Chaplin-Kramer, R., & George, M. R. (2013). Effects of climate change on range forage production in the San Francisco Bay Area. PloS One, 8(3): e57723. doi:10.1371/journal.pone.0057723
Concilio, A. L., Loik, M. E., & Belnap, J. (2013). Global change effects on Bromus tectorum L. (Poaceae) at its high-elevation range margin. Global Change biology, 19(1): 161–72. doi:10.1111/gcb.12032
Fernandez-Going, B. M., and S. Harrison. 2013. Effects of experimental water addition depend on grassland community characteristics. Plant Ecology 214:777–786.ABSTRACT: Plant community biomass and composition on low-productivity soils, such as serpentine, may be more resistant to climate change because they host stress-tolerant species that may respond slowly to change. These communities also host a number of endemic taxa that are of special interest because of their narrow distributions. In a 3-year study, we experimentally tested the response of serpentine and non-serpentine communities to water addition in spring. We also compared the responses of endemics and generalists to water addition, with and without biomass (competitor) removal. In the non-serpentine grassland, peak biomass was significantly greater in the water addition plots compared with control plots, but this effect depended on the year. In the serpentine grassland, there was no effect of water addition on biomass. Survival, biomass, growth rates, and seed production of soil endemics and generalists were all significantly reduced by competition, but were unaffected by water addition. Overall, endemics tended to perform better in serpentine soil and generalists in non-serpentine soil, suggesting that soil is an important factor for the establishment and survival of endemics and generalists. For endemics, the effect of biomass removal was stronger on non-serpentine soil, but for generalists this effect was similar on both soils, indicating that competition can be important in low-resource habitats. In conclusion, our results suggest that low-fertility plant communities may be slow to respond to changes in precipitation compared to communities on more fertile soil.
Mariotte, P., C. Vandenberghe, P. Kardol, F. Hagedorn, and A. Buttler. 2013. Subordinate plant species enhance community resistance against drought in semi-natural grasslands. Journal of Ecology 101:763–773.ABSTRACT: According to the insurance hypothesis, more diverse plant communities are more likely to be resistant to drought. Whilst many experiments have been carried out to determine the effects of plant diversity on plant community insurance, the results are still contradictory. Here, we conducted a drought experiment where we tested whether the presence of subordinate species increases plant community insurance. In Swiss Jura grassland, we combined a removal experiment of subordinate species with a summer drought event using rainout shelters. Plant community composition was determined after the drought and based on biomass measurements; we estimated resistance, recovery and resilience of the plant community for each combination of treatments. Moreover, to assess drought impacts on water-use efficiency (WUE), we analysed carbon isotope ratios (13C values) in plant leaves of two dominants and two subordinates collected at the end of the drought period. We showed that subordinate species are more resistant to drought and increased community resistance by enhancing their above-ground biomass production during the imposed drought. These patterns were associated with decreased competitiveness of dominant species whose biomass decreased during drought. Significant increase in 13C values in plant tissue under drought indicated a better WUE for the measured species. Interestingly, the WUE was significantly higher in plots where subordinates were removed. Recovery and resilience were not affected by the summer drought, but the absence of subordinates reduced overall above-ground biomass in both watered and drought plots. Synthesis. We demonstrated that, independent of plant diversity, the presence of drought-resistant subordinate species increases plant community insurance against drought and, hence, is important for the functioning of grassland ecosystems.
McAdoo, J. K., Schultz, B. W., & Swanson, S. R. (2013). Aboriginal precedent for active management of sagebrush-perennial grass communities in the Great Basin. Rangeland Ecology & Management, 66(3), 241-253.ABSTRACT: Until recently, most contemporary ecologists have ignored or diminished anecdotal historical accounts and anthropologists' reports about aboriginal fire in the Great Basin. Literature review shows that Indians practiced regular use of fire for many purposes, including the obvious reasons of increasing the availability of desired plants, maintaining habitats for animals used as food, and driving game during hunts. Historical accounts of prehistoric anthropogenic firing, inferences from fire-scar data, and data regarding annual production capability of representative sagebrush (Artemisia spp.)-perennial grass ecological sites indicate that prehistoric conditions were neither fuel- nor ignition-limited. According to many sources, this "active management" by Indians was widespread, significant, and more common than lightning-caused fires, resulting in mosaic vegetation patterns that subsequently moderated the behavior of "natural fires." This interaction between Indian-burning and lightning fires may have strongly influenced the pre-Euro-American settlement vegetation of the Great Basin. At the very least, the landscape was a patchwork of areas altered by aboriginal people and areas shaped primarily by bio-physical processes. Based on this prehistoric precedent, current historically unprecedented conditions (fuel load and exotic weed invasion threats), and predicted climate change, contemporary active management of sagebrush-perennial grass communities is paramount. Restoration measures should be scientifically based and tailored to achieve ecological resilience and functionality in specific sites. Prescribed fire is not always ecologically appropriate or judicious, especially in Wyoming big sagebrush (A. tridentata spp. wyomingensis) communities, so managers should consider using other alternatives where an intentional low severity disturbance is deemed necessary. Properly planned active management would disrupt fuel continuity for lightning fires, ensure ecological process and successional integrity, and benefit multiple uses on a landscape scale.
McSherry, M. E., and M. E. Ritchie. 2013. Effects of grazing on grassland soil carbon: a global review. Global change biology 19:1347–57.
ABSTRACT: Soils of grasslands represent a large potential reservoir for storing CO2, but this potential likely depends on how grasslands are managed for large mammal grazing. Previous studies found both strong positive and negative grazing effects on soil organic carbon (SOC) but explanations for this variation are poorly developed. Expanding on previous reviews, we performed a multifactorial meta-analysis of grazer effects on SOC density on 47 independent experimental contrasts from 17 studies. We explicitly tested hypotheses that grazer effects would shift from negative to positive with decreasing precipitation, increasing fineness of soil texture, transition from dominant grass species with C3 to C4 photosynthesis, and decreasing grazing intensity, after controlling for study duration and sampling depth. The six variables of soil texture, precipitation, grass type, grazing intensity, study duration, and sampling depth explained 85% of a large variation (+/- 150gm2yr1) in grazing effects, and the best model included significant interactions between precipitation and soil texture (P=0.002), grass type, and grazing intensity (P=0.012), and study duration and soil sampling depth (P=0.020). Specifically, an increase in mean annual precipitation of 600mm resulted in a 24% decrease in grazer effect size on finer textured soils, while on sandy soils the same increase in precipitation produced a 22% increase in grazer effect on SOC. Increasing grazing intensity increased SOC by 67% on C4-dominated and C4C3 mixed grasslands, but decreased SOC by an average 18% in C3-dominated grasslands. We discovered these patterns despite a lack of studies in natural, wildlife-dominated ecosystems, and tropical grasslands. Our results, which suggest a future focus on why C3 vs. C4-dominated grasslands differ so strongly in their response of SOC to grazing, show that grazer effects on SOC are highly context-specific and imply that grazers in different regions might be managed differently to help mitigate greenhouse gas emissions.
Ryals, R., & Silver, W. L. (2013). Effects of organic matter amendments on net primary productivity and greenhouse gas emissions in annual grasslands. Ecological Applications 23(1): 46–59.
Setterfield, S. A, N. A Rossiter-Rachor, M. M. Douglas, L. Wainger, A. M. Petty, P. Barrow, I. J. Shepherd, and K. B. Ferdinands. 2013. Adding fuel to the fire: the impacts of non-native grass invasion on fire management at a regional scale. PloS One 8:e59144.
Skaer, M. J., D. J. Graydon, and J. H. Cushman. (2013). Community-level consequences of cattle grazing for an invaded grassland: variable responses of native and exotic vegetation. Journal of Vegetation Science 24:332-343.
Vourlitis, G. L., & Kroon, J. L. (2013). Growth and resource use of the invasive grass, Pampasgrass (Cortaderia selloana), in response to nitrogen and water availability. Weed Science, 61(1): 117–125. doi:10.1614/WS-D-11-00220.1