Effects of overstory tree density, site preparation, and ground vegetation on natural Scots pine seedling emergence and survival in northern boreal pine forests

Natural regeneration is a commonly used forest regeneration method in northern Finland. It is not known, however, what would be the optimal overstory density and ground vegetation composition for seedling emergence and survival, and if site preparation is needed to accompany overstory density manipulation. We studied the effects of overstory density (unthinned control and thinning to 50,150, and 250 trees.ha(-1)) and ground vegetation removal (mechanical site preparation with disc trenching) on the number of naturally germinated pine seedlings and survival of individual seedlings over a period of 8 to 11 years. Bare mineral soil was a superior seedbed compared to intact vegetation cover, even though the mortality rate was high on mineral soil. Greater cover of lingonberry, crowberry, and slash had a negative effect on seedling number. Seedling mortality was initially high (60% died during the first 2 years) but decreased throughout the first 5 years. The survival rate of seedlings located in the mineral soil of the upper part of the disc trencher track was twice as high as that of seedlings located in the lower part of the track. High coverage of hair mosses (Polytrichum spp.) was associated with poorer seedling survival. An overstory density of 50-150 trees.ha(-1) with site preparation seems to be an efficient treatment to promote regeneration under these circumstances

Effects of overstory tree density, site preparation, and ground vegetation on natural Scots pine seedling emergence and survival in northern boreal pine forests

Natural regeneration is a commonly used forest regeneration method in northern Finland. It is not known, however, what would be the optimal overstory density and ground vegetation composition for seedling emergence and survival, and if site preparation is needed to accompany overstory density manipulation. We studied the effects of overstory density (unthinned control and thinning to 50,150, and 250 trees.ha(-1)) and ground vegetation removal (mechanical site preparation with disc trenching) on the number of naturally germinated pine seedlings and survival of individual seedlings over a period of 8 to 11 years. Bare mineral soil was a superior seedbed compared to intact vegetation cover, even though the mortality rate was high on mineral soil. Greater cover of lingonberry, crowberry, and slash had a negative effect on seedling number. Seedling mortality was initially high (60% died during the first 2 years) but decreased throughout the first 5 years. The survival rate of seedlings located in the mineral soil of the upper part of the disc trencher track was twice as high as that of seedlings located in the lower part of the track. High coverage of hair mosses (Polytrichum spp.) was associated with poorer seedling survival. An overstory density of 50-150 trees.ha(-1) with site preparation seems to be an efficient treatment to promote regeneration under these circumstances.Peer reviewe

Higher habitual flavonoid intakes are associated with a lower risk of peripheral artery disease hospitalizations

Background The role of nutrition in the primary prevention of peripheral artery disease (PAD), the third leading cause of atherosclerotic cardiovascular disease, is undetermined. Flavonoids may attenuate atherosclerosis and therefore persons who consume flavonoid-rich foods may have a lower risk of developing PAD. Objectives We aimed to examine the association between flavonoid intake and PAD hospitalizations and investigate if the association differs according to established risk factors for PAD. Methods Baseline data from 55,647 participants of the Danish Diet, Cancer, and Health Study without PAD, recruited from 1993 to 1997, were cross-linked with Danish nationwide registries. Flavonoid intake was calculated from FFQs using the Phenol-Explorer database. Associations were examined using multivariable-adjusted restricted cubic splines based on Cox proportional hazards models. Results After a median [IQR] follow-up time of 21 [20–22] y, 2131 participants had been hospitalized for any PAD. The association between total flavonoid intake and total PAD hospitalizations was nonlinear, reaching a plateau at ∼750–1000 mg/d. Compared with the median flavonoid intake in quintile 1 (174 mg/d), an intake of 1000 mg/d was associated with a 32% lower risk of any PAD hospitalization (HR: 0.68; 95% CI: 0.60, 0.77), a 26% lower risk of atherosclerosis (HR: 0.74; 95% CI: 0.62, 0.88), a 28% lower risk of an aneurysm (HR: 0.72; 95% CI: 0.59, 0.88), and a 47% lower risk of a hospitalization for other peripheral vascular disease (HR: 0.53; 95% CI: 0.42, 0.67). A higher total flavonoid intake was also significantly associated with a lower incidence of revascularization or endovascular surgery and lower extremity amputation. The association between total flavonoid intake and PAD hospitalizations differed according to baseline smoking status, alcohol intake, BMI, and diabetes status. Conclusions Ensuring the adequate consumption of flavonoid-rich foods, particularly in subpopulations prone to the development of atherosclerosis, may be a key strategy to lower the risk of PAD

Simulations of column-averaged CO_2 and CH_4 using the NIES TM with a hybrid sigma-isentropic (σ-θ) vertical coordinate

We have developed an improved version of the National Institute for Environmental Studies (NIES) three-dimensional chemical transport model (TM) designed for accurate tracer transport simulations in the stratosphere, using a hybrid sigma-isentropic (σ-θ) vertical coordinate that employs both terrain-following and isentropic parts switched smoothly around the tropopause. The air-ascending rate was derived from the effective heating rate and was used to simulate vertical motion in the isentropic part of the grid (above level 350 K), which was adjusted to fit to the observed age of the air in the stratosphere. Multi-annual simulations were conducted using the NIES TM to evaluate vertical profiles and dry-air column-averaged mole fractions of CO_2 and CH_4. Comparisons with balloon-borne observations over Sanriku (Japan) in 2000–2007 revealed that the tracer transport simulations in the upper troposphere and lower stratosphere are performed with accuracies of ~5% for CH_4 and SF_6, and ~1% for CO_2 compared with the observed volume-mixing ratios. The simulated column-averaged dry air mole fractions of atmospheric carbon dioxide (XCO_2) and methane (XCH_4) were evaluated against daily ground-based high-resolution Fourier Transform Spectrometer (FTS) observations measured at twelve sites of the Total Carbon Column Observing Network (TCCON) (Bialystok, Bremen, Darwin, Garmisch, Izaña, Lamont, Lauder, Orleans, Park Falls, Sodankylä, Tsukuba, and Wollongong) between January 2009 and January 2011. The comparison shows the model's ability to reproduce the site-dependent seasonal cycles as observed by TCCON, with correlation coefficients typically on the order 0.8–0.9 and 0.4–0.8 for XCO_2 and XCH_4, respectively, and mean model biases of ±0.2% and ±0.5%, excluding Sodankylä, where strong biases are found. The ability of the model to capture the tracer total column mole fractions is strongly dependent on the model's ability to reproduce seasonal variations in tracer concentrations in the planetary boundary layer (PBL). We found a marked difference in the model's ability to reproduce near-surface concentrations at sites located some distance from multiple emission sources and where high emissions play a notable role in the tracer's budget. Comparisons with aircraft observations over Surgut (West Siberia), in an area with high emissions of methane from wetlands, show contrasting model performance in the PBL and in the free troposphere. Thus, the PBL is another critical region for simulating the tracer total column mole fractions

Estimates of global dew collection potential on artificial surfaces

Peer reviewe

Polar startospheric cloud observation at sodankyla (SF)

We present some preliminary results of MOANA (Measurements and modelling of Ozone and Aerosols in the Northern Atmosphere) multi-wavelength lidar system, which was operating at Sodankyla (SF) during SESAME. We observed various polar stratospheric cloud (PSC) episodes; in this work we report the measurements of January 12 (JI2) and January 19 (J19), 1995. The J12 PSC has a layered structure and two of the three particle layers show a depolarised backscattering signal. On the other hand the J19 PSC detected between 19 and 24km is likely composed of spherical (liquid) particles because no depolarization shows up. In the last case an analysis of the lidar backscattering at the different wavelengths allows to estimate the optical size distribution of the particles.PublishedSchliersee, Germany1.8. Osservazioni di geofisica ambientaleope

Lidar observations of liquid and solid PSC at Sodankyla

Polar stratospheric clouds (PSC) play a major role in the process of Artic and Antartic ozone depletion due to the surface provided for heterogeneus chemical reactions and the removal of NO2 from the gas phase. Therefore the phase, size and composition of PSC's should be known. The microphysical structure of the PSC's depends on the actual temperature and the corresponding; airmass thermal history. At temperatures below the ice frostpoint, PSC's of ice particles (Type II) are observed, while PSC's seen at temperatures above the frostpoint are classified as PSC Type Ia (anisotropic particles) and PSC Ib (spherical particles). PSC I were believed to consist of nitric acid trihydrate (NA'r). NAT should be stable some degrees above the ice frostpoint with a particle shape depending on the cooling rate [Toon et al., 1990]. However, the explanation of PSC based solely on the NAT-hypothesis can not explain a large amount of data [Toon and Tolbert, 1995]. The spherical shape of PSC Ib can be explained with a liquid supercooled ternary solution (STS) consisting of H2O, HNO3 and H2SO4. Scenarios for the formation of frozen background aerosol (sulfuric acid tetrahydrate, SAT) are now investigated. The described variance in shape and size of the PSC can be sensed by multispectral 2-polarization lidar, measuring range resolved scattering properties of atmospheric aerosols. Here the lidar observations of PSC's during the SESAME campaign are compared to the critical formation temperatures of the different PSC types.PublishedSchliersee, Germany1.8. Osservazioni di geofisica ambientaleope

Results of a trajectory box model simulating the size distribution evolution of stratospheric particles (H2SO4/H2O and H2SO4/HNO3/H2O solutions). A case study during SESAME

A revised interpretation of ER-2 polar stratospheric cloud (PSC) observations during AASE I (1989) and MOE (1987) Tabazadeh et al., 1995) suggests a picture of the PSC formations which evidences the importance of the air mass thermal histories. A series of ER-2 measurements are consistent with the thennodynamical properties of the liquid H2SO4/HNO3/H20 solution particles, but the data collected in other flights are in agreement with the possible formation of amorphous solid solutions of HNO3 and H2O through a peculiar coolingiheating cycle below the solid sulfuric acid tetrahydrate (SAT) melting temperatures and above the water ice saturation temperatures (frost point). During this cycle the liquid H2SO4 stratospheric aerosols may undergo a phase transition to SAT particles, required for the growing of solid nitric acid hydrates. On the other hand Koop et al., (1995) report laboratory experiments which show that H2SO4/HNO3/H20 liquid particles never freeze under stratospheric conditions for temperatures higher than the frost point. despite the change in composition due to the HNO3 uptake when cooling. In addition, when solid particles are heated, they start to become liquid at the SAT melting point. Then the analysis of any PSC data should start from air mass trajectory studies, and some thermodynamical criteria could be used to infer the physical state (liquid or solid) of the sampled particles. We use a trajectory box model to study the microphysical properties of stratospheric clouds observed during SESAME by the MOANA (Measurements and modelling of Ozone and Aerosols in the Northern Atmosphere) lidar at Sodankyla (SF). Our models treats the gas to particle conversion of H2SO4, HNO3, H2O and the microphysics of Aitken particles (ATK), H2SO4/H20 (WS) and H2SO4/HNO3/H20 (WSN) solution droplets; H2SO4 -nH2O (SA) and HNO3 -nH20 (NA) solid hydrates particles are also taken into account. To analyze the MOANA observations, within a prescribed air mass thermal history, we adopt a simple criteria which states that the particles should be liquid just after having performed temperatures above the SAT melting point. while they are solid if the water ice saturation temperatures are reached. The model simulations along the air mass trajectories reaching the lidar site during the observations are in agreement with the aerosol size distribution optically retrieved by the MOANA multiwavelength lidar (Masci et al., .1995).PublishedSchliersee, Germany1.8. Osservazioni di geofisica ambientaleope