Controls on carbon storage and weathering in volcanic soils across a high-elevation climate gradient on Mauna Kea, Hawaii.

Volcanic ash soils retain the largest and most persistent soil carbon pools of any ecosystem. However, the mechanisms governing soil carbon accumulation and weathering during initial phases of ecosystem development are not well understood. We examined soil organic matter dynamics and soil development across a high-altitude (3,560-3,030 m) 20-kyr climate gradient on Mauna Kea in Hawaii. Four elevation sites were selected (~250-500 mm rainfall), which range from sparsely vegetated to sites that contain a mix of shrubs and grasses. At each site, two or three pits were dug and major diagnostic horizons down to bedrock (intact lava) were sampled. Soils were analyzed for particle size, organic C and N, soil pH, exchangeable cations, base saturation, NaF pH, phosphorous sorption, and major elements. Mass loss and pedogenic metal accumulation (hydroxlamine Fe, Al, and Si extractions) were used to measure extent of weathering, leaching, changes in soil mineralogy and carbon accumulation. Reactive-phase (SRO) minerals show a general trend of increasing abundance with increasing rainfall. However carbon accumulation patterns across the climate gradient are largely decoupled from these trends. The results suggest that after 20 kyr, pedogenic processes have altered the nature and composition of the volcanic ash such that it is capable of retaining soil C even where organic acid influences from plant material and leaching from rainfall are severely limited. Carbon storage comparisons with lower-elevation soils on Mauna Kea and other moist mesic (2,500 mm rainfall) sites on Hawaii suggest that these soils have reached only between 1% and 15% of their capacity to retain carbon. Our results suggest that, after 20 kyr in low rainfall and a cold climate, weathering was decoupled from soil carbon accumulation patterns and the associated influence of vegetation on soil development. Overall, we conclude that the rate of carbon supply to the subsoil (driven by coupling of rainfall above ground plant production) is a governing factor of forms and amount of soil organic matter accumulation, while soil mineralogy remained relatively uniform.

Surficial gains and subsoil losses of soil carbon and nitrogen during secondary forest development.

Reforestation of formerly cultivated land is widely understood to accumulate above- and belowground detrital organic matter pools, including soil organic matter. However, during 40 years of study of reforestation in the subtropical southeastern USA, repeated observations of above- and belowground carbon documented that significant gains in soil organic matter (SOM) in surface soils (0-7.5 cm) were offset by significant SOM losses in subsoils (35-60 cm). Here, we extended the observation period in this long-term experiment by an additional decade, and used soil fractionation and stable isotopes and radioisotopes to explore changes in soil organic carbon and soil nitrogen that accompanied nearly 50 years of loblolly pine secondary forest development. We observed that accumulations of mineral soil C and N from 0 to 7.5 cm were almost entirely due to accumulations of light-fraction SOM. Meanwhile, losses of soil C and N from mineral soils at 35 to 60 cm were from SOM associated with silt and clay-sized particles. Isotopic signatures showed relatively large accumulations of forest-derived carbon in surface soils, and little to no accumulation of forest-derived carbon in subsoils. We argue that the land use change from old field to secondary forest drove biogeochemical and hydrological changes throughout the soil profile that enhanced microbial activity and SOM decomposition in subsoils. However, when the pine stands aged and began to transition to mixed pines and hardwoods, demands on soil organic matter for nutrients to support aboveground growth eased due to pine mortality, and subsoil organic matter levels stabilized. This study emphasizes the importance of long-term experiments and deep measurements when characterizing soil C and N responses to land use change and the remarkable paucity of such long-term soil data deeper than 30 cm.

Clinical presentation and pathology of sarcocystosis in psittaciform birds: 11 cases.

Sarcocystosis in psittaciform birds occurs in several different presentations, making ante-mortem diagnosis challenging without specific laboratory tests. This study followed the course of 11 birds diagnosed with sarcocystosis by serologic analysis and/or post-mortem examinations during a 10-month period in 2006-07. The disease presented in three different clinical forms: an acute pulmonary disease (three birds), muscular disease (five), and neurological disease (three). Early diagnosis of sarcocystosis was possible through the combined used of plasma protein electrophoresis and indirect fluorescent antibody serology in birds presented with the neurological and muscular forms of the disease. In three of these birds the plasma electrophoretic patterns revealed marked hypergammaglobulinemia. All of the birds that presented with the acute pulmonary form developed similar gross and microscopic lesions. Definitive diagnosis was ultimately made by microscopic observation of intravascular pulmonary schizonts containing merozoites. Schizonts were identified in the cerebellum and brainstem in two birds with the neurological form of disease. Those birds that initially presented with severe lethargy and weakness were considered to suffer from the muscular form of disease if they had extreme elevations of muscle enzyme activities (creatine phosphokinase, aspartate aminotransferase) and beta and gamma globulins concentrations, and were seropositive for antibodies to Sarcocystis falcatula. In this group the progression of the disease varied. Two birds recovered completely, and secondary aspergillosis was diagnosed in three birds. The histopathological lesions observed are discussed and interpreted in light of earlier findings from experimental infections in budgerigars, which provide insights into the natural course of sarcocystosis in psittaciform birds.

Granulomatous osteomyelitis associated with atypical mycobacteriosis in a bearded dragon (Pogona vitticeps).

The zoonotic potential of Mycobacterium spp has been well documented and has been implicated in cutaneous and subcutaneous nodular disease in humans. Treatment of the infected reptiles is often not recommended, because of the zoonotic potential. Moreover, the often-advanced nature of the disease when diagnosed, the lengthy and expensive treatment regimens, and lack of a reported successful treatment regimen for reptiles usually warrant euthanasia in these patients. Strict attention must be paid to cage hygiene and sanitation to minimize exposure and eliminate the organisms.

Emerging land use practices rapidly increase soil organic matter.

The loss of organic matter from agricultural lands constrains our ability to sustainably feed a growing population and mitigate the impacts of climate change. Addressing these challenges requires land use activities that accumulate soil carbon (C) while contributing to food production. In a region of extensive soil degradation in the southeastern United States, we evaluated soil C accumulation for 3 years across a 7-year chronosequence of three farms converted to management-intensive grazing. Here we show that these farms accumulated C at 8.0 Mg ha(-1) yr(-1), increasing cation exchange and water holding capacity by 95% and 34%, respectively. Thus, within a decade of management-intensive grazing practices soil C levels returned to those of native forest soils, and likely decreased fertilizer and irrigation demands. Emerging land uses, such as management-intensive grazing, may offer a rare win-win strategy combining profitable food production with rapid improvement of soil quality and short-term climate mitigation through soil C-accumulation.