It’s not about plants, not entirely. But it seems that, in one agricultural area, pollinators (bees) under stress have ceded their pollinating responsibility to a couple of species of exotic (read invasive) flies. See: J. R. Stavert, D. E. Pattemore, I. Bartomeus, A. C. Gaskett, J. R. Beggs, “Exotic flies maintain pollination services as native pollinators decline with agricultural expansion, Journal of Applied Ecology (British Ecological Society), 22 January 2018. The only thing surprising about that is that people consider it surprising.
Updated again below, `Plants of the future’, 2018-05-03
While my first thoughts and reasons for this post were simply to collect together a number of links pertaining to an interesting subject, regarding which there appeared to be some controversy, I have received several reactions to the material, many supportive and positive, others strongly adverse. This indicated to me that this is an area worth knowing more about, and, so, I have pulled quote a number of technical articles from the fields of Ecology, Forest Management, and Invasive Species Studies which I am currently reading. I intend to at least supplement the links below with additional ones explaining states of knowledge at present. I may include some comments summarizing what I have read. In other posts, in the future, I may do some modeling along these lines, since diffusion processes modeled by differential equations are of significant interest to me, whether for biological and physical systems, or diffusion of product innovations, via, for instance, the Bass diffusion model. Those results won’t be posted here, though.
Sustainable landscaping as described by Wikipedia, and by Harvard University. See also the Sustainable Sites Initiative. It’s a lot more than eradicating invasive species. In fact, that might be harmful. There’s a lot of questionable information out there, even by otherwise reputable sources like The Trustees of Reservations. There is evidence Roundup (glyphosate) is indeed effective against at least Alliaria petiolata, with little harm for common, commingled biocenostics.
(Above from M. Rejmánek, “What makes a species invasive?”, Ecology, September 1996, 3-13.)
Four inspirational books:
- M. Richardson, D. Jaffe, and the New England Wild Flower Society, Native Plants for New England Gardens, Globe Pequot, 2018.
- T. Dove, G. Woolridge, Essential Native Trees and Shrubs for the Eastern United States, Bunker Hill Studio Books LLC/Charlesbridge, 2018.
- J. D. Ivanko, L. Kivirist, Farmstead Chef, New Society Publishers, 2011.
- P. del Tredici, Wild Urban Plants of the Northeast, Comstock Publishing, 2010.
Perhaps the most well-known example of a “spontaneous” plant is Ailanthus altissima or tree-of-heaven, introduced from China. Widely planted in the Northeast in the first half of the nineteenth century, Ailanthus was later rejected by urban tree planters as uncouth and weedy. Despite concerted efforts at eradication, the tree managed to persist by sprouting from its roots and spread by scattering its wind-dispersed seeds …
Although it is ubiquitous in the urban landscape, Ailanthus is never counted in street tree inventories because no one planted it — and consequently its contribution to making the city a more livable place goes completely unrecognized. When the major of New York City promised in 2007 to plant a million trees to fight global warming, he failed to realize … that if the Ailanthus trees already growing throughout the city were counted he would be halfway toward his goal without doing anything. And that, of course, is the larger purpose of this book: to open people’s eyes to the ecological reality of our cities and appreciate it for what it is without passing judgment on it. Ailanthus is just as good at sequestering carbon and creating shade as our beloved native species or showy horticultural selections. Indeed, if one were to ask whether our cities would be better or worse without Ailanthus, the answer would clearly be the latter, given that the tree typically grows where few other plants can survive.
There is no denying the fact that many — if not most — of the plants covered in this book suffer from image problems associated with the label “weeds” — or, to use a more recent term, “invasive species.” From the plant’s perspective, invasiveness is just another word for successful reproduction — the ultimate goal of all organisms, including humans. From a utilitarian perspective, a weed is any plant that grows by itself in a place where people do not want it to grow. The term is a value judgment that humans apply to plants we do not like, not a biological characteristic. Calling a plant a weed gives us license to eradicate it. In a similar vein, calling a plant invasive allows us to blame it for ruining the environment when really it is humans who are actually to blame. From the biological perspective, weeds are plants that are adapted to disturbance in all its myriad forms, from bulldozers to acid rain. Their pervasiveness in the urban environment is simply a reflection of the continual disruption that characterizes this habitat. Weeds are the symptoms of environmental degradation, not its cause, and as such they are poised to become increasingly abundant within our lifetimes.
(Slight emphasis added by blog post author in a couple of places.)
The fact that ‘r-strategists’ are the best invaders is not surprising because the overwhelming majority of biological invasions take place in human- and/or naturally-disturbed habitats. Our modern landscape is mainly disturbed landscape.
(Above from M. Rejmánek, “What makes a species invasive?”, Ecology, September 1996, 3-13.)
- S. K. Biswas, F. Sciaraffia, “Productive conservation: Utilizing landscape ecology and precision agriculture towards land-water conservation”, 2015 recipient of the American Society of Landscape Architects Student Award.
- Harvard’s sustainability plan.
- Connecticut Department of Energy & Environmental Protection, “Sustainable practices and resources for the landscaping and lawn care industry”, 2018.
- Connecticut Department of Energy & Environmental Protection, “Stormwater and the city”, 2010.
- California Integrated Waste Management Board, “Sustainable landscaping”, 2005.
- I. Riano, “Just a bunch of weeds: An interview with [Professor] Peter del Tredici”, Scenario Journal, 2012.
- GreenCityBlueLake, The Cleveland Museum of Natural History, “Is there a safe alternative to Roundup?” Is Roundup safe? Hint, hint, safe for whom?
- G. L. PéRez, A. Torremorell, H. Mugni, P. RodríGuez, M. Solange Vera, M. Do Nascimento, L. Allende, J. Bustingorry, R. Escaray, M. Ferraro, I. Izaguirre, H. Pizarro, C. Bonetto, Donald P. Morris, H. Zagarese, “Effects of the herbicide Roundup on freshwater microbial communities: A mesocosm study”, Ecological Applications, 2007, 17(8), 2007, 2310-2322.
- R. A. Relyea, “The impact of insecticides and herbicides on the biodiversity and productivity of aquatic communities”, Ecological Applications, 2005, 15(2), 618-627.
- T. Orion, forward by D. Holmgren, Beyond the War on Invasive Species: A Permaculture Approach to Ecosystem Restoration, Chelsea Green Publishing, 2015.
- F. Pearce, The New Wild: Why Invasive Species Will Be Nature’s Salvation, Beacon Press, 2015.
- E. Zefferman, J. T. Stevens, G. K. Charles, M. Dunbar-Irwin, T. Emam, S. Fick, L. V. Morales, K. M. Wolf, D. J. N. Young, T. P. Young, “Plant communities in harsh sites are less invaded: a summary of observations and proposed explanations”, AoB PLANTS, 2015, 1-21.
- J. A. Catford, P. A. Vesk, D. M. Richardson, P. Pyšek, “Quantifying levels of biological invasion: towards the objective classiﬁcation of invaded and invasible ecosystems”, Global Change Biology, 2012, 18, 44-62.
- M. Rejmánek, D. M. Richardson, P. Pyšek, “Plant invasions and invasibility of plant communities”, in Vegetation Ecology, 2nd edition, 2013.
- E. W. Seabloom, J. W. Williams, D. Slayback, D. M. Stoms, J. H. Viers, A. P. Dobson, “Human impacts, plant invasion, and imperiled plant species in California”, Ecological Applications, 2006, 16(4), 1338-1350.
- J. D. Fridley, J. J. Stachowicz, S. Naeem, D. F. Sax, E. W. Seabloom, M. D. Smith, T. J. Stohlgren, D. Tilman, B. von Holle, “The invasion paradox: Reconciling pattern and process in species invasions”, Ecology, 2007, 88(1), 3-17.
Links with some quotes and discussion:
- S. L. Flory, K. Clay, “Invasive shrub distribution varies with distance to roads and stand age in eastern deciduous forests in Indiana, USA”, Plant Ecology, 2006, 184:131-141.
If roads are important corridors for exotic plants or if roadside edges provide good habitat for exotic plant growth, then one would predict decreased exotic plant density with increased distance to roads. In support, the prevalence and cover of exotic plants has been shown to decline with increasing distance to road in a number of ecosystems.
Independent of distance to road, successional age might determine susceptibility of a community to exotic plant invasions. Young forests typically have higher light levels (Levine and Feller 2004), fewer competitors, and less litter than older forests (Leuschner 2002) while mature forest interiors are known to have lower light availability, cooler temperatures, and higher humidity than forest edges (Brothers and Spingarn 1992). We would therefore expect, based on levels of light penetration and microclimatic conditions, that older forests would have higher densities of invasive shrubs near the forest edge than in forest interiors and fewer invasive shrubs overall due to less recent disturbance events and less favourable environmental conditions. We would also expect that younger forests would show weaker correlations of densities of invasive shrubs with increasing distance to road since light levels are higher throughout young forests. This would result in an interaction between distance to road and forest age.
The goal of this study was to quantify the density of invasive exotic shrubs along roads in eastern deciduous forests of varying successional ages in Indiana. Eastern deciduous forests cover much of the landscape east of the Mississippi River. Most of this region has been fragmented by urban and suburban development and roads such that ninety percent of all ecosystem areas in the eastern US are within 1061 m of a road (Riitters and Wickham 2003). We specifically addressed the following questions (1) Does the density of invasive exotic shrubs decline as the distance to a road increases? (2) Does the relationship between density and distance to road differ among exotic shrub species? and (3) Are invasive exotic shrubs less common in mature forests than in young successional forests? Answers to these questions will help develop a predictive framework for plant invasions and better inform management strategies.
This study suggests that roads may contribute to the spread of invasive plants in eastern deciduous forests. We found a highly signiﬁcant eﬀect of distance to road over all species and for four of seven individual species … One possible mechanism for high densities of invasive shrubs along roads is that exotic shrub propagules are distributed evenly by birds with respect to distance to road and simply survived at a greater rate near the road due to better growth conditions. These conditions might include higher light conditions or increased nutrient or water availability … Better survival and growth of exotic shrubs might also be due to decreased competition with native understory species. Native species may not survive as well along roadsides where runoff from pollutants and exposure to herbivores is greater … A second possible mechanism is that exotic shrub seeds are distributed by birds and other animals in a pattern that parallels the distribution of shrubs that we found. This would mean that the density of dispersed seeds declines with increasing distance to the nearest road but that survival is unaffected by distance to road. A third possible mechanism is that exotic shrub propagules were initially distributed along roads by animals and vehicles and are invading the forest from the roadside edge.
Successional age has been shown to aﬀect exotic plant establishment in old ﬁelds in Minnesota with younger successional aged communities more susceptible to invasions and older communities more resistant (Inouye et al. 1987). Our results show that forest successional age plays a similar role in the distribution of invasive shrubs in eastern deciduous forests with invasive shrubs found in greater densities in young and mid-successional forests than mature forests. This is likely due to a combination of factors including differences in light regimes … Exotic shrubs would have survived and grown much more successfully where they did not have to compete with existing trees or intact forests. This hypothesis could help to explain why we found fewer shrubs near the road in mature forests than young and mid-successional forests.
- S. L. Flory, K. Clay, “Effects of roads and forest successional age on experimental plant invasions”, Biological Conservation, 2009, 142, 2531-2537.
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