The relative importance of plant-soil feedbacks for plant-species performance increases with decreasing intensity of herbivory

Under natural conditions, aboveground herbivory and plant-soil feedbacks (PSFs) are omnipresent interactions strongly affecting individual plant performance. While recent research revealed that aboveground insect herbivory generally impacts the outcome of PSFs, no study tested to what extent the intensity of herbivory affects the outcome. This, however, is essential to estimate the contribution of PSFs to plant performance under natural conditions in the field. Here, we tested PSF effects both with and without exposure to aboveground herbivory for four common grass species in nine grasslands that formed a gradient of aboveground invertebrate herbivory. Without aboveground herbivores, PSFs for each of the four grass species were similar in each of the nine grasslands—both in direction and in magnitude. In the presence of herbivores, however, the PSFs differed from those measured under herbivory exclusion, and depended on the intensity of herbivory. At low levels of herbivory, PSFs were similar in the presence and absence of herbivores, but differed at high herbivory levels. While PSFs without herbivores remained similar along the gradient of herbivory intensity, increasing herbivory intensity mostly resulted in neutral PSFs in the presence of herbivores. This suggests that the relative importance of PSFs for plant-species performance in grassland communities decreases with increasing intensity of herbivory. Hence, PSFs might be more important for plant performance in ecosystems with low herbivore pressure than in ecosystems with large impacts of insect herbivores.Plant science

The relative importance of plant-soil feedbacks for plant-species performance increases with decreasing intensity of herbivory

Under natural conditions, aboveground herbivory and plant-soil feedbacks (PSFs) are omnipresent interactions strongly affecting individual plant performance. While recent research revealed that aboveground insect herbivory generally impacts the outcome of PSFs, no study tested to what extent the intensity of herbivory affects the outcome. This, however, is essential to estimate the contribution of PSFs to plant performance under natural conditions in the field. Here, we tested PSF effects both with and without exposure to aboveground herbivory for four common grass species in nine grasslands that formed a gradient of aboveground invertebrate herbivory. Without aboveground herbivores, PSFs for each of the four grass species were similar in each of the nine grasslands—both in direction and in magnitude. In the presence of herbivores, however, the PSFs differed from those measured under herbivory exclusion, and depended on the intensity of herbivory. At low levels of herbivory, PSFs were similar in the presence and absence of herbivores, but differed at high herbivory levels. While PSFs without herbivores remained similar along the gradient of herbivory intensity, increasing herbivory intensity mostly resulted in neutral PSFs in the presence of herbivores. This suggests that the relative importance of PSFs for plant-species performance in grassland communities decreases with increasing intensity of herbivory. Hence, PSFs might be more important for plant performance in ecosystems with low herbivore pressure than in ecosystems with large impacts of insect herbivores

Effects of medroxyprogesterone acetate on appetite, weight, and quality of life in advanced-stage non-hormone-sensitive cancer: a placebo-controlled multicenter study.

Effects of medroxyprogesterone acetate on appetite, weight, and quality of life in advanced-stage non-hormone-sensitive cancer: a placebo-controlled multicenter study. Simons JP, Aaronson NK, Vansteenkiste JF, ten Velde GP, Muller MJ, Drenth BM, Erdkamp FL, Cobben EG, Schoon EJ, Smeets JB, Schouten HC, Demedts M, Hillen HF, Blijham GH, Wouters EF. Department of Pulmonology, University Hospital, Maastricht, the Netherlands. PURPOSE: To investigate the effects of medroxyprogesterone acetate (MPA) on appetite, weight, and quality of life (QL) in patients with advanced-stage, incurable, non-hormone-sensitive cancer. PATIENTS AND METHODS: Two hundred six eligible patients were randomized between double-blind MPA 500 mg twice daily or placebo. Appetite (0 to 10 numerical rating scale), weight, and QL (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire [EORTC-QLQ-C30]) were assessed before the start of treatment (t = 0), and 6 weeks (t = 6) and 12 weeks (t = 12) thereafter. RESULTS: One hundred thirty-four patients (68 MPA and 66 placebo) were assessable at t = 6 and 99 patients (53 MPA and 46 placebo) at t = 12. A beneficial effect of MPA on appetite was observed after both 6 weeks (P = .008) and 12 weeks (P = .01) of treatment. After 12 weeks, a mean weight gain of 0.6 +/- 4.4 kg was seen in the MPA, versus an ongoing mean weight loss of 1.4 +/- 4.6 kg in the placebo group. This difference of 2.0 kg was statistically significant (P = .04). During the study, several areas of QL deteriorated in the total group of patients. With the exception of an improvement in appetite and possible also a reduction in nausea and vomiting, no measurable beneficial effects of MPA on QL could be demonstrated. The side effects profile of MPA was favorable: only a trend toward an increase in (usually mild) peripheral edema was observed. CONCLUSION: In weight-losing, advanced-stage non-hormone-sensitive cancer patients, MPA exhibits a mild side effects profile, has a beneficial effect on appetite, and may prevent further weight loss. However, general QL in the present study was not measurably influenced by MPA treatment. Publication Types: Clinical Trial Multicenter Study Randomized Controlled Tria