CAN POTENTILLA FRUTICOSA LINN. SHRUBS FACILITATE THE HERB LAYER OF HEAVILY GRAZED PASTURE ON THE EASTERN TIBETAN PLATEAU?

The facilitative and competitive effects of shrubs on herbaceous species have been extensively studied, but little is known about the roles of the shrub distribution patterns in such effects. On a heavily grazed pasture on the Tibetan Plateau, we investigated the effects of Potentilla fruticosa Linn. shrubs of different distribution patterns on the small-scale vegetation pattern of the herb layer. We made same-sized releves at five micro-site types, i.e., beneath and outside the canopies of solitary Potentilla individuals, beneath and outside the canopies of edge-of-patch individuals and at the central openings of torus-shaped large Potentilla patches. Shrubs protected certain species by increasing their frequencies of occurrence or flowering. However, only few species benefited from shrubs and more occurred or flowered more frequently outside. The data at community level indicated that species richness and diversity index were higher outside. The patch openings did not benefit species richness, pooled cover, diversity index or evenness of central vegetations. No special species was found growing beneath shrubs exclusively and few species were found with higher occurrences beneath shrubs. Furthermore, no significant difference was found between the two different distribution patterns at either community or species level. Vegetation ordinations confirmed this and vegetations beneath and outside the shrubs were distinguished merely. In conclusion, Potentilla facilitated some species in the herb layer and the patch openings did not show large protective effects. Also, distribution patterns of Potentilla did not affect the difference between vegetations beneath and outside shrub canopies

The Influence of Psychological Variables on Health-Related Quality of Life among HIV-Positive Individuals with a History of Intravenous Drug Use

OBJECTIVE: Intravenous drug use (IDU) remains a prominent pathway of HIV transmission in the United States, though little is know about modifiable factors influencing quality of life among IDUs. The goal of this study was to evaluate the influence of psychological variables (e.g., depression and anxiety) on health related quality of life among HIV-positive individuals with a history of IDU who were enrolled in outpatient treatment for opioid dependence. METHOD: 108 HIV-positive individuals with a history of IDU and participating in current outpatient treatment for opiate dependence who were screened for participation in a depression and adherence study reported sociodemographic data, depressive and anxiety symptoms and health-related quality of life (HRQoL; Multidimensional Health Assessment using the ACTG-SF 21). RESULTS: Multiple regression models controlling for disease stage and background characteristics identified significant negative relationships between General Health Perception and Functioning without Pain for anxiety and depression, and between Role Functioning and Physical Functioning for anxiety. CD4 cell count was significantly related to Physical Functioning only. CONCLUSIONS: Results indicate that distress (both depression and anxiety) contribute significantly to variation in HRQoL over and above the effects of disease variables. Effective depression and anxiety treatment may result in improved overall functioning