Warm-season Growth Research Articles

The potential of marine bivalve Spisula sachalinensis as a marine temperature record

• The potential of Spisula sachalinensis as a high resolution temperature indicator • δ 18 O inversely correlates to seasonal ocean temperature but δ 13 C is less cyclical • Annual growth lines are formed during the warmest part of the year • Annual and non-annual growth lines are distinguishable via stable isotope analysis • Archaeological S. sachalinensis offer a valuable regional palaeoclimate record This paper presents a four year subannual isotope marine temperature record using modern Spisula sachalinensis specimens from Tomakomai (Hokkaido's Pacific coast, Japan). This species is commonly found in pre- and protohistoric shell middens and faunal assemblages from around the Seas of Japan and Okhotsk, so has significant potential as an indicator of past marine and, by inference, climatic conditions. However, previous sclerochronological research on the species’ growth has shown significant geographical variation in growth pattern, rendering palaeoclimatic interpretation difficult. To address this issue, this study applied sequential isotopic analysis to two sectioned modern valves, providing a proxy for sea surface temperature (SST) and allowing the direct identification of seasonality during shell growth. The sequences span four years of growth, as confirmed by visually identified growth patterns and the oxygen stable isotope results, which show clear annual cycles in δ 18 O. δ 13 C seasonality is less clear, but shows a weak inverse correlation with temperature potentially relating to primary productivity. Annual growth lines show that shell growth occurs during both warmer and cooler SSTs, but is more rapid during the cooler seasons. This is consistent with warm-season growth minima seen in shells from Hakodate Bay by Kato and Hamai (1975) , but not with their suggestion that it is associated with shells growing at the southern limits of their distribution. Comparison to average local SST shows that δ 18 O-derived temperature falls within the expected range, but, contrary to expectations given preferential cool-season shell growth, appears biased towards warmer temperatures. Factors that could contribute to this are discussed. Overall, stable isotope analysis of Spisula sachalinensis is considered a useful complement to macro/microscopic sclerochronological research in building a holistic picture of shell growth, and has significant potential as a high resolution proxy for palaeoenvironmental studies of past SST.

Chickpea Performance Compared to Pea, Barley and Oat in Central Europe: Growth Analysis and Yield

An increase of grain legume production is essential for meeting feed protein need in Europe. Warming climates offer the opportunity for adapting crops with a more warm-season growth habit such as chickpea (Cicer arietinum L.) in cool, northern latitude areas. Therefore, yield and growth analysis of chickpea were assessed in a two-year field experiment in Central Europe (Raasdorf, Austria) and compared to pea, barley and oat, which are well adapted crops in that region. Chickpea had a lower above-ground biomass and grain yield compared to pea, barley and oat in 2006, whereas only pea was more productive than chickpea in the dry year of 2007. The relative good performance of chickpea regarding crop growth rate and relative growth rate compared to pea, barley and oat under severe drought in 2007 indicated that chickpea may be an interesting crop in the Central European production area in the face of possible climate change

Non-indigenous grasses impede woody succession

With the proliferation of old fields and the decline of native grasslands in North America, non-indigenous grasses, which tend to colonize and dominate North American old fields, have become progressively more abundant. These new grasses can differ from native grasses in a number of ways, including root and shoot morphology (e.g., density of root mat, height of shoots), growth phenology (e.g., cool season vs. warm season growth), and plant–soil–water relations due to differences in photosynthetic physiology (C3 vs. C4). Woody plants have been slow to colonize some old fields in the prairie-forest border area of North America and it is hypothesized that non-indigenous grasses may be contributing to the poor establishment success of woody plants in this region, possibly through more intense competition for resources. To test this hypothesis, a multi-factorial field experiment was conducted in which water, nitrogen, and grass functional group (non-indigenous C3 and native C4 species) were manipulated in a study of survival of oak seedlings. The grass type variously affected some of the different growth measurements, however, the effects of grass type on seedling growth were small compared to the effects on seedling survival. The results showed that when grown under dry conditions, seedlings growing in non-indigenous grasses experienced up to a 50% reduction in survival compared to those growing in native grasses under the same conditions. Analyses of root and shoot competition showed that the cause for the reduced survival in the non-indigenous grasses was due primarily to underground processes. The findings confirmed our initial hypothesis that non-indigenous grasses are likely contributing to the poor establishment success of woody plants in these old fields. However, the explanation for the reduced oak seedling survival in non-indigenous grasses does not appear to be due to reduced resource availability since soil water levels did not differ between non-indigenous and native grass plots and other resource levels measured (light, NO3, and NH4) were higher in non-indigenous grass plots under dry conditions. An alternative explanation is that the non-indigenous grasses modify the soil environment in ways that, under dry conditions, are deleterious to emerging oak seedlings. Since current climate projections for the upper Midwest are for hotter and drier summers, the results suggest that the resistance of these old fields to oak encroachment will likely increase in the future.

Distribution of biomass of species differing in photosynthetic pathway along an altitudinal transect in southeastern wyoming grassland.

Based on the physiological characteristics and responses of C3, C4, and CAM plants to environmental factors, it is generally predicted that C4 and CAM plants will become more abundant with increasing temperature and decreasing precipitation. To test this prediction, the relative contribution of each photosynthetic type to total plant community biomass was examined at seven study areas along an altitudinal transect in southeastern Wyoming grassland. In going from high (2,652 m) to low (1,405 m) elevation along this transect, mean annual temperature increased and annual precipitation decreased.The percentage of C4 biomass composing each study area decreased with increasing elevation, while the percentage of C3 biomass increased. All elevations had a significantly higher percentage of C4 biomass in August than in June, reflecting the warm season growth characteristic of C4 plants. Regressions of relative abundance of photosynthetic types on climatic variables showed that both mean annual temperature and annual precipitation were equally reliable as predictors of C3-C4 biomass, although we feel that temperature is of primary importance in explaining our observations. CAM species were present at all elevations, but showed no trends in biomass distribution with respect to elevation.

Regional variation in performance of New Zealand × Spanish white clover (Trifolium repensL.) hybrids in New Zealand

Performances were analysed for F1 progenies derived from hybridisation of 12 Spanish white clover plants with 7 New Zealand plants. Progenies were grown at 4 locations in New Zealand and growth data analysed for different seasons. The F1 progenies successfully combined cool-season growth of the Spanish parents with the warm-season growth of the New Zealand parents. Gains in cool-season growth were, however, usually larger and more consistent at Palmerston North than at the other three locations. Differences among progeny groups from individual parent plants were significant for both the New Zealand and Spanish sources in all seasons at all locations. Progeny performances interacted strongly with season and location. However, results suggested that selection for cool-season growth at Palmerston North should produce material with improved cool-season growth at all locations. Relative gains at Lincoln and Gore would be small wherever selection was carried out. Interactions among individual Spanish and New Zealand parent plants were generally absent or weak. Although the Spanish component contributed greatly to winter growth at Palmerston North, the New Zealand population nevertheless made a large contribution to the genetic variance among F1 progenies. Therefore further selection for winter growth within the F1 propulation should take account of both parents.

Potential of new summer grasses in Northland

Abstract Herbage of 22 C4 grasses and 3 C3 grasses grown in Northland was analysed for nutritive quality. Small swards of the grasses were cut at approximately 5-weekly intervals from mid November to mid April to provide forage samples. Digestibility of leaf and stem tissue of a representative range of these grasses assessed by an in vitro technique was not altered significantly by irrigation, and did not alter significantly during the warm-season growth period. Leaf and stem tissue of the various grasses did vary substantially in digestibility, stem tissue usually being lower in digestibility than leaf tissue. Some of the C4 grasses had dry matter digestibilities equivalent to those of the C3 species. The digestibility of herbage from grasses grown at Kaitaia, New Zealand, was frequently higher than that of the same grasses grown in a warmer environment at Lawes, Australia. Crude protein, alcohol soluble sugar, and starch levels were also measured in leaf and stem tissue of the grasses. Crude protein lev...

Potential of new summer grasses in Northland

Herbage of 22 C4 grasses and 3 C3 grasses grown in Northland was analysed for nutritive quality. Small swards of the grasses were cut at approximately 5-weekly intervals from mid November to mid April to provide forage samples. Digestibility of leaf and stem tissue of a representative range of these grasses assessed by an in vitro technique was not altered significantly by irrigation, and did not alter significantly during the warm-season growth period. Leaf and stem tissue of the various grasses did vary substantially in digestibility, stem tissue usually being lower in digestibility than leaf tissue. Some of the C4 grasses had dry matter digestibilities equivalent to those of the C3 species. The digestibility of herbage from grasses grown at Kaitaia, New Zealand, was frequently higher than that of the same grasses grown in a warmer environment at Lawes, Australia. Crude protein, alcohol soluble sugar, and starch levels were also measured in leaf and stem tissue of the grasses. Crude protein lev...