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At least 145 records · Page 8Linked to original sources
PubMed2003

Ecdysone agonists: mechanism and importance in controlling insect pests of agriculture and forestry.

Molting is the result of the expression of a cascade of genes that is sequentially both up and down-regulated by the molting hormone, 20-hydroxyecdysone (20E), which is secreted as a pulse during each instar. Benzoyl hydrazine analogs of 20E act like the native molting hormone at the molecular level by binding with the ecdysone receptor complex and transactivating a succession of molt initiating transcription factors that, in turn, induce the expression of a group of molt-related genes. As a result of the expression of these up-regulated genes, the larva undergoes apolysis and head capsule slippage and takes on the appearance of the pharate larva. However, unlike 20E, which is cleared at this juncture, allowing the down-regulated genes to be expressed, these synthetic analogs bind strongly to the receptors and remain in place and repress all the down-regulatory genes such as the ones necessary for cuticle elaboration, sclerotization, and ecdysis resulting in a developmental arrest in this state. As a result, the treated larva goes into a precocious incomplete molt that is lethal. Two of the analogs, tebufenozide and methoxyfenozide, are lepidopteran specific and have good control potential for open feeding larvae that ingest this material while a third one, halofenozide, acts on coleopteran larvae. Since they specifically act through an insect receptor complex, they have little or no effect on non-target species, making them environmentally attractive pest control agents. Some insects, however, show resistance to these analogs and this could be, inter alia, due to an ATP Binding Cassette Transporter like system that selectively pumps out the analogs.

ATP-Binding Cassette Transporters↗
PubMed2003

["Peculiar infection" with fever, splenomegaly and acute kidney failure in a 24-year-old forestry student].

When confronted by the combination of initial high fever associated with intense malaise, splenomegaly, elevated levels of transaminases, and acute renal failure, consideration must be given to the differential diagnosis of leptospirosis even in Germany. As a rule, the diagnosis is confirmed by serological testing based on the titer curve. Renal involvement is frequent, but usually has a good prognosis, especially if jaundice has not developed. Treatment with doxycycline or penicillin can shorten the disease course and exudation, possibly also the nephritis, or hinder it.

Acute Kidney Injury↗
PubMed1993

Forests and forestry: radiation protection measures with special reference to the Chernobyl accident zone.

A large proportion of the area contaminated by the Chernobyl accident in the former USSR is forested and has presented unique problems when considering appropriate post-contamination management and clean-up techniques. These problems are related to the forest's role as both a source and sink for radioactive contamination. Although it has been suggested that resuspension from forested areas may provide a secondary source of contamination to adjacent land, data collected after the Kyshtym and Chernobyl accidents suggest that forest ecosystems may also be effective in limiting the further spread of contamination away from the point of initial deposition and that this effect will increase over time. Such evidence serves to highlight the importance of these ecosystems in influencing the behaviour of radionuclides immediately after their release to the environment. Management practices for forested areas adopted since 1986 are described and a critical appraisal is presented of engineering-based countermeasures implemented over the initial post-accident period. These were intended to remove large quantities of contaminated materials from the forest environment. However, it is suggested that the natural processes of self-decontamination of trees and forest floor litter layers are sufficiently rapid and efficient to necessitate radical alterations to the technology based approaches adopted in the first 2 years after the Chernobyl accident.

Accidents↗
PubMed2005

The monoculture vs. rotation strategies in forestry: formalization and prediction by means of Markov-chain modelling.

The monoculture strategy of forest management, where the same tree species (e.g., Picea abies) is cultivated in a number of successive planting-growing-felling cycles, is generally considered to be economically efficient, yet not sustainable as it reduces biodiversity in the forest. The sound alternative suggests a long-term strategy of forest management in which different forest types rotate either with planting after clear cutting, or by natural forest succession, yet the commercial output remains dubious. We suggest an approach to formalization and modelling forest dynamics in the long-term by means of Markov chains, the monoculture strategy resulting in an absorbing chain and the rotation one in a regular chain. The approach is illustrated with a case study of Russkii Les, a managed forest located in the Moscow Region, Russia, and the nearby forest reserve having been used as a data source for undisturbed forest dynamics. Starting with conceptual schemes of transitions among certain forest types (states of the chain) in the monoculture and rotation cases, we estimated the transition probabilities by an original method based on average duration of the corresponding states and on the likelihood of alternative transitions from a state into the next one. Formal analysis of the regular chain reveals an opportunity to achieve particular management objectives within the rotation strategy, in particular, to get the distribution of forest types in accordance with an adopted hierarchy of their commercial values, i.e. more valuable types have greater shares.

Biodiversity↗
PubMed1997

Limit theorems and a general framework for risk analysis in clonal forestry.

Use of clonally propagated plantings in reforestation offers management advantages of phenotypic uniformity and high yields. Disadvantages include low genetic diversity and the possibility that the clone or clones chosen are particularly susceptible to attack by an insect or pathogen unforeseen as a problem at the time of clonal selection. In this paper, we continue consideration of the problem of choosing an optimal number of clones to minimize the risk of plantation failure. We present an analysis in which risk of failure for a plantation is represented by the probability that the proportion, S, of ramets that survive until harvest is less than or equal to a prescribed value. Our approach includes most earlier treatments as special cases. We show that the proportion S converges in distribution and, furthermore, that, under general conditions, a moderate number of clones, usually no more than 20 to 40 and often fewer, provides equivalent or better protection against catastrophic loss than does a large number of clones.

Forestry↗
PubMed2003

Quantifying the effects of forestry practices on the recovery of upland streams and lochs from acidification.

Trends in long-term chemistry data are presented for 37 acidified upland streams and lochs, located in four areas (A, B, C and D) across Scotland, to provide a comparison between recovery rates of moorland catchments and forest catchments at different stages of the management cycle. For all sites, non-marine sulfate (nm-SO(4)) showed a significant decline in annual median concentrations, the greatest decline being in streams draining felled catchments, which showed a 50% greater decline than catchments with moorland or young, aggrading forests. A similar pattern was found for chloride (Cl) concentrations in Area C, which reflected the reduced interception of sea-salt aerosols following clearfelling. However, high elevation moorland sites in Area D also revealed significant declines in Cl while trends in aggrading forest sites in this area were insignificant. Alkalinity (ALK) and pH increased more at sites where felling had taken place than at moorland or young forest sites while aggrading forest catchments appeared to be most resistant to changes in pH and ALK. Associated with these acid-base changes was a corresponding decline in labile aluminium (Al-L) concentrations. The pattern of nitrate (NO(3)) change was especially affected by the timing of felling in forested catchments. Large negative trends in NO(3) at stream sites were associated with felling during the early part of the study period. This downward trend was further enhanced as NO(3) concentrations fell below pre-felling levels as the second rotation crop became established. Few forest sites showed significant increases in NO(3) due to felling in the latter part of the study period. Most moorland loch sites showed a small but significant increase in NO(3,) probably in response to similar increases in N deposition and/or climatic impacts. Dissolved organic carbon (DOC) increased significantly at both forest and moorland sites, however, the extent of these increasing trends appeared to be positively correlated with absolute DOC concentrations. Despite the complex response of streams and lochs during the various stages of the forest cycle, especially for NO(3), both forest and moorland catchments showed generally similar and rapid responses to reductions in S deposition. Nevertheless, forested sites are still more acid and have higher concentrations of toxic forms of Al than moorland sites. Although the proposed emission reductions in Europe are likely to result in a continuing decline in S and N loadings to catchments, the continuing policy of planting second rotation forests in these acidified catchments may, in the long-term, delay or halt chemical and biological recovery. However, in the short-term, any increase in the uptake of N deposition by aggrading forests should help to counteract the acidifying effects of a small increase in the interception of S and N compounds.

Acid Rain↗
PubMed2003

Forestry practices increase mercury and methyl mercury output from boreal forest catchments.

We observed significant increases in the runoff output of total mercury (TotHg) and methyl mercury (MeHg) from a small spruce forest catchment (0.071 km2) after clear-cutting and soil treatment. Here we show that forest regeneration practices may act as an important additional source of TotHg and MeHg to forest lakes. TotHg and MeHg in runoff from two small forested catchments were monitored during the period 1994 to 2001. In the autumn of 1997, one of the catchments was clear-cut Soil preparation (mounding) was carried out in the autumn of 1998 and replanting in the summer of 1999. During the 3 years after the silvicultural treatment, medians of monthly flow-weighted TotHg and MeHg concentrations (12.02 ng L(-1) and 0.35 ng L(-1), respectively) and output loads (0.80-0.97 g km(-2) a(-1) and 0.011-0.036 g km(-2) a(-1), respectively) increased significantly compared to the 3 years calibration period (8.13 ng L(-1) and 0.15 ng 1(-1); 2.0-5.3 g km(-2) a(-1) and 0.11-0.16 g km(-2) a(-1), respectively). These results indicate that clear-cutting and/or soil treatment significantly increases the mobility of TotHg and MeHg accumulated in forest soil and may thus be an important factor for the total input of Hg to boreal freshwater ecosystems.

Ecosystem↗
PubMed2004

Effect of dissolved organic carbon on the photoproduction of dissolved gaseous mercury in lakes: potential impacts of forestry.

The production of dissolved gaseous mercury (DGM) in freshwater lakes is induced by solar radiation and is also thought to be linked to processes mediated by dissolved organic carbon (DOC). Studies investigating these processes using comparisons between lakes are often confounded by differences in DOC content and structure. In this study, we investigated the link between DOC concentrations and DGM production by using tangential ultrafiltration to manipulate DOC concentrations in water samples taken from a given lake. In this way, a range of samples with different DOC concentrations was produced without substantial changes to DOC structure or dissolved ions. This was repeated for four lakes in central Quebec: two with highly logged drainage basins and two with minimally logged drainage basins. On two separate days for each lake, water samples (filtered to remove >99% of microorganisms) with varying DOC concentrations were incubated in clear and dark Teflon bottles on the lake surface. DGM concentrations were measured at 3.5-h intervals over the course of 10.5 h. Levels of DGM concentrations increased with increasing cumulative irradiation for all lakes until approximately 4000 kJ m(-2) (400-750 nm, photosynthetically active radiation (PAR)), when DGM concentrations reached a plateau (between 20 and 200 pg L(-1)). When we assumed that DGM production was limited by the amount of photoreducible mercury, reversible first-order reaction kinetics fitted the observed data well (r2 ranging between 0.59 and 0.98, p < 0.05 with the exception of N70 100% DOC, 0% DOC, and K2 0% DOC with p = 0.06, 0.10, and 0.11, respectively). The DGM plateaus were independent of DOC concentrations but differed between lakes. In contrast, photoproduction efficiency (DGMprod) (i.e., the amount of DGM produced per unit radiation (fg L(-1) (kJ/m2)(-1)) below 4000 kJ m(-2) PAR) was linearly proportional to DOC concentration for both logged lakes (r2 = 0.97, p < 0.01) and nonlogged lakes (r2 = 0.52, p = 0.018) studied. Furthermore, logged lakes had a lower DGMprod per unit DOC (p < 0.01) than the nonlogged lakes. In these four lakes, the rate of DGM production per unit PAR was dependent on the concentration of DOC. The DGM plateau was independent of DOC concentration; however, there was a significant difference in DGM plateaus between lakes presumably due to different DOC structures and dissolved ions. This research demonstrates an important mechanism by which logging may exacerbate mercury levels in biota.

Carbon↗
PubMed2002

Collateral biodiversity benefits associated with 'free-market' approaches to sustainable land use and forestry activities.

Concern over the ever more rapid and widespread losses of biodiversity has instigated various remedial actions: whether in situ conservation, such as the establishment of protected areas, or ex situ, such as the conservation of germplasm in gene banks. In the past, such activities were funded and managed by the public sector; however, in recent years, public support has declined and this has spawned a growing interest in conservation opportunities that might arise from 'free-market' approaches to sustainable land use and management. The UN Convention on Biological Diversity (CBD) is the key framework for articulating policies and actions on biodiversity; however, progress in developing suitable economic and market incentives for biodiversity conservation and its sustainable use has been slow, with activities such as bioprospecting and ecotourism making some, albeit limited, headway. Given the United Nations Framework for Climate Change or United Nations Framework Convention on Climate Change's (UNFCCC's) high profile within the public and private sectors, there is some potential for using it to help advance CBD objectives and provide the much-needed economic incentives for conservation, through some of the market-based mechanisms presented under the Kyoto Protocol. Significant potential lies in the fact that many 'natural' forests and certain other ecosystems are both major stores of carbon and areas of valuable biodiversity. Thus, any attempt at conserving these areas has the potential to yield both carbon and biodiversity benefits. So far, however, the conservation of natural forests is not included in the Kyoto Protocol's definition of sinks. Instead the creation of sinks - through the establishment of fast-growing monocultures - may well lead to biodiversity losses, especially if partly degraded lands are cleared for this purpose. If real progress is to be made, our understanding of the relationship between land use and biodiversity benefits needs to be improved, and more appropriate proxies for biodiversity need to be developed. At the same time, we need to have a clear understanding of the precise nature of the potential synergies and be more able to identify possible jointaction opportunities that exist between the UNFCCC, the CBD and the Convention on Combating Desertification and other international trade and economic agreements.

Agriculture↗
PubMed1999

The role of extreme events in the impacts of selective tropical forestry on erosion during harvesting and recovery phases at Danum Valley, Sabah.

Ten years' hydrological investigations at Danum have provided strong evidence of the effects of extremes of drought, as in the April 1992 El Niño southern oscillation event, and flood, as in January 1996. The 1.5 km2 undisturbed forest control catchment experienced a complete drying out of the stream for the whole 1.5 km of defined channel above the gauging station in 1992, but concentrated surface flow along every declivity from within a few metres of the catchment divide after the exceptional rains of 19 January 1996. Under these natural conditions, erosion is episodic. Sediment is discharged in pulses caused by storm events, collapse of debris dams and occasional landslips. Disturbance by logging accentuates this irregular regime. In the first few months following disturbance, a wave of sediment is moved by each storm, but over subsequent years, rare events scour sediment from bare areas, gullies and channel deposits. The spatial distribution of sediment sources changes with time after logging, as bare areas on slopes are revegetated and small gullies are filled with debris. Extreme storm events, as in January 1996, cause logging roads to collapse, with landslides leading to surges of sediment into channels, reactivating the pulsed sediment delivery by every storm that happened immediately after logging. These effects are not dampened out with increasing catchment scale. Even the 721 km2 Sungai Segama has a sediment yield regime dominated by extreme events, the sediment yield in that single day on 19 January 1996 exceeding the annual sediment load in several previous years. In a large disturbed catchment, such road failures and logging-activity-induced mass movements increase the mud and silt in floodwaters affecting settlements downstream. Management systems require long-term sediment reduction strategies. This implies careful road design and good water movement regulation and erosion control throughout the logging process.

Ecosystem↗