Near‐Infrared Hyperspectral Imaging of Fusarium‐Damaged Oats (Avena sativa L.)

The feasibility of hyperspectral imaging (HSI) to detect deoxynivalenol (DON) content and Fusarium damage in single oat kernels was investigated. Hyperspectral images of oat kernels from a Fusarium‐inoculated nursery were used after visual classification as asymptomatic, mildly damaged, and severely damaged. Uninoculated kernels were included as controls. The average spectrum from each kernel was paired with the reference DON value for the same kernel, and a calibration model was fitted by partial least squares regression (PLSR). To correct for the skewed distribution of DON values and avoid nonlinearities in the model, the DON values were transformed as DON* = [log(DON)]³. The model was optimized by cross‐validation, and its prediction performance was validated by predicting DON* values for a separate set of validation kernels. The PLSR model and linear discriminant analysis classification were further used on single‐pixel spectra to investigate the spatial distribution of infection in the kernels. There were clear differences between the kernel classes. The first component separated the uninoculated and asymptomatic from the severely damaged kernels. Infected kernels showed higher intensities at 1,925, 2,070, and 2,140 nm, whereas noninfected kernels were dominated by signals at 1,400, 1,626, and 1,850 nm. The DON* values of the validation kernels were estimated by using their average spectra, and the correlation (R) between predicted and measured DON* was 0.8. Our results show that HSI has great potential in detecting Fusarium damage and predicting DON in oats, but it needs more work to develop a model for routine application.     

Atmospheric deposition and leaching of nitrogen in Chinese forest ecosystems

Data have been compiled from published sources on nitrogen (N) fluxes in precipitation, throughfall, and leaching from 69 forest ecosystems at 50 sites throughout China, to examine at a national level: (1) N input in precipitation and throughfall, (2) how precipitation N changes after the interaction with canopy, and (3) whether N leaching increases with increasing N deposition and, if so, to what extent. The deposition of dissolved inorganic N (DIN) in precipitation ranged from 2.6 to 48.2 kg N ha⁻¹ year⁻¹, with an average of 16.6 kg N ha⁻¹ year⁻¹. Ammonium was the dominant form of N at most sites, accounting for, on average, 63% of total inorganic N deposition. Nitrate accounted for the remaining 37%. On average, DIN fluxes increased through forest canopies, by 40% and 34% in broad-leaved and coniferous forests, respectively. No significant difference in throughfall DIN inputs was found between the two forest types. Overall, 22% of the throughfall DIN input was leached from forest ecosystems in China, which is lower than the 50–59% observed for European forests. Simple calculations indicate that Chinese forests have great potential to absorb carbon dioxide from the atmosphere, because of the large forest area and high N deposition.     

Aluminium sulphate solubility in acid forest soils in Denmark

Ion leaching in 3 sandy spruce forest soils of different origin and pH was investigated in the laboratory. Zero-tension lysimeters containing undisturbed soil columns of varying soil depth were subjected to H₂SO₄ loadings for a period of 9 weeks. The analysis of the resulting leachate supports the hypothesis that Al-sulphate minerals may form in acidic soils when exposed to acid (H₂SO₄) deposition. In the B horizon of a glaciofluvial sandy soil (pH 4.2), both H⁺ and sulphate ions were retained to maintain 2pH + PSO₄ = 11.9 in the leachate solutions. This relation between H⁺ and sulphate activity may be due to an adsorption mechanism or a precipitation mechanism. The precipitation mechanism is favored by the good fit of leachate composition to the conditions for jurbanite [AlOHSO₄] formation from gibbsite [Al(OH)₃]. In the B horizon of a sandy till at pH 3.7, the Al in soil solution (0.5 mmol L^?1) was leached with sulphate. As the sulphate load was increased, some sulphate was retained. This may also be due to the dissolution and precipitation of an Al-sulphate mineral. The ion activity products of leachate solutions from the B horizon of this soil were close to the pK_s reported for jurbanite. The conditions for the possible existence and/or formation of Al-sulphate minerals in acidic soils are discussed.     

Management of urban recreational woodlands: The case of Norway

A questionnaire was mailed to 351 forest supervisors in Norway about the condition and management of urban woodlands important for recreation. The overall respondense rate was 56% and included 29 large urban settlements (10,000 inhabitants) and 168 small urban settlements (200–9999 inhabitants), encompassing about 37% of the Norwegian population. The areas included in the survey cover 194,100 ha, i.e. 1.6% of the forested area. Urban woodlands were defined as the annually most frequently visited forest areas larger than 50 ha. The average size of urban woodlands was about 1000 ha, equal in large and small urban settlements. About 73% of the urban woodlands were closer than 500 m from settlements. The mean proportion of forest in the urban fringe was 40%. Like most forested land in Norway, urban woodlands were mainly privately owned. In large urban settlements the proportion of municipal forest was slightly higher than in small urban settlements. The distributions of forest stand age and tree species composition in urban woodlands did not deviate from the overall forest situation in the region. Silviculture and forest plans were prominent in urban woodlands around both large and small urban settlements, but special plans for recreation and conservation were equally rare. Recreational facilities and conflicts were most common in urban woodlands around large urban settlements. The effect of the recommendations on management of urban woodlands developed during the 1970s is questioned regarding the small differences between urban woodlands and the general forest situation, as well as between woodlands of large and small urban settlements. However, recreational efforts may have been more intensive in smaller neighbourhood woodlands of less than 50 ha, which were beyond the scope of this survey.     

Synthesis of Nitrogen Pools and Fluxes from European Forest Ecosystems

To investigate which ecosystem parameters determine the risk and magnitude of nitrate leaching we compiled data from published and unpublished sources on dissolved inorganic nitrogen (DIN: NO₃ ^-) in throughfall, DIN leaching loss in runoff or seepage water, and other ecosystem characteristics from 139 European forests. Not all data were available for all sites: 126 sites had at least one year's data on DIN inputs and DIN leaching loss; 40-50 sites had some data on soil chemistry and/or vegetation pools of N. DIN inputs in throughfall range between <1 and about 70 kg N ha-1 yr-1 and the losses with seepage or runoff range between <1 and 50 kg N ha-1 yr-1. Retention of N within the ecosystem increases with increasing DIN deposition and increasing proportion of NH₄ ⁺ in deposition. The amount of N in needles and litterfall shows a significant linear relationship with throughfall deposition of DIN, whereas the C:N ratio of the organic (OH) horizon is uncorrelated to the level of throughfall-DIN flux. About 50% of the variability in DIN leaching loss can be explained by the flux of DIN in throughfall. Alternatively, about 60% of the variability in DIN leaching loss can be explained in a two-variable multiple regression combining the C:N ratio of the organic soil and the pH of the mineral soil. The survey data suggest that leaching of DIN from forest ecosystems in Europe is related in part to current DIN deposition and in part to the longer-term internal ecosystem N status as reflected in the chemistry of the humus and acidification status of the soil.     

Phytate degradation in a mixture of ground wheat and ground defatted soybeans during feed processing: effects of temperature, moisture level, and retention time in small- and medium-scale incubation systems

The optimal conditions for degradation of phytate (IP6, myo-inositol hexaphosphate) in a mixture of ground wheat and ground defatted soybeans (1:2, w/w) with added exogenous E. coli phytase were investigated at different temperatures (45, 60, 75, and 95 degrees C), moisture levels (25%, 35%, and 45%), and retention times (2-45 min). All treatment combinations were investigated in a small-scale mixer conditioner (experiment 1). The combined 45 degrees C and 45% moisture treatment was most efficient and reduced the content of IP6 by 86% during 45 min of incubation. This treatment combination was applied in a medium-scale mixer conditioner (experiment 2), and 76% reduction of IP6 at 45 min was obtained. During incubation, the content of lower groups of inositol phosphates, such as IP4 (myo-inositol tetraphosphate) and IP3 (myo-inositol triphosphate), increased significantly as the content of IP6 decreased. The major isomer formed was Ins(1,2,5,6)P(4).     

Nitrogen leaching in response to increased nitrogen inputs in subtropical monsoon forests in southern China

Dissolved inorganic nitrogen (DIN) (as ammonium nitrate) was applied monthly onto the forest floor of one old-growth forest (>400 years old, at levels of 50, 100 and 150 kg N ha⁻¹ yr⁻¹) and two young forests (both about 70 years old, at levels of 50 and 100 kg N ha⁻¹ yr⁻¹) over 3 years (2004–2006), to investigate how nitrogen (N) input influenced N leaching output, and if there were differences in N retention between the old-growth and the young forests in the subtropical monsoon region of southern China. The ambient throughfall inputs were 23–27 kg N ha⁻¹ yr⁻¹ in the young forests and 29–35 kg N ha⁻¹ yr⁻¹ in the old-growth forest. In the control plots without experimental N addition, a net N retention was observed in the young forests (on average 6–11 kg N ha⁻¹ yr⁻¹), but a net N loss occurred in the old-growth forest (−13 kg N ha⁻¹ yr⁻¹). Experimental N addition immediately increased DIN leaching in all three forests, with 25–66% of added N leached over the 3-year experiment. At the lowest level of N addition (50 kg N ha⁻¹ yr⁻¹), the percentage N loss was higher in the old-growth forest (66% of added N) than in the two young forests (38% and 26%). However, at higher levels of N addition (100 and 150 kg N ha⁻¹ yr⁻¹), the old-growth forest exhibited similar N losses (25–43%) to those in the young forests (28–43%). These results indicate that N retention is largely determined by the forest successional stages and the levels of N addition. Compared to most temperate forests studied in Europe and North America, N leaching loss in these seasonal monsoon subtropical forests occurred mainly in the rainy growing season, with measured N loss in leaching substantially higher under both ambient deposition and experimental N additions.     

Litterfall and nutrient return in five tree species in a common garden experiment

Canopy litterfall is a significant pathway for return of nutrients and carbon (C) to the soil in forest ecosystems. Litterfall was studied in five even-aged stands of Norway spruce, Sitka spruce, Douglas-fir, European beech and common oak at three different locations in Denmark; two sandy sites, Ulborg and Lindet in Jutland, and one loamy site, Frederiksborg on Zealand. Litterfall was collected during three years from 1994 to 1996 in all five species and during six years from 1994 to 1999 in Norway spruce, Sitka spruce and European beech. The average total litterfall was in the range of 3200–3700 kg ha⁻¹ yr⁻¹ and did not differ significantly among tree species. There were no significant differences in total litterfall among sites during the short period, but during the longer period the richer site Frederiksborg had significantly higher total and foliar litterfall amounts compared to the more nutrient-poor sites Lindet and Ulborg. There were close relationships between foliar and total litterfall suggesting that foliar litterfall can be reliably estimated from total litterfall. Beech and oak bud scale litter was significantly related to foliar litterfall. The amount of branch and twig litter was significantly higher in oak than in other tree species. The average foliar litterfall was well related to the annual volume increment. The relationship differed markedly from previously reported relationships based on global litterfall data suggesting that such relationships are better evaluated at the regional level. Nutrient concentrations and fluxes in foliar litterfall were not significantly different among the five tree species. However, there was a significant effect of site on most nutrient concentrations of the three litterfall fractions, and foliar fluxes of P, Ca and Mn were all significantly highest at Frederiksborg and lowest at Ulborg. The similarity in litterfall inputs to the forest floor under these five tree species suggested that previous reports of large variability in forest floor accumulation should primarily be attributed to differences in litter decomposition.