Affectation of COVID-19 pandemic on the use and abundance of wild resources in Tabasco, Mexico: A qualitative assessment.

Southern Mexico is particularly rich in natural resources, yet unemployment has risen to 8% during the COVID-19 pandemic. The effect of the pandemic on the use and abundance of Tabasco's wild resources was examined through personal surveys. By using Microsoft Forms® with cell phones 1,963 surveys were collected. Cronbach's alpha, Z-value, and chi2 were calculated using the MAXQDA Analytics Pro program. A higher abundance of wild resources before the pandemic than today (57% vs. 11%) was observed. During the pandemic, people referred more to a high use (28%) of resources than to a low use (20%). This caused the low abundance or scarcity of wild products to be greater during the pandemic than before the pandemic (43% vs. 4%). Wild foods and timber were the most used products. The pandemic has produced a greater use of natural resources probably due to the high unemployment rate in rural areas. Future studies of wild products should address the relevant products in the locality and their even sampling. Finding suitable respondents is highly recommended.

Almacenes de biomasa y carbono aéreo y radicular en pastizales de Urochloa decumbens y Paspalum notatum (Poaceae) en el sureste de México

Introducción: Debido a su extensión actual, la biomasa radicular de los pastizales tropicales es de vital importancia para el almacenamiento del carbono terrestre, pero su estimación ha sido principalmente indirecta y con un rango muy amplio de valores. Objetivo: Documentar a nivel nacional y mundial, y comparar, las existencias de carbono radicular extraídas en forma directa, de dos pastizales de origen y tipo de crecimiento distinto. Método: Se midió la biomasa y carbono total de dos pastizales con más de 40 años de uso, uno nativo de América y de crecimiento estolonífero (Paspalum notatum) y otro introducido de África y de crecimiento en macollos (Urochloa decumbens). El estudio se realizó entre agosto y octubre 2016. Se seleccionaron 3 parcelas de 1 600 m2 por pastizal, con 10 subcuadros (4 m2 c/u) en cada parcela, para determinar composición florística, biomasa y C aéreo. La biomasa y C radicular se estimaron mediante extracción directa en tres trincheras (1.50 m x 0.50 m x 1.0 m) por parcela. El contenido de carbono orgánico se determinó con el método por ignición a una temperatura promedio de 550 °C durante 3 horas. Para el análisis estadístico se usó un ANOVA de dos factores, en el que un factor fueron dos tratamientos (tipo de pastizal) y el otro factor fue la parte morfológica del pasto (aéreo y radicular). Resultados: La composición florística de los dos tipos de pastizal fue diferente debido a su historia de manejo. En promedio se estimó 28.25 MgC ha-1 total para la localidad. El pastizal nativo y de crecimiento estolonífero P. notatum produce casi tres veces más biomasa (42.5 MgC ha-1) que el introducido y de crecimiento en macollos U. decumbens (14 MgC ha-1) debido al almacén radicular (38.5 vs. 11.46 MgC ha-1). El 74.5 % del carbono en P. notatum se localizó en la parte radicular y el 25.5 % en la parte aérea, mientras que en U. decumbens fueron 56.5 y 43.5 %, respectivamente. Conclusión: P. notatum acumuló más biomasa y carbono total y radicular que U. decumbens. La mejor adaptación del pasto nativo, así como la morfología de su sistema radicular, pueden explicar esta diferencia. El 96 % de la biomasa y del C radicular se encuentra en los primeros 0.50 m de profundidad. Debido a la contribución de su porción radicular, los pastizales tropicales pueden constituir importantes reservorios de carbono terrestre, considerando su extensión hoy en día.

Introduction: Due to its current coverage, the root biomass of tropical pastures is of vital importance for the terrestrial carbon storage, but its estimation has been mainly indirect and with a very wide range of values. Objective: To document at national and global level as well as compare, the root carbon stocks extracted directly from two grasslands of different growth type and origin. Methods: The biomass and root carbon stocks were directly extracted from two tropical pastures with more than 40 yr of age. The biomass and total carbon, one native with stoloniferous growth (Paspalum notatum) and one introduced with growth in tillers (Urochloa decumbens) were measured. The study was conducted between August and October 2016. Three plots of 1 600 m2 each were selected per pasture, with 10 sub-squares (4 m2 each) in each plot to determine the floristic composition, aboveground biomass and C. The biomass and root C were estimated by hand in three trenches (1.50 m x 0.50 m x 1.0 m) per plot. The organic carbon content was determined with the ignition method at an average temperature of 550 °C for 3 hours. For the statistical analysis, a two-factor ANOVA was used, where one factor was the treatments that were the type of pasture (2) and the other factor was the section of the grass (above and belowground). Results: The floristic composition of the two types of pasture was different due to its management history. On average, 28.25 Mg ha-1 of total C was estimated for the locality. The native pasture of stoloniferous growth P. notatum yields almost three-fold more biomass (42.5 MgC ha-1) than the introduced with growth in tillers U. decumbens (14 MgC ha-1) due to the radicular storage (38.5 vs. 11.46 MgC ha-1). Seventy-four point five percent of the carbon in P. notatum was located in the radicular part and 25.5 % above-ground, while in U. decumbens 56.5 and 43.5 %, respectively. Conclusions: P. notatum accumulated more total and radicular biomass and carbon than U. decumbens. The best adaptation of the native grass as well as the morphology of its root system may explain this difference. Ninety six percent of the biomass and root C is found in the first 0.50 m depth. Due to the contribution of its radicular portion, tropical pastures can constitute important reservoirs of terrestrial carbon considering its extension nowadays.

Leaf and soil nitrogen and phosphorus availability in a neotropical rain forest of nutrient-rich soil

The nitrogen and phosphorus supply in a lowland rain forest with a nutrient-rich soil was investigated by means of the leaf N/P quotient. It was hypothesised a high N and P supply to the forest ecosystem with a N and P rich soil. Total N and extractable P were determined in the surface (10 cm) soil of three plots of the forest. Total N was analysed by the Kjeldahl method, and P was extracted with HCI and NH4F. The leaf N/P quotient was evaluated from the senesced leaves of 11 dominant tree species from the mature forest. Samples of 5 g of freshly fallen leaves were collected from three trees of each species. Nitrogen was analysed by microkjeldahl digestion with sulphuric acid and distilled with boric acid, and phosphorus was analysed by digestion with nitric acid and perchloric acid, and determined by photometry. Concentrations of total N (0.50%, n = 30) and extractable P (4.11 microg g(-1), n = 30) in the soil were high. As expected, P supply was sufficient, but contrary to expected, N supply was low (N/P = 11.8, n = 11).

A través del cociente foliar N/P, se investigó la disponibilidad de nitrógeno y fósforo en una selva húmeda tropical con suelo fértil. Como hipótesis se esperaba encontrar una alta disponibilidad de N y P en el ecosistema debido a un suelo rico en N y P. Se determinó el N total y el P extraible en el suelo superficial (10 cm) en tres sitios de la selva. El N total se analizó por el método Kjeldahl y el P por extracción con HCl y NH4F. El cociente foliar N/P se evaluó a partir de hojas seniles de 11 especies arbóreas dominantes de la selva madura. Se recolectaron muestras de 5 g de hojas recién caídas de tres árboles de cada especie. El nitrógeno se analizó por digestión microkjeldahl con ácido sulfúrico y destilación con ácido bórico, y el fósforo por digestión con ácido nítrico y ácido perclórico, y determinación con fotometría. Las concetraciones de N total (0.50%, n = 30) y P extraible (4.11 [mi]g g-1, n = 30) en el suelo fueron altas. Tal como se esperaba, la disponibilidad de P fue suficiente, pero contrariamente a lo esperado, la disponibilidad de N fue baja (N/P = 11.8, n = 11).

Leaf and soil nitrogen and phosphorus availability in a neotropical rain forest of nutrient-rich soil.

The nitrogen and phosphorus supply in a lowland rain forest with a nutrient-rich soil was investigated by means of the leaf N/P quotient. It was hypothesised a high N and P supply to the forest ecosystem with a N and P rich soil. Total N and extractable P were determined in the surface (10 cm) soil of three plots of the forest. Total N was analysed by the Kjeldahl method, and P was extracted with HCI and NH4F. The leaf N/P quotient was evaluated from the senesced leaves of 11 dominant tree species from the mature forest. Samples of 5 g of freshly fallen leaves were collected from three trees of each species. Nitrogen was analysed by microkjeldahl digestion with sulphuric acid and distilled with boric acid, and phosphorus was analysed by digestion with nitric acid and perchloric acid, and determined by photometry. Concentrations of total N (0.50%, n = 30) and extractable P (4.11 microg g(-1), n = 30) in the soil were high. As expected, P supply was sufficient, but contrary to expected, N supply was low (N/P = 11.8, n = 11).

Nitrogen and phosphorus resorption in a neotropical rain forest of a nutrient-rich soil

In tropical forests with nutrient-rich soil tree’s nutrient resorption from senesced leaves has not always been observed to be low. Perhaps this lack of consistence is partly owing to the nutrient resorption methods used. The aim of the study was to analyse N and P resorption proficiency from tropical rain forest trees in a nutrient-rich soil. It was hypothesised that trees would exhibit low nutrient resorption in a nutrient-rich soil. The soil concentrations of total N and extractable P, among other physical and chemical characteristics, were analysed in 30 samples in the soil surface (10 cm) of three undisturbed forest plots at ‘Estación de Biología Los Tuxtlas’ on the east coast of Mexico (18°34’ - 18°36’ N, 95°04’ - 95°09’ W). N and P resorption proficiency were determined from senescing leaves in 11 dominant tree species. Nitrogen was analysed by microkjeldahl digestion with sulphuric acid and distilled with boric acid, and phosphorus was analysed by digestion with nitric acid and perchloric acid. Soil was rich in total N (0.50%, n = 30) and extractable P (4.11 µg g-1, n = 30). As expected, trees showed incomplete N (1.13%, n = 11) and P (0.11%, n = 11) resorption. With a more accurate method of nutrient resorption assessment, it is possible to prove that a forest community with a nutrient-rich soil can have low levels of N and P resorption

En las selvas tropicales con suelos fértiles se ha observado que la reabsorción de nutrientes de los arboles de las hojas seniles no siempre es baja. Esta falta de consistencia en el resultado es talvez debida en parte a la metodología de reabsorción de nutrientes utilizada. El objetivo de este estudio fue analizar la reabsorción final de N y P de arboles de la selva húmeda tropical en un suelo rico en nutrientes. La hipótesis planteada fue que en un suelo rico en nutrientes los arboles presentarían una baja reabsorción final de nutrientes. En 30 muestras del suelo superficial (10 cm) de tres sitios de la selva no perturbada, se analizó entre otras características físicas y químicas, la concentración de N total y P extraíble. A través de la concentración de N y P en hojas seniles, se determinó la reabsorción real de 11 especies dominantes de arboles de esta selva. El N se analizó por digestión microkjeldahl con ácido sulfúrico y destilación con ácido bórico, y el P se analizó por digestión con ácido nítrico y destilación con perclórico. El suelo fue rico en N total (0.50%, n = 30) y P extraíble (4.11 µg g-1, n = 30). Tal como se esperaba, los arboles mostraron una reabsorción incompleta para el N (1.13%, n = 11) y P (0.11%, n = 11)

Nitrogen and phosphorus resorption in a neotropical rain forest of a nutrient-rich soil.

In tropical forests with nutrient-rich soil tree's nutrient resorption from senesced leaves has not always been observed to be low. Perhaps this lack of consistence is partly owing to the nutrient resorption methods used. The aim of the study was to analyse N and P resorption proficiency from tropical rain forest trees in a nutrient-rich soil. It was hypothesised that trees would exhibit low nutrient resorption in a nutrient-rich soil. The soil concentrations of total N and extractable P, among other physical and chemical characteristics, were analysed in 30 samples in the soil surface (10 cm) of three undisturbed forest plots at 'Estaci6n de Biologia Los Tuxtlas' on the east coast of Mexico (18 degrees 34' - 18 degrees 36' N, 95 degrees 04' - 95 degrees 09' W). N and P resorption proficiency were determined from senescing leaves in 11 dominant tree species. Nitrogen was analysed by microkjeldahl digestion with sulphuric acid and distilled with boric acid, and phosphorus was analysed by digestion with nitric acid and perchloric acid. Soil was rich in total N (0.50%, n = 30) and extractable P (4.11 microg g(-1) n = 30). As expected, trees showed incomplete N (1.13%, n = 11) and P (0.11%, n = 1) resorption. With a more accurate method of nutrient resorption assessment, it is possible to prove that a forest community with a nutrient-rich soil can have low levels of N and P resorption.