Variation of the infiltration rate as the soil depth increased.

<p>Variation of the infiltration rate as the soil depth increased.</p

Characteristics of the interannual variation of the infiltration rate.

<p>Note: different lowercase letters at the top of the column plot indicate significant differences (P < 0.05).</p

Time required for the wetting front to reach specific soil depths with different rainfall levels (hours).

<p>Note: Three rainfall events were observed during the observation period in 2013 (11 years), i.e., moderate rainfall of 19.7 mm on May 17, heavy rainfall of 38.4 mm on May 25, and torrential rainfall of 73.1 mm on July 17. Beginning when the rain started, the times required for the wetting front to reach different soil depths were recorded. The data represent the mean ± standard error. Different lowercase letters within a column indicate significant differences (<i>P</i> < 0.05). JTCAS: walnut (<i>Juglans regia</i>)-wheat (<i>Triticum aestivum</i>) alley cropping system; JRMS: walnut monoculture system; TAMS: wheat monoculture system.</p><p>Time required for the wetting front to reach specific soil depths with different rainfall levels (hours).</p

Soil infiltration curves for the three land use patterns in August 2013.

<p>Soil infiltration curves for the three land use patterns in August 2013.</p

Planting arrangement and characteristics of the experimental site.

<p>Note: Characteristics of walnut trees at the experimental site during July 2013 (11years). DBH: diameter at breast height.</p><p>Planting arrangement and characteristics of the experimental site.</p

Characteristics of the infiltration rate during the growing season and its relationship with the rainfall temporal distribution.

<p>Note: JTCAS: walnut (<i>Juglans regia</i>)-wheat (<i>Triticum aestivum</i>) alley cropping system; JRMS: walnut monoculture system; TAMS: wheat monoculture system. Different lowercase letters at the top of the column plot indicate significant differences (P < 0.05).</p

Decay and nutrient dynamics of coarse woody debris in the Qinling Mountains, China

<div><p>As an ecological unit, coarse woody debris (CWD) plays an essential role in productivity, nutrient cycling, carbon sequestration, community regeneration and biodiversity. However, thus far, the information on quantification the decomposition and nutrient content of CWD in forest ecosystems remains considerably limited. In this study, we conducted a long-term (1996–2013) study on decay and nutrient dynamics of CWD for evaluating accurately the ecological value of CWD on the Huoditang Experimental Forest Farm in the Qinling Mountains, China. The results demonstrated that there was a strong correlation between forest biomass and CWD mass. The single exponential decay model well fit the CWD density loss at this site, and as the CWD decomposed, the CWD density decreased significantly. Annual temperature and precipitation were all significantly correlated with the annual mass decay rate. The K contents and the C/N ratio of the CWD decreased as the CWD decayed, but the C, N, P, Ca and Mg contents increased. We observed a significant CWD decay effect on the soil C, N and Mg contents, especially the soil C content. The soil N, P, K, Ca and Mg contents exhibited large fluctuations, but the variation had no obvious regularity and changed with different decay times. The results showed that CWD was a critical component of nutrient cycling in forest ecosystems. Further research is needed to determine the effect of diameter, plant tissue components, secondary wood compounds, and decomposer organisms on the CWD decay rates in the Qinling Mountains, which will be beneficial to clarifying the role of CWD in carbon cycles of forest ecosystems.</p></div