Spatial pattern and process at the plant neighbourhood scale: insights from communities dominated by the clonal grass Elymus repens (L.) Gould.

Question: How do clonal traits of a locally dominant grass (Elymus repens (L.) Gould.) respond to soil heterogeneity and shape spatial patterns of its tillers? How do tiller spatial patterns constrain seedling recruitment within the community?Locations: Artificial banks of the River Rhone, France.Material and Methods: We examined 45 vegetation patches dominated by Elymus repens. During a first phase we tested relationships between soil variables and three clonal traits (spacer length, number of clumping tillers and branching rate), and between the same clonal traits and spatial patterns (i.e. density and degree of spatial aggregation) of tillers at a very fine scale. During a second phase, we performed a sowing experiment to investigate effects of density and spatial patterns of E. repens on recruitment of eight species selected from the regional species pool.Results: Clonal traits had clear effects - especially spacer length - on densification and aggregation of E. repens tillers and, at the same time, a clear response of these same clonal traits as soil granulometry changed. The density and degree of aggregation of E. repens tillers was positively correlated to total seedling cover and diversity at the finest spatial scales.Conclusions: Spatial patterning of a dominant perennial grass responds to soil heterogeneity through modifications of its clonal morphology as a trade-off between phalanx and guerrilla forms. In turn, spatial patterns have strong effects on abundance and diversity of seedlings. Spatial patterns of tillers most probably led to formation of endogenous gaps in which the recruitment of new plant individuals was enhanced. Interestingly, we also observed more idiosyncratic effects of tiller spatial patterns on seedling cover and diversity when focusing on different growth forms of the sown species.

Outcome of a Modified Broström-Gould Procedure for Lateral Ankle Instability

Introduction: Ankle sprains affect 200'000 persons/year in Switzerland. Most incidences are successfully treated by conservative measures but 20% require reconstruction for symptomatic chronic lateral ankle instability. This study evaluates the functional outcome after a modified Broström-Gould technique as measured by different clinical scores and compares the functional outcome of this technique with other surgical treatments of ankle instability. Methods: This retrospective cohort study evaluates 47 patients who underwent a modified Broström-Gould procedure using suture anchors to refix the lateral ankle capsuloligamentary structures at our institution from 2005 to 2009 with a minimum follow-up of one year (13-72 Mo). All patients were operated by one single surgeon and evaluated by an independent examiner. The function was assessed using 4 scores including: the AOFAS (American Orthopaedic Foot and Ankle Society's Score) hindfoot score; the FAAM (Foot and Ankle Ability Measurement); the CAIT (Cumberland Ankle Instability Tool); the CAIS (Chronic Ankle Instability Scale). Results: Six patients were excluded leaving 41 patients for examination. 34 patients (83%) thought that their ankle was more stable after the surgery, 7 (17%) did not feel any difference. 27 patients were very satisfied, 11 satisfied and 3 not satisfied. Reasons for non satisfaction included persistent instability and pain. Ankle mobility returned to normal in 93% of patients. Five patients had transcient hypoesthesy in the area of the superficial peroneal nerve. One patient suffered from a superficial infection treated successfully by local measures. 80% had the perception of a normal ankle, 20% thought to be below normal. At follow-up the AOFAS was 89/100 (37-100), the FAAM 85/100% (35-100%), the CAIT 20/30 (5-30), and the CAIS 74/100% (27-100%). Conclusions: The modified Broström-Gould procedure, which belongs to the anatomic ankle stabilizations is relatively simple and offers good outcome that satisfied 93% of the patients in the present study. No active stabilisator is sacrificed. Preservation of the ankle mobility is better and the complication rate is lower than after non-anatomical procedures described in the literature. The CAIT appeared as the most severe score compared to the other scales used in our study.