scholarly journals Resilience of a eucalypt forest woody understorey to long-term (34 - 55 years) repeated burning in subtropical Australia

2012 ◽  
Vol 21 (8) ◽  
pp. 980 ◽  
Author(s):  
Tom Lewis ◽  
Valerie J. Debuse
Keyword(s):  
Woody Plants ◽  
Basal Area ◽  
Fire Frequency ◽  
Understorey Vegetation ◽  
Growth State ◽  
Eucalypt Forest ◽  
Fire Exclusion ◽  
Explained Variance ◽  
Subtropical Australia

We investigated the effects of annual burning since 1952, triennial burning since 1973, fire exclusion since 1946 and infrequent wildfire (one fire in 61 years) on woody understorey vegetation in a dry sclerophyll eucalypt forest, south-eastern Queensland, Australia. We determined the influence of these treatments, and other site variables (rainfall, understorey density, topsoil C : N ratio, tree basal area, distance to watercourse and burn coverage) on plant taxa density, richness and composition. The richness of woody understorey taxa 0–1 m in height was not affected by burning treatments, but richness of woody plants 1–7.5 m in height was lower in the annually burnt treatment than in the triennially burnt treatment from 1989 to 2007. Fire frequency and other site variables explained 34% of the variation in taxa composition (three taxon groups and 10 species), of which 33% of the explained variance was explained by fire treatment and 46% was explained by other site variables. Annual burning between 1974 and 1993 was associated with lower understorey densities mainly due to reduced densities of eucalypts 1–7.5 m in height. Triennial burning during the same period was associated with higher densities of eucalypts 0–7.5 m in height relative to the annually burnt and unburnt treatments. Most woody taxa persisted in the frequently burnt treatments through resprouting mechanisms (e.g. lignotuberous regeneration), and fire patchiness associated with low-intensity burning was also found to be important. Persistence of plants <1 m tall demonstrates the resilience of woody taxa to repeated burning in this ecosystem, although they mainly exist in a suppressed growth state under annual burning.

scholarly journals The response of cerambycid beetles (Coleoptera: Cerambycidae) to long-term fire frequency regimes in subtropical eucalypt forest

2019 ◽  
Vol 44 (4) ◽  
pp. 609-620 ◽  
Author(s):  
Martyn Eliott ◽  
Simon Lawson ◽  
Andrew Hayes ◽  
Valerie Debuse ◽  
Alan York ◽  
...  
Keyword(s):  
Fire Frequency ◽  
Eucalypt Forest ◽  
Cerambycid Beetles

Mitigation of drought stress in forest stands - insights from a throughfall-exclusion and a thinning experiment

2020 ◽  
Author(s):  
Timo Gebhardt ◽  
Benjamin D. Hesse ◽  
Thorsten E.E. Grams ◽  
Christian Ammer ◽  
Karl-Heinz Häberle
Keyword(s):  
Drought Stress ◽  
Forest Management ◽  
Soil Water ◽  
Norway Spruce ◽  
Intraspecific Competition ◽  
Basal Area ◽  
Understorey Vegetation ◽  
Management Measures ◽  
Throughfall Exclusion

&lt;p&gt;Due to climate change suitable forest management measures are required to mitigate the proposed exacerbating drought events as already observed in central Europe in summer 2003, 2015, 2018, and 2019. This contribution summarizes the findings of two long-term field experiments studying different forest management measures aiming at mitigating drought in forest stands.&lt;/p&gt;&lt;p&gt;The first study investigated the potential of mixing tree composition for mitigating drought stress in Norway spruce (Picea abies [L.] Karst.). To this end, a five-year study with repeated summer droughts, experimentally induced via throughfall-exclusion (TE), was performed. The study objects were mature (60-80 years) old stands of Norway spruce in monoculture and mixture with European beech (Fagus sylvatica (L.). The impacts of repeated summer droughts were assessed on about 100 trees distributed on 12 plots and accessible via canopy crane (Kranzberg forest ROOF experiment in southern Germany). Predawn leaf water potentials of Norway spruce reached minima of -1.8 MPa, but were not affected by species mixture. Nevertheless, daily xylem sapflow density was increased up to 40% in mixture compared to pure strands. Likewise, stem growth, i.e. relative basal area increment, showed significantly higher drought resistance in mixture compared to monocultures.&lt;/p&gt;&lt;p&gt;While altering forest stand composition seems to be promising on the long-term, the conversion from monocultures is often economically not suitable for young stands in the short- to medium-term. Therefore, reducing intraspecific competition via thinning is a frequently discussed option investigated in the second, eight-year-long study. In a 26-year old Norway spruce monoculture, three thinning intensities, i.e. unchanged (control), moderate thinning (MT with reduced basal area by 43%) and heavy thinning (HT, reduced basal area by 67%) were applied, potentially mitigating drought by reducing intraspecific competition and increasing soil water availability. Indeed, in both thinning intensities the duration of drought stress for the trees (soil water content below critical value) was reduced compared to controls for up to 5-7 years following the event. However, increased radiation and higher growth rates of the individual trees accompanied by the fast establishment of a vital ground vegetation diminished the difference in stand transpiration between MT and HT within two years. Moreover, belowground competition with the understorey vegetation suppressed fine root recovery under HT compared to MT in contradiction to increased leaf area on HT on tree-level and therefore increased transpirational demand.&lt;/p&gt;&lt;p&gt;The presented studies suggest admixing of broadleaved beech into monocultures of Norway spruce to be a promising management measure in the long-term. In juvenile monocultures of Norway spruce frequent and intense thinning interventions while preventing the establishment of a vital understorey vegetation appears to be a promising forest measure, mitigating drought without losing sight of economic needs.&lt;/p&gt;

scholarly journals Impact of fire frequency on woody community structure and soil nutrients in the Kruger National Park

Koedoe ◽  
2000 ◽  
Vol 43 (1) ◽  
Author(s):  
C.M. Shackleton ◽  
R.J. Scholes
Keyword(s):  
Community Structure ◽  
Soil Nutrients ◽  
National Park ◽  
Basal Area ◽  
Fire Frequency ◽  
Kruger National Park ◽  
Fire Season ◽  
Soil Variables ◽  
And Function

Although fire is recognised as an important determinant of the structure and function of South African savannas, there are few studies of long-term impacts. Controlled burning blocks of contrasting fire season and frequency have been maintained throughout the Kruger National Park for almost 50 years. This paper reports on a quantitative study of the Satara plots to determine the long-term impacts of fire frequency on woody community structure and soil nutrients. Increasing fire frequency significantly decreased woody plant basal area, biomass, density, height, and mean stem circumference. The number of stems per plant and the proportion of regenerative stems increased with increasing fire frequency. Effects on species richness of woody plants were inconsistent. There were no significant differences attributable to fire frequency for any of the soil variables except organic matter and magnesium. Organic carbon was highest in the fire exclusion treatment and lowest in soils from plots burnt triennially. Magnesium levels were greatest in the annually burnt soils and least in the triennial plots.

scholarly journals Decadal changes in fire frequencies shift tree communities and functional traits

2020 ◽  
Author(s):  
Adam F. A. Pellegrini ◽  
Tyler Refsland ◽  
Colin Averill ◽  
César Terrer ◽  
A. Carla Staver ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Fire History ◽  
Vegetation Type ◽  
Basal Area ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Tree Communities ◽  
In Fire ◽  
The Impact

Global change has resulted in chronic shifts in fire regimes, increasing fire frequency in some regions and decreasing it in others. Predicting the response of ecosystems to changing fire frequencies is challenging because of the multi-decadal timescales over which fire effects emerge and the variability in environmental conditions, fire types, and plant composition across biomes. Here, we address these challenges using surveys of tree communities across 29 sites that experienced multi-decadal alterations in fire frequencies spanning ecosystems and environmental conditions. Relative to unburned plots, more frequently burned plots had lower tree basal area and stem densities that compounded over multiple decades: average fire frequencies reduced basal area by only 4% after 16 years but 57% after 64 years, relative to unburned plots. Fire frequency had the largest effects on basal area in savanna ecosystems and in sites with strong wet seasons. Analyses of tree functional-trait data across North American sites revealed that frequently burned plots had tree communities dominated by species with low biomass nitrogen and phosphorus content and with more efficient nitrogen acquisition through ectomycorrhizal symbioses (rising from 85% to nearly 100%). Our data elucidate the impact of long-term fire regimes on tree community structure and composition, with the magnitude of change depending on climate, vegetation type, and fire history. The effects of widespread changes in fire regimes underway today will manifest in decades to come and have long-term consequences for carbon storage and nutrient cycling.

scholarly journals Detection of epileptic activity in presumably normal EEG

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Sara Baldini ◽  
Francesca Pittau ◽  
Gwenael Birot ◽  
Vincent Rochas ◽  
Miralena I Tomescu ◽  
...  
Keyword(s):  
Focal Epilepsy ◽  
Epileptic Activity ◽  
Scalp Eeg ◽  
Vigilance State ◽  
Explained Variance ◽  
Long Term Monitoring ◽  
Interictal Discharges ◽  
The Individual ◽  
Term Monitoring

Abstract Monitoring epileptic activity in the absence of interictal discharges is a major need given the well-established lack of reliability of patients’ reports of their seizures. Up to now, there are no other tools than reviewing the seizure diary; however, seizures may not be remembered or dismissed voluntarily. In the present study, we set out to determine if EEG voltage maps of epileptogenic activity in individual patients can help to identify disease activity, even if their scalp EEG appears normal. Twenty-five patients with pharmacoresistant focal epilepsy were included. For each patient, 6 min of EEG with spikes (yes-spike) and without visually detectable epileptogenic discharges (no-spike) were selected from long-term monitoring recordings (EEG 31–37 channels). For each patient, we identified typical discharges, calculated their average and the corresponding scalp voltage map (‘spike-map’). We then fitted the spike-map for each patient on their (i) EEG epochs with visible spikes, (ii) epochs without any visible spike and (iii) EEGs of 48 controls. The global explained variance was used to estimate the presence of the spike-maps. The individual spike-map occurred more often in the spike-free EEGs of patients compared to EEGs of healthy controls (P = 0.001). Not surprisingly, this difference was higher if the EEGs contained spikes (P &lt; 0.001). In patients, spike-maps were more frequent per second (P &lt; 0.001) but with a shorter mean duration (P &lt; 0.001) than in controls, for both no-spike and yes-spike EEGs. The amount of spike-maps was unrelated to clinical variables, like epilepsy severity, drug load or vigilance state. Voltage maps of spike activity are present very frequently in the scalp EEG of patients, even in presumably normal EEG. We conclude that spike-maps are a robust and potentially powerful marker to monitor subtle epileptogenic activity.

scholarly journals Facilitative or competitive effects of woody plants on understorey vegetation depend on N-fixation, canopy shape and rainfall

2013 ◽  
Vol 101 (6) ◽  
pp. 1598-1603 ◽  
Author(s):  
Wilma J. Blaser ◽  
Judith Sitters ◽  
Simon P. Hart ◽  
Peter J. Edwards ◽  
Harry Olde Venterink
Keyword(s):  
Woody Plants ◽  
N Fixation ◽  
Understorey Vegetation ◽  
Competitive Effects

scholarly journals Determination of standards of raw timber natural losses due to shrinkage at long-term dry storage

2021 ◽  
Vol 67 (No. 5) ◽  
pp. 195-203
Author(s):  
Dalibor Šafařík ◽  
Petra Hlaváčková ◽  
David Březina
Keyword(s):  
Woody Plants ◽  
Mean Value ◽  
The Czech Republic ◽  
Long Term Storage ◽  
Upper Limits ◽  
Natural Losses ◽  
Term Storage

The aim of the article is to describe the issue of determining the characteristics and parameters of raw timber natural losses due to shrinkage at long-term storage, defining the theoretical basis for creating standards, and verify its finding by means of a case study in raw timber storing. This issue is very topical in forestry practice in the Czech Republic as well as in other countries. The lower and upper limits of the standards were calculated, and the proposed mean value was grouped according to woody plants that reflected the most frequent commercial usage with respect to subsequent processing. Subsequently, experimental verification was carried out on a representative sample of 2 209.99 m3 of raw timber of Norway spruce (Picea abies /L./ H. Karst.) at selected forest administrations. Furthermore, the article addresses the related accounting and tax issues of the standards of natural losses of raw timber. Currently, no legislation mandates an entity to establish standards.

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