[ad_1]
Hansen Creek, a small stream in southwestern Alaska, is difficult to identify on a map. It's a little over a mile long and about 4 inches deep. The transition from one bank to another takes about five major steps.
Yet this stream is home to one of the densest salmon runs in the Bristol Bay area of Alaska. Each summer, an average of about 11,000 fish return to this stream, furiously climbing the shallow cove to spawn and possibly die.
Over the last 20 years, dozens of researchers from the University of Washington have traveled this stream every day during the spawning period. They counted the live salmon and took a brown bear. After counting a dead fish, the researchers throw it to the ground to remove the carcass and do not count it the next day. The data collection is part of a long-term study on the impact of bear predation on sockeye salmon in this region.
When this effort began in the mid-1990s, Tom Quinn, a professor at the UW's School of Aquatic and Fishery Sciences, decided that everyone should throw the sockeye carcasses on the left side of the creek, facing the water. ;downstream. They might as well be consistent, he thought, and who knows, someday they might see if the discarded carcasses had an effect on that side of the creek.
Twenty years later, Quinn and his colleagues found that two decades of carcasses – nearly 600,000 pounds of fish – thrown off the left side of Hansen Creek had had a noticeable effect: white spruce grew faster than their counterparts in Hansen Creek. . the other side. In addition, salmon-derived nitrogen was present in high concentration in spruce needles on the discarded carcass side.
Essentially, as they report in an article published October 23 in the newspaper Ecologythe sockeye carcasses fertilized the trees.
"Throwing the carcasses on the left side was a simple way of not counting the same fish twice. I thought that sometime in the future, it would be pretty cool to see that if it had an effect, "said Quinn, lead author of the paper, who has taught and led research projects under of the UW Salmon Salmon Alaska program for 25 years.
The researchers were able to say that fertilized trees grew faster by taking a deep slice of the trunk, called the tree's core, on white spruce on both sides of the creek. They examined the growth rings during the 20-year study period (1997 to 2016) as well as for the 20-year period preceding the start of the study (1977 to 1996), examining the spacing of the rings each year. The first 20 years served as a control for the field experiment, as during this period trees on both sides grew at similar densities of salmon carcasses.
In 2016, the authors found that the trees on the enriched salmon side were not much higher, even though they had grown faster during the 20-year study period. This is due to the fact that these trees started earlier and grew more slowly before the start of the study than their counterparts on the other side.
Salmon did not transform these spruces into gigantic giants, but instead stimulated the vegetation on the slow growing side of the creek. Many factors such as soil chemistry, temperature, and light all contribute to tree growth over many years.
"This study demonstrates the importance of salmon carcasses for tree growth, but in the context of an area where tree growth is very slow and where climate and other factors also play a role in their growth." said Quinn.
During the 20-year study period, nearly 200 undergraduate and graduate students, faculty, staff, and visiting scientists cycled through Hansen Creek, which flows into Lake Aleknagik and into the water. 39 other water courses far from the Bristol Bay area. They traveled in groups in case they came across bears, catching fish in streams and often eating only part of the carcass.
At the beginning of the spawning season in July, it is common to see several thousands of sockeye invade the mouth of the creek, their ruby red bodies jostling in waters less than 2.5 cm deep.
"At some point they just go there," said Quinn. "They basically swim on what is little more than wet rocks, feeding through the mouth of the creek and up the creek."
The numbers of sockeye salmon, behavior, and bear predation collected by Quinn and his colleagues for decades are unique. Long-term datasets of this detail on sockeye salmon do not exist anywhere else. Quinn said that many articles were the result of these valuable data, and that this new study is no exception.
"This study contributes to our understanding of salmon 's role in the ecosystem, but also illustrates the importance of patient, conservative and long – term research, as well as educational benefits resulting from". such research at a university, "said Quinn.
More information:
Thomas P. Quinn et al., Multiyear experience shows that fertilization with salmon carcasses improves tree growth in the riparian zone. Ecology (2018). DOI: 10.1002 / ecy.2453
Hansen Creek, a small stream in southwestern Alaska, is difficult to identify on a map. It's a little over a mile long and about 4 inches deep. The transition from one bank to another takes about five major steps.
Yet this stream is home to one of the densest salmon runs in the Bristol Bay area of Alaska. Each summer, an average of about 11,000 fish return to this stream, furiously climbing the shallow cove to spawn and possibly die.
Over the last 20 years, dozens of researchers from the University of Washington have traveled this stream every day during the spawning period. They counted the live salmon and took a brown bear. After counting a dead fish, the researchers throw it to the ground to remove the carcass and do not count it the next day. The data collection is part of a long-term study on the impact of bear predation on sockeye salmon in this region.
When this effort began in the mid-1990s, Tom Quinn, a professor at the UW's School of Aquatic and Fishery Sciences, decided that everyone should throw the sockeye carcasses on the left side of the creek, facing the water. ;downstream. They might as well be consistent, he thought, and who knows, someday they might see if the discarded carcasses had an effect on that side of the creek.
Twenty years later, Quinn and his colleagues found that two decades of carcasses – nearly 600,000 pounds of fish – thrown off the left side of Hansen Creek had had a noticeable effect: white spruce grew faster than their counterparts in Hansen Creek. . the other side. In addition, salmon-derived nitrogen was present in high concentration in spruce needles on the discarded carcass side.
Essentially, as they report in an article published October 23 in the newspaper Ecologythe sockeye carcasses fertilized the trees.
"Throwing the carcasses on the left side was a simple way of not counting the same fish twice. I thought that sometime in the future, it would be pretty cool to see that if it had an effect, "said Quinn, lead author of the paper, who has taught and led research projects under of the UW Salmon Salmon Alaska program for 25 years.
The researchers found that fertilized trees grew faster by taking a deep slice of the trunk, called the tree's core, on white spruce on both sides of the creek. They examined the growth rings during the 20-year study period (1997 to 2016) as well as for the 20-year period preceding the start of the study (1977 to 1996), examining the spacing of the rings each year. The first 20 years served as a control for the field experiment, as during this period trees on both sides grew at similar densities of salmon carcasses.
In 2016, the authors found that the trees on the enriched salmon side were not much higher, even though they had grown faster during the 20-year study period. This is due to the fact that these trees started earlier and grew more slowly before the start of the study than their counterparts on the other side.
Salmon did not transform these spruces into gigantic giants, but instead stimulated the vegetation on the slow growing side of the creek. Many factors such as soil chemistry, temperature, and light all contribute to tree growth over many years.
"This study demonstrates the importance of salmon carcasses for tree growth, but in the context of an area where tree growth is very slow and where climate and other factors also play a role in their growth." said Quinn.
During the 20-year study period, nearly 200 undergraduate and graduate students, faculty, staff, and visiting scientists cycled through Hansen Creek, which flows into Lake Aleknagik and into the water. 39 other water courses far from the Bristol Bay area. They traveled in groups in case they came across bears, catching fish in streams and often eating only part of the carcass.
At the beginning of the spawning season in July, it is common to see several thousands of sockeye invade the mouth of the creek, their ruby red bodies jostling in waters less than 2.5 cm deep.
"At some point they just go there," said Quinn. "They basically swim on what is little more than wet rocks, feeding through the mouth of the creek and up the creek."
The numbers of sockeye salmon, behavior, and bear predation collected by Quinn and his colleagues for decades are unique. Long-term datasets of this detail on sockeye salmon do not exist anywhere else. Quinn said that many articles were the result of these valuable data, and that this new study is no exception.
"This study contributes to our understanding of salmon 's role in the ecosystem, but also illustrates the importance of patient, conservative and long – term research, as well as educational benefits resulting from". such research at a university, "said Quinn.
More information:
Thomas P. Quinn et al., Multiyear experience shows that fertilization with salmon carcasses improves tree growth in the riparian zone. Ecology (2018). DOI: 10.1002 / ecy.2453
Source link
