Regional cycles of agricultural land expansion and abandonment have been
common throughout history in many countries of the world. Following the
cessation of agricultural practice, landscapes undergo the spontaneous
process of ecological succession resulting in significant above and
belowground changes over time. As agricultural lands are often severely
depleted of soil carbon, they represent one of the land types with the
highest potential to act as carbon sinks through the process of soil
carbon sequestration. While best management practices for increasing
soil carbon stocks through sustainable agriculture are understandably a
key focus point in climate change research today, the lasting effect of
the abandonment of agriculture on soil organic carbon has received
relatively less attention. However, significant amounts of farmland have
been abandoned across the globe in both developed and developing
countries, especially over the last several decades. To better
understand the ability of old agricultural lands to act as carbon sinks
through time, this study compiles field and published data to perform a
comprehensive meta-analysis on the impacts of this land use change on
soil organic carbon dynamics. Using a chronosequence approach, three
study sites in Catalonia, Spain, each with four fields representing
different stages of ecological succession post-abandonment spanning
roughly 60 years, were sampled at soil depths of 10, 20, and 30 cm. To
determine soil carbon stocks at each site, bulk density samples were
also collected. Samples were analyzed for organic carbon, nitrogen and
pH. Additionally, published chrononsequence and paired-plot data from
abandoned agricultural lands throughout the Mediterranean region were
also compiled into a database to perform multiple regression analysis.
Our findings are not only meant to test the hypothesis that abandoned
fields can act as carbon sinks over time, but to also determine the rate
of soil carbon stock increase and projected vulnerability in relation to
a variety of environmental and land management variables, thereby
highlighting the climate change mitigation value of an as of yet
understudied global land use change.