Temporal variation of δ13C of larch leaves from a montane boreal forest in Mongolia

Abstract

This paper reports the temporal variation (2002)(2003)(2004) in foliar d 13 C values, which are indicative of long-term integrated photosynthetic and water use characteristics, of Siberian larch (Larix sibirica Ledeb.) trees in a montane forest at Mongonmorit, NE Mongolia. At the stand, the d 13 C value for understory shaded leaves was more negative by 2& on average than that for sunlit leaves sampled concurrently from open and sun-exposed environments in a forest gap. The d 13 C value of both sunlit and shaded leaves showed pronounced intra-but relatively small inter-seasonal variations. The d 13 C value was more positive for juvenile than mature leaves. We conjecture that juvenile leaves may derive carbon reserves in woody tissues (e.g., stems). Regardless of leaf habitats, the d 13 C value was also affected by insect herbivores occurred in mid summer of 2003, being more negative in newly emerging leaves from the twigs after defoliation than in non-defoliated mature leaves. This pattern seems to contrast with that for the juvenile leaves in the early growing season. We surmise that the newly emerging leaves used stored organic carbon that was depleted due to fractionation during remobilization and translocation for leaf regrowth. There was also intra-and inter-seasonal variation in the foliar N concentrations and C:N ratios. A good positive (negative) correlation between the foliar d 13 C values and N concentrations (C:N ratios) was also observed for both sunlit and shaded leaves, suggesting that the relationship between water and nitrogen use is a crucial factor affecting the plant carbon-water relationship in this mid latitude forest with a cold semiarid climate. Our isotopic data demonstrate that the larches in NE Mongolia exhibits relatively higher water use efficiency with a distinct withinseason variability.

Permafrost Regime Affects the Nutritional Status and Productivity of Larches in Central Siberia

“…The highest concentrations of foliar N, P, and K at all permafrost-affected sites were found in the early growing season, when the needles were first produced. A similar pattern was reported for the same elements in Siberian larch from Mongolia [9] and micronutrients (i.e., Cu, B, Na, Ni etc.) in the same habitats for Gmelin's larch [32].…”

“…in the mid-growing season observed in this study are in the lower range of reported values for Eurasia and Northern America [5,9,13,26] (Figure 6). At the permafrost site at Tura, concentrations of N, P, and K in mature needles were 50% less than the optimum contents of major nutrients in larch needles (2.1-2.6% for N, 0.3-0.6% for P, and 0.9-2.0% for K) reported by [13].…”

“…Foliar stoichiometric ratios like N:P or C:N are reported to be good predictors of the nutritional state of plants in nutrient-limited environments [9,25]. At the plant level, N:P ratios of <14 and >16 correspond to N-and P-limited biomass production, respectively, as demonstrated by fertilization experiments [17,25,38].…”

“…In conjunction with high photosynthetic rates, larch species of the Northern hemisphere are characterized by the highest concentrations of nitrogen [2,5,9,13] and other macronutrients (e.g., P and K) [13] in foliage relative to evergreen conifers, very likely due to annually renewed needles. The high nutrient demand to build foliar biomass may constrain the ability of larch taiga on permafrost soils to act as a sink of atmospheric C [14,15].…”

Simulating carbon and water cycles of larch forests in East Asia by the BIOME-BGC model with AsiaFlux data

“…SKT is a Siberian larch (Larix sibirica) forest located at approximately 25 km northeast of the Mongonmorit village in the Tov province of Mongolia (Li et al, 2005(Li et al, , 2006(Li et al, , 2007. The age structure of the larch ranged from ∼ 70 to over 150 years old, but the oldest trees were older than 300 years.…”