01 November 2009

2009-11-01: Litterfall quadrats


My main task for the day was starting the litterfall quadrats at Nkula Field. I want to know how much leaf litter the Tephrosia have dropped, and to estimate this, I am marking small squares (quadrats) within each plot and collecting all the leaf litter therein. It's not a difficult job but it is time-consuming; in four hours' work I finished two of sixteen plots. Since today is a weekend just after payday, there were many drunk men about, and I got a marriage proposal which I rejected. I spent a quiet evening at home doing laundry and cleaning up after an energetic puppy.

Main text:

It's November! By the end of this month, the rainy season will begin. Because of this, I am now making two changes in my day-to-day life:
1. carrying my umbrella;
2. writing shorter blog entries.

Things are going to get pretty busy pretty soon, so, dear readers, you will have to accept somewhat less loquacity on my part.

* * * * *

I had an interesting and novel task awaiting me today: litterfall quadrats. Soon we are going to cut down half of the Tephrosia in the seedling establishment experiment (to determine their biomass and to make room for new seedlings), but before we do this, I want to measure the amount of leaf litter they have dropped. Litterfall seems to be a substantial fraction of the seedlings' living above-ground biomass, and I am afraid that only measuring the living biomass would underestimate their productivity by quite a lot.

It isn't practical to collect all the leaf litter in every plot, so Festus suggested I sample from small sub-plots (quadrats) to make the job more manageable. Thus, I set out for Makoka armed with a tape measure, a bag of sample envelopes, a plastic tub for holding the leaves, and a measure of courage (just kidding - dead leaves are not very formidable opponents).

I got a bit of a late start because I slept in until nine, but I've had enough of these late starts. I keep saying to myself: It's November! There is no time to waste!

* * * * *

Today is Sunday, and it's the beginning of a new month, which means people have just been paid. Therefore, much drunkenness can be observed amongst the populace. When I got a minibus at Total Filling Station, the conductor was drinking a beer and tried to make conversation with me. I restricted my conversation topics to my desired destination on the minibus: "Makoka."

Minibuses are rarely comfortable, but this one was was especially jam-packed and death-defying. We were going over 120 km per hour most of the time - and this on narrow, potholed roads in a rickety vehicle filled to twice capacity. We overtook other vehicles with abandon, as though the right half of the road was a special lane just for us. Had I been the type to pray, I would have prayed to reach Makoka alive.

When I disembarked at Makoka, I said "Zikomo" rather coldly and wanted to add "Thanks for not killing me," but kept quiet. The conductor, who had since finished his beer and thrown the empty bottle out the window, said:

"I want to marry you. I'm a bachelor."

"No thank you," I replied, already walking away.

"I'm a bachelor, I say. Come on. I want to get married."

"Iyayi." (An emphatic no.)

"Come on. I want to marry white girl, have white children."

"Khalani chete!" (Be quiet!)

"Yeah, I want to marry white girl. I want to marry you and have lots of white children."


He continued shouting propositions at me, and I decided just to keep walking and not say anything more. Eventually he turned to the task of helping a boarding passenger load two dozen chickens with their legs tied together.

I was fuming as I walked away. I've had plenty of marriage proposals before, but none that obnoxious. It occurred to me, too late, that I would have been justified in throwing a dirt clod at him. It's probably just as well that I didn't think of it. I probably should have laughed at him.

* * * * *

I'd just missed a phone call from Mr Tambala, and called him back to say I'd be at MZ12 in a few minutes and we could talk in person. Cell phone airtime is so expensive here, long conversations are to be avoided. As it happened, it was nothing important - he just wanted to tell me that the night watchman wanted to swap with him, but he didn't want to swap, which I said was fine.

Since I was embarking from the far end of MZ12, I took a shortcut to Nkula that I haven't taken before, through the football pitch and next to a patch of forest. I heard some peculiar birds calling from the forest - they sounded like babies sobbing or laughing, I couldn't tell which. Perhaps they were... babblers? I got a pretty good look at one - it was s medium-sized grey bird with darker shades around its head and tail. I'd look it up when I got home.

I followed some small paths that paralleled the main road; although I'd never taken this route before, the landscape was open and I could easily see where I was. I walked through fallowed fields, many of which had been recently burned, and accumulated charcoal streaks on my skirt. Shortly before reaching Nkula, I saw a clump of very tall grass with stiff, straight stems. Perfect for making the edges of a quadrat! I cut four of the stems with my panga.

What is a quadrat, anyway? Don't I mean "quadrant?" Nope...
quadrat, n.
a square area of convenient size laid off for close study of the relative abundance of species or of other questions.

It was a cloudy day, pleasant for working in the field. I greeted the watchman and retrieved the basin and other materials that I'd left with him on Friday. Then I went to the first Tephrosia plot and tried to figure out where to start. (A slim bird the size of a robin - some kind of pipit(Anthus sp.), I think - flew ahead of me, perching on several rain shelters in succession.)

OK, now I had to make several decisions:
  • What size should the quadrat be?

  • How many quadrats should I sample in each plot?

  • Where should I place the quadrats?

For the first question, I found a good solution: I'd use four Tephrosia trees for the four corners of each quadrat (they are planted in a grid pattern). Thus, each quadrat would represent one tree's worth of litter, averaged over four trees. Because the planting distances weren't perfect, each quadrat wouldn't be exactly the same size, but it was probably more important to estimate litterfall per tree rather than per area.

I walked through several plots, looking to see how much variation there was in litterfall, and thus how many quadrats I'd need to sample for a good estimate. The litterfall was quite variable, so I decided to do two quadrats per plot. Now, the scope of my task was determined:

      2 quadrats per plot
      2 planting dates
      2 different Tephrosia systems
      2 rainfall treatments
    × 4 replicates
      64 quadrats to sample

I drew a plot diagram and numbered the quadrats (excluding the edges, which are always discarded):

Hey, this was kind of fun! It reminded me of that pencil-and-paper game I used to play with Cliff as a kid, in which you make a grid of dots and take turns drawing lines to connect pairs of adjacent dots. When you are the one to complete the fourth side of a square, you claim the square by writing your initials in it. The winner is whoever has claimed more squares when all the dots are connected.

It's always nice to have a job that reminds you of a game. I wondered if it would still feel like a game by the time I was finished with it.

Now I just had to decide which quadrats to sample. I decided to choose randomly, as long as the random quadrats weren't right next to each other. If they were, I'd choose again.

And how, you wonder, did I generate random numbers in the field? That's where having a digital watch comes in handy. Whenever I happened to think of doing so, I looked at my watch, and if the seconds displayed were between 1 and 48, I assigned that number (or that number divided by two) to be the next quadrat. Thus I gradually accumulated a list of quadrat numbers.

OK, it's not truly random, but good enough - I'm not aiming to publish this in Science, after all!

* * * * *

Now I was ready to start. I was pleased that my idea of using the trees as corner-posts worked quite well; since there are two trees per corner, I could actually insert the grass pieces in between the two trees, holding them firmly in place.

Here I am collecting the litter in my very first quadrat, in a Tephrosia improved fallow:

The first quadrat took me about ten minutes, which was even easier than I expected - but it turned out to be an especially easy one, with only a small amount of litter and not too many weeds mixed in. The second was more time-consuming. While I was working on that one, I got a welcome distraction: a phone call from Cliff. Unfortunately, his calling card soon ran out, and my calling card wasn't working, and I didn't even have credit to send him a text message. I had plenty of Tephrosia leaves, but that was about it.

Here are some photos of the next plot (an early-planted Tephrosia improved fallow), showing my technique. Here's the quadrat before I collect the litter...

...and after.

It took me about 25 minutes to do that, and the litter filled two A4 envelopes. "Why does it take so long?" you wonder. You'd think you could just grab the litter, put it in the basin, and stuff it in an envelope, but there are two complications:
  1. You must handle the litter carefully, lest it blow away or you drop it outside the quadrat. The pieces of litter are awkwardly different shapes; there are small leaflets, big leaflets, stems, and so on; if you grab big handfuls, you'll drop some.

  2. You must exclude leaf litter from other species; stems of weeds and grass; clumps of dirt; termite castings; and anything else that isn't of Tephrosia origin. This is what really consumes the most time.

The plot above is very tidy, but my next plot (a relay intercrop plot) was full of weeds and maize stover, and relatively few Tephrosia leaves. Those quadrats didn't even yield enough litter to fill an A5 envelope. Sorting the leaves from the weeds was picky business; I hope I get faster with practise.

Another complication: I realised that the amount of litter in the quadrat would be expected to depend upon whether all eight of the corner-post trees are alive, and how big they are; fortunately, I now (as of Friday) have that information for every tree!

In mid-afternoon, sleepiness caught up with me and I decided to take a nap under the Tephrosia improved fallow where I have slept before. The carpet of leaves was very comfortable (in fact, it was because of napping there that I first realised I needed to quantify litterfall: if there's enough of it to sleep on, it must be significant.)

The cloudy sky was pleasant, and there were many birds in the field today; I drifted off to sleep listening to them. When I awoke it was nearly an hour later. Lazybones! It's November - lots of work to do!

I completed a few more quadrats uneventfully. It's not a difficult task; it's just a little awkward to do something so precise at ground level. I tried crouching over the quadrat, sitting next to it and leaning over it, and then - eventually - just sitting inside it. Being comfortable was important, otherwise I wouldn't be able to do this all day tomorrow.

Around 4:30, Mr Tambala stopped by on his way home from MZ12. He asked me what I was doing, and I explained as best I could. (Mr Tambala's English is good enough, and he is bright enough, that he can understand pretty much everything I do in the field, as long as I explain it carefully.) He watched me for awhile. Mr Malalo, the Nkula night watchman (who had just arrived), joined and watched too.

I felt silly that the two men were watching me pick dead leaves from a patch of ground. "I know you are watchmen," I said, "but you don't need to watch. It's not that interesting!" They laughed and left me to my work.

* * * * *

At five o'clock I packed up my things; I didn't want to stay too late because it can be difficult to find a minibus on Sunday evenings. I had gotten through two of my sixteen plots, so that was substantial progress but I still had a long way to go.

Hey, finally - a praying mantis! I'd been waiting all day to take a photo of one, and wouldn't you know it, they were hiding today. Now that dusk was approaching, I saw a big tan praying mantis creeping along the edge of a Tephrosia plot. Here is the best photo I could get in the evening light:

I am very fond of these chiswambiya, and they always make me smile. So it was a nice way to end the day's work.

It wasn't so nice to be followed down the driveway by a drunk man on a bicycle who tried to speak Chichewa to me and ignored my protestations of "Sindikumvetsa" (I don't understand). He was probably a guest at the wedding that took place this afternoon at Makoka. Also wedding-related, no doubt, was the large crowd of people in the station yard. (The station is the cluster of buildings where machinery is kept and crops are processed.) Streamers were strung and music was blaring. Nobody was working today except for me!

My trip home was uneventful, except for some rowdy drunk guys shouting on the minibus. When I opened the front door, the puppy dashed inside. He seemed to be in high spirits tonight.

I said hi to my roommates and we talked for a while, then I showered and put some laundry in a bucket to soak, and ate dinner. When I went back into my room, I did a double-take: why was my laundry basket emptied onto the floor? Why were the contents of my rubbish bin strewn around my room?
Oh well, one can't blame a puppy for being a puppy.

* * * * *

For the rest of the evening, I finished washing my laundry, boiled my water for tomorrow, made some tea, slowly worked on my blog, and whiled away some time looking at photos. Tomorrow I will resume the litterfall quadrats where I left off. Eight down, sixty-four to go... I will be very well acquainted with Tephrosia leaves by the time this task is finished.

PS According to my bird book, I think the birds I saw in the forest this afternoon were arrow-marked babblers (Turdoides jardineii).

Chichewa word of the day: nkhwali = francolin


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