Balancing trade-offs between biodiversity and production in the re-design of rangeland landscapes

The conflict that exists between the competing needs of biological conservation and pastoral production is well recognised but few studies have examined these conflicts due to their complexity and the uncertainty that surrounds these relationships. The development of a Bayesian network model that examines the trade-offs between the conservation value of the landscape for a range of taxa (flora, mammals, birds and herpetofauna) and its primary production value under alternative land uses is described. The model emphasises structural diversity of vegetation and ecosystem productivity as key drivers of both biodiversity and agricultural production. Simple scenarios, used to examine the influence of different land uses on multiple components of biodiversity and agricultural productivity, demonstrated the potential for the analysis of the trade-offs associated with alternative landscape designs. The potential of the model, as a planning or policy development tool for land management agencies or regional Natural Resource Management bodies, at multiple scales, is identified.

Field trial assessment of biological, chemical, and physical responses of soil to tillage intensity, fertilization, and grazing

Soil microbial populations can fluctuate in response to environmental changes and, therefore, are often used as biological indicators of soil quality. Soil chemical and physical parameters can also be used as indicators because they can vary in response to different management strategies. A long-term field trial was conducted to study the effects of different tillage systems (NT: no tillage, DH: disc harrow, and MP: moldboard plough), P fertilization (diammonium phosphate), and cattle grazing (in terms of crop residue consumption) in maize (Zea mays L.), sunflower (Heliantus annuus L.), and soybean (Glycine max L.) on soil biological, chemical, and physical parameters. The field trial was conducted for four crop years (2000/2001, 2001/2002, 2002/2003, and 2003/2004). Soil populations of Actinomycetes, Trichoderma spp., and Gliocladium spp. were 49% higher under conservation tillage systems, in soil amended with diammonium phosphate (DAP) and not previously grazed. Management practices also influenced soil chemical parameters, especially organic matter content and total N, which were 10% and 55% higher under NT than under MP. Aggregate stability was 61% higher in NT than in MP, 15% higher in P-fertilized soil, and also 9% higher in not grazed strips, bulk density being 12% lower in NT systems compared with MP. DAP application and the absence of grazing also reduced bulk density (3%). Using conservation tillage systems, fertilizing crops with DAP, and avoiding grazing contribute to soil health preservation and enhanced crop production.

The potential of Collembola to act as indicators of landscape stress in Australia

Collembola have been used to assess the ecological status of a range of ecosystems in Australia over the last 35 years. The traits that Collembola possess that make them valuable as ecological indicators are listed. Examples of situations where they have been used to measure impacts in mainly agricultural landscapes are described and the contributions the results have made to management for ecological sustainability are noted. Densities of exotic and native species in a variety of ecosystems are provided and a list of genera with exotic species in Australia is given. A protocol for comprehensively surveying Collembola is described and a critique of different methods given.

Monitoring soil productive potential

Desertification involves the loss of soil productive potential, but a means of assessing and monitoring the progress of desertification on the soil has been elusive. Soil is so varied and complex that methods of assessing condition are too slow, tedious, and expensive for routine use. Moreover, differences in soil type can be confused with soil condition. This paper presents a structured method of assessing soil condition. This method is based on recognizing and classifying soil surface features and examining soil properties that reflect the status of the processes of erosion, infiltration, and nutrient cycling. Published in the form of a user manual, the method has the following three stages: (1) defining the geomorphic setting of the site, (2) recognizing patch/interpatch associations and the mode of erosion at the landscape scale, and (3) assessing soil surface condition ratings in quadrats sited within the landscape pattern patches. Stage 3 is achieved by observing each of 11 features in the field and classifying their status according to detailed fieldnotes and photographs. The method applies to a wide range of soil types and biogeographical regimes and has proven to be repeatable among observers and quickly transferred to new observers.