Role of sacred groves in southwestern Nigeria in biodiversity conservation, biomass and carbon storage.

Sacred groves are remnants of primary forests with rich biological diversity, protected by indigenous communities. Their role in carbon sequestration and provision of other ecosystem services is being recognized. We investigated four sacred groves (Idanre Hills, Igbo-Olodumare, Ogun-Onire, and Osun-Osogbo) in southwestern Nigeria for biodiversity conservation, biomass production, and carbon storage. A total of 32 temporary sample plots of 800 m2 each were laid across all the sacred groves. Within each plot, all trees with dbh greater or equal to 10 cm were identified, and their diameters and heights measured. Saplings and seedlings were assessed within 100 m2 and 25 m2 sub-plots, respectively. Non-destructive methods were employed in estimating volume, biomass production, and carbon storage. Shannon-Wiener diversity index, Margalef index, and tree species richness in the four groves ranged from 2.63-3.55, 5.64-10.02, and 41-85, respectively, and differed significantly. The four groves were sanctuaries for many indigenous tree species of immense social, religious, ecological, and socio-economic importance. The high densities of seedling and sapling, together with the inverted-J tree diameter distributions, are indications of active regeneration and healthy ecosystem. Mean volume was high (range 244.99 to 343.08 m3 ha-1). The biomass (range 87.8 to 231.85 t ha-1) and carbon stock (range 43.9 to 115.9 t ha-1) of the groves revealed their potentials for climate change mitigation through atmospheric CO2 sequestration. Thus, besides being an effective biodiversity conservation method, sacred groves are important carbon sink. This calls for further conservation of sacred groves to serve as long-term carbon storage mechanism.

Accounting for multiple ecosystem services in a simulation of land-use decisions: Does it reduce tropical deforestation?

Conversion of tropical forests is among the primary causes of global environmental change. The loss of their important environmental services has prompted calls to integrate ecosystem services (ES) in addition to socio-economic objectives in decision-making. To test the effect of accounting for both ES and socio-economic objectives in land-use decisions, we develop a new dynamic approach to model deforestation scenarios for tropical mountain forests. We integrate multi-objective optimization of land allocation with an innovative approach to consider uncertainty spaces for each objective. These uncertainty spaces account for potential variability among decision-makers, who may have different expectations about the future. When optimizing only socio-economic objectives, the model continues the past trend in deforestation (1975-2015) in the projected land-use allocation (2015-2070). Based on indicators for biomass production, carbon storage, climate and water regulation, and soil quality, we show that considering multiple ES in addition to the socio-economic objectives has heterogeneous effects on land-use allocation. It saves some natural forest if the natural forest share is below 38%, and can stop deforestation once the natural forest share drops below 10%. For landscapes with high shares of forest (38%-80% in our study), accounting for multiple ES under high uncertainty of their indicators may, however, accelerate deforestation. For such multifunctional landscapes, two main effects prevail: (a) accelerated expansion of diversified non-natural areas to elevate the levels of the indicators and (b) increased landscape diversification to maintain multiple ES, reducing the proportion of natural forest. Only when accounting for vascular plant species richness as an explicit objective in the optimization, deforestation was consistently reduced. Aiming for multifunctional landscapes may therefore conflict with the aim of reducing deforestation, which we can quantify here for the first time. Our findings are relevant for identifying types of landscapes where this conflict may arise and to better align respective policies.

Life and death of Picea abies after bark-beetle outbreak: ecological processes driving seedling recruitment.

The severity and spatial extent of bark-beetle outbreaks substantially increased in recent decades worldwide. The ongoing controversy about natural forest recovery after these outbreaks highlights the need for individual-based long-term studies, which disentangle processes driving forest regeneration. However, such studies have been lacking. To fill this gap, we followed the fates of 2,552 individual seedlings for 12 years after a large-scale bark-beetle outbreak that caused complete canopy dieback in mountain Norway spruce (Picea abies) forests in southeast Germany. We explore the contribution of advance, disturbance-related, and post-disturbance regeneration to forest recovery. Most seedlings originated directly within the three-year dieback of canopy trees induced by bark-beetle outbreak. After complete canopy dieback, the establishment of new seedlings was minimal. Surprisingly, advance regeneration formed only a minor part of all regeneration. However, because it had the highest survival rate, its importance increased over time. The most important factor influencing the survival of seedlings after disturbance was their height. Survival was further modified by microsite: seedlings established on dead wood survived best, whereas almost all seedlings surrounded by graminoids died. For 5 cm tall seedlings, annual mortality ranged from 20 to 50% according to the rooting microsite. However, for seedlings taller than 50 cm, annual mortality was below 5% at all microsites. While microsite modified seedling mortality, it did not affect seedling height growth. A model of regeneration dynamics based on short-term observations accurately predicts regeneration height growth, but substantially underestimates mortality rate, thus predicting more surviving seedlings than were observed. We found that P. abies forests were able to regenerate naturally even after severe bark-beetle outbreaks owing to advance and particularly disturbance-related regeneration. This, together with microsite-specific mortality, yields structurally and spatially diverse forests. Our study thus highlights the so far unrecognized importance of disturbance-related regeneration for stand recovery after bark-beetle outbreaks.

Impacts of pine plantations on carbon stocks of páramo sites in southern Ecuador.

BACKGROUND: Since the 1990's, afforestation programs in the páramo have been implemented to offset carbon emissions through carbon sequestration, mainly using pine plantations. However, several studies have indicated that after the establishment of pine plantations in grasslands, there is an alteration of carbon pools including a decrease of the soil organic carbon (SOC) pool. The aim of this study is to investigate the impact of the establishment of pine plantations on the carbon stocks in different altitudes of the páramo ecosystem of South Ecuador. RESULTS: At seven locations within an elevational gradient from 2780 to 3760 m a.s.l., we measured and compared carbon stocks of three types of land use: natural grassland, grazed páramo, and Pinus patula Schlltdl. & Cham. plantation sites. For a more accurate estimation of pine tree carbon, we developed our own allometric equations. There were significant (p < 0.05) differences between the amounts of carbon stored in the carbon pools aboveground and belowground for the three types of land use. In most of the locations, pine plantations revealed the highest amounts of aboveground and belowground carbon (55.4 and 6.9 tC/ha) followed by natural grassland (23.1 and 2.7 tC/ha) and grazed páramo sites (9.1 and 1.5 tC/ha). Concerning the SOC pools, most of the locations revealed significant lower values of plantations' SOC in comparison to natural grassland and grazed páramo sites. Higher elevation was associated with lower amounts of pines' biomass. CONCLUSIONS: Even though plantations store high amounts of carbon, natural páramo grassland can also store substantial amounts above and belowground, without negatively affecting the soils and putting other páramo ecosystem services at risk. Consequently, plans for afforestation in the páramo should be assessed case by case, considering not only the limiting factor of elevation, but also the site quality especially affected by the type of previous land use.

Ontogenetic variation in the relative influence of light and belowground resources on European beech seedling growth.

We used height growth data from a 7-year field experiment with European beech (Fagus sylvatica L.) seedlings to test the hypothesis that the effects of above- and belowground resources on height growth depend on seedling size and age. Photosynthetically active radiation (PAR) was determined by hemispheric photography, and estimates of fine root biomass of the overstory trees were used as an inverse proportional surrogate for belowground resource availability. For recently germinated seedlings growing under the canopy of Picea abies (L.) Karst., belowground resource availability affected height growth more than light. During subsequent stages of seedling development, apart from initial seedling size, PAR increasingly determined seedling growth. Besides initial size, seedling age determined the effects of above- and belowground resources on seedling height growth. In seedlings identical in initial size but differing in age, the increase in height growth with increasing PAR was greater in older seedlings than in younger seedlings. The ranking of seedling height by year showed that small differences in size at the end of the first growing season resulted in continuously increasing differences during the following years. Mortality data indicated that the chances of a seedling surviving intraspecific competition was strongly determined by its dominance ranking within the first 5 years after establishment.

Compositional diversity of rehabilitated tropical lands supports multiple ecosystem services and buffers uncertainties.

High landscape diversity is assumed to increase the number and level of ecosystem services. However, the interactions between ecosystem service provision, disturbance and landscape composition are poorly understood. Here we present a novel approach to include uncertainty in the optimization of land allocation for improving the provision of multiple ecosystem services. We refer to the rehabilitation of abandoned agricultural lands in Ecuador including two types of both afforestation and pasture rehabilitation, together with a succession option. Our results show that high compositional landscape diversity supports multiple ecosystem services (multifunction effect). This implicitly provides a buffer against uncertainty. Our work shows that active integration of uncertainty is only important when optimizing single or highly correlated ecosystem services and that the multifunction effect on landscape diversity is stronger than the uncertainty effect. This is an important insight to support a land-use planning based on ecosystem services.

Afforestation or intense pasturing improve the ecological and economic value of abandoned tropical farmlands.

Increasing demands for livelihood resources in tropical rural areas have led to progressive clearing of biodiverse natural forests. Restoration of abandoned farmlands could counter this process. However, as aims and modes of restoration differ in their ecological and socio-economic value, the assessment of achievable ecosystem functions and benefits requires holistic investigation. Here we combine the results from multidisciplinary research for a unique assessment based on a normalization of 23 ecological, economic and social indicators for four restoration options in the tropical Andes of Ecuador. A comparison of the outcomes among afforestation with native alder or exotic pine, pasture restoration with either low-input or intense management and the abandoned status quo shows that both variants of afforestation and intense pasture use improve the ecological value, but low-input pasture does not. Economic indicators favour either afforestation or intense pasturing. Both Mestizo and indigenous Saraguro settlers are more inclined to opt for afforestation.