ABSTRACT
The recovery of ecosystem C and N dynamics after disturbance can be a slow process. Chronosequence approaches offer unique opportunities to use space-for-time substitution to quantify the recovery of ecosystem C and N stocks and estimate the potential of restoration practices for C sequestration. We studied the distribution of C and N stocks in two chronosequences that included long-term cultivated lands, 3- to 26-year-old prairie restorations, and remnant prairie on two related soil series. Results from the two chronosequences did not vary significantly and were combined. Based on modeling predictions, the recovery rates of different ecosystem components varied greatly. Overall, C stocks recovered faster than N stocks, but both C and N stocks recovered more rapidly for aboveground vegetation than for any other ecosystem component. Aboveground C and N reached 95% of remnant levels in only 13 years and 21 years, respectively, after planting to native vegetation. Belowground plant C and N recovered several decades later, while microbial biomass C, soil organic C (SOC), and total soil N recovered on a century timescale. In the cultivated fields, SOC concentrations were depleted within the surface 25 cm, coinciding with the depth of plowing, but cultivation apparently led to redistribution of soil C, increasing SOC stocks deeper in the soil profile. The restoration of prairie vegetation was effective at rebuilding soil organic matter (SOM) in the surface soil. Accrual rates were maintained at 43 g C x m(-2) x yr(-1) and 3 g N x m(-2) x yr(-1) in the surface 0.16 Mg/m2 soil mass during the first 26 years of restoration and were predicted to reach 50% of their storage potential (3500 g C/m2) in the first 100 years. We conclude that restoration of tallgrass prairie vegetation can restore SOM lost through cultivation and has the potential to sequester relatively large amounts of SOC over a sustained period of time. Whether restored prairies can retain the C apparently transferred to the subsoil by cultivation practices remains to be seen.
Subject(s)
Carbon/metabolism , Ecosystem , Nitrogen/metabolism , Poaceae/metabolism , Soil/analysis , Carbon/analysis , Conservation of Natural Resources , Crops, Agricultural/metabolism , Illinois , Nitrogen/analysis , Time FactorsABSTRACT
Se presentan 19 casos de embarazo tubario no complicado tratados con metotrexato en el Servicio de Obstetricia y Ginecología del Hospital Clínico Regional de Valdivia, entre diciembre de 1991 y mayo de 1999. Se discuten las vías de administración del metotrexato y sus contraindicaciones. El tratamiento fue exitoso en un 84 por ciento y hubo 3 fracasos. Se comprobó permeabilidad tubaria en el 75 por ciento de los casos en que se efectuó histerosalpingografía (7 de 9). Una de las pacientes con trompa obstruida tenía más de 30.000 mUl/ml de hormona gonadotrofina coriónica. Al analizar el pronóstico reproductivo, 6 pacientes tuvieron embarazo de término, una tuvo un aborto retenido y 2 pacientes repitieron un embarazo tubario
Subject(s)
Humans , Female , Pregnancy , Methotrexate , Pregnancy, Tubal , Fallopian Tubes , Follow-Up Studies , Hysterosalpingography , Prognosis , Reproductive HistoryABSTRACT
Se presentan los resultados de una serie clínica de 15 pacientes portadoras de cáncer escamoso de cuello uterino localmente avanzado, estadios clínico I B2-II B, a quienes se les administró una quimioterapia neoadyuvante con cisplatino, vincristina y bleomicina durante 3 ciclos y luego fueron evaluadas para cirugía radical. Se logró una respuesta parcial o completa que permitió realizar la cirugía en 14 de las 15 pacientes tratadas. Cuando los márgenes o los ganglios estuvieron positivos para tumor se agregó raditerapia pelviana
Subject(s)
Humans , Female , Adult , Middle Aged , Chemotherapy, Adjuvant , Uterine Cervical Neoplasms/drug therapy , Bleomycin/adverse effects , Bleomycin/pharmacology , Cisplatin/adverse effects , Cisplatin/pharmacology , Hysterectomy , Uterine Cervical Neoplasms/radiotherapy , Uterine Cervical Neoplasms/surgery , Vincristine/adverse effects , Vincristine/pharmacologyABSTRACT
El diagnóstico de la situación de crisis acumulada por la salud en todos sus niveles, ya ha identificado y en gran medida dimensionado, sus pricipales factores causales. Es así que no corresponde postergar una vez más, con la supuesta necesidad de mayuores estudios, la dicisión de iniciar la implentación de las medidas de correción estimadas como prioritarias
Subject(s)
Humans , Primary Health Care/organization & administration , Community Health Services , Decision Support Techniques , Health Planning Councils , Health Programs and PlansABSTRACT
The concentration of atmospheric carbon dioxide was increased by 200 microliters per liter in a forest plantation, where competition between organisms, resource limitations, and environmental stresses may modulate biotic responses. After 2 years the growth rate of the dominant pine trees increased by about 26 percent relative to trees under ambient conditions. Carbon dioxide enrichment also increased litterfall and fine-root increment. These changes increased the total net primary production by 25 percent. Such an increase in forest net primary production globally would fix about 50 percent of the anthropogenic carbon dioxide projected to be released into the atmosphere in the year 2050. The response of this young, rapidly growing forest to carbon dioxide may represent the upper limit for forest carbon sequestration.
ABSTRACT
The prevalence of intestinal parasites in 200 persons of bank side Lake was studied. Age, sex and environmental sanitary conditions were considered in each case. A modified Telemann method was performed for examining stool samples from each individual. Infection by pathogenic or commensal helminths and protozoa was detected in 55.6% of samples. Correlation with sex and environmental sanitary conditions was observed. Infection by Diphyllobothrium sp. was not found.
