Chemical composition,in vitro dry matter digestibility and in sacco degradability of selected browse species used as animal feeds under semi-arid conditions in Northern Ethiopia

The study was conducted in Abergelle district of Tigray, northern Ethiopia with the objectives of evaluating the chemical composition, in vitro dry matter digestibility (IVDMD) and in sacco degradability characteristics of foliages of major browse species. Samples of foliages from 12 and 10 browse species were collected during the wet and dry seasons, respectively. The samples of the browse species were collected based on their abundance in the district, preference by livestock to browse them, accessibility to browsing and their additional uses other than livestock feed. The neutral detergent fiber (NDF) was higher in the browse species during the wet compared to the dry season except for Sterculia africana and Ziziphus spina-christi. Similar trends were observed for acid detergent fiber (ADF) content except for Acacia asak. The condensed tannins content and the IVDMD of the browse species had inverse relationships in both seasons. The in sacco dry matter (DM) and nitrogen degradability parameters of the browse species were seasonally variable. Based on in sacco potential DM and nitrogen degradation of the browse species in both seasons, Acacia oerfota, Acacia tortilis, Balanites aegyptiaca, Boswellia papyrifera, Sterculia africana, Terminalia brownii and Ziziphus spina-christi were ranked to be superior in their nutritive value, and thus can have better use as animal feeds. Consequently, these browse species could be considered in agro-forestry systems for better integration of livestock production with available feed resources in semi-arid areas.     

Mill variation in bending strength and stiffness of in-grade Douglas-fir No. 2 2 × 4 lumber

Visually graded Douglas-fir (DF) has wide variability within grade. Variability for 2 × 4 lumber has likely increased because harvest has shifted from federal forests to private plantation forests that contain high percentages of juvenile wood. To investigate resource variability, six No. 2, 2 × 4 DF packages were acquired from six mills. From each package, 124 samples were destructively tested in bending. Mean modulus of elasticity (MOE₁₅) ranged from 9.8 to 13.4 GPa, and three mills did not meet the grade requirements (11.0 GPa). Bending strength (F _b) ranged from 5.5 to 11.3 MPa, and three mills did not meet the grade requirements (9.3 MPa). ANOVA of MOE₁₅ % and F _b showed significant differences at the 0.05 significance level. MOE₁₅ explained from 50 to 78 % of the variability in strength. These data suggest that variation between mills is high and destructive testing is critical for more accurate characterization of lumber properties.     

Mill variation in bending strength and stiffness of in-grade southern pine No. 2 2 × 4 lumber

Visually graded southern pine (SP) has wide variability within grade. For 2 × 4 lumber, this variability has increased because it is harvested from both natural forests and plantation forests where trees contain high percentages of juvenile wood. To investigate resource variability, six kiln-dried No. 2 2 × 4 SP packages were acquired from six mills. From each package, 124 samples were destructively tested in bending. Mean modulus of elasticity (MOE₁₅) ranged from 9.2 to 13.1 GPa, and three mills did not meet the design values (11.0 GPa). Bending strength (F _b) ranged from 7.6 to 11.9 MPa, and four mills did not meet the design values (10.3 MPa). Analysis of variance of MOE₁₅ and F _b showed significant differences between mills. MOE₁₅ explained from 33 to 51 % of the variability in F _b. These data suggest that variation between mills is high and destructive testing is critical for more accurate characterization of lumber properties.     

Relating visual crown conditions to nutritional status and site quality in monoclonal poplar plantations (Populus × euramericana)

The area covered by plantations of hybrid poplar in Europe is increasing greatly because of the high profitability of these trees. However, the productivity varies widely depending on nutritional status, and it is therefore essential to identify the limiting nutrients. The aims of this study were (a) to identify the main nutrients limiting the growth and vitality of monoclonal poplar (Populus × euramericana) plantations and (b) to develop a means of early detection of nutrition-related problems in growth, based on visual crown conditions (crown transparency, VCT, and visual crown discoloration, VCD). The study was carried out in one of the most suitable areas for this species in Southern Europe. Thirty-two Populus × euramericana (clone I-214) stands displaying different levels of decline were selected for study, and tree growth, nutritional status (soil properties and foliar nutrient concentrations) and crown conditions were assessed. The stands, which were growing in soils with high contents of coarse fragments, displayed low growth rates, poor crown conditions and deficiencies in Fe, B, N, P, K, and to a lesser extent, Zn and Cu. The deficiencies increased with the age of the stand, presumably because of the higher nutrient demand in older trees. Visual crown conditions were related to growth rates and nutritional status. Predictive models were developed to relate crown conditions to the nutritional status identified by analysis of soil properties and foliar concentrations of nutrients.     

Development and commercialisation of the Pinus patula × P. tecunumanii hybrid in response to the threat of Fusarium circinatum

During the last 20 years a program to develop and commercialize the Pinus patula × Pinus tecunumanii hybrid, as a replacement for P. patula, has been successfully implemented. The first crosses were initiated during the early 1990s and lead to establishment of field trials across a wide variety of sites. This work gained further impetus when it became apparent that Fusarium circinatum, was causing poor post-planting survival of newly established stands of P. patula. P. tecunumanii, has been shown to be tolerant to this disease and thus a second, more comprehensive hybrid testing phase was implemented. Improvements in controlled pollination techniques and propagation methods, as well as access to genetically improved parent-stock and the use of molecular marker technology for fingerprinting was effectively utilized to greatly improve the process during this second phase. The use of artificial inoculation trials have demonstrated that the hybrid, in particular when using the low elevation (LE) provenances of P. tecunumanii, had substantially greater tolerance to F. circinatum than P. patula and survival figures from field trials support these results. Four-year volumes also indicate large growth improvements, although frost damage on certain sites presents a challenge for deployment on colder sites; and this is being tackled through breeding and accurate mapping of frost risk. Large-scale controlled pollinations and vegetative multiplication are now utilized commercially to produce the P. patula × P. tecunumanii (LE) hybrid as an alternative to P. patula.     

The tolerance of Pinus patula × Pinus tecunumanii, and other pine hybrids, to Fusarium circinatum in greenhouse trials

The field survival of Pinus patula seedlings in South Africa is frequently below acceptable standards. From numerous studies it has been determined that this is largely due to the pitch canker fungus, Fusarium circinatum. Other commercial pines, such as P. elliottii and P. taeda, show good tolerance to this pathogen and better survival, but have inferior wood properties and do not grow as well as P. patula on many sites in the summer rainfall regions of South Africa. There is, thus, an urgent need to improve the tolerance of P. patula to F. circinatum. Operational experience indicates that when P. patula is hybridized with tolerant species, such as P. tecunumanii and P. oocarpa, survival is greatly improved on the warmer sites of South Africa. Field studies on young trees suggest that this is due to the improved tolerance of these hybrids to F. circinatum. In order to test the tolerance of a number of pine hybrids, the pure species representing the hybrid parents, as well as individual families of P. patula × P. tecunumanii, a series of greenhouse screening trials were conducted during 2008 and 2009. The results indicated that species range in tolerance and hybrids, between P. patula and these species, are intermediate in tolerance to F. circinatum. Within P. patula × P. tecunumanii, large family variation exists when pollen from the high elevation source of P. tecunumanii is used. The results of these studies illustrate the importance of developing pine hybrid breeding programs to overcome the susceptibility of our pure species to pathogens such as F. circinatum.     

Genetic control of intra-ring wood density variation in hybrid larch (Larix gmelinii var. japonica × L. kaempferi) F1

Genetic parameters for various wood density traits were estimated in 29-year-old trees of 18 full-sib families of hybrid larch (Larix gmelinii var. japonica × Larix kaempferi) F₁. Intra-ring density variation (IDV) was also evaluated using a model that expresses the pattern curve from earlywood to latewood as a power function. A high IDV indicates an abrupt change in wood density from earlywood to latewood. The ring width and wood density traits of individual rings were determined by X-ray densitometry. Overall wood density (RD) was shown to increase with increasing ring number, ranging from 0.42–0.59 g/cm³, whereas IDV of individual rings decreased gradually from pith outwards. Estimates of individual tree narrow-sense heritability of RD and IDV were 0.66 and 0.67, respectively. IDV showed negative genetic and phenotypic correlations with RD (r _g = −0.99, r _p = −0.72). The predicted genetic gains in latewood proportion and IDV were higher than that of RD. These results suggest that the intra-ring density variation is under moderate genetic control equivalent to wood density. The trend of increasing wood density from earlywood to latewood was associated with changes in both tracheid diameter and cell wall thickness.     

Object-based forest biomass estimation using Landsat ETM+ in Kampong Thom Province, Cambodia

Information about forest biomass distribution is important for sustainable forest management and monitoring fuelwood supply. The objective of this study is to develop an accurate forest biomass map for Kampong Thom Province, Cambodia. We used a new technique (object-based approach) and a conventional technique (pixel-based approach) for the estimation of forest biomass using Landsat Enhanced Thematic Mapper Plus (ETM+). The object-based approach created segments of images, and calculated statistical and textural attributes. Our results showed that estimation accuracy of the object-based approach, with the use of band 1 and an exponential fit, was the best (R ² = 0.76), and this accuracy was comparable to that of the pixel-based approach (R ² = 0.67). Although several textural variables were related to forest biomass, they did not contribute significantly to improvement of estimation accuracy. However, the object-based method can be used for image segmentation so that the image objects are spectrally more homogeneous within individual regions than with their neighbors. Hence, they can be regarded as management units for policy-related spatial decisions. Therefore, it is possible to select either of the two methods depending upon what the situation demands.     

Genetic worth and diversity across 18 years in a Nordmann fir clonal seed orchard

• Context  

Many tree breeding programmes rely entirely on clonal seed orchards as the link between breeding activities and forestry, and are thereby also exposed to yearly fluctuations in the orchard crops.     

Tree and stand structure of the non-native Pinus contorta in relation to native Pinus sylvestris and Picea abies in young managed forests in boreal Sweden

Managed forest stands are typically younger and structurally less diverse than natural forests. Introduction of non-native tree species might increase the structural changes to managed forest stands, but detailed analyses of tree- and stand-structures of native and non-native managed forests are often lacking. Improved knowledge of non-native forest structure could help clarify their multiple values (e.g. habitat for native biodiversity, bioenergy opportunities). We studied the structural differences between the introduced, non-native Pinus contorta and the native Pinus sylvestris and Picea abies over young forest stand ages (13–34 years old) in managed forests in northern Sweden. We found that P. contorta stands had greater mean basal areas, tree heights, diameters at breast height, and surface area of living branches than the two native species in young stands. The surface area of dead attached branches was also greater in P. contorta than P. abies. Although this indicates greater habitat availability for branch-living organisms, it also contributes to the overall more shaded conditions in stands of P. contorta. Only one older 87 years old P. contorta stand was available, and future studies will tell how structural differences between P. contorta and native tree species develop over the full forestry cycle.     

Spatial pattern of trees influences species productivity in a mature oak–pine mixed forest

Spatial pattern has a key role in the interactions between species in plant communities. These interactions influence ecological processes involved in the species dynamics: growth, regeneration and mortality. In this study, we investigated the effect of spatial pattern on productivity in mature mixed forests of sessile oak and Scots pine. We simulated tree locations with point process models and tree growth with spatially explicit individual growth models. The point process models and growth models were fitted with field data from the same stands. We compared species productivity obtained in two types of mixture: a patchy mixture and an intimate mixture. Our results show that the productivity of both species is higher in an intimate mixture than in a patchy mixture. Productivity difference between the two types of mixture was 11.3 % for pine and 14.7 % for oak. Both species were favored in the intimate mixture because, for both, intraspecific competition was more severe than interspecific competition. Our results clearly support favoring intimate mixtures in mature oak–pine stands to optimize tree species productivity; oak is the species that benefits the most from this type of management. Our work also shows that models and simulations can provide interesting results for complex forests with mixtures, results that would be difficult to obtain through experimentation.     

Changes within collembolan communities in windthrown European montane spruce forests 2 years after disturbance by fire

• Context   

In July 2005, a wildfire occurred in windthrown spruce forests in High Tatra Mountains and damaged roughly 229 ha of previously clear-cut area.     

Tree spatial patterns of Abies alba and Fagus sylvatica in the Western Carpathians over 30 years

The decline of Abies alba (fir) in natural fir–beech forests in Europe has fascinated scientists for over a century. During this period, Fagus sylvatica (beech) became the dominant species in this forest type. We hypothesised that (1) the success of beech over fir is significantly connected with the fact that beech suffers less than fir from the presence of conspecific neighbours; that (2) shade tolerance is not a factor which favours beech over fir; and that (3) this is due to a significantly reduced proportion of litter treethrow mounds with suitable conditions for the successful regeneration of fir. We investigated these hypotheses by means of tree spatial pattern analysis. Eight rectangular plots (2–8 ha) were analysed in mountain fir–beech forests of the Outer Western Carpathians, Czech Republic. Various types of the pair correlation function and L function were used to describe the tree density variability of trees with DBH ≥10 cm. The analyses were carried out on datasets from the 1970s, 1990s and 2000s. Our results suggest that negative density dependence is not responsible for the current decline of fir. It seems that a higher shade tolerance of the advanced regeneration could be one of the factors which favour beech over fir. It is evident that fir trees have a markedly stronger positive association to mounds than beech trees.     

Field performance of conifer and hardwood species 5 years after nursery inoculation in the Canadian Prairie Provinces

The field performance of conifer and hardwood species inoculated with different inoculation treatments was evaluated 5 or 3 years after outplanting in the field trials established in the Canadian Prairie Provinces. In conifer trials, the growth of white spruce, black spruce, lodgepole pine, and larch seedlings observed on different sites varied greatly to different inoculation treatments depending on plant and fungal species involved. Five years after outplanting, most of the introduced fungi were replaced by several indigenous ectomycorrhizal fungal species except for Laccaria bicolor strain. Survival rates of most of the inoculated seedlings were not significantly different from control seedlings naturally colonized by other resident fungi. In hardwood trial, the effects of nursery inoculation of different poplar clones, aspen and balsam poplar were very limited. Growth and survival data were combined into seedling volume and plot volume index (PVI) for measurement of total growth response of seedlings. Our results demonstrated that certain inoculated plant-fungus combinations have played a positive role during the initial establishment of these seedlings in the field, which was reflected on significantly greater stem volume and PVI compared to non-inoculated control seedlings. The results from this study provided useful information on field evaluation for potential benefits of mycorrhizal inoculation in nursery.     

Ecologically based height growth model and derived raster maps of Norway spruce site index in the Western Carpathians

The purpose of this study was to find the ecological factors that most affect height growth of Norway spruce (Picea abies Karst.) over the Western Carpathians. The specific aim was to find climate and soil parameters which are influenced by climate change and can thus be used to make a forest growth model more sensitive to climate. From the results, a regression model was built which can predict top height growth of Norway spruce from ecological parameters. Data collected on 201 plots established within National Forest Inventory of Slovakia were used. The plots selected for the study were distributed almost over the whole Western Carpathians. Mean height of the 20 % largest spruce trees was used as dependent variable. From all investigated ecological factors, the growing season length explained as the number of days with temperature over 5 °C, the carbon-to-nitrogen ratio and soil acidity were shown to have the major impact on top height growth of Norway spruce. Finally, 76 % of total variability in top height was explained by the mentioned site variables. To obtain a user-friendly output, a probability matrix was developed showing the likelihood of a discrete site index to occur on different combinations of site factors. Moreover, raster maps showing the site index of spruce and its probability distribution were developed.     

Soil and plant N-budget 1 year after planting of a slash-and-mulch agroforestry system in the eastern Amazon of Brazil

Nutrient losses during slash-and-burn clearing in tropical forests, coupled with demand by food crops, can deplete nutrients and result in crop abandonment after 1–2 years. Slash-and-mulch technology prevents nutrient losses from burning, while mulch decomposition may serve as a nutrient source. This research investigates the release of nutrients from the mulch and potential uptake of released N by plant biomass after a multi-species agroforestry system was planted in June 2005, following the clearing of a 1 ha of 7-year-old forest with a mulching tractor in Igarapé Açu, Brazil. The study evaluated soil conditions, mulch decomposition, and nutrient concentrations of Manihot esculenta and native vegetation under treatments of P+K fertilization in combination with four native tree species and N-fixing Inga edulis, or with three native tree species without I. edulis. Mulch layer N, Ca and Mg content decreased in response to fertilization, while mulch layer P and K content increased. Nutrient content increased in M. esculenta stems and tubers with fertilization and in the presence of I. edulis, and in competing vegetation with fertilization. Estimated tree N content increased 311 % with fertilization, but by 154 % in the presence of I. edulis. Fertilization with P+K, as well as the presence of I. edulis, increased N stocks in total biomass.     

Genotype × environmental interaction by AMMI and GGE biplot analysis for the provenances of <Emphasis Type="Italic">Michelia chapensis</Emphasis> in South China

A provenance trial of Michelia chapensis Dandy in the south of China was carried out in three sites to assess yield and stability analyses. The trials were conducted as randomized, complete block designs with four replications at each site. Additive main effects and multiplicative interaction (AMMI) and genotype main effect and genotype × environment interaction (GGE) were employed in the evaluation of provenances; AMMI analyses showed that significant genotype × environment interaction effects (P < 0.05) existed between provenances, capturing 15.11 % of the total sum of squares. The AMMI stability value revealed that provenance 2 was stable, but had low yield. GGE-biplot models showed that provenances 7, 8, 10, and 11 were more stable and high-yielding. The GGE results also confirmed that among the three sites, site JiuQuShui was the most ideal environment for representation and discrimination.