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Janet Morrison – Invasive non-indigenous plants

IMG_1030purple loosestrife stand800px-Lythrum_salicaria,_purple_loosestrife,_Boxborough,_Massachusetts_2

In addition to our current research on invasive plants, which is  focused on Alliaria petiolata (garlic mustard) and Microstegium vimineum (Japanese stilt-grass) in suburban forests (see the Deer x Invasives2 web page here), I also have investigated the ecology of several other non-native, invasive plants.

One is the grass Andropogon virgincus (broomsedge), which is native to eastern North America, but introduced in the Pacific basin and invasive in Hawaii (see my Plant-Pathogen Interactions web page here; broomsedge also has an interesting smut fungus parasite).

We also have studied Acer platanoides (Norway maple), which can form dense stands in forests that are typically near landscape plantings of this tree, and the wetland invader Lythrum salicaria (purple loosestrife).

Publications and conference presentations

(All co-authors were TCNJ undergraduate students)

Morrison, J.A. and K. Mauck. 2007. Experimental field comparison of native and non-native maple seedlings: natural enemies, ecophysiology, growth, and survival. Journal of Ecology 95: 1036-1049.
Morrison, J.A. 2002. Wetland vegetation before and after experimental purple loosestrife removal. Wetlands 22: 159-169.
August, 2006.  Plant Biology 2006: Joint Annual Meeting of the American Society of Plant Biologists and the Canadian Society of Plant Physiologists, Boston, MA.

Morrison, J.A. and K. Mauck. 2006. Comparison of native Acer saccharum and non-native Acer platanoides seedling biology.  PDF

April 2005.  Annual Meeting of the Delaware Valley Chapter of the Society for Conservation Biology.
Dunn, B. and J.A. Morrison. 2005. Competition and natural enemies in the forest floor plant community.
We investigated the complex interactions of native and non-native plant species in the presence and absence of interspecific competition and herbivores.  Two non-native invasive herbs, Japanese stilt grass (Microstegium vimineum-MV) and garlic mustard (Alliaria petiolata-GM) and a native tree species, sugar maple (Acer saccharum-SM) were grown in combinations of a single focal individual with or without two heterospecific competitors, in three forests.  Half of these were then provided with cages to eliminate large herbivores.  Percent herbivory data were collected from focal plants every two weeks for a total of four censuses for each focal plant.  At the end of the experiment, we collected the roots and shoots of focal plants to determine dry biomass, root to shoot ratios, and mortality. The end-season mortality showed that while a significant difference in mortality rates was present among the three species, the native sugar maple fell in between the rates of the two non-natives.  This adds insight to both the enemy release hypothesis and the environmental resistance hypothesis for biological invasions.  Furthermore, the data showed a lack of a two-way interaction between species and competition on herbivory, meaning that herbivory rates were constant with regard to what the focal species was.  Competition treatments did, however, show a general trend in the increase of herbivory rates in all three species, calling into question the enemy release hypothesis.
McCartney, K.M. and J.A. Morrison. 2005. The role of plant competition and natural enemy attack in forest seedling success. PDF
August 2001. Ecological Society of America Annual Meeting.

Morrison, J.A. 2001. Wetland vegetation before and after purple loosestrife removal.

March 1999. Annual Meeting of the Delaware Valley Chapter of the Society for Conservation Biology.

Camera, N. and J.A. Morrison. 1999. Seedlings of invasive Norway maple (Acer platanoides) and native trees: vulnerability and canopy influence.