Entity

Time filter

Source Type


Yu L.Z.,CAS Shenyang Institute of Applied Ecology | Yu L.Z.,Chinese Academy of Sciences | Yu L.Z.,Liaoning Key Laboratory for Management of Non commercial Forests | Miao J.,Yan Tai Institute of Forestry Science | And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

Broad-leaved Korean pine forest (BKPF) is one of several zonal climax vegetation types dominated by Korean pine (Pinus koraiensis) in the temperate forest region of Northeast China. Unfortunately, intense human activities and extreme natural disturbances have continuously affected the succession of the BKPFs for the past century. Most of the historic areas of BKPFs have succeeded into secondary forests that are not dominated by Korean pine. As a result, since the 1960s, P. koraiensis seedlings have been planted under the canopy of secondary forests in an effort to restore the BKPFs. The status of the survival and growth of P. koraiensis saplings under the canopy of secondary forests has been considered to be an important indicator demonstrating the success of these efforts. Many reports suggested that light was one of the most important environmental factors affecting the regeneration and growth of P. koraiensis. Generally, P. koraiensis is considered to be both a tolerant and intolerant species, having a dual response to light conditions in forest communities depending on its habitat and age classes. P. koraiensis seedlings are able to survive under closed canopy conditions; canopy openness ranging from 0.5 to 0.6 is optimal for the survival and growth of P. koraiensis seedlings. However, as the saplings grow, they need more and more light and finally become intolerant to shaded conditions. For example, compared with seedlings, slightly more mature trees will grow under a forest canopy with a canopy openness of 0.7 for the long-term, but they grow poorly and eventually die under those conditions over an extended period of time. Selective thinning is almost always carried out when P. koraiensis saplings reach an age of 8 to 10 years. However, the needles of P. koraiensis may turn yellow after the selective thinning indicating that the type and quantity of photosynthetic pigments in needles changes in response to the selective thinning. This study was conducted to analyze the response of the photosynthetic pigments in P. koraiensis needles to selective thinning in an effort to understand the relationships between the light environment and the regeneration of P. koraiensis. The experiments were conducted at Qingyuan Experimental Station of Forest Ecology, Chinese Academy of Sciences, located in Changsha, Qingyuan County, Fushun City, Liaoning Province, China. We compared the content of chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids (Car), and total chlorophyll (Chl T) in P. koraiensis needles under three light environments: low-, mid- and high light levels in a secondary forest. The results showed that canopy openness decreased from a high-level light to low-level light environment from spring through summer to autumn. In spring, the chlorophyll content and the ratio of Chl a/b increased, but the ratio of Car/Chl T decreased as the light levels changed from a low-level to high-level light environment. However, the Car content did not change significantly during spring. In summer, no significant differences in pigment content were observed among the three light levels, but the pigment content was higher than that in spring for all pigments analyzed here. In autumn, the ratio of Chl a/b was higher in the high-level and mid-level light environments than that in the low-level light environment. The photosynthetic pigment content increased in all three light levels from spring to summer, but the ratio of Car/Chl T decreased significantly during the same time period. In summary, these results suggest that thinning management designed to increase light-transmittance should be conducted in spring and a mid-level thinning intensity is suitable for improving the photosynthetic capability and for accelerating growth of P. koraiensis under the canopy of secondary forests. Source


Song L.,CAS Shenyang Institute of Applied Ecology | Song L.,Liaoning Key Laboratory for Management of Non commercial Forests | Zhu J.,CAS Shenyang Institute of Applied Ecology | Zhu J.,Liaoning Key Laboratory for Management of Non commercial Forests | And 5 more authors.
Agroforestry Systems | Year: 2015

Dieback of Mongolian pine (Pinus sylvestris var. mongolica) wide windbreaks often emerges 35 years after planting in agroforestry systems. Water stress is considered to be the main cause for such dieback, but there is little knowledge about how water use efficiency of trees changes with their age. We measured needle δ13C as a proxy for intrinsic water use efficiency (iWUE), combined with specific leaf area, leaf dry matter content, soil water content, and groundwater level in 9-, 21-, and 41-year-old pine stands in 2011. Results showed that the mean δ13C value of 9-year-old trees was lower by 0.66 and 0.48 ‰ than that of 21- and 41-year-old trees, respectively, but the mean δ13C value in 21-year-old trees was higher by 0.17 ‰ than that in 41-year-old trees. Soil water content for 9-year-old trees was highest. Specific leaf area for 21-year-old trees was lowest. Compared with the other two tree ages, tree roots reached groundwater levels for 41-year-old trees. These results suggested that (1) 9-year-old trees with the lowest iWUE applied a prodigal water use strategy due to higher soil moisture, (2) 21-year-old trees with the highest iWUE employed a more conservative water use strategy and experienced significant water stress because of lower soil moisture and specific leaf area, and (3) the water use strategy of 41-year-old trees was between that of 9- and 21-year-old trees, likely due to both aging and uptake of groundwater. Dieback of Mongolian pine trees at older age (e.g., more than 35 years old) might occur when the groundwater level declines suddenly in years of extremely low rainfall. © 2015, Springer Science+Business Media Dordrecht. Source


Song L.,CAS Shenyang Institute of Applied Ecology | Song L.,Liaoning Key Laboratory for Management of Non commercial Forests | Song L.,Chinese Academy of Sciences | Zhu J.,CAS Shenyang Institute of Applied Ecology | And 9 more authors.
Agricultural Water Management | Year: 2015

Dieback of Mongolian pine (Pinus sylvestris var. mongolica) forests in the semiarid sandy region of northern China occurs when the trees are approximately 30-35 years old. Water deficit was the most important reason for this dieback, but the water sources used by pine trees are poorly understood. We aimed to identify the water sources utilized by pine trees and to explore the potential mechanisms inducing Mongolian pine dieback. The δD and δ18O of water in twig xylem, soil, rain and groundwater were analyzed in a 29-year-old pine stand during two consecutive years 2010 and 2011. Soil water content (SWC), tree transpiration and groundwater level were measured concurrently. The results demonstrated that trees utilized soil water in spring (April-May) and autumn (September-October). In contrast, trees used both soil water and groundwater in summer (June-August) during the two observed years. Additionally, 70.1% of water used by trees came from soil water when the SWC was high (6.6%), but 55.8% of water used by trees came from groundwater when the SWC was low (3.5%). The groundwater contribution to tree transpiration increased from 10.0% to 14.4% with the rainfall decreasing from 580mm to 460mm, with a mean value of 12.2%. However, in the year of 60% of the long-term annual rainfall, the mean SWC only was 2.7%. These findings indicate that groundwater was increasingly critical with decreasing rainfall. Groundwater should be thus the primary water source for the growth and survival of pine trees in the years of extreme low rainfall. The dieback of Mongolian pine forests occurred when the groundwater level declined suddenly in the years of extreme low rainfall. © 2015 Elsevier B.V. Source


Song L.,CAS Shenyang Institute of Applied Ecology | Song L.,Chinese Academy of Sciences | Song L.,Liaoning Key Laboratory for Management of Non commercial Forests | Zhu J.,CAS Shenyang Institute of Applied Ecology | And 8 more authors.
Environmental and Experimental Botany | Year: 2016

Mongolian pine (Pinus sylvestris var. mongolica) plantations in semiarid sandy lands play an important role in the prevention and control of desertification in northern China, but plantation dieback often occurs approximately 30-35 years after planting due to water deficiency. However, the seasonal changes in the water sources used by Mongolian pine trees of different ages remain unclear, and these changes influence the management of the plantations. During two consecutive years, 2012 and 2013, stable isotopes of hydrogen and oxygen from twig xylem water, soil water at different depths (0-20, 20-40, 40-60 and 60-100cm), precipitation and groundwater were analyzed in 10-, 22-, 32- and 42-year-old Mongolian pine plantations to identify the sources of water used by the trees during different seasons (spring, summer and autumn). The soil water content, groundwater level and δ13C of the needles were measured concurrently, and the results showed that the 10- and 22-year-old trees only used soil water during the two years of observation, but the 32- and 42-year-old trees utilized both soil water and groundwater. In spring (late May), when soil water content was low, the 10- and 22-year-old trees used water from the 20-60cm soil layer, but the 32- and 42-year-old trees utilized water from the 40-100cm soil layer and groundwater. In summer (mid or late July), when soil water content was high, the trees of different ages used water from the 0-60cm soil layer, and in autumn (mid or late September), when the soil water content was relatively high (2012), the trees of different ages used water from the 20-100cm soil layer. However, when the soil water content was relatively low (2013), the 10- and 22-year-old trees continued to use water from the 20-100cm soil layer, but the 32- and 42-year-old trees absorbed water from both the 60-100cm soil layer and the groundwater. The contribution of groundwater to tree transpiration increased with decreasing soil moisture for the 32- and 42-year-old trees, and groundwater was the dominant water source (e.g., 60.2% of tree transpiration in the 42-year-old trees) when the soil moisture was approximately 20% of field capacity (3.5%). In addition, the significantly higher δ13C in the needles of the 22-year-old trees relative to the four ages of pine trees suggested higher water use efficiency in the 22-year-old trees. These findings suggest that the old Mongolian pine plantations (e.g., 30-35 years old) will experience greater mortality in the future if the groundwater level suddenly declines under drought conditions, but the young Mongolian pine plantations would suffer only slightly because their roots are unable to reach the saturated zone. © 2016 Elsevier B.V. Source

Discover hidden collaborations