Estimating carbon carrying capacity in natural forest ecosystems across heterogeneous landscapes: addressing sources of error

Evaluating contributions of forest ecosystems to climate change mitigation requires well‐calibrated carbon cycle models with quantified baseline carbon stocks. An appropriate baseline for carbon accounting of natural forests at landscape scales is carbon carrying capacity (CCC); defined as the mass of carbon stored in an ecosystem under prevailing environmental conditions and natural disturbance regimes but excluding anthropogenic disturbance. Carbon models require empirical measurements for input and calibration, such as net primary production (NPP) and total ecosystem carbon stock (equivalent to CCC at equilibrium). We sought to improve model calibration by addressing three sources of errors that cause uncertainty in carbon accounting across heterogeneous landscapes: (1) data‐model representation, (2) data‐object representation, (3) up‐scaling. We derived spatially explicit empirical models based on environmental variables across landscape scales to estimate NPP (based on a synthesis of global site data of NPP and gross primary productivity, n=27), and CCC (based on site data of carbon stocks in natural eucalypt forests of southeast Australia, n=284). The models significantly improved predictions, each accounting for 51% of the variance. Our methods to reduce uncertainty in baseline carbon stocks, such as using appropriate calibration data from sites with minimal human disturbance, measurements of large trees and incorporating environmental variability across the landscape, have generic application to other regions and ecosystem types. These analyses resulted in forest CCC in southeast Australia (mean total biomass of 360 t C ha^?1, with cool moist temperate forests up to 1000 t C ha^?1) that are larger than estimates from other national and international (average biome 202 t C ha^?1) carbon accounting systems. Reducing uncertainty in estimates of carbon stocks in natural forests is important to allow accurate accounting for losses of carbon due to human activities and sequestration of carbon by forest growth.     

Why do some species in arid lands increase under grazing? Mechanisms that favour increased abundance of Maireana pyramidata in overgrazed chenopod shrublands of South Australia

While the abundance of some plant species decreases under high grazing intensity, others become more abundant. Release from competition by decreaser species contributes to this pattern in mesic systems, but this may not be the case in xeric systems where competition may be less intense. Here we examine three mechanisms that may be involved: (i) increased recruitment and growth because of soil changes produced by grazing, for example, increased soil nutrient availability through dung accumulation; (ii) increased recruitment favoured by the breaking up of the lichen crust; and (iii) reduced competition because of the decline of decreaser species. We used field and glasshouse experiments to determine the possible contribution of these mechanisms to the increase of the chenopod Maireana pyramidata around a watering point in a chenopod shrubland of South Australia. There was no evidence of nutrient accumulation close to the watering point, and while seedlings of M. pyramidata responded to nutrient addition, their growth was the same in soil collected from areas with different grazing intensity. While a broken lichen crust increased the emergence of both M. pyramidata and the decreaser Atriplex vesicaria, the effect was larger for the former. We found no competition between seedlings of the two species or between juveniles of A. vesicaria and seedlings of M. pyramidata in glasshouse experiments. Adult plants of both A. vesicaria and M. pyramidata produced similar growth reduction in seedlings of M. pyramidata. Furthermore, a field removal experiment failed to detect any competitive effect of A. vesicaria on M. pyramidata. Our data indicate that the disintegration of the soil crust by grazer activities can be a major factor controlling floristic changes in overgrazed rangelands. These results imply that factors that control establishment may be more important than competition in shaping shrub population dynamics in these systems. Ground surface itself can affect establishment opportunities, and this should be taken into account in management and restoration efforts in arid lands.     

Sound Intensity of Booming in Lesser Prairie-Chickens

ABSTRACT Wildlife managers traditionally monitored lesser prairie-chicken (Tympanuchus pallidicinctus) populations using road-based lek surveys and assumed booming can be heard ≥1.6 km from a lek. To assess this assumption, we measured sound intensity (decibels) of booming lesser prairie-chickens. Our results indicated sound intensity 1.6 km from a lek would be less than or equal to the sound intensity of a whisper. Thus, 1.6 km is probably too great a distance for audible detection of booming in many conditions.     

Within-cultivar differences in relative leaf growth rates at low temperature of onion seedlings are not heritable

Onion seedlings of two open-pollinated cultivars were grown either at a constant 10°C or outdoors in spring and were selected for high, medium or low relative leaf growth rate, R_L. Flowering plants within each R_L group were crossed using controlled pollination for the 10°C selections and as a fly-pollinated polycross for the outdoor selections. The pollen donors of the 10°C selections were also selfed. Despite the wide variation of R_L in the parent populations, there was no indication of heritability of R_L. Mean R_L was significantly lower for the progeny from self-rather than cross-pollinations as was initial leaf area and rate of seedling emergence.     

PRINCIPLISM AND THE ETHICAL APPRAISAL OF CLINICAL TRIALS

For nearly two decades, the process of reviewing the ethical merit of research involving human subjects has been based on the application of principles initially described in the U.S. National Commission's Belmont Report, and later articulated more fully by Beauchamp and Childress in their Principles of Biomedical Ethics. Recently, the use of ethical principles for deliberating about moral problems in medicine and research, referred to in the pejorative sense as “principlism”, has come under scrutiny. In this paper we argue that these principles can provide a foundation for the source of ethical appraisal of human research, but are not themselves wholly adequate for this purpose. Therefore, we further propose that (1) principles should be understood as heuristics that can be “specified” as described by DeGrazia (1992), and (2) that the principle-based approach should be supplemented by formally incorporating “sensitivity to context” into the evaluation of clinical trials     

The Evolving Role of Botanical Gardens and Natural Areas: A Floristic Case Study from Royal Botanical Gardens, Canada

As leaders calling for the conservation of the world's plants, botanical gardens protect plants within living collections. Many also study, manage and restore plants in natural habitats. Royal Botanical Gardens (Ontario,Canada) has integrated both horticultural and natural heritage in its mission for decades. Envisioned by municipal leaders in the 1920s as a combination of nature sanctuaries and civic gardens, RBG now includes forests, wetlands and other habitats, gardens and built spaces. Today RBG is Canada's largest botanical garden on the basis of area.In the 1950s RBG began to inventory plant diversity. The checklist of spontaneous vascular plants now exceeds 1 170 species, of which 752 are native. This is 37% of Ontario's native vascular plants and 19% of the native vascular flora of Canada. The RBG nature sanctuaries are among the richest locations in Canada for species-level diversity.We examine the history of fioristic exploration within RBG and compare plant species-area relationships among protected natural areas in Ontario. This comparison supports the contention that the nature sanctuaries, and in particular Cootes Paradise, could be considered an important area for plants in Canada, and relative to the nation's flora, a biodiversity hotspot. The fact that a candidate vascular plant hotspot for Canada lies within a major botanical garden presents opportunities for raising public awareness of the importance of plant diversity, as well as focusing attention on the scientific and conservation biology needs of communities and individual species in this area.