The contrasting effect of biocrusts on shallow‐rooted perennial plants (hemicryptophytes): Increasing mortality (through evaporation) or survival (through runoff)

Abstract

The effect of biocrusts on plants is ambiguous. At the Nizzana research site (Negev Desert, Israel), frequent droughts in the last 2 decades resulted in high shrub mortality, which has been explained by the negative effect of the low‐albedo crusts on soil water evaporation. Nevertheless, shallow‐rooted perennial plants, such as Stipagrostis plumosa and Cyperus sp., exhibit relatively little mortality. We hypothesized that these hemicryptophytes (HCs) grow at or adjacent to small 2‐ to 4‐m2 depressions (termed IDDEP) in the interdune (ID), which are scattered within the undulating terrain (termed IDINC) of ID, and as previously found, serve as sink for short‐distance runoff from IDINC to IDDEP. To test this, we randomly demarcated 50 5 × 5 m plots in the ID and semistable uncrusted dune crest (CR), and the cover of live HCs in the three habitats CR, IDINC, and IDDEP were monitored. In addition, the available water content (AWC) for the 0‐ to 80‐cm depth was measured during 2012–2014. Although AWC exhibited a clear pattern with IDDEP > CR > IDINC, HCs were almost absent from IDINC (above ground biomass of 0.3 kg/ha) but relatively high in IDDEP (55.3 kg/ha) and CR (113.0 kg/ha). The high biomass at CR and IDDEP is explained by higher AWC due to lower evaporation or runoff addition, respectively. The findings highlight the contrasting role played by the biocrust: Although responsible for the mortality of most perennials at IDINC due to increased evaporation, biocrusts assist the survival of relatively shallow‐rooted perennials at IDDEP through runoff generation.

Biocrust research: A critical view on eight common hydrological‐related paradigms and dubious theses

“…Loci in which ponded conditions take place were monitored in the Jornada Experimental Range in the Chihuahuan Desert (Kidron & Gutschick, ) or at the NRS in the Negev Desert (Kidron, ; Kidron & Aloni, ). Even at the relatively flat interdunes of NRS, the effect of the depressions as run‐off sinks on plants was confined to only ~6% of the interdune (Kidron & Aloni, ), with actual ponded conditions taking place in <2–3% of the interdune. It implies that ponded conditions take place in only <1% of the entire research site (Kidron et al, ).…”

Does biocrust successional stage determine the degradation of vascular vegetation via alterations in its hydrological roles in semi‐arid ecosystem?

“…sis, consequent the energy flow into the ecosystem, and thus plant growth in arid and semi-arid areas(Noy-Meir, 1973;Wang, Schaffer, Yang, & Rodriguez-Iturbe, 2017;Kidron & Aloni, 2018). Biocrusts play a major role in soil moisture availability in these areas by changing soil hydrological properties.…”

Biohydrology—Walking on drylands and swimming through pores

“…Run‐off redistribution from biocrusts leads to greater soil water availability under the plants, promoting more photosynthetically active biomass, net carbon uptake rates, and water‐use efficiency than plants under run‐on exclusion. Kidron and Aloni () also found an increase of survival and biomass of shallow‐rooted perennial plants ( Stipagrostis plumosa and Cyperus sp.) in the Negev desert associated with a higher available water content explained by run‐off addition and lower evaporation from biocrusts.…”