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- Mountain runoff ultimately reflects the difference between precipitation (P) and evapotranspiration (ET), as modulated by biogeophysical mechanisms that intensify or alleviate drought impacts. These modulating mechanisms are seldom measured and not fully understood. The impact of the warm 2012–15 California drought on the heavily instrumented Kings River basin provides an extraordinary opportunity to enumerate four mechanisms that controlled the impact of drought on mountain hydrology. Two mechanisms intensified the impact: (i) evaporative processes have first access to local precipitation,...AuthorsRoger C. Bales, Michael L. Goulden, Carolyn T. Hunsaker, Martha H. Conklin, Peter C. Hartsough, Anthony T. O’Geen, Jan W. Hopmans, Mohammad SafeeqKeywordsSourceScientific Reports. 8(1): 690Year2018
- Urban forests produce ecosystem services that can benefit city dwellers, but are especially vulnerable to climate change stressors such as heat, drought, extreme winds and pests. Tree selection is an important decision point for managers wanting to transition to a more stable and resilient urban forest structure. This study describes a five-step process to identify and evaluate the performance of promising but infrequently used tree species. The approach is illustrated for the Central Valley of California, USA and has been implemented in the Inland Empire and Southern Coastal regions of...AuthorsE. Gregory McPherson, Alison M. Berry, Natalie S. van DoornKeywordsSourceUrban Forestry & Urban Greening. 29: 28-39Year2018
- Many forest ecosystems with a large pine component in the western United States have experienced environmental stress associated with climate change and increased competition with forest densification in the absence of fire. Information on how changes in climate and competition affect carbon allocation to tree growth and defense is needed to anticipate changes to tree vigor and, ultimately, stand structure. This study retrospectively examined the influence of annual climate and competition measures on the growth and defense of 113 large sugar pines (Pinus lambertiana) in a mixed-conifer...AuthorsAndrew Slack, Jeffrey Kane, Eric E. Knapp, Rosemary SherriffKeywordsSourceForests. 8(7): 244Year2017
- Theory predicts that higher biodiversity in the tropics is maintained by specialized interactions among plants and their natural enemies that result in conspecific negative density dependence (CNDD). By using more than 3000 species and nearly 2.4 million trees across 24 forest plots worldwide, we show that global patterns in tree species diversity reflect not only stronger CNDD at tropical versus temperate latitudes but also a latitudinal shift in the relationship between CNDD and species abundance. CNDD was stronger for rare species at tropical versus temperate latitudes, potentially...AuthorsJoseph A. LaManna, Scott A. Mangan, Alfonso Alonso, Norman A. Bourg, Warren Y. Brockelman, Sarayudh Bunyavejchewin, Li-Wan Chang, Jyh-Min Chiang, George B. Chuyong, Keith Clay, Richard Condit, Susan Cordell, Stuart J. Davies, Tucker J. Furniss, Christian P. Giardina, I. A. U. Nimal Gunatilleke, C. V. Savitri Gunatilleke, Fangliang He, Robert W. Howe, Stephen P. Hubbell, Chang-Fu Hsieh, Faith M. Inman-Narahari, David Janík, Daniel J. Johnson, David Kenfack, Lisa Korte, Kamil Král, Andrew J. Larson, James A. Lutz, Sean M. McMahon, William J. McShea, Hervé R. Memiaghe, Anuttara Nathalang, Vojtech Novotny, Perry S. Ong, David A. Orwig, Rebecca Ostertag, Geoffrey G. Parker, Richard P. Phillips, Lawren Sack, I-Fang Sun, J. Sebastián Tello, Duncan W. Thomas, Benjamin L. Turner, Dilys M. Vela Díaz, Tomáš Vrška, George D. Weiblen, Amy Wolf, Sandra Yap, Jonathan A. MyersKeywordsSourceScienceYear2017
- Frequent-fire forests were historically characterized by lower tree density, a higher proportion of pine species, and greater within-stand spatial variability, compared to many contemporary forests where fire has been excluded. As a result, such forests are now increasingly unstable, prone to uncharacteristically severe wildfire or high levels of tree mortality in times of drought stress. While reducing tree density might help to restore resilience, thinning treatments are frequently seen as conflicting with management for other resources such as wildlife habitat, in part because standard...AuthorsEric E. Knapp, Jamie Lydersen, Malcolm P. North, Brandon M. CollinsSourceForest Ecology and Management. 406: 228-241Year2017
- Large landslides can exert a lasting influence on hillslope and channel form and can continue to contribute to high in-stream sediment loads long after the event. We used discharge and suspended sediment concentration data from the Caspar Creek Experimental Watersheds to evaluate the temporal distribution of sediment inputs from 11 landslides of 100 to 5500 m3. Slide-related suspended sediment loads were estimated as deviations from expected loads referenced to nearby control watersheds. For the two largest slides, suspended sediment export during the year of the slide accounted for 5 and...AuthorsElizabeth Keppeler, Sue Hilton, Leslie M. ReidSourceGen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 135-147.Year2017
- Long-term flow records from sub-watersheds in the Caspar Creek Experimental Watersheds were used to test the accuracy of four methods commonly used to estimate peak flows in small forested watersheds: the Rational Method, the updated USGS Magnitude and Frequency Method, flow transference methods, and the NRCS curve number method. Comparison of measured and calculated results for 10-year return-interval flows demonstrates that, under the conditions tested, the direct flow transference method provides the most reliable results if suitable data are available; results for 100-year flows show...AuthorsPeter H. Cafferata, Leslie M. ReidSourceGen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 175-186Year2017
- Precommercial or early thinning of regenerating redwood forests can support management objectives including maximizing yield, forest structure restoration, and promoting carbon sequestration. We present data collected over 30 years following a precommercial thinning (PCT) in a 19 year-old naturally regenerated and planted coast redwood (Sequoia sempervirens(D. Don) Endl.) and coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stand. The study site is typical of most regenerating redwood forests with spatial variation in tree distribution from stump sprouting (coppice)...AuthorsLynn A. Webb, John-Pascal Berrill, James L. LindquistKeywordsSourceGen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 267-278Year2017
- California has recently experienced one of the worst droughts on record, negatively impacting forest ecosystems across the state. As a major source of the region’s water supply, it is important to evaluate the vegetation and water balance response of these montane forested watersheds to climate variability across the range of rain- to snow-dominated precipitation regimes. The Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI) were used to capture the hydrologic drought signal, and MODIS vegetation indices (i.e., the normalized difference vegetation index and the...AuthorsPhilip Saksa, Mohammad Safeeq, Salli DymondKeywordsSourceForestsYear2017
- Information on reproduction is essential to understanding population dynamics and developing conservation plans for wildlife. However, research on reproduction with species in the Martes Complex in wild settings can be challenging due to their low population densities, elusive behaviours, and tendency to hide young in cryptic den structures such as tree cavities or snow burrows. Answering basic questions about life history parameters in the Mattes Complex involves specialized techniques that have been increasingly refined by researchers over the last half-century. We present a review of...AuthorsRebecca E. Green, Michael Joyce, Sean Matthews, Kathryn L. Purcell, J. Mark Higley, Andrzej ZalewskiKeywordsSourceThe Martes Complex in the 21st century: ecology and conservation.Year2017