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The variations in plant growth of 32 Quercus acutissima provenances in three sites (Yongfeng, Jiangxi; Kaihua, Zhejiang and Chuzhou, Anhui) were studied. The AMMI model was used to analyze the stability of growth traits and to select the best provenances. The results showed that tree height, diameter at breast (ground) height, and aboveground biomass (AGB) per individual of the provenances were significantly different in the three sites. The AGB per individual was significantly affected by site, provenance, and the interaction of provenance × site. Site had the greatest impact on the variation of tree growth, followed by provenance and provenance × site. The growth performance of these superior provenances in different sites varied greatly in the seedling stage (1-3 years old) and young forest stage (4-11 years old). Based on the AGB per individual in the 11st year, the best provenances were selected in each site. Seven superior provenances of Yongfeng, Jiangxi were selected, with the average AGB per individual increased by 15.6%-57.8% compared with the ave-rage value. Seven superior provenances of Kaihua, Zhejiang were selected, with the average AGB per individual increased by 19.2%-45.2%. Eight superior provenances of Chuzhou, Anhui were selected,with the average AGB per individual increased by 24.9%-63.3%. According to the growth performance and stability, four superior provenances were selected to develop short-rotation charcoal forest cultivation across three sites, with an average AGB per individual of 36.55 kg and an average stability parameter of 0.97.

We analyzed the rules of Metasequoia glyptostroboides along with latitude, including leaf length, leaf width, leaf perimeter, leaf area, ratio of leaf length to width, specific leaf area (SLA), and leaf dry mass based on eight stands growing at different latitudes in the coastal area of eastern China, as well as their relationships with climatic and soil factors. The results showed that the leaf length, leaf width and leaf perimeter increased with increasing latitude, while the leaf area and SLA firstly increased and then decreased. The mean annual temperature and annual precipitation were the major environmental factors affecting the leaf traits along latitude gradient. With the increase of soil N content, the SLA decreased firstly and then increased, while the leaf mass decreased significantly. With the increase of soil P content, the SLA increased, and the leaf mass decreased significantly.

In order to explore the variations in leaf stoichiometry based on the method of forest tree breeding, we determined the leaf carbon (C), nitrogen (N), phosphorus (P) stoichiometry among 29 Quercus acutissima provenances grown at 3 sites. The results indicated that the site (environment) effect was statistically significant on leaf stoichiometry, with 13.2%-66.7% of the total variations accounted for leaf C, N, P, C/N, C/P and N/P, while the provenance effect was insignificant and only accounted for 2.9%-11.0% of total variations for leaf stoichiometry. The leaf N and C/N, N and N/P, P and C/P, P and N/P were significantly correlated, and the common standardized major axis slope was also observed among three sites and two provenance groups. It could be concluded that the leaf stoichiometry of Q. acutissima, was mainly determined by its growing environment, due to the similar C, N and P biochemical pathways at species level. The stable correlation coefficients among sites and provenances implied the coupling ratios of leaf stoichiometry were independent of environment and provenance, which supported the leaf stoichiometric homeostasis.

The stand environment and tree growth could be changed as well as carbon storage be affected by thinning. Thus it is important to conduct the research on changes of carbon stock in plantations after thinning for assessing the dynamics of forest ecosystem carbon pool. The carbon storage and its distribution of various components in 22-year-old Cunninghamia lanceolata plantations were studied with control and different treatments such as moderate and heavy thinning. Moderate (thinning intensity was 35%) and heavy (thinning intensity was 50%) thinning treatments were conducted twice at the age of 7 and 14 years, respectively. The stand of control was thinned 15% in the 14th year. The results showed that the proportion of stem carbon storage increased with the increasing thinning intensity, while the proportion of carbon storage in branches, leaves and roots slightly decreased, which suggested that thinning was beneficial for carbon stocking in stem. However, the carbon storage in arbor layer decreased with the thinning intensity in C. lanceolata plantation under moderate and heavy thinning treatments, accounted for 89.0% and 83.1% of the control, respectively. The arbor carbon storage decreased in followed two years after the first thinning. The carbon storage in arbor layer had a fast recovery rate within eight years after the second thinning, and the increment of carbon storage in arbor layer had no difference with the control for the heavy thinning treatment. The carbon storage in understory vegetation, litter and soil layers also had no significant difference under the different thinning treatments. Generally total ecosystem carbon storage under the control, moderate and heavy thinning treatments reached 169.34, 156.65 and 154.37 t x hm(-2), respectively. There was no significant difference among the three treatments. Therefore, it could be concluded that the carbon storage in C. lanceolata plantation did not reduce after thinning in more than 15 years.

Quercus acutissima is a tree species widely planted in Jianghuai hilly lands. In this study, the Q. acutissima plantations after five years of different thinning [15% (T15), 30% (T30), 50% (T50) and un-thinning (CK)] were selected, and a sampling plot investigation was made to analyze the carbon density and its spatial distribution in these plantations. In treatments T15, T30 and T50, the tree carbon density increased by 9.1%, 29.6% and 28.4%, respectively, as compared with CK. The carbon density in tree organs was in the order of stem > root > branch > bark > leaf. With increasing thinning intensity, the carbon density in litters decreased while that in 0-50 cm soil layer had a slight increase, but no significant difference was observed between thinning and un-thinning. The total carbon density of the Q. acutissima stands under different thinning intensities was in the order of T30 > T50 > T15 > CK, with an increase of 16.3, 14.5 and 3.6 t C x hm(-2) in treatments T15, T30 and T50, respectively, as compared with CK, but there were no significant differences among the treatments. In treatments T15, T30 and T50, soil respiration was also higher than that in CK, and the difference was significant between treatments T30 and CK. Overall, thinning was helpful to the enhancement of carbon storage in the Q. acutissima plantations in Jianghuai hilly lands, and 30% thinning could be the best.

The photosynthetic characteristics of Quercus acutissima from Feixian, Chuzhou and Wanyuan provenances were investigated under NaCl stress at 5 concentrations. For the three provenances, their leaf chlorophyll a (Chl a) and chlorophyll b (Chl b) contents and net photosynthetic rate (Pn) decreased with increasing salt stress, among which, the maximal decrement of Chl a content was 21.5%-36.1% for Feixian provenance, and 3.5%-19.8% for Wanyuan provenance. The diurnal variation of Pn, in control groups had a single peak, and no midday photosynthetic depression was observed. Under high salt stress, all the provenances presented midday photosynthetic depression. Path analysis indicated that the major factors affecting Pn were vapor pressure deficit (VPD) and leaf temperature (Tl) , while the minor factors were stomatal conductance (Gs) , intercellular CO2 concentration (Ci), and photosynthetically active radiation (PARi). In the control groups, the photosynthetic characteristics mainly depended on the climate factors of provenance location. Based on the variations of leaf chlorophyll contents and Pn among the provenances under different salt stress, Wanyuan provenance had the highest salt tolerance, followed by Chuzhou provenance, and Feixian provenance.