The study presents an analysis of forest spatial structure and diversity in the Federal State of ... more The study presents an analysis of forest spatial structure and diversity in the Federal State of Durango where the majority of the forests consist of pure pine stands or pine mixed with oak. Natural forests of greater diversity and of high ecological significance are found only in a few isolated localities in the Santa Bárbara valley. These forests, with rare conifers including the genera Picea, Abies and Pseudotsuga are found on particular sheltered, humid sites. For one such rare site, a detailed analysis of forest spatial structure was made, based on three one-quarter hectare plots where all the trees and their coordinates had been assessed. The objective of the study was to provide a quantitative description of the spatial structure of the plots, using new parameters of spatial diversity and to present a method for comparative analysis of the three forest sites. The analysis is using a new approach for describing complex forest structures in a straightforward manner. To evaluate the spatial attributes, it is not necessary to measure distances between trees or to establish tree coordinates. The spatial characteristics can be established merely on the basis of evaluating the immediate neighbourhood of a given number of reference trees. The variables describe the distributions of spatial mingling, size differentiation and contagion, which can be easily interpreted allowing quantitative comparisons between complex forest structures.
Five Pseudotsuga menziesii chronologies from the Sierra Madre Occidental were used for comparativ... more Five Pseudotsuga menziesii chronologies from the Sierra Madre Occidental were used for comparative climate-growth association purposes. Two new site chronologies were constructed for the first time; dated total tree-ring raw data of three additional site chronologies, previously documented, were used to compute comparable chronologies. Correlation analysis among the five chronologies reveals significant statistical association between most of them (r = 0.33-0.72; p < 0001). All chronologies were used individually to examine climate-growth associations considering both, local and regional climate data obtained from four meteorological stations in the region. Total regional precipitation correlated extremely well with standardized growth indices (up to r = 0.84; p < 0.0001); maximum temperature had an inverse association with growth, correlating lowly but significantly (up to r = À0.62; p < 0.0001), while minimum and mean temperatures did not correlate at all. The Las Bayas, a new chronology, was the highest correlated with regional November-May and November-August total precipitation (r = 0.80; p < 0.0001 and r = 0.84; p < 0.0001, respectively). Using Las Bayas chronology total November-May regional precipitation was reconstructed from 1681 to 2001 and used to identify the main dry and wet periods during the last three centuries. Most of the drought and wet episodes identified were consistent with those reported earlier for northern Mexico; an important exception was the 1950s interval that has been recognized widely as one of the most severe droughts in this region, and that based on reconstruction presented in this study was identified as a rather wet episode. The presence of wintertime El Niño events and chronologies were statistically related indicating that wet and cold winters in the Sierra Madre mountain range www.elsevier.com/locate/foreco
The study presents an analysis of forest spatial structure and diversity in the Federal State of ... more The study presents an analysis of forest spatial structure and diversity in the Federal State of Durango where the majority of the forests consist of pure pine stands or pine mixed with oak. Natural forests of greater diversity and of high ecological significance are found only in a few isolated localities in the Santa Bárbara valley. These forests, with rare conifers including the genera Picea, Abies and Pseudotsuga are found on particular sheltered, humid sites. For one such rare site, a detailed analysis of forest spatial structure was made, based on three one-quarter hectare plots where all the trees and their coordinates had been assessed. The objective of the study was to provide a quantitative description of the spatial structure of the plots, using new parameters of spatial diversity and to present a method for comparative analysis of the three forest sites. The analysis is using a new approach for describing complex forest structures in a straightforward manner. To evaluate the spatial attributes, it is not necessary to measure distances between trees or to establish tree coordinates. The spatial characteristics can be established merely on the basis of evaluating the immediate neighbourhood of a given number of reference trees. The variables describe the distributions of spatial mingling, size differentiation and contagion, which can be easily interpreted allowing quantitative comparisons between complex forest structures.
Five Pseudotsuga menziesii chronologies from the Sierra Madre Occidental were used for comparativ... more Five Pseudotsuga menziesii chronologies from the Sierra Madre Occidental were used for comparative climate-growth association purposes. Two new site chronologies were constructed for the first time; dated total tree-ring raw data of three additional site chronologies, previously documented, were used to compute comparable chronologies. Correlation analysis among the five chronologies reveals significant statistical association between most of them (r = 0.33-0.72; p < 0001). All chronologies were used individually to examine climate-growth associations considering both, local and regional climate data obtained from four meteorological stations in the region. Total regional precipitation correlated extremely well with standardized growth indices (up to r = 0.84; p < 0.0001); maximum temperature had an inverse association with growth, correlating lowly but significantly (up to r = À0.62; p < 0.0001), while minimum and mean temperatures did not correlate at all. The Las Bayas, a new chronology, was the highest correlated with regional November-May and November-August total precipitation (r = 0.80; p < 0.0001 and r = 0.84; p < 0.0001, respectively). Using Las Bayas chronology total November-May regional precipitation was reconstructed from 1681 to 2001 and used to identify the main dry and wet periods during the last three centuries. Most of the drought and wet episodes identified were consistent with those reported earlier for northern Mexico; an important exception was the 1950s interval that has been recognized widely as one of the most severe droughts in this region, and that based on reconstruction presented in this study was identified as a rather wet episode. The presence of wintertime El Niño events and chronologies were statistically related indicating that wet and cold winters in the Sierra Madre mountain range www.elsevier.com/locate/foreco
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Papers by Javier Jiménez