Litter Decomposition and Nutrient Dynamics in Fire-Affected Larch Forests in the Russian Far East

Abstract

Russian boreal forests hold a considerable carbon (C) stock and are subjected to frequent surface fires that unbalance C storage and ecosystem function. Although postfire ecological changes aboveground are well understood, biological C flows (e.g., decomposition in the postfire period) remain unclear. We present the results of a long-term field litterbag experiment on needle litter decomposition in typical Larix gmelinii boreal forests in the Russian Far East. For 3 years, we measured mass loss, C and nitrogen (N) concentrations, lignin and manganese dynamics, respiration intensity and enzyme activity in decaying needles, and environmental conditions (temperature and litter moisture). The decomposition rate at 850 days was 0.435 and 0.213 yr−1 in a control forest and in a forest 15 years after a surface fire, respectively. Early stages of needle decay did not differ among sites, whereas decomposition slowed in later stages in burned forest relative to the control (p < 0.01). This was supported by hampered respiration, slow lignin accumulation in decaying needles, and low peroxidase activity in burned forest. We found no direct N release, and decaying litter immobilization was more pronounced in the control forest. In the later stages, we revealed restrained mass loss and associated C release from larch litter in burned forest. Slow and delayed N release may alter organic matter accumulation, the N cycle, and regeneration of the fire-disturbed larch ecosystem. Our investigations highlight hampered C flow from aboveground litter to soil humus even decades after surface fire in a larch ecosystem. Given the climate-induced increase of fire activity, C retained in the litter layer represents a pool that is more vulnerable to the next fire event.

Short-Term Litter Manipulations have Strong Impact on Soil Nitrogen Dynamics in Larix gmelinii Forest of Northeast China

“…Inconsistent with other study area, the litter decomposition mainly concentrates on May to September in our study area when the litter decomposition rate is higher, while it is stagnant in winter. The litter decomposed at the study period, losing more than 23% of the initial mass (Figure 3), which is close to previous study in temperate region [37,38]. The rapid mass loss and leaching at this study period may have significant effects on soil N dynamics.…”

The Effects of Fire Disturbance on Litter Decomposition and C:N:P Stoichiometry in a Larix gmelinii Forest Ecosystem of Boreal China

“…Our results showed that the k value did not continue to accelerate after disturbance by fire (Figure 3, Tables 2 and A1). This result was different from the initial increase of k value [30][31][32] and the decrease after fire disturbance [1,[49][50][51][52] as well as the research results that there is no change in the early stage 15 years after fire disturbance, and it was suppressed in the later stage [53] (Table A2). For boreal forest ecosystems, sunlight and rain become important regulatory factors in the upper litter layer in the short term after fire disturbance [54].…”