Challenges and constrains of conservation and management of even-aged and uneven-aged Nothofagus forests at Southern Patagonia: Adaptation strategies in the current socio-political framework.

MARTÍNEZ PASTUR, G; LENCINAS, MV; CELLINI, JM; BARRERA, MD; PERI, PL

Workshop; 11th. IUFRO Workshop on Uneven-aged silviculture: challenges for increasing adaptability.; 2018

Native forests tends to uneven-aged structures on time, increasing their ecosystem services (ES) and biodiversity values. However, traditional silviculture promote the even-aged structures, increasing the timber quality values and decreasing the operational costs. These silviculture proposals make feasible the forest industry at large scale, generating simplified forest structures, and open a great debate about their sustainability compared to multifunctional landscapes. The challenge for the new silvicultural proposals is to develop alternatives that maintain the ecological functionalities of the uneven-aged forests into these managed landscapes. Two research strategies are indispensables to this task: (i) BACI approach beforeafter-control-impact), and (ii) long-term monitoring. Both strategies were included in the PEBANPA network (Biodiversity and Ecological Long-Term Plots in Southern Patagonia), and the outputs from the last 25 years are discussed here. Shelterwood cuts and clearcuts, as well as thinning cuts, were proposed as tools to homogenize the native forest structure, generating significant impacts over biodiversity and ES values. Some variables presented a negative trend (e.g. biodiversity and supporting ES), while others were positives (provisioning ES). Variable retention approach was proposed as an alternative to decrease the impacts of these traditional silviculture, leading to uneven-aged stands by patches, decreasing the impacts both, at stand and landscape level. This proposal allowed to decrease the impacts in all the studied variables in the first 20 years of the management cycle. Also, their implementation was feasible to implement for large scale timber operations, decreasing the harvesting costs, and maintaining the yield compared to the first cut of the shelterwood cuts. The advantages of the variable retention approach can be explained in the promotion of the uneven-aged structure in-situ, leading to heterogeneous landscapes combining different management objectives in each managed stand. Knowledge gaps and silviculture challenges will be also presented and discussed.