USDA-ARS Jornada Experimental Range, PO Box 30003, MSC 3JER, Las Cruces, NM 88003, USA.
Oecologia. 2010 May;163(1):215-26. doi: 10.1007/s00442-009-1530-7. Epub 2009 Dec 18.
Increased variability in precipitation, including frequency of drought, is predicted for many arid and semiarid regions globally. The ability of soils to retain water can increase resilience by buffering vegetation communities against precipitation extremes. Little is known, however, about water retention by carbonate-cemented soil horizons, which occur extensively in arid and semiarid ecosystems. It has been speculated that they may significantly modify vertical and temporal distribution of plant-available water (PAW). To investigate this hypothesis, PAW was monitored at three sites in a mixed shrub-grass community in southern New Mexico, USA, across soils with differing degrees of carbonate horizon development: no carbonate horizon, a horizon partially cemented with carbonates (calcic), and a horizon continuously cemented with carbonates (petrocalcic). Results are presented from 3 years that included extremely dry and wet periods. Both carbonate-cemented horizons absorbed and retained significantly greater amounts of PAW for several months following an extremely wet winter and summer compared to the non-carbonate soil. Following a wet summer, continuously cemented horizons retained very high PAW (16-18% volumetric or approximately 72-80% of soil water holding capacity) through early spring of the following year, more than double the PAW retained by similar depths in the non-carbonate soil. Drying dynamics indicate both carbonate-cemented horizons release stored water into the grass rooting zone during growing seasons following extreme wet events. Water dynamics of these horizons during extreme events provide a mechanism to explain previous observations that perennial grasses exhibit greater resilience to drought when carbonate-cemented horizons occur at shallow depths (<50 cm). Water holding capacity of the entire profile, including horizons cemented with carbonates, should be considered when evaluating the potential resilience of vegetation communities to disturbance, including the increased variability in precipitation expected to occur as a result of global climate change.
在许多干旱和半干旱地区，降水的变率增加，包括干旱的频率增加，这是可以预测的。土壤保持水分的能力可以通过缓冲植被群落免受降水极端情况的影响来提高弹性。然而，对于碳酸盐胶结土壤层的水分保持能力，人们知之甚少，而这些土壤层在干旱和半干旱生态系统中广泛存在。有人推测，它们可能会显著改变植物可用水（PAW）的垂直和时间分布。为了验证这一假说，在美国新墨西哥州南部的一个混合灌丛-草地群落的三个地点监测了 PAW，这些地点的土壤具有不同程度的碳酸盐层发育：没有碳酸盐层、部分碳酸盐胶结的 A 层（钙结层）和连续碳酸盐胶结的 A 层（石化钙结层）。研究结果来自 3 年的数据，其中包括非常干燥和湿润的时期。与非碳酸盐土壤相比，在经历了一个非常湿润的冬季和夏季之后，两个碳酸盐胶结层在几个月内吸收和保留了大量的 PAW。在一个湿润的夏季之后，连续胶结层在次年早春保留了非常高的 PAW（16-18%体积或大约 72-80%的土壤持水能力），是类似深度非碳酸盐土壤中保留的 PAW 的两倍多。干燥动态表明，在经历极端湿润事件后的生长季节，两个碳酸盐胶结层都会将储存的水分释放到草根系区。这些层在极端事件中的水分动态为先前的观察结果提供了一种解释机制，即在浅（<50cm）处出现碳酸盐胶结层时，多年生草更能抵御干旱。在评估植被群落对干扰的潜在弹性时，包括由于全球气候变化预计会增加的降水变率，应考虑整个剖面的持水能力，包括与碳酸盐胶结的土壤层。
