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2. ERFURTER TAGUNG: Schnellwachsende Baumarten - Erntetechniken, -verfahren und Logistik
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Competition for above- and below-ground resources depends on their availability and results in varied growth partitioning. This becomes clear as the supply and limitation of the main resources influence the slope of the size-growth relationship in stands. Nevertheless, growth partitioning among trees, especially among black locust (R. pseudoacacia) trees is not understood in sufficient detail. To scrutinize and estimate the mode of competition of R. pseudoacacia, this research analyzed 1333 trees in Germany in 10 study sites, consisting in total 27 sample plots, with similar climate but varying soil conditions. The stand age ranged from 2 to 32 years, with a diameter at breast height ranging from 0.6 to 29.1 cm. The main focus of the study was to evaluate the impact of nitrogen, phosphorus, and water supply on the competition mode of R. pseudoacacia by varying growth partitioning. We applied the size–growth relationship in a mixed-effects model with a random intercept and slope. Fixed effects were the basal area, phosphorus, water, the sunlight competition index, and the interactions between below- and above-ground resources. Site specific effects of the analyzed stands were quantified with the aid of the random effects. Depending on the supply and limitation of phosphorus and water, this study determined how the competition mode as well as the growth partitioning among R. pseudoacacia trees were influenced. Hence, if phosphorus and water availability increased, then the competition for above-ground resources (primarily sunlight) and the slope of the size–growth relationship increased. Large trees grew disproportionately more than smaller trees. If the available phosphorus and water decreased, then the competition for the below-ground resources increased and the slope of the size–growth relationship decreased – to be more flattened. Moreover, it was found that available nitrogen as a below-ground resource had no influence on the mode of competition. In summary, phosphorus was the most important nutrient and, together with water, was the main driver of growth partitioning among R. pseudoacacia trees.
Black locust is a drought-resistant tree species with high biomass productivity during juvenility; it is able to thrive on wastelands, such as former brown coal fields and dry agricultural areas. However, research conducted on this species in such areas is limited. This paper aims to provide a basis for predicting tree woody biomass for black locust based on tree, competition, and site variables at 14 sites in northeast Germany that were previously utilized for mining or agriculture. The study areas, which are located in an area covering 320 km × 280 km, are characterized by a variety of climatic and soil conditions. Influential variables, including tree parameters, competition, and climatic parameters were considered. Allometric biomass models were employed. The findings show that the most important parameters are tree and competition variables. Different former land utilizations, such as mining or agriculture, as well as growth by cores or stumps, significantly influenced aboveground woody biomass production. The new biomass models developed as part of this study can be applied to calculate woody biomass production and carbon sequestration of Robinia pseudoacacia L. in short rotation coppices in previous mining and agricultural areas.
Black locust (Robinia pseudoacacia L.) is a fast growing tree species native to temperate North America, and widely diffused and naturalized in Europe. It is one of the candidate species for establishing bioenergy plantations on marginal lands in temperate and sub-Mediterranean regions. This potential is in contrast to its well-known invasive habit, leading to a potential damage to plant biodiversity in many European countries. Advise against black locust plantation in regions where it is already invasive has been issued by several international reports, as well as the adoption of mitigation measures (e.g., “containment” buffer zones) to prevent the spread of the species into natural and semi-natural habitats. In the Mediterranean basin, however, no studies have been carried out aimed at quantifying the escape rate of black locust saplings from plantation stands and its recruitment into natural habitats, together with the effectiveness of a buffer zone in reducing the spread. In this study we investigated the spread of black locust along 35 transects surrounding three 20-year- old plantations and including three different land cover types: abandoned arable land, semi-natural woodland and a buffer zone (orchards) with a low degree of farming input. In addition, the effect of soil disturbance on seed propagation was investigated. Our results demonstrate that the density of black locust regeneration is strongly affected by the land cover, abandoned agricultural land being the most prone to black locust colonization. Contrastingly, the spread was minimal in the buffer zone and negligible in semi-natural woodland. During the investigated year, seed generative propagation was also negligible. The semi-natural woodland seems to resist well to black locust invasion, though further observations are needed to assess the consequences of stand harvesting disturbance as well, according to local standard forest management. Buffer zones seem to be very effective in controlling black locust invasion. Best management practices, with active farming inputs, are also discussed.
http://www.sisef.it/iforest/contents/?id=ifor1526-009
Legume nodules are plant tissues with an exceptionally high concentration of phosphorus (P), which, when there is scarcity
of P, is preferentially maintained there rather than being allocated to other plant organs. The hypothesis of this study was
that nodules are affected before the P concentration in the organ declines during whole-plant P depletion. Nitrogen (N2) fixation and P concentration in various organs were monitored during a whole-plant P-depletion process in Medicago truncatula. Nodule gene expression was profiled through RNA-seq at day 5 of P depletion. Until that point in time P concentration in
leaves reached a lower threshold but was maintained in nodules. N2-fixation activity per plant diverged from that of fully nourished plants beginning at day 5 of the P-depletion process, primarily
because fewer nodules were being formed, while the activity of the existing nodules was maintained for as long as two weeks
into P depletion. RNA-seq revealed nodule acclimation on a molecular level with a total of 1140 differentially expressed genes.
Numerous genes for P remobilization from organic structures were increasingly expressed. Various genes involved in nodule
malate formation were upregulated, while genes involved in fermentation were downregulated. The fact that nodule formation
was strongly repressed with the onset of P deficiency is reflected in the differential expression of various genes involved
in nodulation. It is concluded that plants follow a strategy to maintain N2 fixation and viable leaf tissue as long as possible during whole-plant P depletion to maintain their ability to react to
emerging new P sources (e.g. through active P acquisition by roots).
Several factors influence land availability for the growth of short rotation coppices (SRC) with fast-growing tree species, including the nationwide availability of agricultural land, economic efficiency, ecological impacts, political boundaries and environmental protection regulations. In this study, we analysed the growing potential of poplar and willow SRC for bioenergy purposes in Germany without negative ecological impacts or land use conflicts. The potential biomass production using SRC on agricultural land in Germany was assessed taking into account ecological, ethical, political and technical restrictions. Using a geographic information system (GIS), digital site maps, climate data and a digital terrain model, the SRC biomass production potential on cropland and grassland was estimated using water supply and mean temperature during the growing season as parameters. From this analysis, a yield model for SRC was developed based on the analysed growth data and site information of 62 short rotation plantations in Germany and France. To assess the technical, ethical and ecological potential of SRC, restrictions in protected areas, technical constraints and competition with food and feed production were investigated. Our results revealed that approximately 18% (2.12 Mio. ha) of cropland and 54% (2.5 Mio. ha) of grassland in Germany were highly suitable for SRC plantations, providing favourable water supplies and mean temperatures during the growing season. These identified sites produced an average yield of more than 14 tons of dry matter per hectare per year. Due to local climate and soil conditions, the federal states in northern and eastern Germany had the highest theoretical SRC potential for agricultural land. After considering all ecological, ethical, political and technical restrictions, as well as future climate predictions, 5.7% (680 000 ha) of cropland and 33% (1.5 Mio. ha) of grassland in Germany were classified as suitable for biomass production with fast-growing tree species in SRC.
Plant competition is usually one-sided. This asymmetry is primarily due to competition for light. -from Authors
This book, which summarizes research progress on Melampsora rust on willows and poplars, is based mainly on papers presented at the "International Symposium on Melampsora on Salicaceae" held in Belfast, Northern Ireland, on 11-13 September 2003. This book, intended for research workers, teachers and students, consists of 5 parts focusing on taxonomy and overview of rusts (part 1), occurrence and population biology of Melampsora (part 2), rust resistance and infection process (part 3), rust management (part 4), and rust mycoparasites and their potential for biological control (part 5).
Robinia pseudoacacia, invaded many countries a long time ago and is now a common part of the Central European landscape. Positive economic but negative environmental impacts of Robinia result in conflicts of interest between nature conservation, forestry, urban landscaping, beekeepers and the public when defining management priorities. Because current legislation will determine the future distribution of Robinia in the landscape, a comprehensive view of this species is necessary. Although this species is well studied, most of the scientific papers deal with the economic aspects. Other information is published in local journals or reports. Therefore we reviewed the ecological and socioeconomic impact of Robinia placing particular emphasis on the species' history, vegetation ecology, invasiveness and management. In Central Europe, Robinia is limited climatically by late spring frost combined with a short vegetation period, soil hypoxia, shade and frequent major disturbances. The long historical tradition of using Robinia for afforestation has resulted in its popularity as a widespread forest tree and it being an important part of the economy in some countries. The main reasons are its fast growth, valuable and resistant wood, suitability for amelioration, reclamation of disturbed sites and erosion control, honey-making and recently dendromass production. On the other hand, a side-effect of planting this nitrogen-fixing pioneer tree, very tolerant of the nature of the substrate, is its propagation and spread, which pose a problem for nature conservation. Robinia is considered invasive, threatening especially dry and semi-dry grasslands, some of the most species-rich and endangered types of habitat in the region, causing extinction of many endangered light-demanding plants and invertebrates due to changes in light regime, microclimate and soil conditions. Other often invaded habitats include open dry forests and shrubland, alluvial habitats, agrarian landscapes, urban and industrial environments and disturbed sites, e.g. post-fire sites, forest clearings or degraded forestry plantations. Without forestry, black locust abundance would decrease during succession in forests with highly competitive and shade tolerant trees and in mature forests it occurs only as admixture of climax trees. The limited pool of native woody species, lack of serious natural enemies and a dense cover of grasses and sedges can suppress forest succession and favour the development of Robinia monodominant stands over 70 years old. A stratified approach, which combines both tolerance in some areas and strict eradication at valuable sites, provides the best option for achieving a sustainable coexistence of Robinia with people and nature.
Adequate supplies of phosphorus (P) and iron (Fe) to legumes have been shown to be crucial in obtaining high nitrogen fixation rates and growth. These responses are anticipated as a result of the high requirement for P in energy transfer processes in the nodule and for Fe as a constituent of nitrogenase and leghemoglobin. However, little attention has been given to documenting the response of nitrogen fixation rates resulting from concentrations of P and Fe that actually exist in nodules. In particular, an open question is whether there is an interaction between nodule P and Fe concentrations that maximize nitrogen fixation activity. This study was designed to induce various concentrations of P and Fe in the nodule and to measure the resultant nitrogen accumulation and nitrogen fixation rates. Plant nitrogen accumulation was linearly correlated with both nodule P and Fe concentration, and with total plant nitrogen fixation rate as measured by acetylene reduction rate. Therefore, total nitrogen fixation rate was also correlated with nodule P and Fe concentrations, but a higher linear correlation was obtained for Fe as compared to P concentration. Surprisingly, nodule ureide concentration, which is generally assumed to be a positive index of nitrogen fixation rate, was negatively correlated with nodule P and Fe concentrations. These results indicated that higher concentrations of P and Fe in the nodules not only stimulated higher nitrogen fixation rates, but were associated with an enhanced ability to export ureides from the nodules. Since there was a linear response to both P and Fe over the range of nodule concentrations induced in these experiments, no evidence for optimum interactive concentrations of these two elements in the nodules was obtained.
Soil-solution chemistry was measured over a 15-month period in three forest stands of contrasting nitrogen mineralization and nitrification rates in the southern Appalachians of North Carolina, U.S.A., using porous-cup lysimeters. In a black-locust-dominated stand, soil solution NO3N was 3.73 and 5.04 mg l-1 at 30- and 60-cm depth respectively, and dissolved organic N (don) was 0.718 and 0.582 mg l-1 respectively. Values at 30 and 60 cm for a pine/mixed-hardwood stand were 0.032 and 0.058 mg l-1 NO3N, and 0.201 and 0.168 mg l-1 don (values are means over the whole duration of the study). At both depths, soil solution conductivity, pH, Ca, Mg, K and PO4P were higher in black locust than in pine/mixed-hardwoods, and there were no differences in soil solution Na. In an oak/hickory stand, soil solution NO3N at 30-cm depth was 0.008 mg l-1, and don was 0.357 mg l-1. At 30-cm depth, soil-solution conductivity, Ca, Mg and PO4P were higher in black locust than in oak-hickory, with no differences in pH, K and Na; don, pH and K were higher in oak/hickory than in pine/mixed-hardwoods. In the oak/hickory and pine/mixed-hardwoods forest stands, with relatively lower soil N turnover rates, don was a major portion of soil solution N.