Parasitism rate differs between herbivore generations in the univoltine, but not bivoltine, range

With climate change, plant-feeding insects increase their number of annual generations (voltinism). However, to what degree the emergence of a new herbivore generation affects the parasitism rate has not been explored. We performed a field experiment to test whether the parasitism rate differs between the first and the second generations of a specialist leaf miner (Tischeria ekebladella), both in the naturally univoltine and bivoltine parts of the leaf miner's distribution. We found an interactive effect between herbivore generation and geographical range on the parasitism rate. The parasitism rate was higher in the first compared to the second host generation in the part of the range that is naturally univoltine, whereas it did not differ between generations in the bivoltine range. Our experiment highlights that shifts in herbivore voltinism might release top-down control, with potential consequences for natural and applied systems

The standardization and certification procedures of cryogenic equipment in Kazakhstan

The complex of procedures on stepwise carrying out actions of standardization and certification of liquid nitrogen, argon and oxygen gasificator G-200 is considered. In the process of organization of standardization and certification procedures the set of regulatory documents was developed that allow starting small-scale production of gasificators in Kazakhstan. Thus the emphasis on the potential incorporation of the requirements of such documents is placed from the Eurasian Economic Union

Mixed-severity natural disturbance regime dominates in an old-growth Norway spruce forest of northwest Russia

Questions: What were the long-term disturbance rates (including variability) and agents in pristine Norway spruce-dominated (Picea abies (L.) Karst.) forests? Have soil moisture conditions influenced disturbance rates across this boreal spruce-dominated forest? Were the temporal recruitment patterns of canopy dominants associated with past disturbance periods? Location: Interfluvial region of Northern Dvina and Pinega rivers, Arkhangelsk, northwest Russia. Methods: We linked dendrochronological data with tree spatial data (n trees=1659) to reconstruct the temporal and spatial patterns of canopy gaps in a 1.8-ha area from 1831-2008, and to develop a growth-release chronology from 1775-2008. Results: No evidence of stand-replacing disturbances was found within selected forest stands over the studied period. Forest dynamics were driven by small- to moderate-scale canopy disturbances, which maintained a multi-cohort age structure. Disturbance peaks were observed in the 1820s, 1920s, 1970s and 2000s, with decadal rates reaching 32% of the stand area disturbed. Conclusions: The overall mean decadal rate was 8.3% canopy area disturbed, which suggests a canopy turnover time of 122yr, with a 95% confidence envelop of 91-186yr. Bark beetle outbreaks (possibly exacerbated by droughts) and wind-storms emerged as the principal disturbance agents. Recruitment of both Norway spruce and downy birch was associated with periods of increased canopy disturbance. Moisture conditions (moist vs mesic stands) were not significantly related to long-term disturbance rates. The studied spruce-dominated boreal forests of this region apparently exhibited long-term forest continuity under this mixed-severity disturbance regime. These disturbances caused considerable structural alterations to forest canopies, but apparently did not result in a pronounced successional shifts in tree species composition, rather occasional minor enrichments of birch in these heavily spruce-dominated stands

Marginal imprint of human land use upon fire history in a mire-dominated boreal landscape of the Veps Highland, North-West Russia

Dendrochronological reconstructions inform us about historical climate-fire-human interactions, providing a means to calibrate projections of future fire hazard. Most of these reconstructions, however, have been developed in landscapes with a considerable proportion of xeric sites that could potentially inflate our estimates of the historic levels of fire activity. We provide a 420-year long reconstruction of fires in a mire-dominated landscape of the Veps Nature Park, North-West Russia. The area has mostly escaped large-scale forestry operations in the past and is an example of pristine mid-boreal vegetation with a high (approximately 30% for the area studied) proportion of waterlogged areas with ombrotropic mires. The historical fire cycle was 91.4 years (90% confidence intervals, CI 66.2-137.6 years) over the 1580-1720 period, decreasing to 35.9 (CI 28.1-47.6 years) between 1730 and 1770, and then increasing again to 122.7 years (CI 91.0-178.0 years) over the 1780-2000 period. Early season fires dominated over late season fires during the reconstruction period. We documented a higher fire activity period between 1730 and 1780, resulting from the increase in early season fires. This period coincided with one of the largest multi-decadal declines in the reconstructed spring precipitation since 1600 CE, although we found no significant relationship between fire and precipitation over the whole reconstructed period. The nine largest fire years were associated with negative summer precipitation and positive summer temperature anomalies over the study region. Land-use history of the area did not appear to have an effect on historical fire dynamics. Modern (1996-2016) fire records indicate a regional fire cycle of ~ 1300 years, featuring a pronounced pattern with early (April-May) and late (July-September) season fires. The uniform fire cycle in the area since 1780, occurrence of nine largest fire years during years with spring-summer droughts, and low ignition frequencies over the last 420 years (0.005 to 0.037 ignitions per year and km2) suggest that the fire regime of the Veps Highland remained largely natural until the onset of the 20th century