Temporal Dynamics of Abiotic and Biotic Factors on Leaf Litter of Three Plant Species in Relation to Decomposition Rate along a Subalpine Elevation Gradient

He X (2013) Temporal Dynamics of Abiotic and Biotic Factors on Leaf Litter of Three Plant Species in Relation to Decomposition Rate along a Subalpine Elevation Gradient. PLoS ONE 8(4): e62073. doi:10.1371/journal.pone.0062073 Temporal Dynamics of Abiotic and Biotic Factors on Leaf Litter of Three Plant Species in Relation to Decomposition Rate along a Subalpine Elevation Gradient Jianxiao Zhu 0 Wanqin Yang 0 Xinhua He 0 Ben Bond-Lamberty, DOE Pacific Northwest National Laboratory, United States of America 0 1 Insititute of Ecological Forestry, Sichuan Agricultural University , Chengdu , China , 2 Key Laboratory for Earth Surface Processes, Ministry of Education, Department of Ecology, Peking University , Beijing , China , 3 School of Life Sciences, Yunnan Normal University , Kunming, Yunnan , China , 4 School of Plant Biology, University of Western Australia , Crawley, WA , Australia Relationships between abiotic (soil temperature and number of freeze-thaw cycles) or biotic factors (chemical elements, microbial biomass, extracellular enzymes, and decomposer communities in litter) and litter decomposition rates were investigated over two years in subalpine forests close to the Qinghai-Tibet Plateau in China. Litterbags with senescent birch, fir, and spruce leaves were placed on the forest floor at 2,704 m, 3,023 m, 3,298 m, and 3,582 m elevation. Results showed that the decomposition rate positively correlated with soil mean temperature during the plant growing season, and with the number of soil freeze-thaw cycles during the winter. Concentrations of soluble nitrogen (N), phosphorus (P) and potassium (K) had positive effects but C:N and lignin:N ratios had negative effects on the decomposition rate (k), especially during the winter. Meanwhile, microbial biomass carbon (MBC), N (MBN), and P (MBP) were positively correlated with k values during the first growing season. These biotic factors accounted for 60.0% and 56.4% of the variation in decomposition rate during the winter and the growing season in the first year, respectively. Specifically, litter chemistry (C, N, P, K, lignin, C:N and lignin:N ratio) independently explained 29.6% and 13.3%, and the microbe-related factors (MBC, MBN, MBP, bacterial and fungal biomass, sucrase and ACP activity) explained 22.9% and 34.9% during the first winter and the first growing season, respectively. We conclude that frequent freeze-thaw cycles and litter chemical properties determine the winter decomposition while microbe-related factors play more important roles in determining decomposition in the subsequent growing season. - Funding: This work was supported by National Natural Science Foundation of China(31170423 and 31270498): http://www.nsfc.gov.cn/Portal0/default166.htm and Sichuan Youth Sci-tech Foundation (2012JQ0059 and 2012JQ0008): http://xmgl.scst.gov.cn/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Litter decomposition is a fundamental biogeochemical process and plays an important role in the terrestrial carbon (C) cycle [1 3]. The ongoing global warming will increase the decomposition rate of litter, particularly under cold biomes such as high latitude and altitude alpine forests, which accumulate large amounts of dead plant material and soil organic C [4]. An increase of associated CO2 release into atmosphere with an increased litter decomposition rate could have profound repercussions for the subalpine and alpine forest [5,6]. Studies have revealed that the initial litter quality, including C and nitrogen (N) concentrations [7], C:N ratio [8], lignin concentrations [9] and lignin:N ratio [1,10], regulates the litter decomposition process. Meanwhile, a greater decomposable litter with high N but low C and lignin would support greater microbial biomass and decomposer communities, which in turn would enhance litter decomposability. In addition, the subsequent quality of litter that is produced during the decomposition and senescence process has also been studied in a given biome [11,12]. Moreover, litter decomposition process and rate may change with the change of soil temperature, which directly affects on microbial communities and litter chemistry [13]. To better understand whether the decomposing litter quality and microbial compositions are important drivers of decomposition in the subalpine forests, a test needs to be explored: whether the changed litter quality and the accompanied changed composition of the litter microbial communities in litter correlate with the decomposition rate among species and elevations. Environmental gradients, especially elevation gradients, have helped to qualify the influence of environmental conditions on forest ecosystem processes [1417]. Along a 2,800 m elevation gradient in Peruvian tropical forests with no constraints on soil moisture and little seasonality in soil temperature, temperature plays the most important role in leaf litter decomposition [18]. However, theoretically, the severely low temperature seriously limits the processes of material cycling, including litter decomposition, particularly during winter and early spring in subalpine and alpine regions [19]. In contrast, physical and chemical losses of organic compounds from leaching and other processes related to the duration of freezing and thawing in winter may change litter quality and contribute to litter decomposition [2022]. As a consequence, the drivers of litter decomposition during the subsequent growing season following a freezing and thawing stage may be different among elevations. Unfortunately, less attention has been paid to the ecological linkages of litter decomposition between winter and a subsequent growing season [23,24]. On the other hand, soil freezing and thawing event during winter is one of the most significantly environmental factors on litter decomposition in subalpine regions [22,25]. Repeated soil freeze-thaw cycles (FTCs) that destroy microbial cells would release nutrients for the surviving microbes, which are highly active during the thawing stage [26]. In general, changed litter microbial biomass and decomposers play more central roles in determining a later litter decomposition during the growing season [13]. However, information about the effects of elevation variations of soil FTCs and the changed litter quality on the subsequent decomposition is limited. In this study, we focus on the effects of changing litter chemistry, microbial biomass, extracellular enzymes and decomposer communities on the decomposition rate at sampling dates. We also focus on the effects of soil freeze-thaw cycles during the winter and the altered litter quality during the subsequent growing season on litter decomposition. To examine whether changes in litter quality over time affect litter decomposability, in a field decomposition exper (...truncated)