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Plants and biological soil crusts (biocrusts) are the key producers in drylands, but biocrusts seldom show net CO2 uptake. I hypothesized that biocrusts could augment CO2 fixation by incorporating plant-derived carbon. I collected biocrusts located at the base of Gutierrezia sarothrae (C3 forb), Bouteloua gracilis (C4 grass), and from bare interspaces between plants, and from a mesocosm experiment with live B. gracilis or dead B. gracilis roots. To trace carbon sources, I determined 13C values of the biocrust community, isolated cyanobacteria and lichen, and plant leaves because the photosynthetic pathway distinguishes the tissue 13C values. Biocrust communities and washed cyanobacteria and cyanolichen in G. sarothrae microsites were depleted by ~2‰ relative to other locations. Biocrust δ13C did not differ between the interspace and live or dead B. gracilis. Potential mechanisms for the trend in biocrust δ13C adjacent to C3 plants include differences in microsite conditions, biocrust communities, use of respired CO2 in the soil matrix for photosynthesis, or mixotrophic use of plant photosynthates. Further investigation of this observation may improve understanding of the degree to which the activities of dryland primary producers are coupled.

Premise of the study Productivity in drylands may depend on the sensitivity of interactions between plants and biocrusts. Given future climate variability, it is essential to understand how interactions may be context-dependent with precipitation regime. Furthermore, little is known about the additional interactions of these producers with the belowground biota (e.g., roots, fungi, microarthropods). We evaluated the effect of removal (such as could occur following disturbance) and net interaction of plants and biocrusts and additionally manipulated the abiotic and biotic context. Methods We established field mesocosms containing grass (Bouteloua gracilis) and surrounding biocrusts, then clipped the plant or heat-sterilized the biocrust to simulate the loss of dryland producers. To test for context-dependency on the precipitation pattern, we imposed a large, infrequent or small, frequent precipitation regime. A mesh barrier was used to impede belowground connections that may couple the dynamics of producers. Productivity was assessed by plant biomass and biocrust chlorophyll content. Key results Biocrusts increased chlorophyll content more when plants were removed than when they were present in the first year, but only in the small, frequent precipitation regime. In contrast, plant growth slightly declined with biocrust removal. Plant biomass and biocrust chlorophyll content were negatively correlated in the second year, suggesting net competition. Belowground connectivity weakly promoted overall biocrust relative productivity, but was generally weakly detrimental to plant relative productivity. Conclusions Altered precipitation patterns can amplify positive effects of plant removal on biocrust producers. Furthermore, we discovered that belowground networks contributed to dryland productivity by promoting biocrust performance.

Pinon–juniper (PJ) woodlands have recently undergone dramatic drought-induced mortality, triggering broad scale structural changes in this extensive Southwestern US biome. Given that climate projections for the region suggest widespread conifer mortality is likely to continue into the next century, it is critical to better understand how this climate-induced change in vegetation structure alters ecosystem function (e.g., productivity, biogeochemical cycling, energy partitioning) in PJ woodlands. Data from satellite remote sensing could potentially help to gain some of this understanding. However, relatively little is known about the suitability of satellite remote sensing for monitoring mortality induced structural and functional changes in PJ woodlands, a semi-arid biome characterized by sparse vegetation that complicates remote sensing of vegetation properties. Here we examined the potential role of satellite remote sensing to better understand structural and functional changes that take place in PJ woodlands as they respond to and recover from climate induced mortality events. We used time series medium (30 × 30 m) and high (≤ 5 × 5 m) spatial resolution satellite data in concert with eddy covariance-based gross primary productivity (GPP) data collected in a PJ woodland mortality manipulation near Mountainair, NM. Our results showed that both high and medium resolution satellite remote sensing data can provide ecosystem level assessments of overall canopy mortality and subsequent regrowth in these semi-arid woodlands. However, high spatial resolution data allowed detecting the disturbance almost a full year earlier and enabled us to describe the spatially heterogeneous patterns of recovery typical for such complex. The ability of satellite remote sensing to be used to provide information about changes in ecosystem function was conditional on the presence of sufficient soil moisture; when soil moisture was present the strength of the linear relationship between GPP and spectral vegetation indices improved at the manipulated site (e.g. for high resolution NDVI data R2 = 0.13 during drought conditions, R2 = 0.46 when wet, P

Not too fast, not too slow, somewhere in between In early depictions, dinosaurs lumbered slowly, dragging their tails. More recently, we have imagined them lifting their tails and running. The question boils down to whether dinosaurs had energetic systems closer to those of rapidly metabolizing mammals and birds, or to those of slower reptiles that do not internally regulate their body temperature. However, determining the metabolic rate of extinct organisms is no easy task. Grady et al. analyzed a huge data set on growth rate in both extinct and living species, using a method that considers body temperature and body size. Dinosaur metabolism seems to have been neither fast nor slow, but somewhere in the middle—so, dinosaurs did not fully regulate their internal temperature but they were also not entirely at the whim of the environment; neither slow goliaths nor supercharged reptiles. Science , this issue p. 1268

Finding ecologically and economically effective ways to establish matrix species is often critical for restoration success. Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) historically dominated large areas of western North America, but has been extirpated from many areas by large wildfires; its re-establishment in these areas often requires active management. We evaluated the performance (survival, health) and economic costs of container and bare-root stock based on operational plantings of more than 1.5 million seedlings across 2 200 ha, and compared our plantings with 30 other plantings in which sagebrush survival was tracked for up to 5 yr. Plantings occurred between 2001 and 2007, and included 12 combinations of stock type, planting amendment, and planting year. We monitored 10 500 plants for up to 8 yr after planting. Survival to Year 3 averaged 21% and was higher for container stock (30%) than bare-root stock (17%). Survival did not differ among container-stock plantings, whereas survival of bare-root stock was sometimes enhanced by a hydrogel dip before planting, but not by mycorrhizal amendments. Most mortality occurred during the first year after planting; this period is the greatest barrier to establishment of sagebrush stock. The proportion of healthy stock in Year 1 was positively related to subsequent survival to Year 3. Costs were minimized, and survival maximized, by planting container stock or bare-root stock with a hydrogel dip. Our results indicate that outplanting is an ecologically and economically effective way of establishing Wyoming big sagebrush. However, statistical analyses were limited by the fact that data about initial variables (stock quality, site conditions, weather) were often unrecorded and by the lack of a replicated experimental design. Sharing consistent data and using an experimental approach would help land managers and restoration practitioners maximize the success of outplanting efforts.

D’Emic and Myhrvold raise a number of statistical and methodological issues with our recent analysis of dinosaur growth and energetics. However, their critiques and suggested improvements lack biological and statistical justification.

Activity in small mammals is affected by local environmental conditions. Shrews have high metabolic requirements for water, so microclimatic humidity should influence activity patterns. Six different B. brevicauda individuals were trapped and monitored for time spent feeding, drinking, out of a den area, and using a wheel in an experimental chamber for 48 hours under conditions of low (24%), moderate (60%) and high (86%) relative humidity. Time spent drinking was significantly higher in the high humidity level (P < 0.05) and was the only significant difference other than significant variation among individuals. High humidity may have reduced evaporation across the integument, causing an increase in heat load and stimulation of drinking behaviors. Other activity may not have been affected by humidity level because there was abundant, available food and water and no natural dangers. Additionally, the temperature was below the thermal neutral zone for this species, so there was no water loss due to ...

Were dinosaurs ectotherms or fast-metabolizing endotherms whose activities were unconstrained by temperature? To date, some of the strongest evidence for endothermy comes from the rapid growth rates derived from the analysis of fossil bones. However, these studies are constrained by a lack of comparative data and an appropriate energetic framework. Here we compile data on ontogenetic growth for extant and fossil vertebrates, including all major dinosaur clades. Using a metabolic scaling approach, we find that growth and metabolic rates follow theoretical predictions across clades, although some groups deviate. Moreover, when the effects of size and temperature are considered, dinosaur metabolic rates were intermediate to those of endotherms and ectotherms and closest to those of extant mesotherms. Our results suggest that the modern dichotomy of endothermic versus ectothermic is overly simplistic.

Introduction: Communities change over time due to disturbances, variations in climate, and species invasions. Biological soil crust communities are important because they contribute to erosion control and nutrient cycling. Crust types may respond differently to changes in environmental conditions: single-celled organisms and bryophytes quickly recover after a disturbance, while lichens are slow growing and dominate favorable sites. Community change in crusts has seldom been assessed using repeated measures. For this study, we hypothesized that changes in crust composition were related to disturbance, topographic position, and invasive vegetation. Methods: We monitored permanent plots in the Columbia Basin in 1999 and 2010 and compared changes in crust composition, cover, richness, and turnover with predictor variables of herbivore exclosure, elevation, heat load index, time since fire, presence of an invasive grass, and change in cover of the invasive grass. Results: Bryophytes were cosmopolitan with high cover. Dominant lichens did not change dramatically. Indicator taxa differed by monitoring year. Bryophyte and total crust cover declined, and there was lower turnover outside of herbivore exclosures. Lichen cover did not change significantly. Plots that burned recently had high turnover. Increase in taxon richness was correlated with presence of an invasive grass in 1999. Change in cover of the invasive grass was positively related to proportional loss and negatively related to gain. Conclusions: Composition and turnover metrics differed significantly over 11 years, though cover was more stable between years. This study can be a baseline for assessing change in crust composition due to anthropogenic influences.