ecolonaught

Chronicles of a 21st century naturalist.


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brewing up good science

One of the great things about being co-supervised by people at Landcare Research is that I get to engage to top notch scientists, ask them about their research, and sometimes help them in the field!

From May 8th – 10th I was able to lend a hand to Barbara Anderson and her Master’s student Rob with their field work at Mt. Cardrona.

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The view from Mt Cardrona Summit. Fiordlands are seen snowcapped in the distance.

Rob’s research is on soil decomposition. When large organisms like trees and other plants die their organic matter become incorporated in to the soil. In areas with lots of vegetation the plant debris and litter that covers the ground is called the “O Horizon”. After awhile the plant material becomes partly decomposed and mixed with the next layer down, forming a nutrient rich environment called the “A layer”. It is here that most microbes reside and respire.

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Dead plant material gathering on the soil surface, forcing the litter layer. As particles decrease in size they are incorporated into the soil, forming the A horizon.

Understanding the metabolic action of these microbes is important because they are vital to nutrient cycles. They decompose previously living tissue and extract bound carbon, nitrogen, and other nutrients to be released into the environment once again so that other organisms may reuse these resources to grow.

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The snowy summit of Cardrona. Field work isn’t all fun and games!

Global soils store 3-4 times the amount of carbon than what is stored in global plant biomass. Therefore, understanding what, and how, factors influence soil nutrient cycling is paramount, especially in light of climate change. Two factors that are likely to have a major influence over soil microbial activity are temperature and humidity.

To elucidate the influence of these factors, Rob will be using the tea index across elevation and aspect gradients. The sites are positioned every 100m from the summit (~2000m) to the paddock (500m) spanning a ridge that has a sunny side and a shaded side. This range of elevation and ridge aspect encompasses a range of environmental conditions constrain microbial activity.

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Rob exhuming the first tea bag from the summit.

But how can we measure the metabolism of microscopic organisms on the top of a mountain? Cue the tea bag index. Microbes digest dead plant material. The rate at which they digest can be estimated by measuring the rate of weight loss in the dead plant material they eat. If we were able to develop a  unit of recoverable plant mass that could sit in ground for long times and have standardized weights, we could use these units to estimate soil decomposition rates across locations. This is what the tea bag index does.

Two flavors of tea are used – green and rooibos. Green tea is made of young leaves and roobios has mature leaves that are more lignified. The two break down at different rates, which allows Rob to estimate both the steep and shallow slope of the mass exponential decay function.

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Science is exciting!

By burying mass produced tea bags in the ground at different locations we can gain information about the factors that influence decomposition rates by comparing weight losses. There’s nothing better than science with a strong cup of tea! I’ll be following up this post with results when they are in.

 

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Takahe Valley

My most recent field expedition was to Takahe Valley; a place with an interesting conservation narrative, beautiful scenery, and a fantastic place to do research.

I went to Takahe Valley March 7th – March 10th with along with two Landcare colleagues and another PhD student. Our purpose was to assist with end of the summer field data collection.

The  crew grabbing lunch.

The crew grabbing lunch.

Those of you well versed in your New Zealand native birds will recognize the name takahe (Porphyrio hochstetteri). The species was thought extinct when the last 4 known individuals were captured and killed in 1898. However, Geoffrey Orbell rediscovered a remnant population of the birds in a place isolated from human activities near Lake Te Anu (Takahe Valley) in 1948. Concerted conservation efforts since rediscovery have resulted in relatively successful recovery. The Fiordland National Park was created to ensure them a safe home, and deer control is carried out within the park to reduce competition for food. The wild population estimate as of 2013 is 263.

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A takahe in captivity. Phtoto by New Zealand Department of Conservation (http://blog.doc.govt.nz/2014/12/01/takahe-finds-love-te-anau/)

I wasn’t able to see any of these beautiful birds (locally “blue chickens”), but I was able to see signs of their presence including well traveled tracks, digestive remains, freshly munched tussock grass, and tracks. Hopefully next time I will be able to sneak a peak!

I was able to see some other charismatic birds though including a Kea (Nestor notabilis), NZ rock wren (Xenicus gilviventris), rifleman (Acanthisitta chloris), and tomtit (Petroica macrocephala).

A Kea investigating our campsite, as well as me, to see if it can get an easy feed.

A Kea investigating our campsite, as well as me, to see if it can get an free feed.

The Fiordland foothills are composed of gneiss (metamorphosed from mostly granite and diorite). Apparently this is some of the oldest rock in NZ, originating from the Ordovocian period. The valleys and basins were etched through glacial erosion during the last ice age. Alpine areas have exposed rock or scree substrate, while basins soil is composed of podzolised gley and organic soils. The vegetation in our valley ranged from sub-alpine herbs up on the exposed rock and scree at the valley ridges to wetland species down in the basin. Beech forests and tussock grasses can be seen covering and deferentially partitioning large swaths of the valley.

The basin has a river flowing through it. This area is dominated by wetland vegetation.

The basin has a river flowing through it. This area is dominated by wetland vegetation.

Tussock grass vegetation dominates portions of the basin, as well as some portions of the lower and upper walls, of the valley. Forest dominates most of the midsection.

Tussock grass vegetation dominates portions of the basin, as well as some portions of the lower and upper walls, of the valley. Forest dominates most of the midsection.

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We camped partially up the valley, at the head wall. This area has some tussocks but also some sub-alpine herbs due to the higher elevation and some wetland plants from the the head water flow.

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The head wall ridge. This area has exposed rock and screes, mostly dominated by sub-alpine plants with some small tussocks.

The main purpose of our trip was research. There are transects of tussock grasses here that have been measured for over a decade, investigation the masting events of the tussocks (Chionochloa sp.). Masting is the phenomena of some plants to usually not produce many flowers/seeds most years, but every few years they will all create massive amounts of flowers/seeds. In North America most oak trees (Quercus sp.) display some level of masting.

A feather’s fate; only to drift on the low breeze; never to fly again

Another component of the research is to investigate the interacting influences of anticipated climate change, increasing soil N, and increasing soil C on tussock growth as well as reproduction. Climate change is simulated by putting translucent plastic around the bases of the tussock (creating a mini green house gas effect). Soil N is increased by adding fertilizer. Soil C is increased by sprinkling sugar on the plots. We had to count the number of tillers (stems) on every experimental plant (counts ranged from ~30 to ~800). The cages are to protect the tussocks from takahe, as this is their favorite food.

These are the experimental plots on the red tussock (C. rubra).

These are the experimental plots on the red tussock (C. rubra).

We also collected invertebrate data for each plot to see if the treatments (temperature * N * C) had an influence on invertebrate diversity or community composition.

Me emptying invertebrates from pitfall traps. These traps passively capture insects by trapping them in a cup filled with death liquid.

It was a fantastic trip filled with good company, good weather and goo food. I eagerly await my next expedition into Takahe Valley!

-Greg


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Recent developments

It has been way too long since my last post. My three new priorities for the year were (1) kick butt in my program (2) get more exercise & (3) write more blog posts. I’ve made some good progress on the first two, so now I’m on to the third.

A quick synopsis of my life since the last post:

– returned to the US for Christmas and New Year; enjoyed the company of my amazing friends and family

My sister in a stand of oaks, surrounded by native prairie.

My sister in a stand of oaks, surrounded by Wisconsin native prairie.

– visited my partner in NYC

JP

Tyrannosaurus rex skeleton at the American Museum of Natural History.

– attended a statistics course in Halifax

– returned to NZ, began seriously getting into research mode

– I was a teaching assistant for an undergraduate ecology field course in the Catlins

Me standing at the rocky shore edge of Curio Bay, in the Catlins.

Me standing at the rocky shore edge of Curio Bay, in the Catlins.

– assisted with some field work investigating the effects of land use and native vegetation herbivory

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Me checking to see if native seeds and seedlings survived mice and rat herbivory.

– assisted with field work investigating the effects of climate change on tussock ecosystems in fiordland

My colleges field research site, Takahe Valley in the fiordlands.

My colleague’s field research site, Takahe Valley in the fiordlands.

That gets you caught up on pretty much everything! More pictures and in depth analysis to come.

-GTN


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NZ Ecology Society Conference

My birthday was last week, and I had a great time! Although I don’t really have any insightful statements, I do have a lot of ecology to talk about. I celebrated by attending this year’s Ecology Conference at Massey University in Palmerston North. I was able to learn a great deal about New Zealand ecology by sitting in on some great talks as well as speaking with some inspiring scientists. I will be summarizing the highlights here.

I’ve always been fascinated by the trade-offs between sexual and asexual reproduction. Sexuality reaps the benefit of genetic diversity, but is a density dependent interaction (you need to be able to find a mate).  Being able to do a direct comparison is difficult because species usually can’t do both – but some do! Like the NZ snail. It reproduces sexually in a diploid state, but is able to switch to diploid (3 or 4 sets of chromosomes) as subsequently reproduces asexually. Laboratory experiments demonstrated the the asexual snails outperform sexual snails in every fitness metric (growth rate, strength, reproduction time, and reproductive output), but are only found in watersheds that are high in nutrients. This suggests that polyploidy is a competitive advantage if there are enough resources for extra sets of chromosomes but is unable to persist in low nutrient conditions, driving asexual populations locally extinct. Mechanisms related to how this with is made remain, but it is certainly a line of research worth continuing.

One research lab investigated the flammability of different types of plants by putting them in a grill! (with standardized procedures)

Through analysis of a wealth of extraordinarily preserved fossils and amber specimens it has been shown that although New Zealand’s contemporary insect communities are quite disparate, in the past a wealth of invertebrate diversity existed on the islands. These specimens date to before the last ice age, and so it is likely that changing climates and range reductions drove many of them extinct.

In an amazing demonstration of stabilizing selection pressure, it was demonstrated that a serious NZ invasive weed, gorse, has evolved larger seeds outside of its home range. In Europe it is paracitized by a beetle larvae, which feasts upon its seeds when young. It prefers larger seeds because they contain more food, thus when the beetle is present it exerts a pressure for smaller seed size. When the beetle is removed from the equation when gorse is transported to new territory that pressure is removed, seed sizes become larger over a few generations as larger seeds mean greater survivability in general. Neat!

I can’t wait to be presenting my own exciting findings next year!

 


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Pine Tree Massacre

Hello! It has been awhile but I have had some exciting developments, and will highlight them here for you.

First off, I will be spending the next week and the NZ Ecological Society Conference in Palmerston North. There are many exciting talks on the schedule and I hope to be inspired to develop some new research ideas. I will outline my thoughts in my next post. I also have begun preparations for my first experiment! Once I get this set up I will provide an overview as well as some pictures.

This past weekend I went on a trip to Mid Dome, Southland on a wilding tree control exercise with the Wilding Tree Trust. Two species of pine tree (Pinus mugo & Pinus contorta) were introduced as erosion control species and have subsequently become aggressive invasive, domineering native grasslands and forests. In order to preserve native diversity the spread of these trees must be stopped. Their source population is relatively remote, so we had to fly in by helicopter! 10-11 IX10-11VIII

I, along with a number of conservation minded kiwis, set out to control their spread by uprooting and felling small trees. Sir Alan Mark, a famous NZ conservationist, joined us for the trip as he play an active role in managing the program.10-11 XIIIDSCN7722

 

 

 

 

 

 

 

 

Over the course of two days I personally killed over 100 trees. The combined efforts of the group proved formidable, as we completely cleared the faces of two foothills.

 

All in all, it was a great trip full of interesting people and amazing views. It felt great to contribute to my new natural surroundings and lend a hand in preserving what makes New Zealand such an amazing place. I plan on going future trips so hopefully more success stories will follow!10-11 X