Bart Johnson

... is rap-idly evolving (Boxes 1-1 to 1-4). New ideas for ... Meanwhile the established design professions have increasingly recognized the need for ecological awareness ... future professional and research col-laborations among many fields, including landscape architecture, urban ...

Projected changes in climate are expected to have widespread effects on plant community composition and diversity in coming decades. However, multi-site, multi-factor climate manipulation studies that have examined whether observed responses are regionally consistent and whether multiple climate perturbations are interdependent are rare. Using such an experiment, we quantified how warming and increased precipitation intensity affects the relative dominance of plant functional groups and diversity across a broad climate gradient of Mediterranean prairies. We implemented a fully factorial climate manipulation of warming (+2.5-3.0°C) and increased wet-season precipitation (+20%) at three sites across a 520-km latitudinal gradient in the Pacific Northwest, USA. After seeding with a nearly identical mix of native species at all sites, we measured plant community composition (i.e., cover, richness and diversity), temperature, and soil moisture for three years. Warming and the resultant dr...

A key challenge in global change ecology is understanding how climate change will impact biodiversity through changes in species range distributions. It is increasingly recognized that a mechanistic approach that fuses theory with experimentation, synthesized using demographic models, is needed to understand the controls on species range limits. Experiments must measure multiple demographic parameters to predict both population viability within existing ranges and the ability to establish new populations beyond current ranges. Because many biotic and abiotic factors at multiple scales control species’ range limits, combining multi-factor climate manipulations across natural climate gradients is essential to establish underlying mechanisms.

ABSTRACT Background/Question/Methods Changing climactic conditions will shift the position along the continuum from parasite to mutualist of many plant symbionts. Arbuscular mycorrhizae fungi (AMF) provide nutrients in exchange for photosynthate, but they can also increase drought tolerance. Epichloë produce alkaloid compounds, which can protect hosts from herbivory. Climate change models predict warming and increased seasonality of precipitation in the Pacific Northwest (PNW), which may exaggerate plant drought stress in the region. Thus, the interaction between Epichloë endophytes and AMF has implications for plants’ ability to adapt to these climactic changes. We hypothesized that with warming and drought stress, grasses that host both symbionts will favor AMF at the expense of Epichloë. We tested this hypothesis in a manipulative climate change study embedded within a 520-km natural climate gradient in three PNW grasslands. The climate treatments are a full factorial crossing of heat (+3.0˚C) and precipitation (+20%) at each site. We collected the grasses Bromus hordeaceus and Agrostis capillaris from all plots in which they were available. The grasses were tested for Epichloë infection using an immunoblot test, and AMF colonization was quantified along with dark septate root endophytes (DSE), a poorly understood, polyphyletic group of root-colonizing ascomycetes. Results/Conclusions In B. hordeaceus, heating increased AMF colonization (p=0.071, n=30), while Epichloë infection decreased AMF colonization (p=0.047, n=30). There was also a non-significant trend for Epichloë infection to decrease with heating. There was no interaction between the DSE and AMF. However, Epichloë infection decreased colonization by DSE (p=0.003, n=30), in the same way that it decreased colonization by AMF. One major effect of heating is faster drying of the soil, and plants experienced drought stress in heated treatments. There is evidence for apparent competition between AMF and Epichloë in Bromus hordeaceus. The fact that Epichloë infection decreased both DSE and AMF colonization, but the two did not seem to affect each other, indicates inhibition of other symbionts by Epichloë-produced alkaloid compounds, rather than competition for photosynthate. Since AMF colonization is higher in the heated plots, while Epichloë infection is more rare, it is possible that the host plants encourage AMF over Epichloë thereby increasing their drought tolerance.

Living with fire is a challenge for human communities because they are influenced by socio-economic, political, ecological and climatic processes at various spatial and temporal scales. Over the course of 2 days, the authors discussed how communities could live with fire challenges at local, national and transnational scales. Exploiting our diverse, international and interdisciplinary expertise, we outline generalizable properties of fire-adaptive communities in varied settings where cultural knowledge of fire is rich and diverse. At the national scale, we discussed policy and management challenges for countries that have diminishing fire knowledge, but for whom global climate change will bring new fire problems. Finally, we assessed major fire challenges that transcend national political boundaries, including the health burden of smoke plumes and the climate consequences of wildfires. It is clear that to best address the broad range of fire problems, a holistic wildfire scholarship must develop common agreement in working terms and build across disciplines. We must also communicate our understanding of fire and its importance to the media, politicians and the general public.

The ability to anticipate urbanization impacts on streamflow regimes is critical to developing proactive strategies that protect aquatic ecosystems. We developed an interdisciplinary modeling framework to evaluate the effectiveness of integrated stormwater management (i.e., integration of strategic land-use
organization with site-scale stormwater BMPs) or its absence, and two regional growth patterns for maintaining streamflow regimes. We applied a three-step sequence to three urbanizing catchment basins in Oregon, to: (1) simulate landscape change under four future development scenarios with the agentbased
model Envision; (2) model resultant hydrological change using the Soil and Water Assessment Tool (SWAT); and (3) assess scenario impacts on streamflow regimes using 10 flow metrics that encompass all major flow components. Our results projected significant flow regime changes in all three basins.
Urbanization impacts aligned closely with increases in flow regime flashiness and severity of extreme flow events. Most changes were associated with negative impacts on native aquatic organisms in the Pacific Northwest. Scenario comparisons highlighted the importance of integrated stormwater management for reducing flow alterations, and secondarily, compact growth. Based on a flow metric sensitivity
typology, six flow metrics were insensitive to development in multiple basins, and four were sensitive to development and manageable with mitigation in multiple basins. Only three metrics were ever sensitive to development and resistant to mitigation, and only in one basin each. Our findings call for regional flow-ecology research that identifies the ecological significance of each flow metric, explores potential remedies for resistant ones and develops specific targets for manageable ones.