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首页> 外文期刊>Ecohydrology >Spatial and temporal patterns of water availability in a grass-shrub ecotone and implications for grassland recovery in arid environments
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Spatial and temporal patterns of water availability in a grass-shrub ecotone and implications for grassland recovery in arid environments

机译：灌木丛过渡带中可用水的时空格局及其对干旱环境下草地恢复的影响

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Encroachment of woody shrubs into historic desert grasslands is a major problem throughout the world. Conversion of grasslands to shrub-dominated systems may result in significant alteration of biogeochemical processes and reduced resource availability in shrub interspaces, making grassland recovery difficult. Soil petrocalcic horizons, which are common in arid and semi-arid regions globally, have been shown to dramatically alter plant water availability. To assess how soil water dynamics are affected by woody encroachment in petrocalcic soils under contrasting precipitation patterns, we conducted a 3-year replicated study in a mixed shrub-grass system measuring soil water in unvegetated interspaces and under mesquite canopies. Plots were instrumented with time-domain reflectometry (TDR) moisture probes, both above and within the soil petrocalcic horizon. Soils under both cover types maintained large increases in available water content for several months during a wetter than normal winter and summer (increases of 0·08-0·16 m~3 m~(-3)). Interspace soils absorbed significantly greater quantities of water during the winter and retained more water into the spring than soils under shrubs. In contrast, soils under shrubs initially absorbed greater volumes of water during and following summer rains. Differing seasonal dynamics were attributed to interactions between the unique properties of soils with petrocalcic horizons and canopy-induced variability in evapotranspiration. Observed patterns of plant-available water do not support the hypothesis of greater resource availability under shrubs. Similar or greater water availability in shrub interspaces indicates that concentration of soil water under shrubs may not be a process limiting grass recovery on these soils. Published in 2010 by John Wiley & Sons, Ltd.
机译：木本灌木丛侵占历史悠久的沙漠草原是全世界的一个主要问题。将草地转化为灌木为主的系统可能会导致生物地球化学过程发生重大变化，并减少灌木间空间中的资源可利用性，从而使草地恢复变得困难。在全球干旱和半干旱地区普遍存在的土壤石油钙质层位已显着改变了植物的水分利用状况。为了评估在相反的降水模式下钙钙化土壤中木质侵蚀对土壤水分动态的影响，我们在混合灌木-草丛系统中进行了为期三年的重复研究，测量了无植被空间和豆科灌木冠层下的土壤水分。用时域反射计（TDR）湿度探头在土壤岩石钙质层之上和之内对地块进行测量。与正常的冬季和夏季相比，这两种类型的土壤在潮湿状态下的水分保持了几个月的大量增加（增加了0·08-0·16 m〜3 m〜（-3））。在冬季，与灌木下的土壤相比，空间土壤吸收的水分要多得多，并且在春季保留的水分更多。相反，在夏季降雨期间和之后，灌木下的土壤最初吸收了大量的水。不同的季节动态归因于具有石油钙层的土壤的独特性质与冠层诱发的蒸散量之间的相互作用。观察到的植物可用水的模式不支持在灌木下获得更多资源的假说。灌木间空间中相似或更多的水可利用量表明，灌木下土壤水的浓度可能不是限制这些土壤上草回收的过程。 John Wiley＆Sons，Ltd.在2010年出版。

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