Redoximorphic Bt horizons of the Calhoun CZO soils exhibit depth-dependent iron-oxide crystallinity

Journal of Soils and Sediments - Iron (Fe) oxyhydroxides and their degree of ordering or crystallinity strongly impact the role that Fe plays in ecosystem function. Lower crystallinity phases are...     

Simulating and assessing the evolution of collapsing gullies based on cellular automata-Markov and landscape pattern metrics: a case study in Southern China

Purpose

Collapsing gullies, which involve considerable erosion and extreme landform changes, frequently occur in the granite region of Southern China. Capturing the evolution of collapsing gullies is useful and effective for predicting erosion amount and landform changes. However, the evolution of collapsing gullies is too complex to simulate using conventional models. The aim of this study is to modify the traditional cellular automata (CA)-Markov model for simulating the evolution of collapsing gullies and then quantify their morphology using landscape pattern metrics.

Materials and methods

A hillslope eroded by collapsing gullies located in Longmen Town of the granite region of Southern China is used as a case study. Three digital elevation models (DEMs) were derived on 11 March 2017, 21 July 2017, and 2 December 2017 from a remotely piloted vehicle and global positioning system (GPS) real-time kinematics. Rainfall data for the corresponding time was recorded by a tipping-bucket rain gauge. Using these data, the CA-Markov model for simulating the evolution of collapsing gullies was developed, and then the most accurate one was chosen to predict the evolution on 2 December 2018. Evolution of the case study hillslope was interpreted and assessed using landscape metrics to capture the erosional trends of collapsing gullies.

Results and discussion

The area differences of the modified CA-Markov model are lower than those of the traditional model while the kappa coefficients of the modified CA-Markov model are higher than those of the traditional model; that is, the modified CA-Markov model performs better for simulating and predicting the evolution of collapsing gullies. The kappa coefficients also demonstrate that both scouring and gravity impact collapsing gullies, and scouring force is more effective than gravity. Based on the evolution prediction, the erosion amount of collapsing gullies in the subsequent year is predicted to be 904.1 m³. Spatial pattern analysis showed that the mid-lower part of a hillslope eroded by collapsing gullies will continue to be intensively eroded and the ground surface will become more fragmented.

Conclusions

The use of a modified CA-Markov model and landscape pattern metrics provide an improved and effective method for understanding the spatial and temporal variations of collapsing gullies landform and ground surface, as well as better capturing the erosional trends of collapsing gullies.

     

Observations on the in vitro behavior of digital tendons

The force/strain behavior of the common and lateral extensor tendons, the extensor branches of the interosseus muscle, and the superficial flexor tendon have been examined in vitro. The flexor tendon acted as a hard-spring with an initial large strain with small load followed by progressively less strain with increasing load, The distal part of the common extensor tendon and the extensor branches behaved in the same manner during dorsiflexion of the fetlock joint/palmar flexion of the coffin joint. The common extensor tendon behaved in a softening manner during palmar flexion of the fetlock and coffin joints while the lateral extensor and the extensor branches behaved in a nearly linear manner.     

Hybrid dysgenesis in D. melanogaster is not a general release mechanism for DNA transpositions

Many spontaneous mutations are caused by the insertion or excision of DNA elements. Since most mutations are deleterious, evolution should favor a mechanism for genetically controlling the rate of movement of transposable elements in most, if not all, organisms. In Drosophila melanogaster a syndrome of correlated genetic changes, including mutation, chromosome breakage, and sterility, is observed in the hybrid progeny of crosses between different strains. This syndrome, which is termed hybrid dysgenesis, results from the movement of P-DNA elements. What is not clear is whether the movement of other types of transposable elements is under the same coordinated control. In this study the ability of hybrid dysgenesis to increase the rate of excision of 12 DNA elements at 16 mutant alleles and to induce insertion-bearing mutations to change to other mutant states was tested. The data show that hybrid dysgenesis caused by P-element transpositions does not act as a general stimulus for the movement of other Drosophila transposable elements.     

Luteal maintenance in cattle after conceptus death during the first trimester of gestation.

The objectives of this experiment were to evaluate effect of age of the conceptus at death on subsequent interval to estrus and to determine whether prostaglandin F2 alpha (PGF) treatment after induced conceptus death would reduce interval to estrus. Sixty-four beef cows were diagnosed pregnant by ultrasonography between 24 and 50 d of gestation. Nine pregnancy groups were identified; each encompassed a 3-d interval from d 24 through 50 of gestation. Cows were allocated at random within pregnancy group to be treated with colchicine to induce conceptus death. Forty-eight hours after colchicine treatment, conceptus death was verified by ultrasonography and each animal received either saline or PGF. There was no evidence of an effect of age of conceptus at death on the subsequent interval to estrus after either saline or PGF. Interval to estrus after saline was 13.5 +/- .8 d, which was greater (P less than .01) than the 6.2 +/- .8 d after PGF. After saline, the estimate for the linear effect of time on serum progesterone (P4) was -1.32 +/- .36 ng/d and was less (P less than .05) than -2.83 +/- .36 ng/d for cows given PGF. Cows were exposed to fertile bulls at the first postabortion estrus. Pregnancy rates were 37.5% for cows given saline vs 31.3% for those given PGF. These results indicate that interval to estrus after conceptus death between 24 and 50 d of gestation is not affected by the age of the conceptus and can be reduced by PGF treatment.     

Testosterone propionate treatment of stallions: Effects on secretion of luteinizing hormone and follicle stimulating hormone in daily samples and after administration of gonadotropin releasing hormone

Ten stallions were used to determine if the stallion responds to administration of testosterone propionate (TP) with an increase in follicle stimulating hormone (FSH) secretion after administration of gonadotropin releasing hormone (GnRH) as has been previously observed for geldings and intact and ovariectomized mares. Five stallions were treated with TP (350 μg/kg of body weight) in safflower oil every other day for 11 days; control stallions received injections of safflower oil. The response to GnRH (1.0 μg/kg of body weight) was determined for all stallions before the onset of treatment (GnRH I) and at the end of treatment (GnRH II). Blood samples were also withdrawn daily from 3 days prior to treatment through GnRH II. Treatment with TP decreased (P<.10) concentrations of FSH in daily blood samples. However, treatment with TP did not affect (P>.10) the GnRH-induced secretion of FSH. Concentrations of luteinizing hormone (LH) decreased (P<.05) in daily blood samples averaged over both groups of stallions and were lower (P<.10) in TP-treated stallions than in controls during the latter days of treatment. We conclude that TP administration to stallions does not alter the FSH response to GnRH as has been observed for geldings and for mares of several reproductive states.     

Equine hydatidosis: A review of the current status in great britain and the results of an epidemiological survey

An appraisal of the current status of animal and human hydatidosis in Great Britain is given. Attention is drawn to the fact that, whereas the disease occurs largely in localised districts in domestic food animals, (especially sheep), it is widespread in horses, having reached epidemic proportions within the last decade.Epidemiological and experimental evidence indicates that dogs belonging to hunting packs are the major definitive host. The role of the fox is still uncertain.A survey of the feeding, housing and general husbandary of hunting dogs has shown that they have access to raw uninspected horse flesh and offal. Following the Second World War, economic pressures and labour shortages have been the main factors behind a change in the dietary practices at hunt kennels leading to an increase in the feeding of raw flesh and offal. The survey revealed that of 21 hunts inspected 11 (52%) harboured infected dogs. Worms recovered from infected dogs were identified as the horse “strain” of Echinococcus granulosus.The potential public health hazards which could yet arise, as a consequence of the increased prevalence of equine hydatidosis, are discussed.