Do the Leaves of Multiple Invasive Plants Decompose More Easily than a Native Plant’s under Nitrogen Deposition with Different Forms?

Abstract

This study aimed to clarify the differences in the decomposition rates, soil carbon and nitrogen contents, soil enzyme activities, and the structure of the soil bacterial community between the four Asteraceae invasive plants (AIPs), Bidens pilosa L., Conyza canadensis (L.) Cronq., Solidago canadensis L., and Symphyotrichum subulatum (Michx.) G.L. Nesom, and the native plant Pterocypsela laciniata (Houtt.) Shih under the artificially modeled nitrogen with four forms (including nitrate, ammonium, urea, and the mixed nitrogen forms with an equal mixture of three individual nitrogen forms). The mixed nitrogen forms significantly increased the decomposition rate of the four AIPs and P. laciniata. The positive effects of the mixed nitrogen forms on the decomposition rate of the four AIPs and P. laciniata were obviously greater than those of individual nitrogen forms. Nitrogen with four forms visibly up- or down-regulated the dominant role of predominant soil bacterial biomarkers, and significantly increased the species number, richness, and phylogenetic diversity of the soil bacterial community, as well as the number of most of the functional gene pathways of the soil bacterial communities involved in the decomposition process. The decomposition rate of the four AIPs was similar to that of P. laciniata. The leaves of C. canadensis decomposed more easily than those of S. subulatum. The decomposition process of the four AIPs caused remarkable changes in the relative abundance of several taxa of the soil bacterial community and soil bacterial beta diversity, and caused apparent up- or down-regulation in the dominant role of predominant soil bacterial biomarkers and the number of several functional gene pathways of the soil bacterial communities involved in the decomposition process.

Litter Mass Loss of the Invasive Rhus typhina L. and Native Koelreuteria paniculata Laxm. Trees Alters Soil N-Fixing Bacterial Community Composition under Different N Forms

“…These observations are also inconsistent with the results of previous research which has shown that invasive plants either degrade more rapidly [18][19][20][21], or significantly more slowly than native plants [58][59][60]. This phenomenon may be due to the similar proportions of soluble and recalcitrant components in the litter of the two trees [28]. In other words, the two trees had similar litter quality, probably because they coexist in the same habitat and have similar growing seasons, growing environments, and lifestyles.…”

“…Previous studies also showed that invasive plants can increase [65,66,68,69] or decrease soil enzyme activities [48,[70][71][72], or have no significant on soil enzyme activities [67,[73][74][75]. Thus, the effects of invasive plants on soil enzyme activities may be species-dependent [28,76] and N-form-dependent [48,77], mainly due to the differences in soil physicochemical properties and the level of available soil nutrients under different plant species and/or different forms of N.…”

“…Soil pH and moisture were determined in situ using a digital soil acidity-moisture meter (ZD-06; ZD Instrument Co., Ltd., Taizhou, China) [28,48,49].…”