Forest conversion to agriculture can induce the loss of hydrologic functions linked to infiltration. Infiltration-friendly agroforestry land uses minimize this loss. Our assessment of forest-derived land uses in the Rejoso Watershed on the slopes of the Bromo volcano in East Java (Indonesia) focused on two zones, upstream (above 800 m a.s.l.; Andisols) and midstream (400–800 m a.s.l.; Inceptisols) of the Rejoso River, feeding aquifers that support lowland rice areas and drinking water supply to nearby cities. We quantified throughfall, infiltration, and erosion in three replications per land use category, with 6–13% of rainfall with intensities of 51–100 mm day⁻¹. Throughfall varied from 65 to 100%, with a zone-dependent intercept but common 3% increase in canopy retention per 10% increase in canopy cover. In the upstream watershed, a tree canopy cover > 55% was associated with the infiltration rates needed, as soil erosion per unit overland flow was high. Midstream, only a tree canopy cover of > 80% qualified as “infiltration-friendly” land use, due to higher rainfall in this zone, but erosion rates were relatively low for a tree canopy cover in the range of 20–80%. The tree canopy characteristics required for infiltration-friendly land use clearly vary over short distances with soil type and rainfall intensity.

In tropical regions, land-use pressures between natural forest, commercial tree plantations, and agricultural land for rural communities are widespread. One option is to increase the functionality of commercial plantations by allowing agroforestry within them by rural communities. Such land-sharing options could address wider societal and environmental issues and reduce pressure on natural forest. To investigate the trade-offs involved, we used InVEST to model the ecosystem services provided by growing coffee under commercial pine plantations in Indonesia against other land-use options. Pine–coffee agroforestry provided worse supporting and regulating services (carbon, sediment and nitrogen retention, catchment runoff) than natural forest; however, it provided greater provisioning services (product yield) directly to smallholders. Converting pine monoculture into pine-coffee agroforestry led to increases in all ecosystem services, although there was an increased risk to water quality. Compared with coffee and root crop monocultures, pine–coffee agroforestry provided higher levels of supporting and regulating services; however, product yields were lower. Thus, opening up pine plantations for agroforestry realises additional income-generating opportunities for rural communities, provides wider ecosystem service benefits, and reduces pressure for land-use change. Lower smallholder yields could be addressed through the management of shade levels or through Payments for Ecosystem Services schemes.

Turning Volcanic Ash into Fertile Soil: Farmers’ Options in Coffee Agroforestry After the 2014 Mount Kelud Eruption

Coffee agroforestry systems have great potential in optimizing the dual function of carbon and biodiversity conservation, especially in areas with high land use pressure. However, although coffee agroforestry has been widely practiced in Indonesia, the specific relationship pattern between carbon stocks and vegetation biodiversity is still not well understood. This study aimed to evaluate (1) the role of coffee agroforestry in maintaining vegetation diversity and carbon sequestration compared to disturbed forests (HT) and (2) the relationship between carbon stocks and biodiversity at various plant growth stages. Three land use systems were selected such as HT and complex (AFM) and simple (AFS) coffee-based agroforestry systems. The number of trees, species richness (R), Shannon-wiener index (H’), species evenness (E), and carbon stocks were measured in 12 plots (100 m x 20 m) for each vegetation growth stages (seedlings, saplings, poles, and trees). The results showed that the H index in coffee agroforestry was generally low to moderate (0.57-2.05), with the highest diversity in the tree category. The diversity level of AFM could mimic HT. In terms of carbon stock, HT had the highest stock (82±19 Mg ha-1), while total carbon stock showed a positive relationship with H index in all vegetation stages (R2=0,13-0,57). In contrast, the relationship between soil carbon stock and H index tended to be weak (R2=0,10). This study emphasizes the importance of maintaining total carbon stock through diverse vegetation in agroforestri systems to support climate change mitigation and biodiversity conservation.

Agroforestry systems have significant potential for development in increasing coffee production in Indonesia. Besides providing economic benefits, agroforestry can also have ecological impacts, such as improving soil structure, reducing erosion, and other environmental services. There is a complex interaction between trees, soil, and crops in agroforestry systems, making modeling a valuable approach to unraveling these processes. We utilized the spatial and temporal explicit model WaNuLCAS to (i) evaluate the model's performance in depicting actual events (through coffee production and soil water content), (ii) assess the dynamic processes influencing coffee production and the environmental impact of management patterns, (iii) formulate and simulate optimal scenarios for coffee production optimization. Data from a one-year period involving five agroforestry management patterns for coffee-pine in UB Forest were used as input for the model. The model validation results showed satisfactory and acceptable outcomes for coffee production and groundwater dynamics. WaNuLCAS simulation results indicated that pruning and thinning management are crucial factors in increasing coffee production and are related to creating optimal conditions for coffee plants (light, humidity, and inter-plant competition). Additionally, fertilization management can be combined as a supporting factor to meet the nutritional needs of coffee plants. WaNuLCAS simulation results also suggested that pruning and thinning can improve soil physical properties, but thinning increases surface runoff within the system. This research provides insights into how modeling can be used as a decision-making tool.

Bromo Tengger Semeru National Park (BTS-NP) in East Java, Indonesia showcases a breathtaking volcanic landscape and cultural allure, drawing hundreds of thousands of domestic and international visitors. Recreational activities involving human and animal trampling and motorized-vehicle traffic caused soil disturbance along their networks of paths, trails, or roads, potentially having a detrimental long-term effect on the tourism industry and environmental services provided by the national parks. However, the extent of the impact of these disturbances on soil properties remains unclear. This study assessed the impact of different disturbance intensities, consisting of undisturbed locations as a control (zone 1), low to medium- (zone 2), and high- (zone 3) disturbance intensities on five different BTS-NP tourism hotspots, including Entrance Wonokitri (EW), Whispering Sand (WS), Parking Temple (PT), Teletubbies Hill (TH), and Entrance Bromo Stairs (EB), on soil properties, including soil compaction represented by soil penetration resistance, and soil infiltration. This study revealed that the higher severity impact of recreational activities on soil compaction was parallel with higher disturbance intensity, particularly in EW and TH. In these particular locations, higher soil compaction is significantly linked to lower soil infiltration, thus needing extra attention and protection. Meanwhile, in WS, PT, and EB, soil infiltration was more controlled by the establishment of a cemented topsoil layer consisting of mixed sand, sulfur, and water. Better management strategies, such as the use of proper trails and road infrastructures, particularly on EW and TH, might be relevant to minimize the impact of recreational activities on these ecologically, economically, and culturally important areas.