05/17/11

Sweet clover aids native species in a stressful environment

Sweet yellow clover (Melilotus officinalis)

Melilotus officinalis, a nitrogen-fixing legume, widely planted by livestock producers and bee keepers has been shown to form both positive and negative relationships with native plant species depending on the surrounding environmental conditions. A consistently strong and positive relationship exists between Melilotus cover and native species cover in a semi-arid habitat (Badlands sparse vegetation) while in a less ‘stressed’ mesic environment (western wheatgrass prairie) Melilotus competes weakly with native species.

These results are consistent with the predictions of the stress-gradient hypothesis (Bertness and Callaway, 1994). The mechanism through which positive relationships form in Badlands sparse vegetation is likely to be habitat amelioration, possibly nitrogen enrichment of soil or protection from dessication, wind or erosion. More studies will need to be done in order to confirm this.

This economically valuable plant also forms positive relationships with other non-native species in Badlands sparse vegetation posing a potential conservation dilemma. The authors suggest that management should focus on control of the non-native species positively affected by Melilotus.

References: Van Riper, L., & Larson, D. (2008). Role of invasive Melilotus officinalis in two native plant communities Plant Ecology, 200 (1), 129-139 DOI: 10.1007/s11258-008-9438-6
Bertness, M., & Callaway, R. (1994). Positive interactions in communities Trends in Ecology & Evolution, 9 (5), 191-193 DOI: 10.1016/0169-5347(94)90088-4

05/16/11

If we can’t turn the tide, should we not try to ride it?

we cannot turn back the tide

I command you to come no further! Waves, stop your rolling!

It has been my sentiment for a long time that non-native species get too much bad press. No one ever looks on the bright side. Large-scale environmental change is not avertible, we will have no choice but to embrace the change and find ways to work with it. Too frequently, it is forgotten that many non-native species are necessary additions, fulfilling requirements unable to be provided by native species thus they have proven to be incredibly beneficial the world over; socially, culturally and economically. Over 70% of the world’s food comes from 9 crops (Prescott-Allen et al, 1990) each cultivated far beyond its natural range while 85% of industrial forestry plantations are cultivated from 3 genera (Evans, 1992). The ecological cost of increasing natural resource consumption is the rapid degradation, fragmentation and loss of habitats; such widespread disturbance drives species towards extinction through a series of population losses over their entire range (Hobbs and Mooney, 1998). This is the principle cause of global biodiversity reduction; the problems caused by non-native species are symptomatic of an increasing human population, global lifestyles and economic decision making.

While there are justifiable reasons for favouring ‘natives’ or controlling ‘non-natives’, the terms themselves are arbitrary and inflexible. When considering the need to control a species, its native or non-native status is unimportant. The only criteria for control should be species potential for degrading an ecosystem in a particular place, at a particular time. This is the most pragmatic approach, such criteria allows continual reassessment of a situation and the flexibility to change priorities if needed, without needing to cut through the red tape surrounding alien/native status.

So I am more than a little joyful to see the publication of ‘The Potential Conservation Value of Non-Native Species’ in the June issue of Conservation Biology. The article examines the ways in which non-native species currently contribute to conservation objectives and speculates that non-native species might contribute to achieving conservation goals in the future because they may be more likely than native species to persist and provide ecosystem services in areas where climate and land use are changing rapidly and because they may evolve into new and endemic taxa. Hurray. I for one, would particularly welcome more research on the positive effects of non-native species.

References: Schlaepfer MA, Sax DF, & Olden JD (2011). The Potential Conservation Value of Non-Native Species. Conservation biology : the journal of the Society for Conservation Biology, 25 (3), 428-437 PMID: 21342267
Prescott-Allen, R., & Prescott-Allen, C. (1990). How Many Plants Feed the World? Conservation Biology, 4 (4), 365-374 DOI: 10.1111/j.1523-1739.1990.tb00310.x
Hobbs, R., & Mooney, H. (1998). Broadening the Extinction Debate: Population Deletions and Additions in California and Western Australia Conservation Biology, 12 (2), 271-283 DOI: 10.1046/j.1523-1739.1998.96233.x

05/3/11

Goodbye Tamarisk, hello Box elder

box elder ousts tamarisk

Box elder (Acer negundo): I am in your riparian environment taking back the resources.

Now this is what I am talking about – biological control using native species. The insidious Box elder sneaks in under the Tamarisk radar, just like a ninja (if ninjas dressed like little green seedlings) and ousts the enemy from the home territory. Goodbye Tamarisk, hello Box elder (a.k.a. Control Agent Bottom-Up).

In a nutshell: Tamarisk appears to facilitate the establishment of Box elder through the provision of shade. This ameliorates environmental conditions (reducing air temperature and evapotranspiration in the sub-canopy) and allows the Box elder seedling to get a grip on the ground and its resources. On maturation, the competitively superior Box older ousts the Tamarisk.

I have one question (apart from is it really feasible or desirable) – how will the birds react?

References: DeWine, J., & Cooper, D. (2009). Habitat Overlap and Facilitation in Tamarisk and Box Elder Stands: Implications for Tamarisk Control Using Native Plants. Restoration Ecology, 18 (3), 349-358 DOI: 10.1111/j.1526-100X.2008.00494.x |Personal Ref: NF 0019|
Sogge, M., Sferra, S., & Paxton, E. (2008). Tamarix as Habitat for Birds: Implications for Riparian Restoration in the Southwestern United States. Restoration Ecology, 16 (1), 146-154 DOI: 10.1111/j.1526-100X.2008.00357.x |Personal Ref: NF 0019 (1)|

10/20/10

At the starting line…

Ischnura elegans - Blue-tailed Damselfly

Ischnura elegans Blue-tailed Damselfly

I rescued this little beauty from a spider web at Gibraltar Point National Nature Reserve in Lincolnshire (it has still got a strand of spider web attached) (yes, yes, I know I’m meant to stand by and watch). Unfortunately, my rescue attempt failed, its wings were too damaged to fly and shortly after release it dive-bombed into the nearby pond. I can only hope death by water was better than struggling for existence in a sticky net. C’est mort.

Finally started M.Phil, will transfer to Ph.D after a year if things go well. Currently wading through tons of papers and growing steadily confused. Funny how you think you have a handle on things until you start to dig deep. Present subject of interest is ‘positive interactions between species’. Biggest cause of confusion right now is the interchangability of the term ‘facilitation’ with ‘positive interaction’. Are they the same thing? Some papers talk as if facilitations are a blanket term for positive interactions while others define facilitation as a type of positive interaction. It has me banging my head against the wall.

09/14/10

Behaviourally-mediated facilitation by an invasive species

Arctosa fulvolineata

Wolf spider (Arctosa fulvolineata)

A spider best known for its resurrection capers gets a little help from an invasive plant.

I got really excited when I first saw the title of this paper. Firstly, I just really like the enunciation of the word inundation and secondly, salt marshes are a very stimulating environment and with wolf spiders to boot – who could resist? It turned out to be not as exciting as I hoped, the invasive species in question was but a simple native. I’d have preferred a non-native involvement but you know, you take what you can find and I think the underlying message is the same – where there is habitat modification there are winners and there are losers.

References: Pétillon, J., Lambeets, K., Montaigne, W., Maelfait, J., & Bonte, D. (2010). Habitat structure modified by an invasive grass enhances inundation withstanding in a salt-marsh wolf spider. Biological Invasions, 12 (9), 3219-3226 DOI: 10.1007/s10530-010-9714-y |Personal Ref: |