An important challenge for silvicultural practices is the conservation of tree diversity while fulfilling the traditional objectives of forest management, most notably timber harvesting. The purpose of this study was to compare the tree diversity before and after the application of silvicultural treatments in a temperate forest in northern Mexico. Fifteen experimental plots, each measuring 2500 m², were established to evaluate the immediate effect of four silvicultural treatments. These treatments were identified by their levels of management: intensive (clearcut, removal 100%), semi-intensive (removal of 59–61% of basal area), conservative (removal of 29–31% of basal area), and a control group. New forest guidelines, in contrast to conventional approaches, were applied to the semi-intensive and conservative treatments based on health and diversity conditions. Basal area, canopy cover, tree and total volume were measured in each plot. The Importance Value Index, alpha diversity, and evenness were estimated before and after treatments. Eighteen species belonging to five genera and five families were found in the study area. The species with the highest ecological values were Pinus durangensis, P. teocote, Quercus sideroxyla, and Quercus convallata with IVI numbers between 13.6 and 24.5%. Alpha diversity was intermediate (Margalef: 2.9 to 3.8), while dominance and evenness were above average compared to other studies (Simpson: 0.69 to 0.77; Shannon-Wiener: 1.44 to 1.6; Pielou: 0.76 to 0.85). The species evenness index in the conservative treatment was high (Sorensen, Jaccard, quantitative Sorensen and Morisita-Horn; 88 to 99%), although abundance decreased. Overall, there were no significant differences in IVI values and diversity indicators before and after treatments, with the exception of the clearcut treatment. When associating the diversity indices with stand variables, only the Pielou’s evenness index showed a significant relationship between them. We concluded that both the conservative and semi-intensive treatments did not generate significant changes in tree diversity, but the former had slightly higher alpha diversity indices. These results can provide a better insight on silvicultural practices and their effects on species composition.

Austrapotamobius pallipes is the only native species of crayfish in the Iberian Peninsula. The continuous reduction of density, distribution range and loss of native crayfish populations in the Iberian Peninsula and a growing commercial demand of this product generated the idea of introducing American plague-resistant species for aquacultural trials. Several species of crayfish have been introduced with commercial purposes with a different degree of success in Spain. Up to the present date, out of six species of crayfish that have been object of introduction, only P. clarkii, P. leniusculus, and C. destructor are naturalized. Native populations of A. pallipes were greatly reduced in abundance or become extinct due to habitat alteration, human disturbance, large-scale over-exploitation of natural populations, crayfish plague and the exotic species from North America that are vectors of the Aphanomyces astaci. At present, there are few populations of native crayfish in Spain, and relicts populations in Portugal. P. clarkii accounts for the largest catch. Nearly, all red swamp crayfish is produced in Guadalquivir marshes. Portugal produces a small, but growing volume. Maximum production of red swamp crayfish in Spain was about 5000 tons during 1986, but this production decreased due to inadequate management of the resource and severe drought. The intention of introducing P. leniusculus in Spain was mainly to replace A. pallipes in waters devastated by the plague. The catch of P. leniusculus is at least 600 kg annually and the catch of A. pallipes is less than one ton. However, it must be pointed out that the data on catches available from most regions are estimates. Crayfish production in Iberian Peninsula is growing, especially due to good stocking results with the red swamp crayfish P. clarkii. The signal crayfish P. leniusculus has proved to be an excellent substitute to the indigenous crayfish for recreational purposes. Nevertheless, both species have caused considerable damage to the native crayfish habitats. We briefly review the status of crayfish populations in Spain and Portugal, with special emphasis on P. clarkii, since this species is, by far, the most widespread with wide spread effects. Conservation and management measures for the native and alien species are proposed, with the purpose to make the best of a bad situation.