2006
Howard, Jeanette K.; Cuffey, Kurt M.
Factors controlling the age structure of Margaritifera falcata in 2 northern California streams Journal Article
In: Journal of the North American Benthological Society, vol. 25, no. 3, pp. 677-690, 2006.
Abstract | Links | BibTeX | Tags: age structure, annual rings, California, discharge, freshwater mussels, Margaritifera falcata, mortality, recruitment
@article{Howard2006b,
title = {Factors controlling the age structure of Margaritifera falcata in 2 northern California streams},
author = {Jeanette K. Howard and Kurt M. Cuffey},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Howard_2006_Bentho.pdf},
doi = {10.1899/0887-3593(2006)25[677:FCTASO]2.0.CO;2},
year = {2006},
date = {2006-01-01},
journal = {Journal of the North American Benthological Society},
volume = {25},
number = {3},
pages = {677-690},
abstract = {Freshwater mussels are long-lived and relatively stationary organisms that form annual rings, so they provide excellent opportunities for studying how population properties such as age structure relate to environmental influences on recruitment and mortality. We investigated population dynamics of the freshwater pearl mussel, Margaritifera falcata, in 2 northern California Coast Range rivers, the South Fork Eel and the Navarro. We used field observations and inverse theoretical modeling to assess age structures and identify factors that control population demographics. Distinctly different mortality rates for young (<20 y) and old (≥20 y) mussels were observed in the South Fork Eel, and recruitment and mortality both were related to river discharge regimes. Margaritifera falcata recruited more successfully during low-discharge than during high-discharge years, and a 2-fold increase in discharge caused a 60% decline in recruitment success. Active annual recruitment (˜1100–1800 ind./y) was observed in the South Fork Eel, whereas recruitment has been low or nonexistent during the past 30 y in the Navarro. This difference probably is a consequence of the influence of 2 non-mutually exclusive factors: landuse history and host-fish abundance. The Navarro watershed has extensive timber harvesting and orchard/vineyard agriculture and has had severe declines in fish populations, whereas large sections of the South Fork Eel pass through protected land and the river has retained its historical fish populations. Investigation of the factors that shape local M. falcata population age structures yielded insights into the influence of environmental variables and history on mortality and recruitment that will aid conservation of this endangered family.},
keywords = {age structure, annual rings, California, discharge, freshwater mussels, Margaritifera falcata, mortality, recruitment},
pubstate = {published},
tppubtype = {article}
}
Freshwater mussels are long-lived and relatively stationary organisms that form annual rings, so they provide excellent opportunities for studying how population properties such as age structure relate to environmental influences on recruitment and mortality. We investigated population dynamics of the freshwater pearl mussel, Margaritifera falcata, in 2 northern California Coast Range rivers, the South Fork Eel and the Navarro. We used field observations and inverse theoretical modeling to assess age structures and identify factors that control population demographics. Distinctly different mortality rates for young (<20 y) and old (≥20 y) mussels were observed in the South Fork Eel, and recruitment and mortality both were related to river discharge regimes. Margaritifera falcata recruited more successfully during low-discharge than during high-discharge years, and a 2-fold increase in discharge caused a 60% decline in recruitment success. Active annual recruitment (˜1100–1800 ind./y) was observed in the South Fork Eel, whereas recruitment has been low or nonexistent during the past 30 y in the Navarro. This difference probably is a consequence of the influence of 2 non-mutually exclusive factors: landuse history and host-fish abundance. The Navarro watershed has extensive timber harvesting and orchard/vineyard agriculture and has had severe declines in fish populations, whereas large sections of the South Fork Eel pass through protected land and the river has retained its historical fish populations. Investigation of the factors that shape local M. falcata population age structures yielded insights into the influence of environmental variables and history on mortality and recruitment that will aid conservation of this endangered family.
1997
Hunter, John C.
Fourteen years of change in two old-growth Pseudotsuga-Lithocarpus forests in northern California Journal Article
In: Journal of the Torrey Botanical Society, vol. 124, no. 4, pp. 273-279, 1997, ISSN: 1095-5674.
Abstract | Links | BibTeX | Tags: Arbutus, Douglas-fir, madrone, mixed evergreen forests, mortality, shade-tolerance, stand dynamics, tanoak
@article{Hunter1997b,
title = {Fourteen years of change in two old-growth Pseudotsuga-Lithocarpus forests in northern California},
author = {John C. Hunter},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Hunter_TorreyBotanicalSociety1997.pdf},
issn = {1095-5674},
year = {1997},
date = {1997-00-00},
journal = {Journal of the Torrey Botanical Society},
volume = {124},
number = {4},
pages = {273-279},
abstract = {For the Pseudotsuga-Litkocarpus forests of California and Oregon, this study presents the first documentation of stand dynamics in permanently marked plots. Two 0.25 ha plots of old-growth forest in Mendocino County, California were inventoried in 1981 and 1995. These plots were dominated by Pseudotsuga menziesii (Pinaceae), Lithocarpus densiflorus (Fagaceae) and Arbutus menziesii (Ericaceae), and contained nine additional tree species. During the 14 yr interval, Lithocarpus accounted for 98% of recruitment of new stems, and had greater recruitment into taller height classes and a much lower mortality rate in the understory than did Arbutus or Pseudotsuga. Lithocarpus was also the only species filling canopy gaps. However, its relative basal area increased only 3% because death of canopy trees partially offset growth. There was no recruitment of Arbutus or Pseudotsuga. Arbutus suffered mortality and extensive crown die-back, and its density and relative basal area dropped. Mortality of small stems reduced Pseudotsuga's density, but no canopy stems died and growth increased Pseudotsuga's relative basal area 4%. These results indicate that in the absence of fire, Arbutus decreases and Lithocarpus increases in importance, and due to Pseudotsuga's great potential longevity and size, these forests remain co-dominated by Lithocarpus and Pseudotsuga.},
keywords = {Arbutus, Douglas-fir, madrone, mixed evergreen forests, mortality, shade-tolerance, stand dynamics, tanoak},
pubstate = {published},
tppubtype = {article}
}
For the Pseudotsuga-Litkocarpus forests of California and Oregon, this study presents the first documentation of stand dynamics in permanently marked plots. Two 0.25 ha plots of old-growth forest in Mendocino County, California were inventoried in 1981 and 1995. These plots were dominated by Pseudotsuga menziesii (Pinaceae), Lithocarpus densiflorus (Fagaceae) and Arbutus menziesii (Ericaceae), and contained nine additional tree species. During the 14 yr interval, Lithocarpus accounted for 98% of recruitment of new stems, and had greater recruitment into taller height classes and a much lower mortality rate in the understory than did Arbutus or Pseudotsuga. Lithocarpus was also the only species filling canopy gaps. However, its relative basal area increased only 3% because death of canopy trees partially offset growth. There was no recruitment of Arbutus or Pseudotsuga. Arbutus suffered mortality and extensive crown die-back, and its density and relative basal area dropped. Mortality of small stems reduced Pseudotsuga’s density, but no canopy stems died and growth increased Pseudotsuga’s relative basal area 4%. These results indicate that in the absence of fire, Arbutus decreases and Lithocarpus increases in importance, and due to Pseudotsuga’s great potential longevity and size, these forests remain co-dominated by Lithocarpus and Pseudotsuga.