Conservation and reservation of non-vascular plants in Tasmania,with special reference to lichens

Conservation management of the Tasmanian flora is now focusing on non-vascular plants. Major problems include the low level of information on the composition of the flora and the low number of competent specialists available to deal with the plants. Collation of information from literature and from collections in herbaria is required to establish exactly which data are available and their reliability. An environmental domain analysis covering all ecosystems would indicate which environments were under-represented or absent from current reserves and where needs for conservation lie. Within practical time-frames, this process is probably the best method of capturing unknown components of the flora whilst also catering for widespread species and those closely associated with particular environments. It also incorporates regional variability. Minor habitats, which are often floristically rich, and very rare species are best dealt with on an individual basis. Basic research into taxonomy and ecology is paramount. Reservation and conservation management must be based on well-established and maintained databases which are in turn based on a coherent taxonomy and sound biogoographical information. It is only by pursuing an active research programme that the necessary accurate information can be obtained and the success of the management procedures can be gauged.     

The effect of increased deposition of atmospheric nitrogen on Calluna vulgaris in upland Britain

Regular (monthly) additions of NH₄NO₃ (4–12 g N m⁻² yr⁻¹) were made over a period of 8 yr (1989–98) to areas of moorland in North Wales dominated by the ericaceous shrub Calluna vulgaris . Results from the early stages of the experiment (1990–94) have shown marked and dose-related increases in shoot extension and canopy height in response to the nitrogen treatments, with significantly higher shoot nitrogen contents. The nitrogen-related stimulation in the growth of the C. vulgaris canopy over this period has resulted in large accumulations of litter on the high-nitrogen-treated plots (6.6 kg m⁻² in plots treated with 12 g N m⁻² yr⁻¹, compared with 3.8 kg m⁻² for the water controls). Litter nitrogen concentrations were also significantly increased at the higher rates of nitrogen addition, leading to a doubling of the total return of nitrogen to the litter layer over the experimental period. These changes in vegetation structure were associated with large reductions in the abundance of the bryophyte and lichen species normally present under the untreated canopy. Results since 1994, however, show little increase in shoot extension in response to the nitrogen treatments, with no clear dose response to increasing levels of addition. These findings are associated with a dose-related increase in the susceptibility of the nitrogen-treated areas of the C. vulgaris canopy to late winter injury, characterized as browning of the shoot tips in early to late spring. These results indicate that deleterious effects are now accumulating as a result of the long-term addition of nitrogen to these moorland plots.     

Biological Soil Crust Rehabilitation in Theory and Practice: An Underexploited Opportunity

Biological soil crusts (BSCs) are ubiquitous lichen–bryophyte microbial communities, which are critical structural and functional components of many ecosystems. However, BSCs are rarely addressed in the restoration literature. The purposes of this review were to examine the ecological roles BSCs play in succession models, the backbone of restoration theory, and to discuss the practical aspects of rehabilitating BSCs to disturbed ecosystems. Most evidence indicates that BSCs facilitate succession to later seres, suggesting that assisted recovery of BSCs could speed up succession. Because BSCs are ecosystem engineers in high abiotic stress systems, loss of BSCs may be synonymous with crossing degradation thresholds. However, assisted recovery of BSCs may allow a transition from a degraded steady state to a more desired alternative steady state. In practice, BSC rehabilitation has three major components: (1) establishment of goals; (2) selection and implementation of rehabilitation techniques; and (3) monitoring. Statistical predictive modeling is a useful method for estimating the potential BSC condition of a rehabilitation site. Various rehabilitation techniques attempt to correct, in decreasing order of difficulty, active soil erosion (e.g., stabilization techniques), resource deficiencies (e.g., moisture and nutrient augmentation), or BSC propagule scarcity (e.g., inoculation). Success will probably be contingent on prior evaluation of site conditions and accurate identification of constraints to BSC reestablishment. Rehabilitation of BSCs is attainable and may be required in the recovery of some ecosystems. The strong influence that BSCs exert on ecosystems is an underexploited opportunity for restorationists to return disturbed ecosystems to a desirable trajectory.     

Rapid photosynthetic recovery of a snow-covered feather moss and Peltigera lichen during sub-Arctic midwinter warming

Background: Arctic lichens and mosses are covered by snow for more than half the year and are generally considered as being dormant for most of this period. However, enhanced frequency of winter warming events due to climate change can cause increased disturbance of their protective subnivean environment.

Aim: To further understand cryptogamic responses to midwinter warming we compared the ecophysiological performance of one lichen and one moss species during a simulated warming event.

Methods: We measured photosynthesis and dark respiration in samples of the moss Hylocomium splendens and the lichen Peltigera aphthosa removed from under snow, and on natural refreezing after the warming event, which was simulated by using infrared heaters suspended above the ground.

Results: The moss exposed to light at +5 °C immediately after removal from their subnivean environment and from warmed plots showed positive net gas exchange within 332 s; the lichen required 1238 s. Photosynthesis and nitrogen fixation rates were equal to that, or higher than, during the preceding growing season. Upon refreezing after the event, moss photosynthesis declined considerably.

Conclusions: The moss, and to a lesser extent the lichen, may contribute to subnivean midwinter ecosystem respiration, and both are opportunistic, and can take advantage of warmer winter phases for photosynthesis and growth. This ought to be taken into account in vegetation change projections of cryptogam-rich ecosystems.     

Geoecology of Erratic Lichens of Xanthoparmelia vagans in an equatorial Andean Paramo

A population of 166 lichens of Xanthoparmelia vagans (Nylander) Hale, an obligatory erratic species, was investigated at 4530 m in the Venezuelan Andes. Lichen size and shape were strongly correlated; larger specimens were less spherical and compact than smaller ones. This was related to a greater frequency of disturbance – mainly by wind and frost – of small lichens, which are transported more easily than larger, heavy ones. Constant movement produces nearly spherical specimens, but as lichens grow larger, they are rotated less frequently and rest on a single side for increasingly longer periods; these immobile lichens become progressively more flattened and lenticular in shape. Many large lichens had two distinctive sides, an upper and a lower one, with different coloration. The upper face was pale yellowish green to olive gray (Munsell 5Y 8/4–5/2), the lower one black to very dark brown (10YR 2/1–2/2). Small lichens usually showed no differences between sides. Color variation is also induced by lichen movement. In frequently rotating lichens, thalli grow evenly in all directions due to a uniform insolation. In stationary lichens, thalli remain permanently oriented facing upwards, and their upper and lower sides diverge in coloration. The largest lichens break up easily. Some large specimens were in the process of fragmentation; these had a distinctive kidney-shaped form. Experimental splitting of 16 lichens showed that reduction in size by fragmentation also results in more equant specimens than the original ones. Laboratory experiments on aeolian transport indicated that wind speeds in the paramo are capable of carrying the erratic lichens, but soil areas covered by soil nubbins (miniature mounds produced by needle ice) can trap moving lichens, and greater wind velocities are then needed to re-mobilize them. Lichens were able to quickly absorb and store large amounts of water. Large lichens retained less water than small ones, but lost moisture at much slower rates. Needle-ice growth delivers water to the paramo soil surface, where lichens can readily imbibe it. The water relations of Xanthoparmelia, considered to be ecologically crucial for lichen growth and survival, are discussed in detail.     

The ones we left behind: Comparing plot sampling and floristic habitat sampling for estimating bryophyte diversity

An efficient method for estimating bryophyte diversity in forest stands must consider more than just the dominant forest mesohabitat. We compared two methodologies commonly used for estimating diversity in forest ecosystems. Floristic habitat sampling (FHS) utilizes stratification of all forest mesohabitats, which includes the natural diversity of microhabitats found within and stratifies a mosaic of mesohabitats (e.g. forest, streams, seeps, and cliffs) and microhabitats (e.g. rocks logs, etc.) that are often not considered in forest research projects that use plot sampling to estimate species diversity. In Canadian cedar hemlock forest, FHS methodology recorded more than twice as many bryophyte species as plot sampling (PS). A comparison of the dominant forest mesohabitat concluded that plot sampling was not as efficient as FHS in estimating bryophyte diversity and that plot sampling can result in different interpretations of species diversity. Rare species ordination of stands sampled using FHS showed strong clustering of sites with respect to biogeoclimatic zones and age since the last major disturbance (fire or logging) as compared with rare species ordinations from PS data, which showed no delineation of stands along temporal gradients. Plot sampling has many useful applications in ecology, but floristic habitat sampling is more efficient for quantifying overall bryophyte diversity. FHS provides an excellent way to record a comprehensive list of species.     

Altitudinal zonation of Andean cryptogam communities

To test whether cryptogamic plant communities in tropical Andean rain forests are distributed in floristically discrete communities corresponding to altitudinal belts, I subjected the elevational distribution of pteridophytes along two elevational gradients in Bolivia, and of bryophytes and lichens along two transects in Peru and Colombia (data from Gradstein & Frahm, 1987 ; Wolf, 1993 ) to an analysis of deviance. All well‐defined elevational boundaries in floristic composition were related to marked ecological changes: the transition from the steep mountains to the hilly lowland zone coupled with a change in geological substrate at 400 m along the Bolivian Carrasco transect, a strong humidity gradient at 1000 m at the Bolivian Masicurí transect and at 1250–1980 m along the Colombian transect, and the transition from mixed cloud forests to forests dominated by Polylepis or Podocarpus at 3400–3600 m in Carrasco, at 1650–1800 m in Masicurí, and at 3670 m in Colombia. Consequently, floristic elevational belts appear to be well‐defined at strong environmental boundaries and in fairly species‐poor forest communities where the presence or absence of one or a few tree species influences the whole ecosystem while they are ill‐defined in species‐rich communities such as tropical forests at low to mid‐elevations.