Bending the carbon curve: fire management for carbon resilience under climate change

Context

Forest landscapes are increasingly managed for fire resilience, particularly in the western US which has recently experienced drought and widespread, high-severity wildfires. Fuel reduction treatments have been effective where fires coincide with treated areas. Fuel treatments also have the potential to reduce drought-mortality if tree density is uncharacteristically high, and to increase long-term carbon storage by reducing high-severity fire probability.

Objective

Assess whether fuel treatments reduce fire intensity and spread and increase carbon storage under climate change.

Methods

We used a simulation modeling approach that couples a landscape model of forest disturbance and succession with an ecosystem model of carbon dynamics (Century), to quantify the interacting effects of climate change, fuel treatments and wildfire for carbon storage potential in a mixed-conifer forest in the western USA.

Results

Our results suggest that fuel treatments have the potential to ‘bend the C curve’, maintaining carbon resilience despite climate change and climate-related changes to the fire regime. Simulated fuel treatments resulted in reduced fire spread and severity. There was partial compensation of C lost during fuel treatments with increased growth of residual stock due to greater available soil water, as well as a shift in species composition to more drought- and fire-tolerant Pinus jeffreyi at the expense of shade-tolerant, fire-susceptible Abies concolor.

Conclusions

Forest resilience to global change can be achieved through management that reduces drought stress and supports the establishment and dominance of tree species that are more fire- and drought-resistant, however, achieving a net C gain from fuel treatments may take decades.

     

High-resolution climate change mapping with gridded historical climate products

The detection of climate-driven changes in coupled human-natural systems has become a focus of climate research and adaptation efforts around the world. High-resolution gridded historical climate (GHC) products enable analysis of recent climatic changes at the local/regional scales most relevant for research and decision-making, but these fine-scale climate datasets have several caveats. We analyzed two 4 km GHC products to produce high-resolution temperature trend maps for the US Northeast from 1980 to 2009, and compared outputs between products and with an independent climate record. The two products had similar spatial climatologies for mean temperatures, agreed on temporal variability in regionally averaged trends, and agreed that warming has been greater for minimum versus maximum temperatures. Trend maps were highly heterogeneous, i.e., a patchy landscape of warming, cooling and stability that varied by month, but with local-scale anomalies persistent across months (e.g., cooling ‘pockets’ within warming zones). In comparing trend maps between GHC products, we found large local-scale disparities at high elevations and along coastlines; and where weather stations were sparse, a single-station disparity in input data resulted in a large zone of trend map disagreement between products. Preliminary cross-validation with an independent climate record indicated substantial and complex errors for both products. Our analysis provided novel landscape-scale insights on climate change in the US Northeast, but raised questions about scale and sources of uncertainty in high-resolution GHC products and differences among the many products available. Given rapid growth in their use, we recommend exercising caution in the analysis and interpretation of high-resolution climate maps.     

Bird response to future climate and forest management focused on mitigating climate change

Context

Global temperatures are projected to increase and affect forests and wildlife populations. Forest management can potentially mitigate climate-induced changes through promoting carbon sequestration, forest resilience, and facilitated change.

Objectives

We modeled direct and indirect effects of climate change on avian abundance through changes in forest landscapes and assessed impacts on bird abundances of forest management strategies designed to mitigate climate change effects.

Methods

We coupled a Bayesian hierarchical model with a spatially explicit landscape simulation model (LANDIS PRO) to predict avian relative abundance. We considered multiple climate scenarios and forest management scenarios focused on carbon sequestration, forest resilience, and facilitated change over 100 years.

Results

Management had a greater impact on avian abundance (almost 50% change under some scenarios) than climate (<3% change) and only early successional and coniferous forest showed significant change in percent cover across time. The northern bobwhite was the only species that changed in abundance due to climate-induced changes in vegetation. Northern bobwhite, prairie warbler, and blue-winged warbler generally increased in response to warming temperatures but prairie warbler exhibited a non-linear response and began to decline as summer maximum temperatures exceeded 36 °C at the end of the century.

Conclusion

Linking empirical models with process-based landscape change models can be an effective way to predict climate change and management impacts on wildlife, but time frames greater than 100 years may be required to see climate related effects. We suggest that future research carefully consider species-specific effects and interactions between management and climate.

     

The challenges of forest modeling given climate change

Forest landscape modeling encompasses many core principles of landscape ecology: spatial resolution and extent, spatially explicit local and regional context, disturbance dynamics, integration of human activity, and explicit links to management and policy. Models of forest change inform land managers about strategies to adapt to the effects of an altered or changing environment across large, forested landscapes. Despite past successes, major challenges remain for landscape ecologists representing the dynamics of complex systems with a computer model, particularly given climate change. Here, I review major modeling challenges unique to climate change and suggest paths forward as climate change increasingly becomes a focus of landscape modeling efforts.     

Potential climate change impacts on green infrastructure vegetation

This study investigated the impacts of successive simulated droughts and floods on two plant species (Carex lurida and Liriope muscari) commonly installed in green-infrastructure (GI) sites built in the urban northeast USA. The instantaneous stomatal conductance, and belowground biomass growth (in a second drought experiment only) were used as metrics, since they are indicators of the ability of plants to provide ecosystem functions such as transpiration and carbon uptake. The results indicate that both species have greater tolerance for floods than for droughts. Signs of stress were only evident after a simulated flood exceeding the duration of 95% of all storms that occurred in this geographic region between 1950 and 2000. By contrast, simulated droughts had a more pronounced effect on both the instantaneous conductance measures during drought and the recovery following the cessation of drought in both species. Liriope subjected to drought treatments were all able to recover and to re-establish stomatal conductance levels similar to those displayed by a control group even after repeated drought treatments. By contrast, Carex showed reduced recovery after multiple droughts, in two separate rounds of experiments. However, regardless of moisture conditions and treatment, Carex generally displayed higher stomatal conductance than Liriope, indicating greater transpiration, and CO₂ uptake than Liriope. The belowground biomass results supported this finding, i.e. Carex gained more belowground biomass than Liriope during all experiments. At the end of the experiment, the Carex subjected to drought had less than one sixth the belowground biomass of the control treatment, whereas for Liriope this ratio was only 50% (drought to control). The drought treatments, therefore, reduced the biomass of Carex more than it did Liriope, when compared to the respective control plants. Nonetheless, both species survived repeated cycles of droughts and floods, suggesting that these particular species are both likely suitable for use in GI facilities, despite projected future increases in the frequency and intensity of floods and droughts in this geographic region. From a practical perspective, the results suggest no need for irrigation or potential replacement of plants in GI systems in a changed climate.     

Synergistic effects of climate and land cover: grassland birds are more vulnerable to climate change

Context

Climate change is not occurring over a homogeneous landscape and the quantity and quality of available land cover will likely affect the way species respond to climate change. The influence of land cover on species’ responses to climate change, however, is likely to differ depending on habitat type and composition.

Objectives

Our goal was to investigate responses of forest and grassland breeding birds to over 20 years of climate change across varying gradients of forest and grassland habitat. Specifically, we investigated whether (i) increasing amounts of available land cover modify responses of forest and grassland-dependent birds to changing climate and (ii) the effect of increasing land cover amount differs for forest and grassland birds.

Methods

We used Bayesian spatially-varying intercept models to evaluate species- and community-level responses of 30 forest and 10 grassland birds to climate change across varying amounts of their associated land cover types.

Results

Responses of forest birds to climate change were weak and constant across a gradient of forest cover. Conversely, grassland birds responded strongly to changing climatic conditions. Specifically, increasing temperatures led to higher probabilities of localized extinctions for grassland birds, and this effect was intensified in regions with low amounts of grassland cover.

Conclusions

Within the context of northeastern forests and grasslands, we conclude that forests serve as a possible buffer to the impacts of climate change on birds. Conversely, species occupying open, fragmented grassland areas might be particularly at risk of a changing climate due to the diminished buffering capacity of these ecosystems.

     

Genetically-informed population models improve climate change vulnerability assessments

Landscape Ecology - Climate change will cause species extinctions that will be exacerbated by human-caused landscape changes, preventing species from tracking shifting climatic niches. Although...     

Spatial resilience of forested landscapes under climate change and management

Context

Resilience, the ability to recover from disturbance, has risen to the forefront of scientific policy, but is difficult to quantify, particularly in large, forested landscapes subject to disturbances, management, and climate change.

Objectives

Our objective was to determine which spatial drivers will control landscape resilience over the next century, given a range of plausible climate projections across north-central Minnesota.

Methods

Using a simulation modelling approach, we simulated wind disturbance in a 4.3 million ha forested landscape in north-central Minnesota for 100 years under historic climate and five climate change scenarios, combined with four management scenarios: business as usual (BAU), maximizing economic returns (‘EcoGoods’), maximizing carbon storage (‘EcoServices’), and climate change adaption (‘CCAdapt’). To estimate resilience, we examined sites where simulated windstorms removed >70% of the biomass and measured the difference in biomass and species composition after 50 years.

Results

Climate change lowered resilience, though there was wide variation among climate change scenarios. Resilience was explained more by spatial variation in soils than climate. We found that BAU, EcoGoods and EcoServices harvest scenarios were very similar; CCAdapt was the only scenario that demonstrated consistently higher resilience under climate change. Although we expected spatial patterns of resilience to follow ownership patterns, it was contingent upon whether lands were actively managed.

Conclusions

Our results demonstrate that resilience may be lower under climate change and that the effects of climate change could overwhelm current management practices. Only a substantial shift in simulated forest practices was successful in promoting resilience.

     

Scenarios of long-term farm structural change for application in climate change impact assessment

Towards 2050, climate change is one of the possible drivers that will change the farming landscape, but market, policy and technological development may be at least equally important. In the last decade, many studies assessed impacts of climate change and specific adaptation strategies. However, adaptation to climate change must be considered in the context of other driving forces that will cause farms of the future to look differently from today’s farms. In this paper we use a historical analysis of the influence of different drivers on farm structure, complemented with literature and stakeholder consultations, to assess future structural change of farms in a region under different plausible futures. As climate change is one of the drivers considered, this study thus puts climate change impact and adaptation into the context of other drivers. The province of Flevoland in the north of The Netherlands was used as case study, with arable farming as the main activity. To account for the heterogeneity of farms and to indicate possible directions of farm structural change, a farm typology was developed. Trends in past developments in farm types were analyzed with data from the Dutch agricultural census. The historical analysis allowed to detect the relative importance of driving forces that contributed to farm structural changes. Simultaneously, scenario assumptions about changes in these driving forces elaborated at global and European levels, were downscaled for Flevoland, to regional and farm type level in order to project impacts of drivers on farm structural change towards 2050. Input from stakeholders was also used to detail the downscaled scenarios and to derive historical and future relationships between drivers and farm structural change. These downscaled scenarios and future driver-farm structural change relationships were used to derive quantitative estimations of farm structural change at regional and farm type level in Flevoland. In addition, stakeholder input was used to also derive images of future farms in Flevoland. The estimated farm structural changes differed substantially between the two scenarios. Our estimations of farm structural change provide a proper context for assessing impacts of and adaptation to climate change in 2050 at crop and farm level.     

Recovery dynamics and climate change effects to future New England forests

Context

Forests throughout eastern North America continue to recover from broad-scale intensive land use that peaked in the nineteenth century. These forests provide essential goods and services at local to global scales. It is uncertain how recovery dynamics, the processes by which forests respond to past forest land use, will continue to influence future forest conditions. Climate change compounds this uncertainty.

Objectives

We explored how continued forest recovery dynamics affect forest biomass and species composition and how climate change may alter this trajectory.

Methods

Using a spatially explicit landscape simulation model incorporating an ecophysiological model, we simulated forest processes in New England from 2010 to 2110. We compared forest biomass and composition from simulations that used a continuation of the current climate to those from four separate global circulation models forced by a high emission scenario (RCP 8.5).

Results

Simulated forest change in New England was driven by continued recovery dynamics; without the influence of climate change forests accumulated 34 % more biomass and succeed to more shade tolerant species; Climate change resulted in 82 % more biomass but just nominal shifts in community composition. Most tree species increased AGB under climate change.

Conclusions

Continued recovery dynamics will have larger impacts than climate change on forest composition in New England. The large increases in biomass simulated under all climate scenarios suggest that climate regulation provided by the eastern forest carbon sink has potential to continue for at least a century.

     

Forest fragmentation, climate change and understory fire regimes on the Amazonian landscapes of the Xingu headwaters

Understory fire modeling is a key tool to investigate the cornerstone concept of landscape ecology, i.e. how ecological processes relate to landscape structure and dynamics. Within this context, we developed FISC??a model that simulates fire ignition and spread and its effects on the forest carbon balance. FISC is dynamically coupled to a land-use change model to simulate fire regimes on the Amazonian landscapes of the Xingu Headwaters under deforestation, climate change, and land-use management scenarios. FISC incorporates a stochastic cellular automata approach to simulate fire spread across agricultural and forested lands. CARLUC, nested in FISC, simulates fuel dynamics, forest regrowth, and carbon emissions. Simulations of fire regimes under modeled scenarios revealed that the major current and future driver of understory fires is forest fragmentation rather than climate change. Fire intensity proved closely related to the landscape structure of the remaining forest. While climate change may increase the percentage of forest burned outside protected areas by 30% over the next four decades, deforestation alone may double it. Nevertheless, a scenario of forest recovery and better land-use management would abate fire intensity by 18% even in the face of climate change. Over this time period, the total carbon balance of the Xingu??s forests varies from an average net sink of 1.6?ton?ha^?1?year^?1 in the absence of climate change, fire and deforestation to a source of ?0.1?ton?ha^?1?year^?1 in a scenario that incorporates these three processes.     

Adaptive planting design and management framework for urban climate change adaptation and mitigation

Implementing measures to adapt and mitigate climate change effects in cities has been considered increasingly urgent since the quality of life, health, and well-being of urban residents is threatened by this change. Novel communities of plant species that emerge and thrive in the harsh conditions of cities may represent a promising opportunity to address climate change adaptation and mitigation through the planting design and management of urban green spaces. The objective of this study is to develop an adaptive planting design and management framework. The proposed framework is grounded on previous adaptive approaches and focuses on the opportunities emerging from novel plant communities in urban conditions. The framework comprises three main steps (1 – Climate change assessment, 2 – Plant species database, and 3 – Planting design and management procedure). A proposal on how the framework could be tested was developed for the city of Porto, Portugal. Still, the application of the framework can also be adjusted to other urban contexts, offering a starting point for experimentation and assessment of plants’ adaptation and mitigation capacities through design and management. As lack of knowledge and uncertainty about climate change limits global capacity to implement robust adaptation and mitigation strategies, building knowledge in an adaptive way and context-specific locations will be of paramount interest to tackle climate change in cities.     

气候资源变化对陕西省猕猴桃生产的影响分析

基于陕西省关中地区的陈仓、眉县、杨凌、周至、户县、长安、灞桥、蓝田、临渭、华阴、华县和陕南地区的城固、洋县、勉县、佛坪等15个称猴桃主产县区1961-2010年的气象资料,利用趋势分析、线性回归、突变检验等气候统计方法,重点分析该地区50年来影响猕猴桃生长发育的年平均气温、负积温、≥5℃年有效积温、≥10℃年有效积温、年降水量、4一10月猕猴桃生长期降水量等光热水资源的年际、周期以及时空分布变化趋势的规律与特点,分析了50年来气候资源变化对陕西省猕猴桃生产的影响。结果表明,猕猴桃主产县区热量资源增加明显,年平均气温和≥10℃年有效积温总体上呈现上升趋势,种植区初霜日推迟、终霜日提前,无霜期呈明显增加趋势。降水变化趋势不明显,而年日照时数呈现明显减少趋势。除降水外,光热资源的变化均发生了突变,且关中地区的变化比陕南地区较为显著。从气候变化的特点上看,关中地区的光热资源变化增加了称猴桃生产的不确定性,而汉中盆地的气候资源变化趋势相对较弱,建议在该区域可适度增加猕猴桃种植规模。同时,气候变化的加剧,极端天气事件明显增多,猕猴桃的萌芽期冻害、高温热害等由于全球变化引起的气象灾害发生频率也呈现明显增加趋势,为猕猴桃优质生产带来了很大的不确定性,因此后期针对猕猴桃主要气象灾害风险进行研究是关注的重点。