Landscape Partnership Resources Library
The Relative Impact of Harvest and Fire upon Landscape-Level Dynamics of Older Forests: Lessons from the Northwest Forest Plan
Interest in preserving older forests at the landscape level has increased in many regions, including the Pacific Northwest of the United States. The North- west Forest Plan (NWFP) of 1994 initiated a sig- nificant reduction in the harvesting of older forests on federal land. We used historical satellite imagery to assess the effect of this reduction in relation to: past harvest rates, management of non-federal forests, and the growing role of fire. Harvest rates in non-federal large-diameter forests (LDF) either decreased or remained stable at relatively high rates following the NWFP, meaning that harvest reductions on federal forests, which cover half of the region, resulted in a significant regional drop in the loss of LDF to harvest. However, increased losses of LDF to fire outweighed reductions in LDF harvest across large areas of the region. Elevated fire levels in the western United States have been correlated to changing climatic conditions, and if recent fire patterns persist, preservation of older forests in dry ecosystems will depend upon practical and coordi- nated fire management across the landscape. Key words: disturbance; fire; landsat; forest management; Northwest Forest Plan; old growth.
Linking forest fires to lake metabolism and carbon dioxide emissions in the boreal region of Northern Quebec
Natural fires annually decimate up to 1% of the forested area in the boreal region of Que ́bec, and represent a major structuring force in the region, creating a mosaic of watersheds characterized by large variations in vegetation structure and composition. Here, we investigate the possible connections between this fire-induced watershed heterogeneity and lake metabolism and CO2 dynamics. Plankton respiration, and water–air CO2 fluxes were measured in the epilimnia of 50 lakes, selected to lie within distinct watershed types in terms of postfire terrestrial succession in the boreal region of Northern Que ́ bec. Plankton respiration varied widely among lakes (from 21 to 211lgCL1day1), was negatively related to lake area, and positively related to dis- solved organic carbon (DOC). All lakes were supersaturated in CO2 and the resulting carbon (C) flux to the atmosphere (150 to over 3000 mg C m2 day1) was negatively related to lake area and positively to DOC concentration. CO2 fluxes were positively related to integrated water column respiration, suggesting a biological component in this flux. Both respiration and CO2 fluxes were strongly negatively related to years after the last fire in the basin, such that lakes in recently burnt basins had significantly higher C emissions, even after the influence of lake size was removed. No significant differences were found in nutrients, chlorophyll, and DOC between lakes in different basin types, suggesting that the fire-induced watershed features influence other, more subtle aspects, such as the quality of the organic C reaching lakes. The fire-induced enhancement of lake organic C mineralization and C emissions represents a long-term impact that increases the overall C loss from the landscape as the result of fire, but which has never been included in current regional C budgets and future projections. The need to account for this additional fire-induced C loss becomes critical in the face of predictions of increasing incidence of fire in the circumboreal landscape. Keywords: boreal, carbon dioxide flux, climate, forest fire, lakes, organic carbon, plankton respiration,
Wildfire responses to abrupt climate change in North America
It is widely accepted, based on data from the last few decades and on model simulations, that anthropogenic climate change will cause increased fire activity. However, less attention has been paid to the relationship between abrupt climate changes and heightened fire activity in the paleorecord. We use 35 charcoal and pollen records to assess how fire regimes in North America changed during the last glacial–interglacial transition (15 to 10 ka), a time of large and rapid climate changes. We also test the hypothesis that a comet impact initiated continental-scale wildfires at 12.9 ka; the data do not support this idea, nor are continent-wide fires indi- cated at any time during deglaciation. There are, however, clear links between large climate changes and fire activity. Biomass burning gradually increased from the glacial period to the begin- ning of the Younger Dryas. Although there are changes in biomass burning during the Younger Dryas, there is no systematic trend. There is a further increase in biomass burning after the Younger Dryas. Intervals of rapid climate change at 13.9, 13.2, and 11.7 ka are marked by large increases in fire activity. The timing of changes in fire is not coincident with changes in human population density or the timing of the extinction of the megafauna. Although these factors could have contributed to fire-regime changes at individual sites or at specific times, the charcoal data indicate an important role for climate, and particularly rapid climate change, in deter- mining broad-scale levels of fire activity. biomass burning charcoal comet Younger Dryas
Four-year response of underplanted American chestnut (Castanea dentata) and three competitors to midstory removal, root trenching, and weeding treatments in an oak-hickory forest
American chestnut (Castanea dentata) has been killed or reduced to recurrent stump sprouts throughout its range following the importation of multiple pathogens in the 19th and early 20th centuries. Under- standing what drives chestnut growth and survival would aid the development of appropriate silvicultural guidelines for restoring the species once blight resistant stock is available. Here we compare the response of planted American and hybrid chestnut seedlings to that of important competitors, northern red oak (Quercus rubra), sugar maple (Acer saccharum) and red maple (A. rubrum), under treatments designed to evaluate the effects of various sources of competition on seedling growth and survival. After four years, American and hybrid chestnut was significantly taller in trenched plots (181.8 ± 12.4 cm; mean ± SE) compared to untrenched plots (127.5 ± 7.9 cm), weeded plots (174.5 ± 12.7 cm) compared to unweeded plots (130.1 ± 6.5 cm) and in midstory removal plots (156.6 ± 7.8) versus full canopy (88.8 ± 11.7 cm), and had outperformed the other species in most competitive environments. Chestnut was the only species to respond to every treatment with significant growth increases, displaying a nota- ble ability to capture growing space when it became available. We suggest that American chestnut res- toration may be more successful where early stand management provides chestnut a brief period of reduced competition. Specifically, midstory removal can increase survival and growth of underplanted American chestnut, and when combined with multi-stage shelterwood removals of the overstory and some amount of competition control, may constitute a viable restoration strategy for chestnut in many of the eastern oak-hickory forests where it was originally dominant.
Long-term aspen cover change in the western US
Quaking aspen (Populus tremuloides Michx.) is one of the most important tree species in the western United States due to its role in biodiversity, tourism, and other ecological and aesthetic values. This paper provides an overview of the drivers of long-term aspen cover change in the western US and how these drivers operate on diverse spatial and temporal scales. There has been substantial concern that aspen has been declining in the western US, but trends of aspen persistence vary both geographically and tem- porally. One important goal for future research is to better understand long-term and broad-scale changes in aspen cover across its range. Inferences about aspen dynamics are contingent on the spatial and temporal scales of inquiry, thus differences in scope and design among studies partly explain varia- tion among conclusions. For example, major aspen decline has been noted when the spatial scale of inquiry is relatively small and the temporal scale of inquiry is relatively short. Thus, it is important to consider the scale of research when addressing aspen dynamics. Successional replacement of aspen by conifer species is most pronounced in systems shaped by long fire intervals and can thus be seen as part of a normal, long-term fluctuation in forest composition. Aspen decline was initially reported primarily at the margins of aspen’s distribution, but may be becoming more ubiquitous due to the direct effects of climate (e.g. drought). In contrast, the indirect effects of recent climate (e.g. forest fires, bark beetle outbreaks, and compounded disturbances) appear to favor aspen and may facilitate expansion of this forest type. Thus, future aspen trends are likely to depend on the net result of the direct and indirect effects of altered climate.
PHENOLOGY OF MIXED WOODY–HERBACEOUS ECOSYSTEMS FOLLOWING EXTREME EVENTS: NET AND DIFFERENTIAL RESPONSES
We present responses of a mixed woody–herbaceous ecosystem type to an extreme event: regional-scale pinon pine mortality following an extended drought and the subsequent herbaceous green-up following the first wet period after the drought. This example highlights how reductions in greenness of the slower, more stable evergreen woody component can rapidly be offset by increases associated with resources made available to the relatively more responsive herbaceous component. We hypothesize that such two-phase phenological responses to extreme events are characteristic of many mixed woody– herbaceous ecosystems. Key words: die-off; disturbance; drought; extreme events; fire; Mesita del Buey; mortality; normalized difference vegetation index; phenology; pin ̃on; semiarid woodlands; woody and herbaceous plants.
Impacts of the EU biofuel policy on agricultural markets and land use
The European Union's Renewable Energy Directive (RED)1 sets an overall target of 20% of the EU's energy used to come from renewable sources by 2020. As part of this target, at least 10% of total transport fuel consumption is to come from renewable energies (RE). In parallel, the Fuel Quality Directive (FQD)2 requires fuel suppliers to reduce the carbon intensity of road fuels they supply by 6% in 2020. The EU Member States were required to report their expectations and plans on how to meet these targets in National Renewable Energy Action Plans (NREAP) by 30 June 2010, including the technology mix and the trajectory to reach them. However, in the end the extent to which the 2020 mandate will be met is uncertain. During the 2012 Workshop on 'Commodity Market Development in Europe – Outlook'3, held in Brussels, many participants highlighted the difficulty to reach such a level of biofuel consumption. In addition, according to the 2012 ECOFYS report on renewable energy progress and biofuels' sustainability, in 2012 the objectives for transport were already not being met. The European car industry is indeed not ready to use blends with high shares of biodiesel and ethanol. Moreover the contribution of second-generation biofuels towards meeting the target is expected to remain small. Furthermore the repeated droughts in recent years have put pressure on food prices and put forward the world food security debate. The use of food crops to produce biofuels instead of feeding the world has been criticised. Sustainability of biodiesel is especially questioned. In order to reduce the indirect land use change (ILUC) which may be caused by higher demand for food and feed crops for biofuel, on 17 October 2012 the European Commission (EC) published a proposal to amend the RED (COM(2012)595). It proposed to cap the amount of first-generation biofuels that can count towards the 10% renewable energy target at 5%4. In addition, the use of advanced biofuels, with no or low ILUC emissions, would be promoted by weighting their contribution towards fulfilling the target more favourably. The estimated ILUC emissions are also included in the greenhouse gas balance of biofuels for the purpose of compliance with the reporting obligations under the RED and FQD. Therefore the development of the biofuel market is highly uncertain, especially in the European Union (EU). This report aims to analyse different scenarios that could occur in the EU in the years to come.
Top 10 Places to Save for Endangered Species in a Warming World
If your house were on fire, what would you save? Would it be the precious items passed down in your family from genera- tion to generation? Or would you choose the irreplaceable photos that would disappear forever? Where do you even start? What if it wasn’t just your house, but your whole planet that was on fire?That is the scenario we face today. Climate change has arrived. No longer clouds gathering in the distance, the storm is here now—melting our titanic glaciers, drying our mighty rivers and setting our deserts ablaze. What do we save? For the Endangered Species Coalition, the answer is easy: we start with our endangered species. They are already on the brink of extinction, so vulnerable that a stressor such as climate change acts as a bulldozer, steaming full force ahead with the potential to shove them right over the edge of extinction.And where do we begin? We asked our member groups and our scientists, “If we want to save endangered species from climate change, what habitats do we need to protect?” Together, they identified ten ecosystems that are critical to conserve if we are to protect our nation’s endangered species from the ravages of climate change.
Sediment Trapping by Dams Creates Methane Emission Hot Spots
Inland waters transport and transform sub- stantial amounts of carbon and account for ∼18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (∼0.23 mmol CH4 m−2 d−1 vs ∼19.7 mmol CH4 m−2 d−1, respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation- driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%.
Increased River Alkalinization in the Eastern U.S.
The interaction between human activities and watershed geology is accelerating long-term changes in the carbon cycle of rivers. We evaluated changes in bicarbonate alkalinity, a product of chemical weathering, and tested for long-term trends at 97 sites in the eastern United States draining over 260 000 km2. We observed statistically significant increasing trends in alkalinity at 62 of the 97 sites, while remaining sites exhibited no significant decreasing trends. Over 50% of study sites also had statistically significant increasing trends in concentrations of calcium (another product of chemical weathering) where data were available. River alkalinization rates were significantly related to watershed carbonate lithology, acid deposition, and topography. These three variables explained ∼40% of variation in river alkalinization rates. The strongest predictor of river alkalinization rates was carbonate lithology. The most rapid rates of river alkalinization occurred at sites with highest inputs of acid deposition and highest elevation. The rise of alkalinity in many rivers throughout the Eastern U.S. suggests human-accelerated chemical weathering, in addition to previously documented impacts of mining and land use. Increased river alkalinization has major environmental implications including impacts on water hardness and salinization of drinking water, alterations of air−water exchange of CO2, coastal ocean acidification, and the influence of bicarbonate availability on primary production.
Linking primary production, climate and land use along an urban–wildland transect: a satellite view
Variation of green vegetation cover influences local climate dynamics, exchange of water–heat between land and atmosphere, and hydrological processes. However, the mechanism of interaction between vegetation and local climate change in subtropical areas under climate warming and anthropogenic disturbances is poorly understood. We analyzed spatial–temporal trends of vegetation with moderate-resolution imaging spectroradiometer (MODIS) vegetation index datasets over three sections, namely urban, urban–rural fringe and wildland along an urban–wildland transect in a southern mega-city area in China from 2000–2008. The results show increased photosynthetic activity occurred in the wildland and the stable urban landscape in correspondence to the rising temperature, and a considerable decrease of vegetation activity in the urban–rural fringe area, apparently due to urban expansion. On analyzing the controlling factors of climate change and human drivers of vegetation cover change, we found that temperature contributed to vegetation growth more than precipitation and that rising temperature accelerated plant physiological activity. Meanwhile, human-induced dramatic modification of land cover, e.g. conversion of natural forest and cropland to built-up areas in the urban–rural fringe, has caused significant changes of green vegetation fraction and overall primary production, which may further influence local climate. Keywords: vegetation greenness, environmental gradients, urban, transect, climate change, remote sensing, rural
Rethinking wedges
Stabilizing CO2 emissions at current levels for fifty years is not consistent with either an atmospheric CO2 concentration below 500 ppm or global temperature increases below 2 ◦C. Accepting these targets, solving the climate problem requires that emissions peak and decline in the next few decades, and ultimately fall to near zero. Phasing out emissions over 50 years could be achieved by deploying on the order of 19 ‘wedges’, each of which ramps up linearly over a period of 50 years to ultimately avoid 1 GtC y−1 of CO2 emissions. But this level of mitigation will require affordable carbon-free energy systems to be deployed at the scale of tens of terawatts. Any hope for such fundamental and disruptive transformation of the global energy system depends upon coordinated efforts to innovate, plan, and deploy new transportation and energy systems that can provide affordable energy at this scale without emitting CO2 to the atmosphere.
Sectoral contributions to surface water stress in the coterminous United States
Here, we assess current stress in the freshwater system based on the best available data in order to understand possible risks and vulnerabilities to regional water resources and the sectors dependent on freshwater. We present watershed-scale measures of surface water supply stress for the coterminous United States (US) using the water supply stress index (WaSSI) model which considers regional trends in both water supply and demand. A snapshot of contemporary annual water demand is compared against different water supply regimes, including current average supplies, current extreme-year supplies, and projected future average surface water flows under a changing climate. In addition, we investigate the contributions of different water demand sectors to current water stress. On average, water supplies are stressed, meaning that demands for water outstrip natural supplies in over 9% of the 2103 watersheds examined. These watersheds rely on reservoir storage, conveyance systems, and groundwater to meet current water demands. Overall, agriculture is the major demand-side driver of water stress in the US, whereas municipal stress is isolated to southern California. Water stress introduced by cooling water demands for power plants is punctuated across the US, indicating that a single power plant has the potential to stress water supplies at the watershed scale. On the supply side, watersheds in the western US are particularly sensitive to low flow events and projected long-term shifts in flow driven by climate change. The WaSSI results imply that not only are water resources in the southwest in particular at risk, but that there are also potential vulnerabilities to specific sectors, even in the ‘water-rich’ southeast. Keywords: water resources, surface water, water stress
The Latest on Volcanic Eruptions and Climate
2nd paragraph: It is well known that large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with a life- time of several months to about 2 years. The radiative effects of these aerosol clouds produce global cooling and are an important natural cause of climate change. Regional responses include winter warming of Northern Hemisphere continents and weakening of summer Asian and African monsoons. Even though there has not been a large eruption since the eruption of Mount Pinatubo in the Philippines on 15 June 1991, research contin- ues to produce interesting results.
The False Spring of 2012, Earliest in North American Record
2nd paragraph: As global climate warms, increasingly warmer springs may combine with the random climatological occurrence of advective freezes, which result from cold air moving from one region to another, to dramatically increase the future risk of false springs, with profound ecological and economic consequences [e.g., Gu et al., 2008; Marino et al., 2011; Augspurger, 2013]. For example, in the false spring of 2012, an event embedded in long-term trends toward earlier spring [e.g., Schwartz et al., 2006], the frost damage to fruit trees totaled half a billion dollars in Michigan alone, prompting the federal government to declare the state a disaster area [Knudson, 2012].
Rapid growth in CO2 emissions after the 2008–2009 global financial crisis.pdf
1st paragraph: Global carbon dioxide emissions from fossil-fuel combustion and cement production grew 5.9% in 2010, surpassed 9 Pg of carbon (Pg C) for the first time, and more than offset the 1.4% decrease in 2009. The impact of the 2008–2009 global financial crisis (GFC) on emissions has been short-lived owing to strong emissions growth in emerging economies, a return to emissions growth in developed economies, and an increase in the fossil-fuel intensity of the world economy.
Persistent reduced ecosystem respiration after insect disturbance in high elevation forests
Amid a worldwide increase in tree mortality, mountain pine beetles (Dendroctonus ponderosae Hopkins) have led to the death of billions of trees from Mexico to Alaska since 2000. This is predicted to have important carbon, water and energy balance feedbacks on the Earth system. Counter to current projections, we show that on a decadal scale, tree mortality causes no increase in ecosystem respiration from scales of several square metres up to an 84 km2 valley. Rather, we found comparable declines in both gross primary productivity and respiration suggesting little change in net flux, with a transitory recovery of respiration 6–7 years after mortality associated with increased incorporation of leaf litter C into soil organic matter, followed by further decline in years 8–10. The mechanism of the impact of tree mortality caused by these biotic disturbances is consistent with reduced input rather than increased output of carbon. Keywords Carbon balance, disturbance, ecosystem respiration, gross primary productivity, insect outbreak, lodgepole pine, mountain pine beetle, mountain West, subalpine forest.
Global shifts towards positive species interactions with increasing environmental stress
The study of positive species interactions is a rapidly evolving field in ecology. Despite decades of research, controversy has emerged as to whether positive and negative interactions predictably shift with increasing environmental stress as hypothesised by the stress-gradient hypothesis (SGH). Here, we provide a synthesis of 727 tests of the SGH in plant communities across the globe to examine its generality across a variety of ecological factors. Our results show that plant interactions change with stress through an outright shift to facilitation (survival) or a reduction in competition (growth and reproduction). In a limited number of cases, plant interactions do not respond to stress, but they never shift towards competition with stress. These findings are consistent across stress types, plant growth forms, life histories, origins (invasive vs. native), climates, ecosystems and methodologies, though the magnitude of the shifts towards facilitation with stress is dependent on these factors. We suggest that future studies should employ standardised defini- tions and protocols to test the SGH, take a multi-factorial approach that considers variables such as plant traits in addition to stress, and apply the SGH to better understand how species and communities will respond to environmental change. Keywords Biotic interactions, community ecology, ecosystems and climates, environmental stress, facilitation, invasive species, meta-analysis, plant traits, the stress-gradient hypothesis.
How does climate change influence demographic processes of widespread species? Lessons from the comparative analysis of contrasted populations of roe deer
How populations respond to climate change depends on the interplay between life history, resource avail- ability, and the intensity of the change. Roe deer are income breeders, with high levels of allocation to reproduction, and are hence strongly constrained by the availability of high quality resources during spring. We investigated how recent climate change has influenced demographic processes in two populations of this widespread species. Spring began increasingly earlier over the study, allowing us to identify 2 periods with contrasting onset of spring. Both populations grew more slowly when spring was early. As expected for a long-lived and iteroparous species, adult survival had the greatest potential impact on population growth. Using perturbation analyses, we measured the relative contribution of the demographic parameters to observed variation in population growth, both within and between periods and populations. Within peri- ods, the identity of the critical parameter depended on the variance in growth rate, but variation in recruit- ment was the main driver of observed demographic change between periods of contrasting spring earliness. Our results indicate that roe deer in forest habitats cannot currently cope with increasingly early springs. We hypothesise that they should shift their distribution to richer, more heterogeneous landscapes to offset energetic requirements during the critical rearing stage. Keywords Age-structured populations, demographic change, income breeding, perturbation analysis, population growth, Recruitment, Stochastic environment, Survival.
Genetic diversity in widespread species is not congruent with species richness in alpine plant communities
The Convention on Biological Diversity (CBD) aims at the conservation of all three levels of biodiversity, that is, ecosystems, species and genes. Genetic diversity represents evolutionary potential and is important for ecosystem functioning. Unfortunately, genetic diversity in natural populations is hardly considered in conservation strategies because it is difficult to measure and has been hypothesised to co-vary with species richness. This means that species richness is taken as a surrogate of genetic diversity in conservation plan- ning, though their relationship has not been properly evaluated. We tested whether the genetic and species levels of biodiversity co-vary, using a large-scale and multi-species approach. We chose the high-mountain flora of the Alps and the Carpathians as study systems and demonstrate that species richness and genetic diversity are not correlated. Species richness thus cannot act as a surrogate for genetic diversity. Our results have important consequences for implementing the CBD when designing conservation strategies. Keywords alpine vascular plants, Alps, biodiversity conservation, Carpathians, genetic diversity, species richness.
