Chin J Plan Ecolo ›› 2016, Vol. 40 ›› Issue (2): 151-164.DOI: 10.17521/cjpe.2015.0360

Special Issue: 稳定同位素生态学

• Research Articles • Previous Articles     Next Articles

Interspecific water use strategies of a Juglans regia and Isatis tinctoria/Senna tora agroforestry

Chun-Xia HE1,2, Ping CHEN1,3, Ping MENG1,2,*(), Jin-Song ZHANG1,2,*(), Hong-Guo YANG1,2,*   

  1. 1Key Laboratory of Tree Breeding and Cultivation, State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China;

    2Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China;

    3Hebei Research Institute of Investigation Design of Water Conservancy Hydropower, Tianjin 300250,China
  • Online:2016-02-10 Published:2016-03-08

Abstract:

Aims Understanding the interspecific water relations is important for designing agroforestry systems. The objective of this study was to determine the water use strategies of component species in a walnut (Juglans regia)-woad (Isatis tinctoria)/sicklepod (Senna tora) agroforestry system.Methods Water sources of component species in a walnut-woad/sicklepod agroforestry system were investigated with the technique of stable deuterium isotope tracing at a site of hilly area in Northern China during 2012-2013.Important findings Results showed that the soil water content in the agroforestry system was 26.74% and 7.93% greater than in the pure woad field in the first half year, and 17.39% and 13.65% greater than in the pure sicklepod field in the second half year (sicklepod growth period), in 2012 and 2013, respectively. The lowest water content was found in the middle of tree rows, and the highest water content was found in the northern side of tree rows or under the trees. In the soil layers measured, the pure woad and pure sicklepod systems had greater hydrogen stable isotope ratios (&#x003b4 D value) of soil water than in the agroforestry system. During the period of woad growth, more than half of the water absorbed by walnut was from the deeper soil layer (30-80 cm). In contrast, the walnut trees mainly utilized shallow layer (0-30 cm) soil water during the period of sicklepod growth. These findings suggest that walnut has a two-state root system: during the period of woad growth, shallow roots of walnut are not active when soil is dry whereas the sicklepod growth occur in rainy season, and the shallow roots of walnut are active and utilize more shallow soil water supplemented by rainwater. More than 85% of water used by both the woad and the sicklepod were from the shallow layer soil. At the seedling stage, the roots of woad, cannot grow into the deeper soil layer, and the absorbed water is completely from the shallow layer in the pure woad system. However, 5.7% of the water absorbed by the intercropped woad was from the deeper soil layer in 2012, and the proportion increased further (9.7%) in the following year when there was less precipitation. The results confirmed that hydraulic lift effect of walnut occurred on shallow layer crop in dry season, and this effect become greater under drier conditions. Therefore, deeper roots of walnut improved water condition in the walnut- woad/sicklepod agroforestry systems compared to pure crop systems. The walnut mainly utilized water from the deeper layer to avoid water competition with the shallow layer. In the dry season, crops benefited from the water provided by walnut roots through hydraulic lift. Walnut and intercropped plants exhibited water facilitation in the agroforestry systems, suggesting that this configuration is a suitable practice in this area.

Key words: agroforestry system, walnut (Juglans regia), woad (Isatis tinctoria), sicklepod (Senna tora), hydrogen stable isotope ratio (&amp, #x003b4, D), interspecific water relation