1. Forest floor invasion results, 2002 Questions we asked: 1. Last year we found woody stem density was 65% lower in Vinca areas than on the natural forest floor. Is that difference consistent thru time? 2. What environmental conditions differ between Vinca areas and the natural forest floor? This year we measured soil conditions, looking for hints about why young trees don’t seem to grow up underneath Vinca. 3. If we remove Vinca, will the forest floor return to its former condition? If so, how fast?

2. Differences in % plant cover are obvious. Plant cover in the Removal plots is already equivalent to that on the normal forest floor.

3. Taxonomic richness does not vary significantly among treatments The standard error bars on the site-specific means are larger than those on the overall means. That’s because small spots of habitat (1 m 2 quadrats) differ from one-another more than the average conditions across larger areas (i.e. 4 m 2 of total area sampled in each site).

4. Woody stem density is 3 times higher in natural than in Vinca sites (consistent with last year’s findings) No evidence of recovery in the Removal treatment yet. The large standard errors illustrate that counts of woody stem density by different groups varied widely. We need to better define “woody stems” to reduce this variation in future years.

5. Moisture levels in the soil were uniformly dry in all treatments Note that the Houses site (V2) was slightly moister than the River site.

6. Soil organic matter concentrations were slightly higher in Vinca/Removal sites than in Natural forest areas. Organic matter was measured as a difference in weight between a dried soil sample before and after burning in a furnace at 500C. (The slightly higher organic matter levels in the River (V1) site may mean that the drier soil there limited decomposition rates more there than in the Houses site (V2).)

7. Conclusions: 1. Either Vinca is reducing the number of new trees developing on the forest floor, or conditions that are good for Vinca also happen to be bad for tree regeneration. We undertook a manipulative experiment to disentangle these two possibilities. If woody stem density begins to increase in our Removal plots in future years, we’ll have proof that Vinca is the culprit, not just local conditions. 2. The soil moisture and organic matter measurements we made are aimed at figuring out why young trees don’t seem to be coming up under Vinca cover. Next year we’ll repeat the moisture measurements and try some new environmental variables. Thanks for helping!