ABSTRACT: • Introduction
This study presents a method for estimating the minimum area which exhibits a balanced diameter distribution, and the corresponding
number of trees, for different tree species and forest types in the Santiago Papasquiaro region in the State of Durango, Mexico.
The balanced structure area is defined as the minimum contiguous area that is required for sustainable management of a multi-sized
selection forest. A multi-sized forest represents a balanced structure unit if the relationship between harvest and growth
can be maintained, using a defined target diameter distribution and disregarding major natural disturbances. The study is
based on 17,577 sample plots in uneven-aged forests, which are selectively harvested by local communities.
• Results and discussion
The minimum structure areas that provide a balanced diameter distribution in the diameter at breast height (DBH) interval of 12 to 57 cm vary from 0.4 to 122ha, depending on the particular tree species. This study has shown that it
is possible to identify silvicultural treatments that are conducive to sustainable use.
Future management monitoring in the unique forests of Durango will reveal unsustainable harvesting practices more effectively
and in a more comprehensive way than before, using the methods presented in this study.
KeywordsDiameter distribution–Sustainable management–Species diversity–Covariation–Permutation test–Uneven-aged silviculture–Selective harvesting
Annals of Forest Science 04/2012; 68(2):385-394. · 1.79 Impact Factor
ABSTRACT: The two most important components of biodiversity, species diversity and genetic diversity, have generally been treated as separate topics, although a coordination between both components is believed to be critical for ecosystem stability and resilience. Based on a new trait concept that allows for the assessment of genetic diversity across species, the relationship between species diversity and genetic diversity was examined in eight forest tree communities composed of different tree genera including both climax and pioneer species. It was intended to check whether a trade-off exists between the two diversity components as was found in a few studies on animal species.Using several isozyme-gene systems as genetic markers, the genetic diversity across species within each of the tree communities was determined by two measures, the commonly used intraspecific genetic diversity averaged over species and the recently developed transspecific genetic diversity per species. Both data sets were compared with the corresponding community-specific species diversity resulting in a positive relationship between the two diversity components. A statistically significant positive correlation was established between the transspecific genetic diversity per species and the species diversity for three isozyme-gene systems. Beyond that, consistent results were obtained using different parameters of the diversity measure which characterize the total, the effective and the number of prevalent variants. The number of prevalent variants reflected most significantly the non-randomness of the observed diversity patterns.These findings can be explained by the observation that the pioneer tree species reveal a by far higher genetic diversity than the climax tree species, which means that an increase in species diversity, due to the addition of several pioneer species at the expense of one or two climax species, goes along with an increase in the level of genetic diversity. Forest tree communities with the highest degree of species diversity exhibit therefore the highest transspecific genetic diversity per species. This result was discussed with regard to the particular composition and stability of forest tree communities.
Plant Ecology 04/2012; 185(1):151-161. · 1.83 Impact Factor
ABSTRACT: The ability to precisely describe forest spatial structures, and their modifications through timber harvesting, is of prime
importance for sustainable management of complex forest ecosystems, especially regarding uneven-aged, multi-species forests.
For this purpose, forest managers require statistical indices that are meaningful descriptors of the spatial structure of
a given forest ecosystem. This paper presents a new sensitive permutation test of spatial randomness for solving the classification
problem of three nearest neighbour-based indices. The test enables a categorisation of a spatial pattern as a whole into one
of three groups: regular, random or cluster, with a sensitivity comparable to that of Ripley’s L test, at finer scales. The examples illustrate how the Clark and Evans, the uniform angle, and the mean directional indices
can be used for precise detection of departure from spatial randomness. The results show that these three indices should be
used simultaneously because they are sensitive to slightly different types of processes.
KeywordsClark and Evans, uniform angle, and mean directional indices-Complete spatial randomness-Spatial distribution of trees
Journal of Forest Research 04/2012; 15(4):218-225. · 0.77 Impact Factor
ABSTRACT: In view of the progressive destruction of the biosphere, biodiversity research plays an important role in the search for factors
affecting species diversity and in the analysis of the effects of species diversity on ecosystems. However, research into
how species diversity and composition are related to genetic structures is still at the beginning. In this study, we combined
population genomics, new correlative approaches, and randomization permutation methods to identify adaptive genetic differentiation
in populations of the Norway spruce Piceaabies L. that display different levels of species diversity. We detected a significant positive large covariation (C) between species diversity (ν
) and genotype frequency at a gene locus, resulting from differential selection by species diversity or by environmental factors.
The results may contribute to understand the interplay between ecological and evolutionary processes in determining community
structure and dynamics.
KeywordsCovariation-Community genetics-Genetic differentiation-Permutation test-AFLP
Plant Ecology 04/2012; 208(1):47-54. · 1.83 Impact Factor