Photo of the Week – March 13, 2014

Here are two photos that caught my attention as I was going through timelapse imagery the other day…

In my last post, I showed some timelapse photos from a fenceline at The Nature Conservancy’s Niobrara Valley Preserve in north-central Nebraska.  At the time, I promised a good story about the trail that developed on the cattle side (right side) of the fence.  As a reminder, the fence in these photos was installed in what had been a cattle pasture, but the left side is now grazed by bison (light stocking rate) and the right side is grazed by cattle (moderate stocking rate).  More details on the stocking rates below…

The first photo in which cattle appear in their pasture is this one, taken on June 21 at 6:36 pm.

Cattle

June 21, 2013.  6:36 pm

Notice the absence of a cattle trail in this first photo.  Then look at the photo below, which was taken ONE HOUR LATER.

trail

June 21, 2013.  7:41 pm

Seriously?  A trail formed the very first time cattle walked along the fenceline??

I’m not surprised or bothered by the development of the trail, but I’m relatively shocked that it only took one pass by cattle to make it!  I would have expected the gradual development of a path over a few weeks.  On the other hand there were 110 cows and 110 calves in the pasture.  Rich Walters, Niobrara Valley Preserve manager, pointed out that if all those cattle followed the fence line in single file formation, that was 880 hooves stepping on those relatively loose sandy soils.  I suppose that would have an immediate impact.

Here’s one more surprise.  The cattle were brought into this pasture on June 2.  Why did it take until June 21 for them to (apparently) make their way to the north edge to graze and then create a trail?  I can’t say for sure that they hadn’t explored this part of the pasture prior to the 21st, but there isn’t any indication of grazing impact in the timelapse photos taken between June 2 and June 21.  It may be that the cattle had enough forage further south (and closer to their water tank) that they just never wandered very far, but I would have expected them to have made an exploratory pass around the pasture within the first few days – just to see what they had to work with…

Before I go further, I’m sure some people are already mentally condemning cattle for their trail-making and other faults, but that’s not the point I’m making here.  As I wrote in a recent post, I think cattle are very useful as prairie management tools, and are comparable to bison in most respects – though the formation of these narrow trails is certainly one difference between the two animals.  Sure, cattle trails can cause problems, especially in chronically overgrazed sites with steep slopes and erodible soils, but the vegetation beneath cattle trails can also recover pretty quickly if given the chance.  In the meantime, trails can provide valuable habitat for reptiles and invertebrates looking for a place to warm up in the morning sun, and are used as transportation corridors by many other animals besides cattle.

Oh, and in case you doubted me, the photo below proves that there truly were bison on the left side of the fence in 2013, though their numbers and the relative size of their pasture to the cattle pasture on the right created a very different grazing environment.

Bison grazing on the left side of the fence.  August 10, 2013

Bison grazing on the left side of the fence. August 10, 2013

The two sides of the fence looked pretty different from each other by the time cattle were removed, in terms of vegetation height and density.  After my last post, several of you asked about the stocking rates on each side.  There were approximately 225 bison (cows, calves, and bulls) in the 10,000 acre bison pasture to the left of this fence in 2013.  They were grazing year round, but had plenty of room to roam since the Preserve staff had cut back their numbers pretty drastically following the big wildfire in 2012.  At that stocking rate, bison didn’t graze very intensively in most parts of the pasture, including the area shown in this photo.  On the cattle side of the fence, the 110 cow/calf pairs were restricted to only 640 acres of pasture.  Even though they were only in the pasture for about 5 weeks (June 2 – July 12), that’s still a much higher effective stocking rate than that in the bison pasture.  The difference in the height of vegetation between the left and right sides of the fence, then, is due to stocking rate, not grazer species.

I’m already learning an awful lot from looking at the first year of timelapse imagery at the Niobrara Valley Preserve, and much of what I’m learning has been unexpected.  The rapid formation of a cattle trail is a great example.  I’ll be sharing another example within the next week or two, though it’s more of a mystery than a lesson at this point.  For now, I’ll just tease that post by saying it has to do with a stick that moves by itself…  You can have fun thinking about that for a while!

Fenceline Timelapse

I got my hands on another batch of timelapse imagery for our Niobrara Valley Preserve last week.  I now have images from all nine of the Preserve’s cameras for the 2013 growing season (late April through the middle of October).  The photos from those cameras document the first year of recovery from the drought and major wildfire back in the summer of 2012.  As I work through the many thousands of images, I’ll be sharing some of the interesting stories I see.

I’ll start with a series of images from a camera set along a new fenceline.  As the staff at the Preserve set out to rebuild fences after the wildfire, they took advantage of the opportunity to shift the location of some fence lines.  In this case, they moved the south boundary fence of the east bison pasture and enlarged that pasture to more than 10,000 acres.  The fence was constructed through what had been a traditional cattle pasture (unplowed sandhills prairie that had been conservatively grazed by cattle for many years).  We chose to place a camera along that new fence for two reasons.  First, it was a good place to watch the recovery of the prairie plant community following the fire.  Second, it provided a good chance to look for differences between bison-grazed and cattle-grazed prairie.

Here is a slideshow of images from the 2013 season from May through mid-October.  If you hover your mouse over the images, you can click on the arrows and fast forward (or backward) through the photos to look at changes over time.  The left side of the fence is now bison pasture, while the right side is still cattle pasture.  Below the slideshow, I’ve written about some of what I see as I look through the photos.

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The first thing that’s obvious in the images is the rapid recovery of the prairie’s plant community from an intense drought and wildfire.  In the first image (May 2) it looks like there is nothing but bare ground.  Even the ash from the fire was washed/blown away, leaving almost nothing above ground.  However, as spring arrived, both annual and perennial plants seemed to jump out of the ground and fill the landscape with green vibrant vegetation.  It’s difficult to identify many of the plants, given the scale and resolution of the images, but there are two major flushes of blooms – the very pale pink flowers of wild roses (Rosa arkansana) in June and the yellow plains sunflower (Helianthus petiolaris) in August.  You might remember reading about the abundance of sunflowers across much of the sandhills from an earlier post.

One of the reasons I chose this particular location for the camera was to watch the yucca (aka soapweed or Yucca glauca) plants over time.  There is very little yucca in our bison pastures at the Niobrara Valley Preserve, but it is fairly common in cattle pastures.  That has less to do with bison grazing vs. cattle grazing than with the fact that the bison are in the pastures through the winter and the cattle are pulled out in the fall.  Both bison and cattle will graze on yucca during the winter because while the leaves are tough and spiny, they are green when almost nothing else is.  I think we’ll get to watch through time as the yucca on the left side of the fence gradually disappears through years of winter grazing by bison while the yucca on the right grows relatively unhindered.  We’ll see!  To see the yucca, it’s best to start on the last image of the slideshow (October 21) and look for the spiny green plants surrounded by brown vegetation.  Then you can watch those plants grow as you click from May through October.  Since I haven’t seen the images from this past winter yet, I don’t know if bison have been grazing the yucca, but I sure hope so (for the sake of the story…).

One difference that can already be seen between the bison side of the fence (left) and the cattle side is the formation of a trail along the cattle side of the fence.  I will provide more information on that in a post that will come out very soon, so I won’t talk much about it here except to say that while the formation of numerous trails are definitely a real difference between bison and cattle pastures, they are not necessarily a bad thing.  More on that topic, with a VERY interesting couple of timelapse photos, coming soon.

One last observation is that either the camera or fence moved quite a bit through the season, and since the fence clearly didn’t move, it had to be the camera.  I’m not sure how to explain that.  I don’t think it was being bumped when the memory cards were swapped out every month or two because the movements occurred in between those events as well.  I imagine the most likely scenario is simply that the massive wooden post we stuck in the ground (with concrete) shifted in the sandy soil.  We’ll see if that continues over time or if it settles into a location.  It’s not a problem, just something interesting.

Finally, one of the great things about timelapse imagery is the opportunity to capture beautiful images without having to be there to click the shutter on the camera.  Here are three photos from this camera that I thought were particularly pleasing.

Sunrise on August 19, 2013.

Sunrise on August 19, 2013.

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Moonlit prairie on the same day as the above photo - August 19, 2013

Moonlit prairie on the same day as the above photo – August 19, 2013

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Lightning during the night on June 21, 2013.  Wild rose flowers can be seen in the glow of the lightning.

Lightning during the night on June 21, 2013. Wild rose flowers can be barely seen in the glow of the lightning.

Many thanks to Mike Forsberg, Jeff Dale, David Weber, and everyone else at Moonshell Media that has been working on this timelapse photography project with us.  Special thanks also to the Nebraska Environmental Trust for funding the installation of the cameras as a way to help us better understand the effects of wildfire on Nebraska’s ecosystems.