Effects of Experimental Nitrogen and Phosphorus Addition on Litter Decomposition in an Old-Growth Tropical Forest

Abstract

The responses of litter decomposition to nitrogen (N) and phosphorus (P) additions were examined in an old-growth tropical forest in southern China to test the following hypotheses: (1) N addition would decrease litter decomposition; (2) P addition would increase litter decomposition, and (3) P addition would mitigate the inhibitive effect of N addition. Two kinds of leaf litter, Schima superba Chardn. & Champ. (S.S.) and Castanopsis chinensis Hance (C.C.), were studied using the litterbag technique. Four treatments were conducted at the following levels: control, N-addition (150 kg N ha−1 yr−1), P-addition (150 kg P ha−1 yr−1) and NP-addition (150 kg N ha−1 yr−1 plus 150 kg P ha−1 yr−1). While N addition significantly decreased the decomposition of both litters, P addition significantly inhibited decomposition of C.C., but did not affect the decomposition of S.S. The negative effect of N addition on litter decomposition might be related to the high N-saturation in this old-growth tropical forest; however, the negative effect of P addition might be due to the suppression of “microbial P mining”. Significant interaction between N and P addition was found on litter decomposition, which was reflected by the less negative effect in NP-addition plots than those in N-addition plots. Our results suggest that P addition may also have negative effect on litter decomposition and that P addition would mitigate the negative effect of N deposition on litter decomposition in tropical forests.

Nutrient addition effects on tropical dry forests: a mini-review from microbial to ecosystem scales

“…This is consistent with evidence that N addition effects depend on the form of added N (Lv et al, 2013), litter chemistry or quality (Kwabiah et al, 1999), and site-specific characteristics such as annual rainfall and soil nutrient availability (Bejarano et al, 2014a). In another fertilization experiment in a seasonal tropical forest in China, added P increased decomposition rates while the addition of N inhibited decomposition (Chen et al, 2013). Lab experiments also find that P and micronutrients accelerate leaf litter decay in TDF, while added N retards it (Powers and Salute, 2011).…”

Soil microbial processes and resource limitation in karst and non‐karst forests

“…Modelled SOC decomposition was high in the karst forest (0.21%/day, corresponds to 76.6% mass loss per year), because it was similar to the litter decomposition rate (ranged from 5.7% to 308% mass loss per year) that has been reported for tropical/subtropical regions (Chen et al., ; Mo, Brown, Xue, Fang, & Li, ; Wang & Xu, ), where high decomposition rates are well known. As a result, microbial respiration rate was also high in the karst forest (8,098 mmol C m −3 day −1 , which corresponds to 4.1 μg C g −1 h −1 ), which falls within the range (0.52–9.17 μg C g −1 h −1 ) of soil microbial respiration rates that was measured in other subtropical karst regions (Cui, Luo, Yuan‐Chun, & Shu, ).…”

Responses of soil acid phosphatase and beta-glucosidase to nitrogen and phosphorus addition in two subtropical forests in southern China

“…b-glucosidase is mostly produced by asymbiotic microbes, such as bacteria and asymbiotic fungi [20,66]. Though soil bacterial and fungal biomasses were not measured in our study, our previous studies in the same forest (MEBF) revealed that N addition had no effect on fungal biomass but significantly decreased soil bacterial biomass, as indicated by phospholipid fatty acid analysis (PLFA) profiles [31]. This implies that decreased soil bacterial biomass following N addition may be a possible cause of the lack of a positive BGA-s response to N addition in MEBF.…”

“…Therefore, variations in the biomass of asymbiotic microbes have the potential to cause variations in microbial production of soil b-glucosidase. Our previous studies in MEBF revealed that long-term (>4 years) P addition had no significant effect on total bacterial PLFA and total fungal PLFA [31,32] but increased the relative abundance of AM fungi (symbiotic fungi) [32]. Thus, the relative abundance of asymbiotic fungi was decreased following P addition, and therefore might have reduced the production of b-glucosidase in MEBF.…”

“…P addition has been suggested as an effective management practice because P addition may mitigate the negative effects caused by adding N alone, such as mitigating the decrease in litter decomposition rates [31], microbial biomass [32] and live fine root biomass [33]. According to previous studies, adding P alone seems to only affect soil phosphatase activity but not b-glucosidase activity.…”