Productive coexistence and gain of populations were studied using nine years’ data from field experiments of Taxodium ascendens-intercrop systems in Lixiahe, Jiangsu province, China. A theoretical framework for productive coexistence in agroforestry was developed. Interaction patterns between trees and intercrops were presented within the framework. A model framework was developed to describe the coexistence gain and interaction of populations in T. ascedens-intercrop systems. Facilitation and resource sharing were identified as main contribution to the advantage of species combination in agroforestry. The model of population interaction developed in the present study was accepted for describing the interaction of populations in T. ascendens -intercrop system, because it explained a high proportion of the variance of experimental data and fitted well the observations in most intercropping types. The model provides flexibility for describing different patterns of intra- and inter-specific interactions. Model coefficients were applied to the determination of the ecological compatibility of species.
Managed T. ascendens-intercrop systems were advantageous as compared to a monoculture of trees or arable crops. In T. ascendens stands up to the age of three, arable crops contributed about 50–80% of the total biomass yield of agroforestry. The diameter height growth of T. ascendens was not significantly influenced by intercrops. When the trees were young (during the first three years), T. ascendens did not depress the crop yields, and a land equivalent ratio greater than unity was obtained together with a high yield of both components. The diameter and height of the trees were similar in four spacing configurations with an equal number of trees per hectare up to the age of 8, but wider between-rows open range were beneficial for the intercrops. The relationship between open-ranges and species coexistence was also analysed and the distribution of soil nutrients studied.
The information on ecological niches of the Marula tree, Sclerocarya birrea (A. Rich.) Horchst. subspecies are needed for sustainable management of this tree, considering its nutritional, economic, and ecological benefits. However, despite Tanzania being regarded as a global genetic center of diversity of S. birrea, information on the subspecies ecological niches is lacking. We aimed to model ecological niches of S. birrea subspecies in Tanzania under the current and future climates. Ecological niches under the current climate were modelled by using ecological niche models in MaxEnt using climatic, edaphic, and topographical variables, and subspecies occurrence data. The Hadley Climate Center and National Center for Atmospheric Research's Earth System Models were used to predict ecological niches under the medium and high greenhouse gases emission scenarios for the years 2050 and 2080. Area under the curves (AUCs) were used to assess the accuracy of the models. The results show that the models were robust, with AUCs of 0.85–0.95. Annual and seasonal precipitation, elevation, and soil cation exchange capacity are the key environmental factors that define the ecological niches of the S. birrea subspecies. Ecological niches of subsp. caffra, multifoliata, and birrea are currently found in 30, 22, and 21 regions, and occupy 184 814 km2, 139 918 km2, and 28 446 km2 of Tanzania's land area respectively, which will contract by 0.4–44% due to climate change. Currently, 31–51% of ecological niches are under Tanzania’s protected areas network. The findings are important in guiding the development of conservation and domestication strategies for the S. birrea subspecies in Tanzania.
In the southwestern pre-Saharan arid zone of Morocco, the endemic argan forest (Argania spinosa) had been almost completely destroyed in the 1960s due to intensive coal mining and mixed cereal-livestock farming. These activities turned out to be unviable and a massive rural exodus occurred in the 1970s. Local populations started to develop maintenance-free prickly pear (Opuntia ficus-indica) cultivation at large scale in order to keep their land ownership rights, while reducing their traditional agropastoral activity. We conducted a survey in order to characterize the relationships between the age of prickly pear orchards and argan tree regeneration. We also explored facilitating factors, such as soil organic matter and mycorrhiza. Results showed a high positive correlation (r2 = 0.75, p < 0.001) between the age of prickly pear orchards and argan tree resprouts, but with differences depending on a continentality gradient. The soil organic matter content also showed highly significant differences (p < 0.001) depending on the age of the prickly pear plantation, while spora density did not show such differences. The recent high economic value attributed to prickly pear fruits, and to both argan and prickly pear seed oil, has given farmers the opportunity to develop a lucrative agricultural activity, while promoting the recovery of native vegetation. This situation constitutes a remarkable example of speculative agricultural development in a very harsh environment, in phase with ecological priorities for combating desertification. It could represent an alternative to the externally-generated projects sustained by high levels of public funding, with ecological, economic and social impacts which are sometimes questionable.
Forestry in Malå, northern Sweden, coexists with other land uses. Reindeer husbandry is in the area for centuries and requires large areas of grazing land. Competing land uses may threaten the Malå Sami village. The aim of the study was to evaluate increased consideration in forest management towards 1) reindeer husbandry, 2) nature and 3) a combination of the two. These scenarios were compared with forest management as it was in 2009. Results indicate that all three scenarios lead to a decrease in annual harvesting volumes of 0.2 to 0.4 million m3. Forest industry dominated the economic viability in the area. Forest management adapted to the needs of reindeer husbandry resulted in less potential for yearly harvest, employment and profits from forest industry. On the other hand, it led to an increase in growing stock and consequently the potential for carbon sequestration over time. Indeed the increased sequestration would compensate for all fossil emissions of carbon from the Forest Wood Chain (FWC). The nature scenario had minor effects on economic result and on the emissions of fossil carbon. The combined scenario gave a reduced economic performance for the FWC. A scenario based on forest management accommodating the needs of reindeer husbandry gave the best economic result for the reindeer chain, due to high survival rate of the reindeer. However the economic importance of reindeer husbandry in the region was small compared to the FWC. Results from scenario analysis could serve as a platform for mutual understanding between stakeholders.