Plant Resprouting Research Articles

A systematic review of resprouting in woody plants and potential implications for the management of urban plantings.

Naturalistic plantings, such as meadow-style plantings, can improve the quality of urban green spaces through aesthetic, biodiversity and low maintenance features. Species selection for, and maintenance of naturalistic plantings are key to their success. While herbaceous and grassy meadows can be mowed, naturalistic plantings with woody plants require more intense maintenance to remove biomass and promote resprouting. We aim to understand woody plant responses to diverse disturbance regimes to potentially inform the selection and management of woody species in urban plantings. We conducted a quantitative systematic literature review of 72 papers and investigated what main external (climate, disturbance regime) and internal (buds, life stage, storage reserves) factors influence the resprouting response of woody plants. We found resprouting literature is geographically widespread for woody plants, but studies are skewed towards Temperate climates in USA and Australia, with a focus on high severity and high frequency fire disturbance. Resprouting response was mostly defined as a continuous response to disturbance dependent on disturbance regime, climate and plant traits. Maintenance and management of naturalistic woody plantings, through hard pruning techniques such as coppicing, may be informed by analogous high severity and high frequency disturbance studies. However, the literature on woody plant resprouting has several knowledge gaps for lower severity and lower frequency disturbance regimes and in more arid climates. Future research should evaluate the response of naturalistic woody plantings to disturbance in specific urban contexts.

Drivers of post‐fire resprouting success in restored Banksia woodlands

AbstractDisturbances can alter persistence trajectories of restored ecosystems. Resprouting is a common response of plants to disturbances such as fire or herbivory. Therefore, understanding a plant's resprouting response can inform successful restoration. We investigated patterns and drivers of resprouting following fire in fire‐prone Banksia woodlands restored after sand mining in the Mediterranean‐climate region of Western Australia. We applied experimental fire to samples of nine species with different resprouting types (rhizome, root crown, root sucker and lignotuber) across a 4‐ to 27‐year‐old restoration chronosequence. We investigated the influence of pre‐fire plant size, restoration age and soil conditions on resprouting success, defined by: (i) the probability of resprouting (measured ~5 months after fire), (ii) the probability of surviving the first summer and, (iii) vigour (both measured ~12 months post‐fire). We found that the probability of initial resprouting was high across most species, but summer survival was lower but comparable to that in other post‐mining restored ecosystems following fire. Generally, pre‐fire plant size did not influence probability of resprouting, while size and soil conditions were important for two species survival. Pre‐fire plant size was a significant predictor of vigour for all species with soil conditions influencing four species. Restoration age significantly influenced survival of three species. However, as our models explained low amounts of variation in probabilities of resprouting and survival (R2 = <0.11), other factors influencing resprouting success remain unidentified. Resprouting response to fire disturbance in restored Banksia woodlands are species and resprouter type specific, with plant size and soil conditions potentially more informative for understanding responses to disturbances than restoration age alone.

A 6-year study on the mortality dynamics of sprouts germinated on Schima superba after a severe ice storm in southern China.

Natural disturbances modify forest structure by affecting regeneration dynamics and can change main ecosystem functions. An ice storm unusually took place in southern China in early 2008, which caused huge damage to forests. Resprouting of woody plants in a subtropical forest has received little attention. The role of survival time and mortality has been assessed for newsprouts after an ice storm. In this study, damage types, in addition to the annual number and mortality rates of sprouts for all tagged and sampled resprouted Chinese gugertree (Schima superba Gardner & Champ.) individuals more than or equal to 4 cm in basal diameter (BD), were monitored. A total of six plots (20 m × 20 m) wererecorded in a subtropical secondary forest dominated by S. superba in Jianglang Mountain, China. This investigation had been conducted for six consecutive years. The results showed that the survival rates of the sprouts were dependent on the year they sprouted. The earlier the year they boomed, the lower the mortality. The sprouts produced in 2008 were of the highest vitality and survival rates. Sprouts of the decapitated trees exhibited a better survival rate than those of uprooted or leaning trees. Sprouting position also plays a role in regeneration. Sprouts at the basal trunks of uprooted trees and the sprouts at the upper trunksof the decapitated trees exhibited the lowest mortality. The relationship between the accumulative mortality rate and the average diameter of new sprouts isaffected by damage types. We reported the mortality dynamics of sproutsin a subtropical forest after a rare natural disaster. This information could serve asa reference for the construction of a branch sprout dynamic model ormanagement of forest restoration after ice storms.

Drought Timing Modulates Soil Moisture Thresholds for CO2 Fluxes and Vegetation Responses in an Experimental Alpine Grassland

Drought timing determines the degree to which dry events impact ecosystems, with the ability of key processes to withstand change differing between drought periods. Findings indicate that drought timing effects vary across ecosystems, with few studies focusing on alpine grasslands. We conducted a mesocosm experiment using small grassland monoliths collected in September from the high Alps and left to overwinter at 0 °C until the experiment began in lowland Italy under late-winter outdoor conditions. Together with watered controls, we imposed three different drought treatments (zero precipitation): (1) one-month early-drought immediately after simulated snowmelt; (2) one-month mid-drought a month after melt-out; and (3) continuous two-month drought across the entire experimental period. Ecosystem responses were assessed by measuring CO2 fluxes, while vegetation responses were investigated by measuring aboveground net primary production (ANPP) of graminoids and forbs and post-harvest resprouting after one-month rehydration. We found that ecosystem respiration and gross ecosystem production (GEP) during the day were more negatively affected by mid-season drought compared to drought starting early in the season. By the end of treatments, GEP reduction under mid-season drought was similar to that of a continuous two-month drought. ANPP reduction was similar in early- and mid-drought treatments, showing a greater decrease under an enforced two-month period without precipitation. Plant resprouting, however, was only reduced in full- and mid-season drought pots, with forbs more negatively affected than graminoids. Seasonal soil moisture variation can account for these patterns: remaining winter moisture allowed almost full canopy development during the first month of the season, despite precipitation being withheld, while soil moisture depletion in the second month, resulting from higher temperatures and greater biomass, caused a collapse of gas exchange and diminished plant resprouting. Our data illustrates the importance of the timing of zero-precipitation periods for both plant and ecosystem responses in alpine grasslands.

Coppicing as a driver of plant resprouting and the regeneration of a Caatinga dry forest

Resprouting is a widespread mechanism through which woody plants recover from biomass loss and/or abiotic stress, particularly in fire-prone ecosystems. Here, we assess the resprouting responses to coppicing exhibited by woody plant species in a human-modified landscape of Caatinga dry forest, in the northeast of Brazil. A total of 150 resprouts from 19 species (trees and shrubs) were experimentally coppiced. Shoot performance (number of new shoots, length, diameter and coppicing capacity) and mortality were monitored through a 15-mo period. Resprout diameter, chronic disturbance and environmental factors (rainfall, soil fertility and light availability) were assessed as explanatory variables. Of the144 coppiced resprouts, 72.2 % produced new shoots, with a total of 217 new shoots across the 19 focal species and emerged vigorously across all resprout types (root, root collar and stem). Shoot density reached 1.5 ± 1.2 shoots per resprout, with a length of 11.33 ± 10.1 cm and a diameter of 0.2 ± 0.1 cm. When pooling all new shoots across species, resprout diameter was found to have a positive effect on shoot number, length, diameter and coppicing capacity. At species level, resprout diameter was also the most important predictor. However, chronic disturbance had both negative and positive effects on some performance indicators of some species, as did rainfall, soil fertility and leaf area index. Finally, mortality rate was not affected by any of the explanatory variables assessed, neither at species nor community level. Our findings suggest that in human-modified landscapes of Caatinga dry forest, woody flora probably contain a large number of resprouting species (dominant species, in some cases), which are able to vigorously produce new shoots in response to biomass loss. Furthermore, we found shoot performance to be mediated by variables that affect plant growth. Although the Caatinga dry forest flora did not evolve in the presence of fire, resprouting is expected to play a key role in its regeneration and dynamics.

Resprouting ability differs among plant functional groups along a soil acidification gradient in a meadow: A rhizosphere perspective

Abstract Soil acidification as a global change factor can devastatingly affect plant growth and productivity. In frequently disturbed ecosystems, plant resprouting ability strongly determines biomass reconstruction and resilience after above‐ground damage. However, how plant regrowth responds to soil acidification remains largely unknown for, especially regarding the role of rhizosphere in mediating this response. We manipulated a soil‐acidification gradient via adding purified elemental sulphur powder at various rates (0–50 g S m−2 year−1) in a frequently mown meadow. Shoot regrowth of functional groups were measured after clipping and supporting roles of rhizosphere versus bulk soils were disentangled using isotope labelling along the acidification gradient. Regrowth of grasses and sedges increased while forbs decreased along the acidification gradient. The results suggest that grasses were competitors capable of taking up nutrients from both rhizosphere and bulk soils, while sedges were acid‐tolerators with lower sensitivity to decreased nitrogen‐mineralization rates. Forbs, as typical ruderals, were vulnerable to N competition with microbes, particularly in the rhizosphere soil. Therefore, biomass regrowth of forbs was explained more by physicochemical and biological parameters from the rhizosphere than bulk soil. Synthesis. Divergent interplay between plant functional groups and rhizosphere soils was the prominent driver for biomass regrowth responding to soil acidification.

Effects and response of the Cerrado ground-layer to frost along the canopy cover gradient.

Frost effects on savanna plant communities have been considered as analogous to those from fire, both changing community structure and filtering species composition. However, while frost impacts have been well-studied for the woody component of savannas, it is still poorly explored for the ground-layer community. Here, we investigated effects of frost in the Cerrado along a gradient of tree cover, focusing on ground-layer plant species, near the southern limit of the Cerrado in Brazil. We aimed to elucidate if the pattern already described for the tree layer also extends to the ground layer in terms of mimicking the effects of fire on vegetation structure and composition. We assessed how damage severity differs across species and across the tree-cover gradient, and we examined the recovery process after frost in terms of richness and community structure along the canopy cover gradient. Frost caused immediate and widespread dieback of the perennial ground-layer, with greatest impact on community structure where tree cover was lowest. However, frost did not reduce the number of species, indicating community resilience to this natural disturbance. Although frost mimicked the effects of fire in some ways, in other ways it differed substantially from fire. Unlike fire, frost increases litter cover and decreases the proportion of bare soil, likely hindering crucial processes for recovery of plant populations, such as seed dispersal, seed germination and plant resprouting. This finding calls attention to the risk of misguided conclusions when the ground layer is neglected in ecological studies of tropical savannas and grasslands.

Do mineral fertilisers have a deleterious effect on soil fertility? – case report

In the present case study, the aim is to show an example of the effect on residual fertility parameters (particularly with regard to the re-sprouting of plants after the harvesting of the aerial part), taken from a pot experiment, where modalities without fertilization, with mineral fertilization, with organic fertilization and with mixed fertilization were contrasted. Within this context it is possible to conclude the following: Mineral fertilization, alone, leads to a drastic inhibition of plant re-sprouting, that even in mixed fertilization situations (mineral + organic) it is considerable; in terms of residual microbiological activity, this phenomenon seems to be better correlated with reduced dehydrogenase activity than with β-Glucosidase activity.

Coppicing as a Driver of Plant Resprouting and the Regeneration of a Caatinga Dry Forest

Coppicing as a Driver of Plant Resprouting and the Regeneration of a Caatinga Dry Forest

Epicormic bud protection traits vary along a latitudinal gradient in a neotropical savanna

Regrowth via production of epicormic shoots is an important strategy for many woody plants after environmental disturbances such as fire, drought, and herbivory. Populations spreading across a broad latitudinal gradient offer opportunities to investigate if essential traits vary with heterogenous environmental conditions, such as in savanna ecosystems. This information can help us predict plant responses to climate change. Here, we evaluated if epicormic bud protection traits varied among populations of three focal savanna species (Miconia albicans, Solanum lycocarpum, and Zeyheria montana) that have a wide distribution and grow under variable climatic conditions. We randomly sampled 225 individuals over five spatially independent sites (7°, 10°, 15°, 18°, and 24° S) in Brazil, totaling 15 individuals per species per area. We analyzed anatomical transverse sections of five buds per species per area to assess the relative area occupied by crystal and phenolic idioblasts, the thickness of the trichome boundary layer, and to test if these traits were associated with climatic conditions. The buds were protected by cataphylls and composed of a variable number of undeveloped leaves enveloping the shoot apex. For M. albicans, we found an association between maximum temperature and both phenolic idioblasts and trichome boundary layer, but no association with crystal idioblasts. In S. lycocarpum, only the trichome boundary layer was associated with maximum temperature plus high radiation. Z. montana showed no variation. Combination of two or more traits can lead to the development of adaptative strategies to different climatic conditions. We present for the first time an analysis of epicormic bud traits in plant populations occurring in an extensive latitudinal gradient and shed light on how maximum temperature is associated with these traits, contributing to a better understanding of plant resprouting capabilities in widespread savanna plant species.

Extensive clonal propagation and resprouting drive the regeneration of a Brazilian dry forest

AbstractWoody plant resprouting has received considerable attention in the last two decades as human disturbances continue to encroach on terrestrial ecosystems globally. We examined the regeneration mechanisms of a Caatinga dry forest in the context of slash-and-burn agriculture and resprouting ability of the local flora. We excavated two old fields (from 32) experiencing early forest regeneration dominated by the tree Pityrocarpa moniliformis (Fabaceae) to map clonal propagation and, in parallel, submitted 260 seedlings from 13 woody plant species to experimental clipping. What seemed to be ‘seedlings’ popping up around P. moniliformis stumps and remaining adults actually were condensed sets of root suckers connected via complex networks of long, ramified shallow horizontal roots without taproots. We mapped respectively 39 and 783 connected root suckers, which summed 96 m and 910 m in root length. Regarding the seedlings, 33% resprouted across nine species with resprouting rates varying between 5–100%. Seedling height before clipping positively influenced resprouting vigour. Our preliminary results suggest that the Caatinga dry forest supports a relatively high proportion of resprouting species, some of them able to clonally propagate and playing an ecosystem-level role by responding to early forest regeneration and high abundance/biomass across both regenerating and old-growth forests.

Control of Ailanthus altissima using cut stump and basal bark herbicide applications in an eighteenth‐century fortress

AbstractThe Cittadella di Alessandria (Italy) is a military fortification that was built in the 18th century. The site has recently been abandoned and is now colonised by weeds, including the invasive Ailanthus altissima. The aim of the study was to compare the efficacy of different herbicides (glyphosate, a mixture of aminopyralid + fluroxypyr and triclopyr + fluroxypyr) applied to cut stumps or to the basal bark of A. altissima. For the cut stump application, plants were first cut at the base and then immediately sprayed and for the basal bark application, the lower 50 cm of the plants was sprayed with the herbicides; untreated cut plants were used as a control, for comparison. Two runs per study were carried out (in summer 2015 and in spring 2016). Efficacy was assessed up to 2018 by counting the resprouts and their height in the cut stump application and, for the basal bark treatment, by measuring the variation in the plant circumference after treatment. The cut stump treatment carried out in summer greatly reduced the number of resprouts, compared to the spring treatment, to less than one sprout per plant when aminopyralid + fluroxypyr was used, and its efficacy lasted for about two years. The basal bark treatment did not control the species, but lower levels of variation in circumference and greater mortality were detected in plants treated with aminopyralid + fluroxypyr. Considering the high level of infestation of the site and the high risk of plant resprouting, repeated cut stump treatments with aminopyralid + fluroxypyr would be preferable to eradicate this invasive species.

Assessment of invasive Gypsophila paniculata control methods in the northwest Michigan dunes

AbstractBaby’s breath (Gypsophila paniculata L.) is an invasive species in Michigan’s northern lower peninsula and is a problem in much of northern North America. It is of particular concern in coastal dune habitats of northwest Michigan, because the areas where it is most dense are also populated by several endemic and threatened species. Current removal methods include manual removal with a spade and directed spray-to-wet foliar application of glyphosate to individual plants using backpack sprayers. We assessed these methods by measuring G. paniculata density and presence–absence frequency before and after treatment using a point-intercept grid, establishing how type and timing of treatment within the growing season influences treatment efficacy and determining the proportion of plants that resprout after treatment. Our results show a consistent reduction in G. paniculata density after treatment with herbicide or manual removal (P < 0.001) but minimal impact on presence–absence frequency. These results indicate a need for quantitative data in the assessment of management efficacy to show a clearer picture of density reduction when extirpation is no longer a viable outcome of management. Through the assessment of treatment timing of manual removal and glyphosate treatments over time, we found no evidence that either treatment type was effective at reducing density when applied before plants flowered, but there was evidence that both treatments were effective when applied later in the growing season when plants were flowering. Resprouting of marked plants occurred in 14% of manually removed plants and 2% of herbicide-treated plants. Our results suggest that managers should treat G. paniculata infestations for consecutive years to remove regrowth and focus treatment during flowering for best control.

Fire-adapted traits of threatened shrub species in riparian refugia: implications for fire regime management

Fire management at the landscape scale may be detrimental to threatened species restricted to fire refugia, such as riparian zones, if their fire response is assumed based on the broader vegetation community type. Conserving threatened plant species in fire-prone habitats requires understanding how life-history traits allow persistence under prevailing fire regimes. Using three threatened Pomaderris species associated with riparian zones in south-east Australia, we tested for evidence of fire-adapted traits to identify if key life-history traits are coupled to specific fire cues and determine how their current distribution relates to prevailing fire regimes. We did this by (i) exposing seeds to heat-shock treatments with fire-related temperatures (60–100 °C) in germination trials; (ii) testing for the presence of a soil-stored seed bank and its response to fire by using ex-situ experimental burns on soil samples and (iii) conducting field surveys of post-fire demographic responses for P. adnata. All species showed maximum germination following heat-shock treatment at 100 °C, strongly suggesting adaptation to high severity fire. Seedling emergence from soil samples was positively affected by fire for P. bodalla and P. walshii, while there was an in situ post-fire germination pulse in P. adnata seedling recruitment and moderate increases in resprouting and survivorship of mature plants. The study demonstrates that these riparian-occurring species have life-history traits that may enable persistence under high severity fire and highlights how the possession of bet-hedging strategies may allow species to use riparian zones as fire refugia in a landscape dominated by an anthropogenically altered fire regime.

Plant resprouting: How many sprouts and how deep? Flexible modelling of multi-species experimental disturbances

Plants can respond to damage through regrowth from meristematic tissue, commonly concentrated in buds. Knowledge of the distribution and abundance of buds within plants can assist in understanding individual, population and species responses to disturbances. Yet belowground buds can be hard to study, as they may be cryptic until initiated in response to damage. Sprouts emerging following disturbance can be studied more easily and represent a realised bud bank.Here we aimed to characterise and compare the vertical distribution of sprouts from a previous study of clip and burn treatments for 42 species of grasses, forbs, subshrubs and woody plants in semiarid eastern Australia (Vesk et al., Oikos 2004 107:72–89). We tested whether depth distributions of sprouts could be explained by growth forms and plant traits, while also asking whether clip and burn treatments influenced those distributions. We combine function regression with a hurdle model to estimate simultaneously the probability of resprouting and the depth distribution of buds, conditional on resprouting (hereafter, sprouts). Function regression models the depth distribution of sprouts as a continuous function, rather than a single value. The hurdle model also allowed us to ask whether sprout depths and the probability of resprouting were similarly related to treatments, growth forms and traits.Depth distributions of sprouts in successfully resprouting plants differed among growth forms. Specifically, we observed similar distributions of sprouts in forbs and woody plants, more and deeper sprouts in grasses, fewer and mainly above-ground sprouts in subshrubs. However, because the probability of subshrubs resprouting was very low, the expected number of sprouts was very low too. Burning resulted in more and deeper sprouts on successfully resprouting plants. Further, species’ traits like maximum height and specific leaf area (SLA) were correlated with different sprout distributions. Taller species had fewer shallow sprouts in general, and high SLA species had more shallow sprouts under clipping but not under burning.This work points to experimental methods and statistical analyses to quantify the depth distribution of the buds from which plants resprout. This serves to inform comparative investigations of buds, sprouts, and disturbance responses, and is likely to improve predictions of responses to disturbances.

Physiological, growth and root biochemical responses of Arbutus unedo and Quercus suber seedlings to UV radiation and water availability before and after aboveground biomass removal

Models predict an increase in solar ultraviolet (UV) radiation, a decrease in precipitation and a higher frequency of disturbances (e.g. fires) in the near future in the Mediterranean basin. Thus, this study examined the effects of enhanced UV radiation (UV-A and UV-B) and diminished water supply on leaf morphology and physiology, plant growth, root reserves and resprouting capacity of two common Mediterranean species, before and after aerial biomass removal (simulating a disturbance, such as a severe fire). An outdoor experiment was conducted growing potted seedlings of strawberry tree (Arbutus unedo) and cork oak (Quercus suber) with enhanced UV-A + UV-B, enhanced UV-A or ambient UV, combined with optimal or reduced watering. Eight months after the start of the experiment, all the plant aerial biomass was removed and new shoots (resprouts) developed for a further 8 months under the UV and watering treatments. For both species, the responsiveness of seedlings (pre-disturbance) and resprouting plants (post-disturbance) to the treatments differed. Enhanced UV-B reduced the leaf relative water content (RWC) in well-watered A. unedo plants (seedlings and resprouts), decreasing also the amount of root phenols in well-watered resprouts of this species. In parallel, however, exposure to enhanced UV-B increased the photosynthetic rates of A. unedo resprouts, regardless of the irrigation level. Seedlings and resprouts of Q. suber responded to enhanced UV-A by hardening the leaves (increased leaf mass per area, LMA), although UV-A-supplemented seedlings allocated less carbon to produce leaves in relation to roots. Most UV effects were found only under optimal irrigation, suggesting a decrease in plant UV sensitivity under low water availability. In Q. suber, water shortage per se reduced leaf:total biomass and the concentration of sugar in roots. Despite some UV and watering effects on the parameters studied, the protective mechanisms displayed by both species were apparently effective since root starch reserves and plant resprouting capacity were not reduced by the treatments.

Tailoring restoration interventions to the grassland‐savanna‐forest complex in central Brazil

Defining the reference system for restoration projects in regions characterized by complex vegetation mosaics is challenging. Here we use the Cerrado region of Brazil as an example of the importance of clearly defining multiple natural and anthropogenically altered states in grassland‐savanna‐forest mosaics. We define three main, natural vegetation types–grassland, savanna, and scleromorphic (cerradão) forest–to (1) distinguish between original and degraded states and (2) set appropriate targets for and guide restoration. We contend that the differences in Cerrado vegetation composition originally were driven by soil conditions and secondarily by fire frequency and precipitation patterns that differ from the core to the edge of the Cerrado region. Grasslands are found on the shallowest, least fertile soils and/or in waterlogged soils; scleromorphic forests are generally located on deeper, more fertile soils; and savannas occupy an intermediate position. In recent decades, this biophysical template has been overlain by a range of human land‐use intensities that strongly affect resilience, resulting in alternative anthropogenic states. For example, areas that were originally scleromorphic forest are likely to regenerate naturally following low‐ or medium‐intensity land use due to extensive resprouting of woody plants, whereas grassland restoration requires reintroduction of grass and forb species that do not tolerate soil disturbance and exotic grass competition. Planting trees into historic grasslands results in inappropriate restoration targets and often restoration failure. Correctly identifying original vegetation types is critical to most effectively allocate scarce restoration funding.

Seed moisture content as a primary trait regulating the lethal temperature thresholds of seeds

Abstract Fire has long shaped biological responses of plants and plant communities in many ecosystems; yet, uncontrolled wildfire frequently puts people and infrastructure at risk. Fuel or hazard reduction burning outside of the historic fire season is a common and widespread practice aimed at reducing the risk of high‐severity fires, which ideally also considers biodiversity values. Within fire‐prone systems, seed banks are critical for plant species’ regeneration, and seeds are typically adapted to survive the passage of fire and to regenerate in response to cues associated with historic fire regimes. However, species‐specific tolerances to the heat from fire exist; likely influenced by a range of physical, physiological, and morphological seed traits, which may differ between seasons. The identification of these tolerances and associated seed traits may inform fire and species management. We determined the lethal temperatures for seeds in relation to their moisture content, and other key traits that we hypothesised may be associated with survival. Seeds from 14 native species and 4 species non‐native to fire‐prone Mediterranean climate Banksia woodlands of south‐west Western Australia were exposed to temperatures between 50 and 180°C for 3 min at three different moisture contents. The temperature at which half the seeds were killed (T50) was estimated using nonlinear modelling. Seed mass, seed shape, embryo type, plant resprouting ability, seed storage syndrome, and native/non‐native status were quantified and modelled for their relationship with T50. Increased moisture content was a significant predictor of elevated seed mortality. Seeds with higher moisture (95% relative humidity [RH]) content perished at much lower temperatures. Seeds with low moisture content (15% or 50% RH) were able to survive significantly higher temperatures (median increase of 38 and 31°C higher respectively). Seeds with basal embryos showed significantly lower T50 than other embryo types. Synthesis. Seeds with elevated moisture contents have lower lethal temperature thresholds, leading to increased seed mortality during fire events when seeds (and soils) are moist. Thermal tolerance varied among coexisting species within this fire‐prone system. These data suggest potential concern for the impacts of aseasonal burning practices (i.e., cool/wet season burning), and highlight the importance of taking seed moisture content into account when planning and implementing prescribed burning.

Vegetative growth response of Cytisus oromediterraneus to fuel reduction treatments

Studies of the effects of fuel reduction treatments on the recovery of shrubland communities have increased substantially in recent years. However, the effects on the resprouting response of shrubs have been less well studied, even though such information would help land managers select the most appropriate treatment. Cytisus oromediterraneus Riv. Mart. is a species characteristic of the Mediterranean basin, where it occupies a vast area of the terrain. It is a facultative resprouter and can thus regenerate asexually, although little is known about its response to prescribed fire or mechanical treatments. In this study, we evaluated the resprouting ability of this species during the first 2 years after the application of prescribed burning and two different types of mechanical treatments (clearing and mastication). Plant mortality after the treatments was low and did not differ between treatments. The number of resprouted shoots was higher after clearing than after both prescribed burning and mastication, but did not differ between the latter two treatments. Most of the shoots are in ramets originated from the rootstocks. The pre-treatment plant size favored the plant resprouting response after fuel reduction treatments. The minimum stem diameter and plant height, proxy measures of treatment severity, were not related to the number of resprouted shoots. The degree of soil compaction after treatments negatively affected the C. oromediterraneus resprouting response. The number of resprouted shoots of C. oromediterraneus was not affected by any of the thermal parameters, indicating its resilience to fire.

Vegetation response to canopy disturbance and season of burn during oak woodland and savanna restoration in Tennessee

The removal of fire’s influence on plant community succession has resulted in the near disappearance of oak (Quercus spp.) woodlands and savannas from the Appalachian region. Negative trends in associated plant and wildlife species could be reversed if these communities are restored, but management has been limited by inadequate canopy disturbance, resprouting of woody plants, and a lack of empirical research. To address these issues, we evaluated herbaceous and woody vegetation response (2008–2012) on the Cumberland Plateau in Tennessee to 5 replicated treatments involving canopy reduction (14m2ha−1 [woodland] or 7m2ha−1 [savanna] residual basal area) and fire-season (mid-March [spring] or early October [fall]) combinations and unmanaged controls. All categories of woody vegetation except large-saplings (⩾1.4m tall and ⩾7.6 but <12.7cm diameter at breast height [DBH]), increased in density as canopy disturbance increased. Fire temporarily reduced small-sapling (⩾1.4m tall and <7.6cmDBH) density, but resprouting resulted in densities equal to or exceeding pre-fire levels. Herbaceous richness increased from 22 to 167 species following canopy disturbance and fire (2008–2012). Native cool-season grasses dominated herbaceous response in treated sites. Herbaceous groundcover, richness, and diversity increased as canopy disturbance increased, and the rate of increase accelerated once basal area was reduced below 15m2ha−1 or 30% canopy closure. Following fire, canopy disturbance remained influential as indicated by greater herbaceous response in savannas than woodlands. Graminoid and forb groundcover, herbaceous richness, and herbaceous diversity were 24X, 11X, 9X, and 8X greater, respectively, in treatments than controls by 2012. Invasive species were rare and increased minimally with increasing disturbance. Our results demonstrate the utility of canopy disturbance in conjunction with fire for restoring oak woodlands and savannas from closed-canopy forest conditions. Basal area reduction to 15 and 7m2ha−1 respectively approximated woodland and savanna canopy conditions, and increased herbaceous-layer development. The less intense October fire had similar effects on vegetation as the more intense March fire, but greater differences could become apparent following repeated burning. Long-term research documenting the response of vegetation to repeated fire is needed to promote successful oak woodland and savanna restoration throughout the Appalachian region.