Testing ecological theory with lianas

Abstract

Contents Summary 366 I. Introduction 366 II. Testing ecological theory: effects of the environment on lianas 369 III. A unified explanation for liana distribution and the maintenance of liana diversity 370 IV. Testing ecological theory: effects of lianas on the environment 373 V. Theoretical effects of lianas on forest diversity 375 VI. Lianas and trophic interactions in forests 375 VII. Unresolved challenges in liana ecology 376 VIII. Conclusions 377 Acknowledgements 377 References 377 SUMMARY: Lianas constitute a diverse polyphyletic plant group that is advancing our understanding of ecological theory. Specifically, lianas are providing new insights into the mechanisms that control plant distribution and diversity maintenance. For example, there is now evidence that a single, scalable mechanism may explain local, regional, and pan-tropical distribution of lianas, as well as the maintenance of liana species diversity. The ability to outcompete trees under dry, stressful conditions in seasonal forests provides lianas a growth advantage that, over time, results in relatively high abundance in seasonal forests and low abundance in aseasonal forests. Lianas may also gain a similar growth advantage following disturbance, thus explaining why liana density and diversity peak following disturbance at the local, forest scale. The study of ecology, however, is more than the effect of the environment on organisms; it also includes the effects of organisms on the environment. Considerable empirical evidence now indicates that lianas substantially alter their environment by consuming resources, suppressing tree performance, and influencing emergent properties of forests, such as ecosystem functioning, plant and animal diversity, and community composition. These recent studies using lianas are transcending classical tropical ecology research and are now providing novel insights into fundamental ecological theory.

Effect of lianas on forest‐level tree carbon accumulation does not differ between seasons: Results from a liana removal experiment in Panama

“…Lianas may also sustain their water potential by either accessing deeper water (Andrade et al, ; Chen et al, ) or different water sources (De Deurwaerder et al, ) than trees or by exercising strong stomatal control under drought conditions. Lianas may therefore have the ability to remain photosynthetically active during periods of seasonal drought (Cai et al, ; Sánchez‐Azofeifa et al, ; Schnitzer, ), thereby taking advantage of the increase in irradiance as a result of reduced cloud cover during the dry season (Graham, Mulkey, Kitajima, Phillips, & Wright, ; Schnitzer, ) to vigorously grow (Schnitzer & van der Heijden, ). However, even though liana biomass increment during the dry season was greater than during the wet season in all 5 years (Figure ), the relative impact of lianas on tree biomass increment did not differ between the seasons (Figure ).…”

Effects of dry‐season irrigation on leaf physiology and biomass allocation in tropical lianas and trees

“…The combination of higher photosynthesis levels and greater physiological regulation (stomatal control) could allow lianas to function more efficiently than trees when water is limited during seasonal drought. The ability of lianas to perform better than competing trees during seasonal drought gives lianas a seasonal growth advantage over trees in seasonal forests that they lack in wet forests, thus explaining higher liana abundance in seasonal forests because they have an extra 3 to 5 months of growth that they lack in ever‐wet forests (Schnitzer , ). Our results (Fig.…”

“…). An explanation for lianas being more abundant relative to trees in seasonal forests is that lianas perform better than trees when water is limited because light is plentiful during dry periods (Schnitzer ). This seasonal growth advantage, however, is thought to be lost in aseasonal wet forests, where light is low year‐round, thus explaining pan‐tropical liana distribution (Schnitzer ).…”

Modeling the impact of liana infestation on the demography and carbon cycle of tropical forests

“…The model assumes that within the patch area, only a limited fraction of small (<10 m) plants survive (see Supporting Information 3). Unlike trees, lianas often survive in gaps after the falling of their host (Putz, ), potentially giving them a competitive advantage in highly disturbed areas (Schnitzer, ; Schnitzer & Carson, ). Therefore, we assumed a higher survivorship probability for attached lianas in the case of tree‐fall (0.8, Table S1).…”

“…Although such studies need to be confirmed with long‐term observations across multiple forests (Schnitzer, van der Heijden, & Powers, ), they provided, for the first time, empirical evidence that lianas have a substantial negative impact on whole‐forest carbon uptake/sequestration. Furthermore, approximately half of the tropical forest area is currently covered with secondary forest (Poorter et al, ), where lianas peak in abundance (Schnitzer, ), which might reduce the potentially rapid rates of carbon sequestration in such secondary forests (Durán & Sánchez‐Azofeifa, ) and further impact the global carbon cycle.…”