Summary1. Many threatened bryophytes are restricted to patchy and temporary substrates such as dead wood and tree stems. Their persistence depends on successful colonizations of new patches. Spore germination may then be limited by substrate quality and wetness. 2.In vitro experiments were used to test the effects of pH and moisture on the establishment of spores of the moss species Neckera pennata Hedw. and Buxbaumia viridis (DC) Moug. & Nestl. 3. Low pH and water potential prolonged the lag phase preceding germination and reduced final germination. The interaction between pH and moisture suggests that high water availability facilitates germination at suboptimal pH, and vice versa . 4. The results reflect the species' habitats: the wood-inhabiting B. viridis had higher capacity to germinate at low pH, while spores of the epiphyte N. pennata showed earlier germination at low water potential and survived longer in a dry state. This supports the notion that bryophytes are most strongly affected by substrate quality during establishment. 5. We suggest that a trade-off exists among moss spores between the ability to colonize substrates with low moisture-holding capacity and low pH, and that the positive effect of high pH is largely that it speeds up germination thereby enabling the spores to exploit short, moist periods.
A field experiment primarily designed for simulating the indirect effects of air pollutants for a 25-year-old Norway spruce stand in SW Sweden is presented (The Skogaby project). Treatment include irrigation; artificial drought; ammonium sulphate addition; nitrogen-free-fertilization and irrigation with liquid fertilizers including a complete set of nutrients. The experiment has a randomized block design with four replicates per treatment. Growth response on an areal basis of basal area, height and dry mass of stems, branches and needles after up to four years of treatment are presented. Dry mass is estimated using allometric equations based on destructive samplings of trees.The stand suffered from temporary water stress during all four years investigated despite 970-1160 mm of annual precipitation. Irrigation resulted in improved above-ground dry mass production (stem, bark, branches, needles, litter fall) by 20% during the first 3 years of treatment, whereas 2 years of drought treatment followed by 1 year of recovery led to 10% reduced dry mass growth. During year 2 of recovery, however, basal area growth was only about half of that of the control.Nitrogen, markedly, was a growth limiting nutrient, although the stand got approx. 20 kg N ha-~ yfrom deposition. Ammonium sulphate addition (100 kg N ha 1 y-l) resulted in 31% improved dry mass production whereas irrigation with liquid fertilization (100kgNha -1 y-l) including all important nutrient elements led to 57% increased dry mass growth after 3 years of treatment. Basal area growth of the latter treatment gradually increased and during year 4 of treatment was 123% larger than the control. Nitrogen-free-fertilization resulted in a small improvement of dry mass production (+10%).After 3 years of treatment, the amount of needles had increased markedly for both treatments including irrigation, whereas drought treated trees instead had decreased their needle amount vs control. The increase in needle amount occurred as a result of both larger formation of needles and higher preservence of old needles, the opposite relations being found for the drought treated trees. At the same point larger needle formation in combination with a higher shedding of older needles was found for trees treated with ammonium sulphate and nitrogen-free-fertilizer.It is concluded that there is no stage of N saturation in the Skogaby site as there is no leaching of N from the control plots and N fertilization results in both increased tree growth and N uptake.
A total of 63 mycorrhizal and 49 saprotrophic species was found in a 30-year-old Picea abies stand in southwestern Sweden. Nitrogen addition had an obvious negative effect; all mycorrhizal species ceased to produce basidiomata in the 4th year of supply. Nitrogen-free fertilization resulted in reduced basidioma number and dry mass production by about 50% compared with the control. An increase in basidioma number was observed as result of irrigation, whereas the dry mass production was unaffected compared with the control. No fructification occurred, however, when nutrients were added together with the water. Artificial drought resulted in reduced basidioma production. The 1st year of recovery from drought resulted in an increase in basidioma number and biomass by a factor of 5 and 9 respectively, compared with the control. Production of Cortinarius species, Lactarius theiogalus, and Russula emetica increased as a result of irrigation, while a decrease was observed in Boletus edulis that instead was favoured by earlier drought. The saprotrophic species were only to a minor extent affected by the treatments. It is concluded that increased N deposition would result in decreased basidioma production and species number of mycorrhizal species and that changed precipitation climate would result in another species composition of mycorrhizal basidiomata in coniferous forests. Key words: irrigation, mycorrhizal fungi, nitrogen, saprotrophic fungi, basidioma production, nitrogen-free fertilization (vitalization).
The above-ground accumulation of N, N uptake and litter quality resulting from improved or deteriorated availability of water and nutrients in a 25 year old Norway spruce stand in SW Sweden (as part of the Skogaby project) is presented. Treatment include irrigation; artificial drought; ammonium sulphate addition; N-free-fertilisation and irrigation with liquid fertilisers including a complete set of nutrients according to the Ingested principle (fertigation).At start of the experiment the stand contained 86.5 t dry mass and 352 kg N ha -1. The following three years the annual N uptake in untreated trees was 32 kg N ha-l to be compared with the annual N throughfall of 17 kg ha-z. Simultaneously, the treatment with ammonium sulphate and liquid fertilisation resulted in 48 and 56 kg ha-i y-l, respectively, in treatment specific N-uptake following an application of 100 kg N ha-~ y-i. Addition of a N-free fertiliser resulted in improved N-uptake by 19 kg N ha-t y-l and irrigation by 10 kg N ha-t y-~, compared to control. A linear relation between total above-ground dry mass production and N-uptake was found for trees growing with similar water availability. Dry mass production increased with increased water availability given the same N-uptake.It is concluded that the studied stand this far is not N saturated', as N fertilisation resulted in both increased N uptake and increased growth. Addition of a N-free-fertiliser resulted in increased uptake of N compared to the control, indicating an increased mineralisation rate or uptake capacity of the root system. The linear relation between N uptake and biomass production shows that at this study site N is a highly limiting factor for growth.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.