Impact of bioenergy crops in a carbon dioxide constrained world: an application of the MiniCAM energy-agriculture and land use model

In the coming century, modern bioenergy crops have the potential to play a crucial role in the global energy mix, especially under policies to reduce carbon dioxide emissions as proposed by many in the international community. Previous studies have not fully addressed many of the dynamic interactions and effects of a policy-induced expansion of bioenergy crop production, particularly on crop yields and human food demand. This study combines an updated agriculture and land use (AgLU) model with a well-developed energy-economic model to provide an analysis of the effects of bioenergy crops on energy, agricultural and land use systems. The results indicate that carbon dioxide mitigation policies can stimulate a large production of bioenergy crops, dependent on the level of the policy. This production of bioenergy crops can lead to several impacts on the agriculture and land use system: decreases in forestland and unmanaged land, decreases in the average yield of food crops, increases in the prices of food crops, and decreases in the level of human demand of calories.

种植密度和降水对冬小麦田N2O排放的影响

为研究种植密度对农田N2O排放的影响和探讨N₂O排放季节性波动的原因,于1999～2000年小麦生长季在南京市郊江宁县进行了不同播种量(0、90、180和270kg/hm²)的大田试验.观测分析结果表明:在相同的气象条件和田间管理下,播种～越冬阶段的N₂O排放不受播种量的影响,返青～成熟阶段的N₂O排放通量与播种量成正比.裸地条件下的N₂O排放与播量为90kg/hm²下的排放无明显差异.造成该生长季内N₂O排放季节性波动的主要原因是降水,返青～成熟阶段的N₂O排放通量随观测日前6d的加权平均降水量呈指数增加.     

A Bayesian approach to multi-source forest area estimation

In efforts such as land use change monitoring, carbon budgeting, and forecasting ecological conditions and timber supply, there is increasing demand for regional and national data layers depicting forest cover. These data layers must permit small area estimates of forest area and, most importantly, provide associated error estimates. This paper presents a model-based approach for coupling mid-resolution satellite imagery with plot-based forest inventory data to produce estimates of probability of forest and associated error at the pixel-level. The proposed Bayesian hierarchical model provides access to each pixel’s posterior predictive distribution allowing for a highly flexible analysis of pixel and multi-pixel areas of interest. The paper presents a trial using multiple dates of Landsat imagery and USDA Forest Service Forest Inventory and Analysis plot data. The results describe the spatial dependence structure within the trial site, provide pixel and multi-pixel summaries of probability of forest land use, and explore discretization schemes of the posterior predictive distributions to forest and non-forest classes. Model prediction results of a holdout set analysis suggest the proposed model provides high classification accuracy, 88%, for the trial site.

Scale-dependent variation in coral community similarity across sites, islands, and island groups

Community similarity is the proportion of species richness in a region that is shared on average among communities within that region. The slope of local richness (alpha diversity) regressed on regional richness (gamma diversity) can serve as an index of community similarity across regions with different regional richness. We examined community similarity in corals at three spatial scales (among transects at a site, sites on an island, and islands within an island group) across a 10 000-km longitudinal diversity gradient in the west-central Pacific Ocean. When alpha diversity was regressed on gamma diversity, the slopes, and thus community similarity, increased with scale (0.085, 0.261, and 0.407, respectively) because a greater proportion of gamma diversity was subsumed within alpha diversity as scale increased. Using standard randomization methods, we also examined how community similarity differed between observed and randomized assemblages and how this difference was affected by spatial separation of species within habitat types and specialization of species to three habitat types (reef flats, crests, and slopes). If spatial separation within habitat types and/or habitat specialization (i.e., underdispersion) occurs, fewer species are shared among assemblages than the random expectation. When the locations of individual coral colonies were randomized within and among habitat types, community similarity was 46-47% higher than that for observed assemblages at all three scales. We predicted that spatial separation of coral species within habitat types should increase with scale due to dispersal/extinction dynamics in this insular system, but that specialization of species to different habitat types should not change because habitat differences do not change with scale. However, neither habitat specialization nor spatial separation within habitat types differed among scales. At the two larger scales, each accounted for 22-24% of the difference in community similarity between observed and randomized assemblages. At the smallest scale (transect-site), neither spatial separation within habitat types nor habitat specialization had significant effects on community similarity, probably due to the small size of transect samples. The results suggest that coral species can disperse among islands in an island group as easily as they can among sites on an island over time scales that are relevant to their establishment and persistence on reefs.     

Clear effects of soil organic matter chemistry, as determined by NMR spectroscopy, on the sorption of diuron

Organic matter has long been recognized as the main sorbent phase in soils for hydrophobic organic compounds (HOCs). In recent times, there has been an increasing realization that not only the amount, but also the chemical composition, of organic matter can influence the sorption properties of a soil. Here, we show that the organic carbon-normalized sorption coefficient (K(OC)) for diuron is 27-81% higher in 10 A11 horizons than in 10 matching A12 horizons for soils collected from a small (2ha) field. K(OC) was generally greater for the deeper (B) horizons, although these values may be inflated by sorption of diuron to clays. Organic matter chemistry of the A11 and A12 horizons was determined using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. K(OC) was positively correlated with aryl C (r2=0.59, significance level 0.001) and negatively correlated with O-alkyl C (r2=0.84, significance level <0.001). This is only the second report of correlations between whole soil K(OC) and NMR-derived measures of organic matter chemistry. We suggest that this success may be a consequence of limiting this study to a very small area (a single field). There is growing evidence that interactions between organic matter and clay minerals strongly affect K(OC). However, because the soil mineralogy varies little across the field, the influence of these interactions is greatly diminished, allowing the effect of organic matter chemistry on K(OC) to be seen clearly. This study in some way reconciles studies that show strong correlations between K(OC) and the chemistry of purified organic materials and the general lack of such correlations for whole soils.     

Socially facilitated egglaying behavior in Mediterranean fruit flies

We examined the behavior of individual mature female Mediterranean fruit flies (medflies), Ceratitis capitata (Wiedemann), transferred from a holding cage without fruit to a clean host kumquat fruit already occupied by another medfly female engaged in ovipositional behavior. A significantly greater proportion of transferred (=test) ovipositionally naive females initiated ovipositor boring into a fruit in the presence than in the absence of an occupying medfly. Moreover, test females commenced boring significantly sooner in the presence than in the absence of another medfly. Interestingly, similar results occurred when a test medfly was transferred to a kumquat occupied by an ovipositing female oriental fruit fly, Bactrocera dorsalis Hendel. In contrast, there was no enhancement of propensity to bore when a test medfly was transferred to a kumquat occupied by a female Biosteres arisanus (Sonan), a parasitoid attacking medfly eggs. The principal proximate stimulus giving rise to the higher tendency to oviposit of a test medfly in the presence of an occupying medfly or oriental fruit fly appeared to be wing-waving by the occupant during an encounter. We consider our findings to be good evidence of socially facilitated ovipositional behavior in ovipositionally naive medflies, and suggest that such females may benefit from acquisition of a cue demonstrating the acceptability of a host for oviposition. Received: 7 July 1997 / Accepted after revision: 30 August 1997     

Interactions between water and land in The Netherlands

The Netherlands are one of the most densely populated coastal countries in the world and there is only limited space for living, working, transport and recreation, while there is also the need to preserve and expand valuable natural habitats. In order to solve many existing and future conflicts of interest, and in order to create ‘added value’, strategies are developed to optimize the use of water-land systems. The principle of ‘building with nature’ is applied in order to integrate land in sea and water in land in such a way that future generations will be able to use coastal resources in a sustainable way, including a minimal effort to maintain the coastline and the promotion of a multiple-use system. The concept of Integrated multifunctional sustainable coastal zone development is introduced. This concept deals with a balanced approach to the lack of space for present and future coastal uses in relation to each other, to the hinterland, and to the sea. Flexible master plans are developed, taking into account many functions of the coastal zone, and facilitating adaptation to future developments—e.g. impacts of climate change and relative sea level rise. In this regard increasing the flexibility of the coastal zone is of vital importance. Large-scale coastal land reclamations in The Netherlands are dealt with, based on two different principles: (1) polder systems (low lying land reclamations surrounded and protected by dikes), (2) systems of ‘building with nature’—land reclamation protected by man-made foreshores, beaches and dunes. In the latter type new flexible dynamic-equilibrium coasts are created for many functions, while coastal vulnerability is reduced and a flexible coast is developed.