Biodiversity increases and decreases ecosystem stability.

Losses and gains in species diversity affect ecological stability1-7 and the sustainability of ecosystem functions and services8-13. Experiments and models have revealed positive, negative and no effects of diversity on individual components of stability, such as temporal variability, resistance and resilience2,3,6,11,12,14. How these stability components covary remains poorly understood15. Similarly, the effects of diversity on overall ecosystem stability16, which is conceptually akin to ecosystem multifunctionality17,18, remain unknown. Here we studied communities of aquatic ciliates to understand how temporal variability, resistance and overall ecosystem stability responded to diversity (that is, species richness) in a large experiment involving 690 micro-ecosystems sampled 19 times over 40 days, resulting in 12,939 samplings. Species richness increased temporal stability but decreased resistance to warming. Thus, two stability components covaried negatively along the diversity gradient. Previous biodiversity manipulation studies rarely reported such negative covariation despite general predictions of the negative effects of diversity on individual stability components3. Integrating our findings with the ecosystem multifunctionality concept revealed hump- and U-shaped effects of diversity on overall ecosystem stability. That is, biodiversity can increase overall ecosystem stability when biodiversity is low, and decrease it when biodiversity is high, or the opposite with a U-shaped relationship. The effects of diversity on ecosystem multifunctionality would also be hump- or U-shaped if diversity had positive effects on some functions and negative effects on others. Linking the ecosystem multifunctionality concept and ecosystem stability can transform the perceived effects of diversity on ecological stability and may help to translate this science into policy-relevant information.

New directions in peritoneal dialysis patient training.

OBJECTIVE: To study the effect of training methods on selected patient outcomes in peritoneal dialysis patients. DESIGN: Multi-center, longitudinal prospective quasi-experimental design study conducted over a 2-year period. SETTING: Thirty-two Gambro Healthcare peritoneal dialysis (PD) home training programs in the United States. SUBJECTS: New patients starting PD were trained on PD technique and diet using either an adult learning theory-based curriculum in the experimental group (PG) or non-standardized conventional training programs in the control group (CG). Excluded were patients who were non-English speaking, legally blind without sighted caregiver, nursing home residents, and those with previous exposure to PD training. METHODS: Information was collected by means of manual data collection tools and though the use of Gambro Healthcare computer system and was analyzed for statistical significance by Gambro Healthcare biostatistician. RESULTS: Compared with the CG, initial training took longer in the PG (PG = 29 hrs; CG = 22.6 hrs; p < .0001), and time required for retraining was less but not statistically significant (PG = 8.7 hrs; CG = 12.5 hrs; p = .1324). The peritonitis rate was less in the PG (28.2 per 1000 patient months) than in the CG (36.7 per 1000 patient months), but did not achieve statistical significance (p = .09783). Exit site infections (ESIs) were less in the PG than the CG (PG = 18.5; CG = 31.8; p = .00349). Dropout from PD to hemodialysis secondary to infection was less in the PG (1.6%) than in the CG (5.6%) (p = .0069). Measured on a scale with 4 being the best score, mean fluid balance scores in the PG were 3.41 compared to 3.25 in the CG (p < .0001), and mean compliance scores for the PG versus the CG were 3.62 and 3.52, respectively (p < .0001). Laboratory parameters between the two groups were significantly different only for Kt/V (PG = 2.4; CG = 2.3; p = 0.0107). CONCLUSION: Use of the adult learning theory-based training method curriculum was positively associated with improved patient outcomes in the PD population studied.