Stages Of Post-fire Succession Research Articles

The Structure of Northern Siberian Spruce–Scots Pine Forests at Different Stages of Post-Fire Succession

The process of post-fire recovery in mixed Siberian spruce–Scots pine forests (Picea obovata Ledeb.-Pinus sylvestris L.), typical for the European North-West, was studied in the Kola peninsula (Russia). We used the spatial–temporal approach to reveal the size structure (diameter at breast height (DBH) distribution) and vital state of Siberian spruce and Scots pine stands, tree regeneration and species structure of the dwarf shrub–herb and lichen–moss layers at different stages of post-fire succession (8–380 years after the fire). It was found that in both forest-forming species, the process of stand stratification results in the allocation of two size groups of trees. In Siberian spruce, these groups persist throughout the succession. In Scots pine, DBH distributions become more homogeneous at the middle of succession (150–200 years after the fire) due to the extinction of small-size individuals. Siberian spruce stands are dominated by moderately and strongly weakened trees at all succession stages. The vitality status of Scots pine stands is higher compared to Siberian spruce up to 150 years after a fire. The dynamics of regeneration activity is similar in both species, with a minimum at the middle of the restoration period. The results indicate that in Siberian spruce–Scots pine forests, the stand structure and regeneration activity differs substantially in the first half of succession (up to 200 years after the fire) and become similar in the late-succession community. The study of lower layers revealed that the cover of moss–lichen and dwarf shrub–herb layers stabilize 150 years after a fire. Changes in species structure in both layers are observed until the late stage of succession. The originality of the structure and dynamics of mixed Siberian spruce–Scots pine forests is revealed based on a comparison with pure Siberian spruce forests in the same region.

Bilberry vs. cowberry in a Scots pine boreal forest: Exclusion or coexistence in a post-fire succession?

Although the famous competition exclusion principle was thoroughly elaborated in the framework of multispecies population models, its illustrations with field data were facing certain obstacles. The data we deal with were collected by 6 consecutive examinations of bilberry (Vaccinium myrtillus) and cowberry (V. vitis-idaea) presence/absence in 20 × 20 cm quadrats located along permanent transects in a Scots pine boreal forest. These data feature a great sample size (2000 quadrats×6 examinations) and a 5-year interval for each pair of examination/re-examination, and the data have enabled us to construct a Markov chain model for the fine-scale dynamics of these dominant species at the later stages of post-fire succession. The discrete-time nonautonomous model consists of the five time-dependent, one-step transition matrices that describe changes occurring in the quadrat status for the 5 years in the following 4 terms: species-free quadrat; bilberry alone, cowberry alone, both species. Calibrated on the data, each one-step transition matrix transforms the current distribution of quadrats among their statuses exactly to the next one observed and yields a steady-state distribution as its (time-specific) positive eigenvector. Step-by-step variations in the elements of transition matrices do affect the components of the corresponding eigenvectors, but do not change the dominance relationships among them.Calculated as the 5-th power matrix root from the product of those five transition matrices (in the chronological order within their product), the geometric average, treated again as a transition matrix, provides for the spatial and temporal characteristics of the observed dynamics summarizing the whole observation period. We reveal the expected terminal stable outcome of species dynamics to be a distribution where 37% of quadrats are occupied by the bilberry alone, 11% by cowberry alone, 38% by the both species, and 14% be species-free. It is shown for the first time that the share of cowberry-alone quadrats decreases notably in the course of succession, whereas the share of species coexistence quadrats increase.The averaged characteristics of cyclicity and status duration in the fine-scale dynamics enable us to estimate the total time of the secondary post-fire succession as 46–50 years (till reaching a distribution close to the terminal one). Of the four statuses considered, the cowberry-alone quadrats have the least mean duration time (9 years), while the bilberry-and-cowberry quadrats have the longest time (18 years), which are explainable by different life spans of the shoots in proper species.

Dynamics of soil respiration at different stages of pyrogenic restoration succession with different-aged burns in Evenkia as an example

An analysis of CO2 emissions and soil microbiological activity has been performed in larch stands of different ages that developed on cryogenic soils and represent different stages of post-fire succession. An abrupt increase in the soil emissions of CO2 (by more than 2 times) in young stands (15–30 years old), as well as a decrease of soil-respiration rate at the later stages of pyrogenic successions because of the restoration of the moss-lichen cover and the closure of the stand canopy was seen. Intraseasonal and interannual variations of soil CO2 fluxes were also revealed; however, their dynamics was largely determined by the local conditions.

Responses to fire of Slender-billed Thornbills, Acanthiza iredalei hedleyi, in Ngarkat Conservation Park, South Australia. I. Densities, group sizes, distribution and management issues

The Slender-billed Thornbill, Acanthiza iredalei hedleyi, was studied in recently burnt, regenerating and mature heath (3, 10 and 22 years since fire respectively) in Ngarkat Conservation Park, South Australia. Data collected between 1991 and 2002 demonstrated that densities peaked seven years after fire at 0.26 birds ha−1, while densities were lower and less variable in unburnt mature heath. Comprehensive searches in spring 2000 confirmed this trend, with densities varying from 0.02 birds ha−1 in mature heath, to 0.06 and 0.07 birds ha1 in burnt and regenerating heath.Between spring 2000 and autumn 2001 group sizes increased in the recently burnt heath from 4.3 to 6.3 birds per group. However, group sizes did not increase over the same period in the regenerating and mature heaths. Between 1991 and 2002 group sizes did not differ significantly between heaths that had been burnt since 1990 (2.7 birds per group) and mature heath burnt in 1978 (2.7 birds per group).In the mature heath, Slender-billed Thornbills demonstrated strong fidelity for certain areas and were observed feeding juvenile birds on a number of occasions. This suggests that birds can persist in mature heath, albeit at low densities and in isolated areas of suitable habitat, and that frequent fires are not essential for population persistence. Furthermore, long-term records suggest that recolonisation of recently burnt heath is likely to occur from adjacent unburnt heath and is more successful after smaller fires. Therefore, in order to protect areas from which Slender-billed Thornbills can disperse into recently burnt habitats in Ngarkat, a spatial mosaic of habitats at different stages of post-fire succession is required.

Comparative root system structure of post-fire Pinus halepensis Mill, and Cistus monspeliensis L saplings.

To describe root system topology of Pinus halepensis and Cistus monspeliensis saplings co-inhabiting natural post-fire sites, 55 P. halepensis and 26 C. monspeliensis saplings were extracted by the total excavation method from a burnt pine stand. Seedlings were individually labelled when emerging after fire and extracted three years later, at the sapling phase. In order to evaluate the effect of inter-specific competition of C. monspeliensis on P. halepensis root system, a stratified sampling was carried out according to density and height of the saplings. Topological parameters considered in the analysis were magnitude, total external pathlength, and altitude of the root systems. Weight and length of roots were also measured in order to estimate the specific root length, an index commonly used in morphological studies. Results clearly evidenced greater variability in root system topology of P. halepensis than C. monspeliensis saplings. Herringbone architecture (i.e., the most ordered pattern possible, with branching confined to the main axis) characterised small pine saplings, regardless of competition from C. monspeliensis, which changed to random branching in large saplings. In medium sized saplings, the root system was affected by inter-specific competition, which delayed changes in root branching. In contrast, C. monspeliensis invariably adopted randomly branched architecture, regardless of intra-specific competition. It is concluded that such different topological patterns make C. monspeliensis more competitive during the early stages of post-fire succession, because its root system is much more transport-efficient in the nutrient-rich environment. Those pines which finally branch roots by random pattern will reach higher stem height and magnitude, a factor which allows them to successfully compete with C. monspeliensis for soil nutrients and water. The morphological analysis showed a significant increase in the specific root length with competition, both in P. halepensis and C. monspeliensis saplings, which could be interpreted as a consequence of the reduction of root diameter in response to nutrient depletion.

Post-fire uptake of nutrients by diverse ephemeral herbs in chamise chaparral.

Diverse populations of ephemeral herbs form the dominant element of community biomass in the first year of growth following a fall burn in chamise chaparral. Ephemeral herbs constituted 337 kg ha-1 of above-ground biomass after the first season of post-fire growth. This was 64% of the total, with the majority of the remaining biomass being in resprouts of Adenostoma fasciculatum. Ephemeral herb biomass following fire in other stands was as high as 1117 kg ha-1. Nutrient contents of ephemeral herbs were 6.68 kg N ha-1, 0.71 kg P ha-1, 10.05 kg K ha-1, 4.75 kg Ca ha-1 and 0.91 kg Mg ha-1. These were 55, 54, 81, 71 and 70% respectively of the above-ground totals. In the second year following fire, the total herb biomass was 40% higher, but the nutrient pool in above-ground biomass of these herbs was only 30-60% of what it had been the first year. Resprouts of A. fasciculatum and short-lived wood shrubs constituted more than 90% of above-ground biomass at this stage of postfire succession.

Landscape Development, Forest Fires, and Wilderness Management

Landscape Development, Forest Fires, and Wilderness Management