Liu Xingliang

Drought-resistant physiological characteristics of four shrub species in arid valley of Minjiang River, China

Abstract The formation of 161 km-long arid valley (170 km2) of Mingjiang River is attributed to the effect of foehn. The arid valley presents harsh conditions for the growth of vegetation, which include higher annual evaporation and transpiration rate (1400–2000 mm), lower annual precipitation rate (400–700 mm), steep slope, and infertile soils. Although the vegetation is dominated by xerophilous bushes and grasses, it plays a significant role in soil and water conservation in watershed and provides important references in the arid valley as it is very difficult to grow trees. Drought-resistant physiological characteristics of four native species, i.e., Sophora davidiana, Bauhinia faberi var. microphylla, Convolvulus tragacanthoides, and Artemisia gmelinii, have been measured. It was found that the content of chlorophyll, free proline and soluble sugars showed an increase, whereas evaporation ratio, WSD, RWC and cytolemma osmosis showed a decrease under drought stress. Integrated assessment of the four species indicated that the integrated drought resistance index was the highest in July (0.507), followed by September, August and June, whereas it was the lowest in May (0.442). The result provided a basis for vegetation restoration, especially it improved survival of planted species in May and June when plant species exhibit the weakest drought resistance.

Root biomass and productivity in dominant plantation populations in the mountainous area in western Sichuan

This study investigated root biomass and productivity in dominant populations in western Sichuan, China. A total of 4 plots (Picea balfouriana plantation for 22 age in Maerkang, 9 trees, mean DBH of population for 10.4 cm and height for 10.5 m; Larix maxteriana plantation for 22 age in Wolong, 9 trees, mean DBH of population for 17.0 cm and height for 13.8 m; Abies fabri plantation for 35 age in Ebian, 18 trees, mean DBH of population for 14.1 cm and height for 11.9 m; Larix kaempferi plantation for 23 age in Miyaluo, 8 trees, mean DBH of population for 17.4 cm and height for 14.5 m; a 20 m×25 m plot located on each of the 4 types in western Sichuan, China) were randomly selected and excavated to a depth of 60 cm for each of the 4 plantation types. To estimate the root biomass of an individual tree using D2H, an exponential model was selected with the highest coefficient ranging from 0.94 to 0.99. The total root biomass per hm2 varied among plantation population types following the order: L. kaempferi (37.832 t/hm2) > A. fabri (24.907 t/hm2) > L. maxteriana (18.320 t/hm2) > P. balfouriana (15.982 t/hm2). The biomass fractions of a given root size class compared to the total root biomass differed among plantation population types. For all 4 studied plantation types, the majority of the roots were distributed in the top 40 cm of soil, e.g., 97.88% for P. balfouriana population, 96.78% for L. maxteriana, 95.65% for A. fabri, and 99.72 for L. kaempferi population. The root biomass fractions distributed in the top 20 cm of soil were 77.13% for P. balfouriana, 77.13% for L. maxteriana, 65.02% for A. fabri and 80.66% for L. kaempferi, respectively. The root allocation in the 0–20, 20–40, and 40–60 cm soil layers gave ratios of 34:12:1 for P. balfouriana, 24:6:1 for L. maxteriana, 15:7:1 for A. fabri, and 64:4:1 for L. kaempferi populations. The root biomass density of dominant plantation population was 10.782 t/(hm2·m) for P. balfouriana, 8.230 t/hm2·m) for L. maxteriana, 24.546 t/(hm2·m) for A. fabri, and 13.211 t/(hm2·m) for L. kaempferi population, respectively. The root biomass productivity was found to be 0.57 t/(hm2·year) for P. balfouriana, 0.83 t/(hm2·year) for L. maxteriana, 0.71 t/(hm2·year) for A. fabri and 1.64 t/(hm2·year) for L. kaempferi population, respectively.