滇南喀斯特地区不同季节土壤和灌木叶片化学计量特征及对水分添加的响应

干旱是影响南方喀斯特地区植物生长的重要限制因子, 气候变化会影响该地区的降水量和分布格局。研究该地区土壤和植物化学计量特征及其水分响应格局, 具有重要意义。自2017年4月开始, 在云南建水喀斯特植物群落进行加水试验, 2018年4月(旱季)和8月(雨季)分别采集土壤和优势灌木鞍叶羊蹄甲(Bauhinia brachycarpa)和假虎刺(Carissa spinarum)叶片样品, 测定碳、氢、氮、磷、硫、钾、钙、镁、铝、钠、铁、锰、锌、铜14种元素含量。结果表明, 水分添加影响了表层土壤中碳、氮、钠的含量, 相比于旱季, 雨季土壤中钠和硫含量明显减少, 其余土壤元素在水分添加和季节变化下并未表现出明显差异。土壤水分含量的增加使得鞍叶羊蹄甲和假虎刺叶片中钾含量下降, 钙含量上升。在水分条件变化下, 两种植物叶元素含量的稳定性与植物中元素的含量有关, 含量越接近极大值(基本元素碳、氢、氮等)或极小值(微量元素铜、锌等)的元素其变异系数越小(越稳定), 两种植物中含量接近于1 mg·g^-1的元素磷、硫、镁的变异系数最高。在土壤水分条件变化下, 假虎刺中碳、氮、磷等大量元素含量的稳定性显著高于鞍叶羊蹄甲。降水变化和水分添加导致的土壤水分变化, 对滇南喀斯特地区土壤和植物中不同元素含量的影响不同, 这些结果将为该地区的土壤、植被修复和管理提供科学参考。

Stoichiometric characteristics of soils and dominant shrub leaves and their responses to water addition in different seasons in degraded karst areas in Southern Yunnan of China

Aims Drought is a limiting factor for plant growth in southern karst areas. Climate change may affect the amount and distribution pattern of precipitation in these areas. It is important to understand the stoichiometric characteristics of soil and plants and how they respond to increasing precipitation in karst areas.
Methods In Jianshui karst areas in southern Yunnan, a water addition experiment was conducted since April 2017 and the concentrations of carbon (C), hydrogen (H), nitrogen (N), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), aluminum (Al), sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu) in the soils and leaves of two dominant shrubs (Bauhinia brachycarpa and Carissa spinarum) were measured in the dry season (April) and rainy season (August) in 2018.
Important findings Water addition affected the content of C, N and Na in the soil. Compared with the dry season, the concentrations of Na and S in the soil significantly decreased in the rainy season. The remaining soil elements did not show any significant differences between treatments and seasons. With the increase of soil moisture content, the concentrations of K decreased while Ca in both plant species increased. These results also indicated that soil moisture changes could significantly affect plant ecological traits. With soil moisture changes, the stabilities of leaf elements were related to their contents. The closer the leaf element contents are to the corresponding maximum or minimum values, the smaller are the coefficients of variation. And the variation coefficients of P, S and Mg with the concentrations close to 1 mg·g^-1were the highest. Under the changes of soil moisture conditions, the stability of C, N, P and other major elements in C. spinarum was significantly higher than that B. brachycarpa. Changes in soil water content, which was caused by both rainfall changes and water addition, had different effects on different the contents of different elements in both soil and plants. These results may shed light on the restoration of soil and plants in karst regions.