Effects of Skidding Operations after Tree Harvesting and Soil Scarification by Felled Trees on Initial Seedling Emergence of Spanish Black Pine (Pinus nigra Arn. ssp. salzmannii)

Manuel Esteban Lucas-Borja,Demetrio Antonio Zema,Mehdi Heydari,Ruben Manso,Isabel Miralles

doi:10.3390/f11070767

Abstract

Skidding operations are thought to have negative impacts on soil emergence because they may increase soil compaction and reduce vegetation cover and the soil’s organic matter content. We investigated whether and to what extent tree harvesting and subsequent skidding initially altered seedling emergence in two Mediterranean forests of Pinus nigra Arn. ssp. salzmannii (Spanish black pine) in the Cuenca Mountains (Spain). Our main objective was to compare the Spanish black pine seedling emergence rate among skid trails, soil areas scarified by felled trees, and areas undisturbed next to harvest operations. In addition, we selected an unmanaged stand as reference, in order to look for evidence of seedling emergence under natural conditions. We measured Spanish black pine seed fall and seedling emergence immediately after harvest operations in two locations in the Cuenca Mountains (Palancares and Majadas forests), which are typical forests in Cuenca Mountains. The results showed that the Palancares site presented higher seed fall in comparison to the Majadas site. In addition, seed fall was higher in the unmanaged stand, as we recorded a higher tree density in this site in comparison to harvested stands (Palancares and Majadas). Furthermore, our results demonstrated differences in seedling emergence between lower elevation drier Palancares and higher elevation wetter Majadas and relative differences in seedling emergence among skid trail, scarified, and undisturbed harvested areas. Finally, the unmanaged stand presented the highest seedling emergence in comparison to scarified, compacted, and non-disturbed harvested areas. Overall, the results suggest a short-term impact of skidding on seedling emergence, which should be considered for future management guidelines of Spanish black pine in the Mediterranean climate.

Highlights

Tree harvesting is used primarily to obtain commercial timber values and improve stand structure, health, and growth, but may be prescribed to regenerate forest stands, reduce possible insect and disease outbreaks as well as limit fire recurrence and safety hazards [1,2,3]
Since parent rock material, respectat to seedling emergence can be associated with climate and the influence of harvest operations on topography, and soil characteristics were similar among study sites
In two Spanish black pine Mediterranean forests subjected to tree harvesting and soil compaction, scarification, or no further disturbance, differences in seed fall quantities were found among sites (Majadas vs. Palancares) and harvested vs. non-harvested sites

Summary

Introduction

Tree harvesting is used primarily to obtain commercial timber values and improve stand structure, health, and growth, but may be prescribed to regenerate forest stands, reduce possible insect and disease outbreaks as well as limit fire recurrence and safety hazards [1,2,3]. The pros (e.g., economic benefits, reduced fire susceptibility, increased worker safety and access) and cons (e.g., increased soil compaction, increased hydrologic responses, and short-term loss of habitat) of tree harvesting have been debated for years. Tree harvesting generates a disturbance, which alters vegetation structure [5,6,7]. Following tree harvesting or logging, pine species regenerate through interactions among materials that function in propagating trees to the stage in their life cycle, including seeds in seed banks and those dispersed into a site [10]. The distribution and persistence of current pinewoods in the Mediterranean landscapes relies on their capacity to successfully regenerate [11]

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