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To truly understand the hydrologic and erosive processes that occur at the catchment scale regarding land use and soil management changes, intensive monitoring is required over a long period. Variables such as precipitation, flow rate and suspended sediment concentration are the fundamentals needed to estimate sediment yield (SY). However, in order to shed more light on the effects of soil management changes on SY, traditional hydrologic monitoring techniques can be paired with sediment tracing to identify sediment sources. In addition, mathematical models that predict erosion and SY can also help understand the dynamics of erosion and deposition between the hillslope and stream channel. Given the above, this article provides an overview of almost 20 years of monitoring (2002–2021) in the Arvorezinha experimental catchment (1.23 km2) located on the edge of the Brazilian meridional plateau in southern Brazil, which is subject to extreme erosion due to a combination of factors related to intensive agriculture and steep slopes. The catchment was selected as a study site to evaluate the effects of land‐use changes and soil conservation management on hydrology and SY. The text reviews the history of the study, synthesizes the main results and describes the evolution of the monitoring techniques used while giving special attention to the fingerprinting approach. In addition, the article discusses the importance of catchment‐scale studies for teaching, generating technical‐scientific knowledge and fostering collaboration between national and international research groups. [ABSTRACT FROM AUTHOR]

The Jacuí Delta drains into Lake Guaíba which is the main source of water for more than two million people in South Brazil and has suffered from pollution with heavy metals and phosphorus. The objective of the current research is to demonstrate how the use of sediment source tracing techniques, in combination with sediment flux monitoring, can improve understanding of the sediment source contributions to one of the largest lakes in South America. The sediment flux monitoring results were based on data obtained from 12-years of records of water flow and suspended sediment concentrations. The sediment source fingerprinting approach was based on the use of geochemical tracers. Based on the study, the respective contributions of the tributaries to the sediment in Lake Guaíba were estimated to be as follows: the Jacuí River (median of 54% - interquartile range (IQR) 34–71%), the Caí River (12%, IQR 7–16%), the Sinos River (5%, IQR 1–20%), and the Gravataí River (16%, IQR 10–30%). These results are similar to those derived from the sediment flux monitoring, namely: the Jacuí River (70%), the Caí River (19%), the Gravataí River (4%), and the Sinos River (7%). These results demonstrate that the sediment source fingerprinting approach combined with sediment flux monitoring can provide a useful means of estimating the respective sediment contributions from individual tributaries in large and complex delta systems and may provide a powerful tool to guide water resource management. [ABSTRACT FROM AUTHOR]

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Abstract: Land‐use/cover change (LUCC), and more specifically deforestation and multidecadal agriculture, is one of the various controlling factors of water fluxes at the hillslope or catchment scale. We investigated the impact of LUCC on water pathways and stream stormflow generation processes in a subtropical region in southern Brazil. We monitored, sampled and analysed stream water, pore water, subsurface water, and rainwater for dissolved silicon concentration (DSi) and 18O/16O (δ18O) signature to identify contributing sources to the streamflow under forest and under agriculture. Both forested and agricultural catchments were highly responsive to rainfall events in terms of discharge and shallow groundwater level. DSi versus δ18O scatter plots indicated that for both land‐use types, two run‐off components contributed to the stream discharge. The presence of a dense macropore network, combined with the presence of a compact and impeding B‐horizon, led to rapid subsurface flow in the forested catchment. In the agricultural catchment, the rapid response to rainfall was mostly due to surface run‐off. A 2‐component isotopic hydrograph separation indicated a larger contribution of rainfall water to run‐off during rainfall event in the agricultural catchments. We attributed this higher contribution to a decrease in topsoil hydraulic conductivity associated with agricultural practices. The chemical signature of the old water component in the forested catchment was very similar to that of the shallow groundwater and the pore soil water: It is therefore likely that the shallow groundwater was the main source of old water. This is not the case in the agricultural catchments where the old water component had a much higher DSi concentration than the shallow groundwater and the soil pore water. As the agricultural catchments were larger, this may to some extent simply be a scale effect. However, the higher water yields under agriculture and the high DSi concentration observed in the old water under agriculture suggest a significant contribution of deep groundwater to catchment run‐off under agriculture, suggesting that LUCC may have significant effects on weathering rates and patterns. [ABSTRACT FROM AUTHOR]

• A. angustifolia growth patterns affected by climate at its northern distribution. • The species shows divergent spatial growth responses to the climate. • Its growth sensitivity to the climate has tended to decrease in recent decades. Temporal instability and spatial inconsistency in tree growth sensitivity to climate have been reported, but little attention has been given to tropical species. Araucaria angustifolia (Bertol.) Kuntze. (Araucariaceae) is a critically endangered South American subtropical and tropical conifer. It offers the potential to evaluate alterations in tree growth responses as it is climate-sensitive and presents a core zone of distribution in the Brazilian meridional highlands (with small disjunct patches occurring in its most southern and northern ranges). Previous dendrochronological studies in the central and most southern distribution range of A. angustifolia showed different climate-related growth responses, which raises the question of whether the growth responses of A. angustifolia to climate are consistent over space and stable over time at the species' northern distribution limit? We developed well-replicated tree-ring chronologies for A. angustifolia at the species' northern distribution limit, examined its growth dynamics, and evaluated climate-growth relationships. The growth patterns of A. angustifolia allowed the synchronization of its tree ring time-series and the construction of two tree-ring width chronologies (at Brejo da Lapa – BL and Vale das Araucárias – VA) of 55 years and 171 years respectively. The chronologies demonstrated stable and robust signal strengths. Climate-growth response analyses indicated significant positive correlations of the VA chronology with precipitation variables, and with temperature variables in the BL chronology. Different diametric growth patterns were detected between BL and VA. We observed consistent reductions of growth responses to the climate in recent decades. Forest structure and dynamics, disturbance regime, local environmental factors, and climate change could generate physiological alterations and explain variations in A. angustifolia 's growth responses and increments. The species showed different sensitivities to climatic factors both spatially and temporally, and different growth patterns at its northern distribution limit. [ABSTRACT FROM AUTHOR]

• There is no common drought response across species. • There is no similar pattern of recovery among species or sites. • The analyzed legume species seem to cope well with the dry periods until now. • Likely, there are different mechanisms preventing decreases in growth. Understanding the behavior of trees and how they will respond to future climate change is a crucial conservation challenge, especially for tropical species. Despite the high diversity of tree species in Brazil, little is known about their tolerance limits. The study of tree rings is a valuable method for the analysis of growth dynamics with superposed epoch analysis being a good way to understand whether past dry years induce decreased tree growth, how long it takes to recover growth after a dry period, and the resilience of trees. This study investigated seven legume species (deciduous and evergreen) from three different sites in the Atlantic Forest in the state of Rio de Janeiro, Brazil. The studied trees seem to have coped well with the drought periods experienced thus far with no common pattern of recovery among species at the same site. The trees were not affected in a similar way and so different mechanisms are likely involved in preventing significant decreases in growth. These data are important for conservation policies because they reveal that each species requires a unique analysis. [ABSTRACT FROM AUTHOR]

Solute and particulate elemental concentrations (C) exhibit different responses to changes in discharge (Q), and those relationships are not well understood in subtropical agricultural environments. The objective is to describe the transport processes of different chemical elements during a set of contrasted rainfall events (2011-2015) that occurred in a small rural catchment under subtropical climate. The study was carried out in the Lajeado Ferreira Creek catchment (1.23 km 2 ), southern Brazil. To this end, the concentrations in dissolved organic carbon (DOC), Cl - , NO 3 - , SO 4 - , ten chemical elements (in either dissolved or particulate forms) and suspended sediment concentrations (SSC) were determined. Metric indices were then calculated to characterize their transport patterns: (i) the best fit slope between log-C and log-Q (β), (ii) the coefficient of variation of C and Q, (iii) shape of the hysteresis loop and hysteresis index, and (iv) the flushing index. All particulate elements along with the dissolved inorganic phosphorus (PO 4 -3 ) were shown to be controlled by the sediment dynamics. Geogenic elements (Fe 2+ , Zn 2+ ) showed a dilution effect with increasing Q values, likely because they were mainly transported with subsurface and base flow. Dissolved elements that are mainly supplied with fertilizers (Na 2+ , Mn 2+ ) as well as DOC showed a dilution effect, although they were mainly transported by surface runoff. Finally, a chemostatic behavior was found for those chemical elements (Mg 4+ ) showed a dilution effect with increasing Q values, likely because they were mainly transported with subsurface and base flow. Dissolved elements that are mainly supplied with fertilizers (Na + and Cl - ) as well as DOC showed a dilution effect, although they were mainly transported by surface runoff. Finally, a chemostatic behavior was found for those chemical elements (Mg 2+ , K + , Ca 2+ , NO 3 - and SO 4 2- ) that are supplied by more than one flow pathways. The results demonstrate that under subtropical climate conditions, the transport of essential nutrients including PO 4 -3 and metals (in particulate form), are mainly transported with surface runoff. Accordingly, runoff control on cultivated hillslopes should be improved to reduce the potential contaminant supply to the river and to reduce the potentially deleterious impacts that they may cause in downstream regions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)