School of Forest Resources and Conservation, P.O. Box 110410, University of Florida, Gainesville, FL 32611-0410, USA.
Tree Physiol. 2010 Mar;30(3):376-92. doi: 10.1093/treephys/tpp118. Epub 2010 Jan 12.
The effect of water availability on water relations of 11-year-old loblolly pine stands was studied over two growing seasons in material from two contrasting seed sources. Increasing soil water availability via irrigation increased transpiration rate, and maximum daily transpiration rate on irrigated plots was similar for both seasons, reaching values of 4.3 mm day(-)(1). Irrigation also changed soil water extraction patterns. In the rain-fed control plots, 73% of the average daily transpiration was extracted from the upper 0.75 m of the soil profile. Under irrigated conditions, 92% of transpired water was extracted from the upper 0.75 m of soil, with 79% of transpired water coming from the upper 0.35 m of the profile; only 10% of total transpiration in this treatment was extracted from the soil below 1 m. There was an irrigation x seed source interaction in the response of canopy conductance to water vapor (G(C)) to vapor pressure deficit (D). Under water-limited conditions, trees from the South Carolina seed source (SC) had stronger stomatal control than trees from the Florida seed source (FL), but this difference was not present when water was not limiting. The transpiration-induced water potential gradient from roots to shoots (DeltaPsi) was relatively constant across treatments (P = 0.52) and seed sources (P = 0.72), averaging 0.75 MPa. This reflects strong stomatal control that maintains relatively constant DeltaPsi but at the same time allows leaf water potential (Psi(l)) to fluctuate dramatically in synchrony with soil water potential (Psi(s)). The two seed sources evaluated also showed differences in foliar N and delta(13)C, possibly reflecting differences in adaptation to ambient humidity and water availability regimes in their respective ranges. These differences among seed sources under different water availability scenarios may be informative to natural resource managers and breeders as they design tree improvement and genetic deployment programs for future climate scenarios. For example, the increased stomatal control of SC under decreased soil moisture availability may make this taxon a more conservative deployment choice than FL under future, drier climate scenarios but perhaps at the risk of lower productivity.
在两个生长季节中，通过灌溉增加土壤水分供应来研究 11 年生火炬松林地的水分关系，该研究在两个来源不同的种子材料中进行。通过灌溉增加土壤水分供应增加了蒸腾速率，两个季节中灌溉处理的最大日蒸腾速率相似，达到 4.3mm·d(-1)。灌溉还改变了土壤水分提取模式。在自然降雨对照处理中，平均日蒸腾量的 73%从土壤剖面的上层 0.75m 中提取。在灌溉条件下，92%的蒸腾水从土壤上层 0.75m 中提取，其中 79%的蒸腾水来自剖面上层 0.35m；在该处理中，只有 10%的总蒸腾量来自 1m 以下的土壤。在冠层水汽导（G(C)）对水汽压亏缺（D）的响应中，存在灌溉和种子源的交互作用。在水分受限条件下，来自南卡罗来纳州种子源（SC）的树木比来自佛罗里达州种子源（FL）的树木具有更强的气孔控制，但在水分不受限时，这种差异并不存在。从根到茎的蒸腾引起的水势梯度（DeltaPsi）在处理之间（P=0.52）和种子源之间（P=0.72）相对稳定，平均为 0.75MPa。这反映了强烈的气孔控制，它保持相对稳定的 DeltaPsi，但同时允许叶片水势（Psi(l)）与土壤水势（Psi(s)）同步剧烈波动。评价的两个种子源在叶片 N 和 delta(13)C 方面也存在差异，这可能反映了它们在各自范围内对环境湿度和水分供应模式的适应差异。在不同水分供应情景下，这些种子源之间的差异可能为自然资源管理者和育种者提供信息，因为他们为未来的气候情景设计树木改良和遗传部署计划。例如，在土壤水分减少的情况下，SC 的气孔控制增强可能使这个分类单元比 FL 更适合在未来更干燥的气候情景下进行保守部署，但可能存在生产力较低的风险。
