Nutrient resorption strategies of three oak tree species in response to interannual climate variability

Background Nutrient resorption is critical for plants toward balancing their nutritional requirements and adapting to environmental variabilities, which further impacts litter quality and nutrient cycling. However, the interannual variability of nutrient resorption under climate change remains unclear. Methods We investigated the five-year nutrient resorption efficiencies (NuRE, %) of 14 elements in three deciduous oak tree species (Quercus aliena var. acuteserrata, Q. glandulifera, and Q. variabilis) in a warm-temperate forest of Central China and assessed their relationships with interannual climate and soil factors. Results Nutrient resorption did not differ between species but varied significantly between different years. For each year, N, P, S, K, C, Mg, and Zn were preferentially resorbed in all of the oak species in contrast to Ca, Na, Mn, Ba, Al, Fe, Cu, which were to some extent discriminated. Among the 14 elements, the NuRE of C, N, P, S, Ca, and Mg was more sensitive to interannual climate variations in the three oak species. The carbon resorption efficiency was significantly increased during the driest year of the study (2014); N resorption efficiency was reduced with temperature; whereas N and P resorption efficiency initially decreased and then increased with precipitation. Moreover, the elements with higher NuREs typically had lower coefficient of variation (CV) in all three oak species. Conclusions Different oak species exhibited analogous nutrient conservation strategies in response to annual climate variabilities, and interannual climate variations strongly impacted plant nutrient resorption. Deciduous plants may establish a tradeoff mechanism to rebalance somatic nutrients for regrowth at the end of the growing season.

Different Stand types Alter Soil Properties and Microbial Community in Warm Temperate Forest

Soil microorganism play an important role in maintaining the structure and function in warm temperate forest ecosystem. In order to explore the characteristics of soil microbial community under different stand types in in warm temperate zone, Illunima Miseq High-throughput Sequencing was used to assess the soil bacteria (16S rRNA) and fungi (ITS rRNA) communities of five forest stands (Pinus tabulaeformis [PT], Juglans mandshurica [JM], Betula platyphylla [BP], Betula dahurica [BD] and Quercus mongolica [QM]) in Songshan Nature Reserve. The results showed that the bacterial diversity under Juglans mandshurica forest was higher than other types, the fungal diversity under Pinus tabulaeformis forest was higher than other types. The dominant phyla and gene of soil bacteria were similar in different stand types, but there were significant differences in abundance and dominant gene of fungal community. VPA analysis showed that soil explained 49.1% of the variance in bacterial community composition and 70.6% of the variance in fungal community composition. RDA analysis showed that the dominant phyla were significantly correlated with soil pH, SOM, TN and AN. Based on our results, there are significant differences in soil microbial community structure among different stand types. Consequently, our results have important implications for understanding the driving mechanisms that control the soil microbial community during warm temperate forest.

Nutrient Resorption Strategies of Three Oak Tree Species in Response to Interannual Climate Variability

Background：Nutrient resorption is critical for plants toward balancing their nutritional requirements and adapting to environmental variabilities, which further impacts litter quality and nutrient cycling. However, the interannual variability of nutrient resorption under climate change remains unclear.Methods: We investigated the five-year nutrient resorption efficiencies (NuRE, %) of 14 elements in three deciduous oak tree species, Quercus aliena var. acuteserrata, Q. glandulifera, and Q. variabilis species in a warm-temperate forest of Central China, and assessed their relationships with interannual climate and soil factors. Results：Nutrient resorption did not differ between species but varied significantly between different years. For each year, nucleic acid-protein elements (N, P, S, and K) were preferentially resorbed in all of the oak species in contrast to photosynthesis-enzymic (C, Mg, and Zn) and structural (Ca, Na, Mn, and Ba) elements, which were to some extent discriminated, and toxic (Al and Fe) elements that were completely excluded. Among the 14 elements, the NuRE of N, P, S, Ca, and Mg was closely associated with interannual climate in the three oak species, showing N and S resorption efficiency were reduced with temperature, while N, P, and S resorption efficiency initially decreased and then increased with precipitation. Moreover, the elemental coefficient variations between different years generally decreased with higher NuREs in all three oak species.Conclusions: Different oak species have analogous nutrient conservation strategies in response to annual climate variability, and interannual climate variations strongly impacted plant nutrient resorption. Deciduous plants may establish a trade-off mechanism to rebalance somatic nutrients for regrowth at the end of growing season.

New palynological data from the East Tasman Plateau (ODP Site 1172) indicate rapid earliest Oligocene warming.

<p>Considered as one of the most significant climate reorganisations of the Cenozoic period, the Eocene-Oligocene (E/O) Transition (ca. 33.9-33.5 Ma) is characterised by global cooling coupled with glacial advance on Antarctica. Combined micropalaeontological (diatom and dinoflagellate) and sedimentological evidence hint of regional reorganisation of ocean currents around Antarctica, in association with the Eocene-Oligocene transition. The late Eocene to early Oligocene deepening of the Tasman Gateway resulted in the flow of warm surface waters from the Australo-Antarctic gulf into the southwestern Pacific Ocean.  However, the extent and effect of these changes in ocean circulation on regional terrestrial climate and vegetation across the E/O Transition is not readily known. Here, we present new well-dated, high resolution palynological (sporomorph) data from the East Tasman Plateau (ODP Site 1172) to reconstruct climate and vegetation dynamics from the late Eocene through to the early Oligocene. Results from our sporomorph data point to four vegetation communities occupying Tasmania under different precipitation and temperature regimes: (i) Paratropical rainforest along the coastlines and temperate rainforests at higher altitude of the hinterlands from 37.97-37.52 Ma; (ii) cool temperate forest expanding into areas previously occupied by the paratropical forests between 37.306-35.60 Ma; (iii) a complex mix of paratropical associations coexisting with frost-tolerant taxa, followed by a period of relative stability shown in the dominance of cold-temperate taxa from 35.50-33.36 Ma; (iv) a warm temperate forest present in the early Oligocene (33.25-33.06 Ma). Our sporomorph record showed a general cooling trend from the latest-middle Eocene to the late Eocene (37.97-35.60 Ma), fluctuations between warm and cold climates (35.50 – 34.19 Ma), a period of relative stable cooling across the E/O transition (33.94-33.5 Ma), and a rather unusual rapid warming right after the E/O transition (earliest Oligocene; 33.36 - 33.06 Ma). Our quantitative estimates of terrestrial temperature change and palaeoecological reconstructions show a close link with previously published dinoflagellate cyst data from this same study site, suggesting a possible vegetation and climate response to tectonic changes (most likely the tectonic opening and deepening of the Tasman Gateway ca. 35.5 Ma) and relative short-term regional reorganisation of ocean currents.</p><p><strong>Keywords: Antarctica, Eocene-Oligocene Transition, sporomorph, temperate rainforest, Tasman Gateway</strong></p>