Environmental Engineering Reference
In-Depth Information
carbon sink ranging between 814 (Negrisia site) and 89 (Serdiana site) g C m
−
2
y
−
1
was measured. Both climate (water availability and PAR) and management (in
particular the presence of permanent grass cover) have a strong impact on the car-
bon balance of the ecosystems. Even if it can be argued that this sink may be only
temporary and the built-up can be substantially disrupted at the end of the vine-
yard life cycle, these results show that there is a concrete possibility of storing car-
bon in agricultural soils. Proper practices can be defined to preserve this storage at
best, greatly contributing to the global carbon budget.
11.1 Introduction
Croplands have been largely overlooked in terms of continuous carbon flux moni-
toring and carbon budget assessment. This is probably due to the common belief
that agricultural fields cannot be net carbon sinks. Indeed, many technical inputs,
heavy periodical harvests, and the repeated disturbances of the upper soil layers, all
contribute to a substantial loss both of the old and newly-synthesized organic mat-
ter. Perennial tree crops, however, could behave differently: they grow a permanent
woody structure, remain relatively undisturbed in the same field for decades, cre-
ate a woody pruning debris, and are often grass-covered. Vineyards are good can-
didates to verify this hypothesis, because (at least in temperate climates) they are
often grown with reduced or no soil cultivation, and are typically long-life crops
that produce plenty of woody pruning material that is often left on the ground.
The global vineyard surface area shrunk in 2011 by 7.6 million hectares, with a
loss of about 262 million hectares since 2000. The same trend with an even higher
vineyard area loss was observed in Italy, with a decrease from 908,000 ha (2000)
to 776,000 ha (2011, OIV
2012
). Despite this, Italy today has the third worldwide
vineyard acreage in the world and, alongside France, is the biggest world wine pro-
ducer and the biggest exporter (around 40 % of the production). The grapevines
are cultivated in every region of Italy, despite the large climatic differences along
the peninsula, due to the plasticity and to the different varieties used in the culti-
vation. To understand the role played by vineyards in the national carbon budget,
Eddy Covariance measurements in three vineyard sites along a north-south transect
have been analyzed (Fig.
11.1
). 2009 was chosen as a reference year for the three
sites, in order to compare carbon budget estimates in areas characterized by differ-
ent meteorological, pedological and geomorphological conditions. A crucial aspect
in estimating the vineyard carbon balance at a national scale is to evaluate the impact
of changes in land use management practices, and vineyard abandonment on the soil
carbon stock. Changes in land use and management practices can easily affect the
processes, which control the accumulation and stabilization of soil organic matter
(SOM) and turn the soil from a C sink into a source of CO
2
, while most of its func-
tions are lost. On the global scale, inaccurate managements have a large impact on
the atmospheric CO
2
concentration (IPCC
2001
; Allmaras et al.
2000
). In particular,
it is well established that land-use change (LUC) is considered the second greatest
