In this study, we examined the regularity of phenological rhythmical change of plant water-soluble compound δ13C (δ13Cwsc) in spring for two typical tree species in the warm temperate zone of China, Pinus tabuliformis and Robinia pseudoacacia. The δ13Cwsc in each organ of those two species in the spring phenological period were measured to explore the relationship between δ13Cwsc and related environmental factors. The results showed that there were significant differences in δ13Cwsc values of each organ between P. tabuliformis and R. pseudoacacia, with higher δ13Cwsc(-25.03‰±0.01‰) in the new shoot of P. tabuliformis. The δ13Cwsc value in the non-photosynthetic organs were 0.83‰-1.8‰ higher than that in the photosynthetic organs, while the δ13Cwsc value in the aboveground part was generally lower than that in the underground part. As spring progressing, different carbon storage strategies were found between two species. When the terminal bud of P. tabuliformis opened, the carbon was obtained from the proximal old leaves. At the beginning of leaf development, photosynthetic products accumulated by old leaves could not meet the growth requirements for new leaves and roots, with 90% of which depending on the carbon reserve in branches and stems. When full leaf having developed, the photosynthetic function of both new and old leaves recovered and the carbon consumed by branches and stems was gradually replenished. For R. pseudoacacia, at the beginning of leaf bud opening and leaf spreading, branches were the main carbon source for new leaves and roots. When leaves were fully unfolded, mature leaves with high capacity of carbon sequestration became the primary carbon source. Results of principal component analysis showed that temperature during observation period, ≥10 ℃ accumulated temperature, sunshine duration and solar radiation were the main factors influencing δ13Cwsc, which could explained 86.3% of the total variation. The δ13Cwsc values of both species was negatively correlated with temperature and relative humidity, but positively correlated with the difference of saturated water pressure, ≥10 ℃ accumulated temperature and sunshine duration. The main environmental factors affecting plant δ13Cwsc varied during the phenological process. Our results could provide a reference for more accurate estimation of spring organ carbon distribution pattern of regional typical tree species, and also a theoretical basis for formulating scientific and reasonable forest management strategy.
为明确植物水溶性化合物δ13C(δ13Cwsc)的春季物候节律性变化规律,以我国暖温带地区典型树种油松和刺槐为研究对象,测定春季物候期两树种各器官的δ13Cwsc,探究其与环境因子的相关性。结果表明: 油松和刺槐各器官的δ13Cwsc差异性显著。油松的新梢最大(-25.03‰±0.01‰),非光合作用器官比光合器官高0.83‰~1.8‰,两树种的地上部分普遍低于地下部分。随着物候节律推移,两树种采取不同的碳存储策略。油松在顶芽开放时所需碳源从近端老叶中获取;展叶始期老叶积累的光合产物不能满足新稍和根系生长所需碳,90%依赖于枝干碳储备;叶充分展开后新老叶光合机能恢复,逐渐补给枝干消耗的碳。刺槐在叶芽开放和展叶始期,枝干作为主要碳源向新生叶和根系传送;叶充分展开后具备光合固碳能力的成熟叶成为主要碳源。主成分分析发现,观测期气温、≥10 ℃积温、日照时长和太阳辐射为δ13Cwsc的主要影响因子,可解释δ13Cwsc变异的86.3%。两树种与气温、相对湿度呈显著负相关,与饱和水气压差、≥10 ℃积温和日照时长呈显著正相关。影响植物δ13Cwsc的主要环境因子随物候进程不断变化。本研究可为准确估算区域典型树种春季器官的碳分配格局、制定科学合理的区域森林经营策略提供参考。.
Keywords: environmental factor; phenological period; plant organ; stable carbon isotope; water-soluble compounds.