Abstract
BackgroundGlobally, vegetation in riparian zones is frequently the target of restoration efforts because of its importance in reducing the input of eroded sediment and agricultural nutrient runoff to surface waters. Here we examine the potential of riparian zone restoration to enhance carbon sequestration. We measured soil and woody biomass carbon stocks, as well as soil carbon properties, in a long-term chronosequence of 42 streambank revegetation projects in northern California rangelands, varying in restoration age from 1 to 45 years old.ResultsWhere revegetation was successful, we found that soil carbon measured to 50 cm depth increased at a rate of 0.87 Mg C ha−1 year−1 on the floodplain and 1.12 Mg C ha−1 year−1 on the upper bank landform. Restored sites also exhibited trends toward increased soil carbon permanence, including an increased C:N ratio and lower fulvic acid: humic acid ratio. Tree and shrub carbon in restored sites was modeled to achieve a 50-year maximum of 187.5 Mg C ha−1 in the channel, 279.3 Mg ha−1 in the floodplain, and 238.66 Mg ha−1 on the upper bank. After 20 years of restoration, the value of this carbon at current per-ton C prices would amount to $US 15,000 per km of restored stream.ConclusionWe conclude that revegetating rangeland streambanks for erosion control has a substantial additional benefit of mitigating global climate change, and should be considered in carbon accounting and any associated financial compensation mechanisms.
Highlights
Riparian zones have long been a focus of conservation efforts because they provide unique and important ecosystem services that are vulnerable to degradation
We anticipated that riparian restoration would increase C sequestration in both the soil and vegetative biomass [19], firstly because the community composition would shift from lower-biomass annual grasslands to higherbiomass forest and shrublands; secondly because the biomass inputs to soil organic matter would have a higher percentage of C when derived from woody plants; and thirdly because preventing erosion would prevent loss of soil C from the riparian zone
We examined patterns of carbon sequestration in biomass and soil resulting from riparian restoration in 42 stream reaches in northern California (Fig. 2)
Summary
Riparian zones have long been a focus of conservation efforts because they provide unique and important ecosystem services that are vulnerable to degradation. Services provided to agricultural producers by intact or restored riparian vegetation may include increases to pollinator diversity and abundance [1, 2]; improved soil stability and resilience to erosion [3, 4], and flood attenuation [5]. In our northern California study system, concern about streambank erosion has animated conservation practices for more than half a century, with initial efforts to maintain agricultural productivity gradually coming into. We retrospectively examine these projects, which were initially aimed at enhancing local, on-farm soil productivity, for their potential to produce the globally relevant ecosystem service of carbon sequestration. We measured soil and woody biomass carbon stocks, as well as soil carbon properties, in a long-term chronosequence of 42 streambank revegetation projects in northern California rangelands, varying in restoration age from 1 to 45 years old
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