1,158 research outputs found
Assessing intra- and inter-regional climate effects on Douglas-fir biomass dynamics in Oregon and Washington, USA
While ecological succession shapes contemporary forest structure and dynamics, other factors like forest structure (dense vs. sparse canopies) and climate may alter structural trajectories. To assess potential sources of variation in structural trajectories, we examined proportional biomass change for a regionally dominant tree species, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), across vegetation zones representing broad gradients in precipitation and temperature with 3510 forest inventory plots in Oregon and Washington, USA. We found that P. menziesii biomass change decreased with P. menziesii biomass stocks and increased with P. menziesii density, remaining positive in older stands only in the wet and warm vegetation zone. Within two of the vegetation zones, biomass change was greatest in warm and wet environments. In dry vegetation zones, positive P. menziesii biomass change responses to initial canopy cover and canopy cover change (i.e., increases with cover loss and decreases with cover gain) indicated shifts in forest structure. Variation in P. menziesii biomass dynamics within and between vegetation zones imply multi-scale climatic controls on forest structural trajectories for P. menziesii and highlight the potential for continued atmospheric carbon sequestration in warm and wet forests of the Pacific Northwest for both young and old forests, given that future climatic conditions support similar forest dynamics
Assessing intra- and inter-regional climate effects on Douglas-fir biomass dynamics in Oregon and Washington, USA
While ecological succession shapes contemporary forest structure and dynamics, other factors like forest structure (dense vs. sparse canopies) and climate may alter structural trajectories. To assess potential sources of variation in structural trajectories, we examined proportional biomass change for a regionally dominant tree species, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), across vegetation zones representing broad gradients in precipitation and temperature with 3510 forest inventory plots in Oregon and Washington, USA. We found that P. menziesii biomass change decreased with P. menziesii biomass stocks and increased with P. menziesii density, remaining positive in older stands only in the wet and warm vegetation zone. Within two of the vegetation zones, biomass change was greatest in warm and wet environments. In dry vegetation zones, positive P. menziesii biomass change responses to initial canopy cover and canopy cover change (i.e., increases with cover loss and decreases with cover gain) indicated shifts in forest structure. Variation in P. menziesii biomass dynamics within and between vegetation zones imply multi-scale climatic controls on forest structural trajectories for P. menziesii and highlight the potential for continued atmospheric carbon sequestration in warm and wet forests of the Pacific Northwest for both young and old forests, given that future climatic conditions support similar forest dynamics
A 10 kDa polypeptide associated with the oxygen-evolving complex of photosystem II has a putative C-terminal non-cleavable thylakoid transfer domain
AbstractThe N-terminal amino acid sequence of the 10 kDa polypeptide associated with the oxygen-evolving complex of wheat photosystem II has been determined and shown to be homologous to the amino acid sequence of the product of the ST-LS1 gene from potato. The N-terminal sequence of the mature protein indicates that the polypeptide is synthesized with a 39 amino acid N-terminal presequence which is similar to chloroplast import sequences but which lacks a hydrophobic domain for transfer of the protein across the thylakoid membrane. The mature polypeptide has a C-terminal hydrophobic region which shows homology to the hydrophobic thylakoid transfer domain of other lumenal proteins and this hydrophobic region of the 10 kDa polypeptide is suggested to facilitate transfer of the protein across the thylakoid membrane
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Tree seedling establishment on heterogenous microsites in Douglas-fir forest canopy gaps
Tree seedling establishment and growth were studied in experimental canopy gaps to determine the effect of structural and environmental heterogeneity on species dynamics within mature and old-growth Douglas-fir forests in the Cascades of central Oregon and southern Washington. Factors examined included forest age, gap size, within-gap position. substrate, year of germination, density of understory vegetation, shading by woody debris, light, moisture, and surface temperature. Four gap sizes, with gap diameter to tree height ratios ranging from 0.2 to 1.0, were created in the fall of 1990. Seeds of Abies amabilis, Pseudotsuga menziesii, and Tsuga heterophylla were sown in controlled microsites and germination, survival, and growth were monitored for two growing seasons. Seedlings established from natural seed rain were also monitored in natural microsites. Seedling establishment was greater in gaps than in closed-canopy areas. but was relatively low in portions of large gaps exposed to direct solar radiation, particularly for Tsuga. Shade from woody debris facilitated establishment in exposed areas, while shade from understory vegetation aided establishment of Pseudotsuga but not of Tsuga. Establishment in shaded portions of gaps declined with vegetation cover, with a greater effect from herbs than from shrubs. Seedling establishment was greatest on decayed wood in closed-canopy areas and small gaps, was similar on mineral soil, litter, and wood in shaded portions of largest gaps, and was lowest on litter in exposed portions of large gaps. Species establishment patterns differed between years, apparently due to
differences in weather. Seedling growth increased with gap size, and was greatest in gap centers. The growth response to increasing light was greatest for Tsuga.
Some evidence for gap partitioning by seedlings was found, although all species
were most abundant in similarly shaded portions of gaps. Establishment and growth of
the different species was related to seed size and interacting gradients of above- and
below-ground resource levels. Heterogeneity at the seedling scale often over-rode
environmental gradients associated with gap size and within-gap position. While gaps
may accelerate development of old-growth characteristics in these forests, establishment of Tsuga heterophylla is particularly sensitive to microsite quality
Constitutive expression of Yes-associated protein (Yap) in adult skeletal muscle fibres induces muscle atrophy and myopathy
Peer reviewedPublisher PD
Improving bycatch mitigation measures for marine megafauna in Zanzibar, Tanzania
This study was conducted to explore the governance processes and socio-economic factors relevant to the potential implementation of bycatch mitigation for various vulnerable marine megafauna (rays, sharks, marine mammals and turtles) in Zanzibar, Tanzania. Questionnaire-based interviews were conducted between February and April 2017 with fishers (n= 240) at eight landing sites. One focus group discussion was held in each site and eleven key informant interviews were carried out. The study showed that current measures to manage bycatch rates are not explicit; no rules govern rays and sharks bycatch; and rules regarding marine mammal and sea turtle bycatch are poorly enforced. Binary logistic regression was used to determine the effect of five selected socio-economic factors (education, age, proportional fishing income, fishing experience, and the number of adults who bring income into the household) on the willingness of fishers to participate in potential future bycatch mitigation measures for marine megafauna. The results indicate that only one factor (the number of adults who bring income into the household) had any significant effect (p=0.016). These findings could benefit the future governance and management of marine megafauna in Zanzibar through a better understanding of what mitigation measures are more likely to be supported
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Tree mortality based fire severity classification for forest inventories: A Pacific Northwest national forests example
Determining how the frequency, severity, and extent of forest fires are changing in response to changes in management and climate is a key concern in many regions where fire is an important natural disturbance. In the USA the only national-scale fire severity classification uses satellite image change-detection to produce maps for large (>400 ha) fires, and is generated by the Monitoring Trends in Burn Severity (MTBS) program. It is not clear how much forested area burns in smaller fires or whether ground-based fire severity estimates from a statistical sample of all forest lands might provide additional, useful information. We developed a tree mortality based fire severity classification using remeasured tree data from 10,008 plots in a probabilistic survey of National Forests System (NFS) lands in Oregon and Washington, using 8 tree mortality and abundance metrics. We estimate that 12.5% (±0.7% SE) of NFS forest lands in the region experienced a fire event during 1993–2007, with an annual rate of 0.96% (±0.05%). An estimated 6.5% of forest lands burned at High Severity or Moderate Severity; 2.1% burned at Very Low severity or only experienced surface or understory fire. A total of 358 of the 507 burned plots were within the MTBS perimeters, with ∼45% having equivalent severity classifications; but for ∼51% of the plots the MTBS classifications suggested lower severity than the tree-mortality based classes. Based on events recorded on plots and the inventory design, we estimate that 20.9% of the forested NFS lands experiencing fires, either wildfires or prescribed burns, were not in the MTBS maps. Tree mortality based fire severity classifications, combined with remotely-sensed and management information on timing and treatments, could be readily applied to nationally-consistent Forest Inventory and Analysis (FIA) data to provide improved monitoring of fire effects anywhere in the USA sampled by remeasured FIA inventories.Keywords: Fire effects, Tree remeasurement, Wildfire, Probabilistic sampling, Forest monitoring, Forest Inventory and Analysis (FIA
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Carbon stocks and changes on Pacific Northwest national forests and the role of disturbance, management, and growth
The National Forest System (NFS) of the United States plays an important role in the carbon cycle because these lands make up a large proportion of the forested land in the country and commonly store more wood per unit area than other forest ownerships. In addition to sustaining natural resources, these lands are managed for multiple objectives that do not always align with maximizing carbon (C) sequestration. The objectives of this study were to determine C stocks and flux in measured pools on Pacific Northwest Region NFS lands and the major ecological drivers of C flux. We compiled tree, dead wood, and understory vegetation data from 11,435 systematically-placed inventory plots and estimated growth, mortality, decay, removals, and disturbance events based on two full measurements spanning 1993–2007. The area of NFS-administered lands increased by 0.3% during this period and the area in formally-designated protected status increased by 0.7%. There was 1293 Tg C (±11.2 Tg standard error) in non-soil C stocks at the first measurement, which increased by 45 ± 2.2 Tg (3.4%), with 59% of the increase in the live tree pool and the remainder in the dead tree pools. C stocks followed broad regional patterns in productivity while C flux varied at local scales. Fires affected <1% of the forested area per year and were most prevalent in Wilderness areas. Fires reduced C stocks on burned plots by only 9%, and had a negligible effect on the region as a whole. Most tree harvest on NFS lands in the region consisted of partial harvest and had comparable impacts to fire during this period. C sequestration rates were higher (1.2 ± 0.09 Mg/ha/yr) on the west side of the Cascade Mountains, and primarily stayed in the live tree pool, compared to lower rates (0.5 ± 0.04 Mg/ha/yr) east of the Cascades where most of the increase was seen in the down wood pool. We discuss challenges to estimating forest ecosystem carbon stocks, which requires the application of a large number of equations and parameters for measured and unmeasured components, some with scant empirical support. Improved measurements and biomass models applied to networks of permanent plots would enable improved ground-based estimates of the drivers and components of regional changes in C.Keywords: Carbon sequestration, Forest inventory, Harvest, Dead woodKeywords: Carbon sequestration, Forest inventory, Harvest, Dead woo
Unbalanced Charge Distribution as a Determinant for Dependence of a Subset of Escherichia coli Membrane Proteins on the Membrane Insertase YidC
Membrane proteins are involved in numerous essential cell processes, including transport, gene regulation, motility, and metabolism. To function properly, they must be inserted into the membrane and folded correctly. YidC, an essential protein in Escherichia coli with homologues in other bacteria, Archaea, mitochondria, and chloroplasts, functions by incompletely understood mechanisms in the insertion and folding of certain membrane proteins. Using a genome-scale approach, we identified 69 E. coli membrane proteins that, in the absence of YidC, exhibited aberrant localization by microscopy. Further examination of a subset revealed biochemical defects in membrane insertion in the absence of YidC, indicating their dependence on YidC for proper membrane insertion or folding. Membrane proteins possessing an unfavorable distribution of positively charged residues were significantly more likely to depend on YidC for membrane insertion. Correcting the charge distribution of a charge-unbalanced YidC-dependent membrane protein abrogated its requirement for YidC, while perturbing the charge distribution of a charge-balanced YidC-independent membrane protein rendered it YidC dependent, demonstrating that charge distribution can be a necessary and sufficient determinant of YidC dependence. These findings provide insights into a mechanism by which YidC promotes proper membrane protein biogenesis and suggest a critical function of YidC in all organisms and organelles that express it
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