Root foraging of birch and larch in heterogeneous soil nutrient patches under water deficit

Abstract

Water and nutrient are two critical factors that limit plant growth to spatial-temporal extents. Tree root foraging behavior has not received adequate attention in heterogeneous soil environments in temperate forest under drought pressure. In this study, birch (Betula platyphylla) and larch (Larix olgensis) seedlings were raised in pots in a split-root system with artificially heterogeneous soil environments to study the root foraging response to drought. Potted space was split into two halves where substrates were mixed with fertilizers in 67.5 mg nitrogen (N) plant-1 (N-P2O5-K2O, 14-13-13) to both halves as to create a homogeneous condition. Otherwise, a rate of 135 mg N plant-1 of fertilizers was delivered to a random half to create a heterogeneous condition. Half of seedlings were fully sub-irrigated every three days with the other half received the drought treatment by being watered every six days. Both birch and larch seedlings showed greater net shoot growth and biomass increment in well-watered condition, while root morphology was promoted by drought. Both species placed more fine roots with higher root N concentration in nutrient-enriched patches. In the heterogeneous pattern, birch showed a higher foraging precision assessed by biomass and greater foraging plasticity assessed in morphology and physiology. In contrast, larch seedlings had higher root N concentration in the well-watered condition. Neither species showed a significant response of N utilization to the heterogeneous pattern, but both used more N when water supply was improved. Overall, birch is better at acclimating to heterogeneous soil conditions, but its ability to seize N was lower than larch when drought was alleviated.

Root Foraging Behavior of Two Agronomical Herbs Subjected to Heterogeneous P Pattern and High Ca Stress

“…Initiation of new roots is a precondition to grow root hair, which is directed by rhizospheric Ca concentration [66]. Higher foraging sensitivity and precision in the heterogeneous pattern concur with findings about fine root difference between contrasting soil patches [21][22][23]. Overall, the contrasting root foraging behaviors between the two plant species result from their strategies to proliferate length and surface area.…”

“…In homogeneous P supply, RF sensitivity is the fine root difference in morphology (length or surface area) of random two sections [21]; in heterogeneous P supply, RF sensitivity is the fine root difference in morphology between the P enriched section and a random no-P section [22,23]. Root total is the total amount of fine root morphology (length or surface area) in a pot.…”

“…Low mobility of P compounds in soils contributes to a basic heterogeneity of P placement in soils [19]. Plants can modify root architecture to place more fine roots in P-enriched soil patches at the lowest cost of root morphology [20][21][22][23]. In calcareous soils, the precipitation of P further increases the heterogeneity of P patches; hence, root foraging behavior in karst plants has uncertainties for P acquisition.…”

“…Therefore, there may be a trade-off between the spatial scale over which plants forage and the precision with which they are able to capture nutrients with fine root proliferation [28]. Both scale and precision are usually used in combination to evaluate different aspects of root foraging behavior [21][22][23]. Root foraging behavior has a higher complexity for plants acclimated to karst soils.…”

Short-term severe drought influences root volatile biosynthesis in eastern white pine (Pinus strobus L)

“…Drought is a multifaceted environmental restraint that can elicit tree responses from the molecular to the forest level ( Li et al., 2021 ; Bradford et al., 2022 ). It affects soil nutrient availability for plants and the uptake capacities of plant roots, and consequently influences the nutrient status of trees ( Bista et al., 2020 ; Tan et al., 2021 ). Drought stress causes elevated production of reactive oxygen species (ROS) in plants ( Vijayaraghavareddy et al., 2022 ).…”