期刊
FOREST ECOLOGY AND MANAGEMENT
卷 355, 期 -, 页码 58-71出版社
ELSEVIER
DOI: 10.1016/j.foreco.2015.04.012
关键词
Cavitation; Drought; Natural stands; Pine; Roots; Transpiration
类别
资金
- DOE BER-TES [7090112, DE-FG02-11ER65189]
- NSF IOS [1146746]
- NSF EAR [1344703]
- USDA-AFRI [2012-00857]
- Pine Integrated Network
- Education, Mitigation, and Adaptation Project (PINEMAP)
- USDA NIFA [2011-68002-30185, 2014-67003-22068]
- USDA Forest Service Eastern Forest Environmental Threat Assessment Center [08-JV-11330147]
- Directorate For Geosciences
- Division Of Earth Sciences [1344703] Funding Source: National Science Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1462486] Funding Source: National Science Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1146746] Funding Source: National Science Foundation
Throughout the southern US, past forest management practices have replaced large areas of native forests with loblolly pine plantations and have resulted in changes in forest response to extreme weather conditions. However, uncertainty remains about the response of planted versus natural species to drought across the geographical range of these forests. Taking advantage of a cluster of unmanaged stands (85-130 year-old hardwoods) and managed plantations (17-20 year-old loblolly pine) in coastal and Piedmont areas of North Carolina, tree water use, cavitation resistance, whole-tree hydraulic (K-tree) and stomatal (G(s)) conductances were measured in four sites covering representative forests growing in the region. We also used a hydraulic model to predict the resilience of those sites to extreme soil drying. Our objectives were to determine: (1) if K-tree and stomatal regulation in response to atmospheric and soil droughts differ between species and sites; (2) how ecosystem type, through tree water use, resistance to cavitation and rooting profiles, affects the water uptake limit that can be reached under drought; and (3) the influence of stand species composition on critical transpiration that sets a functional water uptake limit under drought conditions. The results show that across sites, water stress affected the coordination between K-tree and G(s). As soil water content dropped below 20% relative extractable water, K-tree declined faster and thus explained the decrease in G(s) and in its sensitivity to vapor pressure deficit. Compared to branches, the capability of roots to resist high xylem tension has a great impact on tree-level water use and ultimately had important implications for pine plantations resistance to future summer droughts. Model simulations revealed that the decline in K-tree due to xylem cavitation aggravated the effects of soil drying on tree transpiration. The critical transpiration rate (E-crit), which corresponds to the maximum rate at which transpiration begins to level off to prevent irreversible hydraulic failure, was higher in managed forest plantations than in their unmanaged counterparts. However, even with this higher E-crit, the pine plantations operated very close to their critical leaf water potentials (i.e. to their permissible water potentials without total hydraulic failure), suggesting that intensively managed plantations are more drought-sensitive and can withstand less severe drought than natural forests. (C) 2015 Published by Elsevier B.V.
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