Ikuo Ninomiya

Development of allometric relationships for accurate estimation of above- and below-ground biomass in tropical secondary forests in Sarawak, Malaysia.

We developed allometric relationships between tree size parameters (stem diameter at breast height (dbh), at ground surface ( D 0 ) and tree height) and leaf, stem, small-root (diameter

Photosynthetic Activity in Seed Wings of Dipterocarpaceae in a Masting Year: Does Wing Photosynthesis Contribute to Reproduction?

The photosynthetic rate of seed wings developed from sepals was compared with the leaf photosynthetic rate in nine dipterocarp tree species (Dipterocarpus pachyphyllus, Dryobalanops aromatica, Dryobalanops lanceolata, Shorea beccariana, Shorea ferruginea, Shorea macroptera ssp. bailonii, Shorea macroptera ssp. macropterifolia, Shorea pilosa, and Vatica spp.). The wings showed positive photosynthetic activity, but at much lower rates than in the leaves. The daily CO2 uptake of wings showed slightly negative values in diurnal gas exchange measurements, even in D. aromatica that showed the highest photosynthetic capacity of all nine species. This low photosynthetic rate in the wings may be the result of low nitrogen and chlorophyll contents in the wing compared with leaves. However, the wings had a higher C/N ratio than leaves, and were thicker. Hence, dipterocarp wings have physical strength and defence against herbivores as higher priorities than photosynthetic activity.

Effects of shifting cultivation on soil ecosystems in Sarawak, Malaysia. I. Slash and burning at Balai Ringin and Sabal experimental sites and effect on soil organic matter

Abstract Experimental shifting cultivation was conducted at two sites, Balai Ringin (B. Ringin) and Sabal in Sarawak, Malaysia. The soils at the B. Ringin site were clayey with strongly acidic nature while those at the Sabal site were sandy with a very low nutrient status. The plots (10 x 10 m2) were burned with vegetation biomass (fuel) amounting to 0 (control), 100,200, and 300 Mg ha-1 for the cultivation of upland rice. At both sites, the fire severity was found to range from moderate to high for the treatments with 200 and 300 Mg ha-1 fuel, and from low to moderate for the treatment with 100 Mg ha-1 fuel. At the B. Ringin site, the content of total C (T-C) of the soils decreased during rice cultivation which could be ascribed to the rapid decomposition of soil organic matter (SOM) and the loss of SOM due to soil erosion. One year after burning, the T-C content returned to the initial level before burning, suggesting that SOM was replenished by the addition of fresh organic matter derived from rice straw and other dead plants. The effects of burning on soil microbial properties which tended to be more pronounced with the increase of the amount of fuel, persisted until 1 year after burning. Burning resulted in a yield of 850 kg ha-) of rice on the average, irrespective of the amount of fuel used. On the other hand, at the Sabal site, the T-C content decreased dramatically during rice cultivation. It was assumed that a portion of 80M was washed away by rainfall because of the sandy texture of soil and coarse fragments of 80M. Rice yield was very low due to the low nutrient status of soil and pest infestation

Mortality of coho salmon (Oncorhynchus kisutch) associated with burdens of multiple parasite species

Multiple analytical techniques were used to evaluate the impact of multiple parasite species on the mortality of threatened juvenile coho salmon (Oncorhynchus kisutch) from the West Fork Smith River, Oregon, USA. We also proposed a novel parsimonious mathematical representation of macroparasite distribution, congestion rate, which (i) is easier to use than traditional models, and (ii) is based on Malthusian parameters rather than probability theory. Heavy infections of Myxobolus insidiosus (Myxozoa) and metacercariae of Nanophyetus salmincola and Apophallus sp. occurred in parr (subyearlings) from the lower mainstem of this river collected in 2007 and 2008. Smolts (yearlings) collected in 2007-2010 always harboured fewer Apophallus sp. with host mortality recognised as a function of intensity for this parasite. Mean intensity of Apophallus sp. in lower mainstem parr was 753 per fish in 2007 and 856 per fish in 2008, while parr from the tributaries had a mean of only 37 or 13 parasites per fish, respectively. Mean intensity of this parasite in smolts ranged between 47 and 251 parasites per fish. Over-dispersion (variance to mean ratios) of Apophallus sp. was always lower in smolts compared with all parr combined or lower mainstem parr. Retrospective analysis based on smolt data using both the traditional negative binomial truncation technique and our proposed congestion rate model showed identical results. The estimated threshold level for mortality involving Apophallus sp. was at 400-500 parasites per fish using both analytical methods. Unique to this study, we documented the actual existence of these heavy infections prior to the predicted mortality. Most of the lower mainstem parr (approximately 75%) had infections above this level. Heavy infections of Apophallus sp. metacercariae may be an important contributing factor to the high over-wintering mortality previously reported for these fish that grow and develop in this section of the river. Analyses using the same methods for M.insidiosus and N. salmincola generally pointed to minimal parasite-associated mortality.

Effects of Shifting Cultivation on Soil Ecosystems in Sarawak, Malaysia IV. Chemical Properties of the Soils and Runoff Water at Niah and Bakam Experimental Sites

Experimental shifting cultivation was carried out at two sites, Niah and Bakam in Sarawak, Malaysia. The plots (10 × 10 m2) were treated with burning of vegetation biomass (fuel), amounting to 100, 200 and 300 Mg ha−1 with an untreated control at the Niah site and 20 and 100 Mg ha−1 with an untreated control at the Bakam site. At the Niah site, the soils were acidic with a light clay texture. The levels of pH, exchangeable bases and available P of the soils at the depth of 0–5 cm increased by burning while those of exchangeable Al and Al saturation decreased. The changes tended to be more appreciable in the plot treated with fuel at the rate of 300 Mg ha−1 than in the other plots. Based on a comparison between ash alkalinity and the difference in the content of exchangeable Al at 100 d after burning and before burning, it was assumed that 60% of the alkalinity contained in ash was consumed for inactivating exchangeable Al at the depth of 0–5 cm, which resulted in minimal changes in the soil properties in the deeper layers. The influences of burning persisted at the depth of 0–5 cm in all the burned plots until 1 year after burning, except for exchangeable K and available P. On the other hand, at the Bakam site, the soils showed an acidic nature with a sandy loam to sandy clay loam texture. The changes in the pH values and levels of exchangeable bases and Al were observed only at the depth of 0–5 cm in the plots treated with fuel at the rate of 100 Mg ha−1. During rice cultivation, these values returned to the levels recorded before burning. Comparison of the amounts of nutrients among soils, ash and runoff water during rice cultivation at the two sites showed that 1) the losses of ash nutrients by runoff water, except for N, were negligible compared with the amounts contained in the soils and ash, 2) the N input from ash and output by runoff water were not significant, compared with the large stock in the soils, and 3) the ash addition significantly contributed to the supply of inorganic bases (Ca, Mg, K and Na) and P.

Short-term drought causes synchronous leaf shedding and flushing in a lowland mixed dipterocarp forest, Sarawak, Malaysia

Tropical rain forests are evergreen and experience a climate suitable for plant growth year round (Whitmore 1998). However, most tropical rain-forest trees display periodic shoot growth (Borchert 1991) and show synchronous leaf flushing at the community level (Itioka & Yamauti in press, Medway 1972, Ng 1981). Synchronous leaf flushing may have a great impact on animal population such as herbivores, because young leaves are suitable food resources for many herbivores (Aide 1988, 1992; Coley 1983, Itioka & Yamauti 2004, Lowman 1985).

Effects of shifting cultivation on soil ecosystems in Sarawak, Malaysia: II. Changes in soil chemical properties and runoff water at Balai ringin and Sabal experimental sites

Abstract Experimental shifting cultivation was conducted at the Balai Ringin (B. Ringin) and Sabal sites in Sarawak, Malaysia. At the sites, plots (10 x 10 m2) were burned with the fuel of aboveground biomass amounting to 0 (control), 100, 200, and 300 Mg ha-1. At the B. Ringin site, the soils were clayey and strongly weathered with a strongly acidic characteristic. Ash addition enabled to alleviate the soil acidity and to increase the amounts of nutrients of the soils, especially the surface soils. It was indicated that 1) N addition from ash to the soils was negligible, 2) the losses of nutrients by runoff water were not substantial compared with the amounts of nutrients contained in ash, 3) ash alkalinity seemed to be consumed for inactivating exchangeable AI mainly in the surface soils, and 4) development of variable negative charges could contribute to the retention of inorganic bases derived from ash. After harvest of upland rice, the soil chemical properties in the plots treated with 100 and 200 Mg ha-1 fuel returned to the levels before burning, indicating the rapid loss of nutrients due to leaching and erosion as well as the uptake by plants. However, the soils treated with 300 Mg ha-1 fuel still showed high contents of exchangeable bases and a low content of exchangeable AI. On the other hand, the soils at the Sabal site were sandy and were characterized by a very low nutrient status. The changes in the amounts of nutrients by ash addition were similar to those at the B. Ringin site. However, the changes in the level of exchangeable AI which were not appreciable were probably due to the low AI content. It was postulated that because of the sandy texture and low CEC of the soils, inorganic bases contained in ash were only suspended in the soil solution. Taking into account the low yield of rice and low level of secondary biomass, it appeared that most of the nutrients were lost downward in soils by leaching.

Utilization of seed reserves during germination and early seedling growth by Dryobalanops lanceolata (Dipterocarpaceae)

We studied the resource allocation process of a large-seeded species, Dtyobalanops lanceolata, during germination and early stages of seedling growth in Sarawak, East Malaysia. The seeds contained high contents of starch (74.3% of the total 1.57 g mean dry weight of the cotyledon) and lipid (15.0%). All of these reserves were exhausted by the time the first two pairs of leaves had developed (about 40 d after planting), but relatively little had been reserved in leaf or root by that time. This suggests that the large amount of seed reserve of D. lanceolata is necessary just to form a certain size of stem and the necessary number of leaves to set the plant up for photosynthesis. After seed reserves were exhausted, shoot elongation and new leaf production stopped, and most photosynthate was allocated to the expansion of the root system and to storage in the root as starch. The storage reserves in the root are thought to be used for the next growing stage, not to act as insurance for sprouting in case of shoot damage.

Soil Characteristics under Three Vegetation Types Associated with Shifting Cultivation in a Mixed Dipterocarp Forest in Sarawak, Malaysia

In order to provide appropriate soil information for the rehabilitation of tropical rainforest ecosystems, we examined the soil morphological, physico-chemical, mineralogical properties and charge characteristics in a degraded mixed dipterocarp forest with three type of vegetation, namely grassland, secondary forest, and remnant forest in Japan Sarawak Friendship Forest, Sarawak, Malaysia. We compared the soil properties at six representative locations differing in topography and vegetation types, with special reference to the effect of anthropogenic activities on the catenary sequence. All the soils were acidic or weakly acidic. Contents of clay, exchangeable Al, Alo, Ald and Fed and the values of the cation exchange capacity and Al saturation increased with depth. The clay mineral composition was dominated by kaolin minerals. The value of point of zero salt effect ranged from 3.0 to 4.0, indicating that the soil was not yet strongly weathered. A catenary sequence of the soils was observed; softer in soil hardness, higher contents of total exchangeable bases in the lower slope plots than in the upper slope plots and higher values of Feo/Fed in the surface horizon in the lower slope plots than in the upper slope plots. However, the effect of anthropogenic activities was observed; higher contents of total exchangeable bases in the grassland than in the other vegetation types. Based on the stable condition on weathering and erosion, the upper slope plot of the remnant forest exhibited a thicker O horizon, lower Feo/Fed values and a relatively high amount of chlorite. Soil variability should be taken into account for appropriate management of rehabilitation in tropical rainforests.

Effects of Shifting Cultivation on Soil Ecosystems in Sarawak, Malaysia. III. Results of Burning Practice and Changes in Soil Organic Matter at Niah and Bakam Experimental Sites

The effects of burning on the levels of soil organic matter, soil nitrogen, and soil microbial biomass were studied by carrying out experimental shifting cultivation at two sites, Niah and Bakam in Sarawak, Malaysia. Vegetation biomass was burned in plots (10 × 10 m2) at the rates of 0 (control), 100, 200, and 300 Mg ha−1 at the Niah site and 0, 20, and 100 Mg ha−1 at the Bakam site. At the Niah site, the levels of total C and N of the soils did not change throughout the experiment in spite of enhanced soil respiration until 2 months after burning. Although burning induced an increase in the amount of NH4-N of the soils, the readily available pool of N (the sum of the NH4-N, NO3-N, microbial biomass N, and extractable organic N pools) in the burned plots was depleted appreciably at the end of rice cultivation. The effects of burning on these properties tended to be substantial with increasing amounts of the vegetation biomass burned. On the other hand, the levels of total C and N and the readily available N pool at the Bakam site were low before burning compared with those at the Niah site, and the burning treatments did not affect them appreciably. While the rice yield at the Niah site reached the average value obtained in traditional shifting cultivation in Sarawak, that at the Bakam site was much lower. It was suggested that the flush of NH4-N induced by burning was one of the major factors for rice growth.