Coffee and shade trees show complementary use of soil water in a traditional agroforestry ecosystem

Abstract

Abstract. Globally, coffee has become one of the most sensitive commercial crops, being affected by climate change. Arabica coffee (Coffea arabica) grows in traditionally shaded agroforestry systems in tropical regions and accounts for ∼70 % of coffee production worldwide. Nevertheless, the interaction between plant and soil water sources in these coffee plantations remains poorly understood. To investigate the functional response of dominant shade tree species and coffee (C. arabica var. typica) plants to different soil water availability conditions, we conducted a study during near-normal and more pronounced dry seasons (2014 and 2017, respectively) and a wet season (2017) in a traditional coffee plantation in central Veracruz, Mexico. For the different periods, we specifically investigated the variations in water sources and root water uptake via MixSIAR mixing models that use δ18O and δ2H stable isotope composition of rainfall, plant xylem and soil water. To further increase our mechanistic understanding of root activity, the distribution of below-ground biomass and soil macronutrients was also examined and considered in the model as prior information. Results showed that, over the course of the two investigated dry seasons, all shade tree species (Lonchocarpus guatemalensis, Inga vera and Trema micrantha) relied, on average, on water sources from intermediate (>15 to 30 cm depth: 58± 18 % SD) and deep soil layers (>30 to 120 cm depth: 34±21 %), while coffee plants used much shallower water sources (<5 cm depth: 42±37 % and 5–15 cm depth: 52±35 %). In addition, in these same periods, coffee water uptake was influenced by antecedent precipitation, whereas trees showed little sensitiveness to antecedent wetness. Our findings also showed that during the wet season coffee plants substantially increased the use of near-surface water (+56 % from <5 cm depth), while shade trees extended the water acquisition to much shallower soil layers (+19 % from <15 cm depth) in comparison to drier periods. Despite the plasticity in root water uptake observed between canopy trees and coffee plants, a complementary use of soil water prevailed during the dry and wet seasons investigated. However, more variability in plant water sources was observed among species in the rainy season when higher soil moisture conditions were present and water stress was largely absent.

Precision Techniques and Agriculture 4.0 Technologies to Promote Sustainability in the Coffee Sector: State of the Art, Challenges and Future Trends

“…For more than 25 million small coffee farmers, challenges such as climate change [32] have a drastic impact on coffee production. Plants and grains are very sensitive to global warming, especially the Coffea Arabica [33] which represents around 60-70% of world coffee production [34], [35]. It is estimated that 54% of coffee crops are expected to reach temperatures above 32°C by 2050 [36].…”

“…Produced in more than 70 countries, the largest amount of coffee is produced in developing countries, and the largest consumption of beverage is in developed countries, whose growing demand has doubled the amount of coffee grown in the last decade [45], [46]. Coffee production also has challenges related to shading, carbon sequestration, pest control, soil properties [34], [47] and rust and plant disease that can reduce productivity by up to 50% [48]. It is also important to mention that coffee agriculture and commercialization are responsible for a large volume of harmful waste that generates major environmental impacts.…”

Causes and consequences of pronounced variation in the isotope composition of plant xylem water

“…Hence, the null model attributes any variance in isotopic composition to extraction errors with maximum extraction error ranges of 3 ‰ for δ 2 H samples (0.3 ‰ for δ 18 O) expected for water extraction recovery rates higher than 98 % (e.g., Orlowski et al, 2013). These extraction errors are negatively skewed following the Rayleigh distillation model which predicts that extraction error for incomplete water recovery will be negative and therefore Obs.…”

Investigating the impacts of biochar on water fluxes in tropical agriculture using stable isotopes

“…et al, 2016) are collected and analyzed for their stable isotope composition. The stable isotope composition of the different collected water has allowed researchers to develop new theories whether plants use soil-bound vs. mobile soil water pools (Brooks et al, 2010) or consume water from specific soil layers that change over time (Berry et al, 2018;Beyer et al, 2016;Goldsmith et al, 2012;Koeniger et al, 2016;Muñoz-Villers et al, 2020). Amin et al (2020) compared results from different stable isotopes studies performed in natural catchments and deduced that plants in dry tropical climates consume water from soil layers deeper than 50 cm.…”

“…Despite that stable isotopes have been used to a lesser extent in agricultural systems than in natural systems to investigate plant water sources (Penna et al, 2020), there are successful studies done in coffee (Muñoz-Villers et al, 2020), maize, wheat (Stumpp et al, 2009) and rice cultures (Mahindawansha et al, 2018;Shen et al, 2015). In the case of rice, Shen et al (2015) observed that flooded rice consumed soil water from 0-15 cm deep, while Mahindawansha et al (2018) found that upland rice in dry conditions mostly consumed soil water from up to 50 cm deep except during the maturing stage, when plants shifted to use water from the 10-30 cm soil depth.…”