Effects of burning on soil macrofauna in a savanna-woodland under different experimental fuel load treatments

In West African savanna-woodland, the use of prescribed burning as a management tool has ecological implications for the soil biota. Yet, the effects of fire on soil inhabiting organisms are poorly understood. The aim of this study was to examine the responses of soil macro-invertebrates to early fires in a Sudanian savanna-woodland on a set of experimental plots subject to different fuel load treatments. The abundance of major macro-invertebrate taxa and functional groups, and taxon richness were quantified in soil cores collected from three different soil layers before and immediately after burning. The results indicated that, overall, there was substantial spatial and temporal variation in the composition of macro-invertebrate assemblages. The immediate effects of fire were to reduce total invertebrate numbers and numbers of many invertebrate groups dramatically. This is probably due to the fact that many of the surface-dwelling macrofauna perished as a result of less favorable microclimate due to fire, diminished resources, or migrate to safer environments. Fuel load treatment did not affect the community taxonomic richness or abundance of the soil-dwelling fauna. Furthermore, annual changes in community composition were more pronounced at the burnt site than in the control. This could be related to the inter-annual difference in precipitation pattern recorded during the two-year study period at our site. Since soil macrofauna population declines in fire-disturbed areas, increasing fire prevalence may jeopardize the long-term conservation of fire sensitive macrofauna groups. Special fire management attention is therefore recommended with due consideration to the type of burning and fuel properties to avoid the detrimental effects of intense fire affecting the resilience of savanna soil macrofauna species.     

Is colourful self-sustaining forb vegetation mere fantasy?

Biodiversity in urban and suburban environments can be supported through establishment of low maintenance-requiring herbaceous vegetation types. Here, we attempt to provide a perspective on the possibilities and limitations of establishing forb-dominated vegetation to support local biodiversity and contribute to changing public aesthetics concerning green spaces. Plant ecological theories, methods and experiences are the foundation for the design and establishment of such vegetation types. We emphasise the importance of high plant density and recurrent disturbance for the maintenance of forb communities. Well-established ecological theory tells us that totally self-sustaining herbaceous vegetation is not a realistic possibility. Without intervention, herbaceous vegetation will change over time and eventually be colonized by woody species through the process of succession. However, by applying a creative and strategic approach to establishment and subsequent management involving small scale disturbances, rather than solely a uniform maintenance regime, it may be possible to maintain a colourful, aesthetically appealing and species-rich forb dominated community that will support biodiversity and increase public acceptance of alternatives to conventional lawns in urban and suburban environments.     

Application of body size spectra to nematode trait-index analyses

Current trait-based indices of soil fauna for assessing soil quality rely on extensive knowledge of life history traits for hyper-diverse groups. We look at the effects of clear-cut forest harvesting and subsequent wood ash application on the free-living nematode community using trait-based indices and body size spectra. We test the hypothesis that body size is a unifying trait and that the body size spectra can be used to demonstrate changes in soil quality while overcoming taxonomic impediments. Undisturbed boreal forest floor soils were compared with clear-cut sites amended with zero, one-half calcium equivalent wood ash, equivalent calcium reintroduction, and twice calcium reintroduction. Total abundance, trait-based metrics for the Maturity Index, and two metrics of body size spectra were calculated. Nematode abundance was not a good indicator of soil disturbance, while traditional trait-based approaches (the summed Maturity Index) demonstrated predicted changes in community structure. Analysis of two types of body size spectra elucidated how the community had changed under disturbance, and revealed that smaller bodied organisms were lost under ash amended treatments compared to both clear-cut and undisturbed forest. Using the body size spectra for nematodes is a simple addition to current trait-based approaches that can supplement soil assessments for disturbance and quality without requiring taxonomic expertise.     

昭通南方草山退化及人工改造对土壤种子库的影响

土壤种子库在退化生态系统的恢复中发挥着重要作用。本研究选取了昭通南方草山的4类草地,采集土样后通过萌发实验揭示其土壤种子库特征。结果表明：4类样地的土壤样品中共萌发出45种植物,隶属于20科39属,种子库储量为3 087～18 553粒·m^-2,种子库密度随土层加深均在逐渐降低。与轻度放牧草地相比,过度放牧草地的土壤种子库密度下降,但物种数量和多样性增加;严重退化的稀草裸斑土地种子库密度则显著降低（P<0.05）,物种数量和多样性减少;而人工改造后的草地种子库密度显著增高（P<0.05）、物种数量和多样性也达到最高。昭通南方草山种子库与地上植被的总相似性系数为0.22～0.45,过度放牧草地、稀草裸斑土地和人工改造草地种子库与地上植被的相似系数均高于轻度放牧草地。总之,昭通南方草山退化和人工改造对土壤种子库产生巨大影响,上述结果可为后期退化草地治理提供理论依据。     

Bryophytes as potential indicators of forest integrity

Forest integrity has been proposed as one conservation endpoint that integrates desirable characteristics such as natural biodiversity, stand structure and continuity. Although its defining criteria are still under discussion, any surrogates must effectively represent or predict their status, and be easier to measure than the criteria themselves. Bryophytes have been proposed as such surrogates, because they are important components of forest integrity, and considerable research indicates that some groups are sensitive to the changes associated with specific forest management regimes. The objectives of this paper are (1) to review the issues in determining indicators of forest integrity, including desirable qualities in such indicators, (2) to review the state of knowledge concerning bryophytes as components of forest integrity (i.e. their responses to forest management practices), and (3) to assess bryophytes as potential indicators of forest integrity, in terms of both qualities desirable in indicators and our understanding of bryophyte response patterns. Although bryophytes possess some characteristics that suggest potential indicator value, many challenges prevent their reliable application. I highlight key areas in which research is required to identify operational bryophyte indicators of forest integrity. Along with a standardized protocol to select and calibrate such indicators, we urgently require strategic research to compile data on undisturbed reference forests on which to base selection of endpoints; species-specific ecological tolerances, with consideration of complex interactions; mechanisms of response to disturbance, with consideration of temporal aspects; population viability thresholds; and recruitment effects on community assembly. Whether we succeed in finding bryophyte indicators of forest integrity, this research would also provide the data to monitor and interpret the integrity of the bryophyte community.     

Temporal dynamics of forage succession for elk at two scales: Implications of forest management

Rapid conversion of lodgepole pine (Pinus contorta) dominated landscapes in western Alberta to a mosaic of successional stand ages has long-term implications for elk populations in the region that have not been fully assessed. We developed stand-level models of forage succession using data from 159 cutblocks to simulate forage and cover availability within the home range of an elk under “even-flow” and “pulsed” timber cutting scenarios that are common in this area. We found forage biomass peaked approximately 9 years following felling for both herbaceous (graminoids and forbs) and palatable browse forage. Forage production was determined primarily by the age of the cutblock (time since felling) and to a lesser extent elevation, compound topographic index (a measure of site wetness), and the distance to the nearest deciduous forest patch. Forbs became increasingly abundant as stands matured. Browse composition shifted from palatable species to unpalatable species after approximately 30 years. Within an elk home range (100 km²), we found that simulating an “even-flow” cutting regime resulted in forage availability that was always higher than under the current conditions of 90% forests when more than 10 ha were harvested per year. Further, forest cover (>30$>30$-year-old stands) was never less than the guideline of 60% of the area needed to provide adequate thermal and hiding cover. In contrast, when a “pulsed” harvest scenario was simulated, similar to what occurs for mountain pine beetle control, forage availability changed dramatically over time as a large cohort of harvested timber aged. Without further harvesting the stand conditions in the home range eventually returned to a state of pre-harvest risk for mountain pine beetle outbreak. We demonstrated several additional harvesting scenarios that avoided the potential risk and produced a much higher level of forage than currently exists.     

Structure and regeneration dynamics of dominant tree species along altitudinal gradient in a dry valley slopes of the Bhutan Himalaya

The aim of our study was to characterize the structure and regeneration dynamics of dominant tree species along altitudinal gradient in dry valley slopes of the Bhutan Himalaya. In the typical dry valley slopes of west-central Bhutan, we analyzed forest stratification, tree crown projection, and population structure from lower dry valley bottom (1520 m a.s.l.) to upper humid ridge top (3370 m a.s.l.) across five major forest types: i.e. (1) dry pine forest with Pinus roxburghii as a dominant species; (2) mixed broad-leaved forest with Quercus lanata (evergreen), Quercus griffithii, (deciduous), and Rhododendron arboreum (evergreen) as major canopy species; (3) evergreen broad-leaved forest dominated by Quercus semecarpifolia, Quercus glauca and Quercus oxyodon; (4) cool conifer forest dominated by Abies densa and Tsuga dumosa; (5) cold conifer forest with A. densa and Juniperus recurva as dominants. In general, regeneration pattern of major dominant species shifted from inverse-J (lower altitudes), to sporadic (mid-altitudes), and to uni-modal type (upper altitudes) corresponding to three regeneration trends: (1) invasive at the lower, warm, dry forest under relatively strong human disturbances; (2) stable/balanced at the mid-altitude, in a relatively stable, mature moist evergreen broad-leaved forest with gap regeneration; and (3) poor/low regeneration at the upper, cool, humid conifer forest with a continuously cattle-grazed understory. Overall, regeneration patterns were balanced in all forest types, however care should be taken to prevent excessive exploitation of dry pine forest of lower valley bottom, and to control cattle grazing at higher altitudes. Our findings can be incorporated into management plans for sustainable management and conservation of mountain forests.     

Differential responses of Bolivian timber species to prescribed fire and other gap treatments

We followed the establishment and growth response of 13 commercial tree species to canopy opening, above-ground biomass removal, and experimental burns of low and high intensities in a lowland dry forest in Bolivia. Three patterns of response to treatments were observed among the most abundant commercial tree species. (1) Shade-intolerant species regenerated mostly from seed and had the highest survival and growth rates following high-intensity burns. (2) Shade-tolerant species were abundant in gap control and plant removal treatments. Treatments had little effect on the height growth of these species. (3) Individuals of root sprouting species were most abundant following plant removal and low-intensity burn treatments. Treatments had little effect on the height growth of these species. The wide variation in species responses to gap treatments found in this study not only reinforces the concept that species are distributed along a continuum of shade-tolerance levels, but that other aspects of species biology, such as seed dispersal type or sprouting behavior, further differentiate regeneration strategies. The variety of regeneration strategies found among the species at this forest site will require a flexible management scheme that mixes more intensive silvicultural treatments such as prescribed burning with less intensive treatments.     

Comparison between old-growth stands and secondary stands regenerating after clear-felling in warm-temperate forests of Yakushima, southern Japan

In order to infer successional changes in structure, species composition and diversity of warm-temperate forest, we compared secondary stands regenerating after clear-felling (41–64-years old) with old-growth stands at altitudes between 300 and 800 m on Yakushima Island, southern Japan. Stem density and maximum stem diameter differed between secondary and old-growth stands, but basal area and aboveground biomass did not. At lower altitudes, the dominant species in old-growth stands with a strong sprouting capacity (Castanopsis cuspidata) also dominated secondary stands, and species composition of secondary and old-growth stands was similar. At higher altitudes, by contrast, the dominant species in old-growth stands (Distylium racemosum) had little sprouting capacity and was poorly represented in diverse secondary stands, which were dominated by Castanopsis or other less abundant species. Secondary stands had greater species diversity (Shannon–Wiener index) than old-growth stands, particularly at higher altitudes. This was due to greater species richness resulting from higher stem density per area, but not to greater evenness. We grouped the component species that share ecologically similar traits into four guilds (fagaceous, primary evergreen, secondary evergreen and deciduous species). Secondary stands were characterized by greater numbers of deciduous and secondary evergreen species. We concluded that different sprouting capacities of dominant species and different regeneration traits among guilds are responsible for the change in species composition and diversity during succession.     

Exotic plant species in the southern boreal forest of Saskatchewan

Exotic species possess abilities to harm the ecosystems they invade. This study assesses the density, frequency and cover of exotic plants in roadside right-of-ways, logged areas and wildfire sites within mixedwood sections of the southern boreal forest of Saskatchewan. A total of 23 exotic species were observed including nine species of Gramineae, seven species of Leguminosae and five species of Compositae. Average density of exotic species in areas recently disturbed by timber harvesting or wildfire was 0.2 stems m⁻² with a frequency of 72%. Exotic species adapted for wind dispersal were best represented including common dandelion (Taraxacum officinale), perennial sow thistle (Sonchus arvensis) and annual hawksbeard (Crepis tectorum). Only two exotic species, T. officinale and Canada bluegrass (Poa compressa), were observed in mature forest; both occurred with a frequency of 13% and an average density of 0.002 stems m⁻². A total of 22 exotic species was found in the right-of-ways quadrats with an average density of 117 stems m⁻² and a frequency of 94%. The most frequently observed exotic species in the roadside right-of-way areas were T. officinale, alsike clover (Trifolium hybridum), S. arvensis, creeping red fescue (Festuca rubra) and smooth brome grass (Bromus inermis). These species are either common agricultural weeds or were part of the original seed mixture used to establish a plant cover in the roadside right-of-ways.