Abstract
Over the last century, lands used for livestock and agriculture have been progressively abandoned on mountains across Europe. The afforestation of abandoned agricultural lands leads to significant environmental impacts particularly in karst catchments, which are highly responsive to climate change and human disturbances. Due to the lack of long-term historical records and appropriate methods, these impacts are not yet well investigated. The remote Baget forested catchment (Pyrenees Mountains), where a long-term hydrochemical survey has been conducted since 1979, was chosen to develop a method for reconstructing the evolution of landscapes based on heterogeneous and multi-temporal satellite imagery and aerial photographs from 1942 onwards. An indicator of landscape change is proposed, based on three vegetation groups, compatible with the various supporting data. The spatio-temporal landscape evolution evidenced a regular increase of 31% in forest extension between 1942 and 2019, while pioneer (grassland and heathlands) and open forest (early woodland) stages showed an overall but uneven decrease, marked by an accelerated decline of the latter due to an increase in livestock activities. The trends of streamwater discharge and chemistry were related to these environmental changes. A set of processes influencing the changes in the hydrochemical patterns, particularly the increase in dissolved elements in streamwater originating from carbonate dissolution, is proposed and discussed. The forest recolonization (+0.05 Km2.yr−1) enhanced soil organic matter content, generating an increased pCO2 in soils, which in turn enhanced the carbonate dissolution, expressed by a concentration increase of + 5 μeq.L-1.yr−1 for (Ca2++Mg2+) and of + 10 μeq.L-1.yr−1 for HCO3–. The steeper slope of HCO3– could result from decreasing terrestrial Ca2++Mg2+ export together with decreasing SO42- leaching (−4 μeq.L-1.yr−1) due to decreasing acid atmospheric deposition. In the meantime, the observed increase in air temperature (+0.03 °C.yr−1) favoured tree growth, litter decomposition and water demand by trees. This study has demonstrated the powerful indicator of linking the historical evolution of the landscape, quantified using images, to the observed trends in the hydrochemical composition of stream waters, to highlight the internal processes of the critical zone. However, because of nested effects, it still remains a challenge to strictly quantify their respective impact on streamwater chemistry.
| Original language | English |
|---|---|
| Article number | 109023 |
| Pages (from-to) | 1-15 |
| Number of pages | 15 |
| Journal | Ecological Indicators |
| Volume | 140 |
| DOIs | |
| Publication status | Published - Jul 2022 |
| Externally published | Yes |
Bibliographical note
Funding Information:The BC belongs to the French Karst Network (SNO Karst, Jourde et al. 2018; www.sokarst.org) initiative of the INSU/CNRS (France), which aims to strengthen knowledge-sharing and to promote cross-disciplinary research on karst systems. It is one of the observatories of the French Research Infrastructure called OZCAR (the French network of Critical Zone Observatories, (Gaillardet et al. 2018)) and also a LTSER (Long-Term Socio-Ecological Research) research site of the CNRS, France (National Centre for Scientific Research) collaborative research platform called “Zone Atelier Pyrénées-Garonne (ZA PYGAR)”, which is a French Research Infrastructure called RZA (Réseau des Zones Ateliers, (Bretagnolle et al. 2019). RZA grouped with OZCAR is the French contribution to the European Research Infrastructure eLTER (Long-Term Ecosystem in Europe, (Mirtl et al. 2018). The authors specially thank the support from CNRS INEE and INSU (France), SNO KARST (INSU/CNRS, France), OZCAR and Zone Atelier Pyrénées-Garonne (LTSER ZA PYGAR). The analytical platforms, PAPC (F. Julien, V. Payre-Suc, D. Lambrigot, and W. Amblas) at Laboratory of Functional Ecology and Environment, and the chemical lab service from the GET (C. Causserand and P. Besson) are thanked for their contribution to the analytical work during the more recent years. F. Ulloa-Cedamanos's PhD was supported by a fellowship from the French Ministry of Higher Education, Research and Innovation. Special thanks are given to Thierry Camboulive, Virginie Payre-Suc, Corinne Pautot, Franck Granouillac for their help in the field samplings and/or lab works. The reviewers are particularly thanked for their valuable inputs, which help to improve the clarity of the manuscript.
Funding Information:
This research was supported by the CNRS-INSU (France) within the framework of the SNO Karst and IR OZCAR and by the CNRS-INEE (France) within the framework of the LTSER Zone Atelier Pyrenees-Garonne (LTSER ZA PYGAR), which is part of the IR RZA. The Eva Vrech’s internship was supported by the LTSER ZA PYGAR-INEE-CNRS.
Funding Information:
The BC belongs to the French Karst Network (SNO Karst, Jourde et al., 2018; www.sokarst.org) initiative of the INSU/CNRS (France), which aims to strengthen knowledge-sharing and to promote cross-disciplinary research on karst systems. It is one of the observatories of the French Research Infrastructure called OZCAR (the French network of Critical Zone Observatories, ( Gaillardet et al., 2018 )) and also a LTSER (Long-Term Socio-Ecological Research) research site of the CNRS, France (National Centre for Scientific Research) collaborative research platform called “Zone Atelier Pyrénées-Garonne (ZA PYGAR)”, which is a French Research Infrastructure called RZA (Réseau des Zones Ateliers, ( Bretagnolle et al., 2019 ). RZA grouped with OZCAR is the French contribution to the European Research Infrastructure eLTER (Long-Term Ecosystem in Europe, ( Mirtl et al., 2018 ). The authors specially thank the support from CNRS INEE and INSU (France), SNO KARST (INSU/CNRS, France), OZCAR and Zone Atelier Pyrénées-Garonne (LTSER ZA PYGAR).
Funding Information:
The analytical platforms, PAPC (F. Julien, V. Payre-Suc, D. Lambrigot, and W. Amblas) at Laboratory of Functional Ecology and Environment, and the chemical lab service from the GET (C. Causserand and P. Besson) are thanked for their contribution to the analytical work during the more recent years. F. Ulloa-Cedamanos’s PhD was supported by a fellowship from the French Ministry of Higher Education, Research and Innovation. Special thanks are given to Thierry Camboulive, Virginie Payre-Suc, Corinne Pautot, Franck Granouillac for their help in the field samplings and/or lab works.
Publisher Copyright:
© 2022 The Author(s)
