Abstract
Ecosystems are vulnerable to large areas of rocky desertification, which results in patchy soils and stone-inlaid soils. Karst landforms are typically characterized by heterogeneous phosphorus (P) distributions in soils at high calcium (Ca), but root foraging behavior has not been fully documented in agronomical plants. In this study, Bidens pilosa L. and Plantago asiatica L. were raised in pots in a simulated soil environment with sands at high Ca (2 g kg−1) and low Ca (0.63 g kg−1) levels. Inner spaces were divided into four sections to receive P in homogeneous (Homo.) (four quarters: 2 mg P kg−1) or heterogenous (Hete.) (one quarter: 8 mg P kg−1; three quarters: no-P input) patterns. Both species had longer roots in high P sections compared to no P sections. Foraging scale (highest length or surface-area(SA)) was higher in P. asiatica plants subjected to the Hete. pattern than to the Homo. pattern in low Ca pots. Foraging precision (length or SA differences between P patches as a proportion of the total) was also higher for P. asiatica subjected to the Hete. pattern but did not change in response to Ca level or P placement pattern. Overall, P. asiatica has a higher foraging ability than B. pilosa because of higher levels of foraging scale and precision from high-P (8 mg kg−1) patches in soils subjected to low Ca (0.63 g kg−1).
Highlights
IntroductionKarst topography makes up 20–25% of the ice-free land surface on Earth [2], which is characterized by rocky desertification (RD) [3,4]
Karst ecosystems account for 12% of the world’s total land area [1]
Substrate Ca level and P dose had an interactive effect on fine root length and number of forks in B. pilosa plants, but this interaction generated significant effects on all four types of fine root morphologies in P. asiatica plants (Table 1)
Summary
Karst topography makes up 20–25% of the ice-free land surface on Earth [2], which is characterized by rocky desertification (RD) [3,4]. It is an irreversible ecosystem failure with abundant carbonate rocks like limestone, dolomite, and marble [4], making rocky landforms one of the most fragile terrestrial ecosystems in the world. The driving factor of RD, at least partly, is the high level of soil calcium (Ca) concentration [1,4]. High soil Ca is a predictor of vegetation degradation in RD and is associated with soil bacterial network [4,5], Ca hyperaccumulation in plant roots [1], and arrests of soil organic carbon [6]. More information on the response of belowground karst plant parts to high soil Ca is needed to guide rehabilitation
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