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The smoke tree (Cotinus coggygria Scop.) is not only an important ornamental tree that changes the color of its leaves in autumn but also maintains red juvenile leaves on vigorous sprouting shoots. To elucidate the process of leaf reddening in the smoke tree, we examined the structure and function of its leaf venation system, anthocyanin levels, leaf water conservation ability in red juvenile leaves and green mature leaves, leaf temperature, stomata conductance and snap strength of petiole. A combination of thermography, image analyses and photosynthetic measuring technology was used to study the facts of leaf reddening of smoke tree. We found that spatial and temporal heterogeneity in the pattern of leaf reddening in the smoke tree illustrates the interaction between internal metabolism and environmental factors. These results indicate that there are periods that show water and energy imbalances at leaf lamina and that this phenomenon is essential to leaf reddening, especially during periods of leaf expanding and leaf shedding. We consistently observed a relationship between high temperatures and leaf reddening, which indicates the latter is a photoprotective response induced by imbalances in water and energy.

Super-absorbent polymer (SAP) is a widely studied cross-linked hydrophilic polymer used as water absorbent material. However, little information is available concerning the effects of SAPs on the growth and nutrient accumulation in forest container seedlings. The present study was conducted to quantify the effects of SAP applied with or without fertilizer on the dry matter and nutrient uptake of Pinus pinaster container seedlings. SAP addition with fertilizer increased dry matter along with increased seedling emergence time. However, no effect was found without fertilizer. Compared with fertilizer only, rapid accumulation time of nitrogen (N) and potassium (K) was 7 days longer resulting from SAP addition. The maximum daily N and K accumulations in the fertilized seedlings increased by 9.31 and 10.44 %, respectively, whereas those of the unfertilized seedlings did not differ significantly. SAP addition had little effect on phosphorous (P) uptake, except for an increase in the maximum daily P accumulation under fertilized conditions. The shoot and root of P. pinaster with SAP had 8.61 and 13.70 % higher yields, respectively, than those that received fertilizer only. Compared with fertilizer only, SAP addition with fertilizer increased the N and K contents by 7.15 and 10.04 %, respectively, whereas the P content did not differ significantly. Under fertilized conditions, N, P, and K uptake increased by 17.17, 10.13, and 20.33 %, respectively, from SAP addition. Hence, SAP could be used as a nutrient absorption enhancer (mainly N and K) in forest container seedlings, aside from being a water absorbent material.

The Yellow River Delta region in China is a land area of 1,200,000 ha with rich natural resources. Adverse environmental conditions, such as low rainfall and high salinity, promote the dominance of black locust trees for afforestation. With the increase of CO2 in the atmosphere, this forest and others throughout the world have become valued for their ability to sequester and store carbon. Forests store carbon in aboveground biomass (i.e. trees), belowground biomass (i.e. roots), soils and standing litter crop (i.e. forest floor and coarse woody debris). There are well-developed methods to sample forest ecosystems, including tree inventories that are used to quantify carbon in aboveground tree biomass. Such inventories are used to estimate the types of roundwood products removed from the forest during harvesting. Based on standard plot inventories and stem analyses, carbon sequestration estimates of trees were 222.41 t ha−1 for the Yellow River Delta region accounted for 67.12% of the whole forest. Similar...

Some environmental problems, especially soil salinity hinder the regional sustainable development of eastern China coastal region. Salinity mainly comes from tide weave, seawater flooding and seawater intrusion. Over exploitation of groundwater, which is the result of unfitful land use systems, leads to seawater intrusion and salt concentration increase. Agroforestry systems can enrich soil fertility and prevent soil salinization, furthermore help maintain biodiversity and enhance productivity. For the intergrated multiple ecosystems the most critical issue is to select optimum tree species and rationally arrange these plants. The basics of this multiple ecosystem is that different plants will occupy variable ecological niches within an area, both in space and in soil depth. Shelterbelts and trees intercropping with agricultural crops are major types of the multiple ecosystem. Shelterbelts can reduce wind speed and consequently lessen evaporation and erosion of the soil, increase pasture growth by up to 60% on exposed sites, increase crop yields by up to 25%. Besides intercropping with jujube, other agroforestry multiple ecosystem such as forestry plus agriculture, forestry plus agriculture plus fishery, and forestry plus animal husbandry are the most appropriate ways to utilise land resource in this region.

One of the proposed mechanisms through which plant growth-promoting rhizobacteria (PGPR) enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available regarding cytokinin-producing PGPR inoculation on growth and water stress consistence of forest container seedlings under drought condition. This study determined the effects of Bacillus subtilis on hormone concentration, drought resistance, and plant growth under water-stressed conditions. Although no significant difference was observed under well-watered conditions, leaves of inoculated Platycladus orientalis (oriental thuja) seedlings under drought stress had higher relative water content and leaf water potential compared with those of noninoculated ones. Regardless of water supply levels, the root exudates, namely sugars, amino acids and organic acids, significantly increased because of B. subtilis inoculation. Water stress reduced shoot cytokinins by 39.14 %. However, inoculation decreased this deficit to only 10.22 %. The elevated levels of cytokinins in P. orientalis shoot were associated with higher concentration of abscisic acid (ABA). Stomatal conductance was significantly increased by B. subtilis inoculation in well-watered seedlings. However, the promoting effect of cytokinins on stomatal conductance was hampered, possibly by the combined action of elevated cytokinins and ABA. B. subtilis inoculation increased the shoot dry weight of well-watered and drought seedlings by 34.85 and 19.23 %, as well as the root by 15.445 and 13.99 %, respectively. Consequently, the root/shoot ratio significantly decreased, indicative of the greater benefits of PGPR on shoot growth than root. Thus, inoculation of cytokinin-producing PGPR in container seedlings can alleviate the drought stress and interfere with the suppression of shoot growth, showing a real potential to perform as a drought stress inhibitor in arid environments.

The spatial distribution and characteristics of fine roots (< 2 mm in diameter), and rhizosphere soil properties were studied in a mixed planted forest of black locust ( L.) and velvet ash ( Torr.) 27 years after planting in a coastal saline soil of the Yellow River delta, China. The results of fine root analysis showed that the fine roots of both black locust and velvet ash were mainly distributed in the soil layer at 0â20 cm depth and 50â150 cm from trees. The fine root distribution of both species suggests a strategy of avoiding salinity rather than salt âtolerance. The horizontal spread distance of fine roots of velvet ash was evidently longer than that of black locust. The fine root biomass, specific root length, specific root area, specific root volume and root activity were significantly higher for velvet ash in comparison with black locust. The results of soil analysis showed that rhizosphere soil pH of black locust and velvet ash were significantly lower compared with non-rhizosphere soil. The available N content in rhizosphere soil of black locust was higher than that of velvet ash. However, the contents of soluble salt, organic matter, available P and available K in rhizosphere soil of velvet ash were higher than those of black locust. The above results indicated that the differences between black locust and velvet ash in fine root distribution, characteristics and rhizosphere soil properties were the major reasons for that velvet ash showed stronger acclimation responses than black locust to the coastal saline soil.Robinia pseudoacaciaFraxinus velutina

Plant growth-promoting rhizobacteria (PGPR) are important catalysts that regulate the functional properties of agricultural systems. However, there is little information on the effect of PGPR inoculation on the growth and nutrient accumulation of forest container seedlings. This study determined the effects of a growth medium inoculated with PGPR on the nutrient uptake, nutrient accumulation, and growth of Fraxinus americana container seedlings. PGPR inoculation with fertilizer increased the dry matter accumulation of the F. americana aerial parts with delayed seedling emergence time. Under fertilized conditions, the accumulation time of phosphorous (P) and potassium (K) in the F. americana aerial parts was 13 days longer due to PGPR inoculation. PGPR increased the maximum daily P and K accumulations in fertilized seedlings by 9.31 and 10.44 %, respectively, but had little impact on unfertilized ones. Regardless of fertilizer application, the root exudates, namely sugars, amino acids, and organic acids significantly increased because of PGPR inoculation. PGPR inoculation with fertilizer increased the root, shoot, and leaf yields by 19.65, 22.94, and 19.44 %, respectively, as well as the P and K contents by 8.33 and 10.60 %, respectively. Consequently, the N, P, and K uptakes increased by 19.85, 31.97, and 33.95 %, respectively. Hence, PGPR inoculation with fertilizer can be used as a bioenhancer for plant growth and nutrient uptake in forest container seedling nurseries.

At present the environment in Yellow River delta region is particularly badly eroded. In view of the situation, use of vegetation for environmental protection is most effective. In order to select suitable tree species, some physiological parameters such as proline content, ratio of bound water and free water, relative conductivity of leaves were applied to this experiment to probe the capability of trees to resist salinity stress. Based on the testing results, these tree species such as R. hispida, F. velutina, C. korshinskii, N. sibirica, T. chinensis, R. typhina, S. matsudana, A. fruticosa and A. altissima were chosen and planted in the area. The result of stand inventory implemented in the year showed that these trees grew well, especially for L. chinense, the biggest height increment reached 1.73 m, and the mean was 1.45 m; and the biggest basal diameter was 1.52 cm, the mean was 1.21 cm. Hence it was concluded that planting trees could prevent soils from salinization and protect lands from degradation.

The aim of this research was to determine the effects of plant growth-promoting rhizobacteria(PGPR) fertilizer on the biological characteristics,root activity,growth and construction of Cerasus pseudocerasus(Lindl.) G.Don(sweet cherry).To prepare sweet cherry biological-fertilizer(YMF),dominant bacteria YT-3,a type of PGPR,was extracted from rhizosphere soil of C.pseudocerasus trees by keeping green method and radish cotyledon weight increase method.Sweet cherry biological-fertilizer was prepared by compounding YT-3 and decomposed chicken manure(DCM).The effects of YMF,normal biological fertilizer(NMF) and DCM on biological characteristics of C.pseudocerasus rhizosphere soil were studied in Yiyuan sweet cherry orchards.And the effects of YMF,DCM and NMF on the root activity,growth and construction of C.pseudocerasus were also investigated.The results showed that YMF increased the amount of bacteria and total microorganism amount in rhizosphere soil of C.pseudocerasus,but the fungus amount was decreased significantly.However,YMF had no influence on actinomycetes amount in rhizosphere soil.Root activity in YMF was significantly increased by 15.33%,22.49% and 13.25% than that in CK,NMF and DCM,respectively.YMF had great influence on the root growth and construction of C.pseudocerasus.Root weight,especially fine root weight in 0～40 soil profile of YMF was significantly increased.Rhizosphere soil pH value in YMF decreased by 8.61% than that in NMF.In addition,YMF significantly enhanced available phosphorus and potassium contents by 17.21% and 9.56%,respectively,compared to that in NMF.However,it had no effects on available nitrogen content in sweet cherry rhizosphere soil.Moreover,PGPR fertilizer increased the cation exchange capacity of rhizosphere soil,which benefited the nutrient retain and uptake of C.pseudocerasus.As a result,plant growth-promoting rhizobactera biological-fertilizer benefited the ecological environment of sweet cherry rhizosphere soil,improved nutrient availability and cation exchange capacity,increased the root activity and benefited the root growth,especially fine root growth in top soil(mainly 0～40 cm).