Effects of biological soil crusts on the photosynthetic characteristics of three desert herbs in Gurbantunggut Desert

We examined the influence of biocrusts on the photosynthetic physiology of three habitat-typical desert herbs (Erodium oxyrrhynchum M.Bieb.,Alyssum linifolium Steph.ex Willd.and Hyalea pulchella(Ldb.) C.Koch) from Gurbantunggut Desert in northwest China by biocrust removal.Based on soil nutrients and water distribution,the influence of biocrusts on plant photosynthetic characteristics was synthetically analyzed.Results showed that the effect of biocrusts on the photosynthetic characteristics of the three plant species was the same.The leaf relative water content (RWC),photosynthesis (P _n),stomatal conductance (G _s),transpiration rate (E),water use efficiency (WUE),PSⅡ photochemical efficiency (F _v/F _m),PSⅡ quantum yield (φ_PSⅡ),and chlorophyll content (Chl) of the three species in crusted soils were higher than those in uncrusted soils in the early growth period,but lower in the later growth period.Our findings indicated that the effects of biocrusts on the photosynthetic parameters of the three ephemeral species were consistent with those on growth,possibly through their effects on soil nutrients and moisture.