Edge effects and trampling in boreal urban forest fragments – impacts on the soil microbial community

Fragmentation of forest ecosystems increases the proportion of edge habitat and is accompanied by a change in plant species composition. The recreational use of urban forests leads to decreased vegetation cover and the formation of paths, and thus, to fragmentation at small scales. We studied the impacts of forest and path edge effects on the soil microbial community structure (by using the phospholipid fatty acid (PLFA) method) and microbial activity (measured as basal respiration) in 34 mesic boreal urban forest fragments in Finland. We sampled the humus layer 1) from the forest edge into the interior (0–80 m), and 2) at different distances from paths. Microbial community structure was only slightly affected by the forest edge but differences were found between distances of 0–10 m and over 50 m from the edge. These changes correlated with changes in soil pH. Although changes in the microbial community structure were not pronounced, microbial biomass and activity were 30–45% lower at the first 20 m into the forest fragments, due to a low moisture content of the humus near the edge. The decreased microbial activity detected at forest edges implies decreased litter decomposition rates, and thus, a change in ecosystem nutrient cycling. The microbial community structure differed between paths and surrounding areas and correlated with changes in soil pH. Paths also supported approximately 25–30% higher microbial biomass with a transition zone of at least 1 m from the path edge. Path associated disturbances (mainly alterations in vegetation and soil pH) were reflected in the soil microbial community structure up to 1.5 m from the paths.     

Degradation of Secalins During Rye Sourdough Fermentation

Rye sourdough (RSD) gives rye bread mildly acidic taste and desired flavor. Flavor precursors (amino acids and small peptides) are generated in the proteolytic breakdown of rye proteins. Our aim was to study the protein degradation during RSD fermentations. Two sourdoughs were prepared of flours derived from two rye cultivars (Amilo and Akusti). RSD samples were collected during fermentations. Three protein fractions were obtained by sequential protein extraction and these were analyzed by SDS‐PAGE. Free amino nitrogen (FAN) was measured with a ninhydrin method. In addition, two rye incubations without starter microorganisms (with antibiotics) were made at pH 3.6 and 6.1, and proteinase profiles of the rye cultivars were analyzed at pH 4.3. SDS‐PAGE analysis showed that during RSD fermentations, rye proteins, especially the alcohol‐soluble secalins, were degraded. Secalins also evidently degraded during the incubation without starter microorganisms at pH 3.6. Aspartic proteinases were in the major proteinase group in both rye cultivars. This study confirms that endogenous proteinases of rye, mainly aspartic proteinases, hydrolyze rye proteins, especially secalins, during RSD fermentation. Protein degradation in rye sourdoughs may thus be enhanced by selecting rye flours with high proteolytic activity toward secalins.     

Effect of Baking Method and Fermentation on Folate Content of Rye and Wheat Breads

The effect of baking method on folates of rye and wheat breads, as well as the effect of sourdough fermentation of rye, were examined. Sourdough fermentations were performed both with and without added yeast, and samples were taken throughout the baking process. Samples were analyzed microbiologically for their total folate content after trienzyme extraction. Individual folate vitamers were determined by HPLC after affinity chromatographic purification. The lowest folate contents for both rye and wheat breads were found from breads baked without added yeast. Total folate content increased considerably during sourdough fermentation due to increased amounts of 10‐HCO‐H₂folate, 5‐CH₃‐H₄folate, and 5‐HCO‐H₄folate. Baker's yeast contributed markedly to the final folate content of bread by synthesizing folates during fermentation. Proofing did not influence total folate content but changes in vitamer distribution were observed. Folate losses in baking were ≈25%. The variety of sourdoughs and baking processes obviously lead to great variation in folate content of rye breads. The possibilities to enhance natural folate content of rye bread by improving folate retention in technological processes and by screening and combining suitable yeasts and lactic acid bacteria should be further investigated.     

Inhibition of Angiotensin converting enzyme I caused by autolysis of potato proteins by enzymatic activities confined to different parts of the potato tuber

Autolysis of protein isolates from vascular bundle and inner tuber tissues of potato (Solanum tuberosum) enhanced the inhibition of the angiotensin converting enzyme I (ACE), a biochemical factor affecting blood pressure (hypertension). The physiological age of the tuber affected the strength of ACE inhibition, the rate of its increase during autolysis, and the tuber tissue where ACE inhibition was most pronounced. The highest inhibitory activities (50% reduction in ACE activity achieved following autolysis at a protein concentration of 0.36 mg mL (-1)) were measured in tubers after 5-6 months of storage prior to sprouting. The rate of ACE inhibition was positively correlated with protease activity in tuber tissues. Amendment of the autolysis reaction with protein substrates from which bioactive ACE-inhibitory peptides may be released, for example, a purified recombinant protein or a concentrate of total tuber proteins, also enhanced ACE inhibition. Many tuber proteins including aspartic protease inhibitors were degraded during autolysis. The data provide indications of differences in the enzymatic activities confined to different parts of the potato tuber at different physiological stages. Results suggest that native enzymes and substrate proteins of potato tubers can be utilized in search of dietary tools to manage elevated blood pressure.     

Berry phenolic extracts modulate the expression of p21(WAF1) and Bax but not Bcl-2 in HT-29 colon cancer cells

Previous studies have shown that anthocyanin-rich berry extracts inhibit the growth of cancer cells in vitro. The objective of this study was to compare the effects of berry extracts containing different phenolic profiles on cell viability and expression of markers of cell proliferation and apoptosis in human colon cancer HT-29 cells. Berry extracts were prepared with methanol extraction, and contents of the main phenolic compounds were analyzed using HPLC. Anthocyanins were the predominant phenolic compounds in bilberry, black currant, and lingonberry extracts and ellagitannins in cloudberry extract, whereas both were present in raspberry and strawberry extracts. Cells were exposed to 0-60 mg/mL of extracts, and the cell growth inhibition was determined after 24 h. The degree of cell growth inhibition was as follows: bilberry > black currant > cloudberry > lingonberry > raspberry > strawberry. A 14-fold increase in the expression of p21WAF1, an inhibitor of cell proliferation and a member of the cyclin kinase inhibitors, was seen in cells exposed to cloudberry extract compared to other berry treatments (2.7-7-fold increase). The pro-apoptosis marker, Bax, was increased 1.3-fold only in cloudberry- and bilberry-treated cells, whereas the pro-survival marker, Bcl-2, was detected only in control cells. The results demonstrate that berry extracts inhibit cancer cell proliferation mainly via the p21WAF1 pathway. Cloudberry, despite its very low anthocyanin content, was a potent inhibitor of cell proliferation. Therefore, it is concluded that, in addition to anthocyanins, also other phenolic or nonphenolic phytochemicals are responsible for the antiproliferative activity of berries.     

Sediment,Perch (Perca fluviatilis L.) and Bottom Fauna as Indicators of Effluent Discharged from the Pulp and Paper Mill Complex at Kemi,Northern Finland

This paper compares the long-term data of EOX (Extractable Organic Halogens) determinations in sediments, trichloroguaiacol, i.e. 3,4,5-trichloroguaiacol and 4,5,6-trichloroguaiacol, determinations in the bile of perch (Perca fluviatilis L.) and changes in bottom fauna communities (Pontoporeia affinis L., Mesidotea entomon L., Valvata spp. L.) during 1994–2003. The study area is located at Kemi, on the Gulf of Bothnia, Northern Finland, and is affected by effluent discharged from the pulp and paper mills of Stora Enso Oyj and Oy Metsä-Botnia Ab. The Kemi municipal sewage plant, and River Kemijoki also impose a load in the same area. The main purpose of the study was to assess whether the state of the exposed water ecosystem has improved on the basis of the concentrations of organochlorine compounds in sediment and in perch, due to the modernisation of the wastewater treatment at the mills. In addition, we also investigated whether the changes in the bottom fauna community indicate an improvement in the purification of the effluents. The results indicate that the concentrations of trichloroguaiacols (–1) in perch reflect the decreased discharges of chlorinated substances from the mills. The EOX concentrations in bottom sediments have also decreased to below 50 of Cl g^–1 in most parts of the study area, which is in good agreement with the reduction in the discharge of organochlorines. According to the long-term changes in bottom fauna, the reduction in the discharge of organochlorine compounds due to modernisation of the pulp mills is reflected in a recovery of the benthic fauna, especially Valvata spp. L. and Pontoporeia affinis L.     

Qualitative characterization of benzoxazinoid derivatives in whole grain rye and wheat by LC-MS metabolite profiling

Benzoxazinoids are metabolites occurring in a restricted group of plant species including crops such as rye, wheat, and maize. Focus on the analysis of benzoxazinoid metabolites has typically been due to their importance to plant biochemistry and physiology as highly bioactive molecules that plants use as alleochemicals to defend themselves against predators and infections. However, the potential dietary contribution of these compounds has not been addressed. This study conducted a detailed qualitative characterization of benzoxazinoid metabolites present in the whole grain rye and processed fractions of rye bran, and their presence was also detected in whole grain wheat samples. Several novel benzoxazinoid metabolites of the hydroxamic acids (2,4-dihydroxy-1,4-benzoxazin-3-one, DIBOA; 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one, DIMBOA), lactams (2-hydroxy-1,4-benzoxazin-3-one, HBOA), and benzoxazolinones (1,3-benzoxazol-2-one, BOA) were identified, including double-hexose derivatives of DIBOA, DIMBOA, and HBOA. This paper presents an important addition to the information on the phytochemical composition of rye and wheat grains, which deserves attention in the discussion of the potential health-promoting effects of these grains.     

Old soil carbon is more temperature sensitive than the young in an agricultural field

Changes in the carbon stock of soil in response to climate change would significantly affect the atmospheric carbon dioxide concentration and consequently climate. The isotopes of carbon provide a means to study the temperature sensitivities of different soil carbon fractions. Where C3 vegetation has changed for C4, soil organic matter (SOM) from the different origins have different ¹³C/¹²C ratios. Relying on this feature, we took soil samples from a control field and a field where ordinary grain (C3) vegetation was replaced by maize (C4), 5 years ago. We measured the respiration rate and the ¹³C/¹²C ratio of the CO₂ produced by the samples at different temperatures. Based on these measurements, we quantified that Q₁₀ was 3.4-3.6 for the total CO₂ production while it was 2.4-2.9 at 20 °C for the maize-derived young carbon and 3.6 for the older C3-derived carbon. Our results suggest that climatic warming will accelerate especially the decomposition of the large pool of old soil carbon in these fields.     

Soil vapor extraction of wet gasoline-contaminated soil made possible by electroosmotic dewatering–lab simulations applied at a field site

Purpose

Soil restoration is still mainly carried out ex situ by excavating and replacing the contaminated soil. In situ remediation would reduce the costs of soil transportation and this way, the problem is not merely transferred elsewhere. The present study introduces a field case where the aged, oil-contaminated soil in a former fuel station in Finland was treated in situ sequentially with different methods.

Materials and methods

Several approaches, including soil vapor extraction and biostimulation with electrokinetic pumping, were performed in the field. After these treatments, the dense original portion of the soil beneath the gasoline pump location, ca 100 m³, was still contaminated with petroleum-derived volatile organic compounds (VOCs), with concentrations of nearly 10,000 mg kg^?1 measured at some hotspots. After a period of electroosmotic water circulation, the electrical field (0.5 V cm^?1, DC) was kept connected for 6 months without addition of water, leading to dewatering and warming of the soil.

Results and discussion

In contrast to the situation with the original wet soil, VOCs, in lab conditions, were found to volatilize very efficiently from the dewatered soil. When the soil vapor extraction treatment was renewed using perforated tubing installed horizontally at ca 1 m depth in the dewatered soil at the contaminated site, the treatment was efficient and the soil was decontaminated in 5 months. The final VOC concentrations were on average 190 mg kg^?1 (n = 13) with the highest value of 700 mg kg^?1 at one hotspot. After a risk evaluation, the site was concluded to be sufficiently clean for industrial use.

Conclusions

Since with many former fuel stations, the contamination consists of both volatile fractions that are difficult to degrade by biological means and heavier compounds for which biostimulation is often suitable, a combination of different methods may be worth pursuing.