The conifer, Juniperus seravschanica is a keystone species within Oman, yet its decline is typical of other arid-adapted, montane tree species. This research aimed to identify causes of decline and subsequent viable conservation strategies; strategies that may have wider application for tree conservation. Decline in J. seravschanica is typified by foliar dieback and little regeneration via seed; traits most apparent at lower altitudes. The research evaluated the viability of seeds collected at three different altitudes: 2100-2220m (Low), 2300-2400m (Mid) and 2500-2570m above sea level (High). In addition, seeds and young trees were planted at these altitudes and maintained under differential irrigation. Results showed that trees grown at Low altitude produced fewer, less-viable seed. Transplanting young trees proved more successful than seed sowing in re-establishing plants in the wild. Age of transplant had an effect, however, with 5-year-old stock showing greater survival (> 97%) than 2-year-old trees. The younger trees only established well when planted at High altitude, or provided with irrigation at Mid/Low altitudes. Water availability did not entirely explain survival, and in some locations direct heat stress too may be limiting viability. Practical conservation measures include identifying genotypes with greater drought/heat tolerances and planting only more mature nursery trees. Highlights • Climate change is thought responsible for the decline of the conifer Juniperus seravschanica • Trees from lower altitude have greatest decline, and reduced reproductive potential • Conservation strategies are promoted by the planting of nursery-raised trees • Older specimens had greater establishment success than younger trees • Water stress and possibly heat stress are limiting the viability of J. seravschanica
The first paper in this series outlined the vision for the oman botanic garden and detailed the early plant collections and propagation. this paper focuses on the oman botanic garden collections policy, construction of a new nursery on the site, subsequent expanded production and initial attempts at mature tree translocation.
Climate change poses a serious threat to the survival and distribution of Juniperus seravschanica in the northern mountains of Oman. A better understanding of this species’ responses to environmental changes is essential if the potentially harmful effects of climate change are to be mitigated. One such step is to understand how changes in climate may influence the growth of juniper saplings. Two- and five-year-old saplings were grown under different temperature and watering regimes to determine effects on establishment and growth. Under an optimum growing temperature, reducing water to 50 per cent and 25 per cent of the optimal irrigation regime significantly decreased the growth of juniper saplings. In field studies, saplings re-introduced to three different altitudinal locations showed varying rates in establishment success and growth. Both two-yearold and five-year-old saplings established better at higher altitude. Overall, survival rates were considerably better with the transplantation of five-year-old rather than two-year-old saplings.Applying irrigation improved the survival of two-year-old stock when grown at the lowest altitude, but rates were not always significantly different from other treatments. Apical extension growth was found to be reduced at higher altitude, indicating that temperature influences the growth of juniper saplings. However, it was the combination of drought and high temperatures that reduced the growth of non-irrigated saplings at lower altitudes. These preliminary results suggest there is potential to artificially re-introduce juniper saplings to their natural habitat as part of a conservation programme, but more time is required to judge the success of the transplanting initiative when dealing with slow-growing trees such as juniper.
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