Peak grain forecasts for the US High Plains amid withering waters.

Irrigated agriculture contributes 40% of total global food production. In the US High Plains, which produces more than 50 million tons per year of grain, as much as 90% of irrigation originates from groundwater resources, including the Ogallala aquifer. In parts of the High Plains, groundwater resources are being depleted so rapidly that they are considered nonrenewable, compromising food security. When groundwater becomes scarce, groundwater withdrawals peak, causing a subsequent peak in crop production. Previous descriptions of finite natural resource depletion have utilized the Hubbert curve. By coupling the dynamics of groundwater pumping, recharge, and crop production, Hubbert-like curves emerge, responding to the linked variations in groundwater pumping and grain production. On a state level, this approach predicted when groundwater withdrawal and grain production peaked and the lag between them. The lags increased with the adoption of efficient irrigation practices and higher recharge rates. Results indicate that, in Texas, withdrawals peaked in 1966, followed by a peak in grain production 9 y later. After better irrigation technologies were adopted, the lag increased to 15 y from 1997 to 2012. In Kansas, where these technologies were employed concurrently with the rise of irrigated grain production, this lag was predicted to be 24 y starting in 1994. In Nebraska, grain production is projected to continue rising through 2050 because of high recharge rates. While Texas and Nebraska had equal irrigated output in 1975, by 2050, it is projected that Nebraska will have almost 10 times the groundwater-based production of Texas.

TREHS: An open-access software tool for investigating and evaluating temporary river regimes as a first step for their ecological status assessment.

When the regime of a river is not perennial, there are four main difficulties with the use of hydrographs for assessing hydrological alteration: i) the main hydrological features relevant for biological communities are not quantitative (discharges) but qualitative (phases such as flowing water, stagnant pools or lack of surface water), ii) stream flow records do not inform on the temporal occurrence of stagnant pools, iii) as most of the temporary streams are ungauged, their regime has to be evaluated by alternative methods such as remote sensing or citizen science, and iv) the biological quality assessment of the ecological status of a temporary stream must follow a sampling schedule and references adapted to the flow- pool-dry regime. To overcome these challenges within an operational approach, the freely available software tool TREHS has been developed within the EU LIFE TRIVERS project. This software permits the input of information from flow simulations obtained with any rainfall-runoff model (to set an unimpacted reference stream regime) and compares this with the information obtained from flow gauging records (if available) and interviews with local people, as well as instantaneous observations by individuals and interpretation of ground-level or aerial photographs. Up to six metrics defining the permanence of water flow, the presence of stagnant pools and their temporal patterns of occurrence are used to determine natural and observed river regimes and to assess the degree of hydrological alteration. A new regime classification specifically designed for temporary rivers was developed using the metrics that measure the relative permanence of the three main phases: flow, disconnected pools and dry stream bed. Finally, the software characterizes the differences between the natural and actual regimes, diagnoses the hydrological status (degree of hydrological alteration), assesses the significance and robustness of the diagnosis and recommends the best periods for biological quality samplings.

Variation in the radial patterns of sap flux density in pubescent oak (Quercus pubescens) and its implications for tree and stand transpiration measurements.

Radial variation in sap flux density across the sapwood was assessed by the heat field deformation method in several trees of Quercus pubescens Wild., a ring-porous species. Sapwood depths were delimited by identifying the point of zero flow in radial patterns of sap flow, yielding tree sapwood areas that were 1.5-2 times larger than assumed based on visual examinations of wood cores. The patterns of sap flow varied both among trees and diurnally. Rates of sap flow were higher close to the cambium, although there was a significant contribution from the inner sapwood, which was greater (up to 60% of total flow) during the early morning and late in the day. Accordingly, the normalized difference between outer and inner sapwood flow was stable during the middle of the day, but showed a general decline in the afternoon. The distribution of sap flux density across the sapwood allowed us to derive correction coefficients for single-point heat dissipation sap flow measurements. We used daytime-averaged coefficients that depended on the particular shape of the radial profile and ranged between 0.45 and 1.28. Stand transpiration calculated using the new method of estimating sapwood areas and the radial correction coefficients was similar to (Year 2003), or about 25% higher than (Year 2004), previous uncorrected values, and was 20-30% of reference evapotranspiration. We demonstrated how inaccuracies in determining sapwood depths and mean sap flux density across the sapwood of ring-porous species could affect tree and stand transpiration estimates.

Experimental mandibular regeneration by distraction osteogenesis with submerged devices: preliminary results of a canine model.

The authors describe a new technique for reconstruction of mandibular body defects. The feasibility of distraction osteogenesis with submerged (internal) devices for reconstruction of segmental mandibular defects is investigated in an experiment with five adult dogs. A segmental mandibulectomy was performed on the horizontal ramus. The bony defect was regenerated using distraction osteogenesis (bone transport) at a rate of 1 mm daily. The animals were killed after the consolidation period. Complete bone regeneration of the surgically created gap was successful in three of five dogs. Two animals failed to create new bone. In these two cases, the screws did not offer proper stability to the bony fragments, and this caused a lack of ossification. This experimental study demonstrates the possibility to use internal distraction devices to reconstruct segmental mandibular defects in a canine model. Internal devices show enormous advantages in comparison with the external ones. This method with no donor-site morbidity may become a very useful option in human mandibular reconstruction.