3.1 Height and LWC
The height of O. ochrocephala decreased significantly under
drought stress compared with that of the CK (40.93% and 60.76% under
the D1 and D2 treatments, respectively) (P <0.05). The
heights of K. humilis, P. annua, and S. pulchra increased
by 51.72%, 132.92%, and 137.35% respectively, under the H2 treatment
(P <0.05), while that of O. ochrocephaladecreased significantly (45.15%) (P <0.05). The heights
of K. humilis and S. pulchra increased significantly under
the D2H2 treatment (75.42% and 81.93%, respectively)
(P <0.05) (Figure 1).
The LWC of K. humilis, P. annua, and S. pulchra decreased
significantly (39.75%, 28.12%, and 37.48%, respectively) under the D2
treatment. The LWC of K. humilis and P. annua increased
significantly (P <0.05) under the high temperature and
the combined stress owing to the interaction of drought and heat. The
LWC of S. pulchra increased significantly only under the H2 and
D2H2 treatments (P <0.05). The LWC change of O.
ochrocephala was non-significant in all treatments
(P >0.05). Drought inhibited the LWC of K.
humilis, P. annua , and S. pulchra , while high temperature and
the compound stress of drought and heat promoted an increase in the
moisture content of the leaves (Table 2).
3.2 Aboveground and belowground biomass
The AGB of K. humilis decreased significantly under the H2
treatment (72.66%) (P <0.05). Its BGB increased
significantly under the D2H2 treatment (98.13%) and decreased
significantly under the H2 treatment (35.68%)
(P <0.05). The AGB of P. annua decreased
significantly under the D1H1 treatment (79.84%)
(P <0.05) and increased slightly, but not significantly
(P >0.05), under the D2 treatment (14.48%). The BGB
change of P. annua was not significant for all treatments.
The AGB of O. ochrocephala and S. pulchra decreased with
the high temperature and drought stress increase, as well as under the
compound heat and drought stress. The AGB of O. ochrocephaladecreased significantly under the H2, D1H1, and D2H2 treatments
(86.95%, 73.65%, and 87.95%, respectively) (P <0.05).
The AGB of S. pulchra decreased the most under the D2H2 treatment
(95.50%). The BGB of O. ochrocephala and S. pulchraincreased gradually with the increase of high temperature stress, and
decreased with the increase of the compound heat and drought stress; the
BGB of both species decreased significantly under the D2H2 treatment
(55.47% and 34.42%, respectively) (P <0.05) (Figure
2).