Effects of litter diversity and composition on litter decomposition characteristics and soil microbial community

Litter decomposition is the core process of the nutrient substance cycles in the ecosystem, and the soil microbial community plays an important and irreplaceable role in litter decomposition. Recently, the loss of diversity has become a serious issue because of climate changes and human activities, which would influence litter diversity and composition in the community. Therefore, in the present study, we examined how litter diversity and its composition affect the soil microbial community and litter decomposition characteristics. We focused on the typical steppe community of Hulun Buir in the Inner Mongolia Steppe, China, where the grassland has degraded in the past few decades. In a restoration community, we collected the litter of the first four most abundant species: Leymus chinensis, Artemisia capillaris, Serratula centauroides, and Potentilla bifurca. Litter diversity treatments were set up under controlled conditions: 1-, 2-, and 4-species treatments. The 1-species litter treatment included 4 types of composition(each of the four species), 2-species litter treatment included 6 types of composition(litter of pairwise species among the four species), and 4-species litter treatment included 1 type of composition(all the four species). After 60 days of decomposition, the litter decomposition characteristics were estimated and corresponding soil microorganisms were analyzed using the phospholipid fatty acid(PLFA) method. The results showed as follows(1) Litter diversity only had a significant effect on the C remaining rate. The C remaining rate of mixed litter was significantly lower than that of single litter, whereas litter composition had a significant effect on the four decomposition parameters(mass, C, N remaining rate, and C/N).(2) Litter diversity had a significant effect on bacterial PLFAs content, whereas litter composition had a significant effect on fungal PLFAs content. Both factors had no significant effects on F/B or total PLFAs.(3) The redundancy analysis showed that litter composition had a greater impact on the decomposition parameters(mass, C, N remaining rate, and C/N) and soil microbe(bacteria and fungi) than litter diversity.(4) The structural equation model showed that the initial litter C content had significantly and directly positive effects on litter mass, C and N remaining rate, and C/N. The initial litter lignin content had significantly and directly positive effects on litter mass, C and N remaining rate. The initial litter N