Modelling impacts of alternative farming management practices on greenhouse gas emissions from a winter wheat–maize rotation system in China

Agricultural production plays an important role in affecting atmospheric greenhouse gas concentrations. Field measurements were conducted in Quzhou County, Hebei Province in the North China Plains to quantify carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions from a winter wheat–maize rotation field, a common cropping system across the Chinese agricultural regions. The observed flux data in conjunction with the local climate, soil and management information were utilized to test a process-based model, Denitrification–Decomposition or DNDC, for its applicability for the cropping system. The validated DNDC was then used for predicting impacts of three management alternatives (i.e., no-till, increased crop residue incorporation and reduced fertilizer application rate) on CO₂ and N₂O emissions from the target field. Results from the simulations indicated that (1) CO₂ emissions were significantly affected by temperature, initial SOC, tillage method, and quantity and quality of the organic matter added in the soils; (2) increases in temperature, initial SOC, total fertilizer N input, and manure amendment substantially increased N₂O emissions; and (3) temperature, initial SOC, tillage, and quantity and quality of the organic matter added in the soil all had significant effects on global warming. Finally, five 50-year scenarios were simulated with DNDC to predict their long-term impacts on crop yield, soil C dynamics, nitrate leaching losses, and N₂O emissions. The modelled results suggested that implementation of manure amendment or crop residue incorporation instead of increased fertilizer application rates would more efficiently mitigate GHG emissions from the tested agro-ecosystem. The multi-impacts provided a sound basis for comprehensive assessments on the management alternatives.     

A distributed approach to accounting for carbon in wood products

With an evolving political environment of commitments to limit emissions of greenhouse gases, and of markets to trade in emissions permits, there is growing scientific, political, and economic need to accurately evaluate carbon (C) stocks and flows—especially those related to human activities. One component of the global carbon cycle that has been contentious is the stock of carbon that is physically held in harvested wood products. The carbon stored in wood products has been sometimes overlooked, but the amount of carbon contained in wood products is not trivial, it is increasing with time, and it is significant to some Parties. This paper is concerned with accurate treatment of harvested wood products in inventories of CO₂ emissions to the atmosphere. The methodologies outlined demonstrate a flexible way to expand current methods beyond the assumption of a simple, first-order decay to include the use of more accurate and detailed data while retaining the simplicity of simple formulas. The paper demonstrates that a more accurate representation of decay time can have significant economic implications in a system where emissions are taxed or emissions permits are traded. The method can be easily applied using only data on annual production of wood products and two parameters to characterize their expected lifetime. These methods are not specific to wood products but can be applied to long-lived, carbon-containing products from sources other than wood, e.g. long-lived petrochemical products. A single unifying approach that is both simple and flexible has the potential to be both more accurate in its results, more efficient in its implementation, and economically important to some Parties.     

Chronosequence analysis of two enclosure management strategies in degraded rangeland of semi-arid Kenya

The establishment of enclosures has become an important measure to combat land degradation in many of the world's semi-arid rangelands. In view of the increased pressure exerted by this land reclamation strategy on the neighbouring agricultural lands, knowledge of the time required for restoring vegetation cover and soil health, and of the potential positive impact of an adapted management strategy, is highly required. This paper assesses the vegetation and soil rehabilitation in a 23-year chronosequence of two different enclosure management types. In the severely degraded, semi-arid Njemps Flats plain of the Lake Baringo Basin in Kenya communal enclosures characterised by high quality inputs and strict control, and private enclosures managed by individual farmers, were installed since the 1980s. Six communal enclosures (3–17 years since establishment) and six private enclosures (13–23 years since establishment) were selected. Vegetation cover was estimated along three 50 m transects set within each enclosure and in the adjacent open grazing area using the point-to-line transect method. Five 0.5 m² quadrats systematically placed alongside each transect were sampled for herbaceous standing biomass and topsoil physical, chemical and biological analyses. Grass cover and herbaceous biomass production proved to be the most responsive biotic parameters under both management types, whereas the recovery of the forbs was unsuccessful. Under communal management, the biomass production fully recovered up to its optimal level as recorded in the neighbouring nature reserves. Within private enclosures however, the adopted management strategies seriously restricted biomass production to a significantly lower level. Soil quality generally recovered more slowly with time. Significant improvements compared to the open rangeland were recorded in topsoil bulk density, organic C and total N stocks, and microbial biomass C and N stocks of the communal enclosures. Unlike the communal enclosures, only topsoil bulk density and the microbial biomass C stock showed a significant difference in the private enclosures. With respect to C and total N stocks, and the microbial biomass N a non-significant improving trend was recorded. The level of chemical and biological soil quality obtained under both management types is still low and draws the attention to the importance of careful monitoring of grazing and grass cutting activities under both enclosure management strategies. The chronosequences further highlight the potential of some well-managed private enclosures, whereas intrinsic soil properties such as high alkalinity, as well as changes in management, limit the rehabilitation of some other private as well as communal enclosures.     

The professional humanitarian and the downsides of professionalisation

Criticisms lodged at humanitarian relief often include the belief that professionalisation is needed. The problems associated with humanitarianism would end, it is assumed, if the delivery of aid, and relief workers themselves, were more professional and ‘business like’. To explore this further, the paper asks what comprises a profession, and offers four criteria: 1) specialisation of knowledge; 2) establishment of the profession as a livelihood; 3) organisation and institutionalisation; and 4) legitimacy and authority. A model for understanding professionalisation, as developed by the author, is then presented. The analysis compares six other professions against the same criteria to argue that the humanitarian community already constitutes a profession. Finally, three potential downsides of professionalisation are offered: the distance of the relief worker from the beneficiary, barriers to entry into the humanitarian sector, and adding to risk aversion and a decline in innovation. Based on these findings, professionalisation should be approached with some caution.     

Recovery of insular seabird populations years after rodent eradication

Seabirds have been particularly affected by invasive non-native species, which has led to the implementation of numerous eradication campaigns for the conservation of these keystone and highly vulnerable species. Although the benefits of eradication of invasive non-native species for seabird conservation have been demonstrated, the recovery kinetics of different seabird populations on islands after eradication remains poorly evaluated. We conducted long-term monitoring of the number of breeding pairs of seven seabird species on a small atoll, Surprise Island, New Caledonia (southwestern tropical Pacific). Marine avifauna of the island were surveyed yearly 4 years before to 4 years after rodent eradication (conducted in 2005), and we conducted multiple one-time surveys from ∼10 years before and ∼15 years after eradication. We sought to determine how different seabird species responded to the eradication of invasive rodents in an insular environment. Three species responded positively (two- to 10-fold increase in population size) to eradication with differences in lag time and sensitivity. The number of breeding pairs increased (effect sizes = 0.49–0.95 and 0.35–0.52) for two species over 4 years post-eradication due to immigration. One species had a longer (at least 5 years) response time than all others; breeding pairs increased for over 10 years after eradication. Long-term sampling was necessary to observe the responses of the seabird populations on the island because of the delayed response of a species to eradication not visible in the first years after eradication. Our results confirmed the positive effects of eradication of invasive non-native species on seabirds and emphasize the importance of mid- and long-term pre- and posteradication surveys to decipher the mechanisms of seabird recovery and confirm the benefits of eradication for conservation purposes.     

Comparing spatial conservation prioritization methods with site- versus spatial dependency-based connectivity

Larval dispersal is an important component of marine reserve networks. Two conceptually different approaches to incorporate dispersal connectivity into spatial planning of these networks exist, and it is an open question as to when either is most appropriate. Candidate reserve sites can be selected individually based on local properties of connectivity or on a spatial dependency-based approach of selecting clusters of strongly connected habitat patches. The first acts on individual sites, whereas the second acts on linked pairs of sites. We used a combination of larval dispersal simulations representing different seascapes and case studies of biophysical larval dispersal models in the Coral Triangle region and the province of Southeast Sulawesi, Indonesia, to compare the performance of these 2 methods in the spatial planning software Marxan. We explored the reserve design performance implications of different dispersal distances and patterns based on the equilibrium settlement of larvae in protected and unprotected areas. We further assessed different assumptions about metapopulation contributions from unprotected areas, including the case of 100% depletion and more moderate scenarios. The spatial dependency method was suitable when dispersal was limited, a high proportion of the area of interest was substantially degraded, or the target amount of habitat protected was low. Conversely, when subpopulations were well connected, the 100% depletion was relaxed, or more habitat was protected, protecting individual sites with high scores in metrics of connectivity was a better strategy. Spatial dependency methods generally produced more spatially clustered solutions with more benefits inside than outside reserves compared with site-based methods. Therefore, spatial dependency methods potentially provide better results for ecological persistence objectives over enhancing fisheries objectives, and vice versa. Different spatial prioritization methods of using connectivity are appropriate for different contexts, depending on dispersal characteristics, unprotected area contributions, habitat protection targets, and specific management objectives. Comparación entre los métodos de priorización de la conservación espacial con sitio y la conectividad espacial basada en la dependencia