[en] Estimates of clumping index (Ω) are required to improve the indirect estimation of leaf area index (L) from optical field-based instruments such as digital hemispherical photography (DHP). A widely used method allows estimation of Ω from DHP using simple gap fraction averaging formulas (LX). This method is simple and effective but has the disadvantage of being sensitive to the spatial scale (i.e., the azimuth segment size in DHP) used for averaging and canopy density. In this study, we propose a new method to estimate Ω (LXG) based on ordered weighted gap fraction averaging (OWA) formulas, which addresses the disadvantages of LX and also accounts for gap size distribution. The new method was tested in 11 broadleaved forest stands in Italy; Ω estimated from LXG was compared with other commonly used clumping correction methods (LX, CC, and CLX). Results showed that LXG yielded more accurate Ω estimates, which were also more correlated with the values obtained from the gap size distribution methods (CC and CLX) than Ω obtained from LX. Leaf area index estimates, adjusted by LXG, are only 5%–6% lower than direct measurements obtained from litter traps, while other commonly used clumping correction methods yielded more underestimation. (author)

[en] We evaluated the carbon budget of coarse woody debris (CWD) in a temperate broad-leafed secondary forest. On the basis of a field survey conducted in 2003, the mass of CWD was estimated at 9.30 tC/ha, with snags amounting to 60% of the total mass. Mean annual CWD input mass was estimated to be 0.61 tC/ha/yr by monitoring tree mortality in the forest from 1999 to 2004. We evaluated the CWD decomposition rate as the CO₂ evolution rate from CWD by measuring CO₂ emissions from 91 CWD samples (RCWD) with a closed dynamic chamber and infrared gas analysis system. The relationships between RCWD and temperature in the chamber, water content of the CWD, and other CWD characteristics were determined. By scaling the measured RCWD to the ecosystem, we estimated that the annual RCWD in the forest in 2003 was 0.50 tC/ha/yr or 10%-16% of the total heterotrophic respiration. Therefore, 0.11 tC/ha/yr or 7% of the forest net ecosystem production was sequestered by CWD. In a young forest, in which CWD input and decomposition are not balanced, the CWD carbon budget needs to be quantified for accurate evaluation of the forest carbon cycle and NEP

[en] Samples of biosolids, spiked with increasing amounts of Cu, Ni or Zn were applied to field plots in a Pinus radiata forest, and the nutrient and metal status of the forest litter and underlying mineral soil was monitored over a period of six years following application. The macronutrient status of the forest litter was changed markedly by the biosolids application, with substantial increases in N, P and Ca concentrations, and decreases in Mg and K. The C/N ratio of the litter was also decreased and pH was increased by the biosolids application. The metals applied with the biosolids were retained predominantly in the litter layer, and even with non-metal-spiked biosolids there were substantial increases in litter metal concentrations. There was also firm evidence of some movement of Cu, Ni and Zn into the underlying mineral soil. The potential environmental issues resulting from these changes in nutrient and metal status are discussed. - Biosolids application to forest soils results in substantial build-up of macronutrients and metals in the forest litter layer

[en] Quantifying soil organic carbon (SOC) inputs in the surface soil is a critical component for assessing the potential for carbon sequestration of managed pine forests. This study used a sequential exclusion of aboveground litter inputs (L, litter exclusion) and aboveground plus belowground inputs (LR, litter and root exclusion) to segregate carbon sources contributing to the development and maintenance of SOC in the surface soil supporting juvenile loblolly pine (Pinus taeda L.) in its rapid growth phase. The study spanned the 7th to 10th year of stand growth. Soil physical size fractions (>2 mm, ≤2 mm, 2000-250 μm, 250--150 μm, 150--53 μm, and <53 μm) were used to investigate the change in native SOC over time in the untreated control plots (UC, untreated control) and the effects of exclusion treatments. An accretion rate of 4.6 Mg SOC·ha^-1 of soil-year^-1 was observed in the fine earth fraction (≤2 mm), reflecting the rapid phase of stand growth. The accretion was primarily observed in the upper 10 cm of the soil. Treatment effects were most apparent in soil bulk density, SOC of the fine earth, and 150--53 μm size fractions. In general, changes in SOC observed in the L treatment was an intermediate increase between the UC and LR treatments, where only the removal of roots provided no change in SOC and was significantly different from the control (p = 0.05). We conclude that a major contributor to the maintenance and increase of SOC in this fast-growing pine ecosystem was due to root turnover (60%), with 40% due to aboveground litter inputs. (author)

[en] Compositional and structural characteristics of three forest types, including aspen dominated, maple-birch dominated, and an intervening ecotone, were studied before and after irradiation in northern Wisconsin. Irradiation occurred during the summer of 1972. As of the summer of 1978, establishment of tree seedlings at 10 m from the radiation source continued to be inhibited by the vigorous development of ground vegetation except, in part, in the aspen area where seedling density increased sharply relative to 1977 because of an influx of Acer rubrum. By 1974 many of the seedlings at 20 m had reached the sapling size-class. At the present time it appears that recolonization of the 10 m irradiated zone by the original tree flora will be a very slow process, largely because of a dense growth of Rubus sp. and other heliophytes. As of 1978 the recovery of leaf litter production appeared to be continuing in all three areas although the ratios of tree to shrub litter were still well below preirradiation levels at 10 m and slightly below at 20 m. In most respects, the ecotone has shown properties and responses to radiation intermediate to those observed in the aspen and maple-birch areas. The rate and compositional characteristics of succession in the ecotone relative to aspen and maple-birch forest types is presently under study

[en] Compositional and structural characteristics of three forest types, including aspen dominated, maple-birch dominated, and an intervening ecotone, were studied before and after irradiation in northern Wisconsin. Irradiation occurred during the summer of 1972. By the summer of 1973 the density of viable tree seedlings at 10 m from the radiation source was substantially reduced in all three areas relative to the preirradiation densities of 1971. As of the summer of 1979, establishment of tree seedlings continued to be inhibited by the vigorous development of ground vegetation. In most respects, the ecotone has shown properties and responses to radiation intermediate to those observed in the aspen and maple-birch areas. The rate and compositional characteristics of succession in the ecotone relative to aspen and maple-birch forest types is presently under study

[en] We have studied nutrient related variables such as reallocation, nutrient use efficiency (NUE) and fine litter fall for three years in an oak forest Quercus humboldtii Bonpl. and also in some other forest plantations like pine, Pinus patula, and cypress, Cupressus lusitanica, in Antioquia, Colombia. Leaf litter quantities returned to the soil followed a falling sequence: oak (5313.3 kg ha-1 year-1) > pine (4866.5 kg ha-1 year-1) > cypress (2460.3 kg ha-1 year-1). The coniferous species showed the highest NUE for the majority of elements that were examined, except for P, which reached its absolute maximum in the oak forest -where a clear reallocation of this nutrient was also recorded-, probably because of its reduced availability in these volcanic ash-derived soils. Nutrient reallocation allows the conservation of the nutrients by reducing its loss from leaching and litter-fall, thereby closing the nutrient cycle in this native forest. In fact, P gains from net deposition were found there -this includes foliar leaching and atmospheric deposition-, which indicates that the species absorbs the P contained in rainfall from the leaves before it reaches the forest ground. N slow-efficiency use was probably due to its low availability in soil, given its low mineralization rates in these montane forests. K showed the highest reallocation values. Such figures are influenced by its clearly mobile character, according to the highest net deposition levels also verified for this element. With the exception of Mg, there was no clear relationship between the reallocation process and NUE.

[en] Radioactive contamination effect on the forest areas of Pripyat' Polessie is considered. Radiation processes in damaged pinetree plantations are characterized. Radionuclide migration dependent on soil types and tree stocks is analyzed. The data analysis has shown the evidence of ¹⁴⁴Ce, ¹'3⁷Cs, ¹³⁴Cs, ¹⁰⁶Ru in 3 years after radioactive contamination in the controlled area. By the end of the third year a significant radionuclide migration had occurred between the forest floor and lower aquifers. refs. 2; figs. 2; tabs. 8

[en] Short communications

[en] The deposition of Fukushima-derived radiocesium via falling litter in a coniferous forest 180 km downwind immediately following the nuclear power plant accident was investigated. The litterfall contribution to the transfer of radiocesium from the forest canopy to the forest floor was determined, and this pathway was compared with hydrological pathways. The results demonstrated that during the observation period, a total of approximately 5.5 kBq m"−"2 of Fukushima-derived radiocesium was deposited on the forest floor through throughfall (53%), stemflow (2.3%) and litterfall (45%) routes. The data revealed that the contributions of hydrological pathways became less important as time passed. However, the litterfall route, which transferred approximately 31% (2.5 ± 0.6 kBq m"−"2) of the local fallout within the observation period, continued depositing radiocesium onto the forest floor. - Graphical abstract: Schematic diagram summarizing the depositional routes of radiocesium in the cypress forest during the observation period (March to October, 2011). - Highlights: • Fukushima-derived radiocesium deposition in a coniferous forest was explored. • Approximately 68% of the radiocesium was deposited onto the forest floor. • The ecological half-life of the radiocesium in the forest canopy was 180 days. • The roles of hydrological pathways decreased over time. • The litterfall route continued to deposit radiocesium onto the forest floor