Schima wallichii (DC.) Korth. (Theaceae) is a common canopy trees distributing from tropical to subtropical areas in East Himalaya, Southeast Asia and East Asia. Although many seedlings of S. wallichii are planted to rehabilitate degraded natural forests in West Java, there are few studies of its genetic differentiation and the risk of plantation to disturb the genetic structure. There is also debate whether Schima trees in Java and Ryukyu are in a same species or not. This study was initiated to remedy these deficits by screening genetic differentiations using inter simple sequence repeats (ISSR) analysis with eight primers. Leaves were sampled from 250trees at seven sites in the Mt. Halimun-Salak and Mt. Gede-Pangrango National Parks in West Java, and 32trees at four sites on Amami Islands of the middle Ryukyu Archipelago. Principal component analysis (PCA) of 155 polymorphic bands from 282trees showed that Schima in both regions had high level of genetic variation within a given site. Genetic differentiations among sites in a region was low though some sites had a significantly different mean of PCA scores from other sites. The introduction of seedlings from other sites in the same region may have a low risk of genetic pollution though many mother trees should be prepared to maintain the variation in a site. The first scores of PCA discriminated trees of Java from those of Amami without overlap. Schima in West Java and Amami are probably different subspecies or species from each other.
Many empirical studies have supported the facilitative effect of nurse plants, and several recent studies have reported similar phenomena with non-plant features, such as rocks. Few studies have explored the effect of rock height on plant establishment, although variation in height can affect establishment. This study examined whether rocky outcrops have positive effects on plant establishment, as do classic nurse plants, and explored the mechanisms involved in the nurse effects in a South African grassland. To answer these questions, we compared the number of individual woody plants at the edges of rocky outcrops and in the adjacent grassland matrix, as well as beneath a putative nurse plant (Euclea crispa) and in the adjacent grassland matrix. We also measured the heights of rocky outcrops and E. crispa and the proportions of grass cover. The results showed that larger numbers of woody seedlings occurred at the edges of rocky outcrops and beneath E. crispa compared with in the adjacent grassland matrix. A generalised linear model (GLM) showed that rock and E. crispa height positively affected the number of seedlings; the diaspores of most recorded species showed characteristics associated with dispersal by vertebrates. The GLM analysis showed that the proportion of grass cover had a negative effect on the number of seedlings. These results indicate that in addition to shrubs, rocky outcrops appear to have positive effects on the establishment of woody plants in South African grasslands, likely serving as perching structures for birds and providing favourable microhabitats.
To evaluate the potential of tannins derived from Acacia mangium bark to mitigate soil N2O emissions, a laboratory incubation study was conducted. We prepared a crude tannin extract by water extraction from A. mangium bark, and fractionated the crude extract into high- and low-molecular-weight tannins (HMTs and LMTs, respectively). Soils were incubated with and without the addition of A. mangium bark tannins and commercial tannic acid after KNO3 was added and the water-filled pore space was adjusted to 100%. Acacia mangium bark tannins significantly decreased N2O emissions compared with the control. However, they did not significantly affect CO2 emissions or inorganic N concentrations except for soils with LMTs, where cumulative CO2 emissions were significantly decreased, and for the fact that NH4+ contents in tannin-treated soils were significantly lower than in the control soil at 7 days. These results suggest that the antimicrobial activities of purified tannins of A. mangium bark reduced N2O emissions by inhibiting denitrification regardless of the degree of polymerization. The crude tannin extract, which probably contained other non-tannic C sources, also reduced N2O emissions, suggesting that the toxic effects of HMT and LMT in it would overcome the effects of other C compounds on soil N2O emissions. Tannic acid, which is different in structure from condensed tannins, suppressed the N2O emission but it was not significant and less effective than HMT and LMT. Our results suggest that the application of A. mangium bark tannins has the potential to mitigate N2O emissions from A. mangium plantation soils.
The transformation of land from swidden based to permanent agriculture is an important issue related to the sustainable livelihood and land use system of people in mountain environments. This paper reports the introduction of paddy rice cultivation and its consequences in four swiddener communities in Arunachal Pradesh, India, by focusing on cultivation techniques. The Indian government introduced paddy rice cultivation to Arunachal Pradesh in the 1950s by teaching the required techniques and supplying seed and agricultural tools. However, few swiddeners began rice cultivation because they disliked working in muddy paddies that could not produce non-rice crops. During the “green revolution” in the 1970s, many people decided to create paddy fields after observing the remarkably high yield of new rice varieties. Over 60 years of trial and error, many swiddener communities have developed a unique cultivation system suited to their local environment, while often learning from their neighboring communities of Ahom and Apatani that already practiced paddy rice cultivation. The paddy field has become a symbol of wealth and social status because of the high and stable yield of paddy rice and escalating land prices. However, the communities usually continue some aspects of swidden cultivation, because only a limited amount of land is suitable for paddy rice, people need non-rice crops, or because older people prefer swidden cultivation work and the taste of upland rice. This case study shows the importance of local needs and knowledge of skilled farmers in swidden transformation.