Data_Sheet_2_Wood Nutrient-Water-Density Linkages Are Influenced by Both Species and Environment.docx

Tropical trees store a large amount of nutrients in their woody tissues, thus triggering the question of what the functional association of these elements with other wood traits is. Given the osmotic activity of mineral elements such as potassium, sodium, and calcium, these elements should be strong candidates in mediating the water storing capacity in tropical trees. We investigated the role of wood nutrients in facilitating wood water storage in trees by using branch samples from 48 tropical tree species in South America and examined their associations with wood density (ρ). Wood density varied from 316 kg/m3 in Peru plots, where the soil nutrient status is relatively higher, to 908 kg/m3 in Brazil plots, where the nutrient availability is lower. Phosphorus content in wood varied significantly between plots with lowest values found in French Guiana (1.2 mol/m3) and plots with highest values found in Peru (43.6 mol/m3). Conversely, potassium in woody tissues showed a significant cross-species variation with Minquartia guianensis in Brazil showing the lowest values (8.8 mol/m3) and with Neea divaricata in Peru having the highest values (114 mol/m3). We found that lower wood density trees store more water in their woody tissues with cations, especially potassium, having a positive association with water storage. Specific relationships between wood cation concentrations and stem water storage potential nevertheless depend on both species’ identity and growing location. Tropical trees with increased water storage capacity show lower wood density and have an increased reliance on cations to regulate this reservoir. Our study highlights that cations play a more important role in tropical tree water relations than has previously been thought, with potassium being particularly important.

热带树木的木质组织中储存着大量营养元素，由此引出一个科学问题：这些元素与其他木质部性状之间存在何种功能关联？鉴于钾（potassium）、钠（sodium）、钙（calcium）等矿质元素具有渗透活性，它们极有可能是调控热带树木储水能力的关键因子。本研究以南美48种热带树木的枝条样品为研究材料，探究木质部营养元素在促进树木木质储水过程中的作用，并分析其与木材密度（ρ）之间的关联。木材密度范围为316 kg/m³（秘鲁样地，土壤养分状况相对较高）至908 kg/m³（巴西样地，养分可利用性较低）。不同样地的木材磷含量存在显著差异：法属圭亚那样地的磷含量最低（1.2 mol/m³），秘鲁样地最高（43.6 mol/m³）。反之，木质组织的钾含量在跨物种间存在显著变异：巴西的Minquartia guianensis钾含量最低（8.8 mol/m³），秘鲁的Neea divaricata钾含量最高（114 mol/m³）。本研究发现，木材密度更低的树木，其木质组织储水量更高，且阳离子（cations）尤其是钾，与储水能力呈正相关关系。不过，木质部阳离子浓度与茎部储水潜力之间的具体关联，同时取决于物种特性与生长生境。储水能力更强的热带树木，其木材密度更低，且更依赖阳离子来调控这一储水库。本研究表明，阳离子在热带树木水分关系中的作用比此前认知更为重要，其中钾的作用尤为突出。