Friday, October 27, 2017

Wetlands are Also Amazing Under the Ground

Last year I read this actual good advice on the Internet: 

Eric (@MarshNinja) is my academic BFF, my mud brother, and a fellow marsh person who advised me, “The marsh giveth and the marsh taketh away.”  Through this friendship I got many good times as well as the chance to work on Chesapeake Bay, tend a greenhouse experiment, and ultimately help write a paper about it.  Academic paper writing is the worst, but slightly better with friends. 

"Spatial and temporal variation in brackish wetland seedbanks: Implications for wetland restoration following Phragmites control" is a complicated paper, so I thought I'd try to tackle it visually and in four parts. 

1. Why work on Phragmites?
2. Where and when did Phragmites research happen?
3. What are seedbanks?
4. How did the experiment work out?   

1. Why Phragmites?  Phragmites is terrible, a literal wetland invader that conquers marshes and vanquishes native, nicer wetland plants.  Invading Phragmites is a problem across North America, and once it's in place we struggle to get rid of it.  

2.  Where and when Phragmites was studied.  Chesapeake Bay has been through some stuff.  In addition to being one of the first places invaded by Phragmites, it also supports a lot of people, hosts an international shipping port, and has a watershed covering six states with many potentially polluting land uses.

Eric's PhD work began in 2011, when he started an experiment to remove Phragmites from several wetlands across the Bay and see how marshes he herbicided (removal wetlands) compare to wetlands with untreated stands of Phragmites (control wetlands), and beautiful, uninvaded wetlands (native wetlands).  Eric measured a lot of wetland changes caused by spraying herbicide (like above ground vegetation and soil chemistry), but this paper focused on how seedbanks changed over three years in three types of wetlands (herbicided, Phragmites, and native) in five sub-watersheds with different land uses. 

Are you getting a sense of the scale?  Altogether, Eric and his field helpers took 675 soil cores from frozen Maryland marshes, transported them to Utah, and made them grow in USU greenhouses.  (And that's a conservative guess: 15 cores per plot x three treatment plots per watershed x five watersheds x three years.)

3.  What are seedbanks?  Amazing, that’s what.  Seedbanks are soils chock full of new and old seeds.  Every year wetland plants make flowers, which are pollinated, which then turn into seeds.  Some seeds, like Phragmites seeds, float around in the air and drop to the ground miles away from where they started.  Other seeds float on the water, following ocean currents, tides, or streams to faraway places.  Seeds even hitch rides on animals, either latching to fur or being eaten and pooped, essentially migrating to new lands.  But the majority of seeds fall off their parent plants and end up in the soils near where they started.  

No matter how they got into the seedbank, seeds will wait patiently for the right conditions to sprout (or emerge) into leafy, photosynthesizing plants.  The right light, temperature, and flooding conditions are different for each species, so the actual growing plants in any spot are a small fraction of what is in the seedbank.  Some seeds can wait decades for their chance, just hanging out in the soil as layer upon layer of dead plants, seeds, and dirt build up.  It's called a “seedbank” because it's a sort of plant species savings account that can be cashed in during tough times, like after a hurricane wipes out all the vegetation or grad students kill it all with herbicide.  In an ideal world, seedbanks could be used to help with wetland restoration: if wetland folks can just give the seedbank the right conditions to grow (for example, through removing all the weeds) then good, native plants will come out. 

Eric's experiment involved growing all those seedbank samples in USU's greenhouses under real cushy circumstances: warm, well lit, plenty of water, lots of fertilizer and no competition.  The plant species that sprouted from the seedbank then show the history of each wetland and the potential plant species that would come up if a wetland were restored.  For the life of me, I can't figure out why there aren't more exclamation marks in seedbank papers.  The introduction to all of them should be, “We took chunks of dirt out of the frozen ground, added water, and got the marsh's underground secrets!”   

4.  How did the experiment work out? We used some stats magic to characterize the hundreds of species that sprouted from the seedbanks into a few categories so we could compare all 45 marshes (3 experiment types x 5 watersheds x 3 years).  We were most interested in how big the seedbanks were (total seeds germinated), how many species were in each seedbank (species richness), how much of the seeds were invasive species, and how many different types of plants were in the seedbanks (functional diversity).  We hypothesized that seedbanks would be pretty different between the wetlands that had Phragmites and those that did not.  After three years of Phragmites spraying we also expected that the seedbanks would change, since the plants actually growing on the marshes changed. 

Wetlands do what they want and they don't want to cooperate with our hypotheses. With a couple exceptions (there are always exceptions), the different experimental types (Phragmites removal, Phragmites control, and native) did not have distinctly different seedbank communities.  However, each watershed did have its own unique plant community, which increased the statistical difficulty of this project to DEFCON 2 (war is imminent).  Even more difficult to decipher was the fact that seeds mixed on the tides, so there were differences in the wetland seedbank community between the low and high elevations of any given experimental type.  One more wrinkle: Phragmites stems change how tides come in and out of wetlands, thus changing where tide-transported seeds will settle out.     

Holy Complexity! Each row is a watershed and each column is a year.  Within each box, the different symbol types are the different experimental treatments; the farther away each marker and circle are, the more different the plants within the seedbank.

In order to describe the general differences between wetlands in different watersheds and between experimental treatments, we lumped the seedbank sprouts into groups based on whether they were annual (fast growing species) or perennial (come back each year) species and native or invasive.  The hypothesis (and the hope in restoration) is that when Phragmites is removed you'll see lots of native species and lots of different types (grassy, woody, flowery) coming back to fill in the space Phragmites used to take.  While there were plenty of differences in the proportion of those groups across Chesapeake Bay, there weren't any consistent differences between Phragmites before and after herbicide was sprayed. 

Each row is a different watershed and every year has its own column.  There is a sub-column for each experimental treatment (+/- herbicide, no phrag) and every dot and bar is the number of seeds that sprouted from each plant group: invasive perennial species (IP), native annuals (NA), and native perennials (NP). 

The other part of the seedbanks we looked at was how much of the germinating seeds are Phragmites, since it's a prolific seed producer and could swamp all the other seedlings.  This was a shot of good news: usually Phragmites was a small part of the seedbank, relative to all the other species.  The seedbanks were almost always pretty species rich too, which means that if the seeds in the seedbank were given a chance to grow then the wetlands where Phragmites was removed might look nice.  But here’s the kicker: the seedbanks were showing much different things than the actual plants growing in these wetlands.  Even worse, in some place the wetland melted into the Bay after Phragmites died because no plants came back to replace it.  Turns out Phragmites does have some benefits, especially in tidal wetlands, because it holds the wetlands in place (and a Phragmites-wetland is better than no wetland at all).  

So, what to make of all the plots, other than accepting that wetlands do what they want?  The good news is that wetland seedbanks stay diverse even after Phragmites changes all the above ground diversity to zero.  The bad news is two parts.  First, places like the Chesapeake Bay are so large and complicated that factors we didn’t have time/resources/whatever to measure, like water chemistry or patterns of tidal flooding or history, will determine whether you get a successful restoration.   The amount of wind fetch, water column nutrients, sand dunes, or any other number of things might be more relevant to the seedbank and Phragmites restoration than the things we could actually measure.  Second, even with healthy seedbanks, plants aren't coming back following herbicide spraying so we've got to invest in planting live plants, which is pricey. 

Want to read more of the paper’s juicy details?  Of course you do!  I only covered half of the results here.  You can find the whole thing in the online September issue of Estuaries and Coasts

Full paper details: 
Hazelton, E.L.G., Downard, R., Kettenring, K.M. et al. Estuaries and Coasts (2017). 

Friday, July 14, 2017

Plants are the Coolest. That is All.

Exciting news! I’ve spent the last two years working on a guide to the plants found in Great Salt Lake wetlands and it’s finally published online!  You can download it for free HERE.
First, a word about collaboration.  Group projects get a bad name because they are frustrating while you’re in school.  However, ‘Wetland Plants of Great Salt Lake’ only exists because of a group of coauthors.  I had loads of plant pictures, but Karin and Mark had the vision, encouragement, and funding required to turn my original PowerPoint presentation into an Extension publication.  Maureen brought a passion for communicating science and great bird knowledge to a guide that was originally just about plants.  And Jennifer’s document design and technical communication skills pulled it all into a beautiful and cohesive book.   It was difficult sharing control of a project that was so close to my heart, but I’m happy I did because my coauthors made into something really wonderful.  The peer-reviewers were also great; plant identification is hard and their corrections were awesome.  The plant guide is one of the outputs from grad school I’m most proud of.   

Dichotomous (or ‘two-choice’) keys are the traditional tool for identifying plants.  They’re like a Choose Your Own Adventure. You begin at the top with a plant that could be any one of 400,000 extant species and following a series of decisions based on what you see in your plant you arrive at its one true identify.  Using keys is neither simple nor fun (I have to leave it at that.  I don’t have the emotional energy to address taxonomy or shy plants that won’t show me their sexy bits).  Luckily we have a manageable number of species (136) around the Great Salt Lake (GSL), so the guide relies of pictures and wetland type rather than keys.  This option is both aesthetically pleasing and completely justifies the thousands of plant pictures I have taken. 

Plant ID in it's worst form requires multiple keys, a glossary, and access to the Google.  Rant about that found here.

Four basic types of wetlands exist around GSL and the only key I’ll present is one to help you decide which type of wetland you were standing in when you found the plant you’d like to identify.  

A non-wetland and the four GSL wetland types
One caveat: plants do what they want, so many species can be found in multiple communities and might just pop up in a completely unexpected place.

Start with the best option for Step 1 (1a or 1b), follow to the next step (2a/2b or 3a/3b) until you find your wetland type. 

Plants have four basic parts – flowering parts, stem parts, leafy parts, and underground parts – all of which are modified in cool ways to allow plants to survive in wetlands.  Each part is also important in plant identification. 

In wetlands, water, light, and nutrients – the things plants need to live – are present in extreme quantities.  In order to cope with having too much or too little of what they need, wetland plants have developed bad-ass features like stems that pickle, hitch-hiking seeds, cloning capabilities, and floating parts.  I highly recommend heading out to the wetlands yourself to poke, pluck, and sniff all of the plants yourself, but here’s a quick preview of some of my favorite plants from each wetland type along with their key identifying features.   

Globally, only about 6% of the land surface is actually wetland, so non-wetlands (which we can call ‘uplands’) and their plants show up in or near wetlands.  Upland plants add some nice color to generally green marshes and wildlife like them because it’s nice to hang out in dry places sometimes. 

I’m smitten with the Rocky Mountain bee-plant (Cleome serrulata).  This beautiful, stinky species has big purple or pink flowers.  If you look closely you can see each flower has stamen (the plant parts that hold pollen) sticking out.  Bees trying to get at the nectar deep in the flowers will rub those stamen, taking some pollen in with it, which will be dropped on the next plant that bee visits.  This is pollination and it’s how plants avoid in-breeding without all the travel usually required to move genetic material. 

Playas are the coolest!  They’re only flooded during big storms or high runoff, remaining dry and salty for most of the year.  The plants and bugs in playas only sprout or hatch when conditions are just wet enough for them to complete their life cycle; migratory birds are keyed into that so flooded playas are filled with gorging birds. 

My absolute favorite plant of all time is pickleweed (Salicornia rubra).   Pickleweed leaves and flowers are just scales, which saves lots of water from being wasted.  The segmented stems are plump, a feature called succulence, because they’re full of concentrated salt water, which allows pickleweed to thrive in some of the saltiest places on Earth.  The fluid filled stems are so salty they can actually be used to pickle other plants.  In the fall the stems turn from green to red and spit out the seeds hidden under the scales, a process called dehiscence.  Fun fact, you can and should nibble on pickleweed. 

Meadows are flooded or saturated (i.e., muddy) for most of the year, but it’s hard to see the water because it’s just under the soil surface or covered by lush plant growth.  I have complicated feelings about meadows – there are so many species J, which means a lot of work with dichotomous keys L  – but I really like nodding beggarstick. 

Beggarstick (Bidens cernua) is an aster or composite flower: each flower head is made of many flowers.  The things that look like petals are ray flowers and the pokey things in the center are disk flowers. Each flower produces a seed (that’s a lot of seeds) that is shaped like a trident with 3-prongs, which are perfect for hitching a ride on an animal or ecologist struggling to get through a mass of beggarstick.  This form of seed dispersal makes it possible to again spread genetic material around without having to be mobile.  Plants are crafty like that. 

Emergent wetlands look like your typical marsh: lots of bulrushes and cattails growing up through the shallow water.  Water levels in emergent wetlands often fluctuate from wet to dry so the plants in those wetlands are darn tough. 

Alkali bulrush (Bolboschoenus maritimus) is everyone’s favorite emergent wetland plant.  It forms large loose stands that are ideal for hiding nests in and the seeds are super delicious to ducks.  Just beneath the surface many of the plants are connected through underground stems called rhizomes that store plant food over the winter and sprout new stems each spring if soils stay flooded – this means sometimes all those individual stems are actually clones of each other and can share water, gases, and food between them.  However, alkali bulrush can also sprout from seeds if a wetland dries out – it needs heat and sunlight for that – so this species can live in a huge variety of wet and dry-ish wetlands.  Even cooler, alkali bulrush seeds can survive being in a duck’s stomach and will sprout after being pooped out wherever that duck chose to fly.  It’s almost like a migratory plant species. 

I’ve been using the common plant names, which is frowned upon in academic circles, but it works best for me in wetlands.  First of all, common names are easier to remember and more widely known than scientific names.  Secondly, as taxonomists learn more about how closely or distantly related plant species are they keep changing the scientific names.  I have to assume their intentions are good, but the result is often confusion.  Since I started grad school the genus alkali bulrush belongs to has changed from Scirpus to Schoenoplectus to Bolboschoenus.  Gah!  Using the most recent scientific name is one of the fastest ways to develop a failure to communicate. However, in the guide book linked here we’ve included synonyms – all the common and scientific names a given species could be known by – in order to enhance communication about plants.  Definitely talk with other people about your plants by whatever name your heart recognizes. 

Several years ago, I heard a manager refer to submergent wetlands as ‘duck soup’ – a giant bowl of deliciousness waterfowl gorge on.  Submergent wetlands might look like simple, serene ponds, but at their healthiest the underwater world is teaming with plant and bug life. 

Spiral ditchgrass (Ruppia cirrhosa) is a species of submerged aquatic vegetation – a plant that can grow in the water instead of outside it.  Spiral ditchgrass reproduction is adaptable: it can regenerate through underground parts called tubers or through floating seeds. Even the stems are amazing, they’re flexible enough to droop and spread when water levels fall or they can grow fast when water levels rise and they need to reach sunlight.  The stems and leaves can even photosynthesize under low light levels.  Plus all the parts, from the floating flower parts to the underground tubers, are delicious and nutritious for birds.  The spiraling peduncles (flower stalks) are my second favorite identifying plant feature, fun to say and fun to see. 

Now that you’re armed with a little info on wetland plants, make a visit to your local wetland.  I put together a map of northern Utah wetlands here.  

Go Visit Your Wetlands

Utah doesn't have many wetlands, but the wetlands we have are so great!  I’ve put together a map here with some of the wetlands places along you can visit.

Remember to bring your bug spray, long sleeves, and a broad brimmed hat J.  

Please follow all the posted signs: read fun facts about the wetlands, stay off roads that shouldn’t be driven on, and give nesting birds the space they need. 

Wednesday, March 1, 2017

What is an Invasive Species?

If you do anything with natural resources (the land, water, soil, plants, and animals that support our lives) then you’ve probably heard someone bemoan invasive species.  Invaders are generally viewed as bad, but there are levels of badness, from pretty OK to super-villain, which is what I’d like to explain here through examples from the wetlands I work in around Great Salt Lake.  Plants aren’t the only invasive species - there are plenty of invasive swimming, flying, and running things - but I have the most pictures and knowledge of plants. 

Weeds – Badness Level: Pretty OK

A weed is not actually an invasive species, it’s just an undesirable plant for that place, nothing more.  Undesirable to whom?  Whomever is doing the name calling.  Native cattails (species in the genus Typha) are often regarded as weeds because wetland people would rather see something else, like bulrushes or submerged plants, growing in its place.    
Broadleaf cattail (Typha latifolia) – Don’t be hatin’
Duckweed (Lemna minor) is another example of a wetland weed.  Duckweed is native to North America but disliked because it shades out the water and makes boat travel challenging.
Duckweed (Lemna minor) covering open water, probably hated because it signals something off in the water

Introduced Species – Badness Level: Not Great

An introduced species is a species living outside its native range and that has arrived in its new place through human activity.  Many terms are used to describe these species, including alien, exotic, and non-native.  Some introduced species have been introduced to their new habitats deliberately because they were planted in gardens and then escaped.  Watercress (Nasturtium officinale) is not native to North America, but escaped garden fences and can be found in many slow-moving waterways now.
Watercress (Nasturtium officinale) a pretty introduced species (this will become a theme) that might also taste good
European seaheath (Frankenia pulverulenta), another European species, can be found in more and more Utah wetlands, seeming to follow cattle herds around.  However, the way it got to Utah is likely more accidental. Landowners or managers might try to remove introduced species because they are not native, but they’re usually low priority because they aren’t causing much harm.    
European seaheath (Frankenia pulverulenta) another cute, non-native species

Invasive Species – Badness Level: Villainous

Invasive species are those which are both non-native and likely to cause harm to the environment, economy, or human health.  Who decides when a species has passed beyond introduced into invasive?  I don’t know and I think often invasive species are discussed using all of the terms above.  However, since invasives have been called harmful, people are out there combating the invasion.  Reed canarygrass (Phalaris arundinacea) was deliberately introduced around the U.S. as a plant to prevent erosion following road construction (a common method for the introduction of grasses), but has become a plant bully, pushing aside other plants instead of playing nice alongside them.  Reed canarygrass is often sprayed with herbicide to weaken it. 
Reed canarygrass (Phalaris arundinacea) might not be as foreign as originally thought, but is still considered too pushy to put up with
Saltcedar (Tamarix chinensis) is another pushy, invasive species from Eurasia.  Its ability to grow fast, dense, and deep can prevent other wetland species from reaching the sunlight and water they need to grow.  Controlling tamarisk is done through more interesting means: either by ripping up the entire plant (mechanical control) or by bringing its natural enemy – a beetle – into battle. 
Tamarisk (Tamarix chinensis) was planted as an ornamental tree, but was bound for much greater things

Noxious Species – Badness Level: Worst-est

Noxious species reign supreme among invasive species, both in terms of impact and attention.  Agricultural authorities (in Utah, the Department of Agriculture and Food) have legally declared noxious species ‘injurious to public health, crops, livestock, land, or other property’ and require a counties to develop a combat strategy.  Some species are considered so noxious that they are prohibited from even crossing state borders.  Phragmites (Phragmites australis), undoubtedly the worst-est of the worst, was added to Utah’s Noxious SpeciesList just last year.  What makes Phragmites so odious?  Its ability to actually engineer an ecosystem: it displaces native species, obliterates sunlight at the soil surface, changes the course of water flow, and actually elevates the surface of the wetland. 
Phrag (Phragmites australis): beautiful, mean, and injurious
Many thistles, including musk thistle (Carduus nutans), are noxious species, in addition to their status as unnecessarily pokey.  Musk thistle forms such dense stands of solid thistle it is widely regarded on The Internet as ‘aggressive.’  Further, musk thistle might actually release chemicals that stunt the growth of other native species (a phenomenon called allelopathy).  Supervillain stuff, for sure!
 Musk thistle (Carduus nutans) might have been introduced to the US in ship ballast (water stored in boats to balance them) and then expanded across the country. 

Why?  And what can I do about it?

Why do some many rotten plants invade wetlands?  First, invasive plant species tend to have biological super powers like rapid growth and cloning that allow them to be everywhere (and they use this power for evil).  Second, wetlands tend to be located downstream of sources of invader reproductive bits and experience frequent disturbances like scouring floods.  This means there are plenty of plant bits waiting in wetlands to take advantage of bare soil when it is exposed.  Finally, being downstream of everything also means that wetlands often have lots of nitrogen and phosphorus, which are invasive species steroids. 
Purple loosestrife (Lythrum salicaria): each plant can produce more than 2 million seeds every year.
Water milfoil (Myriophyllumsibiricum): small pieces of the plant can hitch a ride on boat propellers and then create a new clone in a new lake.
Fuller’s teasel (Dipsacusfullonum): often sprouts on bare ground and is capable of growing a 2-foot deep taproot.
Oh my.  I need to step back for a minute.  Invasive species are scary…  

Once they’re established we have a whole suite of poisons, digger and cutter machines, fire starters, and natural enemies (often bugs) to combat the invaders.  However, it’s difficult work and generally the purview of professionals (or hapless graduate students).  So here I’m advocating for preventing the spread of new invasions, which is totally something you can handle.  How?  Don’t plant invasive species in your gardenUniversity Extension programs across the country, local gardening organizations, and a whole variety of herbariums and gardens have guidance on beautiful native species you could use instead.  An added bonus of avoiding non-native species: you’ll be planting something naturally adapted to the environment you live in.  That’s pretty cool. 

Itching for more?  Check out this video I made about my love/hate relationship with Phragmites and then look in on the research the Kettenring Lab at USU is doing on invasions and restorations.  

Tuesday, January 3, 2017

What the Heck? A story about struggle and wetland hydrology

I love wetlands (surprise!). They have the most interesting plants, the coolest soil, and the best birds.  Wetlands have are so cool because they have dynamic hydrology: water comes and leaves often according to increasingly unpredictable schedules.  Unpredictability is a pain in the ass because it’s really hard to know the right pair of shoes and shirts to wear into the field.  One of my favorite wetlands, affectionately known as BRU02, was bone dry for the first two years I visited it, so I assumed that irrigation boots would be appropriate for my Year 3 visit.  Then I forgot my long-sleeved shirt, which is fine when wetlands are dry and bug-free.  Unfortunately, on May 15, 2014 BRU02 was flooded.  This is how every minute of my 1.5 mile walk out to BRU02 went:

I've never seen so many birds there and they were all angry at me for waking their babies and leading away the mosquitoes they were hoping to eat.  I was eaten alive slowly because I was also hauling around 100 pounds of water in my over-topped boots.  Worst of all, once I got out to BRU02 the well I was looking to put a data logger in was gone!  The only reason I walked all the way out there during prime bug season was to leave that data logger and some jag had pulled my monitoring well out of the ground.  This unusual flooding pattern ruined my day and I couldn’t even capture it for analysis.  Three trips later the well was reinstalled with a data logger and the data gathered there is what I’ll cover in this post. 

Spoiler alert: in all my data analysis I haven’t been able to predict what shoes you should wear to the marsh, so bring them all and select according to the volume of water you’re comfortable hauling around. 
Pro tip 1: always wear a long-sleeved shirt.  Mosquitoes don't care about the DEET bath you took if you are the biggest source of blood around.  Pro tip 2: always go into buggy places with someone bigger (i.e., chum).

I’ve tied myself in knots over my 2nd dissertation chapter worrying about whether I gathered enough of the right data and figuring out how to display it.  Every time I look at the data I decide I should just go gather is all over again, then I remember that terrible day.  Thankfully, a do-over is not an option.  The data I gathered are super cool, though adding the keyword ‘super cool’ to a publication probably won’t really sell it, so I’ll be working through some ideas here.

Hydrology is all about the movement of water across the land – how much is moving, how fast it flows, and where it is going.  Measuring flow gets real muddled in wetlands because… Well, take a look at the wetland below and guess which direction water is moving:

A nice Great Salt Lake emergent wetland
It’s going all these places:

A strictly hydrological study would measure each of those arrows and require a lot of instruments: evaporation pans, transpiration sensors, a nest of piezometers to measure water depth and movement to shallow and deep aquifers, and flow gauges where water comes into and out of the wetland.  Fun stuff, for sure, but costly and inappropriate for answering my ecological question.  If you’ll recall, my goal is to figure out the impact of impoundment on Great Salt Lake wetland condition (i.e., are we doing a good thing managing water the way we do?).  To answer that question I need to look at the aspects of hydrology that impact vegetation because the vegetation tells me what condition my wetland is in.  I’ve been really worried about defending my focus on water depth when I could have measured so many other things. In ecology we face a trade-off sometimes between measuring all the possible variables at one place or measuring a few well-selected things at a whole bunch of places.  I’ve chosen the latter option – measuring one of those hydrology arrows above at 50 places.  Measuring water depth from May to September proved a solid idea because it’s the aspect of hydrology most relevant to the plants [1].  Even better, water depth is one variable that reflects changes to water coming in and leaving wetlands (all the arrows) - it integrates all the aspects of hydrologic change.

When wetlands are flooded at the correct depth during the right time the plants grow real big, bugs proliferate, and soil bacteria start changing soil chemistry [2].  The key finding from my dissertation is that impounded wetlands – wetlands that have been diked and turned into shallow reservoirs – are in better condition because they are flooded longer and deeper than un-impounded wetlands.  Impounded wetlands have enough water to do the things wetlands do.  That took four years to figure out definitively, but it only took one year to figure out I needed the details on how long and deeply my wetlands were flooded.  During Year 1, my pilot project year, I installed piezometers at 15 of my 50 wetland sites and found this:

Pressure transducers measure depth to water, 0 cm is total saturation, negative numbers indicate the depth of flooding, positive numbers are the depth below the soil surface where the water table can be found
What?!?!  Is there a pattern hidden in there? What parts of that four month period matter most? It was confusing and cool and great justification for investing in piezometers for each site!  A piezometer is a well with holes or slots drilled into the bottom so that it fills as water tables rise.  Many piezometers are equipped with data loggers called pressure transducers that measure the weight of the water in the well and translate that to a water depth.  The water depth measurement is recorded every hour and stored in the pressure transducers.

Piezometers and the people who work with them
I wanted to answer two questions with my piezometer data: 1) what kind of hydroperiod do Great Salt Lake wetlands have, and 2) what hydroperiod attributes change wetland condition?  My piezometers got A LOT of data, too much, so the first step was to condense hourly data into a single measurement for each day.  Then I calculated as many statistics to describe what the water was doing as I could.  For example:
  • The deepest the water got and when
  • The lowest the water table dropped and the number of times it fell
  • Average and median water depth
  •  Frequency and magnitude of water table fluctuations
  • The length of time a wetland was flooded, muddy, or dry
  •  Water depth at specific times of year
  •  Water regime according to other classifications

I felt pretty clever in some of my calculations because I had a breakthrough with for-loops, but the results were...urm… TBD.  To answer Question 1: Great Salt Lake emergent wetland hydroperiods are semi-permanent: water is deepest in the late spring, driest in mid-summer, and flooded again in the fall. But there is a lot of variability, from temporary to permanent flooding.

A few examples of GSL wetland hydroperiods
Combining the hydroperiod information with the condition data I gathered to answer Question 2 is more interesting.  Getting reference condition (the healthiest) wetlands requires a relatively narrow set of hydrologic conditions: average water depth over the whole growing season should between 5 cm deep and 10 cm below the surface and wetlands should be saturated or shallowly flooded in late summer.  The water should be drawn down a little, but that low point shouldn’t fall below the reach of plant roots and only last a couple weeks.  While the zone of optimal conditions is narrow, periodic deviation from that hydroperiod, like during a dry year, won’t disrupt wetland condition.  Instead, many years of dry conditions or constant flooding are what hurt the condition. And all that variability I saw – well, there are a whole bunch of ways to be in non-reference condition: too wet, too dry, too flashy, too stable….One big caveat – unimpounded wetlands were significantly drier than impounded wetlands and in significantly lower condition – these things are inextricably linked.

Hydroperiods of the best (reference) sites and the worst (poor)
What I found most interesting though is what land managers saw in the hydroperiod data:

I’ll continue working through what the point of it all is.  I'm struggling with staying just a few things about 164 hydroperiods that don't always remain consistent year to year and linking it clearly to the vegetation present (which doesn't always care about what I measured).  If you've got any insights I'd love to hear them.  In the meantime, here are some practical tips, should you be thinking of using piezometers:

1.   Logging the data – as long as you select the correct date for automated pressure transducers to start gathering info, things are stress free.  Batteries remained ~70% full after 3-4 years.  Taking pressure transducers out during the winter gave some piece of mind, but did miss a potentially important window between the thaw and beginning of spring runoff. 

a.    I used In-Situ Rugged TROLL 100 pressure transducers (cost ~ $400) and installed 3 Rugged Baro-TROLL 100 barometers approximately 20 miles away.  Pressure transducers started recording 12-18 hours after they were deployed in the field.  Pressure transducers were deployed in May and gathered in September so I could upload data and check batteries and skip gathering unusable ice data.  I measured water depth at the well when pressure transducers were deployed and during any field visits; these measurements were used to post-correct and validate data.  All data was uploaded using Win-Situ 5.0 software, corrections for barometric pressure were made with the BaroMerge function and then with actual water depth data using the Post Correction function. 

      2.  Piezometer pieces – Wells were 5-feet long in total, the top 4 feet was 2-inch diameter SCH-40 PVC, the bottom foot was 2-inch diameter 0.10 slotted environmental PVC (you can get it from drilling supply companies); sections were glued together with a PVC coupling.  I glued a fitted cap to the bottom and drilled a ¼ inch drain hole.  I used 3-inch diameter slip caps, stainless steel eyelet bolts, and four-feet of paracord to suspend pressure transducers.  Caps were secured with 8-inch plastic zip ties.  The caps and rope, while cheap and easy, were suboptimal.

      3.  Installation – easier than expected, kind of. We used a 3-inch auger to install wells to a depth of 3 feet (not possible with dense clays, caliche layers, oolitic sand, or deep water); wells protruded about 2 feet from the ground.  I recommend installing wells deeper if a wetland is very dry or if there are cows.  We placed wells in the deepest flooded area that had dense, emergent vegetation; the deepest point was thought to be most representative and the vegetation would prevent tampering.

      4.  Troubles – it was difficult to find 2-inch PVC in dense Phragmites and hardstem bulrush (handheld GPS units have an accuracy of 3-5 meters).  Keep in touch with land managers or hidden wells may be burned, bent by an ATV, or mowed over.  Cows are always itchy and will scratch on the sturdiest thing around, just build little fences around them because that scratching will displace pressure transducers and mess up your data. 

Some of the things that can go wrong with monitoring equipment

Further Reading: 
[1] US Environmental Protection Agency.  2008.  Methods for Evaluating Wetland Condition #20: Wetland Hydrology.  Prepared jointly by the U.S. EPA Health and Ecological Criteria Division and Wetlands Division.
[2] Brown, S. C., Smith, K., & Batzer, D. (1997). Macroinvertebrate responses to wetland restoration in northern New YorkEnvironmental Entomology26(5), 1016-1024.