Forest regrowth monitored a year after the severe April 2010 Yazoo City tornado

Transcription

1 Forest regrowth monitored a year after the severe April 2010 Yazoo City tornado Source: NOAA Assessment: July 05, 2011 http: ews.forestthreats.org

2 Doppler radar images from NOAA for April 24, 2010 reveal the remarkable intensity of this lethal F4 event. Note the prominent debris ball southeast of Yazoo City. This image shows storm velocity; the pink shows areas of extremely high wind.

3 Summer 2009 Yazoo City This is how the forested bluff east of Yazoo City, Mississippi appeared the year before the April 24, 2010 tornado hit (Source: 2009 NAIP).

4 Summer 2010 Yazoo City 2011 Aerial View (1m NAIP Imagery) The broad path of this tornado shows up clearly on this 1 meter This radar resolution image aerial shows photo the taken actual a few location months of after a weak the event. EF-1 tornado, (Source: southwest 2010 NAIP). of the town of Park Falls, WI.

5 June 17, 2011 Compared to 8-year baseline % Change in Greenness Yazoo City LESS SAME MORE The long-term effects of the tornado are shown by the Threat Centers Early Warning System (EWS). This June 17, 2011 image compares the current conditions to that of the prior 8 year period. Note the path is still clearly seen in yellow, and that there is extreme forest change just southeast of Yazoo City shown in red. (Gray areas are non-forest).

6 June 17, 2011 Compared to 8-year baseline % Change in Greenness Yazoo City LESS SAME MORE The general path of the tornado based on change in forest greenness. According to NOAA, the actual tornado path covered 149 miles.

7 June 17, 2011 Compared to prior year baseline % Change in Greenness Yazoo City LESS SAME MORE This June 17, 2011 product shows greenness relative to the same three-week period a year earlier (i.e., the three week baseline ending June 17, 2010 that was just 2 months after the tornado struck). Compared to this prior year baseline the tornado path stands out as dark blue against a light blue forest. This shows the expected increase in greenness within the tornado path during the last year.

8 June 17, 2011 Compared to prior year baseline This anomaly appeared in mid March 2011 and gradually grew through April. Based on that behavior, it s probably a large clearcut. % Change in Greenness Yazoo City LESS Note that this small area has not recovered like elsewhere within the tornado s path; but why? SAME MORE

9 This radar image shows the actual location Zooming of in, a it weak is clear EF-1 that these tornado, southwest of the town of Park anomalies Falls, WI. have been recently logged.

10 This radar image shows the actual location of a weak EF-1 tornado, southwest of the town of Park Falls, WI.

11 This radar image shows the actual Comparing location Zooming the of in, a current it weak is clear EF-1 conditions that these to tornado, southwest of the town of the Park anomalies 8-year Falls, baseline, WI. were managed the salvage logged differently areas stand during out the even last year. more.

12 The 2009 aerial imagery shows that This radar image shows the actual location of a weak EF-1 this area was forested the year before tornado, southwest of the town of Park Falls, WI. the tornado struck.

13 Assessment Forest monitoring involves much more than documenting the immediate changes that occur with disturbance. Both the severity of the event and how the forest changes in subsequent months and years is a key part of understanding the effects of disturbance on the landscape. The Threat Centers EWS not only documents the initial disturbance severity, but how land managers and postdisturbance stressors respond after that. Severe disturbances like tornados or fire are often followed by insect outbreaks or salvage logging, and these secondary disturbances can cause substantially different pathways of forest recovery, so they need to be systematically monitored too. As the EWS monitors the forest continuously, it is capable of capturing multiple and cascading disturbances, all within the context of normal seasonal change in vegetation related to leaf phenology. The recovery in greenness following the April 24, 2010 Yazoo City tornado represents the combined response of early successional growth and recovery of surviving vegetation. Salvage logging reduced greenness compared to adjacent areas that were either not salvaged or were logged more lightly. As long as these areas remain in forest and are not developed, continued recovery in greenness is expected over the coming years. For more information: Source: NOAA Steve Norman; EFETAC