Monitoring Programme, which is carried out on approximately 860 selected plots, comprises monitoring of crown condition, forest growth and the chemical status of soil and foliage at all plots and monitoring of deposition, meteorology, soil solution and ground vegetation in a subset of the plots. In order to meet the major objectives of the Intensive Monitoring Programme, studies have been or are presently carried out with respect to the assessment of: (i) correlations between site and stress factors and the “forest ecosystem condition”; (ii) trends in stress factors and/or ecosystem conditions; (iii) critical loads, by evaluating the fate of atmospheric pollutants in the ecosystem with input–output budgets; and (iv) large-scale and long-term impacts of climate and deposition on forests and vice versa. Examples of those studies are given and the potential of the Programme to fulfil the objectives is evaluated.

Assessment of environmental impact zones in the Kola Peninsula forest ecosystems

This paper describes the condition of forest ecosystems subjected to smelter pollution in the Kola peninsula. This assessment is based on the parameters of the biogeochemical cycle. The defoliation index was used to delimit three basic forest states: background, defoliating, sparse. Close to the smelter, due to expansion of the area not covered by vegetation, a fourth type of state, so-called “industrial deserts”, has been observed. The concentrations of sulphur, copper and nickel in the precipitation in the forests generally declined with distance from the smelter. The defoliating forests are noted for the highest Ca, Mg, K concentrations in the summer precipitation. In sparse forests and industrial deserts a decrease in the Ca, Mg, K concentrations in the summer precipitation in comparison with the defoliating forests, despite the particle emissions, could be attributed to the reduction in forest biomass. The higher levels of soil and soil leachate carbon and acidity in the defoliating forests was due to higher litterfall and to the higher dissolution of fulvic acids by the acidic precipitation. This increase in organic matter levels affects soil cation exchange capacity and cation saturation. The pine trees demonstrated significant changes in the uptake of elements in all types of forests under pollution. Elevated levels of S, Ni, Cu and K and reduced levels of Mg, Mn and Zn were found in the needles of different age classes.

The Bioindicators of Forest Condition Project: A physiological, remote sensing approach

Objective measures of forest ecosystem condition are needed to gauge the effects of management activities and natural phenomena on sustainability. The Bioindicators of Forest Condition Project seeks to develop a Forest Condition Rating (FCR) system using a physiological, remote sensing approach. In particular, the goal of the project is to test whether hyperspectral remote sensing may be used to infer stand-level information about pigment concentration, chlorophyll fluorescence, and other physiological features of condition. The project spans a four-year period of intensive sampling in tolerant hardwood forests in Ontario using the Compact Airborne Spectrographic Imager (CASI). For each airborne campaign, concurrent ground-based sampling for leaf physiological features was performed. Controlled laboratory and greenhouse studies were also conducted to derive relationships between leaf-based spectral measurements and physiology in the presence of environmental stresses. The project has identified several promising bioindicators of strain that are discernible from hyperspectral images and related to ground-based physiology. The most promising remote indicator for semi-operational testing is estimation of chlorophyll content, which can be used to classify maple stands on a five-stage scale of health. Chlorophyll fluorescence has also been discerned from spectral signatures, but our studies indicate it may be confounded by chlorophyll content. The intent here is to update the forestry community on progress made, insights gained, and the practical implications of the research. Keywords: chlorophyll fluorescence, hyperspectral, indices, pigments, reflectance, tolerant hardwoods

Sampling methodology for LAI measurements with LAI-2000 in small forest stands

Leaf Area Index (LAI) plays a prominent role as an indicator of forest ecosystem condition in research on change detection. For this, rapid and reliable estimation of the effective LAI (LAIe) — this is the ratio of the total one-sided area of vegetation elements over the unit ground area) — at various scales is of utmost importance. We used the Licor LAI-2000 Plant Canopy Analyzer (PCA) for the acquisition of point LAI values within small (about 1 ha) stands. Canopy influences, external to the stand for which LAI was being assessed, and direct sunlight were excluded from respectively the LAIe computations and the fields of view of the PCA sensors by the use of a 270° viewcap. The effect of sampling scheme and data aggregation method on LAIe was quantified by means of a Monte Carlo simulation. The methodology presented is generalized and can be applied to forest stands with different canopy architectures. Our results show that for our study area the LAIe populations are normally distributed. A power function relationship was shown to exist between the relative accuracy of the acquired LAIe value and the sampling intensity. Based on this information, an appropriate sampling scheme can be selected for a predetermined relative accuracy. The method allowed us to quantitatively assess LAIe in small stands often occurring in very heterogeneous environments, which is typically the case for large parts of Western Europe.

Forest and Chernobyl: forest ecosystems after the Chernobyl nuclear power plant accident: 1986–1994

This paper reports basic features of radionuclide migration and the prediction of the radionuclide redistribution and accumulation by forest phytocoenoses after the Chernobyl Nuclear Power Plant (CNPP) accident. The current ecological condition of forest ecosystems is evaluated and scientific aspects of forest management in the conditions of the large-scale radioactive contamination are discussed.

Consequences of reduced immissions on the ecochemical conditions of forest ecosystems in Saxony (Germany)

With the German reunion in 1989 a strong reduction in industrial emissions occured in the former GDR. However, the acidity in precipitation is still very high. Since 1993 the Saxon State Institute for Forestry (LAF) monitors the element budgets at 6 different forest ecosystems within the scope of the European Level II Programme. The aim of the programme is to get regional informations of ecological risks for forest ecosystems and to achieve recommendations for forest management. Base cation deposition, concentrations of Ca and K as well as pH in soil solution of subsoils have decreased, while large amounts of previously stored sulphur and pedogenic aluminium are released from the soil matrix. This gives rise to concern about an increasing risk for root damages, nutritional imbalances and thus decreasing elasticity of forest ecosystems.

Effects of pH and sulfate on insects and protozoans inhabiting treeholes.

We used laboratory microcosms designed to simulate treeholes to study the effect of changing levels of chemicals found in precipitation in central Pennsylvania (H+ and SO4=) on the treehole insects Aedes triseriatus (a mosquito), Helodes pulchella (a helodid beetle), and Culicoides guttipennis (a ceratopogonid midge), and treehole protozoans. Protozoans were tested in both the presence and absence of insects. We hypothesized that the individual insect species would have differential tolerances to abiotic stresses, and that effects of low pH on protozoans would be especially strong. Survival of helodids was higher than mosquitoes and midges. Emergence and survival of mosquitoes and midges were lower at low pH. Densities of ciliates increased the most at high pH in the absence of insects. Densities of flagellates increased the most at low pH in the absence of insects. The presence of helodids, mosquitoes, and protozoans was associated with higher final [SO4=], as was low pH. Mosquitoes at low pH caused the largest increases in cation concentrations, and protozoans at high pH caused the largest decreases in cation concentrations. It appears that the biota of treeholes are affected by ionic changes in simulated tree stemflow that can be caused by anthropogenic atmospheric deposition. The species studied here were sometimes differentially affected by the common pollutants, [H+] and [SO4=]. The resulting changes in these discrete treehole communities may allow them to be useful bioindicators of the status of forest ecosystems altered by changing atmospheric chemistry.

Defining and Measuring Forest Health

If forest health is to be approached scientifically, it must be defined and measured. Forest health is a condition of forest ecosystems that sustains their complexity while providing for human needs. We developed this broad definition becaue a wisely acceptable definition is lacking, and forest health is a focal point in discussions of how to sustain forest ecosystems in the United States. Steps for measuring forest health are: (1) select a representative set of indicators for a particular ecosystem; (2) establish baseline data, such as a historical range of variability; (3) develop standards against which to compare current conditions; and (4) establish a monitoring program to assess current conditions and modify baseline data as new trends develop.

Acid Rain 2 What about the Effects of Acid Rain on Plant Ecosystem? : Current Status of Forest Ecosystem and Research Activities

Acid Rain 2 What about the Effects of Acid Rain on Plant Ecosystem? : Current Status of Forest Ecosystem and Research Activities

Monitoring the condition of the Canadian forest environment: The relevance of the concept of ?ecological indicators?

The Canadian forest environment is characterized by high spatial and temporal variability, especially in the west. Our forests vary according to climate, landform, and surficial geology, and according to the type, intensity, extent of, and the time since the last disturbance. Most Canadian forests have had a history of repeated acute, episodic disturbance from fire, insects, wind, diseases and/or logging, with a frequency of disturbance varying from a few decades to many centuries. These sources of variability have resulted in a complex and continually changing mosaic of forest conditions and stages of successional development.Monitoring the 'quality' of this dynamic forested landscape mosaic is extremely difficult, and in most cases the concept of a relatively simple index of forest ecosystem quality or condition (i.e. an 'ecological indicator') is probably inappropriate. Such ecological indicators are better suited for monitoring chronic anthropogenically induced disturbances that are continuous in their effect (e.g. 'acid rain', heavy metal pollution, air pollution, and the 'greenhouse effect') in ecosystems that, in the absence of such chronic disturbance, exhibit very slow directional change (e.g. lakes, higher order streams and rivers). Monitoring the effects of a chronic anthropogenic disturbance to forest ecosystems to determine if it is resulting in a sustained, directional alteration of environmental 'quality' will require a definition of the expected pattern of episodic disturbance and recovery therefrom (i.e. patterns of secondary succession in the absence of the chronic disturbance). Only when we have such a 'temporal fingerprint' of forest ecosystem condition for 'normal' patterns of disturbance and recovery can we determine if the ecosystem condition is being degraded by chronic human-induced alteration of the environment. Thus, degradation is assessed in terms of deviations from the expected temporal pattern of conditions rather than in terms of an instantaneous assessment of any particular condition. The concept of 'ecological rotation' (the time for a given ecosystem to recover from a given disturbance back to some defined successional condition) is useful in the definition of these 'temporal fingerprints'. This requires information on the intensity of disturbance, the frequency of disturbance, and the rate of successional recovery. Only when all three of these are known or estimated can statements be made as to whether the ecosystem is in a longterm sustainable condition or not.The somewhat overwhelming complexity of this task has led forest ecologists to use ecosystem-level computer simulation models. Appropriately structured and calibrated models of this type can provide predictions of the overall temporal patterns of ecosystem structure and functions that can be expected to accompany a given frequency and character of episodic disturbance. Such models can also be used to examine the long-term consequences of chronic disturbances such as acid rain and climatic change. Predictive ecosystem-level models should be used in conjunction with some method of stratifying the inherent spatial biophysical variability of the forest environment, such as the biogeoclimatic classification system of British Columbia.