Patterns of biomass allocation in Haloxylon persicum woodlands and their understory herbaceous layer along a groundwater depth gradient

Abstract

a b s t r a c tTo investigate above-and belowground biomass allocation patterns and the relationship of root distribution between different functional groups (shrubs vs. herbs) along a groundwater depth gradient, an experiment was carried out in a Haloxylon persicum woodland. Four sites were selected along the groundwater depth gradient. At each site, five sample plots (20 Â 20 m) and 15 subplots (1 Â 1 m) were established for a vegetation inventory of Haloxylon persicum and the herbaceous layer. The vegetation inventory included plant density, canopy coverage, height, and basal stem diameter of H. persicum. Allometric equations were established for H. persicum based on the biomass of 22 excavated trees, which were then applied to inventory data to provide stand estimates of aboveground biomass (AGB), belowground biomass (BGB), and total biomass (TB) of H. persicum. The AGB of the herbaceous layer was measured in subplots (1 Â 1 m) and BGB was excavated and measured to a depth of 100 cm at 10-cm intervals. Our results indicated that the BGB-to-AGB ratio at the community level in the herbaceous layer increased notably along the gradient of declining groundwater depth. The depth of the soil horizon that contained 65% of the root surface area and 85% of the root biomass was shallower (0-2.5 m) in the deep end of the groundwater depth gradient than in the shallow end (0-3 m) of the gradient. H. persicum adjusted root distribution to capture water in the upper soil layers in response to the decline in groundwater depth. However, this adjustment was not sufficient to compensate for the decline in the water table: the BGB-to-AGB ratio showed no significant increase as AGB declined. On the contrary, herbaceous plants seemed better adapted to changes in the water table by effectively adjusting their BGB-to-AGB ratio. Use of BGB-to-AGB ratios that are specific to groundwater tables will significantly improve our estimates of BGB carbon stocks in these woodlands. Considering the scarcity of information on biomass stocks and partitioning in desert woodlands, our results might be applicable to other desert regions in Central Asia dominated by H. persicum.

Differences in Allometric Relationship of Two Dominant Woody Species Among Various Terrains in a Desert Region of Central Asia

“…These big individuals were usually the ones that surviving from adversities, such as drought and cold, they have developed huge and deep root systems to cope with environmental stresses. According to previous study, the root depth of H. ammodendron and H. persicum could be up to 13.5 and 18 m, respectively (Sheng et al, 2004;Xu et al, 2017). This allowed them to absorb water from deep soil layers for survival and to be more adaptive to environmental changes (Wu et al, 2019a,b).…”

Biotic and Abiotic Contribution to Diurnal Soil CO2 Fluxes from Saline/Alkaline Soils

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Soluble sugar drives plant leaf turgor, restricts plant growth, and regulates plant hydraulic capacity of Haloxylon ammodendron to different groundwater level

“…The stable snow cover can last 100-150 d with depth of 25 cm in winter, which then quickly melts and recharges soil moisture. Therefore, plants in this area experience frequent water deficits in the later growing season (Xu, Yu, & Li, 2017).…”