Changes in the structure and composition of two Pinus nigra subsp. salzmannii forests over a century of different silvicultural treatments

Abstract

Silvicultural treatments imply the felling of trees, which can modify species composition and structural diversity. Consequently, it is important to assess the influence of silvicultural treatments on forest composition and structure. The principal objective of this study was to analyze changes in the composition and structural diversity of two forests: Los Palancares y Agregados (Cuenca Mountain Range, Central-east of Spain) and Navahondona (Cazorla Mountain Range, Southeast of Spain), managed under two different silvicultural methods, i.e. shelterwood and selection. Forest inventory data, covering nearly a century of forest management, were used to follow changes in the number of trees and standing volume. Shannon's index was computed for tree species composition and diameter classes, considering forest comparments as sampling units. Diversity profiles were constructed to follow changes in horizontal diameter class diversity. A partial redundancy analysis (pRDA) was conducted to asses the relative contribution of silvicultural treatments in explaining differences in the current structure of the two study forests. Results showed that silvicultural treatments favoured Spanish black pine and did not benefit other tree species. The number of large trees and the values of Shannon's index decreased in both forests over the study period, but the forest under the uneven-aged silvicultural method showed higher values for both variables. Implications for sustainable forestry are discussed.Key words: Shannon's index; veteran trees; diversity profiles; biodiversity; adaptive management; shelterwood method; selection method. ResumenCambios en la estructura y composición de dos bosques ordenados de Pinus nigra subsp. salzmannii durante un siglo de tratamientos selvícolas diferentes Los tratamientos selvícolas implican la corta de árboles y esto puede modificar la composición y diversidad estructural del bosque. En consecuencia, es importante evaluar la influencia de los tratamientos selvícolas en la composición y estructura de los bosques aprovechados. El objetivo principal de este estudio fue analizar los cambios en la composición y diversidad estructural de dos montes: Los Palancares y Agregados (Serranía de Cuenca, España central) y Navahondona (Sierra de Cazorla, sureste de España), gestionados mediante aclareos sucesivos y entresaca, respectivamente. Se utilizaron datos procedentes de inventarios forestales, que cubrían casi un siglo de gestión forestal, para seguir cambios en el número de árboles y el volumen en pie. El índice de Shannon se calculó para la composición de especies arbóreas y para clases de diámetros, considerando los cantones forestales como unidades de muestreo. Se construyeron perfiles de diversidad para seguir cambios en la distribución de clases de diámetro. La contribución relativa de los tratamientos selvícolas para explicar las diferencias actuales en la estructura de los dos bosques estudiados se evaluó mediante un análisis de redundancia (RDA). Los resultados mostraron que los tratamie...

Genetic Diversity of Pinus nigra Arn. Populations in Southern Spain and Northern Morocco Revealed By Inter-Simple Sequence Repeat Profiles

“…This silvicultural treatment may explain the lower Nei’s genetic diversity in comparison with the two natural populations of P. nigra from Cuenca’s region (TrCU and ArCU). Tiscar-oliver et al [ 24 ] studied the impact of the management in PaCU and NaCA in the structure and composition of P. nigra populations. The authors concluded that the number of large trees and the diameter classes decrease in both populations over time; however the uneven-aged silvicultural method showed higher values of both variables.…”

“…The genetic differences between the Cazorla and Cuenca regions may be due to several factors such as natural barriers, agricultural and forest harvesting, local adaptation and management methods [ 24 ].…”

Short-term effects of prescribed burning on litterfall biomass in mixed stands of Pinus nigra and Pinus pinaster and pure stands of Pinus nigra in the Cuenca Mountains (Central-Eastern Spain)

“…Both stands are natural; the Beteta stand was managed in 1971, but the El Pozuelo stand has not been managed. Spanish black pine forests in the Cuenca Mountains have traditionally been managed using the shelterwood method, with a shelter-phase of 20-25 years and a rotation period of 100-125 years (Tiscar Oliver et al, 2011). Controlled grazing and hunting-based management are also carried out in the stands.…”