Regrowth Development Research Articles

The Road to Functional Recovery: Temporal Effects of Matrix Regeneration on Amazonian Bats

Across the tropics, vast deforested areas are undergoing forest regeneration due to land abandonment. Although secondary forest is an expanding type of landscape matrix that has been shown to buffer some of the negative consequences of forest loss and fragmentation on taxonomic diversity, little is known in this regard about the functional dimension of biodiversity. We took advantage of an ecosystem-wide fragmentation experiment to investigate longer term changes in functional diversity of a mega-diverse Amazonian bat assemblage associated with regrowth development in the matrix. We found that matrix regeneration affected several facets of bat functional diversity in secondary forest over time, increasing functional α diversity, species- and community-level functional uniqueness, altering functional trait composition, and resulting in functional β-diversity changes via trait gains. However, approximately 30 years of matrix regeneration were insufficient for functional diversity to recover to the same levels as in continuous forest. Our results suggest that a combination of natural, human-assisted, and active restoration is likely to be the most successful strategy for restoring functional biodiversity of bats in human-modified tropical landscapes, a finding that most likely also applies to many other taxa.

The effect of seed trees on regrowth development in a mixed-species eucalypt forest

Summary Previous studies have shown that the retention of overwood can have suppressive effects on the development of regrowth. In this study we compared the effect of retaining seed trees (mature Eucalyptus pilularis), and removing seed trees, on the regrowth of E. pilularis and the more tolerant eucalypt species such as E. microcorys, E. propinqua, E. acmenoides, and E. paniculata. The study utilised a mixed hardwood stand located within Pine Creek State Forest, near Coffs Harbour in north-eastern New South Wales. The stand had been regenerated in 1972 leaving 15 seed trees/ha. Half of the seed trees were removed in 1990. Measurements of height, diameter, and distance of regrowth trees to the seed trees indicated that the height of regrowth was significantly affected by distance from seed tree (removed or retained). This suppressive effect was significantly more pronounced for E. pilularis than for more tolerant species. Height development of the regrowth improved significantly where seed trees had been removed. For the intolerant species the height-to-diameter ratio decreased with distance from seed tree (removed or retained), whereas for tolerant species the height to diameter ratio remained constant over all distances. The results of this study confirm that intolerant eucalypt species are more sensitive to overstorey competition than more tolerant species, and that the relative loss of production from the retention of mature trees may be smaller in mixed stands consisting of tolerant and intolerant eucalypt species than in mono-specific stands of intolerant species.

Evaluation of Potassium 3,4‐Dichloroisothiazole‐5‐Carboxylate as a Harvest‐Aid Chemical on Cotton1

Chemical defoliants usually cause varying amounts of leaf abscission when applied to cotton (Gossypium hirsutum L.). This variation is due mainly to environmental factors, but may also be influenced by plant characteristics. The objective of this research was to evaluate the effect of potassium 3,4‐dichloroisothiazole‐5‐carboxylate (TD‐1123) in altering leaf abscission response of cotton to conventional defoliant chemicals. Field and greenhouse studies employed rates of TD‐1123 that varied from 0 to 1.12 kg/ha, and timing of application that ranged from 0 to 4 weeks before defoliant chemical treatments. Measurements were made to determine effects of rate and time of application of this chemical on leaf abscission, regrowth development, yield of seed cotton, and various boll and seed properties.TD‐1123 failed to alter leaf abscission response of greenhouse plants when applied as a mixture with DEF (S,S,S‐tributylphosphorotrithioate), but caused a significant increase in abscission rate and total defoliation when applied 1, 2, or 4 weeks prior to DEF. The 1 and 2‐week pretreatments, however, were the most effective in this respect. Regrowth development was also reduced in the 1 and 2‐week pretreatments of greenhouse plots, but was increased when applied 4 weeks before DEF. The rates of TD‐1123 that gave the greatest abscission response were 0.28 and 0.56 kg/ha. Seed germination, however, was reduced when these rates were applied 4 weeks prior to DEF.Regrowth, yield, and boll components of field cotton were not affected by TD‐1123 at rates of 0.28, 0.56, or 1.12 kg/ha. These rates, however, were equally effective in increasing leaf abscission response to DEF. A 10‐day pretreatment of 0.336 kg TD‐1123/ha also increased leaf abscission with sodium chlorate and with DEF + endothall [7‐oxabicyclo(2.2.1)heptane‐2,3‐dicarboxylic acid] mixtures. This research indicates that TD‐1123 can be an effective harvest‐aid chemical on cotton.