Maximum plant height and the biophysical factors that limit it

Basic engineering theory and empirically determined allometric relationships for the biomass partitioning patterns of extant tree-sized plants show that the mechanical requirements for vertical growth do not impose intrinsic limits on the maximum heights that can be reached by species with woody, self-supporting stems. This implies that maximum tree height is constrained by other factors, among which hydraulic constraints are plausible. A review of the available information on scaling relationships observed for large tree-sized plants, nevertheless, indicates that mechanical and hydraulic requirements impose dual restraints on plant height and thus, may play equally (but differentially) important roles during the growth of arborescent, large-sized species. It may be the case that adaptations to mechanical and hydraulic phenomena have optimized growth, survival and reproductive success rather than longevity and mature size.     

Artificial upwelling to stimulate growth of non‐toxic algae in a habitat for mussel farming

Large‐scale artificial upwelling was tested as a method to enhance the environmental conditions for the growth of non‐toxic algae in a Norwegian fjord (61°0′N, 6°22′E). The experiment was designed to evaluate if nutrient‐rich seawater, brought up from below the mixed zone of a stratified fjord to the euphotic zone by air bubbling, would stimulate the growth of non‐toxic relative to toxic algae. Pumping 44 m³ min^?1 of air at 1 atm through a pipe diffuser submerged at 40 m depth formed a buoyancy flux that lifted 60 m³ s^?1 of deep water to the upper 17 m over a period of 21 days. The supply of silicate, inorganic nitrogen and phosphate to the upper 10 m in the fjord increased, and a significant increase in the biomass of non‐toxic algae was observed. The upwelling gave an increased growth of the non‐toxic dinoflagell ates Ceratium furca and C. tripos. After termination of the experiment, the phytoplankton biomass decreased significantly, whereas a distinct increase occurred in the relative biomass of the potentially toxic Dinophysis spp. The result is considered promising when it comes to creating controlled geographical areas with non‐toxic food for mussel production.     

饲料中补充植酸酶的新策略

本文从多方面介绍了在猪和家禽日粮中添加植酸酶 ,包括植酸酶对其他矿物质、氨基酸、动物饮水量及饲料稳定性的影响。同时也讨论了在现代饲料中添加磷酸盐的注意事项。1　植酸酶对其他饲料成分的作用1 .1　提高植酸磷和钙的消化率　众所周知 ,植酸酶可以提高动物对磷和钙的消化吸收 ,Jongbloed于 1 993年建立了一个关于植酸酶活力与饲料中磷酸盐的当量关系式。在含磷酸盐的饲料中添加50 0 IU植酸酶相当于 1 g来自于磷酸一钙的磷或1 .1 g来自于二水磷酸氢钙的磷 (对猪料 )。但随着植酸酶添加量的增加 ,植酸酶的转化当量随即下降。这个关系…     

Comparison of German and Swiss Rainfall Simulators - Experimental Setup

Rainfall simulators, that are commonly used in erosion research should produce comparable runoff and soil loss. At present five types of field rainfall simulators are used in Germany and Switzerland. The experimental setup on a Hapludalf soil site for testing these simulators and one laboratory rainfall simulator are described. Fifty rainfall simulations were carried out during two days on a homogeneous field. Hence, small deviations in slope steepness (< 2%) resulted in 40% deviations in the S factor of the USLE. This strong influence of slope steepness necessitates a high accuracy in the measurement of this parameter. Soil moisture during the two days was very high. This reduced slaking due to air inclusions and should have helped to detect differences in soil detachment due to the different rain structures and test procedures.     

Nutrient Attenuation in Agricultural Surface Runoff by Riparian Buffer Zones in Southern Illinois,USA

Nutrients in overland flow from agricultural areas are a common cause of stream and lake water quality impairment. One method of reducing excess nutrient runoff from non-point sources is to restore or enhance existing riparian areas as vegetative buffers. A field scale study was conducted to assess the ability of remnant giant cane (Arundinaria gigantea (Walt.) Muhl.) and forest riparian buffer zones to attenuate nutrients in agricultural surface runoff from natural precipitation events. Two adjacent, 10.0 m wide riparian buffers were instrumented with 16 overland flow collectors to monitor surface runoff for nitrate, ammonium, and orthophosphate. Measurements were taken at 3.3 m increments within each buffer. The forest buffer significantly reduced incoming dissolved nitrate-N, dissolved ammonium-N, total ammonium-N, and total orthophosphate masses in surface runoff by 97, 74, 68, and 78 , respectively within the 10.0 m riparian buffer. Nutrient reductions within the cane buffer were 100 for all three nutrients due to relatively high infiltration rates. Significant reductions of total ammonium- N and total orthophosphate were detected by 3.3 m in the cane buffer and at 6.6 m in the forest buffer. Results suggest that both giant cane and forest vegetation are good candidates to incorporate into riparian buffer restoration designs for southern Illinois as well as in other regions within their native range with similar climatic and physiographic conditions.     

Der Hallimasch

Ohne Zusammenfassung     

Sammlung pflanzlicher genetischer Ressourcen in Süditalien — ein Reisebericht aus dem Jahre 1950 mit Bemerkungen zum Schicksal der Landsorten „in situ“ und in der Genbank

Zusammenfassung 1950 wurde in Süditalien eine Reise zur Sammlung pflanzlicher genetischer Ressourcen durchgeführt. Der Bericht über diese Reise wird gegeben. 535 Muster konnten gesammelt werden. Probleme der Erhaltung dieser Kollektion in der Genbank Gatersleben werden diskutiert. Aufgrund neuerer Sammelerfahrungen wird auf den Status der Erhaltung der Landsorten Süditaliens in situ eingegangen. Diese neueren Sammlungen (1980 ... 1986) zeigen eine starke Auswirkung der Generosion bei Arten des Feldbaues, während sie bei den gärtnerischen Kulturpflanzenarten erst in der jüngeren Zeit einsetzt. Ausgewählte Beispiele zur Evaluierung des Materials werden vorgestellt (Krankheitsresistenz, Proteingehalt und -qualität). Der Nutzen der gesammelten Ressourcen für die Lösung der Aufgaben der Züchtungsforschung und Züchtung wird betont.

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Collection of plant genetic resources in South Italy — a report from 1950 with remarks on the fate of the land-races in situ and in the gene bank

Summary A mission for the collection of plant genetic resources was carried out in South Italy, 1950. The report about this mission is presented. 535 accessions were collected. Problems of maintaining this collection in the Gatersleben gene bank are discussed with special reference to non-adapted species. The status of in situ preservation of the land-races of South Italy is demonstrated on the basis of new experience in the collecting area. The missions of 1980 ... 1986 confirm a strong action of genetic erosion für species grown under agricultural conditions whereas the horticultural species are affected only recently. Some results from the process of evaluation of the collected material are presented (disease resistance, protein). The benefits of the collected resources for breeding research and breeding are stressed.

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— 1950 in situ

1950 . 535 . . , in situ. , 1980–1986 , . , . .

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Herrn Prof. Dr. Dr. h. c. mult.H. Stubbe aus Anlaß der 85. Wiederkehr seines Geburtstages gewidmet.     

Spatio-temporal variation in foodscapes modifies deer browsing impact on vegetation

Context

Ungulate browsers often alter plant composition and reduce diversity in forests worldwide, yet our ability to predict browse impact on vegetation remains equivocal. Theory suggests, however, that ungulate distribution and foraging impacts are shaped by scale-dependent decisions based on variation in habitat composition and structure encountered within their home range.

Objective

Examine how variation in habitat composition at landscape (259 ha) scales modulates browse impact on vegetation at local scales.

Methods

We measured vegetation richness and abundance in plots with and without white-tailed deer (Odocoileus virginianus) at 23 northern hardwood forest sites distributed across a 6500 km² area in Pennsylvania, USA. Experimental sites were embedded within landscapes with varying levels of habitat composition and deer densities.

Results

Browsing reduced vegetation richness and cover by as much as 53 and 70%, respectively; however, we found browse impact was modulated by variation in the relative abundance of managed habitats that alter forage availability. Specifically, relative to fenced areas, browse impact weakened and ultimately disappeared as the proportion of forage-rich habitats (e.g., recent harvests) increased to ≥20%. Conversely, vegetation grew increasingly depauperate as landscapes contained greater proportions of forage-poor habitats (i.e., older harvests), particularly when browsed.

Conclusions

Our results underscore how management actions that alter forage availability to ungulates throughout the landscape (i.e. the foodscape) can shape forest-ungulate interactions and suggest a new paradigm whereby managers evaluate and undertake actions at the appropriate spatio-temporal scales to proactively limit the deleterious impact of browsing on plant biodiversity.