Wildfire-contingent effects of fuel treatments can promote ecological resilience in seasonally dry conifer forests

2014 ◽  
Vol 44 (8) ◽  
pp. 843-854 ◽  
Author(s):  
Jens T. Stevens ◽  
Hugh D. Safford ◽  
Andrew M. Latimer
Keyword(s):  
Soil Moisture ◽  
Forest Restoration ◽  
Strong Support ◽  
Ecological Resilience ◽  
Tree Cover ◽  
Ecological Change ◽  
Conifer Forests ◽  
Tree Seedling ◽  
Fuel Treatments ◽  
Seasonally Dry

Fire suppression has made many seasonally dry conifer forests more susceptible to high-severity wildfires, which cause large changes in forest structure and function. In response, management agencies are applying fuel reduction treatments to millions of acres of forest, with the goal of moderating fire behavior by reducing tree density and understory fuel loads. However, despite their wide application, we still lack basic information about the extent to which these treatments contribute to forest restoration by increasing forest resilience to recurring wildfire events. To address this question, we established 664 plots across 12 different sites in California, USA, where wildfire burned through fuel treatments, and measured a suite of forest characteristics relating to overstory structure, understory cover, and woody plant regeneration. We tested a “wildfire-contingency” hypothesis that there should be strong interactions between treatment and fire, specifically that the direction and magnitude of fuel treatment effects on forest characteristics will depend on subsequent disturbance. This interaction hypothesis had strong support, driven largely by effects on trees: without wildfire, live-tree cover was lower in treated stands than in untreated stands, but after wildfire, it was higher in treated stands than in untreated stands. Treated stands had higher soil moisture and more shrub seedlings than untreated stands without wildfire but had greater soil moisture and fewer shrub seedlings than untreated stands after wildfire. Conversely, litter depth, litter cover, and tree seedling abundance were lower in treated stands than in untreated stands without wildfire but higher in treated stands than in untreated stands after wildfire. Ordination revealed that the magnitude of ecological change attributable to wildfire is lower in treated stands than in untreated stands. We conclude that properly implemented treatments can promote resilience to both first-entry and subsequent wildfires.

Variation in vegetation cover and seedling performance of tree species in a forest-savanna ecotone

2019 ◽  
Vol 35 (2) ◽  
pp. 74-82 ◽  
Author(s):  
Hamza Issifu ◽  
George K. D. Ametsitsi ◽  
Lana J. de Vries ◽  
Gloria Djaney Djagbletey ◽  
Stephen Adu-Bredu ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Cover ◽  
First Year ◽  
Transplant Experiment ◽  
Tree Seedling ◽  
Savanna Woodland ◽  
Specific Effects ◽  
Species Specific

AbstractDifferential tree seedling recruitment across forest-savanna ecotones is poorly understood, but hypothesized to be influenced by vegetation cover and associated factors. In a 3-y-long field transplant experiment in the forest-savanna ecotone of Ghana, we assessed performance and root allocation of 864 seedlings for two forest (Khaya ivorensis and Terminalia superba) and two savanna (Khaya senegalensis and Terminalia macroptera) species in savanna woodland, closed-woodland and forest. Herbaceous vegetation biomass was significantly higher in savanna woodland (1.0 ± 0.4 kg m−2 vs 0.2 ± 0.1 kg m−2 in forest) and hence expected fire intensities, while some soil properties were improved in forest. Regardless, seedling survival declined significantly in the first-year dry-season for all species with huge declines for the forest species (50% vs 6% for Khaya and 16% vs 2% for Terminalia) by year 2. After 3 y, only savanna species survived in savanna woodland. However, best performance for savanna Khaya was in forest, but in savanna woodland for savanna Terminalia which also had the highest biomass fraction (0.8 ± 0.1 g g−1 vs 0.6 ± 0.1 g g−1 and 0.4 ± 0.1 g g−1) and starch concentration (27% ± 10% vs 15% ± 7% and 10% ± 4%) in roots relative to savanna and forest Khaya respectively. Our results demonstrate that tree cover variation has species-specific effects on tree seedling recruitment which is related to root storage functions.

scholarly journals Evaluation of Tree Seedling Mortality and Protective Strategies in Riparian Forest Restoration

2008 ◽  
Vol 25 (3) ◽  
pp. 117-123 ◽  
Author(s):  
William S. Keeton
Keyword(s):  
Forest Restoration ◽  
Riparian Forest ◽  
Planting Density ◽  
Tree Seedling ◽  
Seedling Mortality ◽  
Order Stream ◽  
Growing Seasons ◽  
Deer Browse ◽  
Limited Effectiveness ◽  
Protective Strategies

Abstract Riparian forest restoration can be severely constrained by tree seedling mortality. I evaluated the effects of tree shelters and planting density on herbivory and seedling mortality at a restoration site in the Lake Champlain Basin of Vermont. Eighteen experimental units were established along a 5th-order stream and planted with bare-root seedlings of seven species associated with northern hardwood floodplain forests. Two treatments were applied in a factorial design: shelters versus no shelters and high versus low planting density. Mortality and herbivory data were collected over three growing seasons. Survivorship declined to 56.4% after three growing seasons and varied significantly by species. Planting density, presence/absence of shelters, and their interaction had significant effects on survival, browse, or girdling intensity when tested for all species combined. Browse rates were high (44%), whereas girdling rates were low (3.4%). Both browse (P < 0.001) and girdling (P = 0.022) contributed to seedling mortality. High rates of deer browse on seedlings in shelters were due, in part, to the short height (60 cm) of the shelters, suggesting a need for taller shelters. A large portion (39%) of dead seedlings were neither browsed nor girdled, signaling the importance of other mortality agents. An adaptive approach is recommended to compensate for high seedling mortality and the limited effectiveness of protective devices.

scholarly journals The application of resilience concepts in palaeoecology

The Holocene ◽  
2018 ◽  
Vol 28 (9) ◽  
pp. 1523-1534 ◽  
Author(s):  
Althea L Davies ◽  
Richard Streeter ◽  
Ian T Lawson ◽  
Katherine H Roucoux ◽  
William Hiles
Keyword(s):  
Spatial Scales ◽  
Environmental Parameters ◽  
Ecological Resilience ◽  
Ecological Change ◽  
Temporal Behaviour ◽  
Ecological Literature ◽  
Ecosystem Drivers ◽  
Further Development ◽  
Fundamental Limitation

The concept of resilience has become increasingly important in ecological and socio-ecological literature. With its focus on the temporal behaviour of ecosystems, palaeoecology has an important role to play in developing a scientific understanding of ecological resilience. We provide a critical review of the ways in which resilience is being addressed by palaeoecologists. We review ~180 papers, identifying the definitions or conceptualisations of ‘resilience’ that they use, and analysing the ways in which palaeoecology is contributing to our understanding of ecological resilience. We identify three key areas for further development. First, the term ‘resilience’ is frequently defined too broadly to be meaningful without further qualification. In particular, palaeoecologists need to distinguish between ‘press’ vs ‘pulse’ disturbances, and ‘ecological’ vs ‘engineering’ resilience. Palaeoecologists are well placed to critically assess the extent to which these dichotomies apply in real (rather than theoretical) ecosystems, where climate and other environmental parameters are constantly changing. Second, defining a formal ‘response model’ – a statement of the anticipated relationships between proxies, disturbances and resilience properties – can help to clarify arguments, especially inferred causal links, since the difficulty of proving causation is a fundamental limitation of palaeoecology for understanding ecosystem drivers and responses. Third, there is a need for critical analysis of the role of scale in ecosystem resilience. Different palaeoenvironmental proxies are differently able to address the various temporal and spatial scales of ecological change, and these limitations, as well as methodological constraints on inherently noisy proxy data, need to be explored and addressed.

Tree seedling response to LED spectra: implications for forest restoration

2018 ◽  
Vol 152 (3) ◽  
pp. 515-523 ◽  
Author(s):  
Antonio Montagnoli ◽  
R. Kasten Dumroese ◽  
Mattia Terzaghi ◽  
Jeremiah R. Pinto ◽  
Nicoletta Fulgaro ◽  
...  
Keyword(s):  
Forest Restoration ◽  
Tree Seedling

scholarly journals Detecting past changes in vegetation resilience in the context of a changing climate

2019 ◽  
Vol 15 (3) ◽  
pp. 20180768 ◽  
Author(s):  
W. John Calder ◽  
Bryan Shuman
Keyword(s):  
Climate Change ◽  
Fossil Record ◽  
Recovery Time ◽  
Vegetation History ◽  
Complete Recovery ◽  
Ecological Resilience ◽  
Ecological Change ◽  
Return To Equilibrium ◽  
History Record ◽  
Time Required

Anthropogenic climate change is continuously altering ecological responses to disturbance and must be accounted for when examining ecological resilience. One way to measure resilience in ecological datasets is by considering the amount and duration of change from a baseline created by perturbations, such as disturbances like wildfire. Recovery occurs when ecological conditions return to equilibrium, meaning that no subsequent changes can be attributed to the effects of the disturbance, but climate change often causes the recovered state to differ from the previous baseline. The palaeoecological record provides an opportunity to examine these expectations because palaeoclimates changed continuously; few periods existed when environmental conditions were stationary. Here we demonstrate a framework for examining resilience in palaeoecological records against the backdrop of a non-stationary climate by considering resilience as two components of (i) resistance (magnitude of change) and (ii) recovery (time required to return) to predicted equilibrium values. Measuring these components of resilience in palaeoecological records requires high-resolution fossil (e.g. pollen) records, local palaeoclimate reconstructions, a model to predict ecological change in response to climate change, and disturbance records measured at the same spatial scale as the ecological (e.g. vegetation history) record. Resistance following disturbance is measured as the deviation of the fossil record from the ecological state predicted by the palaeoclimate records, and recovery time is measured as the time required for the fossil record to return to predicted values. We show that some cases may involve nearly persistent equilibrium despite large climate changes, but that others can involve a shift to a new state without any complete recovery.

Flowering and fruiting phenologies of seasonal and aseasonal neotropical forests: the role of annual changes in irradiance

2007 ◽  
Vol 23 (2) ◽  
pp. 231-251 ◽  
Author(s):  
Jess K. Zimmerman ◽  
S. Joseph Wright ◽  
O. Calderón ◽  
M. Aponte Pagan ◽  
S. Paton
Keyword(s):  
Soil Moisture ◽  
Seasonal Variation ◽  
Solar Irradiance ◽  
Seasonal Changes ◽  
Light Availability ◽  
Barro Colorado Island ◽  
Wet Season ◽  
Neotropical Forests ◽  
Seasonally Dry ◽  
Solar Declination

The seasonality of both rainfall and solar irradiance might influence the evolution of flowering and fruiting in tropical forests. In seasonally dry forests, to the degree that soil moisture limits plant productivity, community-wide peaks in reproduction are expected during the rainy season, with seedfall and germination timed to allow seedlings to become well established while soil moisture is available. Where soil moisture is never seasonally limiting, seasonal changes in light availability caused by periods of cloudiness or seasonally low zenithal sun angles should favour reproduction during seasons when irradiance levels are high. To evaluate these predictions, we documented the timing of flower and fruit fall for 10 and 15 y at El Verde, Puerto Rico, and Barro Colorado Island (BCI), Panama. At El Verde, rainfall is abundant year-round and solar declination largely determines seasonal variation in irradiance. At BCI, rainfall is abundant throughout the 8-mo wet season while drought develops and average solar irradiance increases by 40–50% over the 4-mo dry season. Seasonal variation in the number of species flowering and fruiting at both sites was generally consistent with the hypothesis that seasonal variation in irradiance limits the evolution of reproductive phenologies. Community-level metrics provided no evidence for a similar role for moisture availability at BCI. Seasonal variation in irradiance also strongly influenced seed development times at both sites. Thus, community-wide phenologies reveal a strong signature of seasonal changes in irradiance, even in those forests that exhibit some degree of seasonality in rainfall.

Vegetation Control and Soil Moisture Depletion Related to Herbicide Treatments on Forest Plantations in Northeastern Oregon

2018 ◽  
Vol 32 (4) ◽  
pp. 461-474 ◽  
Author(s):  
Elizabeth Cole ◽  
Amanda Lindsay ◽  
Michael Newton ◽  
John D. Bailey
Keyword(s):  
Soil Moisture ◽  
First Year ◽  
Forest Plantations ◽  
Vegetative Cover ◽  
Tree Seedling ◽  
Vegetation Control ◽  
Herbicide Treatments ◽  
Inland Northwest ◽  
Comparable Control ◽  
Second Year

AbstractReforestation in the Inland Northwest, including northeastern Oregon, USA, is often limited by a dry climate and soil moisture availability during the summer months. Reduction of competing vegetative cover in forest plantations is a common method for retaining available soil moisture. Several spring and summer site preparation (applied prior to planting) herbicide treatments were evaluated to determine their efficacy in reducing competing cover, thus retaining soil moisture, on three sites in northeastern Oregon. Results varied by site, year, and season of application. In general, sulfometuron (0.14 kg ai ha–1 alone and in various mixtures), imazapyr (0.42 ae kg ha–1), and hexazinone (1.68 kg ai ha–1) resulted in 3 to 17% cover of forbs and grasses in the first-year when applied in spring. Sulfometuron+glyphosate (2.2 kg ha–1) consistently reduced grasses and forbs for the first year when applied in summer, but forbs recovered in the second year on two of three sites. Aminopyralid (0.12 kg ae ha–1)+sulfometuron applied in summer also led to comparable control of forb cover. In the second year after treatment, forb cover in treated plots was similar to levels in nontreated plots, and some species of forbs had increased relative to nontreated plots. Imazapyr (0.21 and 0.42 kg ha–1) at either rate, spring or summer 2007, or at lower rate (0.14 kg ha–1) with glyphosate in summer, provided the best control of shrubs, of which snowberry was the dominant species. Total vegetative cover was similar across all treatments seven and eight years after application, and differences in vegetation were related to site rather than treatment. In the first year after treatment, rates of soil moisture depletion in the 0- to 23-cm depth were correlated with vegetative cover, particularly late season soil moisture, suggesting increased water availability for tree seedling growth.

Rock water as a key resource for ecosystems with thin soils: Digging deep trees subsidize patches of surficial grasses

2020 ◽  
Author(s):  
Nicola Montaldo ◽  
Roberto Corona ◽  
Serena Sirigu ◽  
Luca Piroddi ◽  
Matteo Curreli ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Leaf Area ◽  
Deep Water ◽  
Forest Cover ◽  
Water Flux ◽  
Soil Layer ◽  
Tree Cover ◽  
Hydraulic Redistribution ◽  
Water Yield ◽  
Drought Severity

&lt;p&gt;Mediterranean mountainous areas of shallow soil often display a mosaic of tree clumps surrounded by grass. During dry seasons, evapotranspiration (&lt;em&gt;ET&lt;/em&gt;) cannot be met by soil moisture. However, the combined role and dynamics of water extracted from the underlying rock, and the competition between adjacent patches of trees and grass, has not been investigated. We quantified the role rock water plays in the seasonal dynamics of evapotranspiration, and its components, over a patchy landscape in the context of current and past seasonal climate changes, and land-cover change strategies. Soil water budget, using precipitation (&lt;em&gt;P&lt;/em&gt;), &lt;em&gt;ET&lt;/em&gt;, and soil moisture changes (&amp;#916;&lt;em&gt;S&lt;/em&gt;; ~17 cm soil layer), suggests deep water uptake by roots of trees (&lt;em&gt;f&lt;sub&gt;d&lt;/sub&gt;&lt;/em&gt;; 0.8 &amp;#8211; 0.9 mm/d), penetrating into the fractured basalt below clumps and the surrounding pasture, subsidized grass transpiration in spring through hydraulic redistribution. However, in summer trees used all the deep water absorbed (0.79 mm/d; &lt;em&gt;f&lt;sub&gt;d&lt;/sub&gt;&lt;/em&gt; &gt; tree transpiration). A 15-year dataset shows that, with increasing seasonal drought-severity (potential &lt;em&gt;ET&lt;/em&gt;/&lt;em&gt;P&lt;/em&gt;) to &gt;1.34, the vertical water flux through the bottom of the thin soil layer transitions from drainage to uptake in support of &lt;em&gt;ET&lt;/em&gt;. A hypothetical grass-covered landscape, with no access to deep water, would require 0.68 &amp;#8211; 0.85 mm/d more than is available from &lt;em&gt;P&lt;/em&gt; and &amp;#916;&lt;em&gt;S&lt;/em&gt;, forcing shortened growing season and/or lower leaf area. In summer, &lt;em&gt;ET&lt;/em&gt; in such a landscape would be half that of the existing mosaic, with consequences to energy balance. The vegetation mosaic may represent trending equilibrium, as long-term decreasing winter precipitation and increasing spring potential evaporation suggest drying climate. Intervention policies to increase water yield by reducing tree cover will curtail grass access to rock moisture, while attempting to increase tree-related products by increasing forest cover will limit water availability per tree leaf area. Both changes may further reduce ecosystem stability.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals How Diverse is Tree Planting in the Central Plateau of Burkina Faso? Comparing Small-Scale Restoration with Other Planting Initiatives

Forests ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 227 ◽  
Author(s):  
Michel Valette ◽  
Barbara Vinceti ◽  
Daouda Traoré ◽  
Alain Touta Traoré ◽  
Emma Lucie Yago-Ouattara ◽  
...  
Keyword(s):  
Burkina Faso ◽  
Land Tenure ◽  
Tree Species ◽  
Forest Restoration ◽  
Tree Planting ◽  
Species Selection ◽  
Tree Cover ◽  
Small Scale ◽  
Seed Sources ◽  
Tree Seed

In the Sahelian region, different approaches are being used to halt environmental degradation and restore tree cover, with varying degrees of success. Initiatives vary according to projects’ objectives, type of land to restore, and technical practices used (natural regeneration, farmer-managed assisted regeneration, enrichment planting, etc.). This study investigates tree planting choices and selection of tree seed sources in some villages of the Central region of Burkina Faso. The study targeted 96 farmers and compared planting practices adopted by farmers involved in small-scale forest restoration using fences, with those not involved in this initiative. The objective was to understand what portfolio of tree species were planted, what factors influenced tree species selection, what tree seed sources were used, what collection practices were generally adopted, and whether there were significant differences between types of farmers. The results showed that the use of fencing to promote forest restoration support the planting of a more diverse portfolio of tree species than other small scale efforts and includes a greater representation of indigenous trees. Fenced plots have therefore a conservation value in landscapes where the diversity of tree species is progressively declining. In addition to the use of fences, some other key factors affect tree planting, mainly land tenure, availability of diverse tree seed sources, and availability of land. Farmers tend to collect directly most of the planting material they need, but in the majority of cases they do not follow recommended best practices. In light of the ambitious forest restoration targets of Burkina Faso and the need to provide diverse options to rural communities to enhance their resilience vis-à-vis increasing environmental challenges, strengthening the capacity of farmers in tree planting and establishing a robust tree seed systems are crucial targets.

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