Violeta Tolorza, Christian H. Mohr, Mauricio Zambrano-Bigiarini, Benjamín Sotomayor, Dagoberto Poblete-Caballero, Sebastien Carretier, Mauricio Galleguillos, Oscar Seguel
{"title":"智利海岸山脉的外来植树造林:平衡离散干扰、连通性和持续干旱对集水区侵蚀的影响","authors":"Violeta Tolorza, Christian H. Mohr, Mauricio Zambrano-Bigiarini, Benjamín Sotomayor, Dagoberto Poblete-Caballero, Sebastien Carretier, Mauricio Galleguillos, Oscar Seguel","doi":"10.5194/esurf-12-841-2024","DOIUrl":null,"url":null,"abstract":"Abstract. The Chilean Coastal Range, located in the Mediterranean segment of Chile, is a soil-mantled landscape with the potential to store valuable freshwater supplies and support a biodiverse native forest. Nevertheless, human intervention has been increasing soil erosion for ∼ 200 years, culminating in the intense management of exotic tree plantations throughout the last ∼ 45 years. At the same time, this landscape has been severely affected by a prolonged megadrought. As a result, this combination of stressors complicates disentangling the effects of anthropogenic disturbances and hydroclimatic trends on sediment fluxes at the catchment scale. In this study, we calculate decennial catchment erosion rates from suspended-sediment loads and compare them with a millennial catchment denudation rate estimated from detrital 10Be. We then contrast both of these rates with the effects of discrete anthropogenic-disturbance events and hydroclimatic trends. Erosion and denudation rates are similar in magnitude on decennial and millennial timescales, i.e., 0.018 ± 0.005 and 0.024 ± 0.004 mm yr−1, respectively. Recent human-made disturbances include logging operations throughout all seasons and a dense network of forestry roads, thereby increasing structural sediment connectivity. Further disturbances include two widespread wildfires (2015 and 2017) and an earthquake with an Mw value of 8.8 in 2010. We observe decreased suspended-sediment loads during the wet seasons for the period 1986–2018, coinciding with declining streamflow, baseflow, and rainfall. The low millennial denudation rate aligns with a landscape dominated by slow diffusive soil creep. However, the low decennial erosion rate and the decrease in suspended sediment disagree with the expected effect of intense anthropogenic disturbances and increased structural (sediment) connectivity. Such a paradox suggests that suspended-sediment loads, and thus respective catchment erosion, are underestimated and that decennial sediment detachment and transport have been masked by decreasing rainfall and streamflow (i.e., weakened hydroclimatic drivers). Our findings indicate that human-made disturbances and hydrologic trends may result in opposite, partially offsetting effects on recent erosion, yet both contribute to landscape degradation.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":2.8000,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Exotic tree plantations in the Chilean Coastal Range: balancing the effects of discrete disturbances, connectivity, and a persistent drought on catchment erosion\",\"authors\":\"Violeta Tolorza, Christian H. Mohr, Mauricio Zambrano-Bigiarini, Benjamín Sotomayor, Dagoberto Poblete-Caballero, Sebastien Carretier, Mauricio Galleguillos, Oscar Seguel\",\"doi\":\"10.5194/esurf-12-841-2024\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Abstract. The Chilean Coastal Range, located in the Mediterranean segment of Chile, is a soil-mantled landscape with the potential to store valuable freshwater supplies and support a biodiverse native forest. Nevertheless, human intervention has been increasing soil erosion for ∼ 200 years, culminating in the intense management of exotic tree plantations throughout the last ∼ 45 years. At the same time, this landscape has been severely affected by a prolonged megadrought. As a result, this combination of stressors complicates disentangling the effects of anthropogenic disturbances and hydroclimatic trends on sediment fluxes at the catchment scale. In this study, we calculate decennial catchment erosion rates from suspended-sediment loads and compare them with a millennial catchment denudation rate estimated from detrital 10Be. We then contrast both of these rates with the effects of discrete anthropogenic-disturbance events and hydroclimatic trends. Erosion and denudation rates are similar in magnitude on decennial and millennial timescales, i.e., 0.018 ± 0.005 and 0.024 ± 0.004 mm yr−1, respectively. Recent human-made disturbances include logging operations throughout all seasons and a dense network of forestry roads, thereby increasing structural sediment connectivity. Further disturbances include two widespread wildfires (2015 and 2017) and an earthquake with an Mw value of 8.8 in 2010. We observe decreased suspended-sediment loads during the wet seasons for the period 1986–2018, coinciding with declining streamflow, baseflow, and rainfall. The low millennial denudation rate aligns with a landscape dominated by slow diffusive soil creep. However, the low decennial erosion rate and the decrease in suspended sediment disagree with the expected effect of intense anthropogenic disturbances and increased structural (sediment) connectivity. Such a paradox suggests that suspended-sediment loads, and thus respective catchment erosion, are underestimated and that decennial sediment detachment and transport have been masked by decreasing rainfall and streamflow (i.e., weakened hydroclimatic drivers). Our findings indicate that human-made disturbances and hydrologic trends may result in opposite, partially offsetting effects on recent erosion, yet both contribute to landscape degradation.\",\"PeriodicalId\":48749,\"journal\":{\"name\":\"Earth Surface Dynamics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.8000,\"publicationDate\":\"2024-07-05\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Earth Surface Dynamics\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.5194/esurf-12-841-2024\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOGRAPHY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Earth Surface Dynamics","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.5194/esurf-12-841-2024","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOGRAPHY, PHYSICAL","Score":null,"Total":0}
Exotic tree plantations in the Chilean Coastal Range: balancing the effects of discrete disturbances, connectivity, and a persistent drought on catchment erosion
Abstract. The Chilean Coastal Range, located in the Mediterranean segment of Chile, is a soil-mantled landscape with the potential to store valuable freshwater supplies and support a biodiverse native forest. Nevertheless, human intervention has been increasing soil erosion for ∼ 200 years, culminating in the intense management of exotic tree plantations throughout the last ∼ 45 years. At the same time, this landscape has been severely affected by a prolonged megadrought. As a result, this combination of stressors complicates disentangling the effects of anthropogenic disturbances and hydroclimatic trends on sediment fluxes at the catchment scale. In this study, we calculate decennial catchment erosion rates from suspended-sediment loads and compare them with a millennial catchment denudation rate estimated from detrital 10Be. We then contrast both of these rates with the effects of discrete anthropogenic-disturbance events and hydroclimatic trends. Erosion and denudation rates are similar in magnitude on decennial and millennial timescales, i.e., 0.018 ± 0.005 and 0.024 ± 0.004 mm yr−1, respectively. Recent human-made disturbances include logging operations throughout all seasons and a dense network of forestry roads, thereby increasing structural sediment connectivity. Further disturbances include two widespread wildfires (2015 and 2017) and an earthquake with an Mw value of 8.8 in 2010. We observe decreased suspended-sediment loads during the wet seasons for the period 1986–2018, coinciding with declining streamflow, baseflow, and rainfall. The low millennial denudation rate aligns with a landscape dominated by slow diffusive soil creep. However, the low decennial erosion rate and the decrease in suspended sediment disagree with the expected effect of intense anthropogenic disturbances and increased structural (sediment) connectivity. Such a paradox suggests that suspended-sediment loads, and thus respective catchment erosion, are underestimated and that decennial sediment detachment and transport have been masked by decreasing rainfall and streamflow (i.e., weakened hydroclimatic drivers). Our findings indicate that human-made disturbances and hydrologic trends may result in opposite, partially offsetting effects on recent erosion, yet both contribute to landscape degradation.
期刊介绍:
Earth Surface Dynamics (ESurf) is an international scientific journal dedicated to the publication and discussion of high-quality research on the physical, chemical, and biological processes shaping Earth''s surface and their interactions on all scales.