Impact of hedgerows on the improvement of soil characteristics and vegetation diversity in the semi-arid agricultural landscape of Spain

The loss of ecosystem services in semi-arid climate is closely linked to the rise of intensive agriculture and the disappearance of landscape elements that have served as buffer areas for hydrological processes and biodiversity over the last decades. As a response, environmental and agricultural policies and initiatives are now being implemented to restore these landscape elements and preserve those that remain in agricultural landscapes. Hedgerows are linear landscape elements that provide several ecosystem services. However, this positive impact varies depending on hedgerows’ characteristics and location.

This study analyses vegetation diversity and its impact on soil properties in eight hedgerows in Southern Spain's Cordoba province. To carry out this, 10m sections were defined in each hedgerow, considering two zones for soil sampling (inside the hedgerow, and within the agricultural field near it, hereafter outside the hedgerow). The evaluation of vegetation consisted of the identification of species of interest in terms of diversity, a general description of the current status of the hedgerow, and a floristic composition and dendrometric variables recording. The analysis of soil properties encompasses samples from different shallow depths (0-5 and 5-10 cm, or only 0-10 cm), and it included pH, soil hydraulic conductivity, bulk density, stability of aggregates, soil respiration by microorganisms, soil organic carbon and extractable phosphorus.

74 species were identified in total, with a high variability of the number of species recorded in most of the hedgerows, where 58% of the identified vegetative species appeared only in one of them, showing the relevance of this vegetative element in the preservation of vegetative species. Significant differences between inside and outside were obtained in all soil properties, except in extractable phosphorus and pH. Soil aggregate stability and organic carbon reached average values of 424.3 g kg^-1 and 3.0% inside, versus 265.8 g kg^-1 and 1.4% outside, respectively. There was a large variability in some of these properties among different hedgerows. For example, soil respiration varied from 229.7 to 1936.1 mg CO₂ kg^-1 day^-1 and 117.9 to 561.7 mg CO₂ kg^-1 day^-1 inside and outside the eight hedgerows, respectively. This contribution highlights many variables to be considered in hedgerows’ assessments and their complexity, such as the moment of establishment, current management of neighbouring plots, and state of conservation of the own hedgerow.

 

Acknowledgement: This work was funded by the Spanish Ministry of Science and Innovation (project PID2019-105793RB-I00), financial support from the European Union’s Horizon 2020 under the project SCALE (EUHorizon2020 GA 862695), and a predoctoral fellowship for the first author (PRE2020-093846).