The Role of Climate in the Dynamics of Annual Plants in a Chihuahuan Desert Ecosystem

Question: What is the role of temporal climate fluctuations in the dynamics of desert winter annual plants in the Portal Bajada, and in the sustained irruption of the non-native annual plant species, Erodium cicutarium? Field site: Portal Bajada, San Simon Valley, Arizona, USA. Methods: We counted plants at flowering over a 21-year period on twelve permanent plots and related these numbers to weather data collected at an on-site weather station, supplemented by observations from the National Climate Data Center. Specific summary climate variables considered most relevant to annual plant biology were developed as candidate predictors of plant response variables. Statistical techniques: We removed trends in the data associated with the irruption of E. cicutarium, removed temporal autocorrelation, and applied a technique that sought the strongest climatic predictors of vegetation response variables by testing climate variables against each other in bivariate regression analyses. The validity of this technique was demonstrated by simulation. We supplemented our analysis with multivariate regression for simultaneous tests on multiple response variables. Conclusions: Winter rainfall was the strongest predictor of total annual plant abundance, but number of species was more strongly predicted by average temperature over the total growing season (fall and winter), with cooler weather favouring more species. Average size of a rainfall event, although often thought important in desert plant biology, did not emerge as a significant predictor of the community-level variables, total abundance and number of species, but winter event size did emerge as a significant predictor of differences between the abundances of native species. Our analyses do not support a role for climate in the sustained irruption of E. cicutarium

What Is the Storage Effect, Why Should It Occur in Cancers, and How Can It Inform Cancer Therapy?

Intratumor heterogeneity is a feature of cancer that is associated with progression, treatment resistance, and recurrence. However, the mechanisms that allow diverse cancer cell lineages to coexist remain poorly understood. The storage effect is a coexistence mechanism that has been proposed to explain the diversity of a variety of ecological communities, including coral reef fish, plankton, and desert annual plants. Three ingredients are required for there to be a storage effect: (1) temporal variability in the environment, (2) buffered population growth, and (3) species-specific environmental responses. In this article, we argue that these conditions are observed in cancers and that it is likely that the storage effect contributes to intratumor diversity. Data that show the temporal variation within the tumor microenvironment are needed to quantify how cancer cells respond to fluctuations in the tumor microenvironment and what impact this has on interactions among cancer cell types. The presence of a storage effect within a patient’s tumors could have a substantial impact on how we understand and treat cancer

Water Availability for Cannabis in Northern California: Intersections of Climate, Policy, and Public Discourse

Availability of water for irrigated crops is driven by climate and policy, as moderated by public priorities and opinions. We explore how climate and water policy interact to influence water availability for cannabis (Cannabis sativa), a newly regulated crop in California, as well as how public discourse frames these interactions. Grower access to surface water covaries with precipitation frequency and oscillates consistently in an energetic 11–17 year wet-dry cycle. Assessing contemporary cannabis water policies against historic streamflow data showed that legal surface water access was most reliable for cannabis growers with small water rights (m3) and limited during relatively dry years. Climate variability either facilitates or limits water access in cycles of 10–15 years—rendering cultivators with larger water rights vulnerable to periods of drought. However, news media coverage excludes growers’ perspectives and rarely mentions climate and weather, while public debate over growers’ irrigation water use presumes illegal diversion. This complicates efforts to improve growers’ legal water access, which are further challenged by climate. To promote a socially, politically, and environmentally viable cannabis industry, water policy should better represent growers’ voices and explicitly address stakeholder controversies as it adapts to this new and legal agricultural water user

Työvoiman ikääntyminen ja ikäjohtaminen Suomen kunnissa asiakirja-analyysi kuntien strategioista

In response to a sharp decline in recreational fishing participation in Queensland, Australia, I sought to identify constraints experienced by fishers in Queensland and understand how demographic variables, fishing participation variables, and fishing motivations influence the amount and type of constraints experienced. In a survey of Queensland recreational fishers, 70% reported experiencing constraints-predominantly lack of time, crowding, unavailability of facilities, and costs associated with fishing. Fishers with higher incomes, fishers with higher centrality of fishing to lifestyle, fishers who placed higher importance on motivations related to catching fish and relaxation, and fishers who were male were more likely to experience constraints. With the exception of gender, variables found to have a significant effect on the presence of constraints also had a significant influence on the types of constraints experienced. Results provide insight into factors affecting recreational fishing participation in Queensland; however, additional research-particularly with recent fishing drop-outs-is needed to fully understand recent declines in fishing participation

A comprehensive approach for habitat restoration in the Columbia Basin

The Columbia Basin once supported a diversity of native fishes and large runs of anadromous salmonids that sustained substantial fisheries and cultural values. Extensive land conversion, watershed disruptions, and subsequent fishery declines have led to one of the most ambitious restoration programs in the world. Progress has been made, but restoration is expensive (exceeding US $300 M/year), and it remains unclear whether habitat actions, in particular, can be successful. A comprehensive approach is needed to guide cost-effective habitat restoration. Four elements that must be addressed simultaneously are (1) a scientific foundation from landscape ecology and the concept of resilience, (2) broad public support, (3) governance for collaboration and integration, and (4) a capacity for learning and adaptation. Realizing these in the Columbia Basin will require actions to rebalance restoration goals to include diversity, strengthen linkages between science and management, increase public engagement, work across traditional ecological and social boundaries, and learn from experience.This is the publisher’s final pdf. The published article is copyrighted by Taylor & Francis and can be found at: http://www.tandfonline.com/loi/ufsh20#.VUEib2MywS

THE INFLUENCE OF HERBIVORES ON PLANT COMMUNITIES: EXPERIMENTAL STUDIES OF A SUBALPINE MEADOW ECOSYSTEM (MICROTUS, THOMOMYS, OCHOTONA).

The effects on vegetation of three small mammalian herbivores were determined experimentally in a subalpine meadow in southwestern Colorado. Pikas (Ochotona princeps) inhabit talus and forage on surrounding vegetation. Their foraging was consistent with predictions of central place foraging theory. Amount of foraging decreased with distance from talus, whereas selectivity increased. These patterns are expected to influence the resources used by pikas, and plant abundance and species richness increased with distance from talus, as predicted. Experimental exclusion of pikas demonstrated that a significant portion of the lower vegetational cover and species richness was due to pikas. A model postulating that the effects of pikas on vegetation resulted from a gradient in herbivory, and a corresponding gradient in the relative importance of herbivory and competition among plants, was generally supported. Total vegetational abundance and species richness increased in the absence of pikas. The increase in pika exclosures compared to controls was greatest near talus and decreased with distance. The initial effect of pika exclusion on cushion plants (assumed to be the poorest competitors among the plants in the absence of herbivory) was positive near talus, but was insignificant and tended to be negative at greater distance from talus. The prediction of eventual decline of cushion plant populations in the absence of pikas was supported in two of three sites after three years. The effects on vegetation of two co-occurring herbivores, pocket gophers (Thomomys talpoides) and voles (Microtus montanus), were evaluated using a factorial exclusion experiment. Non-independence of effects was assessed as presence of a significant interaction term in 2-way ANOVA. Gopher x vole interaction terms were at least marginally significant for many analyses. Results only weakly suggested direct foraging interactions between gophers and voles, but showed considerable importance of indirect, plant-plant interactions. Exclusion of either gophers or voles significantly increased vegetational abundance, however, no additional change in abundance resulted when both were excluded simultaneously. Exclusion of either increased forb abundance, and exclusion of gophers increased grass abundance. Only simultaneous exclusion of both, however, altered proportional abundances of plant groups

Direct and indirect effects of herbivores on nitrogen dynamics: voles in riparian areas

Herbivores can directly increase nitrogen mobility by increasing the quality of organic matter entering the decomposition cycle, but they also may decrease nitrogen mobility by decreasing the biomass of high-nitrogen species in the plant community. We assessed effects of voles (Microtus) on nitrogen dynamics using exclosures in two riparian meadows (Crystal Bench and Blacktail Deer Creek) in Yellowstone National Park (USA). At both sites, the quantity of plant litter was decreased by herbivory following a vole population peak in 1992. At Crystal Bench, removal of voles caused a decrease in the nitrogen concentration and an increase in the C:N ratio of plant litter over the four years of the study. The higher quality litter produced in the presence of voles at Crystal resulted in a larger pool of potentially mineralizable nitrogen in soil from control plots relative to soils from plots that had not been accessible to voles. At Crystal, vole removal did not cause a change in plant community composition. However, at Blacktail, after several years of vole exclusion, legumes became more common in exclosures than in control plots that were accessible to voles. Selective herbivory on high-nitrogen legumes kept the litter quality outside exclosures low, whereas higher legume biomass caused a decrease in C:N ratio of plant litter inside exclosures. The removal of voles at Blacktail caused a 15% increase in the fraction of the soil nitrogen that was rapidly mineralizable. Our results show that voles increased nitrogen mobility, especially during and after population peaks. However, that increase was offset by decreases in nitrogen mineralization over longer periods when voles caused a decrease in high-quality plant litter produced by preferred forage plants, especially legumes. Thus, both the mechanisms by which voles affected nitrogen dynamics and the net effects of voles varied over time and space. The balance of direct and indirect effects may provide a general mechanistic explanation of whether herbivores increase or decrease the rate of nitrogen cycling