, 19 tweets, 18 min read
When peatlands get featured in @AGUbiogeo @AGU_Eos, you know it's time for a deep dive into why these ecosystems are so unique! Stick w/ this thread today to learn @ peat, carbon, what is challenging its resilience, & why peatlands are a global treasure. eos.org/articles/resil…
@AGUbiogeo @AGU_Eos What IS a peatland? Seems simple- they are systems that have accumulated at least 40cm of peat. What's peat? It's dead biomass, mostly plant but also microbial & animal remains. So when enough dead stuff vertically accumulates, we call it a peatland. This is where simple ends....
@AGUbiogeo @AGU_Eos First, peat can accumulate for different reasons. Most scientific studies begin with this: "Peat accumulates where ever plant production exceeds decomposition". I have written this many times! But I now realize it's only partly true, & this is really important for resilience.
@AGUbiogeo @AGU_Eos Look at this gorgeous landscape at @BNZ_LTER in Alaska! More than 50% of this image is peatland, and here peat forms because of slow decomposition. In some places the soil is cold (permafrost). In others, it's wet and lack of oxygen slows down decomposers.
@AGUbiogeo @AGU_Eos @BNZ_LTER In the tropics, peat forms more because of fast plant biomass production. So controls on peat accumulation vary around the world. We think that ~80% of the world's peatlands are in the north, but new discoveries abound... …1jg5mt30vexk1-wpengine.netdna-ssl.com/wp-content/upl…
@AGUbiogeo @AGU_Eos @BNZ_LTER So many of us for decades studied plants, decomposition, & hydrology as controls on peat formation. We know that many Sphagnum mosses, which are common in northern peatlands, resist decomposition. And they hang onto water like sponges. Key to resilience!
@AGUbiogeo @AGU_Eos @BNZ_LTER But something that was ignored is the role of fire. Northern continental peatlands do burn but are resilient to moderate burning. i.e., Surface peat can burn but the ecosystems recover over time. Sphagnum hummocks often don't burn at all. I think these look like sheep! Baaa
@AGUbiogeo @AGU_Eos @BNZ_LTER I hope there is a grad student who needs to hear this today. Half-way through my PhD, I returned to harvest data from a big decay experiment and guess what? The entire site had burned and was bulldozed in a fire break. I was a wreak. #phdchat #phdlife
@AGUbiogeo @AGU_Eos @BNZ_LTER I needed help to recover, but wound up incorporating fire into my research. I learned about myself. I learned about ecosystem resilience & my own personal resilience. Not easy, but it was valuable. Sometimes we need setbacks to open our eyes to discovery. #phdchat #phdlife
@AGUbiogeo @AGU_Eos @BNZ_LTER Today I ask a fundamentally different question. Not only - why does peat accumulate in peatlands? But also, why does peat NOT accumulate long-term elsewhere? In the boreal, peat accumulates almost EVERYWHERE. Repeat, EVERYWHERE! It just burns away in some systems and not others.
@AGUbiogeo @AGU_Eos @BNZ_LTER Pristine tropical peatlands are resistant to fire. That means that fire is typically excluded. Climate change and human drainage are reducing the resilience of northern peatlands & we all know what is happening with tropical peatlands and land use. ecowatch.com/indonesia-fire…
@AGUbiogeo @AGU_Eos @BNZ_LTER To recap, factors that keep peat cold (permafrost) & wet (moss, hydrology) are important for northern peat resilience. These are related! Factors that maintain healthy plant community & keep peat wet (& not burning) are important for tropical peat resilience. But why do we care?
@AGUbiogeo @AGU_Eos @BNZ_LTER Let's think about biodiversity. If you hear the boreal is species poor, this likely is ignoring the diversity of peatland moss species. Image from Weston et al. 2014 Plant Cell & Env. The world has a vascular plant-bias but some of us want to change that! Who's with me?
@AGUbiogeo @AGU_Eos @BNZ_LTER You might know that there are 2 main types of peatlands: bogs/fens. Bogs receive water/nutrients mostly from precip; fens are more hydrologically connected. We can classify fens into rich vs poor fens. Rich fens are nutrient rich but this was originally based on plant diversity!
@AGUbiogeo @AGU_Eos @BNZ_LTER Rich fens are "rich" in botanical indicators, have high biodiversity, are rich in nutrients, & are actually quite abundant on the landscape. Most peatland scientists prefer to study simpler Sphagnum-dominated bogs & poor fens, so we know little @ rich fen resilience.
@AGUbiogeo @AGU_Eos @BNZ_LTER Peat is ~50% carbon, so all peatlands are hanging onto a lot of old C - C that used to be in the atmosphere but was taken up by plants & later locked away into wet or cold peat. Because of peatlands, the boreal biome stores at least 30% of the global soil C pool.
@AGUbiogeo @AGU_Eos @BNZ_LTER When we think about the fate of peatlands & peat C, we often think about drying. I think about this a lotl! But what happens when peat gets too wet? Here's the APEX site, which we've been studying for 20yrs. All hell is breaking loose w/ hydrology. It's a fen, it's a lake, eeks!!
I have gone on a tweet 🔥 storm in the past about how we are observing a borealization of the Arctic fire regime. In the northern boreal, changes in the #cryosphere are causing fenification of the landscape. And it’s complicating things a lot!
Peat is a legacy of the past, & legacies always play a role in resilience. I agree w/ the @AGU_Eos article that peatlands are resilient but the ability to cope has limits. I also caution that what little we know focuses on only certain types of peatlands & change. The end. Merci!
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