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.

Post eruption land reclamation consists of hoeing, mixing volcanic ash with soil, adding external organic and/or inorganic fertilizers and making infiltration-pits ('rorak'). This study, after the 2014 eruption of Kelud volcano, aimed to evaluate: (a) soil physico-chemical fertility post eruption, (b) impact of organic inputs interacting with ash in infiltration pits on soil C and N underneath (1 st experiment), (c) biomass loss (decomposition) of local biomass (Trema orientalis and Parasponia andersonii) in a coffee agroforestry system (2 nd experiment). Measurements in the ash-affected (+Ash) Tulungrejovillage (Ngantang-Malang district) were contrasted with an area without recent ash deposits (-Ash) in Krisik (Gandusari-Wlingi district). The 1 st experiment (-Ash site) treatments did not lead to statistically significant influences on soil conditions just below the infiltration pits during 12 weeks of monitoring. The 2 nd experiment quantified rate of biomass loss from litterbags. In +Ash location, litter half-life time (t 50) was 19.5 weeks for coffee or Parasponia as single biomass source to 24 weeks for Coffee+Sengon+Durian. In-Ash location decomposition was slower, with t 50 of 24 weeks for Parasponia to 27 weeks for Coffee+Sengon+Durian biomass. Concentrations of soil NH 4 and NO 3 below the litterbags peaked between 4 to 8 weeks, with nitrification lagging behind on ammonium release.

Volcanic eruptions disturb vegetation at a time it is needed for preventing mudflows. A resilient indigenous non-legume nitrogen-fixing tree that is adapted to the ash and spreads rapidly protects areas downstream in a volcanic landscape in Indonesia. Within the volcanic ring of fire both the long-term benefits (including densely populated, fertile agricultural soils) and short-term ecological disturbance of volcanic ash deposition are clear. Mount Kelud in East Java has erupted on a 15–37-years cycle for the past centuries, most recently in 2014, causing damage to settlements, agricultural land, agroforestry, and watershed protection forests, as the ash deposits caused tree mortality, restricted infiltration, and led to ash flows. Rapid “restoration” or recovery of tree-based vegetation with planted Legume trees (such as Calliandra spp.) has been attempted but is not very effective. However, the non-legume nitrogen-fixing Parasponia rigida, symbiotic with rhizobium bacteria, contrasted to its non-symbiotic sibling (Trema orientalis) has been studied in laboratory conditions, but not in its native environment. We mapped and sampled P. rigida in various locations (upper, middle, and lower elevation positions in ridge-slope-valley toposequences) on the Kelud complex starting 1 year after the latest eruption, estimated biomass development, and quantified P. rigida root nodules in relation to N availability in the ash/soil mixtures in these locations. P. rigida was found as a pioneer tree at elevations between 600 and 1,700 m a.s.l. (above sea level) along ridges, in slope, and valley positions. At lower elevations T. orientalis dominated. Within 3 years of the eruption, stem diameters were 3–10 cm. Up to 93% of P. rigida root nodules were found to be effective, based on the hemoglobin color on cross-sections. Rhizobium bacteria were found in root nodule tissue at densities of two to a hundred times higher than in rhizosphere soil. Between a total soil N content from 0.01 to 0.04% the density of effective nodules decreased from 1,200 to 200 m−2. P. rigida stands in the area, especially at ridges close to the crater deserve to be managed proactively as future seed sources, given the high frequency of eruption episodes, while recovery after eruptions on similar volcanoes can likely be facilitated by tactical assisted seed dispersal if effective seed collection and storage methods can be established.

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.

In the Brantas watershed, the acceleration of development for public welfare is often used as an argument for the exploitation of natural resources. This activity causes the degradation of natural resources. To achieve a healthy watershed, community empowerment in a watershed is one of the main concerns of the Indonesia government and it is urgently needed. Community empowerment through a micro catchment is an innovation. In the first step of the effort, a capacity baseline of the community on implementing soil and water conservation is required. The baseline was obtained through household surveys using a questionnaire. The sample was selected using the proportional random sampling method. A small population of the sample used a hyper geometric distribution approach. The results of the baseline study indicated that the community was still dependent on their land resources. They generally understand the land degradation problem, however some communities still did not realize the importance of environmental protection. The reason for farmers does not apply the soil and water conservation was due to the lack of labour, the demand for economic needs for their livelihood and less funding to carry out soil and water conservation measures. The community could overcome land degradation through community groups and they expect technical assistance and subsidies. They need formed and functioned the Association of Micro-catchment Management. The communities also stated that they needed regular assistance in the management of land resources through field school.