Smiley B P, Trofymow J A
Natural Resources Canada, Canadian Forest Service, 506 West Burnside Road, Victoria, BC, V8Z 1M5, Canada.
Biology Department, University of Victoria, Victoria, BC, V8W 3R4, Canada.
Carbon Balance Manag. 2017 Dec;12(1):15. doi: 10.1186/s13021-017-0083-z. Epub 2017 Jul 14.
To address how natural disturbance, forest harvest, and deforestation from reservoir creation affect landscape-level carbon (C) budgets, a retrospective C budget for the 8500 ha Sooke Lake Watershed (SLW) from 1911 to 2012 was developed using historical spatial inventory and disturbance data. To simulate forest C dynamics, data was input into a spatially-explicit version of the Carbon Budget Model-Canadian Forest Sector (CBM-CFS3). Transfers of terrestrial C to inland aquatic environments need to be considered to better capture the watershed scale C balance. Using dissolved organic C (DOC) and stream flow measurements from three SLW catchments, DOC load into the reservoir was derived for a 17-year period. C stocks and stock changes between a baseline and two alternative management scenarios were compared to understand the relative impact of successive reservoir expansions and sustained harvest activity over the 100-year period.
Dissolved organic C flux for the three catchments ranged from 0.017 to 0.057 Mg C ha year. Constraining CBM-CFS3 to observed DOC loads required parameterization of humified soil C losses of 2.5, 5.5, and 6.5%. Scaled to the watershed and assuming none of the exported terrestrial DOC was respired to CO, we hypothesize that over 100 years up to 30,657 Mg C may have been available for sequestration in sediment. By 2012, deforestation due to reservoir creation/expansion resulted in the watershed forest lands sequestering 14 Mg C ha less than without reservoir expansion. Sustained harvest activity had a substantially greater impact, reducing forest C stores by 93 Mg C ha by 2012. However approximately half of the C exported as merchantable wood during logging (~176,000 Mg C) may remain in harvested wood products, reducing the cumulative impact of forestry activity from 93 to 71 Mg C ha.
Dissolved organic C flux from temperate forest ecosystems is a small but persistent C flux which may have long term implications for C storage in inland aquatic systems. This is a first step integrating fluvial transport of C into a forest carbon model by parameterizing DOC flux from soil C pools. While deforestation related to successive reservoir expansions did impact the watershed-scale C budget, over multi-decadal time periods, sustained harvest activity was more influential.
为了研究自然干扰、森林采伐以及水库建设导致的森林砍伐如何影响景观尺度的碳（C）收支，利用历史空间清查和干扰数据，编制了1911年至2012年期间8500公顷的苏克湖流域（SLW）的回顾性碳收支。为了模拟森林碳动态，将数据输入到碳收支模型-加拿大森林部门（CBM-CFS3）的空间明确版本中。为了更好地掌握流域尺度的碳平衡，需要考虑陆地碳向内陆水生环境的转移。利用来自SLW三个集水区的溶解有机碳（DOC）和流量测量数据，得出了17年期间进入水库的DOC负荷。比较了基线和两种替代管理情景之间的碳储量和储量变化，以了解在100年期间连续水库扩建和持续采伐活动的相对影响。
三个集水区的溶解有机碳通量范围为0.017至0.057 Mg C ha⁻¹ year⁻¹。将CBM-CFS3限制在观测到的DOC负荷范围内，需要对腐殖化土壤碳损失进行参数化，分别为2.5%、5.5%和6.5%。按流域比例缩放，并假设输出的陆地DOC没有呼吸转化为CO₂，我们推测在100年内，高达30657 Mg C的碳可能可用于沉积物中的封存。到2012年，由于水库建设/扩建导致的森林砍伐使流域林地的碳固存比没有水库扩建时少14 Mg C ha⁻¹。持续的采伐活动产生了更大的影响，到2012年，森林碳储量减少了93 Mg C ha⁻¹。然而，在采伐期间作为商品木材输出的碳中，约有一半（~176000 Mg C）可能保留在采伐的木材产品中，从而将林业活动的累积影响从93 Mg C ha⁻¹降至71 Mg C ha⁻¹。
温带森林生态系统中的溶解有机碳通量虽小但持续存在，可能对内陆水生系统中的碳储存产生长期影响。这是通过对土壤碳库中的DOC通量进行参数化，将河流碳输运纳入森林碳模型的第一步。虽然与连续水库扩建相关的森林砍伐确实影响了流域尺度的碳收支，但在几十年的时间里，持续的采伐活动影响更大。
