Community fluctuations and local extinction in a planktonic food web.

Determining statistical patterns irrespective of interacting agents (i.e. macroecology) is useful to explore the mechanisms driving population fluctuations and extinctions in natural food webs. Here, we tested four predictions of a neutral model on the distribution of community fluctuations (CF) and the distributions of persistence times (APT). Novel predictions for the food web were generated by combining (1) body size-density scaling, (2) Taylor's law and (3) low efficiency of trophic transference. Predictions were evaluated on an exceptional data set of plankton with 15 years of weekly samples encompassing c. 250 planktonic species from three trophic levels, sampled in the western English Channel. Highly symmetric non-Gaussian distributions of CF support zero-sum dynamics. Variability in CF decreased while a change from an exponential to a power law distribution of APT from basal to upper trophic positions was detected. Results suggest a predictable but profound effect of trophic position on fluctuations and extinction in natural communities.

Root and shoot growth, assimilate partitioning and cell proliferation in roots of Sitka spruce (Picea sitchensis) grown in filtered and unfiltered chambers.

Rooted cuttings of clonal Sitka spruce (Picea sitchensis (Bong.) Carr.) were grown from April to October in 1 m long tubes sunk into the ground inside open top chambers. The same experiment was repeated in each of two consecutive years using a different clone of Sitka spruce each year. Air was either passed directly into the chambers (ambient air) or passed over charcoal filters which removed the majority of gaseous pollutants before entering the chambers (filtered air). Ambient pollution did not appear to influence the growth of Sitka spruce at least over the experimental period used. No significant differences were found between plants exposed to ambient or filtered air in terms of shoot and root dry mass, needle dry mass, root length, carbohydrate content of roots and needles, and in the percentage of meristematic cells close to the apex in each phase or interphase or undergoing mitosis.

An evaluation of the effectiveness, safety and acceptability of a nurse practitioner in a rheumatology outpatient clinic.

Seventy patients with RA were randomly allocated to either a Rheumatology Nurse Practitioner (RNP) or Consultant Rheumatologist (CR) clinic. They were seen on six occasions in 1 year. Effectiveness and safety were assessed by biochemical, clinical, psychological and functional variables; patient knowledge and satisfaction were measured by questionnaire. At week 0 the groups were well matched clinically and demographically. By week 48 significant improvements had occurred in plasma viscosity and articular index within both groups. In patients managed by the RNP, pain, morning stiffness, psychological status, patient knowledge and satisfaction had all improved significantly (P = 0.001; P = 0.028; P = 0.0005; P < 0.0001; P < 0.0001 respectively), improvements not mirrored by the CR cohort. Between group comparisons also showed significant differences by the end of the study. Compared to the CR patients, the RNP suffered from lower levels of pain (P < 0.05), had acquired greater levels of knowledge (P < 0.0001) and were significantly more satisfied with their care (P < 0.0001).