Thursday, 26 June 2014

The Hauxley time machine pond comparison website

The experimental ponds at Hauxley were dug in the autumn of 1994, to monitor the development of the animal communities from the very origins of the habitats. I had imagined this might go on for a few years but not twenty, but the value of the ponds as a study site increases with every passing year. The photo shows one of the original ponds at the front and, just behind, one of the new pools dug out by postgraduate Scott to explore the links between productivity, water chemistry and carbon accumulation in the sediments. In 1994 the old pond looked just as bare and abrupt as its new neighbour, the exposed clay base glistening in the June sunshine, stamped with heron footprints and jackdaw beak stabs. The old pond is now substantially infilled with debris and this is overlain with a sward of moss. Sticking up through are the stems of curl dock, Rumex crispus, their leaf edges conspicuously waved as if the growing leaves had expanded to some precise oscillation. These docks are common place but do not establish in properly submerged habitats. Here they are evidence of the increasing terrestrialisation of the old ponds. The new ponds have rapidly acquired the same pioneer animals that have now largely vanished from the old sites. In particular swarms of waterfleas, Daphnia obtusa, have appeared. The raw, new ponds seem to hold as many species as their twenty year old neighbours. It looks like the new ponds will follow the same trajectory of colonisations and extinctions as the older ponds.

The pond field is looking very beautiful. This year the greens are especially verdant, and the flowers radiate red, yellow and pink against this perfect backcloth. The clouds of pink are ragged robin, Lychnis flos-cuculi, their flowers seeming to hang in the air as if the slightest breeze can keep their confetti shape aloft.

Tuesday, 17 June 2014

The giant fly attack time of year

Summer now has the wetlands and dunes in its thrall. The warm, wet spring seems to have nurtured the richest greens and every flower is all the more intense against a backcloth of verdant meadow or hedge. At Hauxley yellow buttercups, Barbie doll pink ragged robin and purple spikes of orchids rocketing out of the fields compete to be the most garish. By mid June in some years the land already looks parched, the greens half hearted, but not this year. It is also an in-between time, with many birds having got their nestlings away and the occasional flourish of song suggesting a second brood might be on their minds. At Cresswell Lagoon young little gulls and sandwich terns are already hanging around waiting for something exciting to happen, or, at very least a fish to be brought back by parents who now look smaller than their indolent brood. For me high summer only begins when the meadow brown butterflies appear. Other insects are skipping, hopping, pinging and whirring from every footstep. Get down into the grasses and herbs and the sheer effervescence of life is shocking. as are flies as big as the one above, homing in on me. Nervous readers rest assured, it is not huge, high in the sky coming in from behind the tree, but somewhat smaller and probably disturbed as I crept up on a damselfly, whose turquoise body you can see out of focus bottom right. The marauder turned out to be an Empid (or Dance) fly, which often come with a conspicuous, rigid proboscis on which to skewer smaller brethren and suck them dry. They have perky, upright stance and are often furry too; if it was not for the vicious looking mouthparts they might pass as cute. During this same foray I saw an empid knock down a much larger cranefly and try to find purchase to spear its quarry, although its would be victim managed to buzz free and clamber up a stalk to re-launch itself. Judging by those raised legs and direct approach I got off lightly.

Thursday, 12 June 2014

The chamber of earthly delights and a question of scale


Pete, Dave and Philip are unveiling the latest piece of field work kit. A fine example of the different scales at which people work: Pete seems to be taking a remote sensing view point, Dave bit more hands on, Philip going for the fine detail. The item they are revealing should allow us to work at the scale of whole ponds at Hauxley, the new arrival being a perspex chamber manufactured to fit over individual experimental ponds. This will allow Pete to monitor the gas exchanges from a whole pond, in addition to the more fine grained analyses with smaller floating chambers that we can position over small sections of distinct vegetation types. Initial data show that the individual ponds vary markedly, some ponds exhaling CO2 and methane, others acting as sinks for those same gases at the very same time. The chamber looked surprisingly large when it arrived, (it looked surprisingly large when Pete tried to get it in his car at the factory). It is designed to extend either side of the ponds and wedge down into the surrounding vegetation to create a strong seal. Eventually the lure of bubble wrap got the better of us.

Dave, who is no mean craftsman himself is inspecting the workmanship. The chamber is a hefty and stout piece. The next step is to try this out in the field. We will put the chamber over a pond, and connect it up to the portable gas analyser which samples the air inside the chamber and gives real time measures of the changing concentrations. One unexpected outcome of this approach is the very concrete feel for the ecosystem's processes that you get from watching the numbers tick up on a display screen. Suddenly those invisible gases seem very real, the squidgy ground beneath our feet very lively, as if we are standing on some giant creature, submerged in the swamp.