3-PG模型在天然兴安落叶松林生长因子预测中的应用

[目的]运用过程模型模拟天然林的生物量及蓄积生长。[方法]以大兴安岭落叶松天然林为研究对象,探索研究基于生理过程的动态模型3-PG模型在天然林中的应用情况,通过调整模型内置模块方程的参数,优化实测值与模拟值的拟合结果,最终得出适用于该地区落叶林天然林的模型参数组,并对不同林龄的林分预测效果进行了对比。[结果]模型在胸径、枝干生物量、根生物量、地上生物量、整株生物量的模拟取得了很好的效果,其中枝干生物量与整株生物量的模拟值与实测值的相关系数R2达到了0.98,且平均相对误差均控制在8%以内。对不同林龄林分的整株生物量与胸径预测结果表明,模型对3个龄组都有很好的拟合效果。[结论]在进行参数本地化调整后,3-PG模型可以运用在落叶松天然林的生长预测中,在生物量预测与胸径预测上可以取得较好的效果。

Woody vegetation of protected areas in northern Togo. Cases of Barkoissi, Galangashi and Oti-Keran: ecological and structure analyses of plant communities

The 170 samples obtained from ligneous investigation in Barkoissi,Galangashi and Oti-Keran protected areas（northern Togo） were subjected to floristic processing and several multivariate analyses in order to study plant diversity,life form and chorological type distribution and to classify and identify the main plant communities with their demographic structure.First,the overall life form and phytogeographical type frequencies were calculated to analyze and show the distribution of the 68 plants species in this area.Then plant communities were determined by using the hierarchical clustering with wards method.The plant communities found were identified by the technique of indicator value（IndVal）.For each grouping diversity index such as specific richness,Shannon index and Pielou＇s evenness was set out.The canonical correspondence analysis（CCA） was also used to relate the impact of environment factors and the distribution of samples.Finally the variance analysis（ANOVA） associated to post-hoc test was used to compare the similarity between the groupings.From these 170 samples,12 plant communities were discriminated,three for the reserve of Barkoissi,three for the reserve of Galangashi and six for the reserve of Oti-Keran.The samples were well distributed in the factorial plan form by axe 1 and 3 of CCA.The plant communities were distributed along the moisture gradient in the ordination.The Sudano-Zambesian species followed by Sudanian species were the phytogeographical types most found in these areas.The microphanerophytes were the most represented life form.The structural parameters such as diameter and height means,the basal area and the densities determined and submitted to post-hoc test show some important similarity between some groups found.In overall,the vegetation condition of the three protected areas is somehow disturbed while most of the plant communities are stable.These preliminary ecological data obtained are essential and fundamental for the management and protection for these ecosystems.

Long Term Evaluation of Green Vegetation Cover Dynamic in the Atacora Mountain Chain(Togo) and its Relation to Carbon Sequestration in West Africa

The research was done in the Atacora Mountain chain in Togo which tended to assess the change of vegetation cover during a 24-year period.It also aims to evaluate the dynamic of the net primary productivity(NPP) of the living plants over the same period.The Landsat imagery covering three different periods(1987, 2000, and 2011) was pre-processed to correct atmospheric and radiometric parameters as well as gapfilling the 2011 SCL-off images.Then, the vegetation indices such as NDVI(normalized difference vegetation index), SR(simple ratiovegetation index), SAVI(soil-adjusted vegetation index), and CASA(carnegie- ames- stanford approach)model for NPP were applied on these images after masking the study area.The results showed a quiet decrease in the vegetation cover.The vegetation loss was more significant from 2000 to 2011 than from1987 to 2000, and anthropogenic activities can be deemed as the main cause of the vegetation loss.The biomass assessment by NPP computation also showed a decrease over the time.Similar to the change of the vegetation cover, the ecosystem net productivity was very low in 2011 compared to 2000 and 1987.It seems that the general health condition of thevegetation, including its potentiality in carbon sinking,was negatively affected in this area, which has already been under threatened.A perpetual monitoring of these ecosystems by means of efficient techniques could enhance the sustainable management tools of in the framework of reducing emissions from deforestation and forest degradation(REDD).

Assessment and impact of anthropogenic disturbances in protected areas of northern Togo

These days, human activities in the savanna and the remaining dry and riparian forests of the Sudanian ecoregions continue to have their impact. These anthropogenic practices are still the main cause of disturbances in these areas. In order to investigate and assess the importance of these disturbances, caused by people bordering on protected areas and to determine the relation between these activities and the environment in which they are carried out, 220 samples were selected in the three main protected areas of northern Togo. The investigation was mainly qualitative, considering the floristic sampling of this drought area; any anthropogenic activities observed were recorded. A simple investigative questionnaire about the activities of rural people in the reserved areas was distributed to individuals encountered in the study area. Each sample in the investigation ended with a site description of its ecologi- cal characterization, i.e., soil features, topography, fauna footprints, dominant plant species and GPS position; we also took photo- graphs of the site. Data processing was entirely based on descriptive statistics and a factor analysis. The results show that eight kinds of human activities, i.e., the use of pastures, tree cutting, bush fires, charcoal production, harvesting of plant material, fanning, honey harvesting and hunting, were noted to be serious disturbances to the integrity of the ecosystems. Among these disturbances, three are recurrent in all the sampled areas of which the use of pastures accounts for 31.88%, tree cutting for 30.35% and bush fires for 30.13%. Fire and pasture disturbances are closely linked and are responsible for the current features of the savanna area of the region. Tree cutting is more a direct function of the need for the production of wood fuel, generally used by city populations. Hunting, farm- ing and honey production are of lesser importance in the area and therefore, do not pose a significantly negative effect on the growth of fauna and flora. Knowledge of these disturbances in the context of requalification and a renewed demarcation of protected areas in Togo is essential for their sustainable management.

Land use patterns and tree species diversity in the Volta Geological Unit, Togo

The application of remote sensing in understanding tree species structural diversity and land use patterns relationship is imperative for reforestation and biodiversity conservation efforts. This study assesses land use patterns and tree species structural diversity in previously reforested hilly sandstone regions of northern Togo. The physical height, and diameter at breast height(DBH) more than 5 cm of all tree species in each given plot were measured in summer 2017. A total of 75 plots of 900 m^2 installed along the toposequence were recorded. In addition, a semi-supervised classification of Landsat 8 images in January of 2018, was also used to classify the land use patterns. 36 tree species and 19 families were recorded for the entire study area. Meanwhile, 19 tree species and 15 families were recorded for the previously afforested zones. The most abundant species included the Sterculiaceae, Zygophyllaceae, Meliaceae, and Mimosaceae. The trees stand structure represented 8.61 ± 0.57 m, 11.28 ± 1.76 cm, and 0.018 ± 0.009 m^2 per hectare for height, diameter and basal area respectively. Major land use patterns were tree and shrub savannahs, parklands and croplands which represented over 60% of the landscape. It is necessary to examine the regeneration and vegetative multiplication potentials of the most frequent and abundant tree species for any eventual future afforestation programs in these hilly sandstone regions of northern Togo.