Landscapes evolve in response to external forces, such as tectonics and climate, that influence surface processes of erosion and weathering. Internal feedbacks between erosion and weathering also play an integral role in regulating the landscapes response. Our understanding of these internal and external feedbacks is limited to a handful of field-based studies, only a few of which have explicitly examined saprolite weathering. Here, we report rates of erosion and weathering in saprolite and soil to quantify how climate influences denudation, by focusing on an elevation transect in the western Sierra Nevada Mountains, California. We use an adapted mass balance approach and couple soil-production rates from the cosmogenic radionuclide (CRN) 10 Be with zirconium concentrations in rock, saprolite and soil. Our approach includes deep saprolite weathering and suggests that previous studies may have underestimated denudation rates across similar landscapes. Along the studied climate gradient, chemical weathering rates peak at middle elevations (1200-2000 m), averaging 112·3 ± 9·7 t km -2 y -1 compared to high and low elevation sites (46·8 ± 5·2 t km −2 y −1 ). Measured weathering rates follow similar patterns with climate as those of predicted silica fluxes, modeled using an Arrhenius temperature relationship and a linear relationship between flux and precipitation. Furthermore, chemical weathering and erosion are tightly correlated across our sites, and physical erosion rates increase with both saprolite weathering rates and intensity. Unexpectedly, saprolite and soil weathering intensities are inversely related, such that more weathered saprolites are overlain by weakly weathered soils. These data quantify exciting links between climate, weathering and erosion, and together suggest that climate controls chemical weathering via temperature and moisture control on chemical reaction rates. Our results also suggest that saprolite weathering reduces bedrock coherence, leading to faster rates of soil transport that, in turn, decrease material residence times in the soil column and limit soil weathering. a Rock [Zr] measured from exposed tor or bedrock beneath soil at each site: BG (61 ppm), BM (78 ppm), PC (61 ppm), KR (99 ppm), WB (95 ppm). b Where saprolite [Zr] exceeds soil concentrations, saprolite CDF would be negative. In these, we adjust CDF sap to zero.

The weathering and erosion processes that produce and destroy regolith are widely recognized to be positively correlated across diverse landscapes. However, conceptual and numerical models predict some limits to this relationship that remain largely untested. Using new global data compilations of soil production and weathering rates from cosmogenic nuclides and silicate weathering fluxes from global rivers, we show that the weatheringerosion relationship is capped by certain 'speed limits'. We estimate a soil production speed limit of between 320 to 450 t km -2 y -1 and the associated weathering rate speed limit of roughly 150 t km -2 y -1. These limits appear to be valid for a range of lithologies, and also extend to mountain belts, where soil cover is not continuous and erosion rates outpace soil production. We argue that the presence of soil and regolith is a requirement for high weathering fluxes from a landscape, and that rapidly eroding, active mountain belts are not the most efficient sites for weathering. . Ces limites semblent être valides pour une large gamme de roches-mères, et s'appliquent aussi aux zones montagneuses, où les sols ne recouvrent pas toute la surface et où les taux d'érosion dépassent ceux de la production du sol. Nous avançons que la présence d'un sol est un prérequis pour qu'un paysage exporte de fort flux d'altération, et que les chaînes de montagne actives présentant de forts taux d'érosion ne sont pas les sites les plus efficaces pour l'altération.

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Climate controls erosion and weathering on soil-mantled landscapes through diverse processes that have remained diffi cult to disentangle due to their complex interactions. We quantify denudation, soil and saprolite weathering, and soil transport near the base and crest of the western slope of the Sierra Nevada to examine how large differences in climate affect these processes. Depth profi les of fallout radionuclides and fi eld observations show relative differences in erosion and weathering processes at these two climatically diverse sites, and our data suggest fundamentally different patterns of soil production and transport mechanisms: biotically driven soil transport at low elevation, and surface erosion driven by overland fl ow at high elevation. Soil production rates from cosmogenic 10 Be decrease from 31.3 to 13.6 m/Ma with increasing soil depth at low elevation, but show uncertain depth dependence at the high elevation site. Our data also show a positive correlation between physical erosion and saprolite weathering at both sites. Highly weathered saprolites are overlain by weakly weathered and rapidly eroding soils, while chemically less depleted saprolites are overlain by slowly eroding, more weathered soils. Our data are among the fi rst to quantify the critical role of saprolite weathering in the evolution of actively eroding upland landscapes, and our results provide quantitative constraints on how different climates can shape hillslopes by driving processes of erosion and weathering.