Zeng De-hui

Comparison of stand structure and growth between artificial and natural forests ofPinus sylvestiris var.mongolica on sandy land

Mongolian pine (Pinus sylvestiris Linnaeus var.mongolica Litvinov) as a valuable conifer tree species has been broadly introduced to the sandy land areas in “Three North” regions (North, northwest and northeast of China), but many problems occurred in the earliest Mongolian pine plantations in Zhanggutai, Zhangwu County, Liaoning Province (ZZL). In order to clarify the reason, comprehensive investigations were carried out on differences in structure characteristics, growth processes and ecological factors between artificial stands (the first plantation established in ZZL in 1950s) and natural stands (the origin forests of the tree species in Honghuaerji, Inner Mongolia) on sandy land. The results showed that variation of diameter-class distributions in artificial stands and natural stands could be described by Weibull and Normal distribution models, respectively. Chapman-Richards growth model was employed to reconstruct the growth process of Mongolian pine based on the data from field investigation and stem analysis. The ages of maximum of relative growth rate and average growth rate of DBH, height, and volume of planted trees were 11, 22 years, 8, 15 years and 35, 59 years earlier than those of natural stand trees, respectively. In respects of the incremental acceleration of volume, the artificial and natural stands reached their maximum values at 14 years and 33 years respectively. The quantitative maturity ages of artificial stands and natural stands were 43 years and 102 years respectively. It was concluded that the life span of the Mongolian pine trees in natural stands was about 60 years longer than those in artificial stands. The differences mentioned above between artificial and natural Mongolian pine forests on sandy land were partially attributed to the drastic variations of ecological conditions such as latitude, temperature, precipitation, evaporation and height above sea level. Human beings’ disturbances and higher density in plantation forest may be ascribed as additional reasons. Those results may be potentially useful for the management and afforestation of Mongolian pine plantations on sandy land in arid and semi-arid areas.

Effects of peat and weathered coal on the growth ofPinus sylvestris var.Mongolica seedlings on aeolian sandy soil

The experiment was conducted at the Ganqika Sandy Land Ecological Station in Ke’erqinzuoyihouqi County, Inner Mongolia, in a growing season from April 28 to October 28, 2001. Peat and weathered coal were added to the aeolian sandy soil in different ratios. Two-year-oldPinus sylvestris var.mongolica seedlings and plastic pots were used in the experiment. The experimental results indicated that: 1) the peat and weathered coal could significantly improve the physical and chemical properties of aeolian sandy soil, and thus promoted the growth of seedlings; 2) the effect of peat on seedling growth, including height, base diameter, root length and biomass, presented an order of 8%>10%>5%>2%>0 in terms of peat contents, and the effect of weathered coal on seedling growth presented an order of 5%>8%>10%>2%>0 in terms of weathered coal contents for height and basal diameter, 5%>8%>2%>10%>0 for root length, and 5%>2%>8%>10%>0 for biomass; 3) the effects of peat were generally greater than that of weathered coal. Meanwhile, 8% peat was the best treatment to promote the growth ofP. sylvestris var.mongolica seedlings.

Effects of Soil Moisture and Soil Depth on Nitrogen Mineralization Process under Mongolian Pine Plantations in Zhanggutai Sandy Land, P. R. China

The rates of soil N mineralization at soil depths of 0–15, 15–30, 30–45 and 45–60 cm and moisture regimes were measured at three sand-fixation plantations ofPinus sylvestris var.mongolica by laboratory aerobic incubation method. The results showed that average rates of soil net N-mineralization across soil depth varied from 1.06 to 7.52 mg·kg−1·month−1 at soil depths from 0 to 60 cm. Statistical analyses indicated that the effects of different soil depths, moistures and their interactions on net N-mineralization rates were significant (P<0.05). The net N-mineralization rates significantly decreased with increasing soil depths and at depth 0–15 cm accounted for 60.52% of that at depth of 0–60 cm. There was no difference in soil net N-mineralization rates between half and fully-saturated water treatments, however these rates were substantially higher than that without water treatment (P<0.05). The factors influencing N mineralization process have to be studied further in these semiarid pine ecosystems.

Soil animals and nitrogen mineralization under sand-fixation plantations in Zhanggutai region, China

The effects of soil animals on soil nitrogen (N) mineralization and its availability were studied by investigating soil animal groups and their amounts of macro-faunas sorted by hand, and middle and microfaunas distinguished with Tullgren and Baermann methods under three Pinus sylvestris var. mongolica Litv. plantations in Zhanggutai sandy land, China. In addition, soil N mineralization rate was also measured with PVC closed-top tube in situ incubation method. The soil animals collected during growing season belonged to 13 orders, 5 groups, 4 phyla, whose average density was 86 249.17 individuals·m−2. There were significant differences in soil animal species, densities, diversities and evenness among three plantations. Permanent grazing resulted in decrease of soil animal species and diversity. The average ammonification, nitrification and mineralization rates were 0.48 g·m−2·a−1, 3.68 g·m−2·a−1 and 4.16 g·m−2·a−1, respectively. The ammonification rate in near-mature forest was higher than that in middle-age forests, while the order of nitrification and net mineralization rates was: middle-age forest without grazing < middle-age forest with grazing < near-mature forest with grazing (P<0.05). Soil N mineralization rate increased with soil animal amounts, but no significant relationship with diversity. The contribution of soil animals to N mineralization was different for different ecosystems due to influences of complex factors including grazing, soil characteristics, the quality and amount of litter on N mineralization.

Phosphorus fractions and phosphomonoesterase activities in sandy soils under a temperate savanna and a neighboring Mongolian pine plantation

To assess the effects of savanna afforestation on soil phosphorus (P) transformations in eastern Horqin Sandy Land, China, P fractions and phosphomonoesterase activities were examined in two soil horizons (0–5 cm and 5–20 cm) under a savanna and an adjacent 30-year-old Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) plantation on a P-deficient semi-arid sandy soil. The results showed that all soil P fractions and phosphomonoesterase activities decreased with soil depth at both sites except that labile organic P under the plantation was constant with soil depth. In contrast to savanna, soils under Mongolian pine plantation had lower phosphomonoesterase activities and concentrations of all P fractions (with an exception of Al-P), lower proportions of organic P and Ca-P in total P, and higher proportions of labile P, Al-P and Fe-P in total P. These results suggested that P transformations mainly occurred in surface soils, and P recycled through litter-fall was the most important source of plant available P. Mongolian pine afforestation enhanced the bioavailability of both organic P and Ca-P, simultaneously reduced soil P pools, indicating that protection of forest floor and P fertilization are necessary to maintain the sustainable functioning of Mongolian pine plantations.

Transformation and assessment of Chinese pine pure plantations for soil and water conservation in western Liaoning Province, P. R. China

Western Liaoning Province is characterized by huge areas of lowly-efficient Chinese pine (Pinus tabulaeformis Carr.) pure plantations. How to transform these plantations has become an increasingly significant management problem. In this study, the authors summarized the approaches, which are based on close-to-nature silvicultural system, to transform the pure pine plantations. Native broadleaved trees were planted in three methods: 1) after strip clearcutting, 2) after patch clearcutting; 3) on the open forestland and the forest edge. The transformation targets and the selection of tree species were expatiated in this paper. The key techniques and their application conditions for each method were analyzed and discussed. Through investigation and contrastive analysis, the assessment was made to the stands transformed by strip method. Results showed that the mixed stands at 16 years after transformation had an obvious layered structure and the species richness of understorey vegetation increased by 23.5%–52.9%. Soil enzyme activities of urease, phosphatase and sucrase increased by 6%–142%, 46%–99% and 31%–200%, respetively. Moreover, the transformed stands could effectively control the occurrence of pine caterpillars in plantations. Consequently the transformations enhanced the function of soil and water conservation.