Similar tendencies but slight differences in the size of changes were found in deep soil than in surface soil (Figure 5(b)). Most functional group traits in the surface and deep layers of dark brown forest soil increased. 17-AAG However, a completely different pattern was found in saline-alkali soil (Figure 5(c)). In contrast with dark brown forest soil, the addition of fungus extracts to soil colloids from saline-alkali soil reduced the traits of most functional groups from 10% to 35% (Figure 5(c)). Functional group traits that decreased included O�CH bending, C=O stretching, Si�CO�CSi stretching, O�CH stretching, COO? stretching, and carbonate stretching, with the exception of C�CH stretching (a 56% increase) (Figure 5(c)). 3.6.

XPS ResultsSemiquantitative analysis of variable elements with and without the addition of the fungus extract was performed using XPS (Figure 6). In the case of soil colloids from the surface layer of dark brown forest soil, the addition of the fungus extract induced <5% changes in all elements, for example, a 5% increase in C1s and <5% decreases for all O1s, Si2p, N1s, and Ca2p (Figure 6(a)). Changes in variable elements in the deep soil due to the addition of fungus extracts were more evident than those in the surface layers (Figures 6(a) and 6(b)). The changes in C1s, O1s, and Si2p were less than 5%, while 6�C9% decreases in N1s and Ca2p were observed (Figure 6(b)). Figure 6X-ray photoelectron spectroscopy results with and without fungus extract addition. The labels are the same as those for Figure 4.

Compared to the dark brown forest soil, addition of the fungus extract to the saline-alkali soil caused large reductions in variable elements (Figure 6(c)). C1s decreased by 21%, Ca2p by 10%, and O1s, Si2p, and N1s by 5%.Stoichiometric changes induced by fungus extract addition were also found in the ratios among different elements (Table 1). In the case of the surface layer of dark brown forest soil, the ratios of C:N, Si:Ca, and C:Ca increased by 7�C14%. In the case of the deep layer of dark brown forest soil, changes were also mainly found in C:N (6.5%), Si:Ca (20.5%), and C:Ca (17.1%). Stoichiometric changes were much more evident in saline-alkali soil than in dark brown forest soil. Over 25% decreases were found in C:O, C:N, and C:Si, and a 12.7% decrease was found in C:Ca. The Si:Ca ratio increased by 16.39% (Table 1).Table 1Results from X-ray photoelectron spectroscopy of the variation in element ratios with and without the addition of the fungus extract.4. DiscussionHeavy soil degradation is common in China, and rehabilitation via vegetation recovery is mainly conducted in degraded regions, such as the saline-alkali soil region in the Songnen Entinostat Plain [26].