Imperata Grassland Research Articles

A Study on the Socioeconomics of Imperata Grassland Managers at Dargakona Village, Barak Valley, Assam, Northeast India

A Study on the Socioeconomics of Imperata Grassland Managers at Dargakona Village, Barak Valley, Assam, Northeast India

Deciphering nitrous oxide emissions from tropical soils of different land uses

Tropical regions are hotspots of increasing greenhouse gas emissions associated with land-use change. Although many field studies have quantified soil fluxes of nitrous oxide (N2O; a potent greenhouse gas) from various land uses, the driving mechanisms remain uncertain. Here, we used tropical soils of diverse land uses and actively manipulated the soil moisture (35%, 60%, and 95% water-filled pore space [WFPS]) and substrate supply (control, nitrate, and nitrate plus glucose) to investigate the responses of N2O emissions with short-term incubations. We then identified key factors regulating N2O emissions out of a series of soil physicochemical and biological factors and explored how these factors interacted to drive N2O emissions. Land-use changes from primary forest to oil palm or Acacia plantation risks emitting more N2O, whereas low emissions could be maintained by conversion to Macaranga forest or Imperata grassland; these laboratory observations were corroborated by a literature synthesis of field N2O measurements across tropical regions. Soil redox potential (Eh) and labile organic nitrogen (LON; amino acid mixture, arginine, and urea) mineralization were among the factors with greatest influence on N2O emissions. In contrast to common understandings, the control of WFPS over N2O emissions was largely indirect, and acted through Eh. The mineralization of LON, particularly arginine, potentially played multiple roles in N2O production (e.g., bottlenecks of nitrifier-denitrification or simultaneous nitrification-denitrification versus substrate competition for co-denitrification). Structural equation models suggest that soil-environmental factors of different levels (from distal including land use, soil moisture, and pH to proximal such as LON mineralization) drive N2O emissions through cascading interactions. Overall, we show that, despite identical initial soil conditions, land conversion can substantially alter the N2O emission potential. Also, collectively considering soil-environmental regulators and their interactions associated with land conversion is crucial to predict and design mitigation strategies for N2O emissions from land-use change.

Response of Ficus variegata seedling size on their early growth in imperata grassland

Ficus variegata is pioneer species that provides pulp raw materials, soil water protection, beehives tree, animal fodder, and medicinal plants. Introduction of F. variegata seedling at Imperata grassland constrained with low plant survival which caused by stressed plants and stagnant growth. The objective of this research was to determine the effect of five F. variegata seedlings size on the initial growth at Imperata grassland. The research was used Randomized Complete Block Design, with 5 seedling sizes for the treatment, there are size A (seedling height 15-50 cm), size B (51-75 cm), size C (76-100 cm), size D (101-125 cm), and size E (126-150 cm). In this research, we observe some parameters like height and stem diameter increment, canopy width, and plant survival at 1, 6, and 12 months old. Different seedling size has a very significant effect at six months old and very significant effect at 12 months old on the height, diameter and width crown increment. Seedling size 15-50 cm has shown faster height growth but has lower survival than another size in the dry season. For rehabilitation Imperata grassland, it is recommended using seedling size 50-125 cm because more adaptive and shown better growth in all parameters.

Plant diversity and composition at three Imperata grasslands in Bogor, Katingan, and Kupang, Indonesia

Abstract. Usmadi D, Witono JR, Lestari R, Widyatmoko D, Magandhi M, Robiansyah I, Rachmadiyanto AN, Purnomo DW, Zulkarnaen RN, Rivai RR, Helmanto H, Yudaputra A, Damayanti F. 2020. Plant diversity and composition at three Imperata grasslands in Bogor, Katingan, and Kupang, Indonesia. Biodiversitas 21: 2804-2813. Imperata grassland is among the largest proportions of marginal lands in Indonesia. Despite the dominance of Imperata cylindrica grass, certain plant species are able to compete and live together with this species, suggesting window of opportunity that the grasslands can be restored. Yet, the existing diversity and composition of plants in Imperata grasslands may vary due to differences in climatic and soil conditions. This study aims to determine the plant diversity and composition at three Imperata grasslands in Bogor, Katingan, and Kupang, Indonesia. Data were collected using systematic sampling by establishing quadratic observation plots with size of each plot was 1 x 1 m2. The total number of species found in Imperata grasslands in those three study sites was 81 species, belonging to 68 genera and 30 families. In the Bogor site, the dominant species were Imperata cylindrica, Ageratum conyzoides, and Phyllanthus niruri, while in the Katingan site was dominated by I. cylindrica, Scleria ciliaris, and Cyanthillium cinereum and in the Kupang site was dominated by I. cylindrica and Tridax procumbens. The Imperata grassland in Bogor had low species richness, moderate species diversity, the abundance distribution of each species tends to be uniform, and the occurred species did not tend to dominate. The Katingan and Kupang Imperata grasslands had low species richness, low species diversity, the abundance distribution of each species tends to be uneven, and were more dominated by I. cylindrica. Controlling abundance of I. cylindrica is required in those three research sites in order to stimulate the growth of other plant species, which is in turn to maintain and restore biodiversity.

Effects of land use change on turnover and storage of soil organic matter in a tropical forest

Land-use change of tropical forests causes loss of soil organic matter and plant productivity. Effects of fallow or plantation vegetation on soil organic matter storage need to be clarified to optimize land-use that maximizes soil organic matter storage and plant productivity. We compared 30-year changes in soil carbon stocks and litter decomposition under different land-uses (primary dipterocarp forest, Macaranga forest, Imperata grassland, transition of Imperata grassland to Acacia plantation, transition of Imperata grassland to oil palm plantation) in Indonesia. The Imperata grassland maximizes soil carbon stocks for up to 10 years due to considerable root litter inputs, but additional organic matter storage is limited over the following 20 years, due to high grass litter decomposability in the less acidified soil. The conversion of Imperata grassland to oil palm plantation causes greatest loss of soil organic matter, whereas Acacia plantation on Imperata grassland or the Macaranga forest maximizes soil carbon stocks due to input of recalcitrant forest litters and reduced microbial activities in the acidified soils. Farmers could adopt short-term ( 10 years) fallow under Acacia plantation on Imperata grassland or Macaranga regeneration forest to maximize soil organic matter storage. The optimum and feasible land-use strategies should be selected based on the length of fallow period and the original acidity of soil.

Water stable aggregates and the associated active and recalcitrant carbon in soil under rubber plantation

Rehabilitation of the degraded soil is imperative to minimize the effects of soil degradation. It is in this context that stable soil aggregates, essential to providing physical protection to the organic residues, are important indicators of soil restoration or degradation. Thus, the present study was aimed at determining the soil aggregate stability and associated carbon fractions under rubber (Hevea brasiliensis) plantations. The study was conducted on 10, 15, 25, and 34-year-old rubber plantation established on Imperata grassland. Soil samples were collected from 0 to 10, 10–20, 20–50, 50–100 cm depths from different aged rubber plantation and native forest (NF) using a soil core of 5.6 cm inner diameter. Soil aggregates from each depth were separated by the wet-sieving technique, and grouped into three fraction size classes: macro-aggregates (>2 mm), meso-aggregates (0.25–2 mm), and micro-aggregates (<0.25 mm), and analyzed for carbon concentrations. The results showed that macro-aggregates dominated soil under different plantation ages and decreased with an increase in soil depth. The Mean Weight Diameter (MWD) and the Geometric Mean Diameter (GMD) increased with an increase in the age of the plantation and decreased with increase in soil depth. The MWD was the highest in the forest soil (5.8 mm) and the lowest (3.0 mm) under 10-year-old rubber plantation. The highest GMD was found under 34-year-old rubber plantation (2.1 mm) and the lowest under 10-year (1.4 mm) plantation. The SOC concentration under the recalcitrant pool increased with the increase in plantation age, and the highest amount was observed under 34-year old plantation. The increase in aggregate stability, recalcitrant carbon pool, and SOC stock with age chronosequence suggests the ecological role of mature rubber plantations in soil rehabilitation by minimizing the process of soil degradation.

Effects of Reforestation of a Degraded Imperata Grassland on Dominant Flow Pathways and Streamflow Responses in Leyte, the Philippines

AbstractReforestation of degraded grasslands can increase the soil hydraulic conductivity and number of preferential flow pathways. However, it is not clear to what extent these changes affect streamflow responses and whether this depends on the event size. We, therefore, studied the hydrological response of two small catchments near Tacloban, Leyte (the Philippines): a degraded Imperata grassland catchment and a catchment that was reforested 23 years prior to our study. Precipitation, stream stage, and electrical conductivity were measured continuously from June to November 2013. Samples were taken from streamflow, precipitation, groundwater, and soil water for geochemical and stable isotope analyses. Streamflow and electrical conductivity changed rapidly during almost every event in the grassland catchment, but in the reforested catchment, these responses were much smaller and only occurred during large events. Streamflow was a mixture of groundwater and precipitation for both catchments, but the maximum event water contributions to streamflow were much larger for the degraded grassland than for the reforested catchment. The differences in the event water contributions and timing of the streamflow responses were observed across all event sizes, including a large tropical storm. Together with the low saturated hydraulic conductivity in the degraded catchment, these results suggest that overland flow occurred more frequently and was much more widespread in the degraded grassland than in the reforested catchment. We, therefore, conclude that reforestation of a degraded grassland can change the dominant flow pathways and restore the hydrological functioning if the forest soil is allowed to develop over a sufficiently long period.

Water budget and run‐off response of a tropical multispecies “reforest” and effects of typhoon disturbance

AbstractTo examine claims that reforesting degraded Imperata grassland in Leyte (Philippines) made streamflow perennial again, we studied the hydrological behaviour of a 23‐year‐old mixed‐species “reforest” between June 2013 and May 2014. Typhoon Haiyan, one of the strongest events ever, caused major damage to the site in November 2013. Average daily apparent water use (ET) was 5.0 mm day−1 pretyphoon and 3.2 mm day−1 after disturbance. Corresponding ratios of period total quickflow Qq to precipitation were 16% and 44%. Quickflow volume and peak discharge increased rapidly once a threshold value of ~250 mm for soil water storage in the top 60 cm was exceeded. Before disturbance, quickflow consisted predominantly of lateral subsurface flow due to high soil hydraulic conductivities down to 60 cm. After disturbance, shallow groundwater rose regularly to within 10 cm of the surface on foot slopes, and saturation overland flow was observed during several large storms. Comparing estimated annual ET and Qq for undisturbed conditions for the reforest and a nearby degraded Imperata grassland microcatchment suggested that the extra infiltration following reforestation (~240 mm year−1) exceeded the extra ET by the reforest (100–185 mm year−1), implying a net positive trade‐off (55–140 mm year−1) and tentatively confirming local claims of improved dry‐season flow.

Runoff response and sediment yield of a landslide-affected fire-climax grassland micro-catchment (Leyte, the Philippines) before and after passage of typhoon Haiyan

Decades of logging and slash-and-burn agriculture have turned vast tracts of land in tropical South-east Asia into unproductive fire-climax grasslands whose hydrological functioning is poorly known. To help fill this knowledge gap, a 3.2 ha landslide-affected Imperata grassland micro-catchment with perennial flow on Leyte Island (Philippines) was instrumented and monitored for a year. The area was hit by typhoon Haiyan on 8 November 2013, one of the largest events on record. Landslide surfaces covered 3.4% of the catchment prior to typhoon Haiyan and contributed to ‘direct runoff’ (Qq). This basic ‘contributing area’ increased to 7.7% by activation of old landslides and formation of new ones during typhoon Haiyan. Median storm runoff coefficients (Qq/P) based on straight-line hydrograph separation were 9% and 23% before (48 events) and after the typhoon (43 events), respectively, but the ratios of period-total Qq and P were much larger (24% and 47%, respectively). Both storm runoff volumes and peak discharge increased rapidly once a mid-slope water storage threshold for the upper 60 cm of soil of 250 mm was exceeded. Storm runoff contributions above those generated on landslides were most likely in the form of overland flow given the prevailing very low soil hydraulic conductivities. Post-typhoon water use of the heavily disturbed vegetation was reduced initially by nearly 70%, recovering to nearly 80% of the pre-typhoon value after ∼3 months. The high annual sediment yield (∼27 t ha−1) was heavily dominated by post-Haiyan sediment transport (94%); bedload contributed ∼8% of the total sediment yield.

Soil physical characteristics of a degraded tropical grassland and a ‘reforest’: Implications for runoff generation

Imperata grassland soils are widely perceived as having poor physical and chemical properties that render them unproductive and prone to erosion. They are therefore increasingly targeted for reforestation across the tropics. To better understand how reforestation and forest growth affect soil hydrological processes we compared the soil physical characteristics for an Imperata grassland and a 23-year-old ‘reforest’ on Leyte Island, the Philippines. Saturated hydraulic conductivity (Ksat) was determined in the field (Amoozemeter, 20–90 cm depth) and the laboratory (small-core permeametry). Core-based values of Ksat were (much) lower than field-based values, suggesting macropores were not sampled adequately with the small cores. Ksat decreased exponentially with depth in both land-cover types, with a median field-measured Ksat of the grassland of 2.1 mm h−1 at the surface and 2.9 mm h−1 at 20–40 cm depth, declining to ≤1 mm h−1 below 60 cm. Corresponding values for the reforest were 59 (at 20 cm), 37 (at 40 cm) and 7.3 mm h−1 (at 60–100 cm depth). Reforest Ksat-values down to 60 cm depth were significantly higher than corresponding values in the grassland, but the difference disappeared at 90 cm depth. Organic carbon content in the top 40 cm of soil was slightly higher in the reforest than the grassland. Bulk density was higher and porosity marginally lower in the grassland than the reforest at all depths considered. The median five-min rainfall intensity (June 2013–May 2014) was 3.2 mm h−1, suggesting that >50% of the rainfall might generate Hortonian overland flow in the grassland. Overland flow is unlikely in the reforest where lateral flow is likely to be generated around 60 cm depth for ~30% of rain-time, versus 2–3% between 20 and 60 cm. Within the limitations of the space-for-time substitution approach, these results suggest that 23 years of forest development at Manobo had a positive effect on hillslope hydrological functioning.

Net ecosystem productivity and carbon dynamics of the traditionally managed Imperata grasslands of North East India

There have been few comprehensive descriptions of how fire management and harvesting affect the carbon dynamics of grasslands. Grasslands dominated by the invasive weed Imperata cylindrica are considered as environmental threats causing low land productivity throughout the moist tropical regions in Asia. Imperata grasslands in North East India are unique in that they are traditionally managed and culturally important in the rural landscapes. Given the importance of fire in the management of Imperata grassland, we aimed to assess (i) the seasonal pattern of biomass production, (ii) the eventual pathways for the produced biomass, partitioned between in situ decomposition, harvesting and combustion, and (iii) the effect of customary fire management on the ecosystem carbon cycle. Comparatively high biomass production was recorded during pre-monsoon (154 g m−2 month−1) and monsoon (214 g m−2 month−1) compared to the post-monsoon (91 g m−2 month−1) season, and this is attributed to nutrient return into the soil immediately after fire in February. Post fire effects might have killed roots and rhizomes leading to high belowground litter production 30–35 g m−2 during March to August. High autotrophic respiration was recorded during March–July, which was related to high belowground biomass production (35–70 g m−2) during that time. Burning removed all the surface litter in March and this appeared to hinder surface decomposition and result in low heterotrophic respiration. Annual total biomass carbon production was estimated at 886 g C m−2. Annual harvest of biomass (estimated at 577 g C m−2) was the major pathway for carbon fluxes from the system. Net ecosystem production (NEP) of Imperata grassland was estimated at 91 g C m−2 yr−1 indicating that these grasslands are a net sink of CO2, although this is greatly influenced by weather and fire management.

Ecosystem carbon sequestration through restoration of degraded lands in Northeast India

AbstractThis study evaluated the ecosystem carbon (C) stock and sequestration potential for predominant land uses converted from forest in Northeast India to advance the scientific knowledge and minimize the anthropogenic C emissions from land use change (LUC). Field assessments were conducted on 6 predominant land uses including (a) natural forest (NF), (b) degraded forest (DF), (c) rubber (Hevea brasiliensis) plantation (RP), (d) Areca (Areca catechu) plantation (ArP), (e) pan (Piper betle) jhum (slash and mulching) agroforestry (PB), and (f) Imperata grassland (IG) of Northeast India to assess changes in ecosystem C stock with progressive and retrogressive LUC. Ecosystem C stock was the highest for NF (300.5 Mg ha−1) and the lowest under IG (110.4 Mg ha−1). The ecosystem C stock under PB and IG was 11% and 63%, respectively, lower than that under NF. In comparison with DF, the gain in ecosystem C was in the order PB (125%) &gt; RP (99%) &gt; ArP (4%). The ratio of soil organic carbon to ecosystem C stock was ~50% for NF, PB, and RP and that shifted to ~80% for ArP/DF/IG. The LUC and management of DF through PB and RP indicated the ecosystem C sequestration rate of 5 and 4 Mg ha−1 year−1, respectively. Similarly, the ecosystem C sequestration rate was 0.5 and 4 Mg ha−1 year−1, respectively, when IG was converted into ArP and RP. Therefore, restoration of degraded lands (viz., DF and IG) through RP and PB enhanced ecosystem C sequestration rate and reduced CO2 emissions from LUC. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Annual Burning Enhances Biomass Production and Nutrient Cycling in Degraded Imperata Grasslands

AbstractThe invasive species Imperata cylindrica is a dominant grass covering a large part of degraded lands of India. Imperata is managed through traditional annual burning, a practice that is prevalent throughout tropical grasslands. A field experiment was conducted to quantify the effects of burning on aboveground and belowground biomass production and soil organic carbon (SOC), total nitrogen (TN), available phosphorus (Ave P), potassium (K+), calcium (Ca+), and magnesium (Mg+) concentrations in 0‐ to 15‐cm soil depth under Imperata grassland. The burnt site had 44% and 14% higher aboveground and belowground biomass over the un‐burnt control plots after 300 days of the fire event. The concentrations of SOC, TN, and Ave P increased soon after the fire but decreased regressively with time after the fire in both micro and macro soil aggregate size fractions. In contrast, concentrations of K+, Ca+, and Mg+ increased up to 30 days after the fire in both soil aggregate fractions. Burning did not significantly alter the stoichiometric ratios (C : N, C : P, and N : P) in macro aggregates. However, burning significantly reduced the C : N, C : P, and N : P ratios in micro aggregates during the first 0–30 days. Fire increased nutrient stocks (kg ha−1) by 20–35% in the burnt site in comparison to an un‐burnt control site. It is concluded that the conventional practice of annual burning increases soil nutrients in surface soils and supports higher biomass production in Imperata‐covered degraded lands. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Richer histories for more relevant policies: 42years of tree cover loss and gain in Southeast Sulawesi, Indonesia.

Understandings of contemporary forest cover loss are critical for policy but have come at the expense of long-term, multidirectional analyses of land cover change. This is a critical gap given (i) profound reconfigurations in land use and land control over the past several decades and (ii) evidence of widespread 'woodland resurgence' throughout the tropics. In this study, we argue that recent advancements within the field of land change science provide new opportunities to address this gap. In turn, we suggest that multidecadal and multidirectional analyses of land cover change can facilitate richer social analyses of land cover change and more relevant conservation policies and practice. Our argument is grounded in a case study from Southeast Sulawesi, Indonesia. Using a novel analytical platform, Google Earth Engine, and open access to high-quality Landsat data, we map land cover change in Southeast Sulawesi, Indonesia, from 1972 to 2014. We find that tree cover loss constitutes the single largest net change over the period 1972-2014 but that gross rates of tree cover gain were three times higher than gross loss rates from 1972 to 1995 and equivalent to loss rates from 1995 to 2014. We suggest the smallholder tree crop economy likely produced both forest loss and Imperata grassland restoration in this region. This case points to the need to expand rather than collapse the baselines used to study carbon and biodiversity change in tropical regions. It also demonstrates the possible utility of applying such methods to other regions.

Carbon dynamics in anImperatagrassland in Northeast India

Carbon stocks and soil CO 2 flux were assessed in an Imperata cylindrica grassland of Manipur, Northeast India. Carbon stocks in the vegetative components were estimated to be 11.17 t C/ha and soil organic carbon stocks were 55.94 t C/ha to a depth of 30 cm. The rates of carbon accumulation in above-ground and below-ground biomass were estimated to be 11.85 t C/ha/yr and 11.71 t C/ha/yr, respectively. Annual soil CO 2 flux was evaluated as 6.95 t C/ha and was highly influenced by soil moisture, soil temperature and soil organic carbon as well as by C stocks in above-ground biomass. Our study on the carbon budget of the grassland ecosystem revealed that annually 23.56 t C/ha was captured by the vegetation through photosynthesis, and 6.95 t C/ha was returned to the atmosphere through roots and microbial respiration, with a net balance of 16.61 t C/ha/yr being retained in the grassland ecosystem. Thus the present Imperata grassland exhibited a high capacity to remove atmospheric CO 2 and to induce high C stocks in the soil provided it is protected from burning and overgrazing. Keywords: Above-ground biomass, below-ground biomass, carbon stocks, carbon storage, net primary productivity, soil CO 2 flux. DOI: 10.17138/TGFT(4)19-28

Growth Responses of Acacia mangium and Paraserianthes falcataria Seedlings on Different Soil Origin under Nursery Condition

The objective of the present study was to examine the growth responses of Acacia mangium (mangium) and Paraserianthes falcataria (sengon) seedlings growing on different soil origin under nursery condition. This study was started in September 2012 and terminated in March 2013. The seedlings were grown from seeds sown in a plastic box filled with sterilized sands. One week after sowing, the seedlings were transplanted into polybags contained sterilized soils originated from secondary forest, Imperata cylindrica grassland and ex-coal mining. The number of all seedlings were 180 seedlings consisted of 3 different soils, 2 species of seedlings with 10 seedlings replicated 3 times. Assessment was conducted one week after transplanting, then subsequently monitored every 2 weeks, except dry weighing and counting nodules were performed at the end of the study. A completely randomized design was used in this study. The data was analyzed using Costat software. The study resulted that the different of soil origin influenced on all growth variables of mangium and sengon of 4.5 months old. The survival rate of seedlings, height and diameter increments, dry weight and root nodules were better in both species of seedlings growing on soil originated from secondary forest and Imperata grassland compared with the soil from ex-coal mining. But the survival rates of sengon seedlings were higher than that of mangium on these three soils. The highest dry weight of sengon seedlings was achieved on soil originated from secondary forest. In the present study, soil originated from secondary forest increased more in weight of shoot than root, so that the shoot-root ratio was unbalanced more than one. Based on the results of this study, it is recommended that soil from secondary forest and Imperata grassland can be used as growing media for mangium and sengon seedlings in the nursery.

PEMBUATAN ASAM OKSALAT DARI ALANG-ALANG (Imperata Cylindrica) DENGAN METODE PELEBURAN ALKALI

Imperata grassland is one of the wild plant which have a low economic value but containing high cellulose. Therefore it is potentially to be used as raw material for oxalic acid manufacturing. The oxalic acid can be produced from imperata grassland through 4 steps: alkaline hydrolysis, precipitacion, acidification and crystallization. Experiments are carried out in a three necks glass equipped with thermometer, mixer, heater and condenser. Cooking solution NaOH were varied 3,5 N; 4 N and 4,5 N and cooking time 50, 60, 70 and 80 minutes. According to the result from the experiment, at the condition 98oC of cooking temperature, the highest yield of oxalic acid about 44,39% is obtained at 4 N concentration of sodium hydroxide and 60 minute of cooking time. Oxalic acid produced has 104oC of melting point and 1,2 of degree of acidity (pH).

Does Tree Planting Change Minds? Assessing the Use of Community Participation in Reforestation to Address Illegal Logging in West Kalimantan

Gunung Palung National Park in West Kalimantan, Indonesia has been persistently threatened by illegal logging for the past several decades. Subsequent fires have led to the encroachment of noxious grasses such as Imperata cylindrica, which have arrested succession to secondary forest within and around the park. Since 2009, local NGO Alam Sehat Lestari (ASRI) has reforested 20 hectares of degraded Imperata grassland within the park, with the goal of restoring forest area and decreasing the incidence of illegal logging inside the park by providing jobs and income to local people. In February 2013, a survey was conducted to assess the social impacts of the reforestation program, and to test the hypothesis that participation in reforestation can reduce instances of illegal logging through two pathways: (1) economic improvement for participants; (2) altering perceptions towards illegal logging. Structured interviews were conducted with 50 local residents, one-third of which identified as former illegal loggers, to gauge their perceptions towards forest conservation and illegal logging. The survey found that 80% of respondents believed that the reforestation program helped to reduce illegal logging in the park. However, the pathways through which this change occurred were different from those hypothesized. There was little evidence supporting the “perceptions change” pathway, but greater evidence supporting the “economic improvement” pathway through the medium of skill-building rather than direct economic improvement. Approximately 50% of participants reported engaging in self-directed tree planting activities post-involvement. These results suggest that forest restoration can effectively be used as a community-engagement tool to address illegal logging.

PENGARUH SISTEM OLAH TANAH TERHADAP TOTAL BAKTERI TANAH PADA PERTANAMAN KEDELAI MUSIM TANAM KEDUA SETELAH PERTANAMAN JAGUNG DI LAHAN BEKAS ALANG-ALANG (Imperata cylindrica. L)

This study aims to determine the effect of tillage systems on Imperata grasslands are used as a soybean crop after the second growing season maize to total soil bacteria. The research this performed using by randomized block design (RBD) with three treatments tillage systems namely: TOT = No Tillage, OTM = Minimum Tillage, OTI = Intensive Tillage, with six replications. Soil samples were taken two weeks before tillage, one day after tillage, vegetative the maximum, and one day before harvest soybean plants. Soybean crop is used as an indicator of response to the treatment applied. The data obtained were tested homogeneity with Bartlett test and additivity tested by Tukey’s test. Test the correlation between the main variables of total soil bacteria with supporting variable pH, C-organic, N-total, temperature, and soil moisture. Data were analyzed by analysis of variance followed by LSD test 5%. Tillage treatments were not significantly different to the total bacteria in the soil two weeks before the observation tillage, one day after tillage, vegetative period and the maximum one day before harvest soybean plants. There is a correlation between soil pH (HO) with total soil bacteria in the observation of one day before harvest soybean plants.

Soil Organic Matter Dynamics Upon Secondary Succession in Imperata Grassland, East Kalimantan, Indonesia

Soil organic matter (SOM) dynamics upon secondary succession in Imperata grassland was studied by stable carbon isotope analysis. The data of litter and soil samples of twenty plots in four different stages of succession were compared. These different stages were represented by plots that were; (1) last burned 3 years before sampling ( Imperata grassland), (2) last burned 9 years before, (3) a secondary forest (≥15 years) and (4) a primary forest. Result showed that isotopic signatures of all soil horizons of the regeneration stages were statistically different from those of the primary forest. The A-horizon under the 3-years Imperata plot still contained 23% forest (C3) carbon, and this fraction increased to 51% in the-B-horizon. In the 9-years plot and in the secondary forest, the C3 carbon on the A-horizon increased to 51% and 96%, respectively. In the topsoil, the loss of C4-C between the 3-years and the 9-years plot was significant, while it appeared negligible in the AB-horizon. The strong decay in the topsoil under Imperata grassland may be due to the rather high carbohydrate content of the SOM, which is considered easily decomposable. Further research is needed especially to explore the relation between carbon stocks and chemical of SOM composition. Such insight may help to better understand and predict soil carbon changes in relation to climate and vegetation change.