|
| ||
|
|
||
Black Alder (black + alder)
Selected AbstractsPhomopsis alnea, the cause of dieback of black alder in ItalyPLANT PATHOLOGY, Issue 6 2002S. Moricca Black alder (Alnus glutinosa) occurs naturally on moist soils and along streams and rivers throughout most of its range. Groves of this species in north-central Italy were recently found to be attacked by the mitosporic coelomycete Phomopsis alnea, which causes perennial stem cankers and dieback. The fungi Melanconium apiocarpium and a Hymenopsis sp. were also frequently found on necrotic alder tissue, occasionally invading the living bark. All these fungi were tested for pathogenicity in two seasonal inoculation trials on seedlings of black alder, Italian alder (Alnus cordata) and green alder (Alnus viridis) that were either normally watered or water-stressed. Phomopsis alnea actively colonized the seedlings and reproduced the symptoms observed in the field. The other fungi behaved as weak parasites, only occasionally spreading to apparently healthy bark tissue. It appears that these fungi are saprobes, commonly colonizing bark and twigs already killed by P. alnea. Symptoms caused by P. alnea in the field were exacerbated on dry sites and by seasonal drought stress. On artificially inoculated and water-stressed seedlings, both the incidence and severity of P. alnea also increased, causing extensive mortality. The data provide evidence for the belief that P. alnea becomes a factor in the dieback of natural black alder woodlands when trees are first impaired by wounding agents and then subjected to unusual extended drought. [source] Groundwater input affecting plant distribution by controlling ammonium and iron availabilityJOURNAL OF VEGETATION SCIENCE, Issue 4 2006Esther C.H.E.T. Lucassen Abstract Question: How does groundwater input affect plant distribution in Alnus glutinosa (black alder) carrs? Location: Alder carrs along the river Meuse, SE Netherlands. Methods: Three types of site, characterized by groundwater flow, were sampled in 17 A. glutinosa carrs. Vegetation and abiotic data (soil and water chemistry) were collected and analysed using a Canonical Correspondence Analysis. Based on the results, a laboratory experiment tested the effect of groundwater input (Ca2+) on pore water chemistry (NH4+ availability). Results: Environmental factors indicating groundwater input (Ca2+ and Fe2+), correlating with the NH+4 concentration in the pore water, best explained the variation in plant distribution. NH4+ availability was determined by Ca2+ input via the groundwater and subsequent competition for exchange sites in the sediment. As a result, nutrient-poor seepage locations fully fed by groundwater were dominated by small iron resistant plants such as Caltha palustris and Equisetum fluviatile. More nutrient-rich locations, fed by a combination of groundwater and surface water, allowed the growth of taller iron resistant plant species such as Carex paniculata. Nutrient-rich locations with stagnating surface water were hardly fed by groundwater, allowing the occurrence of fast growing and less iron tolerant wetland grasses such as Glyceria fluitans and G. maxima. Conclusion: Groundwater input affects plant composition in A. glutinosa carrs along the river Meuse by determining nutrient availability (ammonium) and concentrations of toxic iron. [source] Phomopsis alnea, the cause of dieback of black alder in ItalyPLANT PATHOLOGY, Issue 6 2002S. Moricca Black alder (Alnus glutinosa) occurs naturally on moist soils and along streams and rivers throughout most of its range. Groves of this species in north-central Italy were recently found to be attacked by the mitosporic coelomycete Phomopsis alnea, which causes perennial stem cankers and dieback. The fungi Melanconium apiocarpium and a Hymenopsis sp. were also frequently found on necrotic alder tissue, occasionally invading the living bark. All these fungi were tested for pathogenicity in two seasonal inoculation trials on seedlings of black alder, Italian alder (Alnus cordata) and green alder (Alnus viridis) that were either normally watered or water-stressed. Phomopsis alnea actively colonized the seedlings and reproduced the symptoms observed in the field. The other fungi behaved as weak parasites, only occasionally spreading to apparently healthy bark tissue. It appears that these fungi are saprobes, commonly colonizing bark and twigs already killed by P. alnea. Symptoms caused by P. alnea in the field were exacerbated on dry sites and by seasonal drought stress. On artificially inoculated and water-stressed seedlings, both the incidence and severity of P. alnea also increased, causing extensive mortality. The data provide evidence for the belief that P. alnea becomes a factor in the dieback of natural black alder woodlands when trees are first impaired by wounding agents and then subjected to unusual extended drought. [source] Contribution to understanding the historical evolution of meandering rivers using dendrochronological methods: example of the Ma,a Panew River in southern PolandEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2006Ireneusz Malik Abstract The Ma,a Panew is a meandering river that flows 20 km through a closed forest. During times of high discharge the riverbed and floodplain are transformed under the influence of riparian trees. The changes provide the opportunity to measure the intensity of erosion and sediment accumulation based on tree ages, the dating of coarse woody debris (CWD) in the riverbed, and the dating of eccentric growth of tilting trees and exposed roots. The bed and floodplain in reaches of the Ma,a Panew River with low banks were greatly altered as a result of long periods of flooding between 1960 and 1975. Banks were undercut during these floods and black alders tilted. Those parts of alder crowns or stems which tilt and sink generate small sand shadows. When erosion is intensive alder clumps are undercut from concave banks and become mid-channel islands, while on the other side of the channel meandering bar levels are created. The reaches with higher banks were altered by large floods, especially in 1985 and 1997. The concave banks are undercut and sediment with CWD is deposited within the riverbed, forming sand shadows behind the CWD. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||