Redwood Reader

Study Finds Deer Hurt Wisconsin Diversity
http://story.news.yahoo.com/news?tmpl=story&cid=624&ncid=753&e=10&u=/ap/20040611/ap_on_sc/fading_forests
Biodiversity (Weeds vs. Non-Weeds) – Summary
http://www.co2science.org/subject/b/summaries/weedsvsnonw.htm
Native vs. Nonnative Invasive Plants in a CO2-Accreting Atmosphere
http://www.co2science.org/journal/v7/v7n23b1.htm
An interesting story appeared today from AP about a study done in Wisconsin involving a biological resampling of 62 plots sampled fifty years ago. This is an interesting study on many levels, the first of which is that there are only a few places sampled we can go back to. We should recognize the value of revisiting study sites. The study found deer apparently are the determining factor in plant diversity. Where deer populations were highest there was the greatest loss of diversity. All the plots lost some native species. To-thirds of the plots had invasive species, compared to only one fifty years ago. They found that generalist plants filled in after heavy browsing along with aggressive exotic and invasive species. These provide less food and habitat than native regrowth.
Year round deer hunting on tribal lands together with strict controls on development keep the deer population at about half the surrounding management zone average. Here is found the greatest diversity of native plant species. The lowest were in parks with no deer control at all. All areas had lost some density of diversity, an average 19%, while there was an eighty percent rise in exotic species. The total number of plant species in the 62 sites was 138 a half century ago and 134 currently. Forty sites had lost some species, and diversity declined at 45 of 62 sites.
University of Wisconsin botanists John T. Curtis and Grant Cottam had done the earlier studies. University researchers now plan to resurvey other parts of the state surveyed by the two fifty years ago.
All in all this is a really interesting study. Deer have long been known to be taking advantage of the edge habitat created by development and agriculture, increasing from better forage, removal of predators, protection from hunting, and more consistent availability of browse. The large number of deer here can only mean trouble for restoring plant diversity once the landscape is stabilized. Anyone who has gardened around here knows how much trouble deer are. They are not afraid of people or their lights or homes. Dogs send them just out of earshot, where the deer wait for the dogs to go to sleep so they can slip back into their private pantry, your garden. Only horses can find blooming roses on a mountain faster.
On another level, how long will it take to wonder about species restoration in the context of watershed restoration. Tree planting has been shown to be an effective method for stabilizing landscapes, but the loss of plant life was complete and I have no sources for many flowers and shrubs. I have wondered if I should move species from one property to another, or were they from dissimilar situations? An interesting study in CO2 Science magazine this week shows native prairie plant species better able to handle increased carbon dioxide, actually benefiting from it in above and below ground biomass, while introduced species showed no effect. I think this will be found to be a result of fungal action being enhanced by the carbon dioxide, and the introduced species having no associated fungi. Allowed to run for a while, it would appear native plants will slowly regain the edge that allowed them to survive in the first place. Under enhanced carbon dioxide levels they will out compete exotics unable to take advantage of the atmospheric fertilization.
This study found fast growing invasive species seriously hampered by shade, and less able to take advantage of wet years, actually losing biomass in the wet year. Native plants fared well in the dry year, in the shade, and exceptionally well in the wet year. Two invasive species showed most of the productivity in the study. Japanese honeysuckle, the lesser of the invaders, registered a three fold increase in production in the enriched atmosphere while the leading biomass producer, Nepal grass, showed no gain in the dry year and a forty percent loss in the wet year. Native non-weed plants increased productivity 9-14% in the dry year and 10-25% in the wet year.
Studies of various C3 and C4 plants showed no favoritism toward weeds in enriched Carbon atmospheres, and some species showed no gain at all from elevating the levels. This may have been due to lack of fungal partners. Field mustard, a brassica, showed uniform enhanced growth with elevated carbon dioxide. Finally, bracken showed no increase in biomass although net photosynthetic activity was up 30 to 70 percent. In fact, frond size went down. The likely explanation is heavy exudates for subsoil partners.
The authors go on to say, “In this study, native understory vegetation in a closed canopy forest made significant advances against the huge productivity advantage currently enjoyed by two nonnative invasive species as a consequence of an approximate 185-ppm increase in the air's CO2 concentration.” Remember, too, the productivity of the invaders dropped significantly in the shade.