Fertilization in northern forests – biological,economic and environmental constraints and possibilities

Forests of northern ecosystems respond slowly to management activities and the possibilities to increase the growth in a short-term perspective and meet swift increases in society's demand for biomass are small. An exception among the silvicultural measures is fertilization which can be applied in combination with present management systems and, almost instantly, enhances forest productivity. There may, however, be both economic and environmental constraints to large-scale applications of fertilizers in forest. Here we review the literature concerning biomass production of forests under different fertilization regimens, environmental constraints and possibilities in northern forests on mineral soils. Further on we discuss the implications of both extensive and more intensive fertilization in relation to the developing bioeconomy, which encompasses the production and conversion of renewable biological resources into food, health and industrial products and energy. Fertilization in Sweden and Finland is currently practiced by extensive fertilization regimens where nitrogen fertilizers are applied once, or up to three times, during a rotation period, mainly in mature forest. This type of fertilization gives, in most cases, a small and transient effect on the environment as well as a high rate of return to the forest owner with low-economic risk. The increase in biomass production, however, is relatively small and consequently the impact on the processing industry and the bioeconomy is limited. More intensive fertilization regimens implying intensive fertilization starting in young forests may, on the other hand, considerably increase the biomass supply and value for the industry. The economic and environmental risks of this type of fertilization may, however, be larger and more research is needed on the effects on the stand level, and especially on the landscape level, including late rotation management of the forest.     

Understanding how built urban form influences biodiversity

This study seeks to contribute to a more complete understanding of how urban form influences biodiversity by investigating the effects of green area distribution and that of built form. We investigated breeding bird diversity in three types of housing development with approximately the same amount of tree cover. No significant differences in terms of bird communities were found between housing types in any of the survey periods. However, detached housing, especially with interspersed trees, had more neotropical insectivores and higher overall diversity of insectivores. Based on our results and theory we suggest a complementary approach to managing biodiversity in urban landscapes – instead of maximising the value and quality of individual patches efforts could go into enhancing over-all landscape quality at the neighbourhood scale by splitting up part of the green infrastructure. The relatively small differences in bird communities also suggest that different stakeholder groups may be engaged in management.     

Ungulate-adapted forest management: effects of slash treatment at harvest on forage availability and use

Forest management strongly influences the interactions between ungulates and their food resources. Different ungulate-adapted measures have been proposed in forestry to improve forage availability or to reduce browsing damage. However, the potential and feasibility of such measures are inadequately known. We studied the effects of harvest timing and slash treatment in final felling and commercial thinning on the availability of Scots pine Pinus sylvestris forage and its use by ungulates during winter in the Swedish boreal forests. Pellet group counts showed that moose (Alces alces) was the dominating species using the post-harvest stands. Under conventional slash treatment, final felling stands held on average 226 kg pine forage ha^?1 after harvesting and commercial thinning stands 137 kg ha^?1. Ungulate-adapted slash treatment increased the available forage biomass by 20 %, but had no significant effect on consumption of forage by ungulates. Time since harvest had the strongest effect on forage consumption; for example, under conventional slash treatment, there was a tenfold increase in consumption (3 vs. 33 kg ha^?1) following final felling as exposure time increased from 2–3 to 4–5 months. Consumption was higher in thinned stands than in final felling stands for the first 3 months but not later. To increase ungulate use of the forage made available at harvest, pine-dominated stands should be harvested in the late autumn or early in the winter.     

Apparent digestibility coefficient of duckweed (Lemna minor), fresh and dry for Nile tilapia (Oreochromis niloticus L.)

Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso‐N fish diets fed to Nile tilapia (Oreochromis niloticus). The control diet contained fishmeal (35%), corn (29%), wheat (20%), wheat bran (10%), fish oil (3%), diamol (2%) and premix (1%). Partial replacement of dry matter of fishmeal, corn grain, wheat grain, wheat bran and fish oil by 20% and 40% of dry matter of duckweed, in a dry and fresh form, was performed. Diets of treatments 1 and 2 included 20% and 40% of duckweed, respectively, in a dry form. In treatments 3 and 4, tilapia received formulated diets 4 and 5 in addition to 20% and 40% fresh duckweed providing the same amount of dry matter and protein as in control. The specific growth rates (SGRs) of tilapia were 1.51±0.07, 1.38±0.03, 1.31±0.06, 1.44±0.02 and 1.33±0.05, in control and treatments 1–4. There was no significant difference between SGR for the control diet and the diet with 20% fresh duckweed, while the other treatment groups had significantly lower SGR. All the treatment diets provide good values for feed conversion ratios (FCRs) and protein efficiency ratio (PER). Dry matter of diets ranged from 61.8% in treatment 4 to 85.2% in control. All the diets have high PD (88.4–93.9%) and high‐energy digestibility (78.1–90.7%). Dry matter of duckweed were 66.8, 63.3, 45.8 and 28.3 in treatments 1 to 4 respectively. Protein values were 78.4, 79.9, 77.6 and 75.9, while ED values were 59.8, 60.9, 64.5 and 58.4 in treatments 1 to 4 respectively. Analysis of body composition shows that tilapia fed diets with duckweed contain significantly (P<0.05) higher phosphorus and protein content and significantly (P<0.05) lower lipid content. In contrast, tilapia fed control diet had a significant higher (P<0.05) dry matter content and lower ash content.     

Lévy walks evolve through interaction between movement and environmental complexity

Ecological theory predicts that animal movement is shaped by its efficiency of resource acquisition. Focusing solely on efficiency, however, ignores the fact that animal activity can affect resource availability and distribution. Here, we show that feedback between individual behavior and environmental complexity can explain movement strategies in mussels. Specifically, experiments show that mussels use a Lévy walk during the formation of spatially patterned beds, and models reveal that this Lévy movement accelerates pattern formation. The emergent patterning in mussel beds, in turn, improves individual fitness. These results suggest that Lévy walks evolved as a result of the selective advantage conferred by autonomously generated, emergent spatial patterns in mussel beds. Our results emphasize that an interaction between individual selection and habitat complexity shapes animal movement in natural systems.     

Natural cortisol production is not linked to the sexual fate of European sea bass

Fish Physiology and Biochemistry - In this study, we aimed to investigate the relationship between cortisol and the determination of sexual fate in the commercially important European sea bass...     

Feasibility of pedigree recording and genetic selection in village sheep flocks of smallholder farmers

Pedigree recording and genetic selection in village flocks of smallholder farmers have been deemed infeasible by researchers and development workers. This is mainly due to the difficulty of sire identification under uncontrolled village breeding practices. A cooperative village sheep-breeding scheme was designed to achieve controlled breeding and implemented for Menz sheep of Ethiopia in 2009. In this paper, we evaluated the reliability of pedigree recording in village flocks by comparing genetic parameters estimated from data sets collected in the cooperative village and in a nucleus flock maintained under controlled breeding. Effectiveness of selection in the cooperative village was evaluated based on trends in breeding values over generations. Heritability estimates for 6-month weight recorded in the village and the nucleus flock were very similar. There was an increasing trend over generations in average estimated breeding values for 6-month weight in the village flocks. These results have a number of implications: the pedigree recorded in the village flocks was reliable; genetic parameters, which have so far been estimated based on nucleus data sets, can be estimated based on village recording; and appreciable genetic improvement could be achieved in village sheep selection programs under low-input smallholder farming systems.     

A quantification of short-term macroaggregate dynamics: influences of wheat residue input and texture

Soil structure and soil aggregation play an important role in an array of processes such as soil erodibility, organic matter protection and soil fertility. Modeling attempts of these processes would benefit substantially from including soil structural parameters such as soil aggregation. However, quantitative data on soil structural dynamics is lacking. Therefore, we conducted short-term (3 weeks) incubations to acquire necessary soil structural parameters for modeling purposes. Prior to incubation, all structures >53 μm were destroyed from three soils with varying texture but under similar management. Five different amounts of wheat residue, ranging from 0 to 3 wt%, were added to each of these soils. After 3 weeks, samples were analyzed for large water-stable macroaggregates (>2000 μm) using a wet sieving method and for fungal growth using epifluorescence microscopy. Aggregate formation increased linearly with increasing amounts of residue at a rate of 12.0±1.24 g aggregates g⁻¹ residue added. We found no differences in aggregate formation among the three soils, even though the equilibrium level of macroaggregates differed in the field. While amounts of water-stable macroaggregates in the sandy loam and the silt loam soil corresponded well with fungal lengths, this was not the case for the silty clay loam soil. This suggests that fungi are less important in aggregate formation in more clayey soils. Cumulative respiration correlated well (r=0.89-0.91) with water-stable macroaggregates for all three soils. A model assuming an aggregate formation rate proportional to the respiration rate was very successful in fitting the measured aggregate amounts. This model predicted about 65% of the changes in aggregation when different amounts were added, and about 85% of the changes in aggregation over time. This model yielded a macroaggregate turnover time of 40-60 days. The quantitative results presented here can directly be incorporated into models describing and predicting soil aggregate dynamics, as a determining factor for physical protection of organic matter within a soil.     

Microbial biomass and activity in an agricultural soil with different organic matter contents

Changes in soil fertility caused by various organic and N-fertilizer amendments were studied in a long-term field trial mostly cropped with cereals. Five treatments were included: (I) fallow, (II) cropping with no C or N addition, (III) cropping with N-fertilization (80 kg ha ^?1 yr^?1), (IV) cropping with straw incorporation (1800kg Cha^?1 yr^?1) and N-fertilization (80 kg ha^?1yr^?1), and (V) cropping with addition of farmyard manure (80 kg N + 1800kg Cha^?1yr^?1). The treatments resulted in soil organic matter contents ranging from 4.3% (I) to 5.8% (V). Microbial biomass and activity were determined by chloroform fumigation, direct counting of fungi (fluorescein diacetate (FDA)-staining and Jones-Mollison agar-film technique) and bacteria (acridine orange staining), most probable number determinations of protozoa, esterase activity (total FDA hydrolysis) and respiration. Both biomass estimates and activity measurements showed a highly significant correlation with soil organic matter. Microbial biomass C ranged from 230 to 600 μg C g^?1 dry wt soil, as determined by the fumigation technique, while conversions from direct counts gave a range from 380 to 2260 μg C. Mean hyphal diameters and mean bacterial cell volumes decreased with decreasing soil organic matter content.