Changing wildfire, changing forests: the effects of climate change on fire regimes and vegetation in the Pacific Northwest, USA
In this second episode of Fire Ecology Chats, Fire Ecologyeditor Bob Keane interviews Jessica Halofsky, USDA Forest Service, and David Peterson, University of Washington, to discuss the key points of their paper that synthesizes understanding of the potential effects of changing climate and fire regimes on Pacific Northwest forests.
We estimate the ecosystem service value of water supplied by the San Bernardino National Forest in Southern California under climate change projections through the 21st century. We couple water flow projections from a dynamic vegetation model with an economic demand model for residential water originating from the San Bernardino National Forest. Application of the method demonstrates how estimates of consumer welfare changes due to variation in water supply from public lands in Southern California can inform policy and land management decisions. Results suggest variations in welfare changes over time due to alterations in the projected water supply surpluses, shifting demand limited by water supply shortages or surpluses, and price increases. Results are sensitive to future climate projections—in some cases large decreases in welfare due to supply shortages—and to assumptions about the demand model.
Monitoring vegetation phenology is important for managers at several scales. Across decades, changes in the timing, pattern, and duration of significant life cycle events for plant groups can foreshadow shifts in species assemblages that can affect ecosystem services. In the shorter term, managers need phenological information to time activities such as grazing, ecological restoration plantings, biocontrol of pests, seed collection, and wildlife monitoring. However, tools to deliver timely seasonal development have been limited either spatially (data from a single tower or weather station, or on a single species, or both) or temporally (annually, quarterly, or monthly summaries). We developed another option called PhenoMap. This is a weekly assessment of land surface “greenness” across the continental United States that employs the Normalized Differential Vegetation Index (NDVI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. Here we present the PhenoMap Web map and its validation by using 54 in situ PhenoCam camera sites representing six vegetation structure types and 31 different ecoregions. We found that PhenoMap effectively tracks phenology on grasslands, shrublands, deciduous broadleaf and mixed forests. Results for evergreen needleleaf sites were poor owing to the low green-up signal relative to the total amount of foliage detected by NDVI. Issues of extent and field of view were critical when assessing remotely sensed data with in situ oblique camera imagery.
Climate change is projected to impact ecosystem functioning, however its effect on the provision of ecosystem services is uncertain. This is particularly relevant on federal lands which harbor extensive tracts of natural vegetation. We assessed change in four ecosystem services (water runoff, groundwater recharge, carbon storage, and biodiversity) and one disservice (sediment export) in southern California between current and end-of-century (2070–2099). We used five general circulation models ranging from warmer wetter (CNRM-CM5, CCSM4) to hotter, marginally drier (IPSL-CM5A-LR) to hotter drier (FGOALS-g2, MIROC-ESM) under RCP8.5. We found greatest projected change in water runoff, from an increase of 127% under a warmer wetter GCM to a decrease of −60% under a hotter drier future. Carbon storage is projected to change the least, from an increase of 52% to a decrease of −31% across GCMs. We also determined that one-third of high biodiversity areas are threatened by high change in climatic water deficit. We estimated the current monetized annual value of sediment removal costs to be $172 million per year and the economic value of carbon storage as $7.5 billion. Understanding the impacts of climate change on ecosystem services can help develop climate-smart strategies for the sustainable management of natural resources.
Extensive bark beetle outbreaks have recently occurred in western North American forests, resulting in overstory tree mortality across millions of hectares. Annual aerial surveys are currently used to operationally monitor bark beetle induced tree mortality, though this method is subjective and can exclude some forest areas. Daily Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data oer a potential alternative means to develop regional tree mortality maps. Accurate methods using such data could aid natural resource managers in surveys of forests with frequent overstory mortality, helping to prioritize forest treatment and restoration activities. This paper discusses a study to test the potential of using MODIS data to detect tree mortality. We developed and tested an approach to use 250-m resolution MODIS Normalized Dierence Vegetation Index (NDVI) data products collected during a mountain pine beetle (MPB) outbreak and related tree mortality event in the northern Rocky Mountains of Colorado, USA. The 94 km2 study area is predominantly lodgepole pine forest with most of the MPB-caused mortality occurring between 2003 and 2008. We used a 2.4-m forest conditions map from 2008 aerial multispectral imagery to calculate percentage of mortality within 240-m pixels for use as reference data. Using either daily or 16-day products, MODIS NDVI change products were calculated for 2008 versus either 2000 or 2003 baselines. MODIS change products were used as predictors in linear regression analysis to assess correlation between MODIS data and the aerial percent forest mortality map. Depending on the MODIS product, linear regression analyses yielded r2 values ranging from 0.362 to 0.544 without outliers removed and from 0.406 to 0.570 with extreme outliers removed. Daily MODIS NDVI products from 2003 and 2008 were used with exponential regression to improve the r2 to 0.593. The project showed some MODIS NDVI data potential for mapping percent tree mortality in forests subjected to regional bark beetle outbreaks and severe drought.
The Qinghai-Tibet Plateau constitutes unique mountain ecosystems that can be used for early detection of the impacts of climate change on ecosystem functions. We use the MAPSSCENTURY 2 (MC2), a dynamic global vegetation model, to examine the potential responses of terrestrial ecosystems to climate change in the past (1961–2010) and future (2011–2080) under one medium-low warming scenario (RCP4.5) at a 1-km spatial resolution in the Upper Heihe River Basin (UHRB), northwestern China. Results showed that 21.4% of the watershed area has experienced changes in potential natural vegetation types in the past and that 42.6% of the land would undergo changes by the 2070s, characterized by a sharp increase in alpine tundra at the cost of cold barren land. Net primary productivity (NPP) and heterotrophic respiration (RH) have increased sharply since the mid-1980s and are projected to remain at reduced rates in the future. Overall, UHRB switched from carbon neutral to a carbon sink in 1961–2010, and the sink strength is projected to decline after 2040. Additionally, future climate change is projected to drive a decrease in water yield due to a slight decrease in precipitation and an increase in evapotranspiration (ET). Furthermore, we find large spatial variations in simulated ecosystem dynamics, including an upward trend of NPP, RH, and ET in the alpine zone, but a downward trend in themid-elevation forest zone. These results underscore the complexity of potential impacts of climate change on mountain watersheds that represent the headwaters of inland river systems in an arid environment.
Tropospheric ozone (O3) is an important stressor in natural ecosystems, with well documented impacts on soils, biota and ecological processes. The effects of O3 on individual plants and processes scale up through the ecosystem through effects on carbon, nutrient and hydrologic dynamics. Ozone effects on individual species and their associated microflora and fauna cascade through the ecosystem to the landscape level. Systematic injury surveys demonstrate that foliar injury occurs on sensitive species throughout the globe. However, deleterious impacts on plant carbon, water and nutrient balance can also occur without visible injury. Because sensitivity to O3 may follow coarse physiognomic plant classes (in general, herbaceous crops are more sensitive than deciduous woody plants, grasses and conifers), the task still remains to use stomatal O3 uptake to assess class and species’ sensitivity. Investigations of the radial growth of mature trees, in combination with data from many controlled studies with seedlings, suggest that ambient O3 reduces growth of mature trees in some locations. Models based on tree physiology and forest stand dynamics suggest that modest effects of O3 on growth may accumulate over time, other stresses (prolonged drought, excess nitrogen deposition) may exacerbate the direct effects of O3 on tree growth, and competitive interactions among species may be altered. Ozone exposure over decades may be altering the species composition of forests currently, and as fossil fuel combustion products generate more O3 than deteriorates in the atmosphere, into the future as well.
The backlog of active restoration needs on national forests in Oregon and Washington has stimulated interest in new ways to prioritize projects and improve the efficiency of restoration and fuel management programs.
Scientists developed an assessment approach and planning framework to address gaps in local planning and broad-scale prioritization of federal and state assistance to mitigate wildfire risk on federal lands near high-risk communities.
Scientists evaluated surface fuel load; vegetation cover; and forest structure before and after mechanical and fire-only treatments over 8 years across 11 national forests in California: the Inyo; Klamath; Lassen; Modoc; Mendocino; Plumas; San Bernardino; Shasta-Trinity; Stanislaus; and Tahoe National Forests and the Lake Tahoe Basin Management Uni
A forest plant’s environment can play a life-or-death role in its likelihood of succumbing to disease. The environment can include changing temperatures, humidity, drought or rainfall, soils and nutrients, weeds, insects, bacteria, fungi, and viruses.