Global Change Ecology (BIO347)

Global change affecting trophic interactions between plants and other interactions

Climate change influences trophic interactions. Drivers of global change (e.g. increased CO2 or nitrogen levels or invasions) can alter competitive interactions between different trophic levels. These drivers can perform effects on intensity of pathogen infection, herbivory, predation or they can be helpful for new invasive species (1).

Truth is that global change drivers could have some positive impacts on nature f.e. risen CO₂ or N levels can have positive effects for plant growth (2) or nectar production (3), but negative effects are probably more frequent. Example of negative effect could be competition of pollinator between native and alien plant (4, 5) or shift in timing of plant activities (in their phenology; 6,7). In first case native plant could not be pollinated because pollinator will prefer alien plant and in second case specific pollinator and pollinated plant have “bad timing” because pollinator will not be present at the time when plant is flowering. For pollination mutualisms could be also destructive land use and habitat fragmentation which can easily affect plants through loss of pollinator diversity (8).

Alien plant species could also alter fungal and microbial communities in soil (9) which could have an effect on N and P deposition or they can just overgrow native species because of lack of natural predators.

Global change drivers could also favour some species, for example C4 plants could grow in higher temperatures (9) which can then be more competetively successful, and they can also affect plant-herbivory interactions for example when CO₂ levels are increased, herbivore activity often decline (11). Alien plants can also support herbivores which have then higher reproductive capacity and they can more readily attack native species (12). Invasions of plants into new localities could alter either belowground biota, but in longer term also another (native) plants, like Myrica faya in Hawaii where this plant caused more than fourfold increase of soil nitrogen input and subsequent increase of ecosystem productivity (13).

Examples mentioned above shows either positive but also negative impacts of global change drivers on trophic interactions. Plant abundance is affected by both belowground and aboveground trophic level interactions. These species interactions will alter during climate change, and this will result that some species became rare or even extinct and some will became more abundant.

 

 

1 Tylianakis, J. M., Didham, R. K., Bascompte, J., & Wardle, D. A. (2008). Global change and species interactions in terrestrial ecosystems. Ecology letters, 11(12), 1351-1363.

2 Muñoz, A., Celedon-Neghme, C., Cavieres, L.A. & Arroyo, M.T.K. (2005). Bottom-up effects of nutrient availability on flower production, pollinator visitation, and seed output in a high-Andean shrub. Oecologia, 143, 126–135.

3 Davis, M.A. (2003b). Biotic globalization: does competition from introduced species threaten biodiversity? Bioscience, 53, 481–489.

4 Lopezaraiza-Mikel, M., Hayes, R., Whalley, M. & Memmott, J. (2007). The impact of an alien plant on a native plant–pollinator network: an experimental approach. Ecol. Lett., 10, 539–550.

5 Aizen, M.A., Morales, C.L. & Morales, J.M. (2008). Invasive mutualists erode native pollination webs. PLoS Biol., 6, e31.

6 Memmott, J., Craze, P.G., Waser, N.M. & Price, M.V. (2007). Global warming and the disruption of plant–pollinator interactions. Ecol. Lett., 10, 710–717

7 Cleland, E. E., Chuine, I., Menzel, A., Mooney, H. A., & Schwartz, M. D. (2007). Shifting plant phenology in response to global change. Trends in ecology & evolution, 22(7), 357-365.

8 Chacoff, N.P. & Aizen, M.A. (2006). Edge effects on flower-visiting insects in grapefruit plantations bordering premontane subtropical forest. J. Appl. Ecol., 43, 18–27.

9 Mummey, D.L. & Rillig, M.C. (2006). The invasive plant species Centaurea maculosa alters arbuscular mycorrhizal fungal communities in the field. Plant Soil, 288, 81–90.

10 Pringle, A., Adams, R. I., Cross, H. B., & Bruns, T. D. (2009). The ectomycorrhizal fungus Amanita phalloides was introduced and is expanding its range on the west coast of North America. Molecular Ecology, 18(5), 817-833.

11 Bezemer, T.M. & Jones, T.H. (1998). Plant–insect herbivore interactions in elevated atmospheric CO₂: quantitative analyses and guild effects. Oikos, 82, 212–222.

12 Rand, T.A. & Louda, S.M. (2004). Exotic weed invasion increases the susceptibility of native plants to attack by a biocontrol herbivore.Ecology, 85, 1548–1554

13 P. M. Vitousek, L. R. Walker, Ecol. Monogr. 59, 24(1989).   M. J. Swift, O. W. Heal, J. M. Anderson, Decompositio

 

 

Tomáš Figura

Are European orchids threatened by anorganic nitrogen -one of the main drivers of global change?

fig.1 oligotrophic canopy of P.albida, in albania distr. Tropoje         

           

fig.2 oligotrophic canopy of P.albida with local sheppard in Albania, Tropoje, 2nd Photo by Jaroslav Vojta

 

A quarter of species of the second world biggest plant family – Orchidaceae is at risk of extinction. This could be caused due to smuggling, habitat loss and impact of climate change (1). Orchids have specific physiology, and many researchers have been studying them in last decades either due to their commercial production, their loss from nature or their specific biology. One of their specific trait is that they have minute seeds, almost without nutrients, and they germinate only under specific conditions. Many species are cultivated for commercial or research purposes but some species have never been germinated in conditions in vitro (or in situ), and we do not know why they are not growing. This was the case of Pseudorchis albida, which is and not just according to our study (2), extremely strongly inhibited by inorganic nitrogen. P.albida will not grow when there is even very low concentration of inorganic nitrogen in substrate (2 mg of No3 per liter of growing media).

In Europe, concentrations of anorganic nitrate in soil are between 0.1 – 100 mg/l NO3 (3, 4, 5), and globally N levels are rising. When we look at hygienic limit for concentration of nitrates in tap water in EU, it is 50 mg/l, and this concentration is sometimes reached, or even exceeded. The real data shows e.g. 37,6 and 19,2 mg per liter for Prague (6). But when we look into other sources (7) we can see that the concentration of nitrates in most European water sources is already above 100 mg/l. According to this we can conclude that this species will not grow when watered with tap water from almost all European water sources, because just concentration of 50 mg/l of nitrates inhibits germination 44 times and when sowed on concentration 100 mg/l this species is not growing at all ! (2)

This specific inhibition on seed germination and subsequent growth is not specific just for Pseudorchis albida, but we found similar extremely strong inhibition also on many other orchid species, which are evolutionary or ecologically common to Pseudorchis albida and also some effect on species Orthilia secunda, which belongs to Ericaceae family (yet unpublished data).

We can just speculate why those plants have this inhibition or where is the evolutionary purpose of this inhibitory effect; it could be some mechanism which is protecting the seed from germinating on places which are rich on inorganic nitrogen, and therefore place like this could be easily inhabited by expansive or/and ruderal species, and subsequently that place would not be suitable for growing of an orchid. However it is obvious that many orchid species are disappearing from nature and it looks like that some of them probably just due to the nitrogen – one of the main drivers of global change.

Important information which we should keep in our minds is that because of increased use of fertilizers, there is very steep increase of nitrogen levels in nature in last years (f.e. 8) and one of bad consequences of this could be potential loss of some orchids from nature. This can happen really quickly and even before we find out how to save those species at least using in vitro/in situ cultivation.

 

fig.3.: mycoheterotrophic protocorm of P. albida

 

1 Swarts, N.D., Dixon, K.W.: Terrestrial orchid conservation in the age of extinction. – Ann. Bot. 104: 543-556, 2009.

2 Ponert, J., Figura, T., Vosolsobe, S., Lipavska, H., Vohnik, M., & Jersakova, J. (2013). Asymbiotic germination of mature seeds and protocorm development of Pseudorchis albida (Orchidaceae) are inhibited by nitrates even at extremely low concentrations. Botany

3 Callesen, I., Raulund-Rasmussen, K., Gundersen, P., and Stryhn, H. 1999. Nitrate

concentrations in soil solutions below Danish forests. For. Ecol. Manage.

114(1): 71–82.

4 Fetter, J.C., Brown, R.N., Görres, J.H., Lee, C., and Amador, J.A. 2012. Nitrate and

phosphate leaching under turfgrass fertilized with a squid-based organic

fertilizer. Water Air Soil Pollut. 223(4)

5 Pedersen, A., Petersen, B.M., Eriksen, J., Hansen, S., and Jensen, L.S. 2007. A

model simulation analysis of soil nitrate concentrations — Does soil organic

matter pool structure or catch crop growth parameters matter most? Ecol.

Modell. 205(1-2)

6 http://www.pvk.cz/res/data/001/000205.pdf?seek=2

7 Commision of the europaean communities (2007):Comission staff working

dokument: Accompanying document to the Report to the commission to the council and the europaean parliament on implementation of Council Directive 91/676/EEC concerning the protection of waters against pollution caused by nitrates from agricultural sources for the period 2000-2003 COM (2007) 120 final

8 Tilman, D., Fargione, J., Wolff, B., D’Antonio, C., Dobson, A., Howarth, R., … & Swackhamer, D. (2001). Forecasting agriculturally driven global environmental change. Science, 292(5515), 281-284.

 

Tomáš Figura

All Strangers are not foes

Conservation writer Emma Marris points that many ecologists and conservationists are prejudiced towards non-native species and preoccupied with the ‘native good and non-native bad’ dogma [1]. ‘non-native bad’ notion has much been influenced by philosophical standpoint regarding ‘nature’ and ‘natural’ and also by some overwhelmimg facts associated with some non-native species which have invaded new areas. An anlysis by Davis wilclove shows that Invasive Alien Species (IAS) is the second largest threat to bidiversity in the United states [2]. Much popular ‘IUCN Red List of Threaned species’ also points that IAS is a major cause of species threat and extinctions particularly of birds, fishes and mammals [3]. Many birds and mammals in oceanic islands have already been wiped out by feral species introduced intentionally or accidently. Brown tree snake on Guam-which eradicated 15 native birds, or the Nile Pearch-which caused extinction of 200 fish epitomises non-native species for many. Ecologists are worried that complex and heterogenous ecosystems are turning towards simple and monotonous with increased non-native species.

Of course, introduced species which turned themselves into invasive are real environmental and economic burden and they deserve management intervention, however, considering all non-natives as negetive appers too simple generalization. Management of invasive species is much influenced by native versus non-native dichotomy as pinted by Mark Davis [4].

‘non-native’ species have been vilified for driving beloved ‘native’ species to extinction and generally polluting ‘natural’ environ­ments. Such characteri­zations have helped to create a pervasive bias against alien species that has been embraced by the public, conservationists….….. throughout the world.

It seems that ‘non-native species bad’ has been taken for granted by many policy makers and ecologists which creates bias towards non-natives. Here, I attempt to show that all non-natives are not bad rather they play role in conservation and restoration. And argue native non-native dichotomy largely overlooks social and ecolgical contribution of non-native species.

Ecologists have documented cases where introduced species have played substantial role to enhance biodiversity. Ascension island in the Atlantic-once considered as very poor by Darwin when he visited almsot 200 years ago- now is substantially richer in biodiversity compred to Darwin’s time. Now the area has been forested, species diversiy has manifolded-only one native tree has been accompained by 39 guest tree species [1]. Dov sax published a much counterintuitive result from a mata-anlysis ivolving all the oceanic islands aross the globe[5]. In the islands species brought by human have outnumbered the extinctin and the richness is higher than that would be in absence of introduction by humans. Ariel Lugo in Puerto Rico found that introduced tree plantation performed better in species diversity, biomass accumulaion and nutrient cycling than the native forests [6]. Similarly, a study comparing plant species richness between introduced and native pine forest in islands of western coast of norway reports higher richness in nn-native plantatins [7]. There are several instances where non-native species have supported and conserved native species by providing food and shelter, conserved rare species and substituted extant taxa [8].

But all biologists and ecologists can not enertain the ‘high biodiversity’ and restored ecosystems that contain non-native species. Instead of getting appreciation for their role in conserving other species and maintining diversity those species are getting an axe from environmental managers simply because they were originated somewhere else. Here ‘non-native bad/unnatural’ notion plays to rejection of diversity by nn-natives.

Contrary to ‘non-native bad’ generalization, there are several instances where non native species have played role in restoring the degraded ecosystems. US forest service scientist John Ewel opion that we can consider non-native species in restoration provided they do not pose serious threat to ecosystem health and provide social and ecological services [9]. Ariel Lugo based on his long term research at Puerto Rico concludes [6]:

The invasion of a site and the formation of an alien dominated forest serve important ecological functions, such as repairing soil structure and fertility, and restoring forest cover and biodiversity at degraded sites.

Pinus patula?, a native of mexican highlands brought to Nepal by Australian foresters has been successfully been used to restore degraded forest in hills of Nepal. This species made ground to regenerate native species. Now native broadleaved species are regenerating luxuriantly under the crown of non-native species.

Most of the extinction of native species particularly birds in ocenic islands is resulted from intertrophic interaction- by predation rather than competition. There are very rare instances of extincation in which introduced plant species is attributable culprit. Plant species do not predate but they may pose threat by altering habiat [10]. Therefore, categorically blaming non-native as cause of extincation is also biased.

Movement of species is pervasive and continous, we accept non-natives in fields, avenue plantations and cityscapes. It is likely that more species will move from one parts of world to other to meet aesthetic and economic needs. Eucalypts and mahogany for timber and cherries for urban beauty are accepted away from their origin. During remote past propagules of species might have transported far away from their historic ranges by storm, floods and birds. Species will move towards cooler places to respond global warming. Currently there are translocations of wildlife to save small population crashing. There are attempt even to introduce wildlife as proxy of extant species [1]. These continous flux of species questions the way non-natives are defined. Who knows, species capable of surviving in new environment may best fit in future climate and land use scenarios.

Spread of non-native species has became common phenomenon, definitely not an exception. Public, plicy makers and scientists should admit that environmenal threat has been posed by a small subset of non-native species. Judging species based on ‘what economic and ecological roles they play in new ecosystems’ may be more smart over judgement based on ‘where they originated’ [4, 11]. Native non-native dichotomy should be abandoned and and new classification of species based on their damage to ecosystem health and biodiversity may help manage non-native based on their ecological and economic roles.

References

1. Marris E. 2011. Rambunctious GardenWilcove DS. 1997. Bioscience:
2. Wilcove DS et al 1997. Bioscience 48(8):607-615
3. IUCN 2004 IUCN Red List of Threatened Species.
4. Davis MA et al.2011. Nature 474:153–154
5. Sax DF. 2004. The American Naturalist. 160(6): 766-783
6. Lugo AE 2004. Frnt Ecol Env. 2(5): 265–273
7. Vetaas OR et al 2013. ?:1-13.
8. Schlaepfer MA et al. 2011. Conservation Biology 25(3): 428-437
9. Ewel JJ, Putz FE. 2004. Front Ecol Environ 2(7): 354–360
10. Davis MA 2003. Bioscience 53(5): 481-489
11. Warren CR 2007. Progress in Human Geography 31(4): 427–446

Lila Nath Sharma