Abstract
Understory vegetation plays a crucial role in carbon and nutrient cycling in forest ecosystems; however, it is not clear how understory species affect tree litter decomposition and nutrient dynamics. In this study, we examined the impacts of understory litter on the decomposition and nutrient release of tree litter both in a pine (Pinus sylvestris var. mongolica) and a poplar (Populus × xiaozhuanica) plantation in Northeast China. Leaf litter of tree species, and senesced aboveground materials from two dominant understory species, Artemisia scoparia and Setaria viridis in the pine stand and Elymus villifer and A. sieversiana in the poplar stand, were collected. Mass loss and N and P fluxes of single-species litter and three-species mixtures in each of the two forests were quantified. Data from single-species litterbags were used to generate predicted mass loss and N and P fluxes for the mixed-species litterbags. In the mixture from the pine stand, the observed mass loss and N release did not differ from the predicted value, whereas the observed P release was greater than the predicted value. However, the presence of understory litter decelerated the mass loss and did not affect N and P releases from the pine litter. In the poplar stand, litter mixture presented a positive non-additive effect on litter mass loss and P release, but an addition effect on N release. The presence of understory species accelerated only N release of poplar litter. Moreover, the responses of mass loss and N and P releases of understory litter in the mixtures varied with species in both pine and poplar plantations. Our results suggest that the effects of understory species on tree litter decomposition vary with tree species, and also highlight the importance of understory species in litter decomposition and nutrient cycles in forest ecosystems.
Highlights
Litter decomposition is one of the key processes in terrestrial ecosystems, affecting nutrient availability and the carbon (C) cycle [1,2]
In the pine stand, the litter quality of pine was lower than that of its corresponding two understory species (A. scoparia and S. viridis), while the converse was true in the poplar stand with the poplar having higher quality of litter compared to the two understory species (E. villifer and A. sieversiana, Table 1)
Decomposition of pine litter mixed with understory litter In this study, we found that in the pine stand, the litter mixture of Mongolian pine and its understory vegetation showed an additive effect on litter mass loss during decomposition with no significant difference between observed and predicted mass remaining (Fig. 2A)
Summary
Litter decomposition is one of the key processes in terrestrial ecosystems, affecting nutrient availability and the carbon (C) cycle [1,2]. Litter decomposition rates and nutrient dynamics are influenced by abiotic and biotic factors, such as climate, litter quality, and the composition of the decomposer community [3,4]. Most previous studies have only focused on single-species litter decomposition rates and nutrient release. In both natural and artificial ecosystems, plant litter does not decompose alone; it usually decomposes together with coexisting plant species [5,6]. Litter diversity can influence litter decomposition rates and nutrient dynamics, either by generating non-additive effects (synergistic or antagonistic) or additive effects [7,8]. Litter decomposition of single species does not sufficiently represent litter decomposition processes at an ecosystem level
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