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Cui C.,Northwest University, China | Cai J.,Northwest University, China | Jiang Z.,Qinling National Forest Ecosystem Research Station | Jiang Z.,Northwest University, China | Zhang S.,Northwest University, China
Allelopathy Journal | Year: 2011

To determine the allelopathic effects of root exudates of walnut trees, the root exudates of 2, 3, and 4-years-old walnut (Juglans regia L.) trees were extracted with the neutral, acidic (pH 3.0), and alkaline (pH 8.0) components of ethyl acetate extract. The bioactivity of these 3-components (neutral, acidic and alkaline) were separately investigated on the seed germination, seedling growth, the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and the content of malondialdehyde (MDA) of turnip (Brassica rapa L.). The 3-components of ethyl acetate extract of root exudates of walnut trees inhibited the seed germination and seedling growth of turnip as compared to control. Of all the enzymes assayed (SOD, POD, CAT and MDA), the SOD and the POD activity played a cooperative effect in clearing the reactive oxygen radicals. In 3-treatments (neutral, acidic and alkaline) of root exudates of 4-years-old walnut trees, the activities of SOD, POD and CAT enzymes in turnip were higher than the 3-treatments of root exudates of 2 and 3-years-old walnut trees, whereas the acitivity of MDA was lower. Thus in-vitro allelopathic effects of walnut root exudates were more pronounced with the increasing age of walnut trees. The in-vitro inhibitory/stimulatory effects of root exudates of walnut trees varied with the pH of ethyl acetate extract and with the age of walnut trees. Source

Zhao X.J.,Northwest University, China | Zhang S.L.,Northwest University, China | Zhang S.L.,Qinling National Forest Ecosystem Research Station | Ma G.D.,Northwest University, China
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

hinning intensity is an important factor affecting water quality within a forest ecosystem. However, there has been little research on the effects of forest thinning on water quality. This study investigated the relationship between forest thinning and rainwater chemistry to quantify the effects of thinning intensity on forest water quality. Five experimental field plots with different thinning intensities (0%, 5%, 10%, 15%, and 20%) were established in a natural prunus armandii forest of the Huoditang in Qinling Mountains. Rainwater samples were collected twice a month from June to September in 2012 and 2013. Water chemistry was measured to analyze the chemical effects of tending and thinning intensity on throughfall and litterthrough. Our results showed that thinning intensity had strong relationships with forest water chemistry. Rainwater was slightly acidic, and both the forest canopy and litter layer could reduce the pH value of rainwater, which decreased with increasing thinning intensity. The pH value was 0.48 in throughfall and 0.65 in litterthrough, which was highest in the plot with a thinning intensity of 5%. The concentrations of SO4 2-, NO3 -, and PO4 3- increased as they passed through the forest ecosystem. Both the canopy and litter layers showed strong SO4 2- purification in the plot with 20% thinning intensity. The increases of SO4 2- concentration were statistically significant when compared with NO3 - and PO4 3- concentrations in the control plots, with fewer significant relationships in the plots with higher thinning intensities. The increase of SO4 2- concentration was 4.422 mg/L in throughfall and 1.5 mg/L in litterthrough, compared to the concentration in the thinning plots. A sharp decline in NO3 -, NH+ 4, and PO4 3- concentrations was observed in the 5% thinning plots, compared to concentrations within the control plot, with decreases of 56.3%, 46%, and 9.2% in throughfall and 64.6%, 45%, and 60.8% in litterthrough, respectively. The capability for K+, Ca2+, and Mg2+ leaching in the plots with a thinning intensity of 10% was significantly greater than the leaching capability in the other plots. The increasing fractions of Ca2+and Mg2+ were as high as 89.9% and 120%, respectively, in throughfall, whereas the rising fractions were only 72.4% and 40%, respectively in litterthrough. The increase of K+ was not significant. The rainwater in throughfall and litterthrough contained little Pb2+, Zn2+, and Cd2+ because of the interceptions of different forest layers. The thinning intensity was also strongly related to the changing tendency of heavy metal ions. Compared with the control field plot, the concentrations of Pb2+, Zn2+, and Cd2+were lower than those in the thinning plots. The plots with 20% thinning intensity showed the highest capability for intercepting and aborting heavy metals. The concentrations of Pb2+, Zn2+, and Cd2+ reduced by 10.6%, 22.4%, and 33.5%, respectively. Therefore, the canopy and litter layer in the plot with 20% thinning intensity had the strongest ability to intercept Pb2+, Zn2+, and Cd2+ from rainwater. © 2015, Ecological Society of China. All rights reserved. Source

Zhang S.,Northwest University, China | Zhang S.,Qinling National Forest Ecosystem Research Station | Zhang S.,Key Laboratory For Agri Res And Envi Remediation In Loess Plateau Of Agriculture Ministry Of China | Liang C.,Northwest University, China
Environmental Earth Sciences | Year: 2012

This study investigated the effect of a pine/oak forest canopy on rainfall chemistry in the Qinling Mountains. The area is an important water source for China's North-to-South Water Transfer Project. Rainfall and throughfall samples were collected at the Huoditang Natural Forest in 1999, 2004, and 2009. Analyses of the samples indicated that the forest canopy had several important effects on rainfall chemistry. Rainfall pH generally increased as water passed through the canopy. On average, the rainfall pH increased by 0. 54 pH units. The canopy's effect declined after deciduous trees lost their leaves late in the sampling season. Rainfall NO 3 - concentrations generally declined as water passed through the forest canopy, but PO 4 3- concentrations generally increased. On average, rainfall NO 3 - concentration declined by 0. 135 mg/L as it passed though the forest canopy and PO 4 3- increased by 0. 85 mg/L. The forest canopy had a mitigating effect on the base cation content of throughfall. Specifically, K +, Na +, Ca 2+ and Mg 2+ were leached from the canopy when the concentration of these cations in rainfall was low. In contrast, K +, Na +, Ca 2+ and Mg 2+ were absorbed by the canopy when the concentration of these cations in rainfall was high. The pH of rainfall, as well as its K +, Ca 2+ and Mg + concentration, influenced the effect of the forest canopy on the base cation content of throughfall. The concentration of Cd, Pb, and Zn in rainfall generally decreased as water passed through the forest canopy, but the concentration of Fe in rainfall generally increased. The Cd concentration decreased by an average of 3. 938 μg/L, the Pb concentration decreased by an average of 8. 457 μg/L, and the Zn concentration decreased by an average of 0. 986 mg/L. The Fe concentration increased by an average of 0. 009 mg/L. The canopy's ability to absorb Cd declined after several rainfall events in which rainfall Cd concentrations were relatively high. © 2012 Springer-Verlag. Source

Hou L.,Northwest Agriculture and Forestry University | Hou L.,Qinling National Forest Ecosystem Research Station | Xi W.,Texas A&M University-Kingsville | Zhang S.,Northwest Agriculture and Forestry University | Zhang S.,Qinling National Forest Ecosystem Research Station
Russian Journal of Ecology | Year: 2015

Lacking of detail data, forest carbon stock estimation with forest inventory data usually excludes or underestimates understory carbon storage. To quantify the effects of understory on carbon sequestration in a natural secondary Pinus tabulaeformis forest, organ biomass models for arbor, shrub to their growth indices were regressed. Biomass of herbage was estimated in a stratified sampling method. Soil respiration in forest land was measured. Based on above data, carbon budget of Pinus tabulaeformis forest was assessed as 1.882 CO2 Mghm−2year−1, 37.04% of the entire vegetation’s yearly net carbon storage belonging to understory. © 2015, Pleiades Publishing, Ltd. Source

Chen S.,Northwest University, China | Chen S.,Qinling National Forest Ecosystem Research Station | Chen C.,Northwest University, China | Zou B.,Oklahoma State University | And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

The interception of precipitation by vegetation and subsequent evaporation during and after rain events is an important component of the hydrological budget of forest ecosystems, particularly for forests in ecologically and hydrologically sensitive regions such as Qinling National Forest. This forest was incorporated into the State Natural Forest Protection Project and is managed solely for soil and water conservation. The Qinling Mountains are a major mountain range in China and are the major headwater source for one of the three routes of the South-to-North Water Transfer Project. The evergreen Pinus tabulaeformis is the dominant canopy species at elevations from 1400 to 1700 m. Extensive studies have been conducted to examine the canopy interception, throughfall and stemflow in P. tabulaeformis forest ecosystems across China, mostly in juvenile (≤30 years) or middle-aged (31-50 years) plantations. However, information on rainfall partitioning in natural forests, especially near-mature stands (51-60 years), is lacking, which impedes our understanding of the hydrological ecosystem services in this region. The objective of this study was to understand rainfall partitioning characteristics and lag effects in the Qinling natural secondary P. tabulaeformis forest. Fifty-five-year-old stands of P. tabulaeformis in Ningshan, Shaanxi, were chosen and the precipitation, canopy interception, throughfall and stemflow were measured from 2006 to 2008 (recorded in 5-10 months of each year). One-hundred times complete measurement data were analyzed. Total precipitation was 1576. 4 mm. Rainfall was partitioned as follows: 62. 4% throughfall, 4. 4% stemflow and 33.2% interception by the tree canopy. The redistribution of precipitation by the canopy was more closely related to the rainfall classes. In a single rainfall event, the higher the rainfall class, the greater the stemflow and throughfall rate and the lower the interception rate. The relationships between throughfall (TF), stemflow (SF), crown interception (I) and total rainfall (P) were described significantly by linear, quadratic and power functions, respectively (TF = 0. 6548P -0.4937, R 2 = 0. 9596; SF = -0. 2796 + 0. 0452P + 0. 0005P 2, R 2 = 0. 8179; I = 0. 5958P 08175, R 2 = 0.8064). Under similar rainfall conditions, the higher the rainfall intensity, the shorter the time to saturate the canopy. The timing of throughfall, stemflow and rainfall events after precipitation were not synchronous, and lag periods ranged from (78.5±8.8) min to (16.0±0.0) min and from (111.0 ± 33.0) min to (41.2 ± 0.0) min following precipitation for throughfall and stemflow, respectively. The time lag shortened gradually as rainfall class increased. After precipitation had ceased, especially, when the rainfall is greater than 10.0 mm, the termination of throughfall also lagged from (3.2±2.6) min to (12.0±0.0) min. However, with regard to stemflow prior to termination of rainfall, the smaller the rainfall class, the earlier termination occurred from (-58.3±21.5) min to (-9.8±0.0) min. Source

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