Effect of land cover and hydro‐meteorological controls on soil water DOC concentrations in a high‐elevation tropical environment

Abstract

Páramo soils store high amounts of organic carbon. However, the effects of climate change and changes in land cover and use (LC/LU) in this high‐elevation tropical ecosystem may cause a decrease in their carbon storage capacity. Therefore, better understanding of the factors influencing the Páramo soils' carbon storage and export is urgently needed. To fill this knowledge gap, we investigated the differences in dissolved organic carbon (DOC) content in the soil water of four LC/LU types (tussock grass, natural forest, pine plantations, and pasture) and the factors controlling its variability in the Quinuas Ecohydrological Observatory in south Ecuador. Weekly measurements of soil water DOC concentrations, meteorological variables, soil water content, and temperature from various depths and slope positions were monitored within the soils' organic and mineral horizons between October 2014 and January 2017. These data were used to generate regression trees and random forest statistical models to identify the factors controlling soil water DOC concentrations. From high to low concentrations, natural forest depict the highest DOC concentrations followed by pasture, tussock grass, and pine forest. For all LC/LU types, DOC concentrations increase with decreasing soil moisture. Our results also show that LC/LU is the most important predictor of soil water DOC concentrations, followed by sampling depth and soil moisture. Interestingly, atmospheric variables and antecedent evapotranspiration and precipitation conditions show only little influence on DOC concentrations during the monitoring period. Our findings provide unique information that can help improve the management of soil and water resources in the Páramo and other peat dominated ecosystems elsewhere.

DOC Transport and Export in a Dynamic Tropical Catchment

“…The authors determined one of the largest DOC export fluxes in a forested tropical catchment (13.79 ± 2.07 g C · m ‐2 · year ‐1 ). Contrary to the latter findings, Pesántez et al () reported that changes in land cover and use are the most important predictor of DOC concentrations in high‐elevation ecosystems of Ecuador, with minimal influence of precipitation conditions. Table shows a summary of DOC export fluxes in a wide range of tropical, temperate, arctic, and large river systems across the globe for comparison purposes.…”

Water transport and tracer mixing in volcanic ash soils at a tropical hillslope: A wet layered sloping sponge

“…Below the polypropylene plates, the remaining part of the wicks were placed inside a flexible silicon tube and protected with a 60 cm long and 3/4″ diameter plastic pipe to ensure an unhindered and constant vertical suction of approximately 60 hPa (Windhorst, Kraft, Timbe, Frede, & Breuer, ). Each silicon tube was routed to a centralized collection pipe (Ø = 50 cm) where it was connected to a 1.5‐L glass bottle where collected water was stored until analysis (Pesántez et al, ). The wick samplers were installed at 10, 35, and 65 cm depths at each sampling site.…”

“…The study was carried out at a tropical alpine (Páramo) experimental hillslope situated in the headwaters of the Quinuas Ecohydrological Observatory in south Ecuador (2°47′S, 79°13′W) between 3,900 and 4,100 m a.s.l. The hillslope (Figure a) has a steep gradient (42%; similar to the average slope of the Quinuas Observatory; Pesántez, Mosquera, Crespo, Breuer, & Windhorst, ) and is covered by the dominant Páramo vegetation, consisting primarily of tussock grass ( Calamagrostis intermedia ), locally known as “pajonal,” which covers more than 75–80% of conserved Páramo areas (Mosquera, Lazo, Célleri, Wilcox, & Crespo, ). The soils at the study region resulted from the accumulation of volcanic ash deposits during Quaternary activity in combination with the humid and cold local climate conditions (Buytaert et al, ).…”

Comparison of Natural Regeneration in Natural Grassland and Pine Plantations across an Elevational Gradient in the Páramo Ecosystem of Southern Ecuador

“…Also, the Ksat of pine plantation soils showed a negative relationship with the herbaceous species richness and its cover. This relationship is due to the fact that plantations with a high Ksat show a high speed of water movement in the soil, causing fast drying [74] and loss of SOM [87], limiting the development of herbaceous plants. Therefore, we can conclude that besides elevation, herbaceous species richness and its cover within plantations depend substantially on the attributes of the plantations as well as on the properties of the soils.…”