Litter dynamics and phenology of Melaleuca quinquenervia in south Florida

We monitored litterfall biomass at six different sites of melaleuca (Melaleuca quinquenervia (Cav.) S.T. Blake) forested wetlands in South Florida from July 1997 to June 1999. Annual litterfall of melaleuca varied between sites from 6.5 to 9.9 t dry wt ha(-1) yr(1) over the two-year period. Litterfall was significantly higher (p < 0.0001) in scasonally flooded habitats (9.3 t ha(-1) yr(1)) than in non-flooded (7.5 t ha(-1) yr(1)) and permanently flooded habitats (8.0 t ha(-1) yr(1)). Leaf fall was the major component forming 70% of the total litter, woody material 16%, and reproductive material 11%. Phenology of flowering and leaf flush was investigated by examination of the timing and duration of the fall of different plant parts in the litter traps, coupled with monthly field observations during the two-year study. In both years, flowering began in October and November, with peak flowers production around December, and was essentially completed by February and March. New shoot growth began in mid winter after peak flowering, and extended into the spring. Very little new growth was observed in melaleuca forests during the summer months, from May to August, in South Florida. In contrast, the fall of leaves and small wood was recorded in every month of the year, but generally increased during the dry season with higher levels observed from February to April. Also, no seasonality was recorded in the fall of seed capsules, which apparently resulted from the continual self-thinning of small branches and twigs inside the forest stand. In planning management for perennial weeds, it is important to determine the period during its annual growth cycle when the plant is most susceptible to control measures. These phenological data suggest that the appropriate time for melaleuca control in South Florida might be during late winter and early spring, when the plant is most active

VERTICAL INTEGRATION AND TRADE POLICY: THE CASE OF SUGAR

The degree of vertical integration in the U.S. sugar industry between raw sugar processing and sugar refining cannot be explained using theories of vertical integration based on transaction costs (e.g. Williamson). We graphically decompose the economic rents accruing to each level in the marketing channel. Different strategies of several major sugar producing, processing and refining entities with regard to sugar quota policy are explored.Agribusiness, Industrial Organization,

Cellulosic Biofuels

Cellulosic biofuels are not as far off as often assumed. EESI's investigation of this issue found some pilot scale cellulosic biofuel production facilities already online and many more demonstration and commercial scale biorefineries under construction or on the drawing board. In fact, 55 cellulosic biorefineries are complete, under construction or in the planning stage in a total of 31 states across the country, adding up to an expected nameplate capacity of 629.5 million gallons per year (MGY) and a potential expansion to 995 MGY. Most of the demonstration and commercial scale facilities are scheduled to start operation in 2009 or 2010

Evaluation of shoreline change using optical satellite images, case study of Progreso, Yucatán

A technique to extract the shoreline from optical satellite images has been developed, evaluated and applied to the case study site of Progreso, Yucatán, México. This site was chosen as it is frequently subject to hurricanes, shows shoreline erosion and has a paucity of coastal data. The area under investigation is an 8 km length of shoreline that faces north into the Gulf of México. A novel method to extract satellite-derived shorelines (SDS) was developed ensuring the maximum contrast between sea and land. The SDS was validated using quasisimultaneous in situ shoreline measurements from one day in two different years (2008 and 2010). The in situ shoreline measurements recorded the instantaneous shorewards extent of the wave run-up when walking along the beach. The validation of SDS revealed that the SDS locates consistently seawards of the in situ shoreline, explained by: a) the water depth that an optical satellite image requires to identify a pixel either as sea or land, and b) the shorewards extent of the wave run-up. At Progreso, the overall distance between SDS and in situ shoreline is 5.6 m on average and standard deviation of 1.37 m (in the horizontal) over 8 km of shoreline. For an accurate location of the mean SDS, estimation of the shorewards extent of the wave run-up, tidal level and inter-tidal beach slope were required. In situ measurements regarding the beach profile, shoreline location and water levels were taken into consideration to achieve this. The shoreline change observed over a 6.5 year period allowed the estimation of intraannual and inter-annual shoreline changes and progressive changes in the shoreline location. The intra-annual shoreline change revealed seasonality in the shoreline position. The shoreline position from late winter (March 20, 2004) was landwards (approx. 5 to 9 m) in relation to the earlier winter shoreline position (November 11, 2003). The assessed SDSs from the hurricane season (June to November) are at the landwards envelope limit during the year, between -30 to 15 m in relation to the estimated mean SDS. The largest landward movement (100 m) is related to Hurricane Ivan, detected 13 days after the hurricane passed by Yucatán. The inter-annual shoreline change highlighted that an approximate length of 6 km of shoreline is retreating at a rate between -2.4 and -1.2 m per year. Such estimates of shoreline change would not be possible using other available coastal information at this site. The results of this research show that optical satellite images can be used to study shoreline change over large spatial scales (> 5 km), as well as in short (< 1 yr) and long (> 5 yrs) temporal scales.CONACy

Use of thermal inertia determined by HCMM to predict nocturnal cold prone areas in Florida

Surface temperatures derived from HCMM data were compared with to those obtained by GOES satellite and the apparent thermal inertia (ATI) calculated. For two dates, the HCMM temperatures appear to be about 5 C lower than the GOES temperatures. The ATI for excessively-drained to well-drained mineral soils was greater than for drained organic soils possibly because of long periods of low rainfall during late 1980 and early 1981. Organic soils cropped to sugar cane showed lower ATI after a severe killing freeze. With dead leaves, there was less transpiration and more solar radiation probably reached the dark soil surface. This would explain the larger diurnal temperature amplitude observed

Performance characterization of a multiplexed space-to-ground optical network

Advances in phased array systems for multi-beam free space optical communications are a key enabler for a new space-to-ground network architecture, namely a multiplexed optical architecture. The fundamental idea of a multiplexed space-to-ground optical network is the utilization of a multi-beam optical payload that allows each spacecraft to establish links with multiple ground stations within its line of sight. Information is then downlinked in parallel, from the satellite to the ground, through the subset of links not disrupted by clouds. In this paper we evaluate the performance of a multiplexed optical space-to-ground architecture from a systems perspective, with particular emphasis on the effect of cloud correlation in the network throughput. In particular, we first derive the expected data volume returned in a multiplexed architecture as a function of the optical network availability and the system total capacity. Then, we compare the performance of the proposed multiplexed architecture against a traditional single-beam downlink system that utilizes site diversity to mitigate cloud coverage effects. This comparison is based on two canonical scenarios, a global highly uncorrelated network representative of a geosynchronous satellite; and local, highly correlated, network representative of a low Earth orbit spacecraft. Through this analysis, we demonstrate that multiplexed architectures can improve the throughput of a space-to-ground optical network as compared to that of a single ground telescope without requiring a beam switching mechanism

Competitiveness of Regional Sugar Production under Alternative Production Conditions and Policies

Agricultural and Food Policy, Production Economics,

Apartheid in Miami: Transit Workers Challenge the System

[Excerpt] The story that follows will show how Dade County officials and the downtown Miami business establishment attempted to bust the transit union and dismantle a vital public transportation service to Miami\u27s minority, elderly and working-class communities. In the name of efficiency, Miami\u27s political and business establishment worked hand-in-hand with the Reagan administration to make minority workers and their communities pay for the mistakes of what experts say is one of the most mismanaged transit systems in the country. This is the story of how the union organized with the community to expose this mismanagement and how the union tried to address bad management practices by offering contract language which would give the union and the workforce a voice in how Dade\u27s transit system is run

The Dynamic Impact of Monetary Policy on Regional Housing Prices in the United States

This paper uses a factor-augmented vector autoregressive model to examine the impact of monetary policy shocks on housing prices. To simultaneously estimate the model parameters and unobserved factors we rely on Bayesian estimation and inference. Policy shocks are identified using high-frequency surprises around policy announcements as an external instrument. Impulse response functions reveal differences in regional housing price responses, which in some cases are substantial. The heterogeneity in policy responses is found to be significantly related to local regulatory environments and housing supply elasticities. Moreover, housing prices responses tend to be similar within states and adjacent regions in neighboring states