2010 ISI Impact Factors are now out

You can't ignore the fact that Impact Factors have had a huge effect on publishing trends and the choices authors make about where to publish. This is somewaht unfortunate - I now hear scientists talking in the corridors of universities, or worse, at conferences, about where they published their most recent paper, not what they are publishing on!

Regardless of how much weight you put on Impact Factors (see this damning review as evidence that some don't rate IFs at all), all new PhD students and Post-Docs have to play a game of publishing in (perceived) high impact journals if they are to get that next job.

So what are Impact Factors and how are they calculated?

In a given year, the impact factor of a journal is the average number of citations received per paper published in that journal during the two preceding years. For example, if a journal has an impact factor of 3 in 2009, then its papers published in 2007 and 2008 received 3 citations each on average. The 2009 impact factor of a journal would be calculated as follows:

A = the number of times articles published in 2007 and 2008 were cited by indexed journals during 2009

B = the total number of "citable items" published by that journal in 2007 and 2008. ("Citable items" are research papers; not editorials, book reviews or Letters-to-the-Editor)

2009 impact factor = A/B.

I've included the 2010 Impact Factors for journals in conservation and plant ecology (and compared their "performance" to their 2009 rating). The big winners were Ecology Letters, Trends in Ecology and Evolution and Frontiers in Ecology and the Environment. Interestingly, the IFs of most journals rose over the last year.

Applied Vegetation Science: 1.802 (2010) versus 1.349 (2009)
Austral Ecology: 1.820 versus 1.578
Australian Journal of Botany: 1.681 versus 1.868
Biodiversity and Conservation: 2.146 versus 2.066
Biological Conservation: 3.498 versus 3.167
Conservation Biology: 4.894 versus 4.666
Diversity and Distributions: 4.248 versus 4.224
Ecography: 4.417 versus 4.385
Ecological Applications: 4.276 versus 3.672
Ecology: 5.073 versus 4.411
Ecology Letters: 15.253 versus 10.318
Frontiers in Ecology and Environment: 8.820 versus 6.922
Functional Ecology: 4.645 versus 4.546
Global Change Biology: 6.346 versus 5.561
Global Ecology and Biogeography: 5.273 versus 5.913
Journal of Applied Ecology: 4.970 versus 4.197
Journal of Biogeography: 4.273 versus 4.087
Journal of Vegetation Science: 2.457 versus 2.376
Molecular Ecology: 6.457 versus 5.96
Nature: 36.101 versus 34.480
Oecologia: 3.517 versus 3.192
PNAS: 9.771 versus 9.432
Polar Biology: 1.445 versus 0.582
Science: 31.364 versus 29.747
Trends in Ecology and Evolution: 14.448 versus 11.564

Why ecologists should know a little about geomorphology

I like rocks almost as much as I like plants!! There, I've said it!

And I particularly like the processes that give rise to the landforms that we see - geomorphology. Being able to read a landscape - such as the rock types and the way that they affect topography and drainage, as well as their impact on base level nutrient availability - is one of the most important skills that a plant ecologist can acquire. Indeed, an understanding of geomorphology broadly helps explain the distribution of native vegetation types in southern Australia.

Native grasslands, for example, occur predominantly on plains of low elevation, both in northern and southern Victoria. One might logically think that there is a similar underlying reason for their distribution and the absence of trees. Nothing could be further from the truth! These land surfaces have very different geological and geomorphological histories that have shaped these systems in different ways.

In western Victoria, volcanoes (more than 350 of them) have spewed out lava over the last 20,000 yrs to 5 M yrs, producing the third largest larva plain in the world, exceeded only by the Deccan in western India, and the Snake River Plateau in the United States! The volcanic activity was probably similar to that now active in Hawaii, with the dominant volcanic product being fluid basalt lava with only a small component of pyroclastic material (mainly scoria). Lavas of this type can spread rapidly across the landscape, and in places extend over 50 km from the volcano.

Lava flows must have produced an initially barren surface that required extensive denudation (i.e. modification by weathering) to be a suitable plant habitat, with primary succession proceeding from species derived in the surrounding landscape - this possibly explains why the western plains flora consists of many generalist species, and few endemics have evolved in the relatively short timeframes since volcanism. The soils that developed in situ are fine-textured cracking clays and are very nutrient-rich (indeed they are amongst the most productive in Australia; it also probably explains why weed invasions are so pronounced here too). As a consequence, trees are restricted to stony rises and cinder cones where drainage is best and soil cracking least.


Mt Elephant, as seen from Dundonnell, is one of the larger of the volcanoes found
 on the western plains. It is an example of a steep-sided scoria volcano - true 'fire mountains'
when they erupted. They formed when magma interacted explosively with groundwater,
blasting molten rock high into the air. The ejected material cooled before it hit the ground,
forming fragments of frothy red or black rock called scoria. These fragments quickly
settled around the vent, building cones with deep central craters. (Photo: John Morgan)



The Volcanic Plains of western Victoria - this geological map is a

good approximation of the distribution of the native grasslands(source: http://home.iprimus.com.au/foo7/volcmap.html)

By contrast, the vast native grasslands of northern Victoria are the product of an entirely different land forming process. Here, the landscapes were formed by river flooding spreading coarse alluvium. The alluvial plains are built of sediment derived from the erodible sandstones, mudrocks and igneous rocks of the Victorian Highlands and spread by rivers down the mountain flanks. These sedimentary surfaces are quite unlike the volcanic surfaces of western Victoria and formed under a completely different geological regime. These sediments, deposited and redistributed by rivers and wind, buried the older bedrock surfaces and produced a complex landscape of low relief and gentle slope. Like the volcanic plain, it is a mosaic of materials, ages and forms. And like the volcanic plains, the soils are fine-textured clays that easily waterlog in winter, preventing the growth of trees.

Riverine plains grassland - formed by alluvial processes.
(Photo: Eris O'Brien)

Grasslands also occur up in the highlands on mountain summits, plateaus and high plains, but these are not generally not due to the underlying rocks. Rather, they occur where low temperature or cold air drainage - the so called 'frost hollows' - suppresses tree growth. See Wearne & Morgan for a description of these interesting grasslands in the Mt Hotham region. At the moment, that low temperature envelope is very narrow and occurs generally above 1600 m, but in colder Pleistocene times the tree line may have been as low as 1000 m.

 

So, I've provided a simple example of how land forming processes are responsible for the landscapes we see today. Unfortunately, there's no textbook that adequately introduces geomorphology of Victoria that I can recommend. Rather, you'll need to observe the landscape and ask: what are the rocks that underlay this area? when did this occur? how have aeolian and fluvial processes shaped the landform? Are there obvious associations of vegetation when the above change?

Experimenting with Fire

My PhD primarily revolved around the effects of fire frequency on regeneration dynamics and species coexistence in the endangered temperate grasslands of western Victoria. Here, fire plays an indirect role - frequent fire prevents competitive exclusion of the intertussock forbs from the dominant C4 tussock grasses. In this case, it was the frequency of fire, not the type of fire that seemed most important to the conservation of plant diversity.

In 2003, landscape-scale fires burnt the alpine
vegetation of Victoria. But it was clearly very patchy.
(Photo: John Morgan)

But fires can come in many guises - fires ain't fires - you only need to look at a wildfire to see that it can burn thoroughly or patchily. It's clear to me, however, that we don't understand very much about plant community responses to difference in fire "type". Rather, much of our knowledge (and research) is from the standpoint of the time-since-last fire and, perhaps, the fire frequency (and these assume that fires are much the same). Yet, it is the type of fire that might ultimately affect mortality of established plants, germination cues, and resource levels. Not to mention how much C is returned to the atmosphere.

To learn more about fire and how to measure it, I've just spent a week burning tropical savanna in the Northern Territory Wildlife Park with Dick Williams from CSIRO. This was excellent fun, but also highly informative. The Burning for Biodiversity experiment is an amazing field study examining the effect of fire frequency and timing on a variety of taxa and the dynamics of carbon. Importantly, it relates these outcomes to aspects of fire behaviour. So, what better way to learn about fires than to visit one of the few experiments in Australia that is quantifying fire!

A common measure of fire behaviour is fire intensity – the amount of energy released per unit length of fire front (kW m^-1). It is defined as the product of rate of spread (ROS), fuel load, and the heat released from the fuel during combustion. The higher the fuel load and the ROS, the higher the fire intensity.

Fuel loads are easy to calculate - the amount of fine (<6 mm diameter) fuel is sampled in quadrats pre-fire and weighed. It is the fine fuel that will rapidly combust (flamming combustion) and affect properties of the fire front. Larger diameter fuels burn more slowly (in a process called smouldering combustion), typically after the fire front has passed. These fuels are important to quantify, as they will release much more C into the atmosphere.




Harvesting fuels prior to ignition
(Photo: James Camac)

Savanna in the Northern Territory - awaiting burning
(Photo: John Morgan)



ROS is a little harder to quantify because it is much more dynamic, but plays a critical role on fire intensity. In Darwin, we used two techniques to estimate ROS from our contolled burns. First, we measured the time the fire front takes to reach pre-defined points in the landscape - using points marked with numbered poles (we used six) and a stopwatch, the average rate of spread of the fire between the points can be calculated. As a  backup to the estimates by eye (it can get quite hairy when the fire front is moving quickly), we also used specially designed automatic timers buried in the soil with a small thermocouple left exposed above-ground - these timers record the time at which the thermocouple heats to >200 deg C and, somewhat ingeniously, the residence time (the time that the temperature stayed above 200 deg C).



Lighting the fireline with a drip torch
(Photo: James Camac)

 


Timers, attached to thermocouples, are buried in the soil.

These record the time at which fire passes, and how long
flaming continues at the point. (Photo: James Camac)







Flamming combustion

(Photo: John Morgan)





Smouldering combustion
(Photo: John Morgan)



These are very simple measures that can address fundamental research questions - they should be in the toolbox of all fire ecologists because, if measured, they allow quantification of how fire intensity might affect biodiversity.

We certainly saw large differences in fire intensity in hectare-scale plots burnt on the same day! I look forward to coming back to Darwin in 2012 to observe just why these differences might matter. At this point, I'm not sure when, where, and why fire intensity affects biodiversity - there are simply too few examples in the literature to provide a coherent review. But I know that in future, I'll be quantifying fire intensity in my research (both within and across different fires) to get a better understanding of this primary aspect of fire behaviour.

Habitat loss.....the signature conservation problem of the 21st century

Extinction from habitat loss has been suggested to be the signature conservation problem of the twenty-first century. Indeed, the Millennium Ecosystem Assessment predicts that near-term extinction rates could be 1,000 to 10,000 times higher than background rates. This alarming statistic seems to have got lost in the current focus on climate change, important as that will likely prove to be.

Images from Google Earth highlight just how much
 woodland clearing has occurred 
in western Victoria for cropping and grazing

One key reason species will go locally extinct due to habitat loss is because fragmentation leads to small populations. A central tenet of conservation biology is that small population size makes them much more vulnerable to inbreeding, recruitment failure, and climate extremes.

In our Lab, we've been testing the idea that small populations are more vulnerable to local extinction than large populations. Despite the simplicity of the hypothesis, there is not a lot of good evidence around in the literature to support or reject this idea (at least for plants in Australian ecosystems).

To address this question, we've employed re-visitation studies. This involves using data on species abundance collected at some previous point in time from well-defined places (lets call this the historical dataset, time1), and revisiting the very same places some time later to determine whether species have persisted (lets call this the contemporary dataset, time2). If you have data on abundance at t1, you can start to understand whether the smallest populations at this time are less likely to be present at t2 (as theory would suggest).

We used data collected in 1975 by a superb amateur botanist called Cliff Beauglehole as our t1 for a number of remnant grasslands and grassy woodlands in western Victoria.

Scaly Buttons is one of the common species
in grasslands and woodlands that has declined
over the last three decades
(Photo: John Morgan)

 Beuglehole recorded species lists for these sites (many of which were very diverse at the time) and allocated an 'abundance' measure for each species at each site that approximates a log scale - a few dozen, up to 100, in the 100s, in the 1000s.

We re-visited these same sites (t2) and recorded all species we could find; importantly, we estimated their population size in the same way as Beuglehole. When comparing the data on abundance at t1 versus t2, remembering that small populations should be more vulnerable to local extinction, we found some very interesting results which we have reported in the Journal of Ecology.

As predicted, the liklihood of local extinction over a  31 yr period was highest (34%) for those species whose population was initially very small. But initially small populations did not always decline - indeed, a small number (9%) actually increased and became abundant (in the 100s) or even very abundant (in the 1000s).

Changes in population abundances of native plants species
from 1975 to 2006 in grassy woodlands in western Victoria
(From: Sutton & Morgan Journal of Ecology)

But the story doesn't end there. We uncovered something in our re-visitation study that we had not predicted, nor even expected.

Some of the plant populations that were initially considered abundant or very abundant in woodland remnants had become locally extinct. Hence, having a large population did not guarantee persistence over the three decade period between observations. There could be a number of reasons for this, but we think the main one relates to habitat quality.

Over the 30 yrs between surveys, it is very likely that the habitat has deteriorated for some species - edge effects, weed invasions (by exotic Iridaceae, a curse in grassy woodlands in western Victoria) and inappropriate disturbance regimes have probably all caused a decline in habitat. In particular, the lack of fire is probably a key driver of change. Fire-sensitive shrubs, as well as dominant tussock grasses, have increased at the expense of poor competitors in the groundlayer.

Our study hints that while there is a strong need to find simple, general rules in conservation ecology, these general rules need to be put to the test. Not all small populations are vulnerable to short-term extinction. Indeed, 'common' species deserve our attention as well, as others have suggested.

And it is the common species that drive ecosystem function and provide much of the habitat for fauna. Simple re-vistation studies like ours are an excellent way to monitor trends in remnant vegetation, provided that old datasets are archived in such a way that they can be re-used in the future.

Abundance at 'home' predicts abundance 'away'

One of the best things about teaming up with collaborators, either in your own university, across different institutions, or even across continents, is that it allows you to probe some of the big questions in ecology.

And one of the biggest (and most important) questions that many of us are trying to answer is: why do plants invade new systems? And which species do so? And what are the traits that underpin this?

Recently, I teamed up with a 36-strong global research team that took aim at the reasons for plant invasions in herbaceous ecosystems. Using data collected as part of the Nutnet Project, a research network looking at the importance of top-down and botton-up processes on grassland diversity, we tried to understand why some invaders are common in new habitats, while others are not. Predicting the success of invading species has always relied on the assumption that these plants are more abundant in their new settings than they are in their native communities because they behave in a special way.

Cirsium vulgare - one of the 26 species that
we had data on for the 'home' and 'away' range
(Photo: Royal Botanic Gardens Sydney)

We are not so sure this assumption is correct.

Indeed, we think we have found something pretty cool. Because our study was a global one, we were lucky enough to have data on plant abundance of 26 species in their 'home' range - this allowed us to see which species are common and rare in their natural habitats. For the same 26 species, we had data when they had invaded new habitats (usually grasslands on new continents), which we called the 'away' range.

We discovered two really important things: 1) increases in species abundance in the new range are, in fact, unusual. So, those species that were uncommon in their 'home' range were often uncommon in their 'away' range. 2) We saw quite strong evidence that species common at 'home' were also common 'away' - this might be a really useful way to predict future invader potential.

Hence, success of a plant in its native range can possibly be used to predict its spread at introduced sites – a criterion which currently is not included in biosecurity screening programs.

We've just published this work in Ecology Letters. Check it out.