Adding Tree Rings to North America's National Forest Inventories: An Essential Tool to Guide Drawdown of Atmospheric CO2.

Tree-ring time series provide long-term, annually resolved information on the growth of trees. When sampled in a systematic context, tree-ring data can be scaled to estimate the forest carbon capture and storage of landscapes, biomes, and-ultimately-the globe. A systematic effort to sample tree rings in national forest inventories would yield unprecedented temporal and spatial resolution of forest carbon dynamics and help resolve key scientific uncertainties, which we highlight in terms of evidence for forest greening (enhanced growth) versus browning (reduced growth, increased mortality). We describe jump-starting a tree-ring collection across the continent of North America, given the commitments of Canada, the United States, and Mexico to visit forest inventory plots, along with existing legacy collections. Failing to do so would be a missed opportunity to help chart an evidence-based path toward meeting national commitments to reduce net greenhouse gas emissions, urgently needed for climate stabilization and repair.

Dataset about Mexico's forest diversity: Site locations of tree species, wood densities, and geographic database of forest-vegetation provinces.

A dataset about three topics is provided, as a follow-up to the article "Mexico's forest diversity: common tree species and proposed forest-vegetation provinces" by Ricker et al. [1]. Firstly, 6927 site locations are provided for 22,532 trees of 1452 species. Secondly, measurements of basic wood-densities are reported for 779 tree species, obtained from 5256 trunk-core samples from Mexico's national forest inventory, and ranging from 0.05 to 0.93 g/cm3. Third, the data and maps of the forest-vegetation provinces from [1] were updated with the new cartography of Mexico's vegetation and land use (base year 2018). The maps are available now in an adjusted presentation as a shapefile-set for ArcGIS, as well as map-package and image files.

Does commercialization lead to more intensive management strategies? Decision-making for the utilization of non-timber forest products in a Nahua area of the Sierra Negra, Mexico.

BACKGROUND: The commercialization of non-timber forest products (NTFPs) provides income for rural indigenous households. The integration of NTFPs into formal markets tends to intensify management practices to ensure production and monetary benefits. However, more research is needed to understand the motivations for managing of commercialized species. We examine the influence of social, ecological, and economic factors on traditional management and how they drive the adoption of more or less intensive practices for subsistence and commercially traded NTFPs. METHODS: The study was conducted in the Nahua community of Ixtacxochitla, in the Sierra Negra of central Mexico, where we conducted free lists and semi-structured interviews in 32% of the 88 households to assess socio-ecological variables related to management practices. In addition, we interviewed local traders to assess commercial variables used in a cost-benefit model to calculate the net annual income of commercialized species. Non-metric multidimensional scaling was used to analyze relationships between socio-ecological variables and management practices. We also explored the relationship between management and commercial factors using principal component analysis. RESULTS: We recorded 64 plant and mushroom species of NTFPs used for medicinal, ornamental, ceremonial, and edible purposes, 36 of which are commercialized in the municipal market of Coyomeapan. The commercialized species generated an average annual net income of MXN 67,526 (USD 3924) per family, with five species contributing the most. Species both used for both subsistence and commercialization were managed through incipient in situ gathering, tolerance in ex situ anthropogenic areas, and intensive protection and propagation efforts in ex situ environments. Even the five species with the highest commercial returns were managed across this gradient of practices. Key factors influencing the adoption of more intensive species management practices were feasibility of management, type of species use, ecological abundance, frequency of consumption, and cultural importance. CONCLUSIONS: The intensification of NTFPs management is not solely driven by the commercial value of the products or the level of income generated. Instead, the interaction between socio-ecological and economic factors determines the extent of management practices. The main constraint to the implementation of intensive practices has been the inability to manage species outside their natural habitats, despite their cultural significance and frequent consumption. Understanding the factors involved in the harvesting of NTFPs can serve as the basis for future research aimed at analyzing the conditions for successful and sustainable NTFPs commercialization.

Statistical age determination of tree rings.

Dendrochronology, the study of annual rings formed by trees and woody plants, has important applications in research of climate and environmental phenomena of the past. Since its inception in the late 19th century, dendrochronology has not had a way to quantify uncertainty about the years assigned to each ring (dating). There are, however, many woody species and sites where it is difficult or impossible to delimit annual ring boundaries and verify them with crossdating, especially in the lowland tropics. Rather than ignoring dating uncertainty or discarding such samples as useless, we present for the first time a probabilistic approach to assign expected ages with a confidence interval. It is proven that the cumulative age in a tree-ring time series advances by an amount equal to the probability that a putative growth boundary is truly annual. Confidence curves for the tree stem radius as a function of uncertain ages are determined. A sensitivity analysis shows the effect of uncertainty of the probability that a recognizable boundary is annual, as well as of the number of expected missing boundaries. Furthermore, we derive a probabilistic version of the mean sensitivity of a dendrochronological time series, which quantifies a tree's sensitivity to environmental variation over time, as well as probabilistic versions of the autocorrelation and process standard deviation. A computer code in Mathematica is provided, with sample input files, as supporting information. Further research is necessary to analyze frequency patterns of false and missing boundaries for different species and sites.

Letter to the Editor: About the quality and impact of scientific articles.

It is argued that counting the total number of times a scientific article is cited by others, does neither result in a proxy for its cognitive impact nor for its quality. One would have to distinguish at least substitutable and fundamental references. A supposed correlation between peer review assessments and citation counts is conceptually problematic, because peer review includes objective as well as subjective considerations (convictions). With refined methods, however, a differential citation analysis might be able in the future to answer if a given article did or did not have positive cognitive impact on subsequent research.

Effect of initial soil properties on six-year growth of 15 tree species in tropical restoration plantings.

In restoration plantings in degraded pastures, initial soil nutrient status may lead to differential growth of tropical tree species with diverse life history attributes and capacity for N2 fixation. In 2006, we planted 1,440 seedlings of 15 native tree species in 16 fenced plots (30 × 30 m) in a 60-year-old pasture in Los Tuxtlas, Veracruz, Mexico, in two planting combinations. In the first year, we evaluated bulk density, pH, the concentration of organic carbon (C), total nitrogen (N), ammonia (NO3-), nitrate (NH4+), and total phosphorus (P) in the upper soil profile (0-20 cm in depth) of all plots. The first two axes of two principal component analyses explained more than 60% of the variation in soil variables: The axes were related to increasing bulk density, NO3-, NH4+, total N concentration, and pH. Average relative growth rates in diameter at the stem base of the juvenile trees after 6 years were higher for pioneer (45.7%) and N2-fixing species (47.6%) than for nonpioneer (34.7%) and nonfixing species (36.2%). Most N2-fixing species and those with the slowest growth rates did not respond to soil attributes. Tree species benefited from higher pH levels and existing litter biomass. The pioneers Ficus yoponensis, Cecropia obtusifolia, and Heliocarpus appendiculatus, and the N2-fixing nonpioneers Cojoba arborea, Inga sinacae, and Platymiscium dimorphandrum were promising for forest restoration on our site, given their high growth rates.

A numerical algorithm with preference statements to evaluate the performance of scientists.

Academic evaluation committees have been increasingly receptive for using the number of published indexed articles, as well as citations, to evaluate the performance of scientists. It is, however, impossible to develop a stand-alone, objective numerical algorithm for the evaluation of academic activities, because any evaluation necessarily includes subjective preference statements. In a market, the market prices represent preference statements, but scientists work largely in a non-market context. I propose a numerical algorithm that serves to determine the distribution of reward money in Mexico's evaluation system, which uses relative prices of scientific goods and services as input. The relative prices would be determined by an evaluation committee. In this way, large evaluation systems (like Mexico's Sistema Nacional de Investigadores) could work semi-automatically, but not arbitrarily or superficially, to determine quantitatively the academic performance of scientists every few years. Data of 73 scientists from the Biology Institute of Mexico's National University are analyzed, and it is shown that the reward assignation and academic priorities depend heavily on those preferences. A maximum number of products or activities to be evaluated is recommended, to encourage quality over quantity.

A new method to compare statistical tree growth curves: the PL-GMANOVA model and its application with dendrochronological data.

Growth curves are monotonically increasing functions that measure repeatedly the same subjects over time. The classical growth curve model in the statistical literature is the Generalized Multivariate Analysis of Variance (GMANOVA) model. In order to model the tree trunk radius (r) over time (t) of trees on different sites, GMANOVA is combined here with the adapted PL regression model Q = A · T+E, where for b ≠ 0 : Q = Ei[-b · r]-Ei[-b · r1] and for b = 0 : Q  = Ln[r/r1], A =  initial relative growth to be estimated, T = t-t1, and E is an error term for each tree and time point. Furthermore, Ei[-b · r]  = ∫(Exp[-b · r]/r)dr, b = -1/TPR, with TPR being the turning point radius in a sigmoid curve, and r1 at t1 is an estimated calibrating time-radius point. Advantages of the approach are that growth rates can be compared among growth curves with different turning point radiuses and different starting points, hidden outliers are easily detectable, the method is statistically robust, and heteroscedasticity of the residuals among time points is allowed. The model was implemented with dendrochronological data of 235 Pinus montezumae trees on ten Mexican volcano sites to calculate comparison intervals for the estimated initial relative growth A. One site (at the Popocatépetl volcano) stood out, with A being 3.9 times the value of the site with the slowest-growing trees. Calculating variance components for the initial relative growth, 34% of the growth variation was found among sites, 31% among trees, and 35% over time. Without the Popocatépetl site, the numbers changed to 7%, 42%, and 51%. Further explanation of differences in growth would need to focus on factors that vary within sites and over time.

Measuring scientists’ performance: a view from organismal biologist / Midiendo el desempeño de los científicos: un punto de vista de biólogos organísmicos / Medindo desempeenho dos cientistas: um ponto de vista de biólogos organísmioss

Increasingly, academic evaluations quantify performance in science by giving higher rank to scientists (as well as journals and institutions) who publish more articles and have more citations. In Mexico, for example, a centralized federal agency uses such bibliometric statistics for evaluating the performance of all Mexican scientists. In this article we caution against using this form of evaluation as an almost exclusive tool of measuring and comparing scientists’ performance. We argue that from an economic viewpoint, maximizing the number of journal articles and their citations does not necessarily correspond to the preferences and needs of society. The traditional peer review process is much better suited for that purpose, and we propose "rule-based peer review" for evaluating a large number of scientists.

En la ciencia hay una fuerte tendencia global de cuantificar el desempeño de los científicos (así como a las revistas e instituciones), dando mayor jerarquía a aquellos científicos que publican más artículos y son más citados. En México, por ejemplo, una institución federal centralizada usa tales estadísticas bibliométricas para evaluar el desempeño de todos los científicos del país. En este artículo advertimos sobre los inconvenientes de esta forma de evaluación como una herramienta casi única para medir y comparar el desempeño de los científicos. Argumentamos que, desde un punto de vista económico, la maximización del número de artículos científicos y de la frecuencia de sus citas no necesariamente corresponde a las preferencias y necesidades de la sociedad en general. El proceso tradicional de arbitraje por pares es más adecuado para este propósito, y proponemos el "arbitraje por pares basado en reglas" para evaluar a un número alto de científicos.

Há uma forte tendência global para avaliações acadêmicas que quantifiquem o desempenho nas ciências através de ranquear os cientistas (assim como revistas e instituições) que publicam mais artigos e têm mais citações. No México, por exemplo, um órgão centralizado do governo utiliza tais estatísticas bibliomêtricas para avaliar o desempenho de todos os cientistas mexicanos. No presente artigo, chamamos atenção ao uso desta forma de avaliação como ferramenta quase que exclusiva para medir e comparar o desempenho dos cientistas. Argumentamos de um ponto de vista econômico que maximizar o número de artigos e as suas citações não corresponde necessariamente às preferências e necessidades da sociedade. O processo tradicional de avaliação pelos pares é mais apropriado para esta finalidade, e propomos um sistema baseado em "avaliação pelos pares seguindo regras", que podem avaliar um grande numéro de cientistas.