Polyacrylonitrile (PAN) nanofibers have long been the subject of studies as precursor for high performance materials such as carbon nanofibers. Here, we present the first effort to study the ...mechanical properties of PAN nanofibers fabricated via near field electrospinning, in which bending instability was completely suppressed. The method allowed for the collection of continuous single-strand PAN nanofibers with aspect ratios exceeding 106 on a spool (rotating target). By controlling the electrospinning parameters, such as solution concentration, voltage and distance, we demonstrated that the morphology and diameter of the PAN nanofiber were well controlled. We also realized that slight changes in the distance can significantly change the shape of the cross section of the fibers, from a circular cross section to oval shaped (ribbons), which was explained in terms of solvent residues in the jet and momentum transfer between the fibers and the target, as the fibers reach the target. Our studies on individual PAN nanofibers revealed a strong mechanical size effect, in which reducing the diameter of the nanofibers from ∼290 nm to ∼200 nm, led to a large increase in modulus to as high as ∼9 GPa, among the highest in as-electrospun PAN nanofibers. The strong size effect was attributed to a loss in chain alignment in thicker electrospun nanofibers facilitated by the plasticizing effect of residual solvent. In comparison to conventional electrospinning, the NFES led to a significantly narrower diameter distribution. The demonstrated size-dependent morphology, mechanical properties of NFES PAN nanofibers provides a solid foundation for fabricating polymer nanofiber with controllable patterning and properties through NFES.
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•We demonstrated a path to develop PAN nanofibers with high controllability over morphology by adjusting NFES parameters.•Formation of ribbons or circular cross sections fibers was explained in terms of momentum transfer and solvent residues.•By suppressing the bending instability, we significantly narrowed distribution of fiber diameters by a factor of 2.•Our results point to a two-zone mechanical size effect, unlike what is observed in other types of polymeric nanofibers.•We explained the peculiar size effect in NFES nanofibers in terms of high chain packing and interactions between chains.
•We evaluate the effect of an environmental land registry on landholder behavior.•Registration decreased deforestation for one size-class of landholdings.•This group experienced a unique set of ...incentives from interacting land policies.•Some registrants declared boundaries strategically to fall under policy thresholds.•Securing land claims may motivate local responses to the environmental registry.
Across the tropics, development banks and conservation donors are investing millions in property mapping and registration projects to improve accountability for deforestation. An evaluation of the effectiveness and accuracy of existing environmental registries is crucial to assure the success of future efforts. This study presents an evaluation of deforestation and registration behavior in response to one of the largest of these property registration programs to date — the Rural Environmental Registry (CAR) in the Amazonian state of Pará. From late 2007 to 2013, approximately 100,000 properties covering 30 million hectares of self-declared claims were entered in this digital registry. We used fixed effects regression models and property level data to assess how registration influenced deforestation on different sizes of properties. Registration had little impact on deforestation behavior, with the exception of a significant reduction on “smallholder” properties in the size range of 100–300ha. We link this reduction to interacting incentives from forest protection and land regularization policies and suggest that desire to strengthen land claims motivates these landholders’ response to the environmental registry. We also present evidence that some landholders may be registering incomplete or inaccurate parcels into the self-declared system to strategically benefit from policy incentives. Our results for smallholder properties indicate that environmental registries may have potential to facilitate reductions in deforestation if combined with a favorable combination of incentives. However, in places where land tenure is still being negotiated, the utility of environmental registries for forest policy enforcement and research may be limited without ongoing investment to resolve uncertainty around land claims.
► Deforestation of smallholders vs. largeholders, Transamazon Highway. ► Smallholders (properties <100ha) deforested 23% by 2007. ► Smallholder-dominated areas better performance: forest core area, ...fragmentation, connectivity. ► 1999–2007 Almost zero deforestation rate in smallholder-dominated municipality. ► Smallholders’ potential for landscape stabilization and productive conservation.
Understanding actor-specific responsibility for deforestation in the Brazilian Amazon is key in adjusting policy and resource allocation in the face of current forest destruction. However, previous research shows that there is great variability in such assessments. To contribute to the ongoing discussions on forest conservation and rural development policies in the Amazon, this paper studies actor-specific deforestation and its environmental effects in four municipalities situated along the Transamazon Highway. We used spatially explicit methods that integrate a database of 8281 georeferenced properties with a time series of remote-sensing data covering four periods between 1986 and 2007. We also included landscape ecology metrics as improved indicators of the complex environmental effects of forest fragmentation. The analysis demonstrates that smallholders (defined as colonists who own less than 100ha of land) were responsible for 23% of total deforestation in the study region while accounting for 55% of the total properties. We also explored the relationship between property size and deforestation at the property level, finding that it closely follows a power distribution. Property deforestation increased with property size, while the percentage of property deforestation decreased. In spite of this, compliance with current legal requirements to maintain 50% of property forest cover was not statistically different between smallholders and largeholders. In comparison to municipalities dominated by medium- and large-scale ranchers, the smallholder-dominated municipality of Medicilândia showed better performance in all applied landscape metrics with well-established relationships with the provision of important environmental goods and services. Although all studied municipalities showed severe accumulated deforestation, Medicilândia experienced an abrupt decrease in municipal deforestation after 1999 to just 0.03%year−1, while municipalities dominated by larger holders maintained or increased their previous deforestation rates to between 0.90% and 1.34%year−1 in the same period. This indicates that the smallholders’ productions schemes in our study area might present potential for agricultural frontier stabilization based on improved land-use efficiency. The policy implications of our findings are discussed, especially with regard to the role of smallholders in productive forest conservation.
Once driven by large-scale clearings, Amazon deforestation now occurs mostly in small increments. Did this result from the emergence of a new group of agents or from a strategic adaptation in the ...behavior of those who led deforestation in the past? We address this question using georeferenced data on private rural properties and deforestation. We cross property-level and forest clearing data in an empirical setting designed to detect shifts toward clearing patches that were knowingly invisible to the monitoring system. We are therefore able to assess not only whether deforesters were responding strategically to stricter monitoring of deforestation, but also how this response differed across actor types. Results suggest that centralized policy efforts introduced starting in the mid-2000s inhibited medium- and large-scale deforestation, but had heterogeneous effects on small-scale deforestation. Although the relative participation of small deforestation polygons increased in both sample states, the relative participation of smallholders in total state deforestation increased in Pará, while remaining constant in Mato Grosso. We interpret these results as suggestive — albeit not causal — evidence that landholders strategically responded to the monitoring system by adapting their forest clearings practices to elude monitoring in both Mato Grosso and Pará. In the latter, however, the increase in smallholders’ share of annual deforestation suggests that their clearing practices were relatively less affected by what effectively contained deforestation in large properties. The apparent similarity in scale of deforestation across states conceals relevant baseline differences between the agents engaging in forest clearing in each locality. Tailoring policy to account for such differences could strengthen Brazilian conservation policy.
Riparian buffer zones (RBZs) are an important instrument for environmental policies for water and biodiversity protection in managed forests. We investigate the variation of the cost of implementing ...RBZs within different property size classes across the size range of non-industrial forest owner properties in Southern Sweden. Using the Heureka PlanWise decision support system, we quantified the cost of setting aside RBZs or applying alternative management in them, as the relative loss of harvest volume and of net present value per property. We did this for multiple simulated as well as real-world property distributions. The variation of cost distribution among small properties was 4.2–6.9 times higher than among large properties. The interproperty cost inequality decreased non-linearly with increasing property size and levelled off from around 200 ha. We conclude that RBZs, due to the irregular distribution of streams, cause highly unequal financial consequences for owners, with some small property owners bearing a disproportionally high cost. This adds to previous studies showing how environmental considerations differentially affect property owners. We recommend decision makers to stimulate the uptake of RBZs by alleviating these inequalities between forest owners by including appropriate cost sharing or compensation mechanisms in their design.
Deforestation in Brazilian Amazonia accounts for a disproportionate global scale fraction of both carbon emissions from biomass burning and biodiversity erosion through habitat loss. Here we use ...field- and remote-sensing data to examine the effects of private landholding size on the amount and type of forest cover retained within economically active rural properties in an aging southern Amazonian deforestation frontier. Data on both upland and riparian forest cover from a survey of 300 rural properties indicated that 49.4% (SD
=
29.0%) of the total forest cover was maintained as of 2007, and that property size is a key regional-scale determinant of patterns of deforestation and land-use change. Small properties (≤150
ha) retained a lower proportion of forest (20.7%, SD
=
17.6) than did large properties (>150
ha; 55.6%, SD
=
27.2). Generalized linear models showed that property size had a positive effect on remaining areas of both upland and total forest cover. Using a Landsat time-series, the age of first clear-cutting that could be mapped within the boundaries of each property had a negative effect on the proportion of upland, riparian, and total forest cover retained. Based on these data, we show contrasts in land-use strategies between smallholders and largeholders, as well as differences in compliance with legal requirements in relation to minimum forest cover set-asides within private landholdings. This suggests that property size structure must be explicitly considered in landscape-scale conservation planning initiatives guiding agro-pastoral frontier expansion into remaining areas of tropical forest.
The relationship between property size and property investment yield is an interesting issue in the real estate market. Previous studies usually use the mean-variance criterion to compare the ...return-risk profiles of the yields of different property sizes in the United States. However, this criterion has a few shortcomings. This article provides the first attempt to use a stochastic dominance approach to analyse this issue. We adopt two powerful stochastic dominance tests to compare the yields of five property size classes in the Hong Kong residential property market. In our study, we analyse two possible investment outcomes: (1) investors could not rent out their properties, and thus they would gain/lose from the appreciation/depreciation of residential property prices; (2) investors could also gain from rental incomes. Our empirical results provide strong evidence to show that the yields of smaller property classes stochastically dominate the yields of bigger property classes, suggesting that buying smaller properties is a better investment choice in the Hong Kong residential property market.
On the Ground California landownerships are changing—becoming smaller and more amenity-driven, with important implications for ecosystem service production. Residence on the property, larger property ...size, source of income from the land, having a long-term outlook, and using an advisory service are associated with landowner management for ecosystem services for the owner and for society. Advisory services like Cooperative Extension and the Natural Resources Conservation Service, as well as private consultants and professional organizations, have an important role in the future of ecosystem service production. California landownerships are changing—becoming smaller and more amenity-driven, with important implications for ecosystem service production. Residence on the property, larger property size, source of income from the land, having a long-term outlook, and using an advisory service are associated with landowner management for ecosystem services for the owner and for society. Advisory services like Cooperative Extension and the Natural Resources Conservation Service, as well as private consultants and professional organizations, have an important role in the future of ecosystem service production.
This paper operationalizes the concept of highly optimized tolerance (HOT) for the case of smallholder agriculture in Rondônia, Brazil. It seeks to understand how characteristics of family farms ...shift as a function of property size, arguing that as production intensifies, properties move closer to a HOT state. In this state, resources are committed to maintaining robustness against expected disturbances, such as shifts in yields or crop prices, making property more vulnerable to other unexpected disturbances, such as shifts in input prices or availability. The shifts in production, labor, and costs that occur across scale in the Ji-Paraná River Basin in Rondônia were measured using a survey instrument on a sample of farmers in the basin. Study results show decreasing production intensity with increasing property size in the sample, coupled with decreasing contracted and family labor use intensity, as well as decreased income diversification and off-farm labor. Farms smaller than 60 ha in the sample differed markedly in production and cost structure from those that were larger. For these smaller properties, meeting the requirements of Rondônia’s new environmental licensing program (LAPRO) may lead to an increase in the sale of land parcels to cover debts and a speeding up of land consolidation in the region.
Efficient sampling grids for timber cruises Brooks, J.R; Wiant, H.V. Jr
Northern Journal of Applied Forestry,
06/2004, Volume:
21, Issue:
2
Journal Article, Trade Publication Article
Open access
Equations are provided to permit forest inventory specialists to quantitatively estimate the total field inventory travel distance, and thus time, based solely on inputs of property size, the number ...of inventory samples desired, and the type of systematic grid employed. Total inventory travel time is estimated for square and varying rectangular grid spacings for property sizes from 100 to 10,000 ac to estimate the time savings for rectangular grids over square grid patterns for the same number of inventory samples.
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