Abstract
The bottom-up effects of vegetation have been documented to be strong drivers of the soil food web structure and functioning in temperate forests. However, how the forest type affects the stability of the soil food web is not well known. In the Ziwuling forest region of the Loess Plateau, we selected three typical forests, Pinus tabuliformis Carrière (PT), Betula platyphylla Sukaczev (BP), and Quercus liaotungensis Koidz. (QL), to investigate the soil nematode community characteristics in the dry (April) and rainy (August) season, and analyzed their relationships with the soil properties. The results showed that the characteristics of the soil nematode communities and their seasonal variations differed markedly among the forest types. Compared to P. tabuliformis (PT), the B. platyphylla (BP) and Q. liaotungensis (QL) forests had higher plant diversity and more easily decomposed litters, which were more effective for improving the soil resource availability, thus, leading to more beneficial effects on the soil nematode community. In both the dry and rainy season, the soil nematode abundance was the highest in the BP forest. The Shannon–Wiener diversity index (H’), Pielou’s evenness index (J’), and nematode channel ratio index (NCR) were higher, while the Simpson dominance index (λ) and plant parasite index (PPI) were lower, in the BP and QL forests compared with in the PT forest. From the dry to rainy season, the total nematode abundance and the abundance of fungivores, bacterivores, and omnivore-predators, significantly increased in the QL and PT forests, and the values of the Wasilewska index (WI), maturity index (MI), H’, J’, λ, and NCR showed the most significant seasonal variability in the PT forest, which were mainly driven by changes in the soil labile C and N and the moisture content between the two seasons. Generally, the seasonal stability of the soil nematode communities was the highest in the BP forest and the poorest in the PT forest, probably due to variations in the plant diversity. Our results suggest the importance of tree species and diversity as bottom-up regulating factors of the soil food web structure, function, and seasonal stability, which has important implications for sustainable forest management in the Loess Plateau and other temperate regions.
Highlights
This article is an open access articleAs one of the most abundant and diverse groups of soil organisms [1], nematodes are ubiquitous in the soil and occupy key positions at several trophic levels of soil food webs, including bacterivores, fungivores, plant feeders, predators, and omnivores [2]
Form the dry season (April) to the rainy season (August), the soil moisture content (SMC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC) dramatically increased in all three types of forests, as well as the NH4 + –N in B. platyphylla (BP) and Q. liaotungensis (QL) forests and NO3 − –N in P. tabuliformis (PT)
The results showed that SV(NH4 + –N) had positive linear correlations with SV(MI) and SV(NCR) (Table S3 in Supplementary Materials), while it negatively correlated with SV(PPI/maturity index (MI))
Summary
As one of the most abundant and diverse groups of soil organisms [1], nematodes are ubiquitous in the soil and occupy key positions at several trophic levels of soil food webs, including bacterivores, fungivores, plant feeders, predators, and omnivores [2]. They play a vital role in driving the important processes of soil ecosystems, such as organic matter decomposition and nutrient cycling [3], exerting significant impacts on soil functions. The bottom-up (resource control) effects have been recognized as important regulation forces of the soil food web [18,19,20], which means that changes in the resource entry into soil may trigger bottom-up cascading effects along soil food chains [17,21]
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