Effect of Continuous Cropping on Leaf Nutrient and Growth of Different Species of Poplar Plantation

[Objective]The paper was to study the effect of continuous cropping on leaf nutrient and growth of different species of poplar plantation.[Method] The tree height,diameter at breast height（DBH）,volume of different generations and species of poplar plantation in poplar production area in northern Jiangsu Province,as well as TN,TP and TK content in their leaves were determined through field investigation and indoor experiment.[Result] With the increasing generation,the changes of TN,TP and TK content in the leaves of different ages of two varieties of forest stand were also different.However,with the increasing tree ages,TN,TP and TK contents in leaves showed decrease trend.With the increasing generation,the changes of tree height of I-69 and I-72 poplar showed the similar trend.The effect of increasing generation on tree height of 7-year-old and 10-year-old poplar was relatively stable,showing decrease trend from generation to generation.The tree height of 4-year-old poplar first increased and then decreased with the increasing generation.The changes of DBH along with different generations were basically consistent with the changes of tree height.With the increasing cultivation generations,the volume of 7-year-old and 10-year-old poplar decreased with significant difference.[Conclusion ] The result provided basis for rational fertilization and management of poplar plantation,improvement of productivity of poplar plantation,and achievement of sustainable management of plantation.

Biochar-Induced Priming Effects in Young and Old Poplar Plantation Soils

The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil mass)produced from rice straw at 300℃(B300)and 500℃(B500)to young(Y)and old(O)poplar plantation soils,with the aim of studying the responses of biochar-induced PEs to poplar plantation ages.This incubation included six treatments:Y+CK(control),Y+B300,Y+B500,O+CK,O+B300,and O+B500.Carbon dioxide(CO_(2))emissions were significantly increased(p<0.05)in the B300 amended soils,while it was decreased in the B500 amended soils compared to the CK.The primed CO_(2) emissions were 2.35 times higher in the Y+B300 than the O+B300 treatments,which was measured to be 18.6 and 5.56 mg C·kg^(-1) with relative PEs of 12.4%and 3.35%,respectively.However,there was little difference between the primed CO_(2) emissions in Y+B500 and O+B500 treatments,which were measured to be-24.9 and-29.6 mg·C·kg^(-1) with relative PEs of-16.6%and-17.8%,respectively.Dissolved organic carbon(DOC)was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation,indicating greater C-limit of soil microorganisms in the young poplar plantation soil.Using ^(13)C isotope tracing,neither B300 nor B500 decreased native soil-derived DOC,which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C.In conclusion,the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biochar-induced PEs.Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs.

Quantitative study of poplar plantations in three Iranian provinces

Fast growing poplar species enjoy a highly favored position in Iran’s forest product industries. However, information on poplar plantations, such as areas, growing stock and harvest volumes, are largely obtained by non scientific means and poorly executed methods. A few studies have been conducted to obtain data on the capacity of poplar plantations, their extent, existing growing stock, distribution and species choice in three provinces, i.e., Western Azerbaijan, Kurdistan and Hamedan, with relatively well developed management systems. We opted for a cluster method, a standard sampling method for conducting similar investigations, consisting of two phases. In the first phase we collected library information and conducted half-open interviews with villagers. In the second phase field measurements in the villages of these three provinces were carried out. Information from field measurements on growing stock, cultivated areas, dominant species were used to estimate volumes by way of volume and weight tables. Results obtained from the present study indicate that the average annual volume of timber harvested in the three provinces was 697,723 m3, with an average sampling error of 22.7 per cent. This annual volume of poplar timber harvested from the three provinces was estimated to amount to about 25 per cent of overall harvest; at that rate, the overall annual utilization potential of poplar plantations will be 10 million m3, which constitutes a reliable resource of raw timber for use in wood and paper industries.

Agroforestry, Rural Populations, Poplar Plantations and Marketing

One of the objectives of the 1257/99 EU regulation was that rural populations should be able to gain an extra income. This regulation may not be any longer in force, but soon a new one will replace it. The plantations that are created by Greek farmers more specifically the plantations of poplar trees-have a ten-year rotation at least. This means that the time between the establishment of the plantation and the harvest is high. As a consequence, during this time, the market environment （e.g. prices） may face substantial changes. Frequently, these changes are so immense that producers are driven in economic distress. This situation is also linked to the domestic timber supply and imports, and as a result to the product prices. Concerning the market prices of poplar trees, one additional factor that has probably deteriorated the situation is the E.U. expansion. This paper examines a case study in North Greece. Vital conclusions are made which may be useful for the Greek and E.U. decision makers regarding the process of dealing with current issues such as the 1257/99 regulation replacement （1698/2005）.

A New Multistep Approach to Identify Leaf-Off Poplar Plantations Using Airborne Imagery

Identification of type of leafless trees using both fall imagery and field-based surveys is a global concern in the forest science community. Few studies were devoted to separate leafless trees from others in the growth season using remote sensing imagery. But this study was the first attempt to identify the type of leafless tree in the fall imagery. We investigated the potential of the Simple Linear Iterative Clustering (SLIC) and k-mean segmentation techniques, and texture and color image analyses to identify leafless poplar trees using imagery collected in a leaf-off season. For the first time in this study, the star shaped feature identifier was found through a binary image that was successful in identifying leaf-off poplar plantations. Optimal threshold values of Normalized Difference Vegetation Index (NDVI) and Normalized Green Index (NGI) indices were able to differentiate highly vegetated land, green farms, and gardens from the grasses that sometimes grow between poplar plantation lines. A Coefficient of Variation (CV) of red color intensity and histogram of value were also successful in separating bare soil and other land cover types. Imagery was processed and analyzed in a Matlab software. In this study, leafless poplar plantation was identified with a user accuracy of 84% and the overall accuracy was obtained 81.3%. This method provides a framework for identification of leafless poplar trees that may be beneficial for distinguishing other types of leafless trees.

Effects of Poplar Plantations on the Physical and Chemical Properties of Soils:A Case Study in the North China Plain

In recent years, large areas of farmland in the North China Plain have been converted into short-rotation poplar plantations. To analyze the impacts of poplar plantations on soil, 22 soil samples were collected and assayed from the soil profiles of a corn field and a poplar plantation. The results showed that the average soil moisture content of the soil profile in the poplar field was 2.6 percent lower than that of the arable land. The maximum dif- ference in soil moisture content was found in the upper 0-10 cm of topsoil. Soil organic matter and nitrogen, phosphorus and potassium in the cornfield were significantly higher than in the poplar field. Higher nutrient content in the corn field may result from higher fertilizer inputs and the practice of returning straw to the cropped field. The analysis also showed no significant increase in soil organic matter content in deeper soil layers of the poplar field, which means that the conditions are not favorable for the formation of soil organic matter, or that soil organic matter needs a longer time to develop. Elements such as magnesium, iron, manganese and copper in both the corn field and the poplar field had a tendency to accumulate with increasing soil depth. Magnesium, iron, manganese and copper in the 0-80 cm soil layer of the poplar field were higher than those of the cornfield, but the situation was reversed at depths greater than 80 cm. It is concluded that poplar trees consume a large amount of soil moisture and soil nutrients. Local governments should prevent the development of new plantations of fast-growing trees in farmland and help farmers to recover their farmland from forestry plantations.

Evaluation of soil nutrient status in poplar forest soil by soil nutrient systematic approach

A study was conducted to evaluate the soil nutrient status of poplar plantation by Soil Nutrient Systematic Approach (SNSA) in Jianghan Plain, Hubei Province, China. Soil physiochemical properties were analyzed in laboratory through collection soil samples of study site. Ten treatments of application different fertilizers were designed such as CK, optimum treatment (N, P, K, Zn), N(P, K, Zn), P(N, K, Zn), K(N, P, Zn), +Mg(N, P, K, Zn, Mg), Zn (N,P,K), +2P(N, 2P, K, Zn), +2K(N, P, 2K, Zn), and 2N+2P+2K(2N, 2P, 2K, Zn) for field experiment to test the effect on tree height, diameter (DBH) growth, and dry weight of poplar. The results showed that there was no significant difference in tree heights between treatments with different fertilizers, diameter growth of poplar trees in treatments of lack of N and Zn was significantly slower than that of trees in optimum treatment, and dry weight of poplar dropped significantly for treatment of CK as well as treatments without application N and Zn. It is concluded that N and Zn were main limiting factor for poplar growth. Results from laboratory analysis and field experiment were uniform per-fectly, which proved that SNSA was reliable in evaluating soil nutrient status of poplar plantation.

The influences of biotic and abiotic factors on the occurrence and severity of poplar canker disease in Qingfeng County, China and the management implications

Landscape pathology is a research approach that can provide validation of the effectiveness of regional controls of forest disease at a landscape scale. In this paper, we analyzed the effects of stand features, management approaches, and geographical locations on poplar canker disease incidence （DI） and disease severity index （DSI） of individual trees at a 10 km x 10 km mesoscale landscape in Qingfeng County, China. DI varied significantly with stand age, tree densities, and the degree of canopy closure. DI in stands younger than 4 years old was significantly lower than that in the stands over 6 years old and reached the highest value at a stand age of 8-10 years. Overall, DI was positively correlated with stand age, stand density, andthe degree of canopy closure. DI was significantly lower in agro-forest stand patches than in other three patch types, i.e. isolated patch, pure stand patch, and mixed stand patch. Poplar plantations distributed around and near to villages exhibited significantly higher DI mainly due to human activities and herbivores. Fragmentation or connectivity in this mesoscale landscape seemed not impact disease occurrence. DSI was not significantly correlated with stand density, but varied significantly with tree varieties and trees ages. DSI was highest in stands of 10-12 year trees for all poplar varieties we studied here. Plantation density and plantation age were thus critical factors in determining DI and DSI. A logistic predictive model of disease occurrence was developed for the study area, considering varieties, age, height, density, canopy cover, stand types, patch types, management status, and stand geographical locations. Our study here shows that adjustment of stand density by thinning at different plantation ages is an effective approach controlling the occurrence canker disease in short-rotation poplar plantations at the landscape scale.

Photosynthetic response of poplar leaves at different developmental phases to environmental factors

With economic incentives and interests in fast-growing poplar trees for short-rotation production of fiber and veneer, many new poplar hybrids have been bred and planted in China, but how to match the new poplar clones to suitable sites and maintain their higher growth rates is still not very clear. In this study, the photosynthetic response of poplar leaves at various developmental stages during two seasons (summer and autumn) was explored and mechanistic models for the photosynthesis of poplar leaves at different developmental phases in response photosynthetic active radiation (PAR), temperature, and relatively humidity were established using the optimization software package 1st Opt. Mature poplar leaves in autumn had significantly higher photosynthetic capacity than leaves at other stages and seasons. Based on the models established for poplar leaves at different phases, the main limiting factors for photosynthesis at the research site were high PAR and temperature in the summer and low PAR in the autumn. Our results highlight the importance of selecting suitable sites, pruning and stand density control during the plantation development to maintain higher photosynthetic rates of poplar trees and to establish optimum cultivation patterns for various utilization of poplar plantations.

Natural Resistance of Two Plantation Woods Populus × canadensis cv. and Cunninghamia lanceolata to Decay Fungi and Termites

Natural durability of two plantation woods, Chinese fir and I-214 poplar, was investigated thoroughly by three test- ing methods, namely an accelerated laboratory decay test, a fungus cellar test and a field test. After the decay test using Postia pla- centa and Trametes versicolor, Chinese fir and the I-214 poplar showed 34% and 69% of mass loss, respectively, indicating they should be classified as slightly durable and non-durable wood. This conclusion was confirmed by the fungus cellar test and the field test. Like the performance in the decay test, I-214 poplar showed no resistance to termites either in the laboratory or in the field, whereas Chinese fir would be classified as moderately resistant.

Nutrient resorption and stoichiometric responses of poplar(Populus deltoids)plantations to N addition in a coastal region of eastern China

Aims Leaf nutrient resorption is sensitive to changes in soil nutrients.However,the effects of N deposition on nutrient resorption efficiency(NuRE)in plant macro-nutrients remain unclear.Poplar(Populus deltoids)is one of the most extensively cultivated hardwood species worldwide.We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition.Methods We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar(P.deltoids)plantations(8-and 12-year-old stands)in a coastal region of eastern China.We measured soil and foliar(green and senesced leaves)concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca)and magnesium(Mg)for a series of N addition treatments including N_(0)(0 kg N ha^(−1)yr^(−1)),N_(1)(50 kg N ha^(−1)yr^(−1)),N_(2)(100 kg N ha^(−1)yr^(−1)),N_(3)(150 kg N ha^(−1)yr^(−1))and N_(4)(300 kg N ha^(−1)yr^(−1)).Important Findings Consistent for(both)8-and 12-year-old stands,N addition did not affect the NuRE and stoichiometry(with the exception of CaRE and CaRE:MgRE ratio).N resorption efficiency–P resorption efficiency(NRE–PRE)scaling slopes were consistently less than 1.0 under N addition.These results suggest that NRE generally decouples from PRE within each N treatment.Moreover,these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between NuRE and green leaf nutrient concentrations.Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in the coastal region of eastern China.

A Novel Method for the Fabrication of Granular Hydroxyapatite-bentonite Composite Adsorbents for the Removal of Pb2＋ from an Aqueous Solution

Granular HApB composite adsorbents, with dimensions of 4 mm × 4 mm, were prepared for the removal of lead from an aqueous solution. The effectiveness of the composites for Pb2＋ removal from an aqueous solution with different initial concentrations, adsorbent doses and reaction times were examined. The Langmuir isotherms, Freundlich isotherm models and pseudo-second order kinetic model were used in this analysis. It was found that the Langmuir model fitted the experimental data better than the Freundlich model, with a maximum adsorption capacity of 93.37 mg.g-1. The pseudo-second order kinetic model also fit the experiment data well with an adsorption capacity of 70.73 mg.g-1 after being reused for 3 times. Furthermore, the composites may possibly be used in processes for industrial water treatment.

A Methodology for Collection of Residential Construction Residue in Manaus

Civil construction is one of the largest consumers of raw materials and producers of waste, which has been causing environmental problems both through the extraction of raw materials and through building activity by generation of waste. Notwithstanding the need to find an optimum use for solid construction residue to try to solve or minimize this problem, there are no standards for the process of obtaining the CDR （construction and demolition residue）. Thus, the aim of this study was to develop a method of collecting solid waste at the construction site that is easy and low-cost and thus can be applied throughout the construction industry. This collection method was designed to produce residue with the desired proprieties and obtain the best possible homogeneity. This method permitted to evaluate the factors generating construction residue more precisely.