The mechanism underlying overwintering death in poplar:the cumulative effect of effective freeze-thaw damage

We analyzed the relationships linking overwintering death and frost cracking to temperature and sunlight as well as the effects of low temperatures and freeze–thaw cycles on bud-burst rates,relative electrical conductivity,and phloem and cambial ultrastructures of poplar.Overwintering death rates of poplar were not correlated with negative accumulated temperature or winter minimum temperature.Freeze–thaw cycles caused more bud damage than constant exposure to low temperatures.Resistance to freeze–thaw cycles differed among clones,and the budburst rate decreased with increasing exposure to freeze–thaw cycles.Cold-resistant clones had the lowest relative electrical conductivity.Chloroplasts exhibited the fastest and the most obvious reaction to freeze–thaw damage,whereas a single freeze–thaw cycle caused little damage to cambium ultrastructure.Several such cycles resulted in damage to plasma membranes,severe damage to organelles,dehydration of cells and cell death.We conclude that overwintering death of poplar is mainly attributed to the accumulation of effective freeze–thaw damage beyond the limits of freeze–thaw resistance.     

Seasonal diet of the Great Spotted Woodpecker （Picoides major） in shelterwood plantations of Wulate Qianqi County,Inner Mongolia

The feeding habits of the Great Spotted Woodpecker （Picoides major） were surveyed by field observations and trace checking from 2005 to 2007, in Wulate Qianqi County, Inner Mongolia Autonomous Region, China, during which the woodpecker performed fourteen types of foraging techniques. Pecking and hammering were most common in winter; gleaning and probing were most common at times of high food availability at the trunk and tree branches during the breeding season and in summer. The woodpecker gleans arthropods and insect larvae in the breeding season and summer, seeds and nuts mainly in the winter and pokes holes for sap-sucking in winter. The main diet consisted of arthropods and plant seeds. The diet was significantly different between seasons The Great Spotted Woodpecker primarily consumes defoliators and the food on tree trunks from March to October. The contribution of wood borers to the diet was higher in winter, lower in the breeding season and summer. The proportion of the food on ground was small in the breeding season and high in the Summer and winter.     

Relationships of climate change and tree ring of Betula ermanii tree line forest in Changbai Mountain

Based on the tree-ring growth characteristics of Erman＇s birch （Betula ermanii charm.） and the relationships between it and climatic ）＇actors at elevation of 1950m, the sensitivity of tree lines in Changbai Mountain to climatic factors was assessed. The results indicated tree line forest in Changbai Mountain had an obvious sensitivity to climate factors. However, difference from other study sits is that the main climatic control factor on tree-ring growth was not current growth season temperatures, as might be expected, but previous winter and current March temperature. Although the precipitation in the region was quite abundant, the tree-ring growth was still significantly correlated with the precipitation during previous winter and current spring. Additionally, climatic factors which influenced the Erman＇s birch growth were not the yearly variables, but seasonal and monthly variables. Therefore, the reported increase in yearly mean temperature and total yearly precipitation since 1980s was not responded by sustained increase in ring widths in recent decades.     

Effects of IBA on the rooting of branch cuttings of Chinese jujube (Zizyphus jujuba Mill.) and changes to nutrients and endogenous hormones

‘Zhongqiusucui’ jujube secondary shoots were treated with 3-indolebutyric acid(IBA) at three concentrations, 500, 1000 and 1500 mg/L. Results show that IBA could significantly enhance rooting and root characteristics of cuttings and were best with IBA at 1500 mg/L. In the rooting process, the formation of adventitious roots was related to the consumption and accumulation of nutrients(soluble sugars and proteins) and the changes in endogenous hormones in phloem, leaf tips and leaf bases. The rooting of cuttings had a positive correlation with the consumption of soluble sugars during the period of callus formation and with the accumulation of soluble sugars during adventitious root formation and growth. Rooting was positively related to the breakdown of soluble proteins in the phloem when the callus formed, and had a positive correlation with its accumulation during adventitious root formation and growth. Leaf tips and leaf bases showed a reverse trend in changes of soluble protein. However, together with the phloem, leaf tips and leaf bases regulated and controlled the formation and development of adventitious roots. The main activities of soluble proteins exist in the leaf tips as this was the main source of soluble proteins. The relation between rooting and IAA(indole-3-acetic acid) content in phloem was positive and thus a high concentration of IAA could benefit the induction and formation of adventitious roots. However, rooting was negatively related with ABA(abscisic acid) and GA(gibberellic acid) and a high concentration of both could inhibit the induction and formation of adventitious roots. Rooting had a positive correlation with phloem IAA/ABA ratios, and higher ratios could improve rooting. Low concentrations of ZR(zeatin riboside) triggered the induction of adventitious roots, while higher concentrations promoted root growth.Endogenous hormones in leaf tips and bases had an impact on rooting. The activities of endogenous hormones mainly existed in leaf tips because they play a major role in the production and consumption of IAA and its ABA content increased during rooting. The ZR in leaf tips influenced the rooting of cuttings, especially in the callus formation and rooting stage. Leaf tips were the main source of GA.     

Soil enzyme activities under agroforestry systems in northern Jiangsu Province

The authors presented the enzyme characteristics of catalase, sucrase, urease and alkaline phosphatase under agroforestry systems in northern Jiangsu Province. The results show that soil enzyme activities reduce gradually from top to bottom layer of the soil profile, and the fluctuations of catalase and urease are smaller than those of sucrase and alkaline phosphatase. Soil enzyme activities differe significantly in different samples, and the order is arranged as poplar-crop intercropping segment (A, D) > paulownia-crop intercropping segment (B, C) > CK. Furthermore, soil enzyme activities increase with intercropping age. On the other hand, in the same plot, there are closer relationships between enzymes in the soil samples. Catalase, alkaline phosphatase and urease are negatively related, while alkaline phosphatase and urease are positively related (except in samples B and C). In addition, the enzyme activities have a close relationship with the fertilizers. Catalase is positively correlated with the soil pH value (r = 0.854, 0.804, 0.078 and 0.082, respectively), and is negatively correlated with total N (r = –0.201, –0.529, –0.221 and –0.821, respectively), total P (r = –0.143, –0.213, –0.362 and –0.751, respectively) and available P (r = –0.339, –0.351, –0.576, and –0.676, respectively). Sucrase, urease and alkaline phosphatase are negatively correlated with the pH value, while positively correlated with the other fertilizers (r 1). The authors suggest that enzyme activity will be a great potential as an indicator of soil quality.     

Characteristics of soil organic carbon mineralization and influence factor analysis of natural Larix olgensis forest at different ages

Soil organic carbon(SOC)mineralization is closely related to carbon source or sink of terrestrial ecosystem.Natural stands of Larix olgensis on the Jincang forest farm,Jilin Province were selected to investigate the dynamics of SOC mineralization and its correlations with other soil properties in a young forest and mid-aged forest at soil depths of 0–10,>10–20,>20–40 and>40–60 cm.The results showed that compared with a mid-aged forest,the SOC stock in the young forest was 32%higher.Potentially mineralizable soil carbon(C0)in the young forest was 1.1–2.5 g kg^-1,accounting for 5.5–8.1%of total SOC during the 105 days incubation period and 0.3–1.5 g kg^-1 in the mid-aged forest at different soil depths,occupying 2.8–3.4%of total SOC.There was a significant difference in C0 among the soil depths.The dynamics of the SOC mineralization was a good fit to a three-pool(labile,intermediate and stable)carbon decomposition kinetic model.The SOC decomposition rate for different stand ages and different soil depths reached high levels for the first 15 days.Correlation analysis revealed that the C0 was significantly positively related with SOC content,soil total N(TN)and readily available K(AK)concentration.The labile soil carbon pool was significantly related to SOC and TN concentration,and significantly negatively correlated with soil bulk density.The intermediate carbon pool was positively associated with TN and AK.The stable carbon pool had negative correlations with SOC,TN and AK.     

Feeding performance of <Emphasis Type="Italic">Clostera fulgurita</Emphasis> on three clones of <Emphasis Type="Italic">Populus deltoides</Emphasis>

Poplar leaf defoliator, Clostera fulgurita (Walker) larvae were reared on three Populus deltoides clones (PL1, PL5 and PL7) in the laboratory. The nutritional indices were computed for working out the relationship between food consumption and growth rate of 3rd, 4th and 5th instar larvae on three clones. The result showed that the consumption index (CI), approximate digestibility (AD), growth rate (GR), relative growth rate (RGR) and efficiency of conversion of ingested food (ECI) decreased with the increase in the age of the larvae. Efficiency of conversion of digested food (ECD) increased with increase in age of the larvae. GR and RGR varied significantly, indicating that larval development was enhanced on PL1 as compared to PL5 & PL7. The values of AD, ECI and ECD were not affected by the different clones. Feeding and growth indices could be useful to define a defoliation prediction model.     

Spatial and temporal dynamics of Pai forest vegetation in Pakistan assessed by RS and GIS

Pai, an arid forest in Sindh Province of Pakistan,is important for the environmental, social, economic development and conservation of ecosystems of the province. Considering the significance of the forest for Sindh and the calls from the local population for its deforestation,we quantified the spatial and temporal variation in the vegetation of the forest and land surface temperature(LST)using optical and thermal Landsat satellite data. Our analysis of temporal(1987–2014) images with Arc GIS10.1 revealed that the dense forest area was greatest at725 ha(37 % of the total forest area) during 2013 while it was smallest at 217 ha(11 %) in 1992. The sparse forest area peaked during 1987 at 1115 ha(58 %) under shrubs whereas it was smallest at 840 ha(43 %) in 1992, and the maximum deforestation of Pai forest occurred during 1992.Spatial change in vegetation over a period of about27 years(1987–2014) revealed that vegetation increased on an area of 735 ha(37 %), decreased on 427 ha(22 %),and there was no change on 808 ha(41 %) of the forest.Variation in temperature between shaded(dense forest) and unshaded areas(bare land) of the forest was from 6 to10 °C. While the temperature difference between areas with sparse forest and bare land ranged from 4 to 6 °C. An inverse relationship between LST and NDVI of Pai forest with coefficients of determination of 0.944 and 0.917 was observed when NDVI was plotted against minimum and maximum LST, respectively. The vegetation in the forest increased with time and the areas of more dense Pai forest supported lower surface temperature and thus air temperature.     

Extraction of seed oil from Diospyros lotus optimized using response surface methodology

Oil from seeds of Diospyros lotus was extracted using a conventional method with two different solvents:hexane and petroleum ether. A central composite design with response surface methodology were used to optimize the process. A second-order polynomial equation was employed, and ANOVA was applied to evaluate the impact of various operating parameters including extraction temperature(x_1; 44.9–70.1 °C), extraction time(x_2;5.0–10.0 h) and solvent to solid ratio(x_3;11.6–28.4 mL g^-1), on oil yield. Experiments to validate the model showed decent conformity between predicted and actual values. Extraction conditions for optimal oil yield were 61 °C, 8.75 h extraction duration and 19.25 mL g^-1 solvent to solid ratio. Under these conditions, the oil yield was predicted to be 5.1340%. Oil samples obtained were then analyzed using gas chromatography. The fatty acid composition revealed the major fatty acids to be oleic acid(C18:1) and linoleic acid(C18:2). The analysis of oil also demonstrated a decent ratio between omega-3 and omega-6 fatty acids. The structure of seeds was imaged using scanning electron microscopy. Oil quality was analyzed thermogravimetrically and by Fourier transform infrared spectroscopy. The assigned nutritional features of the D. lotus oil suggested that it can be used as an edible oil in pharmaceutical and food industry in the future.     

Nodule study in Albizia chinensis in relation to nitrogen metabolism,morphology and biomass

Morphology,biomass,nitrate reductase(NR)and nitrogenase activity in Albizia chinensis(Osb.)Merr.nodules were assessed on monthly and seasonal basis for 1 year.Average NR and nitrogenase activity was higher during the rainy season,reaching a maximum in August.Thereafter,activity decreased through autumn and reached a minimum value during winter.Fresh and dry biomass of nodules increased gradually from summer to the rainy season and then started decreasing with the onset of winter as nodules began to senesce.Among four developmental stages of the nodules that correspond to their increasing age,NR and nitrogenase activity remained low in stage 1 nodules and peaked in stage 2.The activity of both enzymes further decreased with increasing age(stage 2 to stage 4).Morphological features such as shape,diameter and color varied considerably among the developmental stages.Stage 1 nodules were cream-colored,oval to heartshaped with smallest average diameter whereas at stage 2,they became bilobed to tetralobed.On the other hand,stage 3 nodules had the largest average diameter and were multilobed in structure.Stage 4 nodules that correspond to the senescing stage were dark brown to black,multilobed,flattened and hollow due to degeneration of nodular tissue.     

Patterns of species dominance,diversity and dispersion in ＇Khasi hill sal＇ forest ecosystem in northeast India

Background： The ＇Khasi hill sal＇ forest ecosystem in Meghalaya, India represents the easternmost limit of sal distribution. We tested if tree diversity and compositional heterogeneity of this ecosystem was higher than other sal-dominated forests due to moister environment. Methods： Vegetation was sampled in 11 transects of 10 m width and up to 500 m length covering 5.2 ha area. All stems ≥10 cm girth at breast height were enumerated. Results： We found a pattern of mixed dominance of Shored robusta （sal） and Schima wollichii and co-dominance of Pinus kesiyo and Careya arborea. The Shannon＇s diversity index （H＇） was 3.395 nats. This value is remarkably high and competitive to that of moist sal forests of eastern Himalayan foothills and sal-dominated forests of Tripura. A high value of H＇ was manifested by： a） high species richness （S = 123）, b） good equitability （70.6%）, c） ＇fair＇ resource apportionment, and d） abundance of rare species （84% species with less than one per cent of total individuals, 67% species with two or less individuals ha-1 and 59% species with one or less individuals ha-1）. The compositional heterogeneity was ＇fair＇ （Whittaker＇sβw = 3.15）. The presence of Fagaceae with six species commanding 4.3% of importance value （IVl） and of a pine （P. kesiya） in sal forest was remarkable. As many as 58 species showed ＇low density （〈 10 individuals ha-1）, uniform dispersion＇, five species achieved ＇higher density （〉 10 individuals ha-l）, uniform dispersion＇ and six of the top 10 species were ＇clumped＇. The forest showed an exponential demographic curve illustrating ＇good＇ regeneration of an expanding community. Vertical stratification was simple with a poor canopy and fair subcanopy, which together with low basal area （15.65 m2 . ha-1 for individuals ≥ 10 cm gbh） indicated logging of mature sal trees in the past. Conclusions： The ＇Khasi hill sal＇ forest ecosystem is richer in alpha and beta diversi     

Forest observational studies-an essential infrastructure for sustainable use of natural resources

This contribution complements Forest Ecosystems＇ Thematic Series on ＂Forest Observational Studies＂. We provide essential clarification regarding the definition and purpose of long-term field studies, review some of the extensive literature and discuss different approaches to collecting field data. We also describe two newly established forest observational networks that serve to illustrate the scope and diversity of forest field studies. The first is a large-scale network of forest observational studies in prominent natural forest ecosystems in China. The second example demonstrates observational studies in mixed and uneven-aged pine-oak forests which are selectively managed by local communities in Mexico. We summarize the potential for analysing and modeling forest ecosystems within interdisciplinary projects and provide argumentation in favour of long-term institutional commitment to maintaining forest observational field studies.     

A spatially-explicit count data regression for modeling the density of forest cockchafer （Melolontha hippocastani） larvae in the Hessian Ried （Germany）

Background： In this paper, a regression model for predicting the spatial distribution of forest cockchafer larvae in the Hessian Ried region （Germany） is presented. The forest cockchafer, a native biotic pest, is a major cause of damage in forests in this region particularly during the regeneration phase. The model developed in this study is based on a systematic sample inventory of forest cockchafer larvae by excavation across the Hessian Ried. These forest cockchafer larvae data were characterized by excess zeros and overdispersion. Methods： Using specific generalized additive regression models, different discrete distributions, including the Poisson, negative binomial and zero-inflated Poisson distributions, were compared. The methodology employed allowed the simultaneous estimation of non-linear model effects of causal covariates and, to account for spatial autocorrelation, of a 2-dimensional spatial trend function. In the validation of the models, both the Akaike information criterion （AIC） and more detailed graphical procedures based on randomized quantile residuals were used. Results： The negative binomial distribution was superior to the Poisson and the zero-inflated Poisson distributions, providing a near perfect fit to the data, which was proven in an extensive validation process. The causal predictors found to affect the density of larvae significantly were distance to water table and percentage of pure clay layer in the soil to a depth of I m. Model predictions showed that larva density increased with an increase in distance to the water table up to almost 4 m, after which it remained constant, and with a reduction in the percentage of pure clay layer. However this latter correlation was weak and requires further investigation. The 2-dimensional trend function indicated a strong spatial effect, and thus explained by far the highest proportion of variation in larva density. Conclusions： As such the model can be used to support forest practitioners in their decision making for regenerati     

Composition,structure and diversity characterization of dry tropical forest of Chhattisgarh using satellite data

The purpose of this study was to characterize the land use, vegetation structure, and diversity in the Barnowpara Sanctuary, Raipur district, Chhattisgarh, India through the use of satellite remote sensing and GIS. Land cover and vegetation were spatially analyzed by digitally classifying IRS 1D LISS III satellite data using a maximum likelihood algorithm. Later, the variations in structure and diversity in different forest types and classes were quantified by adopting quadratic sampling procedures. Nine land-cover types were delineated: teak forest, dense mixed forest, degraded mixed forest, Sal mixed forest, open mixed forest, young teak plantation, grasslands, agriculture, habitation, and water bodies. The classification accuracy for different land-use classes ranged from 71.23% to 100%. The highest accuracy was observed in water bodies and grassland, followed by habitation and agriculture, teak forest, degraded mixed forest, and dense mixed forest. The accuracy was lower in open mixed forest, and sal mixed forest. Results revealed that density of different forest types varied from 324 to 733 trees ha-1, basal area from 8.13 to 28.87 m2·ha-1 and number of species from 20 to 40. Similarly, the diversity ranged from 1.36 to 2.98, concentration of dominance from 0.06 to 0.49, species richness from 3.88 to 6.86, and beta diversity from 1.29 to 2.21. The sal mixed forest type recorded the highest basal area, diversity was highest in the dense mixed forest, and the teak forest recorded maximum density, which was poor in degraded mixed forests. The study also showed that Normalized Difference Vegetation Index(NDVI) was strongly correlated to with the Shannon Index and species richness.     

A model of seasonal foliage dynamics of the subtropical mangrove species Rhizophora stylosa Griff.growing at the northern limit of its distribution

Background： Progress of forest production in response to the environment requires a quantitative understanding of leaf area development. Therefore, it is necessary to investigate the dynamics of seasonal crown foliage in order to understand the productivity of mangroves, which play an important role in the subtropical and tropical coastlines of the world. Method： Crown foliage dynamics of the mangrove Rhizophora styloso were studies to reveal patterns of leaf recruitment, survival and seasonal leaf area growth. Results： Flushing of leaves occurred throughout the year, but both flushing and leaf area growth pattern of leaves varied with season. Maximum flushing occurred in summer, but leaf areas did not differ significantly with season. The half-expansion period is longer, and the intrinsic rate of increase was lower in winter. Summer flushed leaves grew faster at their initial stage and reached their maximum area over a shorter period of time. The difference in temperature and air vapor pressure deficit （VPD） between summer and winter contributed to the present dynamics of foliage patterns. The mean leaf longevity was estimated to be 13.1 month. The crown foliage area was almost stable throughout the year. Conclusions： Homeostatic control of the crown foliage area may be accompanied by the existence of ecophysiological mechanisms in R. stylosa. Integrating crown foliage dynamics into forest models represents an important step towards incorporating physiological mechanisms into the models for predicting growth responses to environmental changes and for understanding the complex responses of tree growth and litter production.     

Using a stand-level model to predict light absorption in stands with vertically and horizontally heterogeneous canopies

Background： Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation （APAR）, and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods： The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results： The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using （tree- or stand-level） models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion： This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.     

Developing a dynamic growth model for teak plantations in India

Background： Tectono grandis （teak） is one of the most important tropical timber species occurring naturally in India. Appropriate growth models, based on advanced modeling techniques, are not available but are necessary for the successful management of teak stands in the country. Long-term forest planning requires mathematical models and the principles of Dynamical System Theory provide a solid foundation for these.
Methods： The state-space approach makes it possible to accommodate disturbances and avarying environment. In this paper, an attempt has been made to develop a dynamic growth model based on the limited data, consisting of three annual measurements, collected from 22 teak sample plots in Karnataka, Southern India.
Results： A biologically consistent whole-stand growth model has been presented which uses the state-space approach for modelling rates of change of three state-variables viz., dominant height, stems per hectare and stand basal area. Moreover, the model includes a stand volume equation as an output function to estimate this variable at any point in time. Transition functions were fitted separately and simultaneously. Moreover, a continuous autoregressive error structure is also included in the modelling process. For fitting volume equation, generalized method of moments was used to get efficient parameter estimates under heteroscedastic conditions.
Conclusions： A simple model containing few free parameters performed well and is particularly well suited to situations where available data is scarce.     

Assessing citizen science opportunities in forest monitoring using probabilistic topic modelling

Background： With mounting global environmental, social and economic pressures the resilience and stability of forests and thus the provisioning of vital ecosystem services is increasingly threatened. Intensified monitoring can help to detect ecological threats and changes earlier, but monitoring resources are limited. Participatory forest monitoring with the help of ＂citizen scientists＂ can provide additional resources for forest monitoring and at the same time help to communicate with stakeholders and the general public. Examples for citizen science projects in the forestry domain can be found but a solid, applicable larger framework to utilise public participation in the area of forest monitoring seems to be lacking. We propose that a better understanding of shared and related topics in citizen science and forest monitoring might be a first step towards such a framework.
Methods： We conduct a systematic meta-analysis of 1015 publication abstracts addressing ＂forest monitoring＂ and ＂citizen science＂ in order to explore the combined topical landscape of these subjects. We employ ＇topic modelling an unsupervised probabilistic machine learning method, to identify latent shared topics in the analysed publications. Results： We find that large shared topics exist, but that these are primarily topics that would be expected in scientific publications in general. Common domain-specific topics are under-represented and indicate a topical separation of the two document sets on ＂forest monitoring＂ and ＂citizen science＂ and thus the represented domains. While topic modelling as a method proves to be a scalable and useful analytical tool, we propose that our approach could deliver even more useful data if a larger document set and full-text publications would be available for analysis.
Conclusions： We propose that these results, together with the observation of non-shared but related topics, point at under-utilised opportunities for public participation in forest monitoring. Citizen science c     

Competition effects in an afrotemperate forest

Background： Information about competition responses is mainly available for monospecific stands or mixed stands with a small number of species. Studies on complex multi-species and highly structured forest ecosystems are scarce. Accordingly, the objective of this study was to quantify competition effects and analyse competition responses in a species-diverse afrotemperate forest in South Africa, based on an observational study with mapped tree positions and long-term diameter increment records. Methods： The sensitivity to competition was analysed for individual species and involved the calculation of the slope of the linear relation between the value of a competition index （CI） and diameter growth as a measure of sensitivity. In a next step different competition indices were combined and tree diameters were grouped in three classes as surrogates for canopy status and ontogenetic stage. Results： Five competition indices were found to be effective in showing sensitivity to competition for a number of canopy and sub-canopy species. Significant linear regressions were fitted for 18 of a total of 25 species. Species reactions varied significantly in their sensitivity to the different CIs. The indices were classified as belonging to two groups, those that responded more to local crowding and those that are more sensitive to overtopping, which revealed species-specific sensitivities to both factors. The analysis based on diameter classes revealed that species clearly changed their sensitivity to crowding or overtopping depending on diameter. Canopy and sub-canopy species showed distinct differences in their reactions. Conclusions： The application of multiple CIs brought novel insights relating to the dynamics of afrotemperate forests. The response patterns to different competition indices that focus on crowding and overtopping are varied and tree diameter dependent, indicating that oversimplified assumptions are not warranted in the interpretation of Cl- growth relations.     

Bio-amelioration of alkali soils through agroforestry systems in central Indo-Gangetic plains of India

A long-term field study was initiated during 1995 at Central Soil Salinity Research Institute, Regional Research Station, Lucknow(26°47′58′′ N and 80°46′24′′ E) to analyze the effect of agroforestry systems on amelioration of alkali soils. Three agroforestry systems(pastoral, silvipastoral and silvicultural) were compared with the control where no agroforestry system was introduced. Tree-based silvicultural and silvipastoral systems were characterized by tree species Prosopis juliflora and Acacia nilotica along with grass species Leptochloa fusca, Panicum maximum, Trifolium alexandrium and Chloris gayana. Growth of ten-year-old Prosopis juliflora and Acacia nilotica planted in combination with grasses was significantly higher over the silviculture system with the same species. Tree biomass yields of P. juliflora(77.20 t?ha-1) and A. nilotica(63.20 t?ha-1) planted under silvipastoral system were significantly higher than the sole plantation of(64.50 t?ha-1 and 52.75 t?ha-1). Fodder yield under the pastoral system was significantly higher than the silvipastoral system during initial years but it was at par with that of silvipastoral systems after eight years of plantation. The microbial biomass carbon in the soils of silvipastoral systems was significantly higher than in soils under sole plantation of trees and control systems. The Prosopis-based silvipastoral system proved more effective in reducing soil pH, displacing Na+ from the exchange complex, increasing organic carbon and available N, P and K. Improvement in soil physical properties such as bulk density, porosity, soil moisture and infiltration rate was higher in the Prosopis-based silvipastoral system than in the silviculture system or control. On the basis of biomass production and improvement in soil health due to tree + grass systems, silvipastoral agroforestry system could be adopted for sustainable reclamation of highly alkali soils.