1,721,043 research outputs found
Conversion of tropical lowland forest reduces nutrient return through litterfall, and alters nutrient use efficiency and seasonality of net primary production
No full textTropical landscapes are not only rapidly transformed by ongoing land-use change, but are additionally confronted by increasing seasonal climate variation. There is an increasing demand for studies analyzing the effects and feedbacks on ecosystem functioning of large-scale conversions of tropical natural forest into intensively managed cash crop agriculture. We analyzed the seasonality of aboveground litterfall, fine root litter production, and aboveground woody biomass production (ANPPwoody) in natural lowland forests, rubber agroforests under natural tree cover (“jungle rubber”), rubber and oil palm monocultures along a forest-to-agriculture transformation gradient in Sumatra. We hypothesized that the temporal fluctuation of litter production increases with increasing land-use intensity, while the associated nutrient fluxes and nutrient use efficiency (NUE) decrease. Indeed, the seasonal variation of aboveground litter production and ANPPwoody increased from the natural forest to the plantations, while aboveground litterfall generally decreased. Nutrient return through aboveground litter was mostly highest in the natural forest; however, it was significantly lower only in rubber plantations. NUE of N, P and K was lowest in the oil palm plantations, with natural forest and the rubber systems showing comparably high values. Root litter production was generally lower than leaf litter production in all systems, while the root-to-leaf ratio of litter C flux increased along the land-use intensity gradient. Our results suggest that nutrient and C cycles are more directly affected by climate seasonality in species-poor agricultural systems than in species-rich forests, and therefore might be more susceptible to inter-annual climate fluctuation and climate change
ndonesia)
No full textNatural forests in South‐East Asia have been extensively converted into other land‐use systems in the past decades and still show high deforestation rates. Historically, lowland forests have been converted into rubber forests, but more recently, the dominant conversion is into oil palm plantations. While it is expected that the large‐scale conversion has strong effects on the carbon cycle, detailed studies quantifying carbon pools and total net primary production (NPPtotal) in above‐ and belowground tree biomass in land‐use systems replacing rainforest (incl. oil palm plantations) are rare so far. We measured above‐ and belowground carbon pools in tree biomass together with NPPtotal in natural old‐growth forests, ‘jungle rubber’ agroforests under natural tree cover, and rubber and oil palm monocultures in Sumatra. In total, 32 stands (eight plot replicates per land‐use system) were studied in two different regions. Total tree biomass in the natural forest (mean: 384 Mg ha−1) was more than two times higher than in jungle rubber stands (147 Mg ha−1) and >four times higher than in monoculture rubber and oil palm plantations (78 and 50 Mg ha−1). NPPtotal was higher in the natural forest (24 Mg ha−1 yr−1) than in the rubber systems (20 and 15 Mg ha−1 yr−1), but was highest in the oil palm system (33 Mg ha−1 yr−1) due to very high fruit production (15–20 Mg ha−1 yr−1). NPPtotal was dominated in all systems by aboveground production, but belowground productivity was significantly higher in the natural forest and jungle rubber than in plantations. We conclude that conversion of natural lowland forest into different agricultural systems leads to a strong reduction not only in the biomass carbon pool (up to 166 Mg C ha−1) but also in carbon sequestration as carbon residence time (i.e. biomass‐C:NPP‐C) was 3–10 times higher in the natural forest than in rubber and oil palm plantations
Forest conversion impacts on the fine and coarse root system, and soil organic matter in tropical lowlands of Sumatera (Indonesia)
No full textDeforestation and land-use change are occurring on an increasing scale throughout Indonesia with profound effects on ecosystem structure and functions marked by consequences in biogeochemical cycles. This study investigates the influence of forest conversion on soil organic matter as well as the fine and coarse root system. Furthermore, the relationships between carbon (C) and nitrogen (N) stocks in the root biomass were related to the total aboveground tree biomass. Root biomass and fine root morphology were investigated in 150 cm-deep soil pits along a gradient of increasing land-use intensity, i.e. in natural forest, rubber under a natural forest cover (jungle rubber'), rubber and oil palm monocultures. Total root biomass generally decreased with increasing land-use intensity together with aboveground tree biomass. Subsequently, carbon and nutrient stocks in the root system were over 50% lower in the monoculture plantations compared to the natural forest. Vertical root distribution showed distinct different patterns across the land-use types with a pronounced logarithmic decrease in vertical total root abundance in the natural forest and the jungle rubber plots that was less distinctive in the plantation systems. However, fine root morphology in the jungle rubber system revealed a large specific root area and specific root tip abundance, therefore partly compensating for the reduction in the fine root system after forest conversion. Soil organic matter was particularly low in rubber plantations. In conclusion, the results of our study suggests that conversion of natural forest to agroforestry and monoculture systems has a profound belowground impact reflected in the decrease of root biomass, nutrient stocks in coarse roots, and total soil organic matter. (C) 2016 Elsevier B.V. All rights reserved.German Research Foundation (DFG); [CRC 990
Nitrogen Resorption and Nitrogen Use Efficiency in Cacao Agroforestry Systems Managed Differently in Central Sulawesi
No full textCacao agroforestry is a traditional form of agriculture practiced by the people of Central Sulawesi. These agroforestry systems vary from a simple system following selective cutting of forest trees, to a more sophisticated planting design. The cacao was planted under remaining forest covers (CF1), under planted trees (CF2), and between shade trees Gliricidia sepium (CP). The objectives of this study were to quantify nitrogen use efficiency (N NUE) and nitrogen resorption in cacao agroforestry systems. The N NUE at the ecosystem scale (N NUEES) for the cacao agroforestry systems were compared with the natural forest. The results showed that CP produced the highest litterfall and cacao foliar nitrogen. CP and CF1 produced litterfall and the nitrogen resorption that not were significantly different. In contrast, CF2 produced the lowest litterfall, hence required lower nitrogen supply. The nitrogen resorption of CF2 was less than that of CF1 and CP. However, N NUE in cacao plant (N NUEC) of CF2 was higher than that of the CP. The N NUEES of either CF1 or CF2 were similar to that of the natural forest, but higher than that of the CP. Using shade trees in cacao plantations increased foliar nitrogen concentration, nitrogen resorption, N NUEC and N NUEES; thus, might be one reason for a higher productivity of cacao in unshaded systems
Carbon and nitrogen stocks in dead wood of tropical lowland forests as dependent on wood decay stages and land-use intensity
Full text linkRapid transformation of natural forests into other land-use systems in the lowlands of Sumatra, Indonesia, strongly reduces total aboveground biomass and affects nutrient cycling. However, the consequences of this conversion for C and N stocks of dead wood remains poorly understood particularly in natural forests and jungle rubber. This study examined the differences in dead wood abundance, and C, N and lignin concentrations of three decay stages of dead wood as well as the stocks of these chemical components stored in dead wood. Standing and fallen dead wood was determined as coarse woody debris with diameter ≥ 10 cm and classified into three decay stages of wood. Mass of dead wood was estimated using allometric equation. Total C and N stocks in dead wood in the natural forests (4.5 t C ha-1, 0.05 t N ha-1, respectively) were three times higher than those in the jungle rubber (1.5 t C ha-1, 0.02 t N ha-1, respectively). The stocks of C and N at early and advanced wood decay stages in the natural forests were also higher than those in the jungle rubber. The decay stages showed pronounced differences in concentrations of chemical components. With advancing stage of wood decay, N concentration increased and C/N ratio decreased, while concentrations of C and lignin were variable. The distribution of dead wood mass and stocks of C, and lignin were found to be higher in the early decay than those in the advanced decay stage. Higher input of dead wood in natural forests indicated a higher importance of dead wood decay in natural forests than in jungle rubber systems. Thus, replacing natural forests with jungle rubber strongly reduces total C and N stocks which might have a marked negative effect on the ecosystems' nutrient turnover and cyle
Tree height effects on vascular anatomy of upper-canopy twigs across a wide range of tropical rainforest species
No full textAbstractVessel diameter variation along the hydraulic pathway determines how much water can be moved against the force of gravity from roots to leaves. While it is well-documented that tree size scales with vessel diameter variation at the stem base due to the effect of basipetal vessel widening, much less is known whether this likewise applies to terminal sun-exposed twigs. To analyze the effect of tree height on twig xylem anatomy, we compiled data for 279 tropical rainforest tree species belonging to 56 families in the lowlands of Jambi Province, Indonesia. Terminal upper-canopy twigs of fully grown individuals were collected and used for wood anatomical analysis.We show that hydraulically weighted vessel diameter (Dh) and potential hydraulic conductivity (Kp) of upper canopy twigs increase with tree height across species although the relationship was weak. When averaged across given tree height classes irrespectively of species identity, however, a strong dependency of tree height on Dh and Kp was observed, but not on the lumen-to-sapwood area ratio (Al:Ax) or vessel density (VD).According to the comparison between actual tree height and the maximum tree height reported for a given species in the stand, we show that the vascular xylem anatomy of their terminal twigs reflects their canopy position and thus ecological niche (understory versus overstory) at maturity. We conclude that the capacity to move large quantities of water during the diurnal peak in evaporative demand is a prerequisite for growing tall in a humid tropical environment.</jats:p
Nitrogen Resorption and Nitrogen Use Efficiency in Cacao Agroforestry Systems Managed Differently in Central Sulawesi
No full textCacao agroforestry is a traditional form of agriculture practiced by the people of Central Sulawesi. These agroforestry systems vary from a simple system following selective cutting of forest trees, to a more sophisticated planting design. The cacao was planted under remaining forest covers (CF1), under planted trees (CF2), and between shade trees Gliricidia sepium (CP). The objectives of this study were to quantify nitrogen use efficiency (N NUE) and nitrogen resorption in cacao agroforestry systems. The N NUE at the ecosystem scale (N NUEES) for the cacao agroforestry systems were compared with the natural forest. The results showed that CP produced the highest litterfall and cacao foliar nitrogen. CP and CF1 produced litterfall and the nitrogen resorption that not were significantly different. In contrast, CF2 produced the lowest litterfall, hence required lower nitrogen supply. The nitrogen resorption of CF2 was less than that of CF1 and CP. However, N NUE in cacao plant (N NUEC) of CF2 was higher than that of the CP. The N NUEES of either CF1 or CF2 were similar to that of the natural forest, but higher than that of the CP. Using shade trees in cacao plantations increased foliar nitrogen concentration, nitrogen resorption, N NUEC and N NUEES; thus, might be one reason for a higher productivity of cacao in unshaded systems
Consequences of tropical rainforest conversion to tree plantations on fine root dynamics and functional traits
No full textDespite the crucial role of fine roots for water and nutrient uptake, soil biological activity and ecosystem carbon cycling, the response of root dynamics to rapidly advancing land-use change in the tropics is still poorly understood. To address this uncertainty, we investigated the consequences of tropical forest conversion to intensively managed tree plantations for a suite of functional fine root traits. We analysed fine root morphology (diameter, specific root length (SRL), tissue density) and chemistry, as well as root lifespans in four prevalent land-use systems in the lowlands of Sumatra (Indonesia), namely natural forest, jungle rubber, rubber and oil palm monocultures. Fine root production was estimated using three independent approaches (sequential coring, ingrowth cores, mini-rhizotrons). Contradicting the expected trend from more conservative to more acquisitive fine root traits with increasing land-use intensity, we found that SRL and tissue density were significantly higher in forest trees, while fine root diameter was largest in rubber trees and root N content lowest in the oil palm system. Median fine root longevity in the top soil was 11% higher in rubber plantations (238 days) than in jungle rubber (211 days), and more than 50% greater than in the forest (140 days) and oil palm plantations (125 days). Fine root production was higher in the forest and oil palm plantations (ranging between 2 and 9 Mg ha−1 year−1) than the rubber stands, but annual totals varied depending on the methodological approach. Conversion of tropical lowland forest to agricultural systems significantly altered community-level fine root morphology, dynamics and longevity, with likely consequences for soil carbon cycling and soil biological activity. However, land-use intensification did not consistently lead to more acquisitive fine root systems; rather, differences in root morphology and dynamics were driven by species-specific root trait syndromes especially of rubber and oil palm
Short Communication: Sex types in flowering of Jatropha curcas
No full textAbstract. Dasumiati, Miftahudin, Triadiati T, Hartana A. 2017. Short Communication: Sex types in flowering of Jatropha curcas. Biodiversitas 18: 275-279. Commonly, Jatropha curcas ( jatropha) produces male and female flowers in the different flower. But, the other jatropha have male and hermaphrodite flowers in the different flower. The combination of those flowers in one plant causes sex differentiation in jatropha. This study aimed to identify the sex types of flowers and plant in jatropha, as well as to know the stability of sex types after stem cuttings propagation. The survey was conducted to the population of jatropha in Cikampek, Karawang and Pakuwon, Sukabumi, West Java, Indonesia. We found three sex types in both plantations: monoecious that have male and female flowers, andromonoecious that have male and hermaphrodite flowers, trimonoecious that have male, female, and hermaphrodite flowers in the same plant. Andromonoecious and monoecious jatropha have stable sex type, but trimonoecious jatropha has unstable sex type. The stability of sex type is related to the number of primary branch and distance between nodes.
Keywords: Andromonoecious, Jatropha curcas, monoecious, trimonoecious</jats:p
- …
