Response of litter decomposition and related soil enzyme activities to different forms of nitrogen fertilization in a subtropical forest

Abstract

With the continuing increase in the impact of human activities on ecosystems, ecologists are increasingly becoming interested in understanding the effects of nitrogen deposition on litter decomposition. At present, numerous studies have investigated the effects of single form of nitrogen fertilization on litter decomposition in forest ecosystems. However, forms of N deposition vary, and changes in the relative importance of different forms of N deposition are expected in the future. Thus, identifying the effects of different forms of N deposition on litter decomposition in forest ecosystems is a pressing task. In this study, two dominant litter types were chosen from Zijin Mountain in China: Quercus acutissima leaves from a late succession broad-leaved forest and Pinus massoniana needles from an early succession coniferous forest. The litter samples were incubated in microcosms with original forest soil and treated with four different forms of nitrogen fertilization [NH 4 + , NO 3 À , CO(NH 2 ) 2 , and a mix of all three]. During a 5-month incubation period, litter mass losses, soil pH values, and soil enzyme activities were determined. Results show that all four forms of nitrogen fertilization significantly accelerate litter decomposition rates in the broadleaf forest, while only two forms of nitrogen fertilization [i.e., mixed nitrogen and CO(NH 2 ) 2 ] significantly accelerate litter decomposition rates in the coniferous forest. Litter decomposition rates with the mixed nitrogen fertilization were higher than those in any single form of nitrogen fertilization. All forms of nitrogen fertilization enhanced soil enzyme activities (i.e., catalase, cellulase, invertase, polyphenol oxidase, nitrate reductase, urease, and acid phosphatase) during the litter decomposition process for the two forest types. Soil enzyme activities under the mixed nitrogen fertilization were higher than those under any single form of nitrogen fertilization. These results suggest that the type and activity of the major degradative enzymes involved in litter decomposition vary in different forest types under different forms of nitrogen fertilization. They also indicate that a long-term consequence of N depositioninduced acceleration of litter decomposition rates in subtropical forests may be the release of carbon stored belowground to the atmosphere.

Endophytic fungus Phomopsis liquidambari and different doses of N-fertilizer alter microbial community structure and function in rhizosphere of rice

“…The largest 13 carbon substrate utilization differences of microbes were in soils treated with high doses of N-fertilizer (Supplementary Table S1). Wang et al 24. recommended that lower carbon metabolism function of soil microbial community is a signal of degradation of soil ecosystem24.…”

Insights into the Effects of Simulated Nitrogen Deposition on Leaf Functional Traits of Rhus Typhina

“…East Asia (mainly China), Western Europe, and North America are currently the major areas of N deposition [1,[3][4]. N deposition can incur changes in ecosystem functions, such as changes in soil pH values, soil microbial community and functioning, plant litter decomposition [5][6][7][8], and plant growth and physiological performance [9][10]. Meanwhile, invasive plants have also triggered serious impacts on native ecosystems on a global scale, especially affecting the structure and function of the ecosystems in which these invasions occur [11][12].…”

“…First, R. typhina can increase soil pH [25][26] because of the preferences of plant N required [27][28] and/or the alkaline substances in the litters and/or root exudations of invasive species [28][29]. Second, soil pH decreased under N fertilization [6][7][8] due to the release of free H + via the nitrifi cation process under N fertilization [30][31]. Third, N fertilization could increase the values of leaf functional traits of R. typhina because N supply could enhance the growth and physiological performance of plant species [9-10, 15, 32].…”

Divergence of dominant factors in soil microbial communities and functions in forest ecosystems along a climatic gradient

“…The litter quality and quantity contribute to the maintenance of soil fertility in forest ecosystems (Wang et al, 2011). In our study, and the C / N ratios were highest, in litter from PCB stands (Table 1), which shows that the soil in the PCB was more N-limited than the other soils because of litter inputs with high C / N ratios (Table 1).…”