An Analysis of Growth and Drought Tolerance in Rubber During the Immature Phase in a Dry Subhumid Climate

Abstract

An experiment with the objective of evaluating the performance of 15 clones of rubber (Hevea brasiliensis) was conducted in the Konkan region of Western India. The clones under evaluation were RRII 5, RRII 6, RRII 105, RRII 208, RRII 308, RRIC 52, RRIC 100, RRIC 102, RRIC 105, RRIM 605, PB 260, PB 310, PB 311, PR 255, and PR 261. The region is a trial environment for the crop and experiences more than seven rainless months and severe drought in the summer months. Data on monthly girth growth w ere collected for six years from a trial with randomized block design. The growth of clones in terms of monthly girth increment growth (GIN, cm month−1) seasonal mean girth increments (MGIN, cm season−1) and mean relative increment rates (MRIR, mm cm−1 season−1) as well as annual MGIN (cm a−1) and MRIR (mm cm−1 a−1) was studied. Correlation analysis was performed to understand the effect of seasonal growth on the final growth. At the beginning of the study, the largest girth noted was for the clone RRII 6 (22. 5 cm) followed by RRII 208 (22.0 cm). PR 261 with a girth of only 14.2 cm was the least vigorous among the clones. A large portion of the growth occurred in the wet season only. During the dry season the growth rates of the clones declined substantially and decreases in girth ranging from 0.2 mm to 0.5 mm were noticed in most of the clones. At the end of the study period the largest girth observed was for clone RRII 208 (49.3 cm) and the lowest for PR 261 (39.3 cm). The highest proportion of tappable trees noted was for clone RRII 208 (52.4%) and the lowest for PR 261 (2.7%). The pooled average of tappable trees was on ly 17.5%. The data revealed that the immaturity period for Hevea in the region will not be less than 9 years under rainfed conditions. From the analysis based on the final girth it was concluded that clones RRII 208, RRIC 52, RRII 6, RRIC 100 and RRIC 102 are more tolerant to drought while RRII 105, RRIC 105, RRII 5, RRIM 605, PB 310, PB 260, PB 311, PR 255, RRII 308 and PR 261 are less tolerant. The results of correlation indicated that by analysing the growth, potentially drought-toleran t clones can be identified.

Local hydrologic effects of introducing non‐native vegetation in a tropical catchment

“…This subsurface water uptake is necessary to increase stem water potential above a certain threshold to allow bud break . In support, a study in northern India showed girth perimeter increasing several weeks before the first rainfall, possibly indicating rehydration of the tree from deep layer water uptake, associated with bud breaking (Chandrashekar et al, 1998). Furthermore, flushing induced by increasing day-length during the late dry season has been observed in many tropical tree species in monsoon forests around the globe Elliott et al, 2006).…”

“…However, because of its economic importance, rubber is now cultivated at higher latitudes and altitudes in South America, Southeast Asia and Africa. In these marginally suitable environments (colder and drier), the productive life of rubber, its yield and its growth are reduced (Chandrashekar et al, 1998;Devakumar et al, 1999).…”

Comparative drought-resistance of seedlings of 28 species of co-occurring tropical woody plants

“…However, few studies have directly compared the extent of growth reduction due to drought between species (e.g., Jarvis and Jarvis 1963;Evans and Etherington 1991;Espigares and Peco 1995;Fernandez and Reynolds 2000). Of the relevant studies of drought effects on growth of woody rainforest plants, most have shown that droughted seedlings, as well as saplings and mature trees, have reduced growth compared to plants under wet conditions (e.g., Unwin and Kriedemann 1990;Fisher et al 1991;Veenendaal et al 1995;Poorter and HayashidaOliver 2000;Ito et al 2000;Chandrashekar et al 1998). Methodological differences and the very limited number of species investigated do not allow comparisons based on the available data.…”

Hydrologic effects of the expansion of rubber (Hevea brasiliensis) in a tropical catchment

“…Since the early 1980s, rubber research institutions have studied productivity and adaptability of Hevea clones to relatively cold and dry environments (Gururaja Rao et al, 1990;Vijayakumar et al, 1998;Priyadarshan et al, 2001). Clones are now adapted to overcoming dry periods and lower temperatures without important loss of latex yield (Chandrashekar et al, 1998;Rodrigo, 2007). Using new genotypes, rubber plantations have now expanded to 27°N latitude and up to 1100 m in elevation (Priyadarshan et al, 2005), well beyond the native environment of 10°N/S of the equator and 400 m above mean sea level (AMSL) (Priyadarshan et al, 2005).…”